power by wire ( electro hydrostatic actuator)

!"# $ $ %& $# !&' ( )*+,-.-/) 0 !'& $3 $3 $3 $ $ # #!# 0 9 $0 & # $ $( !$ 1 2)/2 # $ % " $ $4 # 5 $ !# 7 % $8 $ % 6 $8 7 $ % 8 6 S.No.85, SHASTRI CAMPUS, NDA ROAD,SHIVNAE, PUE-411023 (M.S) This is to certify that project entitled “ Aerospace. Project Guide, : has successfully completed the ” in fulfillment, for the award of B.Tech- 9 DEPARTMENT OF AEROSPACE ENGINEERING Certified that the project work entitled POWER BY WIRE is a Bonafide work done by : bearing Enrollment Number: )*+,-.-/) in the final year seventh semester B.Tech in Aerospace Engineering from IGNOU, New Delhi. Head of department Director Examiner Acknowledgements We owe a great many thanks to people who helped and supported me during this project. The technical assistance, industrial exposure and advice provided by 3 # Pune is greatly appreciated. My deepest thanks to 6 : # $ !$3 #5 % &% $ 6 $3 # & for taking tremendous interest and pains in assembling the components and guiding us through the same. The author would like to express his gratitude to Mr. "$ % # %, Gemini education Pune for the assistance provided with the electronic interfacing and programming. Thanks to 6 of Shah Brothers Mumbai and numerous other suppliers of major equipment and components for making this project possible. I express my thanks to the $7 " % and 6 6 6 0 , for the project approval and support. Darshak Bhuptani Akshay Gupte Mohammed Kapdi Moolchand Bias Nilesh Sawant Nirmal Alex Prajith P.P Vijeet Mehta 0 7 In this project Power by Wire, we aim at developing novel approaches to the design and development of electrically powered actuators used to operate flight control surfaces. Currently, the maturity of PBW technology is lagging behind that of FBW. The development of actuator configurations, efficient electric motors, and high-power electronic drives, although demonstrated in test flights, has yet to be implemented and certified as a production standard application. In this project we aim at developing a low power and low pressure Electro hydrostatic Actuation system employing a hydraulic actuator, pump, motor and the corresponding control mechanism of an acceptable level. The main purpose of the project shall be to determine and implement proper compatibility between these subsystems to achieve the required results. The outcomes and shortcomings if any will be analyzed and suitable mitigation measures will be presented. Power By Wire system employing an Electro-Hydrostatic actuation system has a very wide scope of applications in the near future. It can also be implemented in Unmanned Combat Aerial Vehicles for meeting the requirements of high manoeuvrability and instant response without addition of a heavy centralised hydraulic system throughout the aircraft that might compromise severely with the performance. $3 ; /6 26 '< 7# 4 # 0# 3 % 8 #!3 0# +6 # # & $# 0 # )= #!3 " '% & ))> .6 # /) ,6 $ % +* =6 $ % -6 !%# >/ $ >> $7%! >6 7 " 0# 0!#! #!3 *- *6 3 # *> /)6 '% 8 " ** '< 7# 4 0# #!3 The objective of the project is to demonstrate a working model of a Power By Wire Flight Control System with basic functionality on a smaller scale utilizing easily available off-the-shelf components. 1. Built the Power By Wire system using readily available components so that the system can be built with a simple procedure and a reasonable cost. 2. The system shall be a working scaled down model eliminating parts which are not critical for its functioning such as bypass valves and hydraulic accumulators to reduce the complexity and thus the resulting size and weight. 3. Actuation to be done by using EHA electronically controlled by solid state integrated circuit and powered by minimum possible voltage which can be suitable to be operated by limited power available onboard smaller aircraft or UAV’s. 4. The total package consisting of all the components should be as compact as possible to easily facilitate integration with existing framework without creating much space and interfacing problems. 5. The system should be tested to satisfy minimum functionality and should be free from any kind of operating complexities and safety hazards # 3 % 8 0# #!3 The setup will consist of small double acting single piston hydraulic actuator without any kind of a valve for fluid flow regulation. Phosphate-Easter based hydraulic fluids which are common in aircraft applications will not be utilized due to problems in handling, availability and cost. Instead easily available fluids such as those used in automobiles will be used instead. The actuator will be connected via fluid lines to a bidirectional pump which in turn will be driven by a bidirectional motor powered by a low voltage direct current which might not exceed 12v in any case. The motor will be driven by a solid state motor control circuit with capability of driving the motor very precisely in steps in both the directions to carry out a proportional movement of the actuator. Feedback sensors will be incorporated in the system to sense the end limits of actuation and eliminate any destructive response of the actuator. Finally the input to the whole system will be given to the motor control circuit by an input device such as a keyboard of a personal computer; however the system will be calibrated so that the actuation in either direction is proportional to the physical input. Extensive testing of the system will be done to ascertain the reliability and repeatability of the system as well as the capability of the system to drive as well as sustain loads. # # & $# 0 # " '% & The electric motor should be powered by external voltage of not more than 12 v dc and should not exceed the maximum current rating of 600 mA but should still be able to produce enough torque to power the gear pump comfortably. A correct combination of gearing should be selected so that the RPM and torque is sufficient to pump the fluid at the required rate and also built up enough pressure to actuate the piston respectively. The motor controller circuit should be able to drive the motor in both directions with a very good response time; the response of the motor should be almost instantaneous when the command for actuation is given to the system. The controller is also expected to provide a relatively stable voltage level so that the response of the actuator remains linear and additional calibration need does not arise. The pump should be able to provide enough pressure for actuation of the piston. The fluid flow rate of the pump should be sufficient at the rpm possible by the motor so as to cause appreciable deflection of the actuator within a short time interval of less than a second without causing dead zones and backlash. The actuator should be selected with an appropriate bore and stroke length so that the volume of the fluid required for actuation is within the capacity of the flow rate of the pump being used in the system. Special attention is to be given to the overall simplicity of the system in terms of number of components being used and the assembly of the components. Leakages should be kept as minimum as possible if cannot be eliminated. Last but not the least, a safety device or mechanism is to be incorporated into the EHA system being built. The safety mechanism should prevent the system from causing any self inflicted damage which can be caused by situations such as overloading or actuation attempt in the wrong direction when the piston has already reached the end. # Preliminary Remarks Hydraulic systems have been widely used in industry for decades in applications where it is advantages to have the following features: Ø The ability to manoeuvres’ large loads. Ø High force/torque-to-mass ratio. Ø Obtain accurate control of a state of interest (i.e. position, velocity). Ø Have a self-lubricating system (oil acts as a lubricant). Due to these features hydraulic systems have found applications in aerospace systems, farm equipment, off-road equipment and heavy machinery. In this study, their application to the aerospace industry will be investigated. The Electro-Hydrostatic Actuator (EHA) is used to actuate the aircrafts’ flight surfaces. An EHA is a form of hydrostatic system that uses the flow from the pump to control an actuator as opposed to a directional valve seen in common hydraulic system. Hydrostatic systems have been widely used in industry, primarily in off-road and farm equipment as transmissions, for many years. The primary difference between traditional hydrostatic systems and the EHA is the manner in which fluid is routed to the actuator by the pump. Traditional hydrostatic systems employ a variable-displacement pump attached to single speed motor, which controls the output flow depending on the input angle of the pump swash plate. The EHA employs a fixeddisplacement piston pump attached to a servomotor in which the output flow is proportional to the servomotor rotary speed. Due to the fixed-displacement pump the EHA only requires on- demand rotation of the servomotor. This can greatly enhance energy efficiency. The primary components of the EHA design considered in this research include a fixed-displacement bidirectional internal gear pump, a controlled geared motor, a linear actuator and a feedback system. Compared to common directional valve actuated systems, the EHA has the following advantages: § $7 3" § $7 3 $ 8 § $7 3 & 3!% 1# 1 8 # # 6 00 7 $7 6 # 0# # &6 The increased power-to-weight ratio is achieved by creating an integrated unit where all components are combined into a lumped, modular system. The resulting reduction in weight makes the EHA ideal for aerospace, especially since the performance and fuel efficiency are becoming increasingly important. In aircraft it is especially important to have systems that are fault tolerant and have some form of redundancy. An EHA can satisfy this by combining two systems in tandem so that one can compensate for the other in the event of a malfunction. $4 $# $ % % 8 # ! 0 7 7#! # # & This section provides an introduction into the concept of flight surface actuators used in aircraft. Common mechanisms and their associated mathematical models are discussed along with their advantages and disadvantages. Conventional mechanical and hydraulic systems that are relevant to flight surface actuation are discussed in detail. %8 # $# % $ $ 7 0# Flight control systems on an airplane are typically classified into two categories: primary and secondary. Primary systems in an aircraft typically control all components that safely guide an airplane during flight, which include the ailerons, the elevator and the rudder. Secondary flight controls improve the performance characteristics of the aircraft or relieve the pilot of using excessive control force. Examples of secondary flight controls include the landing gear, flaps and trim systems. Figure 2.1 shows all of the primary flight surfaces and a select number of the secondary flight surfaces on the Boeing 777 aircraft. Figure 2.1.Primary and secondary flight surfaces for the Boeing 777 The primary flight surfaces control the three main axes of the aircraft’s orientation which are yaw, pitch and roll. The rudder, elevator and ailerons control these respectively. A depiction of the movement of an aircraft can be seen in figure 2.2. The focus of this research is in the systems that actuate the primary flight control surfaces. The following sections will describe the types of flight surface actuators used in the history of flight: v 7 v 3 !% 7 7#! # $ 7 $# %% 3 ' & 7 v v % 1 $7 %%$ 1 1 8 6 ? 1 @ ? # &6 @ # &6 $7 %%$ 8 6 Fig 2.2 v $8 7 $7 % $ 8 0 %8 # ! 0 7 7#! # $ When aircraft were in their primitive development phase in the early 20th century their limited size and speed allowed their primary flight surfaces to be actuated using only the force exerted by the pilot on the controls. Linkages using taught wires, pulleys and sometimes counterweights would connect the joystick and foot pedals in the cockpit to the flight surface. This method was simple and reliable but was limited to the size and performance of the aircraft since the power needed to move the flight surface is solely provided by the pilot. With the advent of larger aircraft, particularly after 1931, this method needed to be replaced by systems where the power was provided by an auxiliary system. The replacements included hydraulic and mechanical actuators which were later incorporated into Fly-By-Wire systems and then more recently into Power-By-Wire systems. Even though, mechanical linkages between the cockpit and the flight surface still exist in aircraft such as the Cessna Skyhawk and gliders due to the small size and simplicity of these aircraft. Figure 2.3 shows a simple depiction of a flight surface actuated by mechanical linkages. Control input is given by the pilot through pivoting the control stick which in turn translates motion to taught wires. The taught wires are oriented around the structure of the aircraft using a series of pulleys. At the opposite end of the taught wire is a pivot which is rigidly attached to the flight surface. This pivot will rotate and move the flight surface. Figure 2.3.Flight surface actuation using mechanical linkages. The control stick is often used to control the ailerons and the elevator. Movements to the left and right move the ailerons while movements forwards and backwards move the elevators. To control the yaw foot pedals are typically employed in the cockpit, which is attached to the rudder in a similar fashion seen in figure 2.3. This control setup has remained the common choice in flight surface actuation throughout history. In the event where the flight surface is weighed down due to gravity a counterweight is often employed so that the pilot does not need to force the flight surface to the level position. 34 $# 8 0 0% 8 # ! 0 7 7#! # $ ! $8 & 7 $7 %%$ 8 ( v Simple to design and implement. v Feedback from disturbances on the flight surface can easily be felt by the pilot. v A secondary power source is not required to move the flight surface. 3 34 $# 8 0 0% 8 # ! 0 7 7#! # $ ! $8 & 7 $7 %%$ 8 ( v Limited to flight surfaces that can only be actuated by the power input of the pilot. This limitation is compounded by friction in the controls-to-flight surface connection. v Requires bulky pulleys, wires and counterweights. v Multiple, independent actuation systems for redundancy are extremely difficult to implement. $3! # $ 12= ! " 0 7 0# " 7#! %8 # ! 0 7 ! $8 7#! # $ 7 $7 % $ 8 %8 # ! 0 7 7#! # $ ! $8 3 !% 7 # & From the dawn of flight up until the early 1930’s flight control was dominated by the use of simplistic mechanical linkages where all power to move the surface was provided by the pilot. As the power demands grew due to larger aircraft and control surfaces an auxiliary power assist system was needed. To achieve this hydraulic actuators were employed in the flight surfaces using directional valves. From the 1930’s to the early 1970’s the directional valve was connected to mechanical linkages that were actuated by using manual controls from the cockpit. From the 1970’s and on, with the emergence of communication technology, control of the directional valve has been performed by sending electrical control signals. This concept created the emergence of Fly-By-Wire (FBW) systems where flight surface controls were increasingly being replaced by computerized systems. Both hydraulic actuation through mechanical systems and FBW will be discussed below. v 3 !% 7 # & ! $8 7 $7 % $ 8 Initially, the use of hydraulic systems for flight surface actuation was an extension of using mechanical linkages. Instead of moving the flight surface itself the mechanical linkage controlled a hydraulic directional valve that allowed fluid to move an actuator in a controlled manner. A classical example of this control architecture can be seen in figure Figure 2.4.Examples of hydraulic actuators with mechanical linkages for flight surface actuation Figure 2.4 shows two common hydraulic servomechanisms. In the first example the piston rod, directional valve spool and mechanical linkage are all rigidly attached. Control inputs from the cockpit will initially force the valve spool to move in the desired direction, allowing fluid to move into one of the actuator chambers. As the actuator moves to its desired position the valve spool will gradually move to the neutral position, thus settling the actuator. In the second example the piston rod in the actuator is rigidly attached to the aircraft with the cylinder attached to the flight surface. In the same manner as the first example the valve spool will gradually move back to neutral as the desired actuator position is achieved. Both examples share the same basic hydraulic circuit architecture seen at the bottom of figure 2.4. Both also have the two basic features: the system is controlled in a proportional way in that the actuator response is a function of the pilot’s input through the mechanical linkages; the pilot with little effort to move the control valve has manoeuvre intensity feedback. For the latter of the two the pilot will experience feedback but will not experience the full load condition experienced on the flight surface. This form of hydraulic transmission system is termed as an open-loop style controlled using directional valves. The electric motor is attached to either a fixed or variable-displacement pump though a flexible or rigid coupling. The type of pump can be either an internal gear, an external gear, a vane or piston pump. A relief valve is typically positioned close to the outlet of the pump. This prevents the pressure of the fluid from exceeding a maximum threshold and protects the system from burst failure. The check valve placed just past the outlet of the pump allows the actuator to maintain static pressure without assistance from the pump. This saves energy when the flight surface is in a non-neutral position and requires static hydraulic pressure to hold it in place. In some cases a pressurized accumulator is placed after the check valve to allow pressurized fluid to be stored to assist the pump when the demanded flow-rate is high. The accumulator from the supply system (pump and accumulator) also provides a constant supply pressure, dampens pressure spikes and decreases coupling effects between actuators. The flow then passes through the valve which controls the fluid entering the actuator. In the case seen in figure 2.4 there is an emergency valve connected to the delivery segment of the circuit. If the pressure drops at this section due to loss of electrical power, rupture in the hydraulic lines, etc., it will link the control valve inlet to the reservoir. This will allow the pilot to manually actuate the cylinder. 34 $# 8 %$ 8 0 0% 8 # ! 0 7 7#! # $ # 3 !% 7 7#! # 7 !"% 3 # & 7 $7 % ( v Larger surfaces can be actuated with little effort from the pilot. v The pilot will experience positional feedback through the controls v Relatively simple architecture is employed. 3 & 7 34 $# 8 $7 %%$ 8 0 0% 8 # ! 0 7 7#! # $ # 3 !% 7 7#! # 7 !"% 3 # ( v An artificial feel system needs to be employed so the pilot can experience the load condition on the flight surface. v A secondary power system is required to move the flight surfaces. v Multiple, independent actuation systems for redundancy is still extremely difficult to implement due to mechanical linkages being used. v Requires bulky hydraulic components. $8 -.- 3 !% 7 # & ! $8 7 $7 % $ 8 v 3 !% 7 # & ! $8 % 1 1 ? @ 7 $ % 8 In the early 1970’s the concept of flight actuation through sending electrical signals to control valves was coming into fruition due to emerging communication technology. This idea would replace the mechanical linkages between the cockpit and control valves and replace them with distributed centralized electrical communication architectures that would be controlled by computers. This concept was termed as Fly-by-Wire (FBW), which eliminated the necessity of mechanical linkages to actuate the flight surface control mechanism by replacing them with electrically controlled valves. As these systems were further developed distributed communication architecture became the system of choice due to reduced load on a centralized flight control computer and increased flexibility during architecture development. Another significant advantage of FBW systems is that signals can be inputted to the control valve without any command from the pilot. An example of a FBW system can be seen in the figure below. Figure 2.5.Fly-By-Wire flight surface actuation system In the figure above control input to the directional valve and positional feedback of the flight surface are performed using electrical signals. In many cases there is also a positional sensor on the directional valve itself. Initially in FBW systems, all control was performed using analog signals but recently these have been switched to digital control. All of these signals along with the control input from the pilot and other flight data are processed by computers inside the aircraft. Electrically signaled directional valves are generally controlled either by proportional or servo action. Proportional valves are moved by solenoids that are balanced by opposing springs. The force given to the solenoid (which is proportional to valve opening) is controlled by the amount of current it receives. Higher performance proportional valves have Linear Variable Differential Transducers (LVDT) that feedback spool position for flow control. For flows higher than 2.5x10-3 m3/s (40 GPM) the force required to move the spool is much greater than what a solenoid can provide. In these applications two spools are employed: a pilot spool and main spool. The solenoid actuates the pilot spool which allows pressurized fluid to move the main spool back and forth. Proportional valves that use lower flows tend to use only one spool. Servo valves use a small torque motor attached to a flapper to control the fluid pressure, which in turn, moves the valve spool through pilot-actuation on both ends of the valve. Proportional valves are less complicated, are less susceptible to contamination and inexpensive compared to servo valves. However, servo valves have a quicker response time since the torque motor only controls the pressure and does not have to overcome spring forces and LVDT inertia. Servo valves are more appropriate for high precision applications. Servo valves are bi-directional and are able to channel the return flow to the reservoir. A depiction of a typical servo valve can be seen in figure 2.6. With the advent of FBW systems more involved hydraulic systems were added to aircraft to increase redundancy in the event of any system failure. Although not always the case, several commercial aircraft use 3 separate and independent hydraulic systems that can control the same or separate flight surface actuator or system. The importance of each flight actuator/system will determine the number of hydraulic systems connected to it (i.e. the rudder may have all three hydraulic systems attached for added redundancy while the tail skid may only have one). An example of this form of hydraulic system is seen on the Boeing 767. A depiction of the hydraulic systems can be seen in figure 2.7. Figure 2.7.Hydraulic system network on the Boeing 767 This network shows that the primary system is in the centre. This system uses two separate electric pumps and a Ram Air Turbine (RAT) (air driven pump), which uses a turbine that is deployed under the fuselage to generate power in the event where main electrical power is lost. The left and right systems each use an electric pump and a pump connected directly to the engines on the main wings. The primary flight surfaces can be actuated by all three hydraulic systems combined, by each system alone or a combination of several. This example shows that FBW systems can be employed to more complex aircraft to increase the functionality, redundancy and efficiency of the actuation systems. 34 $# 8 0 0% 8 # ! 0 7 7#! # $ ! $8 # & ( v Weight reduction due to the elimination of mechanical linkages. v The introduction of computer assisted control allows for added features such as increased stability, the ability to tune the pilot’s control demands to protect the aircraft from exceeding airframe load factors, turbulence suppression, thrust vectoring, etc. v Increased redundancy since several hydraulic systems in parallel can be employed. v More control surfaces can be added such as trim for the rudder and other flight surfaces. 3 34 $# 8 0 0% 8 # ! 0 7 7#! # $ ! $8 # & ( v All electrically actuated systems mean that a failure in electrical power will severely limit aircraft control. v Added complexity increases development costs. v Hydraulic failure in one system can still affect the functionality of another system. $8 -=- 3 !% 7 # & ! $8 % 1 1 ? @ 7 $ % 8 v %8 # ! 0 7 7#! # $ ! $8 1' 1 ? @ # & Over the last few decades the performance demands for flight surface actuation have increased and led to the desire of replacing FBW systems with Power-By-Wire (PBW) systems. Although FBW systems give a significant performance advantage compared to conventional mechanical and hydraulic systems previously discussed, there are several disadvantages that still need to be addressed, which include. v Higher complexity and weight. v Energy efficiency: they must maintain hydraulic pressure of 21-42MPa (3000-6000psi) at all times, regardless of demand. v System reliability: a fault in one of the hydraulic lines potentially leads to complete hydraulic failure in the aircraft. The PBW concept has evolved into the more electric aircraft concept where flight surface actuation is achieved by using modular subsystems rather than centralized hydraulics. Figure 2.8 shows the layout of the PBW systems in the F-35 Lightning. This aircraft employs a combination of Electro-Hydrostatic Actuators (EHA’s) and Electric Drive Units. Figure 2.8.Layout of power-by-wire systems in a military aircraft & 0# 0 #! 0 & 3!% # & $7%!3 . v Control power comes directly from the aircraft’s electrical grid, not a centralized hydraulic unit. v Modular design decreases the overall weight required for all actuation systems. v Modularity reduces maintenance costs and simplifies maintenance procedures since the repair of a unit can easily be performed by removing it from the flight surface and replacing it with a new one. v Modularity increases reuse in multiple aircraft platforms hence reducing development costs. v Fault tolerance: one fault in a centralized hydraulic system can cause failure in other systems or reduce overall performance. If a fault occurs in a modular PBW system, it can easily be shut-off and the actuation can be performed by a redundant system. v Power-on-demand feature reduces the overall energy consumption of the aircraft. Figure 2.9 shows the basic structure of a modular PBW flight surface actuation system used in the more electric aircraft concept. Figure 2.9 Basic Structure of a power-by-wire system. The two types of systems typically used for modular power-by-wire flight surface actuation are Electro- Mechanical Actuators (EMA) and Electro-Hydrostatic Actuators (EHA). The EMA will be reviewed briefly while the EHA will be discussed in significant detail as it is the focus of this project. ü % 7# 1 7 $ 7 % 7#! # ? @ In the EMA, a drive motor is connected to a ball screw in order to translate rotary motion into linear motion. The basic components include: v A control system. v A brushless, permanent magnet electric servomotor with a velocity feedback sensor. v A ball screw. v A mechanical linkage between the ball screw and flight surface. v The flight surface. A depiction of a typical EMA structure can be seen in figure 2.10. Figure 2.14.Basic Structure of an EMA. An example of an EMA developed by TRW Aeronautical Systems can be seen in the figure 2.11 below. Typically there are no sensors on the flight surface that feedback position to the controller due to reliability concerns as the sensor would be exposed to harsh environments. However, there are some cases where there is position feedback. Some fighter aircraft have this where the feedback sensor is highly insulated from the environment. ü % 7# 3 # # 7 7#! # $ technology explores novel approaches to the design and development of electrically powered actuators used to operate flight control surfaces. This includes the application and adaptation of electric motor drive technologies (that address the design and development of electric motors and their associated electronic drives) to suit the specific performance, reliability, environmental, and safety objectives of various flight control applications. Currently, the maturity of PBW technology is lagging behind that of FBW. The development of actuator configurations, efficient electric motors, and high-power electronic drives, although demonstrated in test flights, has yet to be implemented and certified as a production standard application. Having eliminated the mechanical transmission circuits in fly-by-wire flight control systems, the next step is to eliminate the bulky and heavy hydraulic circuits. The hydraulic circuit is replaced by an electrical power circuit. The power circuits power electrical or selfcontained electro hydraulic actuators that are controlled by the digital flight control computers. All benefits of digital fly-by-wire are retained. The biggest benefits are weight savings, the possibility of redundant power circuits and tighter integration between the aircraft flight control systems and its avionics systems. The absence of hydraulics greatly reduces maintenance costs. This system is used in the #$ 1+, 8 #$ $8 $3 $ '! +>) backup flight controls. The 7 3 $8 ->- will also incorporate some electrically operated flight controls (spoilers and horizontal stabilizer), which will remain operational with either a total hydraulics failure and/or flight control computer failure. Power By Wire system employing an Electro-Hydrostatic actuation system has a very wide scope of applications in the near future. It can also be implemented in Unmanned Combat Aerial Vehicles for meeting the requirements of high manoeuvrability and instant response without addition of a heavy centralised hydraulic system throughout the aircraft that might compromise severely with the performance. EHA uses fluidic gearing between the electric motor and the surface actuator. Hydraulic fluid provides an intermediate means of transmitting power to the surface. Here, a variable-speed electric motor (typically DC) is used to drive a fixed-displacement hydraulic pump, which in turn, powers a conventional hydraulic piston jack. Change in direction is achieved by the use of a bidirectional motor. A major advantage to this approach is that the EHA operating mode can be managed like a conventional hydraulic actuator. This capability makes the EHA more suitable for primary flight control applications than the EMA. Although EHA technology reintroduces hydraulic components and fluid, it is totally selfcontained within the actuator assembly. Compared to traditional hydraulic actuator systems, the inconvenience of hydraulic disconnection from aircraft supplies and the complications of bleeding the system during reinstallation are not encountered during maintenance. Emerging industry trends demand compact, accurate, electric actuation for control surfaces. Electro hydrostatic actuation (EHA) provides these benefits for applications where high force requirements dictate the use of hydraulic power. EHA’s combine the accuracy of electronic control with the high-force capability of hydraulics in a compact package. +>) ! $8 $8 $7 "% The principle behind the technology consists of using a bi-directional pump with both ports connected to each side of a linear double acting actuator. The pump positions the actuator when driven in either direction by a bidirectional motor. The motor in turn is controlled by a servo controller. EHA actuators do not use valves for control as typically found in electro hydraulic actuation where a servo valve is located between the pump and the actuator. Instead the pump is accurately rotated back and forth to position the actuator using the feedback and servo controller. The pump draws fluid from a pressurized reservoir or accumulator via a set of valves. Advantages of using EHA Technology Several advantages to using EHA actuation instead of using hydraulic controlled and outlined below: · High force: over 25,000 lbf obtainable · Low hysteresis ( <1% ) · Reduced pressure losses ( no control valves ) · Efficiency : flow is controlled on demand and pressure can be controlled electrically · Less loss of heat ( no relief valves ) · Compact : pump, motor, actuator, sensor and controller in one small package · Enhanced reliability: fewer components · Integrated diagnostic capability 34 $# 8 0 1. Higher forces are obtainable along with lower hysteresis. 2. Reduced pressure losses due to absence of control valves. 3. Efficient as flow is controlled on demand and pressure can be electronically controlled. 4. Compact: Pump, motor, actuator and controller in one small package. 5. Enhanced reliability due to fewer components. 6. Centralised high pressure and heavy hydraulic system is not required. 34 $# 8 0 Larger voltages of the order of 270V DC are required for implementation on larger sized aircraft which have been successfully implemented in reality but increase the probability of power shortage during demanding situations which require multiple such actuators to be operated at once. This problem can be overcome by using electrical energy accumulating devices such as electric double-layer capacitors which are capable of storing a large amount of charge and discharging it at will. $ % # % 3 · &" $ $# ! 3 7 "# $ 3 # When a current passes through the coil wound around a soft iron core, the side of the positive pole is acted upon by an upwards force, while the other side is acted upon by a downward force. According to Fleming's left hand rule, the forces cause a turning effect on the coil, making it rotate. To make the motor rotate in a constant direction, direct current commutators change the current direction every through the cycle thus causing the motor to continue to rotate in the same direction. Every DC motor has six basic parts -- axle, rotor, stator, commutator, field magnet(s), and brushes. The stator is the stationary part of the motor -- this includes the motor casing, as well as two or more permanent magnet pole pieces. The rotor (together with the axle and attached commutator) rotates with respect to the stator. The rotor consists of windings (generally on a core), the windings being electrically connected to the commutator. The above diagram shows a common motor layout -- with the rotor inside the stator (field) magnets. The geometry of the brushes, commutator contacts, and rotor windings are such that when power is applied, the polarities of the energized winding and the stator magnet(s) are misaligned, and the rotor will rotate until it is almost aligned with the stator's field magnets. As the rotor reaches alignment, the brushes move to the next commutator contacts, and energize the next winding. This makes the dc motor rotate continuously in a direction. The direction of rotation of the dc motor is reversed simply by reversing the direction or the terminals of the dc power source. In a gear motor, the energy output is used to turn a series of gears in an integrated gear train. In a gear motor, the magnetic current (which can be produced by either permanent magnets or electromagnets) turns gears that are either in a gear reduction unit or in an integrated gear box. A second shaft is connected to these gears. The result is that the gears greatly increase the amount of torque the motor is capable of producing while simultaneously slowing down the motor's output speed. The motor will not need to draw as much current to function and will move more slowly, but will provide greater torque. " 707 # $ ( · 500RPM 12V DC motor with Gearbox · 4mm shaft diameter with internal hole · 125gm weight · 1kgcm torque · No-load current = 60 mA(Max), Load current = 300 mA(Max) · # !&" Gerotor pumps are internal gea gear pumps without the crescent. The rotorr is the internal inter (drive) gear shown below in gray, andd the idler is the external (driven) gear, shown below in ora orange. They are primarily suitable for clean, an, low pres pressure applications such as lubrication systems or hot h oil filtration systems, but can also be found und in low tto moderate pressure hydraulic applications. Working of an internal gear ar pump can bbe described as follows, 1. Liquid enters the suctionn port betwee between the rotor and idler teeth. 2. Liquid travels through the pump bbetween the teeth of the "gear-within-a-gear" gear" principle. princ The close tolerance between the gears rs acts as a se seal between the suction and discharge ports. 3. Rotor and idler teeth mesh compl completely to form a seal equidistant from the dischar discharge and suction ports. This seal forces the liquid out of the discharge port. The internal gear pump is non-pulsing, self-priming, and can run dry for short periods. They're also bi-rotational. The direction of the fluid being pumped can be reversed simply by reversing the rotation of the internal gear. As a rule of thumb, the direction of the fluid being pumped is the same as the direction of rotation of the internal gear. Because internal gear pumps have only two moving parts, they are reliable, simple to operate, and easy to maintain. " 707 # $ ( · Pumping capacity of 0.5 liters per minute at 500 rpm · 300 gm weight · 6 mm external shaft knurled for coupling · Sturdy Aluminum cast body · Three point mounting holes · !'% 7# $8 3 !% 7 % $3 A hydraulic cylinder operates through pressurized fluid (usually oil), which gives the hydraulic cylinder force. The cylinder's driving force is the piston, which is attached to a piston rod that is enclosed in the cylinder's barrel. The bottom of the barrel is closed off by the cylinder cap and the top is closed off by the head. The head contains a round hole, which allows the piston rod to come out of the barrel. The inside of the barrel contains the oil, and the hydraulic pressure that the oil creates acts on the piston rod, causing it to move back and forth in a linear fashion. One end of the piston is attached to the object or machine it is responsible for moving. As the hydraulic pressure of the oil moves the piston rod, the piston rod moves the piston, which in turn moves the attached object. The double acting cylinder is more common than the single acting cylinder. It works at any angle and in any application where hydraulic power is needed. In the double-acting cylinder design, there’s fluid on both the base and rod sides of the piston, and force is delivered in both directions. Even for applications where gravity or weight can assist retraction, hydraulic pressure is often applied to control acceleration, meter the rate of travel and cushion the stoppage. Travel in one direction always differs from travel in the other, all things being equal: the push action requires more force, and is slower, but more work output is generated. The pulling action is faster, but less work output is created. The amazing amount of force a cylinder exerts is due to the simple mechanical principle of pressure exerted on the surface area of the piston. Simply put, the larger the diameter of the cylinder, the more it will lift. The formula for this is Area X Pressure = Force. The piston is inside the cylinder, the diameter of which is known as the ‘Bore’. Technically, the the bore is the inside diameter of the tubing but this difference is of minor significance. The piston needs a piston seal to keep the pressure from bypassing to the other side, which allows it to build the required pressure. The piston is attached to the ‘rod’ (or shaft) of the cylinder, usually with the rod passing through the piston and attached with a large nut on the opposite end. To correctly calculate the pulling force of a cylinder, the surface area of the rod must be subtracted from the formula. The rod is probably the hardest worked component in the whole system. The rod is the largest single chunk of steel in the cylinder, unpainted and exposed to all the elements. It has to be extremely strong (to resist bending), exceptionally hard (to resist corrosion and pitting), and smooth as silk (to keep the rod seals intact to prevent leakage of fluid and pressure). The ‘stroke’ of the cylinder is the total travel possible from the fully retracted length and the fully extended length of the rod. " 707 # $ ( · Bore – 32 mm · Stroke – 200 mm · Brass cylinder material and steel rod · Maximum permissible pressure of 10 bar · Double acting with threaded single rod · 2*+ # $# %% A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults. The L293D is a quadruple high-current half-H driver. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. The device is designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source. Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is high, the associated drivers are enabled and their outputs are active and in phase with their inputs. When the enable input is low, those drivers are disabled and their outputs are off and in the high-impedance state. With the proper data inputs, each pair of drivers forms a full-H (or bridge) reversible drive suitable for solenoid or motor applications. A VCC1 terminal, separate from VCC2, is provided for the logic inputs to minimize device power dissipation. The L293D is characterized for operation from 0°C to 70°C. $ 7 "# $ L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be driven simultaneously, both in forward and reverse direction. The motor operations of two motors can be controlled by input logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions, respectively. · 2+2 $3 A2+2 % 7 &&!$ 7 # $ In computing, a serial port is a serial communication physical interface through which information transfers in or out one bit at a time in contrast to a parallel port. Throughout most of the history of personal computers, data transfer through serial ports connected the computer to devices such as terminals and various peripherals. The term "serial port" usually identifies hardware more or less compliant to the RS232 standard, intended to interface with a modem or with a similar communication device. Modern computers without serial ports may require serial-to-USB converters to allow compatibility with RS 232 serial devices. * $ $$ 7# $ 3 47 ? 7 $$ 7# $@ Male RS232 DB9 $ !&' 7# $ 0 8$ % 1 Carrier Detect (CD) (from DCE) Incoming signal from a modem 2 Received Data (RD) Incoming Data from a DCE 3 Transmitted Data (TD) Outgoing Data to a DCE 4 Data Terminal Ready (DTR) Outgoing handshaking signal 5 Signal Ground Common reference voltage 6 Data Set Ready (DSR) Incoming handshaking signal 7 Request To Send (RTS) Outgoing flow control signal 8 Clear To Send (CTS) Incoming flow control signal 9 Ring Indicator (RI) (from DCE) Incoming signal from a modem RS232 signals are +12V to -12V and are only needed for longer cable lengths. This is the voltage levels on a PC's Serial COMM port and has been an industrial standard for over 40 years and allows easy interfacing to many different devices with high reliability. The PIC's UART (and other processors) are power at 5V or 3.3V so cannot supply the RS232 voltage levels. The data timing is the same on both, logic to RS232 level translator like a MAX232 chip only changes the voltage. The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply TIA/EIA-232-F voltage levels from a single 5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. The MAX232 IC is used to convert the TTL/CMOS logic levels to RS232 logic levels during serial communication of microcontrollers with PC. The controller operates at TTL logic level (0-5V) whereas the serial communication in PC works on RS232 standards (-25 V to + 25V). This makes it difficult to establish a direct link between them to communicate with each other. The intermediate link is provided through MAX232. It is a dual driver/receiver that includes a capacitive voltage generator to supply RS232 voltage levels from a single 5V supply. Each receiver converts RS232 inputs to 5V TTL/CMOS levels. These receivers (R1 & R2) can accept ±30V inputs. The drivers (T1 & T2), also called transmitters, convert the TTL/CMOS input level into RS232 level. The transmitters take input from controller’s serial transmission pin and send the output to RS232’s receiver. The receivers, on the other hand, take input from transmission pin of RS232 serial port and give serial output to microcontroller’s receiver pin. MAX232 needs four external capacitors whose value ranges from 1µF to 22µF. · #& 8 /= 7 7 $# %% The high-performance, low-power Atmel 8-bit AVR RISC-based microcontroller combines 16KB of programmable flash memory, 1KB SRAM, 512B EEPROM, an 8-channel 10-bit A/D converter, and a JTAG interface for on-chip debugging. The device supports throughput of 16 MIPS at 16 MHz and operates between 4.5-5.5 volts. By executing instructions in a single clock cycle, the device achieves throughputs approaching 1 MIPS per MHz, balancing power consumption and processing speed. $ 7 "# $ Digital supply voltage B Ground # ? -66 )@( Port A serves as the analog inputs to the A/D Converter. Port A also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used. Port pins can provide internal pull-up resistors (selected for each bit). The Port A output buffers have symmetrical drive characteristics with both high sink and source capability. When pins PA0 to PA7 are used as inputs and are externally pulled low, they will source current if the internal pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes active, even if the clock is not running. # ? -6 )@( Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. # ? -6 )@( Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running. # ? -6 )@( Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running. ( Reset Input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset. A /( Input to the inverting Oscillator amplifier and input to the internal clock operating circuit. A B 2( Output from the inverting Oscillator amplifier. ( AVCC is the supply voltage pin for Port A and the A/D Converter. It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter. ( AREF is the analog reference pin for the A/D Converter · ' 3 # 0% 7# 4 &" $ $# '< 7#C" ; & # $ This consists of a pair of an Infrared Light Emitting Diode and an Infrared Photodiode facing the same direction and placed adjacent to one another. Both are connected to a common ground and the LED is powered by a 5 volt DC voltage. Whenever an object appears in front of the IR LED, the IR waves are incident on the object and get reflected back from the surface of the obstruction. The reflected waves are incident on the adjacent photodiode which in turn produces an electrical voltage signal proportional to the intensity of the reflected infrared beam. The photodiode does not produce any appreciable voltage in the absence of an object as the emitted infrared beam does not get reflected back. This IR LED-Photodiode pair can be used to detect the presence or absence of an object by measuring the change in output Photodiode voltage. 3 !% 7 %! 3 Standard off the shelf four stroke engine oil can be used as a hydraulic fluid. The oil has high viscosity which indirectly translates into excellent sealing or anti-leakage properties because high viscosity oils cannot easily seep through seals and close tolerances present throughout the hydraulic system like the pump, cylinder, hydraulic lines and their fittings. The engine oil being lubricating oil also has a very good lubricating characteristic and is also non-corrosive by nature. It is also relatively non-toxic by nature and safe to handle bare handed. 7 " 7 8 && $8 The ATmega 16 microprocessor for implementing drive and control in this project was programmed in the embedded C programming language. A freely available software ‘WinAVR’ was used for writing and burning the program to the microcontroller development board. # ( ' &"% & $# # $ 0 # 3 0 # $3 3 % ' & $!0 7#! 3 0$ 3# 7 # $7 !# 7 # $ " 3 0 $ 3 # # 36 # $3 3 % ' 3 4 % "& $# "! " # &"% & $# # $ 0 % 8 7 $3 7 $# % 0 " # 0# " < 7# % 87 !" $ # 7 7! # # $3 3 % ' !# 3 4!%8 $8 $# # 0!$7# $ $% # $3 8$ % D! "& $# 7 $# $ 0!$7# $ % % 4 %3 # % 4 ' $ " 43 3 !%3 $ # ' 7 $ 3 3 0 0 " # 0 6 " 8 & " # E& $67F 0 %0 & 7 7 $# %% $3 " 4 3 3 ' 7#% 6 $3 0! # " < 7# 3 4 % " 3 '# $ 3 $3 ! 3 3 3 4 % "& $# ' 0 3 % 8 75 $ 00 # '# $ 36 # # D! 7 # 7#! 7#! % 7 3 3 4 % " 3 ! $8 # # % 7# 3 3 0 !%# % ' # # 7 7#! # $ # & $3 6 & $ $8 # 0# & 5 # 3 4 % "& $# ' $ & 3 0 # 0!$7# $ 7 $ 7 % 7# 3 $3 # & $!0 7#! $8 3 " $3 $8 6 " 8 &0 ? # # $# % 8 3& # 8 &@ $67 #define F_CPU 8000000UL #include<avr/io.h> #include<util/delay.h> #include "usart.h" #include "adc.h" #include "motor.h" int main(void) { unsigned char key=0; unsigned int ir1=0,ir2=0; USART_init(); motor_init(); USART_string("UART OK"); 7 $# % $3 $0 3 $ while(1) { key=USART_recieve(); ir1=get_adc(0); ir2=get_adc(2); /*usart_int(ir1,4); USART_string("\r\n"); usart_int(ir2,4); USART_string("\r\n");*/ switch(key) { case 'V': if(ir1 < 400) { motor_forward(); _delay_ms(1000); motor_stop(); } break; case 'B': if(ir1 < 400) { motor_forward(); _delay_ms(2000); motor_stop(); } break; case 'N': if(ir1 < 400) { motor_forward(); _delay_ms(3000); motor_stop(); } break; case 'C': if(ir2 < 400) { motor_reverse(); _delay_ms(1000); motor_stop(); } break; case 'X': if(ir2 < 400) { motor_reverse(); _delay_ms(2000); motor_stop(); } break; case 'Z': if(ir2 < 400) { motor_reverse(); _delay_ms(3000); motor_stop(); } break; default: motor_stop(); break; } key=0; } } # $3 3 ? ' ! 3 # $3 3 % ' !$7# $@ 376 #define F_CPU 8000000UL #include<avr/io.h> #include<util/delay.h> int get_adc(int channel) { unsigned int result; long average; // the averaged value (the return value) ADMUX = channel; ADMUX |= (1 << REFS0); // AVCC with external capacitor at AREF pin ADCSRA=0x00; ADCSRA |= (1<<ADEN) | (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0) ; // ADC Enable, 64 prescaler, ADC Interrupt Enable average=0; for (int j=0;j < 4;j++) { ADCSRA |= (1<<ADSC); // Start converting while(!(ADCSRA & (1<<ADIF))); result = ADCW; average += result; ADCW=0x00; } average = average >> 2; return (int) average; } ? # # $3 3 % ' 0!$7# $@ & # 6 #define F_CPU 8000000UL #include <avr/io.h> #include <util/delay> void motor_init(void) { DDRD=0xFF; } void motor_forward(void) { PORTD = 0x30; // _delay_ms(1000); // PORTD = 0x00; // _delay_ms(500); } void motor_right_on(void) { PORTD = 0x20; _delay_ms(1000); PORTD = 0x00; _delay_ms(500); } void motor_left_on(void) { PORTD = 0x10; _delay_ms(1000); PORTD = 0x00; _delay_ms(500); } void motor_reverse(void) { PORTD = 0x49; // _delay_ms(1000); // PORTD = 0x00; // _delay_ms(500); } void motor_stop(void) { PORTD = 0x00; } ? # $3 3 % ' 0!$7# $@ ! #6 #define F_CPU 8000000UL //8MHZ Clock Freq #include<avr/io.h> #include<util/delay.h> void USART_init( void ) { UCSRA = 0x00; UCSRB|= (1<<TXEN)|(1<<RXEN); // transmit_enable UCSRC|= (1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0); UBRRH = 0x00; UBRRL = 0x33; //UBRRL=51 because we set baudrate=9600 bps } unsigned char USART_recieve(void) { unsigned char data; while((UCSRA&(1<<RXC))==0x00); data=UDR; return(data); } void USART_transmit(char d) { while((UCSRA&(1<<UDRE))==0x00); UDR=d; } void USART_string(char *ptr) { while(*ptr != '\0') { USART_transmit(*ptr++); //check UDRE is empty or not _delay_ms(100); } } void usart_int(unsigned int val,unsigned int field_length) { char str[5]={0,0,0,0,0}; int i=4,j=0; while(val) { str[i]=val%10; val=val/10; i--; } if(field_length==-1) while(str[j]==0) j++; else j=5-field_length; if(val<0) USART_transmit('-'); for(i=j;i<5;i++) { USART_transmit(48+str[i]); } } $ %# $ # " 8 & E& $/67F 7 7! # ' ! $8 $% # # &"% "! & " 7# 7 % 7 &"% ; # $4 %4 3 $3 #define F_CPU 8000000UL #include<avr/io.h> #include<util/delay.h> #include "usart.h" #include "adc.h" #include "motor.h" int main(void) { //unsigned char key=0; unsigned int ir1=0,ir2=0; DDRD&=~(1<<PD7); DDRC&=~(1<<PC0); PORTD|=(1<<PD7); PORTC|=(1<<PC0); //USART_init(); '!## $ % # 3 4 % " 3 $ #7 6 84 $ 3 " 8 & 0 0 # &"% 0 " # $ 0# 3 4 % " 3 ;# $ %% 3! $7 "! " $% 6 motor_init(); //USART_string("UART OK"); while(1) { //key=USART_recieve(); ir1=get_adc(0); ir2=get_adc(2); /*usart_int(ir1,4); USART_string("\r\n"); usart_int(ir2,4); USART_string("\r\n");*/ if(bit_is_clear(PIND,7)) { if(ir1 < 400) { motor_forward(); _delay_ms(500); motor_stop(); } } if(bit_is_clear(PINC,0)) { if(ir2 < 400) { motor_reverse(); _delay_ms(500); motor_stop(); } } } } 7 $ # 0# $ B WinAVRTM is a suite of executable, open source software development tools for the Atmel AVR series of RISC microprocessors hosted on the Windows platform. It includes the GNU GCC compiler for C and C++. # & " # $ % 7 8 & 0# " # $ 0# #!" # & '! %# 7 $ ' !&& G 3 0 %% : Suppose that the cylinder rod is approximately at the centre of the full stroke length, i.e. it rod has completed half of the stroke length already. The position of the control surface at this instant is such that the deflection of the control surface is 0 degrees. &" # $# 7 $3 # $( $0 7 $# % ! 0 7 3 $ $ & % 2 $3 / 4 ' $ "% 7 3 ' % $3 ' 4 # " 7# 4 % 6 The IR sensors are placed adjacent to the control surface such that the control surface blocks the view of each of the sensors when it reaches the maximum deflection on either side of the mean position. This means that the sensor IR2 is blocked when the control surface reaches its bottommost position while the sensor IR1 is blocked when the control surface reaches its topmost position. In fact, because of no physical limiting device being incorporated into the system to fix the maximum deflection of the control surface, the position of the IR sensors itself determines the maximum possible deflection of the control surface on both side and not the other way round as may be wrongly interpreted. If IR2 is blocked: The motor will not rotate in the anticlockwise direction further to prevent structural damage to the actuation system. Clockwise functionality will not be affected. If IR1 is blocked: The motor will not rotate in the clockwise direction further to prevent structural damage to the actuation system. Anticlockwise functionality will not be affected. $ % !%# " $ # $"!# Keyboard input ‘Z’ - IR2 sensor checked to verify position - Motor rotates anticlockwise - Fluid pumped into the rod side - Rod and rack moves to the right - Pinion moves anticlockwise - Control surface gets deflected downward - Actuation stops after 3 seconds Keyboard input ‘X’ - IR2 sensor checked to verify position - Motor rotates anticlockwise - Fluid pumped into the rod side - Rod and rack moves to the right - Pinion moves anticlockwise - Control surface gets deflected downward - Actuation stops after 2 seconds Keyboard input ‘C’ - IR2 sensor checked to verify position - Motor rotates anticlockwise - Fluid pumped into the rod side - Rod and rack moves to the right - Pinion moves anticlockwise - Control surface gets deflected downward - Actuation stops after 1 seconds Keyboard input ‘V’ - IR1 sensor checked to verify position - Motor rotates clockwise - Fluid pumped into the piston side - Rod and rack moves to the left - Pinion moves clockwise - Control surface gets deflected upward - Actuation stops after 1 seconds Keyboard input ‘B’ - IR1 sensor checked to verify position - Motor rotates clockwise - Fluid pumped into the piston side - Rod and rack moves to the left - Pinion moves clockwise - Control surface gets deflected upward - Actuation stops after 2 seconds Keyboard input ‘N’ - IR1 sensor checked to verify position - Motor rotates clockwise - Fluid pumped into the piston side - Rod and rack moves to the left - Pinion moves clockwise - Control surface gets deflected upward - Actuation stops after 3 seconds %# $ # " # $ ! $8 # " 8 & & $/67 Push button input ‘switch 1’ - IR1 sensor checked to verify position - Motor rotates clockwise - Fluid pumped into the piston side - Rod and rack moves to the left - Pinion moves clockwise - Control surface gets deflected upward - Actuation stops after 3 seconds Push button input ‘switch 2’ - IR2 sensor checked to verify position - Motor rotates anticlockwise - Fluid pumped into the rod side - Rod and rack moves to the right - Pinion moves anticlockwise - Control surface gets deflected downward - Actuation stops after 3 seconds ' 4 # $ For 7mm forward stroke length we get a deflection of 220. This is because of the rack and pinion mechanism. From engineering mechanics we know that angular deflection of a gear is directly proportional to the gear diameter for a given stroke length. Thus for a higher deflection we require a less diameter for given stroke length. Sr No Time (sec) Stroke length Deflection for Deflection for (mm) r = 25mm r = 30mm 1 3 CW 5 FW 11.45 9.549 2 2CW 3FW 6.875 5.729 3 1CW 2FW 4.583 3.879 4 1CCW 2R 4.583 3.879 5 2CCW 3R 6.875 5.729 6 3CCW 5R 11.45 9.549 Key: CW: Clockwise CCW: Counter clockwise FW: forward R: Reverse %7!% # $ The pressure developed by the Gerotor Pump at 500 RPM (p) = 0.6 bar Diameter of the piston (d) = 32 mm Area of the piston = (π/4) * d2 =(π/4) * 0.0322 =8.0424*10-4 meters square We know that, by the law of hydraulic multiplication, Force = Pressure * Area Force = 0.6 bar * area Force = 0.6 * 101325 * 8.0424 * 10-4 Force = 48.89 Newton Therefore, the force produced at the output of the cylinder during actuation is approximately 48.89 Newton. 48.89 Newton = 48.89 * 9.81 = 4.98 kilograms ;" $3 #! 0# < 7# &" $ $# "" ; & # Actuator and hydraulic fluid lines Rs.1700 Motor Rs.300 Controller Rs.2700 Bidirectional Pump Rs.450 Hydraulic Fluid Rs.300 Miscellaneous Components: · · · · · · · · · · LED and sensors Wooden structure Wire Acrylic Box Travelling M-seal Nut, bolts and screws Iron and aluminium plates Tee Paint and brush # % Rs.300 Rs.790 Rs.80 Rs.1050 Rs.870 Rs.60 Rs.40 Rs.70 Rs.400 Rs.140 Rs.9250 7 $7%! $ The EHA system was constructed incorporation a low pressure hydraulic system and was tested successfully. The following observations were made. The time interval remaining the same, the displacement of the piston was greater in the return stroke than the forward stroke. This problem mainly originated because of the asymmetry in the volume of the fluid caused by the presence on the piston rod on only one side of the cylinder. " '% & 7 $ ' 4 7 & $# 0 %% $8 ( v Using a double acting double rod hydraulic cylinder. Because of the presence of rod on both sides of such cylinders, the volume on both the sides is symmetric and so the stroke length will be the same in the forward as well as the return stroke for a given amount of fluid. ' 7 0# "" 7 ( However, the force output of the system will be affected due the reduction in available diameter which will reduce the force, pressure remaining constant (In accordance to the law of hydraulic multiplication.) v Using a variable rpm servo motor or stepper motor. Using a motor whose RPM can varied by the controller, the motor can be made to rotate faster in the forward stroke and slower in the return stroke. Variable RPM will ensure that the fluid will be pumped faster in the forward and slower in the return stroke so that the displacement of the piston will remain nearly the same for both the strokes. However, there are a number of drawbacks of this approach: The control of such a variable RPM motor will be difficult to implement. The motor controller will have to be programmed to drive the motor differently in the opposite directions. This can be done by difference in driving voltage in case of servo motors and change in frequency of stator voltage rotation in case of a stepper motor. The program for implementing such logic might get too complex to the extent that it might be taken up as an altogether different project. This does not solve the problem of asymmetric force produced because the areas are still unequal. The problem of unequal forces will only be aggravated further as motor rotating at different RPM will produce different pressure. The pressure in the return stroke will be lower than the forward stroke and this will cause an even lower output force in the return stroke. 8 Minor leakages were observed during the operation of the system which affected the performance and the response time of the system in the longer run, i.e. after repeated forward and backward cycles. The primary reason for leaks was found to be the asymmetric volume requirements. Additional fluid was required during the forward stroke than was available from the piston side. Similarly, during the return stroke the fluid available from the piston side exceeded the requirements of the stroke volume. Since there was no method to intake additional fluid when required or to bleed off extra fluid to a reservoir, the system leaked during situations of high pressure built up. In the situation of fluid scarcity, air entered the system to make up for the additional volume. The presence of air in the hydraulic system led to very minute lags and springy action due to the compressible nature of gas. It is also possible that over a period of long time consisting of large number of cycles, the continued seepage of air might lead to intermittent action of the actuator and response lags seriously affecting the functionality. Dry running of the pump could also lead to the complete loss of functionality. " '% & 7 $ ' 4 7 & $# 0 %% $8 ( v Use of Double acting double rod cylinders as mentioned in the previous problem. v Implementation of a reservoir with check valves and pilot valves to automatically control the fluid demands. 3 !% 7 7 7! # 7 $ ' &% # # $ ' % ( &' % 3 Continuous line - flow line Dashed line - pilot, drain Envelope - long and short dashes around two or more component symbols. Diamond –Fluid conditioner (filter, separator, lubricator, heat exchanger) Spring Flow Restriction bidirectional fixed displacement pump Check valve -free flow one direction, blocked flow in other direction pilot operated check valve, pilot to open Line pressure is limited to the setting of the valve; secondary part is directed to tank. Such a system shall be leak proof and nearly perfect in operation. However, the high cost of incorporating so many devices should be justified according to the specific application. Also owing to the complexities in the circuit and pressure losses due to the valve operation this method can only be employed in high pressure systems. !%# 0# < 7# $3 # $ A low pressure Electro hydrostatic system was built to demonstrate the promising technology. The system response was well within expectations. The output of the system was well controlled, uniform and repeatable over a number of cycles. The EHA components were mounted so as to occupy minimum space as required by the problem statement. External flow control devices like check valves and flow limiting and reversing valves and solenoids were not used and the actuation was controlled solely by the driving motor. This reduced the assembly and control complexities. Another allied advantage was reduction in size and troubleshooting. Easily available off the shelf components were used in the project and no custom made component was used in any part of the project. Alternate products easily available in the market were used where specific technical requirements did not meet. This facilitated minimum time consumption in component acquisition. Another important achievement is the remarkably low cost which would have not been possible otherwise. Interfacing was done by using simple three wire interface of a standard pc serial communication port using the universally accepted RS232 standards. Simple 8-bit low power microcontroller was used to program the system for overall operation. This should ideally lead to minimum problems with interfacing and compatibility. Problems which were encountered such as leakage and disproportional stroke length were analysed and satisfactory solutions to these were found out and mentioned in the project report. It was found that among all solutions, using a double acting double rod cylinder will solve most of these problems encountered in the project. Last but not the least, the overall system did not pose any known safety hazard to the operator or the system itself owing to the successful incorporation on safety devices and low pressures. $# &"% & $# # $ 0 ü +>) 0% 8 # 7 $# % 1!" 7% The Airbus A380 has two elevators on each side of the horizontal stabilizer. Each elevator has one hydraulic and one electro hydrostatic actuator (EHA). There are two rudder surfaces, each of which uses two electrical backup hydraulic actuators (EBHAs). These add backup electrical power through a local electric motor and an associated hydraulic pump. EBHAs are hydraulically powered in the normal mode and electrically powered in backup mode. The tail’s trimmable horizontal stabilizer (THS) will be driven by a ball screw actuator powered by two hydraulic motors and a standby electric motor. Each elevator surface has dualredundant power sources, as the four independent sources are distributed across the control surfaces. Each rudder surface has quad-redundant power sources. The new aircraft features three ailerons per wing, each moved by two actuators. Inboard and median ailerons use one hydraulic and one EHA actuator, while the outboard ailerons use two hydraulic actuators. Spoilers (eight per wing) are hydraulically powered. Two or three of the spoiler actuators on each wing, however, will have backup electrical power, combining servo control and EHA functions in a single unit, the EBHA. Wing flaps and slats are driven by mechanical rotary actuators connected to powered control units (PC Us) by means of a torque shaft transmission system. The flap PC U includes two hydraulic motors; the slat PC U includes one hydraulic and one electric motor. "% $ 07 % The use of electrically powered actuators, however, allows designers to efficiently segregate power distribution channels and save weight, the Airbus paper adds. Increased hydraulic pressure in the remaining hydraulic circuits–from 3,000 psi to 5,000 psi–also saves weight. It reduces the size of components, generation equipment, tubing, and the amount of fluid required, and makes installation easier. Overall, the benefits are clear: improved reliability and maintainability; reduced weight and increased cost savings; and increased safety margin because of the use of dissimilar power sources. "Because of the dissimilar [flight control] architecture, if we lose hydraulic power, the aircraft does not lose any flight handling capabilities," . "There is no impact on the performance of the aircraft." Electro hydrostatic actuation will generate large weight savings. "The combination of the higher hydraulic pressure and the more electric flight control architecture led to a weight reduction of approximately [3,307.5 pounds] 1,500 kg for the aircraft," . For variable-frequency power generation, "weight was not the driver". "It’s clear that Airbus is oriented more and more toward the more electric aircraft". "Airbus worked more than 10 years on electro hydrostatic actuators to see whether we could have a more dissimilar architecture for flight control." Airbus has defined a "two-plus-two" architecture, he explains. "The flight control actuation system is powered from four independent power sources–two hydraulic and two electrical circuits. 7 " 0 !#! #!3 Electro-hydrostatic actuators (EHAs) are an emerging aerospace technology that aims at replacing hydraulic systems with self-contained actuators operated solely by electrical power. EHAs would eliminate the need for separate hydraulic pumps and tubing, simplifying aircraft layout and improving safety and reliability. EHA offers a high degree of maintainability and combat survivability of the aircraft's flight control system because all the actuator's elements are collocated. The resulting design is not only robust with respect to actuator parameter variations and flight condition and insensitive to sensor noise, but, in addition, the controlled actuator's phase lag is significantly reduced, thus improving the performance of the overall flight control system. Additionally, the EHA has the advantage that it only draws power when it is being moved; the pressure is maintained internally when the motor stops. This can reduce power use on the aircraft by eliminating the constant draw of the hydraulic pumps. EHAs also reduce weight; allow better streamlining due to reduced internal routing of piping, and lower overall weight of the control system. Because of such outstanding features, Electro-hydrostatic actuators are a perfect choice for the actuation and control needs of future ‘more electric’ aircraft as well as high performance unmanned aerial combat vehicles. They can be also utilized in other industries like robotics, CNC machines and other high precision control applications. 3 # Name : Bhuptani Darshak Krishnkant Fathers Name : Krishnkant Harilal Bhuptani Date of Birth : 25th of December 1990 Branch B.Tech in Aerospace Engineering : Enrollment number: 093574710 Date of Enrollment: Jan, 2009 Educational Qualification: Sr. No. Qualification Score Year of passing Board/University College/Institute 1 SSC 78.93% 2006 Maharashtra State Board Holy Angels High School Mumbai-81 2 HSC 75.67% 2008 Maharashtra State Board NES Ratnam Jr. college of Science, Mumbai-78 Indira Gandhi National Open University Indian Institute for Aeronautical Engineering and Information Technology, Pune-52. 3 B.Tech in Aerospace Engineering Sem 5 79.62% 2011 Sem 4 80.85% 2010 Sem 3 84.11% 2010 Sem 2 82.11% 2009 Sem 1 71.28% 2009 Darshak Bhuptani '% 8 " · Flight Control Actuation Technology for Next-Generation All-Electric Aircraft - Stephen L. Botten, Chris R. Whitley, and Andrew D. King - · IGNOU BME-006 Mechatronics Block · Compact EHA Electro-Hydraulic Actuators for high power density applications - · Parker Hannifin Corporation Catalogue HY22-3101D 3/11 Performance of an Electro-Hydrostatic Actuator on the F-18 Systems Research Aircraft NASA/TM-97-206224 - · Young and Franklin - Actuation Technologies - · ! ! " # ! A380: 'More Electric' Aircraft - http://www.aviationtoday.com/av/commercial/A380-More-ElectricAircraft_12874.html