Speed Control

The growing cost of tuning and managing computer systems is leading to out-sourcing of commercial services to hosting centers. These centers provision thousands of dense servers within a relatively small real-estate in order to host the applications/services of different customers who may have been assured by a service-level agreement (SLA). Power consumption of these servers is becoming a serious concern in the design and operation of the hosting centers. The effects of high power consumption manifest not only in the costs spent in designing effective cooling systems to ward off the generated heat, but in the cost of electricity consumption itself. It is crucial to deploy power management strategies in these hosting centers to lower these costs towards enhancing profitability. At the same time, techniques for power management that include shutting down these servers and/or modulating their operational speed, can impact the ability of the hosting center to meet SLAs. In addition, repeated on-off cycles can increase the wear-and-tear of server components, incurring costs for their procurement and replacement. This paper presents a formalism to this problem, and proposes three new online solution strategies based on steady state queuing analysis, feedback control theory, and a hybrid mechanism borrowing ideas from these two. Using real web server traces, we show that these solutions are more adaptive to workload behavior when performing server provisioning and speed control than earlier heuristics towards minimizing operational costs while meeting the SLAs.

Three other methods are considered trapezoidal integration, backward Euler, and Gear second order The equation of interest has the form y = i%y,t) Let Ar, be the time step of a numerical solution Let tn = nAt, yn = y(tn) and fn = f{yn,tn) The formula for trapezoidal integration is given by /n+1 = Yn +-~( fn^+ fn) (D When trapezoidal integration is used for differentiation by letting f= xand solving forx, the following formula results trapezoidal integration However, a> 0 results in a better behavior as a differentiator, at the expense of accuracy For values of a< 1,the accuracy over the useful time step sizes of the method is very good when compared to other numerical integration methods Values of a> 1 can be used to attain empirical deliberate damping of physical oscillations xn+1 *n + A Wn+ 1 ¦Yn)

In this paper, the dynamic model of a wheeled inverted pendulum (e.g., Segway, Quasimoro, and Joe) is analyzed from a controllability and feedback linearizability point of view. First, a dynamic model of this underactuated system is derived with respect to the wheel motor torques as inputs while taking the nonholonomic no-slip constraints into considerations. This model is compared with the previous models derived for similar systems. The strong accessibility condition is checked and the maximum relative degree of the system is found. Based on this result, a partial feedback linearization of the system is obtained and the internal dynamics equations are isolated. The resulting equations are then used to design two novel controllers. The first one is a two-level velocity controller for tracking vehicle orientation and heading speed set-points, while controlling the vehicle pitch (pendulum angle from the vertical) within a specified range. The second controller is also a two-level controller which stabilizes the vehicle's position to the desired point, while again keeping the pitch bounded between specified limits. Simulation results are provided to show the efficacy of the controllers using realistic data.

This paper presents the development and test of a flexible control strategy for an 11-kW wind turbine with a back-to-back power converter capable of working in both stand-alone and grid-connection mode. The stand-alone control is featured with a complex output voltage controller capable of handling nonlinear load and excess or deficit of generated power. Grid-connection mode with current control is also enabled for the case of isolated local grid involving other dispersed power generators such as other wind turbines or diesel generators.

A large portion of the power budget in server environments goes into the I/O subsystem-the disk array in particular. Traditional approaches to disk power management involve completely stopping the disk rotation, which can take a considerable amount of time, making them less useful in cases where idle times between disk requests may not be long enough to outweigh the overheads. This paper presents a new approach called DRPM to modulate disk speed (RPM) dynamically, and gives a practical implementation to exploit this mechanism. Extensive simulations with different workload and hardware parameters show that DRPM can provide significant energy savings without compromising much on performance. This paper also discusses practical issues when implementing DRPM on server disks.

This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear input-output mapping. Based on this nonlinear mapping, the wind speed is estimated from the measured generator electrical output power while taking into account the power losses in the WTG and the dynamics of the WTG shaft system. The estimated wind speed is then used to determine the optimal DFIG rotor speed command for maximum wind power extraction. The DFIG speed controller is suitably designed to effectively damp the low-frequency torsional oscillations. The resulting WTG system delivers maximum electrical power to the grid with high efficiency and high reliability without mechanical anemometers. The validity of the proposed control algorithm is verified by simulation studies on a 3.6 MW WTG system. In addition, the effectiveness of the proposed wind speed estimation algorithm is demonstrated by experimental studies on a small emulational WTG system.

This paper presents a scalable rate control (SRC) scheme based on a more accurate second-order rate-distortion model. A sliding-window method for data selection is used to mitigate the impact of a scene change. The data points for updating a model are adaptively selected such that the statistical behavior is improved. For video object (VO) shape coding, we use an adaptive threshold method to remove shape-coding artifacts for MPEG-4 applications. A dynamic bit allocation among VOs is implemented according to the coding complexities for each VO.

This paper addresses the design and off-design analysis of a hybrid system (HS) based on the coupling of a recuperated micro gas turbine (MGT) with a high temperature solid oxide fuel cell (SOFC) reactor. The SOFC reactor model is presented and discussed, taking into account the in¯uence of the reactor lay-out, the current density, the air utilisation factor, the cell operating temperature, etc. The SOFC design and off-design performance is presented and discussed; the design and off-design models of a recuperated micro-gas turbine are also presented. The operating line, the in¯uence of the micro gas turbine``variable speed'' control, and the ef®ciency behaviour at part load are analysed in depth.

A sensorless torque control system for induction motors is developed. The system allows for fast and precise torque tracking over a wide range of speed. The paper also presents the identification and parameter estimation of an induction motor model with parameters varying as functions of the operating conditions encountered in hybrid electric vehicles applications. An adaptive sliding mode speed-flux observer is developed and a cascade of discrete time sliding mode controllers is used for flux and current control. Simulation and experimental results prove the validity of the approach.

Automatic control represents one of the most important factors responsible for the e$ciency and reliability of wind power conversion systems. Thus far, only a few isolated applications of conventional control to wind power systems have appeared in the literature. To make wind power generation truly cost-e!ective and reliable, advanced control techniques are imperative. In this paper we develop a control scheme for wind turbine using nonlinear and adaptive control theory. Based on both mechanical and electrical dynamics, nonlinear and adaptive control algorithms are derived to on-line adjust the excitation winding voltage of the generator. This method is shown to be able to achieve smooth and asymptotic rotor speed tracking, as justi"ed by both analysis and computer simulation.

The paper describes a variable speed wind generation system where fuzzy logic principles are used for efficiency optimization and performance enhancement control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which pumps power to a utility grid or can supply to an autonomous system. The generation system has fuzzy logic control with vector control in the inner loops. A fuzzy controller tracks the generator speed with the wind velocity to extract the maximum power. A second fuzzy controller programs the machine flux for light load efficiency improvement, and a third fuzzy controller gives robust speed control against wind gust and turbine oscillatory torque. The complete control system has been developed, analyzed, and validated by simulation study. Performances have then been evaluated in detail.

This paper presents a novel speed control scheme of an induction motor (IM) using fuzzy-logic control. The fuzzy-logic controller (FLC) is based on the indirect vector control. The fuzzy-logic speed controller is employed in the outer loop. The complete vector control scheme of the IM drive incorporating the FLC is experimentally implemented using a digital signal processor board DS-1102 for the laboratory 1-hp squirrel-cage IM. The performances of the proposed FLC-based IM drive are investigated and compared to those obtained from the conventional proportional-integral (PI) controller-based drive both theoretically and experimentally at different dynamic operating conditions such as sudden change in command speed, step change in load, etc. The comparative experimental results show that the FLC is more robust and, hence, found to be a suitable replacement of the conventional PI controller for the high-performance industrial drive applications.

This paper presents a novel speed control technique for an interior permanent-magnet synchronous motor (IPMSM) drive based on newly developed adaptive backstepping technique. The proposed stabilizing feedback law for the IPMSM drive is shown to be globally asymptotically stable in the context of Lyapunov theory. The adaptive backstepping technique takes system nonlinearities into account in the control system design stage. The detailed derivations of the control laws have been given for controller design. The complete IPMSM drive incorporating the proposed backstepping control technique has been successfully implemented in real-time using digital signal processor board DS1102 for a laboratory 1-hp motor. The performance of the proposed drive is investigated both in experiment and simulation at different operating conditions. It is found that the proposed control technique provides a good speed tracking performance for the IPMSM drive ensuring the global stability.

This paper discusses how the switched reluctance generator (SRG) converts energy as directed by a controller. Beginning with a review of the electromechanics of generation, the paper identifies the implications of the energy conversion process on how the SRG is controlled. The structure of the SRG controller for speed-control and power-control applications is discussed. Practical implementation details for commutation of the SRG are reviewed. Concepts are illustrated with a 6-kW SRG designed to serve as a starter/alternator in automotive applications.

Number of pole pairs. Rotor speed at electrical angle. Rotor position at electrical angle. Rotor inertia. Frictional constant. Electromagnetic torque. Load torque. Control matrix. System state matrix. Partial derivative system matrix. Output matrix. Kalman filter gain matrix. State covariance matrix. System noise covariance matrix. Measurement noise covariance matrix. Weighting matrix of noise. State vector. Output vector. Disturbance input and output vectors. Superscripts Estimate quantities. Reference quantities. Transposed matrix. Sampling index. Two-axis synchronous frame quantities. Two-axis stationary frame quantities. I. INTRODUCTION R ECENTLY, the development and availability of very high energy permanent magnet materials has contributed to an increased use of the permanent magnet synchronous motor (PMSM) in high performance variable speed motors in many industrial applications. The inherent advantages of using a PMSM drive is that it has a high ratio of torque to weight, high power factor, faster response, rugged construction, easy maintenance, ease of control and high efficiency. The high performance speed or position control requires an accurate knowledge of rotor shaft position and velocity in order to synchronize the phase excitation pulses to the rotor position. This implies the need for speed or position sensors such as an absolute encoder or a magnetic resolver attached to the shaft of the motor. However, in most applications, these sensors present several disadvantages, such as reduced reliability, susceptibility

Enhanced 2,3-butanediol (BD) production was carried out by Klebsiella pneumoniae SDM. The nutritional requirements for BD production by K. pneumoniae SDM were optimized statistically in shake flask fermentations. Corn steep liquor powder and (NH 4 ) 2 HPO 4 were identified as the most significant factors by the two-level Plackett-Burman design. Steepest ascent experiments were applied to approach the optimal region of the two factors and a central composite design was employed to determine their optimal levels. The optimal medium was used to perform fed-batch fermentations with K. pneumoniae SDM. BD production was then studied in a 5-l bioreactor applying different fed-batch strategies, including pulse fed batch, constant feed rate fed batch, constant residual glucose concentration fed batch, and exponential fed batch. The maximum BD concentration of 150 g/l at 38 h with a diol productivity of 4.21 g/l h was obtained by the constant residual glucose concentration feeding strategy. To the best of our knowledge, these results were new records on BD fermentation.

This paper proposes a hybrid terminal sliding mode observer based on the nonsingular terminal sliding mode and the high-order sliding mode for the rotor position and speed estimation in the permanent magnet synchronous motor control system. A nonsingular terminal sliding mode manifold is utilized to realize both fast convergence and better tracking precision. Meanwhile, a high-order sliding mode control law is designed to guarantee the stability of the observer and eliminate the chattering. Therefore, the smooth back electromotive force (EMF) signals can be obtained without a low pass filter. According to the back EMF equations, the rotor position and speed can be calculated. Simulation results show that, compared to the conventional sliding mode observer, the hybrid terminal sliding mode observer avoids the phase lag in the back EMF signals, and improves the estimation precision of the rotor position and speed.

This paper investigates formation control of a fleet of ships. The control objective for each ship is to maintain its position in the formation while a (virtual) Formation Reference Point (FRP) tracks a predefined path. This is obtained by using vectorial backstepping to solve two subproblems; a geometric task, and a dynamic task. The former guarantees that the FRP, and thus the formation, tracks the path, while the latter ensures accurate speed control along the path. A dynamic guidance system with feedback from the states of all ships ensures that all ships have the same priority (no leader) when moving along the path. Lyapunov stability is proven and robustness to input saturation is demonstrated using computer simulations.

This paper addresses the identification and control of nonlinear systems by means of Fuzzy Hammerstein (FH) models, which consist of a static fuzzy model connected in series with a linear dynamic model. For the identification of nonlinear dynamic systems with the proposed FH models, two methods are proposed. The first one is an alternating optimization algorithm that iteratively refines the estimate of the linear dynamics and the parameters of the static fuzzy model. The second method estimates the parameters of the nonlinear static model and of the linear dynamic model simultaneously by using a constrained recursive least-squares algorithm. The obtained FH model is incorporated in a model-based predictive control scheme and a new constraint-handling method is presented. A simulated water-heater process is used as an illustrative example. A comparison with an affine neural network and a linear model is given. Simulation results show that the proposed FH modeling approach is useful for modular parsimonious modeling and model-based control of nonlinear systems.

Recent developments of high-energy permanent magnet (PM) materials such as neodymium-iron-boron have focused attention on the use of PM synchronous motors supplied from inverters for a wide variety of speed control applications. PM motor drives are readily applicable where full torque is required up to full or base speed. They are, however, limited in their ability to operate in the power-limited regime where the available torque is reduced as the speed is increased above its base value. In contrast with the field weakening approach used in dc drives, the magnet is permanent. The torque-speed operating limits of PM motor drives, of conventional design are explored, and then design measures which can substantially extend operation into the power-limited regime are proposed. A trade-off between the low speed-torque limit and the extent of the speed range above base speed is achieved by variations in magnet dimensions and the depth of inset of the magnets in the rotor iron. Experimental results are presented for two motors of different design, each using neodymium magnets and each supplied from a currentcontrolled inverter with hysteresis control of current waveshape.

The implementation of a monitoring and control system for the induction motor based on programmable logic controller (PLC) technology is described. Also, the implementation of the hardware and software for speed control and protection with the results obtained from tests on induction motor performance is provided. The PLC correlates the operational parameters to the speed requested by the user and monitors the system during normal operation and under trip conditions. Tests of the induction motor system driven by inverter and controlled by PLC prove a higher accuracy in speed regulation as compared to a conventional V f control system. The efficiency of PLC control is increased at high speeds up to 95% of the synchronous speed. Thus, PLC proves themselves as a very versatile and effective tool in industrial control of electric drives.

In a recent paper [(Espinosa-Perez and Ortega, 1994). State observers are unnecessary for induction motor control. Syst. & Control Lett., 23, 315-3231 Espinosa and Ortega presented an output feedback globally stable speed tracking controller for induction motors. The performance of the scheme is limited by the fact that the convergence rate of the speed tracking errors is determined by the natural mechanical damping of the motor. In this brief note we overcome this drawback and show that by simple linear filtering of the speed tracking error we can inject mechanical damping to the closed loop. This allows us to improve the transient performance of the scheme in Espinosa-Perez and Ortega (1994) in position and speed tracking applications without significantly increasing the computational requirements, while preserving the global stability properties. Further, it is shown that if the inverter can be modelled as a current source and the desired speed is constant, our passivity-based scheme exactly reduces to the wellknown indirect field-oriented control scheme, hence providing a solid theoretical foundation to this popular control strategy.

In this paper a sensorless closed-loop speed control for the synchronous reluctance motor is presented. The sensorless control is based on the torque vector control algorithm. It has been implemented using a high-speed digital processor DSP96002. Experimental results for a 120 W axially-laminated synchronous reluctance motor are presented and compared with operation with a speed sensor and simulations. A base speed range of 400-1500 rpm has been achieved. The top speed was extended to 2750 rpm using flux-weakening. The drive can be applied a full-load step-change within this speed range without losing synchronism.

Position and rate control are the two common manual control modes in teleoperations. Human operator performance using the two modes is evaluated and compared. Simulated three-axis pick-andplace operations are used as the primary task for evaluation. First, ideal position and rate control are compared by considering several factors, such as joystick gain, joystick type, display mode, task, and manipulator work space size. Then the effects of the manipulator system dynamics are investigated by varying the natural frequency and speed limit. Experimental results show that ideal position control is superior to ideal rate control, regardless of joystick type or display mode, when the manipulation work space is small or comparable to the human operator's control space. Results also show that when the manipulator system is slow, the superiority of position control disappears. Position control is recommended for small-work-space telemanipulation tasks, while rate control is recommended for slow wide-work-space telemanipulation tasks.

Previous work on stabilization of compressor surge is extended to include control of the angular velocity of the compressor. First a low-order centrifugal compressor model is presented where the states are mass flow, pressure rise, and rotational speed of the spool. Energy transfer considerations are used to develop a compressor characteristic. In order to stabilize equilibria to the left of the surge line, a close coupled valve is used in series with the compressor. Controllers for the valve pressure drop and spool speed are derived. Semiglobal exponential stability is proved using a Lyapunov argument.

This paper describes a study and experimental verification of sensorless control of Permanent Magnet Synchronous Motor. There are proposed novel estimation strategy based on the Unscented Kalman Filter, using only the measurement of the motor current for on-line estimation of speed, rotor position and load torque reconstruction. The Kalman filter is an optimal state estimator and is usually applied to a dynamic system that involves a random noise environment. Control structure such as Kalman filtering, in real time requires a very fast signal processor in special way, adapted to perform complex mathematical calculations. During verification, it is concerned on behaviour of control system in result of desired speed changing. Experimental results confirm the validity of the novel proposed estimation technique. Presented results show good properties of proposed observer.

This paper describes a newly developed speed sensorless drive based on neural networks. A backpropagation neural network is used to provide real-time adaptive identification of the motor speed. The estimation objective is the sum of squared errors between a target trajectory and the neural network model output. A backpropagation algorithm is used to adjust the motor speed, so that the neural model output follows the target trajectory. Backpropagation forces the estimated speed to follow precisely the actual motor speed. The zero-speed crossing phenomena is also described, and experimental results are presented and analyzed.

In some surgical specialties (eg, orthopedics), robots are already used in the operating room for bony milling work. Otological surgery and otoneurosurgery may also greatly benefit from the enhanced precision of robotics. Experimental study on robotic milling of oak wood and human temporal bone specimen. A standard industrial robot with a six-degrees-of-freedom serial kinematics was used, with force feedback to proportionally control the robot speed. Different milling modes and characteristic path parameters were evaluated to generate milling paths based on computer-aided design (CAD) geometry data of a cochlear implant and an implantable hearing system. The best-suited strategy proved to be the spiral horizontal milling mode with the burr held perpendicular to the temporal bone surface. To reduce groove height, the distance between paths should equal half the radius of the cutting burr head. Because of the vibration of the robot&#39;s own motors, a high oscillation of the SD of for...

Results of a field experiment in which a 35-km long stretch of road was subjected to an increase in police enforcement-mostly as stationary speed controls-are presented. A group of police officers was invited to plan and perform the enforcement based on their own experience and ideas. The level of enforcement reached a daily average of nine hours throughout an enforcement period of six weeks. Speed measurements were done in 60 and 80 km/h speed-limit zones before, during and after enforcement withdrawal, and were compared to another stretch of road. Average speeds were reduced by 0.9-4.8 km/h in both speed-limit zones and for all times of day. For some time intervals, the average speed and the percentage of speeding drivers were reduced for several weeks of the after-period, demonstrating a time-halo effect of eight weeks at most. The percentage of speeding drivers was reduced in both speed-limit zones for all hours of the day except the morning rush hours 6.00-9.00 A.M. It is suggested that commuting drivers in the morning rush hours are most resistant to speed reduction. These results were statistically significant at ~=0.01. 0 1997 Elsevier Science Ltd

of the machine in this application. Thus, research has been undertaken to identify, analyze, and simulate the various fault modes of the SR generator. This research included an investigation of the generator's excitation requirements with and without faults. The investigation makes it possible to determine the size of the excitation source required during the initial buildup of the generator's output voltage and under fault conditions. The SR machine, controller, EMI filter, excitation source, and load were all modeled and integrated into a Matlab-Simulink model in order to analyze the SR generator system.

In this paper, the application of model predictive control (MPC) for high-performance speed control and torsional vibration suppression in the drive system with flexible coupling is demonstrated. The control methodology presented in this paper relies on incorporating the drive's safety and physical limitations directly into the control problem formulation so that future constraint violations are anticipated and prevented. In order to reduce the computational complexity, the standard MPC controller is replaced by its explicit form. The resulting explicit controller achieves the same level of performance as the conventional MPC, but requires only a fraction of the real-time computational machinery, thus leading to fast and reliable implementation. The simulation results are confirmed by laboratory experiments.

This paper introduces a neuro-fuzzy controller (NFC) for the speed control of a PMSM. A four layer neural network (NN) is used to adjust input and output parameters of membership functions in a fuzzy logic controller (FLC). The back propagation learning algorithm is used for training this network. The performance of the proposed controller is verified by both simulations and experiments. The hardware implementation of the controllers is made using a TMS320F240 DSP. The results are compared with the results obtain from a Proportional + Integral (PI) controller. Simulation and experimental results indicate that the proposed NFC is reliable and effective for the speed control of the PMSM over a wide range of operations of the PMSM drive.

This paper presents a summary of the most important characteristics of wind turbine generators applied in modern wind power plants. Various wind turbine generator designs, based on classification by machine type and speed control capabilities, are discussed along with their operational characteristics, voltage, reactive power, or power factor control capabilities, voltage ride-through characteristics, behavior during short circuits, and reactive power capabilities.

Theoretical, design, and experimental aspects of the control of the drive with an elastic coupling are considered in this paper. Control structures suitable for application in industrial high-dynamic drives are developed. In such drives, the first resonance frequency can be higher than a hundred hertz, and the next frequency can be a thousand hertz or higher. The solution is oriented to industrial plants, whose computation ability is lower and signal delay is greater than in laboratory plants based on DSP. The authors discuss the problem and show methods of suppressing torsion vibrations in speed-control systems with only one sensor, i.e., a motor position encoder. The presented solution is based on an adequately designed PID controller.

Problem: It is essential that driver licensing authorities have a valid and reliable system for evaluating older drivers' continuing competency; road tests are usually required as part of such a system. This study sought to find information about the nature of driving errors made during license review tests, and about relationships between error type and test outcome for older drivers. Method: Data from licensing authority files from 533 road tests during a 12-month period were analyzed; medical and other referral information was included. Average driver age was 76 years. Performance scores were generated for intersection negotiation, lane changing, low speed manoeuvres, positioning and speed control, safety margin, and car control. Results: Logistic regression analysis showed that test outcome was well predicted by a subset of driving performance scores; adding driver age to the model explained very little variance. Age alone was strongly associated with outcome. Relationships between referral information and test outcome are also reported. Impact: Results highlight several factors relevant to the development of more valid and reliable road tests for older drivers.

This paper models theoretically and investigates empirically the consequences on local economic performance of state mandates on financially distressed authorities. In particular, I analyze the switch from systematic state bailout of regional health care deficits to selectively mandated hikes in regions’ own business income tax rates that took place in Italy around the mid 2000s, and exploit such dramatic switch to identify the impact of tax policy on the economy. I model factor input use within a multi-jurisdiction neoclassical framework, where production takes place in plants, and physical capital requires energy in fixed proportions depending on the size of energy-saving capital that is installed along with physical capital. Energy-saving capital can be interpreted either as tangible information technology (IT) equipment (e.g., computer-aided line speed control devices) or as intangible assets (e.g., process design skills) lowering a plant energy requirement. The estimation resul...

In this paper, we study temperature-constrained realtime systems, where real-time guarantees must be met without exceeding safe temperature levels within the processor. We give a short review on temperature issues in processors and describe how speed control can be used to trade-off task delays against processor temperature. In this paper, we describe how traditional worst-case execution scenarios do not apply in temperature-constrained situations. As example, we adopt a simple reactive speed control technique. We show how this simple reactive scheme can improve the processor utilization compared with any constantspeed scheme.

CITATIONS 44 READS 157 3 authors: Some of the authors of this publication are also working on these related projects: TIMON: Enhanced real time services for optimized multimodal mobility relying on cooperative networks and open data View project