Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005.
There are several applications where the motor is operating in continuous non-stationary operatin... more There are several applications where the motor is operating in continuous non-stationary operating conditions. Actuators in the aerospace and transportation industries are examples of this kind of operation. Diagnostics of faults in such applications is, however, challenging. A novel method using windowed Fourier ridges is proposed in this paper for the detection of rotor faults in BLDC motors operating under continuous non-stationarity. Experimental results are presented to validate the concept and depict the ability of the proposed algorithm to track and identify rotor faults. The proposed algorithm is simple and can be implemented in real-time without much computational burden.
Electric motors work continuously under operating conditions that rapidly vary with time. Motor d... more Electric motors work continuously under operating conditions that rapidly vary with time. Motor diagnostics in a non-stationary environment is challenging due to the need for sophisticated signal processing techniques. In this paper, the use of quadratic TFRs is presented as a solution for the diagnostics of rotor faults in Brushless DC (BLDC) motors operating under constantly changing load and speed conditions. Four time-frequency representations are considered in this paper-short-time Fourier transform (STFT), Wigner-Ville distribution (WVD), Choi-Williams Distribution (CWD), and the Zhao-Atlas Marks Distribution (ZAM). The drawbacks of these distributions and methods to overcome them are also presented. The TFRs are implemented in real-time and their load computations are compared in order to study their suitability for implementation in a commercial system.
2005 5th IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives, 2005
Electric motors often operate under operating conditions that are constantly changing with time. ... more Electric motors often operate under operating conditions that are constantly changing with time. Most of such applications demand high reliability from the motor. Early detection of developing motor faults could help provide this needed reliability. While diagnostics of faults in motors operating under steady state conditions is straight forward due to the use of the well known Fourier transformation, diagnostics of motors operating under non-stationary conditions may need more sophisticated signal processing. In this paper, the Wigner-Ville family of time-frequency distributions is presented as an alternative to short time Fourier transforms (STFTs) and wavelets, for the diagnostics of rotor faults in a BLDC motor. Wigner-Ville distributions possess better frequency resolution than the STFT and wavelets. Several variants of the Wigner-Ville distributions are presented. The drawbacks of these distributions and methods to overcome them are also presented. Simulation and experimental results demonstrate that the Wigner-Ville distributions can be a viable tool to analyze rotor faults in BLDC motors operating under continuous nonstationarity.
This paper presents a direct and approximate model of PV cell that considers variations in surrou... more This paper presents a direct and approximate model of PV cell that considers variations in surrounding temperature and solar irradiation. The method uses the one diode model approximation and PV parameters from the manufacturer's data, together with a selective (first or second order) Taylor series. In this paper, a recursive solution for the PV cell's complete implicit model equations supplies data supporting the proposed approximate method results. The proposed model allows adjustment of the MPPT algorithm to simplify in real time the inverter control algorithm. It also provides a way to find the temperature and solar irradiation or errors produced by nonuniform irradiation on the solar panels.
En este trabajo se comparan dos metodologías para la detección de cortocircuitos y fallas entre c... more En este trabajo se comparan dos metodologías para la detección de cortocircuitos y fallas entre chapas de núcleos magnéticos, para lo cual se realizaron los ensayos sobre las chapas que conforman el estator de un motor de inducción, con el objetivo de determinar el método de detección más eficaz. Los métodos sometidos a comparación son: Método de la prueba de aislamiento del laminado del nú- cleo del estator, recomendado por el estándar IEEE-56 Guide for Insulation Maintenance of Large Alternating - Current Rotating Machinery (10000 KVA and Larger) y el método de variaciones de flujo, el cual permite mediante dos electroimanes o bobinas (sensora y patrón) sobre las chapas, determinar las variaciones en magnitud y fase de la corriente que circula por las mismas, ubicando los puntos de falla.
2008 International Conference on Condition Monitoring and Diagnosis, 2008
A breakdown of the electrical insulation system causes catastrophic failure of the electrical mac... more A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. To determine the conditions of the stator insulation system of motor drive systems, various testing and monitoring methods have been developed. This paper presents an in-depth literature review of more than 20 existing methods, including the most common methods to assess the phase-to-ground, phase-to-phase, and turn-to-turn insulation conditions. The methods are categorized into as online and offline methods, each of which are further grouped into specific areas according to their physical nature. The paper focuses on turn-to-turn insulation testing and monitoring of low-voltage machines, which is a rapidly expanding area for both research and product development efforts. Finally, a new approach to online monitoring of turn-to-turn insulation faults for low-voltage induction motors is recommended.
2015 IEEE International Conference on Industrial Technology (ICIT), 2015
A predictive control scheme to control the phase currents of a three-phase power converter couple... more A predictive control scheme to control the phase currents of a three-phase power converter coupled to the electric grid by means of an LCL network is developed. This kind of coupling offers several advantages when compared to pure inductive coupling networks, namely a greater attenuation of switching harmonics and a smaller size. Equations that model the behavior of the current through the LCL network in terms of the applied voltages are, however, more complicated to obtain. In this paper the difference equations required to implement a discrete predictive control scheme are obtained and tested by simulations when it is operated as an inverter and as a controlled rectifier.
Proceedings of the 1998 Second IEEE International Caracas Conference on Devices, Circuits and Systems. ICCDCS 98. On the 70th Anniversary of the MOSFET and 50th of the BJT. (Cat. No.98TH8350)
This work presents a new PC-based Integrated System for MAchine Drives (ISMAD), which allows to a... more This work presents a new PC-based Integrated System for MAchine Drives (ISMAD), which allows to analyze and test chopper drives for DC motors and inverter drives for AC motors, operated under scalar control techniques. This system has been designed using IGBTs and includes a Control Card to be inserted in a PC, and a Drive and Power stage to operate the machines. With ISMAD both open loop and close loop systems can be implemented, making possible to perform several useful experiments, for teaching or testing new strategies in the research laboratory.
2006 IEEE/PES Transmission & Distribution Conference and Exposition: Latin America, 2006
A comp arison between space vector and classic steady state models of the induction motor is perf... more A comp arison between space vector and classic steady state models of the induction motor is performed dur ing the start up conditio n at industr ial full voltage and frequency. This work shows several imprecisions obta ined when the impact over the system is analyzed using classic mod els, specially during the start up. Pulsating torque effects and magnitude of maximum torque are considered. A deep bars model of the squir rel cage motor in space vector coordinates was developed, and its parametri c estimati on is performed to match the motor data sheet and experimental results with the machine performan ce in tran sient behavior. The wound rotor machine is modeled in space vector coord inates, comp ared with the classic mod el and its parameters obtained by an estimati on algorithm. Electri c transient behavior, harmonic analysis, dy namics and source unbalances can be bette r analyzed using space vector tran sformati on, because a reduce ord er syst em is obtained and power electronic converters could be included.
A new method using the analytic wavelet transform of the stator current signal is proposed for de... more A new method using the analytic wavelet transform of the stator current signal is proposed for detecting dynamic eccentricity in brushless direct current (BLDC) motors operating under rapidly varying speed conditions. As wavelets are inherently suited for non-stationary signal analysis, this method does not require the use of any windows nor is it dependent on any assumption of local stationarity.
The Journal of the Acoustical Society of America, 2001
Brake squeal is an annoying phenomenon, generally occurring when vehicles brake at slow speeds. S... more Brake squeal is an annoying phenomenon, generally occurring when vehicles brake at slow speeds. Significant effort is expended by the automotive industry to avoid squeal during the development of brake systems. Nonetheless, expensive warranty claims still occur when such efforts are not completely successful. Recent research demonstrated that introducing dither control into a brake is an effective means of suppressing squeal. Dither control is a method by which high-frequency disturbances are introduced into a system. This suppresses the friction induced squeal response at lower frequencies, thus eliminating the audible brake squeal. Dither control, when applied at a 100% duty cycle, is an effective means of suppressing brake squeal. This presentation focuses on the potential to use burst mode dither control for squeal suppression. Burst mode dither control is characterized by duty cycles of less than 100%. Dither is introduced to a brake by placing a piezoelectric stack actuator in...
In this paper, the space-vector transformation used in machine vector control is applied to power... more In this paper, the space-vector transformation used in machine vector control is applied to power system analysis. The proposed method is used to model electric machines, power electronic converters, transformers, and transmission lines and to analyze power sources and loads with different connections (delta and wye). This method can also be applied to analyze steady-state (or transient phenomena) and unbalanced sources, including harmonics. Models obtained with this method are as simple as those of the per-phase approach. With the space-vector transformation, instantaneous active and reactive power concepts can be generalized, and new power system control strategies can be developed when power electronic converters are used. Steady-state, transient behavior, and harmonic analyses examples and applications are presented to illustrate the performance and advantages of the proposed method. This method can be extended to unbalanced systems (e.g., unsymmetric faults) using instantaneous symmetrical components in polyphase balanced circuits.
This paper proposes a method that allows the operation with direct torque control under incipient... more This paper proposes a method that allows the operation with direct torque control under incipient faults of the power switching devices in single DC-link dual-inverters. Once the fault onset of the switching device is detected the troubled devices are put under trigger suppression to regain operation. The proposed control algorithm makes use of additional states, termed opportunistic states to maintain control of the induction machine. Simulations and experimental results confirm the capabilities of the technique for up to six devices under trigger suppression.
Fault detection in electric motors operating under non-stationary operating conditions has been g... more Fault detection in electric motors operating under non-stationary operating conditions has been gaining importance, due to the fact that motors are used in many applications such as actuators in the aerospace and transportation industries operate under conditions that rapidly vary with time. In recent times, a plethora of new time-frequency distributions have appeared that are inherently suited to the analysis of non-stationary signals while offering superior frequency resolution characteristics. The Zhao-Atlas-Marks (ZAM) distribution is one such distribution. This paper proposes the use of these new time-frequency distributions to enhance non-stationary fault diagnostics in electric motors. One common myth has been that the quadratic time-frequency distributions are not suitable for commercial implementation. This paper addresses this issue in detail too. Optimal discrete time implementations of some of these quadratic time-frequency distributions are explained. These TFRs have been implemented on a digital signal processing (DSP) platform to demonstrate that the proposed methods can be implemented commercially.
A new method for sensorless speed estimation of AC machines, using the analytic wavelet transform... more A new method for sensorless speed estimation of AC machines, using the analytic wavelet transform of the stator current signal, is proposed for a Direct Torque Control drive. A comparison with results obtained using the short time Fourier transform is included. The proposed method can be implemented in real time on a DSP. The time-frequency resolution obtained and the computation time required by the proposed algorithm are improved in comparison to existing techniques, and the method can be applied over the entire speed range.
A breakdown of the electrical insulation system causes catastrophic failure of the electrical mac... more A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. Preventive maintenance and online monitoring are some of the methods to improve the reliability and to reduce unscheduled downtime. One of the main reasons for the failure of the machine is the breakdown of the stator turn insulation. The offline surge test is the most commonly used offline test to assess the condition of the turn insulation. There is no online monitoring method that is applicable to low-voltage machines and has the same capabilities as the surge test. This paper introduces new concepts to implement an online surge test. The possibilities and limitations of the online surge test are presented, as well as the simulation and experimental results, to validate the concepts.
A new method using the analytic wavelet transform of the stator-current signal is proposed for de... more A new method using the analytic wavelet transform of the stator-current signal is proposed for detecting dynamic eccentricity in brushless direct current (BLDC) motors operating under rapidly varying speed and load conditions. As wavelets are inherently suited for nonstationary signal analysis, this method does not require the use of any windows, nor is it dependent on any assumption of local stationarity as in the case of the short-time Fourier transform. The proposed technique uses analytic wavelets, which are smooth wavelets that possess both magnitude and phase information. This makes them particularly suitable for motorfault diagnostics. Experimental results are provided to show that the proposed method works over a wide speed range of motor operation and provides an effective and robust way of detecting rotor faults such as dynamic eccentricity in BLDC motors.
Most researchers characterize brake squeal as a vibration of the brake rotor that produces an irr... more Most researchers characterize brake squeal as a vibration of the brake rotor that produces an irritating noise to automobile passengers. Recently, the concept of dither control was successfully used to suppress the resonant vibration of components of a brake system, thereby eliminating its acoustic disturbance. Dither control is a high frequency periodic disturbance signal introduced into a brake system to quench friction-induced oscillations. This paper presents results of the measurement of dynamic forces transmitted to the inboard pad of a floating caliper brake system during suppression of squeal using dither control. A stack of piezoelectric elements was placed inside the brake piston to induce a high frequency displacement to the inboard pad. A 20 kHz voltage was applied over the piezoelectric stack to dither the brake's normal clamping force. Measurements of the dynamic force transmitted to the brake pad were made with a load cell that was placed in line with the stack inside the caliper. The dynamic force was measured during squeal and during its control. Squeal suppression through dither control typically required the application of a 200 Newton modulation to the static normal force.
Fourtieth IAS Annual Meeting. Conference Record of the 2005 Industry Applications Conference, 2005.
There are several applications where the motor is operating in continuous non-stationary operatin... more There are several applications where the motor is operating in continuous non-stationary operating conditions. Actuators in the aerospace and transportation industries are examples of this kind of operation. Diagnostics of faults in such applications is, however, challenging. A novel method using windowed Fourier ridges is proposed in this paper for the detection of rotor faults in BLDC motors operating under continuous non-stationarity. Experimental results are presented to validate the concept and depict the ability of the proposed algorithm to track and identify rotor faults. The proposed algorithm is simple and can be implemented in real-time without much computational burden.
Electric motors work continuously under operating conditions that rapidly vary with time. Motor d... more Electric motors work continuously under operating conditions that rapidly vary with time. Motor diagnostics in a non-stationary environment is challenging due to the need for sophisticated signal processing techniques. In this paper, the use of quadratic TFRs is presented as a solution for the diagnostics of rotor faults in Brushless DC (BLDC) motors operating under constantly changing load and speed conditions. Four time-frequency representations are considered in this paper-short-time Fourier transform (STFT), Wigner-Ville distribution (WVD), Choi-Williams Distribution (CWD), and the Zhao-Atlas Marks Distribution (ZAM). The drawbacks of these distributions and methods to overcome them are also presented. The TFRs are implemented in real-time and their load computations are compared in order to study their suitability for implementation in a commercial system.
2005 5th IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives, 2005
Electric motors often operate under operating conditions that are constantly changing with time. ... more Electric motors often operate under operating conditions that are constantly changing with time. Most of such applications demand high reliability from the motor. Early detection of developing motor faults could help provide this needed reliability. While diagnostics of faults in motors operating under steady state conditions is straight forward due to the use of the well known Fourier transformation, diagnostics of motors operating under non-stationary conditions may need more sophisticated signal processing. In this paper, the Wigner-Ville family of time-frequency distributions is presented as an alternative to short time Fourier transforms (STFTs) and wavelets, for the diagnostics of rotor faults in a BLDC motor. Wigner-Ville distributions possess better frequency resolution than the STFT and wavelets. Several variants of the Wigner-Ville distributions are presented. The drawbacks of these distributions and methods to overcome them are also presented. Simulation and experimental results demonstrate that the Wigner-Ville distributions can be a viable tool to analyze rotor faults in BLDC motors operating under continuous nonstationarity.
This paper presents a direct and approximate model of PV cell that considers variations in surrou... more This paper presents a direct and approximate model of PV cell that considers variations in surrounding temperature and solar irradiation. The method uses the one diode model approximation and PV parameters from the manufacturer's data, together with a selective (first or second order) Taylor series. In this paper, a recursive solution for the PV cell's complete implicit model equations supplies data supporting the proposed approximate method results. The proposed model allows adjustment of the MPPT algorithm to simplify in real time the inverter control algorithm. It also provides a way to find the temperature and solar irradiation or errors produced by nonuniform irradiation on the solar panels.
En este trabajo se comparan dos metodologías para la detección de cortocircuitos y fallas entre c... more En este trabajo se comparan dos metodologías para la detección de cortocircuitos y fallas entre chapas de núcleos magnéticos, para lo cual se realizaron los ensayos sobre las chapas que conforman el estator de un motor de inducción, con el objetivo de determinar el método de detección más eficaz. Los métodos sometidos a comparación son: Método de la prueba de aislamiento del laminado del nú- cleo del estator, recomendado por el estándar IEEE-56 Guide for Insulation Maintenance of Large Alternating - Current Rotating Machinery (10000 KVA and Larger) y el método de variaciones de flujo, el cual permite mediante dos electroimanes o bobinas (sensora y patrón) sobre las chapas, determinar las variaciones en magnitud y fase de la corriente que circula por las mismas, ubicando los puntos de falla.
2008 International Conference on Condition Monitoring and Diagnosis, 2008
A breakdown of the electrical insulation system causes catastrophic failure of the electrical mac... more A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. To determine the conditions of the stator insulation system of motor drive systems, various testing and monitoring methods have been developed. This paper presents an in-depth literature review of more than 20 existing methods, including the most common methods to assess the phase-to-ground, phase-to-phase, and turn-to-turn insulation conditions. The methods are categorized into as online and offline methods, each of which are further grouped into specific areas according to their physical nature. The paper focuses on turn-to-turn insulation testing and monitoring of low-voltage machines, which is a rapidly expanding area for both research and product development efforts. Finally, a new approach to online monitoring of turn-to-turn insulation faults for low-voltage induction motors is recommended.
2015 IEEE International Conference on Industrial Technology (ICIT), 2015
A predictive control scheme to control the phase currents of a three-phase power converter couple... more A predictive control scheme to control the phase currents of a three-phase power converter coupled to the electric grid by means of an LCL network is developed. This kind of coupling offers several advantages when compared to pure inductive coupling networks, namely a greater attenuation of switching harmonics and a smaller size. Equations that model the behavior of the current through the LCL network in terms of the applied voltages are, however, more complicated to obtain. In this paper the difference equations required to implement a discrete predictive control scheme are obtained and tested by simulations when it is operated as an inverter and as a controlled rectifier.
Proceedings of the 1998 Second IEEE International Caracas Conference on Devices, Circuits and Systems. ICCDCS 98. On the 70th Anniversary of the MOSFET and 50th of the BJT. (Cat. No.98TH8350)
This work presents a new PC-based Integrated System for MAchine Drives (ISMAD), which allows to a... more This work presents a new PC-based Integrated System for MAchine Drives (ISMAD), which allows to analyze and test chopper drives for DC motors and inverter drives for AC motors, operated under scalar control techniques. This system has been designed using IGBTs and includes a Control Card to be inserted in a PC, and a Drive and Power stage to operate the machines. With ISMAD both open loop and close loop systems can be implemented, making possible to perform several useful experiments, for teaching or testing new strategies in the research laboratory.
2006 IEEE/PES Transmission & Distribution Conference and Exposition: Latin America, 2006
A comp arison between space vector and classic steady state models of the induction motor is perf... more A comp arison between space vector and classic steady state models of the induction motor is performed dur ing the start up conditio n at industr ial full voltage and frequency. This work shows several imprecisions obta ined when the impact over the system is analyzed using classic mod els, specially during the start up. Pulsating torque effects and magnitude of maximum torque are considered. A deep bars model of the squir rel cage motor in space vector coordinates was developed, and its parametri c estimati on is performed to match the motor data sheet and experimental results with the machine performan ce in tran sient behavior. The wound rotor machine is modeled in space vector coord inates, comp ared with the classic mod el and its parameters obtained by an estimati on algorithm. Electri c transient behavior, harmonic analysis, dy namics and source unbalances can be bette r analyzed using space vector tran sformati on, because a reduce ord er syst em is obtained and power electronic converters could be included.
A new method using the analytic wavelet transform of the stator current signal is proposed for de... more A new method using the analytic wavelet transform of the stator current signal is proposed for detecting dynamic eccentricity in brushless direct current (BLDC) motors operating under rapidly varying speed conditions. As wavelets are inherently suited for non-stationary signal analysis, this method does not require the use of any windows nor is it dependent on any assumption of local stationarity.
The Journal of the Acoustical Society of America, 2001
Brake squeal is an annoying phenomenon, generally occurring when vehicles brake at slow speeds. S... more Brake squeal is an annoying phenomenon, generally occurring when vehicles brake at slow speeds. Significant effort is expended by the automotive industry to avoid squeal during the development of brake systems. Nonetheless, expensive warranty claims still occur when such efforts are not completely successful. Recent research demonstrated that introducing dither control into a brake is an effective means of suppressing squeal. Dither control is a method by which high-frequency disturbances are introduced into a system. This suppresses the friction induced squeal response at lower frequencies, thus eliminating the audible brake squeal. Dither control, when applied at a 100% duty cycle, is an effective means of suppressing brake squeal. This presentation focuses on the potential to use burst mode dither control for squeal suppression. Burst mode dither control is characterized by duty cycles of less than 100%. Dither is introduced to a brake by placing a piezoelectric stack actuator in...
In this paper, the space-vector transformation used in machine vector control is applied to power... more In this paper, the space-vector transformation used in machine vector control is applied to power system analysis. The proposed method is used to model electric machines, power electronic converters, transformers, and transmission lines and to analyze power sources and loads with different connections (delta and wye). This method can also be applied to analyze steady-state (or transient phenomena) and unbalanced sources, including harmonics. Models obtained with this method are as simple as those of the per-phase approach. With the space-vector transformation, instantaneous active and reactive power concepts can be generalized, and new power system control strategies can be developed when power electronic converters are used. Steady-state, transient behavior, and harmonic analyses examples and applications are presented to illustrate the performance and advantages of the proposed method. This method can be extended to unbalanced systems (e.g., unsymmetric faults) using instantaneous symmetrical components in polyphase balanced circuits.
This paper proposes a method that allows the operation with direct torque control under incipient... more This paper proposes a method that allows the operation with direct torque control under incipient faults of the power switching devices in single DC-link dual-inverters. Once the fault onset of the switching device is detected the troubled devices are put under trigger suppression to regain operation. The proposed control algorithm makes use of additional states, termed opportunistic states to maintain control of the induction machine. Simulations and experimental results confirm the capabilities of the technique for up to six devices under trigger suppression.
Fault detection in electric motors operating under non-stationary operating conditions has been g... more Fault detection in electric motors operating under non-stationary operating conditions has been gaining importance, due to the fact that motors are used in many applications such as actuators in the aerospace and transportation industries operate under conditions that rapidly vary with time. In recent times, a plethora of new time-frequency distributions have appeared that are inherently suited to the analysis of non-stationary signals while offering superior frequency resolution characteristics. The Zhao-Atlas-Marks (ZAM) distribution is one such distribution. This paper proposes the use of these new time-frequency distributions to enhance non-stationary fault diagnostics in electric motors. One common myth has been that the quadratic time-frequency distributions are not suitable for commercial implementation. This paper addresses this issue in detail too. Optimal discrete time implementations of some of these quadratic time-frequency distributions are explained. These TFRs have been implemented on a digital signal processing (DSP) platform to demonstrate that the proposed methods can be implemented commercially.
A new method for sensorless speed estimation of AC machines, using the analytic wavelet transform... more A new method for sensorless speed estimation of AC machines, using the analytic wavelet transform of the stator current signal, is proposed for a Direct Torque Control drive. A comparison with results obtained using the short time Fourier transform is included. The proposed method can be implemented in real time on a DSP. The time-frequency resolution obtained and the computation time required by the proposed algorithm are improved in comparison to existing techniques, and the method can be applied over the entire speed range.
A breakdown of the electrical insulation system causes catastrophic failure of the electrical mac... more A breakdown of the electrical insulation system causes catastrophic failure of the electrical machine and brings large process downtime losses. Preventive maintenance and online monitoring are some of the methods to improve the reliability and to reduce unscheduled downtime. One of the main reasons for the failure of the machine is the breakdown of the stator turn insulation. The offline surge test is the most commonly used offline test to assess the condition of the turn insulation. There is no online monitoring method that is applicable to low-voltage machines and has the same capabilities as the surge test. This paper introduces new concepts to implement an online surge test. The possibilities and limitations of the online surge test are presented, as well as the simulation and experimental results, to validate the concepts.
A new method using the analytic wavelet transform of the stator-current signal is proposed for de... more A new method using the analytic wavelet transform of the stator-current signal is proposed for detecting dynamic eccentricity in brushless direct current (BLDC) motors operating under rapidly varying speed and load conditions. As wavelets are inherently suited for nonstationary signal analysis, this method does not require the use of any windows, nor is it dependent on any assumption of local stationarity as in the case of the short-time Fourier transform. The proposed technique uses analytic wavelets, which are smooth wavelets that possess both magnitude and phase information. This makes them particularly suitable for motorfault diagnostics. Experimental results are provided to show that the proposed method works over a wide speed range of motor operation and provides an effective and robust way of detecting rotor faults such as dynamic eccentricity in BLDC motors.
Most researchers characterize brake squeal as a vibration of the brake rotor that produces an irr... more Most researchers characterize brake squeal as a vibration of the brake rotor that produces an irritating noise to automobile passengers. Recently, the concept of dither control was successfully used to suppress the resonant vibration of components of a brake system, thereby eliminating its acoustic disturbance. Dither control is a high frequency periodic disturbance signal introduced into a brake system to quench friction-induced oscillations. This paper presents results of the measurement of dynamic forces transmitted to the inboard pad of a floating caliper brake system during suppression of squeal using dither control. A stack of piezoelectric elements was placed inside the brake piston to induce a high frequency displacement to the inboard pad. A 20 kHz voltage was applied over the piezoelectric stack to dither the brake's normal clamping force. Measurements of the dynamic force transmitted to the brake pad were made with a load cell that was placed in line with the stack inside the caliper. The dynamic force was measured during squeal and during its control. Squeal suppression through dither control typically required the application of a 200 Newton modulation to the static normal force.
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