Fuzzy two-degrees-of-freedom speed controller for motor drives

A fuzzy two-degrees-of-freedom (2-DOF) controller and its application to the speed control of an induction motor drive are presented in this paper. The proposed controller is composed of two fuzzy controllers to obtain good tracking and regulating responses. Unlike the conventional fuzzy controller, the error between the outputs of a reference model and the controlled drive is used to drive the proposed fuzzy controller. The drive rotor speed response can closely follow the trajectory produced by the reference model, and good load speed regulating response can also be obtained simultaneously owing to the possession of two-degrees-of-freedom in structure. Moreover, these performances are rather insensitive to the operating condition changes. The dynamic signal analysis as well as the construction of fuzzy control algorithms are described in detail. Some simulated and measured results are provided to demonstrate the effectiveness of the proposed fuzzy controller     

A robust adaptive controller for PM motor drives in roboticapplications

The paper deals with theoretical development and practical implementation of an adaptive speed and position regulator suitable for robotic applications. The proposed adaptive control scheme is characterized by a reduced amount of computation and is based on the model reference adaptive control approach to compensate the variations of the system parameters, such as inertia and torque constant. A disturbance torque observer is employed to balance the required load torque and reduce the complexity of the adaptive algorithm. Simulation tests of a robotic drive, including an interior type permanent magnet synchronous (IPMS) motor, are reported in order to compare the proposed control scheme with standard speed and position regulators. Experimental results, obtained from a prototype based on a commercial PC board, are also reported in order to practically evaluate the feasibility and the features of the proposed adaptive control scheme     

A deadbeat current controller for field oriented induction motor drives

Accurate stator current control is essential in high performance field orientation-controlled induction motor drives. Any current error degrades the drive's performance in the same way as an incorrectly tuned field orientation. This paper presents an efficient current control scheme that can achieve high accuracy and a fast dynamic response. This scheme uses voltage decoupling and deadbeat control loops. The decoupling controller provides the voltage needed to oppose the motor's back EMF. The deadbeat controller reduces the current error as fast as possible and stabilizes the system. The control law does not require knowledge of the rotor flux and is independent of the field orientation control tuning. Good static and dynamic performances were obtained in both the simulation and experimental verifications. Because the motor leakage inductance and resistance information were required for this control method, the influence of the estimation errors for these parameters was also investigated. The results show that the leakage inductance model error might cause a current ripple. However, this parameter can be tuned to its correct value easily by inspecting the current response.     

A direct field-oriented controller for induction motor drives usingtapped stator windings

The implementation of a direct method of field orientation that requires little knowledge of machine parameters and uses only readily measurable quantities is discussed. The system uses tapped stator windings to measure the air-gap flux. The signals from the tapped windings are also used in a flux-regulation loop. A speed controller is implemented using the ripples created in the tapped windings by the motion of the rotor slots through the flux for speed information     

A hybrid speed estimator of flux observer for induction motor drives

This paper proposes a hybrid speed estimator that gives the synergetic effect between the model- and the saliency-based field orientations for induction motor drives. The model-based field orientation consists of a flux observer with an adaptive speed estimator that has unstable regions at zero frequency and zero speed. Saliency-based flux orientation utilizes magnetic saliencies caused by saturation and high-frequency injection that causes the torque ripples due to the chattering. The chattering is caused by the higher cutoff frequency of the flux-angle estimation to keep its high dynamics. The proposed method compensates both faults and realizes complete speed estimation from zero to high-speed condition including zero stator frequency.     

Adaptive speed control for induction motor drives using neuralnetworks

In this paper, the adaptive speed control of induction motor drives using neural networks is presented. To obtain good tracking and regulating control characteristics, a digital two-degree-of-freedom (2DOF) controller is adopted and a design procedure is developed for systematically finding its parameters according to prescribed specifications. The parameters of the controller corresponding to various drive parameter sets are found off-line and used as the training patterns to estimate the connection weights of neural networks, Under normal operation, the true drive parameters are real-time identified and they are converted into the controller parameters through multilayer forward computation by neural networks. The parameters of the 2DOF controller can be adapted to match the desired specifications under various operating conditions     

New hybrid fuzzy controller for direct torque control induction motor drives

A new hybrid fuzzy controller for direct torque control (DTC) induction motor drives is presented in this paper. The newly developed hybrid fuzzy control law consists of proportional-integral (PI) control at steady state, PI-type fuzzy logic control at transient state, and a simple switching mechanism between steady and transient states, to achieve satisfied performance under steady and transient conditions. The features of the presented new hybrid fuzzy controller are highlighted by comparing the performance of various control approaches, including PI control, PI-type fuzzy logic control (FLC), proportional-derivative (PD) type FLC, and combination of PD-type FLC and I control, for DTC-based induction motor drives. The pros and cons of these controllers are demonstrated by intensive experimental results. It is shown that the presented induction motor drive is with fast tracking capability, less steady state error, and robust to load disturbance while not resorting to complicated control method or adaptive tuning mechanism. Experimental results derived from a test system are presented confirming the above-mentioned claims.     

Current sensorless position–flux tracking controller for induction motor drives

An innovative indirect field-oriented output feedback controller for induction motor drives is presented. This solution is based on output feedback since only speed and position of the motor shaft are measured, while current sensors are avoided. This approach is suitable for low cost applications, where the position sensor cannot be removed to guarantee accurate position tracking.The proposed method provides global asymptotic tracking of smooth position and flux references in presence of unknown constant load torque. It is based on the natural passivity of the electromagnetic part of the machine and it guarantees asymptotic decoupling of the induction motor mechanical and electrical subsystems achieving at the same time asymptotic field orientation. Lyapunov analysis and nonlinear control design have been adopted to obtain good position tracking performances and effective torque–flux decoupling. The cascaded structure of the controller allows performing a constructive tuning procedure for speed and position control loops.Results of experimental tests are presented to demonstrate the tracking and robustness features of the proposed solution.     

Low-frequency signal-demodulation-based sensorless technique for induction motor drives at low speed

The paper presents a method to compute the air-gap flux position in induction motors at very low including zero-stator frequency. A low-frequency (50 /spl divide/ 100 Hz) sinusoidal stationary signal is added to the normal stator variables to provide the machine with a suitable permanent excitation. Such an additional excitation modulates the saturation level of the magnetic core of the machine according to the angular position of the air-gap flux. As a result, a new zero-sequence stator-voltage component is generated that contains useful information about the position of the air-gap flux unaffected by load variation. Such a zero-sequence voltage can be easily employed to provide a wide bandwidth measurement of the air-gap flux position. A key feature of the proposed approach is that a low-frequency (0 /spl divide/ 5 Hz) signal is demodulated, thus avoiding any drawback featured by previous sensorless techniques operating with high-frequency signal injection.     

New antiwindup PI controller for variable-speed motor drives

The windup phenomenon appears and results in performance degradation when the proportional-integral (PI) controller output is saturated. A new antiwindup PI controller is proposed to improve the control performance of variable-speed motor drives, and it is experimentally applied to the speed control of a vector-controlled induction motor driven by a pulsewidth modulated (PWM) voltage-source inverter (VSI). The integral state is separately controlled, corresponding to whether the PI controller output is saturated or not. The experimental results show that the speed response has much improved performance, such as small overshoot and fast settling time, over the conventional antiwindup technique. Although the operating speed command is changed, similar control performance can be obtained by using the PI gains selected in the linear region     

A microprocessor-controlled speed regulator with instantaneousspeed estimation for motor drives

A method for estimating instantaneous speed, suited for a microprocessor-based speed regulator for motor drives, and the characteristics of the speed control system are described. Features of the proposed method include the estimation of instantaneous speed at a real-time point using values of average speed detected by counting for a certain time the output pulses of an encoder as well as the estimated value as the speed feedback signal for the speed regulator. Since this method allows compensation to be made for the lag time of the feedback signal caused by detection of the mean value, it contributes to improved stability of the speed regulator. In particular, this provides a significant suppression of the vibrations that are generated in motor-driven machinery     

Quick-response torque-controlled induction motor drives usingphase-locked loop speed control with disturbance compensation

This paper presents an excellent speed control scheme for induction motor drives. Phase-locked loop (PLL) techniques based on proportional-integral derivative (PID) feedback of the phase difference is employed to provide extremely accurate speed regulation. The quick-response torque control of an induction motor is used to provide better torque characteristics. In addition, a disturbance is estimated by a disturbance observer and the estimated value is fed back to eliminate the disturbance effect on the motor speed. The proposed system combines the precise speed regulation of PLL technique and the advantage of the quick-response torque control, with the insensitivity to disturbance by the disturbance compensation. A phase-plane analysis is used to evaluate the effects of gain coefficients of PID feedback of phase difference. Experimental results are presented to verify the characteristics of the proposed system     

A pulse frequency modulated PWM inverter for induction motor drives

A PWM pulse pattern optimization method using pulse frequency modulation (PFM) is described. In conventional PWMs the pulse frequency is kept constant. In the proposed PFM, however, the pulse frequency is adjusted. The PFM technique is intended to not only reduce the magnetic acoustic noises of driven motors but also to improve the performance of sinusoidal inverters. The PWM pulse patterns are basically controlled so that the time-integral function of the voltage vectors in the space vector notation may draw a circular locus. In addition to this, the pulse frequency, of PWM is also controlled so that the performance index (PI), which represents the degree of achieved objectives, may be minimized. Two PIs, one for minimizing the distortion of output currents and the other for minimizing the torque pulsation of driven motors, are employed. The method is implemented using a single-chip microprocessor, and the experimental results demonstrate its validity     

A digital current control technique for voltage-fed induction motor drives

Precise control of stator current is essential to high performance field orientation controlled induction motor drives. Any current error degrades the performance of the drive in the same way as incorrect tuning of field orientation. Previous research has shown that accurate current control can be achieved with intelligent but complex control algorithms. This paper presents a new current control scheme which can achieve high accuracy and fast dynamic response but which is very simple for microprocessor implementation. The scheme was derived using the discrete state space modelling of the induction motor. The control law does not require knowledge of rotor flux and was independent of the field orientation control tuning. Good static and dynamic performances were obtained in both the simulation and experimental verifications. The results also show that the leakage inductance model error might cause a current ripple. However, this parameter can be tuned to its correct value easily by inspecting the current response.     

A fault-tolerant control architecture for induction motor drives in automotive applications

This paper describes a fault-tolerant control system for a high-performance induction motor drive that propels an electrical vehicle (EV) or hybrid electric vehicle (HEV). In the proposed control scheme, the developed system takes into account the controller transition smoothness in the event of sensor failure. Moreover, due to the EV or HEV requirements for sensorless operations, a practical sensorless control scheme is developed and used within the proposed fault-tolerant control system. This requires the presence of an adaptive flux observer. The speed estimator is based on the approximation of the magnetic characteristic slope of the induction motor to the mutual inductance value. Simulation results, in terms of speed and torque responses, show the effectiveness of the proposed approach.     

A MRAS-based adaptive pseudoreduced-order flux observer for sensorless induction motor drives

The performance of vector-controlled sensorless induction motor drives is generally poor at very low speeds, especially at zero speed due to offset and drift components in the acquired feedback signals, and the increased sensitivity of dynamic performance to model parameter mismatch resulting especially from stator resistance variations. The speed estimation is adversely affected by stator resistance variations due to temperature and frequency changes. This is particularly significant at very low speeds where the calculated flux deviates from its set values. Therefore, it is necessary to compensate for the parameter variation in sensorless induction motor drives, particularly at very low speeds. This paper presents a novel method of estimating both the shaft speed and stator resistance of an induction motor. In this novel scheme, an adaptive pseudoreduced-order flux observer (APFO) is developed. In comparison to the adaptive full-order flux observer (AFFO), the proposed method consumes less computational time, and provides a better stator resistance estimation dynamic performance. Both simulation and experimental results confirm the superiority of the proposed APFO scheme for a wide range of resistance variations from 0 to 100%.     

Decoupling control of induction motor drives

The decoupling control of induction machines is investigated. Three different schemes for decoupling-control methods based on stator flux, airgap flux, and rotor flux field regulation are developed. The control dynamics of each scheme are outlined and studied. Simulation results are presented to verify that these schemes provide decoupling control with excellent dynamic behavior. The transient and steady-state relationships between slip frequency and torque, under constant stator flux, airgap flux, and rotor flux operations, are simulated and compared. The sensitivity characteristics of the three methods of flux-control, machine fed by impressed currents and voltages, are also compared and studied. A prototype torque-drive system is implemented to demonstrate the decoupling control of a squirrel-cage induction machine     

A newly robust controller design for the position control ofpermanent-magnet synchronous motor

A robust controller which is designed by employing variable-structure control and linear-quadratic method is presented for a permanent-magnet synchronous motor (PMSM) position control system. It is to achieve accurate control performance in the presence of plant parameter variation and load disturbance. In addition, it possesses the design flexibility of the conventional state feedback control. It is applied to the position control of a PMSM. Simulation and experimental results show that the proposed approach gives a better position response and is robust to parameter variations and load disturbance