Showing papers in "IEEE Transactions on Industrial Electronics in 1996"

Pulsating torque minimization techniques for permanent magnet AC motor drives-a review

Abstract: Permanent magnet AC (PMAC) motor drives are finding expanded use in high-performance applications where torque smoothness is essential. This paper reviews a wide range of motor- and controller-based design techniques that have been described in the literature for minimizing the generation of cogging and ripple torques in both sinusoidal and trapezoidal PMAC motor drives. Sinusoidal PMAC drives generally show the greatest potential for pulsating torque minimization using well-known motor design techniques such as skewing and fractional slot pitch windings. In contrast, trapezoidal PMAC drives pose more difficult trade-offs in both the motor and controller design which may require compromises in drive simplicity: and cost to improve torque smoothness. Controller-based techniques for minimizing pulsating torque typically involve the use of active cancellation algorithms which depend on either accurate tuning or adaptive control schemes for effectiveness. In the end, successful suppression of pulsating torque ultimately relies on an orchestrated systems approach to all aspects of the PMAC machine and controller design which often requires a carefully selected combination of minimization techniques.

Genetic algorithms: concepts and applications [in engineering design]

Abstract: This paper introduces genetic algorithms (GA) as a complete entity, in which knowledge of this emerging technology can be integrated together to form the framework of a design tool for industrial engineers. An attempt has also been made to explain "why" and "when" GA should be used as an optimization tool.

Phase-locked loop techniques. A survey

Abstract: Phase-locked loop (PLL) is a technique which has contributed significantly toward the technology advancement in communication and motor servo control systems in the past 30 years. Inventions in PLL schemes combined with novel integrated circuit (IC) technology have made PLL devices important system components. The development of better modular PLL ICs is continuing. As a result, it is expected that they will contribute to the improvement in performance and reliability of future communication systems. They will also contribute to the development of higher accuracy and higher reliability servo control systems, such as those involved in machine tools. This paper provides a concise review of the basic PLL principles applicable to communication and servo control systems, gives the configurations of PLL applications and reports a number of popular PLL chips.

Robust motion controller design for high-accuracy positioning systems

Abstract: This paper presents a controller structure for robust high speed and accuracy motion control systems. The overall control system consists of four elements: a friction compensator; a disturbance observer for the velocity loop; a position loop feedback controller; and a feedforward controller acting on the desired output. A parameter estimation technique coupled with friction compensation is used as the first step in the design process. The friction compensator is based on the experimental friction model and it compensates for unmodeled nonlinear friction. Stability of the closed-loop is provided by the feedback controller. The robust feedback controller based on the disturbance observer compensates for external disturbances and plant uncertainties. Precise tracking is achieved by the zero phase error tracking controller. Experimental results are presented to demonstrate performance improvement obtained by each element in the proposed robust control structure.

Sensorless PM brushless DC motor drives

Abstract: To control PM brushless DC motors, position and speed sensors are indispensable because the current should be controlled depending on the rotor position. However, these sensors are undesirable from standpoints of size, cost, maintenance, and reliability. There are different ways of approaching this problem, depending on the flux distribution. The paper presents the speed and position sensorless control of PM brushless DC motors with a sinusoidal flux distribution. Two approaches are presented and compared with each other; one is based on the voltage model of the motor and another is based on the current model. The starting procedure is also a very difficult problem under sensorless drives, because the sensorless drive algorithm uses voltage and current for estimation of rotor position, but no information is available before starting. A novel starting method is presented by using a salient-pole machine. Experimental results based on DSP-TMS320C25 controller are shown for comparisons, which demonstrate desired characteristics both in steady-state and starting conditions.

Identification and compensation of torque ripple in high-precision permanent magnet motor drives

Abstract: Permanent magnet synchronous machines generate parasitic torque pulsations owing to distortion of the stator flux linkage distribution, variable magnetic reluctance at the stator slots, and secondary phenomena. The consequences are speed oscillations which, although small in magnitude, deteriorate the performance of the drive in demanding applications. The parasitic effects are analyzed and modeled using the complex state-variable approach. A fast current control system is employed to produce high-frequency electromagnetic torque components for compensation. A self-commissioning scheme is described which identifies the machine parameters, particularly the torque ripple functions which depend on the angular position of the rotor. Variations of permanent magnet flux density with temperature are compensated by on-line adaptation. The algorithms for adaptation and control are implemented in a standard microcontroller system without additional hardware. The effectiveness of the adaptive torque ripple compensation is demonstrated by experiments.

Analysis of brushless permanent magnet synchronous motors

Abstract: A brief design review of permanent magnet synchronous motors has been presented. A procedure has been developed to predict the steady state and dynamic performances of a brushless permanent magnet synchronous motor. Finite element analysis has been combined with a lumped parameter circuit model in order to provide satisfactory engineering information. To this end, two coordinated steps are involved. One is to develop a unified lumped parameter circuit model for both steady state and dynamic analysis. The second step is to extract the individual lumped parameters from finite element solutions based on corresponding equivalent circuits, each with a pre-determined topology. The proposed techniques have been experimentally verified in a laboratory permanent magnet synchronous motor.

Loss minimization in induction motor adjustable-speed drives

Abstract: A loss model controller (LMC) for determining the optimal air-gap flux that minimizes the losses in scalar controlled induction motor drives is presented. The suggested LMC is simple, and its implementation does not affect significantly the cost and the complexity of the drive. Although the conception of the suggested LMC is based on the loss model of the induction motor, it is shown that its realization does not require knowledge of the loss model.

Vibration suppression in 2- and 3-mass system based on the feedback of imperfect derivative of the estimated torsional torque

Abstract: In this paper, a new vibration-suppression control method for 2- and 3-mass system is proposed, which uses imperfect derivative feedback of the estimated torsional torque. This controller consists of three simple elements: the disturbance observer, the imperfect derivative filter, and the feedback gain. By adequately adjusting this feedback gain, the damping factor of original flexible system can be controlled so that the vibration caused by the mechanical resonance can be effectively suppressed. Due to the simplicity of the proposed controller, it can be easily applied to various flexible systems with other regulators. The combination of this method with P&I regulator shows good performances in vibration suppression and disturbance rejection which are shown in both simulations and experiments.

Novel permanent magnet motor drives for electric vehicles

Abstract: Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electromagnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described.

A nonlinear reduced order observer for permanent magnet synchronous motors

Abstract: This paper introduces a nonlinear reduced order observer for speed and rotor position estimation in permanent magnet synchronous motors (PMSMs). The observer is based on a model of the motor represented by stationary two-axes coordinates. The theoretical principles of the proposed observer are discussed. Sufficient conditions for convergence as well as convergence speed are established. The observer is designed and tested by simulation. The results show that the observer gives a good estimation of speed and rotor position. In addition, it has low sensitivity to torque disturbances and perturbations of the mechanical parameters.

Remarks on Discrete-time Variable Structure Control Systems

Abstract: In this note we point out that the control law for uncertain systems, which was introduced by W. Gao et al. in [1], does not guarantee existence of a quasi-sliding mode and does not satisfy the so-called reaching condition defined by the authors. We show that an additional inequality must hold in order to satisfy the condition. We also consider the control law presented in the same paper for the nominal system and we show that the region in the state space, within which the system's state remains in the steady-state is evaluated by the authors too conservatively.

A simple frequency-independent method for calculating the reactive and harmonic current in a nonlinear load

Abstract: A basic criterion that determines the behavior of an active power filter is the method of calculating the reference current. There are many ways of generating this reference, but the methods are generally complex and hard to tune. This paper describes a simple and effective method for calculating the reference current necessary to feed a shunt active power filter to compensate the power factor and harmonic currents generated by a nonlinear load. Simulations and experimental results are presented, showing that the proposed circuit may operate at frequencies ranging from 40 to 65 Hz without adjustment.

A fuzzy-logic architecture for autonomous multisensor data fusion

Abstract: Fuzzy logic techniques have become popular to address various processes for multisensor data fusion. Examples include the following: (1) fuzzy membership functions for data association; (2) evaluation of alternative hypotheses in multiple hypothesis trackers; (3) fuzzy-logic-based pattern recognition (e.g., for feature-based object identification); and (4) fuzzy inference schemes for sensor resource allocation. These approaches have been individually successful but are limited to only a single subprocess within a data fusion system. At The Pennsylvania State University, Applied Research Laboratory, a general-purpose fuzzy-logic architecture has been developed that provides for control of sensing resources, fusion of data for tracking, automatic object recognition, control of system resources and elements, and automated situation assessment. This general architecture has been applied to implement an autonomous vehicle capable of self-direction, obstacle avoidance, and mission completion. The fuzzy logic architecture provides interpretation and fusion of multisensor data (i.e., perception) as well as logic for process control (action). This paper provides an overview of the fuzzy-logic architecture and a discussion of its application to data fusion in the context of the Department of Defense (DoD) Joint Directors of Laboratories (JDL) Data Fusion Process Model. A new, robust, fuzzy calculus is introduced. An application example is provided.

A new motor speed estimator using Kalman filter in low-speed range

Abstract: In this paper, a new machine drive technique using novel estimation strategy for the very low-speed operation to estimate both the instantaneous speed and disturbance load torque is proposed. In the proposed algorithm, a Kalman filter is incorporated to estimate both the motor speed and the disturbance torque. The Kalman filter is an optimal state estimator and is usually applied to a dynamic system that involves a random noise environment. The effects of parameter variations are discussed, and it is verified that the system is stable to the modeling error. Experimental results confirm the validity of the proposed estimation technique.

A 50-150 kHz half-bridge inverter for induction heating applications

Abstract: A half-bridge resonant-type IGBT inverter suitable for heating magnetic and nonmagnetic materials at high-frequency is described A series-parallel arrangement of capacitors is adopted and an optimum mode of operation is proposed In this mode, the inverter is operated at unity power factor by PLL control irrespective of load variations, with maximum current gain, maximum overall system efficiency, and practically no voltage spikes in the devices at turn-off The actual performance was tested on a 50-150 kHz prototype rated at 6 kW The low-cost developed hybrid inverter is characterized by its simplicity of design and operation, yet is versatile in performance A simplified analysis and detailed experimental results are presented

Design and analysis of permanent magnet-type bearingless motors

Abstract: Magnetic bearings have been applied to high speed and high power electric machines for machine tools, turbomolecular pumps, etc. Bearingless motors can be expected to realize high speed and high power ratings because magnetic bearing functions are integrated into high-speed motors, which results in a simplified structure with short shaft length. In this paper, permanent magnet type bearingless motors, having built-in capability to achieve high power factor and high efficiency, are proposed. The shaft is suspended and centered by electromagnetic forces produced by currents in the additional radial force windings of the stator slots. At first the relationships of these radial forces, currents and voltages are derived analytically. Moreover, the relationships between radial forces and permanent magnet thickness are found. The optimal permanent magnet thickness is determined. The ratio of radial force over current as well as the peak air-gap flux density are discussed. These relationships are confirmed by prototype machines.

DSP control of high-power UPS systems feeding nonlinear loads

Abstract: Many facilities, such as patient health care centers, data processing systems, and critical telecommunication links, rely on uninterruptible power supplies (UPS) to maintain a continuous supply of power in case of a line outage. In addition to requiring continuous power, many critical nonlinear loads are sensitive to incoming line transients and input harmonic voltage distortion. Conventional UPS systems operate to protect against such disturbances using complex filtering schemes, often employing large passive components. This paper presents the advantages of using real time digital signal processing (DSP) control of UPS systems. A DSP controlled UPS inverter and harmonic conditioning system is described and the performance is verified on a 150 kVA system.

Mode switching control design with initial value compensation and its application to head positioning control on magnetic disk drives

Abstract: To meet an increasing demand for high performance and large-capacity in magnetic hard disk drives, both fast response and precise positioning are strongly required for the head positioning control. A mode switching control (MSC) system, which includes a track seeking controller, a track following controller, and a switching function, is widely used to meet this requirement. The issue for MSC is to confirm a design method of servo mode switching. This paper proposes the initial value compensation method (IVC). The IVC inputs certain initial values in the controller state variables at mode switching in order to improve the transient response after switching. There are two approaches to determine the values: (1) minimizing a linear-quadratic function of the plant state variables; and (2) cancelling the unfavorable poles of the transfer function between initial values and head position by relocating zeros. Some experimental results are shown to be effective.

Multiobjective gas turbine engine controller design using genetic algorithms

Abstract: This paper describes the use of multiobjective genetic algorithms (MOGAs) in the design of a multivariable control system for a gas turbine engine. The mechanisms employed to facilitate multiobjective search with the genetic algorithm are described with the aid of an example. It is shown that the MOGA confers a number of advantages over conventional multiobjective optimization methods by evolving a family of Pareto-optimal solutions rather than a single solution estimate. This allows the engineer to examine the trade-offs between the different design objectives and configurations during the course of an optimization. In addition, the paper demonstrates how the genetic algorithm can be used to search in both controller structure and parameter space thereby offering a potentially more general approach to optimization in controller design than traditional numerical methods. While the example in the paper deals with control system design, the approach described can be expected to be applicable to more general problems in the fields of computer aided design (CAD) and computer aided engineering (CAE).

Mobile robot localization: integrating measurements from a time-of-flight laser

Abstract: This paper presents an algorithm for environment mapping by integrating scans from a time-of-flight laser and odometer readings from a mobile robot. The range weighted Hough transform (RWHT) is used as a robust method to extract lines from the range data. The resulting peaks in the RWHT are used as feature coordinates when these lines/walls are used as landmarks during navigation. The associations between observations over the time sequence are made in a systematic way using a decision directed classifier. Natural geometrical landmarks are described in the robot frame together with a covariance matrix representing the spatial uncertainty. The map is thus built up incrementally as the robot moves. If the map is given in advance, the robot can find its location and navigate relative to this a priori given map. Experimental results are presented for a mobile robot with a scanning range measuring laser having 2-cm resolution. The algorithm was also used for an autonomous plastering robot on a construction site. The sensor fusion algorithm makes few erroneous associations.

Genetic optimization of a fuzzy system for charging batteries

Abstract: A large variety of nickel-cadmium (Ni-Cd) batteries have been developed to meet a wide range of user needs, ranging from low-current-level uses like emergency power sources for semiconductor memories to very high-power applications such as motor-operated cordless drills. This paper presents a genetic algorithm approach to optimize a fuzzy rule-based system for charging such high-power Ni-Cd batteries. For the optimization of the fuzzy system, a special objective function is developed which is based on the entropy of a fuzzy system. The resulting fuzzy system is able to charge high-power Ni-Cd batteries in about 10 min with a current of 6 A.

A novel fuzzy friction compensation approach to improve the performance of a DC motor control system

Abstract: The compensation of friction nonlinearities for servomotor control has received much attention due to undesirable and disturbing effects that the friction often has on conventional control systems. Compensation methods have generally involved selecting a friction model and then using model parameters to cancel the effects of the nonlinearity. In this paper, a method using fuzzy logic for the compensation of nonlinear friction is developed for the control of a DC motor. The method is unique in that a single fuzzy rule is used to compensate directly for the nonlinearity of the physical system. As a result, the method introduces fewer adjustable parameters than a typical fuzzy logic approach while still incorporating many advantages of using fuzzy logic such as the incorporation of heuristic knowledge, ease of implementation and the lack of a need for an accurate mathematical model. The general approach, analysis and experimental results obtained for an actual DC motor system with nonlinear friction characteristics are presented and the effectiveness of the fuzzy friction compensation control technique is discussed. The smoothness of response, response times and disturbance rejection of a PI control system with and without the proposed fuzzy compensator are analyzed and discussed to illustrate the effectiveness of the proposed method.

Environment perception for a mobile robot using double ultrasonic sensors and a CCD camera

Abstract: To move efficiently in an unknown or uncertain environment, a mobile robot must use observations taken by various sensors to construct information for path planning and execution. A reasonably accurate representation of the external world would also be very useful for robot self-localization. One of the merits of applying multiple sensors to a mobile robot is the enhancement of environment recognition. In this paper, the authors propose to use sensory information combined from double ultrasonic sensors and a CCD camera. They developed an algorithm based on a dual-transducer design to eliminate errors resulting from the beam opening angle of ultrasonic sensors. An extended discrete Kalman filter (EDKF) was designed to fuse raw sensory data and to reduce the influence of specular reflection of ultrasonic type transducers, thereby providing a more reliable representation for environment perception. Computer simulation, as well as practical experimental results demonstrate that this sensory system can provide useful and comprehensive environment perception for intelligent robotics.

Stable adaptive control of multivariable servomechanisms, with application to a passive line-of-sight stabilization system

Abstract: This paper considers the problem of controlling multivariable servomechanisms where there exist cross-couplings, or interactions, between the axes. An adaptive control strategy using a feedforward paradigm is proposed, and by incorporating direct adaptive methodologies, it is shown in the paper that uniformly stable operation is achieved together with asymptotic tracking of the reference command signals. In the paper, real-time experimental results in applying the proposed adaptive controller to a passive line-of-sight stabilization system are presented which demonstrates the effectiveness of the adaptive controller, and provides experimental verification of the main analytical results.

A new control strategy to achieve sinusoidal line current in a cascade buck-boost converter

Abstract: This work presents a detailed theoretical analysis and experimental results of a novel means of obtaining sinusoidal input current and unity power factor (UPF) via a cascade buck-boost power converter. Using the new configuration, sinusoidal line current in phase with the bus voltage is achieved, thanks to a new and simple to implement control strategy. Comparison between the input and output voltages is used to select the instantaneous operating mode of the converter. Offline references are calculated and stored in two EPROM circuits and then compared to measured currents to generate the gating signals of the appropriate switches. Complete theoretical analysis, simulation results and experimental data on a 500 W power converter are presented, to demonstrate the superiority of the new control strategy. Low order harmonics in the input current are eliminated and the input power factor is found to be over 0.99.

Improvement of transient response by means of variable set point weighting

Abstract: A new approach is introduced for speeding up the transient set point response of a control system by adapting the set point weighting factor in the controller. For a proportional-integral-derivative (PID) controller, the initial set point weighting factor, the instants at which this factor should be varied, and the adapted value of the set point weighting factor are all given by a set of correlation formulae which can be used in conjunction with the refined Ziegler-Nichols tuning formula. Analysis has also led to an equivalent block diagram more suitable for its implementation as a set point filter with a variable zero in its transfer function.

Genetic algorithm tuning of Lyapunov-based controllers: an application to a single-link flexible robot system

Abstract: In this paper, a systematic controller design approach is proposed to guarantee both closed-loop stability and desired performance of the overall system by effectively combining genetic algorithms (GAs) with Lyapunov's direct-controller design method. The effectiveness of the approach is shown by using a simple and efficient decimal GA optimization procedure to tune and optimize the performance of a Lyapunov-based robust controller for a single-link flexible robot. The feedback gains of the controller are tuned by the GA optimization process to achieve good results for tip motion control of the single-link flexible robot based on some suitable fitness functions. The paper includes results of simulation experiments demonstrating the effectiveness of the proposed genetic algorithm approach.

Structured genetic algorithm for robust H/sup /spl infin// control systems design

Abstract: A structured genetic algorithm (SGA) approach is developed for robust controller design based on the concept of an H/sup /spl infin// loop-shaping technique and the method of inequalities. Such an SGA is capable of simultaneously searching the orders and coefficients of the precompensator and postcompensator for the weighted plant. It is, therefore, not necessary to predefine the order of compensators as in usual practice. A multiple objective ranking approach is also incorporated so that the design criteria of extreme plants can be easily achieved. The effectiveness of such a technique is illustrated by a high-purity distillation column design example.

ASIC implementation of a digital tachometer with high precision in a wide speed range

Abstract: A common method in adjustable speed drives uses an incremental shaft encoder and an electronic circuit for velocity estimation. The usual method of counting pulses coming from the encoder in a fixed period of time produces a high-precision velocity estimate in the high-speed range. High precision in the low-speed range can be achieved measuring the elapsed time between two successive pulses coming from the encoder. In this paper, a mixed method that combines the best of the two previously mentioned approaches has been implemented using a simple electronic circuit based on one field-programmable gate array (FPGA) and one read-only memory (ROM).