Analysis of torque ripple due to phase commutation in brushless DC machines
07 Oct 1990-Vol. 28, Iss: 3, pp 632-638
TL;DR: In this paper, an analytical study concerning the torque undulation due to phase commutation on brushless DC motors is presented, showing that the relative ripple is independent of current, varies with speed, and may reach 50% of the average torque.
Abstract: An original analytical study is developed concerning the torque undulation due to phase commutation on brushless DC motors. The results indicate that the relative ripple is independent of current, varies with speed, and may reach 50% of the average torque. The amplitude of the torque undulation and the duration of the commutation are analyzed, showing how this affects the torque-speed curve of the drive. Simulation and experimental results are presented that validate the theoretical analysis. >
Citations
More filters
TL;DR: 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 are reviewed.
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.
978 citations
TL;DR: 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, and is implemented in a standard microcontroller system without additional hardware.
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.
275 citations
Cites background from "Analysis of torque ripple due to ph..."
...The commutation between the stator phase windings requires finite time intervals, during which the torque magnitude changes considerably [1, 2]....
[...]
08 Oct 1995
TL;DR: In this paper, a direct torque controller was proposed to maximize the torque:copper loss ratio, taking account of mutual torque, reluctance torque and saturation effects, in a DSP-based drive system.
Abstract: Many permanent magnet motor drives use an open loop form of torque control, based on the assumption that output torque is proportional to applied current. In a practical motor this assumption may not always be correct, due to suboptimal alignment of magnets, nonuniformity of magnetic material, current sensor nonlinearities, and current controller limitations. These factors, together with nonoptimized current references, can lead to undesirable levels of torque ripple and copper loss. This paper describes a method of estimating the electromagnetic torque from the rate of change of coenergy with respect to position, thus taking account of mutual torque, reluctance torque and saturation effects. The paper shows how the estimator can be used in a direct torque control scheme. The direct torque controller maximizes the torque:copper loss ratio. Implementation of the direct torque controller in a digital signal processor (DSP)-based drive system is described, with steady-state and transient experimental results illustrating the effectiveness of the direct torque control scheme.
246 citations
11 Dec 2006
TL;DR: In this paper, an improved implementation of direct torque control (DTC) to a permanent-magnet brushless dc (BLDC) drive is described, based on the criterion of minimizing the error between the commanded torque and the estimated torque and does not require knowledge of the conduction duration of the three-phase switching mode.
Abstract: This paper describes an improved implementation of direct torque control (DTC) to a permanent-magnet brushless dc (BLDC) drive. The commutation torque ripple, which occurs every 60deg elec. in a conventional three-phase BLDC machine with two-phase 120deg elec. conduction, is reduced by employing a hybrid two- and three-phase switching mode during the commutation periods. It is based on the criterion of minimizing the error between the commanded torque and the estimated torque and does not require knowledge of the conduction duration of the three-phase switching mode. It adaptively adjusts the phase-current waveform to maintain constant electromagnetic torque so that commutation torque ripple, which would have resulted with conventional DTC, particularly at high rotational speeds, is effectively eliminated, as confirmed by both simulations and measurements.
190 citations
Cites background or methods from "Analysis of torque ripple due to ph..."
...Its effectiveness is validated by both simulations and measurements....
[...]
...Torque ripple due to phase current commutation is usually considered to be one of the main drawbacks of BLDC drives, compared to brushless ac (BLAC) drives with sinusoidal back-EMF and current waveforms....
[...]
...In this paper, an improved approach for reducing commutation torque ripple in DTC BLDC drives is proposed....
[...]
01 Aug 1994
TL;DR: In this paper, a review of PMAC machine control techniques for brushless DC and sinusoidal PMAC machines is presented, including sensor elimination techniques and robust servocontrol algorithms.
Abstract: Motion control techniques have been developed to exploit the high efficiency and extremely fast dynamic response capabilities of permanent-magnet AC (PMAC) machines. Control techniques are reviewed separately for the two major classes of PMAC machines referred to as trapezoidal (i.e., brushless DC) and sinusoidal machines. While trapezoidal PMAC machine drives are distinguished by their controls simplicity and minimal sensor requirements, sinusoidal PMAC machine drives offer opportunities for extremely smooth torque production and extended high-speed operating ranges. Advanced PMAC machine control topics including sensor elimination techniques and robust servocontrol algorithms are reviewed, concluding with a discussion of PMAC machine drive application trends. >
188 citations
Cites methods from "Analysis of torque ripple due to ph..."
...Various techniques have been proposed for modifying the current PWM regulation scheme in order to prevent these overcurrents and to reduce the amplitude of the resulting torque transients [lY], [ 20 ]....
[...]
References
More filters
Book•
22 Jun 1989
TL;DR: In this paper, permanent magnet versus electromagnetic excitation slotless motors ripple torque in sinewave motors is discussed. But the authors focus on brushless d.c. motors with 120 degrees and 180 degrees magnet arcs.
Abstract: Introduction: motion control systems why adjustable speed? structure of drive systems new technology which motor? - the d.c. and PM d.c. commutator motors, the induction motor drive, the brushless d.c. PM and PM a.c. synchronous motors. Part 1 Principles of sizing, gearing and torque production: sizing an electric motor choice of gear ratio in geared drives basic principles of torque production. Part 2 Permanent-magnet materials and circuits: B-H loop and demagnetization characteristics temperature effects - reversible and irreversible losses mechanical properties, handling and magnetization application of permanent magnets in motors. Part 3 Squarewave permanent-magnet brushless motor drives: why brushless d.c.? magnetic circuit analysis on open-circuit squarewave brushless motor - torque and e.m.f. equations torque/speed characteristic - performance and efficiency alternative formulations for torque and e.m.f. motors with 120 degrees and 180 degrees magnet arcs - commutation squarewave motor - winding inductances and armature reaction controllers computer simulation. Part 4 Sinewave permanent-magnet brushless motor drives: ideal sinewave motor - torque, e.m.f. and reactance sinewave motor with practical windings phasor diagram sinewave motor - circle diagram and torque/speed characteristic torque per ampere and kVa/kW of squarewave and sinewave motors permanent magnet versus electromagnetic excitation slotless motors ripple torque in sinewave motors. Part 5 Alternating-current drives with PM and synchronous-reluctance hybrid motors: rotors A.c. windings and inductances steady-state phasor diagram circle diagram and torque-speed characteristic cage-type motors. Part 6 Switched reluctance drives: the switched reluctance motor poles, phases and windings static torque production partition of energy and the effects of saturation dynamic torque production converter circuits control, current regulation, commutation solid rotors.
950 citations
TL;DR: A phase variable model of the BDCM is developed and used to examine the performance of a BDCm speed servo drive system when fed by hysteresis and pulsewidth-modulated (PWM) current controllers, indicating that the small- and large-signal responses are very similar.
Abstract: For ptI see ibid, vol25, no2, p265-73 (1989) The authors develop a phase variable model of the BDCM (brushless DC motor) and use it to examine the performance of a BDCM speed servo drive system when fed by hysteresis and pulsewidth-modulated (PWM) current controllers Particular attention was paid to the motor large-signal and small-signal dynamics and motor torque pulsations The simulation included the state-space model of the motor and speed controller and real-time model of the inverter switches Every instance of a power device turning on or off was simulated to calculate the current oscillations and resulting torque pulsations The results indicate that the small- and large-signal responses are very similar This result is only true when the timing of the input phase currents with the back EMF (electromotive force) is correct The large-signal and small-signal speed response is the same whether PWM or hysteresis current controllers are used This is because, even though the torque pulsations may be different due to the use of different current controllers, the average value which determines the overall speed response is the same >
672 citations
TL;DR: In this article, the angular width of the magnet relative to the tooth-plus-slot dimension is chosen to reduce the cogging torque in a permanent magnet motor, which arises from the interaction of the rotor magnets with the steel teeth on the stator.
Abstract: Cogging torque in a permanent magnet motor, which arises from the interaction of the rotor magnets with the steel teeth on the stator, can be reduced by skewing the stator teeth, but only at the expense of added complexity in stator construction and some loss of output torque. It is shown that by appropriate choice of the angular width of the magnet relative to the tooth-plus-slot dimension, the cogging torque can be reduced to about 1% of rated torque. A further reduction to about 0.3% resulted from a rotational shift of one pair of poles with respect to the other pair in a four-pole motor. The analysis of cogging torques with both surface mounted and inset magnet rotors as well as experimental confirmation are reported. >
372 citations
01 Oct 1989
TL;DR: In this article, the torque ripple attenuation of permanent magnet synchronous motors caused by EMF harmonics and cogging torque is analyzed. Butler et al. analyzed the effect of attenuation methods such as stator slot skewing, permanent magnet shifting and combinations of the two.
Abstract: The authors study the torque ripple attenuation of permanent magnet synchronous motors caused by EMF harmonics and cogging torque. First, the magnet arc influence upon these variables is analyzed. Next, the impact on the harmonic contents caused by attenuation methods such as stator slot skewing, permanent magnet shifting and combinations of the two are presented. The last method makes it possible, using results of the simplest case (nonskewed slots and aligned magnets), to obtain the waveform of the EMF and cogging torque in more complex cases. The best combinations of the magnet arc and harmonic attenuation methods for minimizing electric torque harmonics and cogging torque are suggested. An analysis of cogging torque sensitivity to errors in the slot skewing angle is discussed. >
60 citations
Proceedings Article•
13 Sep 1989
TL;DR: In this paper, the authors deal with permanent magnet machines with rectangular induction and current waveforms and deal with different ways of combining these torque curves so as to come to the best use of the air gap and minimize the resulting torque ripple.
Abstract: The authors deal with permanent magnet machines with rectangular induction and current waveforms. In order to minimize the machine torque ripple, the evolution of the torque curves of the different windings supplied with constant current in function of the position of the rotor, must have a trapezoidal shape comprising a plateau with the correct width. They must be correctly juxtaposed by an adequate choice of the supply sequences. Moreover, in order to get the most out of the torque, an optimal use of the air-gap must be made by making the largest number of conductors work simultaneously. The influence of different parameters on the constant current torque curve shape are examined. The different ways of combining these torque curves are analysed so as to come to the best use of the air-gap and minimize the resulting torque ripple at the same time. >
18 citations