Torque Observer Research Articles

Experimental observation of the optical spin transfer torque

The spin transfer torque is a phenomenon in which angular momentum of a spin polarized electrical current entering a ferromagnet is transferred to the magnetization. The effect has opened a new research field of electrically driven magnetization dynamics in magnetic nanostructures and plays an important role in the development of a new generation of memory devices and tunable oscillators. Optical excitations of magnetic systems by laser pulses have been a separate research field whose aim is to explore magnetization dynamics at short time scales and enable ultrafast spintronic devices. We report the experimental observation of the optical spin transfer torque, predicted theoretically several years ago building the bridge between these two fields of spintronics research. In a pump-and-probe optical experiment we measure coherent spin precession in a (Ga,Mn)As ferromagnetic semiconductor excited by circularly polarized laser pulses. During the pump pulse, the spin angular momentum of photo-carriers generated by the absorbed light is transferred to the collective magnetization of the ferromagnet. We interpret the observed optical spin transfer torque and the magnetization precession it triggers on a quantitative microscopic level. Bringing the spin transfer physics into optics introduces a fundamentally distinct mechanism from the previously reported thermal and non-thermal laser excitations of magnets. Bringing optics into the field of spin transfer torques decreases by several orders of magnitude the timescales at which these phenomena are explored and utilized.

Fuzzy Sliding Mode Speed Controller for PM Synchronous Motors With a Load Torque Observer

This paper investigates the robust stabilization problem of a permanent magnet synchronous motor (PMSM). A fuzzy sliding mode speed controller with a load torque observer is designed, which can effectively mitigate chattering and guarantee robust speed control of a PMSM under model parameter and load torque variations. Furthermore, the proposed control method considers the disturbance inputs representing the system nonlinearity or the unmodeled uncertainty. The proposed control algorithm is implemented using a TMS320F28335 floating point DSP. Finally, simulation and experimental results are presented to validate the effectiveness of the proposed scheme.

Workspace Based Controller Design and Performance Evaluation of MDOF Force Sensorless Bilateral System

SUMMARY Redundant multi-degree-of-freedom (MDOF) bilateral system in workspace is expected to be a key technology for the development of next-generation robots because of the variety of feasible tasks. Nowadays, four-channel bilateral structures based on acceleration control have been introduced to realize both position and force tracking in a bilateral control system. Additionally, torque observers have been implemented to facilitate force feedback without the use of torque/force sensors. However, differences in controller composition between the joint space and workspace are still unclear. In particular, observer designs in both spaces are important for a realization of torque/force sensorless bilateral control. This paper presents a performance evaluation of an MDOF force sensorless bilateral system performed by considering the design space of observers by numerical and experimental analyses. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 70–80, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22481

Modeling and observation of hysteresis lost motion in elastic robot joints

Abstract In this paper the modeling and observation of elastic robot joints with hysteresis is addressed. An adequate model of the joint torque transmission which could capture the hysteresis lost motion is of outstanding interest for design and control of flexible joint robots. A method of describing the significant joint nonlinearities such as dynamic friction and state-dependent stiffness with hysteresis is proposed. The joint dynamics is considered as an interplay between the propulsion and reactive torque. Direct and inverse hysteresis models of state-variant joint stiffness are introduced and identified from experiments. The proposed joint torque observer can serve as a “virtual” sensor of hysteresis lost motion without measuring the joint output.

Robust speed control method for permanent magnet synchronous motor

This study develops a Takagi–Sugeno (T–S) fuzzy model-based robust controller which can precisely track a reference trajectory by cancelling out the effects of unknown external noises and parameter uncertainties on a surface-mounted permanent magnet synchronous motor (SPMSM). Furthermore, the speed tracking control algorithm demands the load torque information, so a simple load torque observer is used to estimate it. The stability of the proposed controller and the load torque observer is mathematically studied. The proposed control scheme is executed on a PMSM drive using a digital signal processor (TMS320F28335). Finally, the simulation and experimental results are presented to verify that the proposed methodology achieves a better robust performance, a less steady-state error and a faster dynamic response than the non-linear control method in the presence of unknown external noises and SPMSM parameter uncertainties.

Robust Performance Analysis of a Load Torque Observer for PMSM Using Singular Perturbation Theory

This paper examines the robust performance of a load torque observer for the position control of a surface-mounted permanent magnet synchronous motor (PMSM) under parameter uncertainties. The load torque observer has been widely employed to compensate for unknown slow-varying disturbances without explicit analysis on the robustness against parameter uncertainties. By using the singular perturbation theory this paper presents an analysis on the robust performance of the load torque observer based on the reduced-order estimator. As the observer poles are placed sufficiently left of the complex plane, the feedforward compensation with estimation can recover nominal system performance without parameter uncertainties and load torque disturbance. An example shows the performance of the load torque observer.

Coordinated Engine Control for Automatic Transmission during the Inertia Phase of Upshifting

Coordinated engine control is an essential method to improve the shift quality.The relationship between the output torque fluctuation of upshifting and shift quality is analyzed.In order to reduce the output torque fluctuation,an output torque observer is designed based on the torque converter model,and then a torque based coordinated engine control strategy is proposed.Finally the experimental study is carried out on the test bench.The experimental results show that the torque response of the diesel engine with electronic unit pump can meet the requirement of coordinated control during the shifting process;and the torque based engine control strategy can make the output torque fluctuation reduced and shift quality improved apparently.

Integrated Powertrain Control for Gear Shifting

Drivability and fuel economy are continuously emphasized during the development of automobiles, and shift quality is the most important part of the drivability. To improve the shift quality, the integrated powertrain control strategy for gear shifting is presented in this paper. First of all, the transmission control strategy based on the turbine speed trajectory is proposed. Furthermore, an output torque observer is determined to implement the coordinated engine control, and then the torque based coordinated engine control is presented. Finally, the integrated powertrain control strategy is studied by experiments. The experimental results show that the integrated powertrain control reduces the shift jerk and the dissipated clutch energy during gear shifting.

MW급 직접구동형 풍력터빈시스템을 위한 영구자석 동기발전기의 게인 스케쥴링 속도제어기에 대한 연구

This paper presents a new gain scheduling speed controller of permanent magnet synchronous generators(PMSG) for MW-class direct-driven wind turbine systems. The proposed gain scheduling speed controller performs the speed tracking at more than one operating point, and the first-order torque observer estimates the turbine torque which is needed to precisely control the speed of PMSG. The proposed speed controller verifies that the PMSG can successfully follow the reference speed which is determined via the maximum power point tracking(MPPT) control and pitch control under turbulent wind conditions. The proposed speed control algorithm is simulated using Simulink and its performance is confirmed through comparison with the results by PI control method.

Robust Control with Input-Output Decoupling Technique for an Interior Permanent Magnet Synchronous Motor in Electrical Vehicle System

A new interior permanent magnet synchronous motor (IPMSM) control method is presented for electrical vehicle drive system. Based on the differential geometry theory, the nonlinear system is changed into a linear system with input-output decoupling technique. Then, by the maximum torque per ampere (MTPA) control strategy, the output torque of the drive system is added. And then, a load torque observer is designed to resist the variable load. In the end, Based on the linearization model, an controller is given. Simulation results show that the electrical vehicle drive system based on decoupling robust control has fast transient responses, good load disturbance resistance responses and good tracking responses.

Geared PM coreless motor modelling for driver’s force feedback in steer-by-wire systems

Gearboxes allow for changes in the motor’s torque and speed ranges, thus allowing the motor to function at its best operation ranges. As a consequence, smaller and low cost motors can be used in comparison with direct drive motors. Nevertheless, gearboxes introduce nonlinearities to the system such as friction, backlash and flexibility. When geared motors are employed, a controller using a torque sensor or a torque observer is normally required to compensate for the drawbacks associated with the gearbox and the servo-amplifier. The design of such a controller requires the comprehensive knowledge of the system’s dynamics. In this paper, a general approach to model accurately amplifier–motor–gearbox assemblies has been developed. This approach that takes into account backlash, flexibility, friction for stiction and sliding, identification procedures, is applicable to a wide range of amplifier–motor–gearbox assemblies. It is explained by applying it to a particular case: an amplifier–motor–gearbox assembly for a driver’s force feedback system. In the design of driver’s force feedback systems for steer-by-wire systems or for high fidelity Human in the Loop (HiL) driving simulators, either direct drive motors or geared motors are used, independently of the motor type. The assembly considered here is composed of a two stage planetary gearbox, a coreless PMDC motor and a linear four quadrant servo-amplifier. It is installed in an X-by-wire (XBW) vehicle prototype, Both the amplifier and the mechanical components were built in the model. The four quadrant operating modes of the amplifier were taken into account. Friction within both the motor and the gearbox are modelled using a modification of the LuGre friction model that allows friction to be considered as load-dependent. Backlash and flexibility in the gearbox are considered together using a fifth order polynomial for each rotational direction. The identification procedures necessary to calculate the parameters of the model are presented. Because all the parameters of the model have a direct physical significance, these identification procedures are easy to realize. Comparisons between simulations realized with Simulink and the experimental data for three typical driving situations show that the model is highly accurate at representing real system dynamics.

Optimization of contact pressure profile for performance improvement of a rotary elastomeric seal operating in abrasive drilling environment

Abstract The magnitude and profile of seal-contact pressure are critical in the sealing performance of downhole equipment being operated in an abrasive drilling environment. Recently, a design analysis was conducted with the assistance of finite element software to visualize the seal contact pressure profile. A set of design criteria was followed to achieve the preferred contact pressure profile for sealing performance improvement. As per the prescribed optimization criteria, a new seal with a unique contact pressure profile was designed and then tested on a rotary seal tester against the benchmark o-ring design. Testing data indicated that the proposed design greatly extended the service life of the sealing system. Seal performance improvement was corroborated by the observation of lower frictional torque, surface temperature, and material loss. Surface wear scars also indicated that the proposed design was more effective in impeding the ingression of abrasive particles than the o-ring seal.

Pulsewidth Modulation Technique for BLDCM Drives to Reduce Commutation Torque Ripple Without Calculation of Commutation Time

This paper presents a three-phase pulsewidth modulation (PWM) technique for brushless dc motor (BLDCM) drives to reduce the commutation torque ripple. As compared to previous approaches, the presented technique does not require any torque observer and calculation of commutation time which may be sensitive to motor parameters and may require more calculation time. The commutation time for the presented technique is determined by a detection circuit which consists of simple comparator circuit. The experimental results derived from a field programmable gate array based controlled BLDCM drive show that the commutation current ripple can be significantly reduced by the presented PWM technique.

Design of nonlinear shaft torque observer for trucks with Automated Manual Transmission

Knowledge of drive axle shaft torque improves the longitudinal dynamic performance of vehicles. An axle shaft torque observer is proposed for vehicles with stepped ratio transmissions, which is a class of switching systems. Model uncertainties, including the steady state error and the unmodeled dynamics, are considered as an additive disturbance input and the observer is designed such that the error dynamics is input-to-state stable for all gear positions. The lowest possible gain of the designed observer is achieved by solving a set of LMIs. In the designed reduced-order observer, the complex nonlinear characteristics of powertrain systems are included and appears as their usual form of MAPs. Finally, the proposed observer is tested on an AMESim powertrain simulation model of a medium-duty truck.

Superior low-speed control of a permanent magnet synchronous motor with digital encoder

Low-speed control is indispensable to several servo applications. Generally, motor speed acquired from the so-called M method is averaged by counting the number of pulses from the encoder at a fixed time period. As a result, a long detection delay, due to speeds lower than the minimum measurable value determined by the sampling frequency and the resolution of the encoder, may degrade the performance or even make systems unstable. In this paper, instead of using disturbance torque observers, a reference model derived from a full-order observer to denote the permanent magnet synchronous motor (PMSM) model is employed to approach instantaneous speed and improve the low-speed control performance. Two structures of model reference control are proposed. A proportional—integral—differential (PID) controller is located on the feedback path for one structure and on the forward path for the other. Additionally, in the latter structure, a composite signal obtained by adding motor speed and the estimated speed timed respective weighting factors is fed back to the input terminal to compare the speed command. This will further improve the performance. A digital signal processor-based drive provides experimental results, which show the improved speed resolution from 7.5 r/min to 1 r/min and the effectiveness of the system with loading.

영구자석 동기전동기를 위한 퍼지 관측기 기반의 퍼지 제어기의 설계 및 안정도 해석

본 논문에서는 영구자석 동기전동기(PMSM)의 강인한 속도 제어를 위하여 퍼지 부하 토크관측기와 퍼지 속도제어기를 제안한다. 또한, 퍼지 부하 토크관측기와 퍼지 속도제어기가 존재하기 위한 LMI 조건을 유도하고, 관측기 및 제어기의 이득을 계산한다. 제안된 제어시스템의 안정도가 보장됨을 해석적으로 증명한다. 본 연구에서 제안된 관측기 기반의 퍼지 속도제어기의 성능을 검증하기 위하여, 시뮬레이션 및 실험 결과가 주어졌다. 본 결과를 통하여 제안된 제어 알고리즘은 영구자석 동기전동기의 속도를 정확하게 제어할 수 있음을 검증하였다. This paper proposes a new fuzzy load torque observer and a fuzzy speed regulator to guarantee a robust speed control of a permanent magnet synchronous motor (PMSM). Also, the LMI conditions are given for the existence of the fuzzy load torque observer and fuzzy speed controller, and the gains of the observer and controller are calculated. The stability of the proposed control system is analytically proven. To validate the effectiveness of the proposed observer-based fuzzy speed controller, the simulation and experimental results are presented. Finally, it is definitely demonstrated that the proposed control algorithm can be used to accurately control the speed of a PM synchronous motor.

영구자석 동기전동기의 강인한 디지털 속도 제어기법

This paper proposes a robust digital speed regulator for a surface-mounted permanent magnet synchronous motor(SPMSM). The proposed speed controller uses a simple digital load disturbance resistance scheme which does not require a load torque observer, so it can be easily and simply implemented without degrading the control performance. To validate the effectiveness of the proposed control algorithm, experimental results as well as simulation results are shown under motor parameter variations using a prototype SPMSM driving system. Finally, it was confirmed that the proposed method can precisely regulate the speed of the SPMSM.

The Automotive Electronic Throttle Control Based on the Non-Linear Torque Observer

This paper introduces the structure and working principles of the automotive electronic throttle control system. After analyzing the non-linear factor of the system, mathematical model of the system is built up. And the working principle of non-linear torque observer is described. Then incremental PID controller and non-linear torque compensator were designed and simulated in the matlab/simulink. From the result, we can see that the control precision of incremental PID controller is poor, and it also easily has an overshoot. However, PID controller based on non-linear torque observer has a better tracking performance. It can meet control requirements very well.

Torque Observers Design for Spark Ignition Engines With Different Intake Air Measurement Sensors

This paper presents a design approach and an experimental evaluation of torque observers for Spark Ignition (SI) engines. An engine model simplified from the generally used mean value model is proposed. Based on the developed model, torque observers are designed for engine systems with different intake air measurement sensors. The torque production model is introduced first to give a nominal value of torque estimation. Then, using the rotational dynamic equation of the crankshaft, an online adjusting term is added to modify the nominal estimation. The intake pressure, as an input of the torque production model, is directly measured if a pressure sensor is used. When an air mass flow sensor is adopted instead, an additional intake pressure observer is included in the torque observer. Simulation and experimental results are shown finally to demonstrate the proposed observers.

Integrated Synchronized Motion Control for a Force Sensorless Power-Assisted Wheelchair

AbstractA power-assisted wheelchair driven by dual electric-motors is required to operate on rough roads properly, where the right and left wheels encounter disturbances independently. This paper presents a synchronized motion control scheme which integrates the force sensorless controller such that the movement of the power-assisted wheelchair can maintain a desired motion path on rough surfaces. The dynamic behavior of a dual-drive power wheelchair is employed to analyze its synchronized motion error, and a torque observer is adopted to develop a force sensorless control system. Experiments are given to verify the control performance of the synchronized motion control of the proposed power-assisted control system.