Torque Compensation Research Articles

Research on Torque Control Distribution between Motor and Engine in P2.5 Hybrid Vehicle

The normal torque distribution of the P2.5 hybrid system is based on the strategy of open-loop engine control, dynamic engine torque estimation and the motor torque compensation. To meet the rapid acceleration and the deceleration, the motor torque is compensated according to the estimated engine torque to satisfy the driver torque request first, and then satisfy the battery charge torque. Other torque distribution strategies are defined according to the special working conditions below:1) To improve the efficiency of the engine and the response of the system and to avoid the drop of engine speed, the motor compensation enabled condition and torque distribution strategy is defined.2) To enhance the performance of fuel consumption and emission during the catalyst heat phase, the catalyst heat phase is divided into two phases and the torque distribution strategy is defined. 3) To decrease the battery heat time and extend the battery health life, the battery heat enabled condition and torque distribution are defined. The vehicle results are conducted and show that the normal torque distribution control can meet the acceleration and deceleration goal and drivability performance. The motor compensation can meet the driver torque by the motor and avoid the drop of the engine speed. The control of the catalyst heat phase can do good to the emission and fuel consumption.

로드셀을 이용한 이륜형 셀프 밸런싱 로봇 주행기기의 실시간 편심 추정 및 보상 기법

When a two-wheeled self-balancing robotic vehicle moves, the rider’s unexpected movement or the posture variation of the integrated mobile manipulator may work as a significant disturbance to the postural stability of the inverted pendulum due to the change of the overall COG (Center of Gravity). In this study, we developed a method to estimate the variation of COG in real time and compensate for the eccentric effect to the posture control system by using load cells. For the lateral eccentricity, the load cells can detect the difference between the normal reactions acting on the two wheels and a proper compensation torque proportional to the difference can be applied. For the longitudinal eccentricity, an equilibrium pitch angle is generated as the reference input to the pitch control loop to keep the robot at its static equilibrium point. The experimental results proved that the posture control performance of a self-balancing robot could be considerably improved by applying the real-time eccentricity compensation technique.

Sensorless PMSM Drive Inductance Estimation Based on a Data-Driven Approach

In the permanent magnet synchronous motor (PMSM) sensorless drive method, motor inductance is a decisive parameter for rotor position estimation. Due to core magnetic saturation, the motor current easily invokes inductance variation and degrades rotor position estimation accuracy. For a constant load torque, saturated inductance and inductance error in the sensorless drive method are constant. Inductance error results in constant rotor position estimation error and minor degradations, such as less optimal torque current, but no speed estimation error. For a periodic load torque, the inductance parameter error periodically fluctuates and, as a result, the position estimation error and speed error also periodically fluctuate. Periodic speed error makes speed regulation and load torque compensation especially difficult. This paper presents an inductance parameter estimator based on polynomial neural network (PNN) machine learning for PMSM sensorless drive with a period load torque compensator. By applying an inductance estimator, we also proposed a magnetic saturation compensation method to minimize periodic speed fluctuation. Simulation and experiments were conducted to validate the proposed method by confirming improved position and speed estimation accuracy and reduced system vibration against periodic load torque.

Power on gear shift control strategy design for a parallel hydraulic hybrid vehicle

The power on gear shift control of a parallel hydraulic hybrid vehicle (PHHV) is researched in this paper. A multibody dynamic model is built to capture the main vibration characteristics of PHHV powertrain, based on which the power on gear shift control strategy is designed and verified. To avoid the vehicle driving torque interruption during gear shift, power on gear shift control strategy is designed. In the control strategy, hydraulic pump/motor (HPM) compensates the engine torque when the engine clutch is disengaged for gear shift. The engine clutch engagement process is carefully controlled by LQR control strategy to mitigate the vehicle powertrain vibration and improve the vehicle driving comfort. Extended Kalman filter (EKF) is adopted to estimate the PHHV parameters required by LQR control. The available HPM torque depends on its working pressure which varies a lot with different accumulator state of charge. So the HPM torque compensation capability is investigated by analysing the traction force requirement during gear shift. To obtain the gear shift traction force demand, a gear shift schedule considering both vehicle fuel economy and dynamic performance is designed. The simulation results show that the HPM could satisfy most of the torque compensation requirements during gear shifts with the designed gear shift schedule in typical driving cycles.

Model Predictive Control for Torque Ripple Suppression Caused by Misalignment of the Gearbox

This paper presents a model predictive control (MPC) based harmonic current injection method (HCIM) to suppress the torque ripple caused by misalignment in gearbox. As it is inefficient to determine the amplitude and phase of harmonic currents manually, the MPC is used to search the appropriate harmonic currents to implement HCIM efficiently. A cost function for MPC is designed to minimize a resultant torque ripple which is calculated by summing the misalignment torque ripple and compensation torque. The compensation torque is an input variable of the predictive model. In order to predict the resultant torque ripple accurately, an estimation method of the misalignment torque ripple with torque sensor is also proposed. The calculated compensation torque is converted into harmonic currents and the harmonic currents can be injected into a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current. As a result, the misalignment torque ripple can be suppressed. Experimental results demonstrate verification for estimation method of misalignment torque ripple, and effectiveness of the HCIM. In addition, the proposed MPC-HCIM is also verified by experiments, and the misalignment torque ripple is effectively suppressed by using the proposed method. By using the proposed method, high degree of precision in torque control can be achieved with low quality gearbox which has misalignment.

Control methods for variations in natural gas composition in air–fuel controlled natural gas engines

In the present study, the countermeasures are proposed to minimize the problem on torque and power output performance and exhaust gas emissions of natural gas engine with use of lower calorific gas. An experiment was conducted to identify thermal efficiency and harmful exhaust gas emission characteristics under partial load conditions in order to improve efficient fuel use in engines affected by the introduction of low calorific gases. A countermeasure for coping with emission gas regulations and preventing thermal efficiency deterioration under rated power operating conditions was then presented. An 11 L six-cylinder turbo-charged engine for city buses compliant with the EURO 6 regulation was used in the experiment, and the results obtained using the reference natural gas fuel were compared with those obtained using simulated low calorific gases. Pure methane (CH 4) was also used to investigate the effects of gas composition changes on thermal efficiency and exhaust gas emissions.When N2 is added or pure CH 4 is used under partial load operating conditions, the combustion rate decreases; consequently, the optimum ignition timing is additionally advanced relative to that obtained when the reference natural gas fuel is used. If the N2 mixing ratio is increased to a minimum of 4.7% under rated power operating conditions, combustion becomes unstable. Stable operation can be secured by increasing the set base fuel amount, 2.35% and 9.41% for pure CH 4 and 8% N2, respectively; however, torque decreases in proportion to the combustion speed of the gas fuel. The strategy of boost pressure control for the torque compensation can minimize the decrease in thermal efficiency.

A Vibration Control Method for Hybrid-Structured Flexible Manipulator Based on Sliding Mode Control and Reinforcement Learning.

The hybrid-structured flexible manipulator has a complex structure and strong coupling between state variables. Meanwhile, the natural frequency of the hybrid-structured flexible manipulator varies with the motion of the telescopic joint, so it is difficult to suppress the vibration quickly. In this article, the tip state signal of the hybrid-structured flexible manipulator is decomposed into elastic vibration signal and tip vibration equilibrium position signal, and a combined control method is proposed to improve tip positioning accuracy and trajectory tracking accuracy. In the proposed combined control method, an improved nominal model-based sliding mode controller (NMBSMC) is used as the main controller to output the driving torque, and an actor-critic-based reinforcement learning controller (ACBRLC) is used as an auxiliary controller to output small compensation torque. The improved NMBSMC can be divided into a nominal model-based sliding mode robust controller and a practical model-based integral sliding mode controller. Two sliding mode controllers with different structures make full use of the mathematical model and the measured data of the actual system to improve the vibration equilibrium position tracking accuracy. The ACBRLC uses the tip elastic vibration signal and the prioritized experience replay method to obtain the small reverse compensation torque, which is superimposed with the output of the NMBSMC to suppress tip vibration and improve the positioning accuracy of the hybrid-structured flexible manipulator. Finally, several groups of experiments are designed to verify the effectiveness and robustness of the proposed combined control method.

Hybrid Control Strategy for Force and Precise End Effector Positioning of a Twisted String Actuator

In this article, we propose a new control approach for the twisted string actuation system; a hybrid control scheme consisting of two nested loops, considering the motor angle and the axial force at the clamping point of the actuator as the system outputs. We show that measuring the axial force at the base of the actuator, we can effectively estimate and compensate the coupling torque between the motor and the external load. Then, compensation of the coupling torque allows formulating a linear control law to control the angular position of the actuator and, at the same time, implement an external control loop to regulate the force applied by the actuator. Simulated and experimental results validate the proposed original control scheme. Furthermore, we highlight the contributions of this article in the broader context of control of twisted string actuators.

Modeling and disturbance suppression for spacecraft solar array systems subject to drive fluctuation

The vibration of flexible solar array during sun-tracking drive has been one of the challenging problems in modern space technology. In this work, the vibration disturbance of the drive induced solar array vibration (DISAV) to spacecraft platform is studied. A vibration disturbance model considering both the effect of rigid-flexible coupling and the drive unstable excitation is established for a typical solar array system. It extends the traditional dynamic model of the solar array system in terms of an explicit description for the vibration disturbance. Then, an external torque compensation scheme considering both vibration suppressing and driving reliability is proposed based on a failure-protection magnetorheological actuator. The extended minimal control synthesis algorithm is adopted to achieve the compensatory torque for vibration suppression. The numerical results indicate that the energy of the vibration disturbing the spacecraft is mainly provided by the unstable drive while the flexible vibration diffuses the disturbance. And the vibration disturbance suppression should be a main task for the vibration control during the sun-tracking drive. The reliability and effectiveness of the DISAV control with a magnetorheological actuator are theoretically demonstrated from the aspect of the failure protection and active control. The maximum disturbance torque is reduced up to 68.75% during the normal sun-tracking, which demonstrates the good suppression of DISAV by the proposed torque compensation scheme.

An MPPT Control of a PMSG-Based WECS with Disturbance Compensation and Wind Speed Estimation

The paper presents simulation research on a variable structure control scheme of a small variable-speed fixed-pitch wind energy conversion system (WECS) with a three-phase permanent magnet synchronous generator (PMSG) in variable wind conditions. The WECS is connected to a power grid through two back-to-back voltage source converters (VSCs) with a DC link. The presented control algorithm is based on feedforward compensation of the wind turbine aerodynamic torque estimated using a linear disturbance observer (DOB). The torque estimate is employed to determine the effective wind speed, required for setting the reference angular speed, using numerical zero search of a nonlinear function. The simulation model, built in the Matlab/Simulink environment using the Simscape Electrical toolbox, includes the field-oriented control of the PMSG via the machine VSC, performed by cascaded angular velocity and current/torque PI controllers, as well as synchronization with the grid and the reactive power control via the grid VSC. The presented results are focused on the performance of the proposed control in the maximum power point tracking (MPPT) operating region of the WECS for various wind speed profiles.

Research on Compound Coordinated Control for a Power-Split Hybrid Electric Vehicle Based on Compensation of Non-Ideal Communication Network

To improve the mode switching quality of the power-split hybrid electric vehicle (PS-HEV), a compound torque coordinated control strategy is proposed. Aiming at the problem of engine dynamic response lag, the engine real-time torque estimator is designed, and then the torque ripple at the output end of the power coupling mechanism is reduced through the basic motor torque compensation. On this basis, considering the existence of non-ideal communication networks in actual vehicle control systems, the tremendous impact of communication network time delay and interruption on the mode switching stability and vehicle fuel consumption has been deeply revealed. Then the compound coordinated control strategy including the BP-smith predictive controller, motor torque change rate limiting module, network transmission mechanism with fixed communication priority and fault-tolerant torque coordinated control module is put forward and verified by simulation and hardware-in-the-loop test. The results show that the compound coordinated control strategy could still guarantee the system stability, mode switching smoothness and vehicle fuel economy under the interference of stochastic communication delay and interruption.

Linear active disturbance rejection control with torque compensation for electric load simulator

This study proposes a design of an inner control loop for the load torque control of an electric load simulator (ELS), which is specifically designed to simulate load torque (i.e., load) for mechanical equipment. By mainly drawing on linear active disturbance rejection control, a mechatronic model-based inner loop controller of ELS is designed using measured torque to reduce the complexity of the estimator. A phase-locked loop observer is introduced to suppress the negative effects of the measurement error, thereby resulting in good performance for surplus torque suppression and the dynamic behavior of the control system. Simulations and experiments on a prototype machine are performed to verify the effectiveness of the proposed control method.

Perfect Torque Compensation of Planar 5R Parallel Robot in Point-to-Point Motions, Optimal Control Approach

SUMMARYIn this paper, a new approach is presented for perfect torque compensation of the robot in point-to-point motions. The proposed method is formulated as an open-loop optimal control problem. The problem is defined as optimal trajectory planning with adjustable design parameters to compensate applied torques of a planar 5R parallel robot for a given task, perfectly. To illustrate the effectiveness of the approach, the obtained optimal path is used as the reference command in the experiment. The experimental outputs show that the performance index has been reduced by over 80% compared to the typical design of the robot.

Design and Evaluation of Torque Compensation Controllers for a Lower Extremity Exoskeleton.

In this article, we present an integrated human-in-the-loop simulation paradigm for the design and evaluation of a lower extremity exoskeleton that is elastically strapped onto human lower limbs. The exoskeleton has three rotational DOFs on each side and weighs 23 kg. Two torque compensation controllers of the exoskeleton are introduced, aiming to minimize interference and maximize assistance, respectively. Their effects on the wearer's biomechanical loadings are studied with a running motion and predicted ground reaction forces (GRFs). It is found that the added weight of the passive exoskeleton substantially increases the wearer's musculoskeletal loadings. The maximizing assistance controller reduces the knee joint torque by 31% when compared with the normal running (without exoskeleton) and by 50% when compared with the passive exoskeleton case. When compared with the normal running, this controller also reduces the hip flexion and extension torques by 31% and 38%, respectively. As a result, the peak activations of the biceps short head, gluteus maximus, and rectus femoris muscles are reduced by more than a half. Nonetheless, the axial knee joint reaction force increases for all exoskeleton cases due to the added weight and higher ground reaction forces. In summary, the results provide sound evidence of the efficacy of the proposed controllers on reducing the wearer's musculoskeletal loadings. And it is shown that the human-in-the-loop simulation paradigm presented here can be used for virtual design and evaluation of powered exoskeletons and pave the way for building optimized exoskeleton prototypes for experimental evaluation.

Optimal starting control of zero-synchronous shock AMT based on torque compensation.

This article first puts forward the shortcomings of current AMT starting control in the preface. Then, in the second chapter, the dynamic analysis of the starting process was carried out, and the three requirements of starting control were clarified: dynamic requirements, smoothness requirements and low slippage requirements; it was clarified that dynamic requirements were the main control objectives of starting control, smoothness Performance requirements and low clutch wear requirements are constraints.In the third chapter, the optimal control principle of the AMT starting is proposed; the clutch target engagement amount is determined according to the power requirements, the engine speed control strategy and the engine target speed are determined according to the low slip wear requirements, according to the requirements of ride comfort, the clutch engagement speed and synchronous compensation torque are determined, and an optimal starting control method with zero synchronous shock based on torque compensation is proposed. Based on this, the optimal starting controller with three control loops is designed in Chapter 4, it realizes the functions of closed-loop control of driver torque demand, closed-loop control of sliding impact degree, closed-loop control of zero synchronous impact, and closed-loop control of engine speed with low sliding power.Finally, the vehicle test and simulation verification in Chapter 5 confirms that the control method proposed in this paper can effectively meet the starting control goal and eliminate the synchronization shock simply and efficiently.

Coordinated Control for Driving Mode Switching of Hybrid Electric Vehicles

Taking a hybrid electric vehicle using double-row planetary gear power coupling mechanism as a research object, this study proposes a coordinated control algorithm of “torque distribution, engine torque monitoring, and motor torque compensation” in an attempt to realize coordinated control for driving mode switching. Characteristic analysis of the power coupling mechanism was carried out, and the control strategy model in MATLAB/Simulink was built. Subsequently, the analysis of mode switching from the electric mode into joint driving mode was simulated. In addition, a multibody dynamics model of the power coupling mechanism was established and the simulation analysis during mode switching process was carried out. The results show that the proposed coordinated control strategy serves to effectively reduce the torque fluctuation and the impact degree during the mode switching process and improve the ride comfort of the vehicle. In the meantime, the time-domain and frequency-domain characteristics of gear meshing force and bearing restraint force indicate that the mode switching process of the dynamic coupling mechanism is quite stable and this control strategy contributes to improving the characteristics such as vibration and noise.

Finite Control Set Model‐Predictive Speed Control with a Load Torque Compensation

This paper presents a gain tuning method of the load torque compensator for direct speed control based on finite control set model predictive control (FCS‐MPC). In this method, the transfer function between the error in predicted speed and the load torque is constructed and used for gain parameter tuning of a load torque observer‐based prediction error correction. By using the proposed method, the stability and the responsiveness of FCS‐MPC with a load torque compensation can be improved without a fully simulating the electric drive systems and experiments. The simulation and experimental results obtained with a permanent magnet synchronous motor, fed by a two‐level three‐phase voltage source inverter, show that the tracking performance of the direct speed control tuned by the proposed method was excellent under load torque conditions. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A new joint friction model for parameter identification and sensor-less hand guiding in industrial robots

PurposeThe purpose of this paper is to propose a new joint friction model, which can accurately model the real friction, especially in cases with sudden changes in the motion direction. The identification and sensor-less control algorithm are investigated to verify the validity of this model.Design/methodology/approachThe proposed friction model is nonlinear and it considers the angular displacement and angular velocity of the joint as a secondary compensation for identification. In the present study, the authors design a pipeline – including a manually designed excitation trajectory, a weighted least squares algorithm for identifying the dynamic parameters and a hand guiding controller for the arm’s direct teaching.FindingsCompared with the conventional joint friction model, the proposed method can effectively predict friction factors during the dynamic motion of the arm. Then friction parameters are quantitatively obtained and compared with the proposed friction model and the conventional friction model indirectly. It is found that the average root mean square error of predicted six joints in the proposed method decreases by more than 54%. The arm’s force control with the full torque using the estimated dynamic parameters is qualitatively studied. It is concluded that a light-weight industrial robot can be dragged smoothly by the hand guiding.Practical implicationsIn the present study, a systematic pipeline is proposed for identifying and controlling an industrial arm. The whole procedure has been verified in a commercial six DOF industrial arm. Based on the conducted experiment, it is found that the proposed approach is more accurate in comparison with conventional methods. A hand-guiding demo also illustrates that the proposed approach can provide the industrial arm with the full torque compensation. This essential functionality is widely required in many industrial arms such as kinaesthetic teaching.Originality/valueFirst, a new friction model is proposed. Based on this model, identifying the dynamic parameter is carried out to obtain a set of model parameters of an industrial arm. Finally, a smooth hand guiding control is demonstrated based on the proposed dynamic model.

On stability and performance of disturbance observer-based-dynamic load torque compensator for assistive exoskeleton: A hybrid approach

A disturbance observer-based-dynamic load-torque compensator for current-controlled DC-drives, as joint actuator of assistive exoskeletons, has been recently proposed. It has been shown that this compensator can effectively linearize and decouple the coupled nonlinear dynamics of the human-exoskeleton system, by more effectively compensating the associated nonlinear load-torques of the exoskeleton at the joint level. In this paper, a detailed analysis of the current controlled DC drive-servo system using the said compensator, with respect to performance and stability is presented, highlighting the key factors and considerations affecting both the stability and performance of the compensated servo system. It is shown both theoretically and through simulation results that the stability of the compensated servo system is compromised as performance is increased and vice-versa. Based on the saturation state of the servo system, a new hybrid switching control strategy is then proposed to select stability or performance-based compensator and controller optimally. The strategy is then experimentally verified both at the joint and task space level by using the developed four active-degree of freedom exoskeleton test rig.

A state observation and torque compensation–based acceleration slip regulation control approach for a four-wheel independent drive electric vehicle under slope driving

Wheel slipping of four-wheel independent drive electric vehicle on slope will reduce vehicle controllability and driving stability, thereby reducing vehicle safety. In order to solve the problem of wheel slipping and optimize the speed control performance of four-wheel independent drive electric vehicle on slope, an acceleration slip regulation control strategy of slope drive is proposed in this paper. First, we design a road identification algorithm to identify the current road conditions of the four-wheel independent drive electric vehicle, and calculate the optimal slip ratio of the current road surface by curve fitting method. Then, with the optimal slip ratio as the control objective, the acceleration slip regulation control strategy is designed to maximize the utilization of wheel adhesion coefficient to prevent wheel slip. Third, a slope identification algorithm based on Luenberger state observer is designed to identify the various slopes of the uphill and downhill road, after which a torque compensation algorithm is designed according to the identification slope, to compensate for the longitudinal component of vehicle gravity at different slopes. Fourth, a slope torque distribution algorithm is proposed based on acceleration slip regulation and slope identification. Finally, through the joint simulation platform of MATLAB/Simulink and CarSim, it is shown that the proposed control strategy can better restrain wheel slipping on the uphill and downhill road, and has better dynamic characteristics and stability.