Torque Compensation Research Articles

Regenerative brake torque compensation control for dual-motor PHEV considering backlash and hydraulic brake nonlinearity

This paper presents a novel nonlinearity-considered regenerative brake torque compensation control (NL-TCC) strategy, aimed at enhancing the brake stability for plug-in hybrid electric vehicles (PHEVs) with dual-motor powertrain. The dynamics models of hybrid brake system considering gear backlash and hydraulic brake nonlinearity are established in MATLAB/Simulink environment. Furthermore, the fluctuation of half-shaft torque is adopted as performance indexes to design the NL-TCC strategy for PHEVs with dual-motor powertrain, and the grey wolf optimizer (GWO) is used to obtain the optimal weight coefficients of different stage error functions. Finally, by means of hardware-in-the-loop (HiL) test, it is concluded that the vehicle jerk of the proposed NL-TCC strategy decreases by a minimum of 51.2% than the strategy without torque compensation control.

Coordination Control Algorithm for Wheel Torque of Parallel Hybrid Vehicle

When the Parallel Hybrid Vehicle (PHV) wheel’s torque is coordinated and controlled, the issue of coordination control of wheel torque under mode switching has some limitations. Therefore, the experiment proposed a novel wheel torque coordination control technique for parallel hybrid vehicles. The feedforward and feedback joint control technique of the Wheel Drive Torque (WDT) control algorithm may be used to implement the wheel torque drive control. The technique for the wheel braking Torque Control (TC) is applied to obtain the wheel braking torque through the Fuzzy PID controller (F-PID). A Dynamic Coordination Controller (DCC) is created and the engine output torque is adjusted using the PID control technique of wheel angular velocity difference. The motor provides the compensation torque. The deviation of the intended angular velocity from the actual angular velocity is adjusted intime to realize the wheel's dynamic coordination while being controlled by a mode switch. The results demonstrates that the reaction time of the proposed algorithm can be reduced to 0.08s; The overall output TC precision is improved by 11.1%. The precision of the predicted velocity of vehicle speed tracking has risen by 8.0%. The vehicle dynamics during the transition procedure is improved by 4.4%, which enhances the ride comfort and the PHV’s power.

A powered simple walking model explains the decline in propulsive force and hip flexion torque compensation in human gait

Excessive hip flexion torque to prioritize leg swings in the elderly is likely to be a factor that reduces their propulsive force and gait stability, but the mechanism is not clear. To understand the mechanism, we investigated how propulsive force, hip flexion torque, and margin of stability (MoS) change when only the hip spring stiffness is increased without changing the walking speed in the simple walking model, and verified whether the relationship holds in human walking. The results showed that at walking speeds between 0.50 and 1.75 m/s, increasing hip spring stiffness increased hip flexion torque and decreased the propulsive force and MoS in both the model and human walking. Furthermore, it was found that the increase in hip flexion torque was explained by the increase in spring stiffness, and the decreases in the propulsive force and MoS were explained by the increase in step frequency associated with the increase in spring stiffness. Therefore, the increase in hip flexion torque likely decreased the propulsive force and MoS, and this mechanism was explained by the intervening hip spring stiffness. Our findings may help in the control design of walking assistance devices, and in improving our understanding of elderly walking strategies.

An Electro-Hydraulic-Load-Sensitive System on the Basis of Torque Open-Loop Control

Facing the development trend of electrification of construction machinery, in view of the drawbacks of the existing electro-hydraulic-load-sensitive system in terms of dynamic characteristics and usage of energy, based on the drive source of a servo motor-driven quantitative pump, an electro-hydraulic-load-sensitive system on the basis of torque open-loop control was proposed. Firstly, the working principle of the system was introduced and the system’s operating characteristics and energy consumption characteristics were theoretically analyzed. Secondly, in order to balance the system’s energy usage and maneuverability, a control strategy with a variable pressure margin was designed. Meanwhile, in order to solve the problem that the hydraulic pump’s mechanical efficiency causes system pressure control deviation, a torque compensation method based on offline data and speed prediction was proposed. Finally, simulation and testing were used to confirm the viability of the control strategy. The test results show that: the system could realize stable pressure margin control, and the response rise time was within 0.7 s under a variety of flow circumstances; the system could follow the control instruction to change linearly and the flow rate changed smoothly in the adjustable pressure gap control; after using the compensation method, the deviation of the pressure gap control was within 2%.

Inertia compensation for wind turbine emulator based on anticipation deviation suppression

The wind turbine emulator (WTE) is an important tool for dynamic emulation experiments of wind turbines. This paper studies the problem of high-frequency fluctuation of the rotating speed of the dynamic emulation platform when emulating the mechanical dynamics of large inertia wind turbine under fluctuating wind speed. Through the time domain analysis of the discrete mathematical model of the WTE, it is found that the torque compensation loop of the transmission system will incur the acceleration deviation because of the influence of the time delay, and this anticipatory deviation increases with the increase of the compensation multiple. As a result, the acceleration of the transmission chain oscillates, resulting in high-frequency fluctuations in the rotational speed. To this end, this paper proposes an inertia compensation scheme for the WTE based on the anticipation deviation suppression. Based on the principle of zero-pole configuration, a feedforward suppressor is designed to offset the zero-pole of the closed-loop transfer function of the transmission chain system, in order to eliminate the high-frequency fluctuation of the rotating speed caused by the torque deviation. The effectiveness of the proposed strategy is validated using the maximum power point tracking control experiment.

Design and Implementation of Hybrid Exoskeleton for Oil Palm Harvester to Reduce Muscle Strain

When it comes to safety at the workplace, palm oil harvesters are highly exposed to body pain and muscular fatigue, which in the long term may lead to permanent spinal or shoulder damage that will undoubtedly result in different extreme societal difficulties. Meager investment in safety and long hours of manual work in awkward posture is the main challenge in ensuring safety in the palm oil field. This study aimed to develop a novel light hybrid exoskeleton exclusively built for palm oil harvesting to reduce muscular strain, maintain minimum cost, and ensure material availability in the local market. The iso-elasticity approach and DC linear motor were used for gravitational and muscular torque compensation and position control. Muscular EMG signal was taken and filtered to investigate the muscle strain reduction after implementing the developed hybrid exoskeleton. The result shows that the overall muscle strain was reduced by 16% using the passive exoskeleton and 23% using the hybrid exoskeleton compared to freehand. According to the results, it is evident that the developed exoskeleton can be implemented in palm oil harvesting, which will reduce the pain level of the workers at a significant rate.

An aircraft brake control algorithm with torque compensation based on RBF neural network

The wheel brake system of an aircraft is the key to ensure its safe landing and rejected takeoff. A wheel’s slip state is determined by the brake torque and ground adhesion torque, both of which have a large degree of uncertainty. It is this nature that brings upon the challenge of obtaining high deceleration rate for aircraft brake control. To overcome the disturbances caused by the above uncertainties, a braking control law is designed, which consists of two parts: runway surface recognition and wheel’s slip state tracking. In runway surface recognition, the identification rules balancing safety and braking efficiency are defined, and the actual identification process is realized through recursive least square method with forgetting factors. In slip state tracking, the LuGre model with parameter adaptation and a brake torque compensation method based on RBF neural network are proposed, and their convergence are proven. The effectiveness of our control law is verified through simulation and ground experiment. Especially in the experiments on the ground inertial test bench, compared to the improved pressure-biased-modulation (PBM) anti-skid algorithm, fewer wheel slips occur, and the average deceleration rate is increased by 5.78%, which makes it a control strategy with potential for engineering applications.

The single flapping rotor: detailed physical explanations

A motor-driven helicopter rotor generates a reaction torque. This torque would accelerate the airframe of the helicopter about the yaw axis opposite to the rotor rotation if no measures are taken to compensate it. In the early days of helicopter development, a diversity of measures was considered: Henrich Focke has discussed these different measures. Not well known is a torque compensation measure which is restricted to only one main rotor, thus skipping the tail rotor or any additional rotor as well. This principle is worth looking into the details of the physical mechanism involved. The German scientist Prof. Hans-Georg Küssner of the AVA-Göttingen, Germany (Aerodynamic Research Institute with heads at this time: L. Prandtl and A. Betz) was the first to study the method successfully. He constructed a wind tunnel model and showed that the reaction torque could indeed be completely compensated. The present author has reviewed Küssner’s experimental data and could show that numerical calculations are in good correspondence with the measured results. In the present paper, the details of the method to compensate the reaction torque will be discussed. Corresponding numerical data will be presented taking into account Navier–Stokes calculations on rotor blade sections. Blade element theory will then be applied and combined with the Navier–Stokes data. Calculated forces and moments of a complete four-bladed helicopter rotor will be presented.

Improvements of tooth movement efficiency and torque control in expanding the arch with clear aligners: a finite element analysis.

Objectives: The purpose of this study was to analyze the effect of different movement strategies, embossment structures, and torque compensation of the aligner on tooth movement during arch expansion using clear aligners by finite element analysis. Methods: Models comprising the maxilla, dentition, periodontal ligament, and aligners were created and imported into a finite element analysis software. The tests were performed using the following: three orders of tooth movement (including alternating movement with the first premolar and first molar, whole movement with second premolar and first molar or premolars and first molar), four different shapes of embossment structures (ball, double ball, cuboid, cylinder, with 0.05, 0.1, 0.15-mm interference) and torque compensation (0°, 1°, 2°, 3°, 4°, and 5°). Results: The expansion of clear aligners caused the target tooth to move obliquely. Alternating movement resulted in higher movement efficiency with lower anchorage loss as compared with whole movement. Embossment increased the efficiency of crown movement but did not contribute positively to torque control. As the angle of compensation increased, the tendency of oblique tooth movement was gradually controlled; however, the movement efficiency decreased concurrently, and stress distribution on the periodontal ligament became more even. For each 1° increase in compensation, the torque per millimeter of the first premolar would decrease by 0.26°/mm, and the crown movement efficiency eliminate decreased by 4.32%. Conclusion: Alternating movement increases the efficiency of the arch expansion by the aligner and reduces anchorage loss. Torque compensation should be designed to enhance torque control in arch expansion using an aligner.

High Integrated Methodology and Evaluation for Switched-Reluctance Type Bearingless Motors with Five Degree of Freedom Magnetic Levitation

To make bearingless motors more competitive in military and industrial applications, the volume and cost issues for the system need to be taken into account. In this paper, a series of highly integrated five degree of freedom (DOF) bearingless switched reluctance motors (BSRMs) without rare earth materials are proposed. The features of the novel topologies include the conical pole, the conical disk, the conical cylinder, and the thrust cylinder. The magnetization current is applied to generate the radial and axial fluxes based on these topologies. The axial levitation can be implemented by the two units without axial levitation windings. The two rotors are assembled on the shaft in parallel with 15 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> shifted for the torque compensation, and the four-DOF radial levitation can be implemented as well. According to the simulation and experiment results, the characteristics of the proposed topologies are evaluated. These novel topologies have a greater axial bearing capacity, and the capacities of the torque and the five-DOF levitation are guaranteed. In addition, the proposed topologies have broad application prospects in high-speed rotation and high-integration fields.

Regenerative braking torque compensation control based on improved ADRC

Electro-hydraulic braking (EHB) compensation is an effective method to solve the insufficient regenerative braking of electric vehicles, but the accuracy and speed of executive pressure response are still insufficient. In order to solve this problem, a brake pressure compensation control method based on EHB system is proposed and verified. Firstly, adaptive LuGre friction model and braking dead time compensation are introduced to obtain a more accurate friction model. Then, an electro-hydraulic braking control strategy based on Improved Active Disturbance Rejection Control (IADRC) is proposed. Finally, the effectiveness of the proposed method is verified by simulation experiments and hardware-in-the-loop (HIL) simulation experiments. The test results show that the proposed control method can achieve accurate control of brake pressure compensation in time. The research results promote the research and application of EHB system to a certain extent.

Smooth Speed Control of Permanent Magnet Synchronous Machine Using Back Propagation Neural Network

Torque ripple is one of the most critical problems in PMSM system. In this paper, a neural network (NN) torque compensator is combined with a conventional extended state observer (ESO)-based active disturbance rejection controller (ADRC) system to suppress the torque ripple at wide machine operation speed range by generating the optimal current reference. The ESO is able to estimate and reject the low-frequency component in the torque ripple, while the remaining disturbances can be learned and compensated by the neural network. Compared with commonly used schemes, the proposed method does not need to analyze the influence of various sources of the torque ripple, such as the cogging torque, non-sinusoidal back-EMF, parameter variations, and unmodeled disturbances. In addition, the simple structure of the neural network helps reduce the computation time and save computer memory. The effectiveness of the proposed neural network compensator with both the rotor position and mechanical angular velocity as inputs is verified in the experiment under different operation speeds.

Fast and Precise Positioning With Coupling Torque Compensation for a Flexible Lightweight Two-Link Manipulator With Elastic Joints

This study presents an effective two-degrees-of-freedom controller, considering coupling torque compensation, with the aim of achieving fast and precise positioning of a flexible lightweight two-link robot with elastic joints. Coprime factorization-based feedforward control and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_\infty$</tex-math></inline-formula> control are cooperatively applied to the quasi-full-closed-loop control structure, forming a fundamental control strategy with improved reference tracking and residual vibration suppression capability, compared with the original proportional–proportional integral control. However, satisfactory outcomes for control performance are not realized due to the coupling effect between the robot joints. Previous studies have often addressed the coupling issue for the semiclosed-loop control structure, based on the approximate rigid-body dynamics, but the existing methods are not applicable to the quasi-full-closed-loop control structure. In this research, a flexible three-mass model-based feedforward coupling torque compensation scheme appropriate for the quasi-full-closed-loop control structure is proposed, combined with a position reference filter design. The simulation and experimental results obtained confirm the superiority of the proposed method over the conventional methods, and the control specifications are consistent with those of the rigid manipulators. The proposed controller design is beneficial for industrial robotics applications that demand flexibility but without deterioration in control performance.

Multiple Adaptive Model Predictive Controllers for Frequency Regulation in Wind Farms

Frequent and inadequate power regulation could significantly impact the main shaft mechanical load and the fatigue of wind turbines, which imposes a stringent requirement to perform frequency regulation. However, the existing work on frequency regulation mainly uses torque compensation to improve the frequency response, while few of them consider the mechanical fatigue of the main shaft caused by torque compensation of the frequency controller. In this paper, the mechanical fatigue of the main shaft can be mitigated in all of the speed sections thanks to the proposed frequency regulation controllers. Precisely, a multiple adaptive model predictive controller (MAMPC), which seamlessly integrates the multiple model predictive control (MMPC) and the real-time AutoRegressive with eXogenous inputs (ARX) model, is proposed. It nicely handles the rate of change in compensation torque to mitigate the mechanical load on the shaft in all of the speed sections. The effectiveness of our method is verified through extensive simulations. With the proposed method, the minimum frequency deviation can be reduced, and the number of fatigue cycles of the main shaft can be extended.

Improved torque compensation control based-maximum power point tracking strategy for large scale floating offshore wind turbines

The main problems of Floating Offshore Wind Turbines (FOWT) are the slow dynamic response of Maximum Power Point Tracking (MPPT) control and the low wind energy conversion efficiency. This paper proposes an Improved Torque Compensation (ITC) control strategy, which includes three parts. Firstly, the Torque Compensation (TC) strategy is optimized to mitigate the large fluctuation in output power caused by the increased response speed. Secondly, the control gain for ITC is reasonably adjusted by the Fuzzy Inference System (FIS) based on the rotor speed acceleration and the platform pitch motion acceleration. Thirdly, the power coefficient curve of the Wind Turbine (WT) is optimized, so that the WT performs blade pitch operation below the rated wind speed. Not only further improve the wind energy conversion efficiency of the WT, but also solve the problem of increasing the platform pitch angle caused by ITC. The above three parts of the ITC strategy finally are applied to the MPPT control for the FOWT under the action of wind and waves. The effectiveness of the ITC control strategy is verified by comparing with the three existing MPPT control strategies.

Data-Driven-Model-Based Full-Region Optimal Mapping Method of Permanent Magnet Synchronous Motors in Wide Temperature Range

To improve the motor efficiency and expand the actual external characteristic region of electric vehicle permanent magnet synchronous motor (PMSM) drive systems, the optimal operation of mapping torque to d-q axis current is usually applied. Nevertheless, it is difficult to deal with the complex mechanism factors such as parameter saturation and temperature change for the traditional optimization method based on the basic voltage equation of PMSM. In this paper, a black-box-model-based torque–current optimization method is proposed, which does not rely on any information of the inner mechanism model, and the derivative-free, optimal, improved Nelder–Mead Simplex(NMS) method is used to minimize the copper loss and maximize the electromagnetic torque in the flux-weakening region. Moreover, a synchronous online compensation of the electromagnetic torque and optimal current angle is implemented, in view of the time variation of permanent magnet flux with temperature. Finally, through a comparison experiment with the nominal-parameters-based formula maximum torque per ampere (MTPA) method, the proposed method achieves higher torque accuracy and better efficiency performance in a wide temperature range with regard to a reasonable response speed.

Study on Braking Energy Recovery Control Strategy for Four-Axle Battery Electric Heavy-Duty Trucks

Regenerative braking can extend the driving range and reduce PM emissions from abrasion for battery electric heavy-duty trucks (BETs). The composite braking control strategy including torque distribution and dynamic coordinated control for the four-axle BET equipped with the electromechanical braking system is studied. A segmented torque distribution strategy is proposed to maximize energy recovery while ensuring braking stability. The simulation results reveal that the strategy shows better comprehensive braking performance than the two benchmark strategies, and the energy recovery rate in different load states under CHTC-D is above 40%. The proposed coordinated control strategy takes advantage of regenerative braking’s rapid response and precise control to compensate for torque deviations caused by the hysteresis of friction braking. For two common braking mode transition conditions, regenerative braking torque correction and advance of the mode switching timing are adopted to enable the motor to obtain the torque compensation ability. This method leads to a slight loss of braking energy, and the maximum torque deviation during the mode switching process is suppressed to less than 1.4 kN·m, and the jerk and braking distance is reduced accordingly, which is of great importance in improving driving comfort and braking safety.

Coordinated control strategy for mode switching of power-split hybrid electric bus

In the dynamic process of mode switching of the power-split hybrid electric bus, the vehicle will have longitudinal shock due to the drastic change of the two motors’ torque and the engine’s slow response. To solved this problem, this paper will focus on the process of switching from pure electric mode to hybrid drive mode, considered the operational state changes before and after engine ignition, limited the torque fluctuation transmitted from the front planetary set to the output shaft based on the idea of motor compensation, and calculated the motor compensation torque of the rear planetary set to compensate the torque fluctuation of the output shaft, to reduce the jerk. Firstly, the dynamic models of the transmission system before and after the engine ignition are established, respectively, and then the dynamic torque of the engine is estimated by XGBoost. The estimated value is input into the model predictive controller (MPC) to track the engine speed and calculate the torque fluctuation generated by the front planetary set on the output shaft. Then, according to the estimated value of the engine torque and the predicted value of the engine’s speed, the compensation torque is calculated by the sliding mode controller (SMC). Finally, the vehicle model is built with AVL CRUISE and MATLAB/Simulink software to verify the mode switching control effect of hybrid electric bus under typical urban conditions in China. The results showed that this control strategy significantly reduces the jerk of the mode switching process.

Active Vibration Control Strategy for Online Application in a Range Extender

Noise, vibration and harshness are a big issue for hybrid vehicles especially in range extenders. Traditional vibration control and active damping control are generally used for suppressing vibration. Compared with traditional vibration control, active damping control is more flexible and effective in suppressing vibration. The basic idea of active damping control is controlling electric motor compensating for the torque of engine and reducing the vibration from the source. The reduction of vibration is highly depended on the compensation torque of the electric motor. A differently designed compensation torque has a significant impact on the active damping control effect. In this paper, an active damping control method for online application is proposed. And several kinds of compensation torque are designed for this method. Experiments on vibration performance are conducted to compare the effect of different compensation torque design in reducing vibration. And the results show that the compensation torque in the shape of square wave has potential for reducing vibration in all directions. Finally, a guiding tool for compensation design is proposed by correlation analysis and the relationship between designing factors and vibration is revealed.

Control of PMSM Drive Using Lookup Table Based Compensated Duty Ratio Optimized Direct Torque Control (DTC)

There are several ways to reduce the ripple magnitude for direct torque-controlled permanent magnet synchronous motor (PMSM) drives. In this work, the compensated duty ratio optimized direct torque control (DDTC-TC) method was proposed to reduce the ripple for three-phase PMSM. The proposed control strategy employs the simplicity of conventional DTC (CDTC) and compensation of the reference torque to enforce the developed torque to oscillate around the required value. A torque error square minimization technique is employed to determine the duty ratio. The magnitude of the developed torque by the PMSM depends on the torque slope during the active and null voltage periods. The slope of the torque during each period is computed online. Based on the online computed slopes, the magnitude of the switching period and compensation torque were calculated. The ripple reduction capability of the proposed control scheme is tested using Matlab Simulink and a hardware in loop system. Results indicate that the control scheme is effective. Specifically, the torque and speed ripples are very small. The torque ripple during speed fluctuation is less for open-end winding PMSM. In addition, the proposed scheme is tested for four-quadrant operation, and the scheme is effective for four quadrant operation. Finally, verification of the effectiveness of the proposed scheme is performed using OPAL-RT-RT (OP4500). Verification indicates that the proposed scheme is effective.