Torque Optimization Method Research Articles

Regenerative Braking Strategy of Dual-Motor EV Considering Energy Recovery and Brake Stability

The dual-motor EV (Electric Vehicle) is increasingly favored by manufacturers for its excellent performance in terms of power and economy. How to further reduce its energy consumption and make full use of the dual-motor energy recovery is an important support to improve the overall vehicle economy and realize the “dual carbon” strategy. For the dual-motor EV architecture, the motor model, power battery loss model and vehicle longitudinal braking force model are established and the energy recovery-dominated regenerative braking torque distribution (RBD) rule of the dual motors is designed. Based on genetic algorithm (GA) theory and taking into account SOC, vehicle speed and braking intensity, a regenerative-braking torque optimization method is proposed that integrates energy recovery and braking stability. The braking intensity of 0.3 and the initial vehicle speed of 90 km/h are selected for verification. Compared with the rule method, the energy recovery and stability are improved by 22.8% and 4.8%, respectively, under the genetic algorithm-based and energy recovery-dominated regenerative-braking torque distribution (GA-RBD) strategy. A variety of conditions are selected for further strategy validation and the result shows that compared with the rule-based method, both energy recovery and braking stability are improved as braking speed and braking intensity increase under the GA-RBD strategy.

Torque Optimization Method of a 3-DOF Redundant Parallel Manipulator Based on Actuator Torque Range

Abstract The small actuator torque range brings advantages for the high-accuracy control of a manipulator. By taking the minimum actuator torque range into account, this paper proposes a novel torque optimization method of a 3-DOF redundantly actuated parallel manipulator for friction stir welding. The dynamic model of the 3-DOF redundant parallel manipulator with four kinematic chains is derived by using the principle of virtual work. The solution of the dynamics is not unique, and the range of four actuator torques constitutes a 4D generalized rectangle. A torque optimization method that minimizes the actuator torque range is presented by determining the generalized 4D rectangle with minimum side length. The proposed optimization method is a global solution corresponding to one trajectory of the moving platform, and it is compared with the least square method which is a local solution corresponding to one pose of the moving platform.

Analysis of a Combined-Type Axial-Flux Permanent Magnet Machine

A combined-type axial-flux permanent magnet machine is proposed in this paper. The structure of the proposed machine is introduced. The torque density characteristics of the proposed combined-type axial-flux permanent magnet machine are studied, and the torque density advantages of this kind of machine are analyzed by comparing with radial-flux permanent magnet machines. The magnetic field analysis method of the machine is studied. In the process of magnetic field analysis, an air gap permeance element is proposed to improve the traditional magnetic equivalent circuit method, which can facilitate the establishment of magnetic equivalent circuit model at different times. The calculation results of the proposed method are verified by finite element method. The cogging torque optimization of this machine is investigated, which includes magnet skewing with different reference modes. The optimal magnet skewing angle is calculated and verified, and the characteristics of different cogging torque optimization methods are summarized.

Analytical Average Torque Optimization Method of Parallel Magnetized Surface‐Mounted Permanent‐Magnet Machine with Third‐Order Harmonic Shaping Method

AbstractOn the basis of existing studies presented in literature on optimizing permanent magnet (PM) shaping with third harmonic for the tile‐shaped magnetic poles under radial magnetization, this paper proposes a method for PM shape optimization using third harmonic for bread‐shaped magnetic pole under parallel magnetization. Furthermore, the optimal value of third harmonic that should be injected for achieving maximum torque output of a surface‐mounted permanent‐magnet (SPM) motor under parallel magnetization is obtained. The accuracy of the analytical calculation is verified using the finite element method. Furthermore, electromagnetic properties, including back‐EMF waveform, cogging torque, average torque, and torque ripple of the SPM motor obtained under different PM shaping conditions, i.e., without PM shaping, sinusoidal PM shaping, and sinusoidal PM shaping with third harmonic are compared. The comparison results indicate that injecting the optimal value of third harmonic into the PM being subject to sinusoidal shaping can greatly improve the average torque and power density of the SPM motor without increasing the torque ripple. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Influence of Introducing the Rotor MMF Harmonic on Torque Performance of Spoke Type Permanent Magnet Motor With FSCW

This article proposes a torque optimization method that introduces the rotor magnetomotive force (MMF) harmonics, aiming to increase the average torque without increasing the cogging torque and torque ripple. A spoke type permanent magnet direct drive motor with fractional slot concentrated winding (FSCW) is designed. The FSCW can improve the utilization rate of the winding, but at the same time, it brings a wealth of MMF harmonics. First, the electromagnetic torque expression is derived using the principles of magnetic energy and virtual power. It means that the constant electromagnetic torque is generated when the stator and rotor MMF harmonics with the same space and time order are the same as the main wave speed. The analytical method is then used to analyze the influence of the stator and rotor MMF harmonics on the electromagnetic torque of the three-phase FSCW permanent magnet motor. On this basis, a rotor shape that introduces the third rotor MMF harmonics is proposed. Finally, the finite element software is used to compare and analyze the torque performance of motor before and after optimization. The finite element simulation and experiment results prove the correctness and effectiveness of the method.

Simulation Study of Two Torque Optimization Methods for Direct Torque-Controlled Induction Motors

The simplicity and excellent dynamic performance of Direct Torque Control (DTC) make Induction Motor (IM) drives attractive for many applications that require precise torque control. The traditional version of DTC uses hysteresis controllers. Unfortunately, the nature of these controllers prevents the optimization of the inverter voltage vectors inside the flux hysteresis band. The inverter voltage vector optimization can produce fast torque response of the IM drive. This research proposes two torque optimization methods for IM systems utilizing DTC. Analysis and Matlab simulations for the proposed optimization methods prove that the torque and, consequently, the speed responses, are greatly improved. The performances of the drive system controlled by the proposed optimization methods and the traditional DTC are compared. Conversely, the effects of the parameters on the proposed optimization methods are introduced. The proposed methods greatly improve the torque and speed dynamic performances against the traditional DTC technique. However, one of the proposed optimization methods is more sensitive to IM parameter variations than the other.

A magnetic torque optimization method for a hydraulic – magnetic coupling-drive cuttings cleaning tool

During the drilling process, cuttings carrying in the horizontal well section is relatively difficult, and cuttings beds form easily. A new type of hydraulic – magnetic coupling transmission cuttings cleaning tool is proposed, but the magnetic torque transmission influence mechanism, the optimal magnetic circuit structure and the magnet configuration are still yet to be studied. To this end, the finite element numerical simulation method is applied to analyze the influence of magnetic circuit structure and permanent magnet geometry on magnetic torque. The results of numerical simulation and laboratory experiments show that (1) the magnetic torque transmission efficiency can be improved by increasing the air gap flux density, reducing the magnetic reluctance and increasing the magnetostatic energy accumulation; (2) the magnetic torque increases first and then decreases as the number of pole-pair increases. The magnetic torque of 12 pairs of pole pairs reaches the maximum value; (3) by the coupling of the amount of magnets under the constraints of the effective section magnet coverage area percentage and the thickness of the magnet, it is obtained that when the thickness of the permanent magnet is 8.4 mm and the magnet coverage area percentage on the effective section of the tool is 71%, the maximum magnetic torque is generated per unit volume of magnet; (4) the absolute error of the indoor experimental result and the numerical simulation result is less than 17%, which can meet the engineering calculation accuracy requirements. It is concluded that the established numerical simulation model is reasonable and can be used as a technical means for the optimization analysis of the tool structure.

Cogging Torque Shape Optimization of an Integrated Generator for Electromechanical Energy Harvesting

In contrast to widely applied cogging torque (CT) or detent torque optimization methods, where well-known concepts for achieving a low-ripple torque as stator and/or rotor skewing are applied, this paper proposes an approach for shaping the stator geometry of a permanent-magnet (PM) synchronous machine, such that an arbitrary CT pattern can be obtained. This is achieved by an iterative algorithm, which adds sinusoidal air gap modulation components on an initial machine geometry. The CT profile is calculated using 2-D FEM simulations, and iterations are repeated until the desired CT pattern is achieved. The proposed approach is applied to an application example, where an outrunner PM generator is integrated in an electromechanical energy harvester (EEH). For this application, the generator's CT is beneficially shaped toward a four-pole sinusoidal pattern with an amplitude of 100 N $\cdot$ mm. The optimized CT of the PM generator is used to counteract the holding torque of the EEH, where a reduction in the start-up speed of the EEH by a factor of 4 is observed. Moreover, the presented CT shaping approach is extended beyond the EEH example to illustrate that the described method is also suitable for axially short machines, where skewing is not feasible.

Research on Joint Torque Optimization Method of Redundant Space Manipulators with Vibration Suppression

The space manipulator can exert its advantages of high efficiency and low cost, which can assist or even replace astronauts to complete a variety of space operations. However, the research has less consideration on joint torque optimization method with considering the influence of flexible factors on the manipulator. A joint torque optimization method of redundant space flexible manipulator with vibration suppression is proposed in this paper. The bending deformation of flexible connecting rod is described by the assumed mode method and the dynamic model of space flexible manipulator system is derived by the Lagrange method. On the basis of decomposing the dynamic equation of the flexible redundant manipulator, the joint torque is optimized as well as restraining the terminal vibration through introducing the Lagrange multiplier. Finally, simulation result shows that the increase rate of joint torque is not very obvious based on the Particle Swarm Optimization algorithm compared with the experiment without vibration suppression. The forward torque of first joint increases 20.2% and that of second joint only increases 4.1% while the backward torque of both two joints decrease obviously. Meanwhile, the running trajectory has excellent effect on vibration suppression of end effector of flexible manipulators. The terminal deformation in two directions is reduced by 21.3% and 78.6%. The decline of vibration deformation of end effector is obviously larger than the rise of joint torque, which verifies the feasibility and effectiveness of the algorithm.

Development of a Wearable Robotic Positioning System for Noninvasive Transcranial Focused Ultrasound Stimulation

Transcranial ultrasound neuromodulation has been attracting more and more interest from researchers as a novel modality for brain stimulation. Typical manual positioning for brain stimulation requires the patient to sit still during stimulation for extended periods and readily loses its positioning accuracy if the patient moves. To address these problems of inconvenience and inaccuracy, we proposed a robotic positioning system for targeted ultrasound brain stimulation. The proposed device automatically moves the ultrasound transducer to a desired position and orientation, enabling far more accurate and comfortable automatic positioning of the transducer than when using traditional manual positioning. The device was developed as a wearable design, because it eliminates the necessity for troublesome motion compensation for the user's unintentional movements. Parallel and serial mechanisms were combined and a torque optimization method was proposed so as to obtain a lightweight design, and to implement a sufficient number of degrees of freedom of motion.

F-2-1 7自由度上肢外骨格型パワーアシストロボットにおける零空間を用いた最適化手法の検討(F-2 メカニカルシステムとその知能化-機械と人の視点を中心に,口頭発表:メカニカルシステムとその知能化)

In the upper-limb power-assist exoskeleton robot, one of the most important things for the robot is assisting the joint motion of the user. Specifically, the robot needs to move according to the user's motion intention so that the user can use the robot without the sense of discomfort. EMG signal based impedance control has been proposed for the 7DOF upper-limb power-assist exoskeleton robot to control the robot according to the user's motion intention. In the controller, the 6-dimensional hand force vector calculated from EMG signals is realized with the impedance control in real time. Although Jacobian matrix is used in the controller, it is a singular matrix because the robot has a redundancy, so the pseudo-inverse matrix is used in the controller. In this paper, the torque optimization method with the pseudo-inverse matrix for an upper-limb power-assist robot is discussed. The effectiveness of the proposed method was evaluated by the experiments.

Improving local torque optimization techniques for redundant robotic mechanisms

AbstractTwo techniques that improve existing local torque optimization methods for redundant robotic mechanisms are proposed. The first technique is based on a balancing scheme, which balances a joint torque norm against a norm of joint accelerations. Expressions have been derived utilizing the Lagrangian multipliers method. The other technique is based on a torque optimization method which minimizes torques through accelerations, obtained from the null‐space of the Jacobian matrix. These accelerations are balanced against the minimum‐norm acceleration component in order to improve the performance. Numerical simulations have been carried out which in most cases illustrate good performance capability from the viewpoint of torque optimization and global stability.