Fuzzy Sliding Mode Control Based on Longitudinal Force Estimation for Electro-mechanical Braking Systems using BLDC Motor

This paper focuses on the controller design using fuzzy sliding mode control(FSMC)with application to electro-mechanical brake(EMB)systems using BLDC Motor.The EMB controller transmits the control signal to the motor driver to rotate the motor.The torque distribution of motors is studied in this paper actually.Firstly,the model of the EMB system is established.Then the state observer is developed to estimate the vehicle states including the vehicle velocity and longitudinal force.Due to the fact that the EMB system is nonlinear and uncertain,a FSMC strategy based on wheel slip ratio is proposed,where both the normal and emergency braking conditions are taken into account.The equivalent control law of sliding mode controller is designed on the basis of the variation of the front axle and rear axle load during the brake process,while the switching control law is adjusted by the fuzzy corrector.The simulation results illustrate that the FSMC strategy has the superior performance,better adaptability to various types of roads,and shorter braking distance,as compared to PID control and traditional sliding mode control technologies.Finally,the hardware-in-loop(HIL)experimental results have exemplified the validation of the developed methodology.

Applicability of unique scarf joint configuration in friction stir welding of AA6061-T6:Analysis of torque,force,microstructure and mechanical properties

The present research introduces a unique concept of scarf joint technique in friction stir welding(FSW) of aluminum alloy AA 6061-T6 plates and an investigation on weld quality.A new joint configuration with two distinct scarf angles(75°and 60°) was considered in this study.The various aspects of welding were compared with contemporary simple square butt(SSB) joint configuration.Welding was carried out at a constant tool rotation speed(TRS),tool traverse speed(TTS) and tool tilt angle of 1100 rpm,2 mm/s and2°,respectively.The results are analyzed in terms of force and torque distribution,microstructure,macrostructure,and mechanical property perspective for different joint configurations.The study reveals the minimum amount of force and torque at 60°scarf angle joint configuration compared to that of square butt joint configuration.Macro study shows that all the joints were defect-free,and a prominent onion ring was present in the lower portion of the weld nugget(WN).Fine equiaxed grains with a minimum average grain size diameter of 6.82 μm were obtained in the WN of scarf joint configuration(SJC).The maximum ultimate tensile strength(UTS) and maximum average NZ hardness of 267 MPa and83.82 HV0.1were obtained in SJC3 at a scarf angle of 60°.It has been observed from the investigation that the joint efficiency increases from 72.5%(SSB) to 86%(SJC3) at a 60° scarf angle.This unique characteristic may lay an impetus on probable joint strength enhancement technique without increasing the production cost.

Active Force with Fuzzy Logic Control of a Two-Link Arm Driven by Pneumatic Artificial Muscles

In this paper, the practicality and feasibility of Active Force Control （AFC） integrated with Fuzzy Logic（AFCAFL） applied to a two link planar arm actuated by a pair of Pneumatic Artificial Muscle （PAM） is investigated. The study emphasizes on the application and control of PAM actuators which may be considered as the new generation of actuators comprising fluidic muscle that has high-tension force, high power to weight ratio and high strength in spite of its drawbacks in the form of high nonlinearity behaviour, high hysteresis and time varying parameters. Fuzzy Logic （FL） is used as a technique to estimate the best value of the inertia matrix of robot arm essential for the AFC mechanism that is complemented with a conventional Propor- tional-Integral-Derivative （PID） control at the outermost loop. A simulation study was first performed followed by an experi- mental investigation for validation. The experimental study was based on the independent joint tracking control and coordinated motion control of the arm in Cartesian or task space. In the former, the PAM actuated arm is commanded to track the prescribed trajectories due to harmonic excitations at the joints for a given frequency, whereas for the latter, two sets of trajectories with different loadings were considered. A practical rig utilizing a Hardware-In-The-Loop Simulation （HILS） configuration was developed and a number of experiments were carried out. The results of the experiment and the simulation works were in good agreement, which verified the effectiveness and robustness of the proposed AFCAFL scheme actuated by PAM.

Compliant landing of a trotting quadruped robot based on hybrid motion/force robust control

A compliant landing strategy for a trotting quadruped robot on unknown rough terrains based on contact force control is presented. Firstly, in order to lower the disturbance caused by the landing impact force, a landing phase is added between the swing phase and the stance phase, where the desired contact force is set as a small positive constant. Secondly, the joint torque optimization of the stance legs is formulated as a quadratic programming(QP) problem subject to equality and inequality/bound constraints. And a primal-dual dynamical system solver based on linear variational inequalities(LVI) is applied to solve this QP problem. Furthermore, based on the optimization results, a hybrid motion/force robust controller is designed to realize the tracking of the contact force, while the constraints of the stance feet landing angles are fulfilled simultaneously. Finally, the experiments are performed to validate the proposed methods.

Ground demonstration system based on in-orbit assembly oriented manipulator flexible force control

To eliminate the load weight limit of carrier rockets and reduce the burden on support structures,in-orbit assembly is a key technology to make design of scattering a large diameter telescope into submirror modules,which requires smooth operation of assembly robots,and flexible force control technology is necessary. A ground demonstration system is presented for in-orbit assembly focusing on flexible force control. A six-dimensional force/torque sensor and its data acquisition system are used to compensate for gravity. For translation and rotation,an algorithm for flexible control is proposed. A ground transportation demonstration verifies accuracy and smoothness of flexible force control,and the transportation and assembly task is completed automatically. The proposed system is suitable for the development of in-orbit assembly robots.

Estimation of Longitudinal Tire Force Using Nonlinearity Observer

Tire forces are the major forces propelling the road vehicles. They significantly affect the dynamic behavior of the vehicles. Estimation of the tire forces is essential in vehicle dynamics and control. This paper presents an observer-based scheme for estimation of the longitudinal tire force of electric vehicles in real time.? The observer is based on a nonlinearity observer method. The pole-placement technique is used for determination of the observer gains. Simulation results demonstrate that the observer is able to estimate the tire force successfully. The experiments are implemented on a single-wheel electric vehicle test rig. The test rig comprises an electric motor driven wheel and a free-rolling drum simulating vehicle-on-road situations. Experimental results confirm the effectiveness of the present scheme.

Force Compensation Control for Electro-Hydraulic Servo System with Pump-Valve Compound Drive via QFT-DTOC

Each joint of a hydraulic-driven legged robot adopts a highly integrated hydraulic drive unit(HDU),which features a high power-weight ratio.However,most HDUs are throttling-valve-controlled cylinder systems,which exhibit high energy losses.By contrast,pump control systems offer a high efficiency.Nevertheless,their response ability is unsatisfactory.To fully utilize the advantages of pump and valve control systems,in this study,a new type of pump-valve compound drive system(PCDS)is designed,which can not only effectively reduce the energy loss,but can also ensure the response speed and response accuracy of the HDUs in robot joints to satisfy the performance requirements of robots.Herein,considering the force control requirements of energy conservation,high precision,and fast response of the robot joint HDU,a nonlinear mathematical model of the PCDS force control system is first introduced.In addition,pressure-flow nonlinearity,friction nonlinearity,load complexity and variability,and other factors affecting the system are considered,and a novel force control method based on quantitative feedback theory(QFT)and a disturbance torque observer(DTO)is designed,which is denoted as QFT-DTOC herein.This method improves the control accuracy and robustness of the force control system,reduces the effect of the disturbance torque on the control performance of the servo motor,and improves the overall force control performance of the system.Finally,experimental verification is performed using the PCDS performance test platform.The experimental results and quantitative data show that the QFT-DTOC proposed herein can significantly improve the force control performance of the PCDS.The relevant force control method can be used as a bottom-control method for the hydraulic servo system to provide a foundation for implementing the top-level trajectory planning of the robot.

浅谈正畸临床矫治新技术——球托止动定位轻力5s系统

达成精确的转矩表达和稳定的支抗控制是正畸治疗的关键因素,患者在治疗过程中对口腔健康与矫治感受的重视程度日益增长,球面自锁托槽(球托)在一定程度上满足了这两个方面的需求。球面自锁托槽的球面结构可以降低因佩戴矫治器而引起口腔溃疡的概率,并能减少生物膜附着,降低牙龈和牙周疾病的发生概率。与方形托槽相比,球面自锁托槽的脱落率降低了95%。止动定位系统是球面自锁托槽的核心创新点,主要由螺纹系统、螺丝系统和弓丝系统组成。得益于止动定位系统,球面自锁托槽可以去除余隙角,精准表达转矩,使用止锁螺丝时可增强支抗稳定性。止动定位系统搭配了3种特制的细方丝(0.1524 mm×0.6350 mm、0.2032 mm×0.5842 mm、0.2540 mm×0.5588 mm),用轻力排齐的同时可以表达转矩,控制牙根。球托矫治器以黏膜刺激小、脱落率低、转矩表达精准、支抗保有率高、细方丝轻力矫治等特点引起了广泛关注。

基于力反馈导纳控制的踝关节柔性外骨骼

针对踝关节康复训练的需求,分析踝关节的运动机理,运用模块化驱动单元与鲍登线,设计轻量化、易穿戴的柔性踝关节外骨骼机器人,实现踝关节跖屈/背屈、内/外翻的运动辅助.柔性外骨骼在背屈和跖屈阶段分别采用位置控制和力矩控制.位置控制以传统PID为主;力矩控制以力为反馈信号,建立交互力差值与鲍登线内芯位移补偿之间的导纳模型.通过Sigmoid变形函数实现导纳参数的动态调控,满足辅助力矩输出和人机交互柔顺性的需求.实验结果表明,位置跟踪误差不超过0.46 cm,力输出误差为-1.5~1.5 N,能够满足人体康复训练的需求.

基于AMESim-Matlab联合仿真的拖拉机耕深控制研究

在拖拉机电控液压耕深控制系统的研究中提出力位综合-滑转率的联合控制方法及控制策略,加入滑转率监测控制,在最优滑转率区间允许范围内调节耕深。搭建电控液压悬挂的液压物理模型,并建立仿真模型,设计滑转率模糊控制器、力位综合模糊PID控制器,试验研究基于滑转率逻辑门限的多参数控制效果。试验结果表明在超出滑转率逻辑门限值时系统有较好的响应效果,对滑转率的变化有较优的跟随效果,为拖拉机耕深控制系统多参数控制提供理论基础。

基于关节双位置反馈的柔性协作机械臂零力控制

零力控制是协作机械臂实现拖动示教的核心问题之一,目前方法多依赖于附加力/力矩传感器,其虽能保证测量精度,但会增加系统复杂程度及成本。提出一种基于关节双位置反馈的柔性协作机械臂零力控制方法,该方法可在无外加传感器条件下实现机械臂零力控制。首先,基于波发生器与柔轮柔性特性,建立了谐波传动关节的动力学模型;其次,基于谐波传动关节刚度辨识方法,建立了基于双位置反馈的柔性关节力矩估测方法;再次,建立了简化重力矩补偿模型,并考虑关节转动过程中的粘滞摩擦和Stribeck库伦摩擦,完善了关节摩擦力矩模型,基于此,实现对关节重力矩和摩擦力矩补偿,实现机械臂零力控制;最后,搭建谐波传动一体化关节和机械臂样机平台,并进行了实验研究,结果表明,所提方法可有效实现无附加力/力矩传感器条件下的谐波传动机械臂零力控制。

外加膝关节辅助力矩对下肢关键肌群肌力的影响分析

目的以减小步行时的膝关节合力为目标,基于受试者在正常步行状态下的膝关节合力和膝关节力矩,计算解析减少不同程度的膝关节合力所需的辅助力矩,并研究多种步速下辅助力矩对下肢关键肌群肌力的影响规律。方法通过三维光学动作捕捉系统及测力台采集人体在慢速步速、正常步速以及快速步速下的运动学和动力学数据。基于OpenSim生物力学计算平台计算下肢关键肌群肌力、膝关节合力及膝关节力矩,然后将膝关节合力按照减少5%、10%、15%、20%的目标进行等比缩减,在MATLAB中采用全局优化算法计算得到辅助力矩,最后分析辅助力矩对下肢关键肌群的影响规律。结果辅助力矩随膝关节合力减少的程度而增加,并且不同步速下辅助力矩的平均相关系数为0.87,最高相关系数为0.96。施加辅助力矩后,腘绳肌、股四头肌、腓肠肌的肌力分别在支撑相初期、支撑相中期、支撑相末期和预摆期减少的平均比例最大,并且在慢速步速下上述三个肌群肌力减少的平均比例最大,其值分别为31%、26%和23%。结论膝关节辅助力矩主要通过减弱下肢关键肌群的肌力来减少膝关节合力。本研究的结果提示不同步速下对膝关节施加特定幅度和变化趋势的辅助力矩,能够达到防止膝关节过载损伤等目的,可为主动机械外骨骼等辅助设备的驱动策略提供数据参考。

美太空军联合全域指挥控制发展趋势

为了有效遏制反介入/区域拒止作战,美军提出了联合全域指挥控制的概念,在现有多域作战的基础上全面统筹陆、海、空、天、网等领域的作战行动,提高美军武器级、策略级和战役级作战的多样性。首先,为充分了解美太空军在联合全域指挥控制领域的发展趋势,总结了美军现行指挥控制体系实现全域作战的潜在阻碍;然后,解析了美太空军下一代联合全域指挥控制体系的指挥框架、职能分配和态势引接等关键要素;最后,梳理了美太空军为支撑联合全域指挥控制开展的前沿技术探索。

无力传感器的操纵手柄自适应变阻抗控制

设计了一款轻量化和紧凑型的二自由度操纵手柄,并基于该操纵手柄提出了一种无力传感器的自适应变阻抗控制策略。根据操纵员操纵力大小对阻抗参数进行相应的调整以适应操纵员不同的操纵习惯;除了保证精确的位置控制外,加入了操纵手柄末端的速度控制,增强了操纵员的操纵感受。另外,在变阻抗柔顺控制的基础上加入了操纵力估计控制策略,从而避免了由于加装力传感器的额外接线导致系统复杂度增加以及由此带来的测量噪声。证明了所提控制策略在Lyapunov意义下的稳定性,说明了控制误差是收敛的,整个闭环系统的信号响应是一致极限有界的。最后,通过仿真实验以及实际台架实验验证了上述策略的有效性和稳定性。

机械臂外力的时延强跟踪Kalman估计与自学习控制

为了提高机械臂与环境交互过程中的接触力估计精度和关节控制精度,提出了基于时延强跟踪Kalman滤波的接触力估计方法和基于熵-自学习控制网络的关节角位置控制方法。建立了机械臂系统的关节驱动模型和动力学模型;基于时延估计理论,建立了4自由度机械臂系统的时延模型;在Kalman滤波中引入了渐消因子,使估计残差强行正交,从而提出了基于时延强跟踪Kalman的接触力估计方法。以接触力误差和关节位置误差为输入,以关节力矩为输出构建了自学习控制网络,并提出使用熵聚类确定网络结构和参数,从而设计了熵-自学习控制网络。经仿真验证,基于时延强跟踪Kalman的估计误差区间分布小于标准Kalman和文献[12]柔顺控制,且分布密度在0误差处极高;熵-自学习控制网络对期望轨迹的绝对跟踪误差和收敛时间远小于自学习控制网络和变阻抗阻尼控制。仿真结果验证了本文接触力估计方法和角位置控制方法的优越性。

阻抗模型下的采摘机器人末端柔顺抓取力控制方法研究

果蔬采摘是一项复杂且耗时的任务,需要处理各种动态、不规则的果蔬形状和位置,同时保证果蔬的完整性和新鲜度。因为常规采摘控制方法效率低下,而且容易造成果实损伤,为此,提出一种阻抗模型下的采摘机器人末端柔顺抓取力控制方法。以采摘机器人末端柔顺抓取稳定性为约束条件,根据运动学原理分析手指末端电机的电磁转矩与转速间的关系,利用毕奥-萨伐尔定律获取抓取力控制信号。基于阻抗模型、二阶系统设计抓取力控制器,通过二阶低通滤波器调节电机运转,得出机器人抓取的期望位置、速度及加速度,完成抓取力控制任务。实验结果表明,阻抗模型可应用于各种果蔬采摘场景,且末端柔顺抓取力控制误差小,稳定性高,解决果蔬采摘存在的难题,推动农业生产的现代化和智能化。

波动载荷下旋挖钻机动力头液压系统控制技术

在施工过程中,旋挖钻机的主要作用是成孔,传统旋挖钻机动力头液压系统,在波动载荷下控制的稳定性和控制效果较差,为了提高旋挖钻机动力头在波动载荷下的工作性能,设计一种针对波动载荷环境的旋挖钻机动力头液压系统控制方法。通过对旋挖钻机动力头液压系统的结构展开分析,根据分析结果建立数学模型,研究系统刚体在波动载荷下的受力情况;基于受力情况分析结果建立控制模型,分别控制系统的发电机、液压泵和负载,实现旋挖钻机动力头液压系统的发动机-液压泵-负载联合控制。实验结果表明:设计的方法控制稳定性高,且控制性能好。

Active compliance and force estimation of a continuum surgical manipulator based on the tip-pose feedback

Continuum manipulators have been applied in different surgical scenarios due to their dexterity and multi-DoF(degree of freedom)design compactness.To improve surgery safety,it is preferable to enable active compliance and force sensing abilities for a continuum manipulator.Existing works on active compliance and force sensing often rely on force sensors at the proximal or the distal ends,which inevitably increases the system complexity.In this paper,a shape reconstruction algorithm,a compliant motion controller,and a force estimation method are proposed successively based on the manipulator's tip pose via visual feedback.Four support vector regression(SVR)trainers are constructed and trained to compensate for the actuation residues,which are the differences between the actual actuation lengths outputs at the actuators and the ideal actuation lengths calculated from the estimated shape using the kinematics model,under no-load condition.Then,a compliant motion controller and a force estimation method are realized based on the current actuation residues,compared with the actuation residues under the no-load condition.In this way,no additional sensors are needed as an endoscopic camera is often available in a laparoscopic or endoscopic surgical system.The experiments were conducted on aφ3 mm-continuum manipulator to demonstrate the effectiveness of the proposed algorithms.

四轮转向汽车控制策略及稳定性研究

提出了一种四轮转向横向控制和制动力纵向联合控制(4WS-DYC)的控制策略。建立了二自由度车辆动力学模型,计算稳态时车辆的质心侧偏角和横摆角速度;基于最优控制理论建立了四轮转向LQR控制器和分层制动力纵向控制器;最后验证了双移线工况下控制策略的效果。结果表明:4WS-DYC控制策略有效,相比Car-Sim自带模型,低速时质心侧偏角降低了65%,高速时横摆角速度下降了34%。

Active Compliance Control of a Position‑Controlled Industrial Robot for Simulating Space Operations

An industrial robot with a six-axis force/torque sensor is usually used to produce a zero-gravity environment for testing space robotic operations.However,using traditional force control methods,such as admittance control,causes position-controlled industrial robots to undergo from force divergence owing to intrinsic time delay.In this paper,a new force control method is proposed to eliminate the force divergence.A hardware-in-the-loop(HIL)simulator with an industrial robot is first presented.The free-floating satellite dynamics and the motion mapping from the satellites to simulator are both established.Thus,the effects of measurement delay and dynamic response delay on contact velocity and force are investigated.After that,a real-time estimation method for contact stiffness and damping is proposed based on the adaptive Kalman filter.The measurement delay is compensated by a phase lead model.Moreover,the identified contact parameters are adopted to modify contact forces,and thus the dynamics response delay can be compensated for.Finally,a co-simulation and experiments were conducted to verify the force control method.The results show that contact stiffness and damping could be identified exactly and that the simulation divergence could be prevented.This paper proposes an active compliance control method that can deal with force constrained tasks of a position-controlled robot in unknown environments.