Reinforcement learning based compliance control of a robotic walk assist device

ABSTRACT

Millions of people around the globe have to deal with walking disability. Robotic walk assist devices can help people with walking disabilities, especially those with weak legs. However, safety, cost, efficiency and user friendliness are some of the key challenges. For robotic walk assist devices, light weight structure and energy efficient design as well as optimal control are vitally important. In addition, compliance control can help to improve the safety of such devices as well as contribute to their user friendliness. In this paper, an optimal adaptive compliance control is proposed for a Robotic walk assist device. The suggested scheme is based on bio-inspired reinforcement learning. It is completely dynamic-model-free scheme and employs joint position and velocity feedback as well as sensed joint torque (applied by user during walk) for compliance control. The efficiency of the controller is tested in simulation on a robotic walk assisting device model.     

脊柱手术机器人

针对脊柱手术中的椎弓根钉内固定术,为克服医生操作手术时定位精度难以保证、长时间手术易疲劳等问题,设计了一套脊柱手术机器人系统用于辅助实施椎弓根钉内固定术。机器人为5自由度,充分考虑手术机器人对安全性和工作空间有效覆盖的要求,进行了构型设计,并完成了相应的机器人运动学分析。控制系统是由图像导航下的主动控制和基于力传感器的被动拖拽控制两个模式进行控制。主动控制下,医生通过导航系统提供最优钉道的精确位置信息,机器人根据医生的规划路径自主到达手术点;被动力拖拽控制基于导纳控制原理对医生作用在机器人末端执行器的操作力进行映射,并以此形成跟随拖动动作的机器人运动控制指令。针对力拖拽控制的实验验证了机器人在被动拖拽控制模式下能够柔顺地跟踪医生的操作动作。     

数控机床进给用的伺服系统

本文首先分析了数控机床对进给伺服系统提出的各种要求,指出这些要求兼顾了控制电机系统及驱动电机系统是极其苛刻的,因而,进给伺服系统成为活跃的研究领域.其次,评述了区别于国外简易数控装置的某些简易进给伺服系统.本文还对三种比较流行的进给伺服系统(步进电机系统,小惯量直流伺服电机系统,宽调速直流力矩电机系统)就数控机床的要求及其本身的特点详细地进行了分析比较,并指出了其应用范围.本文还介绍了用计算机控制的交流电机系统的基本概念.最后,对进一步研究数控机床进给伺服系统提出了建议.     

力矩电机脉宽调制控制系统设计

针对伺服系统中力矩电机控制的问题,设计了基于脉宽调制方法的力矩电机控制电路,分析了脉宽调制电路的基本原理,并详细给出了脉宽调制电路的各个组成部分,重点介绍了双门限迟滞比较电路的原理和设计要点,按脉宽调制方法设计的力矩电机控制器经试验具有响应速度快,接口性能好的特点,完全能够满足设计要求。     

Robo-Erectus: a low-cost autonomous humanoid soccer robot

An exoskeleton robot can replace the wearer's motion function by operating the human's body. The purpose of this study is to propose a power assist method of walking, standing up and going up stairs based on autonomous motion of the exoskeleton robot suit, HAL (Hybrid assistive Limb), and verify the effectiveness of this method by experiment. In order to realize power assist of tasks (walking, standing up and going up stairs) autonomically, we used the Phase Sequence control which generates a task by transiting some simple basic motions called Phases. A task was divided into some Phases on the basis of the task performed by a normal person. The joint moving modes were categorized into active, passive and free modes according to the characteristic of the muscle force conditions. The autonomous motions which HAL generates in each Phase were designed corresponding to one of the categorized modes. The power assist experiments were performed by using the autonomous motion with a focus on the active mode. The experimental results showed that the wearer's muscle activation levels in each Phase were significantly reduced. With this, we confirmed the effectiveness of the proposed assist method.     

物探钻机性能参数测试系统设计

根据物探钻机的结构特点和测试需求,设计了一套适用于现有物探钻机的性能参数测试装置,实现了对钻压、空气压力、流量、转速、扭矩、钻井速度6项性能参数的测试,通过数据采集处理器对测试数据自动采集和处理,并开发了一套计算机软件,实现了对测试系统的自动控制和对性能参数的实时监测.现场试验表明,该装置运行稳定、测试精度高、软件运行平稳、存储数据效率高和处理分析准确,对于研究钻机和钻具以及钻井工艺参数优化具有重要作用.     

Mechanisms for actuated assistive hip orthoses

Mobility is often a central problem for people having muscle weaknesses. The need for new devices to assist walking and walk related activities is therefore growing. Lower limb actuated orthoses have already proven their positive impact with paraplegic patients and are potentially promising for assisting people with weak muscles. However, the transfer from the existing systems of mobilization towards assistance implies several technical challenges as the seamless integration and the reduction of power consumption. In this paper two assistive orthoses which use different types of actuation mechanisms are presented and discussed. The first one is based on a ball screw and an excavator-like mechanism while the second one is based on a double differential actuation. Their technical capabilities are compared and contextualized for diverse activities. Objective characteristics such as the range of motion of the devices, the transparency, the maximal torque that they can provide or the RMS torque during cyclic trajectories are compared to point out which device is better adapted for specific situations.     

Ankle–knee prosthesis with active ankle and energy transfer: Development of the CYBERLEGs Alpha-Prosthesis

This paper presents the development of the CYBERLEGs Alpha-Prototype prosthesis, a new transfemoral prosthesis incorporating a new variable stiffness ankle actuator based on the MACCEPA architecture, a passive knee with two locking mechanisms, and an energy transfer mechanism that harvests negative work from the knee and delivers it to the ankle to assist pushoff. The CYBERLEGs Alpha-Prosthesis is part of the CYBERLEGs FP7-ICT project, which combines a prosthesis system to replace a lost limb in parallel with an exoskeleton to assist the sound leg, and sensory array to control both systems. The prosthesis attempts to produce a natural level ground walking gait that approximates the joint torques and kinematics of a non-amputee while maintaining compliant joints, which has the potential to decrease impulsive losses, and ultimately reduce the end user energy consumption. This first prototype consists of a passive knee and an active ankle which are energetically coupled to reduce the total power consumption of the device. Here we present simulations of the actuation system of the ankle and the passive behavior of the knee module with and without the energy transfer effects, the mechanical design of the prosthesis, and empirical results from testing of the physical device with amputee subjects.     

A Human–Computer Interface Using Symmetry Between Eyes to Detect Gaze Direction

In the cases of paralysis so severe that a person's ability to control movement is limited to the muscles around the eyes, eye movements or blinks are the only way for the person to communicate. Interfaces that assist in such communication are often intrusive, require special hardware, or rely on active infrared illumination. A nonintrusive communication interface system called EyeKeys was therefore developed, which runs on a consumer-grade computer with video input from an inexpensive Universal Serial Bus camera and works without special lighting. The system detects and tracks the person's face using multiscale template correlation. The symmetry between left and right eyes is exploited to detect if the person is looking at the camera or to the left or right side. The detected eye direction can then be used to control applications such as spelling programs or games. The game “BlockEscape” was developed to evaluate the performance of EyeKeys and compare it to a mouse substitution interface. Experiments with EyeKeys have shown that it is an easily used computer input and control device for able-bodied people and has the potential to become a practical tool for people with severe paralysis.      

Using passive filters to minimize torque pulsations and noises in surface PMSM derived field oriented control

This paper describes a new dissipative passive filter system to minimize torque pulsation and current harmonic noises in surface PMSM when derived with field oriented control algorithm. The passive filter system consists of complex dissipative filter cascaded by low pass filter. The complex filter has two setting frequency points, one at inverter switching frequency and the other at some average selected frequency point. The filter system is affecting the inverter switching frequency in such a way to decrease stress on the inverter switching elements and reducing the severe of dv/dt on the motor. The filter system uses series dissipative elements to assist in reshaping of the applied voltage waveform in order to provide almost semi-sinusoidal voltage to the motor windings. The simulation results show that the proposed filter system is effectively minimized torque pulsations and harmonic noises in surface PMSM.     

双模自组织自整因子模糊控制器在PMLSM精密伺服系统中的应用

就PMLSM(永磁直线同步电动机)伺服系统,应用新型的自组织自整因子模糊控制器。它可以在经验知识十分缺乏的情况下自动形成良好的控制表,同时改善控制器的动态和静态特性。使用无静差的双模设计,提高了伺服系统动态响应速度和稳态精度。实验证明,该伺服系统具有自组织、自学习能力强、快速跟踪、定位精确、鲁棒性强等特点。     

基于转矩分配的开关磁阻电机模糊PI控制系统

针对开关磁阻电动机调速系统显著非线性造成固定参数在常规控制下不能很好适应工况变化以及转矩脉动比较大的问题,设计了基于转矩分配的模糊PI控制器来实现参数在线优化调整,提高系统动态响应,并抑制转矩脉动。仿真结果表明,该系统具有良好的动、静态性能,能有效减小转矩脉动。     

多微机全数字式同步电动机矢量控制系统研究

本文介绍了作者自行设计的多微机全数字式交交变频器同步电动机矢量控制系统。该系统采用高性能、快速性好的16位单片机组成硬件电路，采用目前流行的可读性好、可靠性高的PLM高级语言编程，系统软、硬件保护功能较全，各种检测电路尽量采用先进的光电检测装置。该系统是为了适应国产挖掘机低速、大转矩的特点而设计的，这一理论的不断完善必将揭开我国挖掘机交流传动取代直流传动的序幕。     

基于模糊免疫PID的左心室辅助装置控制系统仿真

为了提高左心室辅助装置运行的稳定性,研究了模糊免疫PID控制在左心室辅助装置控制系统中的应用.首先,分析了辅助装置的工作原理及其系统建模;其次,对模糊免疫PID控制算法进行分析;最后,进行了基于模糊免疫PID左心室辅助装置控制的仿真.仿真结果表明,模糊免疫PID控制技术比常规PID控制具有更好的控制稳定性.     

基于力矩信息的拖拉机转向动态PID控制方法

针对拖拉机驾驶机器人自主转向系统在转向过程中的阻尼具有非线性和时变性的特点,同时为了提高转向系统的控制性能,设计了基于力矩信号检测的拖拉机转向控制系统,其由力矩传感器、STM32处理器、工控机、驱动器及直流电机等组成.首先通过仿真研究不同力矩时的最优PID控制参数,给出不同力矩时的最优PID参数规律,再通过力矩传感器检测的力矩信号动态调整PID参数来控制电机的转向.仿真及实验结果均表明,基于力矩信号反馈的拖拉机动态PID转向控制方法能够有效控制拖拉机的方向,响应快、超调小、适应性强.     

骨骼服灵敏度放大控制方法研究

为了减少操作者和骨骼服之间的传感器,并在减小操作者施加力矩、提高操作者舒适度的情况下,实现骨骼服跟踪操作者的运动,研究了一种骨骼服灵敏度放大控制方法。利用Matlab的SimMechanics工具箱建立了骨骼服的摆动腿的单自由度和三自由度模型,作为控制对象,根据骨骼服的数学模型设计了灵敏度放大控制器,以PID控制器仿真实现人机之间的交互模型。仿真结果表明：骨骼服运动过程中,在驱动器施加较大力矩的情况下,操作者只需很小的力矩就可以摆动骨骼服,能够有效降低操作者的能量消耗,是一种行之有效的控制方法。     

基于双模控制的直流力矩发动机控制系统设计

针对航控发电机对控制直流力矩发动机性能要求,在分析传统控制系统故障目标精准度定位速度慢基础上,提出了基于双模控制的直流力矩发动机控制系统设计。根据直流力矩发动机双模控制原理,设计系统总体结构。通过转速信号模拟器产生数字信号,在串行A/D转换电路中引入MAX144型号可编程逻辑器件,改善信号转换精准度。使用碳化硅（Sic）智能功率模块,为硬件设备提供合适膨胀匹配系数,改善能耗问题。选择TMS320F28335PGFA型号数字信号处理器,可将信号转换为数字形式。控制电源开关频率在50-100kHz范围内,具有一定抗干扰能力。添加电流环,为发动机提供相对恒定电流。在MPLABI_DE集成开发环境下,采用双模控制磁场补偿方式调试电流环控制程序,选择大小适中的通电电流,设置转子预定位程序,根据系统主程序流程,完成发动机控制系统设计。由试验结果可知,该系统在故障目标精准度定位速度上最快可达到0.05个/s,大大增强了系统鲁棒性能。     

一种基于BP神经网络的扭矩传感器静态校准系统

常用的扭矩传感器校准装置大多为卧式串联结构,存在着结构刚度差、校准效率低、误差来源复杂等缺点。设计了一种立式筒状扭矩传感器校准系统,该系统有着形变量小、稳定性好、可靠性高的优点。在这种校准系统中,待校准扭矩传感器通过止口定位并采用螺钉固定,可以实现快速更换和校准。根据系统安装的同轴度、连接装置的情况等对误差来源进行了分析。由于校准时同轴度等参数无法测量,通过训练神经网络获得底部高精度扭矩传感器和待校准扭矩传感器所测扭矩之间的关系。实验结果表明,本文所设计扭矩传感器静态校准系统可以实现扭矩传感器的校准,精度可以达到0.05%FS。     

Motion Control of Passive Intelligent Walker Using Servo Brakes

We propose a new intelligent walker based on passive robotics that assists the elderly, handicapped people, and the blind who have difficulty in walking. We developed a prototype of the robot technology walker (RT walker), a passive intelligent walker that uses servo brakes. The RT walker consists of a support frame, two casters, two wheels equipped with servo brakes, and it has passive dynamics that change with respect to applied force/moment. This system is intrinsically safe for humans, as it cannot move unintentionally, i.e., it has no driving actuators. In addition, the RT walker provides a number of navigational features, including good maneuverability, by appropriately controlling the torque of servo brakes based on RT. We propose a human adaptive motion control algorithm that changes the apparent dynamics to adapt to user difficulties, and an environmentally adaptive motion control algorithm, which incorporates environmental information to provide obstacle/step avoidance and gravity compensation functions. The proposed control algorithms are experimentally applied to the RT walker to test their validity.     

基于UIO的EPS系统状态反馈最优控制

准确地获知电动助力转向（Electric powering steering,EPS）系统阻力矩是提高行车安全的一个重要因素.针对车辆转向过程中,由不同附着路面上EPS 系统所需辅助力矩与转向路感之间的差别而可能导致的误操纵问题,本文基于2自由度整车动力学的EPS系统模型,结合轮胎特性,以轮胎侧偏角和理想路面附着系数为输入,通过设计非线性观测器估计当前路面的附着系数,以获取EPS系统阻力矩;进而,根据EPS 系统模型,运用未知输入观测器（Unknown input observer,UIO）估算方向盘输入转矩,并基于EPS系统状态反馈以实现对EPS系统的无传感器最优控制.最后,对基于永磁同步电机（Permanent magnet synchronous motor,PMSM）的EPS系统进行仿真实验分析.结果表明： 在以电机q轴电流闭环误差最小为指标函数情形下,本设计的方向盘回正残留角从25°降到0°,能有效抑制系统外界干扰,提高了转向时人-车系统的鲁棒性.