Force control of a very lightweight single-link flexible arm based on coupling torque feedback

In this paper, a feedback control law is proposed for regulating the contact force exerted by a very lightweight single-link flexible manipulator when it comes into contact with a motionless object. This control law is based on a lumped-parameter model. The tracking of the desired contact force is obtained by using a feedback loop control of the coupling torque between the motor and the flexible arm. To achieve a good performance on the force control it is only necessary to measure the coupling torque at the root of the arm. Neither the contact force sensor nor the angular position sensor of the motor are used in the control method. A modified PID controller is proposed for this control law. In this work the force control problem is studied for both free and constrained motions of the flexible manipulator, and a collision detection algorithm is also described.     

Genetic algorithm tuning of Lyapunov-based controllers: anapplication to a single-link flexible robot system

In this paper, a systematic controller design approach is proposed to guarantee both closed-loop stability and desired performance of the overall system by effectively combining genetic algorithms (GAs) with Lyapunov's direct-controller design method. The effectiveness of the approach is shown by using a simple and efficient decimal GA optimization procedure to tune and optimize the performance of a Lyapunov-based robust controller for a single-link flexible robot. The feedback gains of the controller are tuned by the GA optimization process to achieve good results for tip motion control of the single-link flexible robot based on some suitable fitness functions. The paper includes results of simulation experiments demonstrating the effectiveness of the proposed genetic algorithm approach     

Intelligent switching control of a pneumatic muscle robot arm using learning vector quantization neural network

Pneumatic cylinders are one of the low-cost actuation sources used in industrial and prosthetic application, since they have a high power/weight ratio, high-tension force and long durability. However, problems with the control, oscillatory motion and compliance of pneumatic systems have prevented their widespread use in advanced robotics. To overcome these shortcomings, a number of newer pneumatic actuators have been developed, such as the McKibben Muscle, Rubber Actuator and Pneumatic Artificial Muscle (PAM) Manipulators. In this paper, the solution for position control of a robot arm with slow motion driven by two pneumatic artificial muscles is presented. However, some limitations still exist, such as a deterioration of the performance of transient response due to the changes in the external load. To overcome this problem, a switching algorithm of the control parameter using a learning vector quantization neural network (LVQNN) is proposed in this paper. The LVQNN estimates the external load of the pneumatic artificial muscle manipulator. The effectiveness of the proposed control algorithm is demonstrated through experiments with different external working loads.     

欠驱动柔性机械臂的动力学建模与控制

针对欠驱动柔性机械臂建模、控制困难的问题,文中采用在第一关节安装轻质弹簧的方法来表示机械臂的柔性,从而得到柔性臂的简化模型。将其应用到两连杆欠驱动柔性机械臂中,建立欠驱动柔性机械臂的系统模型,并利用拉格朗日函数法,对该系统进行动力学建模。同时通过构造基于系统能量和驱动杆状态的李雅普诺夫函数,设计该欠驱动柔性机械臂系统的控制律。最后,使用Matlab对该系统及所设计的控制律进行数值仿真。仿真结果表明,所构建的动力学模型以及设计的控制规则具有良好的有效性,且同时具备响应速度快、控制输入小的优点。     

6自由度机械臂远程控制系统研究

机器人控制技术在全球范围内飞速发展,人与机器人之间的交互方式正朝着方便、直观的方向发展。通过体感表征操作人员的骨骼和腕部信息,可以为机器人的远程操控提供必要的控制信息。该文融合视觉和可穿戴体感,研究了交互式6自由度机械手臂控制系统,使用人体肩、肘的旋转角度和握拳动作,来分别控制机械手臂的6个关节和抓取;并构建了分布式远程操控实验平台,数据和指令通过无线方式进行传输。实验结果表明,采用融合视觉和可穿戴体感的交互式机器人能有效直观地控制机械臂进行物体抓取。     

Vibration control of a single-link flexible manipulator using an array of fiber optic curvature sensors and PZT actuators

This paper presents a novel distributed sensing and actuation approach for actively suppressing vibrations within flexible link manipulators. Through vibration suppression, the method acts to regulate the shape of flexible links and, consequently, improves the performance of any independent trajectory controller being employed over the manipulator joints. To demonstrate the approach, a series of piezoceramic actuators (PZTs) are bonded to the surface of a single-link flexible manipulator. Slewing of the flexible link induces vibrations in the link that persist long after the hub stops rotating. The vibration suppression is achieved through a combined scheme of PD-based hub motion control and a PZT actuator controller that is a composite of linear and angular velocity feedback controllers. A Lyapunov approach is used to synthesize the composite controller, and a unique, commercially-available sensor, called ShapeTape^?, that provides the linear and angular velocity feedback. The sensor array is comprised of a series of fiber optic curvature sensors that are laminated on a long, thin ribbon tape which can be embedded into the flexible link and measures the bend and twist of the link’s centerline. Simulation and experimental results show the effectiveness of the proposed approach and the ability of the new sensor to provide the requisite feedback.     

码垛机器人机械臂仿真控制系统设计与实现

随着科技的飞速发展,企业的生产能力大幅提高,传统的人工码垛已经不能满足企业对物流的需求,码垛机器人技术应运而生。高效率的码垛能够大大节省物流时间,提高工作效率。系统利用四轴码垛机械臂仿真控制软件实际控制一台小型的关节型四轴码垛机械臂。机械臂利用舵机作为执行元件,DSP作为控制器控制舵机运动。仿真控制软件根据规划的路径计算出码垛过程中舵机运行的角度,通过串口通信将角度数据传递给DSP,DSP控制舵机的运行并带动码垛机械臂实现码垛功能。     

Modeling and control of the Mitsubishi PA-10 robot arm harmonic drive system

The purpose of this paper is to present our results in developing a dynamic model of the Mitsubishi PA-10 robot arm for the purpose of low-velocity trajectory tracking using low-feedback gains. The PA-10 is ideal for precise manipulation tasks because of the backdrivability, precise positioning capabilities, and zero backlash afforded by its harmonic drive transmission (HDT). However, the compliance and oscillations inherent in harmonic drive systems, and the lack of any technical information on the internal dynamics of the transmission, make the development of an accurate dynamic model of the robot extremely challenging. The novelty of this research is therefore the development of a systematic algorithm to extract the model parameters of a harmonic drive transmission in the robot arm to facilitate model-based control. We have modeled all seven joints of the Mitsubishi PA-10, and we have done several experiments to identify the various parameters of the harmonic drive system. We conclude with a sample trajectory-tracking task that demonstrates our model-based controller for the Mitsubishi PA-10 robot arm.     

基于3DS Max 与OpenGL的机械臂仿真与控制

阐述了在以Vc＋＋6．0为平台的基础上，利用3DSMax与OpenGL对机械臂进行可视化三维仿真的一种方法。为满足蒸汽发生器六轴机械臂检修控制系统的要求，建立一个多功能的实验仿真平台。一方面从正解、反解两个方面对机械臂进行了运动学分析，从而实现了机械臂的各轴在多种控制下的运动；另一方面将OpenGL与3DSMax相结合建立系统模型，给出机械臂在空间运动与抓顶的三维动画实现过程。实验结果证明仿真平台在实际工程中具有一定价值。     

一种单连杆机械臂柔性关节的滑模变结构控制

研究一种带柔性关节的单连杆机械臂的跟踪控制问题,其中体现关节柔性的是连接单连杆机械臂和驱动电机的两个仿腱线弹簧。利用Lagrange方程导出跟踪控制问题的数学模型,引进滑模变结构控制技术,给出Hurwitz多项式的确定以及滑模控制器的设计方法,并讨论Hurwitz多项式的根对控制效果的影响。将滑模控制器的表示式代入跟踪控制问题的数学模型中,得到状态变量的非线性微分方程组,利用Matlab进行仿真,得到了理想的控制输出效果。     

Fault-tolerant control system of flexible arm for sensor fault by using reaction force observer

In recent years, control system reliability has received much attention with increase of situations where computer-controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and to maintain the stability and the control performance (fault tolerance). In this paper, we address the vibration suppression control of a one-link flexible arm robot. Vibration suppression is realized by an additional feedback of a strain gauge sensor attached to the arm besides motor position. However, a sensor fault (e.g., disconnection) may degrade the control performance and make the control system unstable at its worst. In this paper, we propose a fault-tolerant control system for strain gauge sensor fault. The proposed control system estimates a strain gauge sensor signal based on the reaction force observer and detects the fault by monitoring the estimation error. After fault detection, the proposed control system exchanges the faulty sensor signal for the estimated one and switches to a fault-mode controller so as to maintain the stability and the control performance. We apply the proposed control system to the vibration suppression control system of a one-link flexible arm robot and confirm the effectiveness of the proposed control system by some experiments.     

解剖约束条件的数据手套校正及其在机械臂控制中的应用

通过对人手解剖约束条件的分析,把解剖约束条件应用于数据手套中的独立传感器和交叉—耦合传感器的校正,对校正结果进行了分析,使得数据手套能够采集到更准确的人手运动信息,并将校正后的数据手套应用到机械臂的控制中。实验表明,校正之后的数据手套能够更准确地采集信息,极大改善了机械臂控制中的精确性。     

Neural network based-time optimal sliding mode control for an autonomous underwater robot

This paper presents a robot control system using sliding mode control (SMC) as a core controller. The SMC switches according to the Pontryagin’s time optimal control principle, in which the solution is obtained by using neural network approach. The control system is implemented on Chalawan, a six-degree-of-freedom autonomous underwater robot developed at Mechatronics Laboratory, AIT. The control system can be applied to underwater robots, which have similar kind of architecture. Performance of the proposed controller is compared with various classical SMCs and conventional linear control system. The comparison detail results such as controller performance and error phase portrait are presented and analyzed. Such comparisons ensure the implementation success and prove it as a real time-optimal controller. The results also show the controller’s effective capabilities in plant nonlinearity and parameters uncertainties.     

Fuzzy sliding-mode control of a human arm in the sagittal plane with optimal trajectory

Patients with spinal cord injuries cannot move their limbs using their intact muscles. A suitable controller can be used to move their arms by employing the functional electrical stimulation method. In this article, a fuzzy exponential sliding-mode controller is designed to move a musculoskeletal human arm model to track an optimal trajectory in the sagittal plane. This optimal arm trajectory is obtained by developing a policy for the central nervous system. In order to specify the optimal trajectory between two points, two dynamic and static optimal criteria are applied simultaneously. The first dynamic objective function is defined to minimize the joint torques, and the second static optimization is offered to minimize the muscle forces at each moment. In addition, fuzzy logic is used to tune the sliding-surface parameter to enable an appropriate tracking performance. Simulation results are evaluated and compared with experimental data for upward and downward movements of the human arm.     

Exoskeletal master device for dual arm robot teaching

Dual arm robots are used as humanoid or industrial robots for assembly work. Each arm of these robots is generally composed of 7-DOF to mimic the human arm. For motion teaching of this 7-DOF robot arm, upper limb exoskeletal master devices can be used, and each arm of the upper limb exoskeletal master device can also be composed of 7-DOF. However, the motions of the human shoulder are complex and the lack of DOF in the exoskeletal master device limits the wearer's motions and makes the wearer feel uncomfortable. We propose a compact-sized exoskeletal master device, each of whose arms are composed of two serially connected parts. One is a 6-DOF shoulder–elbow mechanism and the other is a 3-DOF wrist mechanism. The 6-DOF mechanism serially connects the base frame near the shoulder to a point on the forearm, and the center of rotation of the shoulder joint is shifted to the outside of the human shoulder. In addition, the 6-DOF mechanism includes a long stroke but short reduced-length prismatic joint. This 6-DOF mechanism enables unconstrained and comfortable shoulder motions. The 3-DOF wrist mechanism corresponds to forearm pronation/supination, wrist flexion/extension, and wrist adduction/abduction. The closed-loop inverse kinematic scheme is applied for the dual arm robot control in the task space. The performance of the exoskeletal master devices and control strategies are verified through experiments using a 14-DOF dual arm slave robot.     

Comparison of model-free and model-based methods for time optimal hit control of a badminton robot

In this research, time optimal control is considered for the hit motion of a badminton robot during a serve operation. Even though the robot always starts at rest in a given position, it has to move to a target position where the target velocity is not zero, as the robot has to hit the shuttle at that point. The goal is to reach this target state as quickly as possible, yet without violating the limitations of the actuator. To find controllers satisfying these requirements, both model-based and model-free controllers have been developed, with the model-free controllers employing a Natural Actor-Critic (NAC) reinforcement learning algorithm. The model-based controllers can immediately achieve the desired motions relying on prior model information, while the model-free methods are shown to yield the desired robot motions after about 200 trials. However, in order to achieve this result, a good choice of the reward function is essential. To illustrate this choice and validate the resulting controller, a simulation study is presented in which the model-based results are compared to those obtained with two different reward functions.     

面向居家养老的智能机器人伴侣

开发机器人伴侣以帮助人类对家庭环境进行交互控制是解决养老问题的重要技术手段。为此,文中提出了一种可自主调整家居环境的智能机器人伴侣的系统设计。通过用户行为姿势的识别,机器人伴侣可作为整套智能家居设备的核心,通过无线网络对智能家居设备进行自主控制。此外,机器人伴侣还集成了语音交互功能以提高用户体验。试验表明,所开发的试验原型能够识别用户的基本行为并自适应控制智能家居设备,同时具有一定的语音交互能力。     

机械臂的多学科设计优化

指出多学科设计优化技术在机器人复杂系统设计方面的优势,探索了将其和机器人系统设计相融合的流程方法。利用多学科优化技术对移动读书机器人机械臂系统进行分解和规划,同时阐明了其中的难点和关键技术。将其分解为运动学、静力学、动力学、控制学四个学科并建立相应的模型进行分布式并行设计,优化计算结果表明了多学科设计优化技术应用在机器人设计领域的可行性及有效性。     

基于串联机械臂的稀疏孔径望远镜装调

为了更好地对稀疏孔径大口径望远镜进行装调,利用旋量理论对串联机械臂在系统装调中的应用进行了研究。首先,利用旋量理论分析了串联机械臂进行稀疏孔径望远镜装调的基本原理。其次,结合旋量理论与基本的几何关系分析了稀疏孔径望远镜装调原理,并对子孔径测量过程进行了误差分析。之后,对串联机械臂携带点光源显微镜（PSM）进行装调的可行性进行了分析与实验,证明了处于串联机械臂携带状态的点光源显微镜与位于实验室环境下像点稳定性相近。最后,分析了串联机械臂结合点光源显微镜在大口径稀疏孔径望远镜装调检测中的应用。     

机械臂的多学科设计优化

指出多学科设计优化技术在机器人复杂系统设计方面的优势,探索了将其和机器人系统设计相融合的流程方法。利用多学科优化技术对移动读书机器人机械臂系统进行分解和规划,同时阐明了其中的难点和关键技术。将其分解为运动学、静力学、动力学、控制学四个学科并建立相应的模型进行分布式并行设计,优化计算结果表明了多学科设计优化技术应用在机器人设计领域的可行性及有效性。