基于比例微分控制器的机器人位置控制研究

考察多关节机器人动力学方程的数学特性,采用李雅普诺夫函数方法对机器人位置控制问题进行研究,基于机器人动力学模型构造能量函数并使用不变集定理分析比例微分控制器的稳定性,通过对理论分析结果进行仿真,研究单位阶跃信号激励下控制系统的动态特性。

PMSM驱动机器人的哈密顿与Fal函数PD协调控制

针对二自由度机器人控制系统位置跟踪控制难以兼顾快速性和准确性的问题,提出了机器人信号与能量协调控制。首先,根据机器人动力学方程建立机器人系统的端口受控哈密顿模型,并且引入积分控制设计能量控制器,实现了系统的稳定性和稳态时的准确性。然后,基于模型补偿与Fal函数的比例-微分控制设计了信号控制器,实现系统在动态过程中的快速响应。然后设计协调控制策略,兼顾信号控制和能量控制的优点实现了信号与能量的协调控制。最后将机器人动力学与关节伺服电机控制相结合,提出了驱动机器人关节的隐极永磁同步电机滑模控制。仿真结果表明所提出的控制方法满足了系统对快速性及准确性的要求。

Force assistant master-slave telerehabilitation robotic system

A prototype of the master slave telerehabilitation robotic system with force feedback is developed. This system contains a pair of robots with the master being operated by the therapist and the slave following the master to guide the patients to exercise. A slave device with a slave controller is designed to stretch and mobilize the impaired elbow joints accurately and safely. A master device with a master controller is designed to control/monitor the procedure of treatment and assess the outcome of treatment remotely and accurately. By using the twoport network theory and the circuit equivalent impedance models, the position-force control scheme is designed to generate force feedback for the therapist who is to be informed of the interaction force between the subject and the robot arm during exercise. Experiments were conducted with a healthy male. Results show that the therapist can guide the patient to exercise by the master arm and can feel the interaction forces between the impaired arm and the robot. Compared with the traditional therapy, this system is more cost-efficient, more convenient and safer for both the stroke patients and the clinicians.

Adaptive hybrid force/position control for an industrial robot： theory and experiments

This paper proposes a feasible force/position control method for industrial robots utilized for such tasks as grinding, polishing, deburring, and so on. Specifically, an adaptive force/position control strategy is designed in this paper which regulates the contact force between a robot and a workpiece to reach any given set-point exponentially fast, and enables the robot to follow a chosen trajectory simultaneously without requiring prior knowledge of the system parameters. The stability of the closed-loop system is analyzed by Lyapunov techniques. To test the validity of the force/position control method, some simulation results are first collected for the closed-loop system. Furthermore, some experiments are implemented on a 5DOF （degree of freedom） industrial robot for the constructed adaptive force controller. Both simulation and experiment results demonstrate the superior performance of the designed adaptive force/position control strategy.

Hybrid H_2/H_∞ force/position control based on neural networks

A neural network control scheme with mixed H2/H∞performance was proposed for robot force/position control under parameter uncertainties and external disturbances. The mixed H2/H∞tracking performance ensures both robust stability under a prescribed attenuation level for external disturbance and H2optimal tracking. The neural network was introduced to adaptively estimate nonlinear uncertainties, improving the system’s performance under parameter uncertainties as well as obtaining the H2/H∞tracking performance. The simulation shows that the control method performs better even when the system is under large modeling uncertainties and external disturbances.

Solving position-posture deviation problem of multi-legged walking robots with semi-round rigid feet by closed-loop control

The semi-round rigid feet would cause position-posture deviation problem because the actual foothold position is hardly known due to the rolling effect of the semi-round rigid feet during the robot walking. The position-posture deviation problem may harm to the stability and the harmony of the robot, or even makes the robot tip over and fail to walk forward. Focused on the position-posture deviation problem of multi-legged walking robots with semi-round rigid feet, a new method of position-posture closed-loop control is proposed to solve the position-posture deviation problem caused by semi-round rigid feet, based on the inverse velocity kinematics of the multi-legged walking robots. The position-posture closed-loop control is divided into two parts: the position closed-loop control and the posture closed-loop control. Thus, the position-posture control for the robot which is a tight coupling and nonlinear system is decoupled. Co-simulations of position-posture open-loop control and position-posture closed-loop control by MATLAB and ADAMS are implemented, respectively. The co-simulation results verify that the position-posture closed-loop control performs well in solving the position-posture deviation problem caused by semi-round rigid feet.

QoE Assessment in Haptic Teleoperation Systems： Position-Position versus Position-Force

In this paper, we make a comparison of haptic control schemes （position-position and position-force control schemes） for two haptic teleoperation systems by QoE （quality of experience） assessment. One is a remote control system with haptic media and video. In the system, we can write characters by controlling a haptic interface device at a remote place with another haptic interface device while watching video. The other is a remote instruction system with haptic media, video and voice. By using the system, a teacher can actively write characters and teach a student how to write the characters. The student can also write characters actively, and the teacher can confirm how the student writes the characters. We investigate the influences of network delay on QoE for the two systems with the two haptic control schemes.

Robotic Path Learning with Graphical User Interface

This paper describes an automated path generation method for industrial robots. Based on force control, a robotic subsystem has been developed for path automatic generation or path learning. Using a dummy tool and roughly taught guiding points around a part contour, the robot moves in position and force controlled hybrid mode, following the order of the guiding points and with contact force direction and value predefined. During the motion, robot actual position is recorded by the robot controller. After the motion, the recorded position data is used to generate a robot path program automatically. Robot lead-through may be used in the guiding point teaching. Furthermore, a GUI （graphical user interface） is developed on the teach pedant to guide through the guiding point creation and teaching, path learning, program verification and execution. The development has been incorporated into a robotic machining product option. Combination of the robot path learning function and GUI enhances the interaction between the robot and operator and drastically increases the level of robotic ease-of-use.

Hybrid position/force control strategy and experiment of the six-cable driven parallel manipulator for the forty-meter aperture radio telescope

This paper mainly analyzes a hybrid position/force control strategy and experiment of a six-cable driven parallel manipulator for a forty-meter aperture radio telescope. Through the establishments of a kinematic model, a catenary model and a cable-force characteristics model, a basic method is presented based on preventing the pseudo-drag problem of a flexible cable and realizing the hybrid position/force control for a six-cable driven parallel manipulator, and a hybrid position/force control system is developed. Some specific experiments in two typical velocities for astronomical observations are carried out. Experimental results show that the tracking accuracy is related to the speed of the movement. The desired tracking accuracy of the support system is achieved through an effective hybrid position/force control strategy, the cable forces are controlled effectively, and the pseudo-drag problem of flexible cable is solved. This study establishes the foundation of achieving the harmonious movement of the six-cable driven parallel manipulator, A-B rotating platform and the Stewart fine tuninz olatform.