cai Shi

A Five-fingered Underactuated Prosthetic Hand System

A five-fingered underactuated prosthetic hand controlled by surface EMG (electromyographic) signals is presented in this paper. The prosthetic hand is designed with simplicity, lightweight and dexterity on the requirement of anthropomorphic hands. Underactuated self-adaptive theory is adopted to decrease the number of motors and weight. The fingers of the hand with multi phalanges have the same size as an adult hand. The prosthetic hand control part is based on an EMG motion pattern classifier which combines VLR (variable learning rate) based neural network with wavelet transform and sample entropy. This motion pattern classifier can successfully identify the flexion and extension of the thumb, the index finger and the middle finger, by measuring the EMG signals through three electrodes mounted on the flexor digitorum profundus, flexor pollicis longus and extensor digitorum. Furthermore, via continuously controlling single fingers motion, the five-fingered underactuated prosthetic hand can achieve more prehensile postures such as power grasp. The experimental results show that the system has a great application value

Development of reconfigurable space robot arm

This paper presents a reconfigurable modular space robot arm including reconfigurable modular mechanics, electronics, and control software. This robot was composed of six same modular joints and one gripper. A configuration similar to PUMA robot was adopted, which made it possible to fold the robot a compact shape, and save space and cost for transporting it into the space. A big central hole in the modular joint was designed for the placement of the cables and plugs in the robot arm, which prevented them from damage of high temperature, radiation in the space environment and the motion of the robot. Joint torque sensor, joint position sensor and temperature sensors etc. were integrated into the fully modular multi-sensor joint, which made the joint more intelligent. A zero gravity experimental system was developed to verify the functions of the robot under zero gravity environment

Development of the Chinese Intelligent Space Robotic System

This paper gives an overview of the Chinese intelligent space robotic system. The system consists of a 6 DOF robot arm, a large-error tolerated gripper with two stereo cameras and onboard computer. The robot arm is composed of six identical modular joints, a big central hole in the modular joint was designed for the placement of the cables and plugs in the robot arm, which prevented them from damage of high temperature, radiation in the space environment and the motion of the robot. Joint torque sensor, joint position sensor and temperature sensors etc.., were integrated into the fully modular multi-sensory joint, which made the joint more intelligent. Also, a large-error tolerated gripper with two stereo cameras has been also designed to capture a microtarget satellite (MTS). A fault-tolerant onboard computer (OBC) with dual processing modules has been developed for the robot control. A zero gravity experimental system was developed to verify the functions of the robot arm under zero gravity environment

Path planning for minimizing base reaction of space robot and its ground experimental study

In free-flying space robotic system, the thruster jets will compensate the disturbances induced by manipulator to keep the attitude of the robot base invariable. For saving the expensive fuel that thruster jets cost, point-to-point path planning method in joint space for minimizing base reaction is proposed in this paper. The sinusoidal and polynomial functions are used here to parameterize the joint motion. This parameterization method can satisfy the kinematical constraints. The optimal object of base reaction is computed by inverse dynamics. In order to limit the joint velocity, an objective function including the constraint of joint velocity is defined. Genetic algorithm is introduced to solve the optimized problem, and the parameters for the minimum objective function value are found. The path planned is very smooth, and it can be applied in practical. According to the experiment on the zero gravity system, the effectiveness of the algorithm is proved.

High integrated modular joint for Chinese Space Station Experiment Module Manipulator

Around 2020, China is going to build its own space station and to carry out space science research of larger scale. Chinese Space Station (CSS) will operate in orbit for about ten years. This period will provide much more opportunities to scientists in China after the international space station. The space manipulators as cost-effective, energy-efficient tools supporting humans on extended space missions have played an important role in space exploration, such as aided cabin docking, cargo handling, supporting EVA and carrying out scientific experiments. So an Experiment Module Manipulator (EMM) was proposed for CSS. The principle prototype of the modular joint has been developed as the crucial component of the EMM and passed through the preliminary thermal vacuum test and dynamics environment tests.

Sliding mode hybrid impedance control of manipulators for complex interaction tasks

This paper presents a sliding mode hybrid impedance controller for complex interaction tasks. For easily implementing the scheme in embedded system, it is developed in discrete difference format. The hybrid impedance control is adopted since it is capable for both target impedance and force tracking. Then, the equivalent control based sliding mode control is introduced for robust to external disturbance. For smoother transitions between stages, the selection matrix is modified. The stability of the control system has been proved theoretically. At last, the effectiveness of the scheme has been validated by a group of simulations. The results provide smooth transitions and robustness to disturbances.

Development of high integrated 2-DOF joint module for space application

This paper presents a high integrated 2-DOF joint module for space application which consists of two modular joints and a control box. The axes of the two joints are orthogonal and intersectant. Based on the TDJM, some new version manipulators with different configuration could be developed with only a little modification in short time, such as four-DOF manipulator or six-DOF manipulator. The TDJM have high reliability with full redundant drive, sensors, power, communication and control system. A big central hole in the modular joint was designed for the placement of the cables in the TDJM, which prevents them from the damage of high temperature, radiation in the space environment and the motion of the joints. A test table was developed to measure the performances of the TDJM.