Research On Reconfigurable Strategy And Structural Design Of 4-DOF Chained Robot

With the continuous development of aerospace industry,space robots have been widely used in challenging environments.Due to the special space environment and the features of space missions,the widely used ordinary manipulators were considered unsuitable for space on-orbit tasks.In order to solve this problem,we design an 4-DOF chained robot which can change its own configuration automatically.This robot consists of a series chain of 1-DOF modules that are capable of change its structure according to the task demand.Additionally,each module includes a communications bus,modular electro-mechanical interface,and the docking mechanisms.Firstly,The module is designed with four joints,an active docking,and a passive docking.Each joint is made up of a motor and a harmonic reducer.Moreover,the joint includes a joint torque sensor,a temperature sensor,a gyroscope,an accelerometer,and a Hall sensor.The drive structure of the active docking is designed using a two-way rotary shape memory alloy(SMA)actuator.And the double cam mechanism and the hooks are used as an executive mechanism.At the same time,the finite element analysis of the key components of the module are carried out using Anasys Workbench.Based on Adams,the motion simulation of th e docking mechanisms are analyzed.Secondly,the electrical control system of the docking mechanisms is built using Arduino Mega 2560.Then,we design the two amplifier circuits which is used to drive SMA for the active connector between different modules.Based on the infrared intensity measurement system,this thesis design the pose measurement module.This module can provide the accurate position and attitude information to the active docking and passive docking.In order to calibrate the systems,an experimental platform is established with the transmitting circuit and receiving circuit.Thirdly,we introduce the three most commonly used configurations of the chained robot.And to the chain configuration,we design the reconfigurable strategy for different modules.Then,we describe the structure of the module,and establish the kinematics equation based on Denavit-Hartenberg(D-H)method.Base on the D-H coordinate system,we can get the D-H parameters of the regenerative robot.According to the rule of D-H transform coordinates,we can establish the transformation matrix for solving the inverse kinematics problem.The initial state and the end state of the regenerative robot based on the inverse kinematics are generated.Moreover,the trajectory planning of two module during the reconfiguration process is presented.The simulation results of the trajectory planning are present using the specify parameters of the modules.Finally,the ground experiment platform of the chained robot is built.The docking experiment based on the tolerance model is carried out by using the two regeneration modules.Then,we present docking experiment between the active docking and passive docking.The experiment results confirm that the advantages and implications of chained robot.