Operation Process Optimization For Robotic Manipulators In Complicated Tasks

Robotic manipulators have been applied widely in industry.The profound research of the robotic operation process makes sense for the improvement of robotic work efficiency and dynamic performance.There are many factors that affect the robotic operation process in the complicated tasks.This dissertation investigates the optimization of the robotic operation process in these complicated tasks such as the changeable operation sequence,the mechanism pairs with clearances,and the remote unstructured unknown environment.The key techniques of robotic motion planning, layout design,dynamics synthesis,and teleoperation with force feedback have been profoundly studied.The inverse displacement analysis is the basis of motion planning for robotic manipulators.In order to deduce the relationships among the joint variables for serial robots with offset wrists,the inverse displacement analysis based on the decoupled degrees of freedom at the cutoff point is proposed.From the geometric character of robotic mechanisms,the kinematic chain is cut into two branches.The decoupling of one component of degrees of freedom for the two branches becomes lowest at the cutoff point.The transcendental equations containing 6 variables turn into a nonlinear equation containing 1 variable.The inverse displacement analysis is performed using one dimensional iterative search.There are many objectives of motion planning in a complex task of a robotic manipulator.In order to facilitate the optimization of robotic task process,the motion planning based on the decomposition of operation process is proposed.In the free motion sub process,the robotic kinematic models of quasi trapezoidal waveform and quasi triangular waveform are adopted,and the trajectory planning based on robotic minimum cycle time is studied.In the constrained motion sub process,the design features of the workpieces are mapped into the machining features,and the path planning based on the feature mapping is studied.The complex task is regarded as the combination of the two sub processes.The layout design of robotic manipulators is one of the prime problems for the design of robotic workstations.In order to reduce the iteration of interaction,and to shorten the robotic work cycle time,a robotic layout method based on the coordinate optimization of the operation sequence and the robotic base position is proposed.The feasible space of the robotic base is split into many discrete spatial grids.The ant colony algorithm is adopted to optimize the operation sequence for each grid.In the grids with the same optimum operation sequence,the pattern search algorithm is applied to find the optimum position and orientation of the robotic base.The motion pair of robotic manipulators makes the adjacent joints move relatively.In order to avoid the collision and impact between pair elements,a method based on trajectory planning for the detachment avoidance of robotic joint elements with clearances is proposed.The virtual links are adopted to model the joint clearances.The robotic trajectory planning is performed using polynomial functions. The joint forces are expressed as functions of the motion parameters of active joints and virtual links.Then the dynamic response spectrum of the joint reaction force is established.The proper time span of the trajectory is chosen from the dynamic response spectrum to avoid the detachment of joint elements during the motion.The teleoperation with force feedback for robotic manipulators is applied widely to the unknown or unstructural work environment.In order to facilitate the remote job for operators,the robotic teleoperation with force feedback based on the enhancement of operation facility is proposed.The fixed-point control mode is presented besides the traditional position and rate control mode.The rate-position-point hybrid control mode is studied for the teleoperation.The operation intent is recognized by the state analysis of the operator's movement,and the online generation method of the virtual fixture based on the intent recognition is studied.For the robotic teleoperation in virtual environment,the continuous generation method of the contact force based on the active guidance is studied to enhance the operator's haptic sense.The software for the operation process simulation of the robotic virtual prototype is developed.The software contains two subsystems,which are the system of robot layout and operation simulation and the system of robotic teleoperation integrated with a virtual environment.The robot layout and operation simulation system is implemented though two technical routes,which are the application development based on UG and the autonomous development based on WTK.