Motion Planning And Control Of Horizontal Underactuated Robots

Underactuated robots that have fewer control inputs than the generalizedcoordinates of the system provide a new way to improve the performances of robotsin terms of dexterity, low energy consumption and compactness. The underactuatedrobots have important theoretical significance and broad application prospects,especially for the growing shortage of energy, the underactuated system have attractedmore and more attention in nowadays and become the advanced topics of roboticresearch.This dissertation is focused on underactuated robots. The main purpose is to findthe intrinsic characteristics of underactuated system. The motion planning, trajectorytracking and position control of underactuated robots are dealt with theoretically andexperimentally based on the characteristic analysis of underactuated system.Firstly, the dynamic model of underactuated robot is developed based on Kanemethod. The integrability, controllability and exact linearization ability of theunderactuated system are analyzed. Criterions of integrability and controllability ofunderactuated system are proposed and the conclusion is made that the system doesnot satisfy the exact state feedback linearization condition. The manipulability indexesof underactuated robots in operation space and joint space that are used to measure theability of active joint acceleration to the endpoint acceleration and passive jointacceleration are proposed respectively for the first time. The manipulability indexesare of significance in the structural design and dynamic control of underactuatedrobots.Secondly, the optimal motion planning and the collision-free motion planning ofunderactuated robots are studied. A new method that based on genetic algorithm isproposed to solve the optimal motion planning of second order nonholonomic system.The virtual spring-damper and penalty methods are proposed for the obstacleavoidance of underactuated robots. Simulation results of 2R and 3R underacutatedrobots indicate the effectiveness of psoposed methods. These methods can beextended to the motion planning of underactuated robots with more degree offreedoms.Thirdly, the real time trajectory tracking in joint space and the geometric pathtracking in operation space of underactuated robots are investigated. The sliding modecontrol method is introduced to fulfill the exact real time trajectory tracking of 2R and3R underactuated robots. For the geometric path tracking, the path tracking under pathcoordinate and GA based tracking method for underactuated robots are proposed. Compare with path tracking under path coordinate method, GAbased tracking methodhas good adaptiability and has no restrictions to the initial status. It can be extended togeometric path tracking of underactuated robots with more degree of freedoms.Fourthly, position control of underactuated robots in operation space and in jointspace is studied. Two new methods called hierarchical fuzzy control and direct fuzzycontrol are proposed respectively based on the combination of intelligent controlmethod and genetic algorithm. The simulation results of 2-DOF and 3-DOFunderacutated robots show the effiectiveness of the designed controllers. The GAbased fuzzy controllers have good adaptability and stability. It provides a new way forthe intelligent control of underactuated robots.Finally, the experimental platform of underactuated system is developed and theexperimental study of underactuated robots is proposed. The motion controllers aredesigned and experiment study is carried out on 2R and 3R underactuated robots withand without brake. The relative control errors between the experiment results and thedesired values are less than 2%, which show the effectiveness of the designedcontrollers.