Cable properties modelling and force control for cable driven parallel robots

Throughout this thesis, first a brief introduction is given to the design of tendon-based serial and parallel robots. The structure of these robots (simply called cable robots) is described, and the mechanical design of a specific series of cable robots called IPAnema (designed and built in Fraunhofer IPA cable robotics lab) is illustrated. The aim of this thesis is to present a method which improves the position accuracy of these cable robots by eliminating the cable elongation effects. To this end, causes of this phenomenon are explained, and different solutions are investigated. In order to implement the proper solution, the kinematics foundation and properties of the cables are studied. In the next step, the model of the cables is extended, and the effects of the cable elongation are introduced to the model. Using PLC structured text programing language, the extended model is applied to the robot control system and the results are presented. In parallel to the work above, the necessity for a proper cable force control method is realized, and a LQR force controller is employed through modelling the dynamics of the system, and setting appropriate control priorities. Following performing several tests, the joint application of the cable elongation correction method and the cable force controller has shown that the position accuracy of the IPAnema cable robot has improved.