Online Recording the Position and Orientation of an End- Effector of a Spatial Cable-Suspended Robot for Close Loop Control Using HybridSensors

All of the Degrees of Freedom including of position and orientation of the end-effector of a spatial cable robot are sensed and recorded with a new sensor fusion method in this paper for being used as feedback. This goal is achieved by employing a hybrid methodology of image processing and distance measurement device. The advantage of the proposed algorithm over encoder solution is its higher accuracy for the cases in which the model suffers from structural uncertainties. Moreover, contrary to other end-effector’s pose measurement devices, this method is able to record all of 6 spatial degrees of freedom in all of environmental conditions and in whole of the workspace of the robot. Both of camera and lasers are calibrated individually to provide an actual data set. The camera is responsible for observing the planar movement of the end-effector while the lasers provide the altitude and rotation data of the end-effector. The final reported data of position and orientation of the end-effector are evaluated eventually by the aid of both the data of the lasers and camera using a perspective based methodology and presented data fusion formulation. The reported position of the end-effector which is captured in an online way is then employed as feedback for the control center of the robot. By using a closed loop way which is based on feedback linearization algorithm, this center controls the end-effector. A simulation study is done on the ICaSbot (IUST Cable Suspended Robot) which is a spatial cable robot with six DOFs using six actuators. The efficiency of the proposed algorithm is proved by comparing the experimental tests conducted on ICaSbot with the related simulation results which are performed in the MATLAB environment. The tests include statistical analysis of accuracy and repeatability and also dynamic movement of tracking and point to point motion. KeywordsComponent; Cable Suspended Robot; Feedback Control; Hybrid Sensor Technology; Image Processing; Laser Sensor