Kinematically Redundant Parallel Haptic Device with Large Workspace

In this paper, a kinematically redundant parallel haptic device with large workspace is presented. The haptic device has a similar kinematic structure to the well-known Delta manipulator. However, it has a special arrangement of actuators and one redundant actuator added to the third leg. The proposed haptic device has essentially 4-DOF, however, only three translational DOF are used for 3-DOF positioning and force reflection, and one rotational DOF by the redundant actuator is used to increase well-conditioned workspace. If the redundant actuator's angle is controlled to follow x and y position, the haptic device has a large cylindrical workspace and can maintain good kinematic and statics performance over the whole workspace. The kinematics and workspace are analysed, and the optimal design method of finding minimum link lengths to satisfy prescribed workspace is presented. Finally, the prototype haptic device and control experiment result are presented