Design of a planar parallel robot to investigate human arm point to point reaching movement

To study human motor control and learning in upper extremities, scientists widely use robotic arms to apply external forces to subject's hand interactively. In this work, we describe the design procedure of a planar parallel manipulandum with five links and 2-DoF in a vertical plane (e.g. sagittal or frontal plane). The manipulandum works in two active and passive modes. In the passive mode, the robotic arm follows the movements of the human arm; while in the active mode, the robotic endeffector guides subject's hand in any desired direction. In both active and passive conditions, the robot arm can be programmed to apply unexpected disturbances to the subjects hand. To control the movement of the manipulandum, we used two PID controllers with local shaft angle feedback to control the manipulandum. For the active mode, we used also a global feedback from endeffector position. As the first step for proof of concept, the whole system was simulated in MATLAB.