Design and Kinematic Analysis of a 3D-Printed 3DOF Robotic Manipulandum

Robotic manipulanda are often used to investigate human motor control of arm movements, as well as for tasks where haptic feedback is useful, e.g., in computer-aided design and in the teleoperation of robotic arms. Here we present the design and implementation of a small, low-cost, torque controlled 3DOF revolute manipulandum which supports translational movement in three-dimensions. All bespoke structural components are 3D printed and the arm lengths are constructed from carbon fiber tubes, which exhibit high stiffness but are very light, resulting in a design that exhibits a low intrinsic endpoint mass at the handle. We use rare-earth BLDC motors employing built-in low-ratio planetary-gearboxes, so the system is back-drivable and arm endpoint force can be controlled. We provide an analysis and simulation in MATLAB of the arm’s forward and inverse kinematics, as well as its static motor torque and endpoint force relationships. We used a microcontroller to operate the motors over their CAN interfaces. Finally, we demonstrate the use of the manipulandum as a robot for general point-to-point movement tasks using a microcontroller implementation of its inverse kinematics.