A Parallel SCARA Robot With Low-Impedance Backdrivability and a Remotely Operated Gripper With Unlimited Rotation

This letter presents a backdrivable (4+1)-degree-of-freedom SCARA parallel robot including a remotely operated gripper with unlimited rotation for intuitive sensorless low-impedance physical human-robot interaction. The kinematic modelling of the robot is first recalled and the novel remotely operated gripper mechanism is presented. This mechanism allows the operation of the gripper from the base actuators while allowing unlimited rotation of the end-effector. The Jacobian matrices are derived and the singularities are briefly discussed. A geometric description of the workspace is then developed to provide insight into the kinematic design of the robot. The design of a prototype is then presented. Experimental results obtained with the prototype are provided, including a demonstration of the force capabilities, the backdrivability and the execution of grasping and pick-and-place tasks. The results clearly demonstrate the low impedance of the robot and its motion and grasping capabilities, which make it ideal for intuitive human-robot interaction without requiring the use of a force/torque sensor.