Collaborative robots (cobots) are intended for direct physical interaction with human operators. A cobot and a human operator share control to produce the motion of the cobot end-effector. The human operator supplies motive forces and moments, while the cobot guides the motion.
The cobot end-effector is coupled to ground through a network of continuously variable transmissions (CVTs). The velocities of a pair of cobot joints, connected by a CVT, are related by its CVT setting. Kinematically, a cobot has just one degree of freedom in task space. However, the allowed direction of motion associated with this single degree of freedom can be servo-controlled. A class of powered cobots, which includes the Arm cobot, is capable of assisting or impeding the motion of its end-effector along its allowed direction of motion.
The Arm cobot employs a four-link parallelogram arm. The arm has three joints, each of which are connected to a common joint, called the power wheel, by a continuously variable transmission (CVT). The ratios of velocities between the arm's joints and the power wheel can be servo-controlled by adjusting the CVT settings.
An actuator, called the power motor, is directly coupled to the power wheel. By actively controlling the power motor, the Arm cobot is capable of operating autonomously and simulating user-defined inertias.