Are parallel manipulators more energy efficient?

The energy efficiency of a robotic manipulator is important, particularly when that manipulator is used in conjunction with a mobile robot with limited battery life. In this paper the energy efficiency (in terms of the electrical energy usage) of a spatial three DOF parallel manipulator is compared to a serial manipulator with the same drive motors and a similar workspace. The effects of end-effector position, velocity and acceleration, and static loading due to gravity are examined. Over a range of conditions, the average energy usage of the parallel manipulator was determined to be 26% of the serial manipulator's. This benefit is not due simply to the reduction in moving mass achieved by the parallel design since its moving mass is 70% of the serial manipulator's. Static loading due to gravity was found to roughly double the power usage of both manipulators without significantly affecting their relative energy efficiency.