Power metrics for robot planning and redundancy resolution

Performance metrics based on power are presented for use in manipulator design, task planning, and real-time control of redundant robots. Screw theory is used to mathematically define the task instantaneously with two screws. The task wrench defines the load applied by a device to the environment, and the task twist describes the motion of the device relative to the environment. Three task types are identified: kinetic, manipulative, and reactive and scalar metrics are developed for each: power efficiency, specific velocity and specific force, respectively. The output power is only a function of the task screws, while device input power is shown to be a function of the task, the device Jacobian, and the actuator type. Expressions for input power are developed for: two common types of actuators, DC servomotors and hydraulic actuators. Ideal actuator models are used which permit illustration of geometric and reactive losses that are present to a significant level in tasks performed by a manipulator