High Bandwidth Control of Flexible Robots: Proof of Concept Experiments for Momentum Management

The authors have proposed in several previous papers that high bandwidth position control of robotic end effecters can be achieved with momentum exchange with essentially collocated masses. The actuator for momentum exchange would typically be a moving coil motor with bandwidth of the order of 10 kHz, thus giving the ability to provide a force to the end-of-arm orders of magnitude quicker than conventional actuation methods and unlike micro-manipulators, without the force being transmitted to the robot arm itself. However, conventional joint servos must be retained for the purpose of removing momentum from the proof mass(es) instead of being the primary positioning device. This paper presents a summary of the theory, but is primarily concerned with a one dimensional experimental proof of concept. Here a simple one-link flexible arm (actually a linear motion) is controlled by two identical linear motors, one at the base and the second to drive the proof mass. Experiments demonstrate the ability of momentum management to provide disturbance rejection in a bandwidth of up to 100 Hz, confirming the potential to overcome the limitations of drive train flexibility. The limit of performance is the result of measurement bandwidth rather than actuation limits.