One-Wire Smart Motors Communicating over the DC Power Bus-Line with Application to Endless Rotary Joints

A system of multi-axis networked smart motors is developed to reduce complex cable harnesses. Motor control signals are sent over the DC power bus line and received by motors with integrated power amplifiers and controllers. Unlike traditional AC power line communication, the noise level and signal attenuation are much lower for the DC power bus communication. This allows for high fidelity, broadband communication among many smart motors without bulky, costly cables. A modem is designed to exploit the features of the DC power bus communication. A power-signal coupling circuit with an impedance trap filter is designed for superimposing control signals over the DC power bus line with a maximum of signal transmissibility and reduced line noise. An experimental setup was developed to identify the noise spectrum and signal transmissibility of the consolidated power-signal line. Optimal carrier frequency and filter parameters are then obtained based on the experiments. A simple protocol for bi-directional communication between the motors and the central controller is designed and tested. Finally, the design of a joint undergoing continuous rotation is proposed utilizing the consolidated power-signal cable connected to endlessly spinning smart motors.