Ramus: A Frequency-Multiplexed Power Bus for Powering, Sensing and Controlling Robots

As robots become more complex, small, and sophisticated, the cost and effort necessary for “wiring” become critical; the complex wiring makes the fabrication costly and necessitates care about space and stiffness of wires, which can inhibit the deformation of soft-bodied robots. The concept of power bus, which powers, controls, and monitors multiple slave modules (e.g., actuators, sensors) via a shared bus is one countermeasure for this challenge. However, handling many slave modules in real-time remains an unsolved issue; prior work suffers from a delay corresponding to the number of slaves or requires a rich signal processing unit in each slave module, which makes them unsuitable for controlling numerous actuators. To address this issue, we propose a frequency-multiplexed power bus, which integrates bandpass filters and load-modulation communication; our method enables us to power, control, and monitor all slave modules at once via a single pair of wires. Through analysis and experiments, we showed that eight nodes can be accommodated within a 9 MHz frequency band and can be independently controlled; finally, a caterpillar-like robot with four sensors and actuators was successfully driven by Ramus.