A Load-Independent Multi-CV-Output WPT System for Driving Multi-Joint-Motors in the Robotic Arm

This paper proposes a load-independent wireless power transfer (WPT) system tailored for motor actuation, aiming to eliminate the physical tethering of joint motors and enhance the operational freedom of the robotic arm. The key is to leverage cascaded coil pairs together with inductor-capacitor-capacitor-series (LCC-S) networks to generate multiple constant-voltage (CV) outputs for concurrently energizing multiple DC motors. Differing from traditional multi-coil WPT systems, where inconsistent CV outputs arise from the inherent resistance of coupled coils, this paper introduces a novel voltage compensation method to guarantee identical CV outputs from each relay unit by optimizing the parameters of the LCC-S compensation alone. Additionally, each joint motor is driven by a receiver-side low-frequency H-bridge inverter, providing flexible control over both the rotating direction and speed. Finally, a 400 W experimental prototype incorporating two coil pairs and two joint motors has been constructed and tested with 9 distinct load-torque scenarios and 4 different speed control cases.