Conform to grip: Joint reaction force-driven adaptive variable admittance control of biped climbing robots

Abstract

Current biped climbing robots encounter persistent challenges in aligning their grippers with structural elements like poles, regardless of teleoperation or perception-based control implementations. To overcome this limitation, we present a joint reaction force-driven adaptive variable admittance control framework that enables autonomous compliant alignment with enhanced precision. The proposed method utilizes unintentional gripper-pole contact-induced joint reaction forces to drive alignment through a variable damping admittance controller. Damping parameters are adaptively regulated through proportional-derivative control law based on real-time joint reaction force errors. By establishing zero reference reaction force, the system concurrently accomplishes dual objectives: gripper pose alignment and reaction force minimization. Experimental validation confirms that our framework significantly enhances alignment efficiency and gripping reliability without requiring explicit gripper-pole pose detection. This methodology proves particularly effective for robotic systems transitioning between open-chain and closed-chain configurations while resolving inherent joint conflicts.