Slip Detection and Recovery for Quadruped Robots via Orthogonal Decomposition

Locomotion on surfaces with insufficient friction poses a significant challenge for quadruped robots. Regular legged control methods derive contact forces by assuming stationary foot contact, which is no longer valid under slippery conditions. This article addresses this issue by designing a systematic antislip approach with a proprioceptive slip detector and a hybrid position/force slip recovery controller. The proposed slip detector estimates the likelihood of slippage occurrence without any external sensors. Meanwhile, the slip recovery controller extends the existing stationary contact constraint to the slippery case, which orthogonally decomposes the task of contact force control and slip recovery position control by projecting them into different subspaces. We also demonstrate that the proposed controller can be utilized to measure the friction coefficient of the contact surface for online parameter tuning. The proposed method is released as an open-source program that can be easily integrated into other model-based quadruped control frameworks and is experimentally validated on a Unitree A1 quadruped robot.