Yaw Slip Handling in Bipedal Robots via Force Allocation
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Solution Overview
Problem
Legged robots face challenges in maintaining stability and correcting yaw slips due to insufficient friction, which can lead to further slipping when attempting to rotate and correct the slip, disrupting the robot's gait and control over other degrees of freedom.
Innovation Solution
The robot determines a force allocation for its foot based on yaw rotation, updating it to reduce yaw moment and adjust shear forces to compensate for reduced traction, and determines a target yaw to correct yaw errors gradually, prioritizing other aspects of its gait to maintain balance and posture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot applies force to rotate and correct yaw slip, then yaw correction is achieved, but friction is insufficient causing further slipping
Solution Approach 1:
The robot applies only a portion of the force needed for complete yaw correction, accepting residual yaw error to avoid exceeding friction limits. The control system deliberately under-applies corrective torque to prevent the foot from slipping, trading incomplete correction for maintenance of traction.
Solution Approach 2:
The robot dynamically adjusts the yaw correction strategy based on real-time friction conditions. When insufficient friction is detected, the system transitions from aggressive correction to gradual correction, modulating the applied torque to match available friction and prevent slipping.
2Reliability
If the robot prioritizes yaw correction, then yaw stability is improved, but control over other degrees of freedom is disrupted
Solution Approach 1:
The robot applies yaw correction selectively and locally, only when and where necessary, rather than continuously prioritizing yaw. The control system modulates correction intensity based on local friction conditions and gait phase, allowing other degrees of freedom to maintain normal operation during periods when yaw correction is not critical.
Solution Approach 2:
The robot implements yaw correction periodically rather than continuously, interrupting correction actions to restore normal gait control. The system alternates between correction phases and normal operation phases, allowing other degrees of freedom to function properly during non-correction intervals.
Data Source
AI summary
An example method may include determining a requested yaw for a body of a robot, where the biped robot comprises a foot coupled to the body via a leg. The robot may then detect, via one or more sensors, a yaw rotation of the body with respect to a ground surface, where the foot is in contact with the ground surface. Based on the detected yaw rotation of the body, the robot may determine a measured yaw for the body. The robot may also determine a target yaw for the body, where the target yaw for the body is between the measured yaw for the body and the requested yaw for the body. The robot may then cause the foot to rotate the body to the target yaw for the body.