Biped Robot Compliance Control for Fast Walking Stability
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Solution Overview
Problem
Fast walking biped robots face challenges in maintaining stability due to external interference, uneven ground, and high-speed centroid movement, which can lead to rollover and instability.
Innovation Solution
A whole-body compliance control method that includes acquiring plantar stress data, calculating the actual zero moment point (ZMP), using centroid and plantar posture compliance controllers to adjust centroid and plantar positions and moments, and employing a double spring-damper model to manage plantar force and position, ensuring stable and compliant walking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the robot walks at high speed, then productivity is improved, but stability deteriorates due to large centroid tracking error and reduced support polygon area
Solution Approach 1:
The patent implements dynamic compliance control that adapts to different walking phases and speeds. The centroid compliance controller dynamically adjusts control parameters based on real-time state, enabling stable high-speed walking through continuous adaptation rather than fixed control parameters
Solution Approach 2:
The patent employs feedback control by continuously monitoring actual ZMP position, plantar stress data, and centroid position, then adjusting control outputs accordingly. The centroid compliance controller uses feedback from ZMP tracking error to generate correction commands that maintain stability during high-speed walking
2Speed
If the foot sole lands early or late, then speed is improved, but stability deteriorates due to excessive impact and plantar rotating moment
Solution Approach 1:
The patent applies beforehand cushioning by using the double spring-damper model to predict and prepare for landing impacts. The compliant plantar posture controller pre-adjusts foot posture and absorbs impact energy before full ground contact, preventing excessive impact and plantar rollover
Solution Approach 2:
The patent changes physical parameters by modeling the plantar system as a double spring-damper mechanism with adjustable stiffness and damping coefficients. This allows dynamic parameter adjustment during different walking phases to optimize impact absorption and maintain stability during speed variations
3Device complexity
If only ankle position is controlled, then device complexity is reduced, but stability deteriorates because comprehensive ankle position and posture control is not achieved
Solution Approach 1:
The patent segments the control system into distinct functional modules: centroid compliance controller for overall balance, and compliant plantar posture controller for foot-specific control. This segmentation allows comprehensive control of both position and posture while maintaining manageable system complexity through modular design
4Device complexity
If the centroid position is not adjusted, then device complexity is reduced, but stability deteriorates due to inability to track desired centroid position and adjust ZMP
Solution Approach 1:
The patent implements a universal centroid compliance controller that simultaneously performs multiple functions: tracking desired centroid position, adjusting ZMP position, and generating commands for both ankle position and posture. This multi-functional approach maintains stability while avoiding the need for separate dedicated controllers for each function
Data Source
AI summary
The present invention provides a whole-body compliance control method applied to a fast and stable walking biped robot, and the control method includes: obtaining a plantar stress and a plantar moment based on information of a foot force sensor to estimate an actual ZMP position of the robot; designing a centroid compliance controller based on the actual ZMP position of the robot to correct a centroid acceleration; designing a plantar position compliance controller based on a double spring-damper model according to the plantar stress to correct a foot height; designing a plantar posture compliance controller based on the plantar moment to correct a plantar posture; adding corrected centroid and foot values into an originally desired trajectory; and obtaining motor angles of various joints. In the method, the plantar position compliance controller is used to reduce the landing impact; the plantar posture compliance controller is used to ensure that the robot lands flat to prevent the robot from rollover; the centroid compliance controller is used to adjust a centroid position to prevent a robot body from bending forward and backward when the robot walks fast, thereby increasing the stability of the biped robot during fast walking.