Biped Robot Walking Control Using ZMP and Capture Point Feedback
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Solution Overview
Problem
Biped robots face challenges in maintaining walking stability on uneven terrain, often resulting in instability or falling, as existing control methods are inadequate for such environments.
Innovation Solution
A robot control method utilizing zero moment point (ZMP) tracking and real-time capture point error calculation to adjust ankle joint torques, ensuring stable foot pose adaptation to uneven surfaces by distributing support forces between feet based on planned ZMP positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional control methods are used for biped robots, then the robot can walk stably on even surfaces, but the robot cannot maintain stability on uneven terrain and may fall over
Solution Approach 1:
The patent implements dynamic control by continuously tracking the zero moment point (ZMP) and capture point (CP) in real-time during robot walking. The control system dynamically adjusts ankle joint torques and foot poses based on current state estimation, allowing the robot to adapt to varying terrain conditions while maintaining stability through continuous feedback control rather than static pre-programmed motions
Solution Approach 2:
The patent employs feedback control mechanisms where the actual robot state (position, velocity, acceleration) is continuously estimated and compared with desired trajectories. The capture point error and ZMP tracking error serve as feedback signals that drive the adjustment of ankle torques and foot poses, enabling the robot to correct deviations and maintain stability on uneven terrain through real-time state correction
2Reliability
If the robot rapidly adapts foot poses to uneven terrain, then walking stability is maintained, but the control complexity and computational requirements increase
Solution Approach 1:
The patent introduces the capture point (CP) as an intermediary concept that simplifies the control of biped walking on uneven terrain. By defining the CP based on the linear inverted pendulum model and using it as a reference for foot placement, the complex problem of maintaining stability on variable terrain is transformed into a more manageable task of tracking the CP and adjusting foot poses relative to it, reducing control complexity while maintaining reliability
Data Source
AI summary
A robot control method includes: determining a planned capture point and a measured capture point of the robot so as to calculate a capture point error of the robot; obtaining positions of a left foot and a right foot of the robot, and a planned zero moment point (ZMP) of the robot so as to calculate desired support forces of the left foot and the right foot; calculating desired torques of the left foot and the right foot according to the capture point error, the desired support forces of the left foot and the right foot; obtaining measured torques of the left foot and the right foot so as to calculate desired poses of the left foot and the right foot; and controlling the robot to walk according to the desired poses of the left foot and the desired pose of the right foot.