Biped Walking Robot Grounding Timing Adjustment
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Solution Overview
Problem
Biped walking robots face instability due to external disturbances and calculation errors, as the grounding timing and position determined by the ZMP equation do not strictly guarantee stable walking, especially when encountering obstacles or floor protuberances.
Innovation Solution
A method that calculates a second leg ZMP position by solving the ZMP equation with provisional grounding timing, adjusting the grounding timing to ensure the ZMP position remains within the leg's permissible area, allowing for real-time changes in both grounding position and timing to maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the grounding position and timing are determined using the ZMP equation under prescribed conditions, then the position and velocity of the center of gravity can be kept within a prescribed range, but stable walking is impaired by external disturbances, calculation errors and floor protuberances
Solution Approach 1:
The patent applies dynamics by making the grounding timing adjustable rather than fixed. The controller dynamically modifies the grounding timing of the leg based on real-time detection of external disturbances, calculation errors, or floor protuberances. This allows the system to adapt to changing conditions while maintaining walking stability, resolving the contradiction between relying on predetermined ZMP equations and responding to unpredictable environmental factors.
2Ease of operation
If the grounding timing is previously determined to calculate the grounding position, then the calculation is simplified, but the walking stability cannot be optimized in response to changing conditions
Solution Approach 1:
The patent applies preliminary action by first calculating the grounding position based on predetermined grounding timing using the ZMP equation, then subsequently adjusting the grounding timing if external disturbances or errors are detected. This two-stage approach maintains the simplicity of preliminary calculation while enabling later optimization for stability, resolving the contradiction between calculation ease and walking reliability.
3Measurement precision
If the ZMP position is calculated to be within the ground contact surface, then stable walking is guaranteed in principle, but the actual ZMP may not be located inside the ground contact area due to various errors
Solution Approach 1:
The patent applies feedback by continuously monitoring the actual ZMP position and comparing it with the calculated ZMP trajectory. When detection indicates that the actual ZMP deviates from the permissible area due to external disturbances, calculation errors, or floor protuberances, the controller provides feedback by adjusting the grounding timing to bring the ZMP back within the stable range, thereby resolving the contradiction between theoretical accuracy and practical reliability.
Data Source
AI summary
Provided is a method for determining a grounding timing of a biped walking robot. Firstly, a ZMP equation which represents a trajectory of a center of gravity including a first single-leg grounded period in which the robot stands only with a first leg and a second single-leg grounded period in which the robot stands only with a second leg, following the first single-leg grounded period, is solved using a predetermined grounding timing. A second leg ZMP position representing a ZMP position in the second single-leg grounded period is then calculated. When the calculated second leg ZMP position is out of the second leg ZMP permissible area, the grounding timing is modified so that the second leg ZMP position is located in a second leg ZMP permissible area which is defined corresponding to a possible grounding area of the second leg.