Swing Leg Trajectory Replanning After Foot Collision in Biped Robots
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Solution Overview
Problem
Legged robots, such as biped robots, face issues with collision and damage when walking on uneven ground or stairs due to errors in external sensory information, leading to potential tripping or falling from low obstacles.
Innovation Solution
A method for controlling legged robots that involves terminating the planned trajectory of the swing leg upon collision, using a foot dragging control mode to calculate a position offset, and replanning the trajectory to prevent further collisions, ensuring stable operation and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot continues to follow the planned trajectory after collision, then the control system maintains simplicity, but the robot will collide repeatedly with obstacles causing damage
Solution Approach 1:
The patent implements feedback by detecting external forces acting on the swing leg during motion and using this information to adjust the trajectory planning. Force sensors detect collisions with obstacles, and this feedback triggers replanning of the swing leg trajectory to avoid repeated collisions and ensure robot safety.
Solution Approach 2:
The patent applies preliminary action by pre-planning multiple trajectory components for the swing leg before motion begins. When a collision is detected, the system selects from pre-prepared alternative trajectories rather than computing entirely new paths, reducing computational complexity while maintaining safety.
2Reliability
If the robot uses external sensory information to detect obstacles, then the robot can avoid obstacles, but errors in sensory information cause the robot to trip or fall
Solution Approach 1:
The patent uses force sensors as an intermediary mechanism between the swing leg and the environment. Instead of relying solely on external sensory information that may be erroneous, the force sensors directly measure contact forces during collision, providing reliable real-time feedback about actual environmental interactions.
Solution Approach 2:
The patent implements dynamic trajectory adjustment based on real-time force detection. Rather than relying on static pre-planned trajectories or potentially erroneous external sensory information, the system dynamically replans the swing leg trajectory in response to detected external forces, adapting to actual environmental conditions.
3Adaptability or versatility
If the swing leg follows a fixed planned trajectory, then the control process is simple, but the robot cannot adapt to unexpected obstacles causing damage
Solution Approach 1:
The patent segments the swing leg trajectory into multiple independent trajectory components that can be individually adjusted. When a collision occurs in a specific direction, only the relevant trajectory component is replanned while other components remain unchanged, reducing computational complexity while maintaining adaptability.
Solution Approach 2:
The patent transforms the static trajectory planning problem into a dynamic one by continuously monitoring external forces and adjusting trajectory components in real-time. The system maintains simplicity through modular replanning of only affected trajectory segments rather than complete replanning, achieving adaptability without excessive complexity.
Data Source
AI summary
A method for controlling a legged robot includes: in response to detection of a collision event associated with a foot of a swing leg of the biped robot, terminating a trajectory component planning of the swing leg in a collision direction; calculating a position offset in the collision direction according to an external force that is received by the foot of the swing leg in the collision direction and obtained in real time, based on a foot dragging control mode, and determining a replanned trajectory component in the collision direction based on the position offset; and controlling the swing leg to move based on the replanned trajectory component in the collision direction and a desired trajectory component of the swing leg in a non-collision direction.