Legged Robot Foot Ground Reaction Force Control
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Solution Overview
Problem
Legged robots face challenges in maintaining balance and preventing slips on uneven or rough terrain due to the inability to accurately control ground reaction forces, which affects their gait stability and efficiency.
Innovation Solution
A legged robot determines the coefficient of friction and gradient of the ground surface, calculates a target ground reaction force, and adjusts its orientation to stay within a threshold to avoid slips, using sensors and processors to control the force applied to the ground, allowing for real-time adjustments during each step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the robot applies larger ground reaction forces to maintain balance on uneven terrain, then balance stability is improved, but the risk of slipping increases due to exceeding friction limits
Solution Approach 1:
The robot dynamically adjusts the orientation and magnitude of ground reaction forces based on real-time terrain parameters (coefficient of friction and gradient). By changing the force parameters to stay within the friction cone defined by μ and terrain angle, the robot maintains balance without exceeding slip thresholds
Solution Approach 2:
The robot uses sensor feedback to continuously monitor terrain conditions (friction coefficient and gradient) and adjusts its ground reaction forces accordingly. This closed-loop control ensures forces remain within safe friction limits while maintaining balance on varying terrain
2Adaptability or versatility
If the robot adjusts ground reaction force orientation frequently to adapt to changing terrain, then adaptability is improved, but control complexity increases
Solution Approach 1:
The robot changes force orientation parameters based on measured terrain gradient and friction conditions. The control system calculates appropriate force directions that adapt to terrain variations without requiring complex adjustment mechanisms
Solution Approach 2:
The robot autonomously determines and adjusts its ground reaction force orientation based on sensor measurements of terrain properties. The system self-regulates force application without external intervention, simplifying overall control architecture
3Productivity
If the robot increases the magnitude of ground reaction forces to improve propulsion efficiency, then productivity is improved, but the likelihood of foot slip increases
Solution Approach 1:
The robot optimizes the magnitude and orientation of ground reaction forces by considering terrain friction and gradient parameters. By adjusting force parameters to maximize propulsion within friction constraints, the robot achieves efficient movement without slipping
Solution Approach 2:
The robot proactively adjusts force application to prevent slip before it occurs by staying within the friction cone. This preliminary adjustment of force magnitude and direction prevents loss of traction while maintaining propulsion efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the robot to maintain balance and stability on varied terrain by precisely controlling ground reaction forces, preventing slips and adjusting to changing conditions, thereby enhancing its operational efficiency and reliability.
Implementation Method 1
determining a threshold orientation for a target ground reaction force on the foot of the robot during a step
Data Source
AI summary
An example method may include i) determining, by a robot having at least one foot, a representation of a coefficient of friction between the foot and a ground surface; ii) determining, by the robot, a representation of a gradient of the ground surface; iii) based on the determined representations of the coefficient of friction and the gradient, determining a threshold orientation for a target ground reaction force on the foot of the robot during a step; iv) determining the target ground reaction force, where the target ground reaction force comprises a magnitude and an orientation; v) determining an adjusted ground reaction force by adjusting the orientation of the target ground reaction force to be within the determined threshold orientation; and vi) causing the foot of the robot to apply a force on the ground surface equal to and opposing the adjusted ground reaction force during the step.