Biped Robot Foot Force Tracking for Uneven-Ground ZMP Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for biped robots fail to accurately track a planned Zero Moment Point (ZMP) and control foot force and moment, especially on uneven ground, leading to instability and inaccuracies in ZMP calculation due to lag and sensor errors, limiting their ability to adapt to varied terrain.
Innovation Solution
A method that calculates desired foot forces and moments based on a planned ZMP, using a force tracking controller to adjust ankle joint trajectories, combined with a double-spring damping model for improved compliance and impact absorption, allowing for precise tracking of foot forces and moments to achieve stable walking on uneven surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ZMP tracking control is used on uneven ground, then the robot can maintain stability through force and moment control, but calculation accuracy of ZMP deteriorates due to theoretical inconvenience and sensor errors
Solution Approach 1:
The patent introduces an admittance controller as an intermediary between force sensing and ZMP calculation. The controller maps foot force and moment measurements to desired ZMP positions through a compliance model, avoiding direct calculation of ZMP from noisy sensor data on uneven ground. This intermediary transformation resolves the contradiction by providing stable control without requiring accurate direct ZMP measurement.
Solution Approach 2:
The patent changes the control parameter from direct ZMP position to foot force and moment parameters. By controlling the robot to generate specific foot forces and moments rather than directly controlling ZMP position, the system can adapt to uneven ground while maintaining stability. This parameter transformation allows the robot to compensate for ground irregularities through force modulation.
2Device complexity
If simple admittance control is used for foot force adjustment, then the control system remains simple, but the adjustment range becomes excessively small and cannot meet control requirements for uneven ground
Solution Approach 1:
The patent implements a dynamic admittance controller with time-varying compliance parameters. The controller adjusts its stiffness and damping characteristics dynamically based on the robot's walking state and ground conditions. This dynamic adjustment enables the controller to handle both flat and uneven ground effectively while maintaining manageable complexity through structured parameter adaptation.
Solution Approach 2:
The patent incorporates feedback mechanisms where the actual foot force and moment measurements are continuously compared with desired values, and the admittance controller adjusts the ankle joint trajectories based on these errors. This closed-loop feedback expands the effective adjustment range while keeping the controller structure relatively simple through proportional-damping control laws.
Data Source
AI summary
The present invention discloses a method of tracking control for a foot force and moment of a biped robot. According to the method, a double-spring damping model is designed, and a force tracking controller is designed by using an LQR optimization method, so as to realize tracking of the foot force and moment of the biped robot. Further, a desired force on a foot and a desired moment on the foot are calculated through a planned ZMP distribution method, thereby eventually achieving better ZMP tracking of the biped robot and adapting to ground of certain unevenness. According to the present invention, the traditional control method of ZMP tracking to realize stable walking of a biped robot and adapting to uneven ground is abandoned; instead, a desired force and moment on a foot enabling stable walking of the robot are directly calculated, and direct control is performed to realize tracking of the force and moment on the foot, so as to carry out stable control in a more essential and easy-to-implement manner, thereby achieving faster control response, stronger capability of adapting to uneven ground, and ideal ZMP tracking effect.