Robot COM Planning With Capture Point Feedback for Stable Walking
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Solution Overview
Problem
Conventional center of mass (COM) planning methods for legged robots lack timely correction, resulting in low accuracy and poor stability during walking.
Innovation Solution
A method that calculates a planning capture point and a measured capture point using six-dimensional force sensors and inertial measurement units, adjusts the zero moment point (ZMP) through a controller, and iteratively updates the COM position to improve stability, incorporating a processor and storage device for real-time execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional COM planning methods are used, then the robot can execute basic walking motions, but the accuracy of COM planning is low and walking stability is poor due to lack of timely correction
Solution Approach 1:
The patent implements a feedback mechanism by calculating both a planning capture point (from desired COM trajectory) and a measured capture point (from actual robot state), then using the difference between these two points to generate corrective control signals. This closed-loop feedback ensures timely correction of COM position, improving both planning accuracy and walking stability
Solution Approach 2:
The patent replaces traditional mechanical control methods with a computational approach using six-dimensional force sensors and inertial measurement units to calculate capture points, then uses algorithmic correction based on the difference between planned and measured values. This substitution of mechanical feedback with sensor-based computational feedback enables more precise and timely COM correction
2Measurement precision
If real-time correction of COM position is implemented using sensors and iterative updates, then the accuracy and stability of COM planning improve, but the device complexity increases
Solution Approach 1:
The patent employs six-dimensional force sensors that simultaneously provide force and moment information, and inertial measurement units that provide acceleration and orientation data. These multi-functional sensors reduce the need for separate dedicated sensors for each measurement, thereby improving COM planning accuracy while limiting the increase in device complexity
Solution Approach 2:
The patent introduces the concept of capture point as an intermediary element that mediates between the COM planning and the actual robot execution. By calculating both planning and measured capture points and using their difference for correction, the system achieves accurate COM control through a computationally efficient intermediary representation, avoiding direct complex control of multiple robot parameters
Data Source
AI summary
A center of mass (COM) planning method includes: obtaining a planning position of the COM and a planning speed of the COM of a robot, and calculating a planning capture point of the robot according to the planning position of the COM and the planning speed of the COM; obtaining a measured position of the COM and a measured speed of the COM, and calculating a measured capture point of the robot according to the measured position the measured speed; calculating a desired zero moment point (ZMP) of the robot based on the planning capture point and the measured capture point; obtaining a measured ZMP of the robot, and calculating an amount of change in a position of the COM according to the desired ZMP and the measured ZMP; and correcting the planning position of the COM according to the amount of change in the position of the COM.