Robot Balance Control via Capture Point and Hip Height Torque Compensation
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Solution Overview
Problem
Current balance control methods for robots, such as ZMP and dynamic walking control, face challenges in achieving stable and natural gait while maintaining energy efficiency and precise position control, especially when dealing with complex environments and kinematic singularities.
Innovation Solution
A balance control apparatus and method that compensates for forces and moments based on a capture point and hip height, distributing compensation forces across multiple legs to maintain an upright pose, using pose detection, angle detection, and servo control to calculate and apply target torques for balance, incorporating forward and inverse kinematics, and Jacobian transformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-based ZMP control method is used to achieve precise position control, then position control precision is improved, but energy consumption increases and joint stiffness becomes high
Solution Approach 1:
The patent replaces the traditional position-based ZMP control method with a torque-based control method. Instead of controlling joint positions directly through high-gain position loops that consume high current, the invention calculates target torques for each joint based on dynamic equations and applies them directly. This substitution of control approach reduces energy consumption while maintaining balance control effectiveness.
2Measurement precision
If position-based ZMP control with inverse kinematics is used, then position control is achieved, but the robot exhibits unnatural gait and cannot handle kinematic singularities
Solution Approach 1:
The patent inverts the traditional control approach by working forward from torque to position rather than backward from position through inverse kinematics. The dynamic equation of motion directly relates joint torques to the acceleration of the center of gravity and joint accelerations. By specifying desired center of gravity motion and solving for required torques, the system avoids inverse kinematics entirely, enabling natural human-like gaits and handling kinematic singularities gracefully.
3Use of energy by moving object
If torque-based dynamic walking control is used, then energy efficiency is improved, but the dynamic equation becomes excessively complicated for robots with 6 degrees of freedom
Solution Approach 1:
The patent segments the control problem by separating balance control (torque-based dynamic control) from gait generation. The dynamic equation is used specifically for calculating balance torques to maintain upright posture, while gait patterns are generated separately. This segmentation allows the complex dynamic equations to be applied only where necessary for balance, rather than for the entire motion control, making the system manageable for 6-DOF robots.
4Use of energy by moving object
If FSM control method is used to achieve torque commands, then energy efficiency is improved, but precise position control is not achieved
Solution Approach 1:
The patent merges the advantages of both FSM torque-based control and position-based control. The system uses torque commands (like FSM) for energy-efficient balance maintenance, while simultaneously incorporating precise position feedback through the dynamic equation to achieve accurate position control. The state machine approach determines when to apply torques, while the dynamic model ensures precise control accuracy.
Data Source
AI summary
A balance control apparatus of a robot and a control method thereof. The balance control method of the robot, which has a plurality of legs and an upper body, includes detecting pose angles of the upper body and angles of the plurality of joint units, acquiring a current capture point and a current hip height based on the pose angles and the angles of the plurality of joint units, calculating a capture point error by comparing the current capture point with a target capture point, calculating a hip height error by comparing the current hip height with a target hip height, calculating compensation forces based on the capture point error and the hip height error, calculating a target torque based on the calculated compensation forces, and outputting the calculated target torque to the plurality of joint units to control balance of the robot.