Walking Robot Pose Control via Torque Servo and Virtual Gravity
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Solution Overview
Problem
Existing walking robot technologies face challenges in maintaining a stable erect pose and balance under external forces or ground tilts, particularly due to high energy consumption and unnatural gait caused by position-based Zero Moment Point (ZMP) control methods.
Innovation Solution
A pose control method for walking robots that calculates the current Center of Gravity (COG) and compensates for balance errors by converting these into virtual acceleration of gravity, distributing moments to legs using a Jacobian matrix, and performing torque servo control to maintain an erect pose and balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-based ZMP control method is used, then precise position control is achieved, but high energy consumption and high stiffness occur
Solution Approach 1:
The patent changes the control parameter from position-based to torque-based control. Instead of controlling joint positions to achieve ZMP constraints, the system directly controls joint torques, which reduces the servo gain requirement and consequently lowers energy consumption while maintaining control precision through torque feedback
2Measurement precision
If position-based ZMP control method is used, then precise position control is achieved, but high stiffness and high impact occur
Solution Approach 1:
The patent changes the control parameter from position to torque, which reduces joint stiffness. By controlling torques directly rather than positions, the system achieves the same control precision with lower stiffness, thereby reducing impact forces on the surrounding environment during robot operation
3Measurement precision
If position-based ZMP control method is used, then walking trajectories are tracked precisely, but unnatural gait occurs
Solution Approach 1:
The patent changes from position-based control to torque-based control, which allows the robot to achieve trajectory tracking through natural balance adjustments rather than rigid position constraints. This torque-based approach enables more human-like gait patterns while maintaining precise trajectory following through feedback control
Data Source
AI summary
A walking robot, respective joints of which are operated through torque servo control to achieve stable pose control, and a pose control method thereof. A virtual acceleration of gravity is calculated using the COG of the robot and gravity compensation torques to apply force to links are calculated from the calculated acceleration of gravity so as to actively cope with external changes including external force or a tilt of the ground, thereby allowing the robot to stably maintain an erect pose and a desired upper body angle. Further, the robot maintains the erect pose with respect to the direction of gravity even under the condition that data regarding whether or not the ground is level or tilted are not given in advance, and maintains uniform poses of an upper body and legs while actively changing angles of ankle joints even if the ground is gradually tilted.