Walking Robot Posture Control via Torque Servo
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Solution Overview
Problem
Existing walking robots using position-based Zero Moment Point (ZMP) control methods face challenges in maintaining a stable upper body angle and balance, especially when external forces are applied or the ground inclination varies, leading to inefficient energy use and unnatural movement.
Innovation Solution
A method and system for controlling a robot's posture by computing the current Center of Gravity (COG) position, setting a desired COG position, calculating compensation forces and torques, and distributing these to control leg postures using torque servo control, incorporating an inertial measurement unit (IMU) for rotation angle measurements and gravity compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-based ZMP control method is used to achieve accurate position control, then position control accuracy is improved, but energy efficiency deteriorates and joint rigidity increases causing big shock to surroundings
Solution Approach 1:
The patent replaces the traditional position-based ZMP control method with a torque-based control method. Instead of controlling joint positions to achieve ZMP constraints, the system directly controls joint torques to maintain balance. This substitution eliminates the need for high servo gains and large currents, thereby improving energy efficiency while maintaining balance control accuracy.
Solution Approach 2:
The patent changes the control parameter from joint position to joint torque. By computing required joint torques based on the relationship between torque and ZMP, the system directly adjusts torque output rather than positioning joints. This parameter change reduces energy consumption and avoids the high joint rigidity issues associated with position-based control.
2Measurement precision
If high servo gain is used to achieve accurate angle control of each joint, then position control accuracy is improved, but energy efficiency deteriorates
Solution Approach 1:
The patent substitutes high-gain position-based servo control with torque-based control. By directly controlling joint torques to achieve the desired ZMP, the system eliminates the need for high servo gains. This approach maintains accurate angle control while significantly reducing energy consumption associated with high-gain feedback control.
3Reliability
If Kinematic Singularity is avoided by bending knees while walking, then control stability is improved, but naturalness of walking deteriorates
Solution Approach 1:
The patent replaces position-based control that requires avoiding kinematic singularities with torque-based control. By controlling joint torques directly, the system can maintain control stability without being constrained by kinematic singularity avoidance requirements. This allows the robot to walk with more natural knee movements similar to human gait patterns.
Data Source
AI summary
A walking robot having joints which move using a torque servo, a posture of the robot being stably controlled, and a method of controlling a posture of the robot. It is possible to maintain a stable angle of the upper body while keeping an erect posture and balance using the COG of the robot and the inclination and the direction of the upper body and the pelvis of the robot, even in an external variation including external force or an inclination angle of the ground. Even in a state in which terrain information is not known in advance, the robot may keep an erect posture in a direction of gravity. Even when a plane where the robot stands is gradually inclined, the postures of the upper body and the legs of the robot may be kept while actively changing the angle of the ankle joint.