Robot Walking Control via Center of Mass Compensation
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Solution Overview
Problem
Existing walking control methods for robots, such as ZMP and torque-based dynamic walking, face challenges in energy efficiency, joint rigidity, and the ability to perform natural and stable walking, especially when navigating complex environments like stairs or avoiding obstacles.
Innovation Solution
A walking control apparatus and method that includes a pose sensing unit, walking state determination unit, knot point compensation value calculator, and desired angle trajectory generator to calculate and compensate for the Center Of Mass (COM) of the robot, allowing for smooth and human-like walking by adjusting joint angles and torques using spline curves and Finite State Machine control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-based ZMP control method is used to achieve accurate position control, then walking trajectory accuracy is improved, but servo gain must be increased which leads to higher energy consumption and joint rigidity
Solution Approach 1:
The patent replaces traditional position-based ZMP control with torque-based dynamic walking control. Instead of controlling joint positions directly with high servo gain, the system calculates desired torques from dynamic equations and controls joint torques directly, substituting the mechanical position control mechanism with a torque control mechanism that is more energy-efficient
Solution Approach 2:
The patent changes the control parameter from position to torque. By formulating dynamic walking control equations that directly compute required joint torques based on robot state and desired trajectory, the system avoids the need for high position servo gain while maintaining accurate trajectory following, thereby reducing energy consumption
2Measurement precision
If position-based ZMP control method is used to achieve accurate position control, then walking trajectory accuracy is improved, but joint rigidity increases causing considerable shock to walking surfaces
Solution Approach 1:
The patent substitutes rigid position-based control with compliant torque-based control. By controlling joint torques rather than positions directly, the system inherently provides compliance that reduces impact shocks to the walking surface while maintaining trajectory accuracy through dynamic modeling
Solution Approach 2:
The patent incorporates dynamic modeling that predicts and compensates for impact forces before they occur. The dynamic equations account for robot mass, inertia, and gravitational effects, allowing the control system to pre-calculate torques that smooth out impacts and reduce shocks to the walking surface
3Use of energy by moving object
If torque-based dynamic walking control method is used to reduce energy consumption, then energy efficiency is improved, but accurate position control becomes difficult
Solution Approach 1:
The patent substitutes direct position control with torque control based on dynamic equations. By calculating the exact torques needed to achieve desired motion from first principles of dynamics, the system achieves accurate position control as a natural consequence of torque control, eliminating the trade-off between energy efficiency and accuracy
Solution Approach 2:
The patent implements feedback control where the actual robot state (joint angles, angular velocities) is continuously measured and fed back to update torque calculations. This closed-loop feedback ensures accurate position control while maintaining energy efficiency by adjusting torques based on actual system state rather than requiring high position servo gain
4Object-generated harmful factors
If FSM control method is used to improve energy efficiency and reduce joint rigidity, then safety is improved, but accurate position control and whole-body motion capability deteriorate
Solution Approach 1:
The patent substitutes FSM-based torque commands with physics-based dynamic control equations. Instead of using pre-programmed torque patterns for discrete states, the system continuously calculates required torques from dynamic models, enabling accurate position control and adaptive whole-body motion while maintaining the safety benefits of compliance
Solution Approach 2:
The patent transitions from static FSM state transitions to continuous dynamic control. The dynamic equations adapt in real-time to changing robot configurations and external conditions, enabling accurate position control and complex whole-body motions like stair climbing and obstacle avoidance while maintaining energy efficiency and safety through inherent compliance
Data Source
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AI summary
A walking control apparatus of a robot includes a joint portion provided in each of a plurality of legs of the robot, a pose sensing unit to sense the pose of the robot, a walking state determination unit to determine a walking state from the pose of the robot, a knot point compensation value calculator to determine a Center Of Mass (COM) of the robot from the pose of the robot and to calculate a knot point compensation value, a desired angle trajectory generator to generate a reference knot point of the joint portion corresponding to the walking state, to compensate for the reference knot point using the knot point compensation value so as to generate a desired knot point, and to generate a desired angle trajectory of the joint portion using the desired knot point. The knot point which is the angle command of the joint portion of each of the legs to perform the next step is compensated for based on the COM, and the compensated desired knot point is smoothly connected using the spline curve such that the robot walks similar to a human. In addition, in order to maintain balance while walking, the angle of the joint portion of the intermediate point of the current step is fed back and the knot point of the next step is predicted and adjusted, such that the robot stably and smoothly walks.