3DOF Robotic Leg Impedance Configuration for Precision and Response
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Solution Overview
Problem
Current impedance control methods for hydraulically-driven legged robots have limited capabilities for improving motion control precision and response, particularly in adapting to different load masses and installation positions across joints, which restricts the control performance of each joint.
Innovation Solution
A novel impedance configuration is generated for a 3DOF robotic leg by performing position-based control on the hip joint and force-based control on the knee and ankle joints, utilizing a mathematical model that includes kinematics, statics, dynamics, and impedance characteristics to optimize control performance across various joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-based control is used for all joints, then control precision is improved, but response speed deteriorates
Solution Approach 1:
The patent applies different control strategies to different joints based on their specific characteristics. Position-based control is applied to the hip joint where precision is critical, while force-based control is applied to the knee and ankle joints where response speed is more important. This localized differentiation resolves the contradiction by optimizing each joint's control mode according to its functional requirements.
2Speed
If force-based control is used for all joints, then response speed is improved, but control precision deteriorates
Solution Approach 1:
The patent differentiates control precision requirements across joints. The hip joint requires high position precision for accurate foot placement, so position-based control is applied. The knee and ankle joints benefit more from fast force response for compliance and adaptation, so force-based control is applied. This resolves the precision-speed contradiction through spatial differentiation of control quality.
3Device complexity
If a unified impedance control method is used for all joints, then system complexity is reduced, but adaptability to different load masses and installation positions deteriorates
Solution Approach 1:
The patent recognizes that different joints experience different load characteristics and installation positions. The hip joint has different mass and position characteristics compared to the knee and ankle joints. By applying position-based control to the hip and force-based control to the knee and ankle, the system adapts to the specific operational requirements of each joint while maintaining manageable overall complexity.
Solution Approach 2:
The patent introduces dynamic adaptability by selecting different control modes based on joint-specific operational requirements. The control system dynamically adjusts its strategy per joint rather than using a static unified approach, enabling better adaptation to varying load masses and installation positions while preserving system manageability.
Data Source
AI summary
The present disclosure relates to a method for generating a novel impedance configuration for a three-degree-of-freedom (3DOF) leg of a hydraulically-driven legged robot. The method includes: separately determining variations of input signals of an inner position-based control loop and an inner force-based control loop of a hydraulic drive unit of each joint based on an obtained mathematical model; generating a novel impedance configuration in which position-based control is performed on a hydraulic drive unit of a hip joint, and force-based control is performed on hydraulic drive units of a knee joint and an ankle joint in a hydraulic drive system of the leg of a to-be-controlled robot; and performing forward calculation by using the leg mathematical model, to obtain an actual position and a force variation of the foot of the leg of the to-be-controlled robot to control motion of the foot of the to-be-controlled robot within motion space.