Wheel-Legged Robot Balance Control Across Changing Motion States
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Solution Overview
Problem
The balance control process for wheel-legged robots is limited in applicability and lacks robustness across different motion states, necessitating improvements in stability and adaptability.
Innovation Solution
The wheel-legged robot is abstracted into an nth-order inverted pendulum model, allowing for the calculation of an equivalent state vector and force/torque instructions to adjust the robot's balance status through whole-body joints, enabling flexible control of multiple joints to enrich poses and improve stability under disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leg mechanism and torso mechanism are considered as a whole with a single joint motor for angle adjustment, then the balancing capability is improved, but the adaptability to different motion states deteriorates
Solution Approach 1:
The patent segments the control system by separating the joint angle control (for balancing) from the motion state-specific parameters. The joint motor controls the angle between mobile wheel and leg mechanism to maintain balance, while motion state parameters (wheel radius, link lengths, masses) are independently adjusted based on different motion scenarios, enabling both stable balancing and adaptive performance across various motion states.
2Ease of operation
If a simplified balance control mechanism is used, then the control process is easier to implement, but the robustness across different motion states deteriorates
Solution Approach 1:
The patent creates a universal balance control framework where the joint motor serves multiple functions: maintaining balance during walking, adapting to different wheel configurations (single wheel, dual wheels), and working with varying link structures. The control method universally applies to different motion states by adjusting motion state parameters while keeping the core balancing mechanism unchanged, thus achieving both simplicity and robustness.
3Ease of manufacture
If the robot structure is fixed with specific link lengths and wheel radius, then the manufacturing is easier, but the adaptability to different motion modes deteriorates
Solution Approach 1:
The patent introduces dynamic adjustability to fixed structural parameters. The motion state parameters including wheel radius, link lengths, and masses can be dynamically adjusted based on different motion modes (e.g., switching between single-wheel and dual-wheel configurations). This allows the robot to adapt its effective structure for different tasks while maintaining a standardized base design for ease of manufacture.
Data Source
AI summary
A wheel-legged robot is considered as nth-order inverted pendulum model including a wheel, n links, and n revolute joints. First links are from at least two leg mechanisms of the wheel-legged robot. The wheel is from mobile wheels respectively connected to the at least two leg mechanisms. A balance control method for the robot includes: obtaining an actual state vector of the wheel-legged robot at a first moment; calculating an equivalent state vector at the first moment based on the actual state vector at the first moment; establishing a sliding surface based on the equivalent state vector at the first moment; determining a force and torque instruction for whole-body joints based on the sliding surface, the equivalent state vector at the first moment, and a dynamics equation of the wheel-legged robot; and separately controlling the n revolute joints at a second moment according to the force and torque instruction.