Legged Robot Knee Joint Auxiliary Link Mechanism
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Solution Overview
Problem
Knee joints in legged robots require motors to rotate at twice the speed of hip joints, leading to higher loads and energy consumption due to larger movement ranges and speeds.
Innovation Solution
A lower limb structure with a hip joint main body, a thigh portion, a hip joint coupling, a knee joint main body, a thigh portion auxiliary link, and a knee joint actuator that adjusts the length of the auxiliary link to reduce the rotation speed of the knee joint, allowing for parallel link action and reduced motor load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If motors are provided to knee joints to enable bending and stretching movements, then the knee joints can achieve required movement ranges and speeds, but the rotation speed of knee joint motors must be twice that of hip joint motors, leading to larger motors and higher loads
Solution Approach 1:
A thigh portion auxiliary link is introduced as an intermediary component between the hip joint and knee joint. This auxiliary link, when extended and contracted by the knee joint actuator, enables the knee joint main body to change its attitude relative to the hip joint main body, thereby reducing the rotation speed requirement of the knee joint motor by half compared to conventional designs.
Solution Approach 2:
The system dynamically adjusts the configuration of the parallel link mechanism during motion. By extending and contracting the thigh portion auxiliary link, the mechanism adapts the knee joint's motion characteristics to reduce speed requirements while maintaining the necessary movement range and operational capability.
2Adaptability or versatility
If knee joints are designed with motors to achieve larger movement ranges and higher speeds, then the bending and stretching movements can be performed, but the motors become larger and consume more energy
Solution Approach 1:
The thigh portion auxiliary link serves as a mediator that enables the knee joint to achieve the required movement range through a parallel link mechanism. This mechanism allows the knee joint main body to change its attitude relative to the hip joint main body, maintaining adaptability while reducing the energy consumption of the knee joint actuator.
Solution Approach 2:
The system changes the operational parameters of the knee joint mechanism by introducing the auxiliary link. This alters the motion transmission path, reducing the rotation speed parameter by half while maintaining the necessary movement range, thereby decreasing energy consumption.
3Power
If the rotation speed of knee joint motors is reduced, then the load and energy consumption are reduced, but the movement range and speed of the knee joint may be insufficient
Solution Approach 1:
The thigh portion auxiliary link acts as an intermediary that resolves the contradiction between reduced motor load and sufficient movement range. By extending and contracting this link, the system maintains the necessary knee joint movement range while operating at half the rotation speed, thus reducing the load on the actuator.
Solution Approach 2:
The parallel link mechanism dynamically adjusts the knee joint's motion characteristics. By changing the attitude of the knee joint main body relative to the hip joint main body through auxiliary link adjustment, the system maintains adequate movement range while operating at reduced speeds and lower power loads.
Data Source
AI summary
Provided is a lower limb structure for a legged robot with which a load on an actuator for driving a knee joint can be reduced. The lower limb structure for the legged robot comprises: a hip joint main body (18); a thigh portion (12a); a hip joint coupling (22) for connecting the thigh portion (12a) to the hip joint main body (18); and a knee joint main body (19) joined to the thigh portion (12a). The lower limb structure for the legged robot provides a thigh portion auxiliary link (31) having one end portion joined to the hip joint main body (18) or the hip joint coupling (22) to be rotatable about one pitch axis and the other end portion joined to the knee joint main body (19) to be rotatable about another pitch axis. A knee joint actuator (4) increases and decreases a length from the one end portion to the other end portion of the thigh portion auxiliary link (31).