Robot Knee Structure With Slack Rubber Member
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Solution Overview
Problem
Biped robots require large torques to transition from a bent knee state to an upright state, leading to increased power consumption and operational costs due to the need for both bending and spring-pulling torques, even when bending knees shallowly.
Innovation Solution
A knee structure with a restoring force applying member attached across the thigh and lower leg, allowing it to be stretched only when the knee is bent deeply, providing auxiliary torque when necessary and minimizing torque required for shallow bending, using a rubber belt-like member that closes the gap between the thigh and lower leg and includes a compression spring for additional restoring force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a spring is attached to the knee joint and pulled according to knee bending, then restoring force is provided when resuming upright state, but torque for bending knee and torque for pulling spring are both needed, increasing power consumption
Solution Approach 1:
The patent changes the attachment configuration of the elastic body from being pulled by knee bending to being compressed between the thigh and lower leg. This parameter change in the mechanical configuration allows the elastic body to provide restoring force without requiring additional pulling torque during knee bending, thereby reducing power consumption while maintaining the restoring force function.
2Reliability
If the spring is pulled each time the knee is bent, then restoring force is generated, but the torque needed for bending the knee becomes larger, increasing operational costs
Solution Approach 1:
Instead of pulling the elastic body when bending the knee (conventional approach), the patent inverts the mechanism by having the elastic body compress automatically when the knee bends. This inversion eliminates the need for additional pulling torque and reduces the torque requirement for knee bending while still generating restoring force when needed.
Solution Approach 2:
The elastic body automatically compresses and generates restoring force without requiring external control or additional actuators. The system uses the knee bending motion itself to compress the elastic body, which then provides the restoring force automatically when the knee needs to extend, achieving self-service functionality.
3Ease of operation
If the restoring force applying member is attached across the thigh and lower leg with slack, then it is pulled only when the leg is bent deeply, but the restoring force is not applied during shallow bending, reducing torque requirement
Solution Approach 1:
The patent makes the restoring force application dynamic by using a slack-attached elastic body that only engages when the knee bends beyond a certain angle. This dynamic characteristic allows the system to provide minimal torque requirement during shallow bending while automatically providing restoring force when deep bending occurs, optimizing the balance between ease of operation and power application.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces power consumption and operational costs by applying restoring force only when needed, specifically when the knee is bent deeply, while maintaining efficient torque assistance for deeper bends and preventing object entry into the knee gap.
Implementation Method 1
the restoring force applying member is made of rubber and is formed in a belt-like shape. Since the restoring force applying member is made of the belt-like rubber, the restoring force applying member easily extends and contracts so that the restoring force can suitably be given to the thigh and the lower leg.
Implementation Method 2
a part to be compressed, attached to either one of the thigh and the lower leg, at a position on the opposite side of the projecting side of the knee joint when the leg is bent from a state where the leg stands straight, and configured to generate a restoring force by being pinched and compressed between the thigh and the lower leg, when the leg reaches a bending angle more than a given angle.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The purpose is to provide a knee structure of a robot in which a torque needed for an actuator bending a knee is kept small, when bending the knee shallowly. A leg includes a thigh, a lower leg disposed below the thigh, a knee joint bendably connecting the thigh with the lower leg, and a rubber member attached to the thigh and the lower leg so as to be across the thigh and the lower leg, with a slack when the leg stands straight. A restoring force caused by the rubber member is given to the thigh and the lower leg, when the leg is bent deeply so that the rubber member is stretched.