Robot Leg Design Reducing Weight and Power via Passive Compliance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Legged robots often require a large number of powered joints for three-dimensional motion, leading to increased weight, power consumption, and stability issues due to backlash in degrees of freedom, making them inefficient and unstable for walking.
Innovation Solution
A leg design for legged robots with three or fewer actuated degrees of freedom, utilizing a hip joint and knee joint configuration that maintains the upper and lower linkages parallel, with a compliant or universal joint connecting the foot to the ankle, allowing for motion in multiple planes with reduced joint complexity and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large number of powered joints are used to achieve three-dimensional motion, then the robot can produce locomotive behavior through stepping motions, but the weight of the robot increases significantly
Solution Approach 1:
The patent extracts and eliminates unnecessary degrees of freedom from the traditional six-DOF leg design. By removing redundant joints and using passive compliance mechanisms instead of active actuators, the design reduces the number of powered joints from six to three per leg, directly reducing robot weight while maintaining essential locomotion capabilities.
Solution Approach 2:
The patent changes the parameter of joint actuation from fully powered to partially passive. By implementing passive compliance in certain joints (allowing them to move without active motors), the system reduces the number of powered joints needed, thereby reducing weight while preserving three-dimensional motion capability through the remaining actuated joints.
2Adaptability or versatility
If more joints are actuated to provide three-dimensional motion, then the robot can achieve greater motion freedom, but power consumption increases
Solution Approach 1:
The patent removes unnecessary active actuation from joints that can function effectively with passive compliance. By extracting the motorization from certain joints and relying on mechanical compliance and gravity, the system reduces power consumption while maintaining motion freedom in the essential degrees of freedom.
Solution Approach 2:
The passive compliant joints serve themselves by utilizing mechanical properties (compliance, gravity, elasticity) rather than requiring external power sources. This self-service mechanism allows joints to move and adapt without consuming electrical energy, reducing overall power consumption while preserving motion capability.
3Adaptability or versatility
If multiple degrees of freedom are implemented in the hip and ankle joints, then the robot can shift weight in the coronal plane for locomotion, but backlash in these joints reduces stability
Solution Approach 1:
The patent replaces complex multi-DOF powered joints with simpler, more reliable alternatives. By using passive compliance and fewer actuated joints, the system eliminates backlash-prone mechanisms while maintaining weight shifting capability through the remaining stable, well-controlled degrees of freedom.
4Adaptability or versatility
If three degree of freedom hip joints are used for sagittal, coronal, and transverse plane motion, then the robot can achieve comprehensive motion, but the device complexity increases
Solution Approach 1:
The patent extracts and removes redundant degrees of freedom from the hip joint configuration. By eliminating the transverse plane rotation joint and relying on passive compliance in other joints, the system reduces hip joint complexity from three DOFs to two actuated DOFs while maintaining comprehensive motion capability through the combination of remaining active joints and passive compliance.
Data Source
AI summary
A robot leg (125) comprises an upper link (101) and a lower link (111). The upper link (101) operates nominally in a first vertical plane, for example the sagittal plane, while the lower link (111) operates nominally in a second vertical plane, nominally orthogonal to the first plane, for example the coronal plane. The leg (125) may also comprise a twist joint in the knee, and may comprise four-bar linkages (102a-b, 103a-d, 112a-b, 113a-d), such that the foot (106) stays parallel to the hip (102a). The leg (125) may be used in a robot to allow the construction of a robot capable of three dimensional movement, using a small number of actuators per leg.