Humanoid Robot Foot With Active Variable Stiffness Leaf Spring
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Solution Overview
Problem
Humanoid robots with simple flat rectangular feet face challenges in mimicking human-like locomotion on uneven terrain and have high energy consumption due to large knee angles during walking, as existing active variable stiffness mechanisms are not suitable for small robot feet.
Innovation Solution
A humanoid robot foot design featuring a flexible toe as a leaf spring with a stiffness adjustment device, comprising a roller assembly and actuation unit, allowing for active adjustment of the toe's stiffness by varying the length and width of the leaf spring, enabling the robot to adapt to different terrains and walking phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple flat rectangular foot using elastic material is employed, then the foot design is simple and easy to manufacture, but it makes it difficult to mimic human-like locomotion on uneven terrain
Solution Approach 1:
The foot is segmented into multiple functional components: a rigid foot base, flexible toes modeled as leaf springs, and active stiffness adjustment mechanisms. This segmentation allows each component to perform its specific function - the rigid base provides structural support while the flexible toes adapt to terrain variations.
Solution Approach 2:
The foot incorporates dynamic stiffness adjustment capability through active variable stiffness mechanisms in the toes. The stiffness of the leaf spring toes can be actively changed during the gait cycle to adapt to different terrain conditions, transforming a static foot structure into a dynamic adaptive system.
2Adaptability or versatility
If active variable stiffness mechanisms are added to the foot, then the stiffness of the flexible toe can be actively adjusted to improve locomotion on uneven terrain, but the device complexity increases
Solution Approach 1:
The active variable stiffness mechanism changes the physical parameter of stiffness by varying the position of a roller assembly along the leaf spring. This positional parameter change directly modifies the effective spring length and thus the stiffness characteristic, providing active control without requiring complex multi-component systems.
Solution Approach 2:
The roller assembly acts as an intermediary element between the actuation unit and the leaf spring. It translates actuation forces into positional changes along the leaf spring, thereby controlling the stiffness characteristic through a simple geometric relationship rather than direct force application.
3Adaptability or versatility
If the spring width is made to vary with position to increase stiffness range, then the adaptability to different terrains is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The leaf spring is designed with non-uniform cross-sectional properties along its length, creating different local stiffness characteristics at different positions. This local variation in geometry allows the spring to provide a range of stiffness values as the roller assembly moves along it, without requiring complex active adjustment mechanisms.
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
The mechanism enables the robot to effectively control toe stiffness, improving locomotion on uneven terrain and reducing energy consumption by providing a range of stiffness values, enhancing its ability to walk on diverse surfaces.
Implementation Method 1
a flexible passive toe has been simply introduced by adding one joint and torsional springs controlling rotation of this joint
Implementation Method 2
an intermediate portion which is not connected to the foot base and is therefore freely deflectable, along with the front portion, as a result of the application of an external force on the front portion
Data Source
AI summary
A humanoid robot foot (10) comprises: a foot base (12), at least one leaf spring (14) acting as a flexible toe of the foot, said at least one leaf spring (14) having a rear portion (14a) rigidly connected to a flat surface (12b) of the foot base (12), a front portion (14b) projecting from the foot base (12) and an intermediate portion (14c) which is not rigidly connected to the foot base (12) and is therefore freely deflectable, along with the front portion (14b), as a result of the application of an external force on the front portion (14b), and a stiffness adjustment device (26) for actively changing the stiffness (K) of said at least one leaf spring (14). The stiffness adjustment device (26) comprises a roller assembly (28), which is held in contact with the intermediate portion (14c) of said at least one leaf spring (14) and is movable relative to said at least one leaf spring (14) along a longitudinal axis (x) of said at least one leaf spring (14), and an actuation unit (34) arranged to move the roller assembly (28), and hence the point of contact (P) of the roller assembly (28) with said at least one leaf spring (14), thereby varying the length (l) of the cantilevered portion of said at least one leaf spring (14), and hence the stiffness (K) of said at least one leaf spring (14).