Robotic Exoskeleton Foot With Leaf Spring Segmentation
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Solution Overview
Problem
Current robotic exoskeleton feet for assisted walking have rigid structures that hinder the replication of natural gait and fail to efficiently absorb shocks and measure forces effectively, particularly during the stance phase.
Innovation Solution
A foot for a robotic exoskeleton comprising three rigid segments connected by leaf springs, allowing rotation about transverse and longitudinal axes, with strain gauges for force measurement, and a curved spring profile to increase stiffness as force increases, preventing end-of-travel positions and enhancing shock absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid structure is used for the foot, then structural strength is improved, but the ability to absorb shocks and replicate natural gait deteriorates
Solution Approach 1:
The foot is divided into three rigid segments (heel segment, middle segment, forefoot segment) that are connected by flexible elements. Each segment maintains structural strength while the segmentation allows relative movement between segments to absorb shocks and replicate natural gait mechanics.
Solution Approach 2:
Leaf springs are used as flexible connection elements between the rigid foot segments. These thin flexible elements allow controlled deformation and rotation, enabling the foot to adapt to ground irregularities and absorb shocks while maintaining overall structural integrity.
2Ease of manufacture
If a rigid structure is used for the foot, then manufacturing simplicity is improved, but shock absorption capability deteriorates
Solution Approach 1:
The foot is segmented into three rigid portions connected by flexible leaf springs. This segmentation allows each rigid portion to be manufactured separately using simple processes, while the assembly provides sophisticated shock absorption through the flexible connections.
Solution Approach 2:
The leaf springs are pre-configured with specific curvature and stiffness characteristics to provide shock absorption before impact occurs. The springs are designed to deflect in anticipation of ground contact, cushioning the shock before it reaches the rigid segments and the user.
3Measurement precision
If strain gauges are added for force measurement, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The leaf springs serve multiple functions: they provide flexible connection between rigid segments, enable shock absorption through deformation, and simultaneously act as force sensing elements with embedded strain gauges. This multi-functionality reduces overall device complexity by combining structural and measurement roles in a single component.
Solution Approach 2:
The strain gauges are integrated directly into the leaf spring structure, merging the flexible connection element with the force sensing element. This integration eliminates separate sensing components and simplifies the overall device architecture while providing accurate force and torque measurements.
4Object-affected harmful factors
If the middle foot segment is elastically suspended, then shock absorption is improved, but structural stability deteriorates
Solution Approach 1:
The middle foot segment is elastically suspended by leaf springs that provide dynamic support rather than rigid fixation. The springs allow controlled movement and deformation in response to loading conditions, providing shock absorption while maintaining structural stability through elastic restoration forces.
Solution Approach 2:
The leaf springs are designed with specific geometric parameters (curvature, thickness, length) that optimize the balance between shock absorption and structural stability. The spring stiffness is tuned to provide sufficient support for stability while allowing adequate deflection for shock absorption during the gait cycle.
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 solution enables efficient shock absorption and force measurement, allowing the robotic exoskeleton to adapt to ground irregularities and replicate natural gait more accurately, providing a structurally simple and effective solution for assisted walking.
Implementation Method 1
a front foot segment elastically connected to the front end of the middle foot segment by means of a first set of leaf springs, and a rear foot segment elastically connected to the rear end of the middle foot segment by means of a second set of leaf springs
Implementation Method 2
These measuring means advantageously comprise strain gauges that are positioned on the leaf springs and therefore allow to detect not only the forces/torques applied onto the foot
Data Source
AI summary
A foot for a robotic exoskeleton includes three rigid foot segments, namely a middle foot segment arranged to be connected to a leg of the robotic exoskeleton, a front foot segment elastically connected to the front end of the middle foot segment by a first set of leaf springs and a rear foot segment elastically connected to the rear end of the middle foot segment by a second set of leaf springs. The foot has laces for fastening the foot to a person's shoe. In the condition where the front foot segment and the rear foot segment are both in contact with the ground, and no load is applied onto the foot, the middle foot segment is not in contact with the ground, but is elastically suspended by the first and second sets of springs.