Ambulatory Exoskeleton Control Using Vertical Force Measurement
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Solution Overview
Problem
Existing ambulatory exoskeleton control methods based on static equilibrium are unsuitable for walking, as they do not allow for natural movement and can be dangerous due to resistance felt by the user, especially during dynamic equilibrium changes like bipedal and unipedal transitions.
Innovation Solution
A method that measures only the normal component of the bearing force under each foot and calculates target balancing forces to control the exoskeleton, using a single uniaxial sensor and a simplified model to determine control setpoints for actuators, allowing for continuous balancing and mimicking natural human gait.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If static equilibrium control methods are used, then the exoskeleton can maintain balance in stationary positions, but the user feels resistance during movement and cannot walk naturally
Solution Approach 1:
The patent transitions from static equilibrium control to dynamic equilibrium control. The processing unit continuously updates balancing torques based on real-time measurement of vertical bearing forces under each foot, allowing the exoskeleton to adapt to dynamic walking conditions while maintaining balance and enabling natural movement.
Solution Approach 2:
The patent implements feedback control by measuring the vertical component of bearing forces under each foot using measurement means, then using these measurements to continuously update the balancing torques applied by actuators. This closed-loop feedback enables the exoskeleton to respond to user movement intentions and maintain natural gait.
2Adaptability or versatility
If six-axis force sensors and accelerometers are used for dynamic calculation, then the exoskeleton can respond to movement, but the sensors have significant drift and require complex processing incompatible with portability
Solution Approach 1:
The patent extracts only the essential measurement needed for walking control - the vertical component of bearing forces under each foot - rather than using complex six-axis force sensors and accelerometers. This simplification reduces sensor drift issues and processing complexity while maintaining dynamic response capability.
Solution Approach 2:
The patent uses a simplified measurement model that copies only the necessary vertical force information from the complex sensor data, processing only the intensity and direction of vertical bearing forces rather than all six elements, making the system compatible with portable processing units.
3Loss of information
If full six-element sensor data is processed, then complete force and moment information is obtained, but very rapid calculation is required that is incompatible with portable processing units
Solution Approach 1:
The patent extracts and processes only the vertical component of bearing forces, ignoring other force components and moments that would require complex processing. This selective extraction maintains sufficient information for walking control while dramatically reducing computational requirements and power consumption.
Solution Approach 2:
The patent applies partial action by processing only the necessary vertical force information rather than complete six-element sensor data. This partial processing approach provides sufficient control information for walking while keeping computational load and energy consumption within portable system limits.
Data Source
AI summary
A method for controlling an ambulatory exoskeleton (1) linked to a user (100), comprising the following steps: —measuring only the vertical component (ZNg, ZNd) of the pressure (Rd, Rg) under each foot (123, 133) of the user (1); —controlling actuators (40, 41, 42, 43) such that the vertical component (ZEd, ZEg) of the resultant of the balancing forces (REg, REd) applied to the exoskeleton (1) and exerted by each foot (23, 33) of the exoskeleton (1) on the ground is a function of the vertical component (ZNg, ZNd) of the pressure (Rd, Rg) measured under the corresponding foot (123, 133) of the user (100).