Adaptive Gait Device Control via Continuous Reference Functions

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Solution Overview

Problem

Current control systems for prosthetic, orthotic, and robotic gait devices are limited in their ability to provide smooth and continuous control, often requiring users to expend more energy due to reliance on passive components and fixed pattern algorithms that are prone to errors, especially when transitioning between different gait activities or speeds.

Innovation Solution

A method involving sensors to measure kinematic and loading states, which are then conditioned and transformed using reference functions to generate continuous commands for actuators, allowing for adaptive control of gait devices that can handle various activities and speeds without decision-making errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive spring-based components are used in prosthetic devices, then the device structure is simple and reliable, but the user must expend more metabolic energy to achieve normal gait

Engineering Contradiction:

Improvedevice reliabilityVSAvoiduser metabolic energy expenditure

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces passive mechanical spring-based energy storage systems with active motorized actuation systems. Motors and control systems are integrated into the prosthetic device to actively generate movement and support, eliminating reliance on user-generated kinetic energy and spring-based passive mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control system continuously monitors user gait parameters through sensors and autonomously adjusts actuator commands to optimize assistance. The system adapts to changing gait conditions without user input, providing seamless energy-efficient support that reduces metabolic expenditure while maintaining natural movement patterns.

Inventive Principle:

Principle #25Self-service

2Device complexity

If fixed pattern control algorithms are used for specific gait patterns, then the control system is simple to implement, but it is limited to a single gait speed and requires modification for different activities

Engineering Contradiction:

Improvecontrol system complexityVSAvoidgait pattern adaptability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The control system transitions from static fixed-pattern algorithms to dynamic adaptive control. Sensors continuously monitor gait parameters including speed, stride length, and phase, allowing the system to dynamically adjust actuator commands in real-time. This enables seamless adaptation across multiple gait speeds and activities without requiring algorithm modification.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system incorporates continuous feedback loops where sensors monitor actual gait performance and feed this information back to the control algorithm. The control system uses this feedback to continuously optimize actuator commands, enabling adaptation to varying gait conditions while maintaining a unified control framework that handles multiple activities.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If decision-making algorithms are used to determine gait phase, then the control system can handle complex gait patterns, but errors occur when gait state transitions are chosen incorrectly

Engineering Contradiction:

Improvegait pattern recognition capabilityVSAvoidcontrol accuracy during state transitions

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent replaces discrete decision-making state machines with continuous function-based control. Instead of using if-then logic to determine gait phase, the system uses continuous mathematical functions that map sensor inputs directly to actuator commands. This eliminates the discrete state transitions that cause errors and provides smooth, error-free control across all gait conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The control system maintains continuous operation without discrete state transitions. Mathematical functions continuously process sensor data and generate actuator commands throughout the entire gait cycle, ensuring uninterrupted and error-free control. This continuous approach eliminates the reliability issues associated with incorrect state transition decisions while maintaining full adaptability to varying gait patterns.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS9622884B2Control systems and methods for gait devices

Publication Date: 2017.04.18 OSSUR ICELAND EHF

AI summary

A method of controlling a gait device includes a first sensor disposed on a first mobile body. A physical state of the first mobile body is measured using the first sensor to obtain a first physical state measurement. A second sensor is disposed on a second mobile body. A physical state of the second mobile body is measured using the second sensor to obtain a second physical state measurement. The first and second physical state measurements are conditioned by pseudo integration. A reference function is based on a gait activity. A reference function is determined by measuring a physical state of an able-bodied human and correlating an output position of the actuator to the physical state of the able-bodied human. A command is generated by inputting the first and second physical state measurements into the reference function to control an actuator of the gait device to match the output position.