Wearable Robot Torque Control via Ground Reaction Force and Knee Angle

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Solution Overview

Problem

Wearable robots struggle to provide an optimal auxiliary torque at the precise time point during standing movements, leading to potential resistance for the wearer, which can hinder the effectiveness of muscle assistance and rehabilitation efforts.

Innovation Solution

A wearable robot system that measures ground reaction force and knee joint angle to detect the exact time point of standing movement initiation, applying an auxiliary torque with a trigonometric function wave shape, generated by overlapping sinusoidal waves, to minimize resistance and enhance muscle support.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If auxiliary torque is applied continuously during standing movement, then muscle assistance is provided, but the wearer feels resistance due to improper timing

Engineering Contradiction:

Improveeffectiveness of muscle assistanceVSAvoidwearer resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The controller detects the initiation of standing movement in advance by monitoring ground reaction force and knee joint angle, and applies auxiliary torque before the movement is fully executed. This preliminary timing ensures the torque assists muscle initiation without creating resistance during the natural movement phase

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors ground reaction force and knee joint angle as feedback signals to detect the exact moment of standing movement initiation. Based on this real-time feedback, the controller dynamically adjusts the timing of auxiliary torque application to match the wearer's actual movement state, preventing resistance

Inventive Principle:

Principle #23Feedback

2Reliability

If auxiliary torque is applied at delayed time point, then the standing movement has already started, but the auxiliary torque cannot assist muscle strength effectively

Engineering Contradiction:

Improveeffectiveness of muscle assistanceVSAvoidresponse time for torque application

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system detects standing movement initiation in advance by monitoring the relationship between ground reaction force variation rate and knee joint angle. By identifying the crossing point of these parameters, the controller applies auxiliary torque at the optimal preliminary moment, ensuring both timely assistance and effective muscle support

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system replaces direct mechanical coupling with sensor-based detection and electronic control. By using ground reaction force sensors and joint angle sensors to detect movement initiation, the system achieves precise timing without mechanical delays, enabling rapid and accurate torque application

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9849004B2Wearable robot and method of controlling the same

Publication Date: 2017.12.26 SAMSUNG ELECTRONICS CO LTD

AI summary

Provided is a method of controlling a wearable robot, the method including: measuring a ground reaction force (GRF) exerted on a wearer's soles; calculating a time variation rate of the measured GRF; measuring the wearer's knee joint angle; and detecting a time point at which the calculated time variation rate of the GRF and the measured knee joint angle cross each other.