Adaptive Rehabilitation Robot Stiffness Control

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Solution Overview

Problem

Current rehabilitation methods, particularly for stroke patients, lack precise control over force and movement guidance, leading to suboptimal therapy intensity and repetition, and do not adapt effectively to individual patient performance.

Innovation Solution

A force-controlled robotic rehabilitation system with end-effectors having multiple degrees of freedom, sensors for position and force measurement, and a controlling unit that adjusts stiffness and damping coefficients online based on statistical analysis of patient performance, providing personalized and adaptive feedback to guide movements along reference trajectories.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a constant stiffness coefficient is used to guide the patient along the reference trajectory, then the patient receives consistent guidance force, but the therapy does not adapt to the patient's performance and may provide excessive or insufficient assistance

Engineering Contradiction:
Improveguidance consistencyVSAvoidtherapy adaptation
Core Design Contradiction:
ReliabilityVSAdaptability or versatility

Solution Approach 1:

The stiffness coefficient is changed online during the exercise session based on the patient's performance. The controlling unit adjusts the stiffness coefficient dynamically - increasing it when the patient deviates from the reference trajectory and decreasing it when the patient follows the trajectory well. This dynamic adjustment allows the robotic device to adapt the level of assistance to the patient's real-time performance, resolving the contradiction between providing consistent guidance and adapting to patient needs.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system continuously monitors the patient's position relative to the reference trajectory and uses this feedback to adjust the stiffness coefficient. The controlling unit receives position information from sensors and modifies the guidance force parameters accordingly. This closed-loop feedback mechanism enables the system to maintain reliable guidance while adapting to the patient's performance level, directly addressing the technical contradiction.

Inventive Principle:
Principle #23Feedback

2Force

If the robotic device generates considerable forces to guide the patient, then the patient receives strong guidance, but the subject is not challenged and may feel personal failure

Engineering Contradiction:
Improveguidance forceVSAvoidchallenge level
Core Design Contradiction:
ForceVSAdaptability or versatility

Solution Approach 1:

The guidance force is made dynamic by adjusting the stiffness coefficient based on patient performance. When the patient performs well (stays close to the reference trajectory), the stiffness coefficient decreases, reducing the guidance force and challenging the patient to maintain performance with less assistance. When the patient struggles (deviates from trajectory), the stiffness coefficient increases, providing stronger guidance force. This dynamic force adjustment resolves the contradiction between providing strong guidance and challenging the patient.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system changes the stiffness coefficient parameter online during the exercise based on measured performance metrics. By modifying this key parameter, the robotic device can vary the guidance force level to match the patient's capability, ensuring neither excessive force (which would prevent challenge) nor insufficient force (which would provide inadequate guidance). This parameter change approach directly addresses the contradiction between force magnitude and patient challenge.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If one-to-one interaction between therapist and patient is used, then personalized therapy can be provided, but high intensity and high repetition training is limited

Engineering Contradiction:
Improvepersonalized therapyVSAvoidtraining intensity
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The robotic device performs the functions of the therapist by automatically adjusting the stiffness coefficient based on patient performance without requiring continuous therapist intervention. The system monitors patient position, calculates deviation from the reference trajectory, and autonomously modifies guidance parameters. This self-service capability allows the system to provide personalized adaptive therapy while enabling high-intensity, high-repetition training that would be difficult to deliver manually, resolving the contradiction between personalization and training intensity.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces the manual mechanical interaction of therapist-patient with an automated robotic system. The robotic device uses sensors to detect patient position and a controlling unit to compute and apply appropriate guidance forces. This substitution of mechanical therapy with an automated control system enables both personalized adaptive guidance and high-intensity repetitive training, directly addressing the limitations of manual one-to-one interaction.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

4Adaptability or versatility

If the stiffness coefficient is changed online based on patient performance, then the therapy adapts to patient needs, but the system complexity increases

Engineering Contradiction:
Improveperformance-based adaptationVSAvoidcontrol system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system implements a feedback loop where the controlling unit continuously monitors patient position through sensors, compares it to the reference trajectory, and adjusts the stiffness coefficient accordingly. This feedback mechanism provides performance-based adaptation but requires increased control system complexity to process position data and modify guidance parameters in real-time, directly reflecting the trade-off between adaptability and system complexity.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The online adjustment of the stiffness coefficient parameter based on patient performance creates adaptive therapy but necessitates a more complex controlling unit capable of real-time parameter modification. The system must continuously calculate deviation metrics and translate them into appropriate parameter changes, increasing the computational and control complexity while achieving performance-based adaptation.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentUS10806657B2Rehabilitation system and method
Publication Date: 2020.10.20 UNIVERSITE CATHOLIQUE DE LOUVAIN
  • US10806657B2 patent drawing

AI summary

A rehabilitation system for rehabilitation of a subject including at least one end-effector for interacting with the subject, the end-effector having at least two degrees of freedom of motion, at least one actuator for actuating the at least one end-effector, at least one sensor for measuring at least the position and the speed of the at least one end-effector; at least one sensor for measuring the interaction force between the subject and the end-effector; a memory including at least two initial coefficients and a session including at least one exercise including at least one reference trajectory to be carried out by the subject through actuation of the end effector; and an actuator controlling unit. The memory delivers the initial coefficients and the session, the sensors deliver measurement signals to the controlling unit, and the controlling unit provides a force-controlled feedback based on the initial coefficients.