Wearable Inertial Sensor System for Tri-Planar Motion Capture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current technologies for range of motion (ROM) and rehabilitation assessment face challenges such as limited accuracy, high equipment costs, and user unfriendliness, particularly in remote settings, due to issues with inter-observer agreement, equipment placement, and the inability to provide individualized and asynchronous coaching.
Innovation Solution
A wearable inertial sensor system with multiple sensors connected via a computing system, providing user interfaces for rehabilitative exergames, which calculates joint angles in real-time using quaternion data and corrects for gravity and magnetic misalignment, enabling accurate and individualized ROM assessment and training.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If goniometers and inclinometers are used for ROM assessment, then measurement capability is provided, but inter-observer agreement is limited due to variability in positioning
Solution Approach 1:
The patent replaces manual mechanical measurement tools (goniometers, inclinometers) with electronic inertial sensors that automatically capture motion data. This substitution eliminates the need for manual positioning and measurement by observers, thereby improving inter-observer agreement while maintaining ROM measurement capability.
Solution Approach 2:
The patent uses video recording to capture movement data as a copy of the actual motion, which can be analyzed multiple times by different observers without affecting the original measurement. This creates an objective reference that improves reliability across different observers.
2Loss of information
If videographic methods are used for ROM assessment, then visual recording of movement is provided, but inter-observer agreement is low due to differences in camera positions and 2D limitations
Solution Approach 1:
The patent transitions from 2D video recording to 3D spatial measurement using inertial sensors that capture movement in three dimensions. This dimensional enhancement provides complete spatial information about joint motion, eliminating the limitations of 2D projection and improving measurement reliability.
Solution Approach 2:
The patent replaces the visual recording system (camera-based) with an electronic sensing system (inertial sensors) that directly measures motion parameters. This substitution provides more reliable and objective data that is not affected by camera positioning or viewing angles.
3Loss of information
If Kinect sensor is used for ROM assessment, then 3D position information for multiple joints is provided, but measurement accuracy is limited by placement requirements and inability to measure certain joint movements
Solution Approach 1:
The patent divides the measurement system into multiple independent inertial sensor units, each attached to specific body segments. This segmentation allows direct measurement of joint angles between segments, providing more accurate and comprehensive joint angle data compared to the single-camera Kinect approach.
Solution Approach 2:
The patent replaces the optical camera-based Kinect system with inertial measurement units that directly sense acceleration and orientation. This substitution enables accurate measurement of joint movements including forearm pronation-supination, which the Kinect cannot measure, and improves overall measurement precision.
4Measurement precision
If commercial wearable inertial sensors are used for motion capture, then motion data is provided, but rehabilitation application is limited by cost of custom software and extensive data analysis requirements
Solution Approach 1:
The patent implements automated processing algorithms that enable the system to self-analyze the collected motion data and automatically generate rehabilitation assessments. This self-service capability eliminates the need for extensive manual data analysis by researchers or clinicians, reducing complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces automated software algorithms as an intermediary between the inertial sensors and the rehabilitation assessment. This intermediary automatically processes raw sensor data, extracts meaningful metrics, and generates clinical insights, thereby reducing the burden of data analysis while preserving measurement accuracy.
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 system provides accurate, real-time joint angle measurements, improving inter-observer agreement and enabling individualized coaching, thus enhancing the effectiveness of ROM assessment and rehabilitation, particularly in remote settings.
Implementation Method 1
inertial sensors, which include inertial measurement units (IMU) and magnetic, angular rate, and gravity (MARG) sensors that measure the linear acceleration and angular velocity of a rigid body to which they are attached
Implementation Method 2
corrects for gravity and magnetic misalignment
Implementation Method 3
corrects for gravity and magnetic misalignment
Data Source
AI summary
Disclosed is a wearable inertial sensors (WIS) system and methods for real-time simultaneous tri-planar motion capture of the upper extremity (UE). The sensors simultaneously capture in the frontal, sagittal, and horizontal planes UE range of motion (ROM), which is critical to assess an individual's movement limitations and determine appropriate rehabilitative treatments. Off-the-shelf sensors and microcontrollers are used to develop the WIS system, which wirelessly streams real-time joint orientation for UE ROM measurement. Key developments include: (i) two novel approaches, using earth's gravity (EG approach) and magnetic field (EGM approach) as references, to correct misalignments in the orientation between the sensor and its housing to minimize measurement errors; (ii) implementation of the joint coordinate system (JCS)-based method for tri-planar ROM measurements for clinical use; and (iii) an in-situ guided mounting technique for accurate sensor placement and alignment on human body.