Torso-Mounted IMU Speed Estimation Without GPS

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Solution Overview

Problem

Existing methods for calculating athlete speed indoors using GPS-based technologies are limited, as they require GPS signal availability and subject-specific calibration, making them unsuitable for environments where GPS signals are unavailable and requiring multiple IMUs or non-torso mounting locations.

Innovation Solution

A method utilizing a single torso-mounted inertial measurement unit (IMU) that calculates horizontal speed without GPS data or subject-specific calibration, employing a novel algorithm to correct drift errors in IMU-measured acceleration data, which is validated through comparison with video-based motion capture (MOCAP) data.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If GPS-based methods are used to calculate athlete speed, then speed estimation is available outdoors, but the method becomes unusable indoors where GPS signals are unavailable

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidspeed estimation reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an inertial measurement unit (IMU) as an intermediary device that measures acceleration directly on the athlete's body, bypassing the need for GPS signals. This mediator enables speed calculation in environments where GPS is unavailable by using local inertial measurements instead of satellite-based positioning.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the GPS-based electromagnetic positioning system with a mechanical inertial measurement system. Instead of relying on satellite signals and complex sensor fusion algorithms, the system uses direct acceleration measurements from the IMU, simplified by mounting it at the center of mass, thereby substituting a complex electromagnetic system with a simpler mechanical one.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If existing GPS-free techniques are used to estimate athlete speed, then GPS signal availability is not required, but the method requires subject-specific calibration or multiple IMUs

Engineering Contradiction:

Improveenvironmental adaptabilityVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent makes the IMU mounting location universal by placing it at the center of mass, which is a common reference point for all athletes regardless of their specific biomechanics. This universal mounting location eliminates the need for subject-specific calibration while maintaining accuracy across different individuals and sports.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines multiple functions into a single IMU unit mounted at the center of mass. Instead of using multiple IMUs distributed throughout the body or requiring separate calibration procedures, the system merges position sensing, acceleration measurement, and speed calculation into one centralized device, thereby reducing system complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Productivity

If IMU data is used to calculate athlete speed without drift correction, then calculation is simple, but accuracy degrades over time due to integration drift

Engineering Contradiction:

Improvecalculation efficiencyVSAvoidspeed measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of drift into a benefit by using the known center of mass location to establish a fixed reference frame. The drift that would normally accumulate over time is corrected by continuously referencing measurements to the known center of mass position, thereby transforming the drift problem into a solvable reference-based correction system.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements feedback by continuously comparing IMU measurements against the known center of mass location and using this information to correct integration drift. The system feeds back the position information from the center of mass reference to adjust and maintain accuracy in speed calculations over time, preventing error accumulation.

Inventive Principle:

Principle #23Feedback

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 method provides accurate and reliable athlete speed estimation, with a root mean square error of 0.14 m/s and high correlation (r=0.98) with MOCAP data, suitable for indoor sports like basketball, and maintains accuracy even with short integration times relevant to dynamic sports.

Implementation Method 1

With the near ubiquity of MEMS inertial measurement unit (IMU) and GPS technologies

Methodology Applied

Scientific EffectMEMS (Microelectromechanical Systems): Microelectromechanical Systems

Implementation Method 2

a method for calculating the horizontal speed of an athlete using a single, torso-mounted IMU which does not require subject specific calibration or the use of GPS data

Methodology Applied

Scientific EffectNumerical integration:

Data Source

PatentUS9213889B2Athlete speed prediction method using data from attached inertial measurement unit

Publication Date: 2015.12.15 THE RGT UNIV OF MICHIGAN

AI summary

An apparatus and method for calculating athlete speed non-invasively, on the field/court of play using data from a torso-mounted inertial measurement unit. The method complements existing, GPS-based methods for calculating athlete speed by enabling use in environments where GPS signal is unavailable (i.e. indoors).