Toe-Mounted Motion Sensor Calibration for Jump Height Accuracy
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Solution Overview
Problem
Existing motion sensors, such as those used by JAWKU, face challenges in accurately measuring jump height due to excessive noise from body motion, particularly when placed near the center of mass, leading to inaccuracies in determining the true take-off and landing points, and are affected by factors like knee bending and arm movements.
Innovation Solution
A toe-mounted motion sensor with a calibration method using either an external Vertec device or high-speed video recording to determine a personalized scale factor, which corrects for the delay between the true body center of mass motion and the sensor data, enhancing accuracy by minimizing noise and accounting for individual variations in jumping technique.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motion sensor is placed near the center of mass to measure body motion, then the sensor can detect body center of mass motion, but excessive noise from skin/muscle motion and body movement prevents accurate determination of jump height
Solution Approach 1:
The patent extracts the motion sensor from the noisy body center of mass location and relocates it to the toe area, where it can still detect jump-related motion while being mechanically coupled to the ground to minimize body-induced noise. This spatial extraction resolves the contradiction by removing the sensor from the harmful noise environment while preserving its measurement capability.
Solution Approach 2:
The patent introduces a calibration scale factor as an intermediary element that bridges the gap between the toe-mounted sensor readings and the actual body center of mass motion. The calibration process uses known reference data to compute a correction factor that translates the noisy toe sensor signals into accurate jump height measurements, effectively mediating between the sensor's limited placement options and the need for precise body motion measurement.
2Measurement precision
If the motion sensor is placed on the ankle area to measure motion, then the sensor can detect motion, but unwanted motion noise from foot movement affects the accuracy and repeatability of jump height measurement
Solution Approach 1:
The patent extracts the sensor from the ankle/foot area where foot motion noise occurs and relocates it to the toe area. The toe location provides a mechanical advantage by being closer to the ground contact point, where the foot is less mobile during the jump phase, thereby reducing the transmission of foot motion noise to the sensor while still capturing the essential jump motion.
3Measurement precision
If the toe-mounted sensor is used to detect take-off and landing points, then the sensor can clearly detect jump signals, but the body not being a rigid body during take-off creates an unknown time delay between true body center of mass motion and sensor data
Solution Approach 1:
The patent performs preliminary calibration before actual jump measurements to determine the relationship between toe sensor readings and actual body center of mass motion. During calibration, the sensor reads are compared with reference measurements (such as video analysis or known jump heights) to compute a calibration scale factor that accounts for the time delay and spatial offset. This preliminary action allows the system to compensate for the non-rigid body effects during subsequent actual measurements.
Solution Approach 2:
The calibration process establishes a feedback mechanism where the system continuously compares toe sensor readings with expected body center of mass motion patterns and adjusts the calibration scale factor to account for variations in body rigidity and motion characteristics. This feedback loop allows the system to compensate for the time delay and non-rigid body effects in real-time during jump measurements.
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 toe-mounted sensor, combined with calibration techniques, provides more accurate jump height measurements by reducing noise and accounting for individual variations, allowing for precise calculation of jump height with improved repeatability and reliability.
Implementation Method 1
measuring jumping height of an athlete using a 6-DOF (degrees of freedom) 3 axis accelerometer/3 axis gyroscope sensors
Implementation Method 2
The takeoff and landing times are conveniently measured at the −4 g/−4 g takeoff and landing points
Data Source
AI summary
An athlete wearing footwear measures jump heights with a motion sensor mounted on the footwear over toes of the athlete. By sensing vertical jump start motions the sensor detects jump start and finish times of −4 g start and −4 g landing. The sensor, a body wearable mems sensor developed by JAWKU, L.L.C., has a previously installed generic factory scale calibration factor. The athlete replaces this calibration factor with a new calibration scale factor selecting an “absolute” external reference device which measures jump height. This device measures several jump heights then inputted to an algorithm app in the sensor to calculate the new calibration scale factor customized to the actual athlete. The motion sensor has built in programming apps to periodically receive an upgraded factory scale calibration factor which upgrade is based on an ever increasing data pool of jump heights. The updated factory calibration factor is then again replaced by the athlete personally taking several new measured jumps which jump heights are in turn inputted to the sensor. The progress made in evolving jumping skills based on training and specific conditioning exercises can thus be motion sensor evaluated.