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Auto-calibrated Wearable System for Load Vertical Location Estimation During Manual Lifting

Diliang Chen, Nozhan Ghoreishi, John LaCourse, Sajay Arthanat, Dain LaRoche

TL;DR

A novel barometer-based LVL measurement method, which automatically calibrates the measured LVL using known wrist vertical location at reference points, which can be detected by the proposed wearable system during frequently used working activities, such as standing and walking.

Abstract

Lifting during manual material handling is a major cause of low-back pain (LBP). As an important risk factor that directly influences the risk of LBP, the Load vertical location (LVL) during lifting needs to be measured and controlled. However, existing solutions for LVL measurement are inefficient, inaccurate, and impractical for real-world workplace environments. To address these problems, an unobtrusive wearable system, including smart insoles and smart wristbands, was proposed to measure LVL accurately in workplace environments. Different from traditional methods which rely on Inertial Measurement Unit (IMU) and suffer from integral drifting errors over time, a novel barometer-based LVL measurement method was proposed in this study. To correct the environment-induced LVL measurement errors in the barometer-based method, a novel Known Vertical Location Update (KVLU) method was proposed. This method calibrates the measured LVL using a known wrist vertical location at known postures during frequently used daily activities such as standing and walking. The proposed wearable system achieved a mean absolute error (MAE) of 5.71 cm in LVL measurement. This result indicates that the proposed system has the potential to reliably measure LVL and assess the risk of LBP in manual lifting tasks.

Auto-calibrated Wearable System for Load Vertical Location Estimation During Manual Lifting

TL;DR

A novel barometer-based LVL measurement method, which automatically calibrates the measured LVL using known wrist vertical location at reference points, which can be detected by the proposed wearable system during frequently used working activities, such as standing and walking.

Abstract

Lifting during manual material handling is a major cause of low-back pain (LBP). As an important risk factor that directly influences the risk of LBP, the Load vertical location (LVL) during lifting needs to be measured and controlled. However, existing solutions for LVL measurement are inefficient, inaccurate, and impractical for real-world workplace environments. To address these problems, an unobtrusive wearable system, including smart insoles and smart wristbands, was proposed to measure LVL accurately in workplace environments. Different from traditional methods which rely on Inertial Measurement Unit (IMU) and suffer from integral drifting errors over time, a novel barometer-based LVL measurement method was proposed in this study. To correct the environment-induced LVL measurement errors in the barometer-based method, a novel Known Vertical Location Update (KVLU) method was proposed. This method calibrates the measured LVL using a known wrist vertical location at known postures during frequently used daily activities such as standing and walking. The proposed wearable system achieved a mean absolute error (MAE) of 5.71 cm in LVL measurement. This result indicates that the proposed system has the potential to reliably measure LVL and assess the risk of LBP in manual lifting tasks.

Paper Structure

This paper contains 19 sections, 5 equations, 9 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Related Works
  3. Methods
  4. Wearable System Design
  5. LVL calibration with KVLU
  6. KVLU Reference Point Identification During Standing
  7. KVLU Reference Point Identification During Walking
  8. Estimate the wrist vertical location at the KVLU reference point
  9. LVL calibration with the KVLU reference point
  10. Experiment and Results
  11. Performance of the wearable system in identifying KVLU reference points and estimating the known vertical location during standing and walking
  12. Experiment Design
  13. Results of KVLU Reference Point Detection During Standing and Walking
  14. Accuracy of the Estimated Wrist Vertical Location at the Detected KVLU Reference Points
  15. Accuracy of the LVL measurement with KVLU calibration
  16. ...and 4 more sections

Figures (9)

  • Figure 1: An overview of the unobtrusive wearable sensing system for reliable LVL measurement.
  • Figure 2: Hardware details of the unobtrusive wearable system. (a) Hardware dimension and electronic components of the smart wristband; (b) the flexible pressure sensor array of the smart insole; and (c) the PCB dimension and electronic components of the smart insole.
  • Figure 3: The KVLU reference points with a known vertical location for calibrating the LVL measurement.
  • Figure 4: Flowchart of the proposed method for detecting KVLU reference points during standing
  • Figure 5: Flowchart of the proposed method for detecting KVLU reference point during walking
  • ...and 4 more figures