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Controller design and experimental evaluation of a motorised assistance for a patient transfer floor lift

Donatien Callon, Ian Lalonde, Mathieu Nadeau, Alexandre Girard

TL;DR

The paper addresses caregiver injuries during patient transfers by designing a motorized fifth-wheel floor lift and evaluating admittance-based control strategies. It implements both linear and variable-damping admittance controllers, selecting variable admittance for comprehensive robustness across friction and weight variations. Experimental results with seven participants show a 28% maneuverability improvement and a 66% reduction in pushing effort, while maintaining patient comfort within ISO guidelines. The work demonstrates a practical, safer enhancement to patient transfer devices and outlines steps toward hospital-based validation and comparison with existing motorized lifts.

Abstract

Patient transfer is a challenging, critical task because it exposes caregivers to injury risks. Available transfer devices, like floor lifts, lead to improvements but are far from perfect. They do not eliminate the caregivers risk of musculoskeletal disorders, and they can be burdensome to use due to their poor maneuverability. This paper presents a new motorized floor lift with a single central motorized wheel connected to an instrumented handle. Admittance controllers are designed to 1) improve the device maneuverability, 2) reduce the required caregiver effort, and 3) ensure the security and comfort of patients. Two controller designs, one with a linear admittance law and a non-linear admittance law with variable damping, were developed and implemented on a prototype. Tests were performed on seven participants to evaluate the performance of the assistance system and the controllers. The experimental results show that 1) the motorized assistance with the variable damping controller improves maneuverability by 28%, 2) reduces the amount of effort required to push the lift by 66% and 3) provides the same level of patient comfort compared to a standard unassisted floor lift.

Controller design and experimental evaluation of a motorised assistance for a patient transfer floor lift

TL;DR

The paper addresses caregiver injuries during patient transfers by designing a motorized fifth-wheel floor lift and evaluating admittance-based control strategies. It implements both linear and variable-damping admittance controllers, selecting variable admittance for comprehensive robustness across friction and weight variations. Experimental results with seven participants show a 28% maneuverability improvement and a 66% reduction in pushing effort, while maintaining patient comfort within ISO guidelines. The work demonstrates a practical, safer enhancement to patient transfer devices and outlines steps toward hospital-based validation and comparison with existing motorized lifts.

Abstract

Patient transfer is a challenging, critical task because it exposes caregivers to injury risks. Available transfer devices, like floor lifts, lead to improvements but are far from perfect. They do not eliminate the caregivers risk of musculoskeletal disorders, and they can be burdensome to use due to their poor maneuverability. This paper presents a new motorized floor lift with a single central motorized wheel connected to an instrumented handle. Admittance controllers are designed to 1) improve the device maneuverability, 2) reduce the required caregiver effort, and 3) ensure the security and comfort of patients. Two controller designs, one with a linear admittance law and a non-linear admittance law with variable damping, were developed and implemented on a prototype. Tests were performed on seven participants to evaluate the performance of the assistance system and the controllers. The experimental results show that 1) the motorized assistance with the variable damping controller improves maneuverability by 28%, 2) reduces the amount of effort required to push the lift by 66% and 3) provides the same level of patient comfort compared to a standard unassisted floor lift.
Paper Structure (28 sections, 10 equations, 8 figures, 2 tables)

This paper contains 28 sections, 10 equations, 8 figures, 2 tables.

Table of Contents

  1. INTRODUCTION
  2. REQUIREMENTS
  3. Maneuverability
  4. Effort
  5. Patient's Comfort
  6. SYSTEM AND MODELISATION
  7. The Fifth Wheel Concept
  8. Dynamic Model
  9. Controller Design
  10. Control scheme selection
  11. Admittance Controller Design
  12. Diminution of the Patient's Swings: An Unsuccessful Approach
  13. Variable Admittance Control
  14. PERFORMANCE EVALUATION
  15. Testing Protocol
  16. ...and 13 more sections

Figures (8)

  • Figure 1: Patient transfer with a floor lift
  • Figure 2: Schematic representation of the motorized fifth wheel concept, composed of a mass m in translation and a suspended mass M in rotation. The user and the motorized fifth wheel are pushing on the lift. A pivot point is created by the fifth wheel, allowing the user to turn the lift easily.
  • Figure 3: Architecture
  • Figure 4: Three options of control approaches
  • Figure 5: Comparison of the different angular responses depending on which speed command is sent to the motorized wheel
  • ...and 3 more figures