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Torso-Based Control Interface for Standing Mobility-Assistive Devices

Yang Chen, Diego Paez-Granados, Modar Hassan, Kenji Suzuki

Abstract

Wheelchairs and mobility devices have transformed our bodies into cybernic systems, enhancing our well-being by enabling individuals with reduced mobility to regain freedom. Notwithstanding, current interfaces of control primarily rely on hand operation, therefore constraining the user from performing functional activities of daily living. In this work, we propose a design of a torso-based control interface with compliant coupling support for standing mobility assistive devices. We consider the coupling between the human and robot in the interface design. The design includes a compliant support mechanism and mapping between the body movement space and the velocity space. We present experiments including multiple conditions, with a joystick for comparison with the proposed torso control interface. The results of a path-following experiment demonstrated that users could control the device naturally using the hands-free interface, and the performance was comparable with the joystick, with 10% more consumed time, an average cross error of 0.116 m and 4.9% less average acceleration. In an object-transferring experiment, the proposed interface demonstrated a clear advantage when users needed to manipulate objects during locomotion. Lastly, the torso control scored 15% less than the joystick on the system usability scale for the path-following task but 3.3% more for the object-transferring task.

Torso-Based Control Interface for Standing Mobility-Assistive Devices

Abstract

Wheelchairs and mobility devices have transformed our bodies into cybernic systems, enhancing our well-being by enabling individuals with reduced mobility to regain freedom. Notwithstanding, current interfaces of control primarily rely on hand operation, therefore constraining the user from performing functional activities of daily living. In this work, we propose a design of a torso-based control interface with compliant coupling support for standing mobility assistive devices. We consider the coupling between the human and robot in the interface design. The design includes a compliant support mechanism and mapping between the body movement space and the velocity space. We present experiments including multiple conditions, with a joystick for comparison with the proposed torso control interface. The results of a path-following experiment demonstrated that users could control the device naturally using the hands-free interface, and the performance was comparable with the joystick, with 10% more consumed time, an average cross error of 0.116 m and 4.9% less average acceleration. In an object-transferring experiment, the proposed interface demonstrated a clear advantage when users needed to manipulate objects during locomotion. Lastly, the torso control scored 15% less than the joystick on the system usability scale for the path-following task but 3.3% more for the object-transferring task.
Paper Structure (34 sections, 24 equations, 14 figures, 2 tables)

This paper contains 34 sections, 24 equations, 14 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Related works
  3. Control interfaces for robotic walkers
  4. Neck and head-based approach
  5. Upper-body based approach
  6. Shoulder based approach
  7. Central torso-based approach
  8. Proposal
  9. Methodology
  10. Compliant coupling mechanism
  11. Kinematics
  12. Quasi-static force analysis
  13. Selection of suitable stiffness
  14. Control Method: Sensing and Mapping
  15. Mapping between sensor space and pointer space
  16. ...and 19 more sections

Figures (14)

  • Figure 1: Overview of the torso control, motion sequence of one participant controlling the device while transferring objects from one table to another.
  • Figure 2: The proposed interface and its components.
  • Figure 3: (a) (b) Kinematics and quasi-static force of the support mechanism. $C$ and $C^\prime$ denote the contact point between the torso and the upper support bar. $F$ and $F^\prime$ denote the supporting force from the bar, $N$ and $N^\prime$ denote the support force from the harness. (c) Simplified dynamic model of the user and mobility device in sagittal plane.
  • Figure 4: Changed in $\theta$ and $\Dot{x}$ with time for spring coefficient $k_s$ of 2000 $N/s$ and 3000 $N/s$ respectively.
  • Figure 5: Mapping between bending angle $\theta_b$ and velocity magnitude $P$.
  • ...and 9 more figures