Torso-Based Control Interface for Standing Mobility-Assistive Devices
(2312.01543)Abstract
Wheelchairs and mobility devices have transformed our bodies into cybernic systems, extending our well-being by enabling individuals with reduced mobility to regain freedom. Notwithstanding, current interfaces of control require to use the hands, therefore constraining the user from performing functional activities of daily living. In this work, we present a unique design of torso-based control interface with compliant coupling support for standing mobility assistive devices. We take the coupling between the human and robot into consideration in the interface design. The design includes a compliant support mechanism and a 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 showed that users were able to 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. The result of an object-transferring experiment showed the advantage of using the proposed interface in case users needed to manipulate objects while locomotion. The torso control scored 15% less in the System Usability Scale than the joystick in the path following task but 3.3% more in the object transferring task.
Overview
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The paper introduces a new control interface for mobility assistive devices that utilizes the torso for directing movements, aiding users with limited hand functionality.
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A torso-based control interface with a compliant support mechanism is developed to support users and capture their torso movements to operate the device.
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The control interface maps torso movements to mobility device movements and allows for customization through hardware and software modifications.
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Experiments showed that the new interface could match traditional joystick performance, particularly in tasks requiring hand use, with slight delays in command execution.
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Initial user feedback suggests the interface is natural and intuitive, although some improvements are desired; it shows promise for future hands-free assistive device control.
Overview of Torso-Based Control for Mobility Devices
Introduction to Torso Control in Mobility Devices
Mobility assistance devices, such as powered wheelchairs, are crucial for individuals with spinal cord injuries or limited mobility. These devices traditionally rely on hand-operated controls like joysticks, limiting the user's ability to use their hands for other tasks. Autonomous control and voluntary control are two primary approaches to address this issue – the former focusing on automated navigation, while the latter on user-initiated movements. The innovation detailed in this work lies within the voluntary control category, introducing a control interface utilizing the torso for directing standing mobility devices.
Development of the Torso Control Interface
This work involves the creation of a torso-based control interface equipped with a compliant support mechanism, which serves dual objectives: providing support to users and capturing torso movements to operate a mobility device. The interface consists of multiple parts including a back support belt, upper and lower support bars interconnected by a compliant segment, and a posture adjustment mechanism.
Mechanism and Control Strategy
The core of the control strategy is the ability to map the user’s torso movements into corresponding movements of the mobility device. The compliant segment of the support system is designed to react flexibly under stress, serving a cushioning function during rapid deceleration, as well as providing users with tactile feedback on their movements. A model including dynamic simulations helped in optimizing the stiffness of the support mechanism. The control interface also accommodates customization for individuals through both hardware adaptability and software calibration, focusing on user-preferred postures and movement ranges.
Experimental Results and User Feedback
Experiments were conducted to evaluate both the mechanical properties of the support system and the practicality of the control interface. These included measurements of the force exerted by the compliant segment and user studies where participants navigated through a marked course and transferred objects using the device. The results showed that the torso control interface performance was comparable to that of a traditional joystick, especially highlighted during tasks that required the use of hands, such as object manipulation.
Participants using this new control interface experienced a slight delay in command execution but felt that the benefits in hands-free operation outweighed this disadvantage. Feedback gathered also highlighted the interface's natural and intuitive control, despite some suggestions for improvements like visual feedback aids and additional adjustability features, particularly catering to female users.
Conclusion
The new interface proposed in this work offers a hands-free, intuitive method for controlling mobility assistive devices, capable of supporting the upper body and translating torso movements into smooth and responsive navigation commands. This system not only enhances the user experience by liberating their hands for other essential activities but also represents an impactful step forward in the field of assistive robotics. The positive initial response and feedback from the user study indicate a strong foundation for future development, with the next steps involving further refinement and testing with end-users.
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