Torso-Based Control Interface for Standing Mobility-Assistive Devices (2312.01543v2)

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.

• The paper presents a novel torso-based control interface that translates torso movements into device commands, enabling hands-free operation comparable to traditional joysticks.
• It employs a compliant support mechanism with optimized stiffness and tactile feedback through dynamic simulations to enhance user control.
• User studies revealed intuitive control with minor command delays, highlighting the interface’s potential to improve assistive mobility while freeing users' hands.

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 paper indicate a strong foundation for future development, with the next steps involving further refinement and testing with end-users.