# Peer-to-Peer Ultra-Wideband Localization for Hands-Free Control of a Human-Guided Smart Stroller
## 6 Discussion
### System Usability  
As the novel operation methods, two electrical-assisted interfaces, the proposed interface and joystick, have a lower usability scale than the traditional manual operation across all participants in the stroller scenario. The proposed method seemed no less usable than the joystick, a standard interface with a higher median value usability scale. Furthermore, it has sufficient performance in the completion time of the second task even though the joystick has a faster maximum speed. Gender differences should be considered, as the findings revealed that females achieved significantly higher scores with the hands-free interface than the joystick, with no significant difference from manual operation. In contrast, males did not exhibit significant differences, and their median score for the hands-free interface was lower and significantly different from manual operation. This may be due to the difference in performance between males and females on joystick usage. Similarly, studies [43; 44] reported that men typically outperform women in tasks like video games and VR driving simulations using a joystick. That might be because males and females  
Figure 15: Two examples of human/robot trajectory under the hands-free control and joystick control with different objects. (**a**) Example one (**b**) Example two.  
have different performances in visuomotor tracking. [PERSON] et al. [42] noted that males show a clear advantage in hand tracking accuracy during a visuo-oculo-manual motor task and women exhibit a larger temporal lag between hand motion and target motion. The reasons for this phenomenon were further investigated by [PERSON], [PERSON] [45], and [PERSON] et al. [46]. They hypothesize that the gap in joystick performance is primarily due to varying levels of experience and practice with joystick-based activities, rather than gender itself being a determining factor. In our experiment, most of the female subjects stated that they have less joystick usage experience yet most of the male participants have experience with the joystick. They also mentioned that the unfamiliarity with joystick operations caused them to pay more attention when operating the joystick while maneuvering the stroller, making it harder to check the surroundings. Additionally, female subjects reported that the proposed interface was intuitive to use, and rated it higher on all aspects in the additional questionnaire compared to the joystick. This may explain their preference for the hands-free interface. The proposed interface is thereby indicated to be user-friendly and easy to learn even for those with little to no prior experience with joystick-based activities, such as, female and some elderly users.  
The experiment verified the feasibility and effectiveness of the proposed system in a simplified indoor environment with static obstacles. However, the outdoor condition is more complex with bumpy roads, and slopes we have not tested this time. These factors may affect system performance and user experience, raising challenges to control stability and accuracy. The UWB transmitter and receiver may not remain on the same plane due to the stroller bouncing on bumpy roads and the stroller not being on the same plane as the person while moving uphill or downhill. This could lead to a decrease in the UWB sensor's accuracy in localization, or it could cause minor angular differences even when the person does not intend to steer the stroller to turn. Localization errors will directly impact the vehicle's speed commands; however, the impact can be mitigated to a certain extent by the EKF. Unexpected distance shifts can be offset due to the setting of the velocity dead zone to ensure control stability. We infer our system can be less affected by such road conditions to a certain extent. Furthermore, confined spaces such as the elevator require a system that provides more accurate operation. In these scenarios, switching to manual operation is the best option for controllability and safety.