## 3 Materials and Methods
### User Testing Methodology  
To evaluate the effectiveness of the haptic feedback system and its integration into virtual environments, a series of user tests were conducted. The primary objective of these tests was to compare the performance of wheelchair users in completing a virtual task using different interaction methods and feedback configurations. The following sections detail the methodology employed, the analysis approach, and the comparative framework used for the evaluation. Participants were recruited to represent a diverse sample group, including 21 individuals with varying ages, genders, and wheelchair types. The group comprised eight males and thirteen females, aged between 20 and 63 years. Both manual and motorized wheelchair users were included in the study, with fifteen participants using manual wheelchairs and six using motorized ones. Table 1 summarises the demographic data of the study. The tests were carried out in a controlled virtual environment designed to simulate a typical navigation task. This environment, which can be seen in Figure 5, was displayed using a CAVE (Cave Automatic Virtual Environment) system to provide an immersive experience. The haptic feedback system was integrated into this setup, delivering realistic force feedback based on the virtual terrain, enhancing the overall immersion and realism of the experience. Participants were required to complete the navigation task using three different interaction methods. The first method involved using their wheelchair with the base motors on, activating the haptic feedback system to provide force feedback. The second method was similar but with the base motors off, deactivating the haptic feedback. The third method  
Figure 5: CAVE environment for the test of the device with users. required participants to use a standard joystick to navigate the virtual environment. This setup allowed for a comprehensive evaluation of the haptic feedback system's impact on user performance. Since the feedback system does not make sense for users who use motorized wheelchairs, this test was omitted in these cases. The navigation task involved guiding the wheelchair through a predefined course within the virtual environment. This course was designed to mimic real-world navigation challenges, including various obstacles and terrain types. The task aimed to test the users' ability to maneuver effectively under different conditions. Prior to the actual tests, participants were given a brief training session to familiarize themselves with the virtual environment and the different interaction methods. Each participant then completed the navigation task under each of the three conditions. To mitigate any potential learning effects, the order of the interaction methods was randomized. The time taken to complete the task was recorded for each condition, providing a quantitative measure of performance. Data collection focused primarily on the completion times for each condition, serving as the key metric for analysis. Additionally, qualitative data, based on [PERSON] and [PERSON]'s [22] presence questionnaire, were gathered through participant feedback and observations made during the tests. The Witmer and Singer's Presence Questionnaire is a widely used tool for evaluating the sense of presence in virtual environments. It has demonstrated strong psychometric properties, including good reliability and validity, as reported in previous studies. The questionnaire assesses factors such as involvement, immersion, and the perceived realism of the virtual environment, making it particularly suitable for evaluating the user experience in immersive VR systems. This feedback provided insights into the user experience and any difficulties encountered. The comparative analysis aimed to evaluate performance across the three interaction methods, focusing on efficiency and ease of use. The analysis sought to determine which method allowed for the quickest task completion and whether there were significant performance differences based on wheelchair type.