## 1 Introduction  
Virtual reality (VR) has become increasingly prevalent in our daily lives, driven by significant advancements in both hardware and software. These developments have made it possible to create highly immersive experiences that can transport users from their real-world surroundings into entirely virtual environments where most of their senses are stimulated as if they were experiencing real-life scenarios. Just twenty years ago, the idea of a person fully immersing themselves in a virtual environment with such a high degree of sensory engagement would have been considered science fiction. VR is a computer-generated simulation that allows users to interact with and experience a three-dimensional environment in real time, often using multisensory feedback (visual, auditory, and haptic) to enhance immersion and realism. In this study, we focus on highly immersive VR environments, where the term 'immersive' refers to the user's ability to feel fully enveloped in the virtual space, experiencing natural interaction and realistic feedback through multisensory cues, particularly haptic feedback. The effectiveness of VR is often measured by the sense of presence, which is the user's feeling of \"being there\" in the virtual environment [1]. This sense of presence is crucial for training, simulation, and rehabilitation applications, as it allows users to engage more fully and intuitively with the virtual world. Achieving a high sense of presence typically involves stimulating multiple senses simultaneously, including sight, sound, and touch. However, the rapid advancements in VR technology have primarily benefited a broad audience, often overlooking the specific needs of users with disabilities. While there have been significant improvements in visual, auditory, and even haptic devices for the general population, the progress in developing VR solutions tailored for individuals with mobility impairments has been relatively limited. This disparity highlights the need for more inclusive VR technologies that cater to the diverse needs of all users, including those who rely on wheelchairs for mobility. The use of VR technologies for individuals with disabilities has shown great promise in areas such as rehabilitation, skill training, and accessibility solutions. These technologies provide immersive and customizable environments that enable users to practice real-world tasks and interactions in a safe and controlled manner, improving both functionality and quality of life. At the Institute of Robotics and Information and Communication Technologies (IRTIC) of the University of Valencia, we have embarked on a project aimed at bridging this gap. Our goal is to develop a haptic system that allows wheelchair users to interact with virtual environments in a manner identical to how they would in the real world. This system is designed to provide realistic feedback based on the user's movements and the virtual terrain they navigate, enhancing their sense of presence and immersion. The developed system incorporates two servo-actuators that function as both encoders and force generators, delivering haptic feedback to the user. This feedback can simulate various real-world conditions, such as increased resistance when moving uphill or assistance when moving downhill. By integrating this haptic system into VR environments, we aim to offer wheelchair users a more natural and engaging way to explore and interact with virtual worlds. This paper details the development and evaluation of our haptic system. We conducted tests with 21 wheelchair users, who navigated a virtual course using different interaction methods and feedback configurations. Participants' performance was measured by the time taken to complete the course, and their experiences were assessed through presence and cybersickness questionnaires. The results indicate that users achieved the best performance and reported the highest sense of presence when using their natural interaction method with their wheelchairs.