# Systematic Review of Mecanum and Omni Wheel Technologies for Motor Impairments
## 4 Discussion  
This review identified six key challenges that must be addressed to maximize the usability and efficiency of Mecanum and omni wheel assistive devices. While the selected studies provide valuable insights into the mechanical design, control strategies, and energy management of these systems, real-world implementation remains challenging. Below, we discuss each challenge--terrain adaptation, control systems, energy efficiency, automation, validation, and cost/design--and outline both the progress made and the remaining gaps. Stability and maneuverability on uneven terrain remain significant issues for current systems. Some studies--as discussed in Section 3.1--have introduced innovative curb-climbing and seat-leveling mechanisms [29,33] that improve performance on specific obstacles, but these designs still struggle to consistently handle diverse surface conditions. Several designs work reliably indoors yet falter on rough outdoor terrain; indeed, even systems with active leveling or hybrid wheel configurations reported failure rates above 20% in obstacle-rich environments. This gap between lab optimization and real-world reliability indicates that further refinement is needed to ensure consistent performance across various surfaces. Researchers have responded by integrating advanced suspension systems and novel wheel configurations. For example, adding suspension to each wheel significantly improves stability and comfort when traversing uneven terrain [26,27]. Adaptive suspension can dynamically adjust wheel height or damping to keep all wheels in contact and to reduce vibrations transmitted to the user. Others have combined different wheel types to enhance traction, such as a four-wheel-drive hybrid that pairs conventional tires with omni wheels; this design allows a vehicle to climb small steps while maintaining lateral agility on irregular surfaces. However, truly seamless omnidirectional mobility over very rough terrain has not yet been achieved, suggesting that more radical innovations--like novel wheel geometries or smart suspensions that actively adapt to surface irregularities--will be required to fully address this challenge [45]. Beyond the wheels and suspension, the control architecture and user interface determine how effectively and intuitively a person with motor impairments can operate an omnidirectional wheelchair. A key trend is the development of multimodal control schemes that move beyond the traditional joystick, allowing users with a wide range of abilities to command their devices. Detailed analyses in the Results indicate that despite high reliability and usability, cognitive load remains a challenge, particularly for BCI-based systems. While Section 3.2 outlined the feasibility of gesture-based [36], web-based [38], and EEG-based interfaces [37], few addressed the learning curve or long-term usability. Furthermore, control architectures must balance autonomy and user intent: systems such as CVAR-BCW [50] exemplify this by enabling shared control, where the wheelchair manages navigation details while the user makes high-level decisions. Such hybrid control models appear promising but require further refinement in terms of latency, safety, and adaptability to diverse user needs. In parallel with such novel inputs, researchers are refining traditional controls to make mobility more user-friendly. Improved joystick interfaces and smarter controllers have been introduced to simplify maneuvering in complex environments. A previously described system (Section 3.4) incorporated an intuitive joystick with preset driving modes and memory functions for seat positioning [53]. Even small usability enhancements--like an ergonomic joystick design or automated alignment features--can reduce the cognitive and physical strain on users and caregivers. Additionally, remote control and semi-autonomous functionalities are being tested [38].