\chapter{Conclusion}\label{conclusion}

The objective of the project was to review shared control approaches used in electric powered wheelchairs and to incorporate shared control in the virtual reality wheelchair simulator developed in the Neurophysiology Lab at the University of Strathclyde. A shared control technique providing Obstacle Avoidance, Wall Following and Collision Avoidance assistive modes has been developed and evaluated with the help of a secondary task and NASA Task Load Index assessment procedure.

The wheelchair simulator provides shared control in unfamiliar environments with the help of sonar sensors to assist in obstacle avoidance and preventing collisions. The Obstacle Avoidance assistive behaviour is more effective in areas containing widely spaced obstacles as opposed to narrow spaces where side collisions occur more frequently. Collision Avoidance has been tested and though effective in increasing the safety of the user, it has been the main source of frustration in the tests conducted using 5 volunteers. Blind spots due to insufficient number of sensors must be removed. This would greatly enhance the performance of the shared control behaviours. Wall Following assistance has been achieved with the help of infra-red sensors. The assistance provided by this mode was better accepted by the volunteers. However, it follows a curved or zigzag path at times, which should be changed to a linear path by improvising the algorithm.

The use of secondary tasks has proven to be beneficial in assessing the shared control methods by imposing higher cognitive demands on the user and hence decreasing their wheelchair-driving efficiency. This brought out the effects of shared control, which would otherwise not have been detected since the volunteers were able-bodied people who did not require assistance. The design of the secondary task may be modified to yield better and more consistent results.

The workload scores obtained with the help of the NASA-TLX scales are satisfactory. The assessment procedure has provided a means of identifying the acceptable and annoying behaviours provided by shared control. In addition to these ratings, the feedback received from the volunteers regarding their driving experience in both manual and shared modes, as well as their perception of the usefulness of shared control behaviours, has provided valuable information in understanding the drawbacks of the system.

In conclusion, this study has provided a useful insight of how shared control may be integrated with the virtual reality wheelchair simulator and about the psychology of people interacting with intelligent machines. Future work in this domain can be based on the inferences obtained through evaluation of the shared control system.


