\chapter{Evaluation}\label{evaluation}

In order to evaluate the effectiveness of the shared control strategies developed, 5 able-bodied volunteers were asked to drive the wheelchair in the immersive virtual reality wheelchair simulator. They consisted of 3 men and 2 women aged between 24 and 42 (mean age - 31.60; standard deviation - 8.44). Three of them had no or insignificant previous gaming experience. One of them who belonged to this category had driven the virtual reality wheelchair for a few experiments using both the keypad and joystick about a year ago, but did not demonstrate any additional proficiency and hence was not advantaged.  A number of driving tasks were carried out by each volunteer with and without the accompaniment of a secondary task. Following each task, they rated their experience using the NASA-TLX assessment tool. Prior to the start of the experiment, they were provided with an information sheet, consent form and definitions of the NASA-TLX subscales (see Appendix B). 

\input{chap5_5.1_nasatlx}

\input{chap5_5.2_secondary}

\input{chap5_5.3_expProcedure}

\input{chap5_5.4_results}