\section{Limitations and Recommended Improvisations}\label{limReco}

One of the main drawbacks of the sensor arrangement was side collisions due to insufficient sensor coverage. This was a source of annoyance for the drivers in spite of being told at the beginning of the experiment that this was to be expected.  Others have also reported side collisions (Simpson et al, 1999; Parikh et al, 2005; Petry et al, 2010). This issue can be resolved in a number of ways. The most obvious way is by adding more number of sonar sensors. Use of other sensor modalities such as laser scanners may be considered, which could also help to eliminate blind spots currently present in front of the wheelchair. Moreover, multiple sensors may be employed as explained in \hyperref[examplesensors]{Section 2.3}, to overcome the short-comings of any one sensor. Another solution would be by improvising the shared control strategy using more robust and effective methods for obstacle avoidance such as Potential Field Methods, Minimum Vector Field Histogram etc. 

The curvature of the path followed by the wheelchair in Wall Following mode may be eliminated by revising the algorithm so that it may follow a linear path. This would enable the user to predict its behaviour better and intervene less frequently to correct its path.

It may be noted that the sensors used in this project were those provided by USARSim and hence limited their use to the functionality provided. One of the constraints was that the sonar sensors could not be individually configured to have different beam angles. Hence creating sensors that satisfy the requirements may be considered.
 
The level of user interaction has been used as a measure of the effectiveness of shared control as explained previously in \hyperref[exampleevaluations]{Section 2.4}. However, the current implementation of the obstacle avoidance is such that the user is in control until their safety is compromised. Due to this strategy, the volunteers were not asked to drive the wheelchair using minimal keypad inputs. In order to reduce the user interactions and hence workload, more level of autonomy may be afforded to the wheelchair. This may prove useful particularly in narrow spaces, the regions of the map which caused the greatest frustration, with the help of techniques such as path planning.
