Working on suspension model for the wheelchair was a big task for us.It was very new to us and this concept requires expertise and knowledge in the field.We overcame it with research and produced an efficient and not so complex model.
Moreover,as suggested ,rollers for stair climbing was a hurdle .Although we did manage to build them but implementing it by attaching it to the chassis turned out to be difficult .We watched a lot of videos and at the end of the day it was a lot of knowledge gained and new exposure to different prospects of designing environments within the software.Further enhacement could be installing a segway which would work as rear wheels for stability and provide human help if neccesity.