The goal of our project is to develop and build a powered wheelchair in 10 months. This requires a tight timetable and there is not much room for errors. As a result of this timeframe it is not possible to make a prototype of each module to make sure it is working properly. These modules are: chair, frame, battery system, support system, balancing, tracks, tilt mechanism and drive chain.
We sorted the systems according to their risk and impact on our final system. We decided to build and test the three most critical systems which are crucial for a successful product. These are the balancing system, the clutch and the tracks.
The balancing system shall consist of a Segway-like construction. We wanted to use as many of the final parts as possible. This means using a chain to drive the wheels, the motors and controllers as well as the IMU planned for the final version.
The clutch prototype shall consist of the clutch, a servo motor and an encoder as well as a drive motor. We want to figure out if using a single lever has enough force or if additional constructive measurements have to be made. Also we want to read if the clutch is opened or closed using the encoder built in the servo motor.
The goal of the track prototype is to test the behaviour on the stairs. We calculated the required strength and made estimations for the friction coefficient. Nevertheless it is important to compare this theoretical values with practical experience. For this reason we manufactured a prototype which takes advantage of the tensioning mechanism and the tracks we ordered. For propulsion we used replacement motors from Maxon which give us the same torque as the final ones but at a lower speed.