OK, I will be honest. When I finished, it looked more like a stool than a chair 
My 3 year old called it a table 
! But anyways, let me show you how I built it.
This chair needs to have wheels so that it can be driven around on flat surfaces in homes. So, I wanted to include a base for this such that the base can be tuck under the sofa (those that have space underneath) or similar furniture for sitting and sleeping. Then I needed to have a frame and on top, a surface to sit on. This needs to be as thin as possible so that it can come onto the sofa and one can easily hop onto it from their seating position on the side, without needing to get up and sit on it. Well, that is the point of this project that this device needs to be able to support the sitting up movement so that fragile joints (knee) are not taking all the load.
I found some wood lying around in my garage so I arranged and tried to create something like I described above and here is what they look like.
For the top panel to be able to rotate, I needed to install an axle (or rod) that can be attached to a motor via gears. Lots of axles, gears and bearings to choose from!
To mount it and also the motor, I needed to find some suitable brackets. Luckily, I found some identical brackets in my treasure! You can also see an axle with a gear attached and some bearing support and stop clips.
After some hours of drilling, aligning and more drilling and screwing, I managed to build the frame and mount the motor unit. You might notice here that I had planned to use BLDC motor but attached stepper motor instead. This is because I seem to have fried a component in BLDC motor's driver PCB. I will detail this in my next blog.
Now that my build is almost finished, I started focusing on electronics along with Arduino Nano 33 IoT. Until now, I was thinking of using an encoder or potentiometer to measure angular position of the seat but I had another thought by this time. I was thinking that perhaps I could use in-built IMU on Arduino Nano 33 IoT so that I can sense the angular velocity of the seat using the gyroscope and use this for supplying the appropriate power via stepper motor to assist the intended movement. This would simplify the amount of electronics that might be needed here.