The angle sensors are now in place and I've added the code in the motor controllers to:
- Read the angle sensors
- Set a max movement limit
- Set a min movement limit
- Set a customizable hysteresis to avoid rapid on/off switching at the end stops if the sensor fluctuates.
- A way to read the current position from the host CPU (the Raspberry pi).
I also added acceleration and variable braking. Both are compatible with the Pololu quik controller. The acceleration was needed to avoid jerkyness when entering or leaving the end limits. The braking helps a lot when holding the arm statically and avoids back-drive of the gear motors.
The end stop logic works as I hoped, and I no longer have to worry about crashing into the end of the travel.
Just for fun, I added a visualization of the excavator on a web page. It's just the same 3D model from Fusion 360, but exported to STL to be loadable by three.js in a web page. The web page uses WebSocket to read the current position of the joints from the excavator over WiFi.
Here is a short video:
https://youtu.be/Z60gWvpeJ8I
Stein :-)