I’ve hooked in the demands from the rover to the control board and added a simple PID based speed controller. The three position switch on the remote takes the car from manual control to auto with speed=0 to auto with speed=10 km/h. I’ve hooked in the dial on the remote to change the Ki term so I can fiddle with the response while the car is running.
It worked quite well, but I caused a ding while fiddling: the gain was high enough to cause the speed to oscillate (peak ~= 30 km/h, with about 5 s period) and it surged into the curb. The bumper worked well, but the rover battery moved forward and put a hole in the box.
Next is adding a deadband to give finer control and better limits on the maximum drive and integral.