The PID controller generates {HEAD ~ a command signal} to either modulate the brakes or motor up or down depending on the sign of {TAIL ~ the command signal} 
The PID controller generates { HEAD ~ a command signal } to either modulate the brakes or motor up or down depending on the sign of { TAIL ~ the command signal }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL