OK-here it is-straight out of the Honda Service Manual.
OBSTRUCTION DETECTION FUNCTION
When opening the sliding doors: ( I think it should read "closing")
"A sensor in the sliding door motor outputs pulses at a constant rate. When something is pinched in the sliding door, the pulse rate changes. The control unit detects this and then stops the motor, sounds the buzzer 3 times, and reverses its direction. The door will then open automatically at the same rate it would normally open."
It also says-under a different heading-the pulse sensor determines the fully open position by counting the pulse of the slide motor.
Also-under "Fail safe function" "When a power sliding door is in the half latched position, the obstruction detection function is off. If the corresponding power sliding door control unit recieves any signal from the dash switch,the remote control switch, (inner or outer door handles), or the factory keyless reciever while the in the half latched position, the control unit sounds the buzzer three times and activates the release motor. The release motor pulls the failsafe lever to mechanically disengage the closer motor from the latch. Once the latch and closer motor are disengaged, the slide motor will partially open the door".
I could not find any reference to the motor having to seek any special inputs during the first part of the open or close cycle, such as torque requirements that may be different if vehicle was facing uphill etc. Looks like it's number and speed of the rotational pulses. Might be there, but if it is-I missed it. Page 22-244
Regards
Al