1. Although the SONAR only requires a 10microsec trigger pulse, at 1100 feet per second a five foot sound echo returns (order of magnitude) in a bit less that 10 millisec. I can not trigger both SONARs at the same time. I believe their echos would interfere. I certainly do not have to trigger these devices 50 times per second. Three or four times per second would be enough. This would give the velocity rate calculations more meaning. (Maybe I should make the SONAR activity interrupt dependent, not the PWM activity.)

2. The PIC needs to control the steering. It needs to keep the car traveling parallel to the side wall a given distance (desiredtrack) from that wall. It also needs to turn the car dramatically left when a (corner) wall appears inside a given distance (frontfree) in front. Both 'desiredtrack' and 'frontfree' are VAR WORDs - functions of the POT position (which also influences the speed of the car).

3. There is a totally separate algorithm controlling steering when the car is backing up due to a collision or a very near miss. Basicly steer right and back up a couple of feet then steer left and try to go forward.

4. If the steering were absolutely under control I feel the wheel speed could be pretty much left alone. Check the POT and make the PWM signal to the Electronic Speed Control proportional in seven stages.

5. My PIC really should have four pieces of data to work from.
A. Distance to the right wall.
B. Closing rate to the right wall.
C. Distance from an object in front.
D. Closing rate on the object in front.
If it had this information I think even I could code proportional feed back loops. Note two are rates. Each of these require two readings a known time apart, a subtraction process and some comparisons to fixed estimated values.

6. My model level car can be put under radio control merely by turning on the power to the ratio transmitter. It is selection which PWM signals (radio receiver sourced or PIC sourced) that is done by the DPDT coil driven relay switch. It is driving that relay switch coil that requires the SN7407 current driver.

7. I chose the HPWM to shape the steering and DC motor signals because by trial and error I found parameters that seemed to work at slower speeds. The signals continue no matter what the PIC code is doing. I do wonder whether I screw up a sequence each time I exercise a new HPWM command even if it is a repeat of the previous HPWM command. I do not understand the architecture details of HPWM command.

Ken