PBP projects for R/C models

[Kenjones1935]

I put the car up on blocks and found that when going forward it only turned left in my patented incremental way. It also flashed the SONARs at about 1/2 the usual rate.

The Vcc wire for the right side SONAR had become disconnected.

Soooo with the front SONAR working and the right SONAR always saying zero distance to the wall, the car turns left in little bits except when it approaches a wall head on. Then it brakes and swerves left.

That's exactly what my video shows.

Given that information, what if anything should I fix?

Ken

[mackrackit]

Well now you know exactly where the problem is. Connect the side scan and start tweaking that part of the code.

[Kenjones1935]

The issue is controlling the steering. It is bang-bang but I can modify the length of time and the frequency of each 'bang'. The plastic wheels slide easily. This is true of turning as well as forward or reverse drive.

I hope not to introduce an adjustment POT. It appears that the plastic mechanical parts are not consistent. Kicking the steering wheels back from full reach seems not to be symmetric. Hmmmm.

Ken

[Kenjones1935]

The car turns left when the right SONAR says it is further away from the wall than "desiredtrack". The car then moves a bit more as it rotates (turning right) its distance to the wall increases as a function of its rotation.

So it decides to keep turning right. Wrong!!

I need to think more about this.

Ken

[Kenjones1935]

I typo'd. The car turns left when the right hand SONAR says it is too close to the wall - ie less than "desiredtrack". It then crosses the imaginary "desiredtrack" line which is parallel to the wall.

Now it starts to turn right - as it should. As the right turn aims the front of the car more at the wall, the right SONAR finds that same wall farther away. It exceeds the "desiredtrack" distance and therefore keeps turning right.

CRASH

[ScaleRobotics]

Now it starts to turn right - as it should. As the right turn aims the front of the car more at the wall, the right SONAR finds that same wall farther away. It exceeds the "desiredtrack" distance and therefore keeps turning right.

CRASH

Sounds like you need to limit your angle as you turn into the wall.

When adjusting right to get to your imaginary line (closer to the wall), if front distance < 3 * side distance, then turn left (until front distance > 3 * side distance). Something like this should help keep from making too big of a right turn, but still get you closer to the wall.

Changing the 3 would change the angle you would allow.

[Ioannis]

Sounds like you need to limit your angle as you turn into the wall.

When adjusting right to get to your imaginary line (closer to the wall), if front distance < 3 * side distance, then turn left (until front distance > 3 * side distance). Something like this should help keep from making too big of a right turn, but still get you closer to the wall.

Changing the 3 would change the angle you would allow.

I am pretty sure this method will lead to oscillations. In fact in the Ken's video this really happens. The car "oscillates" around its desired path.

With simple if-then commands this cannot be compensated. As discussed in previous post, a PID loop control can help.

Ioannis