Monday, August 21, 2006


Automating PWM settings on the GM4 controller...

Right now I have the firmware transition the GM4 from whatever speed setting it is at currently to a new one by simply incrementing or decrementing the PWM setting by a set figure till the target speed (in pulses per unit time) is reached. This process can take up to several seconds. After the success in basically eliminating overshoot for the GM4 with a lookup correction table I've decided to use the same approach for setting motor speeds.

Not only will using a lookup table decrease the motor response time to changes, it will also allow me to greatly reduce the PWM adjustment step. That should make for smoother motor speeds.

Over lunch I put the PWM settings table into the firmware of the GM4 motor control board. I also reduced the adjustment factor for controlling PWM settings down from +/-4 to +/- 1.

Beagle was interested in how fast the GM4 could change speeds. I took a tentative look and it seems like now that I've put the PWM settings table in that the transition is faster than the sampling period. I'm going to have to go back and find in my notes what I set the sampling period to. It appears to be about 100 msec. I got that wrong before. Suffice it to say that the GM4 winds up to the speed I've set it to faster than I can punch the command button that sets the time and then punch the command button that checks the speed. That's probably about a half second.

I'll have to write in a check into the firmware to measure this and that will have to be for later, because lunch is over.

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