Grabbing oblong objects

[biojae]

Originally Posted by theprgramerdude

Do you know why your first derivative potentiometer readings may be unstable? I'd recommend trying to instead take the average derivative over a period instead, so either integrate a few derivative values and divide with respect to time, or just take the readings from the potentiometer at a much slower rate (I'd recommend the first one if your ADC+Pot combo is possibly the issue and you have the compute power, it essentially equates to crude oversampling).

The HiTechnic prototype board has 10bits of ADC resolution.

Originally Posted by Hitechnic.com;

The prototyping board update rate may be controlled within a range of 4-100 milliseconds per sample.

So, it can do 10 - 250 samples per second.
The code that I tested was sampling every 10 ms, or 100 times a second.

The mechanism is using a 270 degree linear 10k Ohm potentiometer, and uses almost all of that range ( > 230 degrees)
through gearing, and actual movement range.
with that, there are about 3.79259 ticks per degree on the pot.

While running, the velocity would be about 3 ticks per cycle.
The problem arises when it is not moving, as there are a few readings that have near the same values as when it is not moving.

I will try it with a longer sampling time, in an attempt to get more ticks per cycle, which should allow a better distinction between moving and not moving.

The question then becomes: how do I use the velocity readings to change the setpoint of the PID controller?
I would imagine that a timer would be needed, as I don't want it to think that it was stalled right when it started moving and thus immediately change the setpoint and not move.