68300

Jeff,

I do not know if the TSM is causing problems but stepper motors are very 
fickle unless put into a closed loop system.  You can easily get the 
problems you describe if the drive pulses are not locked to motor 
position.  The random TPU behavior is not welcome.  Maybe someone can 
explain it.

R. Yablonski

At 12:22 AM 11/19/02 +0000, you wrote:
>Hi all,
>I am using the Table Stepper Motor (TSM) function in the TPU to,
>well, run a stepper motor.  I am having two problems that I am hoping
>someone can help me solve.
>
>First, I have some c-code to run the motor in an open-loop mode.
>Every 5mS I read the PRESENT_POSITION register, add an interger (say
>8), then write the result to DESIRED_POSITION. Then update the HSR to
>implement the command. My start rate is around 140 pulses per second
>(pps) and the slew rate is around 2135 pps.  I would expect the motor
>to run at a somewhat constant rate, or at least dither back and forth
>around the given rate based on the discrete acceleration rates in the
>profile lookup table. Instead it is very jerky doing stop and go type
>behavior. The pulse waveform out of the TPU shows both phases pulsing
>as expected, then one phase stops while the other phase keeps
>toggling a few times, then both phases begin pulsing again. This
>occurs somewhat rhythmically.
>
>The second problem is the 1.8 degree per step motor will be rotating
>in the proper direction, suddenly reverse at a somewhat higher rate
>and travel more than one revolution, then reverse again and travel as
>normal. The phasing never changes to warrant the motor changing
>directions. I suspect the anomally above is causing the motor to have
>a resonance problem, but I have never heard of a motor traveling
>backwards for any substantial distance.
>
>Can anyone help me with these problems?
>
>Thanks,
>Jeff
>
>
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