Data Acquisition (DAQ) and Control from Microstar Laboratories

Knowledge Base: Processing

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Q10026 Continuous linear ramped output sequences

Tags: Help, DAP, DAPL, processing commands, PIDRAMP, open loop control

Applies to: DAPL 3000

I need to take measurements while I drive my system with a gradual linear ramp signal. Does the DAPL system have anything that can do this?

The challenge is the ramped motion control signal. Though it is not a completely general solution to the motion control problem, the PIDRAMP command can sometimes work for this.

When it receives a new output level, the PIDRAMP task expands that into a sequence of levels along a smooth transition, from the previous level to the new one. It can generate sequences as long as 4096 updates, but by stringing together a sequence of partial movements you can produce a very long ramp. Select the "LINEAR" ramp shape parameter. The duration of the ramp is determined by the number of samples you specify for the transition, and the update rate of the DACOUT or timed output procedure used to deliver the update values to the output converter port.

If you have a predetermined sequence movements, you can deliver them all in advance, and the PIDRAMP command will pre-compute the entire sequence. To hold a level for a period of time, just make the new target level the same as the previous one.

One feature that is distinctly missing from this scheme, but common in more general motion controls, is the ability to limit the acceleration at the endpoints of each linear movement. The changes of velocity at each end point will be abrupt.


For more information about the PIDRAMP and DACOUT commands, see the DAPL 3000 Reference manual.