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Brian Kelly

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Everything posted by Brian Kelly

  1. Curt Thank you for your response. Overall the feed forward features with this controller are better than what I had used before and I am trying to apply them for best response. Is the preference for not using integral gain during tracking type moves primarily because it introduces lag into the overall response? Also while tuning the outer loop response I was adjusting inner loop parameters as well and inadvertently set the velocity feed forward term to zero, at which point the system immediately became oscillatory. I am curious as why that happened. I understand that every application is different and there are many details not specified so that may be difficult to answer but if anything obvious comes to mind I would appreciate your thoughts. Thanks again. Best
  2. Hello I had a few questions related to cascade loop tuning. We have a force over position cascade configuration where the force loop values are integrated before input to the inner loop. The system works pretty well but I am always looking to see if it can be improved. In the case when the inner loop receives commanded input from the outer loop only, does the PMAC still compute inner loop velocity and acceleration values? I am wondering if the velocity and acceleration feed forward components of the inner loop still play a role in the response? In terms of operation we run in two scenarios 1) a cascaded axis is programmed to maintain a static value e.g. zero force (in our application this will demand the actuator moves, including direction reversals) and 2) the axis is programmed to follow a trajectory (e.g. ramp or nonlinear) force profile. I had always thought that in scenario 1, good disturbance rejection and hence square wave tuning was most important where as in scenario 2 good tracking response and for example, ramp input tuning, is most important. I was just wondering if that thinking was correct? Should I optimize tuning of the inner loop first according to the task? Just wondering if anyone had any experience or suggestions as to how to tune and optimize performance for each scenario. Thanks
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