DRV8711: Resonance using specific motor

Oleg,

Is your high pressure HPLC pump principle similar as this link http://www.lcresources.com/resources/getstart/2b01.htm : Most commercial HPLC pumps are based on a reciprocating piston design, as shown here. A motor-driven cam pulls the piston back and forth in the pump head. A flexible seal around the periphery of the piston prevents leakage of mobile phase out the back of the pump. Check valves mounted in the head open and close in response to small changes in pressure to maintain a one-way flow of solvent.

https://phidgets.wordpress.com/2014/07/28/how-to-avoid-resonance-issues-in-stepper-motors/ gives a clear explanation about the stepper motor resonance at certain speed.

When a stepper takes a single step, it will overshoot its target destination slightly and will oscillate a bit before settling down on target. This is due mostly to the inertia of the rotating mass briefly overpowering the magnetic field of the motor. This isn’t a big deal by itself but when you start chaining multiple steps together to get a larger movement this oscillation occurs at each step taken on the way. If the frequency that the controller is outputting new step commands to the motor matches the natural frequency of the motor then the oscillations will tend to become more severe as they propagate through the motor. Eventually they are so large that they will overpower the magnetic field for long enough on a given step to miss the subsequent step command, and you begin missing steps. Since steppers are typically run in open loop, the controller has no knowledge of these missed steps; The result is the motor will not get to its destination successfully. The effect can become so pronounced that the motor loses torque completely and stops rotating. Depending on the synchronization of the steps, it can even reverse the direction of rotation.

According to above analysis: one option is changing the natural frequency of the motor, such as: adding load(motor mechanical resistance) or "Overall, provided you know about the problem it is fairly easy to avoid. The best thing to do when you get a new stepper is to quickly run it through the available velocity range and find where the motor has trouble keeping torque. That is the region you should avoid in your application."

Another option is reducing each micro-step overshoot, would you try different output current setting or micro-step setting for the 1ml/min speed?

Thank you for your answer!

In fact, things are not so dramatic, as I do not miss steps, but I have less torque (which is not critical), and very loud noise. 

The problem is I cannot change design of whole mechanic assembly, including motor, as it is OEM part I should drive with my electronics. And thus, there is no way avoiding this particular frequency, as HPLC method directs the flow rate.

Now I just decreased the noise by decreasing the driving current of motor to value little less than motor's rating, and torque is still enough to drive pump whith required pressure.

Also I noticed that increasing TOFF parameter will decrease low-frequency resonanse noise, but increase high-frequency noise.