Autotune Velocity Settings

Questions about using encoders with the Roboclaw product line
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simons
Posts: 11
Joined: Thu Nov 08, 2018 2:46 am

Autotune Velocity Settings

Post by simons » Thu Feb 07, 2019 7:51 am

Hello,

I am able to set the velocity in IonMotion (PWM Settings) without a problem in both directions. I am also able to read the current (quadrature) encoder value and speed value (around +-840).

I then tried to control my motor with the python library using the "SpeedM1(adress, 200)" function.
The motor turned at full speed, but was able to stop with "SpeedM1(adress, 0)"

I've read in the documentation, that I have to tune the velocity settings first.

While doing it, the first rotations of the motor were smooth, but after a short period (near the end of the autotune) the motor start making "cracky" noises. Like the gear is getting damaged.

The autotune-function tells me I have 734 QPS , 34929,66863 P, 4840,46089 I and 0.000 D.

Turning the motor now with the velocity control in IonMotion also makes the motor generating this noise.

Turning the motor in PWM mode still works fine.

Turning the motor with "SpeedM1(adress, 200)" now makes it turn at 200, but I still get the noises.


Can you help me out? What could be the reason behind these crackling noises?

Thanks in advance
SimonS

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Basicmicro Support
Posts: 1229
Joined: Thu Feb 26, 2015 9:45 pm

Re: Autotune Velocity Settings

Post by Basicmicro Support » Thu Feb 07, 2019 10:19 am

1. Ion Motion is now deprecated. Please download and install Basicmicro Motion Studio.

2. The autotuner for Ion Motion was agressive. Basicmicro Motion Studios has been tuned down so you should get smoother action. However with any autotuner you will almost always need to make minor adjustments afterward. Reducing the P and I values by equal percentages will reduce the aggressiveness of the unte, raising them by equal percentages will increase it.

If you still need help with tuning please call our support line when you can be in front of your system.

simons
Posts: 11
Joined: Thu Nov 08, 2018 2:46 am

Re: Autotune Velocity Settings

Post by simons » Tue Feb 12, 2019 2:53 am

Thank you. Using Basicmicro Motion Studio solved the problem.

One quick question regard the autotune function:
When I velocity autotune, the QPPS vary in numbers between 375 QPPS and 1500 QPPS. I tested the maximum speed in pwm-mode and it was measured to be around 820 QPPS.
The used motor is turning at 4000rpm (datasheet) with this encoder.

What should be my QPPS and why does it not calculate the right QPPS in Basicmicro Motion Studio ?

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Basicmicro Support
Posts: 1229
Joined: Thu Feb 26, 2015 9:45 pm

Re: Autotune Velocity Settings

Post by Basicmicro Support » Tue Feb 12, 2019 10:23 am

The automatic detection of QPPS is not perfect. It only runs the motors a very short time to take a measurement which leads to aliasing errors. Usually this doesnt matter since QPPS is usually quite high. In your case your maximum speed is so low the autodetect routine is much less accurate. I recommend you measure it manually and set the value to your measured value after the autotune is complete.

Note having a too high qpps is better than having a too low one.

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