Hello,
I am hoping to use one of the Jrk G2 with PID to control the speed a of a motor, the feedback will be coming from a different rotation that is being affected by the rotation of the motor I am controlling. due to gear ratios, the PID must revers the motors direction to achieve the desired rpm on the feedback location. is this possible? theoretically it should not be a problem but I am not sure if this card will do it.
your answer is much appreciated,
The Jrk has options for inverting the feedback direction or the motor direction, so you can configure the Jrk G2 to work with the setup you described.
Brandon
HI Brandon and thank you for the quick reply. I know that I can invert the motor direction manually. I guess my question is, can the PID control reverse the motor’s direction if calculations deems it necessary; in order to achieve the feedback value.
thanks again,
As I mentioned in my previous post, you should be able to configure the Jrk G2 to work in the setup you described. Aside from manually inverting the motor direction, the Jrk also has a software option for inverting the motor outputs.
Brandon
After thinking about this some more and discussing it with another support tech here, I’m less confident that the Jrk can do what you’re describing, but it ultimately depends on your system, which is not very clear to me and might be more complicated than I was originally thinking.
What are all of the components between the DC motor that’s being driven by the Jrk and the rotation that you are measuring for feedback? What kind of sensor are you using to measure the feedback, and what kind of signal will it provide to the Jrk? If the Jrk stops applying power to your motor, will your system slow down and eventually stop?
Brandon
Brandon,
This is a variable gear drive:
There is an input rpm which can vary based on the engine rpm. 700 to 2200 rpm. We do not monitor or control this.
There is an output rpm which we monitor and send back as feedback. This rpm can be between 0 and 3000 in one direction only.
There is a control rpm with we are trying to control with PID. This control rpm affects the output rpm independently from input rpm. It an be between -3000 and 3000 rpm.
Example:
Engine is at 1000 rpm. We want the output RPM to be 2000. We need to spin the control to around 2600 rpm. Now engine is still at 1000 but we want output RPM to come down to zero. The control RPM now must drop all the way to 0 then keep going into negative rpm until the feedback reaches the target with will be around -2600 RPM on the control.
There is no special PID calculation. The error value will force the output into negative. The question remains if the negative PID output will result into switching the output motor rotation; automatically in the software.
By the way, this is not for a toy. If it works out, we will include it into the production of this new stepless gear drive with potential sale of Thousands per year. We will also need to discuss possibilities for packaging and customization.
Regards,
Thank you for the additional information. Can you clarify what kind of feedback signal are you providing to the Jrk?
Brandon
It is a hall effect sensor used with a magnet to produce pulses. Keep in mind that where we are reading the rpm is a single direction rotation.
When the Jrk G2 is in frequency feedback mode, when the target is greater than or equal to 2048, the Jrk never lets the duty cycle go below 0, so it never drives the motor in reverse. (similarly, when the target is less than 2048, it never drives the motor forward). So, if possible, you might consider getting the feedback from the motor that the Jrk is directly controlling.
Brandon
Unfortunately no, we must monitor the output rpm as it is the final product.
Is there a way to change that setting in software? You mentioned frequency feedback, does it behave differently with other types of feedback?
There is no way to adjust that behavior in the software when using frequency feedback. However, when the Jrk G2 is using analog feedback, the motor output is allowed to reverse to achieve the target.
Brandon
Ok, thank you. Can you by any chance recommend an rpm sensor with analog output?
Regards,
Unfortunately, we do not have any encoders or tachometers with an analog voltage output, and I do not have any specific recommendations for one like that.
Brandon
