BLDC motor with hall sensors control

[moranEng]

Hello, 

I am interested using brushless motor hall sensors as my feedback without using encoder additionaly.

My hardware: cRIO, NI-9516 drive interface and an AKD drive to connect the motor.

I was hoping to use SoftMotion high level API in order to build a sequence algorithem,

but I didn't find any guidance or VI example to do so.

Is it possible to use high level API, or some off-the-shelf VI example which implements only hall sensor feedback?

Thank you,

[TimothyDug]

Hi moranEng,

Thanks for your post. I wanted to know why you wanted to avoid using an encoder. Is that just simpler for your implementation?

Essentially, you could use hall sensors, but there is not SoftMotion code setup for doing that with the NI 9516. There is an example for doing this with an NI 9502 module.

If you were able to set it up, as I'm sure you're aware, the Hall sensors would provide a 3-bit signal, and thus would provide poor position accuracy within 120 degrees. However, it should be okay for velocity. 

If you want information on getting an NI 9502, or if you have related followup questions, let me know!

Thanks,

[moranEng]

Hi,

Thank for your answer.

I am aware of the poor resulotion and yet, it fits me well.

I have seen that softmotion has Angle-from-hall VI .

Is it possible to use the full softmotion api and gui, and just change the feedback to that angle-from-hall vi? 

The softmotion gui allows analog feedback.. 

Btw- which control type does the softmotion use for bdlc motors? 

[Karl-G]

I want to add some detail here to help explain why this isn't possible out-of-the-box with any of our toolsets. I'll focus on both setups (cRIO+9516+AKD and cRIO+9502).

cRIO + 9516 Servo Drive Interface Module + Kollmorgen AKD Servo Drive

In this setup, the 9516 module sends an analog voltage to the AKD drive as a torque command, and the AKD drive acts as an amplifier to provide current to the motor. As the motor turns, the 9516 is intended to close the position loop by receiving quadrature encoder feedback from the motor (or drive if using the emulated encoder function).

Unless the AKD can utilize only hall sensors for commutation and feedback to generate a very low resolution encoder output, there is no possibility of using the 9516 with only hall sensors.

cRIO + 9502 Brushless Servo Drive Module

In this setup, the 9502 acts as the drive with the drive 'firmware' created with an FPGA VI. This is a low-power solution focused on hardware density and low-level FPGA customization. SoftMotion includes several examples of how to use the module for both trapezoidal and FOC commutation of motors. With only hall sensors, by default the examples only allow velocity setpoints in trapezoidal mode. For FOC commutation, high resolution encoder feedback is required to know the precise shaft angle. Because of this, the 9502 is primarily intended to be used with a 9411 module to accept quadrature encoder feedback.

Unless you create custom FPGA code using the 9502, there is no out-of-the-box example for doing approximate position moves using only hall feedback. The FPGA VI you mentioned in your post is part of the 9502's shipping examples if you want to see it in context.

[moranEng]

Thank you for your answer.

You said "Unless AKD drive can use hall sensors..."

As far as i know, akd CAN operate on hall sensors alone. 

But the question is how do i use labview to operate it. 

[moranEng]

I was looking at the AKD datasheet again.

It can make speed/torque control as you said, but not position control.

I would like to try using NI 9615+crio+akd to do speed/torque control.

how is that possible?

[Sambad]

Hey,

I am searching for examples to get started with NI9502 module. I have a cRIO 9045 chassis and NI9502 module. I did install Labview 2019, labview FPGA module and Labview Real time module. However, I am not able to find 9502 Trapezoidal Commutation example  in the labview\examples\CompactRIO\
Module Specific\NI 9502\Trapezoidal Commutation directory as mentioned in the mannual. 

Could you please help me out with it? 

Thank you

Sambad