BLDC motor control for speed track

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BLDC motor control for speed track

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marianoT
Contributor III

Hi, we need to control a BLDC motor (turbine blower system to get air flow and pressure) with hall sensors in order to get fast and accurate speed track, fast acceleration (first quadrant) and fast deceleration (second quadrant); for example from 40000 rpm change to 10000 rpm in 50 ms (step down) or from 5000 rpm to 70000 rpm in 50ms (step up), or change speed up or down following a ramp.

 

some motor data:
Parameter    unit        typ    
Voltage    V        24    
current    A        5    
speed max    rpm        75000    

 

Questions:

 

- Is FRDM-KV31F + FRDM-GD3000EVBFRDM-PWRSTG the best solution for this application?

- can motor suite handle this motor ?

- which control do you recommend?

 

- motor suite can be used with HALL sensors?

 

- motor suite libraries can make brake with torque (2 quadrant)?

 

thanks

Labels (1)
1 Solution
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philip_drake
NXP Employee
NXP Employee

The HVP kit has a brake circuit implemented on the platform board. The TWR-LV3PH also has a brake circuit.  The FRDM-MC-LVPMSM does not. You would place a power resistor connected between the terminals.

There are comparators on the KV part that could be used for this function. If V-BUS is above the set threshold, then the MCU would engage the Brake Gate. If you used the MCUs Comparator output to drive the Brake Gate directly it would work automatically with no MCU firmware involvement.

 HVP Brake Circuit

brake_circuit.png

TOWER Users Guide on Brake

3.12 Brake

An external brake resistor can be connected to dissipate regenerative motor energy during periods of active deceleration or

rapid reversal. Under these conditions, motor back EMF adds to the DC bus voltage. Without a means to dissipate excess

energy, an overvoltage condition could easily occur. An external dissipative resistor connected to J4 can serve to dissipate

energy across the DC bus. MOSEFET Q8 is turned on by software when the bus voltage sensing circuit exceeds the level set

in that software. Power dissipation capability depends on the capability of the externally connected dissipative resistor.

The MIC4127YME is a 5.0 V-tolerant, dual MOSFET pre-driver. This board uses its A channel to drive the brakingresistance

MOSFET.

twr_brake_circuit.png

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17 Replies
5,763 Views
marianoT
Contributor III

hi Eduardo and Philip,

we have a very good experience with the development kit ( hardware and software) ;

we have a question related with certifications (FDA and other), our development is in medical field and FDA certification is a must. We need to know what kind of documentation, about kinetic motor suite API,  can NXP provide us to certified FDA.

do you known any case of succeed in FDA certification with kinetic motor suite API?

thanks

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philip_drake
NXP Employee
NXP Employee

Mariano,

I'm glad you have had a good experience with the tools. 

NXP does not have any documentation on the MCU to support certified FDA.  The development kit is not an end-product and should not be used in the production of an end product.  The development kit is sold as a was to develop the firmware that would be programmed into the MCU in your custom designed product. 

Regards,

Philip

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marianoT
Contributor III

hi Philip,

We need software library (NOT Hardware) design documentation and unit test evidence for FDA certification; the hardware will be custom, but for motor control we will use software library that nxp provide, that is the reason why we need documentation and unit test evidence .

thanks

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philip_drake
NXP Employee
NXP Employee

Designed into the MCU are the hardware modules, like watchdog, CRC check, COP, Clock Monitor, etc that allow the developer to create software to meet the various IEC certifications.  The KMS reference project is provided as a base platform to run a motor.  Protections built into the reference project are show in the Protection & Harware section of the KMS documentation. 

The Kinetis MCUs including the Kinetis has documentation for IEC 60730 here.

Include the other documentation provided with KMS including the following. That is all we have to provide.

1) The MCU reference manuals

2) The MCU data sheets

3) the KMS API Reference Manual

4) The KMS User's Guide

5) The KMS Lab Guide

6) The App note Adapting KMS for Custom Hardware

7) The KMS release notes,

This Beyond Bits publications speaks to your needs. 

This FTF presentation also has relevant information.

The Qualification and reliablity data, which speaks to the MCUs ability to perform over voltage, temperature and time are also available on the nxp.com web site.Here is a link to the package and Quality page

We have no unit test evidence for you to use other than this.

Best Regards,

Philip

5,763 Views
marianoT
Contributor III

Hi Eduardo, finally i get the development kit, we started testing with kinetics motor suite software, and it´s works great, but we need fast speed change from high  to a lower one and we found that this returns high voltage to the source, how this can be solve? any ideas? is any way to add a brake resistance?

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5,764 Views
philip_drake
NXP Employee
NXP Employee

The HVP kit has a brake circuit implemented on the platform board. The TWR-LV3PH also has a brake circuit.  The FRDM-MC-LVPMSM does not. You would place a power resistor connected between the terminals.

There are comparators on the KV part that could be used for this function. If V-BUS is above the set threshold, then the MCU would engage the Brake Gate. If you used the MCUs Comparator output to drive the Brake Gate directly it would work automatically with no MCU firmware involvement.

 HVP Brake Circuit

brake_circuit.png

TOWER Users Guide on Brake

3.12 Brake

An external brake resistor can be connected to dissipate regenerative motor energy during periods of active deceleration or

rapid reversal. Under these conditions, motor back EMF adds to the DC bus voltage. Without a means to dissipate excess

energy, an overvoltage condition could easily occur. An external dissipative resistor connected to J4 can serve to dissipate

energy across the DC bus. MOSEFET Q8 is turned on by software when the bus voltage sensing circuit exceeds the level set

in that software. Power dissipation capability depends on the capability of the externally connected dissipative resistor.

The MIC4127YME is a 5.0 V-tolerant, dual MOSFET pre-driver. This board uses its A channel to drive the brakingresistance

MOSFET.

twr_brake_circuit.png

5,763 Views
eduardo_viramon
NXP Employee
NXP Employee

I've attached the trapezoidal BLDC for KV31 FRDM + FRDM-LVBLDC board.

Please download and let me know how it goes.

5,763 Views
Ben
Senior Contributor I

Eduardo,

If you have already a demo project for FRDM-KV31F+FRDM-MC-LVBVDC, but to control motor with the hall sensors (feedback via the additional connector), I will be happy to get it.

I have a project which can't work without sensors feedback, as I need an accurate control through all speeds and with variable load.

TIA

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marianoT
Contributor III

thanks Eduardo, i will get the development boards in three week,

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eduardo_viramon
NXP Employee
NXP Employee

Hi Mariano,

Kinetis Motor Suite is not designed for hall effect sensor applications, it is designed to do Field-Oriented Control (FOC) in either sensorless mode (speed and position estimation through current measurement) or through a high resolution sensor like a quadrature encoder (hall effect sensors do not have enough resolution for FOC).

For hall-effect sensor BLDC control the hardware you mentioned is ok.

I can point you to some hall effect sensor software that would work better but first I would like to know if you have any questions about the above or if you would like more information about KMS even if it's not based on hall effect sensors.

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valiant
Contributor I

Hi Eduardo and Mariano,

I would like to roll back to the original question, can I use FRDM-KV31F + FRDM-GD3000EVBFRDM-PWRSTG for sensorless PMSM?

We actually prefer this setup as we prefer to keep the pre-driver but work with our own design for the power stage board.

I am having trouble to find documentation and/or sample code for this setup. GD3000EVB documentation seems to be oriented towards KL25Z, which is hard to come by (and requires soldering on the sample board) although the GD3000EVB documentation clearly mentions that KV31F has "full" interface support while KL25Z is only partially supported.

Anyway, is there an easy way to interface between KV31F and GD3000, or is there a need to write a library and/or driver from scratch?

Is there a sample evaluation software similar to the software provided for kv31f together with MC-LVPMSM?

Thank you!

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eduardo_viramon
NXP Employee
NXP Employee

Hi Eyal,

To your original question. The GD3000EVB + PWRSTG boards will not work for sensorless PMSM because they do not have the required current sensing hardware.

Luckily the LVPMSM board will and we have great software for it called the Kinetis Motor Suite (KMS). It will allow you to get your motor spinning with sensorless PMSM in a few minutes.

For additional information (including tutorial) and download, go to:

www.nxp.com/kms 

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valiant
Contributor I

Hi Eduardo,

Thank you for the swift reply. I need to ask two question:

1. Is it still possible to use the setup in the original question (FRDM-KV31F + FRDM-GD3000EVBFRDM-PWRSTG) for sensorless BLDC (that is Trapezoidal control)?

2. As I said earlier I want to replace the power stage board with our custom power stage board. Our custom board will include current sensing for all phases.

I like the modularity where gd3000evb offers a pre-driver which is seperated from the MCU and from the power stage board.

In addition I prefer the gd3000evb as it can handle our voltage range which is 50V-60V, while the MC-LVPMSM is rated up to 48V.

Maybe NXP has to offer yet another solution? As far as I know the this range is too low for the high voltage solutions.

Thank you very much!

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philip_drake
NXP Employee
NXP Employee

Hi Eyal,

You can use the (FRDM-KV31F + FRDM-GD3000EVBFRDM-PWRSTG) for sensorless BLDC (that is Trapezoidal control), YES.

If you replace the PWR stage with your customer power stage with current sensing you should be able to do PMSM, FOC control of the motor.

Regards,

Philip Drake

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valiant
Contributor I

Yes, my query was about documentation and/or source code for doing that.

I simply would like to avoid starting from scratch.

Thanks,

Eyal

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marianoT
Contributor III

thanks Eduardo,

I was updated that the motor is PMSM, so i will choose FRDM-KV31F + FRDM-MC-LVPMSM; i need accurate and fast speed control (not position).

"I can point you to some hall effect sensor software that would work better"; yes please, can you point some software?.

" if you would like more information about KMS even if it's not based on hall effect sensors."; yes

thanks.

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eduardo_viramon
NXP Employee
NXP Employee

Hi Mariano,

I am asking for permission from the development team to provide the hall sensor code because it has not been released to the general public yet, but I will get you a beta version.

I also want to clarify something for you:

PMSM and BLDC are types of motors not control algorithms. Typically it is understood that PMSM motors have a little bit more complex construction and their BEMF (back electromagnetic force) is sinusoidal, meaning that the torque characteristic is sinusoidal and meaning that a sinusoidal control method will make them more efficient. On the other hand BLDC motors will typically have a trapezoidal BEMF, meaning that their torque will be trapezoidal, so less smooth, but they are lower cost. Additionally, it means that you can control them with trapezoidal or on/off control instead of the sinusoidal control, which is more complex, to make get the most efficient torque characteristic out of them.

Now the important part: both types of motors can be controlled by both types of control algorithms. Electrically, BLDC and PMSM motors are very similar. The difference is in the internal construction and how the magnetic fields are distributed inside, but from an electrical control perspective they are the same. As stated above, you will get better performance by controlling a PMSM motor with a sinusoidal control method, which is typically Field-Oriented control (FOC) which is what the KMS solution provides. FOC is quite complicated if you are not an expert in motor control, which is why we created the KMS. On the other hand, trapezoidal control is much simpler, simply turn the phases on and off in a specific pattern with PWM modulation.

There are sensored and sensorless solutions for both of these control algorithms. The sensorless options use the BEMF characteristics of the motor to estimate the position. Please note that even though it's an estimate, it is still highly accurate and many applications use it commercially including high speed up and down ramps. The only issue with sensorless algorithms is that the startup is not perfect because the motor needs to spin at a minimum speed (typically around 10% of nominal speed) for the sensorless estimation to be accurate. This means that motor is spun open loop for the initial start-up and then the estimator can take over. If your application does not need lower speeds, sensorless is usually fine and you save cost in sensors and the mechanical complications.

On the other hand, if you do need the sensors, there are 2 possibilities. For FOC, you need a high resolution sensor, typically a quadrature encoder with around >1000 lines per revolution. For trapezoidal control, the hall effect sensors are good enough.

I hope this helps. Let me know if you have further questions. 

For more information about KMS visit: www.nxp.com/kms 

I will send that hall sensor code when I have it.