Kinetis KV31x Motor Control with HALL Sensors (speed control and Torque control)

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Kinetis KV31x Motor Control with HALL Sensors (speed control and Torque control)

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Contributor I

Hello,

My application needs a Hall sensor based BLDC motor control because of high startup torques and motor starting at Full loads conditions. I want to evaluate  Hall sensor based control using KV31x parts. I looked at NXP website and not able to find any Hall sensor based examples with KV series. I am very surprised that i couldn't find any examples of Hall effect based on KV series parts. All I found was sensorless FOC control.

Some of our product required to run at constant RPM and some require Constant Torque, but these motors may have a very high startup torque, load and may hit stall conditions many times in its life time. I would like to evaluate both sensorless and Hall sensor control. I will use KMS for sensoless control, and i am currently need help with Hall sensor based control on KV series and i cannot find any reference examples on any KV  tower boards. 

Thanks,
Naga Penmetsa

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Senior Contributor I

Naga,

Have you tried to use the Sensorless Velocity - Hall Start that was added in KMS v1.2? This uses the Hall Effect sensors in order to begin the rotation of the motor. In our laboratory testing we can start the motor with over 200% rated load. Once the motor is sufficiently spinning, it will transition over to Sensorless Velocity control. I think this would be worth exploring to see if it will meet your application's startup torque requirements.

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Senior Contributor I

Naga,

Have you tried to use the Sensorless Velocity - Hall Start that was added in KMS v1.2? This uses the Hall Effect sensors in order to begin the rotation of the motor. In our laboratory testing we can start the motor with over 200% rated load. Once the motor is sufficiently spinning, it will transition over to Sensorless Velocity control. I think this would be worth exploring to see if it will meet your application's startup torque requirements.

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Contributor I

Thanks for the Suggestion Adam. I will investigate the Hall sensor'd startup in KMS. Is there a way we can modify how long (Target time) or how fast (target speed) the motor need to run before transitioning in to Sensorless FOC ? 

Thanks,

Naga Penmetsa

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Senior Contributor I

Naga,

You can modify the speed at which it transitions between FOC and Hall Start. The only way to modify the time of transition is by changing the acceleration of the motion profile. 

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NXP TechSupport
NXP TechSupport

Hi, Naga,

I have searched on the website, it seems that we do not have the BLDC control solution based on Hall sensor, anyway, I attach the BLDC motor control based on Hall sensor for MC56F84789, the tools for the project of MC56F84789 is CodeWarrior for CU ver10.x or ver11, you can refer to the reference code.

For the KV31, it has three FTM modules, FTM0/FTM1/FTM2, the FTM0 has 8 channels, it can be used to control BLDC 3 Phase. The FTM1/FTM2 have 2 channels each, in other words, you can connect the 3 hall signals to FTM1_CH0, FTM1_CH1 and FTM2_CH0 pins, if hall sensor is 5V logic, I think the voltage level conversion chip may be required, because KV31 requires 3.3V logic. You can configure the FTM1 and FTM2 in capture mode for rising/falling edge, in the capture ISR, you can  read the three hall pins logic via GPIO input register, then you can switch the stator by masking PWM pair or inverting the PWM pair for FTM0 module based on a table, generally, the BLDC manufaturer can provide the table which represents the relationship between the Hall logic and branch turning on/off. For the speed computation, you can count the ticks between the consecutive capture events, figure out the speed.

Hope it can help you

BR

Xiangjun Rong

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