2023-06-04 08:15 PM
PMSM / ACIM emulators have been developed for the automotive industry; they emulate a motor's characteristics for inverter testing and are very accurate and high-powered (50kW+). They have electrical model cycle times of <1us and PWM frequencies of typically hundreds of kHz.
Here is an example of a high-end model: Google search "E-Motor Emulator – Testing Power Electronics without Motor" (first PDF result), because I'm not allowed to add a link :)
I am developing a version of this that is stripped down both in terms of power and accuracy. It is for our internal company use and needs to 'pass off' as the intended motor but not emulate the characteristics exactly. I'd be happy with a 20% deviation in most motor characteristics. I have guesstimated I need an electrical model cycle time of 2-5us; I *think* I can use one of the processors that run on the Nucleo-144.
The high speed task is basically:
-read 6x analogue inputs (3 voltage & 3 current), or at a push only 3 voltage.
-calculate the electrical model of the motor (e.g. induction motor T model). I can't see this being more than 100 lines of C code.
-update the PWM.
There is of course the mechanical model, which interacts with the electrical model, but I didn't mention that above because it can run 3 orders of magnitude slower.
My question is, can one of the processors of the Nucleo-144 dev board achieve this task (with appropriate HSE)? And if yes, which is the ideal? I was thinking the
STM32H743 / NUCLEO-H743ZI2, but was also wondering whether other MCUs have a better combination of ADC speed, clock, etc.
Thanks in advance.
Solved! Go to Solution.
2023-06-06 07:01 PM
Motor focused stm32 family were historically STM32F3 and now STM32G4 which you definitely need to consider.
There are various MC shields using ST Morpho pin expansion headers (check compatibility and solder bridge) for the driver/power stage, with various topologies.
2023-06-06 07:01 PM
Motor focused stm32 family were historically STM32F3 and now STM32G4 which you definitely need to consider.
There are various MC shields using ST Morpho pin expansion headers (check compatibility and solder bridge) for the driver/power stage, with various topologies.
2023-06-06 09:06 PM
Hello S.Ma. Thankyou for the advice.
I need a custom power stage, but will have a look at driver shields.
Are there any advantages of using the STM32F3 / STM32G4 over the STM32H7, other than price & availability?
Basically I need to read 7x analogue signals, calculate the motor model, and update PWM every 100us (100kHz). But I guess that's what all motor applications are doing...
2023-06-06 10:45 PM
G4 is more analog rich, has HW accelerators (CORDIC for fixed point trigo for rotating motors, FMAC....)
It is tailored for motor control. Check the high resolution timer spec in the reference manual. These IP may not be present in the H7 and SW + MHz could be needed for a similar end result.