What to change in FOC code for lower inertia?

[BTrem.1]

I have a BLDC motor running reliably with FOC code on a STM32G431 MCU. For unrelated mechanical reasons we need to drop our inertia by about 4x from where it is running today. For the speed loop I fully understand lowering inertia raises the loop gain and I'll need to lower the gain in the speed loop.

What I need some guidance on is how to adjust the spin up ramp and whether I need to change the observer gains. Without any changes to the code I am now getting a MC_SPEED_FDBK error.

I cannot run this motor on the profiler because it is using a custom MCU board and driver not supported by the profiler. The motor Rm, Kt, Lm and Kb are exactly the same; we are just removing mechanical inertia.

Any guidance is appreciated.

[Laurent Ca...]

Dear @BTrem.1​ 

Welcome to the STM32 Community

Sorry for late answer.

Could you give more details to the STM32 Community about your setup -the material you use- ?

(HW and also SW: CPU(s), tools and versions, board(s), motor(s) and so on)

And more especially did you use STM32 MC tools (such as MC_suite, STM32 MC Motor Profile, STM32 MC SDK, STM32 MC Workbench, the used example, the origin of the base of your application source code, and so on)?

Best regards

[BTrem.1]

For tools I use the STM32CubeIDE v1.5.0 and the Segger J-Link debugger. The MCU is a STM32G431 64kRAM 48-pin device. The board is a custom board with a STSPIN233 5V driver. The start current I use is about 500mA and the run current is about 40mA. The motor control software is MCSDK_v5.4.4. I'm using the FOC sensorless control with 3-shunt current feedback. The original code was profiled on a Nucleo board (64-pin STM32G431) with a IHM17M1 adapter with the STSPIN233 driver.

I don't use the profiler now because it is not compatible with my custom board. I do use the MCSDK software (WorkBench) to manually adjust registers for tuning the software. I had everything working fine with the larger inertia but now the very low inertia load is very unstable and I can't seem to stabilize it by changing just the velocity loop PI controller.