Treading Water

FOC Motor Not Spinning Debug

Symptom

Set to 4000 RPM, the drive draws current but the shaft rocks in place, whatever the start angle. The figure lists plant registers.

Measured starter trace over the 500 ms run: SPEED rocks around zero, 1250 RPM either way at first and about 200 RPM by the end, and never approaches the 4000 RPM setpoint, whose pass band is 20 RPM either side from 250 ms; the largest phase current sits near 20 A the whole run, far over the 6 A ceiling

Circuit

Bench wiring: U1, an STM32F4, reaches the FOC plant over the bus at 0x50062000 and prints to a serial console on USART1; below it, the plant's registers with offset, access and units, including the order SECTOR counts the phases in, and the SRAM setpoint mailbox

Pass condition

By 250 ms SPEED is within 20 RPM of 4000 RPM and stays there. From 250 ms to 480 ms no phase carries more than 6 A, and no FAULT bit latches.

Notes

The test rig posts the setpoint at start-up and the drive runs 500 ms. A hidden case moves the rotor's start angle on every submission. USART1 runs at 9600 baud: BRR = 0x683.

Related challenges

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