STM8S BLDC Speed Closed Loop runaway issue

[samsangani]

Posted on August 19, 2013 at 05:13

Hi,

I am using STM8S three-phase BLDC motor control software library V1.0 to drive BLDC. Everything works great except PI regulator for speed closed loop runways after speed 13000rpm. My settings are: &sharpdefine PWM_FREQUENCY 14400 &sharpdefine SPEED_KP 40  &sharpdefine SPEED_KI 0.01 &sharpdefine SPEED_OUT_MAX 666 &sharpdefine SPEED_KP_DIVISOR 128 &sharpdefine SPEED_KI_DIVISOR 512 &sharpdefine SPEED_PID_SAMPLING_TIME 4 &sharpdefine HALL_MAX_SPEED_01HZ          ((u16)4333) &sharpdefine MOTOR_POLE_PAIRS 2 &sharpdefine MAX_SPEED_RPM 16000 I have checked there is no overflow of PI regulator registers. After 13000rpm, motor speed ramps up rapidly and keeps going on until is stopped. To be safe I stopped motor at 20000rpm. It will be highly appreciated if some one aware of this issue or can think of potential root cause and guide me to solution. #pi-regulator #3phase-motor

[Gigi]

Posted on August 26, 2013 at 17:01

Hello

It is possible that starting from 13000rpm the measured speed is not more measured with good acuracy? When you write that the motor is running at 20000rpm you mean the speed measured by the FW or with another device (such as a Dynamometer)? At high speed the acuracy of the speed measurement become less and less because the FW is counting the number of PWM period between zero crossings. This lose of acuracy can generate the behaviour you mention (but I never see this before). Please take a look at the measured speed and compare it with the real speed measured using another device. Ciao Gigi