The Background:
I have a 48V power supply that can push a current of 32A. I’m trying to drive a large BLDC motor rated at 48V 61A (FL80BLS120), I am using the DRV8301 driver to drive the motor and am controlling the driver with the Adafruit Metro M4 Express Dev board (SAMD51J19A). There are hall sensor encoders attached to the motor so I can determine the velocity and angle of the motor shaft.
Previously I was using an Arduino Uno to move the motor and was using software interrupts to read the 3 hall sensor values. Everything was working fine on the Arduino (no noise from the motor and relatively smooth movement), I was doing this just for ease and sanity but I’m at the point where I need to switch to a SAMD processor and use hardware interrupts to read the hall sensors which is why I’m switching to the Adafruit Metro M4 Express (along with other reasons I wont get into).
The Problem:
The Adafruit Metro M4 Express runs at 120Mhz while the Arduino Uno runs at 16Mhz. Since the clock frequency is much higher, its telling the motor to move at a higher clock speed causing the high pitched sound coming from the motor.
Things I troubleshooted:
- Power supply: I receive the same issue even if I used a 12v or 24v power supply
- MCU: I don’t receive this issue on an Arduino Uno regardless of the power supply used
- Driver: I receive this issue on both the DRV8302 and DRV8301 (though the sound when using the DRV8301 with SPI communication is a bit better)
- Motion Control Types: This sound occurs in both open and closed loop and am using velocity closed loop mode to do my tests at the moment (since I’m working on also tuning PID values)
Research i’ve done:
I scoured the forums to see if I could find any solutions and found that there should be support for the Adafruit Metro M4 express. I found in “drivers/hardware_specific/samd” code to possibly help me configure the pins and timers properly so that they are outputting at a correct pwm clock cycle (like 20khz).
When I print “printAllPinInfos()” from the samd_mcu.cpp file I get:
Pin 00 PA23 E= None F=TCC1-3[7] G=TCC 0-3[3]
Pin 01 PA22 E= None F=TCC1-2[6] G=TCC 0-2[2]
Pin 02 PB17 E= None F= None G=TCC 0-5[5]
Pin 03 PB16 E= None F= None G=TCC 0-4[4]
Pin 04 PB13 E= None F= None G=TCC 0-1[1]
Pin 05 PB14 E= None F= None G=TCC 0-2[2]
Pin 06 PB15 E= None F= None G=TCC 0-3[3]
Pin 07 PB12 E= None F= None G=TCC 0-0[0]
Pin 08 PA21 E= None F=TCC1-1[5] G=TCC 0-1[1]
Pin 09 PA20 E= None F=TCC1-0[4] G=TCC 0-0[0]
Pin 10 PA18 E= TC3-0[0] F=TCC1-2[2] G=TCC 0-0[6]
Pin 11 PA19 E= TC3-1[1] F=TCC1-3[3] G=TCC 0-1[7]
Pin 12 PA17 E= TC2-1[1] F=TCC1-1[1] G=TCC 0-5[5]
Pin 13 PA16 E= TC2-0[0] F=TCC1-0[0] G=TCC 0-4[4]
Pin 14 PA02 E= None F= None G= None
Pin 15 PA05 E= TC0-1[1] F= None G= None
Pin 16 PA06 E= TC1-0[0] F= None G= None
Pin 17 PA04 E= TC0-0[0] F= None G= None
Pin 18 PB08 E= None F= None G= None
Pin 19 PB09 E= None F= None G= None
Pin 20 PB02 E= None F=TCC2-2[2] G= None
Pin 21 PB03 E= None F= None G= None
Pin 22 PB02 E= None F=TCC2-2[2] G= None
Pin 23 PB03 E= None F= None G= None
Pin 24 PA14 E= TC3-0[0] F=TCC2-0[0] G=TCC 1-2[2]
Pin 25 PA13 E= TC2-1[1] F=TCC0-1[7] G=TCC 1-3[3]
When I try to configure the PWM frequency of my pins using “_configure3PWM(24000, 11, 12, 13);” I get an error “SAMD: Bad pin combination!”. I read that we want all the pins to be on the same clock (clock 4 if I’m not mistaken) so I tried “_configure3PWM(24000, 4, 12, 13);” since each of those pins can be used with clock 4 but it didn’t help.
My Code:
#include <Arduino.h>
#define _SAMD51_
#define SIMPLEFOC_SAMD_DEBUG
#include <SimpleFOC.h>
#include <DRV8301.h>
#define INH_A 11
#define INH_B 12
#define INH_C 13
#define EN_GATE 8
#define nFAULT A2
#define nOCTW A3
#define MOTOR1_CS_PIN 7
float target = 0.0; // [rad/s]
HallSensor sensor = HallSensor(2, 3, 4, 8); //Hall sensor instance (hallA, hallB, hallC, pole pairs)
BLDCMotor motor = BLDCMotor(8); // Motor instance (pole pairs)
BLDCDriver3PWM driver = BLDCDriver3PWM(INH_A, INH_B, INH_C);
DRV8301 gate_driver = DRV8301(26, 24, 25, MOTOR1_CS_PIN, EN_GATE, A2); //SPI COMMUNICATION DRV8301 gate_driver = DRV8301(MOSI, MISO, SCLK, CS, EN_GATE, FAULT);
// Interrupt routine intialization for hall sensors
void doA(){sensor.handleA();}
void doB(){sensor.handleB();}
void doC(){sensor.handleC();}
void setupHallSensor(){
sensor.init(); // initialize encoder hardware
sensor.enableInterrupts(doA, doB, doC); // hardware interrupt enable
motor.linkSensor(&sensor); // link the motor to the sensor
}
void serialReceiveUserCommand()
{
// a string to hold incoming data
static String received_chars;
while (Serial.available())
{
char inChar = (char)Serial.read(); // get the new byte:
received_chars += inChar; // add it to the string buffer:
if (inChar == '\n') // end of user input
{
target = received_chars.toFloat(); // change the motor target
Serial.print("Target = ");
Serial.println(target);
received_chars = ""; // reset the command buffer
}
}
}
void setup()
{
Serial.begin(115200);
setupHallSensor();
// driver config
driver.voltage_power_supply = 48; // power supply voltage [V]
driver.voltage_limit = 48;
driver.pwm_frequency = 120000000; // default 20kHz
driver.init();
gate_driver.begin(PWM_INPUT_MODE_3PWM);
motor.linkDriver(&driver); // link the motor and the driver
//Limiting motor movements
motor.voltage_limit = 48; // [V]
motor.velocity_limit = 15; // [rad/s]
motor.current_limit = 30; // [A]
motor.phase_resistance = 0.156; // [Ohm]
motor.voltage_sensor_align = 5; // [V]
//Closed loop velocity properties
motor.PID_velocity.P = 0.6;
motor.PID_velocity.I = 6.0;
motor.PID_velocity.D = 0.04;
motor.LPF_velocity.Tf = 0.15; //Low pass filter [seconds] (0.01 = 10 milliseconds)
motor.motion_downsample = 50; // divider for the motion control loop, used to reduce the load on the mcu
motor.controller = MotionControlType::velocity; // closed loop velocity
motor.useMonitoring(Serial);
SimpleFOCDebug::enable();
motor.init(); // init motor hardware
motor.initFOC(3.14, Direction::CW); // init foc algorithm (foc_angle, direction)
printAllPinInfos();
_configure3PWM(20000, INH_A, INH_B, INH_C); // configure 3PWM outputs
_delay(1000);
}
void loop()
{
serialReceiveUserCommand(); // receive the used commands from serial
motor.loopFOC();
if(nFAULT == 1 || nOCTW == 1){
motor.disable(); // disable motor if driver reports faults
Serial.println("DRV8301 error");
}
else motor.move(target); // set the motor movement to the target velocity
motor.monitor();
}
Would someone be able to help me understand how to properly configure the pins on the Adafruit Metro M4 Express so that I can run the motor without this high pitched noise/while from the motor.
) . Something like 32kHz should be outside of the audible range: