Motors callibration

Navio / Edge Flight stack
1

Hi, I built a small api using your servo example. Trying to create my own flightcontroller.

import time
import math
import sys

sys.path.append("libs")
from Adafruit_PWM_Servo_Driver import PWM
sys.path.append("../Navio/Python")
from Navio import GPIO

class Motor:
  FRONT_LEFT = 3
  FRONT_RIGHT = 4
  BACK_LEFT = 5
  BACK_RIGHT = 6

  def __init__(self, pin_n):
    #drive Output Enable in PCA low
    pin = GPIO.Pin(27)
    pin.write(0)

    PCA9685_DEFAULT_ADDRESS = 0x40
    frequency = 50

    self.NAVIO_RCOUTPUT = pin_n
    SERVO_MIN_ms = 1.250 # mS
    SERVO_MAX_ms = 1.750 # mS

    #convert mS to 0-4096 scale:
    self.SERVO_MIN = math.trunc((SERVO_MIN_ms * 4096.0) / (1000.0 / frequency) - 1)
    self.SERVO_MAX = math.trunc((SERVO_MAX_ms * 4096.0) / (1000.0 / frequency) - 1)

    self.pwm = PWM(0x40, debug=False)

    # Set frequency to 60 Hz
    self.pwm.setPWMFreq(frequency)


  def setSpeed(self, speed):
      
      speed = speed if speed > self.SERVO_MIN else self.SERVO_MIN
      speed = speed if speed < self.SERVO_MAX else self.SERVO_MAX
      print "Max: {}, Min: {} speed: {}".format(self.SERVO_MAX, self.SERVO_MIN, speed)
      self.pwm.setPWM(self.NAVIO_RCOUTPUT, 0, speed)

Now here is a small test

from motors import Motor
import getch

# FRONT_RIGHT min 305
# FRONT_LEFT min 308
# BACK_LEFT min  332
# BACK_RIGHT min 322
m1 = Motor(Motor.FRONT_LEFT)
m2 = Motor(Motor.FRONT_RIGHT)
m3 = Motor(Motor.BACK_LEFT)
m4 = Motor(Motor.BACK_RIGHT)
speed = 270
while True:
  c = getch.getch()

  if c == 'w':
    speed = speed + 1
  if c == 's':
    speed = speed - 1

  m1.setSpeed(speed)
  m2.setSpeed(speed)
  m3.setSpeed(speed)
  m4.setSpeed(speed)

I’ve found out that every motor starts in different points. You can see commented values.
Is it a regular thing? Any suggestions how to fix it, or calibrate in a right way?

I’m using SunnySky motors 980kv, and Afro30A ESC’s

2

You will need to calibrate your ESCs to make them start at the same PWM level.

3

Hi Igor,

DO you have any code examples or links to to do it with python/c++ ?

4

I had something similar, My ESC’s were flashed with fixed range on the pwm values as I’m controlling them directly (range is 1060-1460-1860 as they are reversible 2 started at 1520, 2 started at 1530 only tested to the nearest 10), but 2 motors were 10us above the others for startup speed,
That didnt turn out to be an issue tho as the PID handles it fine later on. I just put it down to small differences in the motors capabilities (or maybe inaccuracies creeping in with the PWM communication between the navio and the ESC)

5

AfroESC manual has a chapter about calibration. Please take a look.

6

I just red the manual that Igor has attached, and did a manual calibration. no it all at the same level.

7

Thanks, Igor! It helped me a lot! I did a manual calibration following the guide.