Autosteer - Brushless Motor

Hardware Autosteer
1

Hi makers !

In order to make the steering wheel easier to drive when autosteer is off but the motor still engaged on the steering wheel, I ordered a Brushless motor.
It has no gear reduction so very low torque when not supplied with power.

I ordered also a ESC (motor controller) for brushless motor to drive it. It will replace the Cytron.
My concern is about the PWM to be sent to the ESC.

The ESC should normally be driven by a remote control reveiver with a “servo-type” PWM, without “DIR” signal.
It means that with
PWM = 0, motor drives full speed left ;
PWM = 50, motor is stopped ;
PWM 100 motor drives full speed right.

Has anyone already modified the Autosteer arduino sketch to send such values out ?

If not, I plan to add an aditionnal Arduino connected to the PCB V2 pwm and dir pin, to read the values comming out from the PCB and “translate” it to my ESC.

It has the advantage to let the Agopengps sketch like it is.

Thanks for your comments.

Motor : Flipsky r 6374 190kv 3250w brushless sensored motor shaft 8mm for electric skateboard rc car Sale - Banggood.com

ESC : Flipsky mini fsesc4.20 50a esc based upon vesc with aluminum anodized heat sink for rc car Sale - Banggood.com

4 Likes
2

I seems to almost be like the ino for a Danfoss valve

3

Is this ESC bidirectionnal ?

4

Yes, for remote controlled car.

1 Like
5

I think maybe a simple little modification in void motordrive might work, there is just map () the PWM output to your need.

Something looking like this (not tested, my bdlc motor are in the cargo) :

  if (pwmDrive > 0)
  {
    pwmESC = map(pwmDrive,0,255,128,255) ;
    analogWrite(PWM1_LPWM, pwmESC);
  }      
  else
  {
    pwmDrive = -1 * pwmDrive;  
    pwmESC = map(pwmDrive,0,255,0,128) ;
    analogWrite(PWM1_LPWM, pwmESC);
  }
1 Like
6

I used a reversible ESC for brushed motors in my combine this fall. I modified the INO to output RC servo signal. When I can, I’ll post the code.

2 Likes
7

I used the standard Servo library
before setup()

#include <Servo.h>
Servo myServo;

in setup()

myServo.attach(PWM1_LPWM);

void motorDrive(void){
  // Used with Cytron MD30C Driver
  // Steering Motor
  // Dir + PWM Signal
  if (aogSettings.CytronDriver){
    pwmDisplay = pwmDrive;
    int pwmServo = pwmDrive;

    //fast set the direction accordingly (this is pin DIR1_RL_ENABLE, port D, 4)
    if (pwmDrive >= 0){
      bitSet(PORTD, 4);  //set the correct direction
      digitalWrite(PWM2_RPWM, 0);
    } else {
      bitClear(PORTD, 4);
      digitalWrite(PWM2_RPWM, 1);
      pwmDrive = -1 * pwmDrive;  
    }

    //write out the 0 to 255 value 
    //pwmDrive = 255 - pwmDrive;
    //analogWrite(PWM1_LPWM, pwmDrive);  // don't need this but still select Cytron in AoG

    if (pwmServo > 0){
      pwmServo += 1;      // +-1 before multiplying
      pwmServo = int(float(pwmServo) * 1.6);  // my motor needs a different gain for this direction, it's not symetrical
    }
    else if (pwmServo < 0) pwmServo -= 1;
    pwmServo *= 2;                                  // *2 gets the pwmDrive into range for Servo microseconds output
    if (pwmServo > 0) pwmServo -= 1;      // revert previous +-1
    else if (pwmServo < 0) pwmServo += 1;
    pwmServo += 1410;                     // offset for 1500 uS servo center output, adjust for your drive
    myServo.writeMicroseconds(pwmServo);
    
  } else {
    // Used with IBT 2  Driver for Steering Motor
    // Dir1 connected to BOTH enables
    // PWM Left + PWM Right Signal     
    pwmDisplay = pwmDrive; 
  
    if (pwmDrive > 0) {
      analogWrite(PWM2_RPWM, 0);  //Turn off before other one on
      analogWrite(PWM1_LPWM, pwmDrive);
    } else {
      pwmDrive = -1 * pwmDrive;  
      analogWrite(PWM1_LPWM, 0);  //Turn off before other one on
      analogWrite(PWM2_RPWM, pwmDrive);
    }
  }
}

You have to select Cytron in AoG but it will output a Servo signal on PWM1_LPWM (IO 3).
I had to play around to find the true center/zero of my ESC, then I entered that in for the center offset (see comments in the above code)

3 Likes
8

Hello,

You can also try the specific ESC library:

Math

1 Like
9

some use this engine and have succeeded in modifying INO?

10

First message has 2 days …let give him little time to test…

2 Likes
11

Still waiting for the ESC, some delivery issues with Banggood (tracking says it is delivered but it never arrived … )

1 Like
12

I too am looking at BLDC motors for steering control as they can result in very compact mechanics. It may even be possible to use a skateboard wheel with inbuilt motor if the gear ratio/ torque works. Looking at the VESC code and tool info, you can setup to drive via servo, uart, ADC or CAN. Other choices are sensored or sensorless, and FOC control or not. Sensored and FOC should in theory give better starting and lower cogging, but are they necessary?

1 Like
13

I believe that a motor with a high pole number and low KV is needed more than anything else, in order to have a lot of starting torque and little speed inertia

1 Like
14

I tried a bdlc this weekend, a 6374-170Kv from amazon / aliexpress, I was disappointed, and I came to the same conclusion … You need a large number of poles.

15

You mean it was working or not ?

16

Difficult to run it properly at low speed and too slow reactivity for my taste, and very noisy.

At low speed, it is as if it has difficulty jumping from pole to pole, and at this point there is almost no torque and makes a lot of noise.

17

Did you use FOC? this should give better control at lower speeds. its basically sine wave PWM control using feedback from hall sensors or backemf.

18

Also was the motor properly set up with the Vesc tool for inductance, motor type , voltage etc? One problem could be running on low tractor voltage 12-14volts, some BLDC motors are designed for much higher voltages to give more torque. But yes, the more poles the better and low KV.

19

Feedback around the WAS loop should make it work though with torque or current control, if the gear ratios are OK

20

I tried with FOC, current control, hall sensors, BUT, at very low rpm the vesc still works in openloop, and in my opinion this can be a problem, maybe try with a high reduction ratio