Hello folks,
I recently bought a wild thumper 4WD and the VNH5019 Motor driver.
As a controller I am using a Feather M0 BLE.
When I drive the wheels of the Thumper I noticed that the wheels on the left side rotate faster than the right ones. I connected each one signal of the rear quadrature encoders and counted their interrupt ticks, which prove my visual observations.
Both PWM signals are supposed to be identical. So:
How can I calibrate the drivers output?
regards
Brushed DC gearmotors like the ones used in the Wild Thumper generally have a tolerance of ±10% on their speed. So, it sounds like the particular set of gearmotors you have results in the right pair rotating fewer times than the left pair. Since you have encoders, you might try implementing some kind of PID feedback to get more uniform rotation (at least between the rear motors).
-Jon
Thanks Jon,
I was afraid that would be the solution.
I noticed another issue in the mean time:
The M2 side of the driver claims ridiculous 2 to 5 A of current draw. I can’t measure however anything on the cables with my multimeter. Moreover I switched the cables on motor side in order to determine motor influence and then I switched the cables on driver side in order to determine if something is wrong with the cables / connection. Again no change. So, is the driver just reporting some meaningless values or could there be another reason for a high current draw?
regards
spyderroque
What kind of current does the M1 side of your driver measure? Can you give me a sample of the raw values that you are measuring from both sides? Also, can you tell me more about your system? How are you supplying power? How much load is on your Wild Thumper? It might help to include pictures of your Thumper.
-Jon
Hi Jon,
the thumper is suspendid in air with the wheels running free. As a battery I am using a 7.4 V LiPo. When the M0 Feather is connected to my PC it is powered by USB. M1 returns mostly values around 250 - 1000 mA, while M2 returns above values. In below picture I am using the Arduino example modified to suit the M0 BLE.
Can you try swapping which pins are reading the shield’s M1CS and M2CS pins to see if the problem stays with the motor? If the problem stays with the motor, can you also check to see that the M2 gearmotor’s encoder is not rubbing or scraping against anything? Which gearmotors with encoders are you using?
Also, it sound likes you are using our VNH5019 Arduino shield library. What modifications did you make? Can you post your entire sketch?
-Jon
Sorry for the late reply,
The modifications are not really note worthy. Basically I changed the PWM Pins in the header file, as they are different on the Feather M0 bord. While doing so I also changed the pin numbers in the cpp file in order to fit them to the Feather.
As for the MxCS Pins, I will give it a try this weekend.
#ifndef DualVNH5019Mod_h
#define DualVNH5019Mod_h
#include <Arduino.h>
class DualVNH5019MotorShield
{
public:
// CONSTRUCTORS
DualVNH5019MotorShield(); // Default pin selection.
DualVNH5019MotorShield(unsigned char INA1, unsigned char INB1, unsigned char EN1DIAG1, unsigned char CS1,
unsigned char INA2, unsigned char INB2, unsigned char EN2DIAG2, unsigned char CS2); // User-defined pin selection.
// PUBLIC METHODS
void init(); // Initialize TIMER 1, set the PWM to 20kHZ.
void setM1Speed(int speed); // Set speed for M1.
void setM2Speed(int speed); // Set speed for M2.
void setSpeeds(int m1Speed, int m2Speed); // Set speed for both M1 and M2.
void setM1Brake(int brake); // Brake M1.
void setM2Brake(int brake); // Brake M2.
void setBrakes(int m1Brake, int m2Brake); // Brake both M1 and M2.
unsigned int getM1CurrentMilliamps(); // Get current reading for M1.
unsigned int getM2CurrentMilliamps(); // Get current reading for M2.
unsigned char getM1Fault(); // Get fault reading from M1.
unsigned char getM2Fault(); // Get fault reading from M2.
private:
unsigned char _INA1;
unsigned char _INB1;
static const unsigned char _PWM1 = 5;
unsigned char _EN1DIAG1;
unsigned char _CS1;
unsigned char _INA2;
unsigned char _INB2;
static const unsigned char _PWM2 = 6;
unsigned char _EN2DIAG2;
unsigned char _CS2;
};
#endif
and for the cpp:
#include "DualVNH5019Mod.h"
// Constructors ////////////////////////////////////////////////////////////////
DualVNH5019MotorShield::DualVNH5019MotorShield()
{
//Pin map
//MODIFIED IN ORDER TO SUIT M0 FEATHER BLE
_INA1 = 12;
_INB1 = 11;
_EN1DIAG1 = 13;
_CS1 = A0;
_INA2 = 0;
_INB2 = 22;
_EN2DIAG2 = 1;
_CS2 = A1;
}
DualVNH5019MotorShield::DualVNH5019MotorShield(unsigned char INA1, unsigned char INB1, unsigned char EN1DIAG1, unsigned char CS1,
unsigned char INA2, unsigned char INB2, unsigned char EN2DIAG2, unsigned char CS2)
{
//Pin map
//PWM1 and PWM2 cannot be remapped because the library assumes PWM is on timer1
_INA1 = INA1;
_INB1 = INB1;
_EN1DIAG1 = EN1DIAG1;
_CS1 = CS1;
_INA2 = INA2;
_INB2 = INB2;
_EN2DIAG2 = EN2DIAG2;
_CS2 = CS2;
}
// Public Methods //////////////////////////////////////////////////////////////
void DualVNH5019MotorShield::init()
{
// Define pinMode for the pins and set the frequency for timer1.
pinMode(_INA1,OUTPUT);
pinMode(_INB1,OUTPUT);
pinMode(_PWM1,OUTPUT);
pinMode(_EN1DIAG1,INPUT);
pinMode(_CS1,INPUT);
pinMode(_INA2,OUTPUT);
pinMode(_INB2,OUTPUT);
pinMode(_PWM2,OUTPUT);
pinMode(_EN2DIAG2,INPUT);
pinMode(_CS2,INPUT);
#if defined(__AVR_ATmega168__)|| defined(__AVR_ATmega328P__) || defined(__AVR_ATmega32U4__)
// Timer 1 configuration
// prescaler: clockI/O / 1
// outputs enabled
// phase-correct PWM
// top of 400
//
// PWM frequency calculation
// 16MHz / 1 (prescaler) / 2 (phase-correct) / 400 (top) = 20kHz
TCCR1A = 0b10100000;
TCCR1B = 0b00010001;
ICR1 = 400;
#endif
}
// Set speed for motor 1, speed is a number betwenn -400 and 400
void DualVNH5019MotorShield::setM1Speed(int speed)
{
unsigned char reverse = 0;
if (speed < 0)
{
speed = -speed; // Make speed a positive quantity
reverse = 1; // Preserve the direction
}
if (speed > 400) // Max PWM dutycycle
speed = 400;
#if defined(__AVR_ATmega168__)|| defined(__AVR_ATmega328P__) || defined(__AVR_ATmega32U4__)
OCR1A = speed;
#else
analogWrite(_PWM1,speed * 51 / 80); // default to using analogWrite, mapping 400 to 255
#endif
if (speed == 0)
{
digitalWrite(_INA1,LOW); // Make the motor coast no
digitalWrite(_INB1,LOW); // matter which direction it is spinning.
}
else if (reverse)
{
digitalWrite(_INA1,LOW);
digitalWrite(_INB1,HIGH);
}
else
{
digitalWrite(_INA1,HIGH);
digitalWrite(_INB1,LOW);
}
}
// Set speed for motor 2, speed is a number betwenn -400 and 400
void DualVNH5019MotorShield::setM2Speed(int speed)
{
unsigned char reverse = 0;
if (speed < 0)
{
speed = -speed; // make speed a positive quantity
reverse = 1; // preserve the direction
}
if (speed > 400) // Max
speed = 400;
#if defined(__AVR_ATmega168__)|| defined(__AVR_ATmega328P__) || defined(__AVR_ATmega32U4__)
OCR1B = speed;
#else
analogWrite(_PWM2,speed * 51 / 80); // default to using analogWrite, mapping 400 to 255
#endif
if (speed == 0)
{
digitalWrite(_INA2,LOW); // Make the motor coast no
digitalWrite(_INB2,LOW); // matter which direction it is spinning.
}
else if (reverse)
{
digitalWrite(_INA2,LOW);
digitalWrite(_INB2,HIGH);
}
else
{
digitalWrite(_INA2,HIGH);
digitalWrite(_INB2,LOW);
}
}
// Set speed for motor 1 and 2
void DualVNH5019MotorShield::setSpeeds(int m1Speed, int m2Speed)
{
setM1Speed(m1Speed);
setM2Speed(m2Speed);
}
// Brake motor 1, brake is a number between 0 and 400
void DualVNH5019MotorShield::setM1Brake(int brake)
{
// normalize brake
if (brake < 0)
{
brake = -brake;
}
if (brake > 400) // Max brake
brake = 400;
digitalWrite(_INA1, LOW);
digitalWrite(_INB1, LOW);
#if defined(__AVR_ATmega168__)|| defined(__AVR_ATmega328P__) || defined(__AVR_ATmega32U4__)
OCR1A = brake;
#else
analogWrite(_PWM1,brake * 51 / 80); // default to using analogWrite, mapping 400 to 255
#endif
}
// Brake motor 2, brake is a number between 0 and 400
void DualVNH5019MotorShield::setM2Brake(int brake)
{
// normalize brake
if (brake < 0)
{
brake = -brake;
}
if (brake > 400) // Max brake
brake = 400;
digitalWrite(_INA2, LOW);
digitalWrite(_INB2, LOW);
#if defined(__AVR_ATmega168__)|| defined(__AVR_ATmega328P__) || defined(__AVR_ATmega32U4__)
OCR1B = brake;
#else
analogWrite(_PWM2,brake * 51 / 80); // default to using analogWrite, mapping 400 to 255
#endif
}
// Brake motor 1 and 2, brake is a number between 0 and 400
void DualVNH5019MotorShield::setBrakes(int m1Brake, int m2Brake)
{
setM1Brake(m1Brake);
setM2Brake(m2Brake);
}
// Return motor 1 current value in milliamps.
unsigned int DualVNH5019MotorShield::getM1CurrentMilliamps()
{
// 5V / 1024 ADC counts / 144 mV per A = 34 mA per count
return analogRead(_CS1) * 34;
}
// Return motor 2 current value in milliamps.
unsigned int DualVNH5019MotorShield::getM2CurrentMilliamps()
{
// 5V / 1024 ADC counts / 144 mV per A = 34 mA per count
return analogRead(_CS2) * 34;
}
// Return error status for motor 1
unsigned char DualVNH5019MotorShield::getM1Fault()
{
return !digitalRead(_EN1DIAG1);
}
// Return error status for motor 2
unsigned char DualVNH5019MotorShield::getM2Fault()
{
return !digitalRead(_EN2DIAG2);
}
In addition to swapping the MxCS pins, if you have a multimeter, another thing you might do is directly measure how much current is drawn from each motor while it is being controlled by the VNH5019 shield.
-Jon