用编码器控制直流电机

Question

我正在尝试使用Arduino Uno和连接到电机的编码器来控制两个直流电机的速度。

我已经写了一个代码来检查编码器的位置是否有变化，并根据它来计算电机的速度。

我在代码中使用了this website：

我在计算编码器的新位置和旧位置之间的差值时遇到了问题。由于某些原因，即使速度保持不变，这种差异也在不断增加。

这是我到目前为止的代码：

#define pwmLeft 10
#define pwmRight 5
#define in1 9
#define in2 8
#define in3 7
#define in4 6

//MOTOR A
int motorSpeedA = 100;
static int pinA = 2; // Our first hardware interrupt pin is digital pin 2
static int pinB = 3; // Our second hardware interrupt pin is digital pin 3
volatile byte aFlag = 0; // let's us know when we're expecting a rising edge on pinA to signal that the encoder has arrived at a detent
volatile byte bFlag = 0; // let's us know when we're expecting a rising edge on pinB to signal that the encoder has arrived at a detent (opposite direction to when aFlag is set)
volatile long encoderPos = 0; //this variable stores our current value of encoder position. Change to int or uin16_t instead of byte if you want to record a larger range than 0-255
volatile long oldEncPos = 0; //stores the last encoder position value so we can compare to the current reading and see if it has changed (so we know when to print to the serial monitor)
volatile long reading = 0; //somewhere to store the direct values we read from our interrupt pins before checking to see if we have moved a whole detent

//MOTOR B
static int pinC = 12; // Our first hardware interrupt pin is digital pin 2
static int pinD = 33; // Our second hardware interrupt pin is digital pin 3
volatile byte cFlag = 0; // let's us know when we're expecting a rising edge on pinA to signal that the encoder has arrived at a detent
volatile byte dFlag = 0; // let's us know when we're expecting a rising edge on pinB to signal that the encoder has arrived at a detent (opposite direction to when aFlag is set)
volatile long encoderPosB = 0; //this variable stores our current value of encoder position. Change to int or uin16_t instead of byte if you want to record a larger range than 0-255
volatile long oldEncPosB = 0; //stores the last encoder position value so we can compare to the current reading and see if it has changed (so we know when to print to the serial monitor)
volatile long readingB = 0;

int tempPos;
long vel;
unsigned long newtime;
unsigned long oldtime = 0;

void setup() {
  //MOTOR A
  pinMode(pinA, INPUT_PULLUP); // set pinA as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
  pinMode(pinB, INPUT_PULLUP); // set pinB as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
  attachInterrupt(0, PinA, RISING); // set an interrupt on PinA, looking for a rising edge signal and executing the "PinA" Interrupt Service Routine (below)
  attachInterrupt(1, PinB, RISING); // set an interrupt on PinB, looking for a rising edge signal and executing the "PinB" Interrupt Service Routine (below)
  //MOTOR B
  pinMode(pinC, INPUT_PULLUP); // set pinA as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
  pinMode(pinD, INPUT_PULLUP); // set pinB as an input, pulled HIGH to the logic voltage (5V or 3.3V for most cases)
  attachInterrupt(0, PinC, RISING); // set an interrupt on PinA, looking for a rising edge signal and executing the "PinA" Interrupt Service Routine (below)
  attachInterrupt(1, PinD, RISING);
  Serial.begin(9600); // start the serial monitor link
  pinMode (in1, OUTPUT);
  pinMode (in2, OUTPUT);
  pinMode (in3, OUTPUT);
  pinMode (in4, OUTPUT);
  digitalWrite (8, HIGH);
  digitalWrite (9, LOW); //LOW
  digitalWrite (7, LOW); //LOW
  digitalWrite (6, HIGH);
  pinMode (pwmLeft, OUTPUT);
  pinMode (pwmRight, OUTPUT);
}

void PinA(){
  cli(); //stop interrupts happening before we read pin values
  reading = PIND & 0xC; // read all eight pin values then strip away all but pinA and pinB's values
  if(reading == B00001100 && aFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
    encoderPos --; //decrement the encoder's position count
    bFlag = 0; //reset flags for the next turn
    aFlag = 0; //reset flags for the next turn
  } else if (reading == B00000100) bFlag = 1; //signal that we're expecting pinB to signal the transition to detent from free rotation
  sei(); //restart interrupts
}

void PinB(){
  cli(); //stop interrupts happening before we read pin values
  reading = PIND & 0xC; //read all eight pin values then strip away all but pinA and pinB's values
  if (reading == B00001100 && bFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
    encoderPos ++; //increment the encoder's position count
    bFlag = 0; //reset flags for the next turn
    aFlag = 0; //reset flags for the next turn
  } else if (reading == B00001000) aFlag = 1; //signal that we're expecting pinA to signal the transition to detent from free rotation
  sei(); //restart interrupts
}

void PinC(){
  cli(); //stop interrupts happening before we read pin values
  readingB = PIND & 0xC; // read all eight pin values then strip away all but pinA and pinB's values
  if(readingB == B00001100 && cFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
    encoderPosB --; //decrement the encoder's position count
    dFlag = 0; //reset flags for the next turn
    cFlag = 0; //reset flags for the next turn
  } else if (readingB == B00000100) dFlag = 1; //signal that we're expecting pinB to signal the transition to detent from free rotation
  sei(); //restart interrupts
}

void PinD(){
  cli(); //stop interrupts happening before we read pin values
  readingB = PIND & 0xC; //read all eight pin values then strip away all but pinA and pinB's values
  if (readingB == B00001100 && dFlag) { //check that we have both pins at detent (HIGH) and that we are expecting detent on this pin's rising edge
    encoderPosB ++; //increment the encoder's position count
    dFlag = 0; //reset flags for the next turn
    cFlag = 0; //reset flags for the next turn
  } else if (readingB == B00001000) cFlag = 1; //signal that we're expecting pinA to signal the transition to detent from free rotation
  sei(); //restart interrupts
}

void loop(){
  analogWrite(pwmLeft, motorSpeedA);
  analogWrite(pwmRight, motorSpeedA);
  if(oldEncPos != encoderPos) {
    newtime = millis();
    tempPos = encoderPos - oldEncPos;
    vel = tempPos / (newtime - oldtime);
    Serial.println(tempPos);
    oldEncPos = encoderPos;
    oldtime = newtime;
    delay(250);
  } 
  if(oldEncPosB != encoderPosB) {
    Serial.println(encoderPosB);
    oldEncPosB = encoderPosB;
  }    
}

如果有任何反馈，我将不胜感激。

谢谢。

编辑：

我发现有一个编码库可以让一切变得更容易。

所以现在我的代码看起来像这样：

#include <Encoder.h>
#define pwmLeft 10
#define pwmRight 5
Encoder myEncA(3, 2);
Encoder myEncB(13, 12);
unsigned long oldtimeA = 0;
unsigned long oldtimeB = 0;
int speedA = 100;
int speedB = 130;

void setup() {
  Serial.begin(9600);

  digitalWrite (8, HIGH);
  digitalWrite (9, LOW); //LOW
  digitalWrite (7, LOW); //LOW
  digitalWrite (6, HIGH);

  pinMode (pwmLeft, OUTPUT);
  pinMode (pwmRight, OUTPUT);
}

long oldPositionA  = -999;
long oldPositionB  = -999;

void loop() {

  analogWrite(pwmLeft, speedA);
  analogWrite(pwmRight, speedB);

  long newPositionA = myEncA.read();
  long newPositionB = myEncB.read();
  if ((newPositionA != oldPositionA) || (newPositionB != oldPositionB)) {
    unsigned long newtimeA = millis ();
    long positionA = newPositionA - oldPositionA;
    long positionB = newPositionB - oldPositionB;
    long velB = (positionB) / (newtimeA - oldtimeA);
    long velA = (positionA) / (newtimeA - oldtimeA);
    oldtimeA = newtimeA;
    oldPositionA = newPositionA;
    oldPositionB = newPositionB;
    Serial.println(velB);
  }
}

我的"B“型发动机仍然有问题，由于某些原因，计算仍然有问题。

发动机"A“工作正常

Answer 1

几个问题，包括loop()中的除以零错误。此扫描会导致重置控制器。在做除法运算时，一定要检查除数的值！

只使用正转换不必要地将读数的分辨率降低2。

Arduino是一个8位控制器...读取int需要多条指令，这意味着您应该在读取由中断例程修改的int之前禁用中断。如果不这样做，将导致vakue读取中出现奇怪的跳跃。这通常是这样做的：

//...
NoInterrupts();
int copyOfValue = value;   // use the copy to work with.
interrupts();
//...

在您的情况下，单字节值可能足以存储移动，每30毫秒重置一次，这将为您提供255个脉冲/30ms= 8500个脉冲/秒或1275000转/分钟的最高速度(对于24刻度/圈的编码器)。:)在这种情况下，不需要禁用读取中断。

对于每30ms一个读数，1Tick /30ms = 33滴答/秒，或85转/分。这对运动来说有点高。您可能需要平均读数，这取决于您的应用程序。

此外，您正在使用的算法肯定不会起作用。主要原因是读取和调整之间的延迟太小。大多数读数将为零。在删除println()调用时会遇到这个问题。我建议读数之间至少30毫秒的起搏。100ms可能会更好一些，这取决于您的应用程序。使用float变量来表示平均速度肯定会有所帮助。

void loop()
{
  //...
  if(oldEncPos != encoderPos) {
    newtime = millis();
    tempPos = encoderPos - oldEncPos;
    vel = tempPos / (newtime - oldtime);   // <--  if newtime == oltime => divide by zero.
    //...
  } 
  //...
}

编码器读取代码看起来非常复杂...

#define PIN_A  2  // encoder bit 0
#define PIN_B  3  // encoder bit 1

volatile char encVal1;
volatile unsigned char encPos1;  // using char 

void OnEncoder1Change()
{
   char c = (digitalRead(pinA) ? 0b01 : 0)
          + (digitalRead(pinB) ? 0b10 : 0);  // read
   char delta = (c - encVal1) & 0b11;        // get difference, mask

   if (delta == 1)                           // delta is either 1 or 3
       ++encPos1;
   else
       --encPos1;
   encVal1 = c;                              // keep reading for next time.
   encPos1 += delta;                         // get position.
   // no need to call sei()
}

setup()
{
  pinMode(pinA, INPUT_PULLUP);
  pinMode(pinB, INPUT_PULLUP);

  // get an initial value
  encValA  = digitalRead(pinA) ? 0b01 : 0;
  encValA += digitalRead(pinB) ? 0b10 : 0;

  // use digitalPinToInterrupt() to map interrupts to a pin #
  // ask for interrupt on change, this doubles .
  attachInterrupt(digitalPinToInterrupt(PIN_A), OnEncoder1Change, CHANGE);  
  attachInterrupt(digitalPinToInterrupt(PIN_B), OnEncoder1Change, CHANGE);


  //...
}

unsigned char oldTime;
unsigned char oldPos;
int speed;
void loop()
{
    unsigned char time = millis();

    if (time - oldTime > 30)        // pace readings so you have a reasonable value.
    {
        unsigned char pos = encPos1;
        signed char delta = pos - oldPos;

        speed = 1000 * delta) / (time - oldTime);  // signed ticks/s

        encPos1 -= pos;  // reset using subtraction, do you don't miss out 
                         // on any encoder pulses.
        oldTime = time;
    }
}