使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。

我编写了一个代码来检查编码器的位置是否发生变化，并据此计算电机的速度。

我用this website 写代码：

我在计算编码器新位置与编码器旧位置之间的差异时遇到问题。出于某种原因，即使速度保持不变，差异也会不断扩大。

这是我目前的代码：

#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;
  }    
}

这两个 if 语句只是为了检查编码器是否正常工作。在第一个 if 语句中，我尝试计算速度。

如有任何反馈，我将不胜感激。

谢谢。

编辑：

我发现有一个编码器库可以让一切变得更容易。

所以现在我的代码如下所示：

#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”电机仍然有问题，由于某种原因，计算仍有一段距离。

电机“A”工作正常

Answer 1

几个问题，包括 loop() 中的除以零错误。此扫描会导致您的控制器重置。做除法时一定要检查除数的值！

仅使用正转换会不必要地将读数分辨率降低 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。不这样做会导致 vakue 读取出现奇怪的跳跃。这通常是这样完成的：

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

在您的情况下，单个字节值可能足以存储运动，每 30 毫秒重置一次，这应该为您提供 255 脉冲/30 毫秒 = 8500 脉冲/秒或 1275000 转/分钟的最高速度（24 滴答声/转动编码器。 :) 在这种情况下，无需禁用读取中断。

每 30 毫秒一个读数，1 个滴答声/30 毫秒 = 33 个滴答声/秒，或 85 RPM。运动有点高。根据您的应用，您可能需要平均读数。

另外，你使用的算法肯定是行不通的。主要原因是读取和调整之间的延迟太小。大多数读数为零。删除 println() 调用时会遇到问题。我建议读数之间至少间隔 30 毫秒。取决于您的应用程序，100 毫秒可能会更好一些。使用float 变量作为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;
    }
}