PID电机调速求探讨
原帖地址：http://blog.solutions-cubed.com/pid-motor-control-with-an-arduino/电路接线图，电路板原理图见附件。
程序：/*
Firstbot PID code:Implements a PID controller using
analog inputs for actual and desired positions.
The circuit:
* RX is digital pin 2 (connect to TX of other device)
* TX is digital pin 3 (connect to RX of other device)
*/
#include <SoftwareSerial.h>
// define some constants
int ActPos = A0; // select the input pin for feedback signal
int DesPos = A1; // select the input pin for control signal
byte PWMOutput;
long Error;
long Accumulator;
long PID;
int PTerm;
int ITerm;
int DTerm;
byte Divider;
/*
The FIRSTBOT has a PIC16F1829 controller that controls the
two MC33926 H-bridges on the board.A oftware serial interface
is used to control that part.
*/
SoftwareSerial mySerial(2, 3); // Receive data on 2, send data on 3
byte SerialTXBuffer;
byte SerialRXBuffer;
void setup()
{
// Open serial communications and wait for port to open:
Serial.begin(9600);
mySerial.begin(9600);
}
/* GetError():
Read the analog values, shift the Error array down
one spot, and load the new error value into the
top of array.
*/
void GetError(void)
{
byte i = 0;
// read analogs
word ActualPosition = analogRead(ActPos);
// comment out to speed up PID loop
//Serial.print("ActPos= ");
//Serial.println(ActualPosition,DEC);
word DesiredPosition = analogRead(DesPos);
// comment out to speed up PID loop
//Serial.print("DesPos= ");
//Serial.println(DesiredPosition,DEC);
// shift error values
for(i=0;i<10;i++)
Error = Error;
// load new error into top array spot
Error = (long)DesiredPosition-(long)ActualPosition;
// comment out to speed up PID loop
//Serial.print("Error= ");
//Serial.println(Error,DEC);
}
/* CalculatePID():
Error is used for latest error, Error with the DTERM
*/
void CalculatePID(void)
{
// Set constants here
PTerm = 2000;
ITerm = 25;
DTerm = 0;
Divider = 10;
// Calculate the PID
PID = Error*PTerm; // start with proportional gain
Accumulator += Error;// accumulator is sum of errors
PID += ITerm*Accumulator; // add integral gain and error accumulation
PID += DTerm*(Error-Error); // differential gain comes next
PID = PID>>Divider; // scale PID down with divider
// comment out to speed up PID loop
//Serial.print("PID= ");
//Serial.println(PID,DEC);
// limit the PID to the resolution we have for the PWM variable
if(PID>=127)
PID = 127;
if(PID<=-126)
PID = -126;
//PWM output should be between 1 and 254 so we add to the PID
PWMOutput = PID + 127;
// comment out to speed up PID loop
//Serial.print("PWMOutput= ");
//Serial.println(PWMOutput,DEC);
}
/* WriteRegister():
Writes a single byte to the PIC16F1829,
"Value" to the register pointed at by "Index".
Returns the response
*/
byte WriteRegister(byte Index, byte Value)
{
byte i = 0;
byte checksum = 0;
byte ack = 0;
SerialTXBuffer = 210;
SerialTXBuffer = 1;
SerialTXBuffer = 3;
SerialTXBuffer = Index;
SerialTXBuffer = Value;
for (i=0;i<6;i++)
{
if (i!=5)
{
mySerial.write(SerialTXBuffer);
checksum += SerialTXBuffer;
}
else
mySerial.write(checksum);
}
delay(5);
if (mySerial.available())
ack = mySerial.read();
return ack;
}
void loop() // run over and over
{
GetError(); // Get position error
CalculatePID(); // Calculate the PID output from the error
WriteRegister(9,PWMOutput);// Set motor speed
}
刚刚接触PID这块，我把设计的文件都看了一遍，这个项目用了2个单片机，uno和PIC16F1829-I/ML，uno用于电机位置的检测和电机状态的控制，而pic这块对uno发出的指令进行处理从而对电机驱动给出控制，达到电机调速并且回复uno，带到串口通信的作用。我这样理解不知道对不对，在这个项目里我没有找到pic程序是怎么写的，还有一点就是可以通过软件实现电机调速和正反转。在里我提出第一个问题：就是pic的作用和功能是如何实现的，还有文章中涉及的就是固件这块的作用是什么？本人学生一枚第一次接触单片机，想把这个东西先照着这个做出来，已经打了电路板，就是想把这些都弄懂。
另外一个问题就是uno程序部分。首先对于电路接线图有一个问题，为什么分别通过模拟脚去接滑动变阻器和编码器，为什么这样就是PID的偏差Error？Error这个为什么是Error【10】不是很懂。
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