PID电机调速求探讨

Stupid

  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：

1. /*
   
2.   Firstbot PID code:  Implements a PID controller using
   
3.   analog inputs for actual and desired positions.
   
4. 
   
5. The circuit:
   
6. * RX is digital pin 2 (connect to TX of other device)
   
7. * TX is digital pin 3 (connect to RX of other device)
   
8. 
   
9. */
   
10. #include <SoftwareSerial.h>
    
11. 
    
12. // define some constants
    
13. int ActPos = A0;    // select the input pin for feedback signal
    
14. int DesPos = A1;    // select the input pin for control signal
    
15. 
    
16. byte PWMOutput;
    
17. long Error[10];
    
18. long Accumulator;
    
19. long PID;
    
20. int PTerm;
    
21. int ITerm;
    
22. int DTerm;
    
23. byte Divider;
    
24. 
    
25. /*
    
26. The FIRSTBOT has a PIC16F1829 controller that controls the
    
27. two MC33926 H-bridges on the board.  A oftware serial interface
    
28. is used to control that part.
    
29. */
    
30. SoftwareSerial mySerial(2, 3); // Receive data on 2, send data on 3
    
31. byte SerialTXBuffer[5];
    
32. byte SerialRXBuffer[5];
    
33. 
    
34. void setup()  
    
35. {
    
36. 
    
37. // Open serial communications and wait for port to open:
    
38.   Serial.begin(9600);
    
39.   mySerial.begin(9600);
    
40. }
    
41. 
    
42. /* GetError():
    
43. Read the analog values, shift the Error array down
    
44. one spot, and load the new error value into the
    
45. top of array.
    
46. */
    
47. void GetError(void)
    
48. {
    
49.   byte i = 0;
    
50.   // read analogs
    
51.   word ActualPosition = analogRead(ActPos);  
    
52. // comment out to speed up PID loop
    
53. //  Serial.print("ActPos= ");
    
54. //  Serial.println(ActualPosition,DEC);
    
55. 
    
56.   word DesiredPosition = analogRead(DesPos);
    
57. // comment out to speed up PID loop
    
58. //  Serial.print("DesPos= ");
    
59. //  Serial.println(DesiredPosition,DEC);
    
60. 
    
61.   // shift error values
    
62.   for(i=0;i<10;i++)
    
63.     Error[i+1] = Error[i];
    
64.   // load new error into top array spot  
    
65.   Error[0] = (long)DesiredPosition-(long)ActualPosition;
    
66. // comment out to speed up PID loop
    
67. //  Serial.print("Error= ");
    
68. //  Serial.println(Error[0],DEC);
    
69. 
    
70. }
    
71. 
    
72. /* CalculatePID():
    
73. Error[0] is used for latest error, Error[9] with the DTERM
    
74. */
    
75. void CalculatePID(void)
    
76. {
    
77. // Set constants here
    
78.   PTerm = 2000;
    
79.   ITerm = 25;
    
80.   DTerm = 0;
    
81.   Divider = 10;
    
82. 
    
83. // Calculate the PID  
    
84.   PID = Error[0]*PTerm;     // start with proportional gain
    
85.   Accumulator += Error[0];  // accumulator is sum of errors
    
86.   PID += ITerm*Accumulator; // add integral gain and error accumulation
    
87.   PID += DTerm*(Error[0]-Error[9]); // differential gain comes next
    
88.   PID = PID>>Divider; // scale PID down with divider
    
89. 
    
90. // comment out to speed up PID loop  
    
91. //Serial.print("PID= ");
    
92. //  Serial.println(PID,DEC);
    
93. 
    
94. // limit the PID to the resolution we have for the PWM variable
    
95. 
    
96.   if(PID>=127)
    
97.     PID = 127;
    
98.   if(PID<=-126)
    
99.     PID = -126;
    
100. 
     
101. //PWM output should be between 1 and 254 so we add to the PID   
     
102.   PWMOutput = PID + 127;
     
103. 
     
104. // comment out to speed up PID loop
     
105. //  Serial.print("PWMOutput= ");
     
106. //  Serial.println(PWMOutput,DEC);
     
107. 
     
108. }
     
109. 
     
110. /* WriteRegister():
     
111. Writes a single byte to the PIC16F1829,
     
112. "Value" to the register pointed at by "Index".  
     
113. Returns the response
     
114. */
     
115. byte WriteRegister(byte Index, byte Value)
     
116. {
     
117. byte i = 0;
     
118. byte checksum = 0;
     
119. byte ack = 0;
     
120. 
     
121. SerialTXBuffer[0] = 210;
     
122. SerialTXBuffer[1] = 1;
     
123. SerialTXBuffer[2] = 3;
     
124. SerialTXBuffer[3] = Index;
     
125. SerialTXBuffer[4] = Value;
     
126. 
     
127. for (i=0;i<6;i++)
     
128.   {
     
129.   if (i!=5)
     
130.     {
     
131.     mySerial.write(SerialTXBuffer[i]);
     
132.     checksum += SerialTXBuffer[i];   
     
133.     }
     
134.   else
     
135.     mySerial.write(checksum);     
     
136.   }
     
137.   delay(5);
     
138. 
     
139.   if (mySerial.available())
     
140.     ack = mySerial.read();
     
141. 
     
142.   return ack;
     
143. }
     
144. 
     
145. void loop() // run over and over
     
146. {
     
147.      GetError();       // Get position error
     
148.      CalculatePID();   // Calculate the PID output from the error
     
149.      WriteRegister(9,PWMOutput);  // Set motor speed
     
150. }

复制代码

      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。