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标题: Reflow oven with PID control [打印本页]
作者: liyf    时间: 2013-9-11 07:44
标题: Reflow oven with PID control
原文：
Hi guys ,

i' currently building a reflow oven with PID control with PICAXE 28X1.I'm using a standard pizza oven and using a relay to control the main power switch.
Since i'm still a newbie in regard of PID control and PWM, i have intergrate the PID control from greencardigan project 'coffee maker' into the source code of my project.

The oven should operate with this parameters
1.heat to 150°C and maintain for 40s
2.heat to 190°C and maintain for 10s
3.heat to 245°C and maintain for 10s
4. Cool down to room tempereature

the code is as followed:
  1. symbol Kp = 1000
  2. symbol Ki = 20
  3. symbol Kd = 10

  5. symbol dt = 1
  6. symbol set_temp =w0
  7. symbol set_time =b0
  8. symbol sensor = 1
  9. symbol cur_temp = w1
  10. symbol cur_time=b1
  11. symbol oven = 7

  13. symbol led_hot =5
  14. symbol led_hold =4
  15. symbol err = b2
  16. symbol pre_temp =b3
  17. symbol INT_MAX = 1000
  18. symbol PRO_MAX = 15000
  19. symbol DER_MAX = 5000
  20. symbol PID_MAX = 52768
  21. symbol PID_MIN = 12768
  22. symbol PID = w2
  23. symbol x=b4
  24. symbol input_button1= pinc.1




  29. '#########################################################################################

  31. INIT:
  32. set_temp =0
  33. set_time =0
  34. PID = 49000

  36. '#########################################################################################


  39. Main:


  42. do
  43. low oven
  44. low led_hot
  45. low led_hold

  47. if input_button1 = 0 then        'Waits in this loop until button1 is pressed
  48.   exit   
  49. endif  
  50.                
  51. gosub get_temp
  52. gosub Phase_1
  53. gosub get_temp

  55. gosub Phase_2
  56. gosub get_temp

  58. gosub Phase_3
  59. gosub get_temp

  61. gosub Phase_4


  64. low oven

  66. loop

  68. goto main



  72. '#########################################################################################


  75. get_temp:        'Reads thermocouple

  77. readadc10 sensor, cur_temp

  79. return


  82. '#########################################################################################

  84. Phase_1:

  86. set_temp =123 'set temperate at 150°C
  87. set_time =40  'hold 150°C for 40s



  91. if cur_temp < set_temp then
  92. gosub get_temp
  93.   high led_hot
  94.   gosub PID_calc
  95.   gosub PID_control
  96. endif

  98. low led_hot  
  99. for  cur_time=1 to set_time
  100. gosub get_temp
  101.   high led_hold
  102.   gosub PID_calc
  103.   gosub PID_control
  104.   pause 1000
  105. next cur_time

  107. low led_hold



  111. return

  113. '#########################################################################################  

  115. Phase_2:

  117. set_temp =156 'set temperate at 190°C
  118. set_time =10  'hold 190°C for 10s

  120. if cur_temp < set_temp then
  121. gosub get_temp
  122.   high led_hot
  123.   gosub PID_calc
  124.   gosub PID_control
  125. endif

  127. low led_hot  
  128. for  cur_time=1 to set_time
  129. gosub get_temp
  130.   high led_hold
  131.   gosub PID_calc
  132.   gosub PID_control
  133.   pause 1000
  134. next cur_time

  136. low led_hold



  140. return



  144. '#########################################################################################  

  146. Phase_3:

  148. set_temp =201 'set temperate at 245°C
  149. set_time =10  'hold 245°C for 10s

  151. if cur_temp < set_temp then
  152. gosub get_temp
  153.   high led_hot
  154.   gosub PID_calc
  155.   gosub PID_control
  156. endif

  158. low led_hot  
  159. for  cur_time=1 to set_time
  160. gosub get_temp
  161.   high led_hold
  162.   gosub PID_calc
  163.   gosub PID_control
  164.   pause 1000
  165. next cur_time

  167. low led_hold



  171. return


  174. '#########################################################################################  

  176. Phase_4:

  178. set_temp =20 'set temperate at 25°C
  179. set_time =10  'go to 25°C to cool down


  182. if cur_temp => set_temp then
  183. gosub get_temp
  184.   high led_hot
  185.   gosub PID_calc
  186.   gosub PID_control
  187. endif

  189. low led_hot
  190. return

  192. '#########################################################################################  

  194. PID_calc:

  196. gosub get_temp

  198. if PID > 49000 then
  199.         PID = 49000
  200. else
  201.         PID = PID
  202. endif


  205. if cur_temp <= set_temp then        'for negative errors
  206.        
  207.         err = set_temp - cur_temp        max 65         'error
  208.        
  209.         w3 = Ki * err * dt max INT_MAX        'INTEGRAL..........................
  210.         PID = PID + w3 max PID_MAX       
  211.                        
  212.         w3 = Kp * err max PRO_MAX        'PROPORTIONAL......................
  213.         PID = PID + w3 max PID_MAX        'Int + Pro
  214.        
  215. else 'for positive errors

  217.         err = cur_temp - set_temp        max 65        'error
  218.        
  219.         w3 = Ki * err * dt max INT_MAX        'INTEGRAL.........................
  220.         PID = PID - w3 min PID_MIN       
  221.        
  222.         w3 = Kp * err max PRO_MAX        'PROPORTIONAL....................
  223.         PID = PID - w3 min PID_MIN        'Int + Pro
  224.        
  225. endif



  229. 'if cur_temp > err then 'temp increasing
  230.         'w3 = cur_temp - err
  231.         'w3 = w3 * Kd max DER_MAX        'DERIVATIVE ......................
  232.         'PID = PID - w3 min PID_MIN        'int + pro + der
  233. 'elseif cur_temp < err then 'temp decreasing
  234.         'w3 = err - cur_temp
  235.         'w3 = w3 * Kd max DER_MAX        'DERIVATIVE ......................
  236.         'PID = PID + w3 max PID_MAX        'int + pro + der
  237. 'else
  238.         'w3 = 0 'no derivative part
  239. 'endif


  242. 'pre_temp= cur_temp


  245. return

  247. '#########################################################################################  


  250. PID_control:

  252. for x = 1 to 1000                                'Manual PWM with 1 second period (adjust pause at end of main routine to get 1 sec period)
  253.         if x > PID then
  254.                 low oven
  255.         else
  256.                 high oven
  257.         endif
  258.        
  259.         pause 6
  260. next x



  264. pause 54                                        'Adjust to get timing right on PID mode (1 sec PWM period)

  266. return

  268. '#########################################################################################
复制代码
The PID controller seems to be not functioning. The oven will heat to 160°C and the picaxe will exit the program.
Can someone spot any mistake?

Thanks

grimmjaws                                               
作者: robter    时间: 2015-10-22 21:52
感谢楼主提供这么好的东东



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