Revision 0:4cf5365df85c, committed 2018-03-20

Comitter:

KDrainEE

Date:

Tue Mar 20 13:55:46 2018 +0000

Commit message:

Working PI control

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Mar 20 13:55:46 2018 +0000
@@ -0,0 +1,106 @@
+#include "mbed.h"
+#include <iostream>
+
+using namespace std;
+
+//constants
+const float scalar = 0.6;
+
+//ticker to compute output
+Ticker sample;
+
+//System IO
+AnalogIn setPoint(PTB0);
+AnalogIn speed(PTB2);
+PwmOut gateDrive(PTB1);
+
+//moving average filter
+float* samples;
+
+//PI controller
+double Input, Output, Setpoint;
+double errSum;
+double ITerm;
+double kp, ki;
+
+//saturation limits
+double outMin;
+double outMax;
+
+
+double sampling_frequency;
+double ti;
+
+void set_tunings(double KP, double KI)
+{
+    kp = KP;
+    ki = KI;
+}
+
+
+/*
+Length 8 moving average filter for noisy inputs
+*/
+float filter_input(AnalogIn input)
+{  
+    int filterLength = 8;
+   for(int i = filterLength -1; i > 0; i--)
+   {
+      samples[i] = samples[i-1]; 
+   }
+   samples[0] = input.read();
+   float sum = 0.0;
+   for(int j = 0; j < filterLength; j++)
+   {
+       sum += samples[j];
+   }
+   return sum/filterLength;   
+}
+
+void update_states()
+{
+    Input = speed.read();
+    Setpoint = filter_input(setPoint);
+//    Setpoint = setPoint.read();
+//   test step response
+//  Setpoint = 1/3.3;
+}
+
+void compute()
+{
+    //proportional
+    double error = Setpoint-Input;
+    
+    //integral
+    errSum +=(error * ti);//potentially the problem
+    ITerm = ki*errSum;
+    if(ITerm > outMax) ITerm = outMax;
+    if(ITerm < outMin) ITerm = outMin; 
+    
+    //compute output
+    Output = kp*error + ITerm;
+    if(Output > outMax) Output = outMax;
+    if(Output < outMin) Output = outMin;    
+}
+
+int main()
+{
+   outMin = 0.0;
+   outMax = 1.0;
+   
+   sampling_frequency = 1e3;
+   ti = 1/sampling_frequency;
+   
+   set_tunings(0.1414,19.7408);//Kp, Ki
+   
+   samples = new float[8];
+   
+   sample.attach(&compute, ti);
+   
+   while(true)
+   {
+    update_states();
+    gateDrive = scalar*Output;
+   }
+   
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Tue Mar 20 13:55:46 2018 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/users/mbed_official/code/mbed/builds/aa5281ff4a02
\ No newline at end of file