I am hooking up an accelerometer to an arduino uno and running it through this pid controller. However the output isnt going to my setpoint. When i move the accelerometer back and forth the data goes to 255 or 0. Any ideas?
Datasheet for accelerometer: https://www.sparkfun.com/datasheets/Components/SMD/adxl335.pdf
I get 336 for the x direction, which is the only direction i'm using, when its set flat on the table, which is my setpoint/desired output.
Note: Is the output the value away from the setpoint or the actual acceleration it calculates through the controller?
#include <PID_v1.h>
#define PIN_INPUT A0
//Define Variables we'll be connecting to
double Setpoint, Input, Output;
//Define the aggressive and conservative Tuning Parameters
double aggKp=4, aggKi=0.2, aggKd=1;
double consKp=1, consKi=0.05, consKd=0.25;
//Specify the links and initial tuning parameters
PID myPID(&Input, &Output, &Setpoint, consKp, consKi, consKd, DIRECT);
void setup()
{
//initialize the variables we're linked to
Serial.begin(9600); //Start a serial session
int xdata = analogRead(PIN_INPUT);
Input = map(xdata, 0, 1024, 0, 255); //Change read scale to analog out scale
int setPoint = 336;
Setpoint = map(setPoint, 0, 1024, 0, 255); //Change read scale to analog out
//turn the PID on
myPID.SetMode(AUTOMATIC);
}
void loop()
{
int xdata = analogRead(PIN_INPUT);
Input = map(xdata, 0, 1024, 0, 255); //Change read scale to analog out scale
double gap = abs(Setpoint-Input); //distance away from setpoint
if (gap < 10)
{ //we're close to setpoint, use conservative tuning parameters
myPID.SetTunings(consKp, consKi, consKd);
}
else
{
//we're far from setpoint, use aggressive tuning parameters
myPID.SetTunings(aggKp, aggKi, aggKd);
}
myPID.Compute();
Serial.print("Setpoint = ");
Serial.print(Setpoint);
Serial.print(" Input = ");
Serial.print(Input);
Serial.print(" Output = ");
Serial.print(Output);
Serial.print("\n");
// analogWrite(PIN_OUTPUT, Output);
}
OUTPUT:
Setpoint = 83.00 Input = 87.00 Output = 0.00
Setpoint = 83.00 Input = 81.00 Output = 0.00
Setpoint = 83.00 Input = 64.00 Output = 255.00
Setpoint = 83.00 Input = 64.00 Output = 255.00
Setpoint = 83.00 Input = 68.00 Output = 255.00
Setpoint = 83.00 Input = 79.00 Output = 0.00
Setpoint = 83.00 Input = 91.00 Output = 0.00
Setpoint = 83.00 Input = 96.00 Output = 0.00
Setpoint = 83.00 Input = 99.00 Output = 0.00
Setpoint = 83.00 Input = 88.00 Output = 0.00
Setpoint = 83.00 Input = 68.00 Output = 0.00
Setpoint = 83.00 Input = 58.00 Output = 255.00
Setpoint = 83.00 Input = 64.00 Output = 255.00
Setpoint = 83.00 Input = 78.00 Output = 255.00
Setpoint = 83.00 Input = 95.00 Output = 0.00
Setpoint = 83.00 Input = 97.00 Output = 0.00
Setpoint = 83.00 Input = 95.00 Output = 0.00
