About Kalman filter

Projects Programming
1 
#include <Wire.h>
#include "Kalman.h"
#include "MPU6050.h"
#include "I2Cdev.h"

Kalman kalmanX, kalmanY, kalmanZ;

MPU6050 accelgyro;

int16_t ax, ay, az, gx, gy, gz;
double accX, accY, accZ, gyroX, gyroY, gyroZ;
double pitch, roll, yaw, AngleX, AngleY, AngleZ, Xrate, Yrate, Zrate;
uint32_t timer;

void setup() {
  Wire.begin();
  Serial.begin(115200);
  
  accelgyro.initialize();
  accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
  
  accX = ax;
  accY = ay;
  accZ = az;
  gyroX = gx;
  gyroY = gy;
  gyroZ = gz;
  
  pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
  roll = atan2(accY, accZ) * RAD_TO_DEG;
  yaw = -atan2(accX, accY) * RAD_TO_DEG;
  
  kalmanX.setAngle(roll);
  kalmanY.setAngle(pitch);
  kalmanZ.setAngle(yaw);
  
  timer = micros();
}

void loop() {
  accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
  
  accX = ax;
  accY = ay;
  accZ = az;
  gyroX = gx;
  gyroY = gy;
  gyroZ = gz;
  
  double dt = (double)(micros() - timer) / 1000000; // Calculate delta time
  timer = micros();
  
  pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
  roll = atan2(accY, accZ) * RAD_TO_DEG;
  yaw = -atan2(accX, accY) * RAD_TO_DEG;
  
  Yrate = gyroY / 131.0; // Convert to deg/s
  Xrate = gyroX / 131.0;
  Zrate = gyroZ / 131.0;
  
  AngleY = kalmanY.getAngle(pitch, Yrate, dt);
  AngleX = kalmanX.getAngle(roll, Xrate, dt);
  AngleZ = kalmanZ.getAngle(yaw, Zrate, dt);
  
  Serial.print(AngleX);
  Serial.print(',');
  Serial.print(AngleY);
  Serial.print(',');
  Serial.println(AngleZ);
}

There was an error during the compilation of the Arduino program.

'kalmanX' does not name a type; did you mean 'Kalman_h'?
I have confirmed that the Kalman library has been imported.

2

Which Kalman library are you using? There are several.

When trying out a new library, it is always a good idea to run the library examples. Make sure that it works as expected, and that you understand how to use the library.

1 Like
3

This error is telling you that the compiler does not recognize the constructor you are using. Sadly, it is a rather indirect message.
The compiler does not know what you are trying to do on that line. So it makes a guess that you are declaring a variable, and that you didn't tell it the type of the variable (e.g int, float, etc). It then takes another stab at it and guesses that you are trying to include a header.

The solution is to look at the header file to see what the correct incantations that are needed are!
According to the first Kalman library that comes up on a search, the class name is KALMAN, and not Kalman. A look at the constructor shows how the name is spelled and that certain parameters are needed.

In addition, as mentioned in the post above, a look at the provided examples is really helpful.

4

This library

5

Where can I find example references?

6

The examples are in the library you linked.

7

I have tried to understand the examples, but I still can't find the reason.

8

Have you studied the theory of Kalman filters? If you have, the library examples are very straightforward. Run the "full" example and see what it does.

9

The full example shows how you could instantiate your objects. Look at this section:

//------------------------------------
/****  MODELIZATION PARAMETERS  ****/
//------------------------------------
.... stuff deleted

KALMAN<Nstate,Nobs> K; // your Kalman filter

You would name yours kalmanX, instead of just K.

10

Do you mean to say this?

#include <Wire.h>
#include "Kalman.h"
#include "MPU6050.h"
#include "I2Cdev.h"

KALMAN<Nstate,Nobs> kalmanX, kalmanY, kalmanZ ;

MPU6050 accelgyro;

int16_t ax, ay, az, gx, gy, gz;
double accX, accY, accZ, gyroX, gyroY, gyroZ;
double pitch, roll, yaw, AngleX, AngleY, AngleZ, Xrate, Yrate, Zrate;
uint32_t timer;

void setup() {
  Wire.begin();
  Serial.begin(115200);
  
  accelgyro.initialize();
  accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
  
  accX = ax;
  accY = ay;
  accZ = az;
  gyroX = gx;
  gyroY = gy;
  gyroZ = gz;
  
  pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
  roll = atan2(accY, accZ) * RAD_TO_DEG;
  yaw = -atan2(accX, accY) * RAD_TO_DEG;
  
  kalmanX.setAngle(roll);
  kalmanY.setAngle(pitch);
  kalmanZ.setAngle(yaw);
  
  timer = micros();
}

void loop() {
  accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
  
  accX = ax;
  accY = ay;
  accZ = az;
  gyroX = gx;
  gyroY = gy;
  gyroZ = gz;
  
  double dt = (double)(micros() - timer) / 1000000; // Calculate delta time
  timer = micros();
  
  pitch = atan(-accX / sqrt(accY * accY + accZ * accZ)) * RAD_TO_DEG;
  roll = atan2(accY, accZ) * RAD_TO_DEG;
  yaw = -atan2(accX, accY) * RAD_TO_DEG;
  
  Yrate = gyroY / 131.0; // Convert to deg/s
  Xrate = gyroX / 131.0;
  Zrate = gyroZ / 131.0;
  
  AngleY = kalmanY.getAngle(pitch, Yrate, dt);
  AngleX = kalmanX.getAngle(roll, Xrate, dt);
  AngleZ = kalmanZ.getAngle(yaw, Zrate, dt);
  
  Serial.print(AngleX);
  Serial.print(',');
  Serial.print(AngleY);
  Serial.print(',');
  Serial.println(AngleZ);
}
11

Yes.
And, of course, you will need to define the number of states and obs before the line that uses them:
e.g
#define Nstate 2

12

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.