Distance measured with IMU

[theonetruthseer]

Hi,
We are trying to create an Inertial Navigation System . For this, we wish to use a HB100 doppler as DVL to reduce error and an IMU for orientation and cross checking of data. So far, we have not integrated the HB100, and have only used the IMU.

We would like some help with how to use the HB100 for speed sensing, with respect to ground. The datasheet of the HB100 is given below
http://www.limpkin.fr/public/HB100/HB100_Microwave_Sensor_Module_Datasheet.pdf

On the other hand, we have used the IMU to at least get a general view of the distance traveled and orientation. For this, we have used the code below, but the results are unsatisfactory

// I2C device class (I2Cdev) demonstration Arduino sketch for MPU9150
// 1/4/2013 original by Jeff Rowberg <jeff@rowberg.net> at https://github.com/jrowberg/i2cdevlib
//          modified by Aaron Weiss <aaron@sparkfun.com>
//
// Changelog:
//     2011-10-07 - initial release
//     2013-1-4 - added raw magnetometer output

/* ============================================
I2Cdev device library code is placed under the MIT license

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of this software and associated documentation files (the "Software"), to deal
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// Arduino Wire library is required if I2Cdev I2CDEV_ARDUINO_WIRE implementation
// is used in I2Cdev.h
#include "Wire.h"

// I2Cdev and MPU6050 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"
#include "MPU6050.h"

// class default I2C address is 0x68
// specific I2C addresses may be passed as a parameter here
// AD0 low = 0x68 (default for InvenSense evaluation board)
// AD0 high = 0x69
MPU6050 accelgyro;
unsigned long prev=0;
int16_t ax, ay, az;
int16_t gx, gy, gz;
int16_t mx, my, mz;
float gyy=0;
float bx,by,bz;
float cx,cy,cz;
float dx,dy,dz;
float s, lv;
float sy, lvy, sz, lvz;
float ac, chax=0;
float chay=0;
float chaz=0;
float cherror;
int count=0;
float inv=0, invy=0, invz=0;
#define LED_PIN 13
bool blinkState = false;
unsigned long previousMillis = 0;
void setup() {
    // join I2C bus (I2Cdev library doesn't do this automatically)
    Wire.begin();

    // initialize serial communication
    // (38400 chosen because it works as well at 8MHz as it does at 16MHz, but
    // it's really up to you depending on your project)
    Serial.begin(115200);

    // initialize device
    Serial.println("Initializing I2C devices...");
    accelgyro.initialize();

    // verify connection
    Serial.println("Testing device connections...");
    Serial.println(accelgyro.testConnection() ? "MPU6050 connection successful" : "MPU6050 connection failed");
     for(int i=0;i<20;i++)
     {
     accelgyro.getMotion9(&ax, &ay, &az, &gx, &gy, &gz, &mx, &my, &mz);
     chax=chax+ax;
     chay=chay+ay;
     chaz=chaz+az;
     }
     
     chax=(float)chax/32768;
   
     
     chay=(float)chay/32768;
     
   
     chaz=(float)chaz/32768;
     
     Serial.println("New Chax");
     Serial.print(chax);
     

    // configure Arduino LED for
    pinMode(LED_PIN, OUTPUT);
}

void loop() {
    // read raw accel/gyro measurements from device
   
   
    count=count+1;
 
    accelgyro.getMotion9(&ax, &ay, &az, &gx, &gy, &gz, &mx, &my, &mz);
     
    bx=(float)ax/(1638.4);
    by=(float)ay/(1638.4);
    bz=(float)az/(1638.4);
    float pitch = atan(bx/sqrt(pow(by,2) + pow(bz,2)));
float roll = atan(by/sqrt(pow(bx,2) + pow(bz,2)));
pitch = pitch * (180.0/PI);
roll = roll * (180.0/PI);
float yawRaw=atan2( (-my*cos(roll) + mz*sin(roll) ) , (mx*cos(pitch) + my*sin(pitch)*sin(roll)+ mz*sin(pitch)*cos(roll)) ) *180/PI;
float YawU=atan2(-my, mx) *180/PI;
    bx=bx-chax;
    by=by-chay;
    bz=bz-chaz;
    cx=gx/65.5;
    cy=gy/65.5;
    cz=gz/65.5;

     
    //Motion in one simple direction, let y=0.
    unsigned long currentMillis =  millis(); //record time of new reading
   float interval = float((float(currentMillis) - float(previousMillis))/1000) ;  //Time of previous reading-Time of Current reading= Interval
if(bx>0.03||bx<(-0.03))
{
    ac=bx*interval; //acceleration x time=velocity
    lv=inv;        // initial velocity=lv, final velocity=inv
    inv=inv+ac;    // vf =vi+1t;
    s=s+(lv*interval)+0.5*ac*interval; // Distance= Previous Distance + Vit + 1/2 x a x t^2
   
}

if(by>0.02||by<(-0.02)){
    ac=by*interval;
    lvy=invy;
    invy=invy+ac;
   
    sy=sy+(lvy*interval)+0.5*ac*interval;
}

if(bz>0.03||bz<(-0.03))
{
    ac=bz*interval;
   
    lvz=invz;
    invz=invz+ac;
   
    sz=sz+(lvz*interval)+0.5*ac*interval;
}


   
   
   Serial.print("\n");
     Serial.print((s*100)); //PRINT
    Serial.print("      ");
    Serial.print((sy*100));
     Serial.print("      ");
    Serial.print((sz*100));
    Serial.print("       ");
    Serial.print(interval);
     Serial.print("       ");
Serial.print(pitch);
 Serial.print("       ");
Serial.print(YawU);
 Serial.print("       ");
Serial.println(roll);

    //Serial.print("      ");
  //   Serial.print(interval,10);
     
     
    previousMillis=millis(); //record current time
   
    // blink LED to indicate activity
    blinkState = !blinkState;
    digitalWrite(LED_PIN, blinkState);
}

Can anyone help us with integrating the DVL, and also finding a more error free way of finding the orientation of the IMU quickly, as we wish to complete it in the next week?

 

We are also having problems with running and accessing the DMP? Could you please help us with this as well. ANY GUIDANCE WILL BE APPRECIATED!

[Guillermo]

You need a magnetometer for direction and Will improve. the acceleremeter is given the gravitty component and the movement increase the value. You can not use the value as it is.

I am trying to do the same and have to switch the MPU 9150 wich has 3 accelerometers, 3 gyroscope and magnetomer 3 axes