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I am making an application that is used to measure the velocity, it has an accelerometer that measures the component acceleration in the XYZ-axis. When the car is moving just straight the measurement is ok, as only linear components are involved.

My doubt came when the car is on a curve, I am not sure if the accelerometer can measure correctly in such situation or if it is necessary to apply a gyroscope to measure any missing component.

The code snippet for measure the total acceleration is shown below, I measure the acceleration in each axis and I remove the gravitational to finally calculate the velocity and the speed

    float AccTotal_X = ((AcX - grav_X)*9.81);
    float AccTotal_Y = ((AcY - grav_Y)*9.81);
    float AccTotal_Z = ((AcZ - grav_Z)*9.81);

float Vx = vx_0 + AccTotal_X*dt;
vx_0 = Vx;
float Vy = vy_0 + AccTotal_Y*dt;
vy_0 = Vy;
float Vz = vz_0 + AccTotal_Z*dt;
vz_0 = Vz;

speed_dt = sqrt(pow(Vx,2)+pow(Vy,2)+pow(Vz,2))*3.6;
Geisterfahrer
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1 Answers1

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I found out the answer to the question in the following article SenSpeed: Sensing Driving Conditions to Estimate Vehicle Speed in Urban Environments

According to the article

When a vehicle makes a turn, it experiences a centripetal force, which is related to its speed, angular speed and turning radius. Thus, by utilizing the accelerometer and the gyroscope, we can derive the tangential speed of a vehicle.

Therefore, just with the accelerometer is not possible to measure the velocity when an object is making a turn, it is necessary a gyroscope also.

The equation to measure the tangential velocity is:

v = Rω (1),

Where v is the tangential speed, R the radius of the curve and ω the angular speed.

As the centripetal acceleration is given by a = ω²R (2), reformulating (2) and substituting in (1), it is obtained:

v = a/ω (3).

Both a and ω are given by the accelerometer and the gyroscope respectively.

Geisterfahrer
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