For a development project we needed the speed of an agricultural vehicle with a sampling frequency of at least 20 Hz. There are different possibilities for this; Radar sensors or encoders can be integrated into the vehicle with appropriate effort. We finally decided on a GPS receiver (or GNSS receiver) with an IMU (Inertial Measurement Unit: three-axis gyro and acceleration sensors) and an integrated Kalman filter. We came across the 3DM-GX5-45 from LORD, which includes all of these functions.
The built-in GNSS receiver updates the position or speed value at 4 Hz. However, this update frequency is too low for the specific measurement application, for example to analyze the braking behavior of the vehicle. This is why the acceleration or gyro sensors placed in the x, y and z directions are used, which are sampled at 1 kHz and are available to the Kalman filter in addition to the GNSS signal. The Kalman filter thus determines the position and speed of the vehicle, which is available at the output of the 3DM-GX5-45 at 100 Hz.
The 3DM-GX5-45 was integrated into a measurement and evaluation system using the PLCnext Control AXC F 3152 PLC from Phoenix Contact. The evaluation tool for all and additional measured values was programmed with LabVIEW. Various test drives with passenger vehicles and an agricultural vehicle show plausible speed data, whereby the correct settings of the 3DM-GX5-45 and correct handling are crucial.