The easiest and the most accurate method of mounting the IMU is by using the integral GPS antenna and IMU roof mount. The VBOX IMU roof-mounting option allows for an IMU04 to be placed directly on the vehicle roof, co-located with the GPS antenna.
The IMU is securely fastened within the machined enclosure which has a magnetic base to ensure that it stays safely in place. The antenna is placed directly above the IMU, ensuring that the data sources are being measured at the same point.
Co-locating the antenna and IMU greatly improves the performance of the Kalman filter. By putting the two together and mounting them on the vehicle’s roof there is no requirement to measure the distance between them as you do in a standard setup, and it is easier to install. With the GPS and inertial data sources coming from the same point, this critical measurement is no longer needed, leaving only the required translation to – typically – the vehicle’s centre of gravity. This method is easier and isn’t prone to human measurement error.
See datasheet for RLACS216 here.
If roof-mounted IMU is not possible the IMU can be fixed inside the vehicle. A flexible way to fix the IMU rigidly within the vehicle is by using the Racelogic mounting arm. The three-part telescopic handle is fully adjustable to any length between 70 and 150 cm to which another 20 cm can be added by extending a third section using the compression lever.
Both ends are fixed to an 8x13cm plate which sits on a joint to accommodate for uneven surfaces. Pressed against the IMU on the floor and the vehicle's ceiling, the mounting prop ensures that the IMU is fixed tightly.
It is possible to fix the IMU firmly to the body of the vehicle. Make sure it is mounted in the direction of travel - as shown in the image below. It is also important to mount the sensor so that it is level with the ground.
For best results, mount the IMU and GPS antenna as close to each other as possible. For example: Bolt the IMU to the seat rails and place the GPS antenna on the roof directly above.
If you are using an IMU04 or IMU03, you must measure the relative position of the antenna in relation to the IMU to within +/- 5cm. These distances must then be entered into the VBOX either via VBOX Tools > VBOX Setup or using a VBOX Manager.