PSI - Issue 77

Francisco Castro et al. / Procedia Structural Integrity 77 (2026) 611–630 Francisco Castro/ Structural Integrity Procedia 00 (2026) 000 – 000

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2.2.3. In motion setup To estimate the CoG height position in motion, two methods were previously estimated for longitudinal motion – equation (11) – and for cornering motion – equation (17) . As mentioned before, some characteristics of the vehicle are necessary to directly measure previously to the experimental tests, such as the vehicle dimensions (wheelbase and width ) , the suspension spring stiffness ( and ), and the vehicle mass ( ℎ ) and its distribution for both axles for the estimation of the CoG longitudinal position. It’s important to note again that the CoG height is a key vehicle parameter which changes with the load and can’t be acquired directly, despite its importance in vehicle safety. Thus, the parameters that need to be measured continuously in order to estimate the CoG height position, are essentially, • Accelerations (for the longitudinal and lateral motion); • Vehicle’s pitch angle (for longitudinal motion); • Roll angle (for cornering motion). It’s important to note that, in regular vehicles , all this parameters needed to estimate the CoG height according to the model developed, which can be obtained directly from the sensors already installed on the vehicles. Although, as already mentioned, the vehicle selected to perform the in-motion road tests doesn´t have any integrated sensor since, given it is a prototype vehicle, thus requiring instrumentation onboard the vehicle. To estimate the pitch angle and the roll angle , a precision angle meter gauge with data transmission in dynamic regime will be used. This parameter can also be measured using a displacement sensor. To estimate the acceleration during braking (longitudinal motion) and the acceleration (cornering motion) an accelerometer will be used. It’s important to note that th ese parameters could also be measured by wheel speed sensors, and the velocity and turn radius (cornering motion tests) by using a GPS unit system. In order to surpass these measurements during the road tests, the following Inertial Measurement Unit (IMU) was selected and installed on the vehicle (Figure 6). The IMU will be used to measure, at each time step, the accelerations, the angular velocities and the angles in the 3 axes. The data from the IMU uses a Kalman filter to present the results and is transmitted by Bluetooth.

Figure 6 – IMU installed on the vehicle (Witmotion WT901BLECL AHRS IMU). The protype vehicle was equipped with an IMU equipment – Witmotion WT901BLECL AHRS IMU (see Figure 3), which measures the acceleration, the angular velocity and the angles in the three cartesian orthogonal axes (x, y, z). The x direction of the equipment is coincident with the direction of movement. The sampling frequency used for data acquisition was 200 Hz. The IMU equipment was installed approximately 0.045 mm behind the frontal axle centre and approximately 0.115 mm from the tire face (see Figure 3). Due to the small dimension of the prototype vehicle, the road tests were conducted in a controlled area with on a smooth surface, with the objective of reducing the influence of the road on the motion state. The algorithm was developed using MATLAB ® .