HVE Vehicle Accelerometers: Validation and Sensitivity

An understanding of the acceleration experienced at various seating positions in a vehicle is important for predicting occupant dynamics during an event. In most accident reconstructions there may not be an opportunity to instrument the accident vehicle with accelerometers and perform tests at the accident site. Therefore, it is desirable to simulate accelerometers using HVE and when doing so it is important to know that the output data is valid. The output data is highly dependent on the input parameters and an understanding of how the available input parameters affect the output data is important. This paper compares the results of physical tests and SIMON simulations over two different sizes of flat-top speed bumps at targeted speeds of 10 km/h and 20 km/h. In addition, three different accelerometer positions were used in the physical testing and the SIMON simulations. The vehicle used in both physical and virtual testing was a 2007 Ford Focus SE hatchback. The methods by which the input and output parameters were measured for each condition are described. Results showed the same characteristic z-axis acceleration pulse in both real and virtual accelerometers, and that associations between them are achievable. For the x and y axes we found that the magnitude of the acceleration was typically below the level of noise from the real-world accelerometer, and therefore no meaningful associations were possible. When considering the test runs in the z-axis with strong-moderate associations, general trends showed good consistency between physical and simulated data for the initial traversing of each axle over the speed bump, and worse consistency for when each axle was near the trailing edge of the speed bump. When considering biomechanical analysis, the simulation should not be used as a sole source for quantifying the magnitude of vibrational acceleration applied to occupants as they travel over speed bumps; however the characteristic pulse shows the general pattern of the applied acceleration. Based on the trends observed in this study, future testing and development should be done before using data from simulated accelerometers that are remote from the CM.