Vehicle safety and crash worthiness tests are vital to regulatory bodies around the world and subsequently the automotive and commercial vehicle industries. New vehicle designs and restraints are continually under development, and each new commercial product needs to be evaluated with respect to standards, regulations, or claimed occurrences.
After decades of scientific endeavor, transportation safety testing has evolved to become an indispensable component in the occupant protection process. Despite these years of evolution, all safety tests and specifically roll-over testing have inherent issues that diminish its practicality and usefulness.
Most methods of roll-over testing result in a destroyed or severely disabled vehicle. This type of destructive evaluation can get extremely expensive, especially when multiple runs are required. Any additional equipment attached to a test vehicle (cameras, Anthropomorphic Test Devices, etc.) is also at risk of needing repair or replacement upon completion of a single run. Outriggers are sometimes affixed to the sides of a vehicle to prevent a complete roll-over, but these types of tests rarely show the full picture.
Time is also a limiting factor. Many hours are devoted to preparing a vehicle to be tested, cleaning up the resulting mess, and readying the next run. Most roll-over tests are performed outdoors so hours of daylight and risk of inclement weather substantially decrease the number of tests that can be executed in one day.
Finally, any fair scientific experiment must be repeatable. Repeatability, even with provided specific input parameters, is unlikely under the current methods of evaluation. Human factors, road conditions, and slight differences between vehicles are all variables that can be responsible for needlessly shifting data points.
A void exists for a facility that can evaluate occupant restraint performance in a roll-over event in a quick, accurate, repeatable, and controllable manner without causing damage to the vehicles being tested. S-E-A’s Vehicle Dynamics Group and Biomechanics Group have created a device to fill this need.
The S-E-A Roll Simulator is an indoor facility that enables the precise control of both linear and rotational motion along a fixed linear track. Vehicles, occupant compartments, or other commercial products can be mounted in almost any orientation on the Roll Simulator test platform.
Anthropomorphic Test Devices (ATD) are then instrumented with sensors throughout their bodies and are placed within the occupant or operator’s space and secured with the occupant restraints being evaluated. An acceleration profile is prescribed—derived through accident reconstruction, computer simulation, or autonomous vehicle testing—and then executed through in-house developed software and control systems.
Simultaneously, the desired roll motion can be entered and executed through a parallel software and control system, also developed by S-E-A. Documenting the entire test are a combination of high-speed video cameras, a motion capture system, vehicle and test platform onboard sensors, and ATD sensors.
An impact attenuation surface preserves the vehicle being evaluated as well as the ATD, thus allowing the operators to continue using the same equipment during subsequent runs. This also limits the variability and time between tests.
Typical methods of vehicle roll-over testing generally permit only a few runs on any given day and, more often than not, necessitate the use of multiple vehicles. The S-E-A Roll Simulator can perform and evaluate many times that number of tests given the same span of time.
Through a careful and dedicated design process, S-E-A’s engineers were able to establish a unique delivery system that can be used for a multitude of vehicles and a variety of simulated events not currently able to be performed with control, accuracy, and repeatability. Two current Roll Simulator setups demonstrate the utility and robustness of this system.
A recreational off-highway vehicle (ROV) roll-over setup is being utilized as part of contract testing with leading manufacturers as well as part of an ongoing effort to support a regulatory investigation into this product market. The ROV roll-over system simulates both untripped and tripped real-world 90° rollovers using the actual ROVs on the Roll Simulator. Multiple days of parametric tests have been completed, collecting data to allow evaluation of occupant kinematics with respect to current as well as alternative occupant restraint designs.
Another setup involves a low roll angle application for common material handling equipment with protocols being developed with a leading material handling equipment manufacturer. This setup provides the initial roll dynamics for such equipment and allows the researchers to evaluate operator responses and operator compartment design in a safe, repeatable, and scientifically valid manner.
S-E-A is currently using the capabilities of the Roll Simulator to evaluate occupant response and protection in a variety of products for development, regulatory compliance, and litigative matters. They will continue to utilize the Roll Simulator for ROV testing while adding additional test protocols to this setup based on real-world events and full scale testing. Development is an ongoing process as S-E-A identifies the material handling equipment low roll angle test protocols along with new test setups.
Looking toward the future, some of the additional setups their engineers are currently evaluating include passenger vehicle minor impacts, passenger vehicle bumper impact performance, lawn equipment roll-overs, agricultural equipment roll-overs, and construction equipment roll-overs.
The use of this technology to evaluate occupant protection and occupant restraint performance is part of an ongoing effort to mitigate the risk to S-E-A’s clients. The Roll Simulator’s availability to S-E-A investigators and scientific experts supports efforts to reveal the cause and enhances the current capabilities both at S-E-A and industry-wide.
This article was written for SAE Off-Highway Engineering by Doug Morr, Senior Project Engineer, S-E-A.