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STEERING SYSTEMS


Autonomous platoons of military convoy vehicles expected in the near future will need robust steering systems capable of withstanding harsh and variable conditions.


Military vehicles steer course to autonomy


S


ince military vehicles inevitably encounter many extreme conditions across a lifespan that’s expected to be significant, there is a lot


that could go wrong. Military steering systems must therefore be engineered to operate in such extremes. With autonomy, there are now other


factors to consider in their design, test and validation. The US army aims to have its first Robotic Combat Vehicles Technology demonstrator ready by 2021 and the technology is well on the way to achieving that. Last year saw the joint US-UK Coalition Assured Autonomous Resupply (CAAR) demonstration in Michigan. This ground-breaking convoy involved a truck leading two follower trucks using integrated on-board robotics to make autonomous decisions regarding speed and steering. This demonstrated the potential of taking humans out of the equation in supply delivery.


TESTING FOR ADVERSITY According to Nick Jordan, technical engineering manager at Pailton Engineering, rigorous physical and environmental testing in the steering industry now means steering components can take on the debris, moisture and temperature variation that is faced in service, without resulting in


16 /// Automotive Test & Validation 2018


water ingress or high torque steering. “Once the bespoke steering is in place, the vehicle stands the best possible chance of taking on extreme conditions and rough terrain. Combined with autonomous driving technology, this holds huge opportunities for the US and UK military industry to develop the most reliable and capable autonomous military vehicles in the world,” he says.


COMPREHENSIVE ENVIRONMENTAL TESTING According to Pailton’s Design and Development Engineer, Eric Sonahee, testing of steering systems is primarily about replicating as near to the same conditions that would be encountered on the road. Theoretical testing using calculations is a good start, but nothing gets closer to reality than physical testing. Using an on-site test facility with purpose built test rigs, it is possible to test a subassembly of the entire steering system, presenting the whole structure with like for like conditions that match the final application. Load and Frequency testing: One of the most important parameters to test is the maximum load. With this information, how much force a part can endure, in both tensile and compression, before a failure occurs can be observed. Pailton Engineering has different rigs to test a


range of force applications up to ±400kN. Applying a large force a few times isn’t


❱ ❱ Military vehicles are exposed to


harsh environments that can quickly erode the complex steering systems


representative of the actual conditions a vehicle will encounter during its entire lifetime. Working loads seen in harsh environments can be just as detrimental to a part’s life as the peak loads. It’s therefore necessary to incorporate the two in order to see how different force affects the part dynamically. Environmental Testing: It is vital that every part of the steering system is able to handle water exposure, changes to temperature and humidity variance. Environmental testing therefore includes salt spray exposure and rotary submersion. If a part can endure underwater movement at varying temperatures without corroding or failing, then the vehicle manufacturer can be confident in putting those steering parts into a military vehicle. Low temperature evaluation is also


undertaken to expose issues with the viscosity of the fluid in lubricated components, which can have detrimental effects on steering torque, or even cause parts to lock up entirely.


According to Emma Cygan, Design


and Development Engineer at Pailton Engineering, the environmental testing process for steering systems needs to be bespoke to the vehicle. “For example, a military vehicle used for semi-submersed and wading applications will have different requirements to an armoured vehicle designed for warfare,” she says.


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