How Ford Europe keeps an eye on wheel dynamics
25 June 2013
Ford Europe commits many man hours to acquiring data from prototype test vehicles at its test track at Lommel in Belgium and, during the past 13 years, much of its Road Load Data (RLD) has been derived using Kistler RoaDyn wheel force sensors over a wide variety of road surfaces.
Ford has now upgraded its test capability with the purchase of ten of the latest Kistler RoaDyn measuring wheels and a set for use on test lab based vehicle simulators to ensure correlation between road and lab, a total investment of approximately €1m. The modular design of the Kistler RoaDyn Wheel Force Sensors enables Ford to test an extensive range of vehicles with wheel sizes from 15in to 19in.
The RoaDyn system is used on prototype vehicles being subject to total vehicle durability testing on a wide variety of road surfaces, from handling tracks to cobblestones and large potholes.
The data from the wheel force sensors are used to predict the durability performance of vehicle chassis and body using CAE tools and also in the laboratory to provide load data to be applied to single suspension components and complete subassemblies, the objective being to combine minimum component weight with maximum durability to reduce total unsprung weight for best suspension performance.
Each RoaDyn wheel uses a number of three component strain gauge sensors to provide data that are used to precisely calculate the forces and moments acting on the rotating wheel. The high measuring accuracy of the precision load cells is retained during transmission as digitisation takes place on the wheel to eliminate transmission interference from brake heat, movement, vibration and so on.
The measurement of individual values with separate load cells also leads to an improvement in the inter-channel crosstalk. As the original load cell signals are known, rapid error diagnostics is possible. Maintaining the system is simply a matter of replacing individual load cells, the overall quality of the sensor being preserved.
RoaDyn comes either as aluminium or carbon fibre reinforced (CFR) wheel rims, depending on wheel size and vehicle load. During test, the measuring wheel replaces the standard wheel and must be as strong as the latter without affecting the kinematics or the handling of the vehicle. CFR proves much closer to the weight of the standard wheel than aluminium or steel and has minimal effect on the kinematics or the handling of the test vehicle.
In the time that Kistler has been supplying this equipment to Ford, its range of vehicle test solutions has been expanded to include Corrivit optical speed and slip sensors, wheel vector systems and laser ride height sensors, which give the automotive industry a complete vehicle dynamics and durability testing combination.
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