Effects on Motorcycle Dynamics Data Using Wheel Force Transducer Systems

Wheel Force Transducers (WFT) are precise and accurate measurement devices that seamlessly integrate into any vehicle. They can be applied in numerous vehicle applications for both on-road and in laboratory settings. The instrumentation requires replacing an OEM wheel with a custom WFT system which is specific to the wheel hub design. An ideal design will minimally impact a vehicle's dynamics, but the vehicle system is inherently modified to some extent from the weight of the measurement device. Research and technical documentation have been published which provide conclusions that reducing the unsprung mass reduces dynamic wheel load. However, there doesn’t appear to be clear compensation techniques for how a modified unsprung mass can be related to the original system, thus allowing the WFT signals to be more accurate to the OEM wheel forces. An experimental study was performed on a prototype motorcycle to better understand these differences. An instrumented “impact bump” acting as a force transducer was designed particularly for this testing to assist in characterizing the dynamic response of a vehicle with variable unsprung mass setups. The motorcycle was equipped with WFT for measured reacted forces, tri-axial accelerometers for vibration, and linear variable differential transducers (LVDTs) for fork and shock travel, and vehicle speed. The test variables included modifying the unsprung mass of the motorcycle’s front wheel by using OEM wheels, WFT wheels, rim masses, hub masses, the speed of impact, and the motorcycle suspension setup. There is great consideration to the time domain and frequency domain for these changes in the system dynamic responses. The measured quantities are analyzed to ensure confidence in a correlated model. In this paper, we calculate and discuss compensation techniques to be applied to motorcycles for the mass added from using WFT systems.