The advantages of a fully automated computer controlled force and moment operational procedure are reduced manpower requirements, increased machine efficiency and improved repeatability and precision in obtaining data. These advantages are especially important when considering the needs of the automobile manufacturers.
Existing apparatus and test procedures at Firestone for determining cornering force, self-aligning torque and rolling resistance have been additionally mechanized through computer usage along with a complex hydraulic control system. These enhancements have sharply improved the control operation and, of course, collection and reduction of the data.
A test that may consist of a tire warm-up and a series of wheel loads and slip angles is well suited to automation. The computer used has a mass storage device which is capable of keeping the various routine procedures on file for quick recall, also the accurate control logic permits the setting of close tolerances for both time and operational conditions. Another advantage for this system is the ability to repeat a procedure without changing the operational sequence.
Data collection through the high speed acquisition system allows for the sampling of sufficient data to give a time averaged value. The use of the time average technique to obtain data is like using a filter that effectively reduces electrical noise and machine vibrations.
Upon completion of the operational function of the force and moment apparatus, the data are analyzed. A polynomial surface analysis is used to obtain cornering force and self-aligning torque as a function of tire load and slip angle. These results can be displayed in tabular and/or graphical form.