| 摘要 |
An off-the-car wheel unbalance measuring system has a rotationally driven wheel mounting shaft supported in a pedestal together with a pair of force transducers mounted in the pedestal adjacent to and spaced along the shaft. The force transducers are coupled mechanically to the shaft and provide periodic electrical output signals indicative of unbalance forces transmitted through the shaft when the shaft is driven rotationally. The angular position of the shaft is monitored with respect to an angular reference position at a predetermined number of angular increments during each full revolution of the shaft. The transducer output signals are converted in electrical circuitry within the system to digital form, and a multiplication operation is performed on the digitized signals at each angular increment using sine and cosine representative factors corresponding to that particular angular increment. The sine and cosine factors are stored in memory and are called up from storage in accordance with the monitored angular position of the shaft. The system circuitry operates to sum the digitized signals including sine and cosine factors thereby providing operating data from which unbalance force magnitude and angular position is calculated. Operation of the system while a known unbalance is mounted on the shaft and also while the shaft is running free provides data from which calibration constants for the system are calculated and thereafter applied to the operating data to correct unbalance measurements for shaft unbalance and transducer idiosyncrasies.
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