Torque and Displacement Measurement with Enhanced Signal Processing for System Lash Estimation of a MDOF Rotating System

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Department of Mechanical Engineering-Engineering Mechanics


Experimental testing for system backlash size relies on speed or displacement measurements of an isolated test apparatus but lack reference to engineered lash tolerances and expected values. These methods are prone to error when the measurement speed is not accounted for and hysteresis impacts the measurement. This study measures backlash on an experimental apparatus to update control model parameters. The results are also confirmed by comparing with analytical part tolerances based on CAE modeling. This is done by comparing three different test methods; output displacement only on a fixed-free apparatus, input torque with measured displacement on a fixed-free apparatus, and in-situ testing with torque and estimated displacement from rotating speed. The torque and displacement techniques recognize the influence of hysteresis and propose signal processing techniques to improve accuracy of the results. This signal processing technique was verified with an analytical model like those tested in the study. The three techniques used were all able to measure results within 31% of the CAE predictions when accounting for manufacturing tolerance. The signal processing method to account for hysteresis was analytically shown to have error less than 8.7% and 4.8% using an input frequency of 24% agreement of CAE projections without the need for a controlled laboratory test environment. These results showed that hysteresis should be accounted for when possible with an updated signal processing technique. The analytical model used to confirm backlash estimates with hysteresis also showed the need for controlled input forcing functions to improve the estimate accuracy. The study also confirms that experimental lash measurements can be collected from in-situ data when torque and displacement estimates are available.

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Experimental Techniques