Design and implementation of ultrasound based lubrication film measurement in a fluid power motor
Student thesis: Master Thesis and HD Thesis
- Jens Rendbæk
- Lasse Almind Jensen
4. term, Electro-Mechanical System Design, Master (Master Programme)
This master thesis treats how an ultrasonic transducer should be mounted in a Calzoni fluid power motor for measurements of lubrication film thickness. The post-processing methods required to obtain an estimation of the film thickness are investigated.
To mount a transducer inside the motor a complete 3D CAD model of the Calzoni motor is created. Using the model, potential mounting locations are discovered and the transducers acoustic and dimensional specifications at each location are found. These specification are found using acoustic wave propagation theory and constraints set by the 3D CAD model.
The mounting method used to attach the transducer is found by creating a series of different solutions. It was found that glueing the transducer to the mounting surface and encasing it using an epoxy cast, provided the best solution.
Several methods for lubrication film thickness estimation are investigated.The domain of measurable lubrication film thicknesses of the spring method, direct method, resonance method and cross-correlation method are investigated and found. To estimate the reflection coefficient of an embedded layer from experimental data the Empirical Transfer Functions Estimate (ETFE) is used. The accuracy of the ETFE is investigated and the presence of resonance is discovered to cause incorrect estimations. Noise robustness of the lubrication film thickness estimation methods are also investigated and they are found to be robust down to a signal to noise ratio of 40dB. A linear regression model is also used to estimate the incident wave from reflections of a lubrication film layer using Least Square Estimation (LSE). The accuracy of the estimations are found to deteriorate as resonance becomes observable in the reflected waves used for estimation.
A transducer is mounted in the Calzoni motor using the proposed mounting solution and a test bench is created. Using this test bench a series of fluid film measurements are obtained from experiments while running the motor at a fixed rotational speed and the behaviour of the fluid film is observed.
To mount a transducer inside the motor a complete 3D CAD model of the Calzoni motor is created. Using the model, potential mounting locations are discovered and the transducers acoustic and dimensional specifications at each location are found. These specification are found using acoustic wave propagation theory and constraints set by the 3D CAD model.
The mounting method used to attach the transducer is found by creating a series of different solutions. It was found that glueing the transducer to the mounting surface and encasing it using an epoxy cast, provided the best solution.
Several methods for lubrication film thickness estimation are investigated.The domain of measurable lubrication film thicknesses of the spring method, direct method, resonance method and cross-correlation method are investigated and found. To estimate the reflection coefficient of an embedded layer from experimental data the Empirical Transfer Functions Estimate (ETFE) is used. The accuracy of the ETFE is investigated and the presence of resonance is discovered to cause incorrect estimations. Noise robustness of the lubrication film thickness estimation methods are also investigated and they are found to be robust down to a signal to noise ratio of 40dB. A linear regression model is also used to estimate the incident wave from reflections of a lubrication film layer using Least Square Estimation (LSE). The accuracy of the estimations are found to deteriorate as resonance becomes observable in the reflected waves used for estimation.
A transducer is mounted in the Calzoni motor using the proposed mounting solution and a test bench is created. Using this test bench a series of fluid film measurements are obtained from experiments while running the motor at a fixed rotational speed and the behaviour of the fluid film is observed.
| Language | English |
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| Publication date | 8 Jun 2017 |
| Number of pages | 107 |
| Keywords | Fluid film, Least square estimation, Ultrasound, Cross-correlation, Acoustic, Fluid power motor, Wave propagation, Ultrasonic transducer |
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