Page - 25 - in Proceedings of the OAGM&ARW Joint Workshop - Vision, Automation and Robotics

B. Frequency detection At the beginning of this project the bought-in tuning device TLA CTS-32-C [8] was used for pitch detection. It communicates with the software part over an USB-Interface and was especially developed for organ builders and their needs. Because of the high price of the tuning device, an own solution for detecting the frequency was developed. Using a variable bandpass filter, it is possible to extract a sinusoidal wave with the fundamental frequency of the pipe from a complex audio signal, which is recorded by a microphone. Through detecting the zero-crossing-rate of this sinus the pitch of the pipe can be calculated directly, using an Arduino platform for this purpose in prototype stage. C. Software For calculating the required movements of the motors from the frequency measurement, appropriate software was developed inC#.Forcontrolling the tuningsystemin thepro- totypingphaseagraphicaluser interface (GUI)wasdesigned. The tuning device and the electronics (described in the following section) are connected via USB to the computer, on which the software is executed. On the GUI the current divergence to nominal frequency is charted in real-time. The motors are not driven continuously, but stepwise. The length of the switched-on pulses depends on the divergence to nominal frequency of the pipe, followed by a stop until the next pulse length is calculated. This stepwise mode is needed because of the very high sensibility of the reed. At the smallest pipes a one micrometer motion of the tuning spring results in 0.5 cents deviation of pitch. D. Electronics To transform the calculated pulses from the software into voltage for the motors, drive electronics and an appropriate logicunit areneeded.Therefore, anArduinoboardwith three motor shields (extension boards) was used. Each board can drive two motors, so six pipes can be connected simultane- ously forprototyping.Furthermore, themotor shields support motor current measurement, so it can be detected without additional sensors, if the motor is stalling, e.g. if the tuning spring has reached its end position. VI. RESULTS After finishing the constructing phase, the prototyping setup was tested extensively. An endurance test was per- formed with one pipe to verify fatigue strength of the system. Thereby the motor moved the tuning spring for about 20 hourscontinuously (3715tuningcycles),untilonegearwheel was abraded. This number of tuning cycles would never be reached in a real organ, so the drive is applicable from this point of view. The precision and the speed of the automated tuning process meet the requirements set for this project. A pipe can be tuned in less than ten seconds with satisfying precision (±0.5 cents), whereby the manual process takes about 30 seconds for each pipe. The system can perform tuning even more accurately, whereby the tuning time increases. Fig. 9. Resulting tuning process of reed pipe (green...nominal value, red...actual value) VII. CONCLUSION AND OUTLOOK Overall, the main aim of this project, to evaluate the possibility of automated reed pipe tuning, was reached at an early stage and extensive additional developmental work was done. Because of the low price and the small size of the implemented actuator the results actually exceeded the author’s own expectations by far. In future work the software should be transformed from PC to an embedded system and should be integrated into the real organ control system. Thereby the organ could be programmed to tune itself at specific dates or tuned by starting the process from a smartphone from anywhere. Using more than one bandpass filter would enable tuning several pipes simultaneously. That would be a significant advantage over to manual pipe tuning. ACKNOWLEDGMENT Firstly, I would like to express my sincere gratitude to my advisor Dr. Markus Trenker for the continuous support of my Master Thesis, for his patience, motivation, and immense knowledge. His experience helped me in all the time of writing this thesis. My sincere thanks also goes to Wendelin Eberle, the CEO of Rieger Orgelbau GmbH, who provided me an opportunity to join his team for this project, and who gave access to the companies knowledge and provided specific tools and organ parts. Without this precious support it would not be possible to conduct this research. REFERENCES [1] Rieger Orgelbau GmbH. [Online]. Available: http://www.rieger- orgelbau.com/ [2] T. Bothe and J. Kablitz, “Selbststimmende Orgelpfeife,” Kiel: FH Kiel, 2014. [3] Elliptec GmbH, “Elliptec Motor X15G,” Dortmund, 2016. [Online]. Available: http://www.elliptec.com/de/produkte/motor-x15g/ [4] Physik Instrumente (PI) GmbH, “Piezomike linearaktoren,” 2016. [Online]. Available: http://www.physikinstrumente.de/technologie/piezomike- linearmotoren.html [5] D. Voigt and M. Voigt, “Pfeifenorgel mit selbstregulierender Stim- mung,” German Patent DE102011013444, 2012. [6] M. Voigt, “Stimmungseinrichtung fu¨r gedackte Orgelpfeifen,” German Patent DE102013012821, 2015. [7] M. Voigt, “Stimmungseinrichtung fu¨r Orgelpfeifen,” German Patent DE102012021644, 2014. [8] Tuning Set CTS-32-C, manual, www.tuning-set.de, 2008. 25