Analysis of a magnetic valve and possibilities of sensorless plunger position estimation

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Supervisor:
Dr. Kovácsházy Tamás
Department of Measurement and Information Systems

For either flow or pressure controlling purposes, e.g. in automatic transmission units or in brakes, linear variable solenoids are used quite often for the role of actuation. My thesis aims at studying such devices in details, and different methods for estimating the position of plunger (opening angle) in a sensorless way are also proposed and analyzed.

A magnetic valve (linear variable solenoid) shows a rather complex structure difficult to model. In the first part of my thesis, such a device is presented elaborately and the major equations for describing its electrical, electromechanical and mechanical subsystems are established. Most important effects related to valve actuators and to their rough working environment are also highlighted, that future controllers must be able to compensate.

With the sensorless principle, system performance and robustness can be greatly improved along with cost reduction, since the transducer characteristics of the actuator device are exploited; therefore any external sensor becomes unnecessary. This thesis investigates the concept of sensorless plunger position estimation regarding solenoid actuators, with two suitable methods also being presented. Compared to those already published in technical literature, the effects of frequency, supply voltage and especially external force, which is not really covered in literature, are studied as well. Major advantage of the proposed methods is that both plunger position and external load can be simultaneously estimated, thus further improving robustness and extending the possible fields of application of such devices. Experimental results are also presented in support of the usability of the methods.

For the purpose of studying the sensorless principle and for extensive solenoid analyses, a complete measuring and testing environment was designed and built, which is also presented. This diploma work was done on behalf of Robert Bosch kft. (RB-HU/GS-TC), with the goal to enhance valve controllers in automatic transmission control units (TCU), developed by Bosch.

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