Piston displacement sensing in electro-pneumatic brake module

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

One of the important components in today’s trucks is the electronic braking system. They not only made possible to reach shorter braking distance through faster actuating but increased the traffic safety because the modern microcontroller-supported braking system notices the changes in vehicle stability and dynamics and it reacts if necessary. Moreover it can warn the driver of significant brake pad wear or overheating brake discs thus the brake status can be easily observed. The electronically controlled braking system is also an essential part of the autonomous cars and trucks that come in the future. Developers can design safety functions that monitor the road for any dangerous situation and decelerate or stop the vehicle if necessary.

The diploma thesis presents the elaborate measurement that was carried out on the electro-pneumatic modulator (EPM) which is an important part of the electronic braking system. The displacement of the piston(s) that situated in the EPM is the object of the measurement. The solution involved the market research of the available displacement measuring devices after that I selected the ones with the highest technical and economic potential for deeper analysis. Based on the conclusions I worked out a Hall Effect sensor-aided measurement method in which the magnet was fixed to the piston while the sensor was placed onto the outer wall of the EPM. It was necessary to record calibration curves to accurately measure the displacement and this data helped choosing the optimal magnet arrangement. To support the fastening of the magnet I designed a 3D-printed element that made possible to start the first measurements. Although their result was usable but we decided to design a processing circuit due to various factors. The electronics were built around a PIC microcontroller that processes the sensor’s signal and transmit it via serial communication to the measurement system at the company’s laboratory. After programming the controller new measurements were carried out resulting excellent data about the piston displacement. Their analysis answered all the questions raised within the company.


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