Measuring airspring level with ultrasonic sensor in commercial vehicle

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Varga Dániel
Department of Automation and Applied Informatics

The modern cars and commercial vehicles are getting more and more complex in relation to their computing capacities as there are more on-board electronic controller units (abbreviated as ECU) installed on them, which are all devoted to different tasks. On the commercial vehicles and buses there is one ECU in particular which I will further examine, that is the ECU of the level controlling system. These vehicles usually transport great loads which raise the need for controlling their chassis’ level dynamically in order to maintain a target level. Without control, the chassis’ level of the fully loaded vehicle would be as low that the supporting springs would got fatigued in a much shorter period of time than expected, not mentioning the fact that without control the equal distribution of the load on the different axles is impossible. The electronic levelling control system executes its task by controlling the quantity of the air inside each of the airbellows installed on the vehicle. The command can be to load, exhaust or hold the air in the airbellow. This system can even distribute the load between the axles and maintain a certain height independently from the load. The level sensor is an obligatory part of this system as it can detect the difference from the target level. There are multiple solutions for level sensors such as measuring the translation or rotation from a reference point, or if the profile of the road is known, measuring the height from the road is also a good method. A third concept is to measure the inner height of an airbellow and calculate the height of the chassis from that value. The goal of my thesis is to design a prototype which is capable of this third method using the measuring principles of the ultrasonic sensors. My task consists of three major parts, the design of the driving circuit for the transmitter and receiver of the ultrasonic sensor, the software for driving the before-mentioned circuit during measurements, and the execution of the actual measurements.


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