Abstract
This study aims to investigate the hysteresis characteristics of a pneumatic braking system for multi-axle heavy vehicles (MHVs). Hysteresis affects emergency braking performance severely. The fact that MHVs have a large size and complex structure leads to more nonlinear coupling property of the pneumatic braking system compared to normal two-axle vehicles. Thus, theoretical analysis and simulation are not enough when studying hysteresis. In this article, the hysteresis of a pneumatic brake system for an eight-axle vehicle in an emergency braking situation is studied based on a novel test bench. A servo drive device is applied to simulate the driver’s braking intensions normally expressed by opening or moving speed of the brake pedal. With a reasonable arrangement of sensors and the NI LabVIEW platform, both the delay time of eight loops and the response time of each subassembly in a single loop are detected in real time. The outcomes of the experiment show that the delay time of each loop gets longer with the increase of pedal opening, and a quadratic relationship exists between them. Based on this, the pressure transient in the system is fitted to a first-order plus time delay model. Besides, the response time of treadle valve and controlling pipeline accounts for more than 80% of the loop’s total delay time, indicating that these two subassemblies are the main contributors to the hysteresis effect.
Highlights
Multi-axle heavy vehicles (MHVs) are usually used as land transport platforms for large-scale equipment
Due to compressibility of gas, pneumatic braking system (PBS) will inevitably perform a hysteresis effect, which may lead to serious traffic accident in an emergency braking condition [2]
The results indicate that treadle valve and controlling pipeline are the main contributors to the hysteresis effect of the service circuit
Summary
Multi-axle heavy vehicles (MHVs) are usually used as land transport platforms for large-scale equipment. MHVs have large inertia and a long wheelbase, and they usually work in complicated and changeable driving conditions. Good braking performance is an important guarantee for fast maneuvering and safe driving. The pneumatic braking system (PBS) is widely employed in MHVs with the advantages of large braking force, good reliability and easy maintenance [1]. Due to compressibility of gas, PBS will inevitably perform a hysteresis effect, which may lead to serious traffic accident in an emergency braking condition [2]. When a vehicle runs at a normal speed of 20 m/s (approximately 70 km/h), if the braking time is delayed 0.5 s, the braking
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