Diagnostic algorithms for air brakes in trucks: Theory and experiments

GALI项目的主要研究目标是研究一类混合动力系统，以期为卡车、公交车和火车等大型车辆的空气制动器开发新的、可靠的车载诊断和监测算法。典型卡车的空气制动系统由10个刹车室组成，这些刹车室的输入(空气质量流量)由驾驶员的刹车踏板输入控制。气压在空气制动室中的演变取决于是否克服了弹簧的预紧力以抵抗活塞和推杆的运动，或者活塞和推杆是否处于运动状态，或者推杆是否运动得足够充分，以至于刹车片与鼓接触。在这个项目中，将解决以下问题：给出一个经过实验证实的每个制动室和相关阀门中压力演变的数学模型，制动踏板输入和每个制动室中的压力测量，是否有可能(1)可靠地检测和诊断空气制动系统中的泄漏，以及(2)可靠地估计推杆的行程？在这一应用的激励下，将考虑顺序混合系统。这类系统由有限个离散状态组成，受一个可能的前向跃迁和一个后向跃迁的约束。然后研究了一般顺序混杂系统过渡条件下的参数辨识问题。卡车、公交车和火车上健康的制动系统对于确保高速公路上车辆及其乘员的安全至关重要。考虑到空气制动器的绝对重量，以及空气制动器对维护的敏感性，对卡车和公共汽车进行定期刹车检查是必要的。这样的检查不仅主观、耗时和基础设施密集，而且有时还不方便检查人员深入车辆底部，特别是对于低净空车辆。制动系统的两个主要缺陷是泄漏和推杆行程超过一定限度。空气泄漏会增加压力响应的时间延迟，并限制可能的最大制动压力，从而降低制动系统的性能。推杆行程越大，死区时间越长，压力响应滞后越大。为此，该项目旨在开发泄漏检测和推杆行程估计算法，以支持开发便携式诊断系统，其中来自传感器的有关空气制动系统的数据被处理并存储在芯片上，检查员可以通过手持设备轻松访问该芯片。从教育的角度来看，这个项目将使本科生和研究生能够解决现实世界的问题，与美驰公司的工业研究人员互动，并在德克萨斯农工大学和美驰公司的测试设施的实验试验台上实施开发的算法。鉴于该项目对安全的影响以及检测最容易发生故障的车辆部件故障的最佳方法，该项目对经济、社会和健康的影响怎么强调都不为过。

ABSTRACTThe principal research objective of this GOALI project is to study a class of hybrid systems with a view towards developing novel, reliable, on-board diagnostic and monitoring algorithms for air brakes in large vehicles such as trucks, buses and trains. An air brake system in a typical truck consists of ten brake chambers whose input (mass flow rate of air) is governed by the brake pedal input from the driver. The pressure evolves in the air brake chamber depending on the whether the preload of the spring resisting the motion of the piston and pushrod has been overcome or whether the piston and pushrod are in motion or whether the pushrod has moved sufficiently that the brake pads have come in contact with the drum. In this project, the following problems will be dealt with: Given an experimentally corroborated mathematical model of the evolution of pressure in each brake chamber and relevant valves, the brake pedal input and the measurement of pressure in each brake chamber, is it possible (1) to reliably detect and diagnose leaks in the air brake system, and (2) to reliably estimate the stroke of the pushrod? Motivated by this application, sequential hybrid systems will be considered. Such systems consist of finite number of discrete states subject to one possible forward transition and one backward transition. The problem of parameter identification in the transition conditions of general sequential hybrid systems will then be investigated. A healthy brake system in trucks, buses and trains is essential to guaranteeing safety of vehicles and their occupants on the highway. Given their sheer weight and given that air brakes are sensitive to maintenance, regular brake inspections are necessary for trucks and buses. Not only are such inspections subjective, time and infrastructure intensive, they are at times inconvenient for inspectors to get underneath the vehicle, especially for vehicles with low clearance. The two main brake system defects are leaks and the pushrod stroke exceeding a certain limit. Air leaks degrade the performance of the brake system by increasing the time lag in the pressure response and by limiting the maximum possible brake pressure. The larger the stroke of the pushrod, the longer is the dead-time and the lag in the pressure response. For this reason, this project aims to develop leak detection and pushrod stroke estimation algorithms in support of developing a portable diagnostic system, where data concerning the air brake system from the sensors is processed and stored on a chip which is readily accessible to inspectors via hand-held devices. From an educational viewpoint, this project will enable the undergraduate and graduate students to work on a real-world problem, interact with industrial researchers at Meritor-WABCO and implement the developed algorithms on the experimental test-beds at Texas A&M University and at Meritor-WABCO's test facilities. The economic, social and health implications of the project cannot be overemphasized in view of the safety implications and the optimal method for detecting faults in the component of a vehicle most prone to malfunctioning.