Research On Delay Time Analysis And Its Control Techniques Of Bus Pneumatic Braking System

Because of the driver reaction, force and signal transmission, actuator movement in the working process of bus pneumatic braking system, the braking time longer than the expectation, this is the delay time of braking system. Obviously, the delay time will affect bus braking performance, and may cause traffic accident due to undesired braking. At present, in the research fields of bus pneumatic braking system and its control, the designer do not consider the time delay characteristics sufficiently, and usually set the delay time for a redundancy value according to experience or experimental data, and that lack of systematic theoretical analysis.Along with the continuously improvement of the requirement of vehicle safety performance, the research and application of bus active safty control problem have been rapidly developing. Pneumatic braking system is an important part of the bus, its time delay and active control problem become prominent. The rapidly development and application of bus electronic and network control technology provide an implementation basis for braking system delay time real-time dynamic control, and propose a new demand for the theory research of delay time and its control, because ’accurate control need accurate theory model’. The paper focuses on the delay time problem of bus pneumatic braking system, adopt the method that combines theoretical research, experiment and simulation, systematically study the theory characteristic of pneumatic circuit pressure response delay, actuator action delay and control network signal transmission delay, and delay time control strategy and method, in order to effectively active control bus pneumatic braking system’s delay time, reduce its influence on braking performance, improve bus braking state. The main researches of this paper as follows:(1) Based on the presentation of bus pneumatic brake system’s structure and its working process, analyse the time characteristic of bus braking process, propose the delay time composition of bus pneumatic braking system, deduce the calculation formula of longitudinal braking distance deviation and lateral displacement which is caused by the delay time of bus pneumatic braking system, thus analyse delay time influence on bus braking performace.(2) By means of the method that combines theoretical analysis and experiment, study the time delay characteristic of bus pneumatic braking system air circuit braking control valve. Establish pneumatic braking system braking circuit pressure response delay time mathematical model, analyse bus pneumatic braking air circuit pressure response delay characteristics by simulation and experiment. Use PWM control mode to carry out bus pneumatic braking system air circuit pressure response time delay control test, prove its controllability, and propose control method.(3) Using equivalent principle, the cumulative action delay problem which is caused by bus pneumatic braking system actuator components is equivalent to the distance change between brake block and disc, establish actuator’s dynamic equation, deduce contact force calculation formula, present actuator action delay time’s calculation method, and verify it by simulation and experiment.(4) Based on the configuration mode, construct the bus pneumatic braking control network system, analyse signal transmission delay time’s composition. According to the communication specification of CAN, propose calculate method of control network’s signal transmission delay time. Build bus pneumatic braking system control network test system, and carry on signal transmission delay test, further analyse its characteristics.(5) In order to carry out bus pneumatic braking time delay control, establish bus pneumatic braking process dynamic model, which is used to describe bus running state in braking process, verify its validity and effectiveness. Based on this, aimed at bus pneumatic braking system time delay, present bus pneumatic braking system delay time control strategy and method.Achievements of this paper are the theoretical basis and application technology of bus pneumatic braking system’s design and development and realize dynamic accuracy control, this will be beneficial to enhance the performance of bus pneumatic braking system and its control, improve bus pneumatic braking safety, stability and accuracy, ensure bus have correct running state in braking, so as to enhance the bus active safety performance.