Study On United Control Theory And Method Of Auxiliary Brake And Automobile Primary Brake Set

The primary braking set of an automobile can efficiently make it slow down or stop at an emergenct situation in a short time, while its continouse braking performance is relatively poor. And, an auxiliary braking set, suitable for continous braking situation, offers smaller braking power. The united control theory and method of the auxiliary and primary braking set is studied for rational use of them. The main research is as follows.1. The influence of auxiliary braking set on braking stability of vehicleAnalyzing the influence of braking force of auxiliary braking set, a method of properly increasing automobile front and rear braking force distribution coefficient is suggested, and its rationality is proofed by simulation calculation using parameters of a given bus.2. Research on the control method of typical auxiliary braking setsConstant speed control system and fuzzy control system are separately designed for engine depression retarder and eddy current retarder, with automobile velocity and deceleration as input parameters, and constant downhill speed as target, relative control tactic and fuzzy control rules.3. Research on the united working method of auxiliary and primary braking set and simulation on the united braking systemWith eddy current retarder as example, the united control theory and method of the united braking system consisted of eddy current retarder and the primary brake is expatiated, and the temperature of the eddy current retarder rotor plate and the primary brake is suggested to be the evidence of distributing the heat load produced when an automobile is braked between the two-type braking sets.The general thermodynamics model of the eddy current retarder and primary brake is derived from the thermal conduct theoretics and the energetic conversation law, and the heat fade models of braking sets are put forward using numerical fitting according to the test bench results, to express the numerical relation of the actual output torque, the maximum output torque and the working temperature of the braking sets.The mathematics model of the united braking system of the eddy current retarder and the primary brake is put forward, which consists of the following sub-models: the dynamics model of an automobile braking process, the braking force model of the primary brake, the braking force model of the eddy current retarder, braking force distribution model of the united braking system of the eddy current retarder and the primary brake, the general thermodynamics model of the eddy current retarder and primary brake, the heat fade models of the eddy current retarder rotor plate and the primary brake.The united braking system braking force distribution coefficient is suggested. With the working temperature of the eddy current retarder rotor plates and the primary brake as input parameters, and the united braking system braking force distribution coefficient as output parameter, and detailed restrict fuzzy control rules, a two-input and one-output fuzzy controller is designed. The calculation results of braking process of a bus on a visual multi-ramp show that the working temperature of the eddy current retarder rotor plate and the primary brake can keep normal, so that the united control theory suggested is valid and rational.4. Composing the optimal algorithms of the united braking system braking force distribution coefficientThe optimal research on the united braking system braking force distribution coefficient is carried through. To the principle of the lowest square root of the temperature of the eddy current retarder rotor plate and the primary brake, the optimal function is established for the braking force distribution of the united braking system, and carried out of automobile at different velocity and on different grade, and lastly, the concrete value of the braking force distribution parameter is suggested.5. Designing and making the controller of the united braking systemMicrocontroller-cored controller is designed and made on the basis of the analysis of the united braking system. Applying pulse-width-module technique, three controlling patterns of eddy current retarder are set in the controller: manual multi-level control, separate constant speed control and united control with the primary brake. The designed controller is tested on the test bench of the eddy current retarder.The major contributions in this paper are summarized as follows.1. Constant speed control system of engine compression retarder and fuzzy control system of eddy current retarder braking torque are designed. 2. A united braking system of auxiliary and primary braking sets is put forward, in which the temperature of the eddy current retarder rotor plate and the primary brake is suggested to be the evidence of distributing the heat load produced when an automobile is braked between auxiliary and primary braking set.3. Braking force distribution model of the united braking system of auxiliary and primary braking set, thermodynamics model and heat fade model of auxiliary and primary braking set are set up to perfect the mathematics model of the united braking system of auxiliary and primary braking sets.4. Fuzzy theory is applied to set up the control theoretics and method of braking force distribution of eddy current retarder and the primary braking sets, and the conception of the united braking system braking force distribution coefficient is suggested. Optimal research on the braking force distribution coefficient is carried through, and the optimal result is summarized.The designed controller is tested on the bench, and the testing results show that eddy current retarder can output braking torque according to the different duty-cycle controlled by the designed controller. The simulation results show that the united braking system consisted of auxiliary and primary braking set can efficiently reduce the heat load of the primary of an automobile, and that the fuzzy rules of the united braking system braking force distribution and the optimal result of the united braking system braking force distribution coefficient can keep normal the braking efficiency of the auxiliary and primary braking sets. It is reasonable to distribute the braking force between auxiliary and primary braking set according to the working temperature of them, and the mathematics model and control theoretics put forward can be refered to the engineering practice.