Research On Road Surface Identification Algorithm Of Anti-lock System For Commercial Vehicle

At present, ABS which is necessary equipment has been installed on many vehicles. ABS, crucial technology is road surface identification which is a hot issue, is researched by many enterprises, schools and research institutes. ABS road surface identification has been researched by many foreigners who put forward many methods of road surface identification, but these methods need supernumerary sensors, high cost and large quantity of training samples, these questions lead to some disadvantages which identification is sweeping, or not detailed. All these disadvantages cause our interesting. However, at present, country encourages independent innovation, grasping core technology, trying to avoid trade monopoly. The research method has been grasped by BOSCH which has applied it to vehicles. In our country, research of ABS is on the initial stage. In addition, most enterprises develop ABS with abroad research institutes. So, developing sovereign ABS can cut down production costs and bring economic benefits. For present states, this paper provides for the development of a premise for ABS.Following contents are developed in the paper:1. Theoretical foundation of ABS road surface identification algorithm for commercial vehicleRoad surface changes constantly when automobile runs. Braking effect of vehicle becomes not good if there is no road surface identification when braking. The relationship of adhesion coefficient and slip ratio is that adhesion coefficient is maximum when slip ratio is optimal value. Road surface identification can identify road. Vehicle is controlled by using logic threshold to stop according to optimal slip ratio and favorable angular acceleration threshold. The paper puts forward a new method of road surface identification according to the thought. The product of slip ratio and adhesion coefficient is calculated by wheel model and Burckhardt tire model, The product of adhesion coefficient and corresponding slip ratio on the road is compared to the product of theoretical adhesion coefficient of five kinds of typical road surfaces and the same slip ratio so that adhesion coefficient of road surface can be identified.2. Practical control algorithm of ABS for commercial vehicleControl algorithms of ABS include logic threshold method, PID control method, fuzzy control method and neural network control method and so on. Simple and mature logic threshold control method is used in the paper. The question of matching of angular acceleration and deceleration is involved in logic threshold control method, larger and minor angular acceleration and deceleration is all not good. Braking distance and braking stability is influenced by them. Calculation methods of reference speed include largest wheel speed method, slope method and so on. These methods have advantages and shortcoming, largest wheel speed method is used in the paper.Choosing of angular acceleration and deceleration on high adhesion coefficient and low adhesion coefficient is researched and analyzed according to former basis. Suitable angular acceleration and deceleration and optimal slip ratio threshold are determined for five kinds of typical roads.3. Model building and vehicle dynamics model simulationBuilding of vehicle dynamics model is necessary for control algorithm. Vehicle dynamics models include air pressure system model, tire model and brake model. Eight-DOF dynamics simulation model of vehicle is built using Matlab/Simulink, control logic is built and simulated using Stateflow which based on finite state machine theory. The simulation result of the paper is compared to the simulation result of other road surface identification methods, control logic developed is verified.4. Hardware in-the-loop simulation and road test of ABS for Commercial vehicleHardware in-the-loop simulation is implemented after off-line simulation, this is necessary for ABS development. Software system, interface system and hardware system of test bed are described. Matlab/Simulink software is applied on software system. Data acquisition card, terminal board and the drive circuit of solenoid valve are used on interface system. Hardware system includes solenoid valve of ABS, implementing agencies and pressure sensors. Hardware in-the-loop simulation test-bed of ABS provides test tool and test platform for research and development of crucial parts of ABS.Road surface identification algorithm is verified on hardware in-the-loop simulation test bed of ABS. Real time simulation can be carried out by connecting the host computer including vehicle model, tire model and brake model to target computer using TCP/IP line. Controller sends out signals to solenoid valves which regulate pressure to increase, decrease and hold by accepting signals of pressure sensors, its purpose is to control vehicle on high adhesion coefficient road, low adhesion coefficient road, high-to-low or low-to-high transition roads.ABS road surface identification algorithm developed is transplanted to the vehicle to conduct road test.Hardware in-the-loop simulation test bed and test conclusion built in the paper have an important role in development of ABS, design of ECU, research of structure parameters and responding feature of solenoid valves. It can provide theory basis for designing solenoid valve and improving structure parameters of solenoid valves, at the same time, dynamics characteristic of solenoid valve can be evaluated by using it.