Research On Composite ABS Control Strategy Of Fuzzy Self-adjusting PID For Electric-wheel Vehicle

Due to the energy and environment problem, the automobile industry needs to makechange urgently, which is to reduce or remove the dependence on unsustainable energy.Electric vehicle with clean, energy-saving features, has incomparable advantage in newenergy vehicles. It also has the advantages of simple structure, convenient maintenance,small size, alleviating the traffic pressure. Therefore, electric vehicle is the main direction ofautomobile industry, the research and development of electric vehicles will initiate the newpattern of the development in automobile industry.The traditional automotives commonly use hydraulic braking system, as electric motoris capable of recycling energy, many vehicles use the composite brake system：motorregenerative braking combined with traditional hydraulic braking. In this article, a vehiclewith four electric wheels was studied. By summarizing the research results at home andabroad, a composite ABS Control Strategy of fuzzy self-adjusting PID for electric-wheelvehicle was proposed on the basis of intelligent control theory. The control strategyconsidered the vehicle braking stability, braking efficiency as well as the braking energyrecovery on different braking mode. It coordinated the hydraulic braking and the motorregenerative braking, achieved a good anti-lock braking control effect. The control method isbetter than the logic threshold control because of its smaller fluctuation, which can be morecomfortable; Comparing with PID control, its parameter setting is simpler, and it also has astronger adaptability.A composite ABS control system for four-wheel independent drive electric vehicles wasstudied, the front and rear wheel braking force was distributed reasonably, and the brakingforce on each wheel was combined with motor braking force and hydraulic braking force.According to the road coefficient and braking strength, The braking force can be distributedand coordinated. A method of pure motor ABS with the help of hydraulic braking force was proposed, this control method can not only ensure the braking energy recovery and guaranteethe braking stability in different conditions. By using the fuzzy self-adjusting PID controlmethod, the road coefficient identification system transmits the road coefficient to the fuzzylogic controller, and the latter adjusts the PID parameters through its internal set of fuzzyrules in real time, so that the vehicle slip ratio under different working conditions is able tomaintain the optimal slip ratio and the anti-lock braking system can achieve high efficiencyin real time.Based on the research and control method above, a vehicle model with15degrees offreedom was constructed in AMESim, it was connected with the control method in Simulinkthrough the Interface. A co-simulation analysis was given, and the results shows that thecontrol method mentioned above can well realize the anti-lock braking control of theresearch object in this article.By redesigning and transforming the traditional automobile ESP test platform, ahardware in the loop test bench based on dSPACE simulation platform was built, thecomposite ABS Control Strategy of fuzzy self-adjusting PID for electric-wheel vehicle wastested on it.According to the theories above, the article discussed the following issues:1. The establishment of the vehicle dynamic model. The vehicle tire model, batterymodel, motor model, hydraulic braking model, aerodynamic model were established. Basedon these models, the whole vehicle dynamic model of15degrees of freedom wasconstructed in AMESim. It provides signal input and receives the control feedbackinformation from Simulink, realizes the ABS co-simulation for four-wheel independent driveelectric vehicles.2. The braking force distribution strategy for electro-hydraulic brake. The braking forcedistribution theory was introduced, and the braking force distribution method of this articlewas proposed; a road coefficient recognition algorithm was given and the judging methodof braking mode was described.3. Research on the fuzzy self-adjusting PID control strategy. The fuzzy control theory,the principle of the fuzzy controller, the design method and its operation process were introduced; the principle of PID control and its adjustment of parameter were described;three kinds of typical fuzzy-PID control method were elaborated; the design process of thefuzzy self-adjusting PID control strategy and its parameter setting were described in detail.4. The off-line simulation and analysis. The simulation model established in AMESimand Simulink was given. A series of simulation were made under different road coefficient.The simulation results show that, the control method can achieve the anti-lock brakingcontrol effectively.5. Experimental study on hardware in the loop simulation. By redesigning andtransforming the traditional automobile ESP test platform, a hardware in the loop test benchbased on dSPACE simulation platform was established, and the composite ABS ControlStrategy of fuzzy self-adjusting PID for electric-wheel vehicle was tesed on it. The resultsshow that, the control strategy can judge the road coefficient and estimate the optimal slipratio according to the vehicle real time status, control the distribution of hydraulic brakingforce and motor braking force, guarantee the slip ratio kept with the optimal slip ratio in thecurrent road coefficient. In the same time, under the control strategy designed, the anti-lockbraking system has faster response speed and smaller fluctuation.The control algorithm proposed in this article can achieve the composite ABS controlrapidly and effectively. The control strategy was tested by off-line simulation and hardwarein the loop simulation. It can laid a foundation for integrated control of electronic stabilitywith electric wheel vehicle in fuzzy logic control area.