| Because of large volume, low cost, high efficient and economic advantages, articulated heavyvehicles are widely used in the goods transport. Due to heavy load, large size, high center of mass,and the coupling between tractor and trailer, accidents are often happened, such as rollover, shimmyand folding, cause huge losses. In view of this, the problem of stability of articulated heavy vehicleshas become a bottleneck to restrict the development of road transportation, and the study ofarticulated heavy vehicles stability is of great significance.This paper is supported by National Natural Science Foundation of China “Research onmulti-targets control for articulated heavy vehicles dynamic stability based on model prediction”(identifier:51075176). Based on the research of articulated heavy vehicles stability control strategytheory and application, at home and abroad, and based on the research and comparative analysis oftwo control strategys, integrated control strategy combined active steering rear axle with differentialbraking,which is for articulated heavy vehicles and is for vehicle all condition, is proposed. Theintegrated control strategy can reduce the path offtracking so that the trailer can follow the tractor inlow speed, can improve the path following and yaw stability in middle high speed condition, canavoid rollover in high speed dangerous working condition. From low adhesion to high adhesion,from low speed to high speed, from smooth working condition to limiting working condition, theintegrated control strategy can achieve good control for articulated heavy vehicles. This articlemainly has carried out the research work of the following several aspects:1. The variable parameters simplified model of articulated heavy vehicles was establishedBased on the analysis on dynamics of the heavy semi-trailer, the3-dof linear model and5-doflinear model, which can computer in real time, was established to describe the vehicle movement characteristics. Considering the articulated heavy vehiclesloads vary greatly, mass center positionwas difficult to determine, goods distribution hypothesis model was established. The parameteridentification method, which was combined two simple models with genetic algorithm, was used toidentify the key parameters of simple model off-line. The key parameters of all conditions wereidentified, and the MAPs were obtained based on the key parameters values. Interpolating to MAPsto obtain the real-time key parameter values,5-dof linear simplified model with real-time keyparameters, provided accurate reference or control simplified model for articulated heavy vehiclesstability control.2. The activing rear axle steering control strategy of articulated heavy vehiclesConsidering the complex working conditions of articulated heavy vehiclesand achieving theoptimal control under the all working condition, active steering control strategy of articulated heavyvehicles is divided into low speed and high speed control strategies.Because of low speed and bigsteering angle of low speed cornering condition, it is difficult to control. So the low speed rear axlesteering control strategy of articulated heavy vehicles is proposed to achieve good path follow,reduce the tire wear and damage of road. Low speed rear axle steering control strategy is estabilishedbased on the rear axle steering strategy and with the aim to control that the trailer rear follows track ofthe fifthwheel. Active steering angle of low speed rear axle steering control strategy is decided usingthe PID control method. The medium high speed rear axle steering control strategy of articulatedheavy vehicles is proposed based on virtual driver and the LQR optimal control method and geneticparticle swarm optimization algorithm is used to optimize the weight coefficients of ontrol strategy.The medium high speed rear axle steering control strategy is divided into path following control androllover control, the two control modes are switched by weight coefficient. Yawing stabilityperformance index of articulated heavy vehicles is improved greatly by Path following control modelusing the path following control weight coefficients, but the rearward amplification reduce rarely.The rearward amplification reduce greatly and rollover is controlled well by rollover mode using therollover control weight coefficients, but the path follow and yawing stability is improved small. Inview of this, the new control model, which the mode of path following control is used to control pathfollow and yawing stability under the smooth working conditions, and rollover control model is usedto control rollover under the dangerous working conditions, is proposed. The way can make full use of the rear axle steering control strategy to control articulated heavy vehicles well.3. The differetial braking control strategy of articulated heavy vehiclesBecause the differetial braking control strategy, which is based on differential braking, doesn’tneed additional hardware and change the vehicle structure, it became common stability controlmethod for articulated heavy vehicles. Considering the articulated heavy vehicles stability control iscomplex and a single goal is difficult to achieve the good control, the differential braking controlstrategy, which is based on multi-objective control, is proposed. In order to calculate the accuratereal-time state reference value of articulated heavy vehicles, the linear variational parameterssimplified model in chapter2is used as reference model. The control strategy weight coefficients areoptimized by genetic particle swarm so that the differetial braking control strategy can controlarticulated heavy vehicles well. Simulation verification for the differential braking control strategy iscarried out, and the results indicate that differential braking control strategy can control effectivelyarticulated heavy vehicles, thereby improve the stability and safety of articulated heavy vehicles.Considering both the active steering rear axle strategy and differential braking control strategycan control articulated heavy vehicles, the two control strategies are researched by simulation in orderto understand the advantage and disadvantage of the two control strategies. The results indicate thatthe rear axle active steering strategy is better than the differential braking strategy control strategy; itis of great significance for the articulated heavy vehicles stability control.4. The variable parameters integrated control strategy combined differential braking with activerear axle steering for articulated heavy vehicles in all conditionsAfter comparing the rear active steering strategy with differential braking control strategy andanalyzing the advantage and disadvantage of the two control strategies, integrated control strategycombined differential braking with activing rear axle steering for articulated vehicle was proposed.Genetic particle swarm optimization algorithm was used to optimize the weight coefficients ofintegrated control strategy, so that prompted the fusion and matching of two single control strategies,and coordinated the two control substrategys. Integrated control strategy is divided into path followcontrol mode and rollover control mode, and the two control modes switch by transforming theweight coefficients of the integrated control strategy. Path follow control mode can achieve the pathfollow and yawing stability under the smooth working condition, and rollover control mode can control vehicle rollover.Simulation verification for the actively rear axle steering, differential braking and integratedcontrol strategy of articulated vehicle was carried out, the results indicate that integrated controlstrategy is similar to the rear axle actively steering strategy under smooth working conditions, but theintegrated control strategy is superior to the rear axle actively steering strategy under dangerousworking conditions. Integrated control strategy is better than differential braking control strategyunder all working conditions. Therefore, integrated control strategy is better than rear axle activelysteering strategy and differential braking strategy, can control articulated heavy vehicles better.Based on the results of articulated heavy vehicles stability control strategy, the variableparameters integrated control strategy, which is combined activing rear axle steering with differentialbraking in all conditions, is proposed. The integrated control strategy is that: at low speed workingcondition, low speed rear axle active steering control strategy is used; at the stable working conditionwhich is at middle high speed and the lateral acceleration is less than0.4g, integrated control strategy,which uses the path follow control parameters, is used; at the dangerous working condition which isat middle high speed and the lateral acceleration is greater than0.4g, integrated control strategy,which uses the rollover control parameters, is used.Simulation and experimental results indicate thatthe variable parameters integrated control strategy can control the articulated heavy vehicles well inall working condition and control effect is better than other articulated heavy vehicles control strategymentioned in this paper.5. Hardware in-the-loop test bench of articulated heavy vehiclesBased on Labview real-time strategy, the hardware in loop test bench, which was combinedwith Simulink software with Trucksim software, was established. Trucksim software,is close to thereal vehicle, was used in hardware in loop test bench. At the same time, the test bench made fulladvantage of data acquisition, data processing and interface display of Labview strategy. Theprogram of the control strategy was compiled by Simulink software and was downloaded to Labviewreal-time strategy by S-function, the articulated heavy vehicles control program is completedcombined with microcomputer program of pressure closed loop. Hardware in loop test benchprovide reliable hardware experiment platform for heavy-duty semi-trailer to test the variableparameters integrated control strategy combined differential braking with activing rear axle steering for articulated heavy vehicles in all conditions.To sum up, this article innovative results are as follows:1. Considering big number of key parameters of simplified model and identificatied difficulty,the identificatied method,which combining double models and genetic algorithm,was used to identifykey parameters of simplified model. Considering the articulated heavy vehicles loads vary greatlyand the working conditions are complex, the simpled model is difficult to match the real-time vehiclestate.Based on goods distribution hypothesis model, the real-time key parameters are obtained byinterpolation to MAP composed by identificatied key parameters of simple model.5dof linearsimplified model, which combines with the real-time parameters, can match the actual state ofvehicle, provides foundation to stability control strategy for articulated heavy vehicles.2. Based on study of actively rear axle steering control strategy and differential brake controlstrategy, the integrated control strategy,which were combined rear active steering with differentialbrake, was proposed. Considering the different objectives at different working conditions, integratedcontrol strategy was divided into path following control mode rollover control mode. Considering theswitch amongst control modes at different working condition, the variable parameters integratedcontrol strategy combined differential braking with activing rear axle steering for articulated heavyvehicles in all conditions was proposed. Good control effect for articulated heavy vehicles wasobtained by the integrated control strategy.In order to ascertain the advantage and disadvantage ofvarious control strategy, the comparison, which was between integrated control strategy and two solecontrol strategy, was operated. This provides theory and method exploration for articulated heavyvehicles stability control strategy.3. In order to obtain good effect for the control strategy and coordinate substrategys of integratedstrategy, the genetic particle swarm optimization algorithm was used to optimize weight coefficientsof control strategy. Simulation and test varication for integrated strategy with optimal weightcoefficients were carried out, the results indicate that integrated strategy with the optimal weightcoefficients can coordinate two single control strategies to promote each other and achieve optimalcontrol for articulated heavy vehicles. |
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