Driving Control Of Commercial Vehicle Platoon Based On Safety Distance Of Emergency Braking

With the progress of society and the development of e-commerce,highway transportation and logistics transportation are developing rapidly.As a large logistics country,China's logistics industry is developing rapidly towards high-quality intelligent logistics,network logistics and other aspects.However,the rapid development of China's ground vehicles is likely to cause environmental pollution,increasingly serious greenhouse effect and frequent traffic accidents.At the same time,the serious shortage of truck drivers affects the development of China's transportation industry and e-commerce.In order to reduce the energy consumption of commercial vehicles and the shortage of truck drivers,platoon has been proposed gradually in recent years.In terms of energy crisis,driving resistance can be greatly reduced when vehicles are in line.In terms of the shortage of truck drivers,the number of standby drivers is reduced due to the automatic driving of the following vehicles by platooning.At the same time,platoon has many advantages.For example,it can effectively solve the problems of fatigue driving caused by the long journey.It can reduce the traffic accidents caused by the driver's mistakes,increase the driving safety and traffic safety,shorten the inter-vehicle interval,increase the traffic flow,and improve the traffic efficiency.Although platoon has significant advantages in reducing fuel consumption and solving driver shortage,due to the tight distance between vehicles when driving in the platoon,it is difficult for the rear drivers to take over the vehicle for response in a short time in case of emergency braking.Therefore,the safety between member vehicles is the top priority in the current research.In view of the safety problems between member vehicles,after in-depth analysis of the front and rear brake process of member vehicles,aiming at avoiding rear end collision between the front and rear member vehicles,a safe distance strategy based on emergency braking is proposed.In addition,in order to improve the control ability of the member vehicles,a sliding mode acceleration controller is designed to ensure the safety of the platoon.Finally,the proposed strategy is simulated offline and verified in the hardware in the loop by the rapid control prototype system.The main work of this paper is as follows:(1)The safety distance model based on the emergency braking of front and rear member cars is established.According to the relevant literature at home and abroad,the existing target spacing strategy of platoon is often simple in structure and difficult to cope with complex conditions.There is a lack of considering the road adhesion coefficient and the braking situation of the front vehicle,while the road condition and the braking situation of the front vehicle are directly related to the driving safety of the member vehicles.The existence of this deficiency can not guarantee the safety of the platoon,especially when driving on the slippery road and other low coefficient of adhesion road,it is easy to rear end collision between the member vehicles in case of emergency braking.In order to solve this problem,the vehicle braking process is analyzed in this paper,real-time calculation method is used to avoid rear end collision,and the road adhesion coefficient,braking acceleration and communication delay of front and rear member vehicles are taken into account,then the communication delay distance,front and rear vehicle braking distance,minimum parking safety distance are obtained,therefore,the emergency safety distance model of braking are obtained.(2)The models at home and abroad are compared and analyzed,and the sliding mode acceleration controller is designed.Various models are introduced in this paper,which advantages and disadvantages are analyzed.Through comparative analysis,the full velocity difference(FVD),which is more adaptable to the driving conditions,is used as the platoon control system.Because the existing car following model needs a lot of data support and has more limitations on the adaptation of driving conditions.In addition,according to the characteristics of platoon,a sliding mode variable structure acceleration controller is designed by integrating the longitudinal dynamic model to calculate the expected acceleration of the member vehicles.Through the off-line simulation of FVD model,the timing distance strategy,the safety distance strategy and the sliding mode acceleration controller are simulated.Through the simulation test of starting and braking conditions,the comparison results show that the safety distance strategy and sliding mode variable structure control has better control effect and faster response speed.(3)The simulation model and working condition of the member vehicles are built.Through the joint simulation of MATLAB and TruckSim software,the acceleration and deceleration condition simulation of the high attached road and the emergency braking condition simulation of the docking road are designed and carried out.The simulation results show that the proposed control strategy has better real-time performance,which can effectively prevent the rear end collision accident and ensure the driving safety in the emergency braking of the docking road.(4)The HardWare-in-the-Loop test bench(HIL)with real-time online simulation of real vehicle and software real-time online simulation are built.The complexity of hardware in the real world is not considered in the simulation verification,and the actual commercial vehicle braking system is air pressure braking,which has obvious characteristics of air pressure lag in the braking process and will directly affect the braking effect.Therefore,the key actuators in the commercial vehicle braking system are embedded in the Rapid Control Prototype(RCP)system,and the vehicle model in TruckSim and hardware equipment are connected through the embedded real-time test NI platform to form the HIL control system.In the test,the pilot car is controlled by the actual driver on the driving simulator of the test bench.The driver presses the electronic accelerator pedal,brake pedal and turns the steering wheel on the test bench to drive the controlled object in TruckSim,realizing the driving behavior.The following member vehicles in TruckSim are controled through the RCP system to follow the pilot vehicle and realize the control of the target inter-vehicle spacing.The results of HIL simulation test show that the proposed control system can effectively ensure driving safety and prevent rear end collision.