Research On Hybrid Driving Control Of Heavy Vehicle Based On Multidisciplinary Simulation

With the increasing demand of heavy vehicles for mobility and the wide application of hybrid technology,multi-axle heavy-duty hybrid electric vehicles have emerged as the times require.The vehicles are widely used with the characteristics of carrying heavy equipment,improving power reserve,enhancing maneuverability,improving transportation efficiency,protecting road surface and bridge.In this paper,six-axle heavy-duty hybrid electric vehicle is taken as the research object.Aiming at the comprehensive optimization of multi-performance indexes during vehicle acceleration,cruising and braking operation,the multi-condition integrated control strategy of vehicle including driving and braking control is studied,so as to improve the dynamic performance and safety of vehicle.The main research work of this paper is as follows.(1)According to the research requirements of driving control and braking control of multi-axle heavy hybrid electric vehicle,this research establishes the power unit,lithium battery pack,wheel motor,transmission system and wheel model,which provides input and output interface for control system parameters,and verifies the correctness of the model through test data.Forward modeling method is used to make the model easy to combine driver’s subjective intention with vehicle’s motion state through the design of control strategy,which provides a simulation platform for the research of control strategy.(2)By analyzing the power demand characteristics of hybrid electric vehicles,this paper raised a dynamic coordinated driving control strategy adapted to flat road,uphill road,low-adhesion road and other road conditions.It includes the strategy of vehicle power demand for the purpose of improving vehicle acceleration ability,so that the vehicle can quickly meet the driver’s acceleration request.In addition,based on the analysis of the longitudinal dynamics of multi-axle vehicle,this paper designs a hierarchical multi-motor torque coordinated allocation control strategy to make the multi-condition vehicle perform better,that is to say,the vehicle has stronger adaptability under off-road conditions,and has better mobility and higher running efficiency in the normal driving time.(3)This paper raised a dynamic braking control strategy which is adapted to downhill amble and flat multi-adhesion road conditions for the purpose of ensuring vehicle braking safety and improving energy utilization.The serial hybrid braking strategy is designed according to battery power and vehicle speed,and the parallel hybrid braking strategy is designed according to motor angular acceleration and battery power.Then the series-parallel hybrid braking strategy is formed by combining the two strategies.By using the physical parameters which are easily obtained in the running process,the problem that the control parameters are difficult to obtain is solved,and the threshold control and fuzzy control methods are synthesized to make the vehicle have better adaptability under various braking conditions.(4)In order to observe the effect of the designed vehicle control system,the simulation comparison between the original control strategy and the designed strategy is carried out under the test conditions.It is found that the acceleration and maximum speed of the vehicle are greatly improved,and the validity of the driving control strategy is verified.In order to verify the adaptability of multi-condition vehicle control strategy,this paper designs many conditions including starting,climbing,accelerating,cruising,slow-moving slope and multi-road adhesion coefficient braking conditions.The comprehensive evaluation of vehicle control strategy is carried out.The results show that the vehicle has strong power,good braking safety under this strategy and has strong adaptability under different conditions,which meets the requirements for better comprehensive performance indicators in a variety of driving conditions.