Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steer...Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control.However,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle.In this paper,the optimum hand wheel torque is designed based on the linear tire model.Considering the uncertainty and disturbance of the steering system and vehicle,an H∞controller is developed to make sure the hand wheel torque follows the reference torque accurately and quickly.The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.展开更多
The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fu...The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fuel burn,and noise when taxiing on the ground at airports.There is an urgent need to reduce aircraft taxiing time on the ground.However,it is too expensive for airports and aircraft carriers to build and maintain more runways,and it is space-limited to tow the aircraft fast using tractors.Autonomous drive capability is currently the best solution for aircraft,which can save the maneuver time for aircraft.An idea is proposed that the wheels are driven by APU-powered(auxiliary power unit)motors,APU is working on its efficient point;consequently,the emissions,fuel burn,and noise will be reduced significantly.For Front-wheel drive aircraft,the front wheel must provide longitudinal force to tow the plane forward and lateral force to help the aircraft make a turn.Forward traction effects the aircraft’s maximum turning ability,which is difficult to be modeled to guide the controller design.Deep reinforcement learning provides a powerful tool to help us design controllers for black-box models;however,the models of related works are always simplified,fixed,or not easily modified,but that is what we care about most.Only with complex models can the trained controller be intelligent.High-fidelity models that can easily modified are necessary for aircraft ground maneuver controller design.This paper focuses on the maneuvering problem of front-wheel drive aircraft,a high-fidelity aircraft taxiing dynamic model is established,including the 6-DOF airframe,landing gears,and nonlinear tire force model.A deep reinforcement learning based controller was designed to improve the maneuver performance of front-wheel drive aircraft.It is proved that in some conditions,the DRL based controller outperformed conventional look-ahead controllers.展开更多
To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random ex...To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of ?10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm; this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle.展开更多
Based on dynamic analysis for the Front Wheel Assist (FWA) tractor, a calculating and analysing method on selecting the optimum coefficient of inharmonious motion for the FWA tractor is described in this paper and the...Based on dynamic analysis for the Front Wheel Assist (FWA) tractor, a calculating and analysing method on selecting the optimum coefficient of inharmonious motion for the FWA tractor is described in this paper and the mathematical models arc also established. The article first time dlefines the ratio of thrust of front wheels to that of rear wheels, which is an important parameter affecting the tractive performance of the FWA tractor and establishes the condition of no power circulation of the FWA tractor. The optimum coefficient of inharmonious motion for a FWA tractor (UTB-445) is also given.展开更多
Selecting design variables and determining optimal hard⁃point coordinates are subjective in the traditional multiobjective optimization of geometric design of vehicle suspension,thereby usually resulting in poor overa...Selecting design variables and determining optimal hard⁃point coordinates are subjective in the traditional multiobjective optimization of geometric design of vehicle suspension,thereby usually resulting in poor overall suspension kinematic performance.To eliminate the subjectivity of selection,a method transferring multiobjective optimization function into a single⁃objective one through the integrated use of grey relational analysis(GRA)and improved entropy weight method(IEWM)is proposed.First,a comprehensive evaluation index of sensitivities was formulated to facilitate the objective selection of design variables by using GRA,in which IEWM was used to determine the weight of each subindex.Second,approximate models between the variations of the front wheel alignment parameters and the design variables were developed on the basis of support vector regression(SVR)and the fruit fly optimization algorithm(FOA).Subsequently,to eliminate the subjectivity and improve the computational efficiency of multiobjective optimization(MOO)of hard⁃point coordinates,the MOO functions were transformed into a single⁃objective optimization(SOO)function by using the GRA-IEWM method again.Finally,the SOO problem was solved by the self⁃adaptive differential evolution(jDE)algorithm.Simulation results indicate that the GRA⁃IEWM method outperforms the traditional multiobjective optimization method and the original coordinate scheme remarkably in terms of kinematic performance.展开更多
A uniform optimization object function for front wheel orientation parameters of a vehicle is reported, which includes the tolerances of practical values and set values of front wheel orientation parameters under full...A uniform optimization object function for front wheel orientation parameters of a vehicle is reported, which includes the tolerances of practical values and set values of front wheel orientation parameters under full load, and the changing value of each parameter with front wheel fluctuation to build a front suspension model for optimization analysis based on the multi-body dynamic (MD) theory. The original suspension is optimized with this model, and the variation law of each parameter with front wheel fluctuation is obtained. The results of a case study demonstrate that the front wheel orientation parameters of the optimized vehicle are reasonable under typical conditions and the variation of each parameter is in an ideal range with the wheel fluctuating within 40 mm. In addition, the driving performance is improved greatly in the road test and practical use.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51375007 and 51205191)NUAA Research Funding(Grant No.NS2013015)
文摘Active front steering(AFS)system has been used as a promising technology which improves the steering portability and handing stability of vehicles.It employs a steering motor to realize the functions of variable steering ratio and vehicle stability control.However,it has a serious problem of unexpected reaction hand wheel torque caused by the additional steering angle.In this paper,the optimum hand wheel torque is designed based on the linear tire model.Considering the uncertainty and disturbance of the steering system and vehicle,an H∞controller is developed to make sure the hand wheel torque follows the reference torque accurately and quickly.The simulation shows that the proposed controller can compensate the unnatural reaction torque and provide a good steering feel for the driver.
基金Funded by National Natural Science Foundation of China(No.51775014)Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems of China(No.GZKF-202010)+1 种基金National Key R&D Program of China(No.2019YFB2004503)the Science and Technology on Aircraft Control Laboratory of China。
文摘The maneuvering time on the ground accounts for 10%–30%of their flight time,and it always exceeds 50%for short-haul aircraft when the ground traffic is congested.Aircraft also contribute significantly to emissions,fuel burn,and noise when taxiing on the ground at airports.There is an urgent need to reduce aircraft taxiing time on the ground.However,it is too expensive for airports and aircraft carriers to build and maintain more runways,and it is space-limited to tow the aircraft fast using tractors.Autonomous drive capability is currently the best solution for aircraft,which can save the maneuver time for aircraft.An idea is proposed that the wheels are driven by APU-powered(auxiliary power unit)motors,APU is working on its efficient point;consequently,the emissions,fuel burn,and noise will be reduced significantly.For Front-wheel drive aircraft,the front wheel must provide longitudinal force to tow the plane forward and lateral force to help the aircraft make a turn.Forward traction effects the aircraft’s maximum turning ability,which is difficult to be modeled to guide the controller design.Deep reinforcement learning provides a powerful tool to help us design controllers for black-box models;however,the models of related works are always simplified,fixed,or not easily modified,but that is what we care about most.Only with complex models can the trained controller be intelligent.High-fidelity models that can easily modified are necessary for aircraft ground maneuver controller design.This paper focuses on the maneuvering problem of front-wheel drive aircraft,a high-fidelity aircraft taxiing dynamic model is established,including the 6-DOF airframe,landing gears,and nonlinear tire force model.A deep reinforcement learning based controller was designed to improve the maneuver performance of front-wheel drive aircraft.It is proved that in some conditions,the DRL based controller outperformed conventional look-ahead controllers.
基金the Postdoctoral Science Foundation of China (No. 2004036396)the Foundation of 985- Automotive Engineering of Jilin University
文摘To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of ?10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm; this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle.
文摘Based on dynamic analysis for the Front Wheel Assist (FWA) tractor, a calculating and analysing method on selecting the optimum coefficient of inharmonious motion for the FWA tractor is described in this paper and the mathematical models arc also established. The article first time dlefines the ratio of thrust of front wheels to that of rear wheels, which is an important parameter affecting the tractive performance of the FWA tractor and establishes the condition of no power circulation of the FWA tractor. The optimum coefficient of inharmonious motion for a FWA tractor (UTB-445) is also given.
基金Sponsored by the National Natural Science Foundation of China(Grant No.71871078).
文摘Selecting design variables and determining optimal hard⁃point coordinates are subjective in the traditional multiobjective optimization of geometric design of vehicle suspension,thereby usually resulting in poor overall suspension kinematic performance.To eliminate the subjectivity of selection,a method transferring multiobjective optimization function into a single⁃objective one through the integrated use of grey relational analysis(GRA)and improved entropy weight method(IEWM)is proposed.First,a comprehensive evaluation index of sensitivities was formulated to facilitate the objective selection of design variables by using GRA,in which IEWM was used to determine the weight of each subindex.Second,approximate models between the variations of the front wheel alignment parameters and the design variables were developed on the basis of support vector regression(SVR)and the fruit fly optimization algorithm(FOA).Subsequently,to eliminate the subjectivity and improve the computational efficiency of multiobjective optimization(MOO)of hard⁃point coordinates,the MOO functions were transformed into a single⁃objective optimization(SOO)function by using the GRA-IEWM method again.Finally,the SOO problem was solved by the self⁃adaptive differential evolution(jDE)algorithm.Simulation results indicate that the GRA⁃IEWM method outperforms the traditional multiobjective optimization method and the original coordinate scheme remarkably in terms of kinematic performance.
文摘A uniform optimization object function for front wheel orientation parameters of a vehicle is reported, which includes the tolerances of practical values and set values of front wheel orientation parameters under full load, and the changing value of each parameter with front wheel fluctuation to build a front suspension model for optimization analysis based on the multi-body dynamic (MD) theory. The original suspension is optimized with this model, and the variation law of each parameter with front wheel fluctuation is obtained. The results of a case study demonstrate that the front wheel orientation parameters of the optimized vehicle are reasonable under typical conditions and the variation of each parameter is in an ideal range with the wheel fluctuating within 40 mm. In addition, the driving performance is improved greatly in the road test and practical use.
