In this paper, a model order reduction strategy is adopted for the static and dynamic behaviour simulation of a high-speed tracked vehicle. The total number of degree of freedom of the structure is condensed through a...In this paper, a model order reduction strategy is adopted for the static and dynamic behaviour simulation of a high-speed tracked vehicle. The total number of degree of freedom of the structure is condensed through a selection of interface degrees of freedom and significant global mode shapes, for an approximated description of vehicle dynamic behaviour. The methodology is implemented in a customised open-source software to reduce the computational efforts. The modelled tracked vehicle includes the sprung mass, the unsprung masses, connected by means of torsional bars, and all the track assemblies, composing the track chain. The proposed research activity presents a comprehensive investigation of the influence of the track chain, combined with longitudinal vehicle speed, on statics and vehicle dynamics, focusing on vertical dynamics. The vehicle response has been investigated both in frequency and time domain. In this last case road-wheel displacements are assumed as inputs for the model, under different working conditions, hence considering several road profiles with different amplitudes and characteristic excitation frequencies. Simulation results have proven a high fidelity in model order reduction approach and a significant contribution of the track chain in the global dynamic behaviour of the tracked vehicle.展开更多
The track model used in the dynamic analysis and design system software is investigated. A home made tank is taken as an example to illustrate the method for modeling an integral tracked vehicle and perform the dynam...The track model used in the dynamic analysis and design system software is investigated. A home made tank is taken as an example to illustrate the method for modeling an integral tracked vehicle and perform the dynamic simulation. The obtained results have demonstrated that the simulation method has the advantage of high efficiency, more convenience and more insight into the dynamical behavior of the system.展开更多
This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics.Considering the spatial randomness of system properties in geo...This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics.Considering the spatial randomness of system properties in geometry,physics and mechanics,the primary work is therefore simulating the uncertainties realistically,representatively and efficiently.With regard to the track irregularity simulation,a model is newly developed to obtain random sample sets of track irregularities by transforming its power spectral density function into the equivalent track quality index for representation based on the discrete Parseval theorem,where the correlation between various types of track irregularities is accounted for.To statistically clarify the uncertainty of track properties in physics and mechanics in space,a model combining discrete element method and finite element method is developed to obtain the spatially varied track parametric characteristics,e.g.track stiffness and density,through which the highly expensive experiments in situ can be avoided.Finally a train–track stochastic analysis model is formulated by integrating the system uncertainties into the dynamics model.Numerical examples have validated the accuracy and efficiency of this model and illustrated the effects of system spatial variability on train–track vibrations comprehensively.展开更多
Based on previous achievements,a dynamic pressure-sinkage equation for saturated clay is established.First,aquasi-static penetration rate is selected,and the ratio of the dynamic penetration rate to the quasi-static r...Based on previous achievements,a dynamic pressure-sinkage equation for saturated clay is established.First,aquasi-static penetration rate is selected,and the ratio of the dynamic penetration rate to the quasi-static rate is used to characterize the degree of dynamic effect,then theβth power of the ratio is used to quantify the dynamic effect of sinkage.The dynamic effect exponentβis obtained using penetration tests with different penetration rates.Then,a dynamic motion resistance equation for a tracked vehicle is established based on the dynamic pressure-sinkage equation.The equation incorporates both penetration and bulldozing resistance.Finally,a series of simulation experiments with varying travel speeds and slip rates is carried out.The results show that an increase in the speed leads to stronger terrain stiffness,resulting in a decrease in sinkage and motion resistance.However,the enhancement effect becomes weaker with an increase in the travel speed.展开更多
Employing theory on vehicle-track coupled dynamics, the equation of motion of a vehicle-track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response ...Employing theory on vehicle-track coupled dynamics, the equation of motion of a vehicle-track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response of the vehicle-track vertical coupled system was calculated under the excitation of the German low-interfer- ence spectrum, and the effects of the vehicle speed, vehicle suspension parameters, and track support parameters on the frequency response of the coupled system were studied. Results show that, under the excitation of the German low- interference spectrum, the vertical vibration of the car body is mainly concentrated in the low-frequency band, while that of the bogie has a wide frequency distribution, being strong from several Hertz to dozens of Hertz. The vertical vibrations of the wheel-rail force, wheelset, and track structure mainly occur at a frequency of dozens of Hertz. In general, the vertical vibration of the vehicle-track coupled system increases with vehicle speed, and the vertical vibrations of the car body and bogie obviously shift to higher frequency. Increasing the vehicle suspension stiffness increases the low- frequency vibrations of the vehicle system and track struc- ture. With an increase in vehicle suspension damping, the low-frequency vibrations of the car body and bogie and the vibrations of the wheel-rail vertical force and track structure decrease at 50-80 Hz, while the mid-frequency and high- frequency vibrations of the car body and bogie increase. Similarly, an increase in track stiffness amplifies the vertical vibrations of the wheel-rail force and track structure, while an increase in track damping effectively reduces the vertical vibrations of the wheel-rail vertical force and track structure.展开更多
Automotive collision avoidance technology can effectively avoid the accidents caused by dangerous traffic conditions or driver's manipulation errors.Moreover,it can promote the development of autonomous driving fo...Automotive collision avoidance technology can effectively avoid the accidents caused by dangerous traffic conditions or driver's manipulation errors.Moreover,it can promote the development of autonomous driving for intelligent vehicle in intelligent transportation.We present a collision avoidance system,which is composed of an evasive trajectory planner and a path following controller.Considering the stability of the vehicle in the conflict-free process,the evasive trajectory planner is designed by polynomial parametric method and optimized by genetic algorithm.The path following controller is proposed to make the car drive along the designed path by controlling the vehicle's lateral movement.Simulation results show that the vehicle with the proposed controller has good stability in the collision process,and it can ensure the vehicle driving in accordance with the planned trajectory at different speeds.The research results can provide a certain basis for the research and development of automotive collision avoidance technology.展开更多
A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities ...A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.展开更多
In order to investigate how model fidelity in the formulation of model predictive control(MPC)algorithm affects the path tracking performance,a bicycle model and an 8 degrees of freedom(DOF)vehicle model,as well as a ...In order to investigate how model fidelity in the formulation of model predictive control(MPC)algorithm affects the path tracking performance,a bicycle model and an 8 degrees of freedom(DOF)vehicle model,as well as a 14-DOF vehicle model were employed to implement the MPC-based path tracking controller considering the constraints of input limit and output admissibility by using a lower fidelity vehicle model to control a higher fidelity vehicle model.In the MPC controller,the nonlinear vehicle model was linearized and discretized for state prediction and vehicle heading angle,lateral position and longitudinal position were chosen as objectives in the cost function.The wheel step steering and sine wave steering responses between the developed vehicle models and the Carsim model were compared for validation before implementing the model predictive path tracking control.The simulation results of trajectory tracking considering an 8-shaped curved reference path were presented and compared when the prediction model and the plant were changed.The results show that the trajectory tracking errors are small and the tracking performances of the proposed controller considering different complexity vehicle models are good in the curved road environment.Additionally,the MPC-based controller formulated with a high-fidelity model performs better than that with a low-fidelity model in the trajectory tracking.展开更多
Based on the analysis of complex terrains and current forest transportation equipment,a forest tracked vehicle prototype LY1352 JP was developed.The road model and the virtual prototype of the chassis were constructed...Based on the analysis of complex terrains and current forest transportation equipment,a forest tracked vehicle prototype LY1352 JP was developed.The road model and the virtual prototype of the chassis were constructed using dynamic simulation software RecurDyn.The optimal tension of the vehicle as well as its capabilities for crossing trenches,climbing vertical walls,uphill and downhill slopes were simulated.The simulation results showed that the optimum tension force of the chassis of the vehicle was 63 kN(kilonewton),accounting for 45%of the total vehicle weight.The maximum trench crossing width and vertical obstacle climbing height were 1.35 m and 0.45 m,respectively.The maximum uphill and downhill angles were 50°and 45°,respectively.Tests on the prototype capacity for crossing trenches,and uphill and downhill driving were carried out.The test results were in agreement with the simulation results.A cross-country performance of a fire truck based on the tracked vehicle chassis was conducted in an old-growth forest.Tests verified that the vehicle has a strong forest trafficability performance and can meet the needs for forest transportation.展开更多
The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling syst...The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.展开更多
A vehicle-track-bridge coupling dynamics model was built based on the theory of vehicle-track coupling dynamics. Using this model, a comparison was made between the dynamic response of an elastic sleeper ballasted tra...A vehicle-track-bridge coupling dynamics model was built based on the theory of vehicle-track coupling dynamics. Using this model, a comparison was made between the dynamic response of an elastic sleeper ballasted track and a common sleeper ballasted track on bridge under the same working conditions. The results show that laying elastic sleepers on the bridge could solve the problem of large track stiffness caused by a thin ballast thickness, and improve the dynamic response of the bridge. This is beneficial to train operation safety and riding comfort.展开更多
We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:de...We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:determine the true track geometry from measured wheelset dynamical reactions.It is known that the method works well for the vertical position of the rails but the computed lateral position is often flawed.We find that the lateral motion of the wheelset often may differ from the track geometry.The cases are investigated closely but the reasons remain unknown.While the wheelset dynamics reflect the larger(>4-6 mm)aperiodic track disturbances and single large disturbances quite well,this does not seem to be the case for general smaller or periodic track irregularities or sections behind single large disturbances.The resulting dynamics of a wheelset to lateral track irregularities are in general not sufficiently accurate to be used as the basis for a description of the track irregularities.展开更多
文摘In this paper, a model order reduction strategy is adopted for the static and dynamic behaviour simulation of a high-speed tracked vehicle. The total number of degree of freedom of the structure is condensed through a selection of interface degrees of freedom and significant global mode shapes, for an approximated description of vehicle dynamic behaviour. The methodology is implemented in a customised open-source software to reduce the computational efforts. The modelled tracked vehicle includes the sprung mass, the unsprung masses, connected by means of torsional bars, and all the track assemblies, composing the track chain. The proposed research activity presents a comprehensive investigation of the influence of the track chain, combined with longitudinal vehicle speed, on statics and vehicle dynamics, focusing on vertical dynamics. The vehicle response has been investigated both in frequency and time domain. In this last case road-wheel displacements are assumed as inputs for the model, under different working conditions, hence considering several road profiles with different amplitudes and characteristic excitation frequencies. Simulation results have proven a high fidelity in model order reduction approach and a significant contribution of the track chain in the global dynamic behaviour of the tracked vehicle.
文摘The track model used in the dynamic analysis and design system software is investigated. A home made tank is taken as an example to illustrate the method for modeling an integral tracked vehicle and perform the dynamic simulation. The obtained results have demonstrated that the simulation method has the advantage of high efficiency, more convenience and more insight into the dynamical behavior of the system.
基金supported by National Natural Science Foundation of China (NSFC) under Grant Nos. 51735012 and 11790283
文摘This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics.Considering the spatial randomness of system properties in geometry,physics and mechanics,the primary work is therefore simulating the uncertainties realistically,representatively and efficiently.With regard to the track irregularity simulation,a model is newly developed to obtain random sample sets of track irregularities by transforming its power spectral density function into the equivalent track quality index for representation based on the discrete Parseval theorem,where the correlation between various types of track irregularities is accounted for.To statistically clarify the uncertainty of track properties in physics and mechanics in space,a model combining discrete element method and finite element method is developed to obtain the spatially varied track parametric characteristics,e.g.track stiffness and density,through which the highly expensive experiments in situ can be avoided.Finally a train–track stochastic analysis model is formulated by integrating the system uncertainties into the dynamics model.Numerical examples have validated the accuracy and efficiency of this model and illustrated the effects of system spatial variability on train–track vibrations comprehensively.
基金Supported by the National Natural Science Foundation of China(51005018)
文摘Based on previous achievements,a dynamic pressure-sinkage equation for saturated clay is established.First,aquasi-static penetration rate is selected,and the ratio of the dynamic penetration rate to the quasi-static rate is used to characterize the degree of dynamic effect,then theβth power of the ratio is used to quantify the dynamic effect of sinkage.The dynamic effect exponentβis obtained using penetration tests with different penetration rates.Then,a dynamic motion resistance equation for a tracked vehicle is established based on the dynamic pressure-sinkage equation.The equation incorporates both penetration and bulldozing resistance.Finally,a series of simulation experiments with varying travel speeds and slip rates is carried out.The results show that an increase in the speed leads to stronger terrain stiffness,resulting in a decrease in sinkage and motion resistance.However,the enhancement effect becomes weaker with an increase in the travel speed.
文摘Employing theory on vehicle-track coupled dynamics, the equation of motion of a vehicle-track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response of the vehicle-track vertical coupled system was calculated under the excitation of the German low-interfer- ence spectrum, and the effects of the vehicle speed, vehicle suspension parameters, and track support parameters on the frequency response of the coupled system were studied. Results show that, under the excitation of the German low- interference spectrum, the vertical vibration of the car body is mainly concentrated in the low-frequency band, while that of the bogie has a wide frequency distribution, being strong from several Hertz to dozens of Hertz. The vertical vibrations of the wheel-rail force, wheelset, and track structure mainly occur at a frequency of dozens of Hertz. In general, the vertical vibration of the vehicle-track coupled system increases with vehicle speed, and the vertical vibrations of the car body and bogie obviously shift to higher frequency. Increasing the vehicle suspension stiffness increases the low- frequency vibrations of the vehicle system and track struc- ture. With an increase in vehicle suspension damping, the low-frequency vibrations of the car body and bogie and the vibrations of the wheel-rail vertical force and track structure decrease at 50-80 Hz, while the mid-frequency and high- frequency vibrations of the car body and bogie increase. Similarly, an increase in track stiffness amplifies the vertical vibrations of the wheel-rail force and track structure, while an increase in track damping effectively reduces the vertical vibrations of the wheel-rail vertical force and track structure.
基金supported by the National Key Research and Development Plan of China (No.2016YFB0101102 )the Suzhou Tsinghua Innovation Initiative(No. 2016SZ0207)+2 种基金the National Natural Science Foundation of China(No.51375007)the Research Project of Key Laboratory of Advanced Manufacture Technology for Automobile Parts(Chongqing University of Technology),Ministry of Education (No.2015KLMT04)the Fundamental Research Funds for the Central Universities (No. NE2016002)
文摘Automotive collision avoidance technology can effectively avoid the accidents caused by dangerous traffic conditions or driver's manipulation errors.Moreover,it can promote the development of autonomous driving for intelligent vehicle in intelligent transportation.We present a collision avoidance system,which is composed of an evasive trajectory planner and a path following controller.Considering the stability of the vehicle in the conflict-free process,the evasive trajectory planner is designed by polynomial parametric method and optimized by genetic algorithm.The path following controller is proposed to make the car drive along the designed path by controlling the vehicle's lateral movement.Simulation results show that the vehicle with the proposed controller has good stability in the collision process,and it can ensure the vehicle driving in accordance with the planned trajectory at different speeds.The research results can provide a certain basis for the research and development of automotive collision avoidance technology.
基金Supported by State Key Laboratory of Robotics and Systems(HIT)(SKLRS-2010-ZD-04)Capital Medical Development Scientific Research Fund(20092098)
文摘A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.
基金Supported by International Graduate Exchange Program of Beijing Institute of Technology。
文摘In order to investigate how model fidelity in the formulation of model predictive control(MPC)algorithm affects the path tracking performance,a bicycle model and an 8 degrees of freedom(DOF)vehicle model,as well as a 14-DOF vehicle model were employed to implement the MPC-based path tracking controller considering the constraints of input limit and output admissibility by using a lower fidelity vehicle model to control a higher fidelity vehicle model.In the MPC controller,the nonlinear vehicle model was linearized and discretized for state prediction and vehicle heading angle,lateral position and longitudinal position were chosen as objectives in the cost function.The wheel step steering and sine wave steering responses between the developed vehicle models and the Carsim model were compared for validation before implementing the model predictive path tracking control.The simulation results of trajectory tracking considering an 8-shaped curved reference path were presented and compared when the prediction model and the plant were changed.The results show that the trajectory tracking errors are small and the tracking performances of the proposed controller considering different complexity vehicle models are good in the curved road environment.Additionally,the MPC-based controller formulated with a high-fidelity model performs better than that with a low-fidelity model in the trajectory tracking.
基金funded by the Fundamental Research Funds for the Central Universities(No.2572019BL02)the National Key Research and Development Program of China(No.2018YFD0600205)。
文摘Based on the analysis of complex terrains and current forest transportation equipment,a forest tracked vehicle prototype LY1352 JP was developed.The road model and the virtual prototype of the chassis were constructed using dynamic simulation software RecurDyn.The optimal tension of the vehicle as well as its capabilities for crossing trenches,climbing vertical walls,uphill and downhill slopes were simulated.The simulation results showed that the optimum tension force of the chassis of the vehicle was 63 kN(kilonewton),accounting for 45%of the total vehicle weight.The maximum trench crossing width and vertical obstacle climbing height were 1.35 m and 0.45 m,respectively.The maximum uphill and downhill angles were 50°and 45°,respectively.Tests on the prototype capacity for crossing trenches,and uphill and downhill driving were carried out.The test results were in agreement with the simulation results.A cross-country performance of a fire truck based on the tracked vehicle chassis was conducted in an old-growth forest.Tests verified that the vehicle has a strong forest trafficability performance and can meet the needs for forest transportation.
文摘The electric transmission system congfiguration-2 is one of the main electric drives for tracked vehicles. The geometrical model for the power-train cabin is established and the preliminary design for its cooling system is implemented. The mathematic model is established for thermal current field computation, simulation and analysis in the powertrain cabin. The three-dimensional structure of the powertrain cabin is optimized. The validity of the cooling system design is proved. The foundation for optimizing the whole electric transmission system configuration is laid.
文摘A vehicle-track-bridge coupling dynamics model was built based on the theory of vehicle-track coupling dynamics. Using this model, a comparison was made between the dynamic response of an elastic sleeper ballasted track and a common sleeper ballasted track on bridge under the same working conditions. The results show that laying elastic sleepers on the bridge could solve the problem of large track stiffness caused by a thin ballast thickness, and improve the dynamic response of the bridge. This is beneficial to train operation safety and riding comfort.
文摘We investigate numerically the dynamical reactions of a moving wheelset model to real measured track irregularities.The background is to examine whether the dynamics are suitable as the input to the inverse problem:determine the true track geometry from measured wheelset dynamical reactions.It is known that the method works well for the vertical position of the rails but the computed lateral position is often flawed.We find that the lateral motion of the wheelset often may differ from the track geometry.The cases are investigated closely but the reasons remain unknown.While the wheelset dynamics reflect the larger(>4-6 mm)aperiodic track disturbances and single large disturbances quite well,this does not seem to be the case for general smaller or periodic track irregularities or sections behind single large disturbances.The resulting dynamics of a wheelset to lateral track irregularities are in general not sufficiently accurate to be used as the basis for a description of the track irregularities.
