The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
T. J. Kazmierski - One of the best experts on this subject based on the ideXlab platform.
-
High-speed analog simulation of CMOS vision chips using Explicit Integration techniques on many-core processors
2020 Design Automation & Test in Europe Conference & Exhibition (DATE), 2020Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This work describes a high-speed simulation technique of analog circuits which is based on the use of state- space equations and an Explicit Integration Method parallelised on a multiprocessor architecture. The Integration step of such Method is smaller than the one required by an implicit simulation technique based on Newton-Raphson iterations. However, given that Explicit Methods do not require the computation of timeconsuming matrix factorizations, the overall simulation time is reduced. The technique described in this work has been implemented on a NVIDIA general purpose GPU and has been tested simulating the Gaussian filtering operation performed by a smart CMOS image sensor. Such devices are used to perform computation on the edge and include built-in image processing functions. Among those, the Gaussian filtering is one of the most common functions, since it is a basic task for early vision processing. These smart sensors are increasingly complex and hence the time required to simulate them during their design cycle is also larger and larger. From a certain imager size, the proposed simulation Method yields simulation times two order of magnitude faster that an implicit Method based tool such us SPICE.
-
FDL - Simulation Acceleration of Image Filtering on CMOS Vision Chips Using Many-Core Processors
2019 Forum for Specification and Design Languages (FDL), 2019Co-Authors: G. Doménech-asensi, T. J. KazmierskiAbstract:This paper describes an efficient numerical solution to speed up transient simulations of analog circuits on a many-core computer. The technique is based on an Explicit Integration Method, parallelised on a multiprocessor architecture. Although the Integration step is smaller than the required one by traditional simulation Methods based on Newton–Raphson iterations, Explicit Methods do not require to compute complex calculations such us matrix factorizations, which lead to long CPU simulation times. The proposed technique has been implemented on a NVIDIA GPU and has been demonstrated simulating Gaussian filtering operations performed by a CMOS vision chip. These type of devices, which are used to perform computation on the edge, include built-in image processing functions, turning them into very complex and time consuming circuits during their design. The proposed Method is faster that Ngspice for different image sizes, and for 128 x 128 pixels image size it achieves a speed up of two orders of magnitude.
-
An Efficient Numerical Solution Technique for VLSI Interconnect Equations on Many-Core Processors
2019 IEEE International Symposium on Circuits and Systems (ISCAS), 2019Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This paper presents a technique to accelerate transient simulations of analog circuits using an Explicit Integration Method parallelised on a many-core computer. Usual Methods used by SPICE-type simulators are based on Newton-Raphson iterations, which are reliable and numerically stable, but require long CPU processing times. However, although the Integration time step in Explicit Methods is smaller than that used in implicit Methods, this technique avoids the calculation of time-consuming computations due to the Jacobian matrix inversion. The proposed Method uses an Explicit Integration scheme based on the fourth order Adams-Bashforth formula. The algorithm has been parallelised on a NVIDIA general purpose GPU using the CUDA programming model. As a case study, the RC ladder model of a VLSI interconnect is simulated on a general purpose graphic processing unit and the achieved performance is then evaluated against that of a multiprocessor CPU. The results show that the proposed technique achieves a speedup of one order of magnitude in comparison with implicit Integration techniques executed on a CPU.
-
ISCAS - An Efficient Numerical Solution Technique for VLSI Interconnect Equations on Many-Core Processors
2019 IEEE International Symposium on Circuits and Systems (ISCAS), 2019Co-Authors: G. Doménech-asensi, T. J. KazmierskiAbstract:This paper presents a technique to accelerate transient simulations of analog circuits using an Explicit Integration Method parallelised on a many-core computer. Usual Methods used by SPICE-type simulators are based on Newton-Raphson iterations, which are reliable and numerically stable, but require long CPU processing times. However, although the Integration time step in Explicit Methods is smaller than that used in implicit Methods, this technique avoids the calculation of time-consuming computations due to the Jacobian matrix inversion. The proposed Method uses an Explicit Integration scheme based on the fourth order Adams–Bashforth formula. The algorithm has been parallelised on a NVIDIA general purpose GPU using the CUDA programming model. As a case study, the RC ladder model of a VLSI interconnect is simulated on a general purpose graphic processing unit and the achieved performance is then evaluated against that of a multiprocessor CPU. The results show that the proposed technique achieves a speedup of one order of magnitude in comparison with implicit Integration techniques executed on a CPU.
-
Simulation Acceleration of Image Filtering on CMOS Vision Chips Using Many-Core Processors
2019 Forum for Specification and Design Languages (FDL), 2019Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This paper describes an efficient numerical solution to speed up transient simulations of analog circuits on a many-core computer. The technique is based on an Explicit Integration Method, parallelised on a multiprocessor architecture. Although the Integration step is smaller than the required one by traditional simulation Methods based on Newton-Raphson iterations, Explicit Methods do not require to compute complex calculations such us matrix factorizations, which lead to long CPU simulation times. The proposed technique has been implemented on a NVIDIA GPU and has been demonstrated simulating Gaussian filtering operations performed by a CMOS vision chip. These type of devices, which are used to perform computation on the edge, include built-in image processing functions, turning them into very complex and time consuming circuits during their design. The proposed Method is faster that Ngspice for different image sizes, and for 128 x 128 pixels image size it achieves a speed up of two orders of magnitude.
Xinbiao Xiao - One of the best experts on this subject based on the ideXlab platform.
-
A study of the derailment mechanism of a high speed train due to an earthquake
Vehicle System Dynamics, 2012Co-Authors: Xinbiao Xiao, Liang LingAbstract:In order to investigate the mechanism of derailment of high-speed trains due to an earthquake, a coupled vehicle/track dynamic model considering the earthquake effect is developed. The vehicle is modelled as a multi-body system of 35 degrees of freedom and the nonlinear suspension characteristic is considered. The slab track model considers the deformable rails, the discrete support of fasteners and the deformable slabs. Rails are assumed to be Timoshenko beams supported by the rail fasteners discretely, and the slabs are modelled with solid finite elements. The coupling of the vehicle and the track considers the track moving with respect to the vehicle running at a constant speed, and such a coupling model can simulate the effect of the periodical discrete rail supports on the vehicle/track interaction. The least-square curve fitting (LSCF) approach is introduced to integrate the originally recorded earthquake acceleration to acquire the velocity and displacement-time series of the earthquake. The system motion equations are solved by means of an Explicit Integration Method in the time domain. The present paper analyses in detail the effect of the earthquake characteristic on dynamical behaviour of the vehicle and the track and the transient derailment criteria. The considered derailment criteria include the ratio of the wheel/rail lateral force to the vertical force, the wheel loading reduction, and the wheel/rail contact point traces on the wheel tread and the wheel rise with respect to the rail top, respectively. The present investigation includes the effect of lateral earthquake motion, vertical earthquake motion, operation speed, and their combined effect on the existing derailment criteria, respectively.
-
Effect of tangent track buckle on vehicle derailment
Multibody System Dynamics, 2011Co-Authors: Xinbiao Xiao, Zefeng Wen, M.-h. Zhu, X S Jin, Wei-hua ZhangAbstract:In order to investigate the effect of a tangent track buckle on the dynamic derailment of a railway vehicle, a coupled vehicle/track dynamics model is developed, in which the vehicle is modeled as a 35 D.O.F. multibody system and the track is modeled as a 3-layer discrete elastic support model. Rails are assumed to be Timoshenko beams supported by discrete sleepers, and the effects of vertical and lateral motions and rolling of the rail on the wheel/rail creepages are taken into account. The sleepers are treated as Euler beams on elastic foundation for the vertical vibration, while as lumped masses in the lateral direction. A moving sleeper support model is developed to simulate the effect of the periodical discrete sleepers on the vehicle/track interaction. The vehicle and the track are coupled by wheel/rail contacts whereas the normal forces and the creep forces are calculated using the Hertzian contact theory and the nonlinear creep theory by Shen et al., respectively. The equations of motion of the coupled vehicle/track system are solved by means of an Explicit Integration Method. A tangent track buckle is simulated with a cosine function, which describes the misalignment of the track with different lengths due to its buckling. In the analysis the effects of the buckle wavelength and amplitude and of the vehicle speed on the dynamic behavior of the coupled vehicle/track system are considered. The present paper analyzes in detail the conventional derailment coefficients which include the ratio of the wheel/rail lateral force to the vertical force, the wheel load reduction, and the new criteria indicating the wheel/rail contact point traces and the wheel rise with respect to the rail. These criteria are simultaneously used to evaluate the risk of derailment of the whole vehicle. The numerical results obtained indicate that the track misalignment caused by the buckle and the vehicle speed have a great influence on the whole vehicle running safety when the vehicle passes through the buckled tangent track.
-
Track dynamic behavior at rail welds at high speed
Acta Mechanica Sinica/Lixue Xuebao, 2010Co-Authors: Guangwen Xiao, Zefeng Wen, Xinbiao Xiao, Jun Guo, X S JinAbstract:As a vehicle passing through a track with different weld irregularities, the dynamic performance of track components is investigated in detail by using a coupled vehicle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are discretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lateral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calculation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an Explicit Integration Method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail profile irregularity caused by hand-grinding after rail welding and track maintenances.
-
effect of unsupported sleepers on wheel rail normal load
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Shuguang Zhang, Zefeng Wen, Xinbiao Xiao, Xuesong JinAbstract:Abstract The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle–track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle–track are solved by means of an Explicit Integration Method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail.
-
Effect of unsupported sleepers on wheel/rail normal load
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Shuguang Zhang, Xinbiao XiaoAbstract:Abstract The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle–track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle–track are solved by means of an Explicit Integration Method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail.
X S Jin - One of the best experts on this subject based on the ideXlab platform.
-
Effect of tangent track buckle on vehicle derailment
Multibody System Dynamics, 2011Co-Authors: Xinbiao Xiao, Zefeng Wen, M.-h. Zhu, X S Jin, Wei-hua ZhangAbstract:In order to investigate the effect of a tangent track buckle on the dynamic derailment of a railway vehicle, a coupled vehicle/track dynamics model is developed, in which the vehicle is modeled as a 35 D.O.F. multibody system and the track is modeled as a 3-layer discrete elastic support model. Rails are assumed to be Timoshenko beams supported by discrete sleepers, and the effects of vertical and lateral motions and rolling of the rail on the wheel/rail creepages are taken into account. The sleepers are treated as Euler beams on elastic foundation for the vertical vibration, while as lumped masses in the lateral direction. A moving sleeper support model is developed to simulate the effect of the periodical discrete sleepers on the vehicle/track interaction. The vehicle and the track are coupled by wheel/rail contacts whereas the normal forces and the creep forces are calculated using the Hertzian contact theory and the nonlinear creep theory by Shen et al., respectively. The equations of motion of the coupled vehicle/track system are solved by means of an Explicit Integration Method. A tangent track buckle is simulated with a cosine function, which describes the misalignment of the track with different lengths due to its buckling. In the analysis the effects of the buckle wavelength and amplitude and of the vehicle speed on the dynamic behavior of the coupled vehicle/track system are considered. The present paper analyzes in detail the conventional derailment coefficients which include the ratio of the wheel/rail lateral force to the vertical force, the wheel load reduction, and the new criteria indicating the wheel/rail contact point traces and the wheel rise with respect to the rail. These criteria are simultaneously used to evaluate the risk of derailment of the whole vehicle. The numerical results obtained indicate that the track misalignment caused by the buckle and the vehicle speed have a great influence on the whole vehicle running safety when the vehicle passes through the buckled tangent track.
-
Track dynamic behavior at rail welds at high speed
Acta Mechanica Sinica/Lixue Xuebao, 2010Co-Authors: Guangwen Xiao, Zefeng Wen, Xinbiao Xiao, Jun Guo, X S JinAbstract:As a vehicle passing through a track with different weld irregularities, the dynamic performance of track components is investigated in detail by using a coupled vehicle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are discretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lateral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calculation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an Explicit Integration Method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail profile irregularity caused by hand-grinding after rail welding and track maintenances.
-
A hybrid model for noise generation from a railway wheel due to wheel/rail impact
Noise and Vibration Mitigation for Rail Transportation Systems, 2008Co-Authors: Xinbiao Xiao, X S Jin, X Z ShengAbstract:A hybrid model is developed for noise generation from a railway wheel due to wheel/rail impact at a rail joint. It consists of a coupled vehicle/track dynamic interaction model working in the time domain and a FE-BE vibro-acoustic model for the wheel working in the frequency domain. In the coupled vehicle/track interaction model, the vehicle is described as a multi-body system, the rail is idealised as a Timoshenko beam resting on discrete sleepers, and the sleepers are treated as Euler beams. The lateral, vertical, and torsional vibrations of the rail are all taken into account. Sleepers are assumed to move backward at the train speed to simulate the travelling of the vehicle along the track. Wheel/rail normal forces are calculated using the Hertzian contact theory and creep forces are determined using Shen's nonlinear creep theory. The differential equations of motion of the vehicle/track system are solved by means of an Explicit Integration Method, giving wheel/rail force time-histories. The wheel/rail force between a wheel and the rail is then transformed into the frequency domain and input to a FE model of the wheel to calculate its dynamic response. Sound radiated from the wheel is then calculated from the surface response of the wheel using the acoustic boundary element Method. Results produced from this hybrid model demonstrate its suitability for predicting noise radiation from a railway wheel due to wheel/rail impact.
-
Effect of unsupported sleepers on wheel/rail normal load
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Shuguang Zhang, Zefeng Wen, Xinbiao Xiao, X S JinAbstract:The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle-track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle-track are solved by means of an Explicit Integration Method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail. © 2007 Elsevier Ltd. All rights reserved.
-
Effect of curved track support failure on vehicle derailment
Vehicle System Dynamics, 2008Co-Authors: Xinbiao Xiao, Yongquan Deng, X S Jin, Zhongrong ZhouAbstract:In order to investigate the effect of curved track support failure on railway vehicle derailment, a coupled vehicle-track dynamic model is put forward. In the model, the vehicle and the structure under rails are, respectively, modelled as a multi-body system, and the rail is modelled with a Timoshenko beam rested on the discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The model also considers the effect of the discrete support by sleepers on the coupling dynamics of the vehicle and track. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the calculation of the coupled vehicle and track dynamics, the normal forces of the wheels/rails are calculated using the Hertzian contact theory and their creep forces are determined with the nonlinear creep theory by Shen et al [Z.Y. Shen, J.K. Hedrick, and J.A. Elkins, A comparison of alternative creep-force models for rail vehicle dynamic analysis, Proceedings of the 8th IAVSD Symposium, Cambridge, MA, 1984, pp. 591-605]. The motion equations of the vehicle/track are solved by means of an Explicit Integration Method. The failure of the components of the curved track is simulated by changing the track stiffness and damping along the track. The cases where zero to six supports of the curved rails fail are considered. The transient derailment coefficients are calculated. They are, respectively, the ratio of the wheel/rail lateral force to the vertical force and the wheel load reduction. The contact points of the wheels/rails are in detail analysed and used to evaluate the risk of the vehicle derailment. Also, the present work investigates the effect of friction coefficient, axle load and vehicle speed on the derailments under the condition of track failure. The numerical results obtained indicate that the failure of track supports has a great influence on the whole vehicle running safety.
Zefeng Wen - One of the best experts on this subject based on the ideXlab platform.
-
Effect of tangent track buckle on vehicle derailment
Multibody System Dynamics, 2011Co-Authors: Xinbiao Xiao, Zefeng Wen, M.-h. Zhu, X S Jin, Wei-hua ZhangAbstract:In order to investigate the effect of a tangent track buckle on the dynamic derailment of a railway vehicle, a coupled vehicle/track dynamics model is developed, in which the vehicle is modeled as a 35 D.O.F. multibody system and the track is modeled as a 3-layer discrete elastic support model. Rails are assumed to be Timoshenko beams supported by discrete sleepers, and the effects of vertical and lateral motions and rolling of the rail on the wheel/rail creepages are taken into account. The sleepers are treated as Euler beams on elastic foundation for the vertical vibration, while as lumped masses in the lateral direction. A moving sleeper support model is developed to simulate the effect of the periodical discrete sleepers on the vehicle/track interaction. The vehicle and the track are coupled by wheel/rail contacts whereas the normal forces and the creep forces are calculated using the Hertzian contact theory and the nonlinear creep theory by Shen et al., respectively. The equations of motion of the coupled vehicle/track system are solved by means of an Explicit Integration Method. A tangent track buckle is simulated with a cosine function, which describes the misalignment of the track with different lengths due to its buckling. In the analysis the effects of the buckle wavelength and amplitude and of the vehicle speed on the dynamic behavior of the coupled vehicle/track system are considered. The present paper analyzes in detail the conventional derailment coefficients which include the ratio of the wheel/rail lateral force to the vertical force, the wheel load reduction, and the new criteria indicating the wheel/rail contact point traces and the wheel rise with respect to the rail. These criteria are simultaneously used to evaluate the risk of derailment of the whole vehicle. The numerical results obtained indicate that the track misalignment caused by the buckle and the vehicle speed have a great influence on the whole vehicle running safety when the vehicle passes through the buckled tangent track.
-
Track dynamic behavior at rail welds at high speed
Acta Mechanica Sinica/Lixue Xuebao, 2010Co-Authors: Guangwen Xiao, Zefeng Wen, Xinbiao Xiao, Jun Guo, X S JinAbstract:As a vehicle passing through a track with different weld irregularities, the dynamic performance of track components is investigated in detail by using a coupled vehicle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are discretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lateral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calculation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an Explicit Integration Method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail profile irregularity caused by hand-grinding after rail welding and track maintenances.
-
effect of unsupported sleepers on wheel rail normal load
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Shuguang Zhang, Zefeng Wen, Xinbiao Xiao, Xuesong JinAbstract:Abstract The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle–track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle–track are solved by means of an Explicit Integration Method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail.
-
Effect of unsupported sleepers on wheel/rail normal load
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Shuguang Zhang, Zefeng Wen, Xinbiao Xiao, X S JinAbstract:The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle-track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle-track are solved by means of an Explicit Integration Method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail. © 2007 Elsevier Ltd. All rights reserved.
Ginés Doménech-asensi - One of the best experts on this subject based on the ideXlab platform.
-
High-speed analog simulation of CMOS vision chips using Explicit Integration techniques on many-core processors
2020 Design Automation & Test in Europe Conference & Exhibition (DATE), 2020Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This work describes a high-speed simulation technique of analog circuits which is based on the use of state- space equations and an Explicit Integration Method parallelised on a multiprocessor architecture. The Integration step of such Method is smaller than the one required by an implicit simulation technique based on Newton-Raphson iterations. However, given that Explicit Methods do not require the computation of timeconsuming matrix factorizations, the overall simulation time is reduced. The technique described in this work has been implemented on a NVIDIA general purpose GPU and has been tested simulating the Gaussian filtering operation performed by a smart CMOS image sensor. Such devices are used to perform computation on the edge and include built-in image processing functions. Among those, the Gaussian filtering is one of the most common functions, since it is a basic task for early vision processing. These smart sensors are increasingly complex and hence the time required to simulate them during their design cycle is also larger and larger. From a certain imager size, the proposed simulation Method yields simulation times two order of magnitude faster that an implicit Method based tool such us SPICE.
-
An Efficient Numerical Solution Technique for VLSI Interconnect Equations on Many-Core Processors
2019 IEEE International Symposium on Circuits and Systems (ISCAS), 2019Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This paper presents a technique to accelerate transient simulations of analog circuits using an Explicit Integration Method parallelised on a many-core computer. Usual Methods used by SPICE-type simulators are based on Newton-Raphson iterations, which are reliable and numerically stable, but require long CPU processing times. However, although the Integration time step in Explicit Methods is smaller than that used in implicit Methods, this technique avoids the calculation of time-consuming computations due to the Jacobian matrix inversion. The proposed Method uses an Explicit Integration scheme based on the fourth order Adams-Bashforth formula. The algorithm has been parallelised on a NVIDIA general purpose GPU using the CUDA programming model. As a case study, the RC ladder model of a VLSI interconnect is simulated on a general purpose graphic processing unit and the achieved performance is then evaluated against that of a multiprocessor CPU. The results show that the proposed technique achieves a speedup of one order of magnitude in comparison with implicit Integration techniques executed on a CPU.
-
Simulation Acceleration of Image Filtering on CMOS Vision Chips Using Many-Core Processors
2019 Forum for Specification and Design Languages (FDL), 2019Co-Authors: Ginés Doménech-asensi, T. J. KazmierskiAbstract:This paper describes an efficient numerical solution to speed up transient simulations of analog circuits on a many-core computer. The technique is based on an Explicit Integration Method, parallelised on a multiprocessor architecture. Although the Integration step is smaller than the required one by traditional simulation Methods based on Newton-Raphson iterations, Explicit Methods do not require to compute complex calculations such us matrix factorizations, which lead to long CPU simulation times. The proposed technique has been implemented on a NVIDIA GPU and has been demonstrated simulating Gaussian filtering operations performed by a CMOS vision chip. These type of devices, which are used to perform computation on the edge, include built-in image processing functions, turning them into very complex and time consuming circuits during their design. The proposed Method is faster that Ngspice for different image sizes, and for 128 x 128 pixels image size it achieves a speed up of two orders of magnitude.
