Search query: OHT vehicle TRACK

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abstract: We present a reinforcement learning based algorithm for route guidance and vehicle assignment of an overhead hoist transport system, a typical form of automated material handling system in semiconductor fabrication facilities (fabs) As the size of the fab increases, so does the number of vehicles required to operate in the fab. The algorithm most commonly used in industry, a mathematical optimization based algorithm that constantly seeks the shortest routes, has been proven ineffective in dealing with fabs operating around 1,000 vehicles or more. In this paper, we introduce Q learning, a reinforcement learning based algorithm for route guidance and vehicle assignment. Q learning dynamically reroutes the vehicles based on the congestion and traffic conditions. It also assigns vehicles to tasks based on the overall congestion of the track. We show that the proposed algorithm is considerably more effective than the existing algorithm in an actual fab scale experiment. Moreover, we illustrate that the Q learning based algorithm is more effective in designing the track layouts.
author_names: Illhoe Hwang

Hyemin Cho

Sang Pyo Hong

Junhui Lee

Seokjoon Kim

Young Jae Jang
title: Q learning based route guidance and vehicle assignment for OHT systems in semiconductor fabs
venue: 2020 31st Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC)
year: 2020

abstract: The high throughput automated material handling system (AMHS) is required to support carrier delivery requirement of 300 mm prime and 450 mm wafer fab. The unified overhead hoisting transport (OHT) system has been used for 300 mm fab to get high throughput and short delivery time; however, it has throughput limitations because of vehicle traffic congestion, especially in the interbay area. This paper describes the dual unified OHT (DUO) system, a new track layout system to reduce interbay congestion and improve delivery throughput. A simulation result is included to compare the throughput performance of the DUO and single unified OHT (SUO) system.
author_names: ChungSoo Han

K Pare

Manabu Tokumoto

Atsushi Aoki
title: High Throughput AMHS Design with Dual Unified OHT System
venue: 2006 IEEE International Symposium on Semiconductor Manufacturing
year: 2006

abstract: Presented in the paper is a virtual commissioning methodology for the design and verification of an OHT (Overhead Hoist Transporter) which is a vehicle that travels on the overhead track in a FAB (Factory for making semiconductor chips) and directly accesses the load port of the stocker or process equipment by the belt driven hoisting mechanism. Since the material flows of a FAB is extremely complicated, it is important to design the OHT control software by considering various situations. The proposed virtual commissioning methodology supports the full verification of the OHT control software by performing the simulation involving a 'virtual OHT model' and a 'real OHT controller' We separate the virtual OHT model into two parts, a physical model (mechanical part) and a logical model (electrical part) to achieve the concurrency of mechanical and electrical designs of an OHT. Virtual commissioning identifies and addresses design flaws and operational faults so that significant savings can be achieved. The prototype of the proposed virtual commissioning methodology has been implemented and tested with several examples.
author_names: Joo Young Lee

Kwanwoo Lee

Sang-Chul Park
title: Virtual commissioning for an Overhead Hoist Transporter in a semiconductor FAB
venue: Int. J. Prod. Res.
year: 2020

abstract: The present invention is an automatic transfer system control relates to automatic transporting device for unmanned travel, etc. assembled on site factory, in particular, is detected by the obstacle in the direction in which the automatic conveying device moving the sensors, effectively driving the art automatic transporting device It relates. Automatic transport system of the present invention in the automatic transport system comprising a plurality of vehicles traveling the track, the vehicle is by monitoring to whether the vehicle that an obstacle is traveling forward with also monitoring the obstacle of the forward running direction of the running control and that is characterized. According to the automatic transport system of the present invention an obstacle in the area in which the direction of travel the vehicle passes it the number to be detected more without damaging the conveying efficiency of the system it is possible to improve the productivity of the whole system compared to the conventional OHT transport system
title: Auto carrying system
year: 2000

abstract: The book represents the life long collection of the author's work with his group in the field of Vehicle Track Coupled Dynamics together with other Chinese contributions. The author is one of the f.
author_names: Hans True
title: Vehicle Track Coupled Dynamics
year: 2020

author_names: Wanming Zhai
title: Vehicle Track Coupled Dynamics
year: 2020

abstract: Theoretical model is the base for the study of vehicle track coupled dynamics problems. In this chapter, the principle and methodology for modeling of vehicle track coupled systems are discussed at first. And then, three types of theoretical models are established: the vehicle track vertically coupled dynamics model, the vehicle track spatially coupled dynamics model, and the train track spatially coupled dynamics model, in which typical passenger coaches, freight wagons, and locomotives as well as typical ballasted and ballastless tracks are included. A new dynamic wheel rail coupling model is also established to connect the vehicle subsystem and track subsystem. Equations of motion of the vehicle and track subsystems are deduced and given in detail.
author_names: Wanming Zhai
title: Vehicle Track Coupled Dynamics Models
venue: Vehicle Track Coupled Dynamics
year: 2019

abstract: There has been a growing interest to carry out the vehicle track bridge (VTB) dynamic interaction analysis using 2D or 3D finite elements based on simplified wheel rail relationships. The simplified or elastic wheel rail contact relationships, however, cannot consider the lateral contact forces and geometric shapes of the wheel and rails, and even the occasional jump of wheels from the rails. This does not guarantee a reliable analysis for the safety running of trains over bridges. To consider the wheel rail constraint and contact forces, this paper proposes a versatile 3D VTB element, consisting of a vehicle, eight rail beam elements, four bridge beam elements, and continuous springs as well as the dampers between the rail and bridge girder. With the 3D VTB element matrices formulated, a procedure for assembling the interaction matrices of the 3D VTB element is presented based on the virtual work principle. The global equations of motion of the VTB interaction system are established accordingly, which can be solved by time integration methods to obtain the dynamic responses of the vehicle, track and bridge, as well as the stability and safety indices of the moving train. Finally, an illustrative example is used to verify the proposed the versatile 3D VTB element for the dynamic interactive analysis of railway bridges under moving train loads.
author_names: Xiang Xiao

Weiqi Ren
title: A Versatile 3D Vehicle Track Bridge Element for Dynamic Analysis of the Railway Bridges under Moving Train Loads
venue: International Journal of Structural Stability and Dynamics
year: 2019

abstract: Abstract In recent years, the stochastic dynamic analysis of vehicle bridge (VB) coupled systems with the random system parameters has attracted much attention. Nevertheless, a little work has yet been carried out to establish the stochastic dynamic model of vehicle track bridge (VTB) systems and the systematical evaluation on stochastic dynamic properties of VTB systems is still very limited. In this regard, an efficient approach for the stochastic dynamic analysis of time dependent VTB systems based on the probability density evolution method (PDEM) is proposed in this study with the stochastic influences of the track structure considered. Firstly, the VTB stochastic model with the stochastic track structure is established and its stochastic motion equations are derived based on the principle of virtual work. Then, the representative parameter sample point sets of the random system parameters can be chosen and their initial probability distribution can be determined by using the number theory method (NTM) An efficient procedure for the stochastic dynamic analysis of the VTB system is presented based on PDEM. A real VTB system constructed in China is taken as an example to examine the feasibility and reliability of the proposed stochastic model and evaluation approach. The parametric study is conducted to investigate the effects of random system parameters on the dynamic responses of the VTB system. The accuracy and efficiency of the proposed approach are verified and some observations of the effects of the stochastic track structure are made.
author_names: Xiang Xiao

Bo Chen
title: Stochastic dynamic analysis for vehicle track bridge system based on probability density evolution method
venue: Engineering Structures
year: 2019

abstract: ABSTRACT A stochastic mathematical model is developed to evaluate the dynamic behaviours and statistical responses of vehicle track systems when random system excitations including crosswinds and track irregularities are imposed. In this model, the railway vehicle is regarded as a multi rigid body system, the track system is modelled by finite element theory. These two systems are spatially coupled by the nonlinear wheel rail contact forces and unsteady aerodynamic forces. The high efficiency and accuracy of this stochastic model are validated by comparing to the robust Monte Carlo method. Numerical studies show that crosswinds have a great influence on the dynamic performance of vehicle track systems, especially on transverse vibrations. When the railway vehicle initially runs into the wind field, it will experience a severe vibration stage, and then stepping into a relatively steady state where the fluctuating winds and track irregularities will play deterministic roles in the deviations of system responses. Moreover, it is found that track irregularities should be properly considered in the safety assessment of the vehicle even in strong crosswinds.
author_names: Lei Xu

Wanming Zhai
title: A model for vehicle track random interactions on effects of crosswinds and track irregularities
year: 2019