SIMULATION: Transactions of The Society for Modeling and Simulation International

Papelis, Yiannis E.; Petty, Mikel D.

doi: 10.1177/0037549718757603pmid: N/A

Mustafee, Navonil; Mittal, Saurabh; Diallo, Saikou; Zacharewicz, Gregory

doi: 10.1177/0037549718758429pmid: N/A

Cardoen, Ben; Manhaeve, Stijn; Van Tendeloo, Yentl; Broeckhove, Jan

doi: 10.1177/0037549717690826pmid: N/A

With the ever-increasing complexity of simulation models, parallel simulation becomes necessary to perform simulation within reasonable time bounds. The built-in parallelism of Parallel DEVS is often insufficient to tackle this problem on its own. Several synchronization protocols have been proposed, each with their distinct advantages and disadvantages. Due to the significantly different implementation of these protocols, most Parallel DEVS simulation tools are limited to only one such protocol. In this paper, we present a Parallel DEVS simulator, grafted on C++11 and based on PythonPDEVS, supporting both conservative and optimistic synchronization protocols. The simulator not only supports both protocols but also has the capability to switch between them at runtime. The simulator can combine each synchronization protocols with either a threaded or sequential implementation of the PDEVS protocol. We evaluate the performance gain obtained by choosing the most appropriate synchronization protocol. A comparison is made to adevs in terms of CPU time and memory usage, to show that our modularity does not hinder performance. We compare the speedup obtained by synchronization with that of the inherent parallelism of PDEVS in isolation and combination, and contrast the results with the theoretical limits. We further allow for an external component to gather simulation statistics, on which runtime switching between the different synchronization protocols can be based. The effects of allocation on our synchronization protocols are also studied.

Goldstein, Rhys; Breslav, Simon; Khan, Azam

doi: 10.1177/0037549717718258pmid: N/A

DesignDEVS is a simulation development environment based on the Discrete Event System Specification (DEVS) formalism. This paper provides an in-depth overview of the software while focusing on the practical considerations influencing its design. Practitioners who stand to benefit from systems engineering will approach formalism-based simulation tools with little knowledge of the underlying theory. It is therefore important that theoretical principles, such as the separation of model and simulator, be emphasized by the user interface. Other practical aspects of DesignDEVS include the simplicity of atomic model code, a focus on coupling for collaboration purposes, the enforcement of essential modeling constraints, and a reliance on best practices in cases where strict enforcement might inconvenience users. In DesignDEVS, an issue we refer to as the Insidious Pointer Problem is aggressively tackled through run-time error handling. By contrast, the separation of output values from state transitions is left as a best practice for the sake of user convenience. The design decisions explained in this paper are relevant to developers of other formalism-based tools seeking widespread adoption of scalable modeling and simulation practices.

Ahmad, F; Hudha, K; Mazlan, SA; Jamaluddin, H; Aparow, VR; Yunos, MR M

doi: 10.1177/0037549717733805pmid: N/A

This paper presents an investigation into the performance of a fixed caliper based electronic wedge brake (FIXEWB) in a vehicle braking system. Two techniques were used as assessment methods, which are simulation via MATLAB Simulink software and experimental study through hardware-in-the-loop-simulation (HILS). In the simulation study, the vehicle braking system was simulated by using a validated quarter vehicle traction model with a validated FIXEWB model as the brake actuator. A proportional–integral–derivative controller was utilized as the brake torque control, whereas proportional–integral and proportional controllers were used as the position and speed control of the actuator, respectively. To study the effectiveness of the FIXEWB, the response of the vehicle using the FIXEWB is compared with the responses of a vehicle using a conventional hydraulic brake. A dynamic test, namely braking in the sudden braking at constant speeds of 40 and 60 km/h was then used as the testing method. The simulation results show that the usage of the FIXEWB with an appropriate control strategy produces similar behavior to that of a hydraulic brake in terms of the produced desired braking torque but with faster time response. To study the performance of the FIXEWB when implemented on a real vehicle, an experimental rig using HILS was designed and the results are analyzed using the same dynamic tests. The performance areas evaluated are vehicle body speed, wheel speed, tire longitudinal slip, and the stopping distance experienced by the vehicle. The outcomes from this study can be considered in the design optimization of an antilock braking system control in a real car in the future.

Rabiei, Peyman; Arias-Aranda, Daniel

doi: 10.1177/0037549717712037pmid: N/A

The relationship between organizational commitment and job satisfaction has received plenty of attention in the literature. However, similar studies in growing economies are scarce. The objective of this study is to cover such a gap by introducing an intelligent algorithm for predicting organizational commitment considering job satisfaction as well as comparing its performance to conventional Multiple Linear Regression (MLR). In doing so, data was collected by distributing questionnaires among 200 employees from the food industry in Shiraz (Iran), which represents one of the most dynamic economies of the country. A 73% response rate was achieved. The respondents completed the questionnaire, which assessed six dimensions of job satisfaction (satisfaction with supervision, overall job, company policy and support, promotion and advancement, pay, and coworkers) and organizational commitment. Using MLR, the results indicated that workers’ had higher satisfaction with overall job, company policy and support, and coworkers, bringing about significantly higher employees’ organizational commitment level. An Adaptive Network-based Fuzzy Inference System (ANFIS) is also developed and tested for the purpose of this study to predict organizational commitment level based on different levels of job satisfaction. Comparing the results obtained from ANFIS and MLR shows that the proposed intelligent algorithm has better performance than conventional MLR and predicts organizational commitment more accurately, based on their root mean square error values (RMSE). A simulation model based on the rules learned by the ANFIS algorithm is also presented to simulate the organizational commitment level of employees by establishing their position on various indexes of job satisfaction. This model can help managers to achieve higher levels of employees’ organizational commitment, since the main aspects of job satisfaction that need more focus are simulated. Different scenarios and situations could be simulated by this system, which is a main contribution of the current work. In terms of presenting an intelligent algorithm in order to predict organizational commitment level based on job satisfaction in food industrial companies, this study is pioneering among other studies.

Ghezavati, VR; Sahihi, A; Barzegar, A

doi: 10.1177/0037549717714332pmid: N/A

In this article, a hybrid meta-heuristic algorithm is applied to solve a green vehicle routing problem with respect to economic aspects. In this research, a transportation model will be studied in which the fleet operates with eco-friendly fuels in order to collect used products in different nodes. By implementing value-added processes, the firm can sell products and gain profit. However, using alternative fuels causes some limitations because of lack of alternative fuel stations. These limitations usually affect the travel distance range of vehicles and, consecutively, route selection to serve desired customers. A proper formulation for this type of problem could be applicable to manage imposed costs of transportation pertaining to alternative fuels and related issues. To reach this goal, the proposed model represents the revenue and purchasing price of used products in the output. These results are attained by using an improved Simulated Annealing (SA) algorithm. The self-modifier of probability of section approach (SMPSA) featured with a SA algorithm can solve the model in less time compared with the classic SA algorithm. In addition, a heuristic algorithm is used to generate each initial solution with higher quality. Finally, the results and running time of the proposed algorithm are compared with the exact method and the SA algorithm without the SMPSA. Then the results are discussed.