Modeling humanoid swarm robots with petri nets

Master's thesis in Computer scienceRobots have become a hot topic in today‟s electronic world. There are many definitions for it. One of the definition in Oxford dictionary states “a robot is a machine capable for carrying out a complex series of action automatically especially one programmable by a computer”. This paper deals with a special kind of robot, which is also known as humanoid robot. These robots are replication of human beings with head, torso, arms and legs. A model of human is presented in this paper as discrete event system adapted from “Modeling and simulating motions of human bodies…”[1]. This model consists of sixteen interrelated limbs defined in 3D space, so most limbs/joints are able to make movement in three different angles (α, β and γ). Full details regarding Range of Motion (ROM) of rigid body in forward kinematic is illustrated. Human motions are categorized into two types: stochastic and deterministic motions. Deterministic motions are demonstrated using gait cycle of walking and running of normal adult person. The main focus of this paper is to model and simulate humanoid robot represented as Discrete Event Systems (DES); in Petri Net using GPenSIM and later expand those group of robots to swarm setting. GPenSIM is General Purpose Petri Net simulator [2] developed as toolbox for MATLAB to model and simulated discrete events using Petri net tools. Each joint‟s angle is treated as a separate Petri Net model which is independent from each other and their movement‟s limits are defined by ROM of normal human body. The instructions relating to the motion of joints for simulation are fed through a file to the instructor. These movements of joints are represented by variation of tokens displayed at the end of simulation in a graphical figure. Further, same structure of model is used in swarm of robots. Instead of feeding instructions to individual robots, a central instructor is created. This instructor acts as a master to robots acting as slaves where slaves include some predetermined commands embedded inside them. With central command system, a proper synchronization is achieved among group of robots working as swarm. A normal routine of group dance or simple group sport can be accomplished with calculated instructions on this swarm of robot

Extracting Petri Modules From Large and Legacy Petri Net Models

Petri nets, even though very useful for modeling of discrete event systems, suffer from some weaknesses such as huge size, huge state space, and slow in simulation. Due to the huge state space, model checking a Petri net is difficult. Also, due to the slowness in simulation, discrete-timed Petri nets cannot be used for real-time applications. Thus, modular Petri nets are suggested as a way of overcoming these difficulties. In modular Petri nets, modules are designed, developed, and run independently, and the modules communicate with each other via inter-modular connectors. This approach is suggested for developing newer Petri net models. However, there exists a large number of Petri net models of real-life systems, and these legacy models are enormous and non-modular. And, these models cannot be discarded as large amounts of time and money were spent to develop these models. This paper presents a unique algorithm for extracting modules from large and legacy Petri net models. The algorithm extracts modules (known as “Petri modules”) that are well-defined for inter-modular collaboration. Also, the extraction method preserves the structural properties. The goal of the paper is to introduce a methodology by which Petri nets can be moved to a new level in which a modular Petri net model can be made of Petri modules. The Petri modules are independent and can be hosted on different computers. These modules communicate via inter-modular components such as TCP/IP sockets. Since Petri modules are compact, also run faster, thus become suitable for supervisory control of real-time systems.publishedVersio

Understanding the IKEA Warehouse Processes and Modeling using Modular Petri Nets

Nowadays, large warehouses handle a huge number of products. Handling the enormity and different types of (range) products also demand complex warehouse processes. In this paper, the IKEA warehouse in Stavanger, Norway, is taken as an example, which stores, manages, and sells ready-to-assemble furniture, kitchen appliances and home accessories. The focus of this paper is to understand the warehouse processes that make the warehouse popular with the customers. Petri net is used to model the processes, and by simulation, the effect of the processes are understood. This paper shows how the processes integrate the large range of products, customer service, and the supply chain. The logistics flow is represented with a modular Petri Net model using the tool known as the General-purpose Petri Net Simulator (GPenSim). The goal of this paper is also to determine and propose any changes for a more efficient warehouse performance.publishedVersio

Design and Application of Templates in GPenSIM

This paper talks about design and application of templates in a new simulation tool called General Purpose Petri Net Simulator (GPenSIM). Firstly, GPenSIM is introduced; GPenSIM is designed for simulation of discrete event systems, e.g. information systems. Secondly, the design and application of templates in GPenSIM is stated. Finally, an application example on the use of templates is given

Developing an online monitor for discrete simulations

Master's thesis in Computer ScienceThis paper covers the design and implementation of a graphical simulation monitoring program. The monitor works in real-time or simulation time. The monitor is compatible with the modelling and simulation tool GPenSIM (General-purpose Petri Net Simulator). The monitor shows the current state of a simulation in a graphical user interface (GUI) window while it is running. The monitor and GPenSIM are both running on the MATLAB platform. The tool is easy to use while enabling user customization. It also includes the ability to show historical data in the form of logging and plotting

Finding Clusters in Petri Nets. An approach based on GPenSIM

Graph theory provides some methods for finding clusters in networks. Clusters reflect the invisible grouping of the elements in a network. This paper presents a new method for finding clusters in networks. In this method, the user can adjust a parameter to change the number of clusters. This method is newly added to the simulator General-purpose Petri Net Simulator (GPenSIM) as a function for network analysis. With this GPenSIM function, in addition to the usual performance analysis of a discrete-event system via a Petri net model, supplementary information about the grouping of the elements can also be found. Finding clusters in discrete-event systems provides valuable information such as the ideal location of the elements in a manufacturing network. This paper also presents an application example on a flexible manufacturing system

Strict Minimal Siphon-Based Colored Petri Net Supervisor Synthesis for Automated Manufacturing Systems With Unreliable Resources

Various deadlock control policies for automated manufacturing systems with reliable and shared resources have been developed, based on Petri nets. In practical applications, a resource may be unreliable. Thus, the deadlock control policies proposed in previous studies are not applicable to such applications. This paper proposes a two-step robust deadlock control strategy for systems with unreliable and shared resources. In the first step, a live (deadlock-free) controlled system that does not consider the failure of resources is derived by using strict minimal siphon control. The second step deals with deadlock control issues caused by the failures of the resources. Considering all resource failures, a common recovery subnet based on colored Petri nets is proposed for all resource failures in the Petri net model. The recovery subnet is added to the derived system at the first step to make the system reliable. The proposed method has been tested using an automated manufacturing system deployed at King Saud University.publishedVersio

Intelligent Colored Token Petri Nets for Modeling, Control, and Validation of Dynamic Changes in Reconfigurable Manufacturing Systems

The invention of reconfigurable manufacturing systems (RMSs) has created a challenging problem: how to quickly and effectively modify an RMS to address dynamic changes in a manufacturing system, such as processing failures and rework, machine breakdowns, addition of new machines, addition of new products, removal of old machines, and changes in processing routes induced by the competitive global market. This paper proposes a new model, the intelligent colored token Petri net (ICTPN), to simulate dynamic changes or reconfigurations of a system. The main idea is that intelligent colored tokens denote part types that represent real-time knowledge about changes and status of a system. Thus, dynamic configurations of a system can be effectively modeled. The developed ICTPN can model dynamic changes of a system in a modular manner, resulting in the development of a very compact model. In addition, when configurations appear, only the changed colored token of the part type from the current model has to be modified. Based on the resultant ICTPN model, deadlock-free, conservative, and reversible behavioral properties, among others, are guaranteed. The developed ICTPN model was tested and validated using the GPenSIM tool and compared with existing methods from the literature.publishedVersio

Optimisation of check-in process focused on passenger perception for using self-service technologies at airports in Australia

Purpose: The use of technology is constantly evolving for various services at airports to enhance the passenger experience. However, the passenger’s perspective towards the technology is different. Design/methodology: A survey was conducted to know these perspectives and find the differences. The collected data was based on the passengers at Australian airports. The CAST software was used to analyse the simulation model. Findings: The collected survey helped in identifying three types of passengers: the number of passengers who prefer traditional service, the number of passengers who prefer technologybased services and the number of passengers who prefer technology-based services only under the specific circumstances such as less crowded and less processing time. Each type of passenger was further analysed based on their provided arriving time at the terminal and processing time for check-in to evaluate the impact on waiting time. Practical implications: The findings suggest that only one third passengers prefer technologybased services at airports and present the resulting impact on the waiting time at check-in facilities. Originality/value: Given the current rate of technological innovations at airports, the findings provide insights for check-in facilities management at airports.Peer Reviewe

Hybrid model for the design of a deep-lane multisatellite AVS/RS

The autonomous vehicle storage and retrieval system (AVS/RS) significantly improves the responsiveness and throughput of the traditional automated storage and retrieval system (AS/RS) in regard to handling unit loads. The AVS/RS consists of multiple tiers connected to an elevator system and is equipped with at least two autonomous vehicles, that is, a shuttle and satellite. Other necessary equipment are the lifts and input/output buffer areas. This paper aims to present and apply an original hybrid analytical-simulative model for the design of a deep-lane and multisatellite AVS-RS by evaluating and controlling the system performance. This AVS-RS is equipped with multiple free and non-free satellites for each tier. As an original contribution, this study reviews the literature on AVS/RS according to the introduction of multiple features categorized into five homogeneous groups: (1) rack configuration, (2) vehicle kinematics and configuration, (3) dispatching rules, (4) modeling approach, and (5) validation. Two of the most critical issues in existing research studies are the random arrival time of storage and retrieval transactions and the random storage policy. The proposed modeling approach is data-driven and based on realistic assumptions, filling the gap between the literature and real applications. This hybrid model is applied to a case study of the beverage industry according to a what-if comparative and competitive multiscenario analysis. This data-driven assessment supports the decision-making process on the number of satellites for each tier, while simultaneously controlling the service and waiting times, system throughput, and vehicle utilization. The analysis based on the maximum system throughput estimation demonstrates that introducing more than two satellites does not increase the productivity of the system