PN4ECSS

Petri Net for Electric Car-Sharing System (ECSS).

Introduction

Implementation and modification of the ECSS Petri Net model in Modelica based on this paper.

Three objective functions have been implemented:

• totalWaitingTime: Calculate the total waiting time of users

• totalChargingTime: Calculate the total charging time of cars

• CarsRented: Calculate the rented cars in total

In an optimization problem, totalWaitingTime and totalChargingTime need to be minimized, CarsRented needs to be maximized.

Demo

Modeling Electric Car-sharing Systems with Petri nets using Modelica and Optimization using MOO4Modelica

https://youtu.be/LOc7q_BexsY

Environments

OpenModelica v1.22.3

PNlib v3.0.0

Model Description

1. Station Subnet

• TCCi: Car return to the station and then in a charging situation.
• PSCi: Number of free places in the station.
• TCRi: Car is ready and available for users after charging operation.
• PSRi: Cars parked at the station, ready and then available for users.
• TUSi: User demand "satisfied" and then "user departure" from station.
• PCU: Car in use.

2. User Demand Subnet

• TUDi: User demand arrival at station.
• PSDi: Users waiting during a given random delay- for available and ready cars in the station.
• TUNi: User demand “not satisfied”, user leaves.

3. Car-sharing Park (Center) Subnet

• TCPc: Car return to station Park by user. This car will be in charging operation.
• TCPR: The car is ready and available for other users, after its charging operation.

4. User Demand (Park) Subnet

• TUNp: User demand “not satisfied” at park. User leaves.

• TUDp: User demand arrival at station park.

• TUSp: User demand “satisfied” and then “user departure” from station park

5. Car Maintenance (Center) Subnet

• TCM: Car picked up for “long” maintenance (e.g. due to an incident/ accident) by service provider
• PCM: Cars under maintenance
• TMPR: After maintenance, car is parked at the station Park. It is ready and available for users

How Tokens are Generated and Flow Through the Model

1. User Arrival and Demand (TUDi and TUDp)

• Tokens representing user demand are generated at the TUDi and TUDp transitions, which simulate user arrivals at the station and park, respectively. The rate of token generation is governed by an exponential distribution based on userPatience.

2. Users Waiting (PSDi)

• Arriving users are represented as tokens in the PSDi place, where they wait for available cars. If cars are available, tokens (users) will move to the TUSi transition where they pick up a car.

3. Car Pickup and Usage (TUSi and PCU)

• Tokens (users) that successfully pick up cars move to the PCU place, representing cars in use by customers. This transition reduces the number of tokens in the PSRi place (cars ready) and increases the tokens in PCU (cars in use).

4. Car Return and Charging (TCCi, TCRi, and PSCii)

• After usage, cars are returned and go through a charging process. The TCCi transition moves tokens from PCU to PSCii (charging state). Once charging is complete, tokens move through TCRi back to PSRi (cars ready).

5. Car Maintenance (TCM, TMPR, and PCM)

• Occasionally, cars require maintenance. The TCM transition moves tokens to PCM (cars under maintenance). After maintenance, tokens move back to the TMPR transition, eventually returning to the pool of available cars.

6. User Departure (TUNi and TUNp)

• If a user waits too long for a car, they leave the system. This is represented by the TUNi and TUNp transitions, which move tokens from the PSDi place without satisfying their demand.