CarSharingSystemSimplified.mo → CarSharingSystemCaseStudy.mo

-model CarSharingSystemSimplified
+model CarSharingSystemCaseStudy
+  
   // Parameters
   parameter Integer numCars = 10 "Number of cars in the system";
-  parameter Integer numUsers = 5 "Number of users in the system";
+  parameter Integer numUsers = 1 "Number of users in the system";
+  parameter Real userArrivalRate = 1.0 "User arrival rate (users per time unit)";
   parameter Real returnRate = 0.5 "Car return rate";
   parameter Real chargingTime = 1.0 "Time to fully charge a car";
   parameter Real usageTime = 1.0 "Car usage time by a customer";
-  parameter Real userPatience = 2.0 "Maximum waiting time for users";
+  parameter Real userPatience = 10.0 "Maximum waiting time for users";
   
   // State variables for objectives
   Real totalWaitingTime(start=0) "Total waiting time for users";
-  Real carUtilization(start=0) "Car utilization over time";
-  Real carsInUse(start=0) "Number of cars in use";
-  
-  // Discrete Variables for Intermediate Calculations
-  discrete Real waitingTimeIncrement(start=0);
-  discrete Real carUtilizationIncrement(start=0);
+  Real totalCarsRented(start=0) "Total number of cars rented";
+  discrete Integer usersLeaving(start=0);
 
   // Discrete Place: Number of free places in the station
   PNlib.Components.PD PSCii(nIn = 1, nOut = 1) annotation(
@@ -38,10 +36,10 @@ model CarSharingSystemSimplified
   PNlib.Components.PD PSDi(nIn = 1, nOut = 2, startTokens = numUsers) annotation(
     Placement(transformation(origin = {-270, 10}, extent = {{-10, -10}, {10, 10}})));
   // Deterministic transition: User demand “not satisfied” at station
-  PNlib.Components.TD TUNi(nIn = 1) annotation(
+  PNlib.Components.TD TUNi(nIn = 1, delay = userPatience) annotation(
     Placement(transformation(origin = {-180, 10}, extent = {{-10, -10}, {10, 10}})));
   // Stochastic Transition: User demand arrival at station
-  PNlib.Components.TES TUDi(nOut = 1, distributionType = PNlib.Types.DistributionType.Exponential, h = 1/userPatience) annotation(
+  PNlib.Components.TES TUDi(nOut = 1, distributionType = PNlib.Types.DistributionType.Exponential, h = 1/userArrivalRate) annotation(
     Placement(transformation(origin = {-314, 10}, extent = {{-10, -10}, {10, 10}})));
   // Stochastic Transition: Car return to station Si by user. Then, the car is in a charging situation
   PNlib.Components.TES TCCi(nIn = 2, nOut = 1, distributionType = PNlib.Types.DistributionType.Exponential, h = 1/chargingTime) annotation(
@@ -84,23 +82,15 @@ model CarSharingSystemSimplified
     Placement(transformation(origin = {-356, 208}, extent = {{-10, -10}, {10, 10}})));
 
 equation
-  // Objective Equations
-  // totalWaitingTime = numUsers * userPatience * (1 - returnRate); // Total waiting time is number of users multiplied by their patience
-  // carUtilization = (numUsers * usageTime) / (numCars * (usageTime + chargingTime + (1 / returnRate))); // Car utilization is based on usage time
- 
-  // Objective Equations
-
-  // Calculate waiting time when users leave without getting a car
-  when change(PSDi.t) then
-    waitingTimeIncrement = (pre(PSDi.t) - PSDi.t) * userPatience;
-    totalWaitingTime = pre(totalWaitingTime) + waitingTimeIncrement;
+  // Update total waiting time when users leave
+  when change(PSDi.tokenFlow.outflow[2]) then
+      usersLeaving = PSDi.tokenFlow.outflow[2]; // Number of users leaving
+      totalWaitingTime = pre(totalWaitingTime) + usersLeaving * userPatience;
   end when;
   
-  // Calculate car utilization
-  when change(PSRi.t) then
-    carsInUse = numCars - PSRi.t;
-    carUtilizationIncrement = carsInUse * usageTime / (numCars * (time + Modelica.Constants.eps));
-    carUtilization = pre(carUtilization) + carUtilizationIncrement;
+  // Update total number of cars rented
+  when change(PSRi.tokenFlow.outflow[1]) then
+    totalCarsRented = PSRi.tokenFlow.outflow[1];
   end when;
   
   // Connections
@@ -153,7 +143,7 @@ equation
   connect(TUSp.outPlaces[1], PCU.inTransition[2]) annotation(
     Line(points = {{106, -6}, {2, -6}, {2, 0}}, thickness = 0.5));
   annotation(
-    uses(PNlib(version = "3.0.0")),
+    uses(PNlib(version = "3.0.0"), Modelica(version = "4.0.0")),
     Diagram(graphics = {Text(origin = {-337, -14}, extent = {{3, 0}, {-3, 0}}, textString = "text"), Text(origin = {-304, 192}, extent = {{42, -20}, {-42, 0}}, textString = "Station subnet"), Rectangle(origin = {-245, 103}, lineColor = {0, 0, 255}, lineThickness = 0.5, extent = {{-103, 71}, {103, -71}}), Rectangle(origin = {-257, 5}, lineColor = {0, 255, 0}, lineThickness = 0.5, extent = {{-91, 23}, {91, -23}}), Text(origin = {-304, -20}, extent = {{42, -20}, {-42, 0}}, textString = "User demand subnet"), Rectangle(origin = {224, 30}, lineColor = {0, 170, 255}, lineThickness = 0.5, extent = {{-132, 72}, {132, -72}}), Text(origin = {121, 136}, extent = {{57, -48}, {-57, 0}}, textString = "User Demand (park) subnet"), Polygon(origin = {342, 55}, lineColor = {255, 85, 255}, lineThickness = 0.5, points = {{-154, 111}, {-154, 57}, {32, 57}, {32, -139}, {142, -139}, {142, 137}, {-154, 137}, {-154, 127}, {-154, 111}}), Text(origin = {273, 201}, extent = {{-81, 25}, {81, -25}}, textString = "Car Maintenance (Center) subnet"), Rectangle(origin = {293, -77}, lineColor = {85, 85, 0}, lineThickness = 0.5, extent = {{-145, 87}, {145, -87}}), Text(origin = {227, -176}, extent = {{-73, 20}, {73, -20}}, textString = "Car-Sharing Park (Center) subnet"), Text(extent = {{-16, 40}, {-16, 40}}, textString = "text"), Text(origin = {-38, 62}, extent = {{-26, 16}, {26, -16}}, textString = "Cars in use"), Text(origin = {-339, 67}, extent = {{-37, 35}, {37, -35}}, textString = "Charging of cars"), Text(origin = {-204, 63}, extent = {{-32, 7}, {32, -7}}, textString = "Cars are ready")}, coordinateSystem(extent = {{-380, 240}, {500, -200}})),
     version = "");
-end CarSharingSystemSimplified;
+end CarSharingSystemCaseStudy;

README.md

@@ -42,3 +42,29 @@ This model generates some stochastic user (demands), you can simulate:
 Here you will find a gif to visualize the simulation result.
 
 ![](./PN4ECSS.gif)
+
+## 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.
\ No newline at end of file