Central Scheduler

The Central Scheduler uses a Stateflow chart to handle package allocation to the robots from thePackage Dispenser. Each robot can carry one package at a time and is instructed to go from the loading to an unloading station based on the required location for each package. The scheduler also tracks the status of the packages and robots and updates theStatus Dashboard. Based on robot poses, the scheduler also sends stop commands to one robot when it detects an imminent collision. This behavior can allow the robots to run local obstacle avoidance if available.

TheFor Each Robot and Package Statesubsystem is aFor Each Subsystem(Simulink)which processes an array of buses for tracking the robot and package states asRobotPackageStatusbus object. This makes it easy to update this model for varying number of robots. For more information about processing arrays of buses using a For-Each Subsystem, seeWork with Arrays of Buses(Simulink).

Scheduler

The following schematic details the signal values of theSchedulerStateflow chart.

Robot Controller

TheRobot Controlleruses aFor Each Subsystem(Simulink)to generate an array of robot controllers for your 5 robots.

The following schematic details the type of signal values associated with theFor Each Robot Controller.

Each robot controller has the following inputs and outputs.

The controller takes delivery commands, which contains the package information, and plans a path for delivering it someone in the warehouse usingmobileRobotPRM. ThePure Pursuit块需要这条路径和生成速度逗号nds for visiting each waypoint. Also, the status of the robot and packages get updated when the robot reaches its goal. Each robot also has its own internal scheduler that tells them the location of unloading stations based on the package information, and sends them back to the loading station when they drop off a package.

The robot controller model uses the same model,warehouseTasksRobotSimulationModel, shown inExecute Tasks for a Warehouse Robot.

Plant

ThePlantsubsystem uses aDifferential Drive Kinematic Modelblock to model the motion of the robots.

Model Setup

Begin to setup various variables in MATLAB® for the model.

Defining the Warehouse Environment

A logical type matrix,logicalMaprepresents the occupancy map of the warehouse. The warehouse contains obstacles representing walls, shelves, and other processing stations. Loading, unloading, and charging stations are also given inxy-coordinates.

loadmultiRobotWarehouseMap.matlogicalMaploadingStationunloadingStationschargingStationswarehouseFig = figure('Name','Warehouse Setting','Units',"normalized",'OuterPosition',[0 0 1 1]); visualizeWarehouse(warehouseFig, logicalMap, chargingStations, unloadingStations, loadingStation);

Checking occupancy at stations

Ensure that the stations are not occupied in the map.

map = binaryOccupancyMap(logicalMap);if(any(checkOccupancy(map, [chargingStations; loadingStation; unloadingStations]))) error("At least one of the station locations is occupied in the map.")end

Central Scheduler

TheCentral Schedulerrequires the knowledge of the packages that are to be delivered so as to send the delivery commands to the robot controllers.

Defining Packages

Packages are given as an array of index numbers of the various unloading stations that the packages are supposed to be delivered to. Because this example has three unloading stations, a valid package can take a value of 1, 2, or 3.

loadpackages.matpackagespackages

packages =1×113 2 1 2 3 1 1 1 2 3 1

Number of Robots

The number of robots is used to determine the sizes of the various signals in the initialization of theSchedulerStateflow chart

numRobots = size(chargingStations, 1);% Each robot has its own charging station;

Collision Detection and Goal-Reached Threshold

TheCentral Schedulerand theRobot Controlleruse certain thresholds for collision detection,collisionThresh, and a goal-reached condition,awayFromGoalThresh.

Collision detection ensures that for any pair of robots within a certain distance-threshold, the robot with a lower index should be allowed to move while the other robot should stop (zero-velocity command). The still moving robot should be able to avoid local static obstacles in their path. You could achieve this with another low-level controller like theVector Field Histogram(Navigation Toolbox)block.

The goal-reached condition occurs if the robot is within a distance threshold,awayFromGoalThresh, from the goal location.

loadexampleMultiRobotParams.matawayFromGoalThreshcollisionThresh

Bus Objects

TheRobotDeliverCommandandRobotPackageStatusbus objects are used to pass robot-package allocations between theCentral Schedulerand theRobot Controller.

loadwarehouseRobotBusObjects.matRobotDeliverCommandRobotPackageStatus

Simulation

Open the Simulink model.

open_system("multiRobotExampleModel.slx")

Run the simulation. You should see the robots drive plan paths and deliver packages.

sim('multiRobotExampleModel');

### Starting serial model reference simulation build. ### Successfully updated the model reference simulation target for: robotController Build Summary Simulation targets built: Model Action Rebuild Reason =========================================================================================== robotController Code generated and compiled. robotController_msf.mexa64 does not exist. 1 of 1 models built (0 models already up to date) Build duration: 0h 1m 16.807s

Metrics and Status Dashboard

For each of the packages, the dashboard in the model shows if the package is "InProgress", "Unassigned", or "Delivered".Robot Statusdisplays the distance travelled, package location, and a package ID.

Extending the Model

This model is setup to handle modifying the number of robots in the warehouse based on availability. Adding more robots requires defining additional charging stations.

chargingStations(6, :) = [10, 15];% Charging Station for the additional 6th robotchargingStations(7, :) = [10, 17];% Charging Station for the additional 7th robot

You can also add more unloading stations and assign packages to it.

: unloadingStations(4) =(30、50);packages = [packages, 4, 4];

AdditionalDifferential Kinematic Modelblocks are also required to match the number of robots. TheexampleHelperReplacePlantSubsystemadds these by updatingnumRobots.

numRobots = size(chargingStations, 1)%,每个机器人都有自己的stati收费on

numRobots = 7

exampleHelperReplacePlantSubsystem('multiRobotExampleModel/Robots', numRobots);

You can also redefine any existing locations. Modify the loading station location.

loadingStation = [35, 20];

Simulation

After making the modifications, run the simulation again. You should see the updated station locations and an increased number of robots.

sim('multiRobotExampleModel');

### Starting serial model reference simulation build. ### Successfully updated the model reference simulation target for: robotController Build Summary Simulation targets built: Model Action Rebuild Reason =========================================================================================== robotController Code generated and compiled. Global variable unloadingStations changed. 1 of 1 models built (0 models already up to date) Build duration: 0h 0m 36.389s

Visualization

TheVisualization Helperoffers some options for changing the view of the warehouse. Open the block mask to switch between variousPreset Viewsof different stations. Toggle path visualization or update robot mesh types. Adjust theSample timeto change the rate of the visualization, which does not affect the execution of the actual robot simulation.