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SIMULATIONS

 

 

SWARM SIMULATION

 

Swarm behaviour is a phenomenon that occurs frequently in nature. Individual members of a population behave as if they were part of a larger whole. This benefits the individuals in terms of collective vigilance when fleeing from predators and energy consumption during movement. In our example, a flock of birds is simulated.

In your programme, you determine the neighbouring nodes by selecting those from the four adjacent cells that are not on the wall and not outside the grid.

A bird in a flock wants to be close to its neighbours, but also wants to avoid collisions. Its behaviour can be described by the following rules:

1. Separation: Each actor maintains a certain distance from its neighbours to avoid possible collisions. The actor's acceleration vector is opposite to the vector of the sum of the positions of its neighbours.

2. Aligment: aims to match the speed and direction to the movement of the neighbours. The speed vector of the actor is formed as the mean value of the speed vectors of the neighbours.

3. Cohesion: aims to keep the swarm together and allows the actor to remain as close as possible to its neighbours. The direction of the actor's acceleration vector points towards the common centre of gravity of the neighbours' point masses.

Program: 

# Swarm.py
from gamegrid import *
import math
import random

class Tree(Actor):
    def __init__(self):
        Actor.__init__(self, "sprites/tree1.png")

class Bird(Actor):
    def __init__(self):
        Actor.__init__(self, True, "sprites/arrow1.png")
        self.r = GGVector(0, 0)  # Position
        self.v = GGVector(0, 0)  # Velocity
        self.a = GGVector(0, 0)  # Acceleration
 
    # Called when actor is added to gamegrid
    def reset(self):
        self.r.x=self.getX()
        self.r.y=self.getY()
        self.v.x=startVelocity*math.cos(math.radians(self.getDirection()))
        self.v.y=startVelocity*math.sin(math.radians(self.getDirection()))
  
    # ----------- cohesion ---------------
    def cohesion(self, distance):
        return self.getCenterOfMass(distance).sub(self.r)

    # ----------- alignment --------------
    def alignment(self, distance):
        align = self.getAverageVelocity(distance)
        align = align.sub(self.v)
        return align

    # ----------- separation -------------
    def separation(self, distance):
        repulse = GGVector()
        # ------ from birds ------
        for p in birdPositions:
            dist = p.sub(self.r)
            d = dist.magnitude()
            if d < distance and d != 0:
                repulse = repulse.add(dist.mult((d-distance)/d))

        # ------ from trees ------
        trees = self.gameGrid.getActors(Tree)
        for actor in trees:
            p = GGVector(actor.getX(), actor.getY())
            dist = p.sub(self.r)
            d = dist.magnitude()
            if d < distance and d != 0:
               repulse = repulse.add(dist.mult((d-distance)/d))
        return repulse
  
    # ----------- wall interaction -------
    def wallInteraction(self):
        width = self.gameGrid.getWidth()
        height = self.gameGrid.getHeight()
        acc = GGVector()
        if self.r.x < wallDist:
            distFactor = (wallDist - self.r.x) / wallDist
            acc = GGVector(wallWeight * distFactor, 0)
        if width - self.r.x < wallDist:
            distFactor = ((width - self.r.x)-wallDist)/wallDist
            acc = GGVector(wallWeight * distFactor, 0)
        if self.r.y < wallDist:
            distFactor = (wallDist - self.r.y) / wallDist
            acc = GGVector(0, wallWeight * distFactor)
        if height - self.r.y < wallDist:
            distFactor = ((height - self.r.y)-wallDist)/wallDist
            acc = GGVector(0, wallWeight * distFactor)
        return acc
  
    def getPosition(self):
        return self.r
      
    def getVelocity(self):
        return self.v

    def getCenterOfMass(self, distance):
        center = GGVector()
        sum = 0
        for p in birdPositions:
            dist = p.sub(self.r)
            d = dist.magnitude()
            if d < distance:
                center = center.add(p)
                sum += 1
        if sum != 0:        
            return center.mult(1.0/sum)
        else:
            return center

    def getAverageVelocity(self, distance):
        avg = GGVector()
        sum = 0
        for i in range(len(birdPositions)):
            p = birdPositions[i]
            if (self.r.x - p.x)*(self.r.x-p.x) + \
               (self.r.y - p.y)*(self.r.y-p.y)<distance*distance:
                avg = avg.add(birdVelocities[i]);
                sum += 1
        return avg.mult(1.0/sum)

    def limitSpeed(self):
        m = self.v.magnitude()
        if m < minSpeed:
            self.v = self.v.mult(minSpeed / m)
        if m > maxSpeed:
            self.v = self.v.mult(minSpeed / m)

    def setAcceleration(self):
        self.a = self.cohesion(cohDist).mult(cohWeight)
        self.a = self.a.add(self.separation(sepDist).mult(sepWeight))
        self.a = self.a.add(self.alignment(aligDist).mult(aligWeight))
        self.a = self.a.add(self.wallInteraction())

    def act(self):
        self.setAcceleration()
        self.v = self.v.add(self.a) # new velocity
        self.limitSpeed()
        self.r = self.r.add(self.v) # new position
        self.setDirection(int(math.degrees(self.v.getDirection())))
        self.setLocation(Location(int(self.r.x), int(self.r.y)))

# global section 
def populateTrees(number):
    blockSize = 70
    treesPerBlock = 10
    for block in range(number // treesPerBlock):
        x = getRandomNumber(800 // blockSize) * blockSize
        y = getRandomNumber(600 // blockSize) * blockSize
        for t in range(treesPerBlock):
            dx = getRandomNumber(blockSize)
            dy = getRandomNumber(blockSize)
            addActor(Tree(), Location(x + dx, y + dy))
                
def generateBirds(number):
    for i in range(number):
        addActorNoRefresh(Bird(), getRandomLocation(), 
                                  getRandomDirection())
    onAct()  # Initialize birdPositions, birdVelocities
     
def onAct():
    global birdPositions, birdVelocities
    # Update bird positions and velocities
    birdPositions = []
    birdVelocities = []
    for b in getActors(Bird):
        birdPositions.append(b.getPosition())
        birdVelocities.append(b.getVelocity())
 
def getRandomNumber(limit):
    return random.randint(0, limit-1)

# coupling constants 
cohDist = 100
cohWeight = 0.01
aligDist = 30
aligWeight = 1
sepDist = 30
sepWeight = 0.2
wallDist = 20
wallWeight = 2
maxSpeed = 20
minSpeed = 10
startVelocity = 10
numberTrees = 100
numberBirds = 50

birdPositions  = []
birdVelocities  = []

makeGameGrid(800, 600, 1, False)
registerAct(onAct)
setSimulationPeriod(10)
setBgColor(Color.blue)
setTitle("Swarm Simulation")
show()
populateTrees(numberTrees)
generateBirds(numberBirds)
doRun()
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ESPRESSO AUTOMAT
 

 

 In everyday life, you encounter many devices and machines that can be considered automatic machines. These include beverage vending machines, washing machines, cash machines, etc. As an engineer and computer scientist, you develop such a machine with the clear idea that it will gradually transition from its current state to a subsequent state, depending on sensor data and the operation of buttons and switches.
 

Here, you are developing an espresso machine that has three states: It can be switched off (OFF), ready for operation (STANDBY) and pumping coffee (WORKING). There are four push buttons for the functions switch on (turnOn), switch off (turnOff), switch on coffee pump (work) and switch off coffee pump (stop).

You can illustrate the function of the coffee machine more clearly with a machine graph. To do this, you represent the states with a circle and the transitions as transition arrows, which you label with the inputs/outputs.

  

Program: 

#Espresso.py
from gamegrid import *

def pressEvent(e):
    global state
    loc = toLocationInGrid(e.getX(), e.getY())
    if loc == Location(1, 2): # off
        state = "OFF"
        led.show(0)
        coffee.hide()
    elif loc == Location(2, 2): # on
        if state == "OFF":
            state = "STANDBY"
            led.show(1)
    elif loc == Location(4, 2): # stop
        if state == "WORKING":
            state = "STANDBY"
            coffee.hide()
    elif loc == Location(5, 2): # work
        if state == "STANDBY":
            state = "WORKING"
            coffee.show()
    setTitle("State: " + str(state))
    refresh()
        
state = "OFF"
makeGameGrid(7, 11, 50, None, "sprites/espresso.png", False, 
             mousePressed = pressEvent)
show()
setTitle("State: " + str(state))
led = Actor("sprites/lightout.gif", 2)
addActor(led, Location(3, 3))
coffee = Actor("sprites/coffee.png")
addActor(coffee, Location(3, 6))
coffee.hide()
refresh()
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