An apartment parking garage has four levels. Rather than having vehicles drive to each level, this one has an elevator t

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An apartment parking garage has four levels. Rather than having
vehicles drive to each level, this one
has an elevator to lift vehicles to each level. See figures 1 and 2
below for an idea of how this is set up.
Vehicles enter at street level and are moved to whichever level has
vacancy.
The elevator car stops at street level with the doors open when
there are no requests. When a vehicle
pulls into the elevator car, the driver pushes a button to close
the door. Then, the elevator moves to the
lowest floor that has vacancy. Floors are filled from the bottom up
and each floor has 10 spaces. If the
entire garage is full, a light on the outside of the building turns
on to indicate the garage is full.
Each floor has a limit switch to determine if the elevator car is
on that floor.
To leave the garage, the tenants push a button on each floor which
requests the elevator car to that
level. Each floor call should have confirmation that the request
was received. The elevator car will move
to that requested floor and open the doors. Once in the elevator,
the driver will push the door close
button and the elevator car will move down to the street level and
the doors will open.
The program must have the ability to process multiple call requests
in the order in which they were
received. The elevator car can only hold one vehicle at a time.
Example: If a request comes from the
third floor, and then another request comes from the second floor
before the first request is complete,
the elevator must complete the first request and deliver the
vehicle to street level, and then process the
request from the second floor.
The elevator car has a sensor to determine if a car is present. If
a request is made and no vehicle is
detected in the elevator for a certain amount of time, the elevator
will go to the next request, or return
to the first-floor “parked” position. (For the sake of testing this
program, you may manually activate the
vehicle presence sensor). The elevator car doors have limit
switches to determine the position of the
door.
The elevator uses a reversing motor to lift and lower the car.
The motor runs in one direction to lower
the car and in the opposite direction to raise the car. The
elevator has a mechanical brake that
automatically engages when the motor is stopped, and automatically
disengages when the motor starts.

Write the PLC code to control the elevator and keep track of the
number of open spaces on each level.
Design an HMI program that will show the number open spaces on each
floor, the location of the
elevator, the status of the elevator doors, and the status of the
lift motor. Include a button to trigger the
vehicle presence sensor for testing. Include the individual floor
request buttons and indication if the
floor has a request.