Elevator Control System – Project Report

Authors: Lorenzo Barbieri and Edoardo Saturno

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Overview

This project presents the design and implementation of an elevator control system developed in the Codesys environment using generalized actuators and well-defined control policies.
The system handles door operations, vertical movement, call management, and emergency/fault conditions to ensure safe and efficient operation.

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Generalized Actuators

1. Doors_GA (Door Management)

A generalized DO/DONE actuator that manages door opening and closing, including presence detection.

Behavior:

• If an obstacle is detected (via presence sensor), the system prevents door closure or interrupts the process and reopens the doors.
• The doors remain open until the obstruction is cleared.

Inputs / Outputs:

Input	Meaning
Do_	Command signal
DoWhat	Action (Open / Close)
Presence_sensor	Detects obstacles
State	Internal state (Init, Busy, Ready)

Output	Meaning
Done	Operation completed
Door_closed / Door_open	Door position
Opening_port / Closing_port	Motor control signals

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2. MovimentoVerticale_GA (Vertical Movement)

A generalized Start/Stop actuator that controls the elevator’s vertical motion.

Behavior:

• Once activated, it moves the elevator up or down as directed.
• Movement stops when the actuator receives the appropriate stop condition.

Inputs / Outputs:

Input	Meaning
Start	Command to begin movement
StartWhat	Direction (Go_up / Go_down)
Stop	Stop signal

Output	Meaning
MotorOn_port	Motor control
Direction_port	Motion direction
State	Internal state (Init, Busy, Ready)

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Nominal Operation Policy

1. Homing Phase:

   • On startup, the elevator closes its doors and moves slowly down to the lower limit switch, then rises to the ground floor.
   • At the ground floor, it opens the doors and waits for a call.

2. Call Handling:

   • Calls can be made from internal or external panels.
   • Once a button is pressed, the corresponding indicator light is turned on.
   • After 2 seconds, the doors close, and the elevator starts moving.

3. Movement Control:

   • The system uses ramp sensors to adjust speed dynamically.
   • The cabin accelerates after the first ramp sensor and slows down before reaching the target floor.

4. Arrival and Next Call:

   • Upon arrival, the system waits 2 seconds before opening the doors.
   • After 5 seconds, it checks for any new pending calls.

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Call Management Policy

The system supports on-the-fly calls and call memory for those that cannot be served immediately.

Key rules:

1. Internal calls have priority over external calls.
2. If moving up, the elevator serves the lowest pending upward call first.
3. If moving down, it serves the highest pending downward call first.

If an immediate stop is possible (e.g., the request comes from a floor ahead of the current position), the elevator performs an intermediate stop; otherwise, the call is stored and served later.

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Emergency Management Policy

When the emergency button inside the cabin is pressed:

• The elevator slows down and stops at the next floor.
• If the button is pressed near a floor (between sensors), it stops at the next available floor to ensure sufficient braking distance.
• Doors open to allow passengers to exit.
• No further operations are allowed until the emergency button is pressed again to reset the system.
• Calls made during the emergency state are stored and will be processed once normal operation resumes.

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Fault Management Policy

1. Floor Sensor Faults

• Detected by monitoring discrepancies in ramp and floor sensor counts.
• When a fault is detected, the elevator slows down and stops at the next floor.
• If the ground floor or top floor sensors fail, the elevator moves slowly to the corresponding limit switch before reversing direction.
• After stopping, no further calls are served.

2. Ramp Sensor Faults

• Detected in a similar way through counting inconsistencies.
• Upon detection, the elevator slows down and stops at the next floor.
• Once stopped, the elevator does not serve additional requests.

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Summary

This project defines:

• Two generalized actuators (Doors_GA and MovimentoVerticale_GA)
• Structured policies for:
  • Normal operation
  • Call handling
  • Emergency and fault conditions

The result is a robust and safety-oriented control system for an elevator capable of handling multiple situations autonomously and efficiently.