PLC - Practical exercises

Industrial roller door

Description:

  • Assumption: At system start the rolling gate is closed.

  • The rolling gate is operated by the gatekeeper by means of a pushbutton. If the button is pressed in the closed state, the gate opens until a limit switch is reached. If the button is pressed in the open state, the gate closes after a waiting time of 5s until a limit switch is reached. If the button is pressed while moving or during the waiting time, the gate stops. If the button is pressed again, the gate moves in the opposite direction than before the stop.

  • Two motors are used (open & close). It must be ensured that only one motor is controlled at a time. When the rolling gate is fully open or closed, the motors are switched off.

  • In addition, there is an emergency stop switch and an acknowledgement button. If the emergency stop button is pressed, the door stops. To restart the rolling door after an emergency stop, the acknowledgement button must be pressed.

  • A safety pressure bar ensures that the gate stops on contact, immediately moves up and remains up.

  • Maintenance is required after N upward movements of the rolling gate (upward movements are counted when the upper limit switch is reached). N is a static variable and is set to the value N=5 for test purposes. The execution of the maintenance is confirmed by means of the acknowledgement button.

  • A signal column (red, green, yellow, blue, orange) indicates the status of the gate. Red: gate closed; Green: gate open; Orange: gate waiting; Yellow: gate in motion; Blue: maintenance required

Todo

Create a principle sketch according to the description.

Hint

Integrate the conditions of each state (entry, do, exit). Define the transitions between the states Follow the hints in the Ilias Wiki “Basics” “Statechart”. Use “speaking names” to designate the variables and the states to make the program more understandable.

Todo

Create a state machine according to the description.

Todo

Implement the state machine in ST. Use the same variable names as in the state diagram. Use an enumeration for the logic of the program; the enumeration contains the names of the previously defined states.

Hint

Use standard visualization components to simulate the following components: Pushbutton; Signal tower (four LEDs); Motors (one LED each); Counter value of maintenance (text field).

Hint

Use a counter function block for the generation of maintenance intervals. In the visualization, show how many passes are missing until maintenance is done.