In today's industrial systems the control and governance of technological processes become increasingly complex. Accurate and reproducible control of successive stages of production, which is translated into the direct control of devices and actuating machines, is a prerequisite for obtaining high-quality products. Automation of the process of production allows to minimize the duration of the process, and thus - to reduce the cost of production. Digital compuuters, which meet all the above requirements, are ideal to accomplish these goals. In many cases, the lowest layer of the applied industrial process control logic can be constructed using programmable logic controllers (PLCs).

PLCs are miniature computers made in order to operate in "difficult" industrial environments: resistant to noise, vibration, and dust, as well as to high and low temperatures.
The main task of the controller is to run control algorithms implemented by the user. Such an algorithm uses the current and past status of the inputs (digital/binary and analog) to generate appropriate output signals which control the process via actuators.

Aim of the course

The task of the Laboratory of programmable logic controllers is to acquaint students with PLCs through learning the principles of operation and the specificity of programming these devices. Moreover, the aim is to teach the practical application of the knowledge on PLCs by tackling the students with different challenges occurring at different laboratory stands. There are five test kits available in the laboratory.

Methodology of working in the laboratory

The students' task is to program the controller to perform certain control tasks on the laboratory object models. In addition to the mastering of the controller-specific programming language, the challenge is to design a control program (algorithm), acting reasonably and correctly. The second principal element of the execution of a laboratory exercise is to master the object model under test. 

Some sensors present in models, though simple in operation, may in practice rise specific technical problems. These problems manifest themselves during the process of creatins the control programs. Some examples include: 

  • the inertia of the drive mechanisms in the models, the shape of counted elements resulting in pulse duplication,
  • imperfections of the object models causing unexpected behavior of these models in certain situations.

Fortunately, the user programming the controller using a program implemented on a PC, has at its disposal the facility to view the current values of all internal variables, timers and counters. 
Through this opportunity, running programs is much easier, and perhaps without it - it would be unworkable.

Another factor, which may perturb the operation of the program, is the ability to manually disrupt the object models, what can be done, for instance, in the case of the assembly line model, by adding or taking off parts outside designated places.

Laboratory sets

  1. GE Fanuc Micro 90 controled assembly line model. In the model there are the following types of sensors: optical (5), loads (4), capacitive (1) and control keys (2). The kit includes several actuators: conveyer belts (1), conveyor belts (1) and electromagnetic punches  (3).
  2. GE Fanuc Versa Max with assembly wheel model. In the model there are optical sensors (8) and the control keys (2), and actuators:
    • engine rotating the wheel (control: on / off, left / right, slow / fast),
    • white and black rings feeder,
    • a sound alarm.
  3. GE Fanuc Versa Max controlled the intersection model with the traffic light. The controller inputs are connected to the following elements:
    • the keys to simulate operation of inductive loops hidden under the road surface (4)
    • demand keys at a pedestrian crossing.
    The outputs in the model (LEDs) carry out traffic lights at the junction (11).
  4. STESAR driver with the elevator model. Lift model used in the kit provides the following information:
    • location of the elevator car (4 optical sensors),
    • information about reaching the end position top / bottom (1).
    There is also a control console with 24 buttons for controlling the elevator model. The controller may activate the elevator car engine running in the upwards or downwards with low or high speed.
  5. The STESAR driver with simulation desktop . This kit is a similar to set 4, but only a control panel is available here. There you can perform any task, simulating virtual object reaction using desktop keys in response to signals issued by the controller.