Most control processes require the completion of several operations to produce an output. Select an example of a PLC-based sequential control process and explain the process with details.
PLCs or Programmable logic computers are predominantly used in industries that require automation and the controlling of certain sequences in a series of process flow. The parameters that include such a workable sequence mostly have level flow, weight and the recording of temperature as one of the primary attributes (Ogawa & Henmi, 2006). The PLC fundamentally acts as the brains of the entire procedure and this type implementation is used in the procurement of solid waste and or treatment of recyclable waste as well. In any given PLC specific hardware is used to interfacing the process while a controlling mechanism is developed to control the level of temperature for the process as well. The most astute aspect of PLCs is that it is implemented in a real time environment making the use of such, extremely feasible in industries that heavily rely on automation and signal processing (Park et al, 2008). PLCs are additionally developed via the use of ladder diagrams while for our current example we will look at the process details of how waste management is done using the help of PLCs – Below is the process flow, with description for each stage:
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Process Tank – Using speed pumps water is transferred into the process tank from the reservoir that holds the unrecycled waste from the local municipality. This process tank is the initializing phase of treating the waste using PLCs.
PLC – Microcontrollers that implement the necessary functionality on the entire system by providing electric signals to every piece of equipment attached.
Temperature Controller – Using ladder logic we can effectively implement on and off sequences based on the input data we receive via the recorded temperature. A temperature controller which is predominantly a backdated technological marvel from the days of PID records the temperature of the waste which can then be used as a measure to either increase or decrease the PH level of the waste.
Weight Measurement – A weight measuring system captures the overall load of the affluent as well as the effluent. This type of a logic controller enables how much discharge should be implemented so that process follow remains coherent and sequencing does not have any bottleneck.
Level Controller – A level controller provides the entire process the ability to implement a sequence of flows that will be incumbent to the sensory input. Objectives such as water level, depth of a tank etc are the core features a level controller ascertains and then using the data generated by this controller we can either increase or decrease the affluent or the effluent.
Outlet Valve Controller – Discharge valve that is controlled once the Process and storage tanks are at full capacity. These instances are measured using the level controller.
Pump Controller – A PLC component that provides a boost in the pressure on water flow and rate of discharge. Predominantly effective in cases such as waste water management and liquid waste processing.
Stirrer Motor Controller – A centrifugal motion oriented controller the stirrer is predominantly used when treating waste water by mixing the latter with chemical compounds and or increase or decreasing the PH level of the reservoir
Power Supply Section – Controls the power consumption of the entire process in play.
Ladder logic and Grafcet are two programming languages that are commonly used to program PLCs. With help of illustrations, explain the characteristics of each of these PLC programming languages.
Grafcet is a comprehensive tool via which we can describe various specifications of a processing control unit that provides the core functionality to an automated system. There are three distinct phases to this; steps, transitions and directed links. After every step there is an output which can be fed back into the system to produce a subsequent step and this feat can be repeated until the program terminates itself due to a certain preconditioned loop not fulfilling the criteria (Bellmunt et al, 2006) – In Grafcet, the first step will always be step 0.
The above partial ladder diagram shows the label connector and the Initial step that would be part of the entire process flow similarly in ladder logic we develop simulations and other illustrations to provide us with the necessary information on viewing whether a PLC would work or not.
Based on the characteristics of both programming languages I believe Grafcet provides a much more stable working platform as using the latter we can effectively check our simulations step by step and isolate an errors when providing signal processing services.
References
Ogawa, M., & Henmi, Y. (2006, October). Recent developments on PC+ PLC based control systems for Beer Brewery Process Automation Applications. In SICE-ICASE, 2006. International Joint Conference (pp. 1053-1056). IEEE.
Park, S. C., Park, C. M., & Wang, G. N. (2008). A PLC programming environment based on a virtual plant. The International Journal of Advanced Manufacturing Technology, 39(11-12), 1262-1270.
Frey, G., & Litz, L. (2000). Formal methods in PLC programming. In Systems, Man, and Cybernetics, 2000 IEEE International Conference on (Vol. 4, pp. 2431-2436). IEEE.
Bellmunt, O. G., Miracle, D. M., Arellano, S. G., Sumper, A., & Andreu, A. S. (2006). A distance PLC programming course employing a remote laboratory based on a flexible manufacturing cell. IEEE Transactions on Education, 49(2), 278-284.
