The overall objective of this assignment is to: • Take a vague specification for a sequence control system and convert it into a precise form, then use a systematic approach to implement it using standard programming techniques. The specific objectives of this assignment are to: • Design a control system that employs a PLC to operate the following mixing system. This will include a ladder logic diagram written on the Mitsubishi software • Design and program a PC-based HMI for the above system written using DAQFactory and connecting over a serial link using the FXdirect protocol. Scenario There is a requirement to monitor and control a batch mixing system. The control will be achieved using a Mitsubishi FX1 (PLC) and monitoring of the system operation will be via an HMI running on a PC via a serial data link. The Process Overview Two ingredients (Qualified Regenerate and Kilo Macerated) are combined in a mixing tank and then agitated; the mixing tank is then evacuated to filling lines at an adjacent bottling plant. Control requirement The mixing system involves two fluids which are pumped into tanks QR and KM. The pipework between the pump and the tank includes a mechanically operated pressure regulated valve which diverts all of the fluid into the tank. When the tank is full the valve then diverts fluid toward the AV valves and this is indicated by LS-QR1 and LS-KM1 inputs, at which point the pump(s) will be turned off. When the mixing tank is empty, the pump (MT) off and the AV (MT) valve closed then the process can move to a filling stage for the mixing tank, at this point all LS1 sensors should be made. The filling sequence would be; open AV-QR, three second delay, open AV-KM and then each QR and KM AV valve would remain open until the level sensors associated with each valve go off, (LS1 followed by LS2 in each case). If the ULS-1 sensor is made then all valves should open and pump MT should operate for five seconds, this would function as a reset and the system would then return to the initial state. The agitator commences operation one second after the final LS-2 has gone off and operates for 410ms, which is a calibrated value shown in the illustration. This value provides the required mass related blend for the fluid. The mixing tank is evacuated by operating the pump for five seconds, this then concludes the process. The process has two start options, one for a single cycle and one for continuous operation. If the stop button is pressed the process should complete the cycle and then wait for either start button to be selected. Process Illustration This will require the following connections to the PLC: Inputs LS-QR1 LS-QR2 LS-KM1 LS-KM2 ULS-1 Stop Button Start Button (one operation) (Starts the one operation mode if it is safe to do so) Start Button (repeated operation) (Starts the repeated operation mode if it is safe to do so) Outputs Pump QR Pump KM AV-QR AV-KM Pump MT Agitator Deliverables: 1. The products 1. A Ladder Logic PLC program for the Mitsubishi FX1 to control the above system. Note that, from a safety point of view, you must choose whether normally open or normally closed contacts and switches are employed and choose the fail safe condition of the valves, i.e., close on signal failure or open on signal failure. 2. An HMI in the form of a mimic type display constructed using DAQFactory utilising the FXdirect protocol to communicate with the FX1 PLC. 2. The report The report is a major part of this assignment. It is a formal document and thus should be laid out in a formal manner. It is your opportunity to explain and demonstrate the various technical and design aspects of your program. It will include: • An introduction detailing the assignment • A list of which inputs and outputs are represented by the various PLC I/O elements • Appropriate diagrams and flowcharts. • Detailed description of the operation of all aspects of the PLC program • Specification of two alternative PLC types, examples would be Siemens and Allen-Bradley. • Wiring connection diagram of the PLC I/O. • Details of the methods used to read / write to the PLC from the HMI (use of channels / arrays) • Appropriate conclusions. As well as the above, your report should contain consideration of what happens if sensors fail or if the power fails. Make recommendations to overcome any problems considered. Also consider what happens, if due to a failure, the system tries to start with one or more tanks full or partially full of process fluid and make recommendations to overcome any problems considered. Justify the recommendations, if necessary making assumptions regarding the process and the process fluids, state any assumptions made. Justify your design choices for the HMI – why have you chosen the elements that you have used? What factors influenced your screen layout etc. You should also indicate any measures that you have taken to ensure usability of your HMI, including legibility, appropriate use of colour (secondary coding of data where appropriate) etc. It is essential that you use the report to demonstrate that you understand the methods and procedures involved in the creation and operation of the program and HMI system. Marks for each component of the assignment PLC Program Component Possible Actual Overall technical implementation / fitness for purpose 20% Code layout / readability / statements & comments 10% Explanation of program design / operation 20% Suggested improvements 5% Diagrams / flowcharts etc. 5% Total for program 60% HMI Component Possible Actual Overall technical implementation / fitness for purpose 20% Explanation of HMI design / operation 10% Total for HMI 30% Report Component Possible Actual Overall presentation / introduction 5% Conclusions 5% Total for report 10%