Academic Session 2016-2017 (weighting=0.3) THE ASSIGNMENT IS SPLIT INTO TWO PARTS. PART 1 AND PART 2 HAVE A WEIGHTING OF 0.15 EACH. In a liquid level control system, an electric pump is used to pump liquid from a reservoir into a tank at a flow rate . The liquid flows out of the tank through an orifice at its bottom. The orifice is fitted with a manually operated flow valve having five (5) operating settings designated as "1"-"5" and represents an orifice area of 0%, 25%, 50%, 75% and 100% respectively. In addition, a level sensor is used to measure the height of liquid in the tank. It is desired to maintain the height of the liquid in the tank by controlling the flow rate of liquid into the tank, using an appropriate controller. PART 1 (Weighting=0.15) Research, design and build a digital control system based on a PC, a Labjack I/O device and MATLAB software to control the level of liquid in the tank to an accuracy of and to monitor the flow rate of liquid into the tank. You must design and build an interfacing circuitry between the Labjack and the pump, level sensor and flow meter on the tank system. Your MATLAB program should include a real time graphical display showing the set point and controlled liquid level. Your program should also enable the time history of these variables to be displayed. Your MATLAB program must also allow the controller parameters, the liquid level set point and the sampling interval, , to be updated without halting the program. Part 1 of the assignment will be assessed on the basis of a demonstration [30%] and a written report [70%]. The report should include a discussion on the optimisation of the controller parameters used and on the stability of the system. The report should also include a critical discussion of the control techniques used in this non-linear application, and suggestions for improvements to the overall system. You may work in a group of no more than four people for part 1, however, each student must produce their own individual report on PART 1. The demonstration shall be by the group. PART 2 (Weighting=0.15) Each student is expected to summarize his/her observations, including Simulink diagrams and plots and attach relevant MATLAB scripts and plots where appropriate. 1. Draw the block diagram and derive the transfer function of the closed loop liquid level control system using a negative feedback [10%]. 2. Design an appropriate controller to ensure the steady state error in the liquid level in the tank when it undergoes a step change is always less than . The settling time and overshoot of the system response should also be less than 1.5seconds and 5% respectively. You may assume the manually operated valve setting is at "position 2" and represents an orifice area of 25% [15%]. 3. Using MATLAB, determine the time constant, settling time (2% criterion), rise time (10-90%) and steady state value of the level control system [15%]. 4. Examine the stability of the closed loop level control system using the Bode and Nyquist stability criteria. Explain whether the system is stable or unstable and comment on the similarity/difference in your answers [20%]. 5. To ensure the level control system is safely operated, the phase margin of the closed loop system must be at least 120ᵒ. Design an appropriate compensator circuit to ensure the process is safely operated. Sketch an electronic circuit that could be used to implement your compensator design. Using Simulink, examine the effect of adding a compensator circuit on the response of the closed loop level control system? [30%]. 6. General presentation of your solutions [10%] You may use the following information: • Pump transfer function, where pump gain and time constant • Valve transfer function, where valve gain and position of the valve • Tank transfer function, where tank gain =24.2 and time constant =3.3[seconds] • Level sensor transfer function, where =1[mV-1].