Control of Industrial Processes - Lab Report Example

Summary Control of industrial processes is a very crucial undertaking because it ensures that all processes are kept within optimum working conditions. An experiment was conducted to provide an analysis of the methods used in ensuring that industrial processes are controlled. The experiment was divided into four sections with each section capturing the various aspects involved in various controllers. The controllers that were studied included the On-Off controllers, the proportional controllers and the integral and the derivative controllers. The controllers were analyzed in relation to how effective they were in ensuring optimization in the functioning of the industrial processes. The general realization is that the On-Off controllers were the least effective and were only applicable in few systems, the proportional controllers were found to introduce instability in systems, while the integral and derivative controllers were found to stabilize the amplitude and stability of industrial systems. Introduction The best way to attain control of industrial processes is to ensure that effective and efficient controllers are incorporated in the processes. One major aspect of consideration according to Patrick (2009), is to ensure that the controller is able to keep the processes within optimal working conditions and to be able to employ a corrective feedback mechanism. Competitiveness of industrial processes depends on their efficiency which ensures that a higher output is registered using a lower input. The objective of the experiment is to conduct an analysis on various industrial controls and techniques used in modern industries. The controller that was analyzed was an electrical air heater simulator. The experiment used a combination of PT 326 Feedback process trainer and the PCS 327 process controller. The experiment was divided into four sections where the first section consisted of a two-step closed control loop with the power button being turned on and off with respect to temperature at given values. The second experiment concerned the proportional control where the ability of the controller to maintain optimal levels with variations in measurements was observed. The third experiment involved the introduction of an external stressor to the system and then observing the response of ths sytem to the external stressor. The fourth experiment involved the application of several fundamental changes that the system might experience and observing the stability and response of the system to the changes. Literature Review The understanding of industrial processes has always been the key factor driving the design for instruments meant to ensure control of the processes. Technological advancements have always aimed at designing control instruments that improve the efficiencies of industrial processes with minimal supervision from technicians. According to Dunn (2009), the basis to any industrial control process lies in the instrumentation. Dunn outlines that the most common industrial processes that are usually controlled are temperature, pressure, distance, and rate of flow. Current approaches have been aimed at designing automatic controllers with the capacity of controlling simultaneously the most of the variables if not all while at the same time ensuring efficiency. Dunn defines process control as the automatic process that involves the sensing of variations in the process against a pre-set value and then providing accurate feedback to the control for effective adjustments to be made (2009). Therefore, a process control should incorporate mechanisms and gadgets that allow it to sense variations, provide feedback and implement corrective measures. The most basic form of a control system can be found in the On-Off control system. The system works on a simple procedure where with respect to any variations with regard to the pre-set value the system will either shut on or off. The best example is the water heater system controller. When the temperature of the heater goes above a pre-set temperature the system automatically switches the heater off, and when the temperature of the heater goes below a certain pre-set value the system automatically switches on the heater. Although the system is simple to operate and to install, the variables that it can control are only limited to one with only two parameters. When a desired value between the maximal and the minimal is required the system is unable to deliver effective control. In addition, continual turning of the system on and off might lead to “overshooting and ripples (Patrick, 2009).” The proportional control is considered more effective in maintaining control as compared to the On-Off controller. The superiority of the proportional controller to the On-Off control lies in its ability to maintain optimal conditions without introducing “ripples and overshooting (Patrick, 2009).” Figure 1 shows a diagrammatically representation of a proportional process control. Figure 1 (Retrieved from Engineering Tool Box, 2011) The Integral and Derivative Controller Actions (PID) is usually made up of three parts namely the proportional, integral and derivative parts. Each of these parts have their own important contributory role to the PID control system. The proportional part plays the role of increasing the “loop gain” to make the system less sensitive to variations. The work of the integral part is to get rid of steady state errors while the derivative part ensures that the loop remains stable. Figure 1 shows an example of the processes involved in the PID controller (Huan, 2008). Figure 1 Theory The guiding equations for the experiment will be as follows: The offset value will be given by, Offset = Tset - Tmeasured ………………………………………. (1) The deviation with regard to the proportional control will be given by, V= KE + M ………………………………………………….. (2) Where V stands for the deviation, K stands for the proportional constant, E stands for the deviation from the measured value and M stands for the input constant at a given value. The calculation for the proportional bandwidth will be conducted using, Gain= ............................................. (3) The following equations will be used to in finding the deviation for the integral action, V= -K2 …………………………………………. (4) Or ………………………………………….... (5) The derivative controller action will be given by, V = K3 ( ………………………………………………….. (6) Methodology The experimental set up was made up of an electrical air heater that took the place of a heating furnace being controlled by a PT 326 Feedback process trainer together with a PCS 327 process controller. The process controllers were then connected to a computer with the relevant software to measure the data variations and provide feedback. The PT 326 set up was made up of a centrifugal fan that drew air into a small pipe to allow for the heating of the air so that PT 326 could keep the heated air at a constant temperature at particular values. The temperature was then measured using a Thermositor. The PCS 327 function was primarily controlling and it had three sockets designated A, B, and C all connected to the PT 326. The function of socket A was to register the signals that control the heater power, the function of socket B was to convey any deviations to PCS 327 and the function of socket C was to examine the signals from channel A. Experiment 1 (On-Off) In experiment one the power supply was turned on and off depending on the predetermined values. After the Oscilloscope was set to zero, the deviation signal was connected to channel B on the Oscilloscope and the power supply connected to channel A. The various parameters were set according to Table 1 Table 1 Set value 308 K Time Base 0.5 sec/div Y- mode Dual-B Channel A 5 volts/div Channel B 5 volts/div Baffle positions 318 K Scope push- buttons in Store , single, others out The air throttle was then varied from 5 to 6 and then to 8 while the heater supply was varied from 1 to 0.7 and the results recorded using the computer. Experiment 2 (Proportional Control) The set up for this experiment is similar to the one in experiment one except that in this case changes are applied continuously. The parameters for use in this experiment are according to Table 2 Table 2 Set value 308 K Bandwidth 100% Time Base 0.5 sec/div Y- mode Dual-B Channel A off Channel B 1 volts/div Baffle positions 318 K Scope push- buttons in Store , single, others out Experiment 3 (Continuous Control) The objective of the experiment was to observe the effect of internal disturbances by varying a set of values. The experimental set up was as shown in Table 3 Table 3 Set value 308 K Bandwidth 100% Time Base 1 sec/div Y- mode Dual-B Channel A off Channel B 1 volts/div Baffle positions 318 K Scope push- buttons in Store , single, others out Experiment 4 (PID) In this experiment the same experimental set were utilized as in experiment three only that in this case the proportional bandwidth was set at 50%. Integral action was set at values between 0.5 and 1 and then the derivative actions were set at values from 0.1 to 0.3 at integral action values of 0.7. Finally, the integral action value action was placed at 1 at derivative action values of 0.1 to 0.3. Results Read More