3442 Industrial Instruments 2 Chapter 12 Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya Univ. Electronic Engineering Dept. 3442 Industrial Instruments 2 Chapter 12 Control-Loop Characteristics Dr. Bassam Kahhaleh Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Configurations Single Variable Independent Single Variable Flow rate Regulation Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Configurations Single Variable Independent Single Variable Interactive Single Variable Flow rate Regulation Temperature Regulation Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Configurations Single Variable Independent Single Variable Interactive Single Variable Compound Variable Example: Maintain A : B = 3 : 5 Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Configurations Cascade Control Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Configurations Cascade Control Example: Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Multivariable Control Systems Analog Control Example: In a reaction vessel, two reactants are mixed, react, and the product is drawn from the bottom. The reaction rate is to be controlled. It is also important to keep the reaction temperature and vessel pressure below certain limits & The level is to be controlled at some nominal value. Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Multivariable Control Systems Analog Control Supervisory & Direct Digital Control (DDC) May use self-adapting algorithms. Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Quality Definition of Quality Loop Disturbance Quality: the degree to which the deviations that result from the disturbances are minimized. Types: 1. Transient 2. Setpoint changes 3. Load change Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Quality Definition of Quality Loop Disturbance Optimum Control Quality: 1. Stability 2. Minimum deviation 3. Minimum duration Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Control System Quality Measure of Quality Overdamped Critically Damped Underdamped Quarter Amplitude Minimum Area Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Stability Stability Criteria A system is stable if the phase lag is less than 180° at the frequency for which the gain is unity. A system is stable if the gain is less than one at the frequency for which the phase lag is 180 ° Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Open-Loop Transient Response Method Known as Process-Reaction Method Only for systems with self-regulation Open the loop (No feedback) by disconnecting the controller’s output from the final element. Introduce a transient disturbance by a small, manual change of the controlling variable using the final control element. Measure the controlled variable (record it versus time). Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Open-Loop Transient Response Method L: lag time in minutes N: reaction time (%/min) Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Open-Loop Transient Response Method Proportional Mode: ¼ Amplitude: Proportional-Integral Mode: ¼ Amplitude: Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Ziegler-Nichols Method Known as Ultimate Cycle Method Reduce any integral and derivative actions to their minimum effect. Gradually begin to increase the proportional gain while providing periodic small disturbances to the process. Note the gain KC at which the dynamic variable just begins to exhibit steady cycling (oscillations about the setpoint). Note the critical period TC of these oscillations Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Ziegler-Nichols Method Proportional Mode: Proportional-Integral Mode: Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics Process Loop Tuning Frequency Response Method If the phase lag is less than 140° at the unity gain frequency, the system is stable. If the gain is 5 dB below unity (gain = 0.56) when the phase lag is 180°, the system is stable. Dr. Bassam Kahhaleh

12: Control-Loop Characteristics Princess Sumaya University 3442 - Industrial Instruments 2 12: Control-Loop Characteristics End of Chapter 12