lecture 1.pdf

Fundamentals of Control Engineering  Control systems Manual Automatic Control systems Control systems  Example for manual Control systems Sensor Control Control Sensor...

Fundamentals of Control Engineering  Control systems Manual Automatic Control systems Control systems  Example for manual Control systems Sensor Control Control Sensor Water temperature control Fluid flow control  Example for manual Control systems  Example for Automatic Control systems  Example for Automatic Control systems Regulating liquid levels in tanks,  Example for Automatic Control systems The rockets fire Self-guided vehicle ‫اطالق الصواريخ وتوجيها‬  Spacecraft ‫المركبة الفضائية‬  Guide the shuttle to and from earth’s orbit  Navigation functions programmed into the shuttle’s computers use data from the shuttle’s hardware to estimate vehicle position and velocity  Ships at sea  Planes  Color mixing to produced a specified color  Thickness control system for a steel plate finishing mill.  X-rays measure the actual thickness and compare it to the desired thickness. Home devices Temperature control system  Examples for Control systems  Examples for Control systems Production line  Digital computer or an onboard computer used as a part of control systems.  Raspberry Pi  Microcontroller  PLC  FPGA board  Embedded systems  All the previous automatically controlled systems that we can create  We are not the only creators of automatically controlled systems  Within our own bodies are numerous control systems, such as  In time of fight or flight ‫ القتال او الهروب او المجهود‬our adrenaline increases along with our heart rate, causing more oxygen to be delivered to our cells.  The pancreas, which regulates our blood sugar.  Our eyes follow a moving object to keep it in view;  Our hands grasp the object and place it precisely at a predetermined location. Control System Definition  A control system consists of subsystems and processes (or plants) assembled for the purpose of obtaining a desired output with desired performance for a given specified input. Input subsystems subsystems subsystems Output Stimulus Response Control System Desired response Actual response For example, consider an elevator Subsystems 1. Hydraulic pump 2. Cars 3. Door motor 4. Display 5. Car lighting 6. Hydraulic piston 7. Controller & Control panel  ‫ الدخل هو الضغط علي المفتاح للدور المطلوب الذهاب اليه‬ ‫الوصول الي الدور المطلوب‬ ‫ الخرج‬ ‫سرعة الوصول الي الدور المطلوب مع نعومة حركة الكبينة مع دقة الوصول الي المكان المحدد‬ ‫ االداء‬ )‫بالظبط (باب الكبينة امام باب المبني‬  When the fourth-floor button is pressed on the first floor, the elevator rises to the fourth floor with a speed and floor-leveling accuracy designed for passenger comfort.  The push of the fourth-floor button is an input that represents our desired output Elevator response ‫المكان المطلوب للكبينه‬ ‫المكان الحالي للكبينه‬ ‫يعتمد علي سرعة حركة الكبينة‬  The performance of the elevator can be seen from the elevator response curve Two major measures of performance are apparent:  The transient response  The steady-state error  Passenger comfort ‫راحة الركاب‬ are dependent upon the  Passenger patience ‫صبر الركاب‬ transient response  If transient response is too fast passenger comfort is sacrificed ‫التضحية‬  If transient response is too slow passenger patience is sacrificed  The steady-state error is another important performance specification since passenger safety and convenience ‫ راحة وسالمة‬would be sacrificed if the elevator did not properly level  Elevators are fully automatic, using control systems to regulate position and velocity Why we need to build a control systems 1. Remote control 2. Power amplification 3. Convenience of input form 4. Compensation for disturbances 1. Remote control  Control systems are useful in remote or dangerous locations.  For example,  A remote-controlled robot arm can be used to pick up material in a radioactive environment  Robots designed by control system principles can compensate for human disabilities 2. Power amplification Darlington Transistor Configurations 2. Power amplification  a radar antenna  Positioned by the low-power rotation of a knob at the input, requires a large amount of power for its output rotation.  A control system can produce the needed power amplification, or power gain ‫تبدو كانها صغيره ولكن في‬ ‫الحقيقة هي كبيره وتحتاج طاقة‬ ‫كبيره لتتمكن من الدوران‬  Radar antenna needs high power for rotation 3. Convenience of input form  Control systems can also be used to provide convenience by changing the form of the input.  For example  In a temperature control system, the input is a position on a thermostat. The output is heat. Thus, a convenient position input yields a desired thermal output ‫ تم التحكم في درجة الحراره او درجة ارتفاع الصوت او سرعة الموتور من خالل تغير قيمة المقاومة‬ 4. Compensation for disturbances  The system must be able to yield the correct output even with a disturbance.  For example  Consider an antenna system that points in a commanded direction.  If wind forces the antenna from its commanded position, or if noise enters internally, the system must be able to detect the disturbance and correct the antenna’s position.  Test yourself 1. With control systems we can move large equipment with True precision that would otherwise be impossible. 2. We can point huge antennas toward the farthest reaches of the universe to pick up faint radio signals ‫اشارات الراديو الخافته‬ True controlling these antennas by hand would be impossible 3. Because of control systems, elevators carry us quickly to our True destination, automatically stopping at the right floor  System Configurations  Two major configurations of control systems 1. Open loop control system 2. Closed loop control system  Show how a digital computer forms part of a control system’s configuration. 1. Open loop control system 1. Open loop control system Block diagram of open loop control system 2. Closed loop control system 2. Closed loop control system Block diagram of closed loop control system 1. Open loop control system Converts the form of the Drives a process or a plant input to that used by the controller 1. Open loop control system Input  Reference Output  Controlled variable  Temperature  Pressure  Level  Flow Open-loop systems Example Domestic toaster Control is exercised by setting a timer which determines the length of time for which the bread is toasted. The brownness of the resulting toast is determined solely by this preset time. There is no feedback to control the degree of browning to a required brownness. For example, toasters are open-loop systems  The controlled variable (output) of a toaster is the color of the toast.  The device is designed with the assumption that the toast will be darker the longer it is subjected to heat.  The toaster does not measure the color of the toast;  It does not correct for the fact that the toast is rye, white, or sourdough,  It does not correct for the fact that toast comes in different thicknesses 1. Example of Open loop control system Microwave Oven  You set a microwave oven to run for 2 minutes  After a minutes, the control system turns a microwave oven off  It has no idea, whether your food is still frozen, burnt or cooked perfectly 1. Example of Open loop control system Open loop drying system 1. Example of Open loop control system  Traffic Light  Washing machine 1. Open loop control system  Disturbances, are shown added to the controller and process outputs via summing junctions, Disturbance 1 controller ‫ بيكون في خرج ال‬disturbance ‫ او‬noise ‫ هنا ال‬  Example for disturbance 1  if the controller is an electronic amplifier and Disturbance 1 is noise, then any additive amplifier noise at the first summing junction will also drive the process, corrupting the output with the effect of the noise. Disturbance 2  The disturbance at the output of an open-loop system Example of disturbance 2 If a person used the heating element to heat a room He might just switch on the 1 kW element heater Disturbance 2 The room will heat up and reach a temperature If there are changes in the conditions, perhaps someone opening a window, We should switch on the 2 kW element heater to compensate but There is no information fed back to the element to adjust it and maintain a constant temperature ‫‪Example of Disturbance 2‬‬ ‫زجاج الباب انكسراثناء فتره التشغيل‬ Example of Disturbance 2 Block diagram of open loop system based on timer  The dryer door opens and heat is lost.  The timing controller continues regardless for the full 30 minutes but the clothes are not heated or dried at the end of the drying process.  This is because there is no information fed back to maintain a constant temperature. Disadvantages of Open loop control system  The distinguishing characteristic of an open-loop system is that it cannot compensate for any disturbances Test yourself  The disadvantages of open-loop systems, namely sensitivity to True disturbances and inability to correct for these disturbances 2. Closed-Loop (Feedback Control) Systems Measures the output response and converts it into the form used by the controller 2. Example of Closed-Loop Systems Error signal Output variable Input transducer Temperature Sensor 2. Example of Closed-Loop Systems Draw the block diagram for the following systems Draw the block diagram for the following systems Draw the schematic diagram for the following block diagram Draw the block diagram for the following systems Draw the block diagram for the following systems Draw the block diagram for the following systems Draw the block diagram for the following systems Draw the block diagram for the following systems Exam question Draw the block diagram for the following systems Cascaded control system Block diagram of cascaded control system Multiloop  Block diagram of cascaded control system  Example Block diagram of multivariable control system Draw the block diagram for the following systems 2. How the closed loop system compensate the disturbance  The closed-loop system compensates for disturbances by measuring the output response, feeding that measurement back through a feedback path, and comparing that response to the input at the summing junction.  If there is any difference between the two responses, the system drives the plant, via the actuating signal, to make a correction.  If there is no difference, the system does not drive the plant, since the plant’s response is already the desired response.  Test yourself  Closed-loop systems monitor the output and compare it to the input. If an error is detected, the system corrects the True output and hence corrects the effects of disturbances. Advantages of open loop control system 1. Relatively simple 2. Consequently low cost 3. Good reliability. Disadvantages of open loop control system 1. Inaccurate since there is no correction for error Closed-loop systems have the following advantages 1. Relatively accurate in matching the actual to the required values.  They are less sensitive to noise, disturbances, and changes in the environment.  Transient response and steady-state error can be controlled more conveniently and with greater flexibility in closed-loop systems, often by a simple adjustment of gain (amplification) in the loop and sometimes by redesigning the controller. Disadvantages of closed loop control system 1. More complex 2. More costly 3. With a greater chance of breakdown as a consequence of the greater number of components (Low reliability)  Test yourself  The control systems engineer must consider the trade-off between ‫ يجب ان ياخذ في االعتبار المفاضلة بين‬the simplicity and True low cost of an open-loop system and the accuracy and higher cost of a closed-loop system. Control systems A control system can be used to 1. Control some variable Temperature, Pressure, Flow, Level, ……….. 2. Control the sequence of events e.g. a washing machine to perform washing cycle 3. Control whether an event occurs or not e.g. a safety lock on a machine ‫‪Analysis and Design Objectives‬‬ ‫درسنا سابقا ان هناك معايير تستخدم للحكم علي اداء النظام‬ ‫‪ Control system performance specifications‬‬ ‫ومن هذه المعايير‬ ‫‪1. Transient response‬‬ ‫‪2. Steady state error‬‬ ‫ما هي باقي هذه المعاييرالتي تستخدم لقياس االداء‬ ‫من خالل دراسة هذه المعايير سوف نتمكن من تحليل اداء النظام ‪analysis the performance‬‬ ‫هل هو ‪...........‬‬ ‫هل هو قوي‬ ‫هل هو بيطء هل هو مستقر‬ ‫هل هو سريع‬ ‫‪ Analysis is the process by which a system’s performance is determined‬‬ Analysis and Design Objectives  Design is the process by which a system’s performance is created or changed. ‫ لو اكتشفنا بعد تحليل اداء النظام ان هناك متطلبات او مواصفات لم تتحقق في االداء‬ ‫ عن طريق تغيير قيمة متغير او اضافة مكون جديد الغرض منه هو‬design ‫ هنا يتطلب عمل تصميم‬ ‫الحصول علي االداء المطلوب‬  If a system’s transient response and steady-state error are analyzed and found not to meet the specifications, then we change parameters or add additional components to meet the specifications.  Test yourself  A control system is dynamic or static Dynamic  A control system is dynamic: It responds to an input by undergoing a transient response before reaching a steady-state response that generally resembles the input. Dynamic Static  Test yourself Discuss three major objectives of systems analysis and design: 1. Producing the desired transient response, 2. Reducing steady-state error, 3. Achieving stability. 4. Cost and the sensitivity of system performance to changes in parameters  Transient response is important. In the case of an elevator  A slow transient response makes passengers impatient ‫ينفد صبرهم‬  Excessively rapid response makes them uncomfortable.  If the elevator oscillates about the arrival floor for more than a second, a disconcerting feeling can result ‫شعور مربك‬  Transient response is important.  Transient response is also important for structural reasons: Too fast a transient response could cause permanent physical damage ‫ اذا كان سريع جدا فانه قد يدمر او يكسر بعض التوصيالت في‬transient response ‫ يجب العلم ان‬ ‫النظام‬  Finally, we adjust parameters or design components to yield a desired transient response  Steady-State Response  Start after transients have decayed to zero, or finished ‫ وغالبا الخرج بيكون وصل لقيمة الدخل المطلوبة‬transient ‫ يبدأ بعد انتهاء‬ ‫ مثل الوصول الي السرعة المطلوبه لموتور او الوصول الي الطابق المطلوب في االسانسير‬  We are concerned about the accuracy of the steady-state response accuracy ‫ تزيد الدقة‬steady state error ‫ كلما يقل ال‬  Test yourself  The steady-state error is a measure of the accuracy a control True system has in tracking a command input.  We tend to design corrective action to reduce the steady- True state error  Stability Total response = Natural response + Forced response Response is dependent only Is dependent on the input on the system, not the input. zero-input response May be dependent on initial condition  Natural response must eventually approach zero ‫ مثال ولكن اذا كان النظام‬initial condition ‫ الخرج ممكن يظهر حتي لو الدخل بصفر كنتيجة لل‬ ‫ فان هذا الخرج سرعان ما يتالشي‬stable ‫ اذا لم يتالشي هذا الخرج وظل النظام يعمل بدون دخل فان النظام قد يتدمر وهنا نقول ان النظام‬ unstable  Eventually, the natural response is so much greater than the forced response that the system is no longer controlled. This condition, called instability could lead to self-destruction of the physical device if limit stops are not part of the design  Example for effects of instability  The elevator would crash through the floor or exit through the ceiling ‫ فانه قد ال يتوقف عن االدوار المحدده ويصطدم باالرض او‬unstable ‫ اذا حدث واصبح نظام االسانسير‬ ‫يخرج من السقف وعندها سوف تتدمر الكبينة‬ Determine the stability of each response  Stability  Control systems must be designed to be stable.  So natural response must decay to zero as time approaches infinity, or oscillate.  In many systems the transient response you see on a time response plot can be directly related to the natural response.  Thus, if the natural response decays to zero as time approaches infinity, the transient response will also die out, leaving only the forced response.  If the system is stable, the proper transient response and steady-state error characteristics can be designed.  Stability Total response = Natural response + Forced response Related to transient response Related to steady state response  Other Considerations ‫ هناك معايير اخري يجب مراعاتها ومنها‬ ‫ حجم المكونات واستهالك الطاقة لكل مكون‬.1 Factors affecting hardware selection, such as motor sizing to fulfill power requirements Choice of sensors for accuracy ‫ دقة الحساسات‬.2 Finances or budget allocations and competitive pricing ‫ التكلفة الكلية‬.3 4. Robust design ‫ المطلوبه يعني مش مع اقل‬performance ‫الحصول علي منتج قوي يقاوم التغييرات دون ان يفقد ال‬  unstable ‫تغيير يصبح‬ Which system of these two systems are slow Fast Slow  Test yourself  Control systems analysis and design focuses on three primary objectives: True 1. Producing the desired transient response 2. Reducing steady-state errors 3. Achieving stability  A system must be stable in order to produce the proper True transient and steady state response.  Test yourself  Transient response is important because it affects the speed of the system and influences human patience and comfort, True not to mention mechanical stress. ‫ناهيك عن االجهاد الميكانيكي‬  Steady-state response determines the accuracy of the control system; it governs how closely the output matches the True desired response  Test yourself 1. Name three applications for feedback control systems. 2. Name three reasons for using feedback control systems and at least one reason for not using them. 3. Give three examples of open-loop systems. 4. Functionally, how do closed-loop systems differ from open-loop systems? 5. State one condition under which the error signal of a feedback control system would not be the difference between the input and the output.  Test yourself 6. If the error signal is not the difference between input and output, by what general name can we describe the error signal? Actuating signal 7. Name two advantages of having a computer in the loop. 8. Name the three major design criteria for control systems. 9. Name the two parts of a system’s response. 10. Physically, what happens to a system that is unstable?  Test yourself 11. Instability is attributable to what part of the total response? 12. Describe a typical control system analysis task. 13. Describe a typical control system design task. 14. Adjustments of the forward path gain can cause changes in the transient response. True or false? 15. Name three approaches to the mathematical modeling of control systems. 16. Briefly describe each of your answers to Question 15.  Test yourself  Control Systems: A system is a combination of components True that act together and perform a certain objective  A control system consists of subsystems and process (or plant) assembled for the purpose of obtaining a desired output with True desired performance, given a specified input.  Test yourself  A disturbance is a unwanted signal that tends to adversely affect the value of the output of a system. If a disturbance is generated within the True system, it is called internal , while an external disturbance is generated outside the system and is an input.  Feedback control refers to an operation that, in the presence of disturbances, tends to reduce the difference between the output of a True system and some reference input and does so on the basis of this difference.  Test yourself  Draw the block diagram of this system  The block diagram  Test yourself  Draw the block diagram of this system  The block diagram  Test yourself  Draw the block diagram of this system  The block diagram  In the next Lecture we continue through the analysis and design sequence and learn how to use the schematic to obtain a mathematical model.  ‫اتعلمنا ايه جديد‬ ‫‪.1‬يعني ايه ‪Control system‬‬ ‫‪.2‬انواعة سواء مانوال او اوتوماتيك‬ ‫‪.3‬انواعة من حيث ‪Open loop & Closed loop‬‬ ‫‪.4‬امثلة كتير ومختلفة علي كل نوع‬ ‫‪.5‬ازاي نرسم ‪ Block diagram‬من ‪Schematic circuit‬‬ ‫‪.6‬المعايير المختلفة للحكم علي اي نظام‬ ‫‪.7‬يعني ايه ‪Transient response, Steady state response, Stability‬‬ ‫‪.8‬ازاي اعرف خواص ‪ curve‬سريع بطيء مستقر او غير مستقر‬