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Questions and Answers
What is the primary focus of control engineering?
Which of the following is NOT one of the six problems addressed by control engineering?
Which approach to control systems is based on complex function theory?
What component is responsible for regulating or directing the system in control engineering?
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In control systems, what does the term 'disturbances' refer to?
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Which part of a control system produces the actual output?
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What is the purpose of a control system?
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What defines an actuator in a control system?
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What effect does increasing feedback gain (H) have on the sensitivity (S) of a control system?
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Which of the following describes a disadvantage of feedback in control systems?
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What is the primary purpose of introducing feedback in a control system?
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How is sensitivity (S) mathematically defined in relation to the transfer function (T(s)) and system gain (G(s))?
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Which of the following applications utilizes control systems for enhancing processes?
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What is the main purpose of optimization in design?
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What characterizes a closed-loop control system?
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How does a deterministic control system differ from a stochastic control system?
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Which statement accurately describes a multivariable control system?
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What is a characteristic of a time-invariant control system?
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What is a primary disadvantage of open-loop control systems?
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Which is NOT a characteristic of a linear control system?
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Which category does a driving system represent?
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What is the defining feature of a servo system?
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Which statement correctly defines negative feedback?
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What is a key feature of closed-loop control systems compared to open-loop systems?
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What is one disadvantage of closed-loop control systems?
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Which type of system is considered more sensitive to disturbances?
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What aspect of closed-loop systems allows them to function effectively with variable parameters?
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Which of the following is NOT an example of a closed-loop control system?
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What determines the output variation in a closed-loop control system?
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What is the main purpose of a servomechanism in a control system?
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Which of the following correctly defines a translational system?
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Which type of force is proportional to velocity in a damping scenario?
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What torque resists rotational motion and is a function of angular velocity?
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What is the definition of Spring Torque?
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In a translational system, what is analogous to the moment of inertia in a rotational system?
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What does the transfer function represent?
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Which of the following is a characteristic of signal flow graphs (SFGs)?
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Which of these components in a mechanical system is analogous to voltage in an electrical system?
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How is a feedback path defined in a signal flow graph?
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What is the role of a dummy node in a signal flow graph?
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In the context of transfer functions, what are poles?
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What does the path gain in a signal flow graph represent?
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Which condition is essential for a transfer function to be defined?
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Study Notes
Basic Concepts of Control Systems
- Control Engineering is concerned with techniques to solve six problems: identification, representation, solution, stability, design, and optimization.
- Conventional Approach: Electrical oriented, based on complex function theory.
- Modern Approach: Mechanical oriented, based on state variable theory.
- Control engineering is applicable to various engineering disciplines such as aeronautical, chemical, mechanical, environmental, civil and electrical engineering.
Basic Terminologies in Control Systems
- System: A combined unit of physical components designed to achieve a specific task.
- Control: The action of directing or managing a system.
- Plant or Process: The component of a system that needs to be controlled.
- Input: Signal or excitation applied to a control system.
- Output: Actual response of a control system.
- Controller: Component that regulates the plant.
- Disturbances: Signals that negatively affect the performance of a control system.
- Control System: A system that manages itself or another system to reach a specific goal.
- Automation: Automatic control of a process.
- Actuator: Device that provides motive power for the output of a system.
- Design: Planning the form, parts, and details of a system to meet a desired purpose.
- Simulation: A model used to analyze a system's behavior using real input signals.
- Optimization: Adjusting system parameters for the most favorable design outcome.
- Feedback Signal: A measure of the system's output, used for feedback control.
- Negative Feedback: Output signal is subtracted from the input signal for feedback control.
- Block Diagrams: Unidirectional blocks representing transfer functions of system elements.
- Signal Flow Graph (SFG): A diagram with nodes and directed branches that graphically represent a set of linear relations.
- Specifications: Detailed statements about the intended function and performance of a system.
- Open-loop Control System: A system that controls the process without using feedback. The output does not influence the input to the process.
- Closed-loop Feedback Control System: Measures the output and compares it to the desired output, utilizing feedback in controlling the process.
- Regulator: A control system that mainly focuses on rejecting disturbances while aiming to maintain a fixed value for the controlled outputs.
- Servo System: A control system where the controlled outputs are mechanical quantities like position, velocity, or acceleration.
- Stability: Describes whether the system remains under control or increases without bound.
- Multivariable Control System: A system with more than one input or output variable.
- Trade-off: A compromise between conflicting criteria in design considerations.
Classification of Control Systems
Natural and Man-made Control Systems
- Natural Control System: A system created by nature (e.g., solar system, digestive systems).
- Man-made Control System: A system created by humans (e.g., automobiles, power plants).
Automatic and Combinational Control Systems
- Automatic Control System: Uses mathematical and engineering principles, commonly incorporating sensors, actuators, and responders.
- Combinational Control System: Blends natural and man-made elements (e.g., driving a car).
Time-variant and Time-invariant Control Systems
- Time-variant Control System: At least one parameter changes over time (e.g., driving a vehicle).
- Time-invariant Control System: No parameters change over time (e.g., a system with only inductors, capacitors, and resistors).
Linear and Non-linear Control Systems
- Linear Control System: Satisfies homogeneity and additive properties (e.g., f(x+y) = f(x) + f(y) and f(?x) = ?f(x)).
- Non-linear Control System: Does not satisfy homogeneity and additive properties (e.g., f(x) = x^3 ).
Continuous-Time and Discrete-Time Control Systems
- Continuous-Time Control System: All parameters are functions of continuous time (e.g., armature type speed control of a motor).
- Discrete-Time Control System: All parameters are functions of discrete time (e.g., microprocessor type speed control of a motor).
Deterministic and Stochastic Control Systems
- Deterministic Control System: Predictable, repetitive output for a specific input or disturbance.
- Stochastic Control System: Unpredictable, non-repetitive output for a given input or disturbance.
Lumped-parameter and Distributed-parameter Control Systems
- Lumped-parameter Control System: Mathematical model represented by ordinary differential equations.
- Distributed-parameter Control System: Mathematical model represented by an electrical network (combination of resistors, inductors, and capacitors).
Single-input-single-output (SISO) and Multi-input-multi-output (MIMO) Control Systems
- SISO Control System: One input and one output.
- MIMO Control System: More than one input and one output.
Open-loop and Closed-loop Control Systems
Open-loop Control System
- Control action depends only on the input signal, independent of the output response.
- Advantages: Simple design, easy construction, economical, easy maintenance, highly stable operation.
- Disadvantages: Not accurate or reliable when input or system parameters change, requires recalibration.
Closed-loop Control System
- Control action depends on both input signal and output response.
- Advantages: More accurate operation, efficient under changing parameters, less nonlinearity effect on output, high bandwidth, automation capability, no need for frequent recalibration.
- Disadvantages: Complex design, difficult construction, expensive, complex maintenance, less stable operation.
Servo-mechanisms
- A feedback unit in a control system where the control variable is a mechanical signal (position, velocity, or acceleration).
- Output signal directly fed to the comparator as feedback in closed-loop systems.
- Used in systems with both command and output signals that are mechanical in nature.
- Examples: Missile launchers, machine tool position control, power steering, roll stabilization in ships.
Mathematical Modeling and Representation of Physical Systems
- An idealized physical system is called a physical model.
- The process of creating a block diagram to analyze performance and determine transfer functions is called mathematical modeling.
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Mechanical Systems:
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Translational or Linear Systems: Motion along a straight line.
- Inertia Force: F(t) = Ma(t)
- Damping Force: FD(t) = Bv(t)
- Spring Force: FK(t)=Kx(t)
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Rotational Systems: Motion around a fixed axis.
- Inertia Torque: T1(t) = J?(t)
- Damping Torque: TD(t) = B?(t)
- Spring Torque: T?(t) = K?(t)
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Translational or Linear Systems: Motion along a straight line.
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Electrical Systems:
- Analogous system components:
- Force <=> Voltage
- Mass <=> Inductance
- Stiffness <=> Reciprocal of Capacitance
- Damping Coefficient <=> Resistance
- Displacement <=> Charge
- Analogous system components:
Effect of Feedback on Sensitivity
- The transfer function with feedback is T(s) = C(s) / R(s) = G / 1 + GH, where:
- T(s) is the transfer function
- C(s) is the output
- R(s) is the input
- G is the open-loop gain
- H is the feedback gain
- Sensitivity is defined as the percentage change in the transfer function to the percentage change in gain: S = %change in T(s) / %change in G(s)
- This can be expressed as: SGT = dT/dG * G/T
- When H increases, (1 + GH) increases, leading to a decrease in sensitivity.
- When H decreases, (1 + GH) decreases, leading to an increase in sensitivity.
- Sensitivity and feedback gain are reciprocally related.
Effect of Feedback on Noise
- Feedback reduces the impact of noise and affects physical activity.
- Feedback influences performance parameters like bandwidth, impedance, transient response, and frequency response.
- The transfer function for noise disturbance is C(s)/Td(s)=1/(G(s).H(s)) = C(s)=Td(s)/G(s).H(s) where:
- C(s) is the output
- Td(s) is the external noise or disturbance
- G(s) is the open-loop gain
- H(s) is the feedback gain
- To decrease noise influence on output, increase G(s).H(s) by increasing either G(s) or H(s).
Advantages of Feedback in Control Systems
- Reduces unwanted external distractions and noise.
- Improves system performance through mitigation.
- Minimizes system error.
- Allows manipulation of the transient behavior.
- Provides a reference point for comparison.
Disadvantages of Feedback in Control Systems
- Increases system complexity.
- Reduces the overall gain of the system, requiring adjustments.
- Requires additional components for implementation.
- May lead to instability, potential oscillation, or deviation from desired output.
- Introduces a reliance on error parameters.
- Changes in output influence the system's input.
Applications of Feedback in Control Systems
- Manufacturing and production processes
- Building and home automation
- Transportation systems
- Power generation and distribution
- Medical equipment
- Agricultural and farming processes
- Military and defense systems
- Robotics
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Description
Explore the foundational concepts of control systems in engineering. This quiz covers both conventional and modern approaches, essential terminology, and applications across various engineering disciplines. Test your understanding of key elements like systems, controls, and disturbances.
