Servo Motors MCQ Quiz in தமிழ் - Objective Question with Answer for Servo Motors - இலவச PDF ஐப் பதிவிறக்கவும்

Explanation:

Servomotor

Definition: A servomotor is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity, and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. Servomotors are used in applications where precise control of position or speed is required, such as in robotics, CNC machinery, or automated manufacturing.

Working Principle: The working principle of a servomotor involves the following key components: a motor, a feedback sensor, a controller, and a drive system. The controller receives the desired position or speed input (often referred to as the setpoint) and compares it to the feedback from the sensor to determine any error. This error is used to adjust the motor's movement to achieve the desired position or speed. The feedback loop ensures that the servomotor can correct any deviations and maintain accurate control over its motion.

Servomotors can be classified into different types based on their design and the type of feedback mechanism used. Some common types include:

• AC Servomotors: These use alternating current (AC) and are known for their high efficiency and precise control. They are commonly used in industrial applications.
• DC Servomotors: These use direct current (DC) and are simpler in design compared to AC servomotors. They are often used in smaller or low-power applications.
• Brushless DC Servomotors: These are a type of DC servomotor that uses electronic commutation instead of brushes, resulting in higher efficiency, reliability, and longer lifespan.

Advantages:

• High Precision: Servomotors provide precise control over position, speed, and acceleration, making them ideal for applications requiring accurate and repeatable motion.
• Fast Response: The feedback mechanism in servomotors allows for rapid correction of any errors, resulting in quick response times and improved performance.
• Versatility: Servomotors can be used in a wide range of applications, from simple positioning tasks to complex motion control systems.

Disadvantages:

• Complexity: The inclusion of feedback sensors and controllers adds complexity to the system, requiring more sophisticated setup and maintenance.
• Cost: Servomotors can be more expensive than other types of motors due to their advanced features and components.

Applications: Servomotors are widely used in various industries and applications, including:

• Robotics: For precise control of robotic arms and joints.
• Automation: In CNC machines, conveyor systems, and automated manufacturing processes.
• Aerospace: For controlling flight surfaces and actuators.
• Consumer Electronics: In devices such as cameras and printers for accurate positioning.

Correct Option Analysis:

The correct option is:

Option 1: Servomotor

A servomotor is specifically designed for precise control of angular position. The feedback mechanism and control system ensure accurate and repeatable positioning, making it the ideal choice for applications that require high precision and fast response times.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: DC Motor

While DC motors can be used for various applications, they do not inherently provide the precise control of angular position that servomotors offer. DC motors are often used in applications where speed control is essential, but additional components are needed to achieve precise positioning.

Option 3: Synchronous Motor

Synchronous motors run at a constant speed determined by the frequency of the AC power supply. They are not typically used for precise control of angular position as their primary function is to maintain a constant speed rather than adjust to specific positions.

Option 4: Induction Motor

Induction motors are widely used in various industrial applications due to their ruggedness and simplicity. However, they are not designed for precise control of angular position. They are more suitable for applications requiring consistent and reliable operation without the need for precise positioning.

Conclusion:

Understanding the specific capabilities and applications of different types of motors is crucial for selecting the right motor for a given task. In this case, servomotors are the best choice for applications requiring precise control of angular position due to their advanced feedback mechanisms and control systems. While other types of motors like DC, synchronous, and induction motors have their own advantages and are suitable for various applications, they do not offer the same level of precision and control as servomotors.

Explanation:

Servo Motor Control Using Pulse-Width Modulation (PWM)

Definition: A servo motor is a rotary actuator or linear actuator that allows precise control of angular or linear position, velocity, and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. Servo motors are widely used in applications that require precision and controlled motion, such as robotics, CNC machinery, and automation systems.

The correct answer to the question "How does a servo motor control its shaft position?" is Option 4: Using pulse-width modulation (PWM) signals. Let us now explore in detail how servo motors utilize PWM to control their shaft position.

Working Principle of PWM in Servo Motors:

PWM is a modulation technique used to encode a message into a pulsing signal. It is a widely used method for controlling the amount of power delivered to electrical devices, especially motors.

In the context of servo motors:

• The servo motor receives a PWM signal as an input from a controller (such as a microcontroller or servo driver).
• The PWM signal consists of a train of pulses, with a fixed frequency and a variable duty cycle. The duty cycle is the percentage of one period in which the signal is "on" (high).
• The width (or duration) of each pulse in the PWM signal determines the desired position of the servo motor's shaft.
• Inside the servo motor, a control circuit compares the received PWM signal with the feedback from the position sensor (usually a potentiometer). This feedback represents the current position of the motor's shaft.
• The control circuit calculates the error between the desired position (from the PWM signal) and the actual position (from the feedback) and adjusts the motor's operation to minimize this error. This process is known as closed-loop control.

Key Features of PWM-Based Servo Motor Control:

• Precise Control: By varying the duty cycle of the PWM signal, the shaft position of the servo motor can be controlled with high accuracy.
• Feedback Mechanism: The feedback sensor ensures that the servo motor achieves the desired position and corrects any deviation.
• Energy Efficiency: PWM allows efficient control of power delivery to the motor, reducing energy wastage.

Example:

Consider a servo motor with a PWM signal operating at a frequency of 50 Hz (20 ms period). The pulse width of the PWM signal determines the position of the motor shaft:

• A pulse width of 1 ms might correspond to the 0° position of the shaft.
• A pulse width of 1.5 ms might correspond to the 90° position.
• A pulse width of 2 ms might correspond to the 180° position.

By adjusting the pulse width within this range, the servo motor can be positioned at any angle between 0° and 180°.

Advantages of PWM-Based Control in Servo Motors:

• High accuracy and repeatability in positioning.
• Cost-effective implementation using standard microcontrollers or drivers.
• Compatibility with a wide range of servo motors and applications.

Applications:

• Robotics: Servo motors are used in robotic arms, grippers, and humanoid robots for precise movements.
• Automation: They are utilized in automated machinery and conveyor systems for controlled motion.
• Remote-Controlled Vehicles: Servo motors control the steering and other mechanisms in RC cars, planes, and boats.
• CNC Machines: They enable accurate positioning of tools and workpieces in computer numerical control machines.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: By adjusting the frequency of the AC supply

This option is incorrect. Adjusting the frequency of the AC supply is a method used in variable frequency drives (VFDs) to control the speed of AC motors. However, this technique is not used to control the shaft position of servo motors, which rely on PWM signals and feedback mechanisms for precise positional control.

Option 2: By changing stator winding resistance

This option is incorrect. Changing the stator winding resistance is a method that could influence the torque or power characteristics of some motors. However, it is not a practical or efficient method for controlling the shaft position of a servo motor. Servo motors achieve position control through PWM signals and feedback, not by altering winding resistance.

Option 3: By varying input voltage

This option is partially correct but not applicable to modern servo motor control. While varying the input voltage can influence the speed or torque of a motor, it does not provide the precision required for positional control. Servo motors use PWM signals and feedback systems for accurate and repeatable position control.

Option 5: Not provided

Since option 5 is not explicitly stated, it cannot be considered a valid choice for this analysis. The correct and most efficient method for controlling a servo motor's shaft position is through PWM signals, as explained above.

Conclusion:

Servo motors are essential components in numerous industries due to their ability to provide precise positional control. The use of PWM signals, combined with feedback mechanisms, allows servo motors to achieve high accuracy, efficiency, and reliability. Understanding the working principle of PWM-based control and its advantages is crucial for effectively utilizing servo motors in various applications.

Servo motors are broadly classified into two main types: AC servo motors and DC servo motors. AC servo motors are powered by alternating current, whereas DC servo motors are powered by direct current.

The most common type of feedback sensor used in servo motors is the encoder. Encoders are preferred due to their high accuracy and ability to provide precise position and speed feedback.

In a servo motor system, the controller's primary purpose is to convert the input signal into a control signal for the motor. This control signal determines the motor's desired position, speed, or torque.

The correct option is option 3, which states that both statements (i) and (ii) are correct. In a DC servomotor, the speed can be controlled by varying the armature voltage (statement i), as the speed is directly proportional to the applied voltage. Additionally, the armature is deliberately designed to have a large armature resistance (statement ii) to provide better control over speed and to improve the stability of the motor by reducing the time constant of the armature circuit.

In an AC servomotor, the main winding and control winding are displaced by 90° electrically. This phase displacement is crucial for creating a rotating magnetic field which is essential for the operation of the servomotor. The 90° electrical displacement between the windings allows for precise control of the motor's position, speed, and torque, making it ideal for applications requiring high precision and responsiveness.