AME 11 End of Unit – SVE Study

AME 11 End of Unit Quiz

1 / 12

What is a potential drawback of using an On-Off control system?

A) It requires complex programming to function.

D) It consumes more energy than other types of control systems.

B) It is unable to achieve precise control, leading to oscillations around the set point.

C) It is more expensive than proportional control systems.

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With reference to engine governors, explain stability.

C) Stability is the measure of how much the governor's set point can drift from the desired speed due to wear and tear. Reason: Set point drift due to wear is not directly related to stability, which focuses on maintaining speed consistency.

D) Stability refers to the governor's ability to handle extreme variations in ambient temperature without affecting engine performance. Reason: While temperature variations can affect performance, stability specifically concerns speed consistency under load changes.

B) Stability describes the governor's capacity to change the engine speed quickly in response to sudden changes in fuel supply. Reason: Rapid response is more related to the governor's responsiveness, not its stability.

A) Stability refers to the governor's ability to maintain a constant engine speed without oscillations or fluctuations when subjected to varying loads. Reason: Stability in governors is about how consistently the engine speed is maintained despite changes in load or other disturbances.

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Describe using control block diagram terms how a governor maintains the speed of a diesel engine driving a generator.

B) The governor compares the actual engine speed to the desired speed setpoint and uses a proportional-integral-derivative (PID) control block to adjust the fuel input and maintain the engine speed.

A) The governor adjusts the fuel input based on the difference between the desired speed setpoint and the actual engine speed (feedback), using a proportional-only control block.

D) The governor uses a feedback loop where the actual engine speed is compared to a fixed reference value, adjusting the fuel input based on a simple on-off control block.

C) The governor uses a manual control block to adjust the engine speed directly without feedback, ensuring the engine speed remains constant regardless of load changes.

4 / 12

Describe integral action in a control system.

D) Integral action adjusts the control output to match the process variable to the setpoint instantly.

C) Integral action maintains a constant control output regardless of changes in the error signal.

B) Integral action increases the control output to eliminate steady-state error over time by integrating the error signal.

A) Integral action adjusts the control output based on the rate of change of the error signal.

5 / 12

Explain proportional bandwidth in control terms.

B) Proportional bandwidth is the range of frequencies over which the proportional controller effectively responds to changes in the process variable.

D) Proportional bandwidth describes the extent to which the proportional controller can correct errors before reaching the maximum output.

A) Proportional bandwidth refers to the range of input values for which the proportional controller provides a linear response.

C) Proportional bandwidth is the width of the proportional band within which the control action is active and varies linearly with the error.

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Explain hysteresis in control terms.

D) Hysteresis is the speed at which a control system can respond to input changes. Reason: This describes response time rather than hysteresis, which involves differences in response based on input history.

A) Hysteresis is the phenomenon where the output of a control system depends on its past input, causing a lag or delay in response. Reason: This describes hysteresis correctly, where the system’s output is influenced by the history of inputs, leading to different responses for increasing versus decreasing inputs.

C) Hysteresis is the effect of system instability caused by rapid changes in input. Reason: This describes system instability or oscillations rather than the lag or memory effect described by hysteresis.

B) Hysteresis is the ability of a control system to adapt its response based on changes in input conditions. Reason: This describes adaptability rather than hysteresis, which specifically deals with lag in response due to past inputs.

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Describe a possible effect of excessive Integral Action.

B) Excessive Integral Action can cause the system to oscillate or exhibit sustained oscillations around the setpoint due to an overcompensation of errors.

D) Excessive Integral Action can increase the system’s ability to predict future errors accurately, leading to improved overall system stability.

A) Excessive Integral Action can lead to a quick and accurate response to setpoint changes, reducing the time required to reach the target value.

C) Excessive Integral Action can make the control system unresponsive to errors, resulting in a steady and stable system performance.

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2. Which of the following is a typical application of an On-Off control system?

A) Speed control of a variable frequency drive.

B) Temperature control in a household thermostat.

C) Pressure regulation in a hydraulic system.

D) Flow control in a proportional valve system.

9 / 12

With reference to engine governors, explain isochronous governing.

B) Isochronous governing allows the engine speed to fluctuate slightly around the set point to accommodate load changes. Reason: This describes droop control rather than isochronous governing, where slight fluctuations are acceptable.

D) Isochronous governing is a technique where the engine speed is allowed to drift with load changes, optimizing fuel efficiency. Reason: Allowing speed drift with load changes describes a droop control system, not isochronous governing.

C) Isochronous governing adjusts the engine speed only during idle periods to maintain stability. Reason: Isochronous governing applies to all operating conditions, not just idle periods.

A) Isochronous governing ensures that the engine speed remains constant regardless of the load applied, maintaining the same speed even with varying demands. Reason: Isochronous governing is designed to keep the engine speed constant, independent of changes in load.

10 / 12

State the reasons for fitting a pneumatic process valve with a volume booster.

C) A volume booster is fitted to decrease the overall air consumption of the valve, thereby improving energy efficiency in the pneumatic system.

A) A volume booster is fitted to increase the flow rate of air to the actuator, enabling faster valve movement and reducing the time required to achieve the desired valve position.

D) A volume booster is fitted to provide redundant control signals to the actuator, ensuring higher reliability in case of signal loss.

B) A volume booster is fitted to reduce the air pressure supplied to the actuator, which helps in minimizing the force required to operate the valve.

11 / 12

State with reasons, the type of actuator fitted to the process valves for a fuel supply system in which the valve must not move on loss of power to the control system.

A) Electric Actuator with Fail-Safe Mechanism: Reason: This actuator includes a fail-safe mechanism that ensures the valve remains in its last position or moves to a predetermined safe position if there is a loss of power.

D) Solenoid Actuator: Reason: This actuator is not suitable as it relies on continuous power to maintain the valve position and will fail to hold the valve in place if power is lost.

C) Hydraulic Actuator with Manual Override: Reason: While this actuator allows for manual control, it is not ideal for maintaining valve position during power loss, as it may require manual intervention to secure the valve.

B) Pneumatic Actuator with Spring Return: Reason: This actuator is designed to return to a default position using a spring when power is lost, which could result in undesired movement or system instability.

12 / 12

Explain repeatability in control terms.

D) Repeatability is the extent to which a control system can minimize oscillations in its output. Reason: This describes the concept of damping or stability, not repeatability.

B) Repeatability is the time it takes for a system to return to its original state after a disturbance has been removed. Reason: This describes settling time rather than repeatability, which is about consistency in output rather than recovery time.

A) Repeatability refers to the ability of a control system to return to the exact same output every time a specific input is applied, assuming no changes in system conditions. Reason: This accurately describes repeatability as the system's ability to consistently produce the same output for the same input under unchanged conditions.

C) Repeatability measures the ability of a system to maintain a stable output despite variations in input signals. Reason: This describes system stability, not repeatability. Repeatability focuses on consistency of output for the same input.

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