SACA Mechatronics 4 — Questions and Answers
Question 1: In a closed-loop mechatronic system, what is the primary function of the error signal?
- To power the actuator directly
- To represent the difference between desired and actual output (Correct answer)
- To calibrate the sensor range
- To set the sampling frequency of the controller
Correct answer: To represent the difference between desired and actual output
The error signal is the difference between the setpoint (desired output) and the process variable (actual output), and it drives the controller's corrective action.
Question 2: Which type of motor is most commonly paired with encoder feedback for precise position control in industrial robots?
- Universal AC motor
- Brushless DC servo motor (Correct answer)
- Induction motor
- Shaded-pole motor
Correct answer: Brushless DC servo motor
Brushless DC servo motors offer high torque-to-inertia ratios and work seamlessly with encoders to achieve precise position and velocity control.
Question 3: A mechatronic designer needs to convert analog sensor voltage to a digital value for a microcontroller. Which component performs this conversion?
- DAC (Digital-to-Analog Converter)
- PWM generator
- ADC (Analog-to-Digital Converter) (Correct answer)
- Comparator with hysteresis
Correct answer: ADC (Analog-to-Digital Converter)
An ADC samples the analog voltage and converts it to a discrete binary number that a digital controller can process.
Question 4: What is the significance of the Nyquist theorem in mechatronic sensor systems?
- It defines maximum actuator force for a given current
- It states the sample rate must be at least twice the highest signal frequency to avoid aliasing (Correct answer)
- It describes the maximum bandwidth of a servo amplifier
- It sets the resolution limit of an optical encoder
Correct answer: It states the sample rate must be at least twice the highest signal frequency to avoid aliasing
The Nyquist theorem requires that the sampling rate be at least twice the highest frequency component to faithfully reconstruct the original signal.
Question 5: In pneumatic mechatronic systems, a proportional pressure control valve differs from an on/off solenoid valve because it:
- Operates only at full supply pressure
- Can modulate output pressure continuously based on an electrical command signal (Correct answer)
- Requires no electrical input
- Is exclusively used for vacuum applications
Correct answer: Can modulate output pressure continuously based on an electrical command signal
Proportional valves adjust flow or pressure in proportion to an analog command signal, enabling fine control unlike binary on/off solenoids.
Question 6: Which control strategy uses a model of the plant to predict and compensate for disturbances before they affect the output?
- Reactive feedback control
- On-off bang-bang control
- Model Predictive Control (MPC) (Correct answer)
- Manual open-loop tuning
Correct answer: Model Predictive Control (MPC)
MPC uses a mathematical model of the system to predict future outputs and compute optimal control actions over a receding time horizon.
Question 7: In a mechatronic system, what does 'backlash' refer to?
- Electrical noise in encoder signals
- The dead zone in a gear or mechanical coupling where motion reversal causes no output movement (Correct answer)
- Thermal expansion of a ball screw
- Resonance frequency of a structural component
Correct answer: The dead zone in a gear or mechanical coupling where motion reversal causes no output movement
Backlash is the lost motion between mating mechanical components, causing positioning error when direction of movement reverses.
SACA Mechatronics 4
In a closed-loop mechatronic system, what is the primary function of the error signal?