About this previous year paper
MECHATRONICS (EEN021)
SECTION – A
(Attempt All | 10 × 2 = 20 Marks)
(a) Sensor vs Transducer
Sensor: Detects a physical quantity (temperature, pressure, displacement).
Example: Thermistor
Transducer: Converts one form of energy into another (usually physical → electrical).
Example: LVDT
(b) Principle of Eddy Current Sensors
They work on electromagnetic induction. When a conductive target enters the magnetic field of a coil, eddy currents are induced, changing coil impedance. This change is used to measure displacement or proximity.
(c) Need for Signal Conditioning
Signal conditioning is required to amplify, filter, isolate, and convert signals so that sensor outputs are compatible with controllers or DAQ systems and free from noise.
(d) Data Acquisition
Data acquisition (DAQ) is the process of collecting, sampling, and converting real-world signals into digital data for processing and analysis.
(e) Symbol of 4/2 DCV and 4/3 DCV
4/2 DCV: Four ports, two positions (forward/reverse flow)
4/3 DCV: Four ports, three positions (center position included)
(Symbols are drawn neatly in exam using standard hydraulic notation.)
(f) Use of Rack & Pinion in Mechanical Actuation
Rack and pinion converts rotary motion into linear motion and vice versa.
Applications: Steering systems, CNC machines, linear actuators.
(g) Serial vs Parallel Communication
Serial: Data sent bit-by-bit (USB, RS-232) – slower but less wiring
Parallel: Data sent simultaneously – faster but requires more wires
(h) Ladder Logic for AND & OR Gates
AND Logic:
Output ON only if both inputs are ON
OR Logic:
Output ON if any input is ON
Truth tables are written clearly in tabular form.
(i) Why Closed-Loop Controllers Are Preferred
Closed-loop controllers use feedback to reduce error, improve accuracy, reject disturbances, and provide better system stability and performance.
(j) Mathematical Model of Spring-Mass-Damper System
For mass m, damping c, stiffness k:
mx¨+cx˙+kx=F(t)m\ddot{x} + c\dot{x} + kx = F(t)mx¨+cx˙+kx=F(t)
This is the standard second-order differential equation.
SECTION – B
(Attempt Any FIVE | 5 × 10 = 50 Marks)
(a) Encoder & Measurement of Velocity
An encoder converts mechanical motion into electrical pulses.
Incremental Encoder:
Produces pulses proportional to rotation
Velocity is measured by counting pulses per unit time
Velocity∝Number of pulsesTime\text{Velocity} \propto \frac{\text{Number of pulses}}{\text{Time}}Velocity∝TimeNumber of pulses
(b) Data Acquisition System & Signal Conditioning
DAQ System Components:
Sensors Signal conditioning unit
Multiplexer ADC
Computer/Controller Filtering: removes noise
Amplification: increases signal level for accurate conversion
(c) Direction Control Valve vs Process Control Valve
Direction Control Valve (DCV): Controls direction of fluid flow
Process Control Valve: Controls process variables like pressure, flow, temperature
(d) Types of Pressure Control Valves
Pressure Relief Valve – limits maximum pressure
Pressure Reducing Valve – maintains reduced downstream pressure
Sequence Valve – ensures operation in sequence
Working explained with neat sketches.
(e) Torsional Spring-Mass-Damper System Equation
Jθ¨+cθ˙+kθ=T(t)J\ddot{\theta} + c\dot{\theta} + k\theta = T(t)Jθ¨+cθ˙+kθ=T(t)
where
J = moment of inertia
c = torsional damping
k = torsional stiffness
(f) Electric Drive System – Working & Applications
Components: Motor, power electronics, controller, sensors
Working: Electrical energy → mechanical motion with controlled speed/torque
Applications: Robotics, conveyors, CNC machines, elevators
(g) Architecture of Microcontroller
Main blocks: CPU
ROM / Flash RAM
I/O Ports Timers/Counters
ADC Serial interfaces
Used for real-time control in mechatronic systems.
(h) PLC Architecture & Ladder Logic for Start-Stop Motor
PLC Architecture: CPU
Input module Output module
Power supply Programming device
Ladder Logic:
Start button (NO) Stop button (NC)
Motor coil with seal-in contact Motor stays ON after start until stop is pressed.
SECTION – C
(Attempt Any TWO | 2 × 15 = 30 Marks)
Case Study: Automobile Engine Control
Modern automobiles use Electronic Engine Control Units (ECU).
Sensors: Oxygen sensor
Throttle position sensor Crankshaft position sensor
Temperature sensors
Functions: Fuel injection control
Ignition timing Emission control
Improved fuel efficiency
The ECU processes sensor data and controls actuators like injectors and ignition coils for optimal performance.
Micromechanical Systems & Computer Printer Case Study
Micromechanical Systems (MEMS):
Miniaturized mechanical and electro-mechanical elements integrated on silicon.
Applications: Accelerometers, pressure sensors, inkjet printers.
Computer Printer Case Study:
MEMS nozzles eject ink droplets precisely using thermal or piezoelectric actuation, achieving high-resolution printing.
Operating Principle of NC Machine
NC (Numerical Control) Machine:
Machine tool controlled by numerical instructions.
Working Steps:
Program preparation
Input to controller
Signal processing
Motor actuation
Tool movement
Advantages:
High accuracy
Repeatability
Reduced human error
Suitable for mass production