ASRB NET — Farm Machinery & Power / Land & Water Management Engineering / Agricultural Structures & Process Engineering · India · Agricultural Scientists Recruitment Board (ICAR)
Original practice questions written to the published syllabus · not past papersSpray drones, machine vision, robots and autonomous tractors — the newest part of the curriculum.
In the exams: Core in the ICAR 6th Deans' Committee B.Tech, with a skill module on drone operation and maintenance; not yet a large exam topic
ASRB NET — Farm Machinery & Power
Recall and short numericals on spray drones, droplet spectra, robot kinematics, stepper and DC motors, and autonomous-machine safety.
How our questions for ASRB NET spread across the units of Agricultural Drones, Robotics & Automation. Difficulty: 30 easy, 40 medium, 12 hard.
| UAV types and payload | 14 | |
| Mechatronic actuators | 14 | |
| Autonomous tractors | 11 | |
| Spray drones: swath, flow rate and application rate | 10 | |
| AI and machine learning for detection | 10 | |
| Machine vision | 8 | |
| Robot end-effectors | 8 | |
| Droplet drift from drones | 6 | |
| Drone regulations (country-specific) | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
How does a multirotor drone with fixed-pitch propellers turn about its vertical axis (yaw)?
B. It speeds up the propellers spinning one way and slows those spinning the other, so reaction torques no longer cancel
Half the propellers turn clockwise and half anticlockwise. Changing the speed of one set relative to the other leaves a net reaction torque that yaws the frame. Front-versus-rear speed changes pitch the aircraft rather than yaw it, and fixed-pitch multirotors have no swashplate.
In the Stokes regime, how does the settling velocity of a 120 µm droplet compare with that of a 40 µm droplet of the same liquid?
B. 9 times faster
Stokes velocity ∝ d². (120/40)² = 9. 3 times assumes proportional to d; 27 times uses d³. Stokes' law slightly overestimates the speed of the larger droplet, but the scaling is the point.
With the same camera sensor, what happens to the field of view when a lens of shorter focal length is fitted?
A. The field of view becomes wider
Field of view depends on sensor size and focal length; a shorter focal length gives a wider angle (and a coarser GSD at the same height).
What is the main advantage of soft, air-driven grippers for picking fruit such as tomatoes or strawberries?
A. They conform to irregular shapes and spread contact pressure, reducing bruising
Compliant fingers wrap around the fruit and limit peak pressure. They still need an actuator (often air), and most designs use a separate detachment method.
An autonomous tractor travels at 12 km/h. Its obstacle detection and braking system has a total latency of 0.4 s and can decelerate at 2.5 m/s². What is its stopping distance after an obstacle is detected?
D. 3.56 m
v = 12/3.6 = 3.333 m/s; distance = v t + v²/(2a) = 1.333 + 2.222 = 3.56 m. 2.22 m ignores latency; 5.78 m drops the 2 in v²/(2a); 33.6 m uses km/h without converting.
What does ISO 25119 deal with?
D. Safety-related parts of control systems on tractors and agricultural and forestry machinery
ISO 25119 is the functional-safety standard for agricultural machinery control systems. ISOBUS is ISO 11783; power and noise tests are covered by OECD tractor codes and other standards.
A differential-drive weeding robot has a track width of 0.6 m. Its right wheels run at 1.2 m/s and its left wheels at 0.8 m/s. What is the radius of the path followed by its centre?
C. 1.5 m
Forward speed v = (1.2 + 0.8)/2 = 1.0 m/s; yaw rate ω = (1.2 − 0.8)/0.6 = 0.667 rad/s; R = v/ω = 1.5 m. 3.0 m doubles the correct radius (using half the track width would instead give 0.75 m); 0.67 is the yaw rate in rad/s, not a radius.
A 24 V supply is switched by pulse-width modulation at 35% duty cycle. What is the average voltage applied to the motor?
D. 8.4 V
Average voltage = duty cycle × supply = 0.35 × 24 = 8.4 V. 15.6 V is the off-time share; 24 V is the peak. 6.9 V divides 24 by 3.5 instead of multiplying by 0.35.
A motor delivers 0.8 N·m at 3,000 rpm into a 25:1 gearbox of 90% efficiency. What output torque is available?
B. 18 N·m
Output torque = 0.8 × 25 × 0.90 = 18 N·m (at 3,000/25 = 120 rpm). 20 N·m ignores losses; 0.029 N·m divides by the ratio; 22 N·m adds rather than subtracts the losses.
What is transfer learning in agricultural image analysis?
B. Starting from a network pre-trained on a large general image set and fine-tuning it on crop images
Pre-trained features (edges, textures, shapes) transfer well, so fine-tuning needs far fewer labelled crop images. Deploying unchanged models elsewhere is not transfer learning and often fails.
Ten here, 82 in the app. The Laisha app has every practice question we have written to ASRB NET in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
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