Robotics interviews are not quizzes. They are tests of whether you can build something that works and explain why it failed. Interviewers expect you to forget a formula; they do not expect you to be unable to describe your own project.
This is the question set that repeats across Indian robotics, automation and embedded roles, with what a strong answer actually contains. Use it to prepare stories from your own builds, not to memorise definitions.
What interviewers are scoring
| Area | What they look for | How they test it |
|---|---|---|
| Fundamentals | Correct mental model, not jargon | Explain a sensor, a motor choice, a control loop |
| Debugging | Ordered reasoning under uncertainty | Describe a failure you fixed |
| Ownership | You built the thing you claim | Deep questions on your own project |
| Judgement | Trade-offs, safety, cost | Why this part, why not the cheaper one |
| Communication | Clear explanation to a non-specialist | Whiteboard explanation, viva-style follow-ups |
Core mechanical and robotics questions
1. What is a degree of freedom, and why does a six-axis arm need six? A good answer separates degrees of freedom from the number of joints, and explains that six lets the tool reach a position and orientation in 3D space, with the wrist handling orientation. Mentioning reachable versus dexterous workspace is a bonus.
2. Forward versus inverse kinematics. Forward computes tool pose from joint angles and is straightforward. Inverse computes joint angles from a desired pose and may have multiple solutions, no solution or singularities. Say where each is used and what happens near a singularity.
3. Accuracy versus repeatability. Accuracy is how close you get to the commanded point; repeatability is how close repeated attempts land to each other. A robot can be very repeatable and only moderately accurate, which is why calibration and TCP setup matter.
4. How would you choose a motor for a wheeled robot? Start with load, wheel radius, required speed and acceleration, then torque, then RPM, then current. Add a safety margin, account for gearbox efficiency, and check the driver’s continuous current against the motor’s stall current.
5. Why does a gearbox help and what does it cost you? It multiplies torque and reduces speed, and it adds backlash, friction and inertia reflected to the motor. Choosing a gear ratio is a trade between torque, speed and control quality.
6. What is backlash and where does it hurt? Lost motion when direction reverses. It hurts positioning, bidirectional repeatability and control stability, especially in low-cost gearboxes and 3D-printed mechanisms.
7. How do you size a battery for a robot? Estimate average current per mode, multiply by time to get watt-hours, derate for usable capacity and aging, then choose voltage and chemistry. Mention BMS, fusing and charge time.
Embedded and electronics questions
8. I2C versus SPI versus UART. Two wires versus four versus asynchronous pair. I2C is shared-bus and slower; SPI is faster and point-to-point with more pins; UART is simple and robust over short links. Mention addressing, clock speed, distance and pull-ups.
9. Interrupt versus polling. Polling wastes cycles and can miss events; interrupts react immediately but must be short. Explain debouncing and why heavy work belongs outside the interrupt.
10. How does an encoder measure position? Incremental encoders count pulses; quadrature gives direction and multiplies resolution by four. Absolute encoders report position directly. Mention CPR versus PPR and the difference between resolution and accuracy.
11. Why does a motor brown out the microcontroller? Startup and stall current pull the supply down; shared grounds and thin wires make it worse. Fixes are separate supplies, bulk capacitance, proper grounding and a driver with current limiting.
12. PWM frequency: what changes? Higher frequency gives smoother current and quieter motors but more switching loss; lower frequency can cause audible whine and torque ripple. Motor inductance and driver ratings set the practical range.
ROS 2 and software questions
13. Topic, service or action? Topics are continuous publish-subscribe streams. Services are request-response and block the caller. Actions are long-running goals with feedback and cancellation. Choosing the wrong one is a common design mistake.
14. Explain the transform tree. map to odom comes from localisation or SLAM; odom to base_link comes from wheel odometry; base_link to sensors comes from static mounts. A missing or duplicated link tears the map or makes the robot jump.
15. What does QoS change? Reliability, durability, history depth and deadline. A best-effort sensor stream behaves differently from a reliable command topic, and mismatched QoS can silently prevent two nodes from connecting.
16. How would you debug a robot that does not move? A strong answer is ordered: check the command topic is publishing, check the subscriber is connected, check the driver is enabled, check power and e-stop, check the transform, then check the controller. Mention logs and rosbag.
Control questions
17. Explain PID to a mechanical engineer. Proportional reacts to present error, integral removes steady-state offset, derivative damps overshoot. Mention windup, derivative noise, sampling time and why tuning starts with P only.
18. Why does a well-tuned simulator loop oscillate on hardware? Latency, friction, sensor noise, compliance and saturation. The fix is usually to slow the loop, filter the derivative, add feedforward and re-tune on the real system.
Project and behavioural questions
19. Walk me through your final-year project. Use four sentences: problem, what you built, the hardest failure, what you measured. Interviewers will then drill into the failure — this is where ownership shows.
20. What would you do differently? Have a real answer. A candidate who says “nothing” either did not build it or cannot evaluate their own work.
21. Tell me about a time you disagreed with a teammate. Describe the decision, the evidence you used, and the outcome. Technical disagreement resolved with a test is a strong story.
Practical tasks you may be given
- Whiteboard a PID loop and explain what happens when you double Kp.
- Read a datasheet and pick a motor for a stated load.
- Debug a wiring diagram with a missing ground or a reversed supply.
- Write pseudocode for a line follower with sensor filtering.
- Explain a failure from a photo of a burnt driver board.
Answers that end the interview
| Answer | Why it fails | Better |
|---|---|---|
| “I used a library, I don’t know how it works” | Suggests no ownership | Explain the library’s inputs, outputs and one thing you tuned |
| “It worked in simulation” | No hardware judgement | Say what changed on hardware and how you fixed it |
| “That’s not my department” | Small-team roles need range | Describe how you would find out |
| Guessing a number | Destroys trust | Estimate out loud, state assumptions, then check |
A four-week preparation plan
- Week 1: Write a one-page story for every project, including one failure and one measurement.
- Week 2: Revise fundamentals from your own notes: motors, sensors, PID, TF, I2C versus SPI.
- Week 3: Practise whiteboard explanations out loud to a friend who is not from robotics.
- Week 4: Do two mock interviews and one hands-on debugging session on your own hardware.
On salary, give a range based on the role and city, and ask what the band is for the position. Fresher offers in India vary widely by company type; our robotics engineer salary guide has indicative bands and what moves you up.
Related: how to become a robotics engineer, robotics skills roadmap, robotics internships, final-year robotics projects, embedded systems career.
What questions are asked in a robotics engineer interview in India?
Most interviews cover kinematics basics, motor and sensor selection, embedded interfaces, control loops, ROS 2 concepts and a deep discussion of your own project. Service companies add debugging and customer-handling scenarios.
Do I need ROS 2 for a robotics job in India?
For mobile robots, drones and research roles, yes. For industrial automation, PLC and robot programming skills matter more. Many job ads list ROS 2 as preferred rather than mandatory.
How should I explain my final-year project?
Use four sentences: the problem, what you built, the hardest failure and what you measured. Then be ready to go deep on any part of it.
What if I do not know the answer?
Say what you do know, state your assumption, and describe how you would find the answer. Interviewers prefer honest reasoning to a confident guess.
How long should I prepare for a robotics interview?
Four weeks of focused preparation is enough for most fresher roles if you already have a real project. The project story and debugging reasoning matter more than memorised definitions.
Interviewers often ask how you start a multi-node system: ROS 2 launch files tutorial.
A common interview question is choosing between a topic, service and action; see ROS 2 communication patterns.
Every bullet on the page is a question waiting to be asked, so write it with the resume structure guide.
For firmware and board level rounds, pair those answers with embedded systems interview questions.
Mechanical rounds go deeper than the general list, as shown in mechanical design interview questions.
Interviewers ask about your own work, so prepare with projects you can defend line by line.
Interviewers ask about what you built, so start with the college robotics club guide and keep the builds documented.
Sources and further reading
- ROS 2 documentation — topics, services, actions, QoS and TF2.
- ISO 9283 — accuracy and repeatability definitions used in robotics interviews.
- Arduino language reference — interrupts, PWM, ADC and serial basics.
- TI motor driver application notes — current limiting, PWM and supply design.
