# Viva questions for a robotic arm project

> Common viva questions for a robotic arm project with what a good answer must cover: degrees of freedom, servo torque, kinematics and payload.

Canonical: https://roboticsengineering.in/free-library/viva-questions-robotic-arm-project/ | Published: 2026-11-03 | Updated: 2026-11-03

**For a robotic arm, expect questions on joints, torque, kinematics and accuracy.** Answer with your own arm.

## Structure

- **How many degrees of freedom does your arm have?** Count the independent joints.
- **What is the work envelope?** The region the hand can reach; it depends on link lengths and joint limits.
- **What is the payload?** State the tested load, and the margin you used.

## Actuators

- **How did you pick the servos?** By torque at the joint with the arm stretched out. See the [servo torque calculator](https://roboticsengineering.in/servo-torque-calculator/).
- **Why does the shoulder need the most torque?** It carries both links and the load at the longest lever arm.
- **How is a servo controlled?** By a 50 Hz pulse of about 1 to 2 ms. See the [servo pulse calculator](https://roboticsengineering.in/servo-pulse-width-pwm-calculator/).

## Kinematics

- **What is forward and inverse kinematics?** Forward gives the hand position from joint angles; inverse gives the angles for a position.
- **Show inverse kinematics of two links.** Use the law of cosines. Try the [arm playground](https://roboticsengineering.in/robot-arm-playground/) and read [the Python guide](https://roboticsengineering.in/inverse-kinematics-2-link-arm-python/).
- **Why are there two solutions?** Elbow up and elbow down.

## Accuracy and testing

- **How accurate is it?** Report repeatability measured by returning to a point many times.
- **What causes error?** Backlash, servo resolution, flex and supply sag.

## Related

[Free Library](https://roboticsengineering.in/free-library/), [Report template](https://roboticsengineering.in/free-library/robotics-project-report-template/), [Viva questions](https://roboticsengineering.in/free-library/viva-questions-for-robotics-projects/), [More viva questions](https://roboticsengineering.in/robotics-project-viva-questions/).

Last reviewed: November 2026. Free to copy and adapt for your own college work. Follow your department format first; its rules override this page.