Top Interview Questions and Answers on Robotic Kinematics, Dynamics, and Control Theory ( 2025 )

Section 1: Robotic Kinematics Interview Questions

1. What is forward kinematics in robotics?

Answer:
Forward kinematics involves calculating the position and orientation of a robot’s end-effector based on the joint parameters (angles for revolute joints, displacements for prismatic joints). It uses a chain of transformation matrices to derive the pose of the end-effector from the base.

Queries - forward kinematics, robotic joints, end-effector position

2. What is inverse kinematics and why is it challenging?

Answer:
Inverse kinematics is the process of determining the joint parameters needed to achieve a specific end-effector position and orientation. It's challenging because:

·         There can be multiple or no solutions.

·         Solutions may not be continuous.

·         Requires solving non-linear equations.

Queries: inverse kinematics problem, IK robotics, joint angle calculation

3. How are Denavit-Hartenberg (D-H) parameters used in robotics?

Answer:
D-H parameters standardize the method of assigning coordinate frames to robotic links and joints. Each transformation is defined by four parameters: link length, link twist, link offset, and joint angle. These are used to construct the transformation matrices between links.

Queries: Denavit-Hartenberg method, robot coordinate transformation, DH convention

Section 2: Robotic Dynamics Interview Questions

4. What is the difference between kinematics and dynamics in robotics?

Answer:

·         Kinematics: Studies motion without considering forces (position, velocity, acceleration).

·         Dynamics: Analyzes the forces and torques causing the motion using Newton-Euler or Lagrangian methods.

Queries: Use terms like kinematics vs dynamics in robotics, robot motion analysis

5. Explain the Newton-Euler method for robot dynamics.

Answer:
The Newton-Euler method is a recursive algorithm used to calculate forces and torques in robotic manipulators. It includes two passes:

·         Forward pass: computes velocities and accelerations.

·         Backward pass: computes joint forces and torques.

Queries: Newton-Euler dynamics, recursive dynamics calculation, robot force analysis

6. What is the Lagrangian approach in robot dynamics?

Answer:
The Lagrangian method uses the scalar quantity L = Kinetic Energy (T) – Potential Energy (V) to derive the equations of motion. It simplifies dynamics by avoiding vector cross products and is particularly useful for complex systems.

Queries: Lagrangian mechanics robotics, robot dynamic equations

Section 3: Control Theory in Robotics Interview Questions

7. What are the main types of control strategies used in robotics?

Answer:

·         Open-loop control: No feedback; suitable for simple or predictable tasks.

·         Closed-loop (feedback) control: Uses sensors to correct deviations.

·         PID control: Proportional-Integral-Derivative control for stable and accurate responses.

Queries: robotic control strategies, PID controller robotics, feedback control robotics

8. How does a PID controller work in robot control?

Answer:
A PID controller calculates an error value and applies a correction based on:

·         Proportional: Immediate reaction to the error.

·         Integral: Accumulates past errors to eliminate steady-state offset.

·         Derivative: Predicts future error to dampen the response.

Queries: PID control theory, robot arm PID tuning, robot motion stability

9. What is trajectory planning in robotics?

Answer:
Trajectory planning involves defining a time-dependent path for the robot’s joints or end-effector to follow. It ensures smooth, collision-free motion within mechanical limits, often using cubic or quintic polynomials.

Queries: Use phrases like robot trajectory planning, path vs trajectory in robotics

10. What is the role of feedback in robotic control systems?

Answer:
Feedback helps correct deviations from the desired motion or state by continuously monitoring sensor data. It's essential for accuracy, stability, and adaptability in real-world environments.

Queries: feedback in robotics, closed-loop control, robot sensor feedback

Bonus Tips for Interview Success

·         Brush up on matrix transformations and Jacobians.

·         Understand the differences between static and dynamic control.

·         Practice with tools like MATLAB, ROS, or Gazebo for simulation and testing.