What is impedance control in robotics, and when would you use it?

• A. A velocity-only control loop for high-speed positioning.
• B. A torque-only control for free-space motion.
• C. A fixed-position control with no compliance.
• D. A force/position control approach where the robot behaves with a virtual compliant impedance; used for safe contact tasks like assembly or human-robot collaboration.

Answer: (D)

Impedance control treats the robot’s end-effector as if it has a controlled mechanical impedance—a virtual mass-spring-damper system that links external forces to motion. This means it’s a force/position control approach, not just pure positioning or torque commands, and it shapes how the robot responds when it contacts or interacts with things.

By tuning stiffness, damping, and sometimes inertia, you define how compliant the robot feels. High stiffness is useful when you need precise, rigid behavior in free space, while lower stiffness provides safe, controlled contact, allowing the robot to yield to forces rather than hard collisions. This approach is ideal for tasks like delicate assembly, surface finishing with contact, or human-robot collaboration where limiting interaction forces is important.

Other methods that are purely velocity-controlled, torque-only, or fixed with no compliance don’t provide this safe, predictable interaction behavior, which is why impedance control is the best fit for safe contact tasks.