Which statement accurately describes the three primary joint controls: position, velocity, and torque?

• A. Position control commands joint torques to reach a target pose.
• B. Velocity control drives joints to target positions; torque control regulates speeds.
• C. Torque control calibrates the robot's zero position.
• D. Position control drives joints to target positions; velocity control regulates speeds; torque control commands joint torques for dynamic interaction and compliant behavior.

Answer: (D)

The idea being tested is that robot joints are controlled in three distinct modes: position, velocity, and torque control. Position control moves a joint to a target position or pose and uses feedback to reduce the position error, adjusting torque as needed to reach the target. Velocity control aims to achieve and maintain a target joint speed, using feedback to keep the velocity on track. Torque control directly commands the joint torques, enabling dynamic interaction with the environment and compliant or impedance-controlled behavior.

The statement that describes all three modes together is that position control drives joints to target positions, velocity control regulates speeds, and torque control commands joint torques for dynamic interaction and compliant behavior. The other options mix up roles or describe only part of the picture, so they aren’t as accurate.