Kinematics

The study of motion's pure geometry — position, velocity, acceleration — without regard to the forces that cause it.

Kinematics is the branch of classical mechanics that studies how points and bodies move — position, velocity, acceleration — without considering the forces that cause the motion, which is why it's sometimes called “the geometry of motion”; the word traces back to a French term coined by André-Marie Ampère. Robot kinematics studies the geometric relationship between joint variables and the poses of the links and end effector, and covers mainly forward kinematics (joint angles to end-effector pose), inverse kinematics (end-effector pose to joint angles), and differential kinematics (joint velocities to end-effector velocity, described by the Jacobian matrix). It only needs geometric parameters like link lengths and joint axis directions — no mass or inertia — which is what separates it from dynamics, which does account for forces and torques. Trajectory planning, teleoperation mapping, and motion retargeting are all built on top of kinematics.

ExampleKnowing how far each joint of an arm has rotated is enough to compute where the gripper currently is; that calculation only uses link dimensions and has nothing to do with how heavy whatever is inside the gripper happens to be — which is exactly why it belongs to kinematics, not dynamics.

Also called

Robot Kinematics

Related

Forward Kinematics (FK) · Inverse Kinematics (IK) · Differential Kinematics · Jacobian Matrix · Dynamics · Kinematic Chain

Sources

Wikipedia: Kinematics
Wikipedia: Robot kinematics