2link

2link is a term used in various technical fields to denote a system composed of two rigid segments connected by joints. There is no single canonical definition, but the two-link model is a common abstraction in mechanical, robotic, and biomechanical analysis. In many contexts, the two-link model serves as a tractable approximation of more complex configurations, capturing essential kinematic or dynamic behavior while remaining analytically manageable.

In robotics and mechanical engineering, a two-link planar manipulator consists of two rigid links connected by rotary joints, typically with the base fixed. The configuration is described by two joint angles. Forward kinematics yield the position of the end effector using trigonometric equations, e.g., x = L1 cos(theta1) + L2 cos(theta1 + theta2), y = L1 sin(theta1) + L2 sin(theta1 + theta2). Inverse kinematics can produce up to two valid configurations, and singularities occur when the arm aligns with its forearm.

In biomechanics, two-link models are used to approximate limb movement, such as upper-arm and forearm or thigh and shank during gait. These models help analyze joint torques, energy transfer, and control strategies, while often simplified by assuming planar motion and neglecting muscle, tissue, or damping effects.

Other uses of the term 2link may appear in software naming, data structures, or project titles where two connected elements are central. Because there is no universally fixed meaning, the interpretation of 2link depends on the domain and context.