MyRoboPath
kinematics17 min readUpdated 2026-03-10Advanced

Inverse Kinematics (IK): Geometric Decoupling & Numerical DLS Solvers

Solve for the required joint angles to place an end-effector at a desired 3D spatial target using analytical trigonometry and Damped Least Squares (DLS) Jacobian optimization.

Dr. Soraya Al-Mansoor
Dr. Soraya Al-Mansoor
Professor of Robotics & Nonlinear Control

Key Engineering Takeaways

  • Analytical IK is deterministic and computes all possible solutions in microseconds; numerical IK works on arbitrary kinematic topologies.
  • A 6-DOF arm has closed-form IK if three consecutive joint axes intersect at a single point (Spherical Wrist).
  • Damped Least Squares (DLS) prevents joint velocity explosion near singular configurations: J* = Jᵀ(JJᵀ + λ²I)⁻¹.
Prerequisites
  • Forward Kinematics
  • Jacobian matrix basics

Analytical Closed-Form vs Numerical Iterative IK

While Forward Kinematics always produces a single unique end-effector pose, **Inverse Kinematics (IK)** is non-linear, non-unique, and may have zero solutions (target outside reachable workspace), multiple solutions (elbow up vs elbow down), or infinite solutions (kinematic redundancy).
Tags:#Inverse Kinematics#IK#Pieper Criterion#Jacobian#DLS#Optimization