Denavit–Hartenberg parameters

Summary

Denavit–Hartenberg parameters are four numbers per joint that describe how consecutive links of a serial robot arm are placed relative to each other. They are a joint angle $\theta$, an offset $d$, a link length $a$ and a twist angle $\alpha$. They are read off from the common normal of two consecutive joint axes. With them, each joint contributes one standard $4 \times 4$ matrix, and forward kinematics becomes a product of such matrices. The convention was introduced by Jacques Denavit and Richard Hartenberg and is a standard in robotics.