- link length
$a_{i-1}$ - link twist $$
- link length
$a_0 = 0$ - link teist
$\alpha_0 = 0$ - if joint 1 is revolute,
$d_1 = 0$ , only have$\theta_1$ - if joint 1 is prismatic,
$\theta_1 = 0$ , only have$d_1$
- link length
$a_n = 0$ - link teist
$\alpha_n = 0$ - if joint n is revolute,
$d_n = 0$ , only have$\theta_n$ - if joint n is prismatic,
$\theta_n = 0$ , only have$d_n$