Recursive Newton-Euler algorithms, modified DH notation

In order to apply the RNE, let us define the following variables (referenced in the
i^{th} coordinate frame if applicable):

- σ
_{i}is the joint type; σ_{i}= 1 for a revolute joint and σ_{i}= 0 for a prismatic joint; - p
_{i}=^{T }is the position of the i^{th}with respect to the i - 1^{th}frame; - z
_{0}=^{T }