Forward Dynamics — The Composite-Rigid-Body Method

Abstract

Forward (or direct) dynamics is the calculation of the acceleration of the robot’s mechanism in response to the applied forces. It is used primarily for simulation, so it is not necessary for forward dynamics to meet the stringent speed requirements of real-time control applications. However, computational efficiency is still important to minimise the cost of simulation. The composite-rigid-body method (or Walker-Orin method) was originally described in [74] as method 3, and is the most efficient method available for calculating forward dynamics in most practical cases; although there are situations where the articulated-body method described in Chapter 6 is more efficient. The composite-rigid-body method has been used in the simulators described in [19], [20], [61]. Some other approaches to dynamics simulation are described in [1], [3], [6], [31], [32], [34], [55], [62].