Small motion robot dynamics simulated in real-time

This paper describes how in a real robotic system there are nonlinear effects such as slip-stick friction, that change discontinuously in small regions and can have large effects, approximately half as large as the worst nonlinear coupling effects. This large discontinuous effect invalidates the small signal model assumptions used in many controllers and makes control difficult as the slip-stick region is reached at low velocities. The paper also considers the depth of modelling required to simulate undesirable effects and the previously ignored effects of motor and load dynamics, to achieve an accurate real-time simulation. Conditions for rejecting the effects of electrical parameters and backlash are also detailed. Due to the requirement for implementation in real-time, appropriate numerical integration methods for the model effects are also evaluated. A description of practical software and hardware arrangement for real-time processing using transputers is given. The simulations undertaken are also designed to simulate practical processing, filtering and sample delays