Sigmoid surface control for mini underwater vehicles by improved particle swarm optimization

Sigmoid surface control (SSC) has been proved to be effective in motion control of underwater vehicles, but it is hard to adjust its control parameters. Particle swarm optimization (PSO) of SSC was proposed, and improved aiming at the problems that PSO may be trapped in local optimum and fails to converge to global optimum. Moreover, intelligent integral of SSC was introduced to eliminate steady-state errors and increase the stability. Finally, simulation experiments are carried out on "WEILONG" mini underwater vehicle. The results show that improved PSO converges faster and the optimized SSC parameters are more approximate to global optimum, so it makes great improvements to SSC in response speed and overshoot.