Decoupling control for two-axis inertially stabilized platform based on an inverse system and internal model control

• Dynamic model of the two-axis ISP has been obtained by using the Newton–Euler equation.
• A pseudo-linear system is constructed by using the inverse system method.
• The uncertainties and unmeasurable disturbances are solved by the internal model control.
• Better decoupling effect and disturbance rejecting ability are validated by simulations and experiments.

This paper describes a decoupling control scheme for a two-axis inertially stabilized platform (ISP) used in the airborne power line inspection system. The dynamic model of the ISP has been obtained by using the Newton–Euler equation first. The inverse system method combining with the internal model control has been proposed to deal with the nonlinearity and coupling of the ISP. The key idea is to design an inverse system with measured system states such as angular positions, rates and accelerations. Then a pseudo-linear system is constructed when the inverse system is connected with the original system in series. As a result, the coupled nonlinear MIMO (Multiple-Input Multiple-Output) system is converted to two linear decoupled SISO (Single-Input Single-Output) subsystems. Model uncertainties or unmeasurable disturbances existing objectively can be solved by introducing internal model control. Better decoupling effect and disturbance rejecting ability are demonstrated by numerical simulations and experiments carried out on a two-axis ISP system.