Sampled output based continuous second order sliding mode observer

Most of state observers implemented in real systems are not able to measure the informtion continuously. The sliding observers are not an exception. Nevertheless, when state observers are used in numerical applications or even in real systems, one must implement a sampled based observer. In this paper, a second order sliding mode observer based on the supertwisting algorithm is studied, tacking into account that the output only can be measure in specific periods of the time, to do this, a zero order hold is proposed to sampling the output. The continuous observer is analized in terms of Lyapunov stability. It have been proposed a strong Lyapunov function to show finite-time convergence into a boundary layer that depends on the sampled period. The result is applied into a two-link robot manipulator and it is compared the observer efficiency between different sampled periods to show how the result is affected by the sampling interval.