Abstract
Most existing Second Order Sliding Mode Control (SOSMC) approaches are achieved under assumptions that 1) all of state variables must be accessible; 2) the second derivative of all state variables must exist, even though mathematical model of systems uses the first order equations. In this paper, a new adaptive SOSMC scheme is proposed for mismatched uncertain systems in which these above assumptions are required. In this proposed method, only output variables are used in the sliding surface and controller design. The advantage of no need of all state variables in controller design makes the method more useful and realistic since it can be applied to a wider class of systems. Finally, a vertical take-off and landing aircraft at the nominal airspeed of 135~knots is simulated to demonstrate the advantages and effectiveness of the proposed approach.
Highlights
Over the past three decades, there has been an increasing research interest in Sliding Mode Control (SMC) theory and application
We extend the concept of second order sliding mode controller, introduced by [19], [22], [23] and [27], for the aim of stabilizing mismatched uncertain systems where only output variables are accessible
This paper has presented a new adaptive Second Order Sliding Mode Control (SOSMC) for mismatched uncertain systems where only output information is available
Summary
Over the past three decades, there has been an increasing research interest in Sliding Mode Control (SMC) theory and application. The authors of [5] have presented a direct way to reduce chattering problems by inserting a fixed or variable boundary layer near the sliding variable so that a smooth continuous control replaces the discontinuous one when the system is inside the boundary layer This approach can produce a chattering-free system but a larger boundary layer width results in larger errors in control accuracy and a finite steady-state error may occur. In [23], a robust chattering-free control scheme was proposed using second-order fast terminal sliding mode control technique for the tracking problem of a class of uncertain systems with matched and mismatched uncertainties. The proposed method can be applied to a wider class of mismatched uncertain systems
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