Control design for a class of multivariable nonlinear system with uncertain control direction: A laser cladding case study

In this work, the design of a controller for a multiple-input multiple-output (MIMO) nonlinear system with uncertain control direction is proposed. A formal Lyapunov stability analysis is presented for the design of the MIMO controller by considering the system with and without parametric uncertainties. The design is applied to an additive manufacturing technology known as Laser Cladding (LC). The proposed MIMO controller is composed of a feedback linearization term (aimed at canceling the known nominal dynamics) and a sliding mode term with the boundary layer technique (aimed at compensating the system uncertainties). The proposed control scheme was tested via simulations by considering tracks of two different powder feedstock, Ti6Al4V and IN718. Simulation results confirm that the control objective is achieved under parametric uncertainties, including variations up to 40% of the convection coefficient. Moreover, the control law is easy to implement and the control signal has a continuous behavior precluding any high-frequency oscillation (chattering effect).