Adaptive control with a guarantee of a given performance

The paper presents a modification of the classical output adaptive control algorithm in order to guarantee that the output signal belongs to a given set specified by the developer at any time. Unlike classical adaptive control schemes, where it is impossible to influence control performances, including transient and steady-state performance, it is proposed here to supplement the classical adaptive control procedure with a nonlinear control law to solve these problems. The nonlinear control law is based on the special coordinate transformation of the output variable so that the problem with constraints is reduced to the problem without constraints. For a transformed system without constraints, any existing adaptive control schemes can be applied to stabilize it. Moreover, in new coordinates, it is not required to guarantee the specified performance of transient processes at any time, and the value of the marginal error is not important. This is due to the fact that inverse transformations will always guarantee that the original signals are within the limits specified by the developer. The problem for plants with a relative degree one is solved in order to avoid cumbersome conclusions. However, all the results obtained can be directly extended to plants with an arbitrary relative degree. An example is given that illustrates the effectiveness of the proposed method and confirms the theoretical conclusions.