Compatible realisation of control and identification of direct adaptive control via probing signal auto-elimination

Abstract

The model reference adaptive control system is an adaptive controller that maintains the control performance even when the uncertainty of the controlled system’s parameters is high, and its design methodology is well established. In particular, the direct MRACS excels in responsiveness; however, it suffers from the problem that its adjustable parameters do not converge to their true values. To converge the adjustable parameters to their true values, a conventional method involves injecting a probing signal to satisfy the PE property; however, this compromises the control performance. Thus, a control error-based probing signal auto-elimination scheme is proposed in this study, which adaptively regulates the probing signal based solely on the control error without predefined elimination timing. This enables the identification of adjustable parameters during transient phases, while automatically suppressing the probing signal once sufficient tracking performance is achieved. Furthermore, unlike existing probing-based methods, the proposed scheme allows re-injection of the probing signal when performance degradation is detected, thereby achieving a compatible realisation of identification and control within a single framework. Therefore, the proposed scheme simultaneously contributes to the identification and control, significantly reducing the tracking error. The validity of the proposed structure was confirmed by simulations under plant variation conditions.