Prescribed‐time regulation of nonlinear uncertain systems with unknown input gain and appended dynamics

• Published in: International journal of robust and nonlinear control Vol. 33; no. 5; pp. 3004 - 3026
• Main Authors: Krishnamurthy, Prashanth, Khorrami, Farshad
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 25.03.2023
• Subjects: adaptive control; Control systems design; Control theory; Convergence; Design; high‐gain control; nonlinear control systems; Nonlinear systems; prescribed‐time stabilization; Stabilization; State vectors; System dynamics; Time dependence; uncertain systems
• ISSN: 1049-8923; 1099-1239
• DOI: 10.1002/rnc.6549

The prescribed‐time stabilization problem for a general class of uncertain nonlinear systems with unknown input gain and appended dynamics (with unmeasured state) is addressed. Unlike the asymptotic stabilization problem, the prescribed‐time stabilization objective requires convergence of the state vector to the origin in a finite time interval that can be arbitrarily picked (i.e., “prescribed”) by the control system designer irrespective of the system's initial condition. The class of systems considered is allowed to have general nonlinear uncertain terms throughout the system dynamics as well as uncertain appended dynamics (that effectively generate a time‐varying non‐vanishing disturbance signal input into the nominal system). The control design is based on a nonlinear transformation of the time scale, dynamic high‐gain scaling, adaptation dynamics with temporal forcing terms, and a composite control law that includes two components. The first component in the composite control law is analogous to prior dynamic high‐gain scaling‐based control designs, but with a time‐dependent function in place of the unknown input gain, while the second component has a non‐smooth form with time‐dependent terms that ensure prescribed‐time convergence in spite of the unknown input gain and the disturbances. The efficacy of the proposed control design is illustrated through numerical simulation studies on two example systems (a “synthetic” fifth‐order system and a “real‐world” electromechanical system).