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This paper investigates the trajectory tracking control problem of a four-wheel independently driven skid-steering mobile robot (FWID-SSMR) while considering friction resistance, parameter variation and external disturbances. Unlike previous studies that only achieved stable tracking control of FWID-SSMR, this paper accomplishes prescribed steady-state and transient performance. Based on the dynamic model of FWID-SSMR, an integer-order prescribed-time controller (IOPTC) is developed first, which can make the tracking errors converge to a predetermined residual set with a preset convergence rate in a prescribed time. Motivated by it, a fractional-order prescribed-time controller (FOPTC) is developed by exploiting the genetic attenuation properties of fractional calculus (FC) for improving the control performance. The feasibility and effectiveness of the developed controller are verified by Lyapunov theoretical analysis and numerical simulation studies. The simulation results show that both the IOPTC and FOPTC outperform the feedback controller (FBC). Moreover, the influence of the performance function on control performance is also tested, which can serve as a reference for selecting the appropriate performance function to use in future applications. [ABSTRACT FROM AUTHOR]

This paper investigates the prescribed-time leader-following output-feedback consensus problem for second order multiagent systems without velocity measurement. Firstly, by introducing a time-scaling function, novel prescribed-time state observers are designed to estimate the second-order states of the agents. Then, a distributed output-feedback scheme is proposed to achieve leader-following consensus, where the transient performance, including the convergence rate and the overshoot, can be offline pre-assigned. It should be noted that the singularity-like problem is solved for the system under measurement errors by adopting a form of piecewise functions. Moreover, the control strategy is modified by introducing an auxiliary system when taking the common saturation problem into account. Finally, the efficiency of the proposed schemes is illustrated by numerical simulation examples. • A novel kind of prescribed-time performance functions is designed. • A form of sine functions is introduced to deal with the singularity-like problem. • The prescribed-time stability of the system is guaranteed by the proposed scheme. [ABSTRACT FROM AUTHOR]