Path planning for wheeled mobile robots on partially known uneven terrain is an open challenge since robot motions can be strongly influenced by terrain with incomplete environmental information such as locally detected obstacles and impassable terrain areas. This paper proposes a hierarchical path planning approach for a wheeled robot to move in a partially known uneven terrain. We first model the partially known uneven terrain environment respecting the terrain features, including the slope, step, and unevenness. Second, facilitated by the terrain model, we use A${}^{\star }$ algorithm to plan a global path for the robot based on the partially known map. Finally, the Q-learning method is employed for local path planning to avoid locally detected obstacles in close range as well as impassable terrain areas when the robot tracks the global path. The simulation and experimental results show that the designed path planning approach provides satisfying paths that avoid locally detected obstacles and impassable areas in a partially known uneven terrain compared with the classical A${}^{\star }$ algorithm and the artificial potential field method.

Interval observer design and related techniques have been researched and applied in many engineering fields and continue to be an active research area in the estimation and control society for the last two decades. An Interval observer is a special class of observers that generates a bounded interval vector for the real state vector in a guaranteed way under the assumption that the uncertainties are unknown but bounded. Some of the basic concepts and the main developments in the designs and applications of interval observer for continuous‐time, discrete‐time (linear and non‐linear), fuzzy and switched systems are reviewed in this work. It also provides a brief discussion of the main approaches in this area with clear descriptions of their structures and future directions.

In this article, the problem of angular velocity trajectory tracking for converter-fed DC motor system with mismatched disturbances/uncertainties is investigated using a continuous nonsingular terminal sliding mode control. The fourth order dynamic model of the system is quite higher than the second order of the traditional one, which makes the control design more challenging in terms of availability of various signals and tuning of the overall control parameters. Also, the actuator dynamics of the converter not only increase the system order but also generate mismatched disturbances/uncertainties, which is difficult to counteract through baseline sliding mode controller. The disturbance estimation information obtained from the finite time disturbance observer is incorporated into the design of nonsingular terminal sliding manifold. Then, a nonsingular terminal sliding mode controller is designed to achieve finite time tracking performance despite matched and mismatched disturbances/uncertainties. In addition, it retains the fine properties of nominal performance recovery as well as chattering alleviation. Finally, the superiority of the proposed method is shown both through numerical simulation and experimental results.