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The tractor-trailer wheeled robot is an articulated nonholonomic vehicle. This paper presents a novel PID-based tracking control law for the tractor-trailer wheeled robot. Theoretical anticipations do not always match the behavior of real systems. This is as a result of the existence of various uncertainties and disturbances. Consequently, controllers that are less dependent on systems' theoretical models are more desirable that is aimed at this research. Therefore, a PID-based kinematic controller is proposed as a non-model based controller to navigate the tractor-trailer wheeled robot follows desired trajectories. Subsequently, a computed torque dynamic controller is investigated to produce kinetic control inputs. The proposed method is implemented on a real-time experimental testbed and obtained results are discussed. These results present the merits of the proposed algorithm.

Autonomous underwater vehicles (AUVs) are highly nonlinear underactuated systems with uncertain dynamics and a challenging control problem. The main focus of this paper is to present a control law that shows desirable performance in the presence of modeling uncertainties. In this study, uncertainties are considered to be bounded and the AUV mathematical model is obtained in the presence of such uncertainties. Forces and torques applied to the AUV are also designed using a nonlinear dynamic controller. Appropriate adaptive rules are also presented to overcome system uncertainties and external disturbances. The adaptive nonlinear dynamic controller is designed based on upper bounds of system uncertainties and its stability is proven using the Lyapunov theory. In this article, the performance of the proposed control algorithm for tracking reference trajectories in an obstacle-rich environment is investigated. Therefore, the control algorithm is combined with potential fields for obstacle avoidance. Obtained results show the efficiency of the proposed controller.

One of the most important and conventional manoeuvres, that is not easy to even skilled drivers, is the high-speed critical lane change on the highways. The main contribution of this study is the development of an integrated longitudinal and lateral guidance algorithm for these manoeuvres. This algorithm consists of two parts: the trajectory planning and the integrated control. In the first part, taking into account the position of the target vehicle for different accelerations, several trajectories are produced. Next, considering the dynamic capabilities of the vehicle, the most appropriate trajectory is selected. Since the proposed trajectory planning approach works algebraically, its computational cost is negligible, which is very valuable for practical implementations. In the second step, using a robust-integrated longitudinal–lateral controller, the control inputs are calculated and transmitted to the brakes, throttle and steering actuators. It should be noted that the trajectory planning and the integrated controller are based on the seven degrees of freedom model of the vehicle, and the nonlinear dynamics of the tyre and the dynamics of the brakes/throttle actuators are also taken into account. To assess the efficiency of the integrated longitudinal–lateral guidance algorithm, the full vehicle model is used in the CarSim–Simulink software. In order to have conditions closer to real applications, it is assumed that the yaw rate and the longitudinal and lateral accelerations of the vehicle are noisy, and the longitudinal and lateral velocities are predicted using the same signals. Obtained results for the critical collision avoidance manoeuvres confirm the effectiveness of the proposed planned trajectory and the good performance of the combined control method. In addition, the results indicate that the integrated control is robust against the variation of friction coefficient and unmodelled dynamics while maintaining the vehicle stability.

SUMMARYTrajectory tracking is one of the main control problems in the context of Wheeled Mobile Robots (WMRs). Control of underactuated systems has been focused by many researchers during past few years. In this paper, tracking control of a Tractor–Trailer Wheeled Mobile Robot (TTWMR) has been discussed. TTWMR includes a differential drive WMR towing a passive spherical wheeled trailer. Spherical wheels in contrast with standard wheels make the robot highly underactuated with severe non-linearities. Underactuation is due to the use of spherical wheeled trailer to increase robots' maneuverability and degrees of freedom. In fact, standard wheels are subjected to non-holonomic constraints due to pure rolling and non-slip conditions, which reduce robot maneuverability. In this paper, after introducing the robot, kinematics and kinetics models are obtained. Then, based on a physical intuition, a novel control algorithm is developed for the robot, i.e. Lyapunov-PID control algorithm. Subsequently, singularity avoidance of the proposed algorithm is discussed and the stability of the algorithm is analyzed. Finally, simulation and experimental results are presented which reveal the effectiveness of the proposed algorithm.