Trong Hieu Bui

Sliding Mode Control of Two-Wheeled Welding Mobile Robot for Tracking Smooth Curved Welding Path

In this paper, a nonlinear controller based on sliding mode control is applied to a two-wheeled Welding Mobile Robot (WMR) to track a smooth curved welding path at a constant velocity of the welding point. The mobile robot is considered in terms of dynamics model in Cartesian coordinates under the presence of external disturbance, and its parameters are exactly known. It is assumed that the disturbance satisfies the matching condition with a known boundary. To obtain the controller, the tracking errors are defined, and the two sliding surfaces are chosen to guarantee that the errors converge to zero asymptotically. Two cases are to be considered : fixed torch and controllable torch. In addition, a simple way of measuring the errors is introduced using two potentiometers. The simulation and experiment on a two-wheeled welding mobile robot are provided to show the effectiveness of the proposed controller.

A hybrid control of active suspension system using H/sub /spl infin// and nonlinear adaptive controls

This paper presents a hybrid control of active suspension system for quarter-car model with two-degree-of-freedom by using H/sub /spl infin// and nonlinear adaptive control method. Suspension dynamics is linear and treated by H/sub /spl infin// method which guarantees the robustness of closed loop system under the presence of uncertainties and minimizes the effect of road disturbance to the system. The nonlinearity of the hydraulic actuator is treated by a nonlinear adaptive controller based on back-stepping control method. Simulation results are given both frequency and time domains to verify the effectiveness of the designed controllers.

Wall-Following Control of a Two-Wheeled Mobile Robot

Wall-following control problem for a mobile robot is to move it along a wall at a constant speed and keep a specified distance to the wall.This paper proposes wall-following controllers based on Lyapunov function candidate for a two-wheeled mobile robot (MR) to follow an unknown wall. The mobile robot is considered in terms of kinematic model in Cartesian coordinate system. Two wall-following feedback controllers are designed: full state feedback controller and observer-based controller. To design the former controller, the errors of distance and orientation of the mobile robot to the wall are defined, and the feedback controller based on Lyapunov function candidate is designed to guarantee that the errors converge to zero asymptotically. The latter controller is designed based on Busawon’s observer as only the distance error is measured. Additionally, the simulation and experimental results are included to illustrate the effectiveness of the proposed controllers.

Adaptive Tracking Control of Two-Wheeled Welding Mobile Robot with Smooth Curved Welding Path

This paper proposes an adaptive controller for partially known system and applies to a two-wheeled Welding Mobile Robot (WMR) to track a reference welding path at a constant velocity of the welding point. To design the tracking controller, the errors from WMR to steel wall is defined, and the controller is designed to drive the errors to zero as fast as desired. Additionally, a scheme of error measurement is implemented on the WMR to meet the need of the controller. In this paper, the system moments of inertia are considered to be partially unknown parameters which are estimated using update laws in adaptive control scheme. The simulations and experiments on a welding mobile robot show the effectiveness of the proposed controller.

Hybrid control of an active suspension system with full-car model using H ∞ and nonlinear adaptive control methods

This paper presents hybrid control of an active suspension system with a full-car model by using H∞ and nonlinear adaptive control methods. The full-car model has seven degrees of freedom including heaving, pitching and rolling motions. In the active suspension system, the controller shows good performance: small gains from the road disturbances to the heaving, pitching and rolling accelerations of the car body. Also the controlled system must be robust to system parameter variations. As the control method, H∞ controller is designed so as to guarantee the robustness of a closed-loop system in the presence of uncertainties and disturbances. The system parameter variations are taken into account by multiplicative uncertainty model and the system robustness is guaranteed by small gain theorem. The active system with H∞ controller can reduce the accelerations of the car body in the heaving, pitching and rolling directons. The nonlinearity of a hydraulic actuator is handled by nonlinear adaptive control based on the back-stepping method. The effectiveness of the controllers is verified through simulation results in both frequency and time domains.