This paper deals with modelling and control of an overhead crane with a flexible cable. The developed dynamical model includes both transverse vibrations of the flexible cable and large swing angles of cable while the trolley is moving horizontally. To carry out the modelling, Rayleigh-Ritz discretization method is used to achieve an ordinary differential equation (ODE) model for transverse deflection of the cable with finite generalized degrees of freedom. Using the Euler-Lagrange formulation, a nonlinear dynamic model of the crane system with a flexible cable is obtained. The control objective is to move the payload position to the desired point and at the same time, to reduce the payload swing and to suppress the cable's transverse vibration. To this end, a static state feedback control combined with integral error feedback is proposed. Simulations are performed using the developed nonlinear model under various conditions to illustrate the effectiveness of the proposed control system.
This paper aims to develop an advanced control system for an overhead crane with transverse vibrations of flexible cable while considering large angle of the cable swing. The control objective is to move the payload to a desired position and at the same time, to reduce the payload swing and to suppress the cable transverse vibrations only by applying a directional (horizontal) driving force to the trolley. The crane system with cable vibrations and large swing angle is categorized as a multi-degree under-actuated system whose characteristics impose serious challenges when applying control methods. One reasonable way to overcome the challenges is to separate the degrees of under actuation. To do so, singular perturbation approach is used to divide the dynamical system into a fast subsystem for cable vibrations (with flexible un-actuated coordinates) and a slow subsystem for trolley motion and cable swing (with one degree of under actuation). Based on two-time scale control method, a composite control system is designed. Accordingly, the control system consists of a linear controller for fast dynamics (for vibration suppression) and a nonlinear controller for slow dynamics (for reducing cable swing and controlling the payload motion). Simulations are performed to demonstrate the effectiveness of the control system for an illustrative example of the crane systems with flexible cable moving a lightweight payload.
An accurate and robust lip region detection algorithm based on skin and lip color segmentation is presented in this paper. Here skin and lip color analysis performs in chromatic and YCbCr color space respectively. The proposed algorithm defines geometrical models for skin and lip color distribution in order to detect skin and lip pixels in color image. The proposed algorithm performs lip detection in two stages. First skin pixels are detected in a given color image and face candidates are extracted. Then lip pixels are investigated within face candidates. We propose a segmentation method based on horizontal and vertical accumulation of the image pixel values. Experimental results show that the proposed method detects lips effectively with high accuracy.
Skin detection is the process of finding skin pixels in a given color image. In this paper, we propose a novel fuzzy rule based system for robust and fast skin detection in color images. The proposed fuzzy system models the skin color distribution in HSV color space. Using the fuzzy model, skin likelihood of the pixel is calculated and if it exceeds a threshold then this pixels is considered as skin pixel. Also we proposed a multi layer perceptron neural network for skin classifier and compare its performance with the proposed fuzzy rule based method.Experimental results show effectiveness of the proposed fuzzy rule based method in comparison with the neural network based and other previous approaches.
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