tailieunhanh - Robotics and Automation in Construction 2012 Part 9

Tham khảo tài liệu 'robotics and automation in construction 2012 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | An Active Technology for Improving the Sound Transmission Loss of Glazed Facades 233 1 N J T 2pci 1 p t 2 ASi 7 being J the total radiated acoustic power p and c the density and sound velocity of wave in air pi the sound pressure values measured at some prescribed measurements points and A Si the surfaces relative to each measurement point. Pressure values are not directly measured but computed from the signals deriving from the reference sensors positioned on the glazed panel through the use of filters . Thus the structural-acoustic coupling is inherent in the definition of the cost function. It was demonstrated by Fuller et al. 1997 and Nelson Elliott 1992 that substituting the opportune expression of radiated sound pressure given Fig. 5. Scheme of an ASAC system for glazed panels integrated in buildings by the superposition of the two contributions of both the disturbance and the control actuators the cost function is scalar. It can be converted into a quadratic expression of complex control voltages and it was demonstrated that this function has a unique minimum. The general form of the equation to be minimized becomes J hTq cTvi 8 where q is the vector of complex input disturbances h is the vector of transfer functions associated with these disturbances c is the control transfer function vector and V is the unknown vector. In this way a vector of voltages Vi is computed minimizing the total radiated field. Once the transfer functions between the reference signal deriving from reference sensors and the acoustic radiated noise is known for a given system the control plant will automatically execute all these steps minimizing the radiated noise even if glazed panels are subject to timedependent input disturbances giving back an automated glazed facade that actively changes its properties according to the disturbance. Before implementing this control system it is necessary to calculate the control transfer functions which requires as a preliminary stage the choice