http://www.mecheng.adelaide.edu.au/anvc/ List of the last 10 recently entered Publications for the ANVC group. &lt;br&gt;&lt;font size=1&gt;&lt;b&gt;Hint:&lt;/b&gt; You can pass the options through the URL by modifying the URL such that &quot;.php&quot; is replaced with &quot;.php?itcount=20&amp;shorttitle=1&amp;dateprefix=0&quot; &lt;/font&gt; en-us Automated (mailto:) Pierre Dumuid (mailto:pierre.dumuid@adelaide_xx_edu_xx_au) Copyright 2008, Adelaide University Thu Aug 21 8:34:44 EIT 2008 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=363 <p>This memo shows that Matlab cannot be used to calculate the mode shapes of clamped beams and clamped plates for high mode numbers (n>10). The problem is caused by Matlab's double precision, when the mathematics requires greater precision. The memo describes the problem, contains Matlab code to demonstrate the problem, and also the solution - use the Matlab Symbolic toolbox (Maple) to calculate the mode shapes. </p> Carl Q. Howard 2006--0-6-T28: 1:0:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=275 <p>Active vibration isolation experiments were conducted using a transducer that measures translational and rotational power transmission from a vibrating mass, through a single axis active isolator and into a beam. The transducer is capable of measuring forces and moments along six axes and an accelerometer array measures its motion. By combining the measured force and velocity signals the translational and rotational power transmission was measured. Comparisons were made of the effectiveness of several cost functions for minimising the vibration transmitted into the beam. The results show that active vibration isolation using power transmission as a cost function to be minimised is limited by the phase accuracy of the transducers. The best results were obtained from the minimisation of the weighted sum of force and velocity.</p> Howard, C.Q. and Hansen, C.H. 2006--0-6-T28: 0:8:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=362 <p> The calculation of the forced vibration response of a clamped beam or clamped plate often involves the calculation of the modal (or generalized) mass. Calculation of this term for simply-supported structures is relatively easy and results in a value that is half the mass of the structure for beams, and a quarter of the mass of the structure for plates and cylinders. However, calculation of this term for clamped beams and clamped plates is algebraically more complicated and has led to the presentation of several formula in research literature that appear vastly different. This paper contains a derivation of the modal mass of a clamped beam and clamped plate and shows that several of the formula for the modal mass in the research literature are equivalent.</p> Carl Q. Howard 2006--0-6-T26: 1:5:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=361 <p>In this paper we propose an approximate backstepping control law for the stabilisation of Six Degree of Freedom symmetric VTOL vehicles. This control law results in closed-loop dynamics with a stable cascade structure. An additional innovation is to design feedback such that the interconnection term between resulting cascaded sub-systems is minimised. The proposed control law is proven to be globally, exponentially stable, and simulation results show aggressive stabilisation and the benefits of minimising the closed-loop interconnection term.</p> Rohin Wood, Ben S. Cazzolato 2006--0-6-T15: 1:6:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=357 <p>Local active noise control systems aim to produce zones of quiet at a number of desired locations within a sound field, such as the ears of an observer. The resulting zones of quiet are usually centered at the error sensors, and are often too small to extend from the error sensors to the observers ears. To overcome these problems, virtual sensing methods have been suggested. These methods are based on estimating the error signals at a number of locations remote from the physical locations of the error sensors. By minimising the estimated error signals, the zones of quiet can be moved away from the error sensors to the locations where noise control is desired, i.e. the virtual locations. In this paper, the active noise control problem under consideration is analysed using a state-space model of the plant. Kalman filtering theory is then used to develop a virtual sensing algorithm that computes optimal estimates of the error signals at the virtual locations. The developed algorithm is implemented on an acoustic duct arrangement, and the real-time estimation performance at a virtual location inside the acoustic duct is analysed. Furthermore, the developed algorithm is combined with the filtered-x LMS, and the results of real-time broadband feedforward control experiments at the virtual location are presented.</p> Petersen, C.D. , Fraanje, R. , Cazzolato, B.S., Zander, A.C., and Hansen, C.H. 2006--0-5-T31: 1:4:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=356 <p>The trivial equilibrium of a van der PolDuffing oscillator under a linear-plus-nonlinear feedback control may change its stability either via a single or via a double Hopf bifurcation if the time delay involved in the feedback reaches certain values. It is found that the trivial equilibrium may lose its stability via a subcritical or supercritical Hopf bifurcation and regain its stability via a reverse subcritical or supercritical Hopf bifurcation as the time delay increases. A stable limit cycle appears after a supercritical Hopf bifurcation occurs and disappears through a reverse supercritical Hopf bifurcation. The interaction of the weakly periodic excitation and the stable bifurcating solution is investigated for the forced system under primary resonance conditions. It is shown that the forced periodic response may lose its stability via a NeimarkSacker bifurcation. Analytical results are validated by a comparison with those of direct numerical integration.</p> Ji, J.C. and Hansen, C.H. 2006--0-5-T22: 1:1:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=355 <p>The trivial equilibrium of a two-degree-of-freedom autonomous system may become unstable via a Hopf bifurcation of multiplicity two and give rise to oscillatory bifurcating solutions, due to presence of a time delay in the linear and nonlinear terms. The effect of external excitations on the dynamic behaviour of the corresponding non-autonomous system, after the Hopf bifurcation, is investigated based on the behaviour of solutions to the four-dimensional system of ordinary differential equations. The interaction between the Hopf bifurcating solutions and the high level excitations may induce a non-resonant or secondary resonance response, depending on the ratio of the frequency of bifurcating periodic motion to the frequency of external excitation. The first-order approximate periodic solutions for the non-resonant and super-harmonic resonance response are found to be in good agreement with those obtained by direct numerical integration of the delay differential equation. It is found that the nonresonant response may be either periodic or quasi-periodic. It is shown that the super-harmonic resonance response may exhibit periodic and quasi-periodic motions as well as a co-existence of two or three stable motions.</p> Ji, J.C., Hansen, C.H., and Li, X. 2006--0-5-T22: 1:1:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=354 <p>The status of active noise ctrol in terms of its application to industrual problems is discussed and reasons for the apparent lack of enthusiasm for the technology by industry are postulated. An industrial installation in which the author was involved is used as an example to illustrate the complexities involved and the reaons why implementation costs are so high. The future of active noise control in industry is dependednt on a number of issues associated with hardware configuration and cost, user friendly software, generalisation of system design, development of low-cost, rugged actuators and sensors together with an acceptance of what is possible and whist is not. Novel approaches to achieving the control objective of reduced noise lelvels at the ears of industrial employees, which sidestep limitations imposed by the physical properties of sound and vibration fields, are also required to enable practical application of the technology in many cases. One such novel approach, which involves virtual sensing combined with very local control and beam steering that tracks a person's ear is discussed.</p> Hansen, C.H. 2006--0-5-T22: 1:1:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=285 <p>The insertion loss of standard acoustic blankets can be significantly improved at low frequencies by the addition of randomly placed mass inclusions to the poro-elastic layers. The improvement is much greater than that due to the mass effect alone. The mass inclusions act as resonant systems and so increase the structure impedance. This paper reports the results of experimental investigations into this phenomenon. Increases in insertion loss of 15dB in the 100Hz third octave band are reported.</p> Kidner, M.R.F, Fuller, C.R., and Gardner, B.K 2006--0-5-T22: 1:0:+00:00 http://www.mecheng.adelaide.edu.au/anvc/abstract.php?abstract=322 <p>Over the past twenty years active control of noise has developed into a mature research field and into a product for some technical companies. This paper reviews the current state of the art in both the research and development fields using the context of a cube of difficulty. The cube illustrates how the three physical quantaties: frequency bandwidth, spatial extent and signal coherence, contribute to the difficulty of achieving control performance. The literature is reviewed and placed within the cube to reveal patterns in research and areas of further work.</p> Kidner, M.R.F. 2006--0-5-T15: 1:0:+00:00