Active Trim Research Articles

ACTIVE CONTROL OF VERTICAL ACCELERATION WITH T-FOIL AND TRIM TAB SYSTEMS IN A FAST FERRY

This study is concerned with the active T-foil placed near the bow on the keel line of the fast ferry and two active trim tab controls placed at the stern to improve the maritime performance of a fast ferry, whilst improving the comfort and safety of passengers and crew. In the scope of the study, the vertical direction of the fast ferry under the random head waves, heave and pitch motions were taken into account. For the control of T-foil and trim Tabs, PID and LQR control methods were used. The purpose of these controllers is to reduce the acceleration of the heave and pitch motions of the fast ferry by changing the operating angles of the T-foil and trim tab wings. A random wave model was created using the Pierson-Moskowitz model, and simulations were done assuming that the fast ferry was subjected to random head waves. Finally, in order to see the effect of vertical acceleration on passengers, the rate of seasickness (MSI) change of the fast ferry in uncontrolled and controlled states was examined. Mathematical models of fast ferry, T-foil and trim tab and their simulations were carried out in MATLAB / Simulink environment. The simulation results show that T-foil and trim tab Active systems can effectively reduce vertical acceleration by improving heave and pitch motions.

Linear and Geometrically Nonlinear Structural Shape Sensing from Strain Data

An aircraft’s shape must be measured during flight to implement active shape controls such as active trim shape, divergence, and sonic boom controls. A basis function method for linear as well as geometrically nonlinear structural shape sensing is proposed in this study. Basis functions can be mode shapes, linear static deformation shapes, and/or geometrically nonlinear static deformation shapes. The proposed basis function method is validated using a high-aspect-ratio wing, a swept test plate, and the National Aeronautics and Space Administration X-59 aircraft. A large structural deformation of a high-aspect-ratio wing is successfully captured using the proposed basis function method with less than 0.3% prediction error at the wing-tip section. The basis function method gives excellent deformation prediction, even with stress concentration. Performance of the basis functions is compared using the X-59 stabilator sample case. In most of the sample load cases, static deformations give a better correlation with the target deformation than do mode shapes. Wing shape sensing with sparse strain data are also demonstrated in this study using the X-59 aircraft. Predicted structural deformations match reasonably with the target deformations, even without strain gauges on some structural components. The predicted deformations have a good match with the target deformations.

MEASURED LOADING RESPONSE OF MODEL MOTION CONTROL STERN TABS


 
 
 Active trim tabs are commonly used as part of the ride control systems of high-speed craft. This paper investigates the lift characteristics of rectangular stern tabs that are commonly fitted to INCAT wave-piercer catamarans. A test apparatus was developed to enable the testing of a model scale trim tab in a circulating water tunnel in the University of Tasmania hydraulics laboratory. The magnitude and location of the lift force produced by the tab were measured over a range of tab angles and flow velocities. From this the lift coefficient of the tab was calculated and the performance of the tab under varying conditions was analysed. The lift force produced by the tab was shown to increase with velocity and tab angle as expected, with the lift coefficient of the tab increasing linearly with tab angle and remaining relatively constant with increases in flow velocity. The magnitude of the measured lift coefficient was lower than had been previously estimated in shallow water tests and the force was found to act forward of the tab hinge, indicating that much of the lift force generated by the tab is due to the increased pressure on the underside of the hull forward of the tab.
 
 

Self-aligned double patterning for active trim contacts with anisotropic pattern pitches in sub-20 nm dynamic random access memories

Background: With continuous decrease in the technology node of dynamic random access memories (DRAMs) down to sub-20 nm, the self-aligned double patterning (SADP) is an effective approach to generate two-dimensional (2-D) patterns, particularly contact arrays. Aim: We demonstrate a patterning scheme using the SADP technique to produce active trim contacts with anisotropic pattern pitches. Approach: The proposed scheme uses two consecutive spacer-formation processes. Results: By making the ellipsoidal core pillars and minimizing the spacer thickness, 2-D critical dimensions (CDs) for self-generated contacts match well with those for core contacts. In addition, an interesting cross-dependence of X -CD and Y -CD variations for the core and self-generated contacts is observed. Conclusion: This patterning approach is useful for forming active trim contacts in sub-20 nm DRAMs using fewer numbers of ArF immersion photolithography steps.

Full-scale experiments on the reduction of propeller-induced aircraft interior noise with active trim panels

Results are presented of full-scale experiments on the active reduction of rotor-induced passenger cabin noise in a Dornier Do728 aircraft. Two active sidewall panels (smart linings) are used to reduce the sound pressure in a control region in front of the linings. The fuselage pressure distribution associated with the first five harmonics of a generic counter-rotating open rotor (CROR) engine is emulated with a loudspeaker array. Each smart lining is equipped with two inertial force actuators. It uses up to eight error microphones and implements an adaptive feedforward controller. The two smart linings are driven in parallel. A maximum SPL reduction of 11.3 dB is achieved in the controlled area. The mean SPL reduction over 18 microphones is 6.8 dB. At the most critical second frequency, a mean SPL reduction of 9.3 dB is achieved by the two smart linings working in parallel. It is observed that the SPLs near the lining (at the window seat positions) are significantly higher than the SPLs near the aisle. This leads to the conclusion that the major part of the sound energy is transmitted through the linings, which is seen as an argument for the suitability of the smart lining concept.

Measured Loading Response of Model Motion Control Stern Tabs

Active trim tabs are commonly used as part of the ride control systems of high-speed craft. This paper investigates the lift characteristics of rectangular stern tabs that are commonly fitted to INCAT wave-piercer catamarans. A test apparatus was developed to enable the testing of a model scale trim tab in a circulating water tunnel in the University of Tasmania hydraulics laboratory. The magnitude and location of the lift force produced by the tab were measured over a range of tab angles and flow velocities. From this the lift coefficient of the tab was calculated and the performance of the tab under varying conditions was analysed. The lift force produced by the tab was shown to increase with velocity and tab angle as expected, with the lift coefficient of the tab increasing linearly with tab angle and remaining relatively constant with increases in flow velocity. The magnitude of the measured lift coefficient was lower than had been previously estimated in shallow water tests and the force was found to act forward of the tab hinge, indicating that much of the lift force generated by the tab is due to the increased pressure on the underside of the hull forward of the tab.

Active vibration control of trim panel using a hybrid controller to regulate sound transmission

This paper presents a method for actively controlling the sound transmission through an aircraft trim panel using a hybrid feedforward/feedback control technique. The method involves measuring the frequency transfer function of the trim panel system and then creating an autoregressive moving average model using frequency domain curve fitting. The control technique is designed to minimize the vibration of a panel that has a limited piston-like motion. The hybrid controller consists of an adaptive feedforward controller that operates in conjunction with a linear quadratic Gaussian feedback controller. The feedback controller increases the damping capacity of the secondary plant to augment the convergence rate of the adaptive feedforward controller. Experimental results indicate that the hybrid controller effectively reduces the vibration of active trim panels and therefore also reduces the sound transmission of the panel.

항공기용 하니콤 트림판넬의 다채널 능동제어

This paper summarizes theoretical work on the multichannel decentralized feedback control of sound radiation from aircraft trim panels using piezoceramic actuators. The aircraft trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. It is motivated by the localization of reduction in vibration of single channel active trim panels. 12-channel decentralized feedback control systems are investigated in terms of the reduction of noise and vibration for three configurations of sensor actuator pairs. Local coupling of the closely-spaced sensor and actuator pairs was modeled using single degree of freedom systems. The multichannel control system is characterized using the state-space model. For the stability point of view, the relative stability or robustness is evaluated by comparing the real part of eigenvalues of the system matrix for the three configurations. The control performance is also evaluated and compared for the three configurations. It is found that the multichannel system can lead to the globalization of the reduction in vibration and radiated noise. It does not appear to yield a significant improvement in the vibration because of decreased gain margin. However, the reduction in the radiated noise is remarkably improved due to the variation of the vibration pattern with the actuation configurations.

AN ANALYTICAL STUDY OF INTERIOR NOISE CONTROL USING SEGMENTED PANELS

This paper presents initial analytical studies of a new method for active interior noise control. The method proposes to control the vibration of segmented trim panels in order to reduce interior noise levels. Since trim panels are often made of light-weight and stiff composite materials, this actuation strategy will enable the creation of active trim panels for interior noise control without using heavy duty structural actuators. The segmentation would provide abilities for both structural sound transmission and active noise control. Numerical studies are performed to demonstrate the effectiveness of segmented trim panels as acoustic control sources. Geometrical design considerations are also studied. A comparison of the forces required for suppressing acoustic pressure is made between segmented trim panels and direct actuation on a single-piece trim panel.

An Impedance Study of Curved Sandwich Trim Panels Driven by Piezoelectric Patch Actuators

Recent research in the area of structural acoustic control for aircraft interior noise suppression has been focused on developing active trim panels. Active trim panels being part of non-critical structures offer many advantages over active controls applied to load critical structures such as aircraft frames and skins. Because there are many flanking paths for the noise to get into the cabin, and because it is not realistic to apply active controls to the entire interior trim panel, the part of the trim that is instrumented with structural controls will inevitably be driven hard enough to cancel the cabin noise. This probably entails high power requirements for active trim panels. The present paper presents an analytical study of cylindrically curved sandwich composite trim and aluminum panels driven by piezoelectric path actuators. An impedance formulation is taken in the study. This paper studies the effect of curvature on the dynamics of the trim panel and the uniform aluminum panel, and has found that the curvature has an opposite effect on the variation of deflection resonance of the composite trim to that of the aluminum panel. Numerical results of mechanical power transfer between the actuator and the host panel are also presented in the paper. This quantity can be used to assess the control authority of the composite trim panels as compared to that of uniform aluminum panels.

Concepts on an Integrated Design Approach to the Active Control of Structurally Radiated Noise (ASAC)

This work describes a range of issues relating to the implementation of active control for noise and vibration problems. It is important in the commercialization of this technology to consider these and many other factors relating to design of these systems. Many of the concepts required for efficient implementation have not been considered and it is important to begin giving design consideration to these aspects. A design technique based upon the eigenbehavior of feedforward controlled systems is developed and applied to control radiation from structures. Integration of the control system with the physical system dynamics allows the eigenproperties to be defined to meet a prescribed design criteria. Here the technique is demonstrated to implement a structural system that inefficiently couples vibration energy to acoustic energy. In addition, an approach to integrate “knowledge” about actuator configurations into an active control system that reduces spillover effects into structural vibrations is demonstrated. This approach has the advantages that no additional hardware is required while also reducing the order of the control system in terms of degrees of freedom. Finally, some design trade-offs between the passive material properties of an active trim panel and control system performance are examined. Improved performance can be attained but at the cost of additional weight.

Concepts on an Integrated Design Approach to the Active Control of Structurally Radiated Noise (ASAC)

This work describes a range of issues relating to the implementation of active control for noise and vibration problems. It is important in the commercialization of this technology to consider these and many other factors relating to design of these systems. Many of the concepts required for efficient implementation have not been considered and it is important to begin giving design consideration to these aspects. A design technique based upon the eigenbehavior of feedforward controlled systems is developed and applied to control radiation from structures. Integration of the control system with the physical system dynamics allows the eigenproperties to be defined to meet a prescribed design criteria. Here the technique is demonstrated to implement a structural system that inefficiently couples vibration energy to acoustic energy. In addition, an approach to integrate “knowledge” about actuator configurations into an active control system that reduces spillover effects into structural vibrations is demonstrated. This approach has the advantages that no additional hardware is required while also reducing the order of the control system in terms of degrees of freedom. Finally, some design trade-offs between the passive material properties of an active trim panel and control system performance are examined. Improved performance can be attained but at the cost of additional weight.

Thick film standard paste temperature sensor applications

Temperature sensors made of standard resistor dielectric paste combinations are incorporated in a bridge network to produce both a simple electronic thermometer and heating table. These units are useful over a wide temperature range up to 120 °C. An active trim is employed to correct offset and set the range.

Algorithmic Trimming on Active Circuitry

The active circuitry for a digital autoranging multimeter has been fabricated on a single hybrie substrate measuring 2.8 X 3.8 cm. The hybrid is realized using tantalum nitride thin film technology. A high temperature passivation process stabilizes the tantalum nitride film. During this process, the absolute value of resistance changes substantially. This change makes the technology unusable in some precision applications. In order to overcome this problem and take advantage of the film's inherently excellent stability, laser trimming is utilized to adjust the absolute value. The result is a stable precision resistor. When the end result of the laser trimming process is a resistor of predetermined value, the operation can be performed by "passive trimming." In many cases, it is desirable to trim the resistor to an unknown value in order to obtain a given circuit response. When this is done to an operating circuit, the procedure is known as "active trimming." In general, a relationship can be determined between a known stimulus and its desired circuit response. The trim procedure can be designed to cause this desired relat onship. Specific algorithms and techniques have been developed to test the sensitivity of a circuit parameter to a given change in trim resistance. The computer controlled system uses this information to determine the succeeding trim magnitude. The use of a computer controller allows the system to handle complicated nonlinear stimulus-response data. Once a hybrid is trimmed, it is effectively a finished product. Since it has been calibrated during the trimming process, there is no need for manual adjustment. One difficulty associated with active laser trimming is duplicating the external circuit while at the same instant connecting the hybrid substrate to noisy probe rings, loading it with capacitances, and subjecting it to-the hostile environment of electromechanical controls. This paper will deal primarily with algorithms developed for active trim and the problems of electrically interfacing the system with the hybrid under test. Most of this experience was achieved during the development of the Hewlett-Packard Model 970A Probe Multimeter.