scholarly journals High Speed Microactuators for Low Aspect Ratio High Speed Micro Aircraft Surfaces

Actuators ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 265
Author(s):  
Ronald Barrett-Gonzalez ◽  
Nathan Wolf
Keyword(s):  
Aspect Ratio ◽  
Flight Control ◽  
High Speed ◽  
High Performance ◽  
Dynamic Range ◽  
Feedback System ◽  
Analytical Models ◽  
Control Surface ◽  
Operational Environment ◽  
Low Aspect Ratio

This paper covers a class of actuators for modern high speed, high performance subscale aircraft. The paper starts with an explanation of the challenges faced by micro aircraft, including low power, extremely tight volume constraints, and high actuator bandwidth requirements. A survey of suitable actuators and actuator materials demonstrates that several classes of piezoceramic actuators are ideally matched to the operational environment. While conventional, linear actuation of piezoelectric actuators can achieve some results, dramatic improvements via reverse-biased spring mechanisms can boost performance and actuator envelopes by nearly an order of magnitude. Among the highest performance, low weight configurations are post-buckled precompressed (PBP) actuator arrangements. Analytical models display large deflections at bandwidths compatible with micro aircraft flight control speed requirements. Bench testing of an example PBP micro actuator powered low aspect ratio flight control surface displays +/−11° deflections through 40 Hz, with no occupation of volume within the aircraft fuselage and good correlation between theory and experiment. A wind tunnel model of an example high speed micro aircraft was fabricated along with low aspect ratio PBP flight control surfaces, demonstrating stable deflection characteristics with increasing speed and actuator bandwidths so high that all major aeromechanical modes could be easily controlled. A new way to control such a PBP stabilator with a Limit Dynamic Driver is found to greatly expand the dynamic range of the stabilator, boosting the dynamic response of the stabilator by more than a factor of four with position feedback system engaged.

Feedback linearization and backstepping: an equivalence in control design of strict-feedback form

2019 ◽  
Vol 37 (4) ◽  
pp. 1049-1069 ◽  
Author(s):  
Thanh T Tran
Keyword(s):  
Flight Control ◽  
Feedback Linearization ◽  
High Performance ◽  
Control Design ◽  
Backstepping Control ◽  
Analytical Models ◽  
Linear Feedback ◽  
Specific Class ◽  
Feedback Form ◽  
Non Linear

Abstract This paper investigates an equivalence between feedback linearization and backstepping control. Implications from equivalence are that stability and performance properties of one method are the same for another method. Thus, a property known to exist only for one method could be used to prove property also holds for another. Also, a suspected advantage of one method over the other could be proven to be a false conjecture. Control laws in both approaches are achieved by coordinate transformations and non-linear feedbacks. Further, resulting non-linear feedback control law achieved by feedback linearization method matches exactly with non-linear controller achieved by the backstepping control design. This equivalence is a general analytical match within the specific class of non-linear dynamic systems under investigation. Demonstrations are considered and validated via flight control of longitudinal dynamics of a high performance aircraft simulation model. Algorithms are tested and evaluated with analytical models and non-linear closed-loop simulation.

Experimental Comparisons to Assure the Similarity Between VIM (Vortex-Induced Motion) and VIV (Vortex-Induced Vibration) Phenomena

2011 ◽  
Author(s):  
Rodolfo T. Gonc¸alves ◽  
Ce´sar M. Freire ◽  
Guilherme F. Rosetti ◽  
Guilherme R. Franzini ◽  
Andre´ L. C. Fujarra ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Water Channel ◽  
Analytical Models ◽  
Mass Ratio ◽  
Water Displacement ◽  
Transform Method ◽  
Number Range ◽  
Vortex Induced Vibration ◽  
Low Aspect Ratio ◽  
Induced Motion

Vortex-Induced Motion (VIM) is another way to denominate the Vortex-Induced Vibration (VIV) in floating units. The main characteristics of VIM in such structures are the low aspect ratio (L/D < 4.0) and the unity mass ratio (m* = 1.0, i.e. structural mass equal water displacement). The VIM can occur in MPSO (Monocolumn Production, Storage and Offloading System) and spar platforms. These platforms can experience motion amplitudes of around their characteristic diameters. In such cases, the fatigue life of mooring and riser systems can be greatly reduced. Typically, the VIM model testing campaigns are carried out in the Reynolds range between 200,000 and 400,000. VIV model tests with low aspect ratio cylinders (L/D = 1.0, 1.7 and 2.0) and unity mass ratio (m* = 1.0) have been carried out at the Circulating Water Channel facility available at NDF/EPUSP. The Reynolds number range covered in the experiments was between 10,000 and 50,000. The characteristic motions (in the transverse and in-line direction) were obtained using the Hilbert-Huang Transform method (HHT) and then compared with results obtained in experiments found in the literature. The aim of this investigation is to definitely establish the similarity between the VIM and VIV phenomena, making possible to increase the understanding of both and, at same time, allowing some analytical models developed for VIV to be applied to the VIM scenario on spar and monocolumn platforms, logically under some adaption.

scholarly journals Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments

1994 ◽  
Author(s):  
S. E. Gorrell ◽  
P. M. Russler
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Stall Inception ◽  
Casing Treatment ◽  
Low Aspect Ratio ◽  
Casing Treatments

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.

Enabling Robust Copper Fill of High Aspect Ratio Through Silicon Vias

2010 ◽  
Vol 2010 (1) ◽  
pp. 000176-000179
Author(s):  
Mark Willey ◽  
Damo Srinivas ◽  
Sesha Varadarajan ◽  
David Porter ◽  
Easwar Srinivasan ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
High Performance ◽  
Process Window ◽  
Seed Technology ◽  
Aspect Ratios ◽  
Reducing Costs ◽  
Electroplating Process ◽  
Silicon Vias

Today's Through Silicon Via (TSV) processes are limited to aspect ratios of 10:1. High performance logic devices drive the need for aspect ratios approaching 20:1 in order to achieve the desired performance while simultaneously reducing costs. The reduced via area required on the wafer enables the designer to utilize less real estate on the die to reduce cost or to potentially add redundant vias to improve yield. However, current conventional processes and techniques are not capable of achieving robust fill on aspect ratios greater than 12:1. This presentation will highlight the technical challenges in achieving robust copper fill on super high aspect ratio TSV structures. Additionally, a compelling, economic solution pathway will be presented that integrates a low temperature conformal high quality dielectric isolation layer, a high step coverage Cu barrier / seed technology and a void free high speed electroplating process with a wide process window that could accelerate the adoption of the high aspect ratio TSV design schemes.

A Numerical Study of Very High Speed Flat Ship Theory

1991 ◽  
Vol 35 (01) ◽  
pp. 63-72
Author(s):  
Todd McComb
Keyword(s):  
Aspect Ratio ◽  
Symbolic Computation ◽  
High Speed ◽  
Numerical Study ◽  
Analytic Solutions ◽  
Low Aspect Ratio ◽  
Lift And Drag ◽  
Very High

This paper uses an asymptotic procedure to generate analytic solutions to the low-aspect-ratio problem of flat ship theory, in the limit for a very fast ship. The first two terms of the solution are worked out for hulls of parabolic planform and with 20 arbitrary constants in the expression for the draft. Optimizations are then performed for lift and drag on a smaller class of hulls. Analytic solutions were found by using symbolic computation, and the results are discussed. Optimal hulls are presented for various values of the ship's speed, optimized with both total lift and static lift held fixed. The optimization solution in the limit as the ship's speed goes to infinity gives independence of some constants in the expression for the hull.

Tip Flow Fields in a Low Aspect Ratio Transonic Compressor

1995 ◽  
Author(s):  
P. Russler ◽  
D. Rabe ◽  
B. Cybyk ◽  
C. Hah
Keyword(s):  
Shock Wave ◽  
Aspect Ratio ◽  
Flow Field ◽  
High Frequency ◽  
High Performance ◽  
Flow Structures ◽  
Transonic Compressor ◽  
Low Aspect Ratio ◽  
Laser Data ◽  
Blade Tip

Experimental data and computational predictions are used to characterize the tip flow field of a high performance, low aspect ratio, transonic compressor. Flow structures near the first stage blade tip are monitored experimentally using two different data acquisition schemes. High frequency pressure and laser fringe anemometry data are used to experimentally define the tip flow structure. The high frequency pressure data were acquired with an array of pressure transducers mounted in the rotor casing. Laser data were acquired through a window in the same position. The transducer and laser data adequately define the shock structure at the tip. Both the movement of the shock wave in the blade passage during changes in compressor loading and the interaction between the shock wave and the tip leakage vortex are detected. Similar flow structures and compressor loading effects are numerically predicted using a three-dimensional Navier-Stokes algorithm. A fundamental understanding of the flow field at the blade tip is obtained using these three complementary methods.

Review of self-induced roll oscillations and its attenuation for low-aspect-ratio wings

2019 ◽  
Vol 233 (16) ◽  
pp. 5873-5895 ◽  
Author(s):  
Tianxiang Hu
Keyword(s):  
Aspect Ratio ◽  
Flight Control ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Micro Aerial Vehicles ◽  
Reynolds Number Flow ◽  
Low Aspect Ratio ◽  
Aerial Vehicles ◽  
Low Aspect Ratio Wings

Micro aerial vehicles are currently receiving growing interest because of their broad applications in many fields. In their flight tests, the onset of unwanted large amplitude roll oscillations was reported, which resulted in difficulties with flight control, and this has become one of the major challenges of current micro aerial vehicles design. In this review type of article, the low Reynolds number flow characteristics of a low-aspect-ratio wing are reviewed, and the self-induced roll oscillations are discussed with special attention being payed to the interaction between the three-dimensional flow structure and wing in reciprocatively rolling motion. The roll attenuation methods are introduced via flow control approaches, which can suppress the roll oscillations effectively by manipulating the leading-edge flow separation and tip vortices of the low-aspect-ratio wings.

An Analytic Approach to Very High Speed Flat Ship Theory

1989 ◽  
Vol 33 (01) ◽  
pp. 29-34
Author(s):  
S. L. Cole
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Analytic Solutions ◽  
Simple Expression ◽  
Analytic Approach ◽  
Leading Order ◽  
Low Aspect Ratio ◽  
Simple Class ◽  
Lift And Drag ◽  
Very High

This paper defines an asymptotic procedure to generate analytic solutions to the low-aspect-ratio problem of flat ship theory in the limit when the ship is traveling very fast. The leading-order solution terms are worked out, by way of example, for the particular class of hulls with slope fx = -(a + b×) and draft f = -[a(×-y2) + (b/2)(x2-y4)] for y2 ≤ x, 0 ≤ × ≤ 1 with a and b arbitrary constants. A simple expression is worked out in terms of the free constants a and b for the lift and drag and an optimization (over this simple class of hulls) is presented.

Sign in / Sign up

Export Citation Format

Share Document