Fretting Behavior of Coated and Treated Titanium Alloy Using an Open-Loop System

2005 ◽  
Author(s):  
G. R. Yantio Njankeu ◽  
J.-Y. Paris ◽  
J. Denape ◽  
L. Pichon ◽  
J.-P. Rivie`re
Keyword(s):  
Titanium Alloy ◽  
Relative Motion ◽  
High Frequency ◽  
Open Loop ◽  
Loop System ◽  
Test Apparatus ◽  
Open Loop System ◽  
Wear Rates ◽  
Low Wear

Titanium alloys are well known to present poor sliding behaviour and high wear values. Various coatings and treatments have been tested to prevent such an occurrence under fretting conditions at high frequency of displacement (100 Hz). An original test apparatus, using an open-loop system instead of a classical imposed displacement simulator, has been performed to directly display the phenomenon of seizure, defined as the stopping of the relative motion between the contacting elements. A classification of the tested coatings has been proposed on the basis of their capacity to maintain full or partial sliding conditions, to present low wear rates and to prevent seizure.

Remarks on the Modelling of Active Structures With Colocated Piezoelectric Actuators and Sensors

1995 ◽  
Author(s):  
N. Loix ◽  
A. Preumont
Keyword(s):  
High Frequency ◽  
Closed Loop ◽  
Transfer Functions ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop System ◽  
Local Effects ◽  
Open Loop System ◽  
Active Structures ◽  
Modelling Techniques

Abstract This paper aims to attract the attention of the designers of active structures on the importance of evaluating properly the feedthrough component of the open-loop transfer functions. It is shown that overlooking the feedthrough component can change significantly the location of the zeros of the open-loop system and, as a result, alter drastically the performance of the closed-loop system. The feedthrough term may result from the quasi-static contribution of the high frequency modes or from local effects that are neglected by over-simplified modelling techniques (e.g. plate or beam instead of shell). The problem is illustrated with a cantilever beam provided with strain actuators.

Multi-Stage System Identification of a Gas Turbine

2017 ◽  
Author(s):  
Amit Pandey ◽  
Maurício de Oliveira ◽  
Chad M. Holcomb
Keyword(s):  
Gas Turbine ◽  
Closed Loop ◽  
Open Loop ◽  
Loop System ◽  
Closed Loop Control ◽  
Input Output ◽  
Open Loop System ◽  
Loop Control ◽  
Multi Stage ◽  
Identification Techniques

Several techniques have recently been proposed to identify open-loop system models from input-output data obtained while the plant is operating under closed-loop control. So called multi-stage identification techniques are particularly useful in industrial applications where obtaining input-output information in the absence of closed-loop control is often difficult. These open-loop system models can then be employed in the design of more sophisticated closed-loop controllers. This paper introduces a methodology to identify linear open-loop models of gas turbine engines using a multi-stage identification procedure. The procedure utilizes closed-loop data to identify a closed-loop sensitivity function in the first stage and extracts the open-loop plant model in the second stage. The closed-loop data can be obtained by any sufficiently informative experiment from a plant in operation or simulation. We present simulation results here. This is the logical process to follow since using experimentation is often prohibitively expensive and unpractical. Both identification stages use standard open-loop identification techniques. We then propose a series of techniques to validate the accuracy of the identified models against first principles simulations in both the time and frequency domains. Finally, the potential to use these models for control design is discussed.

Synthesis of Multivariable Controller With Plant Test Data

1994 ◽  
Vol 116 (2) ◽  
pp. 309-313 ◽  
Author(s):  
Jenq-Tzong H. Chan
Keyword(s):  
Control System ◽  
Test Data ◽  
Open Loop ◽  
Loop System ◽  
Controller Synthesis ◽  
System Model ◽  
Multivariable Control ◽  
Open Loop System ◽  
Plant Test ◽  
Multivariable Controller

A method to synthesize decoupled multivariable control system from a batch of plant test data is introduced. The method is applicable when the system has more inputs than outputs and is open-loop stable. An advantage of this method is that explicit identification of an open-loop system model is not required for controller synthesis.

Teaching particle swarm optimization through an open-loop system identification project

2011 ◽  
Vol 22 (2) ◽  
pp. 227-237 ◽  
Author(s):  
Paulo Moura Oliveira ◽  
Damir Vrančić ◽  
J. Boaventura Cunha ◽  
E. J. Solteiro Pires
Keyword(s):  
Particle Swarm Optimization ◽  
System Identification ◽  
Particle Swarm ◽  
Open Loop ◽  
Loop System ◽  
Open Loop System ◽  
Swarm Optimization

Modelling and Control of HSFDs for Active Control of Rotor-Bearing Systems

1994 ◽  
Author(s):  
A. El-Shafel ◽  
J. P. Hathout
Keyword(s):  
Active Control ◽  
Closed Loop ◽  
Transient Behavior ◽  
Pressure Control ◽  
Fast Response ◽  
Open Loop ◽  
Loop System ◽  
Squeeze Film ◽  
Open Loop System ◽  
Loop Control

This paper summarizes the development of hybrid squeeze film dampen (HSFDs) for active control of rotor vibrations. Previously, it was shown both theoretically and experimentally that HSFDs can be used for controlling rotor vibrations (El-Shafei, 1993). This is done by controlling the flow in a squeeze film damper through movable end seals, thus achieving the ability to change the damper from a short damper to a long damper and vice versa. However, the control of the HSFD was manual. In this paper, an automatically controlled circuit is developed for the HSFD, incorporating a pressure control servovalve for controlling the pressure in the scaling chambers. A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. The transient behavior of the system, including the sealing ring dynamics, illustrates that the open-loop system exhibits well behaved, stable, and fast response. In addition it is shown that the HSFD can achieve any amount of damping between the short and long damper modes through the accurate positioning of the sealing rings. The simulation results illustrate that the automatically controlled HSFD can be a very useful device for the active control of rotors. A closed loop control strategy with feedback on rotor speed is also investigated both from the points of view of steady state and transient behaviors. It is shown that this closed loop strategy results in a much improved behavior of the rotor system.

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