The Rocketdyne Multifunction Tester: Operation of a Radial Magnetic Bearing As an Excitation Source

1991 ◽  
Author(s):  
L. A. Hawkins ◽  
B. T. Murphy ◽  
K. W. Lang
Keyword(s):  
Frequency Response ◽  
Closed Loop ◽  
Magnetic Bearing ◽  
Open Loop ◽  
Excitation Source ◽  
Control Mode ◽  
Test Article ◽  
Wide Range ◽  
Mode Excitation ◽  
Radial Magnetic Bearing

Abstract The operation of the magnetic bearing used as an excitation source in the Rocketdyne Multifunction Tester is described. The tester began operation during the summer of 1990. The magnetic bearing can be used in two control modes: 1) open loop mode, in which the magnetic bearing operates as a force actuator, and 2) closed loop mode, in which the magnetic bearing provides shaft support. Either control mode can be used to excite the shaft; however, response of the shaft in the two control modes is different due to the alteration of the eigenvalues by closed loop mode operation. A rotordynamic model is developed to predict the frequency response of the tester due to excitation in either control mode. Closed loop mode excitation is shown to be similar to the excitation produced by a rotating eccentricity in a conventional bearing. Predicted frequency response of the tester in the two control modes is compared, and the maximum response is shown to be the same for the two control modes when synchronous unbalance loading is not considered. The analysis shows that the response of this tester is adequate for the extraction of rotordynamic stiffness, damping, and inertia coefficients over a wide range of test article stiffnesses.

scholarly journals The Modelling, Simulation and FPGA-Based Implementation for Stepper Motor Wide Range Speed Closed-Loop Drive System Design

Machines ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 56 ◽  
Author(s):  
Chiu-Keng Lai ◽  
Jhang-Shan Ciou ◽  
Chia-Che Tsai
Keyword(s):  
Embedded System ◽  
High Speed ◽  
Closed Loop ◽  
Open Loop ◽  
Drive System ◽  
Stepper Motor ◽  
Motor Drive ◽  
Digital Controllers ◽  
Loop Control ◽  
Wide Range

Owing to the benefits of programmable and parallel processing of field programmable gate arrays (FPGAs), they have been widely used for the realization of digital controllers and motor drive systems. Furthermore, they can be used to integrate several functions as an embedded system. In this paper, based on Matrix Laboratory (Matlab)/Simulink and the FPGA chip, we design and implement a stepper motor drive. Generally, motion control systems driven by a stepper motor can be in open-loop or closed-loop form, and pulse generators are used to generate a series of pulse commands, according to the desired acceleration/run/deceleration, in order to the drive system to rotate the motor. In this paper, the speed and position are designed in closed-loop control, and a vector control strategy is applied to the obtained rotor angle to regulate the phase current of the stepper motor to achieve the performance of operating it in low, medium, and high speed situations. The results of simulations and practical experiments based on the FPGA implemented control system are given to show the performances for wide range speed control.

scholarly journals Recovery of dynamics and function in spiking neural networks by closed-loop control

2015 ◽  
Author(s):  
Ioannis Vlachos ◽  
Taskin Deniz ◽  
Ad Aertsen ◽  
Arvind Kumar
Keyword(s):  
Neural Networks ◽  
Closed Loop ◽  
Brain Activity ◽  
Open Loop ◽  
Spiking Neural Networks ◽  
Delayed Feedback Control ◽  
Loop Control ◽  
Wide Range ◽  
Underlying Network ◽  
And Function

There is a growing interest in developing novel brain stimulation methods to control disease-related aberrant neural activity and to address basic neuroscience questions. Conventional methods for manipulating brain activity rely on open-loop approaches that usually lead to excessive stimulation and, crucially, do not restore the original computations performed by the network. Thus, they are often accompanied by undesired side-effects. Here, we introduce delayed feedback control (DFC), a conceptually simple but effective method, to control pathological oscillations in spiking neural networks. Using mathematical analysis and numerical simulations we show that DFC can restore a wide range of aberrant network dynamics either by suppressing or enhancing synchronous irregular activity. Importantly, DFC besides steering the system back to a healthy state, it also recovers the computations performed by the underlying network. Finally, using our theory we isolate the role of single neuron and synapse properties in determining the stability of the closed-loop system.

scholarly journals Behavioural system identification of visual flight speed control in Drosophila melanogaster

2010 ◽  
Vol 8 (55) ◽  
pp. 171-185 ◽  
Author(s):  
Nicola Rohrseitz ◽  
Steven N. Fry
Keyword(s):  
System Identification ◽  
Flight Control ◽  
Closed Loop ◽  
Speed Control ◽  
Control Model ◽  
Open Loop ◽  
Flight Speed ◽  
Level Control ◽  
Wide Range ◽  
Sensory Motor

Behavioural control in many animals involves complex mechanisms with intricate sensory-motor feedback loops. Modelling allows functional aspects to be captured without relying on a description of the underlying complex, and often unknown, mechanisms. A wide range of engineering techniques are available for modelling, but their ability to describe time-continuous processes is rarely exploited to describe sensory-motor control mechanisms in biological systems. We performed a system identification of visual flight speed control in the fruitfly Drosophila , based on an extensive dataset of open-loop responses previously measured under free flight conditions. We identified a second-order under-damped control model with just six free parameters that well describes both the transient and steady-state characteristics of the open-loop data. We then used the identified control model to predict flight speed responses after a visual perturbation under closed-loop conditions and validated the model with behavioural measurements performed in free-flying flies under the same closed-loop conditions. Our system identification of the fruitfly's flight speed response uncovers the high-level control strategy of a fundamental flight control reflex without depending on assumptions about the underlying physiological mechanisms. The results are relevant for future investigations of the underlying neuromotor processing mechanisms, as well as for the design of biomimetic robots, such as micro-air vehicles.

Calculation of Frequency Response Envelope for Dynamic Systems With Uncertain Parameters

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Wen-Hua Chen
Keyword(s):  
Frequency Response ◽  
Open Loop ◽  
Engineering System ◽  
Uncertain Parameters ◽  
Element Analysis ◽  
Control Engineering ◽  
Wide Range ◽  
Nonlinear Form ◽  
Verification Process ◽  
Frequency Domain Techniques

Frequency response finds a wide range of applications in many engineering sectors. When variations and uncertainties exist during the operation and lifetime of an engineering system, the calculation of frequency response for an uncertain dynamic system is required in order to assess the worst cases in terms of various criteria, for example gain and phase margins in control engineering, or peak magnitude at different modes in the finite element analysis of structures. This paper describes an analytical approach toward the identification of critical interior lines that possibly contribute to the boundary of the frequency response. It is allowed that uncertain parameters perturb transfer function coefficients in a nonlinear form. Conditions for critical interior lines contributing to the boundary of the frequency response are presented. An invariant property of these critical lines under open-loop and closed-loop configurations augmented by control systems or compensators is established, which greatly simplifies the analysis, design, and verification process when using frequency domain techniques. A procedure for computing frequency response and identifying the worst cases is then developed based on the combination of symbolic and numerical computation.

Active vibration control experiments on an AgustaWestland W30 helicopter airframe

2011 ◽  
Vol 226 (6) ◽  
pp. 1504-1516 ◽  
Author(s):  
J E Mottershead ◽  
M Ghandchi Tehrani ◽  
S James ◽  
P Court
Keyword(s):  
Vibration Control ◽  
Frequency Response ◽  
Closed Loop ◽  
Vibration Suppression ◽  
Active Vibration Control ◽  
Input Voltage ◽  
Open Loop ◽  
Control Technique ◽  
Response Functions ◽  
Frequency Response Functions

This article describes the practical application of a vibration control technique, developed by the authors and known as the receptance method, to the AgustaWestland W30 helicopter airframe in the vibration test house at Yeovil. The experimental work was carried out over a total of 5 days in two visits to the Yeovil site during February and March 2011. In the experiments, existing electro-hydraulic actuators were used; they were built into the airframe structure and originally designed for vibration suppression by the methodology known as active control of structural response developed at the AgustaWestland Helicopters site in Yeovil. Accelerometers were placed at a large number of points around the airframe and an initial open-loop modal test was carried out. In a subsequent test, at higher actuator input voltage, considerable non-linearity was discovered, to the extent that the ordering of certain modes had changed. The vibration modes were, in general, heavily damped. Control was implemented using measured frequency response functions obtained at the higher input level. After acquiring the necessary measurements, simulations were carried out and the controller was implemented using MATLAB/Simulink and dSPACE. The closed-loop poles were mostly assigned with small real parts so that the system would be lightly damped and sharp peaks would be clearly apparent in the measured closed-loop frequency response functions. Locations of the open- and closed-loop poles in the complex s-plane were obtained to verify that the required assignment of poles had taken place.

scholarly journals Closed-loop feedback control for microfluidic systems through automated capacitive fluid height sensing

2017 ◽  
Author(s):  
L. R. Soenksen ◽  
T. Kassis ◽  
M. Noh ◽  
L.G. Griffith ◽  
D.L. Trumper
Keyword(s):  
Feedback Control ◽  
Closed Loop ◽  
Cost Effective ◽  
Capacitive Sensor ◽  
Open Loop ◽  
Small Scale ◽  
Microfluidic Systems ◽  
Wide Range ◽  
Loop Feedback ◽  
Closed Loop Feedback

AbstractPrecise fluid height sensing in open-channel microfluidics has long been a desirable feature for a wide range of applications. However, performing accurate measurements of the fluid level in small-scale reservoirs (<1mL) has proven to be an elusive goal, especially if direct fluid-sensor contact needs to be avoided. In particular, gravity-driven systems used in several microfluidic applications to establish pressure gradients and impose flow remain open-loop and largely unmonitored due to these sensing limitations. Here we present an optimized self-shielded coplanar capacitive sensor design and automated control system to provide submillimeter fluid-height resolution (~250 μm) and control of small-scale open reservoirs without the need for direct fluid contact. Results from testing and validation of our optimized sensor and system also suggest that accurate fluid height information can be used to robustly characterize, calibrate and dynamically control a range of microfluidic systems with complex pumping mechanisms, even in cell culture conditions. Capacitive sensing technology provides a scalable and cost-effective way to enable continuous monitoring and closed-loop feedback control of fluid volumes in small-scale gravity-dominated wells in a variety of microfluidic applications.

scholarly journals Analog Integrated Current Drivers for Bioimpedance Applications: A Review

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 756 ◽  
Author(s):  
Nazanin Neshatvar ◽  
Peter Langlois ◽  
Richard Bayford ◽  
Andreas Demosthenous
Keyword(s):  
Integrated Circuit ◽  
Closed Loop ◽  
Harmonic Distortion ◽  
Open Loop ◽  
Phase Delay ◽  
Output Impedance ◽  
Wide Range ◽  
High Output Impedance ◽  
High Output

An important component in bioimpedance measurements is the current driver, which can operate over a wide range of impedance and frequency. This paper provides a review of integrated circuit analog current drivers which have been developed in the last 10 years. Important features for current drivers are high output impedance, low phase delay, and low harmonic distortion. In this paper, the analog current drivers are grouped into two categories based on open loop or closed loop designs. The characteristics of each design are identified.

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