Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

A Human Arm’s Mechanical Impedance Tuning Method for Improving the Stability of Haptic Rendering

Robotica ◽  
2020 ◽  
pp. 1-13
Author(s):  
Xiong Lu ◽  
Beibei Qi ◽  
Hao Zhao ◽  
Junbin Sun
Keyword(s):  
Degrees Of Freedom ◽  
External Disturbance ◽  
Mechanical Impedance ◽  
System Stability ◽  
Tuning Method ◽  
Rigid Objects ◽  
Human Arm ◽  
Human Operators ◽  
And Performance ◽  
The Stability

SUMMARY Rendering of rigid objects with high stiffness while guaranteeing system stability remains a major and challenging issue in haptics. Being a part of the haptic system, the behavior of human operators, represented as the mechanical impedance of arm, has an inevitable influence on system performance. This paper first verified that the human arm impedance can unconsciously be modified through imposing background forces and resist unstable motions arising from external disturbance forces. Then, a reliable impedance tuning (IT) method for improving the stability and performance of haptic systems is proposed, which tunes human arm impedance by superimposing a position-based background force over the traditional haptic workspace. Moreover, an adaptive IT algorithm, adjusting the maximum background force based on the velocity of the human arm, is proposed to achieve a reasonable trade-off between system stability and transparency. Based on a three-degrees-of-freedom haptic device, maximum achievable stiffness and transparency grading experiments are carried out with 12 subjects, which verify the efficacy and advantage of the proposed method.

Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method

2007 ◽  
Author(s):  
S. K. Kakoty ◽  
S. K. Laha ◽  
P. Mallik
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
System Stability ◽  
Rigid Rotor ◽  
Transient Method ◽  
Porous Bearing ◽  
Nonlinear Transient ◽  
Linear And Nonlinear ◽  
The Stability

A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.

Model-Order Reduction by Simultaneous Realization of Eigenvalues and Mode Shapes (SREM)

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Fariborz Fariborzi ◽  
Ramin Bighamian ◽  
Hamid Reza Mirdamadi
Keyword(s):  
Cost Function ◽  
Degrees Of Freedom ◽  
Differential Evolution Algorithm ◽  
Order Reduction ◽  
Mode Shapes ◽  
System Response ◽  
Model Order ◽  
System Information ◽  
Distribution Vector ◽  
The Stability

In this paper, a unique technique “cost function” has been presented to simultaneously realize eigenvalues and mode shape vectors to attain a reduced model. Differential evolution algorithm has been utilized in order to numerically optimize the nonlinear cost function instead of the least squares solution of the characteristic equation of the system. The modal matrix is reduced by effective independence distribution vector (EIDV) method to remove the slave degrees of freedom and retain the master ones which have the most contribution in the system response. EIDV retains those degrees of freedom (DOFs) in such a way as to reserve the system information content, as much as possible. This procedure has been verified with some examples and good results have been obtained. It is shown that the algorithm has several advantages, e.g., the coupling between selected modes of full-order model will be attained to guarantee the stability of closed-loop system.

Vibration Analysis of Statically Indeterminate Rotors With Hydrodynamic Bearings

1998 ◽  
Vol 120 (4) ◽  
pp. 781-788 ◽  
Author(s):  
N. S. Feng ◽  
E. J. Hahn
Keyword(s):  
Vibration Analysis ◽  
Operating Conditions ◽  
System Stability ◽  
Hydrodynamic Bearings ◽  
Hydrodynamic Bearing ◽  
Unbalance Response ◽  
Tilting Pad ◽  
The Stability ◽  
Rotor Bearings ◽  
Stiffness And Damping

In statically indeterminate rotor bearings systems, where the rotor is supported by one or more hydrodynamic bearings, the reactions at each hydrodynamic bearing, and hence its stiffness and damping properties depend not only on the bearing type, the operating conditions and the bearing dimensions but also on the relative lateral alignment between the journal and the bearing housing; the alignment, therefore, has a significant influence on the system stability and unbalance response. Additional complications arise if nonsymmetric bearing types such as elliptic or tilting pad bearings are present. An iterative procedure is outlined which enables the bearing reactions to be determined at any speed, thereby enabling even large systems such as turbomachinery to be rapidly analyzed in conjunction with existing linear rotor bearing vibration analysis software. Sample numerical examples show how misalignment and bearing type can affect the natural frequencies, the stability threshold, and the unbalance response of such statically indeterminate systems.

scholarly journals Pemodelan Direct Quadrate (D-Q) Pada Kendali Kecepatan Motor Induksi Tiga Phasa dengan Field Oriented Control (FOC) Berbasis Kendali P-I

2019 ◽  
Vol 1 (2) ◽  
pp. 25
Author(s):  
Rizana Fauzi ◽  
Jumaddil Khair
Keyword(s):  
Induction Motor ◽  
Induction Motors ◽  
Reference Value ◽  
Operating Conditions ◽  
System Response ◽  
Pi Control ◽  
Field Oriented Control ◽  
Proportional Integral ◽  
Speed Regulation ◽  
The Stability

The utilization of a 3 phase induction motor is increasingly developing, so research on speed regulation in 3 phase induction motors is also increasingly widely studied. This is because the use of 3 phase induction motors in the industry and especially hybrid vehicles are increasingly being developed. But there are some disadvantages of induction motors, one of which is the characteristics of non-linear parameters, especially rotor resistance which has varying values for different operating conditions, so it cannot maintain its speed constantly if there is a change in load. This, of course, can affect the performance of an induction motor. To get a constant speed and better system performance on load changes a controller is needed. This study aims to model direct-quadrate parameters (D-Q) using the Field Oriented Control (FOC) method based on the Proportional-Integral (PI) controller. With the d-q parameter controlled, the induction motor will be more stable, because the d-q parameter determines the stability of the change in torque and flux in the induction motor. Proportional-Integral (PI) control used is a classic control system that is easy because it does not need to look for a mathematical model of the system, but it remains effective because it has a fairly stable system response, by setting the best combination of proportional (Kp) constants and Integrator constants ( Ki). In the results of the implementation, it can be seen that the use of FOC can be used as an approach in terms of setting the speed of the induction motor, and with the use of the PI control can help the output response get better with a shorter response time to reach the reference value.

Effect of the Location and the Properties of Thermostatic Expansion Valve Sensor Bulb on the Stability of a Refrigeration System

2005 ◽  
Vol 127 (1) ◽  
pp. 85-94 ◽  
Author(s):  
Veerendra Mulay ◽  
Amit Kulkarni ◽  
Dereje Agonafer ◽  
Roger Schmidt
Keyword(s):  
Low Temperature ◽  
Thermal Resistance ◽  
Time Constant ◽  
Thermophysical Properties ◽  
System Performance ◽  
System Stability ◽  
System Response ◽  
Refrigeration System ◽  
Expansion Valve ◽  
The Stability

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. The challenge has been to limit the rise in chip temperature. In the past, virtually all commercial computers were designed to operate at temperatures above the ambient. However, researchers have identified the advantages of operating electronics at low temperatures. The primary purpose of low-temperature cooling using a vapor compression system are faster switching times of semiconductor devices, increased circuit speed due to lower electrical resistance of interconnecting materials, and a reduction in thermally induced failures of devices and components. Achievable performance improvements range from 1% to 3% for every 10°C lower transistor temperature, depending on the doping characteristics of the chip. The current research focuses on IBM’s mainframe, which uses a conventional refrigeration system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Although performance has been the key driver in the use of this technology, the second major reason for designing a system with low-temperature cooling is the improvement achieved in reliability to counteract detrimental effects, which rise as technology is pushed to the extremes. A mathematical model is developed to determine the time constant for an expansion valve sensor bulb. This time constant varies with variation in the thermophysical properties of the sensor element; that is, bulb size and bulb liquid. An experimental bench is built to study the effect of variation of evaporator outlet superheat on system performance. The heat load is varied from no load to full load (1 KW) to find out the system response at various loads. Experimental investigation is also done to see how the changes in thermophysical properties of the liquid in the sensor bulb of the expansion valve affect the overall system performance. Different types of thermostatic expansion valves are tested to investigate that bulb size, bulb constant, and bulb location have significant effects on the behavior of the system. Thermal resistance between the bulb and evaporator return line can considerably affect the system stability, and by increasing the thermal resistance, the stability can be further increased.

Multibody Dynamics of a Floating Wind Turbine Considering the Flexibility Between Nacelle and Tower

2018 ◽  
Vol 18 (06) ◽  
pp. 1850085 ◽  
Author(s):  
Vahid Jahangiri ◽  
Mir Mohammad Ettefagh
Keyword(s):  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Multibody System ◽  
Equations Of Motion ◽  
System Response ◽  
Floating Wind Turbine ◽  
Conservation Of Momentum ◽  
The Stability ◽  
Nonlinear Equations Of Motion ◽  
6 Degrees Of Freedom

Stability and dynamic modeling of the floating wind turbine (FWT) is a crucial challenge in designing of the type of structures. In this paper, the tension leg platform (TLP) type FWT is modeled as a multibody system considering the flexibility between the nacelle and tower. The flexibility of the FWT is modeled as a torsional spring and damper. It has 6 degrees of freedom (DOFs) related to the large-amplitude translation and rotation of the tower and 4 DOFs related to the relative rotation between the rotor-nacelle assembly and the tower. First, the nonlinear equations of motion are derived by the theory of momentum cloud based on the conservation of momentum. Then, the equations of motion are solved and the system is simulated in MATLAB. Moreover, the effect of flexibility between the nacelle and tower is investigated via the dynamic response. The stability of the system in three different environmental conditions is studied. Finally, the spring and damping coefficients for the system response to get near to instability are determined, by which the critical region is defined. The simulation results demonstrate the importance of the flexibility between the nacelle and tower on the overall behavior of the system and its stability.

Stability of Rotating Machinery Supported on Active Magnetic Bearings Subjected to Base Excitation

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Clément Jarroux ◽  
Jarir Mahfoud ◽  
Benjamin Defoy ◽  
Thomas Alban
Keyword(s):  
Rotating Machinery ◽  
Magnetic Bearings ◽  
System Stability ◽  
Experimental Investigations ◽  
System Response ◽  
Fe Model ◽  
Active Magnetic Bearings ◽  
Strong Base ◽  
The Stability ◽  
Amb System

Abstract The stability of rotating machinery is a major challenge for the floating production storage and offloading (FPSO) units such as steam turbines or centrifugal compressors. The use of active magnetic bearings (AMBs) in turbomachines enables high operating speeds, active mechatronic system for the diagnostics, and the control and enables downsizing of the whole installation footprint. In case of strong base motions, the rotor can contact its touchdown bearings (TDBs) which are used as emergency and landing bearings. The aim of this study is to assess the stability of a rotating machine supported on AMBs during severe foundation excitation. The combined effect of unbalance forces, base motion excitation, and contact non-linearity on a rotor–AMB system response is analyzed focusing on the capacity of an augmented proportional-integral-derivative controller to maintain the system stable. An academic scale test rig was used for the experimental investigations. The controller was efficient and able to maintain the system stable during and after the application of the excitation, but the dynamic capacity of the AMBs was largely oversized with respect to the studied system. In order to check the capacity of the AMBs, when they are designed as a function of the rotor weight and expected excitation, numerical simulations were carried out (downsized). A finite element (FE) model was developed to model the on-board rotor–AMB system. Predicted and measured responses due to impulse excitation applied on the foundations were compared. The capacity of the controller to maintain the system stability is then discussed.

Design and Implementation of a Distributed Variable Impedance Actuator Using Parallel Linear Springs

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Mohammad Hasan H. Kani ◽  
Hamed Ali Yaghini Bonabi ◽  
Hamed Jalaly Bidgoly ◽  
Mohammad Javad Yazdanpanah ◽  
Majid Nili Ahmadabadi
Keyword(s):  
Degrees Of Freedom ◽  
Piecewise Linear ◽  
Angular Position ◽  
Morphological Structure ◽  
System Stability ◽  
Practical Applications ◽  
Wearable Robots ◽  
Linear Spring ◽  
The Stability ◽  
Actuator Design

This paper introduces a distributed variable impedance actuator that provides independent control of the actuator's angular position and its impedance. The idea for the actuator was inspired by the morphological structure of muscles and tendons. The system to be presented can be used as both a variable impedance actuator as well as a passive piecewise linear spring. Moreover, the actuator has an adequate number of degrees-of-freedom to approximate any nonlinear spring characteristics because of its distributed nature. Using distributed torque production subsystems with small and low power motors makes it possible to use this actuator in many applications such as prosthesis, artificial limbs, and wearable robots. The stability of the system discussed and the conditions that ensure the system stability are presented. Finally, a proof-of-concept actuator design is presented, as well as experimental results which confirm that the proposed distributed variable impedance actuator can be implemented in practical applications.

Coverage and Stability of NHx Terminated Cobalt and Ruthenium Surfaces: a First Principles Investigation

2019 ◽  
Author(s):  
Ji Liu ◽  
Michael Nolan
Keyword(s):  
Metal Surfaces ◽  
High Vacuum ◽  
Atomic Layer ◽  
Nitrogen Plasma ◽  
Operating Conditions ◽  
Ultra High Vacuum ◽  
Bridge Site ◽  
Stable Surface ◽  
Saturation Coverage ◽  
The Stability

<div>In the atomic layer deposition (ALD) of Cobalt (Co) and Ruthenium (Ru) metal using nitrogen plasma, the structure and composition of the post N-plasma NHx terminated (x = 1 or 2) metal surfaces are not well known but are important in the subsequent metal containing pulse. In this paper, we use the low-index (001) and (100) surfaces of Co and Ru as models of the metal polycrystalline thin films. The (001) surface with a hexagonal surface structure is the most stable surface and the (100) surface with a zigzag structure is the least stable surface but has high reactivity. We investigate the stability of NH and NH2 terminations on these surfaces to determine the saturation coverage of NHx on Co and Ru. NH is most stable in the hollow hcp site on (001) surface and the bridge site on the (100) surface, while NH2 prefers the bridge site on both (001) and (100) surfaces. The differential energy is calculated to find the saturation coverage of NH and NH2. We also present results on mixed NH/NH2-terminations. The results are analyzed by thermodynamics using Gibbs free energies (ΔG) to reveal temperature effects on the stability of NH and NH2 terminations. Ultra-high vacuum (UHV) and standard ALD</div><div>operating conditions are considered. Under typical ALD operating conditions we find that the most stable NHx terminated metal surfaces are 1 ML NH on Ru (001) surface (350K-550K), 5/9 ML NH on Co (001) surface (400K-650K) and a mixture of NH and NH2 on both Ru (100) and Co (100) surfaces.</div>

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