scholarly journals Spectral Analysis and Parameter Estimation in Fibre Levitated Optomechanics

2020 ◽  
Author(s):  
◽  
Christopher Dawson
Keyword(s):  
Modulation Depth ◽  
External Disturbance ◽  
Oscillation Amplitude ◽  
Harmonic Oscillators ◽  
Physical Parameters ◽  
Measured Signal ◽  
Centre Of Mass ◽  
Gaussian Random Process ◽  
Position Information ◽  
Mass Temperature

In levitated optomechanics, nano-scale objects are optically trapped so that their motion can be studied. These trapped nanoparticles are held in a 3D quadratic potential and act as damped harmonic oscillators; they are thermally and mechanically decoupled from the apparatus and their position is measured interfer-ometrically to picometre accuracy. These systems are well suited to sensing and metrology applications, as any external disturbance of the particle can be observed using the scattered trapping light.When examining the motion of a levitated nanoparticle, it’s position is recorded and used to estimate a power spectral density (PSD), from which state parameters can be estimated. In this thesis an experi-mental setup is presented, optimised for maximum collection of particle position information in 1D, using a fibre-based parabolic mirror trap and heterodyne measurement system in order to produce spectra with minimal noise and unwanted artefacts.A novel application of the Middleton expansion from RF engineering is used to generate a complete power spectrum that depends on the physical parameters of the system. This method treats the particle as a stochastic harmonic oscillator, phase modulated by a Gaussian random process with known PSD. We reproduce the PSD of intensity at a detector, a quantity that is sinusoidally dependent on particle posi-tion. This technique generates a single, full PSD using modified Bessel functions, and does not depend on assumptions about the relative phases of the interfered fields, highlighting the non-linear dependence of measured signal on position. Theoretical spectra are fitted to a measured PSD and the phase modulation depth is extracted; this is used to calculate the particle oscillation amplitude and, by an equipartition ar-gument, the centre of mass temperature to mass ratio. State parameters are tracked as environmental conditions change and an increase in centre of mass temperature as a function of decreasing background gas pressure is observed.

scholarly journals Sensorless Pedalling Torque Estimation Based on Motor Load Torque Observation for Electrically Assisted Bicycles

Actuators ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 88
Author(s):  
Riccardo Mandriota ◽  
Stefano Fabbri ◽  
Matthias Nienhaus ◽  
Emanuele Grasso
Keyword(s):  
External Disturbance ◽  
State Observer ◽  
Position Estimation ◽  
Load Torque ◽  
Estimation Errors ◽  
Position Information ◽  
Longitudinal Dynamics ◽  
Rotor Position ◽  
Electrically Assisted ◽  
Motor Load

The need for reducing the cost of and space in Electrically Assisted Bicycles (EABs) has led the research to the development of solutions able to sense the applied pedalling torque and to provide a suitable electrical assistance avoiding the installation of torque sensors. Among these approaches, this paper proposes a novel method for the estimation of the pedalling torque starting from an estimation of the motor load torque given by a Load Torque Observer (LTO) and evaluating the environmental disturbances that act on the vehicle longitudinal dynamics. Moreover, this work shows the robustness of this approach to rotor position estimation errors introduced when sensorless techniques are used to control the motor. Therefore, this method allows removing also position sensors leading to an additional cost and space reduction. After a mathematical description of the vehicle longitudinal dynamics, this work proposes a state observer capable of estimating the applied pedalling torque. The theory is validated by means of experimental results performed on a bicycle under different conditions and exploiting the Direct Flux Control (DFC) sensorless technique to obtain the rotor position information. Afterwards, the identification of the system parameters together with the tuning of the control system and of the LTO required for the validation of the proposed theory are thoroughly described. Finally, the capabilities of the state observer of estimating an applied pedalling torque and of recognizing the application of external disturbance torques to the motor is verified.

Minimization of Solar Radiation Pressure Effects for Gravity-Gradient Stabilized Satellites

1966 ◽  
Vol 88 (2) ◽  
pp. 444-450 ◽  
Author(s):  
R. J. McElvain ◽  
L. Schwartz
Keyword(s):  
Solar Radiation ◽  
Radiation Pressure ◽  
External Disturbance ◽  
Solar Radiation Pressure ◽  
Pressure Effects ◽  
Gravity Gradient ◽  
Physical Parameters ◽  
Multiple Reflections ◽  
Minimization Procedure ◽  
Vehicle Configuration

The considerations necessary for minimization of solar radiation pressure effects for gravity-gradient stabilized vehicles are presented here. Owing to the rather weak restoring forces available for gravity-gradient stabilized vehicles, solar pressure torques represent a prime source of attitude errors unless steps are taken to minimize their effects. The solar torque minimization procedure generally consists of four distinct steps for a given vehicle configuration: (a) Derivation of the solar torque expressions for the characteristic vehicle configuration, including such effects as diffuse reflection, multiple reflections, and so on; (b) identification of the relative contribution of the solar torques on the various surfaces, and facilitation of solar torque minimization by balancing torque contributions of similar time variation and opposite sign against one another; (c) minimization of the torque about the vehicle axis with the weakest restoring torque (usually the local vertical) via optimization of reflectance characteristics and other physical parameters (using a steepest descent or similar approach); and (d) determination of the vehicle attitude response for the nominal configuration and reflectances, suggesting any configurational changes which might reduce peak attitude errors if necessary. The minimization procedure is performed in this paper using the NASA / Hughes Applications Technology Satellite (ATS) as a prime example of a gravity-gradient-stabilized satellite in an environment where solar pressure is the predominant external disturbance. The application of the solar balancing techniques to the ATS configuration resulted in peak yaw torques of less than 1 dyne-cm for the synchronous altitude satellite, and corresponding peak attitude errors of less than 1 deg in all axes due to solar pressure torques. Although the torque minimization procedures presented here are applicable in the general sense, the application of the techniques to a specific configuration requires derivation of the solar torque expressions for that particular configuration; therefore, the torque minimization example for the NASA/Hughes ATS vehicle can serve as a guide for other configuration applications.

Basin of Attraction and Limit Cycle Oscillation Amplitude of an Ankle-Hip Model of Balance on a Balance Board

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Erik Chumacero-Polanco ◽  
James Yang
Keyword(s):  
Limit Cycle ◽  
Basin Of Attraction ◽  
Oscillation Amplitude ◽  
Feedback Gain ◽  
Limit Cycle Oscillation ◽  
Physical Parameters ◽  
Risk Of Falls ◽  
Cycle Oscillation ◽  
Three Degree Of Freedom ◽  
Balance Board

The study of upright posture (UP) stability is of relevance to estimating risk of falls, especially among people with neuromuscular deficits. Several studies have addressed this problem from a system dynamic approach based on parameter bifurcation analyses, which provide the region of stability (RoS) and the delimiting bifurcation curves (usually Hopf and pitchfork) in some parameter-spaces. In contrast, our goal is to determine the effect of parameter changes on the size of the basin of attraction (BoA) of the UP equilibrium and the amplitude of the limit cycle oscillations (LCOs) emerging from the Hopf bifurcations (HBs). The BoA is an indicator of the ability of the UP to maintain balance without falling, while LCOs may explain the sway motion commonly observed during balancing. In this study, a three degree-of-freedom model for a human balancing on a balance board (BB) was developed. Analysis of the model revealed the BoAs and the amplitude of the LCOs. Results show that physical parameters (time-delays and feedback control gains) have a large impact on the size of the BoA and the amplitude of the LCOs. Particularly, the size of the BoA increases when balancing on a rigid surface and decreases when either proprioceptive or combined visual and vestibular (V&V) feedback gain is too high. With respect to the LCOs, it is shown that they emerge from both the subcritical and supercritical HBs and increase their amplitudes as some parameters vary.

scholarly journals Leader-Following Multiple Unmanned Underwater Vehicles Consensus Control under the Fixed and Switching Topologies with Unmeasurable Disturbances

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-26
Author(s):  
Zheping Yan ◽  
Yi Wu ◽  
Yibo Liu ◽  
Hongliang Ren ◽  
Xue Du
Keyword(s):  
Feedback Linearization ◽  
External Disturbance ◽  
Underwater Vehicles ◽  
Consensus Control ◽  
Position Information ◽  
State Information ◽  
Unmanned Underwater Vehicles ◽  
Switching Topologies ◽  
Leader Following ◽  
Time Invariant

We propose a consensus control strategy for multiple unmanned underwater vehicles (multi-UUVs) with unmeasurable disturbances under the fixed and switching topologies. The current methods presented in the literature mainly solve tracking consensus problems with the disturbances under the time-invariant and time-varying topologies, respectively. In the paper, considering the complex nonlinear and couple model of the UUV, the technique of the feedback linearization is employed to transform the nonlinear UUV model into a second-order integral UUV model. For unmeasurable disturbances consisting of unknown model uncertainties and external disturbance for each UUV, we design the distributed extended state observer (DESO) to estimate the disturbances using the UUV position information relative to its neighbours. Moreover, leader-following multi-UUVs consensus control algorithm that enables all following UUVs to track the leader UUV state information based on the estimation state information from the DESO is proposed for two types of topologies, the fixed and switching topologies. Finally, simulation results are shown to demonstrate the effectiveness of the algorithm proposed in the paper.

scholarly journals Problems of using active-recuperative suspension and ways to solve them

2020 ◽  
Vol 1 (3) ◽  
pp. 14-22
Author(s):  
V.M. Zamyslov ◽  
◽  
A.E. Yesakov ◽  
Keyword(s):  
Deformation Rate ◽  
External Disturbance ◽  
Oscillation Amplitude ◽  
Oscillatory System ◽  
Correct Selection ◽  
Storage Device ◽  
System Operation ◽  
Active Mode ◽  
Additional Information ◽  
Increased Risk

The aim of the work is to reveal the unobvious disadvantages of active-recuperative suspension, as well as to identify possible options for dealing with them. Such problems are the danger of sus-pension breakdown in the active mode, the impossibility of operating in the regenerative mode when the suspension deformation rate is below the threshold, and the system operation in swing mode. The novelty of the work lies in the fact that these aspects of the functioning of the active-recuperative suspension system were not previously considered. The problem of the increased risk of suspension breakdown is that in the active mode, the deformation of the elastic device occurs not only due to the work of external disturbance (road irregularities), but also due to the work per-formed by the actuator. The following solutions are offered: correct selection of system parameters; collection of additional information about the roughness profile; introduction of preventive measures into the control algorithm. The problem of the impossibility of operating in a regenerative mode at a suspension deformation rate below the threshold is that the electromotive force of induc-tion on the rotor winding at low speeds may be lower than the threshold charging voltage at the terminals of the energy storage device. The following solutions are offered: dry friction in the sus-pension; introduction of a shock absorber with a pronounced degressive characteristic into the sus-pension structure; lowering the charging threshold voltage by separating the supply and charging circuits using a voltage converter; introduction of a “scattering chain” into the armature chain; op-timal control of the excitation circuit. The problem of the system operation in the swing mode is that, under certain conditions, energy is supplied to the oscillatory system through the actuator, re-sulting in a gradual increase in the oscillation amplitude. The following solutions are proposed: the introduction of an additional damper or regenerative connection on the deformation rate of the sus-pension.

Fault diagnosis of rolling element bearing using autonomous harmonic product spectrum method

2021 ◽  
pp. 146441932199498
Author(s):  
AP Patil ◽  
BK Mishra ◽  
SP Harsha
Keyword(s):  
Fault Diagnosis ◽  
Condition Monitoring ◽  
Rolling Element Bearing ◽  
Physical Parameters ◽  
Measured Signal ◽  
Maintenance Planning ◽  
Filtering Method ◽  
Product Spectrum ◽  
Rolling Element ◽  
Element Bearing

Maintenance planning plays a critical role in the process industry, where any unplanned maintenance may lead to a significant loss. Condition monitoring happens to aid maintenance planning and has become an inherent part of the maintenance activity. Physical parameters such as vibration, acoustic emission, current, etc., are used for condition monitoring, out of which vibration is the most preferred parameter and is widely used in the industry. Vibration data is measured near to bearings, which themselves are monitored for their condition, and hence rolling element bearing (REB) is the focus of this study. REBs are monitored for the presence of a fault in them as well as for their severity. Fault diagnosis of REB using harmonic product spectrum (HPS) is proposed in this study. The proposed methodology's novelty lies in the signal pre-processing step, whose output is fed to the HPS method, which is used for defective raceway identification. The efficacy of HPS is assessed with parameter optimized Variational mode decomposition (VMD) and classical bandpass filtering method as pre-processors. It is observed that the HPS delivers better diagnostic results with the VMD method than the bandpass filtering method. Non-dominated sorting particle swarm optimization algorithm is deployed for parameter optimization of VMD. HPS combined with VMD as pre-processor forms an autonomous HPS(AHPS) algorithm, whose input is measured signal and output is defect frequency. The process is so designed that a raw signal, when fed to the algorithm, delivers the result as identification of a defective raceway. Unlike previously developed methods, the proposed method needs no manual intervention. Results obtained from simulated signals and signals recorded through experiments validate that the proposed methodology can be used effectively for fault diagnosis of REB.

scholarly journals Unsteady Oscillatory Flow and Heat Transfer in a Horizontal Composite Porous Medium Channel

2009 ◽  
Vol 14 (3) ◽  
pp. 397-415 ◽  
Author(s):  
J. C. Umavathi ◽  
A. J. Chamkha ◽  
A. Mateen ◽  
A. Al-Mudhaf
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Oscillatory Flow ◽  
Oscillation Amplitude ◽  
Temperature Fields ◽  
Thermal Conductivity Ratio ◽  
Physical Parameters ◽  
Conductivity Ratio ◽  
Medium Parameter ◽  
Flow And Heat Transfer

The problem of unsteady oscillatory flow and heat transfer in a horizontal composite porous medium is performed. The flow is modeled using the Darcy-Brinkman equation. The viscous and Darcian dissipation terms are also included in the energy equation. The partial differential equations governing the flow and heat transfer are solved analytically using two-term harmonic and non-harmonic functions in both regions of the channel. Effect of the physical parameters such as the porous medium parameter, ratio of viscosity, oscillation amplitude, conductivity ratio, Prandtl number and the Eckert number on the velocity and/or temperature fields are shown graphically. It is observed that both the velocity and temperature fields in the channel decrease as either of the porous medium parameter or the viscosity ratio increases while they increase with increases in the oscillation amplitude. Also, increasing the thermal conductivity ratio is found to suppress the temperature in both regions of the channel. The effects of the Prandtl and Eckert numbers are found to decrease the thermal state in the channel as well.

scholarly journals Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue

2019 ◽  
Vol 622 ◽  
pp. A114 ◽  
Author(s):  
K. G. Hełminiak ◽  
A. Tokovinin ◽  
E. Niemczura ◽  
R. Pawłaszek ◽  
K. Yanagisawa ◽  
...  
Keyword(s):  
Ir Spectra ◽  
Main Sequence ◽  
Eclipsing Binaries ◽  
Spectroscopic Binaries ◽  
Physical Parameters ◽  
Centre Of Mass ◽  
Velocity Measurements ◽  
Spectroscopic Binary ◽  
Quadruple System ◽  
First Time

Aims. We present results of the combined photometric and spectroscopic analysis of three detached eclipsing binaries, the secondary components of which are not visible or are very hard to identify in the optical spectra – ASAS J052743–0359.7, ASAS J065134–2211.5, and ASAS J073507–0905.7. The first one is the known visual binary ADS 4022, and we found that it is a quadruple system composed of two spectroscopic binaries, one of which shows eclipses. None of the systems have previously been recognized as a spectroscopic binary. Methods. We used the following telescopes/spectrographs to collect a number of high-resolution optical and IR spectra: Subaru/IRCS, CTIO-1.5 m/CHIRON, Euler/CORALIE, MPG-2.2 m/FEROS, OAO-188/HIDES, and TNG/HARPS-N. We used these data to calculate radial velocities (RVs) and later combined them with MITSuME and ASAS photometry. The Subaru/IRCS IR spectra were crucial for secure identification of the lines of the cooler components. Radial velocity measurements were made with the TODCOR technique, and RV curves were modelled with our own procedure V2FIT. Light-curve modelling was performed with JKTEBOP and PHOEBE codes. Temperatures and metallicities of two systems were estimated from spectra. For the ADS 4022 system we also used the archival WDS data and new SOAR observations in order to derive the orbit of the visual pair for the first time. Ages were estimated by comparing our results with PARSEC isochrones. Results. The eclipsing pair ASAS J052743–0359.7 A (P = 5.27 d) is composed of a 1.03(6) M⊙, 1.03(2) R⊙ primary and a 0.60(2) M⊙, 0.59(2) R⊙ secondary. The components of the P = 21.57 d non-eclipsing pair B likely have masses in between the two eclipsing components, and both pairs are on a ∼188 yr orbit around their common centre of mass. The system ASAS J065134-2211.5 (P = 8.22 d) consists of a 0.956(12) M⊙, 0.997(4) R⊙ primary and a 0.674(5) M⊙, 0.690(7) R⊙ secondary. Finally, ASAS J073507-0905.7 (P = 1.45 d), which consists of a 1.452(34) M⊙, 1.635(12) R⊙ primary and a 0.808(13) M⊙, 0.819(11) R⊙ secondary, is likely a pre-main sequence system. In all cases secondary eclipses are total.

scholarly journals Adaptive Sliding Mode Control of MEMS AC Voltage Reference Source

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Ehsan Ranjbar ◽  
Ali Mehrnezhad ◽  
Amir Abolfazl Suratgar
Keyword(s):  
State Feedback ◽  
Sliding Mode ◽  
External Disturbance ◽  
Adaptive Controller ◽  
Pole Placement ◽  
Reference Source ◽  
Physical Parameters ◽  
Voltage Reference ◽  
Adaptive Sliding Mode ◽  
Adaptive Sliding Mode Controller

The accuracy of physical parameters of a tunable MEMS capacitor, as the major part of MEMS AC voltage reference, is of great importance to achieve an accurate output voltage free of the malfunctioning noise and disturbance. Even though strenuous endeavors are made to fabricate MEMS tunable capacitors with desiderated accurate physical characteristics and ameliorate exactness of physical parameters’ values, parametric uncertainties ineluctably emerge in fabrication process attributable to imperfections in micromachining process. First off, this paper considers applying an adaptive sliding mode controller design in the MEMS AC voltage reference source so that it is capable of giving off a well-regulated output voltage in defiance of jumbling parametric uncertainties in the plant dynamics and also aggravating external disturbance imposed on the system. Secondly, it puts an investigatory comparison with the designed model reference adaptive controller and the pole-placement state feedback one into one’s prospective. Not only does the tuned adaptive sliding mode controller show remarkable robustness against slow parameter variation and external disturbance being compared to the pole-placement state feedback one, but also it immensely gets robust against the external disturbance in comparison with the conventional adaptive controller. The simulation results are promising.

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