Precision Control of Piezo Electric Actuator

芝浦工業大学201

Combined Time and Frequency Domain Approaches to the Operational Identification of Vehicle Suspension Systems

This research is an investigation into the identification of vehicle suspension systems from measured operational data. Methods of identifying unknown parameter values in dynamic models, from experimental data, are of considerable interest in practice. Much of the focus has been on the identification of mechanical systems when both force and response data are obtainable. In recent years a number of researchers have turned their focus to the identification of mechanical systems in the absence of a measured input force. This work presents a combined time and frequency domain approach to the identification of vehicle suspension parameters using operational measurements. An end– to–end approach is taken to the problem which involves a combination of focused experimental design, well established force–response testing methods and vehicle suspension experimental testing and simulation. A quarter car suspension test rig is designed and built to facilitate experimental suspension system testing. A novel shock absorber force measurement set–up is developed allowing the measurement of shock absorber force under both isolated and operational testing conditions. The quarter car rig is first disassembled and its major components identified in isolation using traditional force–response testing methods. This forms the basis for the development of an accurate nonlinear simulation of the quarter car test rig. A comprehensive understanding of the quarter car experimental test rig dynamics is obtained before operational identification is implemented. This provides a means of validating the suspension parameters obtained using operational testing methods. A new approach to the operational identification of suspension system parameters is developed. The approach is first developed under controlled simulated conditions before being applied to the operational identification of the quarter car experimental test rig. A combination of time and frequency domain methods are used to extract sprung mass, linear stiffness and nonlinear damping model parameters from the quarter car experimental test rig. Component parameters identified under operational conditions show excellent agreement with those identified under isolated laboratory conditions

On the adaptive and learning control design for systems with repetitiveness

Ph.DDOCTOR OF PHILOSOPH

Rolling Isolation Systems: Modeling, Analysis, and Assessment

<p>The rolling isolation system (RIS) studied in this dissertation functions on the principle of a rolling pendulum; an isolated object rests on a steel frame that is supported at its corners by ball-bearings that roll between shallow steel bowls, dynamically decoupling the floor motion from the response of the object. The primary focus of this dissertation is to develop predictive models that can capture experimentally-observed phenomena and to advance the state-of-the-art by proposing new isolation technologies to surmount current performance limitations. To wit, a double RIS increases the system's displacement capacity, and semi-active and passive damped RISs suppress the system's displacement response.</p><p>This dissertation illustrates the performance of various high-performance isolation strategies using experimentally-validated predictive models. Effective modeling of RISs is complicated by the nonholonomic and chaotic nature of these systems which to date has not received much attention. Motivated by this observation, the first part of this dissertation addresses the high-fidelity modeling of a single, undamped RIS, and later this theory is augmented to account for the double (or stacked) configuration and the supplemental damping via rubber-coated bowl surfaces. The system's potential energy function (i.e. conical bowl shape) and energy dissipation model are calibrated to free-response experiments. Forced-response experiments successfully validate the models by comparing measured and predicted peak displacement and acceleration responses over a range of operating conditions.</p><p>Following the experimental analyses, numerical simulations demonstrate the potential benefits of the proposed technologies. This dissertation presents a method to optimize damping force trajectories subject to constraints imposed by the physical implementation of a particular controllable damper. Potential improvements in terms of acceleration response are shown to be achievable with the semi-active RIS. Finally, extensive time-history analyses establish how the undamped and damped RISs perform when located inside biaxial, hysteretic, multi-story structures under recorded earthquake ground motions. General design recommendations, supported by critical-disturbance spectra and peak-response distributions, are prescribed so as to ensure the uninterrupted operation of vital equipment.</p>Dissertatio

Modeling and analysis of a class of linear reluctance actuators for advanced precision motion systems

Reluctance actuators (RA) are a type of electromagnetic actuator that offer high forces for short range motions. The RA takes advantage of the electromagnetic reluctance force property in air gaps between the stator core and mover parts. The mover accelerates because the stator generates the magnetic flux that produces an attractive magnetic attraction between the stator and mover. Hysteresis and other non-linearities in the magnetic flux have an impact on the force and have a nonlinear gap dependency. It is demonstrated that the RA has the capacity to produce a force that is effective and suitable for millimeter-range high-acceleration applications. One application for the RA is the short-stroke stage of photolithography machines for example. The RA is available in a wide variety of configurations, such as CCore, E-Core, Maxwell, and Plunger-type designs. The RA requires precise dynamic models and control algorithms to help linearize the RA for better control and optimization. Some nonlinear dynamics include magnetic hysteresis, flux fringing, and eddy currents. The RA is shown to have a much higher force density than any other traditional actuator, with the main disadvantage being the nonlinear and hysteretic behaviour which makes it hard to control without proper dynamic and control models in place. It is important to model the RA accurately for better control. The output force can be significantly impacted by unequal offsets or asymmetries between the mover and stator. In the thesis that follows, a review of RA systems is performed, an investigation that shows the importance of including the mean path length (MPL) term for higher accuracy, a technique for calculating the force of various asymmetrical instances for the C-core RA is demonstrated. This thesis documents currently available knowledge of the RA such as available applications, configurations, dynamic models, measurement systems, and control systems for the RA. The findings presented can allow for future control systems to be designed to counteract multi-axial asymmetric issues of the RA

Development of Magnetorheological Fluid Elastomeric Dampers for Helicopter Stability Augmentation

Conventional lag dampers use passive materials, such as elastomers, to dissipate energy and provide stiffness, but their damping and stiffness levels diminish markedly as amplitude of damper motion increases. Magnetorheological (MR) fluids based dampers have controllable damping with little or no stiffness. In order to combine the advantages of both elastomeric materials and MR fluids, semi-active magnetorheological fluid elastomeric (MRFE) lag dampers are developed in this thesis. In such a damper configuration, magnetic valves are incorporated into the chamber enclosed by elastomeric layers. Preliminary MRFE damper design analysis was conducted using quasi-steady Bingham-plastic MR flow mode analysis, and MRFE damper performance was evaluated analytically. To investigate the feasibility of using a combination of magnetorheological (MR) fluids and elastomeric materials for augmentation of lag mode damping in helicopters, a semi-active linear stroke MRFE lag damper was developed as a retrofit to an existing elastomeric helicopter lag damper. Consistent with sinusoidal loading conditions for a helicopter lag damper, single frequency (lag/rev) and dual frequency (lag/rev and 1/rev) sinusoidal loadings were applied to the MRFE damper. Complex modulus and equivalent damping were used to compare the characteristics of the MRFE damper with the passive elastomeric damper. The experimental damping characteristics of the MRFE damper were consistent with the analytical results obtained from the Bingham plastic analysis of the MR valve. Based on measurements, the Field-OFF MRFE characteristics are similar to the passive elastomeric damping, and controllable damping as a function of different flight conditions is also feasible as the applied current is varied in the MR valve. A second key objective of the present research is to develop an analytical model to describe the nonlinear behavior demonstrated by an MRFE damper. Since the damping behavior of both elastomers and MR fluids is dominated by friction mechanisms, a rate-dependent elasto-slide element is developed to describe the friction characteristics. An MR model developed from a single elasto-slide element successfully emulated the yield behavior of the MR damper, and this model captured nonlinear amplitude and frequency dependent behavior of MR dampers using constant model parameters. Meanwhile, using a distributed elasto-slide structure, an elastomeric model was developed to describe the stiffness and damping behavior of the elastomer as the amplitude of excitation increases. The fidelity of this five parameters time domain model is demonstrated by good correlation between modeling and experimental results for both the complex modulus and steady-state hysteresis cycles. Since an MRFE damper was shown to be a linear combination of the elastomeric and MR component, a time domain MRFE damper model was constructed based on the linear combination of the MR and elastomer models to describe the nonlinear behavior of the MRFE damper. Good correlation between the model and experimental data demonstrates the feasibility of the MRFE model for future MRFE damper applications