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Dual parallel motion systems are mechanisms that drive load jointly by dual parallel motion axes. For these special mechanisms, diminishing desynchronization between parallel axes is essential to harness the potential performance of the whole system. However, a wide variety of synchronization applications tend to have great differences in control objectives and mechanical structures, which makes it laborious and time-consuming to design customized control schemes. Meanwhile, existing generalized synchronous control schemes are simply based on state compensation, which finitely offset mechanical coupling effect and limit the synchronization performance. To overcome these drawbacks, a generalized model of dual parallel motion systems is presented in this article, which can categorize the synchronous control objective into one uniform expression. By applying motion decoupling strategy to the generalized model, an advanced composite synchronous control scheme is proposed, which provides a generalized synchronization solution with comprehensively considering the motion coupling effect. Finally, simulation and experimental results on a dual-driven gantry platform verify that the proposed control scheme can significantly improve the synchronization performance. [ABSTRACT FROM AUTHOR]

In this work, we experimentally investigate the dynamics of pairs of opto-thermally driven, mechanically coupled, doubly clamped, silicon micromechanical oscillators, and numerically investigate the dynamics of the corresponding lumped-parameter model. Coupled limit cycle oscillators exhibit striking nonlinear dynamics and bifurcations in response to variations in system parameters. We show that the input laser power influences the frequency detuning between two non-identical oscillators. As the laser power is varied, different regimes of oscillations such as the synchronized state, the drift state, and the quasi-periodic state are mapped at minimal and high coupling strengths. For non-identical oscillators, coexistence of two states, the synchronized state and the quasi-periodic state, is demonstrated at high coupling and high laser power. Experimentally, this bistability manifests as irregular oscillations as the system rapidly switches between the two states due to the system’s sensitive dependence on initial conditions in the presence of noise. We provide a qualitative comparison of the experimental and numerical results to elucidate the behavior of the system. [2022-0005] [ABSTRACT FROM AUTHOR]

Vibration and acoustic noise in switched reluctance motor (SRM) drives have been investigated and addressed frequently. However, the focus of most the paper is on vibration of the stator frame due to radial electromagnetic forces acting on the stator teeth. In this paper, a comprehensive vibration analysis for a SRM assembly using finite element (FE) method is conducted, which considers the stator and rotor vibrations due to radial electromagnetic force as well as the effect of mechanical coupling on the vibration between the stator and rotor. First, an experimental modal test was performed to extract modal parameters and to observe the coupling effect. The parameters were then used to adjust and validate the FE model that was used to obtain transfer functions for vibration characterization. Using the frequency domain representation of the radial magnetic force vector and the calculated transfer functions, radial and tangential vibration components have been predicted. [ABSTRACT FROM AUTHOR]

Dual-linear-motor-driven gantry systems have been widely used in high-speed or heavy payload precision motion systems. Due to the unique physical properties such as mechanical coupling, the precise synchronization control of such kinds of systems is crucial to achieve good tracking and smooth operation performance. However, the existing synchronization schemes usually focus on the pure motion synchronization only and, thus, have certain inherent performance limitations. In this paper, an accurate multi-input multi-output mathematical model of a dual-driven gantry is presented first, where the complete planar motions of the crossbeam include the traditional linear motion along the guide rails and the previously ignored rotational motion around the mass center. With the better understanding of the mechanical coupling and the internal forces caused by the rotational dynamics, an advanced synchronization control scheme by directly taking into account the additive rotational dynamics is presented, which not only synchronizes the motions of two parallel motors but also regulates the internal forces. In the proposed scheme, the adaptive robust control algorithm is also applied to obtain a guaranteed robust performance in the presence of both parametric uncertainties and uncertain nonlinearities. Comparative experiments with previous control schemes are carried out to show the better synchronization performance and verify the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Amplifying the signal-to-noise ratio of resonant sensors is vital toward the effort to miniaturize devices into the sub-micro and nano regimes. In this paper, we demonstrate theoretically and experimentally, amplification through mechanically coupled microbeams. The device is composed of two identical clamped-clamped beams, made of polyimide, connected at their middle through a third beam, which acts as a mechanical coupler. Each of the clamped–clamped microbeams and the coupler are designed to be actuated separately, hence providing various possibilities of actuation and sensing. The coupled resonator is driven into resonance near its first resonance mode and its dynamic behavior is explored via frequency sweeps. The results show significant amplification in the resonator amplitude when the signal is measured at the midpoint of the coupler compared with the response of the individual uncoupled beams. The static pull-in characteristics of the resonator are also studied. It is shown that the compliant mechanical coupler can serve as a low-power radio frequency switch actuated at low voltage loads. [2016-0100] [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of the impact of process-induced variations on the achievable motional resistance Rx of 1-D, 2-D, cyclic, and cross-coupled architectures of weakly coupled electrostatically transduced microelectromechanical resonators operating in the 250-kHz range. We use modal analysis to find the Rx of such coupled arrays and express it as a function of the eigenvectors of the specific mode of vibration. Monte Carlo numerical simulations, which accounted for up to 0.75% variation in critical resonator feature sizes, were initiated for different array sizes and coupling strengths for the four distinct coupling architectures. Improvements in the mean and standard deviation of the generated Rx distributions are reported when the resonators are implemented in a cross-coupled scheme, as opposed to the traditional 1-D chain. The 2-D coupling scheme proves to be a practical and scalable alternative to weakly coupled 1-D chains to improve the immunity to process variations. It is shown that a 75% reduction in both the mean and standard deviation of the Rx is achieved, as compared with the traditional 1-D chain for a normalized internal coupling \kappa >10^-2 . [2014-0217] [ABSTRACT FROM PUBLISHER]

This paper presents the first results from mechanically coupling multiple resonators in an array in silicon-on-insulator while also employing piezoresistive sensing. By careful design of the couplers, the resonators in the array are synchronized to all resonate in phase and also at the same frequency. By collectively summing the currents from each of the resonators in the array, the net output current is thereby increased. By using piezoresistive sensing, the benefit of arraying is further improved by exploiting the higher electromechanical conversion gain provided by the piezoresistive effect. Further to this enhancement in transduction, our results also show that Q was increased with the coupling. A synchronized array of up to three extensional mode square-plate resonators is demonstrated here, although the concept can be further extended to larger size arrays. We have also formulated a semi-analytical model (with the aid of finite-element analysis) to describe the electromechanical transfer function of the device. Close agreement between our measurements and the model confirms that the observed enhancements afforded by arraying are within theoretical expectations. [ABSTRACT FROM PUBLISHER]

This paper proposes an electromechanically actuated single-pole multithrow RF switch utilizing an axial force coupling mechanism among switching membranes. All switches are evenly distributed and coupled to each other with a pair of microbeams. When one membrane is switching on, the others become stiffer than before by the increased axial force. This enables the individual switch to achieve low switching-on voltage and high power handling capability at an off state simultaneously. The analytic estimation presents a 36% reduced stiffness at switching- on and a 34% increased stiffness in sustaining an off state. The topologies for both of the single pole double throws (SPDT) and single pole triple throws (SP3T) using this technique are designed and implemented. Actuation voltages are as low as 15 V for an SPDT and 20 V for an SP3T. The insertion loss and isolation among throws of the SP3T are measured to be 0.25 and 51.5 dB at 2 GHz, respectively. Significant improvement of isolation (from 37 to 45.7 dB) in the high-frequency band (at 10 GHz) proves the benefit of the proposed concept. Typical switching time of the SP3T is measured to be 7.4 \mu\s for on switching and 3.5 \mu\s for off switching at 20 V. The number of switching cycles has reached \1 \times \10^7 cycles. [ABSTRACT FROM PUBLISHER]

A comb-actuated torsional microscanner is developed for high-resolution laser-scanning display systems. Typical torsional comb-drive scanners have fingers placed around the perimeter of the scanning mirror. In contrast, the structure in this paper uses cascaded frames, where the comb fingers are placed on an outer drive frame, and the motion is transferred to the inner mirror frame with a mechanical gain. The structure works only in resonant mode without requiring any offset in the comb fingers, keeping the silicon-on-insulator-based process quite simple. The design intent is to improve actuator efficiency by removing the high-drag fingers from the high-velocity scanning mirror. Placing them on the lower velocity drive frame reduces their contribution to the damping torque. Furthermore, placement on the drive frame allows an increase of the number of fingers and their capacity to impart torque. The microscanner exhibits a parametric response, and as such, the maximum deflection is found when actuated at twice its natural frequency. Analytical formulas are given for the coupled-mode equations and frame deflections. A simple formula is derived for the mechanical-gain factor. For a 1-mm x 1.5-mm oblong scanning mirror, a 76° total optical scan angle is achieved at 21.8 kHz with 196-V peak-to-peak excitation voltages. [ABSTRACT FROM AUTHOR]

The lateral actuated switch requires an isolation structure to provide mechanical coupling and electrical isolation between the actuator and the contacts. This isolation structure usually imposes extra difficulty on the fabrication process. In previous reports, we demonstrated a thermal actuated lateral switch, where the nitride isolation structure was a weak point, leading to reliability problems. In this paper, we developed a modified switch utilizing undoped polysilicon as the isolation material. The undoped-polysilicon isolation structure requires only one extra step of sheltered implantation, and it provides robust mechanical connection. A 20-μm-long undoped-polysilicon isolation structure has a current leakage of less than 2 nA under a 15-V operation voltage. The proposed switch works under a 12-V driving voltage with 60-mW input power. The time response is measured to be 130 μs, and a maximum operation frequency of 4.5 kHz is reached. An ON-state insertion loss of -0.41 dB at 20 GHz and an OFF-state isolation of -20 dB at 20 GHz have been achieved on the normal low-resistivity silicon substrate. The undoped-polysilicon isolation method can be used in other surface-micromachined lateral switches as well. [ABSTRACT FROM AUTHOR]

Substantial reductions in vibrating micromechanical resonator series motional resistance Rx have been attained by mechanically coupling and exciting a parallel array of corner-coupled polysilicon square plate resonators. Using this technique with seven resonators, an effective Rx of 480 Ω has been attained at 70 MHz, which is more than 5.9X smaller than the 2.82 kΩ exhibited by a stand-alone transverse-mode corner-supported square resonator, and all this achieved while still maintaining an effective Q > 9000. This method for Rx-reduction is superior to methods based on brute force scaling of electrode-to-resonator gaps or dc-bias increases, because it allows a reduction in Rx without sacrificing linearity, and thereby breaks the Rx versus dynamic range tradeoff often seen when scaling. This paper also compares two types of anchoring schemes for transverse-mode square micromechanical resonators and models the effect of support beam parameters on resonance frequency. [ABSTRACT FROM AUTHOR]

There is an active interest in the development of microelectromechanical systems (MEMS) devices using single crystal silicon. Single crystal silicon is known to display anisotropic mechanical properties and several papers have been presented that deal explicitly with various aspects arising from the anisotropy. In this paper we develop comprehensive expressions and graphs to allow for the easy determination of anisotropic coupling effects in beam and plate structures with a particular emphasis upon (100) and (111) wafers. Further, through the use of illustrative examples, we highlight practical issues in modeling single crystal MEMS devices with special attention to the ability of beam and plate models to accurately capture three-dimensional (3-D) behavior. [ABSTRACT FROM AUTHOR]

The use of chip-scale packages (CSPs) has expanded rapidly, particularly in portable electronic products. Many CSP designs will meet the thermal cycle or thermal shock requirements for these applications. However, mechanical shock (drop) and bending requirements often necessitate the use of underfills to increase the mechanical strength of the CSP-to-board connection. Capillary flow underfills processed after reflow provide the most common solution to improving mechanical reliability. However, capillary underfill dispense, flow, and cure steps and the associated equipment add cost and complexity to the assembly process. Corner bonding provides an alternate approach. Dots of underfill are dispensed at the four corners of the CSP site after solder paste print but before CSP placement. During reflow, the underfill cures, providing mechanical coupling between the CSP and the board at the corners of the CSP. Since only small areas of underfill are used, board dehydration is not required. This paper examines the manufacturing process for corner bonding including dispense volume, CSP placement, and reflow. Drop test results are then presented. A conventional, capillary process was used for comparison of drop test results. Test results with corner bonding were intermediate between complete capillary underfill and nonunderfilled CSPs. Finite-element modeling results for the drop test are also included. [ABSTRACT FROM PUBLISHER]

We introduce a backside island isolation method for silicon-on-insulator (SOI)-based microelectromechanical systems technology and demonstrate vertical comb drive-based two-dimensional gimbaled micromirrors with large static rotation using the isolation method. The proposed isolation method provides electrical isolation and mechanical coupling of SOI structures without additional dielectric backfill and planarization by utilizing timed etched backside handle wafer structures. The backside island is a hidden layer beneath the gimbal and allows independent application of actuation potentials to the gimbal and inner mirror. We developed the fabrication process that accommodates the backside island isolation structures into an established vertical comb drive process, thereby allowing implementation of two-axis gimbaled structures. The maximum static optical deflections of the gimbal and mirror are 46° and 15°, respectively. [ABSTRACT FROM PUBLISHER]