Drive-Mode Control for Vibrational MEMS Gyroscopes

This paper presents a novel design methodology and hardware implementation for the drive-mode control of vibrational micro-electro-mechanical systems gyroscopes. Assuming that the sense mode (axis) of the gyroscope is operating under open loop, the drive-mode controller compensates an undesirable mechanical spring-coupling term between the two vibrating modes, attenuates the effect of mechanical-thermal noise, and most importantly, forces the output of the drive mode to oscillate along a desired trajectory. The stability and robustness of the control system are successfully justified through frequency-domain analysis. The tracking error between the real output and the reference signal for the drive mode is proved to be converging with the increase of the bandwidth of the controller. The controller is first simulated and then implemented using field-programmable analog array circuits on a vibrational piezoelectric beam gyroscope. The simulation and experimental results verified the effectiveness of the controller

On Control System Design for the Conventional Mode of Operation of Vibrational Gyroscopes

This paper presents a novel control circuitry design for both vibrating axes (drive and sense) of vibrational gyroscopes, and a new sensing method for time-varying rotation rates. The control design is motivated to address the challenges posed by manufacturing imperfection and environment vibrations that are particularly pronounced in microelectromechanical systems (MEMS) gyroscopes. The method of choice is active disturbance rejection control that, unlike most existing control design methods, does not depend on an accurate model of the plant. The task of control design is simplified when the internal dynamics, such as mechanical cross coupling between the drive and sense axes, and external vibrating forces are estimated and cancelled in real time. In both simulation and hardware tests on a vibrational piezoelectric beam gyroscope, the proposed controller proves to be robust against structural uncertainties; it also facilitates accurate sensing of time-varying rotation rates. The results demonstrate a simple, economic, control solution for compensating the manufacturing imperfections and improving sensing performance of the MEMS gyroscopes

On Control System Design for the Conventional Mode of Operation of Vibrational Gyroscopes

This paper presents a novel control circuitry design for both vibrating axes (drive and sense) of vibrational gyroscopes, and a new sensing method for time-varying rotation rates. The control design is motivated to address the challenges posed by manufacturing imperfection and environment vibrations that are particularly pronounced in microelectromechanical systems (MEMS) gyroscopes. The method of choice is active disturbance rejection control that, unlike most existing control design methods, does not depend on an accurate model of the plant. The task of control design is simplified when the internal dynamics, such as mechanical cross coupling between the drive and sense axes, and external vibrating forces are estimated and cancelled in real time. In both simulation and hardware tests on a vibrational piezoelectric beam gyroscope, the proposed controller proves to be robust against structural uncertainties; it also facilitates accurate sensing of time-varying rotation rates. The results demonstrate a simple, economic, control solution for compensating the manufacturing imperfections and improving sensing performance of the MEMS gyroscopes

Active Disturbance Rejection Control for MEMS Gyroscopes

A new control method is presented to drive the drive axis of a Micro-Electro-Mechanical Systems (MEMS) gyroscope to resonance and to regulate the output amplitude of the axis to a fixed level. It is based on a unique active disturbance rejection control (ADRC) strategy, which actively estimates and compensates for internal dynamic changes of the drive axis and external disturbances in real time. The stability analysis shows that both the estimation error and the tracking error of the drive axis output are bounded and that the upper bounds of the errors monotonously decrease with the increase of the controller bandwidth. The control system is simulated and tested using a field-programmable-gate-array-based digital implementation on a piezoelectric vibrational gyroscope. Both simulation and experimental results demonstrate that the proposed controller not only drives the drive axis to vibrate along the desired trajectory but also compensates for manufacture imperfections in a robust fashion that makes the performance of the gyroscope insensitive to parameter variations and noises. Such robustness, the fact that the control design does not require an accurate plant model, and the ease of implementation make the proposed solution practical and economic for industrial applications

On active disturbance rejection based control design for superconducting RF cavities

Superconducting RF (SRF) cavities are key components of modern linear particle accelerators. The National Superconducting Cyclotron Laboratory (NSCL) is building a 3 MeV/u re-accelerator (ReA3) using SRF cavities. Lightly loaded SRF cavities have very small bandwidths (high Q) making them very sensitive to mechanical perturbations whether external or self-induced. Additionally, some cavity types exhibit mechanical responses to perturbations that lead to high-order non-stationary transfer functions resulting in very complex control problems. A control system that can adapt to the changing perturbing conditions and transfer functions of these systems would be ideal. This paper describes the application of a control technique known as “Active Disturbance Rejection Control” (ARDC) to this problem

Master of Science

thesisMicroelectromechanical gyroscopes are readily used in cars and cell phones. Tactical gyroscopes are available inexpensively and they offer 0.01 to 0.1 % scale factor inaccuracy. On the other hand, strategic gyroscopes with much better performance levels are 100,000 times more expensive. The main objective of this work is to explore the possibility of developing inexpensive strategic grade gyroscopes using microelectromechanical systems technology. Most of the available gyroscopes are surface micromachined due to fabrication issues and misalignment problems involved in multistep fabrication processes necessary to use the bulk of the wafer as the proofmass in MEMS gyroscopes. It can be shown that the sensitivity of the gyroscope is inversely proportional to the natural frequency; so if bulk micromachining technique is used it is possible to decrease the natural frequency further than current limits of surface micromachining in order to increase sensitivity. This thesis is focused on proposing a way to use bulk of the silicon wafer in the gyroscope to decrease the natural frequency to very low levels, such as sub-KHz regime, that cannot be achieved by single mask surface micromachining processes. It then proposes a solution for solving the misalignment problems caused by using multiple fabrication steps and masks instead of using only one mask in surface micromachined gyroscopes. In our design discrete proofmasses are linked together around a circle by compliant structures to ensure the highest effective mass and lowest effective spring constant. By using a proposed double sided fabrication technology the effect of misalignments on frequency mismatch can be reduced. ANSYS software simulations show that 20 µm misalignment between the masks causes a frequency shift equal to 0.3% of the natural frequency that can be compensated using electrostatic frequency tuning. Acceleration parasitic effects can also be a major problem in a low natural frequency gyroscope. In our design a multiple sensing electrode configuration is used that cancels the acceleration effects completely. The sensitivity of the gyroscope with 3126 Hz natural frequency is simulated to be 574 mV/(deg/sec) , or about four times higher than 132 mV/(deg/sec) , which was used as a benchmark for a sensitive gyroscope

Mechanical response of outer frames in tuning fork gyroscope model with connecting diamond-shaped frame

In tuning fork micro-gyroscopes, two outer frames are connected by using the linking elements. The driving vibrations of the two outer frames are required to be exactly opposite to generate the opposite sensing modes perpendicular to driving direction. These opposite driving vibrations are provided by a mechanical structure named the diamond-shaped frame. This paper presents mechanical responses of two outer frames in a proposed model of tuning fork gyroscope when an external force with different types is applied to them. The results show that the presence of a diamond-shaped frame guarantees the absolute anti-phase mode for the driving vibrations of outer frames

Edge-anchored mode-matched micromachined gyroscopic disk resonator

© 2017 IEEE. This paper reports on a vacuum packaged circular disk gyroscopic resonator with T-shape anchors fabricated in a (100) single crystalline silicon substrate. This device topology simplifies the fabrication process as compared to previous approaches to realize center-anchored disk gyroscopes. Mode-matching of the trigonal modes of the disk is realized with open-loop characterization results demonstrating a Quality factor exceeding 1.5 million with an initial modal frequency split of 4.7 Hz and a natural frequency of approximately 0.976 MHz (4.81 ppm split). An approach to effective mode matching of such devices is described

MEMS Gyroscopes for Consumers and Industrial Applications

none2mixedAntonello, Riccardo; Oboe, RobertoAntonello, Riccardo; Oboe, Robert