Showing papers on "Gyroscope published in 1998"

Micromachined inertial sensors

Abstract: This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors.

Miniature six-DOF inertial system for tracking HMDs

Abstract: Current HMD applications are hampered by the limitations of head-tracking technologies now in use. Commercially available magnetic, optical, acoustic, and mechanical head- trackers suffer form various problems such as vulnerability to interference, line-of-sight restrictions, jitter, latency, small range, and high cost. This paper presents inertial-sensor-based hybrid tracking technology that was developed to combat all these problems. Two commercially available products, the IS-300 and the IS-600, are described, both based on the same miniature triaxial inertial sensor device. The IS-300 is a sourceless 3-DOF orientation tracker, using gravimetric tilt-sensing to prevent any gyroscopic drift in pitch and roll, and optical geo-magnetic compassing to prevent any gyroscopic drift in yaw. The IS-600 is a hybrid acousto-inertial 6-DOF position and orientation tracking system. It tracks changes in orientation and position by integrating the outputs of its gyros and accelerometers, and corrects drift using a room- referenced ultrasonic time-of-flight range measuring system. The is paper overviews the theory of operation of both systems, and reports bench-testing results designed to evaluate the resolution, accuracy, and latency of each system.

Feedback Control Law for Variable Speed Control Moment Gyros

Abstract: Variable speed control moment gyroscopes (CMG) are single-gimbal gyroscopes where the fly wheel speed is allowed to be variable. The equations of motion of a generic rigid body with several such variable speed CMGs attached are presented. The formulation is such that it can easily accommodate the classical cases of having either control moment gyros or reaction wheels to control the spacecraft attitude. A globally asymptotically stabilizing nonlinear feedback control law is presented. For a redundant control system, a weighted minimum norm inverse is used to determine the control vector. This approach allows the variable speed control moment gyroscopes to behave either more like classical reaction wheels or more like control moment gyroscopes, depending on the local optimal steering logic. Where classical control moment gyroscope control laws have to deal with singular gimbal angle configurations, the variable speed control moment gyroscopes are shown not to encounter any singularities for many representative examples considered. Both a gimbal angle velocity and an acceleration-based steering law are presented. Further, the use of the variable speed CMG null motion is discussed to reconfigure the gimbal angles to preferred sets. Having a variable reaction wheel speed allows for a more general redistribution of the internal momentum vector

Control of autonomous motion of two-wheel bicycle with gyroscopic stabilisation

Abstract: A bicycle with a gyroscopic stabilisation capable of autonomous motion along a straight line as well as along a curve is described. The stabilisation unit consists of two coupled gyroscopes spinning in opposite directions. It makes use of a gyroscopic torque due to the precession of gyroscopes. This torque counteracts the destabilising torque due to gravity forces. The control law of the actuator drive making the gyroscopes to process is described.

Measurement-while-drilling assembly using gyroscopic devices and methods of bias removal

Abstract: This invention provides a measurement-while-drilling (MWD) downhole assembly for use in drilling boreholes which utilizes gyroscopes, magnetometers and accelerometers for determining the borehole inclination and azimuth during the drilling of the borehole. The downhole assembly includes at least one gyroscope that is rotatably mounted in a tool housing to provide signals relating to the earth's rotation. A device in the tool can rotate the gyroscope and other sensors on the tool at any desired degree. A processor in the tool combines measurements from the sensors taken at a plurality of positions at the same depth to determine the systematic bias in the sensors before further processing. Accelerometers in the MWD tool provide gravity measurements from which the toolface and inclination are determined. The unbiased gyroscopic measurements are used in conjunction with the tool face and inclination measurements to determine the azimuth and tool face with respect to true north. Three axially spaced apart magnetometers may be used to correct for local magnetic disturbances. Additionally, when measurements are made with magnetic, accelerometer and gyroscopic measurements along three different axes, the unbiased measurements may be combined to provide an improved determination of the tool orientation.

Design and fabrication of high-performance polysilicon vibrating ring gyroscope

Abstract: This paper presents a detailed analysis on the design and scaling limits of vibrating ring gyroscopes and their implementation using a combined bulk and surface micromachining technology. A high aspect-ratio p++/polysilicon trench-refill fabrication technology has been used to realize the 30-40 /spl mu/m thick polysilicon ring structure with 0.9 /spl mu/m ring-to-electrode gap-spacing. The theoretical analysis of the ring gyroscope shows that by taking advantage of the high quality factor of polysilicon, sub-micron ring-to-electrode gap spacing, high aspect ratio polysilicon ring structure produced using deep dry-etching, and the all-silicon feature of this technology, tactical grade vibrating ring gyroscopes with random walk as small as 0.05 deg//spl radic/h can be realized, providing several orders of magnitude improvement in performance.

New designs of micromachined vibrating rate gyroscopes with decoupled oscillation modes

Abstract: This paper reports on new vibrating comb-drive rate gyroscope designs featuring decoupling of the actuation and the detection mode. Analytical calculations as well as FEM and system simulations are carried out. It is investigated how to overcome the main drawbacks of these sensors, which are especially the frequency mismatch of the two oscillation modes, the insufficient bandwidth and the effects of levitation. Concepts and simulations of electrostatically controlling both the resonance frequency and the bandwidth are presented. Within these concepts no mechanical balancing of the device is required and thus calibration costs are reduced. Simulations of a new quasi-rotating rate gyroscope show that a resolution of 0.1 ° s −1 is possible at a bandwidth of 50 Hz with 6 mm 2 sensor area only, and that the effects of levitation are actually compensated. The design has been fabricated within the Bosch Foundry process. First measurements of the angular rate show a resolution of 0.5 ° s −1 in a 50 Hz bandwidth.

Temperature insensitive silicon oscillator and precision voltage reference formed therefrom

Abstract: Micromachined, thermally insensitive silicon resonators are provided having accuracy equivalent or superior to that of quartz resonators, and are fabricated from a micromechanical, silicon-on-glass process. In one embodiment, such a resonator is realized using a tuning fork gyroscope (4). Radiation-hard precision voltage references (PVRs) are enabled using the silicon resonators. Thermal sensitivity is reduced relative to that of a silicon-on-silicon process oscillator, providing a thermal sensitivity comparable to that of a quartz oscillator. By employing a micromechanical device based upon a tuning fork gyroscope (4), resonators are made from either or both of the gyro drive and sense axes. A resonator constructed as an oscillator loop (8) whose resonant frequency is compared to a frequency standard provides a bias voltage as a reference voltage (Vref).

Hierarchical Representation and Simulation of Micromachined Inertial Sensors

Abstract: A circuit-level methodology for simulating micromachined inertial sensors based on a hierarchical representation of microelectromechanical systems (MEMS) is presented. In the NODAS methodology ( NO dal Design of Actuators and Sensors), microaccelerometers and microgyroscopes are designed as netlists of general-purpose micromechanical beams, plates, electrostatic gaps, joints, and anchors and evaluated using lumped-parameter behavioral models. The on-chip displacements and global position of each micromechanical element have been separated in the netlist, enabling application of translation and rotation of the chip while simultaneously providing access to on-chip displacements for position sensing and electrostatic actuation. Simulations of static displacements and modal frequencies of a cantilever beam, a crab-leg accelerometer, and a symmetric vibratory-rate gyroscope agree to within 2% of finite-element analysis when using the minimal number of elements. Simulation of a 16 kHz vibratory-rate gyroscope system with dual transresistance sense amplifiers illustrates the ability to perform systemlevel mixed-domain simulation.

Analysis of actuation and dynamic balancing for a single-wheel robot

Abstract: We develop a dynamic model of the steering and actuation mechanism of Gyrover, a single-wheel robot which can be considered as a single wheel, actuated through a spinning flywheel attached through a two-link manipulator at the wheel bearing and a drive motor. The spinning flywheel acts as a gyroscope to stabilize the robot, and at the same time it can achieve steering. We develop a dynamic model, investigate its motion equation, and nonholonomic constraints, and present a simulation study. The work is significant in understanding this type of dynamically stable but statically unstable system, and in developing automatic control of the system.

Laterally oscillated and force-balanced micro vibratory rate gyroscope supported by fish-hook-shaped springs

Abstract: A new concept for a micro vibratory rate gyroscope supported by fish-hook-shaped springs, where the oscillating position sensing and force balancing take place on the wafer surface, has been developed. The gyroscope consists of a grid-type planar mass, LT-shaped position-sensing electrodes to detect the Coriolis motion, pairs of force-balancing electrodes to improve the linearity and dynamic range, prominence-shaped comb-drive electrodes to improve the resolution by increasing the oscillating displacement, and fish-hook-shaped springs to match the first and second modes with the mass oscillating and position-sensing modes, respectively. Due to the relatively high stiffness of the proposed fish-hook-shaped springs except in the desired directions, the gyroscope tends to be quite insensitive to environmental vibrations or shocks, maintaining the electromechanical stability. Also the resonance frequencies associated with lateral vibration modes are independent of the change in thickness of the polysilicon structure, which guarantees a uniform sensitivity of the products. Experimental results show that the gyroscope has an equivalent noise level of 0.1 ° s −1 at 2 Hz, a bandwidth of 100 Hz, and a dynamic range of 90 ° s −1 .

Experimental evaluation of a fiber optics gyroscope for improving dead-reckoning accuracy in mobile robots

Abstract: This paper presents results from the experimental evaluation of a state-of-the-art fiber-optics gyroscope. The purpose of our experiments was to evaluate the suitability of this gyroscope for enhancing dead-reckoning in mobile robots. The evaluated gyroscope was the "Autogyro Navigator" made by Andrews. For a 4/spl times/4 m square path the dead-reckoning error when using this gyro was less than /spl plusmn/1.2/spl deg/ in orientation and about 10 cm (4 in) in position.

Using low-cost MEMS accelerometers and gyroscopes as strapdown IMUs on rolling projectiles

Abstract: Low-cost, micromachined, inertial sensors have been steadily emerging into the commercial marketplace. Some of these commercial off-the-shelf (COTS) sensors were evaluated for their insertion potential into military applications such as test and evaluation (T&E) and smart munition guidance. Performance requirements to provide time, space, position, and attitude information (TSPAI) and allow for navigation capabilities are fast approaching those needed, especially when integrated with a global positioning system (GPS) receiver. Artillery projectiles and rockets, instrumented with commercially available low-cost microelectromechanical systems (MEMS) accelerometers, spin sensors, and custom telemetry units, have been flight tested with good success. Test results suggest that many of these sensors are rugged enough for launch survivability and subsequent operation. Analysis of the accelerometer flight data shows good agreement with ground-based radar and other truth measurements. Ground tests of a MEMS gyroscope on a ballistic flight simulator have also been conducted. The results show promise for directly measuring a projectile's pitching and yawing behavior. This paper will present some of the test results and describe the challenges far using these devices as strapdown inertial measurement units (IMUs) on rolling projectiles.

Vibrators, vibratory gyroscopes, devices for measuring a linear acceleration and a method of measuring a turning angular rate

Abstract: A vibratory gyroscope for detecting a turning angular rate in a turning system is provided. The gyroscope comprises a vibrator, an exciting means for exciting driving vibration in the vibrator, and a detecting means for detecting vibration induced in the vibrator. The vibrator comprises a plurality of vibration systems (1A, 1B, 2A and 2B) which are formed within a specified plane intersecting the turning axis (Z). Vibration systems comprise first vibration systems (1A and 1B) whose vibrations include radial vibration components, in which the center of gravity of first vibration system vibrates in a radial direction in the specified plane with respect to the center of gravity (GO) of the vibrator. The vibration systems also comprise second vibration systems (2A and 2B) whose vibrations include circumferential vibration components, in which the center of gravity of vibration of the second vibration system vibrates in the specified plane along a circle with the center of gravity (GO) as its center.

Determination of zero-angular-velocity output level for angular velocity sensor

Abstract: A technique for determining a gyro zero voltage is provided. A gyroscope ("gyro") 19 is installed in an automobile as a component of an on-board navigation system. The gyro 19 outputs a voltage representing an angular velocity of the vehicle. The gyro 19 output voltage representing zero angular velocity ("gyro zero voltage") is determined by first determining when the vehicle is stationary based upon the amount of noise in the output voltage of the gyro 19. When the vehicle is determined to be stationary, the gyro zero voltage is measured.

Vibration error reduction servo for a fiber optic gyroscope

Abstract: A rectification error reducer for a fiber optic gyroscope, which is an intensity servo or compensator for reducing vibration effects in the optical signals caused by modulation at vibration frequencies induced by the gyroscope operating environment. The vibration effects may be detected in signals from the photodiode output in amplitude form which is used in a control system to null out optical intensity variations at the frequencies of vibration.

Nodal Design of Actuators and Sensors (NODAS)

Abstract: : A circuit-level methodology for simulating micromachined inertial sensors based on a hierarchical representation of microelectromechanical systems is presented. In the NODAS methodology (NOdal Design of Actuators and Sensors), various surface micromachined suspended microstructures are designed as netlists of general-purpose micromechanical beams, plates, electrostatic gaps, electrostatic comb-drives, joints, and anchors and evaluated using lumped-parameter behavioral models. NODAS provides the user with a one to one correspondence between layout and schematic, and the ability to simultaneously perform circuit level simulation on both the microelectromechanical components and the electronics in the schematic. The on-chip displacements and global position of each micromechanical component are separated in the netlist, enabling application of translation and rotation of the chip while simultaneously providing access to on-chip displacements for position sensing and electrostatic actuation. Each of the components is modeled with an Analog Hardware Description Language. Simulations of static displacements and modal frequencies of a cantilever beam, crab-leg flexure, folded-flexure resonator, capacitive accelerometer, and a vibratory-rate gyroscope are done using an ordinary differential equation solver. Simulation results agree to within 5% of finite-element analysis for displacements with small angles (less than 10 degrees). Simulation of a 16 kHz vibratory-rate gyroscope system with dual transresistance sense amplifiers, a demodulator and a filter illustrates the ability to perform system-level mixed-domain simulation with the NODAS methodology.

Modification of piezoelectric vibratory gyroscope resonator parameters by feedback control

Abstract: A method for analyzing the effect of feedback control on the dynamics of piezoelectric resonators used in vibratory gyroscopes has been developed. This method can be used to determine the feasibility of replacing the traditional mechanical balancing operations, used to adjust the resonant frequency, by displacement feedback and for determining the velocity feedback required to produce a particular bandwidth. Experiments were performed on a cylindrical resonator with discrete piezoelectric actuation and sensing elements to demonstrate the principles. Good agreement between analysis and experiment was obtained, and it was shown that this type of resonator could be balanced by displacement feedback. The analysis method presented also is applicable to micromachined piezoelectric gyroscopes.

Vehicle crash data recorder, locator and communicator

Abstract: A vehicle data recorder, utilized to record vehicle operational data, employs accelerometers to sense vehicle acceleration. To compensate for the inherent error in such accelerometers due to their undesired response to gravity, a gyroscope is employed. The gyroscope measures the identical false acceleration component, due to vehicle inclination, as that of the accelerometers. The gyroscope outputs are then subtracted from the accelerometer outputs, resulting in a true reading of vehicle acceleration, from which vehicle velocity is calculated. The vehicle data recorder also includes a communications port for connection to a computer utilized to reconstruct an abnormal vehicle operating condition. Also included is a signal transmitter for sending signals to appropriate rescue authorities and indicative of vehicle conditions such as the vehicle location, the severity of the accident and the time of the accident. A global positioning system is also utilized to allow the vehicle to determine its location on the earth's surface.

Optimal design and noise consideration of micromachined vibrating rate gyroscope with modulated integrative differential optical sensing

Abstract: A novel design of a micromachined vibrating rate gyroscope is presented. The rate gyroscope consists of a suspended proof mass which is attached by indium bumps to a CMOS chip. The proof mass is excited to vibration by electrostatic force. The displacements due to rate are sensed optically, using CMOS-integrated photodiodes and analog electronics. System considerations, including the mechanical behaviour, optical sensing, electronics, and noise sources of the rate gyroscope, are discussed. An expression for the noise equivalent rate (NER) of the system is obtained in order to derive an optimal design approach for the rate gyroscope. Optimal design and simulations of a case study of a rate gyroscope are presented. The device shows the ability of sensing 1 deg/h even at moderate quality factors of the order of 5000 and low-excitation voltages of 2.25 V.

A tunable vibratory microgyroscope

Abstract: A tunable vibratory microgyroscope has been fabricated by surface-micromachining technology. The 7.5 μm thick polysilicon structural layer is deposited using LPCVD at 625 °C. The resonance frequency in the detection mode is designed to be higher than that in the driving mode so that the gyroscope could be matched to the resonance frequencies by applying an inter-plate d.c. bias. The gyroscope is driven in a resonant state by electrostatic force and the output detected is due to a capacitance change between the plate and the polysilicon electrode. The resonance frequencies of the gyroscope in the driving and detection directions are measured to be 10.48 and 10.93 kHz, respectively. The resonance frequency in the detection direction can be shifted to 10.52 kHz by applying a tuning voltage of 4.0 V. The quality factor and resonance frequency of the detection mode are significantly affected by ambient pressure. The electrical noise equivalent rate of this device is about 0.1 ° s −1 at 10 −2 torr.

Gyroscopes and compensation

Abstract: A gyroscope system can detect the amount of movement of the system. The gyroscope system includes a circuit that has a number of different features and detects movement independent of any circuit parameters. The first feature uses a feedback loop to compensate for difference in Q factors between the circuits. Another feature regulates the amplitude of the resonator. Yet another feature extracts the rotation rate signals from the gyroscope in a new way.

A new silicon rate gyroscope

Abstract: HSG-IMIT is developing a new silicon rate gyroscope of very small size, low cost, and high performance. The device is called MARS-RR, which means micromachined angular rate sensor with two rotary oscillation modes. First prototypes, MARS-RRI yielded random walk and bias stability as low as 0.27 deg//spl radic/h and 65 deg/h, respectively. The noise equivalent rate (3 /spl sigma/) corresponds to a resolution of 0.096 deg/s in a 50 Hz bandwidth. This performance is achieved by a new sensor design featuring decoupling of the actuation and the detection oscillation modes. Because of decoupling the modes mechanical and electromechanical crosstalk, one main error source of micromachined gyros, can be reduced and therefore the zero rate output (ZRO) almost disappears. Despite the small sensor area of 6 mm/sup 2/ the detection capacitance amounts to about 3 pF. Thus subatomic deflections are detectable and a high sensitivity is achieved. MARS-RR1 was manufactured within the Bosch Foundry process and therefore it was possible for us to reduce the development time considerably.

Dual-axis microgyroscope with closed-loop detection

Abstract: A dual-axis microgyroscope is fabricated by a surface micromachining process. A 7.0 /spl mu/m-thick polysilicon layer deposited by LPCVD is used for the vibrating structure. We report the closed-loop rate detection of a microgyroscope based on the rotational vibration of the four plates. In particular, the structure utilizes a simple force-balancing torsional torque which does not need another top electrode layer to reduce the intrinsic nonlinearity of a capacitance-type sensor. The gyroscope is tested in a high vacuum chamber for a high Q-factor with hybrid signal-conditioning integrated circuit. The experiment resulted in a noise equivalent signal of 0.1 deg/sec.

Parallel beam micro sensor/actuator unit using PZT thin films and its application examples

Abstract: Piezoelectric materials are used for sensors and actuators. It is difficult to form complicated structures with piezoelectric materials, so the actuators and sensors are simple. Using the hydrothermal method, we can fabricate PZT thin film on a three dimensional titanium substrate. We use this feature for actuators and sensors, and made a new sensor/actuator unit using this method on a parallel beam structure. We propose application examples to a two degrees of freedom actuator, G-sensor, and vibration gyroscope.

Issues associated with the design, fabrication and testing of a crystalline silicon ring gyroscope with electromagnetic actuation and sensing

Abstract: The design of a single-crystal silicon ring with electromagnetic actuation and sensing, for the purpose of producing a gyroscope, is presented which takes into account the anisotropic nature of silicon. Ring structures are fabricated using a reactive ion etching process which is compatible with CMOS fabrication technology. Three methods of reducing electrical coupling between the drive and the sense are considered. The modes of vibration of the ring are measured as a function of frequency and drive amplitude and interpreted in terms of the modes of an ideal structure. Unwanted asymmetry in the ring structure resulting from the fabrication process is responsible for both a frequency mismatch and a large mechanical coupling between the principal modes of the ring and this limits the response as a gyroscope. Improvements to the fabrication of the ring are identified.

Kerr effect compensator for a fiber optic gyroscope

Abstract: An interferometric fiber optic gyroscope having compensation electronics to virtually eliminate rotation rate sensing errors caused by Kerr effect in the IFOG due to differing intensities of the counter-propagating beams relative to each other Compensation accounts for varying intensities of the beams due to all or some changes of: the light beam splitter ratio relative to temperature; fiber coil loss due to temperature and longevity; and the intensity of the light source because of age

Micromechanical devices at JPL for space exploration

Abstract: Space exploration in the coming century will emphasize cost effectiveness and highly focused mission objectives, which will result in frequent multiple missions that broaden the scope of space science and to validate new technologies on a timely basis. Micro electromechanical systems (MEMS) is one of the key enabling technologies to create cost-effective, ultra-miniaturized, robust, and functionally focused spacecraft for both robotic and human exploration programs. Examples of MEMS devices at various stages of development include microgyroscope, microseismometer, microhygrometer, quadrupole mass spectrometer, and micropropulsion engine. These devices, when proven successful, will serve as models for developing components and systems for new-millennium spacecraft.

Vibrator, vibration gyroscope, linear accelerator, and method for measuring rotary angular velocity

Abstract: PROBLEM TO BE SOLVED: To detect the angular velocity of a rotation when the rotation within a specific plane is given to a vibration being extended in a specific plane. SOLUTION: A vibration gyroscope for detecting the rotary angular velocity of a rotary system is provided with a vibrator, a means for exciting a drive vibration for the vibrator, and a means for detecting a detection vibration being generated by the vibrator due to the rotation of the vibrator. The vibrator is provided with at least a plurality of vibration systems 1A, 1B, 2A, and 2B, and a plurality of vibration systems are formed so that they are extended in a specific surface that cross a rotary shaft Z. A plurality of vibration systems are provided with first vibration systems 1A and 1B including a vibration constituent in a radial direction that vibrates in a radial direction within a specific plane with gravity GO of the vibrator as a center and second vibration systems 2A and 2B including a vibration constituent in a peripheral direction that vibrates in a circumferential direction within a specific plane when the center of the gravity of the vibration of the vibration system is the gravity GO.

Dual-atomic-beam matter-wave gyroscope

Abstract: We report improvements to our atom-interferometer based Sagnac gyroscope which uses stimulated Raman transitions to manipulate atomic wavepackets of cesium atoms. Using counter-propagating high-flux atomic beams, we form two interferometers with opposite Sagnac phase shifts that share key components such as Raman atomic state manipulation beams. Subtracting the two interferometer signals allows the common-mode rejection of spurious noise sources and various systematic effects. Preliminary results indicate a short term sensitivity of 3 X 10-9 (rad/s) (root) Hz.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.