Servo-type Accelerometer Research Articles

SEISMIC DAMAGE PREDICTION OF OLD JAPANESE-STYLE WOODEN HOUSE USING PREDOMINANT PERIOD DISTRIBUTION OF GROUND SURFACE LAYER

In general, the evaluation of a site amplification effect is very important in earthquake engineering when a seismic damage to wooden house with a low seismic performance against a strong earthquake will be predicted by an accurate estimation of the seismic intensity at surface ground. In this paper, both horizontal and vertical microtremors at 51 measuring sites in the west district in Maizuru city were measured by servo type accelerometers, and also the predominant periods at 727 sites in the same area were numerically estimated from the predominant periods measured at 51 sites using the Inverse Distance Weighting method. Moreover, a seismic damage prediction of wooden house against a strong earthquake ground motion was conducted by a relationship between a seismic damage function and a maximum drift angle of wooden house.

Fiber-Bragg-Grating Based Single Axial Mode Fabry-Perot Interferometer and Its Strain and Acceleration Sensing Applications

Based on a rigorous mode theory and considering the wavelength dispersion of fiber Bragg grating (FBG), the conditions necessary for FBG-based Fabry–Perot interferometer (BFPI) to operate in single axial mode (SM) were investigated, as an extension of phase-shifted FBG, by analytical formulas and numerical simulation. Following the theoretical results, SM-BFPI of very narrow bandpass was designed and fabricated. Using that, the first of its kind to our knowledge, SM-BFPI-based WDM distributed (four-points) strain sensing was demonstrated which had a point-like ultrahigh spatial resolution of 2.1 mm and very high strain precision of ϵ . Using a specially designed acceleration pick-up and a path-imbalance Mach–Zehnder interferometer for wavelength interrogation, a fully automatic SM-BFPI accelerometer, capable of giving ultrahigh performance, was developed. The performance of the accelerometer, with a very high sensitivity of 0.5 mGal in 0.1–200 Hz for 0−±980 Gal, is superior to that of electric servo-type accelerometer. To enable the accelerometer to exactly work in the field, the interrogator was stabilized against ambient temperature changes and mechanical disturbances by means of a compensation technique, using the constant wavelength of a reference SM-BFPI. In the course of the experimental study, particular attention has been paid to performance comparison with FBG sensors, much improvement against them having been demonstrated.

ESTIMATION OF PREDOMINANT PERIOD OF GROUND SURFACE LAYER USING THE INVERSE DISTANCE WEIGHTING METHOD

The evaluation of a site amplification effect is very important in the earthquake engineering when an earthquake damage distribution of wooden house will be predicted by an accurate estimation of seismic intensity. A predominant period in the microtremor H/V spectral ratio at ground surface corresponds to the natural period of surface ground layer. The microtremor H/V spectral ratio measurement was applied to the east district in Maizuru city. Both horizontal and vertical microtremors at 75 sites in the east district in Maizuru city were measured by servo type accelerometers, and the microtremor H/V spectral ratio and its predominant period at each site were evaluated from microtremor accelerations. Also, the predominant periods at 353 sites were numerically evaluated from the predominant periods measured at 75 sites by the Inverse Distance Weighting method.

変位センサの傾斜設置に起因するアライメント誤差の抑制

In the field of semiconductor manufacturing equipments, acceleration signals from servo-type accelerometers are widely used. In order to apply direct velocity and displacement feedback (DVDFB), it is preferable to use seismo-type absolute displacement sensors which can simultaneously detect acceleration, velocity, and displacement signals. However, the displacement signal includes offset output due to alignment errors of the sensor, even if a PI compensator is utilized. This is because of mechanical and electrical factors. Specifically, the sensor has a mechanical pendulum as well as the servo-type accelerometer, and we have simply implemented electrical circuits of the PI compensator. In this paper, the offset output is modeled by considering input voltage and current offsets of operational amplifiers. In addition, leak currents and dielectric absorbers of capacitors are also considered. Using the models, the alignment errors are calculated and simulated. As a result, it is revealed that the input offset current of the operational amplifier will mainly influence to the offset output.

Extension of measurement bandwidth in an AMB-based gyroscopic sensor

A gyroscopic sensor using active magnetic bearing (AMB) is studied both theoretically and experimentally. The sensor has been proposed to realize high accuracy, compact and low-cost sensors, and it utilizes the control function of the AMB. The sensor works as a two-axis gyroscopic sensor and also as a three-axis servo-type accelerometer. Angular velocities and accelerations are measured based on the control signals for cancelling the inertial effects that act on the AMB rotor. The methods to detect the accelerations and angular velocities have been validated from several experimental results. In addition, it has been indicated that there is an upper limit in the measurement bandwidth of the sensor when the two-axis angular velocity is measured simultaneously. However, factors determining the limit have not been presented in a concrete manner. This paper discusses these factors and presents a methodology that can extend the measurement bandwidth of the sensor. The limiting factors are investigated extensively by analysis, numerical simulations and experiments with the AMB. The relationship between the measurement bandwidth and the control system is also investigated. In addition, the measurement range of the gyro is discussed.

Development of an Accelerometer for Position Estimation of a Mobile Object

In this paper, we present the performance of a novel accelerometer for the position estimation of a mobile object. The advantages of the accelerometer-based method are the easiness of installation and the wide adaptation : the accelerometer can be attached to various objects and it is possible to estimate position on uneven ground and indoors. The detector “Inductcoder” installed to our accelerometer is resistant to the noise because it provides digital data. The accelerometer in this paper is free from the friction that is created on the previous version because the new version consists of a cantilever and weight. Some experimental results show that the estimated distance using this accelerometer is more accurate than that using a capacitance-type accelerometer and is comparable to that using a servo-type accelerometer after corrections.

An Application of Active Magnetic Bearing to Gyroscopic and Inertial Sensors

A new gyroscopic sensor using active magnetic bearing (AMB) is studied both theoretically and experimentally. The proposed sensor works as a two-axis gyroscopic sensor and also as a three-axis servo-type accelerometer, which utilizes the control function of AMB. Angular velocities and accelerations are estimated from the control signals for canceling gyroscopic torque and inertial forces acting on the shaft of the AMB. In measuring two-axis angular velocity simultaneously, the control signals canceling inertial torque must be considered in addition to the gyroscopic toque for precise measurement. This paper presents the principles of two-axis angular velocity and acceleration measurement by AMB. In order to investigate the feasibility of the proposed sensor, several basic studies are carried out with a conventional-size AMB.

Position Estimation for a Mobile Robot, Using an Accelerometer with Impedance-Type Detector.

In this paper, we present a method of position estimation for a mobile robot using a novel accelerometer. Compared to other methods involving landmarks utilization, odometry and GPS, an accelerometor-based method has the following advantages: (1) it is easy to install and (2) it is possible estimate position on uneven ground and indoors. However, because slight acceleration errors cause enormous distance errors, it is difficult to estimate the position by using an accelerometer. Therefore a servo-type accelerometer that has the highest accuracy among conventional accelerometers is used for the position estimation. But the sensor is expensive and is not good at estimating the position of an object that moves slowly like a robot. One of the reasons for the latter is that the data of the sensor is analog and the sensor needs AD converter. In this study we developed a new accelerometer with the aim of an accurate and inexpensive sensor, and proposed a method for using it in position estimation. The detecting module, an Inductcoder, provides digital data. The mobile module consists of a ball and two springs that causes no drift for the fluctuation of the temperature. The performance of this device was evaluated experimentally.

Automatic measurement and control of the attitude of crane lifters: Lifter-attitude measurement and control

The spreaders and lifters on cranes are usually controlled to stop at the same time as their trolleys are stopped. Despite the use of adequate control systems, however, the lifters usually have comparatively large sway movements, due to their free suspension from the trolleys through pulleys, hooks and cables. It is therefore important to accurately measure the attitude of the lifters, in order to suppress such sways by means of secondary control. The authors have previously proposed a maintenance-free automatic measurement and control system which accurately measures the lifter’s attitude, using a servo-type accelerometer and a double-rigid-body pendulum model for the system, and completely eliminates the sway of the lifter. However, the measurement/control system takes action only after the trolleys are stopped. This paper extends the previous approach, and presents an on-line automatic measurement and control system that enables the lifters to stop at the same time as the trolleys are first stopped.

ばね系およびサーボ型加速度センサを用いた船舶ヒービングの高精度計測

ばね系およびサーボ型加速度センサを用いた船舶ヒービングの高精度計測

Automatic on-line measurement of ship's attitude by use of a servo-type accelerometer and inclinometers

For an accurate automatic on-line measurement of the ship's attitude the paper develops an intelligent sensing system which uses one servo-type accelerometer and two servo-type inclinometers which are appropriately located on the ship. By considering the dynamics of the servo-controlled rigid pendulums of the inclinometers, linear observation equations are derived on the rolling and pitching signals of the ship. Moreover, one accelerometer is utilized to extract the heaving signal. Through the introduction of linear dynamic models and the linear observation equations for the three signals, their online measurement is reduced to the state estimation of the linear dynamic systems. A bank of Kalman filters is used to execute the on-line state estimation and to overcome changes in parameters in the dynamic models with time lapse.

サーボ型傾斜計・加速度計を用いた船舶姿勢の適応型オンライン自動計測システムの開発

サーボ型傾斜計・加速度計を用いた船舶姿勢の適応型オンライン自動計測システムの開発

On-line sensing system of dynamic ship’s attitude by use of servo-type accelerometers

For an accurate automatic measurement of ship’s attitude the paper proposes an intelligent on-line sensing system which uses four servo-type accelerometers and one servo-type inclinometer appropriately located on the ship. Through an adequate location of the accelerometers, the heaving, rolling, and pitching signals of the ship are separated from each other with adequate linear combinations of the four sensors’ outputs. Furthermore, the inclinometer is utilized to extract a bias signal of the pitching. By introducing linear dynamic models and linear observation equations on the three signals, their on-line measurement is reduced to the state estimation of the linear dynamic systems. A bank of Kalman filters are used to execute the on-line state estimation and to overcome changes in parameters in the dynamic models with time.

Automatic on‐line measurement of ship's attitude by use of servo‐type inclinometers

AbstractAn accurate measurement of dynamic ship's attitude is important for not only correcting data obtained with sonars in searching seabed patterns but also controlling the attitude of a high‐quality ship. From this viewpoint, a previously developed automatic measurement system measured the heaving, rolling, and pitching of a ship by processing outputs of four servotype accelerome‐ters appropriately located on the ship. However, this measurement system required excessive computational time for data processing because it adopted both the maximum entropy method and an optimization procedure to seek the unknown heaving, rolling, and pitching parameters. To realize the on‐line measurement of the three signals, this paper proposes a new automatic measurement system using two servotype inclinometers and one accelerometer. This measurement system introduces linear dynamic models and linear observation equations on the three signals and reduces the on‐line measurement of the three signals to the state estimation of the linear dynamic systems. A bank of Kalman filters is used to execute the on‐line state estimation and to overcome changes in parameters in the dynamic models with time. Since the proposed measurement system utilizes the two servotype inclinometers and one servotype accelerometer, the measurement system will cost less than the previously proposed one.

サーボ型加速度計を用いた船舶姿勢オンライン自動計測システムの開発

サーボ型加速度計を用いた船舶姿勢オンライン自動計測システムの開発