Resonant-type smooth impact drive mechanism (RSIDM) uses the resonant vibrations of piezoelectric transducer to synthesize approximate saw-tooth wave vibration with high frequency and amplitude, which extends the driving state of piezoelectric impact motor (PIM) from quasi-static state to resonant state with great increase of power driving capability. The key and difficulty for the design of RSIDMs is to seek out two available natural vibration modes and match their resonant frequencies with desired ratio. Although the material and structural parameters can be theoretically and numerically analyzed to obtain the exact ratio of resonant frequencies, there might be a significant gap in the actual situation due to material differences and manufacturing tolerances. A flexible method for the adjustment of frequency ratio is still a critical matter that requires to be solved. This paper proposes a symmetrical structure of Langevin transducer for the RSIDM with a simple frequency match method. The first and second longitudinal vibration modes in the free condition are used to synthesize the resonant saw-tooth wave vibrations in the ends of the transducer. The resonant frequency ratio of the two vibration modes is naturally close to the desired ratio of 1:2. By replacing the materials at the nodes of the two vibration modes, equivalent stiffnesses and masses of two vibration modes are changed in the opposite direction, which lead to a considerable adjusting range of the resonant frequency ratio around 1:2. With finite element simulation, the results of frequency adjustment process is carried out and the effectiveness of frequency match method is validated.
KEYWORDS: Particle swarm optimization, Signal generators, Error analysis, Analog to digital converters, Analog electronics, Signal processing, Particles, Digital electronics, Data communications, Computer hardware
Digital sine wave generators are widely used to provide high-precision analog sine wave signals in integrated devices for detection, communication, and control systems. In the working process of digital sine wave generator, various errors of circuit components, such as DAC, amplifier, and others are difficult to avoid, due to manufacturing defects and working environment, which will lead to corresponding distortions of the actual output signals and performance degradations of the systems. To overcome the error impacts of DAC and other circuit components on the output sine signals of digital sine wave generators, a novel error analysis method is proposed and compared with the traditional methods. A model is built to simulate the offset error, gain error, and nonlinear error of DAC, which will used to generate sine wave signals with different settable errors. The error curves of sine wave signals are extracted with average algorithm from the output signals with noise. A particle swarm optimization algorithm for a sine function is used to fit the error curves and compared with the traditional least squares fitting method for the polynomial error expression. The results demonstrate that the RMSE value of the proposed error fitting method is 23.4478, and the computational time of the algorithm is 0.37 seconds. These metrics are both lower than those of the polynomial error fitting method predicated on the traditional least squares approach. The findings validate the superior performance of the proposed method in the context of error fitting for digital sine signal generators.
Compared to the large monolithic primary mirror, an array of smaller segmented primary mirror is considered as a more feasible solution for both ground and space telescopes with large aperture. Active optics is the key technology to ensure the imaging quality of a segmented mirror, in which edge sensors are used to monitor and provide feedback on the relative position information of the sub mirrors for the surface maintenance of the segmented mirror. The edge sensor needs to maintain a nanoscale measurement accuracy under conditions of large temperature span and long observation period, which is the most demanding and challenging core device in active optics technology. In this paper, a thermostatic cover is designed to remain a relatively stable working environment for the edge sensor. When the external temperature environment changes, if there is no thermostatic cover, the edge sensor working area longitudinal temperature difference changes more than 3°C, in the conditions of a thermostatic cover, the longitudinal temperature difference is not more than 0.3°C; transverse temperature difference is nearly zero. FEA model of fluid-solid heat transformation is built to simulate and analyze the thermal conducting characteristics of the system with sub mirror, the edge sensor, and thermostatic cover. Simulation results show that the thermostatic cover can effectively reduce the temperature influence of the external environment.
Pressure sensors play an important role for the monitoring of gas and liquid conditions in the field of municipal water supply, oil and gas transportation, process industrial production, and many other. Calibration is an essential process before and during the use of sensors to ensure their measurement accuracy. Although the static calibration of pressure sensor is very mature, the technology for dynamic calibration is still underdeveloped. In this paper, a liquid sinusoidal pressure generator based on a symmetrical piezoelectric vibrator is developed for the dynamic calibration of pressure sensor. The structural design and working principle of the generator are explained. Piezoelectric actuation causes a high-frequency simple harmonic vibration of the metal diaphragm, which squeeze the sealed liquid medium to generate dynamic sinusoidal pressure. Finite element models are built to investigate the vibration of symmetrical piezoelectric vibrator and the acoustic structure coupling between the solid vibrator and liquid medium. Two natural vibration modes have intense vibrations of the metal diaphragm, which might be useful for the generation of dynamic pressure. The acoustic-structure coupling analyses show that sinusoidal pressure with high amplitude is generated in the two natural vibration modes with large shifts of the initial resonant frequencies. A prototype sinusoidal pressure generator is manufactured and tested. The experimental results indicate that the generator could provide sinusoidal pressure in the range from 1500 Hz to 6500 Hz. Three peaks of sinusoidal signals with good amplitude and low distortion occur at the frequencies of 2.57 kHz, 3.67 kHz, and 5.97 kHz, respectively.
Adaptive optics is the key technology of large-aperture optical telescopes to eliminate the effects of atmospheric interference on optical imaging. In adaptive optical systems, the distortion of the optical system is detected by the wavefront sensor and corrected by the deformable mirror to improve the resolution and image quality of telescopes. The contactless thin adaptive mirror is considered as the most competitive solution for the large-aperture optical telescope, which uses voice coil motors to drive the deformable mirror and capacitive displacement sensors to measure the mirror shape for feedback control. However, capacitive displacement sensor is very expensive and sensitive to environmental contaminants, such as dust, moisture, etc. In this paper, eddy-current displacement sensor is proposed for the shape measurement of contactless thin adaptive mirror in harsh environment. The structural design and working principle of the single unit with a voice coil motor and an eddy-current displacement sensor are explained. A complete model is built for the simulation of magnetic field interference among the voice coil motor, eddy-current displacement sensor, and other components. The influence of voice coil and permanent magnet on the performances of detecting coil is analyzed. The influence of the detecting coil, conductive target, and other components on the actuation of voice coil is also estimated. The simulation results indicate that the influence of eddy-current displacement sensor on the voice coil motor is limited. But the voice coil motor has a significant influence on the eddy-current displacement sensor, for which special attention should be considered.
The treatment force and moment on the teeth play an important role in orthodontics. However, there are many difficulties to investigate the biomechanical mechanism of tooth movement in vivo. Orthodontic simulation system becomes an acceptable method to reproduce the orthodontic process and measure the mechanical parameters. In this study, an orthodontic mechanics test platform based on a six-axial force/moment sensor is developed to provide a quantitative evaluation of orthodontic forces and moments exerted by the invisible braces. First, the mechanical design and working principle of the test platform are explained. Then, the hardware design and data processing of the six-axial force/moment sensor are illuminated. The calibration of the sensor is described. Finally, the maxillary model of a central incisor with specific displacement are tested and discussed. The experimental results show that the proposed test platform can simulate the position change of the concerned tooth and reflect the magnitude change of their mechanical parameters during the orthodontic treatment. This study provides an effective technical solution for the investigation of the biomechanical mechanism of tooth movement during the orthodontic process.
Adaptive optical systems are originally developed for the field of astronomy to eliminate image blurring aberrations induced by atmospheric disturbance. In some complex applications, such as the contactless thin adaptive mirror for large-aperture ground-based optical telescopes, displacement sensors are needed to measure the deformation of the deformable mirror and construct a local position control loop. In the past adaptive secondary mirrors, capacitive sensors are designed to measure the mirror deformation. However, they suffer problems of manufacturing, maintenance, and environment. In this paper, a high-performance eddy current displacement sensor is proposed for the deformation measurement of adaptive secondary mirrors. Simulation and optimization of the detecting coil and conductive target are carried out. A deliberate signal processing circuit is designed for weak signal detection. Experimental results of the prototype sensor indicate a resolution up to 5 nm and a linearity better than 0.1% within the measuring range of 50 μm and bandwidth of 3 kHz, which meet the basic technical requirements of the adaptive optical systems.
This study presents the design and model of a XY parallel inertial drive mechanism (PIDM) based on piezoelectric bending actuators. Mechanical structure of the PIDM and its working principle are introduced. A dynamic model of the XY PIDM is established with simplification of mechanism and expansion of friction force. With extracted dynamic model parameters, numerical simulations of the XY parallel motions are implemented using software MATLAB/Simulink. Stepping responses of the single DOF motions and cooperative planar motions with various driving parameters are analyzed.
With rapid developments of micro/nano science and technology, precision platforms are widely required in the research and industry fields. This paper presents a 2-DOF parallel linear precision platform utilizing piezoelectric impact drive mechanism. With symmetrical flexible structure and specific piezoelectric driving manner, effective and decoupled actuation of the stator is achieved. FEA simulations are conducted to investigate the characteristics of the stator. With established dynamic model of the platform, motion responses of stator and slider in the two directions are simulated and analyzed. With simultaneous actuation of the 2-DOF motions, a motion interaction phenomenon is raised and discussed.
The large adaptive deformable mirrors were adapted in several large aperture telescopes and has been proved to have great effect in the AO system, however the captive sensors used in the adaptive secondary are very sensitive to the circumstance such as temperature, moisture, dust, So a new adaptive mirror scheme using the Eddy Current Sensors has been proposed in this paper. The technical plan would be discussed in this paper, a number of simulations would be carried out and some experiments result would be posed in this paper.
The segmented mirror active optics technology is one of the key technologies for the extremely large telescope, while edge sensor is one of the essential core components of active optics for the co-phasing maintenance of all segmented mirrors. The main properties of these edge sensors are of high precision of nanometers, high linearity, and low sensitivity to temperature and humidity fluctuations as well as high reliability. This paper presents an eddy current edge sensor design developed cooperatively by Nanjing Institute of Astronomical Optics and Technology and University of Science and Technology of China. The stage work performance results of eddy current sensor prototype under representative operational conditions are also presented.
This paper presents a novel impact piezoelectric linear-rotary motor which is driven by a single piezoceramic tube with two parts of electrodes. From the inner and outer electrodes, longitudinal displacement of the tube is generated and used to actuate the shaft with linear motion ability. From the grooved helical interdigitated electrodes, torsional displacement is generated and used to actuate the shaft with rotary motion ability. Working principle and structural design of the motor are introduced and quasi-static longitudinal and torsional displacements of the tube are estimated. With established kinematics model of the motor, the working behaviors of the motor are investigated numerically with MATLAB/Simulink software. The stepping characteristics of the linear and rotary motions are analyzed, compared, and discussed. With optimized material selection, structural design, and driving parameters, the proposed linear-rotary motor will provide remarkable performances as a miniaturized multi-degree driving device for complex positioning and manipulation applications.
Torsional vibrations of circular tubes, rods, rings, and disks are widely used as operation modes of acoustic wave transducers in various piezoelectric devices. In this paper, a piezoelectric disk with spiral interdigitated electrodes is proposed to generate in-plane torsion in a simple and effective manner. Design and working principle of the torsional transducer are introduced. Vibration characteristics of the transducer with a constant spiral angle are studied. A simplified model is established to investigate the basic dynamic characteristics of torsional vibration accompanying with radial vibration. Electric admittance, resonant frequencies, and mode shapes with different boundary conditions are calculated. Resonant frequencies as functions of several structural parameters are discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.