Transactions of Nanjing University of Aeronautics & Astronautics
Volume 32,Issue 2,2015 Table of Contents
2015, 32(2):137-142.
DOI: 10.16356/j.1005-1120.2015.02.137
Abstract:
The existing resonant linear piezoelectric motors must operate with high working voltage in resonant condition, resulting in their narrow operating frequency range and poor running stability. Here, with the large displacement output characteristics of piezoelectric stacks, the trajectory at the drive foot of stator is firstly produced with two space quadrature piezoelectric actuators excited by sawtooth wave and square wave. Secondly, the friction drive principle of motor is used to analyze the working mechanisms of the continuous stepping motion. Finally, the motor prototype is designed and experiments are carried out. The experimental result shows that the motor can stably operate within the scope of 350 Hz to 750 Hz. When the excitation voltage is 30 V and pre-load is 3 N or 10 N, the lateral amplitude of the drive foot is approximately 4 μm and the stable average interval ranges from 3.1 μm to 3.2 μm with the error rate of 5%-7.5%.
The existing resonant linear piezoelectric motors must operate with high working voltage in resonant condition, resulting in their narrow operating frequency range and poor running stability. Here, with the large displacement output characteristics of piezoelectric stacks, the trajectory at the drive foot of stator is firstly produced with two space quadrature piezoelectric actuators excited by sawtooth wave and square wave. Secondly, the friction drive principle of motor is used to analyze the working mechanisms of the continuous stepping motion. Finally, the motor prototype is designed and experiments are carried out. The experimental result shows that the motor can stably operate within the scope of 350 Hz to 750 Hz. When the excitation voltage is 30 V and pre-load is 3 N or 10 N, the lateral amplitude of the drive foot is approximately 4 μm and the stable average interval ranges from 3.1 μm to 3.2 μm with the error rate of 5%-7.5%.
2015, 32(2):143-147.
DOI: 10.16356/j.1005-1120.2015.02.143
Abstract:
Dielectrophoresis impedance measurement (DEPIM) is a powerful tool for bioparticle detection due to its advantages of high efficiency, label-free and low costs. However, the strong electric field may decrease the viability of the bioparticle, thus leading to instability of impedance measurement. A new design of biochip is presented with high stable bioparticle detection capabilities by using both negative dielectrophoresis (nDEP) and traveling wave dielectrophoresis (twDEP). In the biochip, a spiral electrode is arranged on the top of channel, while a detector is arranged on the bottom of the channel. The influence factors on the DEP force and twDEP force are investigated by using the basic principle of DEP, based on which, the relationship between Clausius-Mossotti (CM) factor and the frequency of electric field is obtained. The two-dimensional model of the biochip is built by using Comsol Multiphysics. Electric potential distribution, force distribution and particle trajectory in the channel are then obtained by using the simulation model. Finally, both the simulations and experiments are performed to demonstrate that the new biochip can enhance the detection efficiency and reduce the negative effects of electric field on the bioparticles.
Dielectrophoresis impedance measurement (DEPIM) is a powerful tool for bioparticle detection due to its advantages of high efficiency, label-free and low costs. However, the strong electric field may decrease the viability of the bioparticle, thus leading to instability of impedance measurement. A new design of biochip is presented with high stable bioparticle detection capabilities by using both negative dielectrophoresis (nDEP) and traveling wave dielectrophoresis (twDEP). In the biochip, a spiral electrode is arranged on the top of channel, while a detector is arranged on the bottom of the channel. The influence factors on the DEP force and twDEP force are investigated by using the basic principle of DEP, based on which, the relationship between Clausius-Mossotti (CM) factor and the frequency of electric field is obtained. The two-dimensional model of the biochip is built by using Comsol Multiphysics. Electric potential distribution, force distribution and particle trajectory in the channel are then obtained by using the simulation model. Finally, both the simulations and experiments are performed to demonstrate that the new biochip can enhance the detection efficiency and reduce the negative effects of electric field on the bioparticles.
2015, 32(2):148-155.
DOI: 10.16356/j.1005-1120.2015.02.148
Abstract:
Piezoelectric cantilever bimorph vibrator is the core component of piezoelectric inertial actuators. Piezoelectric cantilever bimorph vibrator with lumped mass at the end is studied, and a dynamic model is constructed by the proposed method of transforming symmetric electrical signal excitation to equivalent harmonic force excitation. Combining the theory and test, the single-degree-of-freedom damp vibration system consisting of the vibrator is analyzed and the full response is provided. Dynamical system modeling and simulation are conducted by software Matlab/Simulink. The output response of deflection, velocity, acceleration, driving force are solved using the input signal of equivalent harmonic force. Based on the data of theory, simulation and experiments, the deflection of vibrator is analyzed and compared under the excitation of sine wave signal. Result shows that the dynamic deflection results of vibrator from theory, simulation and experiments agree well with each other. The proposed modeling and analysis approaches of the single-degree-of-freedom damp vibration system consisting of the vibrator, have some reference significance for further research of piezoelectric inertial actuators.
Piezoelectric cantilever bimorph vibrator is the core component of piezoelectric inertial actuators. Piezoelectric cantilever bimorph vibrator with lumped mass at the end is studied, and a dynamic model is constructed by the proposed method of transforming symmetric electrical signal excitation to equivalent harmonic force excitation. Combining the theory and test, the single-degree-of-freedom damp vibration system consisting of the vibrator is analyzed and the full response is provided. Dynamical system modeling and simulation are conducted by software Matlab/Simulink. The output response of deflection, velocity, acceleration, driving force are solved using the input signal of equivalent harmonic force. Based on the data of theory, simulation and experiments, the deflection of vibrator is analyzed and compared under the excitation of sine wave signal. Result shows that the dynamic deflection results of vibrator from theory, simulation and experiments agree well with each other. The proposed modeling and analysis approaches of the single-degree-of-freedom damp vibration system consisting of the vibrator, have some reference significance for further research of piezoelectric inertial actuators.
2015, 32(2):156-162.
DOI: 10.16356/j.1005-1120.2015.02.156
Abstract:
Since stick-slip actuators present the advantage of allowing long displacements (several centimeters or even more) at a high speed with an ultra high resolution (<5 nm), a new type of stick-slip piezoelectric actuator is proposed to attain sub-nanometer positioning accuracy. The actuator is composed of a slider and a tower-shaped stator using forced bending vibration in y-z plane to generate tangential vibration on the top of the driving foot. When excited by the sawtooth input voltage, driving foot of the stator is able to generate a tangential asymmetrical vibration on the top, and the slider is thus pushed to move. A prototype and its testing equipment are fabricated and described. Following that, the testing of vibration mode and mechanical characteristics as well as stepping characteristics are conducted. Experimental results show that under the condition that the sawtooth input voltage is 400 VP-P and the pre-pressure is 6 N. Velocity of the actuator reaches its maximum 1.2 mm/s at the frequency of 8 000 Hz and drops to its minimum 35 nm/s at the frequency of 1 Hz. When the excitation signal is the single-phase sawtooth stepping signal, the tower-shaped actuator can directionally move forward or backward step by step. And when excited by the sawtooth stepping signal with 1 Hz and 300 VP-P during 1 cycle (200 ms), the actuator has a minimum stepping distance of 22 nm.
Since stick-slip actuators present the advantage of allowing long displacements (several centimeters or even more) at a high speed with an ultra high resolution (<5 nm), a new type of stick-slip piezoelectric actuator is proposed to attain sub-nanometer positioning accuracy. The actuator is composed of a slider and a tower-shaped stator using forced bending vibration in y-z plane to generate tangential vibration on the top of the driving foot. When excited by the sawtooth input voltage, driving foot of the stator is able to generate a tangential asymmetrical vibration on the top, and the slider is thus pushed to move. A prototype and its testing equipment are fabricated and described. Following that, the testing of vibration mode and mechanical characteristics as well as stepping characteristics are conducted. Experimental results show that under the condition that the sawtooth input voltage is 400 VP-P and the pre-pressure is 6 N. Velocity of the actuator reaches its maximum 1.2 mm/s at the frequency of 8 000 Hz and drops to its minimum 35 nm/s at the frequency of 1 Hz. When the excitation signal is the single-phase sawtooth stepping signal, the tower-shaped actuator can directionally move forward or backward step by step. And when excited by the sawtooth stepping signal with 1 Hz and 300 VP-P during 1 cycle (200 ms), the actuator has a minimum stepping distance of 22 nm.
2015, 32(2):163-173.
DOI: 10.16356/j.1005-1120.2015.02.163
Abstract:
The friction interface matching plays a deterministic role in the motor efficiency, and the microcosmic contact status of friction interface should be investigated to improve the ultrasonic motor performance. The main purpose is to improve the effective output power of ultrasonic motor. Hence, one studies the contact condition of the friction interface of the ultrasonic motor, analyzes the micro condition of contact interface through finite element analysis, optimizes unreasonable structures, and compares the two different-structure ultrasonic motors through experiments. The results reflect the necessity of optimization. After optimization, the stator and rotor deform after pre-pressure and the contact interface of them full contact theoretically. When reaching heat balance the effective output of the motor is 37%, and the average effective output efficiency is 2.384 times higher than that of the unoptimized. It can be seen that the total consumption of the ultrasonic motor system decreases significantly. Therefore, when using in certain system the consumption taken from the system will decreases largely, especially in the system with a strict consumption control.
The friction interface matching plays a deterministic role in the motor efficiency, and the microcosmic contact status of friction interface should be investigated to improve the ultrasonic motor performance. The main purpose is to improve the effective output power of ultrasonic motor. Hence, one studies the contact condition of the friction interface of the ultrasonic motor, analyzes the micro condition of contact interface through finite element analysis, optimizes unreasonable structures, and compares the two different-structure ultrasonic motors through experiments. The results reflect the necessity of optimization. After optimization, the stator and rotor deform after pre-pressure and the contact interface of them full contact theoretically. When reaching heat balance the effective output of the motor is 37%, and the average effective output efficiency is 2.384 times higher than that of the unoptimized. It can be seen that the total consumption of the ultrasonic motor system decreases significantly. Therefore, when using in certain system the consumption taken from the system will decreases largely, especially in the system with a strict consumption control.
2015, 32(2):174-179.
DOI: 10.16356/j.1005-1120.2015.02.174
Abstract:
How to improve the efficiency of the linear ultrasonic motor with hard contact materials (HLUSM) or the precision motion stage driven by HLUSM, becomes a hot issue. Analysis and testing of friction behavior on the contact interface of HLUSM is one of the key issues. Under the action of ultrasonic vibration and impact, the friction behavior on contact interface is very complex due to micro-amplitude and high frequency. Moreover, it is difficult to observe and test it. Focusing on the frictional behavior on the interface of HLUSM, a new method, through testing the vibration of the driving tips (scanning vibrometer PSV-400-3D) and the motion of the slider (displacement sensor LK-G30), respectively, is proposed. Then, take the HLUSM as an example, theoretical analyses and experiments are carried out. Theoretical analysis shows that the average speed of the slider should be 600 mm/s when there is no slippage between the stator and slider during the contact process. Experimental results show that the average speed of the slider is about 390 mm/s. At the same time, the tangential vibration speed of the driving tip of HLUSM is larger than 600 mm/s. Therefore, there must be slippage between the stator and slider of HLUSM. Further experimental results show that the maximum efficiency is less than 10%. The slippage on the contact interface should be the main reason for the low efficiency of HLUSM.
How to improve the efficiency of the linear ultrasonic motor with hard contact materials (HLUSM) or the precision motion stage driven by HLUSM, becomes a hot issue. Analysis and testing of friction behavior on the contact interface of HLUSM is one of the key issues. Under the action of ultrasonic vibration and impact, the friction behavior on contact interface is very complex due to micro-amplitude and high frequency. Moreover, it is difficult to observe and test it. Focusing on the frictional behavior on the interface of HLUSM, a new method, through testing the vibration of the driving tips (scanning vibrometer PSV-400-3D) and the motion of the slider (displacement sensor LK-G30), respectively, is proposed. Then, take the HLUSM as an example, theoretical analyses and experiments are carried out. Theoretical analysis shows that the average speed of the slider should be 600 mm/s when there is no slippage between the stator and slider during the contact process. Experimental results show that the average speed of the slider is about 390 mm/s. At the same time, the tangential vibration speed of the driving tip of HLUSM is larger than 600 mm/s. Therefore, there must be slippage between the stator and slider of HLUSM. Further experimental results show that the maximum efficiency is less than 10%. The slippage on the contact interface should be the main reason for the low efficiency of HLUSM.
2015, 32(2):180-186.
DOI: 10.16356/j.1005-1120.2015.02.180
Abstract:
A novel variable camber wing driven by ultrasonic motors is proposed. Key techniques of distributed layout of drive mechanisms, coordination control of distributed ultrasonic motors as well as novel flexible skin undergoing one-dimensional morphing are studied. The system integration of small variable camber wing is achieved. Distributed layout of parallelogram linkages driven by geared ultrasonic motors is adopted for morphing, aimed at reducing the load for each motor and producing various aerodynamic configurations suitable for different flying states. Programmable system-on-chip (PSoC) is used to realize the coordination control of the distributed ultrasonic motors. All the morphing driving systems are assembled in the interior of the wing. The wing surface is covered with a novel smooth flexible skin in order to maintain wing shape and decrease the aerodynamic drag during morphing. Wind tunnel test shows that the variable camber wing can realize morphing under low speed flight condition. Lift and drag characteristics and aerodynamic efficiency of the wing are improved. Appropriate configurations can be selected to satisfy aerodynamic requirements of different flight conditions. The study provides a practical application of piezoelectric precision driving technology in flow control.
A novel variable camber wing driven by ultrasonic motors is proposed. Key techniques of distributed layout of drive mechanisms, coordination control of distributed ultrasonic motors as well as novel flexible skin undergoing one-dimensional morphing are studied. The system integration of small variable camber wing is achieved. Distributed layout of parallelogram linkages driven by geared ultrasonic motors is adopted for morphing, aimed at reducing the load for each motor and producing various aerodynamic configurations suitable for different flying states. Programmable system-on-chip (PSoC) is used to realize the coordination control of the distributed ultrasonic motors. All the morphing driving systems are assembled in the interior of the wing. The wing surface is covered with a novel smooth flexible skin in order to maintain wing shape and decrease the aerodynamic drag during morphing. Wind tunnel test shows that the variable camber wing can realize morphing under low speed flight condition. Lift and drag characteristics and aerodynamic efficiency of the wing are improved. Appropriate configurations can be selected to satisfy aerodynamic requirements of different flight conditions. The study provides a practical application of piezoelectric precision driving technology in flow control.
2015, 32(2):187-191.
DOI: 10.16356/j.1005-1120.2015.02.187
Abstract:
The use of piezoelectric materials to capitalize on the ambient vibrations surrounding a system is one method that has seen a dramatic rise in use for power harvesting. Lead zirconate titanate, one of the most popular piezoelectric materials, has larger piezoelectric response than piezoelectric materials, such as ZnO and AlN. Ferroelectric films are suitable for vibration energy harvesting. Dense and crack-free (100) oriented PZT piezoelectric thick film is prepared on Pt/Cr/SiO2/Si substrate by sol-gel using PZT nanoparticles as reinforcing phase. The thick film possesses single-phase perovskite structure and perfectly (100) oriented. The influences of crystalline and amorphous PZT nanoparticles on the (100) oriented degree and the influences of the molar concentration ratio of amorphous PZT nanoparticles and PZT sol on surface morphology of PZT piezoelectric thick film are investigated. Experimental results show that, amorphous PZT nanoparticles are more helpful than the crystalline nanoparticles for the PZT thick film preferred orientation growth along the (100) direction. The 3 μm-thick PZT thick film enhanced by amorphous PZT nanoparticles annealed at 700℃ for 5 min has the strongest (100) orientation degree, being 82.3%, and the surface is dense, smooth and crack-free.
The use of piezoelectric materials to capitalize on the ambient vibrations surrounding a system is one method that has seen a dramatic rise in use for power harvesting. Lead zirconate titanate, one of the most popular piezoelectric materials, has larger piezoelectric response than piezoelectric materials, such as ZnO and AlN. Ferroelectric films are suitable for vibration energy harvesting. Dense and crack-free (100) oriented PZT piezoelectric thick film is prepared on Pt/Cr/SiO2/Si substrate by sol-gel using PZT nanoparticles as reinforcing phase. The thick film possesses single-phase perovskite structure and perfectly (100) oriented. The influences of crystalline and amorphous PZT nanoparticles on the (100) oriented degree and the influences of the molar concentration ratio of amorphous PZT nanoparticles and PZT sol on surface morphology of PZT piezoelectric thick film are investigated. Experimental results show that, amorphous PZT nanoparticles are more helpful than the crystalline nanoparticles for the PZT thick film preferred orientation growth along the (100) direction. The 3 μm-thick PZT thick film enhanced by amorphous PZT nanoparticles annealed at 700℃ for 5 min has the strongest (100) orientation degree, being 82.3%, and the surface is dense, smooth and crack-free.
2015, 32(2):192-198.
DOI: 10.16356/j.1005-1120.2015.02.192
Abstract:
Control model of ultrasonic motor is the foundation for high control performance. The frequency of driving voltage is commonly used as control variable in the speed control system of ultrasonic motor. Speed control model with the input frequency can significantly improve speed control performance. Step response of rotating speed is tested. Then, the transfer function model is identified through characteristic point method. Considering time-varying characteristics of the model parameters, the variables are fitted with frequency and speed as the independent variables, and the variable model of ultrasonic motor system is obtained, with consideration of the nonlinearity of ultrasonic motor system. The proposed model can be used in the design and analysis of the speed control system in ultrasonic motor.
Control model of ultrasonic motor is the foundation for high control performance. The frequency of driving voltage is commonly used as control variable in the speed control system of ultrasonic motor. Speed control model with the input frequency can significantly improve speed control performance. Step response of rotating speed is tested. Then, the transfer function model is identified through characteristic point method. Considering time-varying characteristics of the model parameters, the variables are fitted with frequency and speed as the independent variables, and the variable model of ultrasonic motor system is obtained, with consideration of the nonlinearity of ultrasonic motor system. The proposed model can be used in the design and analysis of the speed control system in ultrasonic motor.
2015, 32(2):199-203.
DOI: 10.16356/j.1005-1120.2015.02.199
Abstract:
Nanopositioning stage based on piezoelectric (PZT) actuators and flexure mechanisms has been widely used in dual-stage. Its favorable positioning accuracy and dynamic response can guarantee the high performance of the dual-stage. Here the vertical axis motion dual-stage is designed with piezoelectric actuator for the fine-stage and ball-screw drive integrated with wedge sliding mechanisms for the coarse-stage. The aim of the dual-stage is to meet the stringent requirement of scanning over a relative large range with high accuracy. The design results of the piezo-actuated nanopositioning stage show good static and dynamic performance, validated by the simulation of finite element analysis (FEA). Hysteresis nonlinearity due to the use of piezoelectric stacks for actuation is studied and compensated by a proportional-integral (PI) feedback controller. To qualify the design of the motion ranges and resolutions, an experiment platform is established. The experimental results show that the proposed dual-stage has a full range of 12 mm with the resolution of 40 nm. Guideline is provided for the design methodology of the vertical motion dual-range stages.
Nanopositioning stage based on piezoelectric (PZT) actuators and flexure mechanisms has been widely used in dual-stage. Its favorable positioning accuracy and dynamic response can guarantee the high performance of the dual-stage. Here the vertical axis motion dual-stage is designed with piezoelectric actuator for the fine-stage and ball-screw drive integrated with wedge sliding mechanisms for the coarse-stage. The aim of the dual-stage is to meet the stringent requirement of scanning over a relative large range with high accuracy. The design results of the piezo-actuated nanopositioning stage show good static and dynamic performance, validated by the simulation of finite element analysis (FEA). Hysteresis nonlinearity due to the use of piezoelectric stacks for actuation is studied and compensated by a proportional-integral (PI) feedback controller. To qualify the design of the motion ranges and resolutions, an experiment platform is established. The experimental results show that the proposed dual-stage has a full range of 12 mm with the resolution of 40 nm. Guideline is provided for the design methodology of the vertical motion dual-range stages.
2015, 32(2):204-209.
DOI: 10.16356/j.1005-1120.2015.02.204
Abstract:
For the smaller thrust, it is difficult to achieve 3D trans-scale precision positioning based on previous stick-slip driving. A large thrust trans-scale precision positioning stage is studied based on the inertial stick-slip driving. The process of the movement is divided into two steps, i.e., the ″sliding″ phase and the ″stickness″ phase. In the whole process, the kinematics model of the inertial stick-slip driving is established, and it reveals some factors affecting the velocity of inertial stick-slip driving. Furthermore, a simulation of movement is preformed by Matlab-Simulink software, and the whole process of the inertial stick-slip driving is displayed. After one experimental prototype is designed, the back and forth velocity is tested. Finally, the simulation verifies the accuracy of the kinematics model.
For the smaller thrust, it is difficult to achieve 3D trans-scale precision positioning based on previous stick-slip driving. A large thrust trans-scale precision positioning stage is studied based on the inertial stick-slip driving. The process of the movement is divided into two steps, i.e., the ″sliding″ phase and the ″stickness″ phase. In the whole process, the kinematics model of the inertial stick-slip driving is established, and it reveals some factors affecting the velocity of inertial stick-slip driving. Furthermore, a simulation of movement is preformed by Matlab-Simulink software, and the whole process of the inertial stick-slip driving is displayed. After one experimental prototype is designed, the back and forth velocity is tested. Finally, the simulation verifies the accuracy of the kinematics model.
2015, 32(2):210-217.
DOI: 10.16356/j.1005-1120.2015.02.210
Abstract:
It is difficult for the traditional pan-tilt-zoom (PTZ) system driven by electromagnetic motor to meet the growing demand for video surveillance system. The key challenge is high positioning accuracy, high dynamic performance and miniaturization of the PTZ system. Here a PTZ system driven by two degree-of-freedom obelisk-shaped ultrasonic motor with single stator is presented, and its intelligent control algorithm is studied. The structure and driving mechanism of the presented PTZ system are analyzed by both simulation and experiment. To solve the complex nonlinear factors, e.g. time-variation, dead zone, the fuzzy PID control algorithm and the variable gain cross-coupled control strategy are combined to improve the control performance. The results show that the proposed algorithm has faster response, higher precision than traditional control algorithm, and it also has a good robustness to prevent the effect of interference.
It is difficult for the traditional pan-tilt-zoom (PTZ) system driven by electromagnetic motor to meet the growing demand for video surveillance system. The key challenge is high positioning accuracy, high dynamic performance and miniaturization of the PTZ system. Here a PTZ system driven by two degree-of-freedom obelisk-shaped ultrasonic motor with single stator is presented, and its intelligent control algorithm is studied. The structure and driving mechanism of the presented PTZ system are analyzed by both simulation and experiment. To solve the complex nonlinear factors, e.g. time-variation, dead zone, the fuzzy PID control algorithm and the variable gain cross-coupled control strategy are combined to improve the control performance. The results show that the proposed algorithm has faster response, higher precision than traditional control algorithm, and it also has a good robustness to prevent the effect of interference.
2015, 32(2):218-225.
DOI: 10.16356/j.1005-1120.2015.02.218
Abstract:
The mathematical model of ultrasonic motor (USM) is the foundation of the motor high performance control. Considering the motor speed control requirements, the USM control model identification is established with frequency as the independent variable. The frequency-speed control model of USM system is developed, thus laying foundation for the motor high performance control. The least square method and the extended least square method are used to identify the model. By comparing the results of the identification and measurement, and fitting the time-varying parameters of the model, one can show that the model obtained by using the extended least square method is reasonable and possesses high accuracy. Finally, the frequency-speed control model of USM contains the nonlinear information.
The mathematical model of ultrasonic motor (USM) is the foundation of the motor high performance control. Considering the motor speed control requirements, the USM control model identification is established with frequency as the independent variable. The frequency-speed control model of USM system is developed, thus laying foundation for the motor high performance control. The least square method and the extended least square method are used to identify the model. By comparing the results of the identification and measurement, and fitting the time-varying parameters of the model, one can show that the model obtained by using the extended least square method is reasonable and possesses high accuracy. Finally, the frequency-speed control model of USM contains the nonlinear information.
2015, 32(2):226-231.
DOI: 10.16356/j.1005-1120.2015.02.226
Abstract:
A method based on programmable system-on-chip (PSoC) is proposed to realize high resolution stepping motion control of liner displacement mechanism driven by traveling wave rotary ultrasonic motors (TRUM). Intelligent controller of stepping ultrasonic motor consists of PSoC microprocessor. Continuous square wave signal is sent out by the pulse width modulator (PWM) module inside PSoC, and converted into sinusoidal signal which is essential to the motor's normal working by power amplifier circuit. Subsequently, signal impulse transmission is realized by the counter control break, and the stepping motion of linear displacement mechanism based on TRUM is achieved. Running status of the ultrasonic motor is controlled by an upper computer. Control command is sent to PSoC through serial communication circuit of RS-232. Relative program and control interface are written in LabView. Finally the mechanism is tested by XL-80 laser interferometer. Test results show that the mechanism can provide a stable motion and a fixed step pitch with the displacement resolution of 6 nm.
A method based on programmable system-on-chip (PSoC) is proposed to realize high resolution stepping motion control of liner displacement mechanism driven by traveling wave rotary ultrasonic motors (TRUM). Intelligent controller of stepping ultrasonic motor consists of PSoC microprocessor. Continuous square wave signal is sent out by the pulse width modulator (PWM) module inside PSoC, and converted into sinusoidal signal which is essential to the motor's normal working by power amplifier circuit. Subsequently, signal impulse transmission is realized by the counter control break, and the stepping motion of linear displacement mechanism based on TRUM is achieved. Running status of the ultrasonic motor is controlled by an upper computer. Control command is sent to PSoC through serial communication circuit of RS-232. Relative program and control interface are written in LabView. Finally the mechanism is tested by XL-80 laser interferometer. Test results show that the mechanism can provide a stable motion and a fixed step pitch with the displacement resolution of 6 nm.
2015, 32(2):232-239.
DOI: 10.16356/j.1005-1120.2015.02.232
Abstract:
As the requirements of production process is getting higher and higher with the reduction of volume, microphone production automation become an urgent need to improve the production efficiency. The most important part is studied and a precise algorithm of calculating the deviation angle of four types microphones is proposed, based on the feature extraction and visual detection. Pretreatment is performed to achieve the real-time microphone image. Canny edge detection and typical feature extraction are used to distinguish the four types of microphones, categorizing them as type M1 and type M2. And Hough transformation is used to extract the image features of microphone. Therefore, the deviation angle between the posture of microphone and the ideal posture in 2D plane can be achieved. Depending on the angle, the system drives the motor to adjust posture of the microphone. The final purpose is to realize the high efficiency welding of four different types of microphones.
As the requirements of production process is getting higher and higher with the reduction of volume, microphone production automation become an urgent need to improve the production efficiency. The most important part is studied and a precise algorithm of calculating the deviation angle of four types microphones is proposed, based on the feature extraction and visual detection. Pretreatment is performed to achieve the real-time microphone image. Canny edge detection and typical feature extraction are used to distinguish the four types of microphones, categorizing them as type M1 and type M2. And Hough transformation is used to extract the image features of microphone. Therefore, the deviation angle between the posture of microphone and the ideal posture in 2D plane can be achieved. Depending on the angle, the system drives the motor to adjust posture of the microphone. The final purpose is to realize the high efficiency welding of four different types of microphones.
2015, 32(2):240-249.
DOI: 10.16356/j.1005-1120.2015.02.240
Abstract:
With large scale wind turbines, the issue of aerodynamic elastic response is even more significant on dynamic behaviour of the system. Unsteady free vortex wake method is proposed to calculate the shape of wake and aerodynamic load. Considering the effect of aerodynamic load, inertial load and gravity load, the decoupling dynamic equations are established by using finite element method in conjunction of the modal method and equations are solved numerically by Newmark approach. Finally, the numerical simulation of a large scale wind turbine is performed through coupling the free vortex wake modelling with structural modelling.The results show that this coupling model can predict the flexible wind turbine dynamic characteristics effectively and efficiently. Under the influence of the gravitational force, the dynamic response of flapwise direction contributes to the dynamic behavior of edgewise direction under the operational condition of steady wind speed. The difference in dynamic response between the flexible and rigid wind turbines manifests when the aerodynamics/structure coupling effect is of significance in both wind turbine design and performance calculation.
With large scale wind turbines, the issue of aerodynamic elastic response is even more significant on dynamic behaviour of the system. Unsteady free vortex wake method is proposed to calculate the shape of wake and aerodynamic load. Considering the effect of aerodynamic load, inertial load and gravity load, the decoupling dynamic equations are established by using finite element method in conjunction of the modal method and equations are solved numerically by Newmark approach. Finally, the numerical simulation of a large scale wind turbine is performed through coupling the free vortex wake modelling with structural modelling.The results show that this coupling model can predict the flexible wind turbine dynamic characteristics effectively and efficiently. Under the influence of the gravitational force, the dynamic response of flapwise direction contributes to the dynamic behavior of edgewise direction under the operational condition of steady wind speed. The difference in dynamic response between the flexible and rigid wind turbines manifests when the aerodynamics/structure coupling effect is of significance in both wind turbine design and performance calculation.
2015, 32(2):250-254.
DOI: 10.16356/j.1005-1120.2015.02.250
Abstract:
Interaction between the injected flow from the porous wall and the main flow can reduce drag effectively. The phenomenon is significant to the flight vehicle design. The intensive flux of injection enhances difficulty of numerical simulation and requires higher demands on the turbulence model. A turbulent boundary layer flow with mass injection through a porous wall governed by Reynolds averaged Navier-Stokers (RANS) equations is solved by using the Wilcox's k-ω turbulence model and the obtained resistance coefficient agrees well with the experimental data. The results with and without mass injection are compared with other conditions unchanged. Velocity profile, turbulent kinetic energy and turbulent eddy viscosity are studied in these two cases. Results confirm that the boundary layer is blowing up and the turbulence is better developed with the aid of mass injection, which may explain the drag reduction theoretically. This numerical simulation may deepen our comprehension on this complex flow.
Interaction between the injected flow from the porous wall and the main flow can reduce drag effectively. The phenomenon is significant to the flight vehicle design. The intensive flux of injection enhances difficulty of numerical simulation and requires higher demands on the turbulence model. A turbulent boundary layer flow with mass injection through a porous wall governed by Reynolds averaged Navier-Stokers (RANS) equations is solved by using the Wilcox's k-ω turbulence model and the obtained resistance coefficient agrees well with the experimental data. The results with and without mass injection are compared with other conditions unchanged. Velocity profile, turbulent kinetic energy and turbulent eddy viscosity are studied in these two cases. Results confirm that the boundary layer is blowing up and the turbulence is better developed with the aid of mass injection, which may explain the drag reduction theoretically. This numerical simulation may deepen our comprehension on this complex flow.
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