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Development and application prospects of piezoelectric
precision driving technology
ZHAO Chunsheng, ZHANG Jiantao, ZHANG Jianhui, JIN Jiamei
Front. Mech. Eng.. 2008, 3 (2): 119-132.
https://doi.org/10.1007/s11465-008-0034-1
With the rapid development of science and technology, microelectronics manufacturing, photonics technology, space technology, ultra-precision machining, micro-robotics, biomedical engineering and other fields urgently need the support of modern precision driving theory and technology. Modern precision driving technology can be generally divided into two parts: electromagnetic and non-electromagnetic driving technology. Electromagnetic driving technology is based on traditional technology, has a low thrust-weight ratio, and needs deceleration devices with a cumbrous system or a complex structure. Moreover, it is difficult to improve positioning accuracy with this technology type. Thus, electromagnetic driving technology is still unable to meet the requirements for the above applications. Non-electromagnetic driving technology is a new choice. As a category of non-electromagnetic driving technology, piezoelectric driving technology becomes an important branch of modern precision driving technology. High holding torque and acute response make it suitable as an accurate positioning actuator. This paper presents the development of piezoelectric precision driving technology at home and abroad and gives an in-depth analysis. Future perspectives on the technology’s applications in the following fields are described: 1) integrated circuit manufacturing technology; 2) fiber optic component manufacturing technology; 3) micro parts manipulation and assembly technology; 4) biomedical engineering; 5) aerospace technology; and 6) ultra-precision processing technology.
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Grindability of high-temperature alloy with ceramic
alumina wheels
ZHANG Hongxia, CHEN Wuyi, CHEN Zhitong
Front. Mech. Eng.. 2008, 3 (2): 139-145.
https://doi.org/10.1007/s11465-008-0040-3
The grindability of high-temperature alloy by using ceramic alumina wheels is studied on the basis of extensive analysis of the grinding force, grinding temperature, surface roughness and topography of ground surfaces, residual stress, hardness distribution of surface layer, and morphology of the surface layer from a metallographic point of view. The grinding burn mechanism of high-temperature alloy is unveiled and the feasible grinding parameters to avoid burning are analyzed. Some conclusions are obtained as follows. Increasing the grinding depth or the wheel velocity makes grinding temperature and residual tensile stress of the surface rise, which deteriorates the surface topography. Appropriate liner velocity of the wheel is 18–22 m/s and the depth of grinding should not exceed 0.02 mm in grinding GH2132 alloy with ceramic alumina wheels to assure the surface quality. When ap increases enough to cause grinding burn, the strengthening effect of particles ?′ in ? base decrease and the micro-hardness of the surface is obviously lower than that of the base material, which deteriorates the mechanical properties and heat resistance of GH2132 alloy. Results provide a theoretical and experimental basis for technical optimization in the grinding of high-temperature alloy with high efficiency and high quality.
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Electrorheological damper for the ultra-precision
air bearing stage
ZHU Yu, JIA Songtao, CHEN Yaying, LI Guang
Front. Mech. Eng.. 2008, 3 (2): 158-163.
https://doi.org/10.1007/s11465-008-0031-4
This paper illustrates how the electrorheological damper substantially improves the performance of the ultra-precision air bearing stage. Smart materials such as electrorheological fluids have attracted many researchers’ attention because of their resistance changeable performance in different electric fields. Meanwhile, the ultra-precision air bearing stage driven by the linear-motor is characterized by zero mechanical damping and poor anti-disturbance. To solve this problem and consider the characteristics of electrorheological fluids, an electrorheological damper is proposed in this paper. The electrorheological damper’s characteristics in high electric fields are obtained based on the Eyring constitutive model, which smoothly transits from the pre-yield to post-yield region. To enhance the performance of the electrorheological damper, which takes effect only when the stage is going to decelerate or position, the on-off and sliding mode control methods design and optimize the controller. The results prove that by using the advanced sliding mode control method, the characteristics of the ultra-precision air bearing stage can be effectively improved through the introduction of the electrorheological damper.
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Mobile platform for hydraulic turbine blade repair
robot
GUI Zhongcheng, CHEN Qiang, SUN Zhenguo, ZHANG Wenzeng, LIU Kang
Front. Mech. Eng.. 2008, 3 (2): 164-169.
https://doi.org/10.1007/s11465-008-0035-0
The wall-climbing mobile platform (MP) of a robot for repairing a hydraulic turbine blade onsite is developed. The MP is equipped with ferromagnetic adhesive devices and can work on a spatial curved surface. The contradiction between mobility and load-bearing ability is analyzed, and the problem of self-adaptation to the curved face is solved using differential-driven wheeled locomotion with ferromagnetic adhesive devices. The platform adheres to the blade surface through the force provided by the ferromagnetic devices, and a certain gap exists between the magnetic devices and the blade’s surface. A mechanism of three revolution degrees of freedom, which connects the magnetic devices with the platform’s chassis, is developed to make the platform self-adapt to the complex curved surface of the turbine blade. A proof-of-principle prototype has been manufactured, and experiments prove the success of the MP. The payload of the zero-turn-radius MP with excellent maneuverability exceeds 80 kg. The platform can automatically adapt to complex spatial surfaces, which satisfy the requirements of a hydraulic turbine blade in-situ repair robot.
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Cutting heat dissipation in high-speed machining
of carbon steel based on the calorimetric method
QUAN Yanming, HE Zhenwei, DOU Yong
Front. Mech. Eng.. 2008, 3 (2): 175-179.
https://doi.org/10.1007/s11465-008-0022-5
The cutting heat dissipation in chips, workpiece, tool and surroundings during the high-speed machining of carbon steel is quantitatively investigated based on the calorimetric method. Water is used as the medium to absorb the cutting heat; a self-designed container suitable for the high-speed lathe is used to collect the chips, and two other containers are adopted to absorb the cutting heat dissipated in the workpiece and tool, respectively. The temperature variations of the water, chips, workpiece, tool and surroundings during the closed high-speed machining are then measured. Thus, the cutting heat dissipated in each component of the cutting system, total cutting heat and heat flux are calculated. Moreover, the power resulting from the main cutting force is obtained according to the measured cutting force and predetermined cutting speed. The accuracy of cutting heat measurement by the calorimetric method is finally evaluated by comparing the total cutting heat flux with the power resulting from the main cutting force.
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Intelligent high-speed cutting database system
development
XIANG Kejun, LIU Zhanqiang, AI Xing
Front. Mech. Eng.. 2008, 3 (2): 180-188.
https://doi.org/10.1007/s11465-008-0038-x
In this paper, the components of a high-speed cutting system are analyzed firstly. The component variables of the high-speed cutting system are classified into four types: uncontrolled variables, process variables, control variables, and output variables. The relationships and interactions of these variables are discussed. Then, by analyzing and comparing intelligent reasoning methods frequently used, the hybrid reasoning is employed to build the high-speed cutting database system. Then, the data structures of high-speed cutting case base and databases are determined. Finally, the component parts and working process of the high-speed cutting database system on the basis of hybrid reasoning are presented.
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Stability and coupling dynamic behavior of nonlinear
journal active electromagnetic bearing rotor system
LU Yanjun, HEI Di, WANG Yuan, DAI Rong, LU Yanjun, LIU Heng, YU Lie
Front. Mech. Eng.. 2008, 3 (2): 193-199.
https://doi.org/10.1007/s11465-008-0023-4
The stability and coupling dynamic behavior of a journal active electromagnetic bearing rotor system are analyzed. The gyroscopic effect is considered in the rotor model. The system equations are formulated by combining equations for rotor motion and decentralized proportional integral differential (PID) controllers. A method combining the predictor-corrector mechanism and the Netwon-Raphson method is presented to calculate the critical speed at the corresponding Hopf bifurcation point of the system. For periodic motions, a continuation method combining the predictor-corrector mechanism and shooting method is presented. Nonlinear unbalanced periodic motions and their stability margins are obtained using the shooting method and established continuation method for periodic motions. With the change of control parameters, the system local stability and bifurcation behaviors are obtained using the Floquet theory. The numerical examples show that the schemes not only significantly save computing cost, but also have high precision.
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Compressor performance of two-stage turbocharging
system
HE Yituan, MA Chaochen, WEI Mingshan, ZHU Zhifu, HE Yituan
Front. Mech. Eng.. 2008, 3 (2): 218-221.
https://doi.org/10.1007/s11465-008-0027-0
To study the performance of high and low stage compressors and that of the system as a whole, a two-stage turbocharging system was matched, and a special two-stage turbocharging system test bench was built. For each test curve, the speeds of the two stage turbochargers were adjusted to the fixed data, and a compressor performance experiment was performed. The results showed many differences between the corrected mass flow and the actual mass flow of the high pressure (HP) stage compressor. To find out the actual supercharging effect of the two-stage turbocharging system, it is better to adopt the actual mass flow. The two-stage turbocharging system in this paper has much higher efficiency under most operating conditions if the pressure ratio assignment is 1:1. The system can get very high supercharging pressure when the speeds of the two stage turbochargers are rather low, which ensures the system’s security and reliability.
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Preparation of ultrafine α-AlO using precipitation-azeotropic
distillation method
XIAO Jin, QIN Qi, ZHOU Feng, CHEN Yanbin, WAN Ye
Front. Mech. Eng.. 2008, 3 (2): 226-231.
https://doi.org/10.1007/s11465-008-0029-y
Ammonium aluminum carbonate hydroxide (AACH) was prepared by a precipitation-azeotropic distillation method, which uses aluminum sulfate as the Al source and ammonium carbonate as the precipitant. Then, AACH was calcined into ultrafine ?-Al2O3 powder. The factors that influence the dispersion property of ultrafine ?-Al2O3 powder are discussed in this paper, such as the methods of adding materials, surfactant, and drying methods. The changes of the structure and property of ultrafine alumina in the thermal treatment process are also studied. The morphological structure and properties of AACH are characterized by DTA/TGA, SEM, XRD, and ICP measurements. The results show that ultrafine ?-Al2O3 powder with a uniform particle size and well-distributed property can be synthesized only after aluminum sulfate atomizes into ammonium carbonate, proper amount of PEG1000 is added as the dispersant, and the product is treated by azeotropic distillation. The phase transformation of alumina during the calcination process can be described as amorphous Al2O3 → ?-Al2O3 → ?-Al2O3 → ?-Al2O3. The crystal grain size and density of ultrafine alumina powder increase with the increase of the calcination temperature. After AACH has been calcined at 1200°C for 2 h, the ultrafine ?-Al2O3 with uniform particle size, spherical shape, and more than 99.97% purity is obtained and its powder is well dispersed.
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Dynamic modeling of flexible-links planar parallel
robots
DU Zhaocai, YU Yueqing, ZHANG Xuping, DU Zhaocai
Front. Mech. Eng.. 2008, 3 (2): 232-237.
https://doi.org/10.1007/s11465-008-0032-3
This paper presents a finite element-based method for dynamic modeling of parallel robots with flexible links and rigid moving platform. The elastic displacements of flexible links are investigated while considering the coupling effects between links due to the structural flexibility. The kinematic constraint conditions and dynamic constraint conditions for elastic displacements are presented. Considering the effects of distributed mass, lumped mass, shearing deformation, bending deformation, tensile deformation and lateral displacements, the Kineto-Elasto dynamics (KED) theory and Lagrange formula are used to derive the dynamic equations of planar flexible-links parallel robots. The dynamic behavior of the flexible-links planar parallel robot is well illustrated through numerical simulation of a planar 3-RRR parallel robot. Compared with the results of finite element software SAMCEF, the numerical simulation results show good coherence of the proposed method. The flexibility of links is demonstrated to have a significant impact on the position error and orientation error of the flexible-links planar parallel robot.
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