Some dynamic factors, such as inertial forces and friction, may affect therobot trajectory accuracy. But these effects are not taken into account in robot motion controlschemes. Dynamic control methods, on the other h...Some dynamic factors, such as inertial forces and friction, may affect therobot trajectory accuracy. But these effects are not taken into account in robot motion controlschemes. Dynamic control methods, on the other hand, require the dynamic model of robot and theimplementation of new type controller. A method to improve robot trajectory accuracy by dynamiccompensation in robot motion control system is proposed. The dynamic compensation is applied as anadditional velocity feedforward and a multilayer neural network is employed to realize the robotinverse dynamics. The complicated dynamic parameter identification problem becomes a learningprocess of neural network connecting weights under supervision. The finite Fourier series is used toactivate each actuator of robot joints for obtaining training samples. Robot control system,consisting of an industrial computer and a digital motion controller, is implemented. The system isof open architecture with velocity feedforward function. The proposed method is not model-based andcombines the advantages of close-loop position control and computed torque control. Experimentalresults have shown that the method is validatities to improve the robot trajectory accuracy.展开更多
From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a t...From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a time-dependent failure assessment diagram (TDFAD) isdeveloped on the basis of the time dependent crack tip parameter J integral. According to theproposed TDFAD method, detailed crack initiation and creep crack growth analysis is avoided insafety assessments of high temperature structures by performing simple calculations of stressintensity factor and limit load. To evaluate the creep toughness parameter K_(mat), three differentexpressions are suggested on the basis of experimental load-line displacement, creep crackinitiation and growth parameters as well as the isochronous stress-strain curve. The influence ofservice factors such as temperature and service-time on the proposed TDFAD is discussed by using theproperties of 2.25CrlMo steel and an example is also presented to illustrate the approach.展开更多
From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental st...From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.展开更多
Adaptive control of a flexible beam system preceded by an unknown dead-zonein the driving motor is investigated in state space form. By introducing an important lemma forsimplifying error equation between the flexible...Adaptive control of a flexible beam system preceded by an unknown dead-zonein the driving motor is investigated in state space form. By introducing an important lemma forsimplifying error equation between the flexible beam model and the matching reference model, arobust adaptive control scheme is developed by involving the dead-zone inverse terms. The newadaptive control law ensures global stability of the entire system and achieves desired trackingprecision even when the slopes of the dead-zone are not equal. Simulations performed on a typicalflexible beam system illustrate and clarify the validity of this approach.展开更多
A new method of parameter identification based on linear time-frequencyrepresentation and Hubert transform is proposed to identity modal parameters of linear time-varyingsystems from measured vibration responses. Usin...A new method of parameter identification based on linear time-frequencyrepresentation and Hubert transform is proposed to identity modal parameters of linear time-varyingsystems from measured vibration responses. Using Gabor expansion and synthesis theory, measuredresponses are represented in the time-frequency domain and modal components are reconstructed bytime-frequency filtering. The Hilbert transform is applied to obtain time histories of the amplitudeand phase angle of each modal component, from which time-varying frequencies and damping ratios areidentified. The proposed method has been demonstrated with a numerical example in which a lineartime-varying system of two degrees of freedom is used to validate the identification scheme based ontime-frequency representation. Simulation results have indicated that time-frequency representationpresents an effective tool for modal parameter identification of time-varying systems.展开更多
Aiming at difficult sorting and retrieving complicated structure assembliesin assembly lib, a method for compartmentalizing assembly design resource by conceptual productstructure model is presented. The similar assem...Aiming at difficult sorting and retrieving complicated structure assembliesin assembly lib, a method for compartmentalizing assembly design resource by conceptual productstructure model is presented. The similar assembly retrieval mechanisms of symbol assembly relationgraph matching and symbol assembly relation graph similarity are discussed. The method is validatedby taking valve rod assemblies as example.展开更多
The optimization of injection molding process for polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends is studied using Taguchi method and principalcomponent analysis (PCA). Four controllable process factors ...The optimization of injection molding process for polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends is studied using Taguchi method and principalcomponent analysis (PCA). Four controllable process factors are studied at three levels each in themanufacturing process. The L_9 orthogonal array is conducted to determine the optimum processfactor/level combination for single quality of mechanical properties. In addition, the principalcomponent analysis is employed to trans-form the correlated mechanical properties to a set ofuncorrelated components and to evaluate a comprehensive index for multi-response cases. Then theoptimum process factor/level combination for multiple qualities can be determined. Finally, theanalysis of variance is used to find out the most influential injection molding parameter for singleand multiple qualities problems.展开更多
In this article, low-pressure control methods for a combined arc submerged nanoparticle synthesis system (ASNSS) was proposed and developed for TiO2 nanoparticle fabrication. The photocatalytic reaction is carried out...In this article, low-pressure control methods for a combined arc submerged nanoparticle synthesis system (ASNSS) was proposed and developed for TiO2 nanoparticle fabrication. The photocatalytic reaction is carried out in a photochemical reactor. The UV light is obtained from UV-lamps with wavelength of (253.7±0.8) nm. The UV-Vis spectrometry is used to monitor the absorbance spectra of methylene blue as a function of illumination time. Experimental results show that the rate constant of photocatalytic reaction of TiO2 nanoparticles for methylene blue is 0.0365 min?1. The surface adsorption plays an important role in the decomposition of methylene blue. Experimental results indicate that the TiO2 nanoparticle fluid possesses excellent photocatalytic activity in photodegradation of methylene blue.展开更多
基金This project is supported by National 863 Project of China(No.9802-01).
文摘Some dynamic factors, such as inertial forces and friction, may affect therobot trajectory accuracy. But these effects are not taken into account in robot motion controlschemes. Dynamic control methods, on the other hand, require the dynamic model of robot and theimplementation of new type controller. A method to improve robot trajectory accuracy by dynamiccompensation in robot motion control system is proposed. The dynamic compensation is applied as anadditional velocity feedforward and a multilayer neural network is employed to realize the robotinverse dynamics. The complicated dynamic parameter identification problem becomes a learningprocess of neural network connecting weights under supervision. The finite Fourier series is used toactivate each actuator of robot joints for obtaining training samples. Robot control system,consisting of an industrial computer and a digital motion controller, is implemented. The system isof open architecture with velocity feedforward function. The proposed method is not model-based andcombines the advantages of close-loop position control and computed torque control. Experimentalresults have shown that the method is validatities to improve the robot trajectory accuracy.
文摘From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a time-dependent failure assessment diagram (TDFAD) isdeveloped on the basis of the time dependent crack tip parameter J integral. According to theproposed TDFAD method, detailed crack initiation and creep crack growth analysis is avoided insafety assessments of high temperature structures by performing simple calculations of stressintensity factor and limit load. To evaluate the creep toughness parameter K_(mat), three differentexpressions are suggested on the basis of experimental load-line displacement, creep crackinitiation and growth parameters as well as the isochronous stress-strain curve. The influence ofservice factors such as temperature and service-time on the proposed TDFAD is discussed by using theproperties of 2.25CrlMo steel and an example is also presented to illustrate the approach.
基金This project is supported by National Natural Science Foundation of China (No.50175011).
文摘From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.
基金This project is supported by National Natural Science Foundation of China (No. 59885002).
文摘Adaptive control of a flexible beam system preceded by an unknown dead-zonein the driving motor is investigated in state space form. By introducing an important lemma forsimplifying error equation between the flexible beam model and the matching reference model, arobust adaptive control scheme is developed by involving the dead-zone inverse terms. The newadaptive control law ensures global stability of the entire system and achieves desired trackingprecision even when the slopes of the dead-zone are not equal. Simulations performed on a typicalflexible beam system illustrate and clarify the validity of this approach.
基金Automobile Industrial Science Foundation of Shanghai (No.2000187)
文摘A new method of parameter identification based on linear time-frequencyrepresentation and Hubert transform is proposed to identity modal parameters of linear time-varyingsystems from measured vibration responses. Using Gabor expansion and synthesis theory, measuredresponses are represented in the time-frequency domain and modal components are reconstructed bytime-frequency filtering. The Hilbert transform is applied to obtain time histories of the amplitudeand phase angle of each modal component, from which time-varying frequencies and damping ratios areidentified. The proposed method has been demonstrated with a numerical example in which a lineartime-varying system of two degrees of freedom is used to validate the identification scheme based ontime-frequency representation. Simulation results have indicated that time-frequency representationpresents an effective tool for modal parameter identification of time-varying systems.
基金This project is supported by State High Technology Development Program of China (No.2003AA413310) National Natural Science Foundation of China(No.60375020) 973 Program of China(No. 2004CB719402, No. 2002CB312106).
文摘Aiming at difficult sorting and retrieving complicated structure assembliesin assembly lib, a method for compartmentalizing assembly design resource by conceptual productstructure model is presented. The similar assembly retrieval mechanisms of symbol assembly relationgraph matching and symbol assembly relation graph similarity are discussed. The method is validatedby taking valve rod assemblies as example.
文摘The optimization of injection molding process for polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends is studied using Taguchi method and principalcomponent analysis (PCA). Four controllable process factors are studied at three levels each in themanufacturing process. The L_9 orthogonal array is conducted to determine the optimum processfactor/level combination for single quality of mechanical properties. In addition, the principalcomponent analysis is employed to trans-form the correlated mechanical properties to a set ofuncorrelated components and to evaluate a comprehensive index for multi-response cases. Then theoptimum process factor/level combination for multiple qualities can be determined. Finally, theanalysis of variance is used to find out the most influential injection molding parameter for singleand multiple qualities problems.
文摘In this article, low-pressure control methods for a combined arc submerged nanoparticle synthesis system (ASNSS) was proposed and developed for TiO2 nanoparticle fabrication. The photocatalytic reaction is carried out in a photochemical reactor. The UV light is obtained from UV-lamps with wavelength of (253.7±0.8) nm. The UV-Vis spectrometry is used to monitor the absorbance spectra of methylene blue as a function of illumination time. Experimental results show that the rate constant of photocatalytic reaction of TiO2 nanoparticles for methylene blue is 0.0365 min?1. The surface adsorption plays an important role in the decomposition of methylene blue. Experimental results indicate that the TiO2 nanoparticle fluid possesses excellent photocatalytic activity in photodegradation of methylene blue.