With the ongoing miniaturization in products, there is a growing demand for the development of accurate forming process for mechanical micro-parts. However, in microforming process, the size effects come up and make t...
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ISBN:
(纸本)9783540733737
With the ongoing miniaturization in products, there is a growing demand for the development of accurate forming process for mechanical micro-parts. However, in microforming process, the size effects come up and make the knowledge of the usual forming process can not be used directly. This paper investigates the size effect of H62 with the uniaxial tension experiments, and the results show both the grain size effect and the feature size effect. On the basis of the tension data, the LS-DYNA is used to analysis the micro-extrusion process. The simulation results show that the friction condition affect the microforming process seriously. When the friction condition changes, the stress state of the deformed material also changes. With the increasing of the friction coefficient, the extrusion force increases rapidly.
The stabilization problem of nonholonomic mobile robots that move on uneven surface is investigated. Smooth control laws ensuring practical stabilization are proposed based on the transverse function approach and the ...
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ISBN:
(纸本)9783540733737
The stabilization problem of nonholonomic mobile robots that move on uneven surface is investigated. Smooth control laws ensuring practical stabilization are proposed based on the transverse function approach and the integrator backstepping technique. Firstly, a transverse function which defines a smooth embedded submanifold is constructed, and an augmentation procedure is applied to the kinematic model of the robots. Then, the left-invariance property of the kinematic model is explored, and after the defining of the error variables via group operation, smooth exponential stabilizing control laws are derived for the error dynamic system, thus the kinematic model is rendered practically stable. Finally, the obtained control laws are utilized in the integrator backstepping process to stabilize the dynamic model. Simulations are provided to demonstrate the effectiveness of the algorithm.
Currently, widespread clinical application of medical robots is hindered by not only low security and operation efficiency but also the high cost for robot control system. In response, a framework of medical robot con...
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ISBN:
(纸本)9783540733737
Currently, widespread clinical application of medical robots is hindered by not only low security and operation efficiency but also the high cost for robot control system. In response, a framework of medical robot control system based on PLC was presented according to the clinical requirement of medical robot. In terms of the design process of function analysis, the hardware and software structures were confirmed. Based upon the concern of safety problems that the operation system of medical robot was confronted with, the safety strategy performed in the system and orientation precisions of the system were discussed in detail. The specific safety schemes responding to the above problems were put forward. Clinical experimentations were accomplished in the Neurosurgery Institute of General Navy Hospital. The stable performance was verified.
Tungsten Inert Gas (TIG) arc is the most widely employed type of a plasma torch and enables to produce arc plasma with high energy density. Therefore it is suitable as a heat source especially for processes to require...
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ISBN:
(纸本)9783540733737
Tungsten Inert Gas (TIG) arc is the most widely employed type of a plasma torch and enables to produce arc plasma with high energy density. Therefore it is suitable as a heat source especially for processes to require concentrating the heat input at a point. On the other hand, Tube Cathode Arc (TCA) to be a kind of TIG produces the arc plasma by introducing inner shielding gas through the central hole of the tube cathode. In this paper, as the basic heat source property of argon (Ar) TCA, the property of the arc plasma and the heat input intensity onto a water-cooled copper anode for various inner shielding gas flow rates were numerically analyzed. Furthermore, by employing stainless steel SUS304 anode, the geometry of it's weld penetration was also predicted. The results were compared with those for the conventional TIG. As a result, it was found that since TCA enables to heat the target material uniformly by controlling the inner shielding gas flow rate and preserve it from damage due to excessive heat input during the process, it is suitable for processes such as brazing, buildup or thermal spraying.
An open problem, set by *** in his contribution to the volume "Open Problems in Mathematical Systems and control Theory", ***, *** Eds., 2004, regards regularization of optimal control-affine problems with c...
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ISBN:
(纸本)9783540738893
An open problem, set by *** in his contribution to the volume "Open Problems in Mathematical Systems and control Theory", ***, *** Eds., 2004, regards regularization of optimal control-affine problems with control-independent state-quadratic cost. It is asked whether the infima of the regularized (by adding squared L-2-norm of controls) functionals converge to the infimum of the original functional? We show that this question can be resolved by an elementary argument. We claim that one should study minimizing sequences of the original functional, rather than its infimum. We advocate the relevance of this question, formulating it via notion of order of singularity of an optimal problem. We study this question and provide computations of the order of singularity for arbitrary singular linear-quadratic problem and also for some classes of nonlinear control-affine problems. Some open problems are,set.
A fuzzy controller (FC) was developed to improve deposit dimension accuracy in spray forming process, fuzzy rules of FC were extracted from experimental sample data by dynamic clustering method. Simulation results sho...
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ISBN:
(纸本)9783540733737
A fuzzy controller (FC) was developed to improve deposit dimension accuracy in spray forming process, fuzzy rules of FC were extracted from experimental sample data by dynamic clustering method. Simulation results show that fuzzy controller is available to regulate deposit dimension, main advantage of FC is it has a stronger adaptability for nonlinear process control than PID controller, and FC of identical structure has satisfying control performance for different predetermined target values. FC closed-loop control experimental results show that average deposit thickness is 5.22m in steady growth period, average error between actual size and 5.5mm target value is 0.28mm, and RMS (mean square root) is 0.31mm.
The unfitness of weld and gap variation are salient using traditional TIG procedure for the five-port connector flange. Insufficient reliability and the instability of the weld are catastrophe, which cannot accommodat...
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ISBN:
(纸本)9783540733737
The unfitness of weld and gap variation are salient using traditional TIG procedure for the five-port connector flange. Insufficient reliability and the instability of the weld are catastrophe, which cannot accommodate to new generation type production's requirement. In this study, a finite element model of the five-port connector was built and the distribution of temperature field and deformation were studied. The result shows that welding thermal cycle is greatly different from the ordinary butt weld during welding of the flange and spherical shell. The welding deformation is complex from the direction of UX and UZ. Especially maximum deformation from the direction of UZ is about 4.96mm. According to the result, the optimum welding fixture is designed on the view of the smallest deformation, to critically control the deformation of the both sides of the welding line, finally to accomplish the robotic flexible welding.
A class of two-parameter Poisson-Dirichlet distributions have non-vanishing coefficient of variation. This phenomenon is also known as non-self averaging stochastic multi-sector endogenous growth model. This model is ...
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ISBN:
(纸本)9783540735694
A class of two-parameter Poisson-Dirichlet distributions have non-vanishing coefficient of variation. This phenomenon is also known as non-self averaging stochastic multi-sector endogenous growth model. This model is used to raise questions on the use of means in assessing effectiveness of macroeconomic or other macro-policy effects. The coefficients of variations of the number of total sectors, and of sectors of a given size all remain positive as the model size grows unboundedly.
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