Enlargement of electrode face diameter in resistance spot welding was the main factor that led to undersize nugget diameter. A mathematics model was established to estimate electrode face diameter by applying the char...
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ISBN:
(纸本)9783540733737
Enlargement of electrode face diameter in resistance spot welding was the main factor that led to undersize nugget diameter. A mathematics model was established to estimate electrode face diameter by applying the characteristic that servo gun can detect axial wear online but not equip additional measurement apparatuses. Firstly the precision of servo gun was compensated to assure it can meet the requirement of axial wear measurement online. Then the model was established to estimate electrode face diameter online by a minimum amount of experiment data to determine the numerical constant in the model. To verify the model, electrode life tests for welding different galvanized steels were carried out. It was shown that estimation results of the model agreed well with the experiment results and spot welding the steels with higher electrode wear rate would result in a shorter electrode life.
This paper presents an energy optimization method of the safety door's motion control. Considering the multiple factors that affect the safety door's energy consumption, we establish an objective function and ...
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ISBN:
(纸本)9783540733737
This paper presents an energy optimization method of the safety door's motion control. Considering the multiple factors that affect the safety door's energy consumption, we establish an objective function and a constraint equation, and propose an energy optimization method based on Sequential Quadratic Programming (SQP) algorithm. The controllable curve of the instantaneous linear velocity for the safety door based on the optimization design can be finally obtained. This method has been proved to be effective by experiments.
An energy balance equation with respect to a control contact system provides port outputs which are conjugated to inputs. These conjugate variables are used to define the composition of port contact systems in the fra...
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ISBN:
(纸本)9783540738893
An energy balance equation with respect to a control contact system provides port outputs which are conjugated to inputs. These conjugate variables are used to define the composition of port contact systems in the framework of contact geometry. We then propose a power-conserving interconnection structure, which generalizes the interconnection by Dirac structures in the Hamiltonian formalism. Furthermore, the composed system is again a port contact system, as illustrated on the example of a gas-piston system undergoing some irreversible transformation.
This article challenges Bernstein's problem of redundant degrees of freedom (DOF) that remains unsolved from the control-theoretic point of view as well as from the standpoint of both neuro-physiology and robotics...
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ISBN:
(纸本)9783540738893
This article challenges Bernstein's problem of redundant degrees of freedom (DOF) that remains unsolved from the control-theoretic point of view as well as from the standpoint of both neuro-physiology and robotics. Firstly, a rather simpler but mysterious control problem of movements of human-like multi-joint reaching with excess DOFs is analyzed from Newtonian mechanics and differential geometry. Secondly, another illustrative control problem that seems to be sophisticated and complicated is tackled, which is to find a sensory coordinated control signal for 3-Dimensional stable grasping and object manipulation by a pair of robot fingers with multiple joints under the effect of gravity and nonholonomic constraints. In each illustrative control problem, it is possible to find a simple control signal that renders each corresponding closed-loop dynamics stable on its corresponding equilibrium-point manifold. It is claimed, however, that convergences of solutions of closed-loop dynamics to an equilibrium-point manifold can not be analyzed by using Lyapunov's direct method, because a Lyapunov-like energy form can not be positive definite due to redundancy of DOFs. Instead, a novel definition called "stability on a manifold" based upon the concept of Riemannian distance on the constraint manifold is introduced in both illustrative problems and used in the analysis of convergence of solution trajectories. It is also shown that finiteness of Riemannian metrics plays an important role in evaluation of the performance of control in both problems.
As a key part of the photo-etching facility, the wafer prealigner uses mechanical or optical aligning method to save the time and guarantee the quality of manufacturing. In this paper, a new wafer prealigner is propos...
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ISBN:
(纸本)9783540733737
As a key part of the photo-etching facility, the wafer prealigner uses mechanical or optical aligning method to save the time and guarantee the quality of manufacturing. In this paper, a new wafer prealigner is proposed based on the mass center calculation method. The mass center is measured by a reflection-style laser sensor from the wafer's radial direction, and the position is measured by the notch angle detection using the penetration-style laser senor. A dynamic error compensation method is applied to eliminate the radial runout and wobble of the rotary stage, which have effects on measuring the wafer's mass center. The accuracy is improved through two steps: firstly, a coarse alignment is made by adjusting the mass center;secondly, a precise alignment is processed by aligning the wafer's notch. Experiments show that the accuracy of the wafer prealigner satisfied the system requirement.
In short-circuit CO2 arc welding, the transfer behavior, process stability and weld quality are strongly affected by the molten droplet shape just before short-circuit and the electromagnetic pinch action on the liqui...
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ISBN:
(纸本)9783540733737
In short-circuit CO2 arc welding, the transfer behavior, process stability and weld quality are strongly affected by the molten droplet shape just before short-circuit and the electromagnetic pinch action on the liquid bridge during short-circuit phase. By using Static Force Balance Model, the effects of electromagnetic force, surface tension and gravity on the molten droplet shape during arc phase are simulated, the electromagnetic force being the dominant factor. To obtain a appropriate molten droplet shape in favor of arc stability and metal transfer, it is preferable to adopt a certain large pulse current in arc prophase and a small arc-keeping current in arc anaphase The numerical analysis to the effects of electromagnetic pinch action on the liquid bridge during short-circuit phase shows that a large current at initial stage will block the molten droplet from well spreading into the weld pool, but a large pulse current at metaphase will facilitate the formation of a neck in the liquid bridge. The simulation results are validated experimentally in waveform-controlled short-circuit CO2 arc welding, the welding process being improved to be much stable and gentle.
An algorithm is presented for the computation of the most powerful unfalsified model associated with an observed vector time series in the class of dynamical systems described by linear constant coefficient difference...
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ISBN:
(纸本)9783540735694
An algorithm is presented for the computation of the most powerful unfalsified model associated with an observed vector time series in the class of dynamical systems described by linear constant coefficient difference equations. This algorithm computes a module basis of the left kernel the Hankel matrix of the data, and is recursive in the elements of the basis. It is readily combined with subspace identification ideas, in which a state trajectory is computed first, directly from the data, and the parameters of the identified model are derived from the state trajectory.
Mobile manipulation is a key capability to many robotic applications in construction, space, underwater, nuclear plant and home services. Dynamic modeling and trajectory control for a holonomic omnidirectional mobile ...
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ISBN:
(纸本)9783540733737
Mobile manipulation is a key capability to many robotic applications in construction, space, underwater, nuclear plant and home services. Dynamic modeling and trajectory control for a holonomic omnidirectional mobile manipulator are principle problems for mobile manipulation, and are presented in this paper. Considered the redundantly-actuated property of omnidirectional mobile platform, the kinematic model of the whole mobile manipulator is presented. Then, an integrated dynamic model for the system is developed by the kinematic model and Lagrangian formalism. According to the dynamic model, a modified inverse dynamic control is addressed to track the trajectories of the mobile platform and end-effector simultaneously. Then, the simulations results show the effectiveness of the proposed modeling and control approach.
A particular family of Hamiltonian functions is considered. Such functions are quadratic in the moment variables and arise in spaceflight mechanics when the averaged system of energy minimizing trajectories of the Kep...
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ISBN:
(纸本)9783540738893
A particular family of Hamiltonian functions is considered. Such functions are quadratic in the moment variables and arise in spaceflight mechanics when the averaged system of energy minimizing trajectories of the Kepler equation is computed. An important issue of perturbation theory and averaging is to provide integrable approximations of nonlinear systems. It turns out that such integrability properties hold here.
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