Support Vector Machines (SVM) has been widely used in classification and nonlinear function estimation.However, the major drawback of SVM is its higher computational burden for the constrained optimization programming. This disadvantage has been overcome by Least Squares Support Vector Machines (LS-SVM), which solves linear equations instead of a quadratic programming problem. This paper compares LS-SVM with SVM for regression.According to the parallel test results, conclusions can be made that LS-SVM is preferred especially for large scale problem, because its solution procedure is high efficiency and after pruning both sparseness and performance of LS-SVM are comparable with those of SVM.
Piezoelectric actuators have wide applications because of their indefinite resolution and high stiffness, for use in optical devices, measurement systems and ultra-precision machine tools. In noncircular turning, the tools feeding servo should be longtravel, high-frequency and high-precision. In order to meet these requirements, a new flexure-hinge structure is used to amplify the output displacement of piezoelectric actuators. A hybrid of feedforward control in the disturbance channel, repetitive control and Proportion and Integration control (PI) are also employed to better the tracking precision and robustness of the system.
A revolving electromagnetic actuation mechanism composed of an electromagnetic stator and an electromagnetic rotor has been developed for boring non-circular holes. The main component of the rotor is a flexure-hinged based flexible body. There are four pole-pair coils in the stator supplying actuation currents. The micro-displacement between the stator and rotor can be controlled by changing the currents applied in the pole-pair coils. Through linearization of the actuation force near the static action point, a linear relationship between the control current and the actuation force was established, and the synchronizing control method of the electromagnetic actuation mechanism is presented here. With two-factor analysis of the linearization error of the actuation force, the influences of control current and micro-displacement to the linearization error of the actuation force were studied. Then, the principle for designing the basic parameters of the magnetic actuation mechanism is put forward. The calibration of the mechanism indicates that the relationship between the micro-displacement of the rotor and the control current has linear characteristics in the required micro-displacement range. Simulation tests show that the turning radius of the rotor changes with the control current. The proposed mechanism can feasibly supply a controllable micro displacement to the boring bar.
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