Applied Mechanics and Materials Vols. 263-266

Abstract: To estimate the effect of roller deformation on the workpiece during the rolling process of H-beams, it is essential to consider the force exerted on the rollers and the deformation thereof. For this purpose, a three-dimension thermo-mechanical coupling model has been built with the finite element analytical package ABAQUS to simulate the hot rolling process of H-beams. In particular, the simulation is conducted under the assumption that the rollers are elastic and rolling torque imposed unilaterally, which agrees with the practical rolling conditions. Noting the results of FEM simulation, the metal flow and temperature distribution have been obtained. To verify the effectiveness of the proposed simulation, comparisons of the roller contact reaction and temperature between the simulated and measured values have been made. The simulation is meaningful for preparing continuous rolling procedures of H-beams.

Abstract: This paper presents a multi-robot cooperation strategy with virtual-physics force which includes three kinds of effort: structure formation force, goal force, and obstacle avoidant force. For swarm formation, a virtual robot is located at the center of the polygon. The innovative contribution of the strategy is that robots only having two kinds of forces: structure formation force and obstacle avoidant force while virtual robot having one kind of force: goal force. The motion of the virtual robot depends on the goal force which obtained from the sensor observations of the robots. Once the virtual robot moved to a new place, robots would also move with the forces acted on themselves as a single body and maintain a regular polygon formation. Simulation experiments are carried out, and the results show that the proposed strategy can effectively navigate the mobile robotics swarms to the chemical source in an indoor arena.

Abstract: To improve the machining precision and reduce the geometric errors for 5-axis machine tool, error model and calibration are presented in this paper. Error model is realized by Denavit-Hartenberg matrixes and homogeneous transformations, which can establish the relationship between the cutting tool and the workpiece. The accuracy calibration was difficult to achieve, but by a laser approach, the errors can be displayed accurately which is benefit for later compensation.

Abstract: This paper analysis the control principle of the asynchronous motor soft-start with discrete variable frequency technology．A simulation model for the asynchronous motor soft-starter using discrete variable frequency technology is built based on MATLAB SIMULINK/POWER SYSTEM．In start process, positive sequence sub - frequency such as 13、10、7、4 discrete variable frequency is used in the soft-starter to simplified power circuit and its control. While on the power frequency time slice ,a single neuron PID algorithm is used to limit the current. The simulation results verify the asynchronous motor soft-starter with discrete variable frequency technology not only reduces the initial firing current but also has bigger start torque, which has a faster start speed compared with the normal soft starter with current limit starting control technology.

Abstract: This paper studies the control theory and the methods of the silicon micromachined resonant accelerometers(SMRAs). According to the structure and movement of the resonant accelerometer, the model of its dynamics and the equations of motion are deduced. The model of the closed-loop control is set up with the phase lock loop (PLL). The principle of PLL is expounded in detail. The requirements for phases and gains of the sinusoidal self-drive-oscillation are met by PLL. The average method is to take the average of slowly changing variables within a cycle to find the solutions of nonlinear equations. Using the average method, it analyzes the PLL’s phase control methods in depth and derives the system stability condition. The simulation results verify the correctness of the stability condition. It provides a guiding theory for the realization of SMRA’s precision control.

Abstract: This paper carries research on the method of smooth method of Brushless DC Motor. Brushless DC motor applied in human skeleton booster is required to switch frequently among four-quadrant operation states of forward rotation, backward rotation, electro motion and braking control. Basically, this switch is expected to be soft. That means it is unexpected that motor comes about the phenomenon of impact of great force, speed mutation and so on. According to the requirement, the paper presents the design of driving circuit of brushless DC motor and put forward a corresponding control method. In the end, the paper proved the correct of this method by using simulation and experimental data.

Abstract: This paper carries research on the methods of wide-ranged speed regulation AC servo system based on the permanent magnetic synchronous motor. The permanent magnetic synchronous motor(PMSM) is a kind of motor with high speed and low rotational inertia, which needs overcoming nonsinusoidal magnetic field，cogging effect and the interference produced by chopper circuit when fulfilling wide-ranged speed regulation. In this paper, the authors analyze the phase current wave of PMSM, and put forth an appropriate type of digital filteration, which is proved true by computer simulation and experimental data.

Abstract: In this paper, the dual-input nonlinear controller of permanent magnet wind generators was designed based on energy dissipation theory and Hamiltonian energy approach. Under the action of the Hamiltonian controller, the closed-loop system is asymptotically stable on case of no disturbances and finite-gain L2 stable in the presence of disturbances. The Hamiltonian energy approach provides us a physical insight and a new way to the controller design of nonlinear systems. The simulation results show the effectiveness of the proposed robust controller.

Abstract: Microfluidic PCR implements the PCR as a continuous process for nucleic acid analytics. Main fields of application are the monitoring of continuous processes for rapid identification of contaminants and quality control as well as high throughput screening of cells or microorganisms. The special heater arrangement allows the implementation of up to 40 cycles on the footprint of a sample. Precise temperature control is the key factor of PCR instrument, and optimal algorithm occupies an important position in this instrument. In order to optimizing the microfluidic PCR system thermal cycler perfomants, fuzzy-PID algorithm was designed, which would replace the lead correction algorithm. The simulation model was constructed and experimented with the use of the Simulink of Matlab software．The simulation results show that overshoot of lead correction algorithm is 8.5%, adjustment time is 3.4s. Overshoot of fuzzy-PID algorithm is 1.45%, adjustment time is only 1.94 s. Obviously, fuzzy-PID algorithm would overcome the defect of large overshoot of traditional PID, and the adjustment time becomes shorter also.

Abstract: The causes of voltage ripples in switched reluctance generator (SRG) are analyzed. At first, on the foundation of the driving circuit with a three-level topology, the energy conversion relations in different rotator positions or in different electric level states was set up. Secondly, the SRG outputting voltage was controlled by a new method named direct energy control. Then, the hysteresis control logic of the direct energy control was designed. At last, we conduct the simulation experiments. The simulation results show that this method can effectively decrease the output voltage ripples of SRG.