Design and implementation of double closed-loop system of brushless DC motor based on sliding mode control
In this paper, sliding mode control (SMC) is used in double closed-loop system of brushless dc motor(BLDCM), which improves speed tracking performance of BLDCM. Kinetic equation of motor is established according to mathematical modeling of motor, then design sliding mode controller by using kinetic equation. Sliding mode controller regulates speed in speed loop, and SMC strategy makes speed control of BLDCM have many advantages of quick response, strong robustness, small overshoot and so on. Current loop regulated by proportional-integral-differential(PID) control lets BLDCM limit maximum current to automatically protect system when BLDCM is in a state of overload. Through simulation with Matlab, it is obvious to see that system designed by this proposed scheme has better control effect than double closed-loop system all using PID control. Experimental platform is set up by K60 microcontroller, and it verifies feasibility of controller in actual control.
Modeling and simulation of the double-closed loop control system of counter rotating permanent magnet brushless DC motor
Unmanned underwater vehicle (UUV) has extensive and important use in military and civilian. The traditional power system of UUV adopts rotating propeller propulsion system, and has the following main disadvantages: low efficiency of power system, big noisy and large size. For the shortcomings of UUV power system, the research studies the new power system — counter rotating permanent magnet brushless DC motor (BLDCM). The research infers the mathematical model of counter rotating permanent magnet BLDCM according to the ordinary permanent magnet BLDCM, and designs the speed-adjusting controller. The speed-adjusting controller adopts double-closed loop control system that inner loop is current loop and outer loop is speed loop, and the research conducts the modeling and simulation of counter rotating permanent magnet BLDCM based on Matlab/Simulink. The simulation results show that the design of double-closed loop controlling system is consistent with theoretical analysis. Compared to the previous UUV power system, the new power system improves greatly power system efficiency, reducing significantly noise, and greatly reducing the volume and saving space. Therefore, this research proposes the double-closed loop control system of counter rotating permanent magnet brushless DC motor, and has some value for promotion of UUV power system.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.