This paper is focused in the development of a parallel control loop of the angular velocity and torque for Brushless Direct Current (BLDC) motors. This parallel loop is proposed as an improvement for the performance of those cascaded solutions commonly reported in the body of literature of the field. Performance is improved by reducing the steady state error of the speed considerably when compared with the typical cascaded loop solution under a commanded change of torque. In addition, the steady state response of the parallel loop is reached in a shorter time. Simulations were designed to carry out a comparison between both methodologies. The results of these simulations consider only changes in the set point for speed or torque and are reported here. The control signal was applied to a simulated driver using a switching method known as Direct Torque Control of 2 and 3 phases (DTC-2+3P). These preliminary results show that the parallel control loop outperforms the cascaded control of BLDC motors.

A low power RF amplifier circuit for ion trap applications is presented and described. The amplifier is based on a class-D half-bridge amplifier with a voltage mirror driver. The RF amplifier is composed of an RF class-D amplifier, an envelope modulator to ramp up the RF voltage during the ion analysis stage, a detector or amplitude demodulation circuit for sensing the output signal amplitude, and a feedback amplifier that linearizes the steady state output of the amplifier. The RF frequency is set by a crystal oscillator and the series resonant circuit is tuned to the oscillator frequency. The resonant circuit components have been chosen, in this case, to operate at 1 MHz. In testings, the class-D stage operated at a maximum of 78 mW at 1.1356 MHz producing 225 V peak.

No abstract

No abstract

In the current work, the effect of an annealing process on structural, morphological, and optical behaviors of cadmium sulfide thin films is presented. A chemical bath deposition method for cadmium sulfide deposition is based on the use of glycine as a complexing agent. Cadmium sulfide thin films were grown by chemical bath deposition and annealed in a nitrogen atmosphere at 0, 100, 150, 200, and 250 • C for 30 minutes. Crystallographic and morphological studies of CdS thin films were performed by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray diffraction. The optical behavior of CdS thin films was evaluated by UV-Visible spectroscopy and band gap values were calculated by approximation using a Tauc plot. After annealed, densified CdS films formed by nanostructured crystallites exhibit suitable band gap values and present relatively high transmittance in the visible region, allowing their application as a window material for solar cells.