Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

A Closed-Loop Capacitance-to-Frequency Converter for Single-Element and Differential Capacitive Sensors

Abstract: A novel closed-loop switched-capacitor (SC) capacitance-to-frequency converter (CFC) is presented in this article. The proposed CFC is capable of measuring from either a single-element or a differential capacitive sensor (DCS), providing ratio and ratiometric outputs, respectively. Most of the existing autobalancing schemes for capacitive sensors use the closed-loop approach but require precise sinusoidal ac excitation and provide an analog output that is sensitive to parasitic capacitances. Also, the use of voltage-controlled resistors (VCRs) in many of these schemes limits the linearity and accuracy of their output. The SC-CFC presented in this article employs a simple dc reference for excitation and gives a digital output that is insensitive to parasitic capacitances, by virtue of design. Additionally, the output is linear, irrespective of the sensor characteristic, and independent of the nominal value of the sensor. This feature, along with its compatibility with single-element and DCSs, facilitates its ease of integration with a wide range of capacitive sensors. The CFC has a one-time correction mechanism that significantly reduces the impact of component mismatch. The prototype of the proposed scheme exhibits a maximum nonlinearity error (NLE) of 0.24%, a resolution of 12.59 effective number of bits (ENOB), and a rise time of 6 ms. In addition, the proffered design is fit for integrated circuit (IC) fabrication as it employs an SC approach.

A novel strategy using H infinity theory with optimum weight selection for the robust control of sensorless brushless DC motor

Abstract: A direct implementation of H infinity theory for the robust control of a sensorless brushless direct current motor is proposed in this paper. This provides a better dynamic performance compared to conventional Proportional Integral controller and simulation results of the comparison are presented. For the proper weight selection of H infinity controller, particle swarm optimization technique is employed which results in small sensitivity function in low frequency region and small complementary sensitivity function in high frequency region which is the trade off required for good reference tracking, disturbance rejection, being insensitive to modelling errors and noise. The reduced torque ripples along with improved rise time and steady state error by 0.6% and 25% respectively results in low noise, less vibration and better robust performance irrespective of external disturbances compared to PI controller.