Multiparameter Stability Analysis of Systems with Induction Motor Loads, Weak Interconnections and Series Compensation

Dynamic modeling and stability domain analysis of a system consisting of a synchronous generator sup-plying an induction motor load through a series compensated weak network has been carried out in this paper. The impact of X/Rratio of the feeder and generation control system parameters on the stability domain with respect to series compensation has been examined through eigenvalue calculations and time domain simulations. From the studies conducted, it was observed that the stability domain of the system with respect to series compensation depends on the grid strength in addition to the excitation system parameters. Eigenvalue analysis shows that there is a strong correlation between the exciter gain, time constants of the measurement transducer and exciter, and the series compensation level. The main contribution of this work is to reveal new bifurcations which arise in these systems which has been studied through eigenvalue analysis and time domain simulations for various combinations of system parameters.

Improvement in Performance of the Sulphuric Acid Transport Installation through Modification of Flow Characteristics Using Electric Actuators

The paper presents a flow model of the installation for tank car filling with sulphuric acid (VI). For the mathematical modelling of the flow process in the industrial installation, a model diagram of the object and experiments carried out during the installation work were applied. The analysis of specific experimental series showed unusual shapes of mass flow characteristics vs. the valve opening level (too wide hysteresis), which markedly deviated from typical flow characteristics that are found in standards and literature. As a result of flow modelling in the sulphuric acid installation, a better-shaped characteristic was presented that should be obtained based on the measuring system values in the absence of the inertia-related error. In the experiments carried out according to the selected procedures, effects of the actuator speed on the characteristics of interest were determined. It was observed that the use of a “slower” actuator (i.e., longer transition time) narrows the characteristics in terms of a reduced difference in flow readings between the valve opening and closing courses. In the specified research procedure for the real flow characteristics, effects of the measurement transducer dynamics in the flow meter on the characteristic course were assessed. It was demonstrated that a faster transducer enabled closer flow recordings to the valve nominal characteristics. The variable speed can improve the positioning precision, with the use of the lowest possible speed rule directly before the positioning point.

Current Measurement Transducer Based on Current-To-Voltage-To-Frequency Converting Ring Oscillator with Cascade Bias Circuit

We propose a ring oscillator (RO) based current-to-voltage-to-frequency (I–V–F) converting current transducer with a cascade bias circuit. The I–V–F converting scheme guarantees highly stable biasing against RO, with a rail-to-rail output operation. This device was fabricated using National NanoFab Center (NNFC) 180 nm complementary metal-oxide-semiconductor (CMOS) technology, which achieves a current resolution of 1 nA in a measurement range up to 200 nA. A noise floor of 11.8 pA/√Hz, maximum differential nonlinearity (DNL) of 0.15 in 1 nA steps, and rail-to-rail output with a 1.8 V power supply is achieved. The proposed transducer can be effectively applied to bio-sensing devices requiring a compact area and low power consumption with a low current output. The fabricated structure can be applied to monolithic-three-dimensional integration with a bio-sensing device.

Sensor system for use with low intensity pulsed ultrasound

Purpose Ultrasound is a well-established technology in medical science, though many of the conventional measurement systems (hydrophones and radiation force balances [RFBs]) often lack accuracy and tend to be expensive. This is a significant problem where sensors must be considered to be “disposable” because they inevitably come into contact with biological fluids and expense increases dramatically in cases where a large number of sensors in array form are required. This is inevitably the case where ultrasound is to be used for the in vitro growth stimulation of a large plurality of biological samples in tissue engineering. Traditionally only a single excitation frequency is used (typically 1.5 MHz), but future research demands a larger choice of wavelengths for which a single broadband measurement transducer is desirable. Furthermore, because of implementation conditions there can also be large discrepancies between measurements. The purpose of this paper deals with a very cost-effective alternative to expensive RFBs and hydrophones. Design/methodology/approach Utilization of cost-effective piezoelectric elements as broadband sensors. Findings Very effective results with equivalent (if not better) accuracy than expensive alternatives. Originality/value This paper concentrates on how very cost-effective piezoelectric ultrasound transducers can be implemented as sensors for ultrasound power measurements with accuracy as good, if not better than those achievable using radiation force balances or hydrophones.

Measurement Transducer Impulse Response Using an Exponential Sine Sweep Method

The impulse response of a piezoelectric transducer can be calculated using the electrical equivalent circuit model with the Manson method for bandwidth transducers. Nevertheless, these approaches are not sufficiently precise because the importance of the homogeneous structure medium where the transducer emits the signal in part determines the bandwidth in which it acts due to the medium interactions with the environment. This paper describes preliminary research results on piezoelectric impulse response measurements in a small space, making use of the procedure presented by Angelo Farina for transducers emitting in reverberant spaces. Combining the basics of the exponential sine sweep (ESS) method, techniques of arrival detection, and signal processing it is possible to obtain the impulse response in a piezoelectric transducer emitting in a homogeneous medium.

Design of a Tri-Axial Force Measurement Transducer for Plantar Force Measurements

Transducers for spatial plantar force measurements have numerous applications in biomechanics, rehabilitation medicine, and gait analysis. In this work, the design of a novel, tri-axial transducer for plantar force measurements was presented. The proposed design could resolve both the normal and the shear forces applied at the foot's sole. The novelty of the design consisted in using a rotating bump to translate the external loads into axial compressive forces which could be measured effectively by conventional pressure sensors. For the prototype presented, multilayer polydimethylsiloxane (PDMS) thin-film capacitive stacks were manufactured and used as sensing units, although in principle the design could be extended to various types of sensors. A quasi-static analytic solution to describe the behavior of the transducer was also derived and used to optimize the design. To characterize the performance of the transducer, a 3 cm diameter, 1 cm tall prototype was manufactured and tested under various combination of shear and normal loading scenarios. The tests confirmed the ability of the transducer to generate strong capacitive signals and measure both the magnitude and direction of the normal and shear loads in the dynamic range of interest.

A new preset refueling mode for gasoline dispenser using frequency converter and flow rate signals

Fuel dispenser is an integrated fuel pumping and metering system for automotive refueling at the service station. In this paper, we develop a preset refueling mode for the dispenser. A frequency converter and the flow rate signal from the measurement transducer are utilized instead of the solenoid valve, which is used to control the flow rate in the traditional refueling mode. With variable speed pumping system, the rotational speed of the pump is adjusted to achieve the desired flow rate and head necessary for the application. All the experiments were operated on a real dispenser system. How the frequency influences the refueling accuracy is observed. Through choosing a suitable frequency, not only accuracy but also energy efficiency improves compared with the traditional refueling mode. It is able to provide a reference for authority to fill in gaps in low-quantity (less than 5 L) refueling.