Academic literature on the topic 'Automatic locking differential'

This paper presents a prototype of an auto-ranging phase-locked loop (PLL) with low jitter noise over a wide operating frequency range using the multiband programmable voltage-controlled oscillator (VCO) gain stage with automatic band selection. We successfully reduce the VCO gain (Kvco) and retain the desired frequency band. The proposed PLL comprises a prescaler, phase frequency detector (PFD), charge pump (CP), programmable VCO and automatic band selection circuit. The PLL prototype with all subblocks was implemented using the TSMC 0.18 μm 1P6M process. Contrary to conventional PLL architectures, the proposed architecture incorporates a real-time check and automatic band selection circuit in the secondary loop. A high-performance dual-loop PLL wide tuning range was realized using an ASIC digital control circuit. A suitable way to maintain the Kvco low is to use multiple discrete frequency bands to accommodate the required frequency range. To maintain a low Kvco and fast locking, the automatic frequency band selection circuit also has two indigenous, most probable voltage levels. The proposed architecture provides the flexibility of not only band hopping but also band twisting to obtain an optimized Kvco for the desired output range, with the minimum jitter and spurs. The proposed programmable VCO was designed using a voltage-to-current-converter circuit and current DAC followed by a four-stage differential ring oscillator with a cross-coupled pair. The VCO frequency output range is 150–400 MHz, while the input frequency is 25 MHz. A sequential phase detection loop with a negligible dead zone was designed to adjust fine phase errors between the reference and feedback clocks. All circuit blocks of the proposed PLL were simulated using the EDA tool HSPICE and layout generation by Laker. The simulation and measured results of the proposed PLL show high linearity, with a dead zone of less than 10 pV. The differential VCO was used to improve the linearity and phase noise of the PLL. The chip measured results show rms jitter of 19.10 ps. The PLL prototype also has an additional safety feature of a power down mode. The automatic band selection PLL has good immunity for possible frequency drifting due to temperature, process and supply voltage variations. The proposed PLL is designed for −40 to +85 °C, a wide temperature range.

Abstract. The ability to make high time resolution measurements of gaseous elemental mercury (GEM) concentrations in air is imperative for the understanding of mercury cycling. Here we describe further development and field implementation of a laboratory prototype pulsed cavity ring-down spectroscopy (CRDS) system for high time resolution, continuous and automated measurement of GEM concentrations in ambient air. In particular, we present use of an external, isotopically enriched Hg cell for automated wavelength locking and wavelength stabilization to maintain laser wavelength on the peak of GEM absorption line in ambient air. We further describe implementation of differential absorption measurements using a piezoelectric tuning element that allows for continuous accounting of system baseline extinction losses needed to calculate GEM absorption coefficients. Data acquisition systems and software programs were modified to acquire high-speed ring-down data at 50 Hz repetition rate as well as process and analyze data in real time. The system was installed in a mobile trailer, and inlet systems and temperature controls were designed to minimize effects of changes in ambient air temperature and ozone (O3) concentration. Data that identify technical challenges and interferences that occurred during measurements, including temperature fluctuations, interferences by ambient O3 and drifts in frequency conversion efficiencies are discussed. Successful development of a CRDS system capable of measuring ambient air GEM concentrations with high time resolution is based on minimizing these interferences.

Abstract. We describe further development of a previous laboratory prototype pulsed cavity ring-down spectroscopy (CRDS) sensor into a field-deployable system for high-time-resolution, continuous, and automated measurement of gaseous elemental mercury (GEM) concentrations in ambient air. We employed an external, isotopically enriched Hg cell for automated locking and stabilization of the laser wavelength on the GEM peak absorption during measurements. Further, we describe implementation of differential absorption measurements via a piezoelectric tuning element for pulse-by-pulse tuning of the laser wavelength onto and off of the GEM absorption line. This allowed us to continuously correct (at 25 Hz) for system baseline extinction losses unrelated to GEM absorption. Extensive measurement and calibration data obtained with the system were based on spike addition in both GEM-free air and ambient air. Challenges and interferences that occurred during measurements (particularly in ambient air) are discussed including temperature and ozone (O3) concentration fluctuations, and steps taken to reduce these. CRDS data were highly linear (r2 ≥ 0.98) with data from a commercial Tekran 2537 Hg analyzer across a wide range of GEM concentrations (0 to 127 ng m−3) in Hg-free and ambient air. Measurements during periods of stable background GEM concentrations provided a conservative instrument sensitivity estimate of 0.35 ng m−3 for the CRDS system when time averaged for 5 min. This sensitivity, along with concentration patterns observed in ambient air (with the CRDS system and verified with the Tekran analyzer), showed that the sensor was capable of characterizing GEM fluctuations in ambient air. The value of fast-response GEM measurements was shown by a series of GEM spike additions – highlighting that high-temporal-resolution measurement allowed for detailed characterization of fast concentration fluctuations not possible with traditional analyzers.

Context. Late-type stars in close binary systems can exhibit strong magnetic activity owing to rapid rotation supported by tidal locking. On the other hand, tidal coupling may suppress the differential rotation which is a key ingredient of the magnetic dynamo. Aims. We studied the red dwarf component in the eclipsing binary system V471 Tau in order to unravel the relations between the different activity layers, from the stellar surface through the chromosphere up to the corona. Our aim is to study how the magnetic dynamo in the late-type component is affected by the close white dwarf companion. Methods. We used space photometry, high-resolution spectroscopy, and X-ray observations from different space instruments to explore the main characteristics of magnetic activity. We applied a light curve synthesis program to extract the eclipsing binary model and to analyze the residual light variations. Photometric periods were obtained using a Fourier-based period search code. We searched for flares by applying an automated flare detection code. Spectral synthesis was used to derive or specify some of the astrophysical parameters. Doppler imaging was used to reconstruct surface temperature maps, which were cross-correlated to derive surface differential rotation. We applied different conversion techniques to make it possible to compare the X-ray emissions obtained from different space instruments. Results. From the K2 photometry we found that 5–10 per cent of the apparent surface of the red dwarf is covered by cool starspots. From seasonal photometric period changes we estimated a weak differential rotation. From the flare activity we derived a cumulative flare frequency diagram which suggests that frequent flaring could have a significant role in heating the corona. Using high-resolution spectroscopy we reconstructed four Doppler images for different epochs which reveal an active longitude, that is, a permanent dominant spot facing the white dwarf. From short term changes in the consecutive Doppler images we derived a weak solar-type surface differential rotation with αDR = 0.0026 shear coefficient, similar to that provided by photometry. The long-term evolution of X-ray luminosity reveals a possible activity cycle length of ≈12.7 yr, traces of which were also discovered in the Hα spectra. Conclusions. We conclude that the magnetic activity of the red dwarf component in V471 Tau is strongly influenced by the close white dwarf companion. We confirm the presence of a permanent dominant spot (active longitude) on the red dwarf facing the white dwarf. The weak differential rotation of the red dwarf is very likely the result of tidal confinement by the companion. We find that the periodic appearance of the inter-binary Hα emission from the vicinity of the inner Lagrangian point is correlated with the activity cycle.

In this project work the design and construction of a model of automatic braking system for vehicles in hill station is to be developed. The mechanism has been developed to stop the vehicle from rolling back word when the vehicle is moving in the hill roads. This construction made of two phases in a first deigns of ratchet and pawl mechanism, frame, shaft, etc. is done and in second sensor selection and interference is done. Ratchet and pawl mechanism has been fabricated and assembly with sensor interface is tested. The proposed mechanism is to reverse break using ratchet gear. By reverse locking the differential is disengaged from the axle. Thus the power is directly transmitted to the axle and hence to the wheels. This will considerably reduce the power loss in some occasions when unwanted loss is happening due to the transmission if power from the shaft to the ratchet gear and then to the axle and hence to the wheels. So in mechanism the unwanted power loss in the due course of transmission through the gear wheel is reduced.

This thesis consists of two parts. The first one contains a research about different kinds of divorces in tractors. There is also a description of a modelling in MATLAB, Simulink and Stateflow programs. The second part focuses on designing an algorithm of an automatic locking differential and connection front-wheel drive and its testing on a model of tractor. Furthermore the thesis solves an implementation process of the algorithm into the control unit.