Showing papers on "Slip ratio published in 1996"
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TL;DR: Stokes flow between corrugated plates in microdomains has been analyzed using a perturbation method using the incompressible Navier-Stokes equations, but the velocity-slip is present along the solid-fluid interface.
Abstract: Stokes flow between corrugated plates in microdomains has been analyzed using a perturbation method. This approach used the incompressible Navier-Stokes equations, but the velocity-slip is present along the solid-fluid interface. For the slip flow regime, if we introduce Knudsen number (Kn) herein, 0.01 ≤Kn≤ 0.1, the total flow rate is increasing as a ratio of 1 + 6Knto no-slip Stokes flow. If we consider fixedKncases, the corrugations still decrease the flow rate, consideringO(e2) terms, and the decrease is maximum as the phase shift becomes 180 °.
56 citations
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TL;DR: In this article, the Miropolskiy's slip ratio combined with Lin's frictional pressure-gradient correlations was used to predict the slip ratio in the flow within the capillary tube.
48 citations
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TL;DR: The apparent slip velocity was a constant fraction of the maximal velocity for a given contraction ratio as mentioned in this paper, and was independent of L/D but was strongly influenced by the wall stress, the observed apparent slip velocities being comparable with those determined using the Mooney analysis on capillary flows.
Abstract: Nuclear magnetic resonance imaging has been used to investigate the flow of 0.2% aqueous solutions of xanthan gum. Apparent slip was observed in solutions made from the material supplied by UNAM but not in that supplied by Aldrich or Kelco. The apparent slip velocity was a constant fraction of the maximal velocity for a given contraction ratio. The apparent slip velocity also appeared to be independent of L/D but was strongly influenced by the wall stress, the observed apparent slip velocities being comparable with those determined using the Mooney analysis on capillary flows. After exposure to the action of a syringe pump, which reduced the mean molecular weight of the xanthan, the UNAM xanthan solution no longer exhibited apparent slip. Slip appears to be a function of molecular weight, possibly through sensitivity to the aspect ratio of the molecule.
48 citations
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TL;DR: In this article, a set of experimental measurements with a spinning rotor gauge (SRG) with 3.85, 4.00, and 4.50 mm nominal diameter steel spheres in He, Ar, and Kr is reported.
Abstract: A set of experimental measurements with a spinning rotor gauge (SRG) with 3.85, 4.00, and 4.50 mm nominal diameter steel spheres in He, Ar, and Kr is reported. The experiments covered the continuum and the slip regimes for all three gases. Theoretical results from a companion paper on the SRG, together with a calibration based on known viscosity for helium, are used to extract values of the viscosity, the velocity slip coefficient, and the tangential momentum accommodation coefficient for each of the gases. The measured viscosities are in good agreement with existing literature values.
40 citations
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05 Jul 1996TL;DR: A turn control apparatus for a motor vehicle comprises an arithmetic operation section for acquiring a correction amount for the target slip ratio of a target wheel to be controlled based on the required yaw moment of the vehicle in a situation where an antiskid braking system (ABS) should be activated as mentioned in this paper.
Abstract: A turn control apparatus for a motor vehicle comprises an arithmetic operation section for acquiring a correction amount for the target slip ratio of a target wheel to be controlled based on the required yaw moment of the vehicle in a situation where an antiskid braking system (ABS) should be activated, a computing section for computing the target slip ratio upon reception of the correction amount from the arithmetic operation section, and a section for acquiring actuation modes and pulse widths for inlet and outlet valves for wheel brakes of the individual wheels, based on the target slip ratio when the ABS is in operation.
37 citations
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TL;DR: In this article, the behavior of solid inertia particles carried with significant slip velocity in turbulent gas-solid flow in a horizontal channel is investigated, and it is shown that, for such motion, particles have substantial transversal velocity and so they interact intensively with the walls when the Stokes number exceeds a threshold value.
29 citations
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17 Apr 1996TL;DR: In this paper, a detecting device for detecting the coefficient of friction on the road surface is made up of a section detecting the driving force of wheels to be driven by the engine, a section for detecting a slip ratio of the wheels, and a section based on a correlation between the driving forces and the slip ratio.
Abstract: Either the front wheels or the rear wheels of a front wheel- and rear wheel-drive vehicle are driven by an engine and the other thereof are driven by an electric motor. A detecting device detects a coefficient of friction on a road surface during running of the vehicle. Control circuit controls to operate the electric motor when the vehicle is subsequently started in a condition in which the coefficient of friction on the road surface is equal to or smaller than a predetermined value. The detecting device for detecting the coefficient of friction on the road surface is made up of a section for detecting the driving force of wheels to be driven by the engine, a section for detecting a slip ratio of the wheels, and a section for obtaining the coefficient of friction on the road surface based on a correlation between the driving force and the slip ratio.
27 citations
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12 Mar 1996
TL;DR: In this paper, an anti-skid brake control system, consisting of wheel-speed sensors, a pseudo vehicle speed generator, an arithmetic circuit for calculating a slip ratio of each road wheel, and a controller for controlling a wheel-brake cylinder pressure of each wheel wheel.
Abstract: An automobile anti-skid brake control system, comprises wheel-speed sensors, a pseudo vehicle speed generator, an arithmetic circuit for calculating a slip ratio of each road wheel, and a controller for controlling a wheel-brake cylinder pressure of each road wheel. The controller includes a compensation circuit for compensating a different-diameter wheel speed of a different-diameter road wheel with a small-sized emergency tire, utilizing an error rate of the different-diameter wheel speed with respect to the detected wheel speed of the other road wheel with a usual tire. The error rate is derived on the basis of a ratio of diameter-difference between the different-diameter road wheel and the other road wheel. The ratio of diameter-difference is derived on the basis of a maximum wheel speed corresponding to the different-diameter wheel speed and a second highest wheel speed of the detected wheel speeds. The controller controls each wheel-brake cylinder pressure so that the slip ratio derived from a compensated pseudo vehicle speed based on the compensated different-diameter wheel speed is adjusted to a predetermined reference slip ratio.
24 citations
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TL;DR: In this article, the stability of the slip flow of an Oldroyd-B fluid with slip along a fixed wall is investigated by means of a one-dimensional linear stability analysis and by numerical calculations.
Abstract: In this paper we solve the time-dependent shear flow of an Oldroyd-B fluid with slip along the fixed wall. We use a non-linear slip model relating the shear stress to the velocity at the wall and exhibiting a maximum and a minimum. We assume that the material parameters in the slip equation are such that multiple steady-state solutions do not exist. The stability of the steady-state solutions is investigated by means of a one-dimensional linear stability analysis and by numerical calculations. The instability regimes are always within or coincide with the negative-slope regime of the slip equation. As expected, the numerical results show that the instability regimes are much broader than those predicted by the linear stability analysis. Under our assumptions for the slip equation, the Newtonian solutions are stable everywhere. The interval of instability grows as one moves from the Newtonian to the upper-convected Maxwell model. Perturbing an unstable steady-state solution leads to periodic solutions. The amplitude and the period of the oscillations increase with elasticity.
24 citations
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12 Sep 1996
TL;DR: In this paper, a determining function of which the sign varies when the slip ratio is equal to the target value, and a switching function comprising a time integral of the determining function, are set, and the drive torque target value is set such that it is directly proportional to the switching function.
Abstract: A drive torque of a vehicle drive wheel is controlled so that a slip ratio between the drive wheel and a road surface is equal to a target value. A determining function of which the sign varies when the slip ratio is equal to the target value, and a switching function comprising a time integral of the determining function, are set, and the drive torque target value is set such that it is directly proportional to the switching function. Alternatively, the drive torque target value is set based on the switching function which is set equal to the determining function and corrected based on an angular acceleration of the drive wheel.
19 citations
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01 Jan 1996
TL;DR: In this article, a comprehensive view of friction curves with polymer melt slip over a significant range of slip velocities was proposed, based on using polymers with various molecular characteristics and analyzing the flow curves.
Abstract: Publisher Summary By using polymers with various molecular characteristics and analyzing the flow curves, it has been possible to propose a comprehensive view of friction curves with polymer melt slip over a significant range of slip velocities This chapter discusses slip with additives containing mixture This shows the role of the additives, the wall material and the surface state of the wall Later, linear slip between polymer and wall is discussed The main characteristic of this type of slip is that it occurs at all stress levels; it is difficult to observe experimentally because it supposes the use of ideal surfaces: perfectly smooth and developing no interaction with the flowing polymer The chapter also discusses the cohesive slip with weak interactions The occurrence of slip is highly dependent on the interaction developing between the polymer and the wall The initial situation, prevailing before flow, is called the mushroom regime and the friction law controlling slip is deduced theoretically
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13 Sep 1996
TL;DR: In this article, a vehicle condition is presumed from a deviation of actual yaw acceleration from the desired yaw accelerate corresponding to a steering operation, and the desired slip ratio λoTF of a turning outer wheel side drive wheel is calculated.
Abstract: PROBLEM TO BE SOLVED: To improve maneuverability and controllability in turning a vehicle. SOLUTION: A vehicle condition is presumed from a deviation of actual yaw acceleration from desired yaw acceleration corresponding to a steering operation (S120). When a vehicle tends to be under steer(US), an engine output correction value ΔTEUP and desired slip ratios λ17, λ07 of a drive wheels of turning outer and inner wheels are calculated (S160, S170) and a throttle opening and brak oil pressure of the drive wheel are controlled (S200, S210) to generate a torque difference between the left and right drive wheels, so that yaw moment necessary for turning is generated. Also, when the vehicle to be over steer(OS), ΔTEUP, λiT and λoT are calculated, while the desired slip ratio λoTF of a turning outer wheel side drive wheel is calculated (S160, S170), and the throttle opening and the break pressure of the drive wheel and the turning outer wheel side drive wheel are controlled (S200, S210) so that yaw moment necessary for turning is generated by the torque difference between the left and right drive wheels and a driving force added to the drive wheel. As a result, the maneuverabilit and controllability in the vehicle turning can be together ensured.
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TL;DR: In this article, a supermultiple-point-electrode conductance probe was developed and applied into vertical downward gas-liquid two-phase flow, and the graphics of interfacial profiles were presented on typical flow patterns briefly and on plug and foam flows in detail.
Abstract: Supermultiple-point-electrode conductance probe method has recently become realistic for examining the interfacial structure in gas-liquid two-phase flow. A new instrument based on this method was developed and applied into vertical downward gas-liquid two-phase flow The graphics of interfacial profiles are presented on typical flow patterns briefly and on plug and foam flows in detail. It is pointed out that the plug flow lies in the two regions separated by the foam flow, which was newly found in this study. The interfacial profiles of gas slugs depend strongly on the slip velocity of gas slug to the liquid phase in liquid slug, and the two regions of plug flow are classified into the low and high slip velocity groups. In the former group slip velocity is mostly negative Furthermore, some findings are introduced on the prediction of the void fraction in liquid slug, on its relation with the two flow regions of plug flow, and on a characteristic property observed in the fluctuation of pressure g...
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TL;DR: In this paper, boundary effects for simple Couette flow of granular materials using a dynamical modelling method are examined. But the exact relationship is by no means clear because of the unknown slip at the boundary.
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TL;DR: An analysis of the Rayleigh problem in MHD for a porous wall in a slip flow regime is considered in this paper, where the normal velocity of suction/injection at the wall is assumed to be time dependent.
Abstract: An analysis of the Rayleigh problem in MHD for a porous wall in a slip flow regime is considered. The normal velocity of suction/injection at the wall is assumed to be time dependent. The solution of the problem is obtained in the form of a power series, in terms of known functions. The variations of the velocity field and the skin friction are shown graphically and are followed by a quantitative discussion.
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03 Dec 1996
TL;DR: In this paper, an improved ABS control device which can execute the optimum control in response to a road surface having μ, and can exhibit sufficient anti-skid performance even if an inexpensive system is employed is presented.
Abstract: PURPOSE: To provide an improved ABS control device which can execute the optimum control in response to a road surface having μ, and can exhibit sufficient anti-skid performance even if an inexpensive system is employed CONSTITUTION: An actuator (i) is one which is controlled by an Ich1 solenoid valve making use of a gradual pressure increase effect through throttling A means (f) where the quantitative change in road surface μ is operated based on the quantity of pressure increment during a gradual increase in pressure, and the quantitative change in slip for wheels, and a road surface μ is estimated based on the operated road surface μ, and a means (g) changing the content of an ABS control in response to the estimated road surface μ, are supplemented to a control system where operations are processed based on information on wheel speeds The road surface μ is thereby estimated without using other W/C pressure sensors and the like An estimation is desirably made based on the history of the quantitative change in road surface μ, a slip ratio choosing the peak value of μ is estimated, and if the quantity of a target slip is changed, the slip for the maximum μ can be effectively made use of, and control can be thereby be executed in such a way that the slip choosing the peak value of road surface μ, is targeted at all times even over a road surface different in μ-S characteristics
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TL;DR: In this article, the authors derived analytical solutions for three modes of 1-D strike-slip frictional heating in a strip within a vertical fault zone that is embedded in an otherwise homogeneous medium.
Abstract: SUMMARY
Analytical solutions are derived for three modes of 1-D strike-slip frictional heating in a strip within a vertical fault zone that is embedded in an otherwise homogeneous medium. These include instantaneous and step-heating modes, as well as a preferred decay-heating mode in which the heating declines with time to a sudden end. Modelling results indicate that the evolution of temperature and pore-pressure rises varies with heating mode, but, at a time three times greater than the slip duration, the evolutionary paths for the different modes are practically indistinguishable. Generally the pressure front advances ahead of the temperature front by a distance of 1/D times the temperature-front distance, where D is the square root of the ratio of thermal to hydraulic diffusivity. A model based on the values of one plausible set of physical parameters suggests that temperature can increase by 100–320 K and pore pressure can rise by 5–16 MPa after 1 m slip under a mean resistive stress of 10 MPa. These estimates can be easily raised or lowered by 50 per cent, because some model-parameter values have uncertainties of one to two orders of magnitude.
The estimated pore-pressure rise, being of the same order as the seismic stress drop, requires a large fault slip as a prerequisite. A lower pre-earthquake pore-pressure rise may bear a significant consequence on triggering earthquakes. Once a small aseismic slip begins, regardless of its initiating mechanism, the rise in pore pressure will weaken the frictional strength and lead to more slip. Pressure rise, fault weakening, and slip may reinforce one another through feedback processes that eventually escalate to earthquakes. Massive development of fractures during fault slip enlarges the pore volume; accordingly, the pore pressure is reduced and the frictional strength is raised. When the pore pressure drops below its pre-slip level, the slip stops abruptly. Thereafter, healing, sealing, compaction, and non-frictional heating re-initiate pore-pressure rise within the fault zone, setting the stage for another earthquake episode. Pre- and post-slip pore-pressure rises weaken the fault such that frictional heating is too low to yield an observable heat flow anomaly.
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04 Jun 1996
TL;DR: In this article, an information processing means intensifies and reduces braking pressure on the basis of the detected value or computed value of wheel rotating speed detecting means 41-44, a body speed detecting mean 11, body longitudinal acceleration detecting means 11, a yaw rate detecting means YA, a side slip angle detecting means XA, and the like Braking pressure operating means 19b-19m, 31-64 operate braking pressure according to the determination.
Abstract: PURPOSE: To improve spin suppressing stability by determining the target slip factor to the large value when a side slip angle is enlarged and a friction coefficient is high CONSTITUTION: An information processing means intensifies and reduces braking pressure on the basis of the detected value or computed value of wheel rotating speed detecting means 41-44, a body speed detecting means 11, a body longitudinal acceleration detecting means 11, a yaw rate detecting means YA, a side slip angle detecting means 11, and the like Braking pressure operating means 19b-19m, 31-64 operate braking pressure according to the determination According to a side slip angle and a friction coefficient, the target setting means of the information processing means 11 determines the target slip factor large when the side slip angle and the friction coefficient are large An actual slip factor detecting means computes the actual slip ratio of a wheel by estimation on the basis of each detected value or computed value A pressure intensifying-reducing determining means determines whether to intensify or reduce wheel braking pressure in order to make the actual slip factor coincide with the target slip factor
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TL;DR: In this article, the discharge coefficient of low-density choked flow through a parallel plate channel with a narrow gap is studied experimentally for a wide range of Reynolds numbers, including the slip flow region.
Abstract: Low-density choked flow through a parallel plate channel with a narrow gap is studied experimentally for a wide range of Reynolds numbers. In the region from continuum flow to slip flow, the choked flow is analyzed by one-dimensional flow approximation based on the integrated boundary layer equations, taking into account the slip at the channel walls. The calculated discharge coefficients and pressure distributions agree well with the experimental results for a wide range of Reynolds numbers, including the slip flow region. A nondimensional correlation equation of the discharge coefficient is proposed as a function of Reh s /l for Reh s /l<2x10 2 . In the region from slip flow to molecular flow, the experimental results agree well with those of previous work. A nondimensional correlation equation of C d l/h s is proposed as a function of Re for 7 < Re < 5 x 10'.
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29 Oct 1996
TL;DR: In this paper, the authors proposed a method to prevent a delay in convergence to a target value and to accomplish stable and smooth rotational travel without any slip in a driving wheel by approximating an output characteristic of a wheel to that complying with a sideslip angle.
Abstract: PURPOSE: To prevent a delay in convergence to a target value and to accomplish stable and smooth rotational travel without any slip in a driving wheel by approximating an output characteristic of a wheel to that complying with a sideslip angle. CONSTITUTION: Between a pair of sun gears 28 connected to left and right wheels and a pair of ring gears 35a driven by means of an engine, planetary gears 28 are geared respectively, and motors 25 are individually connected to a pair of carriers 31 supporting the respective planetary gears 32. On the basis of a signal from a vehicle height sensor 22 arranged in a suspension member in each wheel, a wheel load Fz is found, while on the basis of the number V of revolutions in each of wheels 23, 26 and the wheel load Fz, a slip ratio S and a sideslip angle β in each wheel are found, and then, from the slip ratios S in a pair of left and right driving wheels 26, a yaw moment ΔM corresponding to the sideslip angle β is respectively found. The number of revolutions for a motor 25 is respectively controlled for eliminating a deviation between a normal yaw rate γm found from the yaw moment ΔM and an actual yaw rate γr detected by means of a yaw rate sensor 13.
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TL;DR: In this article, three different polymers, a high density polyethylene (HDPE), a polypropylene (PP), and a polycarbonate (PC), were subjected to a flow visualization study in two rectangular channels with different width-to-height ratios, and the flow velocity profile in the channel was determined as a function of polymer melt temperature, channel wall temperature, and mass flow rate, as well as the pressure applied to the polymer melt in a channel and the geometry of the channel.
Abstract: Three different polymers, a high density polyethylene(HDPE), a polypropylene(PP), and a polycarbonate (PC), were subjected to a flow visualization study in two rectangular channels with different width-to-height ratios, and the flow velocity profile in the channel was determined as a function of polymer melt temperature, channel wall temperature, and mass flow rate, as well as the pressure applied to the polymer melt in the channel and the geometry of the channel. The flow velocity data, which were measured by using a particle tracer technique and accumulated in a computer, were analyzed by a CAE program \"POLYFLOW\" developed on the basis of Bird-Carreau model to simulate the flow velocity curves in both vertical and horizontal longitudinal sections which involve the central axis of the channel. The extrapolation of the flow velocity curves to the inner wall surface allowed to estimate the contribution of slip flow on the channel wall (Vs)to the total flow velocity. When HDPE was subjected to the channel flow, the Vs increased with increasing mass flow rate, temperature of running polymer, and temperature of channel wall, but decreased with increasing pressure applied to the melt. More pronounced effects of the melt temperature and the mass flow rate was found on the wall slip phenomena for both PP and PC.
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01 Oct 1996
TL;DR: An anti-lock braking control system (ABS) has the slip of each wheel monitored and the slip ratio (lambda) of at least one of the front wheels measured as discussed by the authors.
Abstract: An anti-lock braking control system (ABS) has the slip of each wheel monitored and the slip ratio (lambda) of at least one of the front wheels measured. In a situation when this is greater than a preset threshold, the ABS action for each of the four wheels is initiated. If the ratio is less than the threshold, a special control procedure is applied to the rear wheels only.
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01 Jul 1996••
TL;DR: In this article, a detailed numerical simulation of a coaxial jet with a secondary parallel moving stream is presented, and the results show that the use of standard κ-e model leads to good agreement between the numerical results and experimental data.
Abstract: Previous experimental work shows that velocity ratio is the principal independent variable to determine the flow behavior of coaxial jets. This study focusing on the effect of velocity ratio on the flow characteristics such as the velocity and kinetic energy profiles, centerline velocity decaying, flow growing and entraining of the jet, presents a detailed numerical simulation of a coaxial jet with a secondary parallel moving stream. It is found that radial profiles of the mean velocity component u depending on the velocity ratio show good similarity in the fully developed zone. Compared with available experimental data, the results show that the use of standard κ-e model leads to good agreement between the numerical results and experimental data.
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17 Jun 1996TL;DR: In this article, the effects of velocity ratio on the near-field generation and development of three-dimensional structure in two-stream mixing layers have been investigated for the first time using a single rotatable cross-wire probe on fine cross-plane grids at four streamwise locations in the near field region.
Abstract: Three-dimensionality in transitioning mixing layers, in the form of streamwise vortical structures, is now well established and understood. In the present investigation, the effects of velocity ratio, or more precisely of velocity difference across the layer, on the near-field generation and development of three-dimensionality in two-stream mixing layers have been investigated for the first time. Detailed time-averaged velocity measurements were obtained using a single rotatable cross-wire probe on fine cross-plane grids at four streamwise locations in the near-field region. The effects of five velocity ratios, ranging from r =0.5 to 0.9, were investigated by keeping the velocity of one stream constant while varying that of the other. The results indicate that the mixing layer three-dimensionality is strongest for the mixing layer with the lowest velocity ratio. The peak mean streamwise vorticity levels decrease with increasing velocity ratio at all the streamwise locations investigated. However, the rate of decrease is highest at the most upstream station and it decreases with increasing downstream distance. The mean streamwise vorticity contours at the first station show that their distribution is quite similar at the different velocity ratios, implying that the generating mechanism and initial disturbance fields remain unchanged with velocity ratio. However, it is conceivable that the amount of stretching in the braid regions due to the spanwise vortical structures is affected by velocity ratio. As the velocity ratio decreases (and the velocity difference across the layer increases), stronger spanwise rollers are generated which increase the amount of stretching in the braid regions and hence the streamwise vorticity is amplified. The splitter plate wake has a lasting effect on the three-dimensional structure of the mixing layers at the higher velocity ratios. The presence and effects of the wake are clearly seen in the mean velocity, mean streamwise vorticity and Reynolds stress contours.
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23 Jan 1996
TL;DR: In this article, a simple speed detector was used to detect engine speed of front and rear wheels and control oil pressure supplied to a grader blade controlling cylinder based on a revolving speed difference calculated with a controller.
Abstract: PURPOSE:To reduce a cost by detecting engine speed of front and rear wheels with a simple speed detector, and controlling oil pressure supplied to a grader blade controlling cylinder based on a revolving speed difference calculated with a controller. CONSTITUTION:In the case snow is to be removed with a grader blade 30, a differential lock mechanism 88 of a distribution machine 54 is in an unlocking state, and differential of output of the front and rear wheels is in an allowable state. After that, speed signals of a front wheel speed detector 154 and a rear wheel speed detector 156 provided respectively to front and rear wheels are supplied to a second controller 48. Then, the controller 48 detects slip ratio in comparison with speed signals of the detectors 154 and 156. A signal of the slip ratio is supplied to a hydraulic adjusting device 34, and hydraulic pressure oil supplied to a hydrulic cylinder device 114 is controlled to lift a blade 30. The blade 30 is pushed against the snow surface so as to obtain an optimum slip ratio. According to the constitution, unexpensive dectors can be used, as reliability and maintenance efficiency can be promoted.
01 Nov 1996
TL;DR: In this paper, a new scheme of controlling wheel slip during comering based upon varying the slip ratio as a function of the slip angle is proposed and dynamically simulated with the model of a front-wheel-driven passenger vehicle.
Abstract: Traction control system is used to prevent the wheel slippage and to maximize the traction force. A new scheme of controlling the wheel slip during comering based upon varying the slip ratio as a function of the slip angle is proposed and dynamically simulated with the model of a front-wheel-driven passenger vehicle. Simulation results show that the proposed scheme is superior to a fixed slip ratio during cornering and lane changes.