Showing papers on "Slip ratio published in 1994"

Effects of temperature and surface roughness on time‐dependent development of wall slip in steady torsional flow of concentrated suspensions

Abstract: A flow visualization technique was applied to investigate the time and temperature‐dependent development of wall slip and the rheological behavior of a concentrated suspension, containing 63% by volume solid glass spheres and a poly (butadiene‐acrylonitrile‐acrylic acid) terpolymer matrix, using steady torsional flow. Flow visualization allowed the concomitant determination of the wall slip velocity and the shear viscosity of the concentrated suspension. The deformation rate, shear stress, and the wall slip velocity values during torsional flow were time dependent and asymptotically reached steady‐state values. The characteristic time necessary to reach steady state decreased with increasing shear rate and temperature. Increasing temperature also increased the wall slip velocity. The flow visualization technique was further utilized to determine the yield stress of the suspension directly, which was found to decrease with increasing temperature. Increased surface roughness prevented the wall slip of the concentrated suspension under certain conditions; however, it frequently resulted in the fracture of the suspension samples. Sample fracture became more pronounced with the preshearing of the samples.

Slip over rough and coated surfaces

Abstract: We study the effect of surface roughness and coatings on fluid flow over a solid surface. In the limit of small-amplitude roughness and thin lubricating films we are able to derive asymptotically an effective slip boundary condition to replace the no-slip condition over the surface. When the film is absent, the result is a Navier slip condition in which the slip coefficient equals the average amplitude of the roughness. When a layer of a second fluid covers the surface and acts as a lubricating film, the slip coefficient contains a term which is proportional to the viscosity ratio of the two fluids and which depends on the dynamic interaction between the film and the fluid. Limiting cases are identified in which the film dynamics can be decoupled from the outer flow.

Molecular slip at the solid‐liquid interface of an acoustic‐wave sensor

Abstract: Molecular slip is expected to occur at the interface between the surface of a bulk‐acoustic‐wave quartz chemical sensor and a liquid with which it is in contact A new property of the interface, called the interfacial slip parameter, accounts for molecular slip It is introduced in the theory of the sensor‐liquid system by generalizing the no‐slip boundary condition The interfacial slip parameter is a complex‐valued quantity which is defined as the displacement of a particle of liquid in contact with the sensor surface divided by the displacement of a particle on the surface of the sensor The theoretical expression for the impedance of the sensor is derived in terms of the interfacial slip parameter The impedance of the sensor is measured by the network analysis method for hydrophilic and hydrophobic surfaces in contact with water‐glycerol solutions The experimental values of impedance are fitted to the theory by nonlinear regression analysis to find the interfacial slip parameter A mechanical model

Measurement and modelling of friction in polymer melts during macroscopic slip at the wall

Abstract: This article examines the flow of two polydimethylsiloxanes, a polybutadiene and a polyethylene, in axisymmetrical capillaries over the entire range of possible flow rates. Measuring and plotting flow curves has shown that macroscopic slip at the wall occurs with these highly entangled polymers as soon as a sufficient level of stress is reached. For each capillary and each flow rate considered, the entry pressure losses at the die inlet was also estimated. A simple method is proposed for determining the polymer's friction curve and it is shown that this curve is scarcely dependent on the dimensions of the dies used. The results obtained for each polymer enables stress variations at the wall to be represented as a function of slip velocity and their general shape to be deduced. The variations are distinctly non-linear, as they introduce a threshold, a maximum and two minimum levels of stress. Finally, on the basis of the experimental measurements, a procedure is proposed for modelling polymer slip at the wall during steady flow. Taking into account the existence of a static friction stress, it can be used to represent the general shape of stress variations at the wall as a function of slip velocity. Combined with the compressibility of the fluid, the law used gives reasonable access to variations in pressure as a function of time during extrusion regimes corresponding to cork flow.

Compressible viscous flow in slits with slip at the wall

Abstract: We study the time‐dependent compressible flow of a Newtonian fluid in slits using an arbitrary nonlinear slip law relating the shear stress to the velocity at the wall. This slip law exhibits a maximum and a minimum and so does the flow curve. According to one‐dimensional stability analyses, the steady‐state solutions are unstable if the slope of the flow curve is negative. The two‐dimensional flow problem is solved using finite elements for the space discretization and a standard fully implicit scheme for the time discretization. When compressibility is taken into account and the volumetric flow rate at the inlet is in the unstable regime, we obtain self‐sustained oscillations of the pressure drop and of the mass flow rate at the exit, similar to those observed with the stick‐slip instability. The effects of compressibility and of the length of the slit on the amplitude and the frequency of the oscillations are also examined.

Braking apparatus for electric vehicle

Abstract: A braking apparatus for an electric vehicle in which a mechanical anti-lock brake and regenerative braking cooperate with each other to improve a braking performance is realized On condition that an accelerator is released off, the wheel rotation number is large, and a brake is trod on, a large regeneration mode is selected by a motor controller when a wheel slip is small, and a regeneration mode is selected when the wheel slip is large When the wheel slip is small, the braking force exerted on each wheel is increased by the brake controller and the regenerative braking force is also increased so that a slip ratio comes quickly closer to 02 When the wheel slip is large, the brake controller reduces the braking force so that the slip ratio comes closer to 02 In this case, the regenerative braking force is smaller than the above case of the small wheel slip to such an extent that the operation of the brake controller is not disturbed On condition that the accelerator is released off, the wheel rotation number is large, and the brake is released off, the regeneration mode is selected when the regeneration switch is turned on, and a coasting mode is selected when the regeneration switch is turned off

Braking force controller for electric vehicle

Abstract: A braking force controller for an electric vehicle properly carries out an anti-lock braking operation by keeping a slip ratio in a stable range. The vehicle has a motor 1 to drive wheels. A central controller 4 calculates regenerative energy according to output signals from an ammeter 51 and a voltmeter 52. If a brake sensor 62 detects a sudden braking operation, the central controller 4 controls the regenerative braking force of the motor 1 through a motor controller 2, to maintain the regenerative energy around a maximal value.

Particle dynamics calculations of wall stresses and slip velocities for couette flow of smooth inelastic spheres

Abstract: The objective of this work is to characterize the effects of boundary geometry on the flow of dry granular materials composed of smooth, inelastic spheres between parallel, bumpy walls in the absence of gravity. Particle dynamic simulations are done in which wall stresses and slip velocities are computed over a wide range of parameters, including shear gap height, geometry of the wall particles, wall to free particle diameter ratio, and normal restitution coefficient. Calculated wall stresses and slip velocities are found to be highly sensitive to boundary roughness, which is characterized in terms of the mean spacing value for the wall particles. Most noticeable is a pronounced stress drop for dense flows with an associated large slip velocity in a system having a narrow shear gap height.

Brake control apparatus for automotive vehicle that includes feedfoward/feedback mixing device

Abstract: In an electric control apparatus for a hydraulic brake control system of a vehicle, a feedback control portion is provided to produce a feedback control pulse signal indicative of a difference between a target slip ratio and an actual slip ratio. A feedforward control portion is provided to successively convert the target slip ratio in relation to a required braking force, a hydraulic braking pressure and an amount of hydraulic braking fluid, in sequence, and to convert the amount of hydraulic braking fluid into a feedforward control pulse signal. A pulse mixing circuit is connected to control portions to mix the control pulse signals for producing a mixed control pulse signal as a distinct control pulse signal. A driving circuit is connected to the pulse mixing circuit to control a hydraulic braking pressure applied to each wheel of the vehicle in accordance with the control pulse signal, regardless of the extent to which a brake pedal of the vehicle is depressed.

Braking device of motor car

Abstract: PURPOSE: To control the rapid sinking of a brake pedal, the generation of an oil violent sound and a G shock and the like due to stepwise rapid deceleration when a regenerative braking mode is changed over to an ABS mode and at the same time to prevent the braking distance of a vehicle from being extended. CONSTITUTION: This braking device comprises a valve means including relief valves 6, 56 and by-pass valves 7, 53 and the like for controlling the transmission of a hydraulic pressure to a wheel cylinder 5 (Fr) and a wheel cylinder 5 (Rr) from a master cylinder 4 and a skid detection means for detecting the slip ratio of the wheel of a front wheel Fr and/or a rear wheel Rr, and when the slip ratio of not less than a predetermined value is detected by the skid detection means, the regeneration due to regenerative braking is reduced and the operation of regenerative braking is changed over to the operation of hydraulic braking.

An original braking controller with torque sensor

Abstract: The present evolution of regulated braking systems requires the knowledge and control of dynamic parameters of the vehicle during the braking process. In a classical ABS system, the chassis speed is only known approximately and this is not sufficient to control the slip ratio. An advanced control principle requiring additional dynamic parameters would allow us to improve the braking performance. The application we have developed is based on a new principle with adaptive algorithms and online control of the braking torque based on the strain measurement on the calliper support. The adaptive principle has been chosen in order to improve robustness and to take account of the parameter variations and the variation of the behaviour when the system is perturbed. Precautions must be taken when algorithms are initialized to ensure good results. Performance improvements have been achieved by simulation and the complexity of the algorithms allows real implementation in a realistic, industrial microprocessor based system. >

Friction transmission with torque detecting function

Abstract: PURPOSE:To protect a transmission system by always monitoring load torque off the transmission system by the use of a simple means, and cutting of transmission when the load torque becomes excessive. CONSTITUTION:A friction transmission is disposed on the way of a transmission system from a prime mover to rotary equipment on a driven side. Load torque is determined on the basis of a slip ratio by the use of such a property of the friction transmission that the slip ratio is varied according to the load torque. The slip ratio is calculated based on the revolution speeds before and after the friction transmission, which are detected by sensors. If the load torque exceeds a predetermined value, a speed change ratio of a speed changing device provided in the transmission system is set to zero. The friction transmission 37 with a torque detecting function is constituted, inside a pulley 1, of a friction surface 5, a planet roller 6, a driven roller 7, and a holding device 8. A pin 12 is adapted to idly rotate the holding device 8 after being sheared in the case where an excessive load torque acts so as to cut off transmission, and it serves as a safety device.

Non-linear robust control for an integrated system of 4ws and 4wd

Abstract: In this paper, an improved control law for integrating 4WS and 4WD is presented. It is based upon a non-linear vehicle mode in which the lateral force acting on the tires changes according to the tire slip angle and slip ratio. The purpose of the system is to make the actual yaw rate follow the desired yaw rate.

Target slip ratio setup device

Abstract: PURPOSE:To provide a target slip ratio setup device capable of setting a target slip ratio based on information such as behavior of a vehicle, etc. CONSTITUTION:In a target slip ratio setup device 30, a target slip ratio to obtain an optimum braking force can be obtained based on a relationship between a target slip ratio and an estimated vehicle speed, a road surface friction coefficient, and a bank angle calculated in an estimated vehicle speed calculation circuit 36, a road surface friction coefficient calculation circuit 54, and a bank angle calculation circuit 42, respectively.

Target slip ratio correcting device

Abstract: PURPOSE:To provide a target slip ratio correcting device capable of maintaining a smooth running condition of a vehicle according to a variation in road surface conditions CONSTITUTION:In a target slip ratio correcting device 30, a road surface friction coefficient is calculated in a road surface friction coefficient calculation circuit 32 based on outputs from sensors 18, 20, and 22 and, according to a variation ratio of the road surface friction coefficient, a correction coefficient is calculated in a correction coefficient decision circuit 34 Also a target slip ratio is set up in a target slip ratio calculation circuit 40 based on the road surface friction coefficient value, and the target slip ratio is set up and multiplied by the correction coefficient to correct the target slip ratio Thus, even if road surface condition is varied largely, a good traveling condition of a vehicle can be maintained

Anti-spin braking system for maintaining directional stability of a vehicle

Abstract: An anti-skid brake system for a vehicle increases and reduces the braking pressure applied to each wheel in response to depression of the brake pedal so that the wheel speed of the wheel falls at a predetermined deceleration or a predetermined slip ratio according to the wheel speed and a pseudo vehicle speed. It is determined that the vehicle is spinning when a state where the braking pressure to none of the wheels is increased keeps for a predetermined time. The braking pressures applied to all the wheels is increased when it is determined that the vehicle is spinning.

Slip control device and control method thereof

Abstract: PURPOSE:To perform slip control along the intention and feeling of a driver so as to improve a driving sensation by correcting the target slip quantity of driving wheels according to whether the steering direction of a steering wheel is in the steering increase or steering back direction. CONSTITUTION:The driving wheel speed of a vehicle is detected by a detecting means 1, and the body speed is detected by a detecting means 2. According to each detection value, the slip quantity of the driving wheel is computed by a computing means 4. The target slip quantity is computed by a computing means 5 with the specified slip ratio part added to the body speed. The steering angle of a steering wheel is detected by a detecting means 3, and the steering direction is judged by a judging means 6. The driving torque output of an engine, that is, a throttle valve 8, for instance, is controlled by a control means 7 so that the driving wheel speed coincides with the target slip quantity. At this time, the computing means 5 corrects the target slip quantity according to the steering direction of the steering wheel.

Method and device for monitoring rotational speed sensors

Abstract: A method for monitoring rotational speed sensors for determining the wheel speed, wherein - is determined on the basis of a first and a second wheel speed an actual slip number (ZN) and - under certain conditions, the actual slip number (ZN) is added up and - an error is detected when the accumulated slip ratio (Z) a first threshold value (IF) exceeds characterized in that the current slip ratio is summed (ZN) when - is the difference between the wheel speeds is greater than a second threshold (ΔVS) and - none of the wheels is spinning.

Brake control device for motor vehicles

Abstract: In an electric control device for a hydraulic brake control system of a motor vehicle there is a feedback control section 100A in order to produce a feedback control pulse signal P1 which is indicative of a difference between a target slip ratio S and an actual slip ratio S, an optimum value control section 100B being provided in order to convert sequentially in succession the target slip ratio S as a function of a required braking force Fx, a hydraulic braking pressure Pb and a quantity of hydraulic brake fluid B and to convert the quantity of hydraulic brake fluid into an optimum value control pulse signal P2. A pulse mixing circuit 121 is connected to the regulation and control sections 100A and 100B in order to produce the control pulse signals P1 and P2 for the production of a mixing control pulse signal as a control pulse signal P3, a driver circuit 122 being connected to the pulse mixing circuit 121 in order to control a hydraulic brake pressure which is applied to each running wheel of the vehicle as a function of the control pulse signal P3 irrespective of the brake pedal of the vehicle being depressed.

Nonskid control device

Abstract: PURPOSE:To provide a stable turning round property and travelling stability by providing a slipping rate correction means to reduce a correction amount at which a slip ratio computed value can easily exceed a standard slip ratio at the time when a road surface friction coefficient state detection value is small CONSTITUTION:Yaw rate deflection 6 is computed by S4 Thereafter a left and right wheel standard slip ratio standard correction amount DELTASRL and a front and rear wheel standard slip ratio standard correction amount DELTASfr are computed by 510, and left and right wheel increased correction gain KRL and front and rear wheel increased correction gain Kfr are set by S10 in accordance with a side acceleration detection value YG Thereafter, a slip ratio Sj is computed by S16 In case of a low mu road surface, in increase correction of the slip ratio, braking pressure increase correction gain KRL, Kfr which is proportional coefficients depending on a road surface friction coefficient is set to become smaller gradually from 1 on a high mu road surface as the side acceleration detection value YG equivalent to a road surface friction coefficient state muis lowered

Acceleration slip control device

Abstract: PURPOSE:To restrain steering that causes a difference in force between the right and left sides, using the braking force of driven wheels, related to an acceleration slip control device which controls driving forces so that right and left driving wheels are rotated during acceleration while keeping the proper slip ratio. CONSTITUTION:Acceleration slip control is performed by generating braking forces independently for right and left driving wheels RL, RR so that the proper slip ratio is maintained as to the right and left driving wheels RL, RR. If the driving wheels RL, RR are in contact with a road surface with different mu, a difference is caused between driving forces that can be generated, and results in steering with a difference in force between the right and left sides, so a braking force is generated on the driven wheel FL on the side of the road with the higher mu. The braking force corresponding to the difference in driving force between the right and left driving wheels RR, RL, i.e., the difference between braking forces generated on the driving wheels RR, RL, is generated on the driven wheel FL on the side of the road with the higher mu, thereby restraining steering that causes a difference in force between the right and left sides.

Antiskid brake device for vehicle

Abstract: PURPOSE:To insure optimum braking force although running condition is changed in any way by providing a means dividing wheels into groups, making different target slip ratio between the groups, and changing the target slip ratio according to the detected running condition by the use of a changing means. CONSTITUTION:For controlling slip ratio, various data, namely, wheel speed from wheel speed sensors 27-30, a lateral G signal from a lateral G sensor 32, longitudinal G signal from a longitudinal G sensor 33, air pressure of each tire from four air pressure sensors 34, and a yaw rate signal from a yaw rate sensor 35 are taken in. Next, friction coefficient of the road surface and body speed are estimated. The lock condition of a wheel is judged based on them, a threshold value variable is set against the wheel, and corrected. At first, a partially charged load of each wheel is estimated by the air pressure of the tire of each wheel, next each threshold value variable B is set, and corrected according to the load W applied on the wheel. Next, correction by the lateral G and the longitudinal G is performed, and hence the threshold value variable is finally decided.

Differential limitting device

Abstract: PURPOSE:To eliminate hunting, to travel by fully using low friction of a road surface and to improve startability on a low frictional road surface with a differential limitting device to automatically control differential limitting torque constantly in accordance with a travelling state of a vehicle. CONSTITUTION:An air inlet valve 13 is arranged in an air passage 12 connecting a pressure cylinder 10 to press a friction clutch in the pressure direction provided between a differential case 2 and a side gear 3 and an air tank 11, and to the air passage 12 on the downstream side of this air inlet valve 13, an exhaust valve 14 communicated to the air is connected. Additionally a controller 15 to control the air inlet valve 13 and the exhaust valve 14 so as to decompress at the time of bth wheel slipping by way of computing a differential value of change of a slip ratio by inputting the number of rotation of four wheels, car speed and a steering angle detection signal and to intensify pressure slowly at the time when the differential value of change of the slip ratio is decreased in the case of one side wheel slipping.

Energy-saving drag device for 1.14KV oil pumping unit

Abstract: The utility model relates to an energy saving dragging device for an oil pumping unit, which is composed of a superhigh slip ratio motor in 1.14KV level and a control protection box which is installed by integrating with the superhigh slip ratio motor. The superhigh slip ratio motor has a very soft mechanical external characteristic; a motor control protector, an R-C resistor capacitor unit, a zinc oxide arrester, a power capacitor, a control transformer, a vacuum alternating current contactor, a control button, and an amperemeter are installed inside the control protection box for performing integrated protection on short circuit, overload, phase lack, overvoltage, etc. of the motor; at the same time, the control protection box is provided with a mechanical cipher lock, and the communication wires of a power supply are laid in fully sealed type. The utility model has good effects of theft protection and energy saving.

Road surface situation judging device

Abstract: PURPOSE:To provide a road surface situation judging device which can judge the situation of a road surface automatically to serve for control of a car body. CONSTITUTION:A road surface situation judging circuit 38 judges whether the situation of a road surface is good on the basis of the presumed car body speed calculated by a computing circuit 36 and the differentiated value of the steering angle sensed by a sensor 26. Accordingly the control of the car body can be conducted with a high precision if a road surface situation judging signal from the judging circuit 38 is fed to a target slip ratio computing circuit 40 to serve for correction of the target slip ratio.

Braking force control device

Abstract: PURPOSE:To miniaturize a piston driving means with ABS control and TRC control performed by one device, by controlling pressure fluid quantity with the piston of a pressure adjusting chamber moved to be held when a slip ratio is smaller than a given value, and with the piston moved through shutting off a fluid passage to release the holding when the slip ratio is the given value or more. CONSTITUTION:Pressure fluid quantity to a braking means 5 is adjusted, by moving a piston 9 to a second position from a first position, where the piston 9 is held by an elastic body 18, by a driving means 32 to hold the position by a holding means 50 when a slip ratio, detected by a slip ratio detecting means 35, is smaller than a given value and by shutting off means 20 and 22 to release the holding and also to control the driving means 32 to move the piston 9 for changing the volume of a pressure adjusting chamber 14 when the slip ratio is a given value or more. As a result force, added to an elastic body when the slip ratio is smaller than the given value, is acted as force for enlarging the pressure adjusting chamber when the slip ratio is the given value or more, allowing a smaller driving means.