CN1295952A - Method for determing reference speed of car anti-blocking brake system and braking control program - Google Patents

Abstract

The present invention relates to a method for defining reference vehicle speed of automobile anti-locking brake system and its brake control program. It is characterized by utilizing definition of wheel cylinder pressure function, utilizing signal of wheel speed sensor to calculate combined wheel cylinder pressure function and solve wheel ground brake force, then solve average deceleration rate, finally calculate reference vehicle speed and control parameter slip rate, then assembly control program to make real-time definition and control. Said invention overcomes and solves the defects and problems of ABS technology, is applicable to various types of vehicles and can directly obtain brake process control parameter and raise control accuracy.

Description

The anti-block braking system of car reference speed is determined method and control of braking program thereof

The present invention is the definite method and the control of braking program thereof of a kind of anti-block braking system of car ABS (anti-lock braking system) reference speed, belongs to the automobile active safety technology.

Anti-block braking system of car ABS is the automobile emergency glancing impact, prevents wheel lockup, makes it to make full use of road-adhesion coefficient φ, increases braking force F _Bi, shorten stopping distance, and keep the glancing impact automobile steering stable, make wheel can bear certain side force.The ABS system of cycle pressure control formula mainly is made of brake pedal, checking cylinder, pressure regulator, control unit, wheel speed sensors, car side brake.When the automobile emergency glancing impact, chaufeur is stepped on brake pedal, brings pressure to bear on checking cylinder, thereby provides pressure source to pressure regulator.Pressure regulator comprises the source of supply of high pressure and low pressure, and in braking procedure, pressure source pressure remains unchanged substantially.Pressure regulator is regulated the pressure of the wheel cylinder of supplying with car side brake under the control of control unit, wheel braking moment is increased or minimizing, and the adhesive ability of road is rationally utilized.Each takes turns wheel speed sensors wheel speed pulse input ABS control unit, judge car brakeing state, wheel braking intensity and ground attaching coefficient scope by control unit, the cooresponding pressure regulator of each wheel (or a certain axletree) is sent corresponding control signal, change the brake-pressure of respectively taking turns drg, the ground attaching coefficient rational and effective is utilized with realization.Automobile is glancing impact not, and four wheel speed basically identicals that the vehicle wheel speed sensors records can be chosen its average as car speed, and the speed of a motor vehicle after the braking beginning is regulated the lock torque and the corresponding road-adhesion coefficient decision of each wheel by control system.For the fault that guarantees the ABS control system does not influence the conventional brake ability, during vehicle launch the ABS system is carried out self check, if the ABS control system has fault then to disconnect the ABS control system, recover conventional brake.In the braking procedure if the speed of a motor vehicle less than certain predetermined value, also with ABS control system recovery conventional brake, guarantees that vehicle reliably stops.The method of automobile ABS system control is by the adjusting to wheel braking moment, prevent wheel lockup and obtain to try one's best high average adhesion coefficient utilization, reduce stopping distance, and keep bigger cornering capacity, prevent that the glancing impact running out the way from exceeding the road width of permission.The car deceleration motion mainly is subjected to the restriction of the vertical adhesion value of wheel, turns to and resist the then main influence by the wheel lateral adhesion coefficient of ability of extraneous transverse force effect.Wheel slip S _iThe proportion that slides in the wheel movement is described.Wheel vertically, lateral adhesion coefficient and slip rate variable condition diagram of curves as shown in Figure 1, slip rate than hour, adhesion value φ is directly proportional with slip rate S, slip rate is about 15%～25% o'clock vertical adhesion value to peaking φ _pSlip rate increases after surpassing the adhesion value peak point again, and vertically adhesion value reduces on the contrary, until being tending towards the definite value adhesion value φ that promptly slides _s, that is to say that vertical adhesion value was φ when slip rate was 100% (being that wheel lockup drags cunning) _sVertically near the slip rate value the adhesion value peak point reflects that in fact the tyre contact patch major part is in extended state, and small part is in slip state, and vertical adhesion value of this moment is near tire and ground-surface coefficient of static friction.Drag when sliding when the complete locking of tire, vertically adhesion value is a coefficient of sliding resistance, so φ _sAlways less than φ _p.On high adhesion value road surface, φ _pAt about 10～20% places of S; On low adhesion value road surface, φ _pAt about 20～40% places of S.In the time of near vertical adhesion value is in peak point, lateral adhesion coefficient also remains on 50～75% of maximum transversal adhesion value, and wheel keeps bigger cornering capacity (maintenance steering capability); When wheel slip was in vertical adhesion value peak point left side, vertically adhesion value increased along with the increase of slip rate, and lateral adhesion coefficient keeps bigger numerical, and this moment, wheel braking was in stabilized conditions.After wheel slip surpassed vertical adhesion value peak point, wheel braking entered unstable state, and the reducing of adhesion value makes that the wheel deceleration/decel increases under certain lock torque, and wheel slip further increases, the rapid locking of wheel; The decline of respective transversal adhesion value is very near zero, and accidental extraneous transverse force acts on the rear axle and will cause serious sideslip, affacts front axle and will lose the directional control ability, and serious safety misadventure might appear in automobile.

The principle of work of ABS is: according to the relation of wheel and ground-surface slip rate-adhesion value, control the rate of braking of each wheel, rationally, effectively utilize ground vertically, lateral adhesion coefficient, wheel slip is controlled near the vertical adhesion value peak point left side, obtains maximum vertical adhesion value and bigger lateral adhesion coefficient.Preventing under the prerequisite of wheel lockup, improving brake efficiency (less stopping distance), guaranteeing certain handling maneuver ability and directional balance; Will be fully and rationally utilize the adhesion value of road, just must regulate the slip rate S of brake wheel _i, make it to be in zone of reasonableness. $S_i=\frac{V-{\mathrm{\ω}}_i*R}{V}----\left(1\right)$

ω in the formula _iBe angular speed of wheel, R is a radius of wheel, and V is the speed of a motor vehicle.General automobile ABS only has wheel speed sensor, can only obtain the vehicle wheel rotational speed signal, can't directly utilize the wheel speed signal to carry out the calculating of vehicle speed signal.The open abs braking technology of introducing, reference speed V _RefDetermine all to point out to utilize ω _i, d ω _i/ dt, character of road, vehicle and brake system structure are carried out suitable combination, can use initial velocity V _oWith mean deceleration dv/dt, obtain the speed of a motor vehicle (being reference speed): $V_{\mathrm{ref}}=V_0+\frac{\mathrm{dV}}{\mathrm{dt}}*\mathrm{\Δt}----\left(2\right)$

In fact mean deceleration dv/dt and initial velocity V _oBe the function of time, can't try to achieve with clearer and more definite easy algorithm, must determine its efficient algorithm by a large amount of roads braking experiment, this is the high key of existing ABS technical costs-must realize controlling according to the different automobile types characteristics.

Purpose of the present invention is exactly to exist in the existing ABS technology and must determine reference speed by a large amount of road braking experiments respectively according to different automobile types in order to overcome and to solve, spended time length, calculation of complex, too high shortcoming and the problem of cost, a kind of energy of research invention is suitable for the definite method and the control of braking program thereof of the anti-block braking system of car reference speed of different automobile types, so that and then calculate the main control parameter slip rate, determine the anti-lock brake process in the reasonable scope, the shortening time, raise the efficiency, cost-cutting.

The present invention realizes by following technical proposals: it is to utilize vehicle wheel speed sensors signal ω _iCalculate d ω _i/ dt is again in conjunction with pressure of wheel braking cylinder function P _i(t) obtain wheel ground braking force F _Bi, obtain available vehicel deceleration dv/dt again, and then calculate reference speed V _Ref, calculate main contral parameter slip rate S then _iSo that whether the braking procedure of determining anti-block braking system of car is in range of control; At first determine pressure of wheel braking cylinder function P _i(t), pressure of wheel braking cylinder function P _i(t) adopt the method for stand test to obtain; Pressure of wheel braking cylinder function P _i(t) devise a stratagem is calculated block diagram as shown in Figure 2 really, pressure of wheel braking cylinder function P _i(t) be subjected to the influence of numerous factors such as structural materials, volume, electromagnetic valve switch characteristic, braking media performance and brake piping layout of brake wheel cylinder, pipeline, theoretical analysis has been determined the order of pressure function, limited stand test and calculating can obtain the pressure function under the different adjustment pattern, its step is as follows: (1) installs control unit, pressure regulator and checking cylinder, car side brake and connects circuit such as pipeline, wheel speed sensors, pressure sensor by the structural arrangement design; (2) on demand the pressure control pattern is divided into boost, boost slowly, pressurize, slow step-down, five kinds of patterns of step-down; (3) the pressure source pressure under the measurement different pressures adjusting pattern and the change curve of pressure of wheel braking cylinder are repeatedly measured, and in the time length Δ t of certain adjusting pattern, its integral mean value is stable; $\frac{1}{N}{\∫}_0^{\mathrm{\Δt}}{P}_i\left(t\right)\mathrm{dt}={\∫}_0^{\mathrm{\Δt}}{P}_i^{-}\left(t\right)\mathrm{dt}$ In the following formula: the number of times of N for measuring, p _i(t) be measured curve, p _i ^-(t) be matched curve; Certain pressure of wheel braking cylinder function match of regulating pattern obtains the pressure of wheel braking cylinder function, in conjunction with the ω of each wheel _i, $\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}}$ And construction parameter, just can calculate the ground brake power F that each is taken turns _Bi, and then obtain car load deceleration/decel aviation value dv/dt, the key parameter-reference speed V that just can calculate the ABS control process _RefSingle-wheel is as shown in Figure 3 stressed in braking procedure, and according to Newton's law, during emergency braking, wheel is subjected to ground braking force F _BiWith brake braking force square M _BiEffect, the rotor inertia J of wheel _iAngular acceleration $\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}}$ Available formula (3) expression: $\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}}=\frac{M_{\mathrm{bi}}-F_{\mathrm{bi}}*R}{J_i}----\left(3\right)$

In the formula: M _BiIt is the brake braking force square; F _BiIt is single-wheel road braking force; R is a radius of wheel; And brake braking force square and pressure of wheel cylinder function P _i(t) relation is suc as formula (4): M _Bi=K _i ^*P _i(t) (4)

In the formula: K _iBe coefficient; Car load braking procedure stressing conditions calculates the influence that reference speed can be disregarded rolling resistance and air resistance as shown in Figure 4 during the anti-block braking system of car emergency braking, the car load mean deceleration can be drawn by (5) formula: $m\frac{\mathrm{dV}}{\mathrm{dt}}=\mathrm{\Σ}{F}_{\mathrm{bi}}----\left(5\right)$ Wherein m is a complete vehicle quality; (3), (4) formula simultaneous can be obtained a certain single-wheel road braking force F _Bi, $F_{\mathrm{bi}}=(K_i*P_i\left(t\right)-J_i\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}})/R----\left(6\right)$ And can judge the road-adhesion coefficient of this wheel at this moment: ${\mathrm{\Φ}}_i=\frac{F_{\mathrm{bi}}}{N_i}----\left(7\right)$ $\frac{\mathrm{dV}}{\mathrm{dt}}=\frac{\mathrm{\Σ}{F}_{\mathrm{bi}}}{m}----\left(8\right)$

Utilize each pressure of wheel braking cylinder function P of fixed braking procedure _i(t), just can calculate F _Bi, just can derive reference speed V from formula (1) and (2) _RefWith slip rate S _iCalculating formula: $V_{\mathrm{ref}}=V_0+\frac{\mathrm{\Σ}{F}_{\mathrm{bi}}}{m}*\mathrm{\Δt}----\left(9\right)$ $S_i=\frac{V_{\mathrm{ref}}-{\mathrm{\ω}}_i*R}{V_{\mathrm{ref}}}----\left(10\right)$

During concrete enforcement, adopt stable high pressure brake-pressure source and can finish pressure of wheel braking cylinder P _i(t), wheel angle speed deceleration/decel d ω _i/ dt, ground braking force F _Bi, road-adhesion coefficient φ _i, reference speed V _RefWith slip rate S _iCalculating, and with set the control unit that threshold value, slip rate setting range compare, implement the boosting of pressure regulator, boost slowly, pressurize, reduce pressure slowly, the control of five kinds of modes such as decompression to be to reach the purpose of control of braking; The control of braking program flow chart as shown in Figure 5, its control of braking program circuit is as follows: the beginning glancing impact, and total cylinder pressure increases, and keeps normal open state when the brake-pressure regulation electromagnetic valve is not received control signal, be equivalent to conventional brake, each wheel braking divides cylinder pressure to increase thereupon; Be subjected to the effect of lock torque, vehicle wheel rotational speed ω _iReduce, wheel phase road pavement produces the movement tendency of slippage, and road surface counteraction simultaneously produces braking force F _BiWheel; The car load braking force is the ground braking force sum of all wheels, obtains deceleration/decel (during emergency braking, ignoring air resistance and rolling resistance of wheel) under the effect of car load braking force; Simultaneously, at lock torque ω _iUnder the combined action of ground braking force, angular speed of wheel changes, and produces angular deceleration; The ABS control system acquisition is analyzed its variation tendency to wheel speed signal, can obtain ω _iWith d ω _i/ dt; ABS control module can calculate this automobile reference speed V this moment on each takes turns the basis of wheel speed signal _RefWith each wheel slip rate S _i, send the next round control signal after relatively with the control thresholding; With reference speed and the minimum effect vehicle velocity V of ABS _MinRelatively,,, can close ABS control, recover conventional brake even wheel lockup safety misadventure can not take place yet if less than the minimum effect speed of a motor vehicle 5～10km/h.

The present invention compared with prior art has following advantage and beneficial effect: (1) the invention solves existing ABS must determine reference speed problem, cost-cutting by a large amount of road braking experiments according to different automobile types; (2) can directly obtain braking procedure main control parameter S by the present invention _iWith road-adhesion coefficient φ _i, can improve control accuracy; (3) reduced the ABS control logic parameter a large amount of road operation test work capacitys of the various vehicles that must carry out, the cost of development of having saved new model ABS.

Below Figure of description is further specified as follows: Fig. 1 is slip rate S _IWith adhesion value φ _iGraph of relation; Fig. 2 is pressure of wheel braking cylinder function P _i(t) determine block diagram; Fig. 3 is the stressed scheme drawing of single-wheel in the abs braking process; Fig. 4 is the stressed scheme drawing of car load in the abs braking process; Fig. 5 is this anti-block braking system of car control of braking program flow chart.Among each figure: φ _iBe road-adhesion coefficient; S _iSlip rate for brake wheel; P is the master cylinder brake-pressure; P _hBe high-voltage power supply; P _LBe low pressure source; P _i(t) be the wheel cylinder force function; J _iBe wheel inertia; F _BiFor wheel is subjected to the ground braking force; M _BiBe the brake braking force square; N _iBe the single-wheel positive pressure; $\frac{\mathrm{dv}}{\mathrm{dt}}$ Be the car load mean deceleration; Mg is a vehicle weight; Hg is the centre of gravity of vehicle height; F _BfBe front wheel brake power; F _BrIt is rear-wheel braking force; N _fIt is the front-wheel positive pressure; N _rIt is the trailing wheel positive pressure; L _fBe that vehicle's center of gravity is to front wheel spindle centre distance; L _rBe that vehicle's center of gravity is from hind axle centre distance; L is the front and back wheel width between centers.

Embodiments of the present invention can be as follows: (1) is implemented condition of the present invention and is: 1. stable high pressure brake-pressure source is arranged, as selecting TOYOTA automobile DENSO type oil pump for use; 2. have and satisfy the controller that control requires, can implement the boosting of pressure regulator, boost slowly, pressurize, reduce pressure slowly, the control of five kinds of modes such as decompression, and controller can be finished pressure of wheel braking cylinder P _i(t), wheel deceleration/decel d ω _i/ dt, ground braking force F _Bi, road-adhesion coefficient φ _i, reference speed V _RefWith slip rate S _iCalculating, and with set threshold value, the slip rate setting range compares, and sends next round control signal to reach the control purpose; (2) press the control chip that program flow chart shown in Figure 5 is compiled control program software and input controller.The contriver implements the present invention and implements successfully on the rich enlightening board NHQ1036QJ type automobile that Chinese Guangdong South Sea motor plant is produced.In the implementation process, the wheel speed sensors that adopts Japanese honda company to produce, the actr and the controller of the DENSD anti-lock braking system(ABS) of Jiamei of Japanese honda company vehicle special use, the pic16c73 control chip that controller has adopted Microchip company to produce, experimental result shows, the anti-lock brake control that the reference speed of determining by the present invention carries out can obviously be shortened stopping distance, prevents wheel lockup.

Claims (2)

1, a kind of definite method of anti-block braking system of car reference speed is characterized in that: it is to utilize vehicle wheel speed sensors signal ω _iCalculate d ω _i/ dt is again in conjunction with pressure of wheel braking cylinder function P _i(t) obtain wheel ground braking force F _Bi, obtain available vehicel deceleration dv/dt again, and then calculate reference speed V _Ref, calculate main contral parameter slip rate S then _iSo that whether the braking procedure of determining anti-block braking system of car is in range of control; At first determine pressure of wheel braking cylinder function P _i(t), pressure of wheel braking cylinder function P _i(t) adopt the method for stand test to obtain; Limited stand test and calculating can obtain the pressure function under the different adjustment pattern, its step is as follows: (1) installs control unit, pressure regulator and checking cylinder, car side brake and connects circuit such as pipeline, wheel speed sensors, pressure sensor by the structural arrangement design; (2) on demand the pressure control pattern is divided into boost, boost slowly, pressurize, slow step-down, five kinds of patterns of step-down; (3) the pressure source pressure under the measurement different pressures adjusting pattern and the change curve of pressure of wheel braking cylinder are repeatedly measured, and in the time length Δ t of certain adjusting pattern, its integral mean value is stable; $\frac{1}{N}{\∫}_0^{\mathrm{\Δt}}{P}_i\left(t\right)\mathrm{dt}={\∫}_0^{\mathrm{\Δt}}{P}_i^{-}\left(t\right)\mathrm{dt}$ In the following formula: the number of times of N for measuring, p _i(t) be measured curve, p _i ^-(t) be matched curve; Certain pressure of wheel braking cylinder function match of regulating pattern obtains the pressure of wheel braking cylinder function, in conjunction with the ω of each wheel _i, dv/dt and construction parameter, just can calculate the ground brake power F of each wheel _Bi, and then obtain car load deceleration/decel aviation value dv/dt, the key parameter-reference speed V that just can calculate the ABS control process _RefAccording to Newton's law, during emergency braking, wheel is subjected to ground braking force F _BiWith brake braking force square M _BiEffect, the rotor inertia J of wheel _iAngular acceleration $\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}}$ Available formula (3) expression: $\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}}=\frac{M_{\mathrm{bi}}-F_{\mathrm{bi}}*R}{J_i}----\left(3\right)$

In the formula: M _BiIt is the brake braking force square; F _BiIt is single-wheel road braking force; R is a radius of wheel; And brake braking force square and pressure of wheel cylinder function P _i(t) relation is suc as formula (4):

M _bi=K _i ^*P _i(t) (4)

In the formula: K _iBe coefficient; Calculate the influence that reference speed can be disregarded rolling resistance and air resistance during the anti-block braking system of car emergency braking, the car load mean deceleration can be drawn by (5) formula: $m\frac{\mathrm{dV}}{\mathrm{dt}}=\mathrm{\Σ}{F}_{\mathrm{bi}}----\left(5\right)$ Wherein m is a complete vehicle quality; (3), (4) formula simultaneous can be obtained a certain single-wheel road braking force F _Bi, $F_{\mathrm{bi}}=(K_i*P_i\left(t\right)-J_i\frac{d{\mathrm{\ω}}_i}{\mathrm{dt}})/R----\left(6\right)$ And can judge the road-adhesion coefficient of this wheel at this moment: ${\mathrm{\Φ}}_i=\frac{F_{\mathrm{bi}}}{N_i}----\left(7\right)$ $\frac{\mathrm{dV}}{\mathrm{dt}}=\frac{\mathrm{\Σ}{F}_{\mathrm{bi}}}{m}----\left(8\right)$

Utilize each pressure of wheel braking cylinder function P of fixed braking procedure _i(t), just can calculate F _Bi, just can derive reference speed V from formula (1) and (2) _RefWith slip rate S _iCalculating formula: $V_{\mathrm{ref}}=V_0+\frac{\mathrm{\Σ}{F}_{\mathrm{bi}}}{m}*\mathrm{\Δt}----\left(9\right)$ $S_i=\frac{V_{\mathrm{ref}}-{\mathrm{\ω}}_i*R}{V_{\mathrm{ref}}}----\left(10\right)$

During concrete enforcement, adopt stable high pressure brake-pressure source and can finish pressure of wheel braking cylinder P _i(t), wheel angle speed deceleration/decel d ω _i/ dt, ground braking force F _Bi, road-adhesion coefficient φ _i, reference speed V _RefWith slip rate S _iCalculating, and with set the control unit that threshold value, slip rate setting range compare, implement the boosting of pressure regulator, boost slowly, pressurize, reduce pressure slowly, the control of five kinds of modes such as decompression to be to reach the purpose of control of braking.

2, the definite control of braking program of a kind of anti-block braking system of car reference speed, it is characterized in that: the beginning glancing impact, total cylinder pressure increases, and keeps normal open state when the brake-pressure regulation electromagnetic valve is not received control signal, be equivalent to conventional brake, each wheel braking divides cylinder pressure to increase thereupon; Be subjected to the effect of lock torque, vehicle wheel rotational speed ω _iReduce, wheel phase road pavement produces the movement tendency of slippage, and road surface counteraction simultaneously produces braking force F _BiGive wheel; The car load braking force is the ground braking force sum of all wheels, obtains deceleration/decel under the effect of car load braking force; Simultaneously, under the combined action of lock torque and ground braking force, angular speed of wheel changes, and produces angular deceleration; The ABS control system acquisition is analyzed its variation tendency to wheel speed signal, can obtain ω _iWith d ω _i/ dt; ABS control module can calculate this automobile reference speed V this moment on each takes turns the basis of wheel speed signal _RefWith each wheel slip rate S _i, send the next round control signal after relatively with the control thresholding; With reference speed and the minimum effect vehicle velocity V of ABS _MinRelatively,,, can close ABS control, recover conventional brake even wheel lockup safety misadventure can not take place yet if less than the minimum effect speed of a motor vehicle 5～10km/h.

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