CN102490704A - Braking force real-time regulating method - Google Patents

Abstract

The invention provides a braking force real-time regulating method, which comprises the following steps: collecting the route of an electronic braking pedal and the actual current of the motors in the electronic mechanical brakes of vehicle front and rear wheels in a real time manner; transferring the route of the electronic braking pedal into shift signals, calculating the blocked current of the motors in the electronic mechanical brakes of vehicle front and rear wheels respectively according to the shift signals, wherein the blocked current is the target current; regulating the actual current of the motors through the variable speed integrating proportion integration differentiation (PID) according to the derivation between the target current and the actual current in a real time manner, so as to ensure the actual current of the motors to approach to the target current, and then regulating, in a real time manner, the actual braking force output by the electronic mechanical brake to which the motor belongs. The braking force real-time regulating method provided by the invention can avoid the integral saturation phenomenon generated in the braking force real-time regulation technology of the prior art and reduce the regulation time of braking force, so that the braking response speed is fast and the braking effect is well.

Description

A kind of braking force real-time regulating method

Technical field

The invention belongs to brake-by-wire (Brake by wire) technical field, be specifically related to a kind of braking force real-time regulating method.

Background technology

Along with the development of automotive technology, people have higher requirement to dynamic property, economy, safety, road-holding property and the traveling comfort of automobile, and the mechanical system in the automobile is changed to electronic mechanical system gradually.

In the moving system of On-line Control, generally carry out brake operating through electronic brake pedal and electric mechanical braking device (EMB).Wherein, the exportable pedal displacement signal of electronic brake pedal, but the motor drive brake dishes in the electric mechanical braking device etc. are braked.Obviously, along with the driver steps on the stroke different (being that the pedal displacement signal is different) of electronic brake pedal, the braking force of electric mechanical braking device output also should be different.Wherein, the braking force of electric mechanical braking device output is relevant with the moment of torsion of its motor output; And the torque T of motor output _bAnd proportional between its actual electric current I, i.e. T _b=C Φ * I, wherein C Φ is the definite value relevant with motor characteristic.Hence one can see that, carries out real-time regulated through the actual current to motor and can realize the adjusting to its output torque, and just the braking force to the output of electric mechanical braking device carries out real-time regulated.

When electronic brake pedal is stepped on an ad-hoc location, can extrapolate the locked rotor current of the motor in each electric mechanical braking device this moment, this locked rotor current is target current I ^*, but actual current I and this target current I of common motor ^*Between can have deviation, for eliminating in real time this deviation, need the real-time regulated actual current to make it near target current.In the prior art,, generally adopt classical PID (proportional-integral-differential) algorithm that the actual current of the motor in the electric mechanical braking device is carried out real-time regulated for more accurately control and the braking force of regulating the output of electric mechanical braking device.

The classical PID algorithm is a kind of controlling of sampling algorithm; It can calculate output valve P (k) according to the error E (k) of sampling instant; This error E (k) is expected value and actual value (sampled value) poor of the variable of required adjusting; This output valve P (k) is controlling quantity (value of the variable that promptly need regulate or increment), and it is used to regulate actual value and makes it near expected value, thereby reduces deviation.Sampling instant t=iT (T is the sampling period, and i is a positive integer), the adjusting formula of classical PID algorithm is following:

$P\left(t\right)=K_P[E\left(t\right)+\frac{1}{T_i}\underset{0}{\overset{t}{\∫}}E\left(t\right)\mathrm{dt}+\frac{T_D\mathrm{dE}\left(t\right)}{\mathrm{dt}}]---\left(1\right)$

With obtaining following formula after formula (1) discretization:

$P\left(k\right)=K_{p}E\left(k\right)+K_I\underset{j=0}{\overset{k}{\mathrm{\Σ}}}E\left(j\right)+K_D[E\left(k\right)-E(k-1)]---\left(2\right)$

In the formula (2): k is a sampling sequence number, k=0, and 1,2 ...; P (k) is the output valve of the k time sampling instant PID regulating control; E (k) is the deviate of the k time sampling instant; E (k-1) is the deviate of the k-1 time sampling instant; K _PBe proportionality coefficient; K _IBe integral coefficient, K _I=K _PT/T _iK _DBe differential coefficient, K _D=K _PT _D/ T.Wherein, the effect of proportional is the speed of response of quickening system, system is made a response, proportionality coefficient K rapidly to the deviation of signal _PBig more, the speed of response of system is fast more, but proportionality coefficient K _PCross conference and cause system vibration to occur, destroy the stability of system.The effect of integral is to eliminate static error, but also can reduce the speed of response of system, increases the overshoot of system, even makes system continuous wave occur, reduces integral coefficient K _ICan reduce system overshoot, but the response process of the system that can slow down.The effect of differential term is the variation that reduces deviation, helps to reduce overshoot, overcomes vibration, system is tended towards stability, but it is to disturbing sensitivity, is unfavorable for the robustness (Robust) of system.

The contriver finds that there is following problem at least in prior art: when adopting the classical PID algorithm that braking force is carried out real-time regulated, be prone to produce the integration saturated phenomenon, cause control duration elongated, the speed of response of drg is slack-off, influences braking effect.For example, if the target current I of motor ^*Increase and maintenance certain hour (suddenly stepping on electronic brake pedal) like the driver suddenly; Can cause the deviation E (k) between target current and the actual current to produce step (promptly sharply becoming big suddenly); The output valve P of classical PID algorithm (k) also will sharply increase, to such an extent as to P (k) surpasses the actual maximum control amount Pmax (for example surpassing the maximum current that motor can reach) that equipment can reach; At this moment, the electric current of PID regulating control " hope " motor continues to rise, but owing to receive the restriction of equipment virtual rating, the actual current of motor no longer increases; So with respect to normal condition, deviation will keep higher value in the longer time, and the integral among the output valve P (k) also during this period in constantly accumulation become big (because deviation E (k) always for more greatly on the occasion of, constantly in integral, add up); At this moment; If reducing, the target current of motor make deviate become negative value (like the loosening electronic brake pedal of driver); Then should reduce the actual current of motor as early as possible; But because the accumulated value of integral is excessive before this among the output valve P (k) of classical PID algorithm, so output valve P (k) still surpasses above-mentioned actual maximum control amount in a period of time, the actual current of motor during this period of time still can remain on maxim; Experience and just begin to reduce after considerable time and eliminate deviation, this is " the forward integration is saturated " phenomenon.Otherwise, then be " reverse integral is saturated " phenomenon.

Summary of the invention

Technical matters to be solved by this invention is to the problems referred to above that exist in the prior art; A kind of braking force real-time regulating method is provided; The integration saturated phenomenon that produces in the time of can avoiding in the prior art the braking force real-time regulated; Reduce the control duration of braking force, braking response speed is fast, good braking effect.

Solving the technical scheme that technical matters of the present invention adopted is a kind of braking force real-time regulating method, and it comprises the steps:

1) gathers the stroke of electronic brake pedal and the actual current of the motor in the vehicle front and rear wheel electric mechanical braking device in real time;

2) stroke with said electronic brake pedal is converted into displacement signal, extrapolates the locked rotor current of the motor in the vehicle front and rear wheel electric mechanical braking device respectively according to said displacement signal, and said locked rotor current is target current;

3) according to the deviation between said target current and actual current; Through speed change integral PID algorithm; The actual current of the said motor of real-time regulated makes it near said target current, thus the braking force of the electric mechanical braking device real output at this motor place of real-time regulated.

Preferably, the stroke of said electronic brake pedal is the pedal unit sensor acquisition through being built in the electronic brake pedal place.

More preferably, for each travel position of electronic brake pedal, said pedal unit sensor can provide a cooresponding displacement voltage value as said displacement signal.

Preferably, the actual current of said motor is gathered through vehicle ECU in real time.

Preferably, in step 2) in, the said locked rotor current of extrapolating the motor in the vehicle front and rear wheel electric mechanical braking device respectively according to said displacement signal comprises:

Said displacement signal is converted into the braking force that vehicle front and rear wheel electric mechanical braking device should be exported;

According to the gearing factor of the physical construction of said drg, the friction coefficient of drg said braking force is converted into the moment of torsion that the motor in this drg should be exported;

Extrapolate the locked rotor current of this motor according to said moment of torsion.

Preferably, said according to the deviation between said target current and actual current in step 3), through speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it to comprise near said target current:

According to the deviation between said target current and the actual current, carry out the speed change integral PID and regulate, obtain the control voltage of the driving circuit of said motor, said driving circuit is the pulsation width modulation converter circuit;

Obtain the pulse width modulation value of this converter circuit according to said control voltage;

Obtain acting on the magnitude of voltage of the armature end of said motor according to said pulse width modulation value, thus the actual current of the said motor of real-time regulated.

Preferably; In step 3); Said according to the deviation between said target current and actual current, through speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it to be specially near said target current: according to the deviation between said target current and actual current; Through non-linear speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it near said target current.

Preferably, said motor adopts dc brushless motor.

Wherein, said speed change integral PID algorithm is a kind of known algorithm, and its basic thought is the speed that adds up that changes integral; Make its size with deviation relevant, when deviation was big, the integration speed of adding up slowed down; The integral effect weakens; And in deviation hour, integration adds up and speeds up, and the integral effect strengthens.For this reason, can be integral coefficient f [E (k)] is set, this coefficient f [E (k)] is the function of deviation E (k), when the absolute value of deviation | E (k) | coefficient f during increase [E (k)] reduces the absolute value of deviation | E (k) | coefficient f when reducing [E (k)] increases.Thus, the formula of speed change integral PID algorithm is:

$P\left(k\right)=K_{P}E\left(k\right)+K_I\left\{\underset{j=0}{\overset{k}{\mathrm{\Σ}}}f\right[E\left(j\right)\left]E\left(j\right)\right\}+K_D[E\left(k\right)-E(k-1)]---\left(3\right)$

Similar with formula (2), k is a sampling sequence number in the formula (3), k=0, and 1,2 ...; P (k) is the output valve of the k time sampling instant speed change integral PID regulating control; E (k) is the deviate of the k time sampling instant input; E (k-1) is the deviate of the k-1 time sampling instant input; K _PBe proportionality coefficient; K _IBe integral coefficient; K _DBe differential coefficient.It is thus clear that, different with the formula of classical PID algorithm, the integral P in the formula of speed change integral PID algorithm _IFor:

$P_I=K_I\left\{\underset{j=0}{\overset{k}{\mathrm{\Σ}}}f\right[E\left(j\right)\left]E\left(j\right)\right\}$ $\left(4\right)$

If wherein if integrating range is A, B, then a kind of formula of coefficient f [E (k)] can be:

$f\left[E\left(k\right)\right]=\left\{\begin{array}{cc}1& \left|E\left(k\right)\right|\&le;B\\ \frac{A\left|E\left(k\right)\right|+B}{A}& B<\left|E\left(k\right)\right|\&le;A+B\\ 0& \left|E\left(k\right)\right|>A+B\end{array}\right.---\left(5\right)$

Can know that by formula (5) value of f [E (k)] is 0 to 1 variation, when the absolute value of deviation | E (k) | during greater than A+B, prove to have got into the saturation region this moment, then make f [E (k)] get zero, thus the integral P among the output valve P (k) _IAlso be 0, the current deviation value that promptly no longer adds up E (k); And when the absolute value of deviation | E (k) | during less than B, make f that [E (k)] gets 1, the current deviation value that adds up whole, this moment, its integral was identical with integral in the classical PID algorithm, and the speed of adding up of integral reaches the highest; Absolute value when deviation | E (k) | in the time of between B and A+B, the part current deviation value E (k) that adds up, the value of the part that adds up 0～| E (k) | between, and along with | E (k) | increase and reduce, make the integral speed that adds up reduce.In the practical application, the value of A and B can be done disposable adjusting, and the interval of A, B is selected greatly more, the speed change integration to the saturated inhibit function of integration just more a little less than, otherwise strong more.

Certainly; The concrete formula of coefficient f [E (k)] also has other polytype, the absolute value of itself and deviation | E (k) | relation can be linear, also can be non-linear; Need only and guarantee that it reduces along with the increase of absolute value of the bias, increase along with reducing of absolute value of the bias to get final product; Other concrete computing formula to this coefficient f [E (k)] just is not described in detail at this.

In a word, in the speed change integral PID algorithm, along with the absolute value of deviation | E (k) | increase, integral P among its output valve P (k) _IThe influence that accumulation is caused reduces gradually, causes the saturated problem of integration thereby can reduce in the classical PID algorithm because of integral accumulative total.

Further; Also comprise non-linear speed change integral PID algorithm in the speed change integral PID algorithm; Output with speed change integral PID algorithm during its basic thought is limited in the efficient range, when its output valve P (k) exceeds the limit of power of equipment, regulates with regard to no longer carrying out conventional speed change integral PID; But make output valve P (k) directly get actual maximum control amount Pmax or actual minimum controlling quantity Pmin, with further minimizing integration saturated phenomenon.That is to say; In the non-linear speed change integral PID algorithm; If the output valve P (k-1) in a last moment is greater than actual maximum control amount Pmax; And the deviation E of this input (k) is greater than 0, and it is just with the output valve P (k) of actual maximum control amount Pmax as this, if regulate because it proceeds conventional speed change integral PID so; Then output valve P (k) still can continue to increase (because of this newly-increased E (k) greater than 0), but the output valve P (k) after increasing is still and exceeds maximum control amount Pmax and can not be implemented; In like manner, if last one constantly output valve P (k-1) less than the minimum controlling quantity Pmin of reality, and the deviation E of this input (k) is less than 0, then it is with the output valve P (k) of the minimum controlling quantity Pmin of reality as this; And in other cases, still carry out conventional speed change integral PID and regulate.

Beneficial effect:

Thereby the present invention is through the locked rotor current real-time regulated braking force of motor in the electric mechanical braking device of current closed-loop speed change integral PID algorithm adjusting vehicle, because speed change integral PID algorithm has been eliminated large deviation (coefficient of integral is little because of this moment, so the integral effect is little) with proportional action; Eliminate little deviation (because this moment, the coefficient before the integral was big, so the integral effect is big) with integral action, thereby reduced available technology adopting classical PID algorithm carries out the real-time regulated appearance to braking force integration saturated phenomenon; Reduced system overshoot greatly; Improved regulation quality, made electric machine control more stable, and following property fast; Reduced the control duration of braking force; Braking response speed is fast, good braking effect, and the while has also been improved the accuracy of brake-power control; Improve the stability of line control brake system, suppressed fluctuation in the brake-power control process and fugitiveness in the prior art.

Description of drawings

Fig. 1 is the diagram of circuit of the braking force real-time regulating method of the embodiment of the invention;

Fig. 2 carries out the principle schematic of real-time regulated for the embodiment of the invention adopts speed change integral PID algorithm to the current of electric of vehicle front and rear wheel electric mechanical braking device;

Fig. 3 carries out the diagram of circuit of real-time regulated for adopting non-linear speed change integral PID algorithm to the current of electric of vehicle front and rear wheel electric mechanical braking device.

The specific embodiment

For making those skilled in the art understand technical scheme of the present invention better, braking force real-time regulating method of the present invention is described in further detail below in conjunction with the accompanying drawing and the specific embodiment.

The present invention provides a kind of braking force real-time regulating method, and it comprises the steps:

1) gathers the stroke of electronic brake pedal and the actual current of the motor in the vehicle front and rear wheel electric mechanical braking device in real time;

2) stroke with said electronic brake pedal is converted into displacement signal, extrapolates the locked rotor current of the motor in the vehicle front and rear wheel electric mechanical braking device respectively according to said displacement signal, and said locked rotor current is target current;

3) according to the deviation between said target current and actual current; Through speed change integral PID algorithm; The actual current of the said motor of real-time regulated makes it near said target current, thus the braking force of the electric mechanical braking device real output at this motor place of real-time regulated.

Embodiment

Preferably, in the present embodiment, the motor in the electric mechanical braking device adopts dc brushless motor.

As shown in Figure 1, the braking force real-time regulating method of present embodiment comprises the steps:

S101. gather the stroke of electronic brake pedal and the actual current of the motor in the vehicle front and rear wheel electric mechanical braking device in real time;

S102. the stroke with electronic brake pedal is converted into displacement signal;

S103. displacement signal is converted into the braking force that vehicle front and rear wheel electric mechanical braking device should be exported respectively;

S104. according to the gearing factor of the physical construction of drg, the friction coefficient of drg braking force is converted into the moment of torsion that the motor in this drg should be exported;

S105. extrapolate the locked rotor current of this motor according to said moment of torsion, just target current I ^*

S106. according to the target current I of up-to-date collection ^*And the deviation between the actual current I is carried out the speed change integral PID and is regulated; Just with I ^*And the gap between the I is as deviation E (k), according to above-mentioned formula (3), formula (5) calculation control amount P (k); Obviously, the various concrete parameter that this speed change integral PID is selected for use in regulating, sampling period for example, K _P, K _I, K _DOccurrence, the concrete computing formula of coefficient f [E (k)], the occurrence of interval A, B etc. all has multiple choices, because speed change integral PID algorithm is known, so just no longer these concrete parameters of choice are elaborated at this;

S107. the result who regulates according to the speed change integral PID; Control voltage by the driving circuit of speed change integral PID regulating control output motor; This driving circuit is pulse width modulation (PWM; Pulse Width Modulation) converter circuit is according to controlling the pulse width modulation value that voltage obtains this converter circuit;

S108. obtain acting on the actual current of the magnitude of voltage of armature end according to the pulse width modulation value with the real-time regulated motor, thus the braking force of the electric mechanical braking device at this motor place of real-time regulated; As shown in Figure 2; Among the present invention; When adopting speed change integral PID algorithm real-time regulated current of electric, the output valve P (k) of speed change integral PID regulating control be the control voltage U ct of motor-drive circuit, owing to the choosing of output valve P (k) can be by the parameter determining of motor itself; Its size should not exceed the parameter area of this motor, therefore controls voltage U ct span and preferably can only be between actual maximum control amount Pmax and the actual minimum controlling quantity Pmin; Motor-drive circuit is the pulsation width modulation converter circuit; Obtain the pulse width modulation value of this converter circuit according to control voltage U ct; And then obtain acting on the magnitude of voltage Udo and the drive motor of armature end; Thereby the actual current of real-time regulated motor is promptly realized the real-time regulated to the braking force of this motor place drg output.

In the process of above-mentioned real-time regulated; S106, s107, s108 step are: the step of " according to the deviation between target current and actual current; through speed change integral PID algorithm; the actual current of real-time regulated motor makes it near target current, thereby the braking force of the electric mechanical braking device real output at this motor of real-time regulated place ".Known, according to the groundwork of pid algorithm, this adjusting belongs to closed loop adjustment, and promptly it can constantly circulate with actual current and carry out according to regulate the up-to-date target current in back (target current also real-time change) in real time; That is to say that s106, s107, s108 step possibly circulate and carry out repeatedly.As target current I ^*When equating, can stop regulating, can think that also control process has got into stabilized conditions (value that is P (k) keeps stable) with actual current I.

Preferably; The stroke of electronic brake pedal is through being built in the pedal unit sensor in real time collection of electronic brake pedal; The pedal unit sensor can obtain the stroke of electronic brake pedal; And being translated into cooresponding displacement voltage value (being displacement signal), each travel position is displacement voltage value of correspondence all.

Preferably, the actual current of motor is to gather in real time through vehicle ECU (Electronic Control Unit, electronic control unit).

Preferably, the speed change integral PID algorithm that adopts in the foregoing description is specially non-linear speed change integral PID algorithm.As previously mentioned; Output with speed change integral PID algorithm during non-linear speed change integral PID basic idea is limited in the efficient range; When its output valve P (k) exceeds the limit of power of equipment, regulate with regard to no longer carrying out conventional speed change integral PID, but make output valve P (k) directly remain on actual maximum control amount Pmax or actual minimum controlling quantity Pmin; Its idiographic flow can be as shown in Figure 3, comprising:

S201. with the target current I of motor ^*Difference E (k) input speed change integral PID regulating control with actual current I;

Whether the output valve P (k-1) that s202. judges a moment on the speed change integral PID regulating control exceeds actual maximum control amount Pmax, in this way, carries out s203; As not, carry out s204;

S203. judge motor target current I ^*Greater than the motor actual current of gathering this moment, promptly whether E (k) in this way, carries out s208 greater than zero; As not, carry out s206;

S204. whether the output valve P (k-1) that judges a moment on the speed change integral PID regulating control in this way, carries out s205 less than its actual minimum controlling quantity Pmin; As not, carry out s206;

S205. judge motor target current I ^*Less than the motor actual current of gathering this moment, promptly whether E (k) in this way, carries out s209 less than zero; As not, carry out s206;

S206. with speed change integral PID algorithm motor actual current I is carried out real-time regulated, controlled amount P (k);

S207. speed change integral PID regulating control is exported controlling quantity P (k);

S208. speed change integral PID regulating control is exported actual maximum control amount Pmax, and with it as controlling quantity P (k);

S209. speed change integral PID regulating control is exported actual minimum controlling quantity Pmin, and with it as controlling quantity P (k).

It is understandable that above embodiment only is the illustrative embodiments that adopts for principle of the present invention is described, yet the present invention is not limited thereto.For the one of ordinary skilled in the art, under the situation that does not break away from spirit of the present invention and essence, can make various modification and improvement, these modification also are regarded as protection scope of the present invention with improving.

Claims (8)

1. a braking force real-time regulating method is characterized in that, comprises the steps:

1) gathers the stroke of electronic brake pedal and the actual current of the motor in the vehicle front and rear wheel electric mechanical braking device in real time;

2) stroke with said electronic brake pedal is converted into displacement signal, extrapolates the locked rotor current of the motor in the vehicle front and rear wheel electric mechanical braking device respectively according to said displacement signal, and said locked rotor current is target current;

3) according to the deviation between said target current and actual current; Through speed change integral PID algorithm; The actual current of the said motor of real-time regulated makes it near said target current, thus the braking force of the electric mechanical braking device real output at this motor place of real-time regulated.

2. braking force real-time regulating method according to claim 1 is characterized in that, the stroke of said electronic brake pedal is through the pedal unit sensor acquisition that is built in the electronic brake pedal place.

3. braking force real-time regulating method according to claim 2 is characterized in that, for each travel position of electronic brake pedal, said pedal unit sensor can provide a cooresponding displacement voltage value as said displacement signal.

4. braking force real-time regulating method according to claim 1 is characterized in that, the actual current of said motor is gathered through vehicle ECU in real time.

5. braking force real-time regulating method according to claim 1 is characterized in that, in step 2) in, the said locked rotor current of extrapolating the motor in the vehicle front and rear wheel electric mechanical braking device respectively according to said displacement signal comprises:

Said displacement signal is converted into the braking force that vehicle front and rear wheel electric mechanical braking device should be exported;

According to the gearing factor of the physical construction of said drg, the friction coefficient of drg said braking force is converted into the moment of torsion that the motor in this drg should be exported;

Extrapolate the locked rotor current of this motor according to said moment of torsion.

6. braking force real-time regulating method according to claim 1; It is characterized in that, in step 3), said according to the deviation between said target current and actual current; Through speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it to comprise near said target current:

According to the deviation between said target current and the actual current, carry out the speed change integral PID and regulate, obtain the control voltage of the driving circuit of said motor, said driving circuit is the pulsation width modulation converter circuit;

Obtain the pulse width modulation value of this converter circuit according to said control voltage;

Obtain acting on the magnitude of voltage of the armature end of said motor according to said pulse width modulation value, thus the actual current of the said motor of real-time regulated.

7. braking force real-time regulating method according to claim 1; It is characterized in that, in step 3), said according to the deviation between said target current and actual current; Through speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it to be specially near said target current:

According to the deviation between said target current and actual current, through non-linear speed change integral PID algorithm, the actual current of the said motor of real-time regulated makes it near said target current.

8. according to any described braking force real-time regulating method in the claim 1 to 7, it is characterized in that said motor adopts dc brushless motor.

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