CN104181816A - Method for controlling safety and smoothness degree of vehicle - Google Patents

Abstract

The invention relates to a method for controlling safety and the smoothness degree of a vehicle. According o the characteristics of a vehicle dynamics model and parameters of the vehicle and uncertainty of road conditions during running of the vehicle, control is implemented according to a separation implementation method controlled by the generalized PID. The method includes the steps of dividing control input into one input portion based on the integral of displacement errors and the other input portion based on the displacement errors, speed errors and acceleration errors, introducing variables to dynamically regulate the form the input portion based on the integral of the displacement errors, eliminating uncertain components and external interference of a vehicle control system, selecting the form of the input portion based on the displacement errors, the speed errors and the acceleration errors according to the controllable ideal mode of the vehicle, determining the coefficients of the displacement errors, the speed errors and the acceleration errors, achieving stable control over an ideal mode composition system at the original point, selecting design parameters, and controlling safety and the smoothness degree of the controlled vehicle. The method can be widely applied to vehicle cruise control and control over unmanned driving and the like.

Description

The control method of a kind of vehicle safety and smooth degree

Technical field

The present invention relates to a kind of control method for vehicle, particularly about the control method of a kind of vehicle safety and smooth degree.

Background technology

Along with the raising of people to the performance requirement such as ride safety of automobile and comfortableness, drive Vehicular intelligent various countries and the research of various driver assistance systems is also progressively goed deep into.As an importance of advanced vehicle control security system (AVCSS) exploitation, automotive self-adaptive control (hereinafter to be referred as ACC, the Adaptive Cruise Control) system of cruising has caused the concern of industry.Automobile ACC system is to grow up on traditional control technology basis of cruising, automobile ACC system is as driver assistance system, its objective is under the traffic operating mode suitable, partly replace driver, vehicle is carried out reasonably longitudinally controlling, to improve active safety and the riding comfort of vehicle.It had both ensured that vehicle had the ability of cruise, ensured that again the information that vehicle has an application onboard sensor adjusts the ability of Vehicle Speed automatically, thereby kept the safe spacing of this car and preceding vehicle.Because automobile ACC system is to improving the great potential of vehicle active safety and riding comfort, thereby obtains domestic and international researchist and more and more paid attention to.In addition, in May, 2014, Google associating founder Xie Er drop cloth woods (Sergey Brin) has been issued the up-to-date pilotless automobile prototype of Google.According to relevant report, the automatic driving car of Google is not equipped with the parts such as bearing circle, throttle, brake, rearview mirror, and it is by car networked system, picks passenger according to the address of its input or reception.This car speed per hour the highest 25 miles (being roughly equal to 40 kilometers), vehicle center has a LCD screen, and user can complete all instructions by screen.No matter vehicle all moves highly stablely on highway or sand ground.Except Google, other are also developing themselves pilotless automobile as the full-sized car manufacturer such as Toyota, Audi.Visible, aspect vehicle control system, ensure that on the basis of safety and comfort, realizing full automatic manipulation is a hot issue of current vehicle control field, and basis and key issue is wherein still the control problem of cruising of vehicle.

At present, ACC systematic research is mainly concentrated on to onboard sensor and information fusion technology thereof both at home and abroad, and ACC system control strategy chooses etc. on software and hardware technology, wherein how choosing control strategy is to realize ACC systemic-function and practical key thereof.And the information how application sensors unit is inputted provides suitable system output and reasonably controls vehicle, be the core that automobile ACC system should further be studied and apply to realize the system control technology of ACC object.The control technology of ACC system mainly comprise the desirable safe distance of vehicle determine, and the choosing etc. of systems control theory and method.

The control target of ACC system is suitably to control the speed of vehicle, keeps safe distance between vehicle, improves riding comfort and the active safety of vehicle.Control target for realizing these, determining after desirable vehicular safety distance, need the control strategy of selecting system and adopt suitable control theory to set up systematic control algorithm.At present, theoretical and fuzzy or intelligent Theory etc. of PID method, the theory of optimal control, sliding die are all applied to the research of ACC system control technology.In the ACC systematic control algorithm that Korea S's Han Yang University proposes, definite method of desirable retarded velocity adopts Linear-Quadratic Problem (LQ) theory of optimal control.Its theoretical analysis and simulation result show, the method still can realize preferably the performance index of ACC system in the situation that considering model error with the delay of system control actuator.In automobile ACC system, adopting vehicle distances error and relative velocity error minimum is the method for optimally controlling of performance index, has also obtained comfortableness that good automobile takes and the stability of vehicle platoon.At ACC, aspect the choosing of theoretical and method, Sliding Mode Control theory also has certain application.As the controller design aspect of vehicle ACC in U.S. PATH (Partners for Advanced Transit Highways) project, adopt Sliding Mode Control theory to determine desirable acceleration.The ACC system of Stuttgart, Germany university research, the control method that adopts the linearization of non-linear Vehicular system state space to combine with Sliding Mode Control theory is determined the desirable acceleration of vehicle.Fuzzy control theory also has certain application at the controller design aspect of ACC, and as the controller of the ACC of Univ Michigan-Ann Arbor USA proposition adopts typical FUZZY ALGORITHMS FOR CONTROL, two conditions that its fuzzy control rule is former piece are determined a behavior of consequent.Two conditions of former piece are respectively vehicle distances and two car relative velocities, and output is accelerator pedal aperture.Except above-mentioned various control theories, the methods such as neural network theory and Model Matching are also applied to the control algolithm of setting up ACC.Above-mentioned various control method can meet the control object of ACC system substantially, but respectively has its relative merits, in actual design, and some performance index that often need to strengthen based on system and select suitable control theory and method.

At present, vehicle ACC systematic research both at home and abroad also exists some technical matterss need to be in addition perfect, mainly comprise: the controller software algorithm of ACC is poor to the adaptability of environment, often for several typical driving cycles, and in the time that environment changes, the validity of algorithm has reduction largely; The application in ACC system of artificial intelligence, especially neural network theory and method needs to further investigate exploitation; The perfect system of the current neither one of evaluation of system performance, can not comprehensive evaluation the performance of different ACC systems.From current both at home and abroad ACC systematic research applicable cases, should pay close attention to following technology: multi-sensor information fusion technology, as the integration technology of Radar for vehicle distance measuring sensor and computer vision information etc.; Mechanics of communication, comprises communication and the communication of vehicle and control center etc. between communication in car, vehicle; The integrated technology of ACC system and other longitudinal direction of car control system, as ACC system and vehicle stop walking (S & G) system, and, early warning system crashproof with vehicle forward direction, and backward crashproof, early warning system is integrated etc.According to above-mentioned analysis, there are problems in the control method of the safety traffic of current guarantee vehicle: (1) haves much room for improvement to the adaptive faculty of vehicle operating environment (road conditions); (2) owing to also there being self uncertainty in vehicle operating process, as bearing capacity, the quality of self etc., existing control method is difficult to adapt to; (3) in original method, seldom consider the control to vehicle acceleration, and this ensures the important step of driving comfort (smooth degree) just.Therefore, control theory and the method for further investigation ACC system, develop efficient, practical vehicle ACC product, by be from now on China in the research direction in this field.

Summary of the invention

For the problems referred to above, the object of this invention is to provide a kind of control method about vehicle safety and smooth degree, make both to make in the face of situations such as different carrying capacities or different road conditions, the control method providing based on the present invention, vehicle still can ensure smooth-ride when guarantee is safe.

For achieving the above object, the present invention takes following technical scheme: the control method of a kind of vehicle safety and smooth degree, and it comprises the following steps: 1) for the controlled Vehicular system with ubiquity of following form:

$\left\{\begin{array}{c}{\stackrel{.}{x}}_1=x_2\\ {\stackrel{.}{x}}_2=x_3\\ {\stackrel{.}{x}}_3=b(x_2,x_3)+a\left(x_2\right)u\\ y=x_1\end{array}\right.---\left(1\right)$

In formula (1), x ₁(t), x ₂and x (t) ₃(t) represent respectively displacement, speed and the acceleration of controlled vehicle, and a[x ₂] and b[x (t) ₂(t), x ₃(t)] there is respectively following form:

$a\left(x_2\right)=\frac{1}{\mathrm{m\τ}\left(x_2\right)}---\left(2\right)$

$b(x_2,x_3)=-\frac{2K_d}{m}{x}_2{x}_3-\frac{1}{\mathrm{\τ}\left(x_2\right)}[x_3+\frac{K_d}{m}{x}_2^2+\frac{d_m}{m}]---\left(3\right)$

In formula (2) and formula (3), m represents the quality of controlled vehicle, and τ represents the time constant of engine, K _drepresent pneumatic drag coefficient, d _mrepresent the mechanical resistance of controlled vehicle, u (t) represents engine input, i.e. control inputs; Suppose that the target of controlling is to allow the actual displacement y=x of vehicle ₁can follow the tracks of the upper displacement y setting _r(t), allow the actual speed of vehicle can follow the tracks of the upper speed of setting allow the actual acceleration of vehicle can follow the tracks of the upper acceleration of setting introduce following displacement error variable e ₁, velocity error variable e ₂with acceleration error variable e ₃:

$\left\{\begin{array}{c}{e}_1=x_1-y_r\\ e_2=x_2-{\stackrel{.}{y}}_r\\ e_3=x_3-{\stackrel{..}{y}}_r\end{array}\right.---\left(4\right)$

According to formula (1) and formula (4), the tracking control problem of vehicle is just converted to the stable problem of following error system in initial point (0,0,0):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u\\ y=x_1\end{array}\right.---\left(5\right)$

Based on a (x ₂) meet constraint condition as the gain of vehicle control inputs: wherein a _mand a _mbe known constant, formula (5) be written as:

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u+a_{m}u\\ y=x_1\end{array}\right.---\left(6\right)$

In formula (6), will $b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u$ Regard total disturbance of the error system of formula (6) expression as, be designated as: $\tilde{d}\left(t\right)=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u;$ Control inputs u (t) is divided into the importation u of the integration based on displacement error _i(t) the importation u of the error of the error, and based on displacement, the error of speed and acceleration _gPD(t), whole control inputs is divided into following two parts:

u＝u _I+u _GPD (7)

By in formula (7) substitution formula (6), the error system that formula (6) represents is reduced to:

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\tilde{d}\left(t\right)+a_m(u_I+u_{\mathrm{GPD}})\\ y=x_1\end{array}\right.---\left(8\right)$

2) carry out the importation u of the integration of dynamic adjustments based on displacement error by introducing a variable μ (t) _i(t) form, forces the motion of vehicle to change according to desirable controlled pattern, and its detailed process is: the variable σ (t) that 1. introduces following form:

$\mathrm{\σ}\left(t\right)=\tilde{d}\left(t\right)+a_m{u}_I\left(t\right)---\left(9\right)$

2. introduce variable μ (t), it is determined by following dynamic equation:

$\left\{\begin{array}{c}\stackrel{.}{\mathrm{\μ}}\left(t\right)=\left\{\begin{array}{cc}-\mathrm{\γsign}\left(\mathrm{\σ}\left(t\right)\right),& \left|\mathrm{\μ}\left(t\right)\right|\≤1\\ -\mathrm{\ω\μ},& \left|\mathrm{\μ}\left(t\right)\right|>1\end{array}\right.\\ \mathrm{\μ}\left(0\right)=\mathrm{sign}\left(\mathrm{\σ}\left(0\right)\right)\end{array}\right.---\left(10\right)$

In formula (10), ω is design parameter, ω > 0; γ represents design parameter, and its feature according to controlled vehicle is chosen, and gets positive number; Sign represents sign function; 3. use variable μ (t) to regulate the importation u of the integration based on displacement error _i(t) form, the importation u of the integration based on displacement error _i(t) relational expression and between variable μ (t) is taken as:

$u_I\left(t\right)=k_0\mathrm{\μ}\left(t\right)\min \left({\∫}_{t_0}^t\right|e\left(s\right)|\mathrm{ds},M)---\left(11\right)$

In formula (11), k ₀all represent design parameter with M, represent to get minimum operation, s represents integration variable; Design parameter γ, k ₀need meet following condition with M:

$k_0\mathrm{\γM}\≥\underset{t\≥t_0}{\sup }\left|\frac{d}{\mathrm{dt}}\right[\tilde{d}\left(t\right)\left]\right|---\left(12\right)$

In formula (12), sup represents to get the computing of supremum, represent total disturbance generalized derivative; 4. by choosing design parameter ω, γ, k ₀and M, ensure that equation σ (t)=0 sets up in finite time; 3) choose the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) form, and the importation u of definite error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient of respective items in, its detailed process is: by formula (9) substitution formula (8), obtain

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\mathrm{\σ}\left(t\right)+a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(13\right)$

Due in step 2) in to the importation u based on displacement error integration _i(t) in, introduce variable μ (t), and chosen design parameter ω, γ, k ₀make σ (t)=0 with M, obtained by formula (13):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(14\right)$

From formula (14), the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) only relevant with the state of controlled vehicle, according to the state of controlled vehicle, choose u _gPD(t) form, can directly choose make power system that formula (14) represents at the stable coefficient of initial point (0,0,0) coefficient k as displacement error item ₁, the coefficient k of velocity error item ₂coefficient k with acceleration error item ₃; 4) according to step 2) definite design parameter γ, k ₀and M, and step 3) coefficient k of definite displacement error item ₁, velocity error item coefficient k ₂coefficient k with acceleration error item ₃, determine the control system of controlled vehicle, that is control by separating displacement, speed and the acceleration of implementation to controlled vehicle, reach the control object to controlled vehicle safety and smooth degree.

Described step 2) in, for simplifying the importation u of variable μ (t) to the integration based on displacement error _i(t) adjusting of form, the importation u of the integration based on displacement error _i(t) relational expression and between variable μ (t) is directly taken as:

u _I(t)＝k ₀μ(t)M (15)

Design parameter γ, k ₀need meet following condition with M:

$k_0\mathrm{\γM}\≥\underset{t\≥t_0}{\sup }\left|\frac{d}{\mathrm{dt}}\right[\tilde{d}\left(t\right)\left]\right|---\left(16\right)$

In formula (16), sup represents to get the computing of supremum, represent total disturbance generalized derivative.

Described step 3) in, the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) adopt linear forms, non-linear form or optimization form.

Described step 3) in, the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) adopt following linear forms:

u _GPD(t)＝k ₁e ₁(t)+k ₂e ₂(t)+k ₃e ₃(t) (17)

Or following non-linear form:

u _GPD(t)＝k ₁|e ₁(t)| ^αsign(e ₁(t))+k ₂|e ₂(t)| ^αsign(e ₂(t))+k ₃|e ₃(t)| ^αsign(e ₃(t)) (18)

In formula (17) and formula (18), k ₁, k ₂and k ₃represent respectively the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient, the coefficient of velocity error item and the coefficient of acceleration error item of displacement error item in, α represents nonlinear index, 0 < α≤1.

Described step 3) in, for ensureing the continuity of control inputs, the sign function in formula (18) is replaced with a kind of saturation function of extend type, that is:

u _GPD(t)＝k ₁fal(e ₁(t),α,δ)+k ₂fal(e ₂(t),α,δ)+k ₃fal(e ₃(t),α,δ) (19)

Wherein,

$\mathrm{fal}(x,\mathrm{\&alpha;},\mathrm{\&delta;})=\left\{\begin{array}{cc}x{\mathrm{\&delta;}}^{\mathrm{\&alpha;}-1},& \left|x\right|\&le;\mathrm{\&delta;}\\ {\left|x\right|}^{\mathrm{\&alpha;}}\mathrm{sign}\left(x\right),& \left|x\right|>\mathrm{\&delta;}\end{array}\right.---\left(20\right)$

In formula (20), x is independent variable, is taken as respectively as required displacement error variable e ₁(t), velocity error variable e ₂and acceleration error variable e (t) ₃(t), α and δ are design parameter, 0 < α≤1,0 < δ≤0.1.

When the actual measured signal of controlled vehicle only has displacement signal y (t), or while containing noise in the displacement signal y (t) of actual measurement, to the displacement of controlled vehicle, speed and acceleration are controlled, it specifically comprises the following steps: 1) utilize two-stage tracking-differentiator to carry out pre-service to the displacement signal y (t) of actual measurement, it specifically comprises: first, adopt first order tracking-differentiator to process the displacement signal y (t) of actual measurement, obtain the derivative signal of estimated signal and the measured displacements of measured displacements, and be still designated as respectively y (t) and secondly, by the derivative signal of this displacement regard the rate signal of controlled vehicle as, the rate signal obtaining is utilized to second level tracking-differentiator, the derivative signal that obtains speed is still designated as and be seen as the acceleration signal of controlled vehicle, finally, use through two-stage tracking-differentiator result after treatment, i.e. first order derivative, the second derivative of the estimated signal of the displacement signal of actual measurement and the displacement signal of actual measurement, replace respectively displacement, speed and the acceleration signal of controlled vehicle reality, 2) adopt and step 1)～4) identical method displacement, speed and the acceleration to controlled vehicle control.

The present invention is owing to taking above technical scheme, it has the following advantages: 1, the present invention is owing to control inputs being divided into the importation of the integration based on displacement error, and the importation of error, the error of speed and the error of acceleration based on displacement, on the one hand, carry out the form of the importation of the integration of dynamic adjustments based on displacement error by the variable of selecting vehicle ideal movements pattern to produce, the impact of the disturbance of getting rid of uncertain composition or road conditions and environment with this on vehicle control; On the other hand, by choosing the form of importation of error, the error of speed and the error of acceleration based on displacement, and the coefficient of displacement error item, the coefficient of velocity error item and the coefficient of acceleration error item, realize the control to vehicle ideal movements pattern.By the combination of above-mentioned two aspects, with a kind of separation implementation method of Generalized PID control, realize the control of displacement, speed and acceleration to controlled vehicle, the present invention can meet the safety traffic requirement of vehicle under different dead weight capacity or different road conditions, do not need again the real-time estimation of and running environment situation uncertain to controlled vehicle, therefore save the requirement of uncertain and disturbance being carried out to real-time identification, simplified the structure of controller.2, in existing vehicle control, conventionally adopt the method based on PID control or Based Intelligent Control, wherein often need to determine design parameter by the technology of " tabling look-up "; The present invention rises to a kind of control theory by above-mentioned control technology, make that control method of the present invention is more scientific, range of application is wider, and adaptive faculty is stronger, simultaneously error, the error of speed and the error of acceleration of corresponding displacement aspect the choosing of corresponding importation, can make full use of the achievement of modern control theory, thereby the present invention erects the bridge between control theory and practical application.3, the present invention is because the separation implementation method with Generalized PID control is implemented to control, and the importation of the error of the error based on displacement, the error of speed and acceleration can adopt linear forms, non-linear form or optimization form etc., therefore adopt the present invention can make adjustment process become simple and be convenient to Project Realization.4, the present invention both can ensure the security of vehicle, can effectively control the acceleration of vehicle again, particularly avoid caused the jolting of acceleration, deceleration degree excessive in Vehicle Driving Cycle, to ensure passenger's comfort level, reduce carsick person's discomfort, the quality of lifting vehicle control.Based on above advantage, the present invention can be widely used in the control of cruising of vehicle, the field such as unmanned.

Brief description of the drawings

Fig. 1 is the structural representation that adopts the corresponding vehicle control system of Generalized PID controller obtaining based on separation implementation method;

Fig. 2 only has displacement signal when the actual output of controlled vehicle, or in the situation that comprises noise in the displacement signal of actual measurement, adopts the structural representation of the corresponding vehicle control system of Generalized PID controller obtaining based on separation implementation method.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in detail.

The present invention adopts the security of Generalized PID controller to vehicle and the control of smooth degree that obtain based on separating implementation method, its ultimate principle is: first, controlled vehicle is regarded as by " uncertain part " and " desirable part " and formed, wherein, uncertain part comprises " variation of the quality of vehicle own " and " external disturbance ", wherein " external disturbance " comprise road condition change and environmental change etc.Secondly, build the PID control form of broad sense, utilize vehicle actual displacement with the array configuration of integration, ratio, derivative and second derivative of error of setting displacement as control inputs.In other words, with actual displacement and integration, the ratio of error (hereinafter to be referred as the error of displacement) of setting displacement, and the error of the error of actual speed and setting speed (hereinafter to be referred as the error of speed), actual acceleration and setting acceleration (hereinafter to be referred as the error of acceleration) builds control variable.Again, for " uncertain part " in vehicle operating and " external disturbance ", utilize the integral feedback of displacement error, regulate the form of this feedback fraction by introducing Dynamic mode, get rid of the impact of " uncertain part " and " external disturbance " with this.Meanwhile, utilize error, the error of speed and the determined importation of the error of acceleration of displacement to control " the desirable part " of vehicle.

Suppose that the object that controlled vehicle is controlled is to select control inputs u (t), makes the actual output of controlled vehicle can follow the tracks of the reference input of setting.Wherein, the actual output of controlled vehicle comprises displacement, speed and the acceleration etc. of the vehicle operating of actual measurement, is designated as respectively the reference input of setting comprises displacement, speed and acceleration etc. that vehicle is set, is designated as respectively

As shown in Figure 1, the control method of vehicle safety of the present invention and smooth degree comprises the following steps:

1) for the controlled Vehicular system with ubiquity of following form:

$\left\{\begin{array}{c}{\stackrel{.}{x}}_1=x_2\\ {\stackrel{.}{x}}_2=x_3\\ {\stackrel{.}{x}}_3=b(x_2,x_3)+a\left(x_2\right)u\\ y=x_1\end{array}\right.---\left(1\right)$

In formula (1), x ₁(t), x ₂and x (t) ₃(t) represent respectively displacement, speed and the acceleration of controlled vehicle, and a (x ₂) and b (x ₂, x ₃) there is respectively following form:

$a\left(x_2\right)=\frac{1}{\mathrm{m\&tau;}\left(x_2\right)}---\left(2\right)$

$b(x_2,x_3)=-\frac{2K_d}{m}{x}_2{x}_3-\frac{1}{\mathrm{\&tau;}\left(x_2\right)}[x_3+\frac{K_d}{m}{x}_2^2+\frac{d_m}{m}]---\left(3\right)$

In formula (2) and formula (3), m represents the quality of controlled vehicle, and τ represents the time constant of engine, K _drepresent pneumatic drag coefficient, d _mrepresent the mechanical resistance of controlled vehicle, u (t) represents engine input, i.e. control inputs.Due to a (x ₂) and b (x ₂, x ₃) in all comprise uncertain composition, the gain a (x of control inputs ₂) be non-vanishing, therefore suppose a (x ₂) satisfied following constraint:

$0<a_m\&le;a\left(x_2\right)=\frac{1}{\mathrm{m\&tau;}\left(x_2\right)}\&le;a_M---\left(4\right)$

In formula (4), a _mand a _mbe known constant.

Suppose that the target of controlling is to allow the actual displacement y=x of vehicle ₁can follow the tracks of the upper displacement y setting _r(t), allow the actual speed of vehicle can follow the tracks of the upper speed of setting allow the actual acceleration of vehicle can follow the tracks of the upper acceleration of setting introduce following displacement error variable e ₁, velocity error variable e ₂with acceleration error variable e ₃:

$\left\{\begin{array}{c}{e}_1=x_1-y_r\\ e_2=x_2-{\stackrel{.}{y}}_r\\ e_3=x_3-{\stackrel{..}{y}}_r\end{array}\right.---\left(5\right)$

According to formula (1) and formula (5), the tracking control problem of vehicle is just converted to the stable problem of following error system in initial point (0,0,0):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u\\ y=x_1\end{array}\right.---\left(6\right)$

Simultaneously due to a (x ₂) uncertainty, formula (6) can be write as to following form according to formula (4):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u+a_{m}u\\ y=x_1\end{array}\right.---\left(7\right)$

In formula (7), will $b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u$ Regard total disturbance of the error system of formula (7) expression as, be designated as: $\tilde{d}\left(t\right)=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u.$

In order to utilize separation implementation to control vehicle, control inputs u (t) is divided into the importation u of the integration based on displacement error _i(t) the importation u of the error of the error, and based on displacement, the error of speed and acceleration _gPD(t), wherein, u _gPD(t) be a kind of ratio and derivative combination of displacement error of broad sense.Be that whole Generalized PID control inputs is expressed as:

u＝u _I+u _GPD (8)

By in formula (8) substitution formula (7), formula (7) can be expressed as:

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\tilde{d}\left(t\right)+a_m(u_I+u_{\mathrm{GPD}})\\ y=x_1\end{array}\right.---\left(9\right)$

2), for adopting the Generalized PID controller based on separating implementation method to follow the tracks of control to controlled vehicle, below will carry out by introducing a variable μ (t) the importation u of the integration of dynamic adjustments based on displacement error _i(t) form, forces the motion of controlled vehicle to change according to desirable controlled pattern, and its detailed process is:

1. introduce the variable σ (t) of following form:

$\mathrm{\&sigma;}\left(t\right)=\tilde{d}\left(t\right)+a_m{u}_I\left(t\right)---\left(10\right)$

Or of equal value have

$\mathrm{\&sigma;}\left(t\right)={\stackrel{.}{e}}_3-a_m{u}_{\mathrm{GPD}}\left(t\right)---\left(11\right)$

2. introduce variable μ (t), it is determined by following dynamic equation:

$\left\{\begin{array}{c}\stackrel{.}{\mathrm{\&mu;}}\left(t\right)=\left\{\begin{array}{cc}-\mathrm{\&gamma;sign}\left(\mathrm{\&sigma;}\left(t\right)\right),& \left|\mathrm{\&mu;}\left(t\right)\right|\&le;1\\ -\mathrm{\&omega;\&mu;},& \left|\mathrm{\&mu;}\left(t\right)\right|>1\end{array}\right.\\ \mathrm{\&mu;}\left(0\right)=\mathrm{sign}\left(\mathrm{\&sigma;}\left(0\right)\right)\end{array}\right.---\left(12\right)$

In formula (12), ω is design parameter, as long as get ω > 0, for the sake of simplicity, ω often gets 0.5; γ represents design parameter, and its feature according to controlled vehicle is chosen, and can be taken as a given positive number; Sign represents sign function.

3. use variable μ (t) to regulate the importation u of the integration based on displacement error _i(t) form, gets u here _i(t) relational expression and between variable μ (t) is:

$u_I\left(t\right)=k_0\mathrm{\&mu;}\left(t\right)\min \left({\&Integral;}_{t_0}^t\right|e\left(s\right)|\mathrm{ds},M)---\left(13\right)$

In formula (13), k ₀all represent design parameter with M; represent to get minimum operation, its effect is to prevent the decline of the overshoot of excessive caused controlled variable or whole vehicle control system stability; S represents integration variable.

For simplifying the importation u of variable μ (t) to the integration based on displacement error _i(t) adjusting of form, can be by the importation u of the integration based on displacement error _i(t) relational expression and between variable μ (t) is directly taken as:

u _I(t)＝k ₀μ(t)M (14)

In formula (13) and formula (14), designing parameters γ, k ₀with choosing of M, need meet following condition:

$k_0\mathrm{\&gamma;M}\&GreaterEqual;\underset{t\&GreaterEqual;t_0}{\sup }\left|\frac{d}{\mathrm{dt}}\right[\tilde{d}\left(t\right)\left]\right|---\left(15\right)$

In formula (15), sup represents to get the computing of supremum, represent total disturbance generalized derivative.

4. by choosing design parameter ω, γ, k ₀and M, can ensure to make σ (t)=0 in formula (10) or (11) in finite time.

3) choose the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) form, and the importation u of definite error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient in, its detailed process is:

By in formula (10) substitution formula (9), obtain

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\mathrm{\&sigma;}\left(t\right)+a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(16\right)$

Due in step 2) in importation u to the integration based on displacement error _i(t) in, introduce variable μ (t), and chosen design parameter ω, γ, k ₀make σ (t)=0 with M, obtained by formula (16):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(17\right)$

From formula (17), the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) only relevant with the state of controlled vehicle.Therefore, can, according to the state of controlled vehicle, choose u _gPD(t) form, the conclusion that can make full use of modern control theory to this realizes, as adopted linear forms, non-linear form or optimization form etc.Conventionally this importation u, _gPD(t) can adopt following linear forms:

u _GPD(t)＝k ₁e ₁(t)+k ₂e ₂(t)+k ₃e ₃(t) (18)

Or following non-linear form:

u _GPD(t)＝k ₁|e ₁(t)| ^αsign(e ₁(t))+k ₂|e ₂(t)| ^αsign(e ₂(t))+k ₃|e ₃(t)| ^αsign(e ₃(t)) (19)

In formula (18) and formula (19), k ₁, k ₂and k ₃represent respectively the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient, α represents nonlinear index, common 0 < α≤1.

For ensureing the continuity of control inputs, the sign function in formula (19) can be replaced with a kind of saturation function of extend type, that is:

u _GPD(t)＝k ₁fal(e ₁(t),α,δ)+k ₂fal(e ₂(t),α,δ)+k ₃fal(e ₃(t),α,δ) (20)

Wherein,

$\mathrm{fal}(x,\mathrm{\&alpha;},\mathrm{\&delta;})=\left\{\begin{array}{cc}x{\mathrm{\&delta;}}^{\mathrm{\&alpha;}-1},& \left|x\right|\&le;\mathrm{\&delta;}\\ {\left|x\right|}^{\mathrm{\&alpha;}}\mathrm{sign}\left(x\right),& \left|x\right|>\mathrm{\&delta;}\end{array}\right.---\left(21\right)$

In formula (21), x is independent variable, and x can be taken as respectively displacement error variable e as required ₁(t), velocity error variable e ₂and acceleration error variable e (t) ₃(t), α and δ are design parameter, conventionally get 0 < α≤1,0 < δ≤0.1.

Directly choose make power system that formula (17) represents at the stable coefficient of initial point (0,0,0) coefficient k as displacement error item ₁, velocity error item coefficient k ₂coefficient k with acceleration error item ₃.

4) according to step 2) definite design parameter γ, k ₀and M, and step 3) coefficient k of definite displacement error item ₁, velocity error item coefficient k ₂coefficient k with acceleration error item ₃, determine the control system of controlled vehicle, that is by the above-mentioned separation implementation of Generalized PID controller displacement, speed and the acceleration to controlled vehicle control, reach the control object to controlled vehicle safety and smooth degree.

In the above-mentioned control that separates the security of implementation method to vehicle and smooth degree based on Generalized PID controller, as shown in Figure 2, if the actual measured signal of controlled vehicle only has displacement signal y (t), or contain noise in the displacement signal y (t) of actual measurement, first utilize two-stage tracking-differentiator to carry out pre-service to the displacement signal y (t) of actual measurement, then adopt and abovementioned steps 1)～4) identical method displacement, speed and the acceleration to controlled vehicle control.Wherein, utilizing two-stage tracking-differentiator to carry out pretreated process to the displacement signal y (t) of actual measurement specifically comprises: first, adopt first order tracking-differentiator to process the displacement signal y (t) of actual measurement, obtain the derivative signal of estimated signal and the measured displacements of measured displacements signal, be still designated as respectively y (t) and secondly, by the derivative signal of this displacement regard the rate signal of controlled vehicle as, the rate signal obtaining is utilized to second level tracking-differentiator, the derivative signal of the speed of acquisition is still designated as and be seen as the acceleration signal of controlled vehicle; Finally use through two-stage tracking-differentiator result after treatment, it is the estimated signal of the displacement signal of actual measurement, and the first order derivative of the displacement signal of actual measurement, second derivative, replace respectively abovementioned steps 1)～4) in displacement, speed and the acceleration signal of controlled vehicle reality.Adopt and abovementioned steps 1)～4) identical method displacement, speed and the acceleration to controlled vehicle control.

The various embodiments described above are only for illustrating the present invention; wherein the structure of each parts, connected mode and method step etc. all can change to some extent; every equivalents of carrying out on the basis of technical solution of the present invention and improvement, all should not get rid of outside protection scope of the present invention.

Claims (6)

1. a control method for vehicle safety and smooth degree, it comprises the following steps:

1) for the controlled Vehicular system with ubiquity of following form:

$\left\{\begin{array}{c}{\stackrel{.}{x}}_1=x_2\\ {\stackrel{.}{x}}_2=x_3\\ {\stackrel{.}{x}}_3=b(x_2,x_3)+a\left(x_2\right)u\\ y=x_1\end{array}\right.---\left(1\right)$

In formula (1), x ₁(t), x ₂and x (t) ₃(t) represent respectively displacement, speed and the acceleration of controlled vehicle, and a[x ₂] and b[x (t) ₂(t), x ₃(t)] there is respectively following form:

$a\left(x_2\right)=\frac{1}{\mathrm{m\&tau;}\left(x_2\right)}---\left(2\right)$

$b(x_2,x_3)=-\frac{2K_d}{m}{x}_2{x}_3-\frac{1}{\mathrm{\&tau;}\left(x_2\right)}[x_3+\frac{K_d}{m}{x}_2^2+\frac{d_m}{m}]---\left(3\right)$

In formula (2) and formula (3), m represents the quality of controlled vehicle, and τ represents the time constant of engine, K _drepresent pneumatic drag coefficient, d _mrepresent the mechanical resistance of controlled vehicle, u (t) represents engine input, i.e. control inputs;

Suppose that the target of controlling is to allow the actual displacement y=x of vehicle ₁can follow the tracks of the upper displacement y setting _r(t), allow the actual speed of vehicle can follow the tracks of the upper speed of setting allow the actual acceleration of vehicle can follow the tracks of the upper acceleration of setting introduce following displacement error variable e ₁, velocity error variable e ₂with acceleration error variable e ₃:

$\left\{\begin{array}{c}{e}_1=x_1-y_r\\ e_2=x_2-{\stackrel{.}{y}}_r\\ e_3=x_3-{\stackrel{..}{y}}_r\end{array}\right.---\left(4\right)$

According to formula (1) and formula (4), the tracking control problem of vehicle is just converted to the stable problem of following error system in initial point (0,0,0):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u\\ y=x_1\end{array}\right.---\left(5\right)$

Based on a (x ₂) meet constraint condition as the gain of vehicle control inputs: wherein a _mand a _mbe known constant, formula (5) be written as:

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u+a_{m}u\\ y=x_1\end{array}\right.---\left(6\right)$

In formula (6), will $b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u$ Regard total disturbance of the error system of formula (6) expression as, be designated as: $\tilde{d}\left(t\right)=b(e_2+{\stackrel{.}{y}}_r,e_3+{\stackrel{..}{y}}_r)-{\stackrel{...}{y}}_r+a(e_2+{\stackrel{.}{y}}_r)u-a_{m}u;$

Control inputs u (t) is divided into the importation u of the integration based on displacement error _i(t) the importation u of the error of the error, and based on displacement, the error of speed and acceleration _gPD(t), whole control inputs is divided into following two parts:

u＝u _I+u _GPD (7)

By in formula (7) substitution formula (6), the error system that formula (6) represents is reduced to:

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\tilde{d}\left(t\right)+a_m(u_I+u_{\mathrm{GPD}})\\ y=x_1\end{array}\right.---\left(8\right)$

2) carry out the importation u of the integration of dynamic adjustments based on displacement error by introducing a variable μ (t) _i(t) form, forces the motion of vehicle to change according to desirable controlled pattern, and its detailed process is:

1. introduce the variable σ (t) of following form:

$\mathrm{\&sigma;}\left(t\right)=\tilde{d}\left(t\right)+a_m{u}_I\left(t\right)---\left(9\right)$

2. introduce variable μ (t), it is determined by following dynamic equation:

$\left\{\begin{array}{c}\stackrel{.}{\mathrm{\&mu;}}\left(t\right)=\left\{\begin{array}{cc}-\mathrm{\&gamma;sign}\left(\mathrm{\&sigma;}\left(t\right)\right),& \left|\mathrm{\&mu;}\left(t\right)\right|\&le;1\\ -\mathrm{\&omega;\&mu;},& \left|\mathrm{\&mu;}\left(t\right)\right|>1\end{array}\right.\\ \mathrm{\&mu;}\left(0\right)=\mathrm{sign}\left(\mathrm{\&sigma;}\left(0\right)\right)\end{array}\right.---\left(10\right)$

In formula (10), ω is design parameter, ω > 0; γ represents design parameter, and its feature according to controlled vehicle is chosen, and gets positive number; Sign represents sign function;

3. use variable μ (t) to regulate the importation u of the integration based on displacement error _i(t) form, the importation u of the integration based on displacement error _i(t) relational expression and between variable μ (t) is taken as:

$u_I\left(t\right)=k_0\mathrm{\&mu;}\left(t\right)\min \left({\&Integral;}_{t_0}^t\right|e\left(s\right)|\mathrm{ds},M)---\left(11\right)$

In formula (11), k ₀all represent design parameter with M, represent to get minimum operation, s represents integration variable;

Design parameter γ, k ₀need meet following condition with M:

$k_0\mathrm{\&gamma;M}\&GreaterEqual;\underset{t\&GreaterEqual;t_0}{\sup }\left|\frac{d}{\mathrm{dt}}\right[\tilde{d}\left(t\right)\left]\right|---\left(12\right)$

In formula (12), sup represents to get the computing of supremum, represent total disturbance generalized derivative;

4. by choosing design parameter ω, γ, k ₀and M, ensure that equation σ (t)=0 sets up in finite time;

3) choose the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) form, and the importation u of definite error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient of respective items in, its detailed process is:

By in formula (9) substitution formula (8), obtain

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=\mathrm{\&sigma;}\left(t\right)+a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(13\right)$

Due in step 2) in to the importation u based on displacement error integration _i(t) in, introduce variable μ (t), and chosen design parameter ω, γ, k ₀make σ (t)=0 with M, obtained by formula (13):

$\left\{\begin{array}{c}{\stackrel{.}{e}}_1=e_2\\ {\stackrel{.}{e}}_2=e_3\\ {\stackrel{.}{e}}_3=a_m{u}_{\mathrm{GPD}}\\ y=x_1\end{array}\right.---\left(14\right)$

From formula (14), the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) only relevant with the state of controlled vehicle, according to the state of controlled vehicle, choose u _gPD(t) form, can directly choose make power system that formula (14) represents at the stable coefficient of initial point (0,0,0) coefficient k as displacement error item ₁, the coefficient k of velocity error item ₂coefficient k with acceleration error item ₃;

4) according to step 2) definite design parameter γ, k ₀and M, and step 3) coefficient k of definite displacement error item ₁, velocity error item coefficient k ₂coefficient k with acceleration error item ₃, determine the control system of controlled vehicle, that is control by separating displacement, speed and the acceleration of implementation to controlled vehicle, reach the control object to controlled vehicle safety and smooth degree.

2. the control method of a kind of vehicle safety as claimed in claim 1 and smooth degree, is characterized in that: described step 2) in, for simplifying the importation u of variable μ (t) to the integration based on displacement error _i(t) adjusting of form, the importation u of the integration based on displacement error _i(t) relational expression and between variable μ (t) is directly taken as:

u _I(t)＝k ₀μ(t)M (15)

Design parameter γ, k ₀need meet following condition with M:

$k_0\mathrm{\&gamma;M}\&GreaterEqual;\underset{t\&GreaterEqual;t_0}{\sup }\left|\frac{d}{\mathrm{dt}}\right[\tilde{d}\left(t\right)\left]\right|---\left(16\right)$

In formula (16), sup represents to get the computing of supremum, represent total disturbance generalized derivative.

3. the control method of a kind of vehicle safety as claimed in claim 1 or 2 and smooth degree, is characterized in that: described step 3) in, the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) adopt linear forms, non-linear form or optimization form.

4. the control method of a kind of vehicle safety as claimed in claim 1 or 2 and smooth degree, is characterized in that: described step 3) in, the importation u of the error of the error based on displacement, the error of speed and acceleration _gPD(t) adopt following linear forms:

u _GPD(t)＝k ₁e ₁(t)+k ₂e ₂(t)+k ₃e ₃(t) (17)

Or following non-linear form:

u _GPD(t)＝k ₁|e ₁(t)| ^αsign(e ₁(t))+k ₂|e ₂(t)| ^αsign(e ₂(t))+k ₃|e ₃(t)| ^αsign(e ₃(t)) (18)

In formula (17) and formula (18), k ₁, k ₂and k ₃represent respectively the importation u of error, the error of speed and the error of acceleration based on displacement _gPD(t) coefficient, the coefficient of velocity error item and the coefficient of acceleration error item of displacement error item in, α represents nonlinear index, 0 < α≤1.

5. the control method of a kind of vehicle safety as claimed in claim 4 and smooth degree, it is characterized in that: described step 3) in, for ensureing the continuity of control inputs, the sign function in formula (18) is replaced with a kind of saturation function of extend type, that is:

u _GPD(t)＝k ₁fal(e ₁(t),α,δ)+k ₂fal(e ₂(t),α,δ)+k ₃fal(e ₃(t),α,δ) (19)

Wherein,

$\mathrm{fal}(x,\mathrm{\&alpha;},\mathrm{\&delta;})=\left\{\begin{array}{cc}x{\mathrm{\&delta;}}^{\mathrm{\&alpha;}-1},& \left|x\right|\&le;\mathrm{\&delta;}\\ {\left|x\right|}^{\mathrm{\&alpha;}}\mathrm{sign}\left(x\right),& \left|x\right|>\mathrm{\&delta;}\end{array}\right.---\left(20\right)$

In formula (20), x is independent variable, is taken as respectively as required displacement error variable e ₁(t), velocity error variable e ₂and acceleration error variable e (t) ₃(t), α and δ are design parameter, 0 < α≤1,0 < δ≤0.1.

6. a kind of vehicle safety as described in claim 1～5 any one and the control method of smooth degree, it is characterized in that: when the actual measured signal of controlled vehicle only has displacement signal y (t), or while containing noise in the displacement signal y (t) of actual measurement, displacement, speed and acceleration to controlled vehicle are controlled, and it specifically comprises the following steps:

1) utilize two-stage tracking-differentiator to carry out pre-service to the displacement signal y (t) of actual measurement, it specifically comprises:

First, adopt first order tracking-differentiator to process the displacement signal y (t) of actual measurement, obtain the derivative signal of estimated signal and the measured displacements of measured displacements, and be still designated as respectively y (t) and secondly, by the derivative signal of this displacement regard the rate signal of controlled vehicle as, the rate signal obtaining is utilized to second level tracking-differentiator, the derivative signal that obtains speed is still designated as and be seen as the acceleration signal of controlled vehicle; Finally, use through two-stage tracking-differentiator result after treatment, i.e. first order derivative, the second derivative of the estimated signal of the displacement signal of actual measurement and the displacement signal of actual measurement, replace respectively displacement, speed and the acceleration signal of controlled vehicle reality;

2) adopt and step 1)～4) identical method displacement, speed and the acceleration to controlled vehicle control.