CN112068432A - Method and device for controlling pole allocation of unmanned vehicle dynamics system - Google Patents
Method and device for controlling pole allocation of unmanned vehicle dynamics system Download PDFInfo
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Abstract
The invention discloses a pole allocation control method for an unmanned vehicle dynamic system, which comprises the steps of firstly determining an expected closed loop pole of the dynamic system in a vehicle stable state through analyzing the target driving performance of an unmanned vehicle, then calculating a yaw moment based on the pole position, and correcting the vehicle posture through an active yaw moment generated by an independent driving motor, so as to realize the closed loop stability of the unmanned vehicle under the design of 'control-following layout'. The invention also provides a control device for the pole allocation of the unmanned vehicle dynamics system. By using the invention, the running closed loop stability can be realized under the structural parameters that the unmanned vehicle is in static instability, thereby improving the flexibility of the overall layout of the unmanned vehicle and meeting the use requirements of the unmanned vehicle under the civil complex scene or the military scene.
Description
Technical Field
The invention relates to a dynamics control system, in particular to a dynamics control method and a dynamics control device under an unmanned vehicle-mounted control layout, and belongs to the technical field of unmanned vehicles and automatic driving vehicles.
Background
Aiming at unmanned vehicles, the adoption of full linear control technology and independent driving/steering/braking technology brings a brand new overall layout form and overall design theory. The completely new overall layout mode necessarily brings completely new vehicle dynamic behavior characteristics, thereby influencing the foundation of a vehicle dynamic and control system. After the technologies of independent driving/steering/braking and the like are adopted, the system control target is more complex, the system control input links are greatly increased, and great challenges are brought to the development of a control system. Therefore, the conventional vehicle dynamics control theory and technology cannot be completely applied, and a completely new research on the dynamics control theory and technology is required.
In the overall design process of a conventional vehicle, "understeer" is a theoretical constraint that must be followed by the overall design of the vehicle, which requires that the overall layout of the vehicle must satisfy the constraint that the "static reserve factor is greater than zero" so that the vehicle lateral dynamics system is a "statically stable" system. For an unmanned vehicle that completely discards human steering mechanisms, its usage scenario, overall layout, etc. requirements are different from those of a conventional automobile, which would severely limit its overall layout flexibility if it continued to follow the theoretical "understeer" constraint.
The following control layout is an unmanned vehicle design method for overall design layout by comprehensively considering a closed loop dynamic system formed by a control system and a mechanical system of an unmanned vehicle platform, and breaks through the theoretical constraint of static stability of the mechanical system in the traditional vehicle overall design layout theory, so that the overall layout flexibility and maneuverability margin of the unmanned vehicle are improved, and the overall design requirement of a novel unmanned vehicle in the future is met. The design method of the 'control following layout' is suitable for a full-wire control unmanned platform, and takes a control system and a mechanical system of an unmanned vehicle as an organic whole for investigation. The design method of the following control layout configures the mechanical structure of the unmanned vehicle to ensure that the transverse dynamics of the unmanned vehicle has the static and unstable characteristics so as to obtain better maneuverability and layout flexibility. If the traditional dynamics control method is adopted, closed-loop stability cannot be realized in the driving process of the unmanned vehicle, which brings challenges to the realization of the closed-loop stability of the system.
Disclosure of Invention
In view of the above, the invention provides a method and a device for controlling unmanned vehicle pole allocation dynamics under an unmanned platform 'control-following layout' design method, and aims to calculate an expected yaw moment by using a reasonable dynamic system pole allocation, realize closed-loop stability of an unmanned vehicle under the 'control-following layout' design, and be used for stability control of all-wheel independent steering and independent driving of the unmanned vehicle.
In order to solve the technical problem, the invention is realized as follows:
a pole allocation control method of an unmanned vehicle dynamics system is suitable for an unmanned vehicle adopting a random control layout, and comprises the following steps:
the method comprises the steps of firstly, determining an expected closed loop pole of a dynamic system in a vehicle stable state;
step two, substituting the expected closed-loop pole into the following closed-loop system pole position expression to obtain a state feedback vector F ═ F1,f2]Two components f1And f2:
Wherein, IzYaw inertia for vehicle, CfAnd CrYaw stiffness of the front and rear wheels, respectively, m vehicle mass, lfAnd lrThe distances between the center of mass of the vehicle and the front axle and the rear axle are respectively, and u is the longitudinal running speed of the vehicle;
step three, taking the active yaw moment M as feedback of the state vector x, and taking the f obtained in the step two1And f2Substituting the expression M of the active yaw moment into-Fx to obtain the active yaw moment, wherein the active yaw moment is used for controlling the vehicle and realizing closed loop stability; wherein the content of the first and second substances,beta is the vehicle mass center slip angle, and r is the vehicle yaw rate.
Preferably, when the stable mode is adoptedDuring control, the expected closed-loop pole under the vehicle steady state is determined as follows:wherein the function of the parameter d is to adjust the expected pole position within a reasonable range;
when agile mode control is employed, the expected closed loop pole at vehicle steady state is determined to be
The invention provides a pole allocation control device of an unmanned vehicle dynamic system, which is suitable for an unmanned vehicle adopting a random control layout and comprises the following components: the system comprises an expected closed-loop pole allocation module, an intermediate calculation module and an active yaw moment calculation module;
the expected closed-loop pole allocation module is used for determining an expected closed-loop pole of a dynamic system in a vehicle stable state and sending the expected closed-loop pole to the intermediate calculation module;
an intermediate calculation module for substituting the expected closed-loop pole into a closed-loop system pole position expression to obtain a state feedback vector F ═ F1,f2]Two components f1And f2Sending the data to an active yaw moment calculation module;
wherein, IzYaw inertia for vehicle, CfAnd CrYaw stiffness of the front and rear wheels, respectively, m vehicle mass, lfAnd lrThe distances between the center of mass of the vehicle and the front axle and the rear axle are respectively, and u is the longitudinal running speed of the vehicle;
an active yaw moment calculation module for obtaining f1And f2Substituting the expression M of active yaw moment into-Fx to obtainThe active yaw moment is used for controlling the vehicle to realize closed loop stability; wherein the active yaw moment M is the feedback of the state vector x,beta is the vehicle mass center slip angle, and r is the vehicle yaw rate.
Preferably, when the steady mode control is employed, the desired closed-loop pole configuration module determines the desired closed-loop pole at the vehicle steady state as:wherein the function of the parameter d is to adjust the expected pole position within a reasonable range;
the expected closed-loop pole configuration module determines an expected closed-loop pole at a vehicle steady state as an expected closed-loop pole when agile mode control is employed
Has the advantages that:
(1) the invention is suitable for the unmanned vehicle adopting the design of the 'control-by-control layout', and can realize the closed loop stability of the running of the unmanned vehicle under the structural parameters that the unmanned vehicle is in static instability, thereby improving the flexibility of the overall layout of the unmanned vehicle and meeting the use requirements of the unmanned vehicle under the civil complex scene or the military scene.
(2) The unmanned vehicle pole allocation dynamics control method provided by the invention is based on the target driving performance requirement of the unmanned vehicle, firstly determines the expected closed-loop pole of a dynamics system in a vehicle stable state, then designs the yaw moment based on the pole position, corrects the vehicle posture through the active yaw moment generated by the independent driving motor, and realizes the closed-loop stability of the unmanned vehicle under the design of 'control-following layout'.
(3) Through the analysis of the pole positions, the invention also provides a corresponding pole position configuration scheme aiming at the stable mode and the agile mode, and the reasonable pole configuration is utilized to calculate the expected yaw moment, thereby realizing the closed loop stability under different modes.
Drawings
FIG. 1 is a flow chart of a method for controlling the pole allocation of an unmanned vehicle dynamics system according to the present invention;
FIG. 2 is a schematic diagram of desired closed loop pole locations;
fig. 3 is a block diagram of the control device for the pole allocation of the unmanned vehicle dynamics system of the present invention.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
When a vehicle mechanical system is configured as a statically unstable system, although the flexibility of the configuration is greatly improved, if the vehicle control system is not enabled, the vehicle is difficult to operate normally. After the unmanned vehicle platform adopts a static and unstable layout, instability is easy to occur in the steering process, and the vehicle is easy to be unstable due to the interference of overhigh vehicle speed or the deflection rigidity of the rear wheel side.
Therefore, aiming at the static instability of the unmanned vehicle in the controlled layout, the invention provides a pole allocation dynamic control scheme for the unmanned vehicle in the controlled layout, which has the following basic idea: and according to the target driving performance expected to be achieved by the unmanned vehicle, acquiring an expected closed-loop pole of a dynamic system in a vehicle stable state, and calculating the yaw moment based on the expected closed-loop pole. Therefore, the method abandons the traditional thought, takes the vehicle in the closed-loop stable state as the premise, takes the closed-loop pole in the vehicle stable state as the design starting point, calculates the expected yaw moment by utilizing the reasonable pole configuration, and designs the active yaw moment meeting the stable state and the lateral dynamics of the vehicle. The required active yaw moment is generated by the independent driving motor, the vehicle posture is corrected, and the closed loop stability of the unmanned vehicle under the design of the 'random control layout' is realized.
The core of the stability control method provided by the invention, namely the closed-loop pole configuration of the vehicle transverse dynamic system, is realized by analyzing the relationship between the closed-loop pole and the active yaw moment. When the method is used, the expected closed-loop pole is substituted into the relation to obtain the active yaw moment for stabilizing the vehicle, and then the yaw moment is exerted through actuating mechanisms such as a steering engine and a driving motor, so that the target pole allocation of the transverse dynamic system is completed.
According to a two-degree-of-freedom model of the vehicle, considering the yaw moment generated by an independent motor as a control input, the two-degree-of-freedom model comprises the following steps:
x=Ax+B+CM (1)
in the formula: x is a state vector; m is the active yaw moment of the vehicle; is a front wheel corner; lfAnd lrThe distances between the center of mass of the vehicle and the front axle and the rear axle are respectively; r is the vehicle yaw rate; beta is the vehicle mass center slip angle; m is the vehicle mass; i iszYawing inertia for the vehicle; u is the longitudinal running speed of the vehicle; cfAnd CrThe cornering stiffness of the front and rear wheels respectively.
The yaw moment M is feedback of a state vector x, and the state feedback vector is F ═ F1,f2]Then, there are:
M=-Fx (2)
the closed loop kinetic model can be described as:
x=(A-CF)x+B (3)
the feature matrix of the closed loop dynamics system is then:
the closed loop system pole positions are further found as follows:
wherein:
the above series of equations shows the closed loop pole p1,2Relation to the active yaw moment M. Then, as shown in fig. 1, the pole allocation control method of the unmanned vehicle dynamics system of the present invention includes the following steps:
step one, determining an expected closed loop pole p under a vehicle steady state1,2。
Step two, the expected closed loop pole p1,2Substituting the pole position expression (4) of the closed-loop system to obtain f1And f2The value is obtained.
Step three, taking the f obtained in the step two1And f2And substituting the active yaw moment expression (2) to obtain an active yaw moment, and controlling the vehicle to realize closed-loop stability.
The relevant parameter values in the formula (4) can be obtained through an online identification algorithm of vehicle dynamic system parameters. Equation (4) shows that the closed-loop pole position of the vehicle lateral dynamics system is determined by the vehicle structure parameter and the control parameter, which is also the typical characteristic of the "control-by-control layout", and the dynamics behavior and stability of the vehicle depend on not only the mechanical configuration but also the control system of the vehicle.
The calculation of the desired closed-loop pole in both modes of the unmanned vehicle is described in detail below with reference to fig. 2.
The pole position reflects the dynamic behavior of the system, and the unmanned vehicle pole allocation dynamics control method provided by the invention can meet different control performance requirements according to the selection of closed-loop poles at different positions. For the manned unmanned vehicle pursuing riding comfort and the military or special unmanned vehicle pursuing traveling performance and quick response capability, the expected pole position can be correspondingly adjusted. The invention proposes two modes of pole allocation: a stable mode and an agile mode.
Fig. 1 shows the initial pole, and the desired pole locations for two different modes. Both modes are premised on stability, with "stable mode" being more favored over smooth and "agile mode" being more favored over rapid response.
In the "steady mode", as shown by the open circles in the figure, the poles appear as conjugate complex poles arranged on a straight line and exist in the second and third quadrants, respectively, that is, the optimal damping ratio of the system is 0.707, and the damping ratio of the expected vehicle steering response is a constant optimal damping ratio in the whole vehicle speed range, so that the steering stability can be improved remarkably. Then the desired closed loop pole position p for "stable moded1Can be determined by the following formula:
where the location of the closed loop pole is desired. It can be seen from this formula that as the vehicle speed increases, the distance between the poles decreases, the distance between the two poles is inversely proportional to the vehicle speed u, and the parameter d is a constant coefficient, which is used to adjust the position of the expected pole within a reasonable range.
In the "agile mode", as shown by the gray ball in the figure, at different vehicle speeds, the desired endpoint location is a negative solid root, representing the critical damping ratio. Neutral-steering vehicles tend to have critical damping with better transient response speed. Desired closed loop pole position p for "agile moded2Can be determined by the following formula:
since two poles coincide to be one pole, Δ 20. Using delta2Expression and equation (4) and pole position pd2Respectively calculate f1And f2。
In order to implement the method, the invention also provides a pole allocation control device of the unmanned vehicle dynamic system, which comprises a desired closed-loop pole allocation module, an intermediate calculation module and an active yaw moment calculation module, as shown in fig. 3.
And the expected closed-loop pole allocation module is used for determining an expected closed-loop pole in a vehicle stable state and sending the expected closed-loop pole to the intermediate calculation module. Wherein, when employing the stable mode control, employing equation (5) to determine the desired closed loop pole; when agile mode control is employed, equation (6) is used to determine the desired closed loop pole.
An intermediate calculation module, configured to substitute the expected closed-loop pole into a closed-loop system pole position expression (4), so as to obtain a state feedback vector F ═ F1,f2]Two components f1And f2And sending the data to an active yaw moment calculation module.
An active yaw moment calculation module for obtaining f1And f2And substituting the active yaw moment expression (2) to obtain an active yaw moment, and controlling the vehicle to realize closed-loop stability.
The above embodiments only describe the design principle of the present invention, and the shapes and names of the components in the description may be different without limitation. Therefore, a person skilled in the art of the present invention can modify or substitute the technical solutions described in the foregoing embodiments; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (4)
1. A pole allocation control method of an unmanned vehicle dynamics system is suitable for an unmanned vehicle adopting a random control layout, and is characterized by comprising the following steps:
the method comprises the steps of firstly, determining an expected closed loop pole of a dynamic system in a vehicle stable state;
step two, substituting the expected closed-loop pole into the following closed-loop system pole position expression to obtain a state feedback vector F ═ F1,f2]Two components f1And f2:
Wherein, IzYaw inertia for vehicle, CfAnd CrYaw stiffness of the front and rear wheels, respectively, m vehicle mass, lfAnd lrThe distances between the center of mass of the vehicle and the front axle and the rear axle are respectively, and u is the longitudinal running speed of the vehicle;
step three, taking the active yaw moment M as feedback of the state vector x, and taking the f obtained in the step two1And f2Substituting the expression M of the active yaw moment into-Fx to obtain the active yaw moment, wherein the active yaw moment is used for controlling the vehicle and realizing closed loop stability; wherein the content of the first and second substances,beta is the vehicle mass center slip angle, and r is the vehicle yaw rate.
2. The method of claim 1, wherein when employing steady mode control, determining the desired closed-loop pole at vehicle steady state is:wherein the function of the parameter d is to adjust the expected pole position within a reasonable range;
3. The utility model provides an unmanned vehicle dynamics system utmost point disposes controlling means, is applicable to the unmanned vehicle who adopts the control-following overall arrangement, its characterized in that includes: the system comprises an expected closed-loop pole allocation module, an intermediate calculation module and an active yaw moment calculation module;
the expected closed-loop pole allocation module is used for determining an expected closed-loop pole of a dynamic system in a vehicle stable state and sending the expected closed-loop pole to the intermediate calculation module;
an intermediate calculation module for substituting the expected closed-loop pole into a closed-loop system pole position expression to obtain a state feedback vector F ═ F1,f2]Two components f1And f2Sending the data to an active yaw moment calculation module;
wherein, IzYaw inertia for vehicle, CfAnd CrYaw stiffness of the front and rear wheels, respectively, m vehicle mass, lfAnd lrThe distances between the center of mass of the vehicle and the front axle and the rear axle are respectively, and u is the longitudinal running speed of the vehicle;
an active yaw moment calculation module for obtaining f1And f2Substituting the expression M of the active yaw moment into-Fx to obtain the active yaw moment, wherein the active yaw moment is used for controlling the vehicle and realizing closed loop stability; wherein the active yaw moment M is the feedback of the state vector x,beta is the vehicle mass center slip angle, and r is the vehicle yaw rate.
4. The apparatus of claim 3, wherein the desired closed-loop pole configuration module determines the desired closed-loop pole at vehicle steady state when the steady mode control is employed as:wherein the function of the parameter d is to adjust the expected pole position within a reasonable range;
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