JP2012126293A - Steering controlling system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering controlling system of a vehicle capable of obtaining a stable controlling performance regardless of a cargo loading state.SOLUTION: A vehicle mass computing unit 41 calculates the mass of the vehicle by using relative displacements H, H, Hand Hdetected by a displacement sensor 36. A yaw inertia moment computing unit 43 calculates a yaw inertia moment from the mass of the vehicle calculated by the vehicle mass computing unit 41. A state feedback gain computing unit 44 sets a state equation of a steering system of which input amount is a target steering angle by using the mass of the vehicle calculated by the vehicle mass computing unit 41 and the yaw inertia moment I calculated by the yaw inertia moment computing unit 43, sets an evaluation function with respect to the set state equation, and calculates a state feedback gain of which set evaluation function is minimum in accordance with a LQ controlling side. A target steering angle computing unit 45 calculates a target steering angle for causing the vehicle to run in accordance with a target course by using the calculated state feedback gain K.

Description

  The present invention relates to a vehicle steering control device that performs automatic steering control.

  In JP 2010-23682, a state equation of a steering system of a vehicle is set, an evaluation function is set as a lane tracking rule, an optimum gain that minimizes the evaluation function is calculated, and the calculated gain is used. A steering control device for calculating a target steering angle is described.

JP 2010-23682 A

  The mass of the vehicle varies depending on the total weight of the load. In particular, in the case of a freight vehicle such as a truck, the vehicle mass, the position of the center of gravity, and the yaw moment of inertia vary greatly depending on the loading state.

  However, in the apparatus of Patent Document 1, the state equation is set with the vehicle mass and the yaw moment of inertia fixed. Therefore, if there is a large gap between these fixed values and actual values, the wobbling of the vehicle in the yaw direction increases, which may lead to control performance, deterioration, and inability to control.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle steering control device capable of obtaining stable control performance regardless of the loaded state of a load.

  In order to achieve the above object, a vehicle steering control apparatus according to the present invention includes vehicle mass detection means, inertia moment estimation means, feedback gain calculation means, and steering control means.

  The vehicle mass detection means detects the mass of the vehicle. The inertia moment estimation means estimates the yaw inertia moment of the vehicle based on the vehicle mass detected by the vehicle mass detection means. The feedback gain calculating means sets and sets a state equation using the target steering angle as an input amount using the vehicle mass detected by the vehicle mass detecting means and the yaw inertia moment of the vehicle estimated by the inertia moment estimating means. An evaluation function for the set state equation is set, and a state feedback gain that minimizes the set evaluation function is calculated. The steering control means controls the steering of the vehicle based on the calculated state feedback gain.

  In the above configuration, the feedback gain calculation means uses the vehicle mass detected by the vehicle mass detection means and the yaw inertia moment of the vehicle estimated by the inertia moment estimation means, and a state equation using the target steering angle as an input amount. Set, set an evaluation function for the set state equation, and calculate a state feedback gain that minimizes the set evaluation function. That is, the calculated state feedback gain is a value corresponding to the loading state of the load on the vehicle. Therefore, it is possible to perform steering control by stable feedback control regardless of the load state of the load.

  According to the steering control device of the present invention, stable control performance can be obtained regardless of the load state of the load.

It is a mimetic diagram of vehicles provided with a steering control device concerning an embodiment of the present invention. FIG. 2 is a block diagram of the steering control device of FIG. 1. FIG. 3 is a block diagram of the controller of FIG. 2. It is a block diagram which shows the control by a state food back gain. It is an example of a wheel load-displacement map. It is a flowchart of the update process of a state feedback gain.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the vehicle 1 according to the present embodiment includes a steering wheel 2, a sensor unit 3, a controller 4, a drive current output unit 5, and a steering actuator 6. The sensor unit 3, the controller 4, the drive current output unit 5, and the steering actuator 6 constitute a steering control device of the present embodiment. The steering control device executes automatic steering control that causes the vehicle 1 to travel while maintaining the lane by LQ control or LQI control.

  The steering wheel 2 is provided in the driver's cab of the vehicle 1, and a driver inputs steering.

  As shown in FIGS. 1 to 3, the sensor unit 3 includes a camera 31 and an image processing unit 32, a yaw rate sensor 33, a steering angle sensor 34, a vehicle speed sensor 35, a displacement sensor 36, and an automatic steering switch 37. Prepare.

  The camera 31 is a CCD camera, images the road surface in the traveling direction of the vehicle 1, and outputs the captured image signal to the image processing unit 32. In the present embodiment, the camera 31 images a white line formed on the road surface in the traveling direction in order to travel on the target path between the white lines formed on both sides of the traveling path of the vehicle 1 by automatic steering.

The image processing unit 32 analyzes the image signal captured by the camera 31 and detects a white line on the road surface. The target route is a travel route on which the vehicle 1 travels by automatic steering, and the road surface is marked with white lines along both sides of the target route. Based on the detected white line, the image processing unit 32 detects the center position (path) between the white line in the traveling direction as the target path, and the distance (lateral displacement) between the target path and the vehicle 1 in the horizontal plane. ) Y _c (m), the lateral movement speed y _c ′ (m / s), which is the temporal change of the lateral displacement, and the angle (yaw angle) φ (rad) of the vehicle 1 with respect to the target course are calculated and calculated. The lateral movement speed y _c ′, the lateral displacement y _c and the yaw angle φ are output to the controller 4.

In this embodiment, in order to detect the lateral displacement y _c , the lateral movement speed y _c ′, and the yaw angle φ (rad), the imaging signal captured by the camera 31 is used. Other information that can specify the position is not limited to the 31 imaging signals. For example, information detected by the GPS may be received, and the target course and the current position may be detected based on the received information. Alternatively, an information generation device may be provided in advance along the target route on the road surface, and the position information of the target route may be acquired from the information generation device to detect the target route, the current position, and the traveling direction. The yaw angle φ may be calculated as a time integral value of a yaw angular velocity φ ′ detected by a yaw rate sensor 33 described later.

  The yaw rate sensor 33 detects a yaw angular velocity φ ′ (yaw rate: rad / s) generated in the vehicle 1 during turning, and outputs the detected yaw angular velocity φ ′ to the controller 4.

  The steering angle sensor 34 detects the steering angle θ (rad) and outputs the detected steering angle θ to the controller 4.

  The vehicle speed sensor 35 detects the vehicle speed V (m / s) of the vehicle 1 and outputs the detected vehicle speed V to the controller 4.

The displacement sensors 36 are respectively provided for the suspensions (not shown) of the front, rear, left and right wheels of the vehicle 1, and the relative displacements (variations with respect to the reference length) H _FL , between the sprung and unsprung portions of the suspensions H _FR , H _RL , and H _RR are detected, and the detected relative displacements H _FL , H _FR , H _RL , and H _RR are output to the controller 4.

  The automatic steering switch 37 is provided in the cab of the vehicle 1 and outputs an on signal and an off signal to the controller 4 in response to an operation input from the driver. The automatic steering switch 37 is set to off at the time of initial setting upon power-on, and is set to on by the driver. The controller 4 executes automatic steering control described later when the automatic steering switch 37 is on, and does not execute automatic steering control when it is off.

  As shown in FIG. 2, the controller 4 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The controller 4 sequentially receives various signals from the sensor unit 3. input. The ROM stores an automatic steering control program, and the CPU executes an automatic steering control process in accordance with the automatic steering control program, whereby a vehicle mass calculation unit 41, a gravity center position distance calculation unit 42, a yaw inertia moment calculation unit 43, It functions as a state feedback gain calculator 44, a target steering angle calculator 45, and an automatic steering current calculator 46. The RAM is a development area for programs read from the ROM, a temporary storage area for various signals (information) input from the sensor unit 3, a temporary storage area for CPU calculation results, and a control permission flag setting area described later. Function.

The vehicle mass calculation unit 41 loads (wheel weight) W _FL , W _FR , W _RL , W loaded on each wheel 7 from the relative displacements H _FL , H _FR , H _RL , H _RR detected by each displacement sensor 36. _RR is obtained, and the mass (total weight) m of the vehicle 1 is calculated from the obtained wheel weights W _FL , W _FR , W _RL , W _RR . That is, each displacement sensor 36 and the vehicle mass calculation unit 41 constitute vehicle mass detection means for detecting the mass m of the vehicle 1.

The center-of-gravity position distance calculation unit 42 calculates the distance L between the front axle (front axle) and the center-of-gravity position from each wheel weight W _FL , W _FR , W _RL , W _RR obtained by the vehicle mass calculation unit 41 and the mass m. _f and a distance L _r between the rear axle (rear axle) and the center of gravity are calculated.

  The yaw inertia moment calculator 43 calculates the yaw inertia moment I from the mass m of the vehicle 1 calculated by the vehicle mass calculator 41. That is, the yaw inertia moment calculation unit 43 constitutes an inertia moment estimation unit that estimates the yaw inertia moment I of the vehicle 1 based on the mass m of the vehicle 1 calculated by the vehicle mass calculation unit 41.

The state feedback gain calculation unit 44 calculates the mass m of the vehicle 1 calculated by the vehicle mass calculation unit 41, the distance L _f between the front axis and the center of gravity position calculated by the center of gravity position distance calculation unit 42, and the rear axis and the center of gravity position. Using the distance _Lr and the yaw moment of inertia I calculated by the yaw moment of inertia calculation unit 43, a state equation of the steering system with the target steering angle (steering angle command value) δ as an input amount is set and set. An evaluation function for the equation is set, and a state feedback gain K that minimizes the set evaluation function is calculated according to the LQ control side. That is, the state feedback gain calculation unit 44 constitutes a feedback gain calculation unit. With the calculated state feedback gain K, automatic steering control of the vehicle 1 is executed with the configuration shown in FIG.

  The target steering angle calculation unit 45 uses the state feedback gain K calculated by the state feedback gain calculation unit 44 to calculate a target steering angle δ for causing the vehicle 1 to travel along the target route.

  The automatic steering current calculator 46 calculates an automatic steering current based on the target steering angle δ calculated by the target steering angle calculator 45. The automatic steering current is a current that drives the steering actuator 6 in order to cause the vehicle 1 to travel along the target path, and is calculated by the automatic steering current calculation unit 46 and input to the drive current output unit 5.

  Next, automatic steering control processing by the steering control device of the present embodiment will be described.

  The automatic steering control process includes a vehicle weight estimation process, a gravity center position distance calculation process, a yaw inertia moment derivation process, a feedback gain calculation process, and a target steering angle calculation process.

The vehicle weight estimation process is executed by the vehicle mass calculation unit 41. In this process, the vehicle mass calculation unit 41 calculates the wheel weights W _FL , W _FR , W _RL , W _RR corresponding to the relative displacements H _FL , H _FR , H _RL , H _RR detected by the displacement sensors 36, Each wheel weight W _FL , W _FR , W _RL , W _RR obtained from a wheel load-displacement map stored in advance (see FIG. 5) is substituted into the following equation (1), and the mass of vehicle 1 (total Weight) m is calculated.

The wheel load-displacement map is set for each wheel 7 corresponding to each characteristic. Further, the above processing is an example in a case where the mass m of the vehicle 1 is _{simply obtained} from the relative displacements H _FL , H _FR , H _RL , H _RR , and a predetermined arithmetic expression is used or a map and an arithmetic expression are used in combination. The mass m may be obtained by another calculation method. Further, the mass m may be obtained from other detected values such as providing a load sensor that directly detects the load.

The gravity center position distance calculation process is executed by the gravity center position distance calculation unit 42. In this processing, the center-of-gravity position distance calculation unit 42 substitutes the wheel weights W _FL , W _FR , W _RL , W _RR obtained by the vehicle mass calculation unit 41 into the following expressions (2) and (3), A distance L _f between the axis (front axle) and the center of gravity position and a distance L _r between the rear axis (rear axle) and the center of gravity position are calculated.

  WB in the above formulas (2) and (3) is a wheelbase of the vehicle 1 stored in advance.

  The yaw inertia moment derivation process is executed by the yaw inertia moment calculator 43.

The inertia moment (yaw inertia moment) I _Z in the yaw plane when the vehicle 1 has the mass M can be simply expressed by the following equation (4).

Since the L _T and L _W of the equation (4) is a value unique to the vehicle 1, a yaw inertia moment I _Z is seen to be proportional to the mass M of the vehicle 1.

  Therefore, the yaw inertia moment calculation unit 43 calculates the yaw inertia moment I by substituting the mass m of the vehicle 1 calculated by the vehicle mass calculation unit 41 into the following equation (5).

I _{0 in the} above equation (5) is the yaw moment of inertia when the vehicle 1 has the mass m ₀ , and is obtained and stored in advance with high accuracy by experiments and simulations.

  The feedback gain calculation process is executed by the state feedback gain calculation unit 44.

  When a general two-wheel equivalent model is used, the state equation of the vehicle 1 can be expressed by the following equation (6).

  The definition of each symbol of the above formula (6) is as follows.

L _f : Distance from the front axle to the vehicle center of gravity (m)
L _r : Distance from rear axle to vehicle center of gravity (m)
C _f : front wheel cornering power (N / rad)
C _r : Rear wheel cornering power (N / rad)
φ ': Yaw angular velocity (rad / s)
φ: Yaw angle (rad)
y _c ′: lateral movement speed y _c : lateral displacement m: mass of vehicle 1 (kg)
I: Yaw moment of inertia (kg · m ² )
V: Vehicle speed (m / s)
N: Steering gear ratio θ: Steering angle Here, in order to execute the steering angle control, the dynamic characteristic between the steering angle command value (target steering angle) δ and the actual steering angle θ is defined as the following equation (7). When the above equation (6) is reconstructed, the following equation (8) is obtained.

In the above equations (7) and (8), ω _n is the natural frequency of the steering angle servo system, s is the Laplace operator, and ζ is the damping ratio of the steering angle servo system. In the above formula (8), a ₁₆ and a ₃₆ are the following formulas (9) and (10), respectively.

a ₁₆ = b ₁₁ = L _f C _f / (IN) (9)

a ₃₆ = b ₃₁ = C _f / (mN) (10)

  Therefore, the state equation and the output equation set by the state feedback gain calculation unit 44 are the following equations (11) and (12), respectively.

  A state feedback gain K for actually executing automatic steering control (lane keeping control) with respect to the above equations (11) and (12) is derived according to the LQ control side (for example, a method using a Riccati algebraic equation). Here, the following formula (13) is set as the secondary form evaluation function J that should be minimized.

  Q and R in the above equation (13) are values set by a designer through trial and error in consideration of plant characteristics.

Thus, the state feedback gain calculation unit 44 calculates the mass m of the vehicle 1 calculated by the vehicle mass calculation unit 41, the distance L _f between the front axis and the center of gravity position calculated by the center of gravity position distance calculation unit 42, and the rear axis. and the distance L _r between the center of gravity position, by using the yaw inertia moment I of yaw inertia moment calculating unit 43 calculates the target steering angle (steering angle command value) the steering system of a state equation of an input quantity [delta] (above formula (8) and (11)) are set, an evaluation function J (the above expression (13)) for the set state equation is set, and a state feedback gain K that minimizes the set evaluation function J is calculated.

The target steering angle calculation process is executed by the target steering angle calculation unit 45. The target steering angle calculation unit 45 substitutes the state feedback gain K (K ₁ , K ₂ , K ₃ , K ₄ ) calculated by the state feedback gain calculation unit 44 into the following equation (14), for example, to A target steering angle δ for traveling along the target course is calculated.

δ = − (K ₁ φ ′ + K ₂ φ + K ₃ y ′ + K ₄ y) (14)

  Next, the state feedback gain K update processing executed by the controller 4 will be described based on the flowchart shown in FIG. This process is repeatedly executed while the vehicle 1 is being driven (the engine is rotating).

  When this process is started, it is determined whether or not the automatic steering switch 37 is on (step S1). When the automatic steering switch 37 is off (step S1: NO), the control permission flag is set to off (Flag = 0) (step S10), and this process ends.

  When the automatic steering switch 37 is on (step S1: YES), it is determined whether or not the vehicle speed V is zero (whether or not the vehicle 1 is traveling) (step S2). When the vehicle speed V is not zero (step S2: NO), since the vehicle 1 is traveling without changing the load capacity of the load, the state feedback gain K is not updated and the control permission flag is turned on (Flag = 1). The setting is made (step S9), and this process ends.

  When the vehicle speed V is zero (step S2: YES), it is during the stop of the vehicle 1 in which the load amount of the load may fluctuate, so the process proceeds to step S3 and the state feedback gain K is updated.

In updating the state feedback gain K, first, the relative displacements H _FL , H _FR , H _RL , H _RR detected by the respective displacement sensors 36 are acquired (step S3), and the acquired relative displacements H _FL , H _FR , H _RL are acquired. , H _RR corresponding to the wheel loads W _FL , W _FR , W _RL , W _RR are read from the wheel load-displacement map (see FIG. 5) (step S4), and the read wheel loads W _FL , W _FR , Substituting W _RL and W _RR into the above equation (1), the mass (total weight) m of the vehicle 1 is calculated (step S5).

Next, the wheel loads W _FL , W _FR , W _RL , W _RR read in step S4 are substituted into the above equations (2) and (3), the distance L _f between the front axis and the center of gravity position, and the rear axis And a distance L _r between the center of gravity position and the center of gravity position are calculated (step S6).

  Next, the yaw inertia moment I is calculated by substituting the mass m of the vehicle 1 calculated in step S5 into the above equation (5) (step S7).

Next, the mass m of the vehicle 1 calculated in step S5, the distance L _f between the front axis and the center of gravity position calculated in step S6, the distance L _r between the rear axis and the center of gravity position, and the yaw inertia calculated in step S7. Using the moment I, a state equation (the above equations (8) and (11)) with the target steering angle δ as an input amount is set, and an evaluation function J (the above equation (13)) for the set state equation is set Then, the state feedback gain K that minimizes the set evaluation function J is calculated, and the calculated state feedback gain K is updated and stored (step S8).

  Finally, the control permission flag is set to ON (Flag = 1) (step S9), and this process ends.

  When the control permission flag is set to ON, the target steering angle calculation unit 45 calculates the target steering angle δ using the latest state feedback gain K, and the automatic steering current calculation unit 46 calculates the automatic steering current. And input to the drive current output unit 5.

  On the other hand, when the control permission flag is set to OFF, the target steering angle calculation unit 45 does not calculate the target steering angle δ, and the automatic steering current calculation unit 46 inputs the automatic steering current to the drive current output unit 5. do not do.

  Thus, according to this embodiment, when the loading state of the load of the vehicle 1 fluctuates, the value of the state feedback gain K is updated according to the fluctuation of the loading state. Therefore, regardless of the load state of the load, automatic steering control that realizes running stability of the vehicle with little fluctuation in the yaw direction while securing the lane keeping characteristic by the LQ control and the LQI control which are model-based control methods. Can do.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the discussion and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it is needless to say that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1: Vehicle 3: Sensor part 4: Controller 5: Drive current output part 6: Steering actuator 31: Camera 32: Image processing unit 33: Yaw rate sensor 34: Steering angle sensor 35: Vehicle speed sensor 36: Displacement sensor (vehicle mass detection means )
41: Vehicle mass calculation unit (vehicle mass detection means)
42: Reception position distance calculation unit 43: Yaw inertia moment calculation unit (moment of inertia estimation means)
44: State feedback gain calculation unit (feedback gain calculation means)
45: Target steering angle calculation unit (target steering angle calculation means)
46: Automatic steering current calculation unit (automatic steering current calculation means)

Claims (1)

Vehicle mass detection means for detecting the mass of the vehicle;
An inertia moment estimation means for estimating a yaw inertia moment of the vehicle based on the detected mass of the vehicle;
Using the detected vehicle mass and the estimated yaw inertia moment, a state equation with a target steering angle as an input amount is set, an evaluation function for the set state equation is set, and the set evaluation function is Feedback gain calculation means for calculating a state feedback gain to be minimized;
Steering control means for controlling steering of the vehicle based on the calculated state feedback gain. A steering control device for a vehicle, comprising:

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