JP2009067118A - Vehicle steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle steering device of an azimuth feedback system capable of shortening an avoidance distance to more enhance a probability of succeeding in a collision avoidance without ruining (diverging and overshooting) avoidance momentum. <P>SOLUTION: This vehicle steering device 10 is constituted of an operation element 11 steered and operated by a driver, a steering angle sensor 14, a front wheel turning mechanism 200 for changing the direction of a turning wheel, a vehicle yaw response characteristic extracting portion 34 for taking out a yaw rate signal SG3 of a yaw rate of a vehicle, a differential arithmetic portion 31B-1 for generating an operational amount change signal according to change amount of the operational amount of the operation element 11, an addition portion 32 for adding an operational amount signal SG1 output from the steering angle sensor 14 and an operational amount change signal SG1' output from the differential arithmetic portion 31B-1, a subtraction portion 32 for subtracting the yaw rate signal and an integration signal of the yaw rate from an added value output from the addition portion 32, and a driving control portion for driving the front wheel turning mechanism 200 according to a deviation signal output from the subtraction portion 32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle steering apparatus, and more particularly, to an electronically controlled vehicle steering apparatus that controls a turning angle of a steered wheel according to a steering input in a steering system that feeds back an azimuth angle signal and a yaw rate signal.

  In the steering control device described in Patent Document 1, the operation element and the steered wheel are mechanically separated, the steering coupling mechanism is replaced by an electronic control device, and the steered wheel is switched with respect to the steering input by the operation element. The present invention is applied to a vehicle steering apparatus configured to be able to arbitrarily control the steering angle. According to this steering control device, when the driver steers the operating element, the content of the steering is converted into an electrical signal. The electrical signal is given to the electronic control device and converted into a control signal. Information on the steering content is given to the steered wheel drive device by this control signal, and the steered angle of the steered wheel is controlled and adjusted. In the electronic control device, the steering angle given by the operation element is set as the target steering angle, for example, the turning angle of the steered wheel obtained by the detection action of the turning angle sensor is set as the actual steering angle, and the actual steering angle matches the target steering angle. Feedback control is performed.

  In an operation element that is steered by a driver, an input target steering angle may be an azimuth angle, and actual information fed back may be an actual azimuth angle. There has been proposed a steering system that includes a control unit that gives a target steering angle by an azimuth angle, feeds back an actual state of the azimuth angle, obtains a deviation signal, and performs a turning drive by the deviation signal. The steering system that feeds back the azimuth has the advantage that the emergency avoidance performance is superior to that of the conventional steering system.

In an azimuth feedback type four-wheel vehicle steering system, the course of the vehicle is automatically maintained even when subjected to a disturbance, so that it is possible to reduce the steering burden on the driver at high speeds. In addition, since the phase is greatly advanced by the response of the vehicle to the steering input, the response during emergency avoidance is fast. Furthermore, since the stability of the exercise is increased by the azimuth feedback method, it is possible to avoid the avoidance exercise from failing even in a situation where the distance to notice the obstacle becomes short and a large steering input has to be entered. For this reason, for example, the distance (avoidance distance) until it crosses a lane in the middle of avoiding to an adjacent lane can be shortened, and the probability of successful collision avoidance can be increased.
Japanese Patent Laid-Open No. 10-264838

  A steering system that performs azimuth feedback generally has an advantage that the course is automatically maintained even when a disturbance is received, and the burden on the driver at high speed can be reduced. In addition, the phase of the vehicle's response to the steering input is greatly advanced, so the response at the time of emergency avoidance is fast, and the stability of the movement is increased due to feedback, so the distance to notice obstacles is shortened, and a large input is input. Even in the unavoidable situation, the avoidance movement can be avoided (divergence and overshoot). For this reason, the distance (avoidance distance) until it crosses a lane in the middle of avoiding to an adjacent lane can be shortened, and the probability of successful collision avoidance can be increased.

  On the other hand, a steering system that feeds back only the azimuth has a characteristic that the turning motion of the vehicle stops at the azimuth corresponding to the steering angle (handle angle) of the operating element because the steady response becomes zero as a compensation for the phase advance. . Therefore, in order to continue the turning motion of the vehicle, it is necessary to always increase the steering angle by turning the operation element. According to the steering system of the azimuth feedback method having such a characteristic, when the vehicle is maintained at a constant steering angle, the vehicle maintains a constant radius and keeps a turning motion. Driving operation increases the burden on the driver.

  Therefore, in an azimuth feedback type steering system, it has been desired to reduce the driver's steering burden on a longer turn without losing the superior characteristics of avoidance performance.

  Therefore, the present inventor has previously proposed a vehicle steering apparatus having a configuration that feeds back an azimuth angle and a yaw rate (Japanese Patent Application No. 2006-53696, filed on February 28, 2006). According to this vehicle steering device, the turning angle of the steered wheels is controlled by an azimuth feedback method or the like with respect to the steering input of the operation element, and driving with a long turning motion is maintained while maintaining the superiority of avoidance performance. Can reduce the steering burden.

  However, in the azimuth feedback type vehicle steering system, the avoidance movement is not broken (divergence or overshoot), the above avoidance distance is shortened, and the probability of successful collision avoidance is further increased. It is the supreme proposition as a system.

  In view of the above problems, an object of the present invention is an azimuth feedback type vehicle steering apparatus, which can further reduce the avoidance distance without causing breakdown (divergence or overshoot), An object of the present invention is to provide a vehicle steering apparatus that can further increase the probability of successful collision avoidance.

  In order to achieve the above object, a vehicle steering apparatus according to the present invention is configured as follows.

  A first vehicle steering device (corresponding to claim 1) includes an operation element that a driver performs a steering operation, an operation amount detection unit that detects an operation amount of the operation element, a turning actuator that changes a direction of a steered wheel, A yaw rate signal acquisition unit (vehicle yaw response characteristic extraction unit) that extracts a yaw rate signal related to the yaw rate (yaw angular velocity) of the vehicle, and a differential calculation unit that generates an operation amount change signal according to the change amount of the operation amount of the operation element; , An addition unit that adds the operation amount signal output from the operation amount detection unit and the operation amount change signal output from the differential operation unit, and an integration signal (yaw rate signal and yaw rate integration signal) from the addition value output from the addition unit A subtraction unit that subtracts the azimuth angle signal), and a drive control unit that drives the steering actuator in accordance with the deviation signal output from the subtraction unit.

  The above-described vehicle steering apparatus has a configuration in which an operation amount signal related to a target azimuth angle is input by an operation element, and the azimuth angle feedback method and the yaw rate feedback method are combined to control the turning angle of the steered wheels. In this vehicle steering apparatus, by adding a differential term of the steering angle of the operating element, that is, the steering wheel angle, the steering stability is improved, the emergency avoidance performance that requires quick steering is improved, and the steering during turning is easy. We are trying to make it easier.

  In the second vehicle steering device (corresponding to claim 2), the gain set by the output adjustment unit provided in the signal route of the differential calculation unit is preferably increased as the vehicle speed increases. It is characterized by that.

  According to the present invention, a yaw rate feedback configuration is added to an azimuth feedback feedback steering system, and a steering wheel differential term is added to a vehicle steering apparatus that combines azimuth feedback and yaw rate feedback. As a result, it is possible to improve the response in the high frequency range, so that the delay in the response such as the driver's dead time is compensated and the avoidance movement is not broken (divergence or overshoot), and the stability of the maneuvering is improved. Thus, the emergency avoidance performance requiring fast steering can be improved and the avoidance distance can be shortened, and the probability of successful collision avoidance by facilitating steering during turning can be further increased.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a schematic device structure of a vehicle steering apparatus according to an embodiment of the present invention, and FIG. 2 shows a block diagram of a control system of the vehicle steering apparatus. 3 shows vehicle speed-gain characteristics relating to two gains Kw0 and Kw1, which will be described later, and FIG. 4 shows steering characteristics realized by the vehicle steering apparatus according to the present embodiment.

  The vehicle steering device 10 is an electronically controlled vehicle that can arbitrarily control the turning angle of a front tire (front wheel) 12 that is a steered wheel in response to a steering input of an operating element 11 (hereinafter referred to as a “handle 11”). It is a steering device.

  When the driver steers the steering wheel 11, the rotation angle generated by the driver's steering operation, that is, the steering angle is based on the control function of the electronic control system. A corresponding turning angle is generated. The driver operates the handle 11 to input information related to the vehicle motion (or vehicle traveling direction) desired by the driver himself / herself to the electronic control system. The steering operation amount by the driver at the steering wheel 11 is detected by the steering angle sensor 14 as an operation amount signal. The steering wheel 11 and the steering angle sensor 14 constitute a steering input device 100.

  In the vehicle steering device 10, the steering angle sensor 14, the steering reaction force generation mechanism 16, and the steering torque sensor 17 are attached to the steering shaft 15 of the handle 11.

  The steering reaction force generation mechanism 16 is for applying a reaction force to the driver via the steering shaft 15 and the handle 11. As described above, since the handle 11 is not connected to the front tire 12 as a mechanical structure, it is necessary to apply a reaction force as a steering feeling for the driver when operating the handle.

  The steering torque sensor 17 detects steering torque generated when the driver steers the handle 11 against the steering reaction force generated by the steering reaction force generation mechanism 16.

  Two front tires 12 are disposed on both sides of the steering drive mechanism 13. The steering drive mechanism 13 includes a steering motor 18 for steering at the center, and further includes a tie rod 19 extended to the outside of both ends and a knuckle arm 20 provided at the tip thereof. The front tire 12 is coupled to the knuckle arm 20. The steered drive mechanism 13 is provided with a steered angle sensor 21 that detects a steered angle generated by driving the steering motor 18.

  The steered drive mechanism 13 and the steering motor 18 constitute a front wheel steered mechanism 200.

  As other detection systems, a vehicle speed sensor 22 and a vehicle behavior sensor 23 that detects or extracts a yaw rate (yaw angular velocity), lateral acceleration, and the like are provided. The vehicle behavior sensor 23 includes a yaw rate signal acquisition unit that extracts yaw rate information.

  Reference numeral 24 denotes an ECU which is an electronic control unit. The ECU 24 forms a control system for the vehicle steering device. Input elements for the ECU 24 are a steering angle sensor 14, an operation torque sensor 17, a turning angle sensor 21, a vehicle speed sensor 22, and a vehicle behavior sensor 23. The output elements for the ECU 24 are a steering reaction force generation mechanism 16 and a steering motor 18 for turning.

  A functional configuration of the control system of the vehicle steering apparatus 10 will be described with reference to FIG. In FIG. 2, the ECU 24 is indicated by a broken-line block, and the internal configuration thereof is indicated in the form of a functional block diagram. The configuration of the control system shown in the functional block diagram is realized mainly by an embedded technology using a microcomputer and software, but can also be realized by a hardware configuration (electric circuit). When the control system is realized by software, a control program is stored in the memory, and the control program is read and executed during operation.

  In the control system for the vehicle steering device 10 provided in the ECU 24, the steering signal (operation amount signal) SG1 output from the steering angle sensor 14 in the steering input device 100 is two first output adjustments arranged in parallel. Input to the sections 31A and 31B. The gain Kw0 is set in one first output adjustment unit 31A, and the gain Kw1 is set in the other first output adjustment unit 31B.

  The gain Kw0 of one first output adjustment unit 31A is variable according to the vehicle speed as shown by characteristic 41 in FIG. 3, and the gain Kw1 of the other first output adjustment unit 31B is set to the vehicle speed as shown by characteristic 42 in FIG. It is variable accordingly. The value of the gain Kw0 has a characteristic 41 that decreases linearly as the vehicle speed increases. The value of the gain Kw1 has a characteristic 42 that increases linearly as the vehicle speed increases. The level and phase of the steering signal SG1 input to the first output adjusting unit 31A are appropriately adjusted according to the state of the vehicle speed based on the characteristic 41 related to the gain Kw0. The level and phase of the steering signal SG1 input to the other first output adjustment unit 31B are appropriately adjusted according to the state of the vehicle speed based on the characteristic 42 related to the gain Kw1.

The steering signal (operation amount signal) SG1 input to the first output adjustment unit 31A is adjusted there, and then input to the subtraction unit 32 in an added state.
The steering signal (operation amount signal) SG1 input to the other first output adjustment unit 31B is adjusted there, and is further subjected to differentiation processing by a differentiation operation unit 31B-1 provided on the output side, then “operation amount change” The signal SG1 ′ ”is input to the subtraction unit 32 in an added state.

Further, as will be described later, the subtraction unit 32 receives an azimuth angle signal SG2 and a yaw rate signal SG3 from the sum signal of the steering signal (operation amount signal) SG1 and its differential signal, that is, the operation amount change signal SG1 ′. Input as a target signal to be subtracted.
Note that the subtracting unit 32 has a function as an adding unit if attention is paid only to the relationship between the steering signal (operation amount signal) SG1 and the operation amount change signal SG1 ′. Accordingly, the subtractor 32 as a whole has a function as an addition / subtraction computing means, and is configured to include an adder at the front stage and a subtractor at the rear stage.

  In the subtracting section 32, a deviation signal obtained by subtracting the yaw rate signal SG3 from the sum signal of the steering signal SG1 and its operation amount change signal SG1 ′ and / or the steering signal SG1 and its operation amount change according to the vehicle speed. A deviation signal obtained by subtracting the azimuth angle signal SG2 from the sum signal with the signal SG1 ′ is output. This deviation signal is supplied to the front wheel steering mechanism 200 via the second output adjustment unit 33. The deviation signal output from the subtracting unit 32 is treated as a control signal. The second output adjustment unit 33 is set with a variable gain Ks according to the vehicle speed, and adjusts the level and phase of the control deviation signal output from the subtraction unit 32 according to the vehicle speed. A signal output from the second output adjustment unit 33 is given as a control drive signal to the front wheel turning mechanism 200 to turn the front tire 12 described above.

  When the front tire 12 turns according to the control signal based on the steering signal SG1, a turning angle is generated in the front tire 12 (state ST1). When a turning angle is generated in the front tire 12 in a traveling vehicle, a movement that changes a traveling direction or a traveling direction occurs in the vehicle. When a motion that changes the traveling direction or the like occurs in the vehicle, the motion state of the vehicle is detected by the vehicle behavior sensor 23 described above. The vehicle behavior sensor 23 includes a yaw rate signal acquisition unit as described above. Therefore, the vehicle yaw state resulting from the vehicle motion state is extracted by the yaw rate signal acquisition means included in the vehicle behavior sensor 23.

  In the control system of FIG. 2, a vehicle yaw response characteristic extracting unit 34 is shown as an element related to taking out and controlling the yaw rate signal. The vehicle yaw response characteristic extraction unit 34 has a function of extracting a change in the motion state of the vehicle as a vehicle yaw response characteristic due to the turning angle generated in the front tire 12, and outputting a yaw rate signal SG3 as a result. . The vehicle yaw response characteristic extraction unit 34 is a functional unit that acquires a yaw rate signal.

  The control of the steering system in the present embodiment has a configuration that feeds back to the subtracting unit 32 from the actual controlled state in the vehicle. The feedback path has two paths. The first feedback path is an azimuth feedback path, and the second feedback path is a yaw rate feedback path.

  The azimuth feedback path includes an integration calculation unit 35 that integrates the yaw rate signal SG3 output from the vehicle yaw response characteristic extraction unit 34, and a third output adjustment unit 36. The integration calculation unit 35 integrates the yaw rate signal SG3 to generate an azimuth angle signal SG2, and outputs the azimuth angle signal SG2. The third output adjustment unit 36 is set with a gain Kφ that is variable according to the vehicle speed, and adjusts the level and phase of the azimuth angle signal SG2 according to the vehicle speed. The azimuth angle signal SG2 output from the third output adjustment unit 36 is input to the subtraction unit 32 in the subtraction format as described above. The gain Kφ of the third output adjustment unit 36 is a feedback gain of an azimuth feedback path that is the first feedback path.

  The yaw rate feedback path is configured by a fourth output adjustment unit 37 that adjusts the yaw rate signal SG3 output from the block 33. The fourth output adjusting unit 37 is set with a variable gain Kr according to the vehicle speed, and the level and phase of the yaw rate signal SG3 are adjusted according to the vehicle speed. The yaw rate signal SG3 output from the fourth output adjustment unit 37 is input to the subtraction unit 32 in the subtraction format as described above. The gain Kr of the fourth output adjustment unit 37 is the feedback gain of the yaw rate feedback path that is the second feedback path.

  The yaw rate signal SG3 output from the block 34 is supplied to the steering reaction force generation unit 16 via the steering reaction force setting unit 38. The steering reaction force setting unit 38 generates a steering reaction force signal SG4 based on the yaw rate signal SG3 according to the vehicle speed. The steering reaction force signal SG4 is supplied to the steering reaction force generation mechanism 16. The steering reaction force generation mechanism 16 generates a steering reaction force based on the steering reaction force signal SG4.

  The vehicle speed signal output from the vehicle speed sensor 22 includes two first output adjustment units 31A and 31B, a second output adjustment unit 33, a third output adjustment unit 36, a fourth output adjustment unit 37, and a steering reaction force setting unit 38. Has been supplied to. The gains of the first output adjusting unit 31, the second output adjusting unit 33, the third output adjusting unit 36, the fourth output adjusting unit 37, and the steering reaction force setting unit 38 are set so as to change according to the vehicle speed. ing. Changes according to the vehicle speeds of the gain Kφ of the third output adjustment unit 36 and the gain Kr of the fourth output adjustment unit 37 will be described in detail later.

  In the above control system, the gains Kw0, Kw1, Ks, Kφ, and Kr of the two first output adjustment units 31A and 31B, the second output adjustment unit 33, the third output adjustment unit 36, and the fourth output adjustment unit 37 are In addition to the level adjustment characteristic, the gain includes a phase advance characteristic as necessary.

  Next, a characteristic configuration and operation of the control system configuration in the vehicle steering apparatus 10 will be described.

  In an azimuth feedback type steering apparatus, steering related to a long turning motion, which has a large steering burden on the driver, is generated by vehicle steering in a relatively low-speed traveling state. On the other hand, high emergency avoidance performance is desired in high-speed driving conditions that are highly susceptible to collision damage.

  Therefore, at low speed, the gain Kr of the fourth output adjustment unit 37 is set to a large value, and the gain Kφ of the third output adjustment unit 36 is set to a small value. As a result, in the subtracting unit 32, the input value of the fed back yaw rate signal SG3 is increased, and the input value of the fed back azimuth angle signal SG2 is decreased. Accordingly, the subtraction unit 32 outputs a deviation signal obtained by subtracting the yaw rate signal SG3 from the sum signal of the steering signal SG1 and the operation amount change signal SG1 '. The subsequent operation control of the front wheel steering mechanism 200 is executed based on the deviation signal by the yaw rate feedback control. As a result, the steering angle of the steering wheel 11 can be reduced in the traveling state of the vehicle at a low speed, and the driver's steering burden can be reduced.

  On the other hand, when the vehicle is traveling at high speed, the gain Kr of the fourth output adjustment unit 37 is set to a small value, and the gain Kφ of the third output adjustment unit 36 is set to a large value. As a result, in the subtracting unit 32, the input value of the fed back yaw rate signal SG3 is reduced, and the input value of the fed back azimuth angle signal SG2 is increased. Accordingly, the subtraction unit 32 outputs a deviation signal obtained by subtracting the azimuth angle signal SG2 from the sum signal of the steering signal SG1 and the operation amount change signal SG1 '. Based on the deviation signal by the azimuth feedback control, the subsequent operation control of the front wheel steering mechanism 200 is executed. Thereby, the success probability of the emergency avoidance exercise can be increased in the traveling state of the vehicle at high speed.

  The set values of gain Kr and gain Kφ set at low speed and high speed, and the change characteristics of each gain value with respect to changes in vehicle speed, the steering response characteristics change smoothly according to the vehicle speed based on the basic characteristics of the vehicle To be decided.

  Further, in the above control system, the target signal for subtracting the yaw rate signal SG3 (at low speed) or the azimuth angle signal SG2 (at high speed) by the subtracting section 32 is output from one first output adjusting section 31A as described above. The sum signal (SG1 + SG1 ′) of the steering signal SG1 and the operation amount change signal SG1 ′ output from the differential operation unit 31B-1 related to the other first output adjustment unit 31B. By appropriately setting the differential element of the steering signal, that is, the signal related to the steering wheel angle, according to each vehicle speed, it is possible to improve the frequency characteristics from low speed to high speed. That is, it is possible to eliminate the delay in the response in the high frequency region.

  The proportional gain Kw0 related to the steering input needs to be adjusted because the yaw rate gain of the vehicle changes when the three gains (Kr, Kφ, Kw1) change. Further, it is desirable to adjust the gain Ks that determines the front wheel turning amount in accordance with the vehicle speed in order to maintain the optimum vehicle response in accordance with the above four gain values.

  Further, in the vehicle steering apparatus 10 according to the present embodiment, the neutral position of the handle 11, that is, the position that becomes the origin of the turning angle of the front tire 12 for the next motion is the azimuth feedback type steering apparatus. Changes according to the azimuth. Therefore, to clearly inform the driver of the situation, the steering reaction force is referred to the vehicle response parameter (for example, the yaw rate) so that the steering reaction force at the steering wheel angular position when the vehicle goes straight is minimized. It is also preferable to control. This control function is provided in the steering reaction force setting unit 38.

  It is also assumed that the desired vehicle response characteristics vary depending on the driver's characteristics and preferences. Therefore, it is possible to prepare a plurality of control programs such as a setting emphasizing turning performance and a setting emphasizing avoidance performance so that the driver can select them.

  FIG. 4 shows steering characteristics (size characteristics (A) and phase characteristics (B)) realized by the vehicle steering apparatus 10 according to the present embodiment. In each of the magnitude characteristic (A) and the phase characteristic (B) in FIG. 4, 51 is a characteristic relating to the vehicle steering apparatus 10, and 52 is a characteristic relating to the steering apparatus not adding a differential term to be compared. According to the steering characteristics of the vehicle steering apparatus 10, a high responsiveness with a low gain up to a high frequency region and a small phase delay as described above is realized.

  The configurations described in the above embodiments are merely shown to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

  The present invention is an electronically controlled vehicle that combines an azimuth feedback system and a yaw rate feedback system, can arbitrarily control the turning angle of a steered wheel with respect to steering input by an operating element, and has improved responsiveness in a high frequency region Used for steering devices.

It is a typical device structure figure of a vehicle steering device concerning the present invention. It is a block block diagram of the control system of a vehicle steering device. It is a graph which shows the vehicle speed-gain characteristic of each of two gains Kw0 and Kw1. It is a graph which shows the steering characteristic (size characteristic (A) and phase characteristic (B)) implement | achieved by the vehicle steering apparatus which concerns on this embodiment.

Explanation of symbols

10 Vehicle Steering Device 11 Handle (Operating Element)
12 Front tire (steering wheel)
DESCRIPTION OF SYMBOLS 13 Steering drive mechanism 14 Steering angle sensor 16 Steering reaction force production | generation mechanism 17 Steering torque sensor 18 Steering sensor 21 Steering angle sensor 22 Vehicle speed sensor 23 Vehicle behavior sensor 24 ECU
31A 1st output adjustment part 31B 1st output adjustment part 31B-1 Differential calculation part 100 Steering input device 200 Front wheel steering mechanism

Claims (2)

An operating element that the driver steers,
An operation amount detecting means for detecting an operation amount of the operation element;
A steering actuator for changing the direction of the steered wheels,
A yaw rate signal acquisition means for extracting a yaw rate signal related to the yaw rate of the vehicle;
Differential operation means for generating an operation amount change signal corresponding to the change amount of the operation amount of the operation element, an operation amount signal output from the operation amount detection means, and the operation amount change output from the differentiation operation means Adding means for adding the signal;
Subtracting means for subtracting the yaw rate signal and the integral signal of the yaw rate from the added value output from the adding means;
Drive control means for driving the steered actuator in accordance with a deviation signal output from the subtracting means;
A vehicle steering apparatus comprising:   2. The vehicle steering apparatus according to claim 1, wherein the gain set by the output adjusting means provided in the signal route of the differential operation means is increased as the vehicle speed increases.

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