JP4404693B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus that steers steered wheels via an electronic control unit based on an operation of a steering wheel or the like.

2. Description of the Related Art Conventionally, in a vehicle such as an automobile, there is a vehicle steering device that detects an operation angle of a steering wheel and the like and controls a steering wheel (generally a front wheel) via an electronic control device. In such a control system, the response of the steering wheel is delayed with respect to the operation of the steering wheel, and the driving feeling may be deteriorated, and various countermeasures have been invented. For example, in Patent Document 1, in addition to the steering amount of the steering wheel by the driver, an auxiliary steering angle obtained by multiplying the steering speed by a predetermined gain (assumed to be a) is superimposed, and based on this superimposed signal. An apparatus for improving responsiveness by steering a steering wheel is disclosed.
By the way, the response of the vehicle to the steering of the driver's steering wheel is determined by the characteristics of the vehicle, and one of the major factors among the characteristics is the cornering power of the steered wheels. That is, if the cornering power of the steering wheel is increased, the response of the vehicle is increased. This cornering power increases when the vehicle is decelerated and the vehicle weight is applied to the front wheels (steering wheels). As a result, the vehicle behavior becomes unstable under such driving conditions. In Patent Document 1, this phenomenon is prevented by reducing the gain (a) described above that is multiplied by the steering speed of the steering wheel according to the deceleration.

However, the change in cornering power is not only due to the change in vehicle weight applied to the front wheels. The cornering power decreases or saturates under low road friction, and changes depending on the type of tire and the air pressure. As a result, the response of the vehicle to the steering wheel operation changes due to such a change in the situation. Since such a phenomenon is a universal phenomenon, the conventional one has a problem that the response of the vehicle to the steering wheel operation often changes and the stability of the control state is lacking. Patent Documents 2 and 3 will be described later.
JP-A-5-310140 JP 2003-312521 A Japanese Patent Application Laid-Open No. 2003-341538 “Vehicle State Detection Device”

  In the conventional vehicle steering system, when the steering wheel is controlled with respect to the steering of the steering wheel, the gain of the control system is changed only by the event of deceleration of the vehicle, and changes in cornering power due to other causes are taken into consideration. Absent. For this reason, there is a problem that the stability of the vehicle behavior with respect to the steering wheel operation is lacking.

  The object of the present invention is to solve the above problems and provide a control method that can cope with changes in tire cornering power caused by road surface friction, tire type, air pressure changes, etc. An object of the present invention is to obtain a vehicle steering device that is prevented.

In the vehicle steering apparatus according to the present invention, a steering wheel angle detection unit that detects a steering wheel angle and outputs a steering wheel angle signal, a steering wheel angular velocity detection unit that detects a steering wheel angular velocity and outputs a steering wheel angular velocity signal, and a steering wheel are steered. A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by
Basic target steering angle setting means for setting a basic target steering angle value of the steering wheel from the steering wheel angle signal;
A steering wheel angle detection means for detecting a current steering angle of the steering wheel;
From the current and steering angle the road surface reaction torque signal of the steering wheel the steering wheel angle detection means detects whether the state of contact between the steering wheel and the road surface is in the saturation region or in the linear region Road surface reaction force state detection means for determining the gain, a gain gradually increasing with time to a predetermined value when determined to be in the linear region, and approximately 0 when determined to be in the saturation region Auxiliary steering angle setting means having gain control means for outputting a gain that gradually decreases with time, and calculating means for calculating the auxiliary steering angle by multiplying the steering wheel angular velocity signal by the gain,
Target steering angle setting means for setting the target steering angle by adding the auxiliary steering angle to the basic target steering angle value;
Steering angle control means for controlling the steering angle of the steering wheel based on the target steering angle is provided.

  According to the vehicle steering apparatus of the present invention, the auxiliary steering angle is controlled by determining whether the road surface reaction force is in a linear region or a saturated region (that is, determining whether or not the vehicle is in a slip state). Therefore, when the road surface reaction force is saturated especially on a slippery road surface, unnecessary auxiliary rudder angle can be suppressed, and control can be performed without unnecessarily suppressing the auxiliary rudder angle in a non-slip state. The effect is obtained.

  In addition, it is judged whether the road surface reaction force is in the linear region or the saturation region, it is judged whether the steering wheel has been increased or turned back, and the road surface reaction force is saturated in the state of being turned off. In this case, the excessive steering is suppressed by suppressing the auxiliary steering angle, and in the state of switching back, the suppression of the auxiliary steering angle is prohibited, so that the effect of assisting the switching back steering can be obtained.

  Further, in a state where the steering wheel is being increased while the road surface reaction force is saturated, the steered ratio is reduced, so that excessive turning of the steering wheel can be suppressed.

  In addition, when the steering wheel is turned up while the road surface reaction force is saturated, the steering ratio is reduced, so that the steering wheel can be prevented from being overcut, and the steering angular velocity, the predetermined gain, and the above-described turning are reduced. Since the auxiliary steering angle is calculated by multiplying the steering ratio, an auxiliary steering angle suitable for the changing steering ratio is obtained, and the responsiveness of the vehicle is improved.

  In addition, when the steering wheel is being increased while the road surface reaction force is saturated, the steering ratio is reduced, so that the steering wheel can be prevented from being overcut and the steering angular velocity, the predetermined gain, and the road surface reaction force are reduced. Since the auxiliary steering angle is calculated by multiplying the basic steering ratio that does not depend on the saturation of the vehicle, the auxiliary steering angle according to the driver's steering speed of the steering wheel is irrelevant to the saturation of the road surface reaction force. To do.

  Further, since the auxiliary steering angle is limited to a predetermined range, excessive auxiliary steering when the driver steers suddenly can be suppressed.

Before describing the embodiments of the present invention, in order to help understanding of the present invention, the response to steering of a vehicle and the grip of a road surface by a tire will be briefly described.
FIG. 2 is a characteristic diagram for explaining response characteristics of a vehicle steering device (hereinafter, a so-called electric steering device in which the steering angle of a steering wheel is driven by an electric motor will be described as an example in the present invention). FIG. 4 is a Bode diagram showing an outline of input / output frequency response characteristics when a driver's steering wheel steering is input and a vehicle yaw rate is output at a certain vehicle speed. The horizontal axis represents frequency, and the vertical axis represents the gain of the entire control system and the phase shift of the transfer function. As shown in part A in the figure, it can be seen that the gain starts decreasing at a frequency higher than about 1 Hz and the phase starts to be delayed. When the device having such characteristics is operated, the driver is delayed in following the yaw rate of the vehicle with respect to the operation of his / her steering wheel (that is, the vehicle does not begin to turn immediately even when the steering wheel is turned off). I feel it is difficult to do.

  In order to solve this problem, as shown in the block diagram of FIG. 3A, a primary advance element having a time constant set to 1 Hz in FIG. 2 is introduced between the steering wheel and the steering wheel. Of course, various control circuits and electric motors (not shown) are inserted in the meantime), and a so-called lead steer technique for compensating for the phase lag in FIG. 2 is known. As shown in FIG. 3B, the frequency response characteristic of the vehicle yaw rate with respect to the steering operation when lead steer is introduced eliminates the phase lag (not shown in the figure, but the bending frequency 1 Hz in FIG. 2 is higher). The frequency between the driver's steering wheel and the vehicle behavior (yaw rate) is reduced, and driving becomes easier. However, such an improvement effect is limited to a case where a grip on the road surface of the steered wheels is secured.

Therefore, next, an outline of the tire characteristics will be described.
FIG. 4 is an explanatory diagram for explaining the change in the road surface reaction force with respect to the steering wheel operation angle θ, using the change in the road surface state as an auxiliary variable. The horizontal axis represents the side slip angle β, and the vertical axis represents the road surface reaction torque Ta. A solid line indicates a road surface reaction torque Ta1 with respect to a dry asphalt road surface, and a broken line indicates a road surface reaction force torque Ta2 with respect to a slippery road surface. As shown in FIG. 4, the characteristic curve (broken line) of the road reaction force torque Ta2 on a slippery road surface decreases at a steering operation angle θ smaller than the characteristic curve (solid line) of the road surface reaction torque Ta1 on a dry asphalt road surface that is difficult to slip. (Saturation) starts, but in the region where the steering wheel operation angle θ is smaller than this value (region where the side slip angle β is small), the same linearity as the characteristic curve Ta1 is maintained. Therefore, on a slippery road surface, the vehicle can be driven by driving almost without turning the steering wheel, but if the vehicle is turned too much, the vehicle becomes unstable (slips). In such a case, if the phase advance described above is inserted, excessive steering of the steering wheel will be increased in the region where the road surface reaction force starts to decrease (the road surface on which the slip is about to occur). Cannot be obtained.

Embodiment 1 FIG.
FIG. 1 shows the configuration of the vehicle steering system according to Embodiment 1 of the present invention. In FIG. 1, a driver (not shown) operates the handle 1. The steering angle of the steering wheel 1 is detected by the steering wheel angle detection means 2 and output as a steering wheel angle signal 201. The basic target steered wheel angle generating means 5 calculates a steered wheel angle that is the basis of a control amount for controlling the steered wheel from the steering wheel angle signal 201 and generates a basic target steered wheel angle 501. The steering wheel angular velocity detection means 3 detects a steering wheel angular velocity from the steering wheel angle signal 201 and outputs a steering wheel angular velocity signal 301.
The directions of the steered wheels 17a and 17b are controlled by the rack and pinion 1501 of the rack and pinion type steering mechanism 15 through the knuckle arms 16a and 16b.
The steering mechanism 15 is provided with a steering mechanism driving means 14 for driving the steering mechanism 15. The steering mechanism driving means 14 includes an electric motor 1401 and a worm gear 1402 that meshes with a worm wheel 1502 of the steering mechanism 15. The rack and pinion 15 is provided with steering wheel angle detection means 18 that detects the steering wheel angles of the steering wheels 17 a and 17 b and outputs a steering wheel angle signal 1081.

Further, road surface reaction force detecting means 4 for estimating or detecting the road surface reaction force generated in the steering wheels 17a and 17b and outputting a road surface reaction force torque signal 401 is provided. The steering wheel angular velocity signal 301 and the road surface reaction force torque signal 401 are input, and auxiliary steering angle generation means 6 is provided that generates and outputs a necessary auxiliary steering angle according to a predetermined procedure.
The target steering angle generating means 7 receives the output 501 of the basic target steering angle generating means 5 and the output of the auxiliary steering angle generating means 6 and inputs the target steering angle 701 according to a predetermined procedure (generally adding both). Is generated. The steered wheel angle control means 8 drives the steered wheel angle control electric motor 1401 so that the target steered wheel angle 701 and the steered wheel angle signal 1801 are equal, and steers the steered wheels 17a and 17b. It controls the corners.

Hereinafter, the operation of the vehicle steering apparatus of FIG. 1 will be described in order for each block. However, with respect to known blocks in FIG. 1, references in which the technology is disclosed are shown, and detailed descriptions thereof are omitted.
First, the road surface reaction force detection means 4 will be described. The road surface reaction force detection means is a means for detecting the road surface reaction force torque Ta determined by the steering state and the road surface state shown in FIG. . Alternatively, measurement may be performed using a detector that directly detects torque. Since the road surface reaction force detection means 4 is a known means, detailed description thereof is omitted.

  Next, operation | movement of the auxiliary | assistant steering angle production | generation means 6 is demonstrated using FIG. 5, FIG. The auxiliary rudder angle generating means 6 increases the gain according to the output of the road surface reaction force state detection means 601 for determining whether the road surface reaction force described above is in the linear region or the saturation region, and the road surface reaction force state detection means 601. A variable gain control unit 602 and a multiplier 603 that multiplies the handle angular velocity signal 301 that is an output of the steering wheel angular velocity detection unit 3 by a gain that is the output of the gain control unit 602. The road surface reaction force state detection means 601 can be appropriately applied with the road surface reaction force saturation detection method disclosed in Patent Document 3, for example.

  The operation of the gain control means 602 in FIG. 5 will be described with reference to FIG. FIG. 6 is a diagram showing the state of signals at various parts when a single lane change (lane change to an adjacent lane) is performed on a slippery road surface. The handle is moved to the left (upward in the figure), then to the right (downward in the figure), and then returned to its original position as shown in FIG. The speed at which the handle is moved (handle angular velocity) is as shown in FIG. As shown in FIG. 6C, the road surface reaction force 401 is a slippery road surface where the road surface reaction force should be a road surface reaction force as shown by a broken line, as shown by a solid line. In addition, saturation occurs in a region where the handle angle (a) is large. At this time, the road surface reaction force state detection means 601 determines whether the road surface reaction force is in the linear region or the saturation region, as shown in FIG. The gain control unit 602 gradually decreases the gain to about 0 with time when the road surface reaction force state detection unit 601 determines that the road surface reaction force is saturated. The speed of this time change is, for example, changing the full span in about 0.1 to 0.3 seconds.

  In addition, when the road surface reaction force state detection unit 601 determines that the contact state with the road surface is linear, the gain is gradually increased to a predetermined value with time. Such a gradual decrease / gradual increase is performed when the road surface reaction force is saturated, and when steering is performed only in the linear region, the predetermined value remains. On the other hand, since the multiplier 603 multiplies the steering wheel angular velocity (FIG. 6 (b)) and the gain (FIG. 6 (f)), an auxiliary steering angle as shown in FIG. 6 (g) is calculated. In FIG. 6 (g), the broken line indicates the auxiliary steering angle when the road surface reaction force does not saturate (same as in FIG. 6 (b)). When the road surface reaction force is saturated on a slippery road surface, the gain becomes zero. It can be seen that the time for the close value becomes longer, and the auxiliary steering angle is suppressed during that time.

  As specific processing for achieving the above-described operation of the block of FIG. 6, the gain is linearly changed by arithmetic processing according to the output of the road surface reaction force detection means 601 as shown in FIG. However, as shown in FIG. 7, as another process, the output of the road surface reaction force state detection means 601 is immediately set to a predetermined value when the road surface reaction force is linear as shown in FIG. When saturated, a low-pass filter 602 (delay filter) having a predetermined time constant (for example, 0.1 to 0.3 seconds) is configured so that it is immediately set to 0 (including such output means). The control close to the gain control can be easily performed. The operation in this case is shown in FIG. 8C is the same as FIG. 6C, FIG. 8D is the same as FIG. 6D, and FIG. 8G is the same as FIG. 6G.

  Next, the operation of the target steering angle generation means 7 will be described. The target steering angle generation unit 7 generates the target steering angle 701 by adding the output 501 of the basic target steering angle generation unit 5 and the output of the auxiliary steering angle generation unit 6. Here, the basic target steering angle generating means 5 calculates a basic target steering angle in accordance with the output 201 of the steering wheel angle detecting means 2, and the auxiliary steering angle generated by the auxiliary steering angle generating means 6 is calculated. When it is 0, the steering wheel angle is used as it is, so that the relationship between the basic steering wheel angle and the steering wheel angle of the vehicle is defined.

The target steering angle generated in this manner is input to the steering wheel angle control means 8, and the steering wheel angle control means 8 is the steering wheel of the steering wheels 7a and 7b as described above. Control the corners.
Note that if the steering wheel angular velocity 301 is extremely large, if there is a concern that the auxiliary steering angle output from the auxiliary steering angle generation means 6 will become abnormally large, as shown in FIG. You may provide the limiter 13 which restrict | limits the made auxiliary steering angle to the predetermined range. As a result, it is possible to suppress the generation of a large auxiliary steering angle at an extremely fast steering angular velocity, and it is possible to prevent overcutting. Since the limiter having the characteristics shown in FIG. 9 is publicly known, the description with the block diagram is omitted.

Embodiment 2. FIG.
The configuration of the auxiliary rudder angle generating means 6 of FIG. 1 of Embodiment 1 can be modified (the deformed auxiliary rudder angle generating means is referred to as second auxiliary rudder angle generating means 6b). This will be described with reference to FIG. FIG. 10 is a diagram showing the configuration of the second auxiliary rudder angle generating means. A switchback determining means 604 is added to the configuration of FIG. 5 of the first embodiment, and the output of the switchback determining means 604 is gain control means. 602 is input. As shown in FIG. 10, the steering wheel angular velocity 301 and the road surface reaction force detection value 401 are input to the switchback determination unit 604. Then, the switchback judging means 604 compares the polarity of the steering wheel angular velocity 301 with the polarity of the road surface reaction force detection value 401 as shown in FIG. It is determined that it is in a state.

  Next, the operation of the second auxiliary steering angle generating means 6b will be described with reference to FIG. FIGS. 12A to 12D are the same as FIGS. 6A to 6D. FIG. 12E shows the output of the switch-back determination unit 604 described above. As described above, the gain control means 602 basically increases the gain gradually over time to a predetermined value when it is determined that the road reaction force state detection means 601 is linear. Is determined to be switched back, the gain is gradually increased to a predetermined value regardless of the output of the road surface reaction force state detecting means (the speed of time change is the same as in the first embodiment). Since the multiplier 603 multiplies the steering wheel angular velocity (FIG. 12 (b)) and the gain (FIG. 12 (f)), an auxiliary steering angle as shown in FIG. 12 (g) is calculated. The broken line shown in FIG. 12 (g) shows the auxiliary rudder angle of FIG. 6 (g) for comparison in order to help the understanding of the present embodiment, and the road surface is being increased on a slippery road surface. It can be seen that when the reaction force is saturated, the auxiliary rudder angle is suppressed, and when turning back, the auxiliary rudder angle is not suppressed.

  As a specific circuit configuration for achieving the function of the block of the second auxiliary rudder angle generating means 6b in FIG. 10, arithmetic processing using a CPU may be performed, but a simpler means is shown in FIG. You may do it. That is, as shown in FIG. 14, the output of the road surface reaction force state detection means 601 is configured to be instantaneously set to a predetermined value when the road surface reaction force is linear, and instantaneously set to 0 when saturated. As shown in FIG. 14, the output of the switchback determination means 604 is instantaneously set to a predetermined value at the time of switchback determination, and 0 otherwise. Then, the maximum value selection means 605 is used to select the maximum value of the two outputs. Further, the gain control means 602 is configured by a low-pass filter having a predetermined time constant (described above), whereby the gain control can be easily performed. The time constant of the low-pass filter is the same as in the first embodiment.

  In the description of the first and second embodiments, a steering mechanism in which the steering wheel and the steered wheel mechanism are not mechanically connected has been described as an example. However, the present invention is not limited to this mechanism, and is widely used by the driver. Any mechanism that can add an auxiliary steering angle to the steering wheel operation can be applied.

Embodiment 3 FIG.
A vehicle steering apparatus according to Embodiment 3 of the present invention will be described with reference to FIG. In FIG. 15, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and detailed description thereof will be omitted. The steered ratio control means 10 calculates a steered ratio that is the ratio of the steering wheel angle and the steered wheel angle from the outputs of the vehicle speed detecting means 9 and the road surface reaction force detecting means 4. The target steering angle generation means 7 generates a target steering angle from the output of the steering wheel angle detection means 2 and the output of the steering ratio control means 10.
The vehicle steering apparatus of the present embodiment controls the steering wheel angle by calculating an appropriate steering wheel angle based on the steering of the handle 1 steered by the driver and the road surface reaction force detection value 401 generated by the steering. Is.

Next, the operation of the apparatus shown in FIG. 15 will be described. As described in the first embodiment, the gain of the yaw rate with respect to steering of the steering wheel changes greatly due to various conditions. In addition, the steering ratio is increased in the low vehicle speed range to increase the convenience by turning a large amount with less steering. Conversely, in the high speed range, the steering ratio is decreased to reduce the yaw rate gain of the vehicle with respect to steering. It is well known that it can be made stable. The apparatus of FIG. 15 also basically has its functions, but detailed description thereof is omitted.
As described in the first embodiment, the problem on the slippery road surface is that the vehicle becomes unstable as the driver further increases the steering wheel despite the fact that the road surface reaction force is saturated. is there. The apparatus of FIG. 15 can solve this problem.

  FIG. 16 is a time chart of the operation when sign steering (manipulating the handle in a sine curve shape) is performed on a slippery road surface in order to explain the operation of the apparatus of FIG. For example, even if the steering wheel is further increased after the road surface reaction force is saturated (solid line in FIG. 16 (b)) at the portion indicated by A in FIG. The steering ratio control means 10 controls the steering ratio to be small ((y) in the same figure) so as to suppress the excessive turning of the actual steering wheel angle.

The above control operation, that is, a method for calculating the turning ratio when the road surface reaction force is saturated will be described. In the state where the driver is turning the steering wheel, in order not to contradict the driver's willingness to steer, it is permissible to prohibit the steering wheel angle from being increased or to reverse the control. Not. Therefore, in order to suppress the unnecessary turning angle of the steered wheel that is faithful to the steering intention, (steering wheel angular velocity / steering wheel angular velocity) is larger than 0 (that the same directionality is maintained), What is necessary is just to control so that it may become smaller than a rudder ratio.
If the steering wheel angle is θ, the steering wheel angle is δ, and the steering ratio is G,

Next, the operation when turning back the handle will be described. Whether or not the steering wheel is turned back can be determined to be switching back when the polarity of the steering wheel angle and the polarity of the steering wheel angular velocity are different (that is, when the steering wheel is turning in a direction in which the absolute value of the steering wheel angle decreases). . When the steering wheel turning-back determination is made, the control of the steering ratio shown in the above equation (6) is prohibited and the steering ratio is held (part B in FIG. 16). Further, when the steering wheel is in the vicinity of the neutral point, the steering ratio is initialized to a predetermined steering ratio (part C in FIG. 16), so at the next increase, steering as intended by the driver is realized. it can.
In order to help understanding, the above operation will be described once again with reference to the diagram showing the relationship between the steering wheel angle and the steering angle shown in FIG. If the steering wheel angle becomes the road surface reaction force saturation region when the road is increased, the steering angle is suppressed, so that the slope of the line on FIG. 15 becomes gentle. Next, when the steering wheel is turned back, as described above, the steering ratio is held, so that the steering wheel angle is turned back to the neutral point in a linear manner as shown in the figure. By doing so, as can be seen from the figure, it can be seen that the steered wheel angle returns to the linear region of the road surface reaction force earlier than when the steering ratio is not controlled.

  In this embodiment, the steering mechanism in which the steering wheel and the steering wheel mechanism are not mechanically connected has been described as an example. However, the steering mechanism is not applicable only to this mechanism, and is widely used for steering the driver's steering wheel. It is obvious that any mechanism that can add an auxiliary steering angle is sufficient.

Embodiment 4 FIG.
Another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the steering ratio control means described in the third embodiment is combined with a slight modification of the apparatus of the first embodiment. However, regarding the portion of the configuration of the first embodiment, the auxiliary steering angle control based on the output of the road surface reaction force detecting means 4 as described in the first embodiment is not performed. This is because when the road reaction force is saturated, the device of the first embodiment suppresses the increase by setting the auxiliary steering angle to 0, whereas in the third embodiment, the road reaction force is saturated when the road reaction force is saturated. This is because a reduction in steering ratio is suppressed by reducing the rudder ratio, so that a synergistic effect cannot be obtained even if both are added. Hereinafter, the operation of the portion added to the apparatus of Embodiment 3 will be mainly described.

In FIG. 18, the auxiliary steering angle generation means 6 receives the output of the steering wheel angular velocity detection means 2 and the output of the steering ratio control means 10, the steering wheel angular speed is ω, the steering ratio is Gr, and a predetermined gain ( If the differential gain is D, the auxiliary steering angle ψ is
ψ = Gr · D · ω (7)
Calculated by Therefore, even if the road surface reaction force is saturated and the steering ratio Gr is reduced, the auxiliary steering angle is also reduced accordingly, so the phase of the frequency characteristic of the yaw rate with respect to the steering of the driver does not change.

  In this embodiment, the steering mechanism in which the steering wheel and the steered wheel mechanism are not mechanically connected has been described as an example. However, this embodiment is not only applicable to this mechanism, and is widely applied to the steering of the driver. Obviously, any mechanism that can add an auxiliary steering angle is sufficient. Furthermore, as described in the first embodiment, the output of the auxiliary rudder angle generating means 6 may be limited to a predetermined range.

Embodiment 5 FIG.
The configuration of the fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, in addition to the apparatus of the third embodiment, the lead steer described in the first embodiment is combined. However, regarding the lead steer, the control of the auxiliary steering angle of the auxiliary steering angle generation unit 6 based on the output of the road surface reaction force detection unit 4 as described in the first embodiment is not performed. This is because when the road reaction force is saturated, the device of the first embodiment suppresses the increase by setting the auxiliary steering angle to 0, whereas in the third embodiment, the road reaction force is saturated when the road reaction force is saturated. This is because a reduction in steering ratio is suppressed by reducing the rudder ratio, so that a synergistic effect cannot be obtained even if both are added. Hereinafter, the operation of the portion added to the apparatus of Embodiment 3 will be mainly described.

In FIG. 19, the first turning ratio control means 11 controls the basic turning ratio of the vehicle described in the third embodiment, and the second turning ratio control means 12 The output of the force detection means 4 is input, and the steering ratio is suppressed depending on the situation of the road surface reaction force. That is, it is equivalent to the steering ratio control means described in the third embodiment. The auxiliary steering angle generation means 6 receives the output of the steering wheel angular velocity detection means 2 and the output of the first steering ratio control means 10, outputs the steering wheel angular speed ω, and the first steering ratio control means outputs. When the steering ratio is Gi and the predetermined gain (differential gain) is D, the auxiliary steering angle ψ is
ψ = Gi · D · ω (8)
It is calculated regardless of the road surface reaction force. On the other hand, as described in the third embodiment, the second turning ratio control means 12 is controlled by the road surface reaction force detection means 4 and the like. Here, when the output turning ratio of the second turning ratio control means 12 (referred to as the second turning ratio for distinction) is Gr, the steering wheel angle is θ, and the basic target steering angle is assumed. The basic target steering angle refining means 7 is:
φ = Gr · θ (9)
The target steering angle refining means 8 adds the equations (8) and (9) to obtain the target steering angle δ,
δ = ψ + φ (10)
Calculate with Therefore, even if the road surface reaction force is saturated and the steering ratio Gr becomes small, the steering ratio Gi with respect to the auxiliary steering angle does not change, so that the auxiliary steering angle can be kept against the driver's sudden steering. it can.

  In this embodiment, the steering mechanism in which the steering wheel and the steered wheel mechanism are not mechanically connected has been described as an example. However, this embodiment is not only applicable to this mechanism and is widely used for steering the driver's steering wheel. It is obvious that any mechanism that can add an auxiliary steering angle is sufficient. Furthermore, as described in the first embodiment, the output of the auxiliary rudder angle generating means 6 may be limited to a predetermined range.

  The vehicle steering apparatus of the present invention is described assuming a so-called automobile such as a passenger car or a truck. However, the vehicle steering apparatus is not limited to an automobile, and is a vehicle that travels on land and whose direction is controlled by steering wheels, such as a forklift. It can also be applied to.

1 is a block diagram of a vehicle steering apparatus according to Embodiment 1. FIG. It is a characteristic view explaining the yaw rate frequency response with respect to the steering wheel angle of the vehicle. It is a characteristic view explaining the yaw rate frequency response with respect to the steering angle of the vehicle when lead steer is introduced. It is a characteristic view explaining the road surface reaction force which arises in a tire. It is a figure explaining the structure of an auxiliary steering angle production | generation means. It is a time chart explaining the operation | movement of FIG. It is a figure which shows another structure of FIG. FIG. 8 is a time chart illustrating the operation of FIG. 7. It is characteristic explanatory drawing of the limiter provided in the thing of FIG. FIG. 6 is a configuration diagram of auxiliary steering angle generation means of a second embodiment. It is a time chart explaining the operation | movement of FIG. It is a time chart explaining the operation | movement of FIG. It is a figure which shows another structure of FIG. It is a time chart explaining the operation | movement of FIG. FIG. 6 is a diagram illustrating a configuration of a vehicle steering apparatus according to a third embodiment. FIG. 16 is a time chart illustrating the operation of FIG. 15. FIG. 16 is a graph of steering wheel angle vs. target steering angle for explaining the operation of FIG. 15. FIG. FIG. 5 is a configuration diagram of a vehicle steering apparatus according to a fourth embodiment. FIG. 6 is a configuration diagram of a vehicle steering apparatus according to a fifth embodiment.

Explanation of symbols

1 handle, 2 handle angle detection means, 3 handle angular velocity detection means,
4 road surface reaction force detection means, 5 basic target steering angle generation means,
6 auxiliary steering angle generation means, 6b second auxiliary steering angle generation means,
7 Target steering angle generation means, 8 Steering wheel angle control means,
9 vehicle speed detection means, 10 steering ratio control means, 13 limiter,
11 first steering ratio control means, 12 second steering ratio control means, 13 limiter,
14 steering mechanism drive means, 15 steering mechanism, 16a, 16b knuckle arm,
17a, 17b steering wheel, 18 steering wheel angle detection means,
201 steering wheel angle signal, 301 steering wheel angular velocity signal,
601 road surface reaction force state detection means, 602 gain control means,
603 multiplier, 1401 electric motor.

Claims (11)

A handle angle detection means for detecting a handle angle and outputting a handle angle signal;
A steering wheel angular velocity detection means for detecting a steering wheel angular velocity and outputting a steering wheel angular velocity signal;
A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by the steering wheel being steered,
Basic target steering angle setting means for setting a basic target steering angle value of the steering wheel from the steering wheel angle signal;
A steering wheel angle detection means for detecting a current steering angle of the steering wheel;
From the current steering angle of the steering wheel detected by the steering wheel angle detection means and the road surface reaction torque signal, whether the steering wheel and the road surface are in a linear region or a saturated region. Road surface reaction force state detection means for determining the gain, a gain gradually increasing with time to a predetermined value when determined to be in the linear region, and approximately 0 when determined to be in the saturation region and gain control means for outputting a gain gradually decreases with time until the auxiliary steering angle setting means and a calculating means for calculating an auxiliary steering angle multiplied by the gain to the steering wheel angular velocity signal,
Target steering angle setting means for setting the target steering angle by adding the auxiliary steering angle to the basic target steering angle value;
A vehicle steering system comprising steering angle control means for controlling a steering angle of the steering wheel based on the target steering angle. The road surface reaction force state detection means outputs a predetermined value when it is determined that the value of the road surface reaction force torque signal is in a linear region, and outputs a substantially zero value when it is determined that it is in a saturation region. Having an output means,
2. The vehicle steering apparatus according to claim 1, wherein the gain control unit includes a delay filter that receives the value output from the output unit and outputs a delayed signal having a predetermined time constant as the gain. . A handle angle detection means for detecting a handle angle and outputting a handle angle signal;
A steering wheel angular velocity detection means for detecting a steering wheel angular velocity and outputting a steering wheel angular velocity signal;
A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by the steering wheel being steered,
Basic target steering angle setting means for setting a basic target steering angle value of the steering wheel from the steering wheel angle signal;
Switchback determination means for comparing the polarity of the steering wheel angular velocity signal and the road surface reaction force torque signal to determine whether the steering wheel is in a switchback state or an increase state.
A steering wheel angle detection means for detecting a current steering angle of the steering wheel;
From the current steering angle of the steering wheel detected by the steering wheel angle detection means and the road surface reaction torque signal, whether the steering wheel and the road surface are in a linear region or a saturated region. Road surface reaction force state detecting means for determining
When it is determined that the contact state between the steered wheel and the road surface is in a linear region, or when the switchback determination means determines that the handle is in a switchback state, it gradually increases over time to a predetermined value. A gain control means for outputting a gain that gradually decreases with time until it is determined that the steering wheel is in the saturation region and the handle is in the increased state; Auxiliary rudder angle setting means having a computing means for calculating an auxiliary rudder angle by multiplying the steering wheel angular velocity signal by the gain,
Target steering angle setting means for setting the target steering angle by adding the auxiliary steering angle to the basic target steering angle value;
A vehicle steering system comprising steering angle control means for controlling a steering angle of the steering wheel based on the target steering angle. When the auxiliary rudder angle setting means determines that the contact state between the steered wheel and the road surface is in the linear region, or when the switchback determination means determines that the handle is in a switchback state Outputs a predetermined value, and when it is determined that it is in the saturation region, and when the switchback determination means determines that the handle is in an increased state, the maximum value that outputs a value of approximately zero is output. Having value selection means,
4. The vehicle according to claim 3, wherein the gain control means includes a delay filter that receives the value output from the maximum value selection means and outputs a delayed signal having a predetermined time constant as the gain. Steering device. Vehicle speed detection means for detecting the vehicle speed and outputting a vehicle speed signal;
A handle angle detection means for detecting a handle angle and outputting a handle angle signal;
A steering wheel angular velocity detection means for detecting a steering wheel angular velocity and outputting a steering wheel angular velocity signal;
A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by the steering wheel being steered,
Wherein based on the vehicle speed signal and the road surface reaction force torque signal, steering angle ratio control means for calculating a steering angle ratio the ratio of the steering wheel angular speed of the steering wheel for a given the steering wheel angular velocity,
A target steering angle setting means for generating a target steering angle value by multiplying the steering angle signal by the steering ratio;
A steering apparatus for a vehicle, comprising steering angle control means for controlling a steering angle of the steering wheel according to an output of the target steering angle setting means. Switchback determination means for comparing the polarity of the steering wheel angular velocity signal and the road surface reaction force torque signal to determine whether the steering wheel is in a switchback state or an increase state.
A steering wheel angle detection means for detecting a current steering angle of the steering wheel;
From the current steering angle of the steering wheel detected by the steering wheel angle detection means and the road surface reaction torque signal, whether the steering wheel and the road surface are in a linear region or a saturated region. Road surface reaction force state detection means for determining
The steering ratio control unit is a case where it is determined that the steering wheel is steered in a state increased cut by previous SL switchback determining means, the output of the road surface reaction force state detecting means to be in the saturation region determination If it is determined that the output steered ratio is smaller than the calculated steered ratio and is a predetermined value equal to or greater than 0, and when it is determined that the steering wheel is steered back The calculated steered ratio is held, and when the steering wheel angle becomes a substantially neutral point, the computed steered ratio is initialized to a predetermined value . Vehicle steering system. Vehicle speed detection means for detecting the vehicle speed and outputting a vehicle speed signal;
A handle angle detection means for detecting a handle angle and outputting a handle angle signal;
A steering wheel angular velocity detection means for detecting a steering wheel angular velocity and outputting a steering wheel angular velocity signal;
A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by the steering wheel being steered,
A steered ratio control means for calculating a steered wheel angle ratio with respect to a steering wheel angle as a steered ratio based on the vehicle speed signal and the road surface reaction force torque signal;
Basic target steering angle setting means for generating a basic target steering angle value by multiplying the steering angle signal by the steering ratio;
An auxiliary steering angle setting means for calculating an auxiliary steering angle by multiplying a steering ratio with respect to the steering wheel angular velocity signal and the steering wheel angle signal by a predetermined gain;
Target steering angle setting means for setting the target steering angle by adding the auxiliary steering angle to the basic target steering angle value;
A vehicle steering system comprising steering angle control means for controlling a steering angle of the steering wheel based on the target steering angle. Compared with the polarities of the steering wheel angular velocity signal and the road surface reaction force torque signal, there is a switching back judging means for judging whether the steering wheel is in the switching back state or the cutting back state.
The steering ratio control unit, when the handle is determined to be steered to a state increased cutting is a steering angle ratio to output smaller than the steering ratio obtained by the calculation, and 0 or more predetermined outputs so that value, the when the handle is determined to be in the state switching back holding the steering angle ratio by the operation, when the steering wheel angle becomes substantially neutral point, given the steering angle ratio by the operation The vehicle steering apparatus according to claim 7, wherein the vehicle steering apparatus is initialized to a value of. Vehicle speed detection means for detecting the vehicle speed and outputting a vehicle speed signal;
A handle angle detection means for detecting a handle angle and outputting a handle angle signal;
A steering wheel angular velocity detection means for detecting a steering wheel angular velocity and outputting a steering wheel angular velocity signal;
A road surface reaction force detecting means for estimating or directly detecting a road surface reaction force torque signal generated by the steering wheel being steered,
Based on the steering angle signal and the vehicle speed signal, the first steering ratio control means for outputting the ratio of the steering wheel angular velocity of the steering wheel relative to the wheel angular velocity as the basic steering ratio,
The first on the basis of the output and the road surface reaction force torque signal of the steering ratio control unit, a second steering angle ratio control means for calculating a second steering ratio,
Basic target steering angle setting means for generating a basic target steering angle value by multiplying the steering wheel angle signal by the second steering ratio output by the second steering ratio control means;
Auxiliary steering angle setting means for calculating an auxiliary steering angle by multiplying the steering wheel angular velocity signal and the output of the first steering ratio control means by a predetermined gain;
Target steering angle setting means for setting the target steering angle by adding the auxiliary steering angle to the basic target steering angle value;
A steering apparatus for a vehicle, comprising steering angle control means for controlling a steering angle of the steering wheel based on the target steering angle. Compared with the polarities of the steering wheel angular velocity signal and the road surface reaction force torque signal, there is a switching back judging means for judging whether the steering wheel is in the switching back state or the cutting back state.
The second steering angle ratio control means, when the handle is determined to be steered to a state increased cut is smaller than the previous SL basic steering ratio as said second steering angle ratio, and 0 or more When the steering ratio is determined to be in the switchback state, the second steering ratio is maintained, and when the steering wheel angle is substantially neutral, The vehicle steering apparatus according to claim 9, wherein the second steering ratio is initialized to a predetermined value . The vehicle steering apparatus according to any one of claims 1 to 4, and 7 to 10, further comprising auxiliary steering angle limiting means for limiting an output value of the auxiliary steering angle setting means to a predetermined range. .

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