JP7188357B2 - Vehicle steering reaction force torque control device - Google Patents

Description

The present invention relates to a steering reaction force torque control device for a vehicle such as an automobile.

As one method of controlling the steering reaction force in a vehicle such as an automobile, the steering reaction force is reduced when steering necessary for proper running of the vehicle is performed, and the steering reaction force is reduced when unnecessary steering is performed for proper running of the vehicle. It is known to control the steering reaction force so that the reaction force is increased.

For example, in Patent Document 1 below, the future of the own vehicle and the driving environment around the own vehicle is predicted, the future necessary steering angle (optimal steering angle) is estimated based on the prediction result, and the actual steering angle is required. A steering reaction force control device is described in which the steering reaction force is reduced when the actual steering angle approaches the desired steering angle, and is increased when the actual steering angle moves away from the required steering angle.

According to the steering reaction force control device described in Patent Document 1, the steering operation to bring the actual steering angle closer to the required steering angle is facilitated by the reduction of the steering reaction force, and the actual steering angle can be changed from the required steering angle. Steering operation to keep away becomes difficult due to an increase in steering reaction force. Therefore, as compared with the case where the steering reaction force is not controlled as described above, the driver is encouraged to perform the steering operation so that the actual steering angle becomes the required steering angle, and the actual steering angle becomes the required steering angle. It is possible to suppress the driver's steering operation to move away from the corner.

JP-A-2003-63430

[Problems to be solved by the invention]
In the steering reaction force control device described in Patent Document 1, the steering reaction force is controlled to increase as the difference between the actual steering angle and the required steering angle increases. It becomes a characteristic like a spring characteristic with the deviation of Therefore, when the actual steering angle deviates from the required steering angle, the steering reaction force increases as the deviation of the steering angle increases, and the effect of suppressing the driver's steering operation increases.

However, if there is a deviation in the steering angle in a situation where the driver has no intention of steering, such as when the steering wheel is held, the actual steering angle is brought closer to the required steering angle, as will be described in detail later. Unnecessary steering reaction force acts. Therefore, when the steering wheel tries to turn even though the driver is not trying to perform a steering operation, it is inevitable that the driver will feel a sense of incompatibility, as if someone else has steered the vehicle.

A main object of the present invention is to provide an improved steering reaction force torque control device that controls the steering friction compensation torque as the steering reaction force torque so as not to cause the above-mentioned problems in conventional control of the steering reaction force. That is.

[Means for Solving the Problems and Effect of the Invention]
According to the present invention, an electric power steering device (22) configured to generate a steering friction compensating torque (Tsf) when the driver operates the steering wheel (16) and the electric power steering device are controlled. There is provided a steering reaction torque control system (10) for a vehicle (14) including a controller (24).

A control device (24) acquires information on an actual steering angle (θ) and a target steering angle (θt) for the vehicle to run along the lane,
When the change in the actual steering angle (θ) approaches the target steering angle (θt), the steering friction compensation torque (Tsf) decreases and the change in the actual steering angle (θ) approaches the target steering angle (θt). is configured to control the steering friction compensation torque as the steering reaction force torque of the electric power steering device (22) so as to achieve at least one of increasing the steering friction compensation torque (Tsf) when the change moves away from there is

According to the above configuration, when the change in the actual steering angle approaches the target steering angle, the steering friction compensation torque decreases, and/or when the change in the actual steering angle moves away from the target steering angle. The steering friction compensation torque increases. Therefore, the steering operation that causes the actual steering angle to change closer to the target steering angle becomes easier, and/or the steering operation that causes the actual steering angle to move away from the target steering angle becomes difficult. Therefore, it encourages the driver to perform a steering operation so that the actual steering angle becomes the required steering angle and/or suppresses the driver's steering operation so that the actual steering angle becomes far from the required steering angle. can do.

Note that the steering friction compensation torque decreases when the actual steering angle changes toward the target steering angle, and the steering friction compensation torque increases when the actual steering angle changes away from the target steering angle. has both of the above effects. That is, it is possible to encourage the driver to perform a steering operation so that the actual steering angle becomes the required steering angle, and to encourage the driver to perform the steering operation so that the actual steering angle becomes far from the required steering angle. can be suppressed.

Further, even if there is a steering angle deviation in a situation where the driver does not intend to perform a steering operation, such as when the steering wheel is held, no steering friction compensation torque is generated unless the actual steering angle changes. Therefore, it is possible to prevent the driver from feeling a sense of incongruity as if he or she received steering intervention from another person due to unnecessary steering reaction torque.

In the above description, in order to facilitate understanding of the present invention, reference numerals used in the embodiments are added in parentheses to configurations of the invention corresponding to the embodiments to be described later. However, each component of the present invention is not limited to the component of the embodiment corresponding to the reference numerals attached in parentheses. Other objects, features and attendant advantages of the present invention will be readily understood from the description of embodiments of the present invention described with reference to the following drawings.

1 is a schematic configuration diagram showing a steering reaction force torque control device for a vehicle according to an embodiment of the present invention; FIG. 4 is a flowchart showing a steering assist torque control routine including control of steering friction compensation torque according to the embodiment; 3 is a map for calculating a target steering assist torque Tst for the entire vehicle based on a steering torque Ts and a vehicle speed V; The upper graph shows an example of changes in the magnitude relationship between the steering angle θ and the target steering angle θt (one-dot chain line) when the steering angle θ increases in the positive range. The lower graph shows changes in the steering friction compensation torque Tsf. is shown. The upper graph shows an example of changes in the magnitude relationship between the steering angle θ and the target steering angle θt (one-dot chain line) when the steering angle θ decreases in the positive range, and the lower graph shows changes in the steering friction compensation torque Tsf. is shown. The upper graph shows an example in which the steering angle θ increases or decreases relative to the target steering angle θt in a situation where the target steering angle θt (one-dot chain line) is constant and the steering operation is performed by the driver. It shows the change in Tsf. FIG. 4 is an explanatory diagram showing a situation in which a driver applies an operation force Fd to the mass body so that the mass body moves to the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by a spring force; be. FIG. 4 is an explanatory diagram showing a situation in which a driver applies an operation force Fd to the mass body so that the mass body moves to the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the frictional force; be. FIG. 4 is an explanatory diagram showing a situation in which the driver does not have the intention to operate the mass body so that the mass body moves to the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the spring force; be. FIG. 10 is an explanatory diagram showing a situation in which the driver does not have the intention to operate the mass body so that the mass body moves to the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the frictional force; be. FIG. 10 is an explanatory diagram showing a situation in which the driver excessively manipulates the mass body so that the mass body moves beyond the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the spring force; be. FIG. 10 is an explanatory diagram showing a situation in which the driver excessively manipulates the mass body so that the mass body moves beyond the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the frictional force; be. FIG. 10 is an explanatory diagram showing a situation in which the driver holds the mass body so that the mass body stays at a position beyond the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by a spring force; . FIG. 10 is an explanatory diagram showing a situation in which the driver holds the mass body so that the mass body stays at a position beyond the target position indicated by the two-dot chain line when the reaction force for steering assistance is given by the frictional force; . FIG. 2 is a steering hysteresis diagram showing a specific example of the relationship between the steering angle θ and the steering reaction force torque Tsre felt by the driver when the steering operation is performed in the same direction as the steering direction of the driving assistance. be. FIG. 5 is a steering hysteresis diagram showing a specific example of the relationship between the steering angle θ and the steering reaction force torque Tsre felt by the driver when the driver does not have the intention of performing a steering operation similar to steering for driving support. A steering hysteresis diagram showing a specific example of the relationship between the steering angle θ and the steering reaction force torque Tsre felt by the driver in the case where the direction of the steering operation by the driver is the same as the steering direction of the driving assistance and the return steering is performed. is. A specific example of the relationship between the steering angle θ and the steering reaction torque Tsre felt by the driver when the driver changes the steering torque within a predetermined range in a situation where the steering angle θ is the target steering angle θt. It is a steering hysteresis diagram shown. 2 is a steering hysteresis line showing a specific example of the relationship between the steering angle θ and the steering reaction torque Tsre felt by the driver when the driver changes the steering torque in a conventional power steering device in which the steering friction compensating torque Tsf is not increased or decreased. It is a diagram. A specific example of the relationship between the steering angle θ and the steering reaction torque Tsre felt by the driver when the driver changes the steering torque beyond a predetermined range in a situation where the steering angle θ is the target steering angle θt. is a steering hysteresis diagram showing .

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, a steering reaction force torque control device 10 according to an embodiment of the present invention is applied to a vehicle 14 having a steering device 12. As shown in FIG. The steering device 12 includes a steering wheel 16 operated by a driver, front wheels 18L and 18R that are steered wheels, and a transmission device 20 that transmits steering force and displacement between the steering wheel 16 and the front wheels 18L and 18R. and includes The steering reaction force torque control device 10 has an electric power steering device 22 that generates a steering assist torque Ta and applies the steering assist torque Ta to the transmission device 20, and an electronic control device 24 that controls the electric power steering device 22. is doing.

In the illustrated embodiment, the electric power steering system 22 is a column assist type electric power steering system (EPS). Note that the electric power steering apparatus may be another type of electric power steering apparatus, such as a pinion assist type or rack assist type electric power steering apparatus, as long as the steering assist torque Ta can be controlled.

As shown in FIG. 1, the transmission 20 includes an upper steering shaft 26 that rotates with the steering wheel 16, an intermediate shaft 28, and a steering mechanism 30. As shown in FIG. The intermediate shaft 28 has an upper end connected to the lower end of the upper steering shaft 26 via a universal joint 32 and a lower end connected to a pinion shaft 36 of the steering mechanism 30 via a universal joint 34 .

The steering mechanism 30 includes a rack and pinion type steering unit 38 and tie rods 40L and 40R. Perform the inverse conversion. The inner ends of the tie rods 40L and 40R are pivotally attached to the tips of the rack bar 42, and the outer ends of the tie rods 40L and 40R are knuckles provided on carriers (not shown) of the left and right front wheels 18L and 18R, respectively. It is pivotally attached to arms 44L and 44R.

Therefore, the rotational displacement and rotational torque of the steering wheel 16 are converted by the transmission device 20 into pivotal motion and rotational torque about the kingpin shafts (not shown) of the front wheels 18 and 18R and transmitted to the front wheels 18L and 18R. . In addition, the pivotal motion and rotational torque about the kingpin axis received by the left and right front wheels 18L and 18R from the road surface 46 are transmitted to the steering wheel 16 by the transmission device 20 as rotational displacement and rotational torque, respectively.

The electric power steering device 22 has an electric motor 48 and a conversion device 50. Although not shown in FIG. Includes wormwheel. Rotational torque of the electric motor 48 is converted into rotational torque of the upper steering shaft 26 by the conversion device 50 and transmitted to the upper steering shaft.

The electronic control device 24 functions as a control device that controls the steering assist torque Ta applied to the upper steering shaft 26 by the electric power steering device 22 by controlling the rotational torque of the electric motor 48, as will be described in detail later. . Signals indicating the steering angle θ and the steering torque T are input to the electronic control unit 24 from a steering angle sensor 52 and a torque sensor 54 provided on the upper steering shaft 26, respectively. The electronic control unit 24 also receives a signal indicating the vehicle speed V from the vehicle speed sensor 56 and information on the front of the vehicle from the CCD camera 58 . The information ahead of the vehicle may be acquired by means other than the CCD camera 58, or may be acquired by a combination of the CCD camera 58 and other means.

The electronic control unit 24 includes a microcomputer having a CPU, a ROM, a RAM, and an input/output port device, which are connected to each other by a bidirectional common bus. You can do it. Moreover, the steering angle sensor 52 and the torque sensor 54 detect the steering angle θ and the steering torque T, with the value being 0 when the vehicle is running straight and the value being positive when the vehicle is being steered to the left. Therefore, when the steering wheel 16 rotates counterclockwise, the time differential value θd of the steering angle θ becomes a positive value.

The electronic control unit 24 calculates a target steering angle θt for driving support control such as running locus control (also called "LKA (lane keeping assist) control") according to the flowchart shown in FIG. For example, the electronic controller 24 may identify a driving lane in a manner known in the art based on the information in front of the vehicle obtained by the CCD camera 58, and set targets for driving the vehicle along the driving lane. Calculate the steering angle θt.

Since the calculation of the target steering angle θt itself does not constitute the gist of the present invention, it can be performed in any manner known in the art, such as the manner described in Japanese Patent No. 5737197. you can Alternatively, the calculation of the target steering angle θt may be performed by another electronic control device that performs driving support control, and a signal indicating the target steering angle θt may be input to the electronic control device 24 from the other electronic control device.

The electronic control unit 24 calculates a basic target steering assist torque Tab based on the steering torque T and the vehicle speed V, and the steering assist torque Ta is the sum of the basic target steering assist torque Tab and the steering friction compensation torque Tsf. The electric power steering device 22 is controlled so as to achieve the assist torque Tat.

In particular, the electronic control unit 24 determines the change in the actual steering angle based on the time differential value θd of the actual steering angle θ, and determines the magnitude of the target steering angle θt for driving support control of the vehicle and the actual steering angle θ. Based on the relationship, it is determined whether or not the change in the actual steering angle approaches the target steering angle. Further, the electronic control unit 24 controls the electric steering so that the steering reaction torque decreases when the actual steering direction matches the required steering direction, and increases when the actual steering direction differs from the required steering direction. It controls the power steering device 22 .

Next, a steering assist torque control routine including steering friction compensation torque control according to the embodiment will be described with reference to the flowchart shown in FIG. Control according to the flowchart shown in FIG. 2 is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is turned on. In the following description, the control of the steering assist torque according to the flowchart shown in FIG. 2 is simply referred to as "control".

First, in step 10, a signal indicating the steering torque T detected by the torque sensor 54 and a signal indicating the vehicle speed V detected by the vehicle speed sensor 56 are read. Further, based on the steering torque T and the vehicle speed V, a basic target steering assist torque Tab is calculated from the map shown in FIG. As shown in FIG. 3, the basic target steering assist torque Tab is calculated so that it increases as the steering torque T increases, and decreases as the vehicle speed V increases. be.

In step 20, based on the information in front of the vehicle obtained by the CCD camera 58, the lane of travel is identified in a manner known in the art, and a target steering angle .theta.t is calculated to keep the vehicle in the lane of travel. is calculated.

At step 30, it is determined whether or not the time differential value .theta.d of the steering angle .theta. is positive, that is, whether or not the driver is turning the steering wheel 16 counterclockwise. Control proceeds to step 70 when a negative determination is made, and control proceeds to step 40 when an affirmative determination is made.

At step 40, it is determined whether or not the steering angle .theta. is greater than the target steering angle .theta.t, that is, whether or not the amount of operation of the steering wheel 16 counterclockwise by the driver is excessive. . When the determination is affirmative, the flag Fs is set to 1 in step 50, and when the determination is negative, the flag Fs is set to -1 in step 60.

At step 70, it is determined whether or not the steering angle .theta. is greater than the target steering angle .theta.t, that is, whether or not the amount of clockwise operation of the steering wheel 16 by the driver is insufficient. When the determination is affirmative, the flag Fs is set to -1 in step 80, and when the determination is negative, the flag Fs is set to 1 in step 90.

Once steps 50, 60, 80 or 90 are completed, control passes to step 100. FIG. In step 100, a gradual change coefficient Gs for gradually changing the steering friction compensation torque Tsf is calculated according to the following formula (2), where Ss is a value (positive constant) represented by the following formula (1). be done. However, when the calculated gradual change coefficient Gs is greater than 1, the gradual change coefficient Gs is set to 1, and when the calculated gradual change coefficient Gs is less than -1, the gradual change coefficient Gs is set to -1. be done.
Ss=Tg/Tc (1)
Gs=2.Fs/Ss+Gsf (2)

In the above equation (1), Tg is the gradual change time (preset positive constant of about 0.1 sec), and Tc is the cycle time of the flow chart shown in FIG. ). Furthermore, in the above equation (2), Gsf is the previous value of the gradual change coefficient Gs, and 2 is a coefficient for changing the gradual change coefficient Gs from -1 to 1. The flag Fs changes from -1 to 1 when the state in which the manipulated variable is insufficient changes to the state in which the manipulated variable is excessive, and when the opposite change occurs, the flag Fs changes from 1 to -1. , and thus the gradual change coefficient Gs varies between -1 and 1.

In step 110, according to the following equation (3), the steering friction compensation torque Tsfbase (positive constant) is set as a preset increase/decrease steering friction compensation torque. calculated to be the product of
Tsf = Tsfbase · Gs (3)

At step 120, the final target steering assist torque Tat is the sum of the basic target steering assist torque Tab calculated at step 10 and the steering friction compensation torque Tsf calculated at step 110 according to the following equation (4). It is calculated so that
Tat=Tab+Tsf (4)

At step 130, the steering assist torque Ta applied to the upper steering shaft 26 is controlled. That is, the current value of the control current supplied to the electric motor 48 of the electric power steering device 22 is controlled so that the steering assist torque Ta becomes the final target steering assist torque Tat.

When the steering wheel 16 is turned by the driver to perform a steering operation, a substantially constant physical force is generated due to friction between relatively moving members in the transmission device 20 and the electric power steering device 22 . A steering friction torque Tsf0 is generated. Further, as the steering angle θ increases, the steering torque Tsa resulting from the self-aligning torque increases. Therefore, the steering friction torque Tsff felt by the driver during steering operation is the sum Tsa+Tsf0+Tsf of the steering torque Tsa, the physical steering friction torque Tsf0, and the steering friction compensation torque Tsf.

The steering friction compensation torque Tsf is increased or decreased between Tsfbase and -Tsfbase by controlling the steering assist torque. Therefore, the steering friction torque Tsff changes between Tsf0+Tsfbase and Tsf0-Tsfbase. Furthermore, when the steering friction compensating torque Tsf is increased or decreased, the steering friction compensating torque Tsf changes gradually over the gradual change time Tg at the start and end of the increase or decrease, thereby preventing a stepped sudden change.

The increasing/decreasing steering friction compensating torque Tsfbase is a value that satisfies the following inequality (5) so that the steering friction compensating torque Tsf is effectively increased/decreased and does not become excessively large with respect to the physical steering friction torque Tsf0. Preferably.
0<2Tsfbase≦Tsf0 (5)

According to the flowchart shown in FIG. 2, the increase/decrease in the steering friction compensating torque Tsf depends on the sign of the time differential value θd of the steering angle θ and the magnitude relationship between the steering angle θ and the target steering angle θt. 1 is controlled.

<Example of cutting steering>
For example, the upper part of FIG. 4 shows the magnitude of the steering angle θ and the target steering angle θt (one-dot chain line) in a situation where the steering angle θ increases in the positive range (when θd>0 and the steering is turned left). It shows an example where the relationship changes. The lower part of FIG. 4 shows changes in the steering friction compensation torque Tsf.

<A> Example in which steering angle θ is indicated by a solid line θ<θt before time tp, and θ>θt after time tp. Therefore, before the time point tp, the steering friction torque Tsff is reduced by the decrease in the steering friction compensation torque Tsf, so that the turning steering operation to bring the steering angle θ closer to the target steering angle θt becomes easier. Conversely, after the time point tp, the steering friction torque Tsff increases due to the increase in the steering friction compensation torque Tsf, so it is difficult to perform a steering operation such that the steering angle θ increases away from the target steering angle θt. Become.

<B> Example in which steering angle θ is indicated by a dashed line Contrary to the above case A, θ>θt before time tp, and θ<θt after time tp. Therefore, before the time point tp, the steering friction torque Tsff is increased by the increase in the steering friction compensation torque Tsf, so that it becomes difficult to perform the turning steering operation so that the steering angle θ becomes larger away from the target steering angle θt. . Conversely, after the time point tp, the steering friction compensation torque Tsf is reduced and the steering friction torque Tsff is reduced, so that the turning steering operation to bring the steering angle θ closer to the target steering angle θt becomes easier.

Although not shown in the figure, in a situation where the steering angle θ decreases in the negative range (when θd < 0, the steering is turned to the right), the difference between the steering angle θ and the target steering angle θt is The magnitude relationship is opposite to the above-described situation where the steering angle θ increases in the positive range.

<Example of steering back>
The upper part of FIG. 5 shows the magnitude relationship between the steering angle θ and the target steering angle θt (one-dot chain line) in a situation where the steering angle θ decreases in the positive range (return steering from the left turning direction when θd > 0). changes. The lower part of FIG. 5 shows changes in the steering friction compensation torque Tsf.

<C> Example in which the steering angle θ is indicated by a solid line θ>θt before time tq, and θ<θt after time tp. Therefore, before the time tq, the steering friction compensation torque Tsf is reduced and the steering friction torque Tsff is reduced, so that the steering operation of the steering back to bring the steering angle θ closer to the target steering angle θt is facilitated. Conversely, after the time tq, the steering friction torque Tsff is increased due to the increase in the steering friction compensation torque Tsf, so that the steering operation for returning the steering angle .theta. It becomes difficult.

<D> Example in which steering angle θ is indicated by a dashed line Contrary to the above case C, θ<θt before time tq, and θ>θt after time tp. Therefore, before the time tq, the steering friction torque Tsff is increased by the increase in the steering friction compensation torque Tsf, so that the steering operation of the steering back is performed so that the steering angle θ becomes too small away from the target steering angle θt. it gets harder. Conversely, after time tq, the steering friction compensation torque Tsf is reduced, thereby reducing the steering friction torque Tsff.

Although not shown in the figure, in a situation where the steering angle θ increases in a negative range (when θd < 0, the steering wheel is turned back from the right turning direction), the steering angle θ and the target steering angle θt is opposite to the situation in which the steering angle .theta. decreases in the positive range.

<E><Example of holding the rudder>
The upper part of FIG. 6 shows an example in which the steering angle θ increases or decreases with respect to the target steering angle θt in a situation where the target steering angle θt (one-dot chain line) is constant positive and the steering operation is performed by the driver. The lower part of shows changes in the steering friction compensating torque Tsf.

θ>θt before time t1, θ<θt after time t1 and before time t2, and θ>θt after time t2. Therefore, before the time tq and after the time t2, the steering friction torque Tsff is reduced due to the decrease in the steering friction compensation torque Tsf, so that the steering operation of the return steering is performed so that the steering angle θ approaches the target steering angle θt. becomes easier. Conversely, after time t1 and before time t2, the steering friction torque Tsff is increased by the increase in the steering friction compensation torque Tsf. It becomes difficult. Therefore, the steering angle .theta. is restrained from departing from the target steering angle .theta.t, and the steering angle .theta. is restrained from approaching the target steering angle .theta.t.

<Gradual change at time of inversion of increase/decrease>
In the examples shown in the upper parts of FIGS. 4 and 5, the reversal of increase and decrease in the steering friction compensation torque Tsf starts at times tp and tq as shown in the lower parts of FIGS. 4 and 5, respectively. In the example shown in the upper part of FIG. 6, as shown in the lower part of FIG. 6, the reversal of increase or decrease of the steering friction compensation torque Tsf starts at times t1 and t2.

According to the embodiment, the process of steps 100 and 110 allows the gradual change coefficient Gs to be between -1 and 1 over the gradual change time Tg when the steering friction compensation torque Tsf changes between decreasing and increasing. gradually changed in between. Therefore, as exaggeratedly illustrated in the lower part of FIGS. 4 and 5, the change at the start and end of the increase/decrease in the steering friction compensation torque Tsf becomes gentle. Therefore, compared to the case where the processing of steps 100 and 110 is not performed and the reversal of the increase/decrease of the steering friction compensation torque Tsf is started and ended stepwise, the driver feels uncomfortable due to the sudden change in the steering friction torque. can be reduced.

Also, in order to reduce the possibility that the driver will feel uncomfortable due to a sudden change in the steering friction torque, the steering friction compensation torque Tsf is increased or decreased as indicated by the two-dot chain line in the lower part of FIGS. It is conceivable to moderate the reversal of However, if the reversal of the increase or decrease in the steering friction compensating torque Tsf is moderated, it becomes difficult for the driver to feel the steering friction torque. unable to do so effectively.

According to the embodiment, the reversal of the increase/decrease in the steering friction compensation torque Tsf itself is not moderated, but the change at the start and end of the increase/decrease in the steering friction compensation torque Tsf is moderated. Therefore, it is possible to effectively promote and suppress the steering operation by means of the steering friction torque so that the driver can perform the steering operation appropriately, while reducing the possibility that the driver will feel uncomfortable due to the sudden change in the steering friction torque. can.

If the changes at the start and end of the increase/decrease in the steering friction compensating torque Tsf are moderated by the processing of steps 100 and 110, it seems that the reversal of the increase/decrease in the steering friction compensating torque Tsf is delayed. However, since the gradual change time Tg is a very short time of about 0.1 sec as described above, the driver does not feel any delay in reversing the increase or decrease of the steering friction compensation torque Tsf. The gradual change time Tg is set to 0.05 in order to prevent the driver from feeling a delay in reversing the increase or decrease in the steering friction compensation torque Tsf and to reduce the possibility of the driver feeling discomfort due to the sudden change in the steering friction torque. ~1.0 sec, and although it depends on the magnitude of the steering reaction torque TSre, it is particularly preferable to be between 0.1 and 0.5 sec.

Further, since the gradual change coefficient Gs varies between -1 and 1 as described above, the steering friction compensation torque Tsf calculated at step 100 as the product of the increasing/decreasing steering friction compensation torque Tsfbase and the gradual change coefficient Gs varies between -Tsfbase and Tsfbase, as shown in the lower part of FIGS. Therefore, the steering friction compensating torque Tsf is a value that satisfies the following inequality (6).
-Tsfbase≤Tsf≤Tsfbase (6)

<Comparison between spring force and frictional force>
Next, referring to FIGS. 7 to 14, as described in the above-mentioned Patent Document 1, the reaction force for steering assistance is given by a spring force, and according to the present invention, the reaction force for steering assistance is given by the frictional force. For ease of understanding, a model in which the driver 100 operates to move the mass body 102 corresponding to the steering shaft or the like along the friction plane 104 will be described. Friction force Fsf0 in FIG. 7 and the like is the friction force corresponding to the physical steering friction torque Tsf0 described above, and friction force Fsf is the friction force corresponding to the steering friction compensation torque Tsf.

<When the direction of the movement operation by the driver is the same as the movement direction of the driving support>
<P1> When the steering assist reaction force is given by spring force, as shown in FIG. When applying an operating force Fd to the body 102, a spring force Fs acts in a direction that promotes movement of the mass body 102. FIG. Therefore, the driver can easily move the mass body 102 to the target position with the assistance of the spring force Fs.

<P2> When the steering assist reaction force is given by frictional force As shown in FIG. When applying the operating force Fd to the body 102, a reduced frictional force Fsf corresponding to the reduced steering friction compensation torque Tsf acts. Therefore, although an assisting force such as the spring force Fs does not act, the driver can easily move the mass body 102 to the target position as compared with the case where the steering friction compensation torque Tsf is not reduced and the frictional force Fsf is not reduced. be able to.

<When the driver does not have the same operation intention as driving support movement>
<Q1> When the steering assist reaction force is given by a spring force As shown in FIG. No operating force Fd is applied to the body 102, but a spring force Fs acts in a direction that promotes the movement of the mass 102. Therefore, since the driver is pulled by the force Fs' corresponding to the difference between the spring force Fs and the frictional force Fsf0, it is inevitable that the driver will feel uncomfortable with the operation intervention by another person.

<Q2> When the steering assist reaction force is given by frictional force As shown in FIG. Since no operating force Fd is applied to the body 102, neither the friction force Fsf0 corresponding to the physical steering friction torque Tsf0 nor the friction force Fsf corresponding to the steering friction compensation torque Tsf acts. Also, the spring force Fs in the direction that promotes the movement of the mass body 102 does not act. Therefore, the driver does not feel uncomfortable with the operation intervention by the other person.

<When the driver tries to operate excessively>
<R1> When the steering assist reaction force is given by spring force As shown in FIG. gives an excessive operating force Fd to the mass body 102, the spring force Fs acts in a direction that hinders the movement of the mass body 102. FIG. Therefore, the driver receives the resistance of the spring force Fs, and is restrained from moving the mass body 102 beyond the target position.

<R2> When the steering assist reaction force is given by frictional force As shown in FIG. gives an excessive operating force Fd to the mass 102, the frictional force Fsf0 corresponding to the physical steering frictional torque Tsf0 in the direction that hinders the movement of the mass 102 and the increased steering friction compensating torque Tsf An increased frictional force Fsf acts. Therefore, the driver receives a high drag force Fsf0+Fsf, and is restrained from moving the mass body 102 beyond the target position.

<When the driver holds the steering wheel against steering assistance>
<S1> When the steering assist reaction force is given by a spring force As shown in FIG. When 100 holds mass 102, a spring force Fs acts to return mass 102 to its target position. Therefore, even though the driver does not attempt to move the mass 102, the driver must exert a force on the mass 102 that opposes the force Fs', which is the difference between the spring force Fs and the frictional force Fsf0. It is inevitable that the driver will feel a sense of incongruity due to intervention by another person.

<S2> When the steering assist reaction force is given by frictional force As shown in FIG. When the person 100 does not move the mass body 102, the friction force Fsf0 corresponding to the physical steering friction torque Tsf0 and the friction force Fsf corresponding to the steering friction compensation torque Tsf do not act. Also, the spring force Fs that tries to return the mass body 102 to the target position does not act. Therefore, the driver does not feel uncomfortable with the operation intervention by the other person.

As can be seen from the above description, when the reaction force for steering assistance is given by the spring force, depending on the situation, the driver may feel uncomfortable with the manipulation intervention by another person due to the spring force. On the other hand, when the reaction force for steering assistance is given by the frictional force according to the present invention, the driver does not feel unnecessary force, so the driver does not feel discomfort due to intervention by another person. can be avoided.

<Specific example of the relationship between the steering angle θ and the steering reaction torque Tsre felt by the driver>
Next, referring to FIGS. 15 to 20, various steering operations are performed by the driver in the embodiment, but when the basic target steering assist torque Tab is not given, the steering angle θ and the steering feeling felt by the driver are calculated. A relationship with the reaction force torque Tsre will be described. 15 to 20, the one-dot chain line indicates the steering torque Tsa caused by the self-aligning torque, and the two-dot chain line indicates the steering torque Tsa caused by the self-aligning torque and the physical steering friction torque Tsf0. The steering reaction force torque Tsre0f is shown when the steering friction compensation torque Tsf is 0. Furthermore, a thin solid line and a thin broken line indicate the steering reaction force torque Tsre when the steering friction compensation torque Tsf is Tsfbase and -Tsfbase, respectively.

<1> When the direction of the driver's steering operation is the same as the steering direction of the driving support (Fig. 15)
This is the steering operation corresponding to the above P2, in which the driver turns and steers so that the steering angle θ approaches the target steering angle θt. In FIG. 15, when the steering angle θ is smaller than the target steering angle θt, the steering reaction torque Tsre is Tsa+Tsf0−Tsfbase, as indicated by the thick solid-line arrow. . On the other hand, when the steering angle θ becomes larger than the target steering angle θt, the steering reaction force torque Tsre becomes Tsa+Tsf0+Tsfbase, which makes it difficult for the driver to turn the steering wheel.

As indicated by the thick dashed arrow in FIG. 15, when the driver attempts to turn back the steering angle θ away from the target steering angle θt, the steering reaction torque Tsre is Tsa−Tsf0− Tsfbase becomes a negative value, which is a drag torque against the return steering, so that it is difficult for the driver to perform the return steering. Therefore, it is possible to reduce the risk of the driver performing unnecessary steering.

<2> When the driver does not have the intention of steering operation similar to steering for driving support (Fig. 16)
This is the steering operation corresponding to the above Q2, in which the driver does not intend to turn the steering wheel so that the steering angle θ approaches the target steering angle θt. In FIG. 16, as indicated by black circles, the steering reaction torque Tsre is Tsa+Tsf0, and the steering angle θ and the steering reaction torque Tsre do not change. never.

As indicated by the thick dashed arrow in FIG. 16, when the driver attempts to turn the steering angle .theta. change as the case may be. This is the same even if the target steering angle θt changes, as indicated by the thick two-dot chain line in FIG. 16 .

Also, although not shown in the figure, when the reaction force of the steering support is given by the spring force as in <Q1> above, the driver is holding the steering wheel without any intention of steering operation. Also, a spring force acts on the steering wheel to bring the steering angle θ closer to the target steering angle θt. Therefore, the driver inevitably feels a sense of incompatibility due to the steering wheel being rotated against his or her will. Furthermore, if the driver holds the steering wheel to prevent it from rotating, the steering reaction torque will decrease, and in this case as well, the driver will inevitably feel uncomfortable.

<3> When the direction of the driver's steering operation is the same as the steering direction of the driving support (Fig. 17)
This is a steering operation opposite to that in <1> above, in which the driver turns back so that the steering angle θ approaches the target steering angle θt. In FIG. 17, when the steering angle θ is greater than the target steering angle θt, as indicated by the thick solid arrow, the steering friction compensation torque Tsf is −Tsfbase and is reduced, so the driver has to turn back. Easy to steer. On the other hand, when the steering angle .theta. becomes smaller than the target steering angle .theta.t, the steering friction compensation torque Tsf increases to Tsfbase, making it difficult for the driver to turn back.

<4> When the driver changes the steering torque within a predetermined range in a situation where the steering angle θ is the target steering angle θt (Fig. 18)
In a situation where the steering angle θ is the target steering angle θt, when the driver performs a steering operation within a predetermined range, the steering reaction force torque Tsre fluctuates within the range indicated by the double-headed arrow X in FIG. do. In this case, since the steering angle .theta. does not change, the steering angular velocity .theta.d is 0, and a negative determination is made in step 30 of the flow chart shown in FIG. Since the steering angle .theta. is the same as the target steering angle .theta.t, a negative determination is made at step 70, and the flag Fs is set to 1 at step 90. FIG. Therefore, the steering friction compensating torque Tsf is increased to Tsfbase, so unless the steering reaction force torque Tsre exceeds the range of Tsa-Tsf0-Tsfbase to Tsa+Tsf0+Tsfbase (predetermined range), the driver unconsciously changes the steering torque. The steering angle .theta. does not change to a value other than the target steering angle .theta.t.

On the other hand, in the case of the conventional power steering apparatus in which the steering friction compensation torque Tsf is not increased or decreased, as shown in FIG. The angle .theta. varies in the blur range indicated by the double-headed arrow Y. FIG. Note that this variation in the steering angle θ is not limited to steering held when the steering angle θ matches the target steering angle θt. It also occurs when

From a comparison of FIGS. 18 and 19, according to the embodiment, it is possible to reduce the risk of unnecessary fluctuations in the steering angle θ due to fluctuations in the driver's steering torque (steering-holding torque) when the steering is held. I understand what you can do.

<5> When the driver changes the steering torque beyond a predetermined range in a situation where the steering angle θ is the target steering angle θt (Fig. 20)
When the steering angle θ is equal to the target steering angle θt, when the driver changes the steering torque so that the steering reaction torque Tsre changes in a range Z exceeding the predetermined range X in FIG. As indicated by the thick arrow, the steering angle changes to a value other than the target steering angle θt. In other words, the steering angle changes even if the driver does not try to change the steering angle θ.

According to the embodiment, when the steering angle θ becomes larger than the target steering angle θt, the steering friction compensation torque Tsf is increased to Tsfbase, so that the driver steers in the direction in which the steering angle θ increases. I feel difficult. Further, when the steering direction changes to the steering-back direction, the steering angle θ becomes closer to the target steering angle θt, and the steering friction compensation torque Tsf is reduced to -Tsfbase. Feels easy to steer to. Therefore, even if the driver's steering torque (steering torque) fluctuates greatly when the steering is held, and the steering angle θ changes unnecessarily, it is possible to suppress unnecessary fluctuations in the steering angle θ. It is possible to make it easier for the driver to perform a steering operation so that the angle θ returns to the target steering angle θt.

<Effects of Embodiment>
As can be seen from the above description, according to the embodiment, when the change in the actual steering angle approaches the target steering angle, the steering friction compensation torque decreases, and the change in the actual steering angle moves away from the target steering angle. When there is a change, the steering friction compensation torque increases. Therefore, the steering operation that causes the actual steering angle to change closer to the target steering angle becomes easier, and the steering operation that causes the actual steering angle to move away from the target steering angle becomes difficult. Therefore, it is possible to encourage the driver to perform a steering operation so that the actual steering angle becomes the target steering angle, and suppress the driver's steering operation so that the actual steering angle becomes far from the target steering angle.

Further, even if there is a steering angle deviation in a situation where the driver does not intend to perform a steering operation, such as when the steering wheel is held, no steering friction compensation torque is generated unless the actual steering angle changes. Therefore, unlike the steering reaction force control device described in Japanese Patent Application Laid-Open No. 2002-200000, unnecessary steering reaction force torque that tends to bring the actual steering angle closer to the target steering angle does not act. Therefore, it is possible to prevent the driver from feeling a sense of incongruity as if he or she received steering intervention from another person due to unnecessary steering reaction torque.

Furthermore, in the case of the steering reaction force control device described in Patent Document 1, in a situation where the magnitude relationship between the actual steering angle and the target steering angle is reversed, the deviation between the actual steering angle and the target steering angle does not increase. and effective steering reaction force is not generated. Therefore, when the magnitude relationship between the actual steering angle and the target steering angle is reversed, the driver is encouraged to perform a steering operation so that the actual steering angle becomes the target steering angle, and the actual steering angle becomes the target steering angle. Therefore, it is not possible to effectively suppress the steering operation by the driver so as to move away from the vehicle.

In contrast, according to the embodiment, even if the magnitude relationship between the actual steering angle and the target steering angle is reversed, the deviation between the actual steering angle and the target steering angle is small as long as the driver is steering. However, the necessary steering friction compensating torque is generated. Therefore, when the magnitude relationship between the actual steering angle and the target steering angle is reversed, the driver is encouraged to perform a steering operation so that the actual steering angle becomes the target steering angle, and the actual steering angle becomes the target steering angle. It is possible to effectively suppress the steering operation by the driver so as to move away from the vehicle.

Furthermore, according to the embodiment, when the change in the actual steering angle approaches the target steering angle, the steering friction compensation torque is reduced, and when the change in the actual steering angle moves away from the target steering angle, the steering friction Compensating torque is increased. Therefore, it is necessary to promote both the driver's steering operation so that the actual steering angle becomes the target steering angle and to suppress the driver's steering operation so that the actual steering angle becomes far from the target steering angle. can be done. Therefore, the driver's steering operation can be promoted and suppressed more effectively than when only one of the reduction and increase of the steering friction compensating torque is performed.

Furthermore, according to the embodiment, when the increase/decrease in the steering friction compensation torque is reversed, the increase/decrease in the steering friction compensation torque is controlled so that the steering friction compensation torque gradually changes at the start and end of the increase/decrease. Therefore, compared to the case where the gradual change control of the steering friction compensating torque is not performed, it is possible to reduce the driver's sense of discomfort due to the stepped sudden change of the steering friction compensating torque. Furthermore, since the steering friction compensating torque is not controlled to gradually change from the start to the end of the increase or decrease, the driver cannot experience an effective steering reaction force. Ineffective suppression can be prevented.

Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

For example, in the above-described embodiment, the steering friction compensation torque is reduced when the actual change in the steering angle approaches the target steering angle, and when the actual change in the steering angle moves away from the target steering angle, the steering torque is reduced. Friction compensation torque is increased. However, it may be modified so that only one of the reduction and increase of the steering friction compensation torque is performed.

In the above-described embodiment, when the increase/decrease in the steering friction compensating torque reverses, the increase/decrease in the steering friction compensating torque is controlled so that the steering friction compensating torque gradually changes at the start and end of the increase/decrease. However, the gradual change control of the steering friction compensation torque at the start and end of the increase/decrease of the steering friction compensation torque may be omitted when the increase/decrease of the steering friction compensation torque is reversed.

In the above-described embodiment, it is determined in step 30 whether or not the time differential value θd of the steering angle θ is positive, and in steps 40 and 70 it is determined whether the steering angle θ is greater than the target steering angle θt. A determination is made as to whether or not. is greater than the target steering angle .theta.t, and in steps 40 and 70 it is determined whether the time differential value .theta.d of the steering angle .theta. may

Furthermore, in the above-described embodiment, in steps 120 and 130, the steering assist torque Ta is controlled to become the final target steering assist torque Tat, which is the sum of the basic target steering assist torque Tab and the steering friction compensation torque Tsf. . However, the final target steering assist torque Tat may include damping compensation torque and/or inertia compensation torque known in the art.

Further, in the above-described embodiment, in step 20, based on the information in front of the vehicle acquired by the CCD camera 58, the driving lane is identified in a manner known in the art, and the vehicle is driven along the driving lane. A target steering angle θt for running is calculated. However, the target steering angle θt is calculated by another electronic control device, and the electronic control device 24 obtains the target steering angle θt by receiving a signal indicating the target steering angle θt from the electronic control device. good too.

DESCRIPTION OF SYMBOLS 10... Steering reaction force torque control apparatus, 12... Steering apparatus, 14... Vehicle, 16... Steering wheel, 18L, 18R... Front wheel, 20... Transmission apparatus, 22... Electric power steering apparatus, 24... Electronic control apparatus, 52... Steering Angle sensor 54 Torque sensor 56 Vehicle speed sensor 58 CCD camera

Claims (1)

A steering reaction force torque control device for a vehicle, including an electric power steering device configured to generate a steering reaction torque when a driver operates a steering wheel, and a control device for controlling the electric power steering device. in
The control device acquires information on the actual steering angle and the target steering angle for the vehicle to run along the lane,
The steering friction compensation torque decreases when the change in the actual steering angle approaches the target steering angle, and the steering friction compensation torque decreases when the change in the actual steering angle moves away from the target steering angle. A steering reaction torque control device for a vehicle configured to control a steering friction compensating torque as a steering reaction torque of the electric power steering device so as to achieve at least one of increasing.

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