JP4372627B2 - Reaction force control device - Google Patents

Description

  The present invention relates to a reaction force control device that controls a reaction force component to be applied to an operator in a vehicle steering system.

  An electric power steering device is known as a vehicle steering device. In the electric power steering apparatus, a steering shaft coupled to a steering wheel and a steering mechanism that steers the steered wheels are mechanically coupled, and an electric motor for assisting a steering force is linked to the steering mechanism. In general, the drive torque command value (drive current value) of the electric motor is controlled such that the auxiliary steering force increases as the steering torque acting on the steering shaft increases.

  Further, in this electric power steering device, in order to suppress the irregular behavior of the vehicle due to disturbance, the vehicle behavior is detected from the yaw rate and the lateral acceleration, and the driving torque correction value in the direction to cancel the vehicle behavior is calculated, Some control the electric motor by subtracting the drive torque correction value from a base drive torque command value set according to the steering torque to obtain a drive torque command value (see, for example, Patent Document 1). In such a configuration, even when yaw rate or lateral acceleration occurs during normal turning, for example, a drive torque correction value is generated in a direction to suppress these, that is, in a direction to return the vehicle to a straight traveling state. Therefore, it can be said that the drive torque correction value is a reaction force component with respect to the assist force.

When the reaction force component is controlled based on the yaw rate information and the lateral acceleration information as described above, in general, the driving torque correction value (reaction force component) is controlled to increase as the yaw rate increases, and the lateral acceleration increases. The driving torque correction value (reaction force component) is controlled so as to increase. In other words, the drive torque control of the electric motor is performed so that the auxiliary steering force by the electric motor decreases as the yaw rate and the lateral acceleration increase. This maintains the stability of steering when the yaw rate and lateral acceleration are large.
Japanese Patent No. 3110891

By the way, conventionally, after calculating separately the driving torque correction value (reaction force component) based on the yaw rate information and the driving torque correction value (reaction force component) based on the lateral acceleration information, they are added together, and the driving torque after the addition is calculated. The drive torque of the electric motor is controlled based on the correction value.
However, with such a control system, maps and tables corresponding to the yaw rate information and lateral acceleration information must be prepared, which is not only cumbersome, but also increases the amount of calculation and complicates the control. .
In addition, since there is a correlation between the yaw rate and the lateral acceleration, the map and table must be created in consideration of this correlation in order to achieve optimal control, and tuning is extremely complicated. It was.
Therefore, the present invention creates a composite signal based on the yaw rate information and the lateral acceleration information, and sets the reaction force component based on the composite signal, thereby enabling optimal reaction force control and simplifying the control system. The present invention provides a reaction force control device capable of satisfying the requirements.

In order to solve the above-mentioned problems, the invention according to claim 1 is directed to an operating element (for example, an implementation to be described later) mechanically coupled to a steering mechanism (for example, a tack shaft 7 and a tie rod 8 in an embodiment to be described later). In this embodiment, a correction current corresponding to the reaction force component is subtracted from a base current determined based on the steering torque and the vehicle speed input to the steering wheel 3), and an auxiliary steering force supply motor (for example, described later). In the reaction force control device that controls the correction current when calculating the target current for the electric motor 10 in the embodiment , the yaw rate detection means for detecting the yaw rate of the vehicle (for example, the yaw rate sensor 18 in the embodiment described later). ), A lateral acceleration detecting means for detecting the lateral acceleration of the vehicle (for example, a lateral acceleration sensor 17 in an embodiment described later), Based on vehicle speed detection means for detecting the vehicle speed of the vehicle (for example, a vehicle speed sensor 19 in an embodiment described later), a detection value of the yaw rate detection means, and a detection value of the lateral acceleration detection means, the lower the vehicle speed, the higher the yaw rate. The composite signal is created so that the contribution rate of the lateral acceleration increases as the vehicle speed increases and the vehicle speed increases, and the reaction force component is set to zero when the reaction force component is set based on the composite signal A reaction force component control means (for example, implementation described later ) has a dead band of a synthesized signal, and the dead zone is set to be smaller as the vehicle speed is higher, and in a region beyond the dead zone, the reaction force component is set to be larger as the synthesized signal is larger. the reaction force correction portion 33) in the form of the correction current calculating means for calculating the correction current corresponding to the reaction force set by the reaction force control means (e.g., to be described later A correction current table 39) in the embodiment is characterized in that it comprises.
With this configuration, a larger reaction force component can be set as the combined signal is larger based on the combined signal of yaw rate information and lateral acceleration information. Moreover, the reaction force component can be set by placing more weight on the yaw rate as the vehicle speed is lower, and can be set by placing more weight on the lateral acceleration as the vehicle speed is higher.

In addition, since the dead zone of the composite signal is set to be smaller as the vehicle speed increases, it is possible to generate a reaction force component from a relatively low composite signal at a high vehicle speed, and a relatively low composite signal at a low vehicle speed. It becomes possible to suppress generation | occurrence | production of the reaction force component until it becomes large.

  According to the first aspect of the invention, the reaction force component can be set based on the combined signal of the yaw rate information and the lateral acceleration information, so that tuning is facilitated and the amount of calculation can be reduced. There is an effect that the control system can be simplified. In addition, the reaction force component can be set by placing more weight on the yaw rate at lower vehicle speeds, and the reaction force component can be set by placing more emphasis on lateral acceleration at higher vehicle speeds, so a wide range of vehicle speeds from low to high vehicle speeds. It is possible to execute the optimum reaction force control for the vehicle behavior in the region.

Further, the generation of the reaction force component can be adjusted according to the vehicle speed, and in particular, the steering stability at high vehicle speed is improved.

Embodiments of the reaction force control apparatus according to the present invention will be described below with reference to the drawings of FIGS. In the following embodiments, the present invention will be described in an aspect applied to an electric power steering device.
First, the configuration of the electric power steering apparatus will be described with reference to FIG. The electric power steering apparatus includes a manual steering force generating mechanism 1, and the manual steering force generating mechanism 1 includes a connecting shaft 5 in which a steering shaft 4 integrally coupled to a steering wheel (operator) 3 has a universal joint. And is connected to the pinion 6 of the rack and pinion mechanism. The pinion 6 meshes with a rack 7a of a rack shaft 7 that can reciprocate in the vehicle width direction, and left and right front wheels 9, 9 as steered wheels are connected to both ends of the rack shaft 7 via tie rods 8, 8. ing. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 3 is steered, and the direction of the vehicle can be changed by turning the front wheels 9 and 9. The rack shaft 7 and the tie rods 8 and 8 constitute a steering mechanism.

  An electric motor 10 that supplies auxiliary steering force for reducing the steering force generated by the manual steering force generation mechanism 1 is disposed on the same axis as the rack shaft 7. The auxiliary steering force supplied by the electric motor 10 is converted into thrust through a ball screw mechanism 12 provided substantially parallel to the rack shaft 7 and is applied to the rack shaft 7. For this purpose, a drive-side helical gear 11 is integrally provided on the rotor of the electric motor 10 through which the rack shaft 7 is inserted, and a driven-side helical gear 13 that meshes with the drive-side helical gear 11 is provided at one end of the screw shaft 12 a of the ball screw mechanism 12. The nut 14 of the ball screw mechanism 12 is fixed to the rack 7.

The steering shaft 4 is provided with a steering speed sensor 15 for detecting the steering speed (angular speed) of the steering shaft 4, and is provided in a steering gear box (not shown) that houses the rack and pinion mechanism (6, 7a). Is provided with a steering torque sensor (steering torque detecting means) 16 for detecting a steering torque acting on the pinion 6. The steering speed sensor 15 outputs an electrical signal corresponding to the detected steering speed, and the steering torque sensor 16 outputs an electrical signal corresponding to the detected steering torque to the steering control device 20, respectively.
Further, at an appropriate position of the vehicle body, a lateral acceleration sensor (lateral acceleration detecting means) 17 for detecting the lateral acceleration of the vehicle, a yaw rate sensor (yaw rate detecting means) 18 for detecting the yaw rate of the vehicle, and the vehicle speed are supported. A vehicle speed sensor (vehicle speed detection means) 19 for outputting the electrical signal is attached. The lateral acceleration sensor 17 outputs an electrical signal corresponding to the detected lateral acceleration, the yaw rate sensor 18 outputs an electrical signal corresponding to the detected yaw rate, and the vehicle speed sensor 19 outputs an electrical signal corresponding to the vehicle speed to the steering control device 20, respectively. . In this embodiment, the output signal of the lateral acceleration sensor 17 and the output signal of the yaw rate sensor 18 are the same type of electrical signal (for example, a current signal).

  The steering control device 20 determines a target current to be supplied to the electric motor 10 based on a control signal obtained by processing the input signals from these sensors 15 to 19, and supplies the electric current to the electric motor 10 via the drive circuit 21. Thus, the output torque of the electric motor 10 is controlled to control the auxiliary steering force in the steering operation.

Next, with reference to the control block diagram of FIG. 2, the current control for the electric motor 10 in this embodiment will be described.
The steering control device 20 includes a base current determination unit 31, an inertia correction unit 32, and a reaction force correction unit (reaction force component control means) 33.
The base current determination unit 31 determines a base current value corresponding to the steering torque and the vehicle speed with reference to a base current table (not shown) based on the output signals of the steering torque sensor 16 and the vehicle speed sensor 19. Here, the base current table is set so that the base current increases as the steering torque increases, and the base current decreases as the vehicle speed increases.
In the inertia correction unit 32, inertia mass compensation of the electric motor 10 is performed on the base current determined by the base current determination unit 31.

The reaction force correction unit 33 subtracts a correction current corresponding to the reaction force component from the current after inertia mass compensation, calculates a target current for the electric motor 10, and outputs the target current to the drive circuit 21. The drive circuit 21 controls the supply current to the electric motor 10 to be a target current, supplies the electric current to the electric motor 10, and controls the output torque of the electric motor 10.
Therefore, in the electric power steering apparatus of this embodiment, the correction current set in the reaction force correction unit 33 can be referred to as a reaction force component for the steering assist force, and the base current set in the base current determination unit 31 is this It can be said that the steering assist force before canceling the reaction force component.
The reaction force correction unit 33 includes a damper correction unit 34 and a vehicle behavior reaction force correction unit 35.
The damper correction unit 34 calculates a first reaction force correction current based on the steering speed, and subtracts the first reaction force correction current from the current after the inertial mass compensation.

The vehicle behavior reaction force correction unit 35 calculates the second reaction force correction current Im2 based on the vehicle behavior, and subtracts the second reaction force correction current Im2 from the current output from the damper correction unit 34 to obtain the target current. calculate.
In this embodiment, the vehicle behavior is detected from the lateral acceleration and the yaw rate, and the vehicle behavior reaction force correction unit 35 basically converts the lateral acceleration detected by the lateral acceleration sensor 17 and the yaw rate detected by the yaw rate sensor 18. Based on this, the second reaction force correction current Im2 is calculated. Hereinafter, calculation of the second reaction force correction current Im2 in the vehicle behavior reaction force correction unit 35 will be described in detail.

  The vehicle behavior reaction force correction unit 35 generates a composite signal y corresponding to the vehicle speed based on the output signals of the lateral acceleration sensor 17 and the yaw rate sensor 18 in the composite signal calculation unit (composite signal calculation means) 36. That is, first, based on the output signal of the vehicle speed sensor 19, the composite ratio Km corresponding to the vehicle speed is calculated with reference to the vehicle speed / composite ratio map 37. Here, the vehicle speed / combination ratio map 37 is constant at a predetermined positive value when the vehicle speed is equal to or lower than the predetermined vehicle speed. When the vehicle speed exceeds the predetermined vehicle speed, the composite ratio Km gradually decreases as the vehicle speed increases. It is set to go. However, the maximum value of the synthesis ratio is set to “1.0” or less.

Then, the product (γ · Km) obtained by multiplying the output signal γ of the yaw rate sensor 18 by the composite ratio Km calculated from the vehicle speed / composite ratio map 37 and the output signal Lg of the lateral acceleration sensor 17 are “1”. The product {Lg · (1−Km)} obtained by multiplying the complement (1−Km) of the composition ratio Km with respect to is added to obtain a composite signal y.
y = (γ · Km) + {Lg · (1−Km)} (1)

In the composite signal y calculated in this way, the contribution rate of the yaw rate increases and the contribution rate of lateral acceleration decreases as the vehicle speed decreases, and the contribution rate of lateral acceleration increases and the contribution rate of lateral acceleration increases as the vehicle speed increases. And the sum of the contribution rate of the yaw rate and the contribution rate of the lateral acceleration is always “1”.
The reason why the contribution rate of the lateral acceleration and the yaw rate to the composite signal y is made variable according to the vehicle speed is based on the control rate for the vehicle motion (vehicle behavior), and this control rate is compared between the lateral acceleration and the yaw rate. Then, when the vehicle speed is low, the yaw rate has a higher control rate than the lateral acceleration, and when the vehicle speed is high, the lateral acceleration has a higher control rate than the yaw rate. This is because the yaw rate gain decreases from a certain vehicle speed as the vehicle speed increases, but the lateral acceleration always increases. Moreover, the fact that the phase delay of the yaw rate increases as the vehicle speed increases is one of the reasons why the contribution rate of the yaw rate decreases as the vehicle speed increases.
In this embodiment, the sum of the contribution rate of the lateral acceleration and the yaw rate is always set to “1” to simplify the control. However, the contribution of the lateral acceleration and the yaw rate according to the concept of the control rate as described above. As long as the rate is variable, the method of calculating the composite signal is not limited to the above equation (1).

Further, the vehicle behavior reaction force correction unit 35 refers to the offset table 38 based on the output signal of the vehicle speed sensor 19 and calculates an offset amount corresponding to the vehicle speed. In the offset table 38, the offset amount is constant at a predetermined positive value in a region where the vehicle speed is low, and when the vehicle speed exceeds the predetermined vehicle speed, the offset amount gradually decreases as the vehicle speed increases, and finally becomes “0”. It is set to be.
Then, the vehicle behavior reaction force correction unit 35 subtracts the offset amount calculated by the offset table 38 from the composite signal y calculated by the composite signal calculation unit 36, and based on the difference signal y ′, the correction current table 39. , Reference correction current (in other words, reference reaction force component) Imb is calculated. When the difference signal y ′ becomes negative, the difference signal y ′ is set to “0”.
Here, the correction current table 39 indicates that the reference correction current Imb is set to “0” when the difference signal y ′ is “0”, and the reference correction current Imb gradually increases as the difference signal y ′ increases. The reference correction current Imb is set to be constant at the upper limit value when the difference signal y ′ becomes greater than or equal to a predetermined value.

The reason why the reference correction current Imb is calculated based on the difference signal y ′ obtained by subtracting the offset amount from the combined signal y created by the combined signal calculator 36 is as follows.
According to the offset table 38, the offset amount is “0” when the vehicle speed is high, and therefore the synthesized signal y and the difference signal y ′ are equal. In this case, the correction current characteristic having the horizontal axis as the combined signal y is as shown in FIG. 3A, that is, the same as the correction current table 39.
On the other hand, since a positive offset amount is set in a region where the vehicle speed is low, the difference signal y ′ is held at “0” until the composite signal y created by the composite signal calculation unit 36 exceeds the offset amount. . In this case, the correction current characteristic having the horizontal axis as the composite signal y is as shown in FIG. 3B, and the reference correction current Imb is set to “0” while the difference signal is “0”. . That is, in the composite signal region where the composite signal y created by the composite signal calculation unit 36 is equal to or less than the offset amount (hereinafter, this region is referred to as a dead zone), the reference correction current Imb (reference reaction force component) is set to “0”. Is set. In the offset table 38, the offset amount decreases as the vehicle speed increases. Therefore, the dead zone decreases as the vehicle speed increases. In the case of the corrected current characteristic diagram shown in FIG. 3A, it can be considered that the dead zone becomes zero.
By making the dead zone variable in accordance with the vehicle speed in this way, it becomes possible to generate a reaction force component at a high vehicle speed from when the composite signal y generated by the composite signal calculation unit 36 is relatively small. Since the generation of the reaction force component can be suppressed until the combined signal y becomes relatively large at the vehicle speed, it is possible to reliably suppress the irregular behavior of the vehicle that is likely to occur as the vehicle speed increases. As a result, the steering stability at high vehicle speed can be improved.

Next, the vehicle behavior reaction force correction unit 35 refers to the vehicle speed ratio table 40 based on the output signal of the vehicle speed sensor 19 and calculates a ratio (amplification factor) R corresponding to the vehicle speed.
Here, in the vehicle speed ratio table 40, when the vehicle speed is “0”, the ratio R is set to “0”, and as the vehicle speed increases, the ratio R gradually increases so that the vehicle speed is equal to or higher than a predetermined value. Then, the ratio R is set to be constant at the upper limit value.
A product (Imb · R) obtained by multiplying the reference correction current Imb calculated by the correction current table 39 by the ratio R calculated from the vehicle speed ratio table 40 is defined as a second reaction force correction current Im2 (Im2 = Imb).・ R).
Since the ratio R is set to increase as the vehicle speed increases and the second reaction force correction current Im2 is set by multiplying the ratio R by the reference correction current Imb, the comparison is made when the magnitude of the composite signal y is the same. The higher the vehicle speed, the greater the reaction force component can be generated, and the higher the vehicle speed, the more likely the irregular behavior of the vehicle can be reliably suppressed, making it ideal for a wide range of vehicle speeds from low to high vehicle speeds. As a result, irregular behavior can be appropriately suppressed in a wide range of vehicle speeds.

  As described above, according to the reaction force control device of this embodiment, the composite signal y is created based on the output signal (detection value) of the yaw rate sensor 18 and the output signal (detection value) of the lateral acceleration sensor 17, Basically, since the second reaction force correction current (reaction force component) Im2 is set based on the composite signal y, tuning is facilitated, and the calculation amount can be reduced as compared with the conventional method. The steering control system can be simplified as compared with the prior art. In addition, since the second reaction force correction current Im2 can be set larger as the composite signal y is larger, a larger reaction force component is generated and the auxiliary steering force is reduced as the lateral acceleration and yaw rate are larger. This makes it possible to maintain steering stability.

In addition, the contribution rate of the lateral acceleration and the yaw rate to the composite signal y is made variable according to the vehicle speed, the contribution rate of the yaw rate is increased and the contribution rate of the lateral acceleration is reduced as the vehicle speed is lower, and the contribution of lateral acceleration is increased as the vehicle speed is higher. Since the contribution rate of the yaw rate is reduced by increasing the rate, it is possible to set the reaction force component by placing more weight on the yaw rate at lower vehicle speeds and setting the reaction force component by placing more weight on the lateral acceleration at higher vehicle speeds. It is possible to perform optimal reaction force control for vehicle behavior in a wide range of vehicle speeds from low vehicle speeds to high vehicle speeds.
In particular, in this embodiment, the dead zone is made variable according to the vehicle speed, and the ratio R is made variable according to the vehicle speed, so that further optimization of the reaction force control is realized in a wide range of vehicle speeds from a low vehicle speed to a high vehicle speed. In addition, it is possible to achieve good steering feeling and suppression of irregular behavior of the vehicle.

  In this embodiment, the same applies when the steering wheel 3 is turned in one direction (for example, the right turning direction) (forward direction) and when the steering wheel 3 is turned back and turned (return direction) thereafter. Although the correction current table 39 is used, a correction current table is prepared separately for each of the forward direction and the return direction of the steering wheel 3, and the correction current table is changed according to the state of the steering operation to change the reference correction current table. It is also possible to calculate Imb. The same applies to the vehicle speed ratio table 40. It is also possible to calculate the ratio R by changing the vehicle speed ratio table for the forward direction and the return direction according to the state of the steering operation. In this way, the steering feeling can be further improved.

Ratio treatment with vehicle speed ratio table 40 described above is not name an essential configuration in reaction force control apparatus according to the present invention.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, the reaction force control device in accordance with the present invention, rather than limited to the application to the electric power steering apparatus of the above-described embodiments, the vehicle steering system of active steering systems, variable gear ratio steering in-vehicle steering system of the system (VGS) Ru applicable der.
Your name, the active steering system, a steering system to be controlled in accordance with the front wheel steering angle and the rear wheel steering angle to the movement state of the steering operation and the driver of the vehicle.
The variable gear ratio steering system is a steering system in which the steering gear ratio can be changed according to the magnitude of the steering angle.

It is a lineblock diagram of an electric power steering device provided with a reaction force control device concerning this invention. It is a block diagram of the current control with respect to the electric motor of an electric power steering device. It is a correction current characteristic diagram at the time of high vehicle speed and low vehicle speed.

Explanation of symbols

3 Steering wheel (operator)
17 Lateral acceleration sensor (lateral acceleration detection means)
18 Yaw rate sensor (yaw rate detection means)
19 Vehicle speed sensor (vehicle speed detection means)
33 reaction force correction unit (reaction force component control means)

Claims (1)

A motor for supplying an auxiliary steering force by subtracting a correction current corresponding to a reaction force component from a base current determined based on a steering torque and a vehicle speed inputted to an operator mechanically connected to a steering mechanism. In the reaction force control device for controlling the correction current when calculating the target current for
Yaw rate detection means for detecting the yaw rate of the vehicle;
Lateral acceleration detecting means for detecting lateral acceleration of the vehicle;
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Based on the detection value of the yaw rate detection means and the detection value of the lateral acceleration detection means, a composite signal is created so that the contribution rate of the yaw rate increases as the vehicle speed decreases and the contribution rate of the lateral acceleration increases as the vehicle speed increases, When setting the reaction force component based on the composite signal, there is a dead band of the composite signal that sets the reaction force component to zero, and the dead zone is set to be smaller as the vehicle speed is larger, and is a region beyond the dead zone. Then, the reaction force component control means for setting the reaction force component larger as the composite signal is larger,
Correction current calculation means for calculating the correction current according to the reaction force component set by the reaction force component control means;
A reaction force control device comprising:

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