JP2017105351A - Vehicular steering support apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular steering support apparatus with the stability of steering improved in comparison with the conventional techniques, when a driver performs steering with steering-wheel grip force reduced, the apparatus performing an inertia compensation in inertia compensation assist torque.SOLUTION: A vehicular steering support apparatus includes: an electric power steering device; and a control device for computing target control current It on the basis of target steering assist torque Tat that includes basic target steering assist torque Tab based on steering torque and target inertia compensation assist torque Tai based on steering angular acceleration ddθ and inertia moment I such as a steering wheel (S180, S200) and controlling the electric power steering device with the target control current (S220). If a steering operation is the operation with steering-wheel grip force reduced, the control device reduces the inertia moment I (S20).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle steering assist device that assists steering by adjusting a steering assist torque.

  A vehicle such as an automobile is generally equipped with a steering assist device that assists steering by adjusting a steering assist torque generated by the electric power steering device. It is desirable that this type of steering assist device not only reduce the driver's steering load, but also improve the driver's steering feeling.

  For example, as described in Patent Document 1 below, it is already known to calculate a target steering assist torque so as to include a target inertia compensation assist torque in addition to a basic target steering assist torque based on the steering torque. . The target inertia compensation assist torque is a target assist torque for reducing the influence of the inertial force of the steering wheel or the like on the force necessary for the driver's steering operation, and is the product of the inertial moment of the steering wheel and the steering angular acceleration. Is calculated based on

JP-A-9-58492

[Problems to be Solved by the Invention]
According to the steering assist device that performs inertia compensation using the target inertia compensation assist torque, it is possible to reduce the degree to which the force due to the inertia of the steering wheel or the like hinders the smooth steering operation of the driver. Therefore, even in a vehicle in which the mass of the steering wheel is large due to an airbag device or the like, the driver's steering feeling can be improved as compared with the case where inertia compensation is not performed.

  When steering operation is performed, part of the driver's upper limb also rotates with the steering wheel, so the moment of inertia used to calculate the target inertia compensation assist torque is not only for the steering wheel but also for the driver's upper limb. It is preferred that the value be considered. The actual moment of inertia varies depending on the gripping state of the driver with respect to the steering wheel. For example, when the steering wheel is rotated by the force received by the steering wheel from the road surface (in the case of reverse input of steering energy) and the rotation direction of the steering wheel is the direction desired by the driver, driving The person reduces the gripping force on the steering wheel. Reducing the gripping force with respect to the steering wheel is referred to as extraction, and the actual moment of inertia decreases when the driver performs extraction steering.

  However, in the conventional steering assist device, since it is not considered that the actual moment of inertia when the driver performs the heavy duty steering is reduced, when the heavy duty steering is performed, the magnitude of the target inertia compensation assist torque is reduced. Become excessive. Accordingly, steering acceleration / deceleration may be induced due to excessive inertia compensation assist torque, and steering stability may be reduced.

  Note that, in the steering assist device described in Patent Document 1, when the input of the steering energy is a reverse input, the inertia compensation by the target inertia compensation assist torque is not performed. Therefore, when steering is performed in a situation where the steering energy is reversely input, the steering feeling cannot be improved by inertia compensation.

  A main problem of the present invention is a steering assist device that performs inertia compensation by inertia compensation assist torque, and the steering assist device in which the stability of steering when a driver performs heavy duty steering is improved as compared with the prior art. Is to provide.

[Means for Solving the Problems and Effects of the Invention]
According to the present invention, a steering torque detection device that detects steering torque, a steering operation amount acquisition device that acquires at least information on steering angular acceleration as a steering operation amount of a driver, and a steering assist torque according to a control current are generated. And calculating a basic target steering assist torque based on the steering torque, and a target inertia compensation assist torque based on a product of at least the inertial moment of the steering wheel and the upper limb of the driver and the steering angular acceleration. A vehicle having a control device that calculates a target control current of an electric power steering device based on a target steering assist torque including a steering assist torque and a target inertia compensation assist torque, and controls the electric power steering device with the target control current A steering assist device is provided.

  The steering operation amount acquisition device acquires information on the steering angular velocity, and the control device determines the state of the driver's steering operation based on the steering torque and the steering angular velocity, and determines that the driver's steering operation is degenerative steering. In some cases, the calculation mode of the target control current is corrected so that the target control current becomes a value calculated by reducing the moment of inertia as compared with the case where it is determined that the driver's steering operation is not the heavy duty steering.

  As will be described in detail later, it is possible to determine whether or not the driver's steering operation is a heavy steering based on the steering torque and the steering angular velocity. According to the above configuration, when it is determined that the driver's steering operation is the heavy duty steering, the target control current has the moment of inertia compared to when the driver's steering operation is determined not to be the heavy duty steering. The calculation mode of the target control current is corrected so that the calculated value becomes smaller.

  Therefore, when the pulling steering is performed, the target control current becomes a value calculated by using the inertia moment reduced in accordance with the actual decrease of the inertia moment due to the pulling. Therefore, compared with the case where the calculation mode of the target control current is not corrected even when the heavy duty steering is performed, the possibility that the magnitude of the inertia compensation assist torque becomes excessive is reduced, and the steering is added by the excessive inertia compensation assist torque. It is possible to reduce a possibility that the deceleration is induced and the steering stability is lowered.

  In addition, even if heavy duty steering is performed, inertia compensation by target inertia compensation assist torque is performed. Therefore, when the input of the steering energy is a reverse input, unlike the steering assist device described in Patent Document 1 in which the inertia compensation by the target inertia compensation assist torque is not performed, the steering fee by the inertia compensation is used. The ring can be improved.

[Aspect of the Invention]
In one aspect of the present invention, the control device is any one of the reduction of the moment of inertia, the reduction of the magnitude of the target inertia compensation assist torque, and the reduction of the current component corresponding to the target inertia compensation assist torque of the target control current. Thus, the calculation mode of the target control current is corrected.

  According to the above aspect, any one of reduction of the moment of inertia, reduction of the magnitude of the target inertia compensation assist torque, and reduction of the current component corresponding to the target inertia compensation assist torque among the target control current is performed. According to the reduction of the inertia moment, the magnitude of the target inertia compensation assist torque calculated based on the product of the inertia moment and the steering angular acceleration can be reduced, so that the inertia controlled based on the target inertia compensation assist torque is reduced. The possibility that the magnitude of the compensation assist torque becomes excessive can be reduced. According to the reduction of the magnitude of the target inertia compensation assist torque, it is possible to reduce the possibility that the magnitude of the inertia compensation assist torque controlled based on the target inertia compensation assist torque becomes excessive. Furthermore, according to the reduction of the current component corresponding to the target inertia compensation assist torque in the target control current, the magnitude of the inertia compensation assist torque generated by the current component corresponding to the target inertia compensation assist torque is reduced, and the inertia compensation is performed. The possibility that the magnitude of the assist torque becomes excessive can be reduced.

  In one aspect of the present invention, in the situation where the calculation mode of the target control current is being corrected, the control operation of the driver is acceleration / deceleration switchback steering based on the steering angular velocity and the steering angular acceleration. Is determined, the target control current is corrected with a correction amount based on the product of the moment of inertia, the steering angular velocity, and the steering angular acceleration, thereby suppressing fluctuations in the steering angular velocity. The acceleration / deceleration switchback steering is switchback steering in which the steering angular velocity increases or decreases.

  In a situation where the driver's steering operation is heavy steering, if the magnitude of the inertia compensation assist torque is reduced, the steering wheel is easily rotated by the force received by the steering wheel from the road surface. In particular, when the driver's steering operation is acceleration / deceleration switchback steering, the self-aligning torque acts, so the steering angular velocity is likely to fluctuate. Further, as described in detail later, the product of the moment of inertia, the steering angular velocity, and the steering angular acceleration represents the driver's steering intensity, and by correcting the target control current with a correction amount based on this product, The fluctuation of the steering angular velocity during acceleration / deceleration return steering can be suppressed.

  According to the above aspect, when it is determined that the steering operation of the driver is acceleration / deceleration switching steering in a situation where the calculation mode of the target control current is corrected, the inertia moment, the steering angular velocity, and the steering angular acceleration are determined. By correcting the target control current with the correction amount based on the product, fluctuations in the steering angular velocity are suppressed.

  Therefore, in a situation where the calculation mode of the target control current is corrected and the magnitude of the inertia compensation assist torque is reduced, the steering angular velocity is reduced due to the steering wheel being rotated by the force that the steering wheel receives from the road surface. The possibility of fluctuations can be reduced.

  In yet another embodiment of the present invention, the control device calculates the moment of inertia as a sum of at least a first moment of inertia based on the mass of the steering wheel and a second moment of inertia based on the mass of the driver's upper limb. When it is calculated and it is determined that the driver's steering operation is the heavy duty steering, the second moment of inertia is reduced to zero.

  According to the above aspect, when it is determined that the driver's steering operation is the heavy duty steering, the second moment of inertia is reduced to 0, so that the moment of inertia used for the calculation of the target inertia compensation assist torque can be ensured. Can be made smaller.

  The upper limbs may be the left and right upper limbs of a driver with a standard physique, and the mass of the upper limbs is not the mass of the entire upper limbs, but the part that rotates with the steering wheel, for example, the arm part beyond the hand and elbow Mass.

  In yet another aspect of the present invention, a setting device is provided for variably setting a correction coefficient for the second moment of inertia operated by a vehicle occupant. If it is determined that the inertia moment is not, the moment of inertia is calculated as the sum of the first moment of inertia and the product of the correction coefficient and the second moment of inertia.

  According to the above aspect, when it is determined that the driver's steering operation is not heavy duty steering, the moment of inertia is calculated as the sum of the first moment of inertia and the product of the correction coefficient and the second moment of inertia. The occupant can variably set the moment of inertia used for the calculation of the target inertia compensation assist torque based on his / her intention.

It is a figure showing the outline of the steering assistance device for vehicles concerning a first embodiment of the present invention. It is a flowchart which shows the steering assist torque control routine in 1st embodiment. It is a flowchart which shows the subroutine of an inertia moment setting in 1st embodiment. It is a flowchart which shows the steering assist torque control routine in 2nd embodiment. 10 is a flowchart illustrating a steering assist torque control routine in a third embodiment with a part thereof omitted. 7 is a map for calculating a target basic steering assist torque Tab based on the steering torque T and the vehicle speed V. 7 is a map for calculating a target inertia compensation steering assist torque Tai based on a product I * ddθ of a steering wheel inertia moment I and a steering angular acceleration ddθ and a vehicle speed V. FIG. 5 is a map for calculating a gain G of feedback control of a control current based on an absolute value of a product I * dθ * ddθ of an inertia moment I, a steering angular velocity dθ, and a steering angular acceleration ddθ of a steering wheel. It is a map used when calculating a correction coefficient K1 for reducing the magnitude of the target inertia compensation assist torque Tai based on the absolute value of the steering angular velocity dθ. In the third embodiment, the map is used when calculating a correction coefficient K3 for reducing the magnitude of the inertia compensation control current Iai based on the absolute value of the steering angular velocity dθ. In the first embodiment, the map is used when calculating a coefficient β for setting the moment of inertia I. The steering angle θ, the steering angular velocity dθ, and the steering angular acceleration are performed when the steering operation is performed after the vehicle is turned up in the right turn direction and then turned back and then turned back in the left turn direction of the vehicle. Changes in ddθ and product dθ * ddθ are shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment]
FIG. 1 is an explanatory diagram showing an outline of a vehicle steering assist device 10 according to the first embodiment of the present invention. The steering assist device 10 is applied to a vehicle 14 that includes a steering device 12. The steering device 12 includes a steering wheel 16 that is operated by a driver, front wheels 18L and 18R that are steering wheels, and a transmission device 20 that transmits a force and displacement related to steering between the steering wheel 16 and the front wheels 18L and 18R. And. The steering assist device 10 includes 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. .

  In the illustrated embodiment, the electric power steering device 22 is a column assist type electric power steering device (EPS). The electric power steering device may be another type of electric power steering device, such as a rack coaxial type electric power steering device, for example, as long as the steering assist torque Ta can be controlled.

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

  The steering mechanism 30 includes a rack and pinion type steering unit 38 and tie rods 40L and 40R. The steering unit 38 converts the rotation of the pinion shaft 36 into a linear movement of the rack bar 42 in the lateral direction of the vehicle, and The reverse conversion is performed. The tie rods 40L and 40R are pivotally attached to the tip of the rack bar 42 at the inner ends, and the outer ends of the tie rods 40L and 40R are knuckle arms 44L provided on the carriers (not shown) of the left and right front wheels 18L and 18R. And 44R.

  Therefore, the rotational displacement and rotational torque of the steering wheel 16 are converted by the transmission device 20 into pivoting and rotational torque around the kingpin shaft (not shown) of the front wheels 18 and 18R and transmitted to the front wheels 18L and 18R. . Further, the pivoting and rotational torque around the kingpin shaft received by the left and right front wheels 18L and 18R from the road surface 46 is transmitted to the steering wheel 16 by the transmission device 20 as rotational displacement and rotational torque, respectively.

  The electric power steering device 22 includes an electric motor 48 and a conversion device 50, which are not shown in FIG. 1, but the conversion device 50 is fixed to a worm gear fixed to the rotating shaft of the electric motor 48 and an upper steering shaft 26. Includes a worm wheel. The rotational torque of the electric motor 48 is converted into rotational torque around 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. . The electronic control unit 24 receives signals indicating the steering angle θ and the steering torque T from the steering angle sensor 52 and the torque sensor 54 provided on the upper steering shaft 26, respectively. The electronic control device 24 also receives a signal indicating the vehicle speed V from the vehicle speed sensor 56.

  The electronic control device 24 includes a CPU, a ROM, a RAM, and an input / output port device, which include a microcomputer connected to each other via a bidirectional common bus. You can do it. Further, the steering angle sensor 52 and the torque sensor 54 detect the steering angle θ and the steering torque T, respectively, assuming that the value when the vehicle is in the straight traveling state is 0 and the value when the vehicle is steered in the left turn direction is positive. The calculated values such as a target basic steering assist torque Tab to be described later are also positive in the left turn direction.

  As will be described later, the electronic control unit 24 calculates the target steering assist torque Tat and controls the rotational torque of the electric motor 48 according to the flowchart shown in FIG. Control is performed so that the torque Tat is obtained. The target steering assist torque Tat is the sum of the target basic steering assist torque Tab for reducing the driver's steering load and the target inertia compensation assist torque Tai for reducing the influence of inertia of the steering wheel 16 and the like. . The electronic control device 24 calculates a target control current It for controlling the electric power steering device 22 to change the steering assist torque Ta to the target steering assist torque Tat based on the target steering assist torque Tat.

The electronic control unit 24 calculates the steering angular velocity dθ as the time differential value of the steering angle θ, and calculates the steering angular acceleration ddθ as the time differential value of the steering angular velocity θd, that is, the twice differential value of the steering angle θ. The target inertia compensation assist torque Tai is calculated based on the product I * ddθ of the inertia moment I of the steering wheel 16 and the steering angular acceleration ddθ and the vehicle speed V, as will be described in detail later. According to the following formula (1), the inertia moment I includes a first inertia moment Istd based on the mass of the steering wheel 16 and a second inertia moment α based on the mass of both arms and both hands beyond the driver's elbow. Calculated as the sum of * β * Iarm.
I = Istd + α * β * Iarm (1)

  The electronic control unit 24 determines whether or not the driver's steering is heavy duty steering by determining whether or not the product T * dθ of the steering torque T and the steering angular velocity dθ is positive. When the electronic control unit 24 determines that the driver's steering is the heavy duty steering, the electronic control unit 24 sets the second inertia moment coefficient α in the above formula (1) to 0, and the driver's steering is not the heavy duty steering. When the determination is made, the coefficient α is set to 1.

  As shown in FIG. 1, the vehicle 14 is provided with a setting dial 58 as a setting device that is operated by an occupant and variably sets the coefficient of second inertia moment β in the equation (1). ing. A signal indicating the dial value di set by the setting dial 58 is input to the electronic control unit 24, and the electronic control unit 24 calculates a coefficient β based on the dial value di as described later.

The electronic control unit 24 determines the state of the steering operation of the driver based on the steering angular velocity dθ and the steering angular acceleration ddθ, and particularly determines whether or not the steering operation is acceleration / deceleration switching back. FIG. 12 shows a steering angle θ and a steering angular velocity dθ when a steering operation is performed in which the vehicle is turned back in the right turn direction and then turned back and further turned in the left turn direction. The change in the steering angular acceleration ddθ and the product dθ * ddθ is shown. Table 1 below shows the signs of the steering angle θ, the steering angular velocity dθ, the steering angular acceleration ddθ, and the product dθ * ddθ when the steering operation is performed, and corresponds to the positive and negative in FIG. Note that the steering angle θ and the like are positive when the steering operation is in the left turn direction.

  As shown in Table 1, the sign of the product dθ * ddθ is negative when the steering operation is increased regardless of the sign of the steering angle θ, and when the steering operation is switchback. Is positive. When the steering operation is constant speed steering, the steering angular velocity dθ and the steering angular acceleration ddθ are both 0, so the product dθ * ddθ is also 0. On the other hand, when the steering operation is acceleration / deceleration steering, the steering angular velocity dθ and the steering angular acceleration ddθ do not become zero, so the product dθ * ddθ also takes a positive or negative value.

  Therefore, when the signs of the steering angular velocity dθ and the steering angular acceleration ddθ are the same, in other words, when the sign of the product dθ * ddθ is positive, the electronic control unit 24 performs acceleration / deceleration of the driver's steering operation. It determines with it being switchback steering. The same applies to the second and third embodiments described later.

  The torque based on the target inertia compensation assist torque Tai acts in the direction opposite to the steering direction when the sign of the steering angular acceleration ddθ is the same as the sign of the steering angular velocity dθ. It can be seen that the user's steering operation is acceleration / deceleration return steering. Therefore, when the steering operation is acceleration / deceleration return steering, the magnitude of the target inertia compensation assist torque Tai so that the magnitude of the current component corresponding to the target inertia compensation assist torque Tai in the target control current It is reduced. Is preferably corrected to be small.

  In particular, in the first embodiment, when the electronic control unit 24 determines that the driver's steering operation is acceleration / deceleration return, the electronic control unit 24 multiplies the target steering assist torque Tat by a correction coefficient K1 smaller than 1. Thus, the corrected target steering assist torque Tat having a reduced magnitude is calculated. Further, the electronic control unit 24 calculates the target control current It based on the corrected target steering assist torque Tat.

  Here, if the steering angle θ is the same, it is assumed that the steering torque T by the self-aligning torque is substantially the same regardless of whether the steering direction is increased or decreased, and the steering direction and the steering are The relationship with the increase / decrease of the assist torque Ta will be examined. The steering torque T acts in a direction to suppress the increase in the increase of the steering when the steering is increased, so that the steering reaction felt by the driver when the steering assist torque Ta acting in the direction of promoting the increase is reduced. Power increases. Conversely, when the switchback steering is being performed, the steering torque T acts in a direction that promotes the switchback. Therefore, when the steering assist torque Ta acting in the direction that suppresses the switchback is reduced, the driver The steering reaction force felt decreases.

  Therefore, when the steering assist torque Ta is reduced, the steering wheel 16 is likely to return (acceleration in the return direction), and conversely, when the steering assist torque Ta is increased, the ease of return of the steering wheel 16 is reduced (return of return). Accelerate in the deceleration direction). Depth steering is an operation for controlling the rotational position of the steering wheel 16 and its change while reducing the force applied to the steering wheel 16 by the driver. Therefore, it is preferable that the change in acceleration / deceleration of the return of the steering wheel 16 is reduced.

Table 2 below shows the case where the steering is degenerative steering and the steering direction is acceleration / deceleration switching back, the rotation direction of the steering wheel 16, the increase / decrease (acceleration / deceleration) of the steering angular velocity, the steering angular velocity dθ, the steering angular acceleration ddθ The relationship between the product I * dθ * ddθ, the sign of the steering angle T, and the preferable increase / decrease of the steering assist torque Ta in order to reduce the change in acceleration / deceleration is shown.

  As shown in Table 2, the sign of the product I * dθ * ddθ is positive in a situation where the increase of the steering assist torque Ta is preferable, and conversely, in the situation where the reduction of the steering assist torque Ta is preferable, the product The sign of I * dθ * ddθ is negative. Therefore, when the steering is heavy duty steering and the steering direction is acceleration / deceleration switching back, in order to reduce the change in steering acceleration / deceleration, the steering assist torque is made to correspond to the sign of the product I * dθ * ddθ. It can be seen that Ta may be increased or decreased. Further, since the product I * dθ * ddθ represents the intensity of steering, the magnitude of the increase / decrease amount of the steering assist torque Ta preferably corresponds to the product I * dθ * ddθ.

  When the driver performs acceleration / deceleration switchback steering and the steering operation is heavy-duty steering, the electronic control device 24 is a product I * dθ * ddθ of the inertia moment I, the steering angular velocity dθ, and the steering angular acceleration ddθ. Based on the above, the correction amount ΔIt of the target control current It is calculated. Then, the electronic control unit 24 calculates the target control current It for controlling the electric power steering device 22 as the sum of the control current Iat for making the steering assist torque Ta the target steering assist torque Tat and the correction amount ΔIt. .

  Further, the electronic control unit 24 controls the steering assist torque so that the steering assist torque Ta becomes the target steering assist torque Tat by performing feedback control of the control current supplied to the motor 48 based on the target control current It. Run.

  Next, a steering assist torque control routine executed by the electronic control unit 24 will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is on. In the following description, the steering assist torque control according to the flowchart shown in FIG. 2 is simply referred to as “control”. The same applies to steering assist torque control of other embodiments described later.

  First, in step 10, the steering angular velocity dθ is calculated as a time differential value of the steering angle θ, and the steering angular acceleration ddθ is calculated as a time differential value of the steering angular velocity θd, that is, a twice differential value of the steering angle θ. Therefore, the electronic control unit 24 that executes Step 10 functions as a steering operation amount acquisition device that acquires information on the steering angle θ, the steering angular velocity dθ, and the steering angular acceleration ddθ in cooperation with the steering angle sensor 52. Prior to step 10, a signal indicating the steering angle θ detected by the steering angle sensor 52, a signal indicating the steering torque T detected by the torque sensor 54, and the like are read.

  In step 20, the moment of inertia I of the steering wheel 16 and the like used for calculating the target inertia compensation assist torque Tai is calculated according to the above formula (1) by the subroutine shown in FIG.

  In step 30, based on the steering torque T and the vehicle speed V, the target basic steering assist torque Tab is calculated from the map shown in FIG. As shown in FIG. 6, the target basic steering assist torque Tab is calculated such that the larger the magnitude of the steering torque T, the larger the magnitude, and the smaller the magnitude as the vehicle speed V increases. The

  In step 50 executed after step 30, the target inertia compensation is performed from the map shown in FIG. 7 based on the product I * ddθ of the inertia moment I of the steering wheel 16 and the steering angular acceleration ddθ and the vehicle speed V. A steering assist torque Tai is calculated. The target inertia compensation steering assist torque Tai is calculated so that the magnitude increases as the product I * ddθ increases, and the magnitude decreases as the vehicle speed V increases.

  In step 70 executed after step 50, it is determined whether or not the driver's steering operation is acceleration / deceleration return. When an affirmative determination is made, the control proceeds to step 120. When a negative determination is made, at step 80, the correction coefficient K1 for reducing the magnitude of the target inertia compensation steering assist torque Tai is set to 1, and The correction amount ΔIt of the target control current It is set to zero. When step 80 is complete, control proceeds to step 110.

  In step 110, based on the absolute value of the product I * dθ * ddθ of the inertia moment I of the steering wheel 16, the steering angular velocity dθ, and the steering angular acceleration ddθ, a control current described later is obtained from the map shown in FIG. A gain G of feedback control is calculated. The gain G is calculated to be 1 when the product I * dθ * ddθ is 0 and a minute value, and to increase in a range larger than 1 as the absolute value of the product I * dθ * ddθ increases.

  In step 120, a correction coefficient K1 is calculated from the map shown in FIG. 9 based on the absolute value of the steering angular velocity dθ. The correction coefficient K1 is calculated to be 0 when the absolute value of the steering angular velocity dθ is 0 and a minute value, and is calculated to be smaller than 1 and smaller in the range larger than 0 as the absolute value of the steering angular velocity dθ increases. The

In step 160 executed after step 120, the product I * dθ * ddθ and the product I * dθ * ddθ are supplied to the motor 48 of the electric power steering device 22 according to the following equation (2). The correction amount ΔIt of the target control current It is calculated as the product of the coefficient Ka to be converted into The calculation of the correction amount ΔIt is performed only when acceleration / deceleration switching back steering is performed by the driver and the steering operation is heavy duty steering.
ΔIt = Ka * I * dθ * ddθ (2)

  In step 170, the gain G of the feedback control of the control current supplied to the electric motor 48 of the electric power steering device 22 is set to 1. When step 110 or step 170 is complete, control proceeds to step 180.

In step 180, the target steering assist torque Tat is calculated as the sum of the target basic steering assist torque Tab and the product K1 * Tai of the correction coefficient K1 and the target inertia compensation steering assist torque Tai according to the following equation (3). The The product K1 * Tai is a corrected target inertia compensation steering assist torque whose magnitude is corrected by the correction coefficient K1.
Tat = Tab + K1 * Tai (3)

In step 200 executed after step 180, the target control current It for controlling the electric power steering device 22 is changed from the steering assist torque Ta to the target steering assist torque Ta in accordance with the following equation (4). Is calculated as the sum of the control current Iat and the correction amount ΔIt.
It = Iat + ΔIt (4)

In step 220 executed after step 200, the electric power steering apparatus 22 is feedback-controlled based on the target control current It. That is, according to the following equation (5), the feedback control amount Ita of the control current is calculated based on the difference between the target control current It and the actual control current Ifb supplied to the electric motor 48 of the electric power steering device 22. . Further, the control current supplied to the motor 48 is controlled based on the feedback control amount Ita, so that the steering assist torque is controlled.
Ita = G (It-Ifb) (5)

  Next, a routine for calculating the moment of inertia I executed in step 20 will be described with reference to the flowchart shown in FIG.

  First, in step 21, it is determined whether or not the driver's steering is a heavy steering by determining whether or not the product T * dθ of the steering torque T and the steering angular velocity dθ is positive. If a negative determination is made, the coefficients α and β are set to 0 in step 22 and then control proceeds to step 25. If an affirmative determination is made, the coefficient α is set to 1 in step 23. Note that one of the coefficients α and β may be set to 0 in step 22.

  In step 24, the coefficient β is calculated by referring to the map shown in FIG. 11 based on the dial value di set by the setting dial 58. As shown in FIG. 11, the coefficient β is calculated as 1 when the dial value di is the standard value di0, and increases as the dial value di increases when the dial value di is larger than the standard value di0. So that the value is larger than 1. On the contrary, when the dial value di is smaller than the standard value di0, the coefficient β is calculated to a value smaller than 1 so as to decrease as the dial value di decreases. Note that step 24 may be executed before step 21 and modified so that only coefficient α is set to 0 in step 22.

  In step 25, according to the above equation (1), the first inertia moment Istd based on the mass of the steering wheel 16 and the second inertia moment α * based on the mass of both arms and both hands ahead of the driver's elbow. The moment of inertia I is calculated as the sum of β * Iarm.

  As can be understood from the above description, in step 20, the inertia moment I of the steering wheel 16 used for calculating the target inertia compensation assist torque Tai is calculated, and in step 30, the target basic steering assist torque Tab is calculated. In step 50, the target inertia compensation steering assist torque Tai is calculated based on the product I * ddθ of the moment of inertia I and the steering angular acceleration ddθ and the vehicle speed V.

  In step 180, the target steering assist torque Tat is calculated as the sum of the target basic steering assist torque Tab and the product K1 * Tai of the correction coefficient K1 and the target inertia compensation steering assist torque Tai. Further, in steps 200 and 220, the electric power steering device 22 is feedback-controlled so that the steering assist torque Ta becomes the target steering assist torque Ta.

  As shown in FIG. 3, when it is determined that the driver's steering is not heavy duty steering, the inertia moment I is based on the first inertia moment Istd based on the mass of the steering wheel 16 and the driver's elbow. Is calculated as the sum of the second moment of inertia β * Iarm based on the mass of both arms and hands. On the other hand, when it is determined that the driver's steering is the heavy duty steering, the inertia moment I is calculated to a value of only the first inertia moment Istd based on the mass of the steering wheel 16, thereby the driver's steering. Is smaller than the case where it is determined that the steering is not heavy duty steering.

  Therefore, it is possible to reduce a possibility that the magnitude of the target inertia compensation steering assist torque Tai becomes excessive as compared with the case where the inertia moment I is not reduced even when the driver's steering is the heavy duty steering. Therefore, it is possible to reduce a possibility that steering acceleration / deceleration is induced by excessive inertia compensation assist torque Tai and steering stability is lowered.

  When the driver performs acceleration / deceleration switchback steering and the steering operation is heavy duty steering, in step 160, the correction amount ΔIt of the target control current It is calculated based on the product I * dθ * ddθ. Further, the target control current It for controlling the electric power steering device 22 is calculated as the sum of the control current Iat and the correction amount ΔIt for changing the steering assist torque Ta to the target steering assist torque Ta at step 200. . That is, the control current Iat is corrected with the correction amount ΔIt, and the increase or decrease in the control current due to the correction amount ΔIt corresponds to the sign of the product I * dθ * ddθ.

  When the steering operation is heavy duty steering, the magnitude of the inertia compensation assist torque Tai is reduced by reducing the inertia moment I as described above. Therefore, when acceleration / deceleration switchback steering is performed and the steering operation is heavy duty steering, the steering angular velocity is likely to fluctuate due to self-aligning torque. However, according to the first embodiment, since the control current Iat is corrected by the correction amount ΔIt, it is possible to suppress the fluctuation of the steering angular velocity due to the reduction of the inertia moment I. This effect is also obtained in the second and third embodiments described later.

  In particular, according to the first embodiment, the setting dial 58 is provided for variably setting the coefficient β of the second moment of inertia operated by the passenger. The occupant can variably set the second inertia moment coefficient β in the above equation (1) by setting the dial value di with the setting dial 58. Therefore, the occupant can set the degree of influence of α * β * Iarm of the second inertia moment on the inertia moment I.

  Further, according to the first embodiment, if it is determined in step 70 that the driver's steering operation is acceleration / deceleration switching back, in step 120, the steering angular velocity dθ is based on the absolute value of the steering angular velocity dθ. A positive correction coefficient K1 smaller than 1 which is smaller as the absolute value of is larger is calculated.

  That is, when it is determined that the driver's steering operation is acceleration / deceleration switching, the magnitude of the target inertia compensation steering assist torque Tai is reduced and corrected by the correction coefficient K1, and the corrected target inertia compensation steering assist torque is corrected. Based on this, the target steering assist torque Tat is calculated. Therefore, in a situation where acceleration / deceleration switching is performed, by reducing the magnitude of the inertia compensation assist torque, the driver will continue switching steering beyond the position where the driver intends to end switching switching. It is possible to reduce the size of the inertia torque. Therefore, since the degree of the inertia compensation assist torque hindering the driver's completion of the switchback steering can be reduced, the steering feeling in the situation where the acceleration / deceleration switchback is performed can be improved compared to the conventional case. it can. This effect is also obtained in the second and third embodiments described later.

[Second Embodiment]
FIG. 4 is a flowchart showing a steering assist torque control routine in the second embodiment. In FIG. 4, the same step number as the step number shown in FIG. 2 is assigned to the same step as the step shown in FIG. The same applies to the third embodiment described later.

  As understood from the comparison between FIG. 4 and FIG. 2, in the second embodiment, steps 10, 30 to 70, 110, 120, 160, 170, 200 and 220 are the same as those in the first embodiment. To be executed. Step 20 of the first embodiment is not executed. When a negative determination is made in step 70, in step 90, correction coefficients K1 and K2 for reducing the magnitude of the target inertia compensation steering assist torque Tai are set to 1, and the correction amount of the target control current It is set. ΔIt is set to zero. When step 90 is complete, control proceeds to step 110.

  In step 130 executed after step 120, as in step 20 of the first embodiment, the driver determines whether the product T * dθ of the steering torque T and the steering angular velocity dθ is positive. It is determined whether or not the steering is the heavy duty steering. When it is determined that the driver's steering is not heavy duty steering, the correction coefficient K2 is set to 1. When it is determined that the driver's steering is heavy duty steering, the correction coefficient K2 is K20 (a positive value smaller than 1). Constant). When step 130 is complete, control proceeds to step 160. The mass of the steering wheel 16 is Ms, and the mass of both arms and both hands ahead of the standard elbow driver's elbow is Md, and K20 is preferably a value corresponding to Ms / (Ms + Md). .

When step 110 or step 170 is complete, control proceeds to step 190. In step 190, the target steering assist torque Tat is calculated according to the following equation (6).
Tat = Tab + K1 * K2 * Tai (6)

  According to the second embodiment, when it is determined in step 130 that the driver's steering is not the heavy duty steering, the correction coefficient K2 is set to 1, and it is determined that the driver's steering is the heavy duty steering. In some cases, the correction coefficient K2 is set to K20, which is a positive constant smaller than one. And then. In step 190, the target steering assist torque Tat is calculated as the sum of the target basic steering assist torque Tab and the inertia compensation assist torque Tai reduced and corrected by the correction coefficient K2.

  Therefore, since the component of the control current based on the inertia compensation assist torque Tai is reduced, the magnitude of the steering assist torque corresponding to the target inertia compensation steering assist torque Tai compared to the case where the correction by the correction coefficient K2 is not performed. Can reduce the risk of excess. Therefore, it is possible to reduce a possibility that steering acceleration / deceleration is induced by excessive inertia compensation assist torque Tai and steering stability is lowered.

[Third embodiment]
FIG. 5 is a flowchart showing a steering assist torque control routine in the third embodiment.

  As can be seen from the comparison between FIG. 5 and FIG. 4, in the third embodiment, steps 10, 30, 50, 70, 110, 160, 170 and 220 are executed in the same manner as in the second embodiment. Is done. Also in the third embodiment, step 20 of the first embodiment is not executed. When step 30 is complete, control proceeds to step 40, and when step 50 is complete, control proceeds to step 60.

  In step 40, based on the target basic steering assist torque Tab, a basic steering assist torque control current Iab for making the basic steering assist torque the target basic steering assist torque Tab is calculated.

  In step 60, based on the target inertia compensation assist torque Tai, an inertia compensation control current Iai for making the inertia compensation assist torque the target inertia compensation assist torque Tai is calculated.

  When a negative determination is made in step 70, in step 100, the correction coefficient K3 for reducing the magnitude of the inertia compensation control current Iai is set to 1, and the correction amount ΔIt of the target control current It is 0. Set to On the other hand, when an affirmative determination is made in step 70, in step 140, the correction coefficient K3 is calculated from the map shown in FIG. 10 based on the absolute value of the steering angular velocity dθ. Like the correction coefficient K1, the correction coefficient K3 is 1 when the absolute value of the steering angular velocity dθ is 0 and a minute value, and decreases in a range smaller than 1 as the absolute value of the steering angular velocity dθ increases. Is calculated.

  In step 150, a correction coefficient K4 for reducing the magnitude of the inertia compensation control current Iai is set in the same manner as the correction coefficient K2 of the second embodiment. That is, when it is determined that the driver's steering is not heavy steering, the correction coefficient K4 is set to 1. When it is determined that the driver's steering is heavy steering, the correction coefficient K4 is K40 (1 Smaller positive constant). K40 is also preferably a value corresponding to Ms / (Ms + Md).

When step 110 or step 170 is complete, control proceeds to step 210. In step 210, a target control current It for controlling the electric power steering device 22 is calculated according to the following equation (7).
It = Iab + K3 * K4 * Iai + ΔIt (7)

  According to the third embodiment, in step 40, the basic steering assist torque control current Iab is calculated based on the target basic steering assist torque Tab, and in step 60, the inertia compensation torque is calculated based on the target inertia compensation assist torque Tai. A control current Iai is calculated.

  If it is determined in step 70 that the driver's steering operation is acceleration / deceleration switching, after the correction coefficient K3 similar to the correction coefficient K1 in the first and second embodiments is calculated in step 120, Step 150 is executed. If it is determined in step 150 that the driver's steering is a heavy steering, the correction coefficient K4 for reducing the magnitude of the inertia compensation control current Iai is set to K40, which is a positive constant smaller than 1. Is done.

  In step 210, the target control current It is the sum of the basic steering assist torque control current Iab, the inertia compensation control current Iai whose magnitude is corrected by the correction coefficients K3 and K4, and the control current correction amount ΔIt. Is calculated as Further, in step 220, feedback control is performed so that the control current supplied to the electric power steering device 22 becomes the target control current It.

  Therefore, according to the third embodiment, since the magnitude of the inertia compensation control current Iai is reduced and corrected by the correction coefficient K4, the target inertia compensation steering is compared with the case where the correction by the correction coefficient K4 is not performed. The possibility that the magnitude of the steering assist torque corresponding to the assist torque Tai becomes excessive can be reduced. Therefore, it is possible to reduce a possibility that steering acceleration / deceleration is induced by excessive inertia compensation assist torque Tai and steering stability is lowered.

  Note that, according to the first to third embodiments, the larger the absolute value of the steering angular velocity dθ, the larger the amount of reduction in the magnitude of the target inertia compensation steering assist torque Tai and the like. The magnitude of the steering assist torque can be reduced.

  Further, according to the first to third embodiments, in step 180, control is performed based on the absolute value of the product I * dθ * ddθ of the moment of inertia I of the steering wheel 16, the steering angular velocity dθ, and the steering angular acceleration ddθ. A gain G of current feedback control is calculated. The gain G is calculated so as to increase in a range larger than 1 as the absolute value of the product I * dθ * ddθ increases. Further, in step 180, feedback control is performed so that the control current supplied to the electric power steering apparatus 22 using the gain G becomes the target control current It or the corrected target control current Ita.

  Therefore, the larger the absolute value of the product I * dθ * ddθ and the higher the driver's steering intensity, the more efficiently the control current can be controlled to the target control current It or the corrected target control current Ita. In the first to third embodiments, when acceleration / deceleration is switched back, the magnitude of the current component corresponding to the inertia compensation assist torque is reduced. Therefore, even if the gain G fluctuation range is set large, It can be avoided that the inertia torque resulting from the inertia compensation assist torque is excessively large.

  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. This will be apparent to those skilled in the art.

  For example, in the first embodiment, the first moment of inertia Istd used for the calculation of the moment of inertia I in step 20 is a moment of inertia based on the mass of the steering wheel 16. However, the first moment of inertia Istd may be corrected to a moment of inertia based on the mass of the steering wheel 16 and the upper steering shaft 26 rotating therewith.

  In the first embodiment, a setting dial 58 is provided as a setting device for variably setting the coefficient β used for the calculation of the moment of inertia I. However, the setting dial 58 may be omitted, and in that case, the coefficient β in the flowchart shown in FIG. 3 is also omitted.

  In each of the above-described embodiments, the correction amount ΔIt is calculated based on the product I * dθ * ddθ in step 160, and the target control current It is corrected with the correction amount ΔIt in step 200 or 210. It has become. However, the calculation of the correction amount ΔIt and the correction of the target control current It by the correction amount ΔIt may be omitted. Further, a correction amount ΔTat for the target steering assist torque Tat is calculated as a correction amount corresponding to the correction amount ΔIt based on the product I * dθ * ddθ, and the target steering assist torque Tat is corrected to be corrected by the correction amount ΔTat. May be.

  In each of the embodiments described above, in step 110, the gain G of the control current feedback control is determined based on the absolute value of the product I * dθ * ddθ of the moment of inertia I, the steering angular velocity dθ, and the steering angular acceleration ddθ. Calculated. However, the variable setting of the gain G may be omitted.

  Further, in each of the above-described embodiments, the target steering assist torque Ta is calculated as a value including the target basic steering assist torque Tab and the target inertia compensation steering assist torque Tai. However, the target steering assist torque Tat is used to return the assist torque for steering damping control, the assist torque for steering friction control, and the steering wheel 16 to the neutral position in addition to the target basic steering assist torque Tab and the target inertia compensation steering assist torque Tai. It may be calculated as a value including at least one of the return torques.

DESCRIPTION OF SYMBOLS 10 ... Steering assistance device, 12 ... Steering device, 14 ... Vehicle, 16 ... Steering wheel, 18L, 18R ... Front wheel, 20 ... Transmission device, 22 ... Electric power steering device, 24 ... Electronic control device, 52 ... Steering angle sensor, 54 ... Torque sensor, 56 ... Vehicle speed sensor, 58 ... Setting dial

Claims (5)

Steering torque detection device that detects steering torque, steering operation amount acquisition device that acquires at least information on steering angular acceleration as a steering operation amount of a driver, and electric power steering device that generates steering assist torque according to a control current Calculating a basic target steering assist torque based on the steering torque and a target inertia compensation assist torque based on a product of at least the inertial moment of the upper limbs of the steering wheel and the driver and the steering angular acceleration; A control device that calculates a target control current of the electric power steering device based on a target steering assist torque including a target inertia compensation assist torque, and controls the electric power steering device with the target control current; In the steering assist device,
The steering operation amount acquisition device acquires information on the steering angular velocity,
The control device determines the state of the driver's steering operation based on the steering torque and the steering angular velocity, and determines that the driver's steering operation is not the heavy duty steering when the driver's steering operation is determined to be the heavy duty steering. Comparing the calculation mode of the target control current so that the target control current becomes a value calculated by reducing the moment of inertia as compared with the determination.
A steering assist device for a vehicle.   2. The vehicle steering assist device according to claim 1, wherein the control device reduces the inertia moment, reduces the magnitude of the target inertia compensation assist torque, and sets the target inertia compensation assist torque among the target control currents. 3. A vehicle steering assist device that corrects a calculation mode of the target control current by any of the corresponding reduction of current components.   3. The vehicle steering assist device according to claim 1, wherein the control device performs a steering operation of the driver based on a steering angular velocity and a steering angular acceleration in a situation where the calculation mode of the target control current is corrected. A vehicle that suppresses fluctuations in steering angular velocity by correcting the target control current with a correction amount based on a product of the moment of inertia, steering angular velocity, and steering angular acceleration when it is determined that acceleration / deceleration return steering is performed; Steering assist device.   3. The vehicle steering assist device according to claim 1, wherein the control device is a sum of at least a first moment of inertia based on a mass of a steering wheel and a second moment of inertia based on a mass of a driver's upper limb. A vehicle steering assist device that calculates the moment of inertia and reduces the second moment of inertia to zero when it is determined that the steering operation of the driver is heavy duty steering. 5. The steering assist device for a vehicle according to claim 4, wherein a setting device is provided for variably setting a correction coefficient for the second moment of inertia operated by an occupant of the vehicle, and the control device is provided with a steering operation by a driver. A vehicle steering assist device that calculates the moment of inertia as a sum of the first moment of inertia and the product of the correction coefficient and the second moment of inertia when it is determined that is not a heavy duty steering.

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