JP2020185824A - Electric power steering device - Google Patents

Abstract

To suppress variations in a steering force according to a steering speed and improve steering feeling in each of steering and steering back.SOLUTION: An electric power steering device 100 includes an assist base current calculating part 121 which calculates an assist base current value Ia based on a steering torque T, a static friction compensation current calculating part 130 which calculates a static friction compensation current value If based on a steering speed of a steering member 1, a control current calculating part 180 which corrects the assist base current value Ia by the static friction compensation current value If and calculates a control current value Isum, a motor control part 9 which controls an electric motor 10 based on the control current value Isum, and a steering state determination part 110 which determines a steering state of the steering member 1, in which when the steering state is in a steering back state, the static friction compensation current value If is larger than that in the case where the steering state is in a steering state.SELECTED DRAWING: Figure 3

Description

The present invention relates to an electric power steering device.

In Patent Document 1, when the steering state is the cutting state, the cutting current value calculated based on the steering torque is output as an assist current value, and when the steering state is the returning state, it is based on the steering torque. A vehicle steering device (electric power steering device) that outputs the return current value calculated in the above manner as an assist current value is disclosed.

Japanese Unexamined Patent Publication No. 2010-274822

However, in the electric power steering device described in Patent Document 1, the assist current value is determined based on the steering torque, and the value related to the steering speed is not taken into consideration. Therefore, the steering force may vary depending on the steering speed. There is.

Here, it is conceivable to determine the assist current value in consideration of the value related to the steering speed. However, when the assist current value is determined by similarly taking into account the values related to the steering speed between the cut-in steering and the return steering, the variation according to the steering speed is appropriately applied in each of the cut steering and the return steering. It may not be possible to suppress it. For example, even if the variation in steering force according to the steering speed can be suppressed in the cut-in steering, the variation in steering force according to the steering speed may not be suppressed in the return steering.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress variations in steering force according to steering speed and improve steering feeling in each of incision steering and return steering. ..

The present invention is an electric power steering device, which is a steering shaft connected to a steering member steered by the driver and rotating as the driver steers the steering member, and an electric motor that applies rotational torque to the steering shaft. Based on the torque detection unit that detects the steering torque input from the steering member, the assist base current calculation unit that calculates the assist base current value based on the steering torque, and the value related to the steering speed of the steering member. A static friction compensation current calculation unit that calculates the static friction compensation current value for compensating the static friction of the steering system, and a control current calculation unit that corrects the assist base current value by the static friction compensation current value and calculates the control current value. A motor control unit that controls the electric motor based on the control current value and a steering state determination unit that determines the steering state of the steering member are provided, and the static friction compensation current value is the assist base current when the steering torque increases. The value is set to increase, the assist base current value is set to decrease when the steering torque decreases, and the static friction compensation current value is set when the steering state is in the cut state when the steering state is in the return state. It is characterized by being larger than in some cases.

In the present invention, since the control current value is calculated based on the value related to the steering speed, it is possible to suppress the variation in the steering force according to the steering speed. Further, since an appropriate rest friction compensation current value can be set in each of the incision steering and the return steering, it is possible to suppress the variation in the steering force according to the steering speed in each of the incision steering and the return steering, and the steering fee. The ring can be improved. In particular, when the steering state is in the return state, the static friction compensation current value is made larger than when the steering state is in the cut state. Therefore, the control current value is measured during the return steering after the steering member is cut. Can be quickly reduced to prevent a sudden decrease in steering torque. As a result, it is possible to suppress variations in steering force according to the return steering speed and improve the steering feeling during return steering.

In the present invention, the value related to the steering speed is the time change rate of the steering torque, the vehicle speed coefficient that the static friction compensation current calculation unit increases according to the increase in the vehicle speed detected by the vehicle speed detection unit, and the steering. The static friction compensation current value is calculated based on the time change rate of torque, and the vehicle speed coefficient becomes larger when the steering state is in the return state than when the steering state is in the cut state. It is characterized in that it is set as follows.

In the present invention, since the static friction compensation current value is calculated based on the vehicle speed coefficient that increases as the vehicle speed increases, the variation in steering force according to the vehicle speed can be suppressed, and the steering feeling is further improved. be able to.

The present invention further includes a steering angle detecting unit that detects the steering angle of the steering member, and the static friction compensation current calculation unit is compared with a case where the steering angle is less than a predetermined angle when the steering angle is equal to or more than a predetermined angle. It is characterized by including a processing unit that reduces the static friction compensation current value.

In the present invention, when the steering angle is less than a predetermined angle, the variation of the steering force according to the steering speed at the time of return steering is suppressed, and when the steering angle is equal to or more than the predetermined angle, the feeling of reaction force to the driver is large. It is possible to prevent it from becoming too much.

According to the present invention, in each of the incision steering and the return steering, it is possible to suppress the variation in the steering force according to the steering speed and improve the steering feeling.

It is a block diagram of the electric power steering apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of the electric power steering apparatus which concerns on 1st Embodiment of this invention. It is a functional block diagram of the static friction compensation current calculation part which concerns on 1st Embodiment of this invention. It is a time chart of the steering angle of the electric power steering apparatus which concerns on the comparative example of this embodiment. It is a time chart of the steering force of the electric power steering apparatus which concerns on the comparative example of this embodiment. It is a functional block diagram of the static friction compensation current calculation part which concerns on 2nd Embodiment of this invention.

<First Embodiment>
The electric power steering device 100 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4B.

FIG. 1 is a configuration diagram of the electric power steering device 100. As shown in FIG. 1, the electric power steering device 100 is connected to a steering wheel 1 as a steering member steered by the driver, and the driver steers the steering wheel 1 (hereinafter, referred to as "steering steering"). It includes an input shaft 2 that rotates in accordance with the above, a rack shaft 5 that steers the wheels 6, an output shaft 3 that is linked to the rack shaft 5, and a torsion bar 4 that connects the input shaft 2 and the output shaft 3. The steering shaft 7 is composed of the input shaft 2, the output shaft 3, and the torsion bar 4.

A pinion gear 3a that meshes with the rack gear 5a formed on the rack shaft 5 is formed below the output shaft 3. When the steering wheel 1 is steered, the steering shaft 7 rotates, the rotation is converted into a linear motion of the rack shaft 5 by the pinion gear 3a and the rack gear 5a, and the wheel 6 is steered via the knuckle arm 14.

The electric power steering device 100 operates with an electric motor 10 which is a power source for assisting the driver in steering the steering wheel 1, a speed reducer 11 which reduces and transmits the rotation of the electric motor 10 to the output shaft 3. A torque sensor 12 for detecting the steering torque acting on the torsion bar 4 by the relative rotation of the input shaft 2 and the output shaft 3 due to steering by a person, and a controller 30 for controlling the electric motor 10 are further provided.

The electric motor 10 is provided with a motor rotation angle sensor 10a that acquires the rotation angle of the electric motor 10. The motor rotation angle sensor 10a is composed of a resolver.

The speed reducer 11 has a worm shaft 11a connected to the output shaft of the electric motor 10 and a worm wheel 11b connected to the output shaft 3 and meshed with the worm shaft 11a. The torque output by the electric motor 10 is transmitted from the worm shaft 11a to the worm wheel 11b and applied to the output shaft 3.

The torque sensor 12 is a torque detection unit that detects the steering torque input from the steering wheel 1. The steering torque applied to the input shaft 2 due to the steering by the driver is detected by the torque sensor 12, and the torque sensor 12 outputs a signal corresponding to the steering torque to the controller 30. The torque sensor 12 detects the steering torque applied to the torsion bar 4 based on the relative rotation of the input shaft 2 and the output shaft 3.

The torque sensor 12 outputs 0 [Nm] as the steering torque when there is no relative rotation between the input shaft 2 and the output shaft 3. When the torsion bar 4 is twisted to the right, a steering torque with a + (positive) sign is output, and when the steering wheel 1 is twisted to the left, a steering torque with a minus (negative) sign is output. To do.

As will be described later, the controller 30 calculates a control current value (target current value) for the electric motor 10 based on the detection result from the torque sensor 12, and causes the electric motor 10 to generate a predetermined torque. Control the drive of 10. The electric motor 10 applies rotational torque to the steering shaft 7 via the speed reducer 11. In this way, the electric power steering device 100 detects the steering torque input from the steering wheel 1 to the input shaft 2 by the torque sensor 12, and the controller 30 drives the electric motor 10 based on the detection result. Assists the driver in steering the steering wheel 1.

The input shaft 2 is provided with a steering angle sensor 15 as a steering angle detecting unit that detects a steering angle that is a rotation angle of the steering wheel 1. The rotation angle of the input shaft 2 and the steering angle of the steering wheel 1 are equal to each other. Therefore, the steering angle of the steering wheel 1 can be obtained by detecting the rotation angle of the input shaft 2 with the steering angle sensor 15. The detection result of the steering angle sensor 15 is output to the controller 30.

Although not shown, the steering angle sensor 15 includes, for example, a center gear that rotates integrally with the input shaft 2 and two outer gears that mesh with the center gears, and is based on a change in magnetic flux accompanying the rotation of the two outer gears. Therefore, the rotation angle of the center gear, that is, the rotation angle of the input shaft 2 is calculated.

The steering angle sensor 15 outputs 0 [°] as the steering angle when the steering wheel 1 is in the neutral position. When the steering wheel 1 is steered to the right from the neutral position, the steering angle with a + (positive) sign is output according to the rotation of the steering wheel 1. On the other hand, when the steering wheel 1 is steered to the left from the neutral position, the steering angle with a negative sign is output according to the rotation of the steering wheel 1.

The detection result of the vehicle speed sensor 16 as the vehicle speed detection unit that detects the traveling speed of the own vehicle (hereinafter referred to as the vehicle speed) is input to the controller 30.

The controller 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a storage unit such as a RAM (Random Access Memory), an input / output interface (I / O interface), and other peripheral circuits as an operating circuit. It consists of a microcomputer. The controller 30 can also be composed of a plurality of microcomputers. As the operating circuit, an MPU (Micro Processing Unit), a DSP (Digital Signal Processor), an ASIC (application specific integrated circuit), an FPGA (Field Programmable Gate Array), or the like can be used instead of or together with the CPU. ..

The CPU of the controller 30 controls the operation of the electric motor 10, the ROM of the controller 30 stores control programs and setting values necessary for the processing operation of the CPU, and the RAM of the controller 30 stores the torque sensor 12 and the torque sensor 12. Information detected by various sensors such as the steering angle sensor 15 and the vehicle speed sensor 16 is temporarily stored.

The control of the electric motor 10 by the controller 30 will be described with reference to FIGS. 2 and 3. FIG. 2 is a block diagram of the electric power steering device 100, and FIG. 3 is a functional block diagram of the static friction compensation current calculation unit 130.

As shown in FIG. 2, the controller 30 time-differentiates the steering torque T detected by the torque sensor 12 and time-change rate Tv of the steering torque T, which is a value related to the steering speed of the steering wheel 1 (hereinafter, It includes a differential device 111 that calculates the torque change rate Tv), and a steering state determination unit 110 that determines the steering state of the steering wheel 1.

When the sign of the steering torque T detected by the torque sensor 12 and the sign of the torque change rate Tv calculated by the differentiator 111 are the same, the steering state determination unit 110 determines that the steering state is the cut state. .. When the sign of the steering torque T detected by the torque sensor 12 and the sign of the torque change rate Tv calculated by the differentiator 111 are not the same, the steering state determination unit 110 determines that the steering state is the return state. ..

Further, the controller 30 includes an assist base current calculation unit 121 that calculates the assist base current value Ia based on the steering torque T detected by the torque sensor 12 and the vehicle speed v detected by the vehicle speed sensor 16, and the torque change rate Tv and the torque change rate Tv. The static friction compensation current calculation unit 130 that calculates the static friction compensation current value If for compensating the static friction of the steering system based on the vehicle speed v, and the assist base current based on the static friction compensation current value If and various other current values. The control current calculation unit 180 that corrects the value Ia and calculates the control current value Iso for the electric motor 10, and the current supplied to the electric motor 10 so that the detected current value of the electric motor 10 matches the control current value Iso. A motor control unit 9 that controls the electric motor 10 by controlling the electric motor 10 is provided. Although not shown, other various current values include, for example, a Coulomb friction compensation current value, a viscous friction compensation current value, an inertia compensation current value, and a return current value.

The static friction compensation current value If can be calculated by, for example, the following equation.
If = If1 + If2
If1 = f1 × Tv
If2 = f2 × a

If 1 is a reference static friction compensation current value, and If 2 is a corrected static friction compensation current value. f1 is a first vehicle speed coefficient that increases as the vehicle speed v increases, and f2 is a second vehicle speed coefficient that increases as the vehicle speed v increases. a is a code coefficient. The sign coefficient a is set to any of an, 0 (zero), and ap based on the torque change rate Tv. an is an arbitrarily determined negative value, and is stored in advance in the storage unit of the controller 30. ap is an arbitrarily determined positive value and is stored in advance in the storage unit of the controller 30. The reference static friction compensation current value If1 is a term for compensating for a linear component proportional to the static friction of the steering system, and is obtained by multiplying the first vehicle speed coefficient f1 by the torque change rate Tv in the present embodiment.

The relationship between the detected current of the electric motor 10 and the motor output torque of the steering shaft 7 becomes non-linear due to the influence of friction between the electric motor 10 and the speed reducer 11. Therefore, in the present embodiment, the corrected static friction compensation current value If2 for compensating the non-linear component is added to the reference static friction compensation current value If1. The corrected static friction compensation current value If2 is a term for compensating for the non-linear component of the electric motor 10 and the speed reducer 11, and is obtained by multiplying the second vehicle speed coefficient f2 by the code coefficient a in the present embodiment.

As shown in FIG. 3, the static friction compensation current calculation unit 130 includes a reference static friction compensation current calculation unit 141, a correction static friction compensation current calculation unit 142, an addition unit 143, and a limiter 149.

The reference static friction compensation current calculation unit 141 calculates the reference static friction compensation current value If1 based on the first vehicle speed coefficient f1 and the torque change rate Tv. The corrected rest friction compensation current calculation unit 142 calculates the corrected rest friction compensation current value If2 based on the second vehicle speed coefficient f2, which is different from the first vehicle speed coefficient f1, and the code coefficient a set by the torque change rate Tv.

The reference static friction compensation current calculation unit 141 calculates the first vehicle speed coefficient setting unit 141a for setting the first vehicle speed coefficient f1 and the first vehicle speed coefficient f1 set by the first vehicle speed coefficient setting unit 141a with the differentiator 111. A multiplication unit 141b for calculating a reference static friction compensation current value If1 by multiplying the obtained torque change coefficient Tv is provided.

The corrected static friction compensation current calculation unit 142 is a second vehicle speed coefficient setting unit 142a for setting the second vehicle speed coefficient f2 and a setting unit for setting the code coefficient a for setting the sign of the corrected static friction compensation current value If2. A certain code setting unit 142b and the second vehicle speed coefficient f2 set by the second vehicle speed coefficient setting unit 142a are multiplied by the code coefficient a (any of an, 0, ap) set by the code setting unit 142b. A multiplication unit 142c for calculating the corrected static friction compensation current value If2 is provided.

The first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 are coefficients that increase in accordance with an increase in the vehicle speed v detected by the vehicle speed sensor 16, and are the first vehicle speed characteristics Cv11, Cv12 and stored in the storage unit of the controller 30. It is calculated based on the second vehicle speed characteristics Cv21 and Cv22. In the storage unit of the controller 30, the first vehicle speed characteristic Cv11 for notch steering referred to during the notch steering of the steering wheel 1 and the first vehicle speed characteristic for return steering referred to during the return steering of the steering wheel 1 are stored. Cv12 is stored in a table format. When the vehicle speed v is the same, the first vehicle speed characteristic Cv12 is set so that the first vehicle speed coefficient f1 is larger than the first vehicle speed characteristic Cv11. Further, in the first vehicle speed characteristic Cv12, the rate of increase of the first vehicle speed coefficient f1 with respect to the vehicle speed v (that is, the amount of increase of the first vehicle speed coefficient f1 with respect to the amount of increase of the vehicle speed v) is larger than that of the first vehicle speed characteristic Cv11. It is set.

In the storage unit of the controller 30, the second vehicle speed characteristic Cv21 for cut-in steering referred to during the cut-in steering of the steering wheel 1 and the second vehicle speed characteristic for return steering referred to during the return steering of the steering wheel 1 are stored. Cv22 is stored in a table format. When the vehicle speed v is the same, the second vehicle speed characteristic Cv22 is set so that the second vehicle speed coefficient f2 is larger than that of the second vehicle speed characteristic Cv21. Further, in the second vehicle speed characteristic Cv22, the rate of increase of the second vehicle speed coefficient f2 with respect to the vehicle speed v (that is, the amount of increase of the second vehicle speed coefficient f2 with respect to the amount of increase of the vehicle speed v) is larger than that of the second vehicle speed characteristic Cv21. It is set.

A method of calculating the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 when the steering state of the steering wheel 1 is determined to be in the cutting state by the steering state determination unit 110 will be described. When the steering state is the cut-in state, the first vehicle speed coefficient setting unit 141a refers to the first vehicle speed characteristic Cv11 for the cut-in steering, and based on the vehicle speed v detected by the vehicle speed sensor 16, the first vehicle speed coefficient f1 To set. When the steering state is the cut state, the second vehicle speed coefficient setting unit 142a refers to the second vehicle speed characteristic Cv21 for the cut steering, and based on the vehicle speed v detected by the vehicle speed sensor 16, the second vehicle speed coefficient f2. To set.

A method of calculating the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 when the steering state of the steering wheel 1 is determined to be in the return state by the steering state determination unit 110 will be described. When the steering state is the return state, the first vehicle speed coefficient setting unit 141a refers to the first vehicle speed characteristic Cv12 for return steering, and based on the vehicle speed v detected by the vehicle speed sensor 16, the first vehicle speed coefficient f1 To set. When the steering state is the return state, the second vehicle speed coefficient setting unit 142a refers to the second vehicle speed characteristic Cv22 for return steering, and based on the vehicle speed v detected by the vehicle speed sensor 16, the second vehicle speed coefficient f2. To set.

The sign setting unit 142b sets the code coefficient a to be multiplied by the second vehicle speed coefficient f2 based on the torque change rate Tv. When the absolute value | Tv | of the torque change rate Tv is less than the predetermined threshold value T0, the sign setting unit 142b sets the sign coefficient a to “0 (zero)”. When the torque change rate Tv is equal to or higher than a predetermined threshold value (+ T0), the sign setting unit 142b sets the code coefficient a to “ap (> 0)”. When the torque change rate Tv is equal to or less than a predetermined threshold value (−T0), the sign setting unit 142b sets the code coefficient a to “an (<0)”.

In this way, the sign coefficient a is set to 0 (zero) when the absolute value | Tv | of the torque change rate Tv is less than the threshold value T0, so that the corrected static friction compensation current value If2 is also 0 (zero). Become. That is, the threshold value T0 of the torque change rate Tv is used to determine whether or not the corrected rest friction compensation current value If2 is set to 0, and is set to a value for setting the dead zone of the corrected rest friction compensation current value If2. Equivalent to.

The multiplication unit 141b calculates the reference static friction compensation current value If1 by multiplying the first vehicle speed coefficient f1 by the torque change rate Tv. The multiplication unit 142c calculates the corrected rest friction compensation current value If2 by multiplying the second vehicle speed coefficient f2 by the sign coefficient a.

The addition unit 143 adds the corrected static friction compensation current value If2 calculated by the corrected static friction compensation current calculation unit 142 to the reference static friction compensation current value If1 calculated by the reference static friction compensation current calculation unit 141. The calculation result in the addition unit 143 is subjected to upper and lower limit processing by the limiter 149, and is output as a static friction compensation current value If.

The static friction compensation current value If calculated by the static friction compensation current calculation unit 130 is added to the assist base current value Ia together with various other current values, and the control current value Isum is calculated (see FIG. 2).

As described above, in the present embodiment, since the control current value Isum is calculated based on the torque change rate Tv, which is a value related to the steering speed, it is possible to suppress the variation in the steering force according to the steering speed. Further, in the present embodiment, different values are adopted for the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 in the case of the same vehicle speed v and the same torque change rate Tv in the cut state and the return state.

In the present embodiment, the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 are the absolute values of the static friction compensation current value If when the steering state is in the return state and more than when the steering state is in the cut state | If. | Is set to be large. Here, a case where the same values are adopted for the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 in the cut state and the return state will be described as a comparative example of the present embodiment.

In the comparative example of the present embodiment, the first vehicle speed characteristic Cv11 and the second vehicle speed characteristic Cv21 are stored in the storage unit of the controller, but the first vehicle speed characteristic Cv12 and the second vehicle speed characteristic Cv22 are not stored. The controller according to the comparative example of the present embodiment sets the first vehicle speed coefficient f1 based on the vehicle speed v with reference to the first vehicle speed characteristic Cv11 regardless of the steering state of the steering wheel 1, and sets the first vehicle speed coefficient f1 and the second vehicle speed characteristic Cv21. The second vehicle speed coefficient f2 is set based on the vehicle speed v with reference to.

With reference to FIGS. 4A and 4B, in the comparative example of the present embodiment, the steering wheel 1 is cut and steered from the neutral position to one side (to the right), and the steering wheel is held at a predetermined steering angle θa [°]. The change in steering force when the steering wheel is returned to the other side (left side) will be described. FIG. 4A is a time chart of the steering angle θ of the electric power steering device according to the comparative example of the present embodiment, and FIG. 4B is a time chart of the steering force of the electric power steering device according to the comparative example of the present embodiment. ..

In FIGS. 4A and 4B, the characteristic shown by the solid line is the characteristic when the torque change rate Tv is turned at Tva and the return steering is performed, and the characteristic shown by the alternate long and short dash line is the characteristic when the torque change rate Tv is turned at Tvb and the return steering is performed. It is a characteristic when the torque change rate Tv is turned at Tvc, and the characteristic shown by the broken line is a characteristic when the return steering is performed. The magnitude relationship of Tva, Tvb, and Tvc is Tva <Tvb <Tvc.

A case where the torque change rate Tv is Tva for cut steering and return steering will be described. When the steering wheel 1 is steered in a cut (time point t0), the steering force increases as the steering angle θ increases. When the steering wheel 1 is rotated to a predetermined steering angle θa, the incision steering is completed (time point t1). When the cut-in steering is completed, the steering wheel 1 is held at a predetermined steering angle θa (time point t1 to time point t2). Here, when the incision steering is completed and the steering is shifted to the steering, the steering force rises to Fa and then decreases to Fb, and the steering force F is maintained at Fb while the steering is being held.

When the return steering is performed with respect to the steering wheel 1 (time point t2), the steering force decreases as the steering angle θ decreases. When the steering wheel 1 is rotated to a predetermined steering angle θb (θb <θa), the return steering is completed (time point t3). When the return steering is completed, the steering wheel 1 is held at a predetermined steering angle θb. Here, when the return steering is completed and the rudder shifts to steering, the steering force decreases to Fc1 and then increases to Fd, and the steering force F is maintained at Fd while the steering is being held.

Here, as shown in the figure, the maximum value of the steering force at the time of shifting from the incision steering to the steering holding is almost Fa regardless of the steering speed, and the same result is obtained. On the other hand, the minimum value of the steering force at the time of shifting from the return steering to the steering holding has resulted in variation depending on the steering speed. In the comparative example, when the torque change rate Tv is Tva, the minimum value of the steering force is Fc1 [N], and when the torque change rate Tv is Tvb, the minimum value of the steering force is Fc2 [N] smaller than Fc1 [N]. ]. Further, when the torque change rate Tv was Tvc, the minimum value of the steering force was Fc3 [N], which was smaller than Fc2.

As described above, the reason why the steering force varies depending on the torque change rate Tv is that when the return steering is performed, the return operation of the rack shaft 5 is delayed with respect to the return steering. When the return steering is performed, the input shaft 2 rotates so that the twist of the torsion bar 4 is eliminated. The faster the steering speed, the larger the twist of the torsion bar 4 is eliminated, the difference in the twist angle between the input shaft 2 and the output shaft 3 becomes smaller, and the minimum value of the steering force becomes smaller.

Therefore, in order to suppress the variation in the steering force according to the torque change rate Tv, it is sufficient to improve the responsiveness of the rack shaft 5 to the return steering when the return steering is performed. In order to improve the responsiveness of the rack shaft 5 to the return steering, the static friction compensation may be stronger during the return steering than during the cut steering, and the control current value Isom of the electric motor 10 may be quickly reduced. ..

Therefore, in the present embodiment, as described above, different values are adopted for the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 in the cut state and the return state in the case of the same vehicle speed v and the same torque change rate Tv. .. As a result, in the present embodiment, in the case of the same vehicle speed v and the same torque change rate Tv, the absolute value | If | of the static friction compensation current value If | at the time of return steering becomes the static friction compensation current value If at the time of cut steering. It becomes larger than the absolute value | If |.

Here, the static friction compensation current value If is set to increase the assist base current value Ia when the steering torque T increases, and is set to decrease the assist base current value Ia when the steering torque T decreases. To torque.

The assist base current value Ia is a positive value when the steering wheel 1 rotates in one direction (to the right). On the other hand, the static friction compensation current value If is when the steering wheel 1 rotates to one side (to the right) and the steering torque T increases (that is, when the torque change rate Tv is a positive value). Is a positive value, and when the steering torque T decreases (that is, when the torque change rate Tv is a negative value), it becomes a negative value.

On the other hand, the assist base current value Ia is a negative value when the steering wheel 1 rotates to the other side (leftward). On the other hand, the static friction compensation current value If is when the steering wheel 1 rotates to the other side (to the left) and when the absolute value | T | of the steering torque T increases (that is, the torque change rate Tv increases). When the value is negative), it becomes a negative value, and when the absolute value | T | of the steering torque T decreases (that is, when the torque change rate Tv is a positive value), it becomes a positive value.

For example, if the steering wheel 1 in a state of being held at a predetermined steering angle on one side (right side) of the neutral position is further turned to one side (right side), the steering torque T increases, so that the assist base Both the current value Ia and the static friction compensation current value If are positive values. That is, the static friction compensation current value If is corrected so as to increase the assist base current value Ia. On the other hand, when the steering wheel 1 in a state of being held at a predetermined steering angle on one side (right side) of the neutral position is returned to the other side (left side), the steering torque T decreases, so that the assist base current While the value Ia is a positive value, the static friction compensation current value If is a negative value. That is, the static friction compensation current value If is corrected so as to reduce the assist base current value Ia.

Then, the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 become larger when the steering state is in the returning state and when the steering state is in the cutting state. Therefore, the absolute value | If | of the static friction compensation current value If | becomes larger when the steering state is in the return state than when the steering state is in the cut state. In other words, compared to the case where the static friction compensation current value If is calculated regardless of the steering state (comparative example above), the absolute value of the static friction compensation current value If when the steering state is in the return state | If | Can be increased, and the control current value Isum can be decreased.

As described above, in the present embodiment, when the steering wheel 1 is returned and steered, the static friction compensation is strongly applied and the control current value Isum of the electric motor 10 is quickly reduced as compared with the case where the incision steering is performed. it can. By lowering the control current value Isom before the steering torque T suddenly drops, the responsiveness of the rack shaft 5 can be improved and the sharp drop in the steering torque T can be suppressed.

According to the above-described embodiment, the following effects are exhibited.

(1) The controller 30 calculates the assist base current value Ia based on the steering torque T, and is stationary to compensate for the static friction of the steering system based on the torque change rate Tv related to the steering speed of the steering wheel 1. The friction compensation current value If is calculated, the assist base current value Ia is corrected by the static friction compensation current value If, the control current value Isum is calculated, and the electric motor 10 is controlled based on the control current value Isum. Further, the controller 30 determines the steering state of the steering wheel 1. Then, the controller 30 has a static friction compensation current value If | so that the absolute value | If | of the static friction compensation current value If | becomes larger when the steering state is the return state than when the steering state is the cut state. Is calculated.

As described above, in the present embodiment, since the control current value Isum is calculated based on the torque change rate Tv related to the steering speed, it is possible to suppress the variation in the steering force according to the steering speed. Further, in the present embodiment, the vehicle speed characteristics Cv11 and Cv21 for incision steering and the vehicle speed characteristics Cv12 and Cv22 for return steering are set. By individually setting the vehicle speed characteristics during the cut-in steering and the return steering, it is possible to set an appropriate rest friction compensation current value If for each of the cut-in steering and the return steering. Therefore, in each of the incision steering and the return steering, it is possible to suppress the variation in the steering force according to the steering speed and improve the steering feeling.

In particular, when the steering state is in the return state, the absolute value | If | of the static friction compensation current value If is larger than that in the case where the steering state is in the cut state, so that after the steering wheel 1 is cut. It is possible to quickly reduce the control current value Iso during return steering and prevent a sudden decrease in steering torque T. As a result, it is possible to suppress variations in steering force according to the return steering speed and improve the steering feeling during return steering.

(2) Since the static friction compensation current value If is calculated based on the vehicle speed coefficient (first vehicle speed coefficient f1 and second vehicle speed coefficient f2) that increases as the vehicle speed v increases, the steering force according to the vehicle speed v is calculated. The variation can be suppressed, and the steering feeling can be further improved.

<Second Embodiment>
The electric power steering device 100 according to the second embodiment of the present invention will be described with reference to FIG. In the following, the points different from those of the first embodiment will be mainly described, and in the drawings, the same configurations as those described in the first embodiment or the corresponding configurations are designated by the same reference numerals and the description thereof will be omitted. ..

In the second embodiment, the control current value Isum is calculated by adding the static friction compensation current value If only when the steering angle θ of the steering wheel 1 is small, and when the steering angle θ of the steering wheel 1 is large, it is stationary. The control current value Isum is calculated without taking into account the friction compensation current value If. The details will be described below.

FIG. 5 is a functional block diagram of the static friction compensation current calculation unit 230 according to the second embodiment of the present invention. As shown in FIG. 5, the static friction compensation current calculation unit 230 according to the second embodiment has an absolute value | θ | of the steering angle θ when the absolute value | θ | of the steering angle θ is greater than or equal to the predetermined angle θ0. The steering angle gain processing unit 248 is provided as a processing unit that reduces the absolute value | If | of the static friction compensation current value If, as compared with the case where is less than the predetermined angle θ0.

The steering angle gain processing unit 248 has a steering angle gain calculation unit 248a that calculates the steering angle gain Ga based on the steering angle θ detected by the steering angle sensor 15, and an output value (If1 + If2) output from the addition unit 143. , A multiplication unit 248b for multiplying the steering angle gain Ga calculated by the steering angle gain calculation unit 248a.

The steering angle gain Ga is a value that decreases as the steering angle θ detected by the steering angle sensor 15 increases, and is calculated based on the steering angle gain characteristic Gang stored in the storage unit of the controller 30. The steering angle gain characteristic Gan is stored in the storage unit of the controller 30 in a table format. In the steering angle gain characteristic Gan, the steering angle gain Ga becomes the maximum gain Ga0 (> 0) in the range where the absolute value | θ | of the steering angle θ is 0 [°] or more and less than θ0 °, and the absolute value | θ of the steering angle θ. In the range where | is greater than or equal to θ0 [°] and less than θ1 [°], the steering angle gain Ga decreases as the absolute value | θ | of the steering angle θ increases, and the absolute value | θ | of the steering angle θ becomes θ1 [. °] Or higher, the characteristic is 0 (zero). Note that θ1 is larger than 0 and θ2 is larger than θ1 (0 <θ1 <θ2).

The steering angle gain calculation unit 248a calculates the steering angle gain Ga based on the steering angle θ with reference to the steering angle gain characteristic Gan.

According to the second embodiment, when the absolute value | θ | of the steering angle θ is less than the predetermined angle θ0, the variation of the steering force according to the steering speed at the time of return steering is suppressed, and the steering angle θ When the predetermined angle θ0 or more, that is, when the self-aligning torque acts strongly, it is possible to prevent the reaction force feeling toward the driver from becoming too large.

The following modifications are also within the scope of the present invention, and the configurations shown in the modifications and the configurations described in the above-described embodiments can be combined, the configurations described in the above-mentioned different embodiments can be combined, and the following differences can be made. It is also possible to combine the configurations described in the modified example.

<Modification example 1>
In the above embodiment, an example in which the time change rate Tv of the steering torque T is used as a value related to the steering speed has been described, but the present invention is not limited thereto. For example, the angular velocity of the steering wheel 1 may be used as a value related to the steering speed. The angular velocity of the steering wheel 1 is calculated by time-differentiating the steering angle θ detected by the steering angle sensor 15 with a differentiator.

<Modification 2>
In the above embodiment, an example in which different values are adopted for the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 in the case of the same vehicle speed v and the same torque change rate Tv in the cut state and the return state has been described. Is not limited to this. For example, in the case of the same vehicle speed v and the same torque change rate Tv in the cut state and the return state, one of the first vehicle speed coefficient f1 and the second vehicle speed coefficient f2 may have the same value. That is, one of the first vehicle speed characteristic Cv12 and the second vehicle speed characteristic Cv22 may be omitted.

<Modification example 3>
In the above embodiment, an example of setting the vehicle speed coefficient so that the absolute value | If | of the static friction compensation current value If | becomes larger when the steering state is the return state than when the steering state is the cut state will be described. However, the present invention is not limited to this. For example, when the steering state is the return state, the calculation result in the addition unit 143 is determined so that the absolute value | If | of the static friction compensation current value If is larger than that when the steering state is the cut state. You may multiply by the gain. In this case, the vehicle speed characteristics Cv12 and Cv22 can be omitted.

<Modification example 4>
In the above embodiment, the so-called 1-pinion type electric power steering device 100, which applies the driving force of the electric motor 10 to the output shaft 3 on which the pinion gear 3a is formed, has been described as an example, but the present invention is not limited thereto. The present invention can also be applied to a so-called 2-pinion type electric power steering device in which a shaft having an assist pinion that transmits the rotation of the electric motor 10 to the rack shaft 5 is provided separately from the output shaft 3. The present invention can also be applied to a so-called column-type electric power steering device in which the torque sensor 12 and the assist mechanism are arranged in the vehicle interior away from the rack shaft 5.

The configuration, operation, and effect of the embodiment of the present invention configured as described above will be collectively described.

The electric power steering device 100 is connected to a steering member (steering wheel 1) steered by the driver, and is connected to a steering shaft 7 and a steering shaft 7 that rotate as the driver steers the steering member (steering wheel 1). The assist base current value Ia is calculated based on the electric motor 10 that applies rotational torque, the torque detection unit (torque sensor 12) that detects the steering torque T input from the steering member (steering wheel 1), and the steering torque T. Based on the assist base current calculation unit 121 and the value (torque change rate Tv) related to the steering speed of the steering member (steering wheel 1), the static friction compensation current value If for compensating the static friction of the steering system is set. The static friction compensation current calculation units 130 and 230 to be calculated, the control current calculation unit 180 to correct the assist base current value Ia by the static friction compensation current value If and calculate the control current value Iso, and the electric motor based on the control current value Isom. A motor control unit 9 that controls the motor 10 and a steering state determination unit 110 that determines the steering state of the steering member (steering wheel 1) are provided, and the static friction compensation current value If is assisted when the steering torque T increases. The base current value Ia is set to increase, the assist base current value Ia is set to decrease when the steering torque T decreases, and the static friction compensation current value If is set when the steering state is in the return state. It is larger than when the steering state is the notch state.

In this configuration, since the control current value Isum is calculated based on the value related to the steering speed (torque change rate Tv), it is possible to suppress the variation in the steering force according to the steering speed. Further, since an appropriate static friction compensation current value If can be set in each of the incision steering and the return steering, the variation in the steering force according to the steering speed is suppressed in each of the incision steering and the return steering, and the steering is performed. The feeling can be improved. In particular, when the steering state is in the return state, the static friction compensation current value If is made larger than when the steering state is in the cut state, so that the return steering after cutting the steering member (steering wheel 1) is performed. At this time, the control current value Isom can be quickly lowered to prevent a sudden decrease in the steering torque T. As a result, it is possible to suppress variations in steering force according to the return steering speed and improve the steering feeling during return steering.

In the electric power steering device 100, the value related to the steering speed is the time change rate (torque change rate Tv) of the steering torque T, and the static friction compensation current calculation units 130 and 230 are the vehicle speed detection units (vehicle speed sensor 16). Static friction based on the vehicle speed coefficient (first vehicle speed coefficient f1, second vehicle speed coefficient f2) that increases with the increase in vehicle speed v detected in, and the time change rate (torque change rate Tv) of the steering torque T. Compensation current value If is calculated, and the vehicle speed coefficient (first vehicle speed coefficient f1, second vehicle speed coefficient f2) is the static friction compensation current value when the steering state is in the return state than when the steering state is in the cut state. If is set to be large.

In this configuration, the static friction compensation current value If is calculated based on the vehicle speed coefficient (first vehicle speed coefficient f1 and second vehicle speed coefficient f2) that increases as the vehicle speed v increases, so that the steering force according to the vehicle speed v is calculated. It is possible to suppress the variation of the coefficient and further improve the steering feeling.

The electric power steering device 100 further includes a steering angle detection unit (steering angle sensor 15) that detects the steering angle θ of the steering member (steering wheel 1), and the static friction compensation current calculation unit 230 has a steering angle θ of a predetermined angle. A processing unit (steering angle gain processing unit 248) that reduces the static friction compensation current value If is smaller when the steering angle θ is less than the predetermined angle θ0 when θ0 or more is provided.

In this configuration, when the steering angle θ is less than the predetermined angle θ0, the variation in the steering force according to the steering speed at the time of return steering is suppressed, and when the steering angle θ is the predetermined angle θ0 or more, the reaction to the driver is suppressed. It is possible to prevent the feeling of power from becoming too large.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

1 ... Steering wheel (steering member), 7 ... Steering shaft, 9 ... Motor control unit, 10 ... Electric motor, 12 ... Torque sensor (torque detection unit), 15 ... Steering Angle sensor (steering angle detection unit), 16 ... vehicle speed sensor (vehicle speed detection unit), 30 ... controller, 100 ... electric power steering device, 110 ... steering state determination unit, 121 ... assist Base current calculation unit, 130, 230 ... Static friction compensation current calculation unit, 180 ... Control current calculation unit, 248 ... Steering angle gain processing unit (processing unit), Ia ... Assist base current value, If ... static friction compensation current value, Isum ... control current value, T ... steering torque, f1 ... first vehicle speed coefficient (vehicle speed coefficient), f2 ... second vehicle speed coefficient (vehicle speed coefficient) , V ... vehicle speed, θ ... steering angle, θ0 ... predetermined angle

Claims (3)

It is an electric power steering device
A steering shaft that is connected to a steering member that is steered by the driver and that rotates as the driver steers the steering member.
An electric motor that applies rotational torque to the steering shaft,
A torque detection unit that detects the steering torque input from the steering member, and
An assist base current calculation unit that calculates an assist base current value based on the steering torque,
A static friction compensation current calculation unit that calculates a static friction compensation current value for compensating the static friction of the steering system based on a value related to the steering speed of the steering member.
A control current calculation unit that corrects the assist base current value with the static friction compensation current value and calculates the control current value,
A motor control unit that controls the electric motor based on the control current value,
A steering state determination unit for determining the steering state of the steering member is provided.
The static friction compensation current value is set to increase the assist base current value when the steering torque is increased, and is set to decrease the assist base current value when the steering torque is decreased.
An electric power steering device characterized in that the static friction compensation current value is larger when the steering state is in the return state than when the steering state is in the cut state. The electric power steering device according to claim 1.
The value related to the steering speed is the time change rate of the steering torque.
The static friction compensation current calculation unit calculates the static friction compensation current value based on the vehicle speed coefficient that increases with the increase in vehicle speed detected by the vehicle speed detection unit and the time change rate of the steering torque.
The vehicle speed coefficient is set so that the static friction compensation current value becomes larger when the steering state is in the returning state than when the steering state is in the cutting state. .. The electric power steering device according to claim 1 or 2.
A steering angle detecting unit for detecting the steering angle of the steering member is further provided.
The static friction compensation current calculation unit is characterized by including a processing unit that reduces the static friction compensation current value when the steering angle is equal to or greater than a predetermined angle as compared with the case where the steering angle is less than the predetermined angle. Electric power steering device.

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