Electric power steering control device and electric power steering device

Abstract

Provided is a feature capable of improving steering feel in an electric power steering control device. The electric power steering control device is provided with a base control amount calculation unit (611) that calculates a base control amount corresponding to steering by a driver, a friction force calculation unit (612) that calculates a friction force corresponding to at least one of a yaw rate and a lateral acceleration by using a friction model, and calculates a friction-cause control amount obtained from the calculated friction force, and a control amount calculation unit that calculates a steering control amount from the base control amount and the friction-cause control amount.

Description

TECHNICAL FIELD

[0001] The present application relates to an electric power steering control device that controls steering and an electric power steering device. BACKGROUND

[0002] In the related art, steering devices that assist steering operation by rotation of an electric motor are known (for example, Patent Documents 1 and 2). In these steering devices, the current value of the motor is controlled so that appropriate friction torque is applied to the steering device in accordance with the vehicle speed and the steering angle.

[0003] LIST OF CITATIONS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: JP 2009-126244 A (published on June 11, 2009)

[0006] Patent Document 2: WO 2011 / 062145 (published on May 26, 2011) SUMMARY

[0007] PROBLEMS

[0008] In an electric power steering control device, it is preferable to improve steering feel.

[0009] An object of the present application is to provide a technology capable of improving steering feel in an electric power steering control device.

[0010] METHOD FOR SOLVING THE PROBLEM

[0011] In order to achieve the object, the present application provides an electric power steering control device that calculates a steering control amount that steers a steering device. The electric power steering control device includes a basic control amount calculation unit configured to calculate a basic control amount corresponding to steering by a driver, a friction calculation unit configured to calculate a friction force corresponding to at least one of a yaw rate and a lateral acceleration using a friction model, and calculate a friction-cause control amount caused by the calculated friction force, and a control amount calculation unit configured to calculate the steering control amount in accordance with the basic control amount and the friction-cause control amount calculated by the friction calculation unit.

[0012] EFFECT OF THE INVENTION

[0013] According to the present application, steering feel can be improved in an electric power steering device. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a diagram showing a schematic configuration of a vehicle according to a first embodiment of the present application.

[0015] Figure 2 is a block diagram showing a schematic configuration of an ECU according to a first embodiment of the present application.

[0016] Figure 3 is a block diagram showing a configuration example of a steering control unit according to the first embodiment of the present application.

[0017] Figure 4 is a block diagram showing a configuration example of a friction force calculation unit according to the first embodiment of the present application.

[0018] Figure 5 is a diagram showing a steering control amount of the steering control unit according to the first embodiment of the present application.

[0019] Figure 6A is a diagram showing a steering reaction force when steering control is performed using only the base control amount.

[0020] Figure 6B is a diagram showing a steering reaction force when steering control is performed using only the friction cause control amount.

[0021] Figure 6C is a diagram showing a steering reaction force when steering control is performed using the steering control amount calculated by the addition unit.

[0022] Figure 7 is a block diagram showing a configuration example of a steering control unit according to a second embodiment of the present application.

[0023] Figure 8 is a block diagram showing a configuration example of a steering control unit according to a third embodiment of the present application.

[0024] Figure 9A is a diagram showing a steering reaction force when steering control is performed using only the base control amount.

[0025] Figure 9B is a diagram showing a steering reaction force when steering control is performed using the steering control amount calculated by the calculation unit.

[0026] Figure 10 is a block diagram showing a configuration example of a steering control unit according to a fourth embodiment of the present application.

[0027] Figure 11 is a diagram showing a steering control amount of the steering control unit according to the fourth embodiment of the present application.

[0028] Figure 12 is a diagram showing a friction portion of a mechanical member according to a fifth embodiment of the present application.

[0029] Reference mark list

[0030] Steering member 410

[0031] Steering shaft 420

[0032] Torque sensor 430

[0033] Steering angle sensor 440

[0034] Torque application unit 460

[0035] ECU 600

[0036] Steering control unit (steering control device) 610, 610a, 610b, 610c

[0037] Base control amount calculation unit 611

[0038] Friction force calculation unit 612

[0039] Vehicle model calculation unit 613

[0040] Existing friction offset calculation unit 614

[0041] Calculation unit (correction control amount calculation unit) 616

[0042] Subtraction unit 617

[0043] Auxiliary motor 620

[0044] Rotary transformer 625

[0045] Coulomb friction portion F, F1, F2, F3

[0046] Elastic portion K, K1, K2, K3 DETAILED DESCRIPTION

[0047] [First Embodiment]

[0048] Hereinafter, a first embodiment of the present application will be described in detail.

[0049] (Configuration of vehicle 900)

[0050] Figure 1 is a diagram showing a schematic configuration of a vehicle 900 according to the present embodiment. As shown in FIG. 1, the vehicle 900 includes a steering system 100, a steering control unit 610, a steering member 410, a steering shaft 420, a torque sensor 430, a steering angle sensor 440, a torque application unit 460, an ECU 600, an auxiliary motor 620, a rotary transformer 625, a coulomb friction portion F, an elastic portion K, and a vehicle model calculation unit 613. Figure 1As shown, the vehicle 900 includes a suspension device (suspension) 100, a vehicle body 200, wheels 300, tires 310, a steering member 410, a steering shaft 420, a torque sensor 430, a steering angle sensor 440, a torque application unit 460, a rack-and-pinion mechanism 470, a rack shaft 480, an engine 500, an electronic control unit (ECU) (control device, control unit) 600, a power generation device 700, and a battery 800. Here, the suspension device 100 and the ECU 600 constitute a suspension device according to the present embodiment.

[0051] The steering member 410, the steering shaft 420, the torque sensor 430, the steering angle sensor 440, the torque application unit 460, the rack-and-pinion mechanism 470, the rack shaft 480, and the ECU 600 constitute an electric power steering device according to the present embodiment. The ECU 600 includes an electric power steering control device that controls a steering device of the vehicle 900 on the basis of the electric power steering device.

[0052] The wheels 300 on which the tires 310 are mounted are suspended from the vehicle body 200 by the suspension devices 100. Since the vehicle 900 is a four-wheel vehicle, four suspension devices 100, four wheels 300, and four tires 310 are provided.

[0053] The tires and wheels on the left front side, the tires and wheels on the right front side, the tires and wheels on the left rear side, and the tires and wheels on the right rear side are also referred to as the tires 310A and the wheels 300A, the tires 310B and the wheels 300B, the tires 310C and the wheels 300C, and the tires 310D and the wheels 300D, respectively. Hereinafter, similarly, configurations related to the left front side, the right front side, the left rear side, and the right rear side can be shown with reference numerals “A”, “B”, “C”, and “D”, respectively.

[0054] The suspension device 100 includes a hydraulic shock absorber, an upper arm, and a lower arm. For example, the hydraulic shock absorber includes a solenoid valve, which is an electromagnetic valve that adjusts a damping force generated by the hydraulic shock absorber. However, the present embodiment is not limited thereto, and the hydraulic shock absorber can also use an electromagnetic valve other than the solenoid valve as an electromagnetic valve for adjusting the damping force. For example, as the electromagnetic valve, an electromagnetic valve that applies electromagnetic fluid (magnetic fluid) can be used.

[0055] The power generation device 700 is attached to the engine 500, and electric power generated by the power generation device 700 is stored in the battery 800.

[0056] The steering member 410 operated by the driver is connected to one end of the steering shaft 420 so as to be able to transmit torque, and the other end of the steering shaft 420 is connected to the rack-and-pinion mechanism 470.

[0057] The rack-and-pinion mechanism 470 is a mechanism that converts rotation around the axis of the steering shaft 420 into displacement in the axial direction of the rack shaft 480. When the rack shaft 480 is displaced in the axial direction, the wheels 300 (300A, 300B) are steered by the tie rods 482 (482A, 482B) and the knuckle rods 484 (484A, 484B).

[0058] The torque sensor 430 detects a steering torque applied to the steering shaft 420, that is, a steering torque applied to the steering member 410, and provides a torque sensor signal indicating the detection result to the ECU 600. More specifically, the torque sensor 430 detects torsion of a torsion bar provided in the steering shaft 420 and outputs the detection result as the torque sensor signal. As the torque sensor 430, a known sensor such as a Hall IC, an MR element, a magnetostrictive torque sensor, or the like can be used.

[0059] The steering angle sensor 440 detects a steering angle of the steering member 410 and provides the detection result to the ECU 600.

[0060] The torque application unit 460 applies an assist torque or a reaction force torque to the steering shaft 420 in accordance with a steering control amount provided from the ECU 600. The torque application unit 460 includes an assist motor 620 that generates an assist torque or a reaction force torque in accordance with a steering control amount (also referred to as a motor control amount), and a torque transmission mechanism that transmits the torque generated by the assist motor 620 to the steering shaft 420. The torque application unit 460 includes a motor rotation speed sensor that detects the rotation speed of the assist motor 620, and a resolver 625 that functions as a motor rotation angle sensor that detects the rotation angle of the assist motor.

[0061] Specific examples of the "control amount" in this specification include a current value, a duty ratio, a damping rate, a damping ratio, and the like.

[0062] In the above description, "connected so as to be able to transmit torque" means that the members are connected to each other such that rotation of one member causes rotation of the other member, and at least includes, for example, a case where one member is formed integrally with the other member, a case where one member is directly or indirectly fixed to the other member, and a case where one member is connected to the other member via a linking member so as to be interlocked with each other, and the like.

[0063] Further, in the above example, a steering device in which the steering member 410 and the rack shaft 480 are always mechanically connected is exemplified, but this does not limit the present embodiment, and the steering device according to the present embodiment can be, for example, a steer-by-wire steering device. The matters described below in this specification can also be applied to a steer-by-wire steering device.

[0064] In Figure 1In the embodiment, a column assist type steering apparatus in which the torque application unit is provided on the steering shaft is shown, but this does not limit the present embodiment. A rack assist type steering apparatus in which the torque application unit is provided on the rack shaft can be used.

[0065] The ECU 600 controls various electronic devices provided in the vehicle 900 as a whole. More specifically, the ECU 600 controls the magnitude of the assist torque or reaction force torque applied to the steering shaft 420 by adjusting the steering control amount provided to the torque application unit 460.

[0066] The ECU 600 controls the opening and closing of the solenoid valve provided in the hydraulic shock absorber included in the suspension apparatus 100 by providing a suspension control amount to the solenoid valve. In order to achieve this control, a power line for supplying driving power from the ECU 600 to the solenoid valve is provided.

[0067] The vehicle 900 includes a wheel speed sensor 320 provided for each wheel 300 and detecting the wheel speed of each wheel 300, a lateral G sensor 330 detecting the lateral acceleration of the vehicle 900, a longitudinal G sensor 340 detecting the longitudinal acceleration of the vehicle 900, a yaw rate sensor 350 detecting the yaw rate of the vehicle 900, an engine torque sensor 510 detecting the torque generated by the engine 500, an engine revolution sensor 520 detecting the number of revolutions of the engine, and a brake pressure sensor 530 detecting the pressure of the brake fluid applied to the brake apparatus. The detection results of these various sensors are provided to the ECU 600.

[0068] Although not shown, the vehicle 900 includes a brake apparatus that can be controlled by an anti-lock brake system (ABS) that is a system for preventing the wheels from locking during braking, a traction control system (TCS) that prevents the wheels from spinning during acceleration and the like, and a vehicle stability assist system (VSA) that is a vehicle behavior stability control system having an automatic brake function for yaw moment control during cornering, a brake assist function, and the like.

[0069] Here, the ABS, the TCS, and the VSA compare the wheel speed determined from the estimated vehicle body speed with the wheel speed detected by the wheel speed sensor 320, and determine that the vehicle is in a slip state when the values of the two wheel speeds differ from each other by more than a predetermined value. By this processing, the ABS, the TCS, and the VSA stabilize the performance of the vehicle 900 by performing optimal brake control and traction control in accordance with the running state of the vehicle 900.

[0070] The detection results of various sensors are provided to the ECU 600 and control signals are transmitted from the ECU 600 to the corresponding units by a controller area network (CAN) 370.

[0071] The signals provided to the ECU 600 via the CAN 370 include, for example, the following signals (the acquisition source is shown in parentheses).

[0072] Wheel speeds of the four wheels (wheel speed sensors 320A to 320D)

[0073] Yaw rate (yaw rate sensor 350)

[0074] Longitudinal gravitational acceleration (longitudinal gravitational acceleration sensor 340)

[0075] Lateral gravitational acceleration (lateral gravitational acceleration sensor 330)

[0076] Brake pressure (brake pressure sensor 530)

[0077] Engine torque (engine torque sensor 510)

[0078] Engine revolution number (engine revolution number sensor 520)

[0079] Steering angle (steering angle sensor 440)

[0080] Steering torque (torque sensor 430)

[0081] Figure 2 is a diagram showing a schematic configuration of the ECU 600.

[0082] As shown in Figure 2 , the ECU 600 includes a steering control unit (steering control device) 610.

[0083] The steering control unit 610 determines the magnitude of the steering control amount to be provided to the torque application unit 460 with reference to the detection results of various sensors included in the CAN 370.

[0084] In this specification, the expression "reference" can include the meanings of "use", "consider", "depend on", and the like.

[0085] The process of "determining the magnitude of the control amount" includes the case where the magnitude of the control amount is set to zero, i.e., the case where the control amount is not provided.

[0086] (Steering Control Unit)

[0087] Next, the determination of the magnitude of the steering control amount will be described with reference to Figure 3The steering control unit 610 is described in more detail. Here, the steering control unit 610 of the present embodiment is an example of the steering control unit described in the claims. Figure 3 is a block diagram showing a configuration example of the steering control unit 610.

[0088] As shown in Figure 3 , the steering control unit 610 includes a base control amount calculation unit 611, a friction calculation unit 612, and an adding unit 615. Here, the adding unit 615 is an example of the control amount calculation unit described in the claims. In the present embodiment, the base control amount calculation unit 611, the friction calculation unit 612, and the adding unit 615 are collectively referred to as a steering control amount calculation unit that calculates a steering control amount. The steering control amount calculation unit calculates the steering control amount in accordance with a base control amount calculated by the base control amount calculation unit 611 and a friction-cause control amount calculated by the friction calculation unit 612.

[0089] The base control amount calculation unit 611 refers to the steering torque provided from the torque sensor 430 and calculates a base control amount that corresponds to the steering of the driver and that is used to control the magnitude of the assist torque or the reaction force torque.

[0090] The friction calculation unit 612 calculates a friction using a friction model in accordance with at least one of the yaw rate provided from the yaw rate sensor 350 and the lateral gravitational acceleration (lateral acceleration) provided from the lateral gravitational acceleration sensor 330. The friction calculation unit 612 calculates a friction-cause control amount caused by the calculated friction. The friction calculation unit 612 can be configured to calculate the friction-cause control amount further in accordance with a steering angle-related value that is a value related to the steering angle of the steering device other than the yaw rate and the lateral acceleration using the friction model. The friction calculation unit 612 provides the calculated friction-cause control amount to the adding unit 615.

[0091] The adding unit 615 calculates the steering control amount by adding the friction-cause control amount calculated by the friction calculation unit 612 to the base control amount calculated by the base control amount calculation unit 611. The steering control amount calculated by the adding unit 615 is provided to the assist motor 620 of the torque application unit 460.

[0092] Here, the steering angle-related value has two values, namely, a steering member side steering angle-related value that uses a value on the steering member 410 side via a torsion bar provided inside the steering shaft 420, and a gear box side steering angle-related value that uses a value on the gear box side including the rack and pinion mechanism 470. The friction calculation unit 612 calculates the friction using one of the two values.

[0093] Here, by using the rotation angle of the assist motor 620, which is a pinion case side steering angle related value in which the amount of friction is large, among the steering angle related values, the friction force can be more appropriately calculated. Here, the assist motor 620 is a motor that applies an assist torque or a reaction force torque to the steering device based on a steering control amount.

[0094] For example, the friction force calculating unit 612 acquires a rotation angle signal indicating the rotation angle of the assist motor 620 from the resolver 625, calculates the rack position with reference to the acquired rotation angle signal, and calculates the friction force corresponding to the calculated rack position using the friction model.

[0095] The rotation angle signal indicating the rotation angle of the assist motor 620 output from the resolver 625 has high resolution. Therefore, by calculating the friction force using the output from the resolver 625 having high resolution, the friction force calculating unit 612 can more accurately calculate the friction-cause control amount caused by the friction force. By calculating the rack displacement using the assist motor 620 in a region in which the rack displacement is small, the rack displacement can be more accurately estimated.

[0096] As described above, since the rotation angle of the assist motor 620 output from the resolver 625 is applicable to the friction model, by utilizing the superposition effect obtained by using the rotation angle of the assist motor 620 and the friction model, the friction force calculating unit 612 can more appropriately calculate the friction-cause control amount caused by the friction force.

[0097] (Friction force calculating unit)

[0098] The friction force calculating unit 612 determines the friction model used to calculate the friction force in accordance with the magnitude of the steering angle provided from the steering angle sensor 440. For example, the friction force calculating unit 612 calculates the friction force using a friction model based on the following equation.

[0099] When -a < θ < a (first range): F = f(d)

[0100] When a ≤ θ < b or -b < θ ≤ -a (second range): F = f(Y) + α

[0101] When b ≤ θ or θ ≤ -b (third range): F = f(a t ) + α + β

[0102] where

[0103] θ: steering angle

[0104] F: friction force

[0105] d: rack displacement

[0106] Y: yaw rate

[0107] a t : lateral acceleration

[0108] α and β: arbitrary constants

[0109] f() represents a function. a and b are arbitrary constants satisfying a < b. α is a maximum value of the friction force calculated by F = f(d), for example, and β is a maximum value of the friction force calculated by F = f(Y), for example. As the steering angle θ used here, a pinion angle, a rack position, a steering angle, or the like can be used. The first range, the second range, and the third range are set to gradually increase in the order of the first range, the second range, and the third range in a range region of the steering angle θ.

[0110] As described above, when the steering angle is in the first range, the friction force calculating unit 612 calculates the friction-cause control amount caused by the friction force corresponding to the rack displacement by using the friction model corresponding to the rack displacement. Here, the first range is a range related to a micro-steering range in which the steering member 410 is micro-steered, for example.

[0111] When the steering angle is in the second range, the friction force calculating unit 612 calculates the friction-cause control amount caused by the friction force corresponding to the yaw rate by using the friction model corresponding to the yaw rate. In this friction model, since the friction-cause control amount is calculated corresponding to the value of the yaw rate, it is possible to control the friction characteristics in consideration of the vehicle condition. In the friction force in the second range, by adding the maximum value of the friction force calculated by F = f(d) as a constant, it is possible to make the line of the friction force curve straight at the time of transition from the first range to the second range. As a result, it is possible to realize a sense of unity of the flow of the vehicle steering by the driver and the change in the vehicle condition.

[0112] When the steering angle is in the third range, the friction force calculating unit 612 calculates the friction-cause control amount caused by the friction force corresponding to the lateral acceleration by using the friction model corresponding to the lateral acceleration. In this friction model, since the friction-cause control amount is calculated corresponding to the value of the lateral acceleration, it is possible to control the friction characteristics in consideration of the vehicle condition. In the friction force in the third range, by adding the maximum value of the friction force calculated by F = f(d) and the maximum value of the friction force calculated by F = f(Y) as constants, it is possible to make the line of the friction force curve straight at the time of transition from the second range to the third range. Thereby, it is possible to realize a sense of unity of the flow of the vehicle steering by the driver and the change in the vehicle condition.

[0113] In the friction force calculating unit 612 described above, the configuration in which the frictional cause control amount is calculated in the friction model according to the value of any one of the friction force corresponding to the yaw angular velocity and the friction force corresponding to the lateral acceleration has been described, but the invention described in this specification is not limited to this. The friction force calculating unit 612 in the present embodiment can be configured to use the following friction model: the friction model calculates the frictional cause control amount according to the values of both the friction force corresponding to the yaw angular velocity and the friction force corresponding to the lateral acceleration. The friction force calculating unit 612 in the present embodiment can be configured to use the following friction model: the friction model calculates the frictional cause control amount according to the values of the friction force corresponding to the steering angle related value and the friction force corresponding to the yaw angular velocity. The friction force calculating unit 612 in the present embodiment can be configured to use the following friction model: the friction model calculates the frictional cause control amount according to the values of the friction force corresponding to the steering angle related value and the friction force corresponding to the lateral acceleration.

[0114] In the friction force calculating unit 612 described above, the configuration in which the friction model to be referred to is switched according to the magnitude of the steering angle has been described, but the invention described in this specification is not limited to this. The friction force calculating unit 612 in the present embodiment can be configured to switch the friction model according to the rack displacement and the steering angle related value such as the steering angle of the steering member 410.

[0115] The present inventors have found that, as the steering angle increases, the state quantity that affects the driving feeling of the driver changes in the order of the steering angle related value, the yaw angular velocity, and the lateral acceleration. Therefore, in the present invention, by switching the configuration for calculating the frictional cause control amount in the order of the steering angle related value, the yaw angular velocity, and the lateral acceleration in correspondence with the steering angle region, it is possible to achieve control that provides a more comfortable driving feeling to the driver.

[0116] Here, the configuration of the friction force calculating unit 612 will be described in more detail. Figure 4 The configuration of the friction force calculating unit 612 will be described in more detail. Figure 4 is a block diagram showing an example of the configuration of the friction force calculating unit 612. As an example, Figure 4 A case in which the steering angle provided from the steering angle sensor 440 is used as the steering angle related value is shown.

[0117] As Figure 4 shown, the friction force calculating unit 612 includes a first determination unit 6121, a second determination unit 6122, a third determination unit 6123, a rack displacement conversion unit 6124, a first frictional cause control amount calculating unit 6125, a second frictional cause control amount calculating unit 6126, a third frictional cause control amount calculating unit 6127, an addition unit 6128, and an addition unit 6129.

[0118] The first determination unit 6121 determines whether or not to cause the first friction cause control amount calculation unit 6125 to calculate a friction cause control amount from the provided steering angle related value. More specifically, when the first determination unit 6121 determines that the provided steering angle related value is included in the above-described first range, the first determination unit 6121 causes the first friction cause control amount calculation unit 6125 to calculate a friction cause control amount.

[0119] The second determination unit 6122 determines whether or not to cause the second friction cause control amount calculation unit 6126 to calculate a friction cause control amount from the provided steering angle related value. More specifically, when the second determination unit 6122 determines that the provided steering angle related value is included in the above-described second range, the second determination unit 6122 causes the second friction cause control amount calculation unit 6126 to calculate a friction cause control amount.

[0120] The third determination unit 6123 determines whether or not to cause the third friction cause control amount calculation unit 6127 to calculate a friction cause control amount from the provided steering angle related value. More specifically, when the third determination unit 6123 determines that the provided steering angle related value is included in the above-described third range, the third determination unit 6123 causes the third friction cause control amount calculation unit 6127 to calculate a friction cause control amount.

[0121] The rack displacement conversion unit 6124 calculates a rack position based on the rotation angle of the auxiliary motor provided from the resolver 625. The rack displacement conversion unit 6124 provides the calculated rack position to the first friction cause control amount calculation unit 6125.

[0122] The first friction cause control amount calculation unit 6125 stores a friction model that calculates a friction force from a rack position and is a friction model in which an elastic portion K and a Coulomb friction portion F are connected in series. When the first determination unit 6121 determines that the steering angle related value is in the first range, the first friction cause control amount calculation unit 6125 calculates a friction force from the rack position provided from the rack displacement conversion unit 6124 using the friction model. The first friction cause control amount calculation unit 6125 calculates a friction cause control amount caused by the calculated friction force. The first friction cause control amount calculation unit 6125 provides the calculated friction cause control amount to the addition unit 6128. The friction model in which the elastic portion K and the Coulomb friction portion F are connected in series will be described in detail later.

[0123] The second friction cause control amount calculation unit 6126 stores a table (map) indicating a relationship between the yaw rate and the frictional force. When the second determination unit 6122 determines that the steering angle related value is in the second range, the second friction cause control amount calculation unit 6126 calculates the frictional force from the yaw rate supplied from the yaw rate sensor 350 using the table. The second friction cause control amount calculation unit 6126 calculates the friction cause control amount caused by the calculated frictional force. The second friction cause control amount calculation unit 6126 supplies the calculated friction cause control amount to the addition unit 6129. Here, for example, the table indicating the relationship between the yaw rate and the frictional force is created using a friction model. The friction cause control amount can be calculated using a friction model that derives the frictional force from the yaw rate.

[0124] The third friction cause control amount calculation unit 6127 stores a table (map) indicating a relationship of the frictional force corresponding to the lateral acceleration. When the third determination unit 6123 determines that the steering angle related value is in the third range, the third friction cause control amount calculation unit 6127 calculates the frictional force from the lateral acceleration supplied from the lateral gravitational acceleration sensor 330 using the table. The third friction cause control amount calculation unit 6127 calculates the friction cause control amount caused by the calculated frictional force. The third friction cause control amount calculation unit 6127 supplies the calculated friction cause control amount to the addition unit 6129. Here, for example, the table indicating the relationship between the lateral acceleration and the frictional force is created using a friction model. The friction cause control amount can be calculated using a friction model that derives the frictional force from the lateral acceleration.

[0125] The addition unit 6129 adds the friction cause control amount obtained from the second friction cause control amount calculation unit 6126 to the friction cause control amount obtained from the third friction cause control amount calculation unit 6127, and supplies the calculated friction cause control amount to the addition unit 6128.

[0126] The addition unit 6128 adds the friction cause control amount obtained from the first friction cause control amount calculation unit 6125 to the friction cause control amount obtained from the addition unit 6129, and supplies the calculated friction cause control amount to the addition unit 615.

[0127] The configuration in which both the friction cause control amount obtained from the second friction cause control amount calculation unit 6126 and the friction cause control amount obtained from the third friction cause control amount calculation unit 6127 are used to calculate the friction cause control amount has been described as an example, but the application described in this specification is not limited to this. The addition unit 6129 according to the present embodiment can be configured to obtain the friction cause control amount from either one of the second friction cause control amount calculation unit 6126 and the third friction cause control amount calculation unit 6127 and provide the obtained friction cause control amount to the addition unit 6129.

[0128] Here, details of the friction model in which the elastic portion K and the Coulomb friction portion F stored in the first friction cause control amount calculation unit 6125 are connected in series will be described. Figure 4 The friction model described in the first friction cause control amount calculation unit 6125 is an example of a model in which the elastic portion K and the Coulomb friction portion F are connected in series, which is used to calculate the frictional force in accordance with the rack position. As shown in Figure 4 The first friction cause control amount calculation unit 6125 calculates the frictional force in accordance with the rack position by using a plurality of models in which the elastic portion K and the Coulomb friction portion F are connected in series. The first friction cause control amount calculation unit 6125 can calculate the frictional force using, for example, a Masing model in which a plurality of models in which the elastic portion K and the Coulomb friction portion F are connected in series are connected in parallel to each other.

[0129] The first friction cause control amount calculation unit 6125 calculates the frictional force in accordance with the rack position by using a plurality of models in which the elastic portion K and the Coulomb friction portion F are connected in series. The first friction cause control amount calculation unit 6125 can calculate the frictional force using, for example, a Masing model in which a plurality of models in which the elastic portion K and the Coulomb friction portion F are connected in series are connected in parallel to each other.

[0130] Figure 4 An example of a Masing model in which three models are connected in parallel, i.e., a model in which the elastic portion K l and the Coulomb friction portion F l are connected in series, a model in which the elastic portion K2 and the Coulomb friction portion F2 are connected in series, and a model in which the elastic portion K3 and the Coulomb friction portion F3 are connected in series is shown. The first friction cause control amount calculation unit 6125 is not limited to this, and, for example, a large number of such models, such as ten or more, can also be used to calculate the frictional force.

[0131] In the plurality of models, the elastic constants of the respective elastic portions K l , K2, and K3 and the respective Coulomb friction portions F lThe ratio between the Coulomb friction of F1, F2, and F3 is different for each model. The ratio between the elastic constant and the Coulomb friction of F1 / K1, F2 / K2, and F3 / K3 of the model is set to satisfy, for example, F1 / K1 < F2 / K2 < F3 / K3. The ratio between the elastic constant and the Coulomb friction of F1 / K1, F2 / K2, and F3 / K3 of the model can be freely set in consideration of the ideal friction force waveform output by driving the model. The first friction cause control amount calculation unit 6125 outputs a current proportional to the friction force signal as the friction cause control amount to the addition unit 6129 according to the rack position, where the friction force signal is output by driving the model in which the elastic portion K1 to K3 and the Coulomb friction portion F1 to F3 are connected in series.

[0132] Figure 5 is a diagram showing a friction force waveform created using a model in which the elastic portion K1 to K3 and the Coulomb friction portion F1 to F3 are connected in series. As shown in Figure 5 the first friction cause control amount calculation unit 6125 fixes all the models of the Coulomb friction portion between the rack position A0 and the rack position A1 after the rack position indicates that the steering member 410 is reversed. As a result, a friction force waveform in which the friction force increases from C0 to C1 is realized. The increase in the friction force from C0 to C1 increases at a steep angle compared to the increase from C1 to C2 and the increase from C2 to C3, which will be described later.

[0133] Next, between the rack position A1 and the rack position A2, the first friction cause control amount calculation unit 6125 slips the model in which the elastic portion K1 and the Coulomb friction portion F1 are connected in series with the smallest ratio between the elastic constant and the Coulomb friction of the three ratios. As a result, a friction force waveform in which the friction force increases more gently from C1 to C2 than from C0 to C1 is realized.

[0134] Next, between the rack position A2 and the rack position A3, the first friction cause control amount calculation unit 6125 slips the model in which the elastic portion K1 and the Coulomb friction portion F1 are connected in series with the smallest ratio between the elastic constant and the Coulomb friction of the three ratios, and slips the model in which the elastic portion K2 and the Coulomb friction portion F2 are connected in series with the ratio between the elastic constant and the Coulomb friction being the middle value of the three ratios. As a result, a friction force waveform in which the friction force increases more gently from C2 to C3 than from C1 to C2 is realized. Here, in other words, the first friction cause control amount calculation unit 6125 outputs a friction cause control amount output by connecting a plurality of elastic portions K and Coulomb friction portions F in series in the order of increasing the ratio between the elastic portion and the Coulomb friction in the model.

[0135] Finally, the first friction cause control amount calculation unit 6125 slips the model in which the elastic portion Kl All of the plurality of model slips in which the elastic portion K and the Coulomb friction portion F1 to F3 are connected in series are added together. As a result, the frictional force is kept at a constant value C3.

[0136] In this way, by linking in series the plurality of model slips of the elastic portion K and the Coulomb friction portion F in order with the ratio between the elastic portion and the Coulomb friction force in the model being raised, the first friction cause control amount calculation unit 6125 realizes a frictional force waveform in which the frictional force increases gently. By increasing the number of models in which the elastic portion K and the Coulomb friction portion F are linked in series that are used by the first friction cause control amount calculation unit 6125, it is possible to create a frictional force waveform in which the frictional force increases more gently.

[0137] When the frictional force is calculated by using a plurality of models in which the elastic portion K and the Coulomb friction portion F are linked in series, the frictional force waveform follows the point-symmetrical path between the forward path and the return path of the steering member 410 and is guided to the previous reversal point. Therefore, the first friction cause control amount calculation unit 6125 is able to realize an ideal frictional force waveform by using a plurality of models in which the elastic portion K and the Coulomb friction portion F are linked in series without having to detect whether the steering member 410 is the forward path or the return path.

[0138] Here, in addition to the rack position, it is also possible to realize an ideal frictional force waveform by further taking into consideration at least one of the yaw angular velocity and the lateral acceleration. As such a method, for example, there is a method of calculating the frictional force corresponding to the rack position using a plurality of models in which the elastic portion K and the Coulomb friction portion F are linked in series, and at least one or both of a frictional force portion calculated from the yaw angular velocity and a frictional force portion calculated from the lateral acceleration are added to the frictional force. As another method, in a plurality of models in which the elastic portion K and the Coulomb friction portion F are linked in series, a number of models in which the elastic portion K and the Coulomb friction portion F are linked in series calculate the frictional force corresponding to the rack position, and other models in which the elastic portion K and the Coulomb friction portion F are linked in series are used to calculate the frictional force corresponding to one or both of the yaw angular velocity, the lateral acceleration. By realizing the frictional force waveform with this method, it is possible to realize control that provides a more comfortable feeling of driving to the driver. In other words, the friction calculation unit 612 according to the present embodiment is able to form a hysteresis shape that takes into consideration the yaw angular velocity or the lateral acceleration or a hysteresis shape that takes into consideration the yaw angular velocity and the lateral acceleration in the relationship between the rack position and the frictional force, and calculate the frictional force based on this hysteresis shape.

[0139] In this case, the line between the friction cause control amount calculated by the first friction cause control amount calculation unit 6125 and the second friction cause control amount calculation unit 6126, the line between the friction cause control amount calculated by the first friction cause control amount calculation unit 6125 and the third friction cause control amount calculation unit 6127, or the line between the friction cause control amounts calculated by the first friction cause control amount calculation unit 6125, the second friction cause control amount calculation unit 6126, and the third friction cause control amount calculation unit 6127 has a hysteresis shape in the relationship between the rack displacement and the force.

[0140] The value calculated by the first friction cause control amount calculation unit 6125 using the above-described model has hysteresis in the relationship between the steering angle-related value and the friction cause control amount. The first friction cause control amount calculation unit 6125 can have a hysteresis map indicating the relationship between the steering angle-related value and the friction cause control amount calculated in advance using the above-described model in advance. The first friction cause control amount calculation unit 6125 can calculate the friction cause control amount using the obtained steering angle-related value and the hysteresis map.

[0141] The first friction cause control amount calculation unit 6125 can calculate the friction force using a friction model other than the above-described Maxwell model. Examples of the friction model other than the Maxwell model include a Maxwell model, a Dahl model, a Lugre model, and the like, and a model obtained by combining various friction models can also be used. In the case of the Maxwell model, the friction force can be calculated by series connection of a rigid portion and a damping portion. The designer can freely create a waveform desired by the designer using these friction models.

[0142] Figure 6A is a graph showing the steering reaction force when the steering control is performed using only the base control amount calculated by the base control amount calculation unit 611.

[0143] Figure 6B is a graph showing the steering reaction force when the steering control is performed using only the friction cause control amount calculated by the friction force calculation unit 612.

[0144] Figure 6C is a graph showing the steering reaction force when the steering control is performed using the steering control amount calculated by the addition unit 615.

[0145] In this way, the steering control unit 610 controls the steering device with a steering control amount obtained by adding the friction cause control amount to the base control amount calculated by the base control amount calculation unit 611. The friction cause control amount is caused by the friction calculated by the friction calculation unit 612 using a plurality of models in which an elastic portion K and a Coulomb friction portion F are connected in series. Thus, it is possible to smoothly increase the friction at the initial stage of steering, which contributes to a slight steering operation. Since the change in the steering force is noticeable with respect to a slight change in the steering angle, it is possible to perceive the slight change in the steering angle by the sense of touch, thereby improving the steering feel.

[0146] [Second Embodiment]

[0147] In the first embodiment, the configuration in which the steering control unit 610 uses the yaw rate and the lateral acceleration provided from the sensors provided in the vehicle 900 when the friction calculation unit 612 calculates the friction has been described as an example, but the invention described in this specification is not limited to this. In addition to the configuration of the first embodiment, the steering control unit 610a according to the present embodiment further includes a vehicle model calculation unit 613 that calculates a vehicle model. For ease of explanation, the same reference numerals are affixed to the components having the same function as those described in the above-described embodiments, and the description thereof is not repeated.

[0148] Figure 7 is a block diagram showing a configuration example of the steering control unit 610a of the present embodiment.

[0149] As shown in Figure 7 , the steering control unit 610a differs from the steering control unit 610 described in the first embodiment in the following points.

[0150] That is, the steering control unit 610a includes the vehicle model calculation unit 613. In the present embodiment, the base control amount calculation unit 611, the friction calculation unit 612, the vehicle model calculation unit 613, and the adding unit 615 will be collectively referred to as a steering control amount calculation unit.

[0151] The vehicle model calculation unit 613 stores a vehicle model of the vehicle 900, and calculates a yaw angular velocity and a lateral acceleration of the vehicle 900 by inputting a vehicle speed provided via the CAN 370 and a rotation angle of the assist motor provided from the resolver 625 to the vehicle model. The vehicle model calculation unit 613 provides the calculated yaw angular velocity and lateral acceleration to the friction force calculation unit 612. Here, the vehicle model calculation unit 613 can be configured to calculate the rack position with reference to the rotation angle signal of the assist motor obtained from the resolver 625. In this case, the vehicle model calculation unit 613 calculates the yaw angular velocity and the lateral acceleration of the vehicle 900 by inputting the vehicle speed provided via the CAN 370 and the calculated rack position to the vehicle model. The friction force calculation unit 612 calculates the friction cause control amount of the second friction cause control amount calculation unit 6126 using the calculated yaw angular velocity, and calculates the friction cause control amount of the third friction cause control amount calculation unit 6127 using the calculated lateral acceleration. As a result, in the steering control unit 610a according to the present embodiment, since the first friction cause control amount calculation unit 6125, the second friction cause control amount calculation unit 6126, and the third friction cause control amount calculation unit 6127 are each able to calculate the friction cause control amount using the source input as the rack position, the hysteresis shape that applies the Masing model having better connection can also be reproduced at the time when the signal for calculating the friction cause control amount is shifted.

[0152] The friction force calculation unit 612 calculates the friction force in accordance with at least one of the yaw angular velocity and the lateral acceleration provided from the vehicle model calculation unit 613. As described above, the friction force calculation unit 612 according to the present embodiment is able to calculate the friction force after estimating the yaw angular velocity and the lateral acceleration generated in the vehicle 900, and calculate the friction cause control amount caused by the friction force. As a result, the steering control unit 610a according to the present embodiment is able to accurately operate the reaction force in accordance with the vehicle condition, and improves the steering feeling.

[0153] [Third Embodiment]

[0154] In the first embodiment, the configuration in which the steering control unit 610 calculates the steering control amount from the base control amount corresponding to the steering amount and the friction-cause control amount calculated by the friction force calculation unit 612 has been described as an example, but the application described in this specification is not limited to this. In addition to the configuration of the first embodiment, the steering control unit 610b according to the present embodiment further includes a present friction cancellation amount calculation unit 614 that calculates a friction cancellation control amount for canceling the friction of the electric power steering device. The steering control unit 610b calculates the steering control amount from the base control amount, the friction-cause control amount, and the friction cancellation control amount calculated by the present friction cancellation amount calculation unit 614. Here, the steering control unit 610b of the present embodiment can further include the vehicle model calculation unit 613 of the second embodiment. In the following description, the configuration of the steering control unit 610b that does not include the vehicle model calculation unit 613 will be described. For ease of explanation, the same reference numerals are affixed to components having the same function as those described in the above-described embodiments, and the description thereof will not be repeated.

[0155] Figure 8 is a block diagram showing a configuration example of the steering control unit 610b according to the present embodiment.

[0156] As Figure 8 shown, the steering control unit 610b differs from the steering control unit 610 described in the first embodiment in the following points.

[0157] That is, the steering control unit 610b includes the present friction cancellation amount calculation unit 614. In the present embodiment, the base control amount calculation unit 611, the friction force calculation unit 612, the present friction cancellation amount calculation unit 614, and the calculation unit 615a are collectively referred to as a steering control amount calculation unit.

[0158] The present friction cancellation amount calculation unit 614 calculates the friction amount of the steering device, that is, the friction amount corresponding to the present friction characteristics of mechanical components such as the steering member 410, the steering shaft 420, the torque application unit 460, the rack-and-pinion mechanism 470, and the rack shaft 480.

[0159] The present friction cancellation amount calculation unit 614 calculates the present friction amount from at least one of the steering angle of the steering member 410 detected by the steering angle sensor 440 at the time of steering of the steering device and the steering torque generated in the steering member 410 and detected by the torque sensor 430.

[0160] Here, when the existing amount of friction is calculated using the steering angle, the motor rotation angle calculated by the resolver 625 and the steering torque detected by the torque sensor 430 can be used to calculate the steering angle. Specifically, a correction angle calculated based on the steering torque can be added to the motor rotation angle to obtain the steering angle. In this case, the correction angle calculated based on the steering torque can be calculated by multiplying the detected steering torque by a predetermined coefficient (for example, the inverse of the coefficient of elasticity of the torsion bar). As a result, even without the steering angle sensor 440, the steering angle can be accurately determined and the existing amount of friction can be calculated.

[0161] The existing friction cancellation amount calculation unit 614 calculates a friction cancellation control amount for subtracting (cancelling) the existing amount of friction from the final steering control amount based on the calculated existing amount of friction.

[0162] The calculation unit 615a calculates the steering control amount by subtracting the friction cancellation control amount calculated by the existing friction cancellation amount calculation unit 614 from the sum of the base control amount and the friction cause control amount. The steering control amount calculated by the calculation unit 615a is supplied to the assist motor 620 of the torque application unit 460.

[0163] Figure 9A is a graph showing the steering reaction force when the steering is controlled using only the base control amount calculated by the base control amount calculation unit 611.

[0164] Figure 9B is a graph showing the steering reaction force when the steering is controlled using the steering control amount calculated by the calculation unit 615a.

[0165] According to the above configuration, the steering control unit 610b calculates the steering control amount by subtracting the friction cancellation control amount from the sum of the base control amount and the friction cause control amount. Therefore, the steering control unit 610b can calculate the desired steering control amount corresponding to the friction characteristics of the mechanical components of the electric power steering apparatus.

[0166] [Fourth Embodiment]

[0167] In the third embodiment, the case in which the steering control unit 610b calculates the steering control amount by subtracting the friction offset control amount from the sum of the base control amount and the friction cause control amount has been described, but the application described in this specification is not limited to this. The steering control unit 610c according to the present embodiment includes a calculation unit (correction control amount calculation unit) 616 in place of the calculation unit 615a in the configuration of the third embodiment. The steering control unit 610c outputs the base control amount calculated by the base control amount calculation unit 611 and a correction control amount obtained by subtracting the friction cause control amount from the friction offset control amount. Here, the steering control unit 610c of the present embodiment can also include the vehicle model calculation unit 613 of the second embodiment. In the following description, the configuration of the steering control unit 610c that does not include the vehicle model calculation unit 613 will be described. For the convenience of explanation, the same reference numerals are affixed to the components having the same functions as those described in the first and second embodiments, and the description thereof will not be repeated.

[0168] Figure 10 is a block diagram showing a configuration example of the steering control unit 610c according to the present embodiment.

[0169] As shown in Figure 10 , the steering control unit 610c differs from the steering control unit 610b described in the third embodiment in the following points.

[0170] That is, the steering control unit 610c does not include the calculation unit 615a, but includes the calculation unit 616.

[0171] The calculation unit 616 calculates the correction control amount by subtracting the friction cause control amount calculated by the friction force calculation unit 612 from the friction offset control amount calculated by the existing friction offset amount calculation unit 614.

[0172] In the subtraction unit 617, the correction control amount calculated by the calculation unit 616 is subtracted from the base control amount calculated by the base control amount calculation unit 611.

[0173] In the present embodiment, the base control amount calculation unit 611, the friction force calculation unit 612, the existing friction offset amount calculation unit 614, the calculation unit 616, and the subtraction unit 617 are collectively referred to as a steering control amount calculation unit. The control amount calculation unit calculates the steering control amount by subtracting the correction control amount from the base control amount.

[0174] Figure 11 is a graph showing a waveform of the steering control amount calculated by the control amount calculation unit. In Figure 11In this case, Fr_curve1 indicates a waveform of the steering reaction force when steering control is performed using the base control amount calculated by the base control amount calculating unit 611, and Fr_curve2 indicates a waveform of the steering reaction force when steering control is performed using the ideal steering control amount. Fr_diff indicates the difference between the ideal steering reaction force and the steering reaction force when the base control amount is used.

[0175] The correction control amount calculated by the calculating unit 616 from the friction offset control amount and the friction cause control amount corresponds to Fr_diff. As shown in Figure 11 the control amount calculating unit calculates the desired steering control amount (corresponding to Fr_curve2) by subtracting the correction control amount (corresponding to Fr_diff) calculated by the calculating unit 616 from the base control amount (corresponding to Fr_curve1) calculated by the base control amount calculating unit 611.

[0176] The control amount calculating unit supplies the calculated steering control amount to the assist motor 620 of the torque applying unit 460.

[0177] According to these configurations, the control amount calculating unit calculates the correction control amount by subtracting the friction cause control amount from the friction offset control amount, and calculates the steering control amount by subtracting the calculated correction control amount from the base control amount. As a result, the friction force can be smoothly increased, and the influence of the vibration disturbance on the calculation of the steering control amount can be prevented. Therefore, when the steering operation of the steering angle / steering wheel is repeatedly slightly increased, the slight change in the steering angle can be perceived from the feeling, and the steering feeling is improved.

[0178] [Fifth Embodiment]

[0179] In the fifth embodiment, in the electric power assisted steering apparatus described in the first, second, and third embodiments, a configuration for further improving the flexibility of the friction portion of the mechanical member to improve the steering feeling will be described. The configuration of the fifth embodiment can be applied to any one of the first, second, and third embodiments.

[0180] Figure 12 is a view showing the rack shaft 480 and the rack guide 495, which are examples of the friction portion of the mechanical member in the electric power assisted steering apparatus. As shown in Figure 12 the resin bearing 496 is provided between the rack shaft 480 and the rack guide 495. A recess 495a is formed in the rack guide 495 along the extension direction of the rack shaft, and the resin bearing 496 is fitted into the recess.

[0181] In Figure 12 the y-axis direction indicates the direction in which the rack shaft 480 extends, the z-axis indicates the vertical direction perpendicular to the y-axis, and the x-axis indicates the direction perpendicular to the y-axis and the z-axis.

[0182] As Figure 12 shown, by increasing the thickness (thickness in the z-axis direction) of the resin bearing 496, the frictional force when the rack shaft 480 starts to slide against the reverse torque is smoothly increased due to the deformation of the resin bearing 496.

[0183] As Figure 12 shown, it is preferable to change the thickness (thickness in the z-axis direction) of the resin bearing 496 in the x-axis direction. As a result, the amount of deformation until the rack shaft starts to slide against the reverse torque can be differentiated depending on the respective positions of the resin bearing 496, and the frictional force is smoothly increased in a curved shape rather than in a stepped shape.

[0184] In addition to the frictional portion between the rack shaft 480 and the rack guide 495, among the frictional portions of various mechanical components in the electric power steering apparatus, by increasing the thickness of the resin bearing and further making the thickness uneven, the frictional force generated by the steering operation in the electric power steering apparatus can be smoothly increased, and the steering feel can be improved.

[0185] [Example of implementation by software]

[0186] The control block (steering control unit 610) of the ECU 600 can be implemented by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or can be implemented by software using a central processing unit (CPU).

[0187] In the latter case, the ECU 600 includes a CPU that executes program instructions, the program serving as software that implements various functions; a read-only memory (ROM) or storage device (referred to as a "recording medium") in which programs and various types of data are recorded so that they can be read by a computer (or CPU); and a random access memory (RAM) or the like in which the program is deployed. The object of the present application is achieved by the computer (or CPU) reading the program from the recording medium and executing the program. Examples of the recording medium include "non-transitory tangible media" such as magnetic tapes, magnetic disks, cards, semiconductor memories, and programmable logic circuits. The program can be provided to the computer via any transmission medium (for example, a communication network or a broadcast wave) capable of transmitting the program. The present application can also be implemented in the form of a data signal embedded in a carrier wave, in which the program is implemented by electronic transmission.

[0188] The present application is not limited to the above-described embodiments, various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included within the technical scope of the present application.

Claims

1. An electric power steering control device for calculating a steering control amount that steers a steering device, the electric power steering control device comprising: a base control amount calculation unit configured to calculate a base control amount corresponding to steering by a driver; a friction force calculation unit configured to calculate a friction force corresponding to at least one of a yaw angular velocity and a lateral acceleration using a friction model, and to calculate a friction-cause control amount caused by the calculated friction force; and a control amount calculation unit configured to calculate the steering control amount from the base control amount and the friction-cause control amount calculated by the friction force calculation unit, the friction model is a model in which an elastic portion and a Coulomb friction portion are connected in series, and the friction force calculation unit is configured to calculate the friction force using the model in which the elastic portion and the Coulomb friction portion are connected in series.

2. The electric power steering control device according to claim 1, wherein the friction force calculation unit is configured to calculate a friction force corresponding to the yaw angular velocity and a friction force corresponding to the lateral acceleration, and to calculate the friction-cause control amount caused by the friction force corresponding to the yaw angular velocity and the friction force corresponding to the lateral acceleration.

3. The electric power steering control device according to claim 1 or 2, wherein the friction force calculation unit is configured to also calculate a friction force corresponding to a steering angle-related value that is a value related to a steering angle of a steering device, and to calculate the friction-cause control amount caused by the calculated friction force.

4. The electric power steering control device according to claim 3, wherein the friction force calculation unit is configured to calculate the friction-cause control amount based on the friction force corresponding to the steering angle-related value and the friction force corresponding to the yaw angular velocity.

5. The electric power steering control device according to claim 3, wherein the friction force calculation unit is configured to calculate the friction-cause control amount based on the friction force corresponding to the steering angle-related value and the friction force corresponding to the lateral acceleration.

6. The electric power steering control device according to claim 3, wherein the friction force calculation unit is configured to select a signal value used for calculation of the friction-cause control amount in accordance with the steering angle-related value, and the friction force calculation unit is configured to: calculate a friction-cause control amount based on the friction force corresponding to the steering angle-related value when the steering angle-related value is included in a first range, calculate a friction-cause control amount based on the friction force corresponding to the yaw angular velocity when the steering angle-related value is included in a second range that is larger than the first range, and calculate a friction-cause control amount based on the friction force corresponding to the lateral acceleration when the steering angle-related value is included in a third range that is larger than the second range.

7. The electric power steering control device according to claim 3, wherein the steering angle-related value is calculated from a motor rotation angle signal of an electric motor that applies an assist torque or a reaction force torque to the steering device based on a steering control amount calculated by the control amount calculation unit.

8. The electric power steering control device according to claim 1, wherein the friction force calculation unit is configured to calculate the friction force using a plurality of models that link the elastic portion and the Coulomb friction portion in series, each of the plurality of models has an elastic constant and a Coulomb friction force, and a ratio between the Coulomb friction force and the elastic constant differs for each of the plurality of models.

9. The electric power steering control device according to claim 1 or 2, further comprising: a present friction offset amount calculation unit configured to calculate a friction offset control amount for offsetting a friction force of the steering device, wherein the control amount calculation unit is configured to calculate the steering control amount from the base control amount, the friction cause control amount, and the friction offset control amount.

10. The electric power steering control device according to claim 9, wherein the control amount calculation unit is configured to calculate the steering control amount by subtracting the friction offset control amount from a sum of the base control amount and the friction cause control amount.

11. The electric power steering control device according to claim 9, wherein the control amount calculation unit is configured to calculate a correction control amount by subtracting the friction cause control amount from the friction offset control amount, and to calculate the steering control amount by subtracting the correction control amount from the base control amount.

12. The electric power steering control device according to claim 9, wherein the present friction offset amount calculation unit is configured to calculate the friction offset control amount from a steering torque generated when the steering device is steered.

13. An electric power steering device comprising the electric power steering control device according to any one of claims 1 to 12.

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