JP2014227036A - Steering controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify adjustment operation for achieving desired steering feeling.SOLUTION: A viscosity coefficient calculation unit 25a generates a viscosity coefficient C used for adjusting viscosity feeling provided to a driver when a driver operates a steering wheel according to driver power W using a viscosity adjustment map prepared in advance. A viscosity correction amount calculation unit 25c generates a viscosity correction amount ΔC for compensating for a difference between rigidity feeling expected by a rigidity adjustment torque Tkgenerated on the basis of a rigidity equivalent coefficient K and actually obtained rigidity feeling. An adder 25d adds the viscosity correction amount ΔC to the viscosity coefficient C to generate a corrected viscosity coefficient C+ΔC. A multiplier multiplies the corrected viscosity coefficient C+ΔC by a motor speed ω (corresponding to a steering speed) to generate a viscosity adjustment torque Tc.

Description

  The present invention relates to a steering control device that adjusts a feel during steering by assist torque.

  Conventionally, a steering control device that assists a steering force applied to a steering member (handle) of a vehicle by an assist torque (auxiliary steering torque) generated by a motor is known. As a technology applied to this type of device, assist torque is generated using a standard steering model that defines the relationship between the steering angle and steering torque in the steering member, and the mechanical impedance that characterizes the standard steering model is determined by the vehicle speed and A technique for changing the steering feeling by changing the steering angle in accordance with the steering angle is known (for example, see Patent Document 1).

  The mechanical impedance (inertia, viscosity, rigidity) mainly affects the force sense of the driver who operates the steering wheel, and creates the basic weight and response in the steering feeling (feel during steering).

Japanese Patent No. 4232471

  The prior art described in Patent Document 1 is configured to independently adjust the inertia, viscosity, and rigidity of the mechanical impedance. For this reason, there has been a problem that a great deal of labor is required for the adaptation work for realizing a desired steering feeling.

  For example, adjusting the rigidity increases or decreases the spring reaction force, and increasing the spring reaction force increases the feeling of returning the handle. In order to suppress this feeling of return, it is necessary to adjust the viscosity appropriately. Thus, since rigidity and viscosity influence each other, when the rigidity is changed, it is necessary to adjust the viscosity accordingly. Since the rigidity is affected by the adjustment of the viscosity, the adjustment of the rigidity and the adjustment of the viscous line are repeated. In other words, in order to balance the steering feeling, it is necessary to adjust the rigidity and the viscosity by subtle changes in numerical values, so that much effort is required to obtain a desired steering feeling.

  In order to solve the above-described problems, an object of the present invention is to simplify adjustment work for realizing a desired steering feeling.

The steering control device of the present invention includes a steering state amount generating means, a stiffness adjusting torque generating means, a viscosity adjusting torque generating means, and a command value generating means.
The steering state quantity generating means generates a steering state quantity representing an operation applied to the steering member. The stiffness adjusting torque generating means generates a stiffness adjusting torque that is a target value of the steering torque for adjusting a stiffness coefficient of a mechanical impedance that defines a relationship between the steering torque detected by the steering shaft and the steering angle according to the steering state quantity. To do. The viscosity adjustment torque generating means generates a viscosity adjustment torque that is a target value of the steering torque for adjusting the viscosity coefficient of the mechanical impedance according to the steering state quantity. The command value generation means generates a command value for controlling the motor from the rigidity adjustment torque and the viscosity adjustment torque. However, the viscosity adjustment torque generating means is linked to the adjustment contents of the rigidity adjustment torque generating means so that the difference between the expected rigidity feeling and the actually obtained rigidity feeling is compensated for the change in the stiffness coefficient. To change the viscosity coefficient.

According to such a configuration, it is not necessary to adjust the viscosity coefficient when the stiffness coefficient is adjusted, so that the adjustment work for realizing a desired steering feeling can be simplified.
Reference numerals in parentheses described in the claims indicate a correspondence relationship with specific means described in the embodiments described later as one aspect, and do not limit the technical scope of the present invention. . The present invention can be realized in various forms such as a program for causing a computer to function as each means constituting the steering control device, a steering control method, and the like in addition to the above-described steering control device.

It is a block diagram showing schematic structure of an electric power steering system. It is a block diagram showing schematic structure of the control mechanism of ECU. It is a block diagram showing the structure of a base assist part. It is a graph which shows the content of the correction amount production | generation map used in a viscosity correction amount calculating part. It is a graph which shows the relationship between the rigidity equivalent coefficient obtained when a rigidity equivalent coefficient is changed, and a rigidity value. It is a graph which shows the relationship between the rigidity value obtained when a rigidity value is changed, and a viscosity value.

Embodiments of the present invention will be described below with reference to the drawings.
<Overall configuration>
As shown in FIG. 1, the electric power steering system 1 of the present embodiment assists an operation of a handle (steering member) 2 by a driver with a motor 6. The handle 2 is fixed to one end of a steering shaft 3, and a torque sensor 4 is connected to the other end of the steering shaft 3, and an intermediate shaft 5 is connected to the other end of the torque sensor 4. In the following description, the entire shaft body from the steering shaft 3 through the torque sensor 4 to the intermediate shaft 5 is also collectively referred to as a steering shaft. Hereinafter, the rotation angle of the steering shaft is also referred to as a steering angle, the rotation angular velocity of the steering shaft is also referred to as steering speed, and the rotation angular acceleration of the steering shaft is also referred to as steering acceleration.

  The torque sensor 4 is a sensor for detecting the steering torque Ts. Specifically, a torsion bar that connects the steering shaft 3 and the intermediate shaft 5 is provided, and a torque applied to the torsion bar is detected based on a twist angle of the torsion bar.

  The motor 6 assists the steering force of the handle 2 and its rotation is transmitted to the intermediate shaft 5 via the speed reduction mechanism 6a. That is, the speed reduction mechanism 6a is constituted by a worm gear provided at the tip of the rotating shaft of the motor 6 and a worm wheel provided coaxially on the intermediate shaft 5 in mesh with the worm gear. The rotation of the motor 6 is transmitted to the intermediate shaft 5. Conversely, when the intermediate shaft 5 is rotated by the operation of the handle 2 or the reaction force from the road surface (road surface reaction force), the rotation is transmitted to the motor 6 via the speed reduction mechanism 6a, and the motor 6 also rotates. .

  The motor 6 is a brushless motor in the present embodiment, and includes a rotation sensor such as a resolver, and is configured to output the rotation state of the motor 6. The motor 6 of the present embodiment is configured to be capable of outputting at least the motor speed ω (information indicating the rotational angular speed) as the rotational state from the rotation sensor. Instead of the motor speed ω, a steering speed obtained by multiplying the motor speed ω by the gear ratio of the speed reduction mechanism 6a may be used.

  The other end of the intermediate shaft 5 opposite to the end to which the torque sensor 4 is connected is connected to the steering gear box 7. The steering gear box 7 is configured by a gear mechanism including a rack and a pinion gear, and the rack teeth mesh with a pinion gear provided at the other end of the intermediate shaft 5. Therefore, when the driver turns the handle 2, the intermediate shaft 5 rotates (that is, the pinion gear rotates), thereby moving the rack to the left and right. Tie rods 8 are attached to both ends of the rack, and the tie rods 8 reciprocate left and right together with the rack. Accordingly, the tie rod 8 pulls or pushes the knuckle arm 9 ahead, thereby changing the direction of each tire 10 that is a steered wheel.

A vehicle speed sensor 11 for detecting the vehicle speed V is provided at a predetermined part of the vehicle.
With this configuration, when the driver rotates (steers) the handle 2, the rotation is transmitted to the steering gear box 7 via the steering shaft 3, the torque sensor 4, and the intermediate shaft 5. Then, in the steering gear box 7, the rotation of the intermediate shaft 5 is converted into the left-right movement of the tie rod 8, and the left and right tires 10 are steered by the movement of the tie rod 8.

  The ECU 15 is operated by electric power from an in-vehicle battery (not shown), and assist torque based on the steering torque Ts detected by the torque sensor 4, the motor speed ω of the motor 6, and the vehicle speed V detected by the vehicle speed sensor 11. Command Ta is calculated. Then, by applying a drive voltage Vd corresponding to the calculation result to the motor 6, the assist amount of the force with which the driver turns the steering wheel 2 (and thus the force to steer both tires 10) is controlled.

  In this embodiment, since the motor 6 is a brushless motor, the drive voltage Vd output (applied) from the ECU 15 to the motor 6 is specifically the three-phase (U, V, W) drive voltages Vdu, Vdv, Vdw. is there. The rotational torque of the motor 6 is controlled by applying the drive voltages Vdu, Vdv, Vdw of each phase from the ECU 15 to the motor 6 (energizing the drive current of each phase). A method for driving a brushless motor with a three-phase drive voltage (for example, PWM drive) and a drive circuit (for example, a three-phase inverter) for generating the three-phase drive voltage are well known. Omitted.

  The ECU 15 controls the steering characteristic by controlling the motor 6 by directly controlling the drive voltage Vd applied to the motor 6. It can be said that the steering system mechanism 100 to be driven is controlled, and therefore the control target of the ECU 15 can be said to be the steering system mechanism 100. The steering system mechanism 100 indicates the entire mechanism excluding the ECU 15 in the system configuration diagram shown in FIG. 1, that is, the entire mechanism that transmits the steering force of the handle 2 from the handle 2 to each tire 10.

<ECU>
Next, a schematic configuration (control mechanism) of the ECU 15 is shown in a block diagram of FIG. Note that, in the control mechanism of the ECU 15 shown in FIG. 2, each part except the current feedback (FB) unit 42 and part of the functions of the current FB unit 42 are actually determined by a CPU (not shown) included in the ECU 15. This is realized by executing a control program. That is, FIG. 2 shows various functions realized by the CPU divided into functional blocks. However, it is only an example that the control mechanism shown in each figure is realized by software, and the whole or a part of the control mechanism shown in FIG. 2 or the like is realized by hardware such as a logic circuit. Needless to say, it may be.

ECU15, as shown in FIG. 2, the base assist unit 20 that generates a base assist command Tb ^*, a correction unit 30 for generating a correction torque command Tr, adding the base assist command Tb ^* and the correction torque command Tr And an adder 41 for generating an assist torque command Ta, and a current feedback (FB) unit 42 for energizing and driving the motor 6 by applying a drive voltage Vd to the motor 6 based on the assist torque command Ta. .

The base assist unit 20 realizes the characteristic of the steering reaction force (steering torque) according to the road surface reaction force (road surface load), that is, the reaction (reaction force) corresponding to the road surface load is transmitted quasi-steadily to the driver. This makes it easier for the driver to grasp the vehicle and road surface conditions, and adjusts the hand feeling (sensory hardness, stickiness, and weight from the steering wheel to the tire) according to the steering state. This is a block for realizing an improvement in the feel during steering. Based on the steering torque Ts, the motor speed ω, and the vehicle speed V, the base assist unit 20 assists the operation of the steering wheel 2 so as to realize the transmission feeling according to the road surface load and the feel according to the steering state. The base assist command Tb ^* is generated.

  The correction unit 30 is a block for making sure that the road surface condition (road information) is accurately transmitted to the steering wheel and for compensating for a feel during steering that cannot be adjusted by the base assist unit 20 alone. The correction unit 30 generates the above-described correction torque command Tr based on the steering torque Ts and the motor speed ω.

The adder 41 generates an assist torque command Ta by adding the base assist command Tb ^* generated by the base assist unit 20 and the correction torque command Tr generated by the correction unit 30.

  Based on the assist torque command Ta, the current FB unit 42 is configured so that an assist torque (assist steering force) corresponding to the assist torque command Ta is applied to the steering shaft (particularly on the tire 10 side with respect to the torque sensor 4). A drive voltage Vd is applied. Specifically, a target current (target current for each phase) to be energized to each phase of the motor 6 is set based on the assist torque command Ta. Then, by detecting and feeding back the energization current Im of each phase and controlling the drive voltage Vd (controlling the energization current) so that the detected value (the energization current Im of each phase) matches the target current, A desired assist torque is generated for the steering shaft.

  The correction unit 30 and the current FB unit 42 are known techniques (see, for example, Japanese Patent Application Laid-Open No. 2013-52793), and thus description thereof is omitted here. The following description relates to the main part of the present invention. The base assist unit 20 will be described in detail.

<Base assist part>
As shown in FIG. 3, the base assist unit 20 includes a load estimator 21, a basic load amount calculation unit 22, a driver work rate calculation unit 23, a stiffness adjustment amount calculation unit 24, and a viscosity adjustment amount calculation unit 25. The inertia adjustment amount calculation unit 26, the differentiator 261, the target calculation unit 27, the deviation calculation unit 28, and the controller unit 29 are provided.

The load estimator 21 estimates the road load based on the base assist command Tb ^* (corresponding to the assist torque) and the steering torque Ts. The basic load amount calculation unit 22 is a basic component that is a basic component of the target value of the steering torque based on the road surface load (estimated load Tx) estimated by the load estimator 21 and the traveling speed (vehicle speed V) of the host vehicle. Torque Tf ^* is generated.

  The driver power calculation unit 23 calculates the driver power W by multiplying the steering speed obtained by multiplying the motor speed ω by the gear ratio of the speed reduction mechanism 6a by the steering torque Ts. However, the steering torque Ts and the motor speed ω (and thus the steering speed) both have opposite polarities when the handle 2 is rotated clockwise and when it is rotated counterclockwise. Further, the steering torque Ts has a reverse polarity value when the steering wheel 2 is rotated clockwise from the neutral position and counterclockwise when the position of the handle 2 where Ts = 0 is set to the neutral position. The neutral position is a position where the vehicle is moved straight during normal driving when the tire is gripped, and a neutral position is a direction in which the tire slides when a spin is caused by oversteer. Here, it is assumed that it is positive when rotating left and negative when rotating right.

  Therefore, when the steering torque Ts and the motor speed ω have the same polarity and the driver power W is positive, it is a value generated by the operation of turning the steering wheel, and the polarity of the steering torque Ts and the motor speed ω is different. When the driver power W is negative, it indicates that the value is generated by the operation of turning back the steering wheel. If the driver power W is zero, the steering power is maintained.

  That is, when the steering wheel is cut to the left or right from the neutral position, the polarities of the steering torque Ts and the motor speed ω are the same, so the driver power W has a positive value. If it is held with the steering wheel turned off (steering state), the motor speed ω is zero, so the driver power is zero. When the steering wheel is turned back from this state of steering holding, the polarity of the motor speed ω is reversed from that when the steering wheel is turned, and the polarity of the steering torque Ts and the motor speed ω are different from each other. Is a negative polarity value. Note that the steering torque Ts increases as the tire direction deviates from the traveling direction of the vehicle, and increases as the motor speed ω steers more rapidly, and depends on the degree of these operations (operation amount). The absolute value of the driver work rate W takes a large value.

  Since the steering speed is a value proportional to the motor speed ω, the motor speed ω may be regarded as the steering speed, and the motor speed ω multiplied by the steering torque Ts may be used as the driver work rate W.

The differentiator 261 generates a motor acceleration α corresponding to the steering acceleration by differentiating the motor speed ω corresponding to the steering speed.
The stiffness adjustment amount calculation unit 24 is one of the adjustment components (adjustment torque) included in the target steering torque Ts ^* based on the driver power W, the estimated load Tx, and the vehicle speed V, and is a steering system that is given to the driver during steering. A rigidity adjustment torque Tk ^* for adjusting the rigidity of the mechanism 100 is generated. The viscosity adjustment amount calculation unit 25 is one of adjustment components included in the target steering torque Ts ^* based on the driver power W, the motor speed ω, and the vehicle speed V, and the viscosity of the steering system mechanism 100 given to the driver during steering. A viscosity adjustment torque Tc ^* for adjusting the sexual feeling is generated. The inertia adjustment amount calculation unit 26 is one of adjustment components included in the target steering torque Ts ^* based on the driver power W and the motor acceleration α, and adjusts the inertial feeling of the steering system mechanism 100 given to the driver during steering. Inertia adjustment torque Ti ^* is generated.

The target calculator 27 calculates the target steering torque Ts ^* by adding the basic torque Tf ^* , the rigidity adjustment torque Tk ^* , the viscosity adjustment torque Tc ^* , and the inertia adjustment torque Ti ^* . The deviation calculator 28 calculates a torque deviation which is a difference between the steering torque Ts and the target steering torque Ts ^* . The controller unit 29 includes a differentiator, an integrator, and the like, and generates an output for adjusting the feeling of transmission according to the road load applied to the driver during the steering operation and the feel according to the steering state quantity.

Based on the torque deviation (difference between the steering torque Ts and the target steering torque Ts ^* ), the controller unit 29 performs control so that the torque deviation becomes zero, that is, the steering torque Ts follows the target steering torque Ts ^*. Thus, a base assist command Tb ^* for generating an assist torque (also referred to as an assist amount) that realizes a feeling of transmission according to the road surface load and a feel according to the steering state amount is generated.

The load estimator 21 includes an adder that adds the base assist command Tb ^* and the steering torque Ts, and a low-pass filter (LPF) that extracts a band component below a predetermined frequency from the addition result. The extracted frequency component is output as the estimated load Tx. Usually, since the driver mainly operates by relying on the steering reaction force information of 10 Hz or less, the frequency component of approximately 10 Hz or less is allowed to pass (extract) and the frequency component higher than 10 Hz is cut off.

The basic load amount calculation unit 22 allows the driver to feel that the steering operation is heavy or light according to the road surface reaction force, or the driver's steering reaction force (or steering torque) with respect to an increase in the road surface reaction force. The target steering torque Ts ^* for realizing the degree of increase (gradient) is generated. The basic load amount calculator 22 of the present embodiment actually maps the target steering torque Ts ^* corresponding to the estimated load Tx and the vehicle speed V, and generates the target steering torque Ts ^* based on the map. To do.

The stiffness adjustment amount calculation unit 24 includes a stiffness coefficient calculation unit 24a and a multiplier 24b. The stiffness coefficient calculating unit 24a is a stiffness equivalent coefficient K (a value corresponding to the stiffness coefficient of the mechanical impedance) that is a coefficient for adjusting the stiffness feeling (spring feeling) given to the driver during the steering operation according to the driver work rate W. Are generated using a stiffness adjustment map prepared in advance. The multiplier 24b generates the stiffness adjustment torque Tk ^* by multiplying the stiffness equivalent coefficient K by the estimated load Tx. That is, the stiffness equivalent coefficient K can be said to be an adjustment gain for the road surface load (estimated load Tx). The stiffness equivalent coefficient K is supplied to the viscosity adjustment amount calculation unit 25.

The viscosity adjustment amount calculation unit 25 includes a viscosity coefficient calculation unit 25a, a multiplier 25b, a viscosity correction amount calculation unit 25c, and an adder 25d. The viscosity coefficient calculation unit 25a generates a viscosity coefficient C used to adjust the feeling of viscosity given to the driver during the steering operation using the prepared viscosity adjustment map in accordance with the driver power W. . The viscosity correction amount calculation unit 25c compensates for the difference between the stiffness feeling expected by the stiffness adjustment torque Tk ^* generated based on the stiffness equivalent coefficient K and the actually obtained stiffness feeling according to the stiffness equivalent coefficient K. For this purpose, a viscosity correction amount ΔC is generated and will be described in detail later. The adder 25d adds the viscosity correction amount ΔC to the viscosity coefficient C to generate a corrected viscosity coefficient C + ΔC. The multiplier 25b generates the viscosity adjustment torque Tc ^* by multiplying the corrected viscosity coefficient C + ΔC by the motor speed ω (corresponding to the steering speed). That is, the corrected viscosity coefficient C + ΔC can be said to be an adjustment gain with respect to the motor speed ω (and consequently the steering speed).

The inertia adjustment amount calculation unit 26 includes an inertia coefficient calculation unit 26a and a multiplier 26b. The inertia coefficient calculation unit 26a generates an inertia coefficient I for adjusting the inertia feeling given to the driver during the steering operation using the prepared inertia adjustment map according to the driver power W. The multiplier 26b calculates the inertia adjustment torque Ti ^* by multiplying the motor acceleration α generated by the differentiator 261 by the inertia coefficient I. That is, it can be said that the inertia coefficient is an adjustment gain with respect to the motor acceleration α (and hence the steering acceleration).

  Incidentally, the mechanical impedance (stiffness coefficient, viscosity coefficient, inertia coefficient) defines the relationship between the force F applied to the object and the displacement amount x of the object, and is represented by the relational expression (1). In particular, in the case of rotational motion, F is regarded as the torque applied to the object, and x is regarded as the amount of rotation of the object.

Here, x represents a steering angle (motor rotation angle), a first derivative value represents a steering speed (motor speed ω), and a second derivative represents a steering acceleration (motor acceleration α). In other words, the stiffness adjustment amount calculation unit 24, the viscosity adjustment amount calculation unit 25, and the inertia adjustment amount calculation unit 26 obtain torque necessary for adjusting the feel given to the driver when operating the handle according to the equation (1). However, in this embodiment, since the estimated load Tx is used instead of the steering angle x for calculating the stiffness adjustment torque Tk ^* , a stiffness equivalent coefficient K corresponding to the stiffness coefficient is used instead of the stiffness coefficient. . The relationship between the steering angle x and the stiffness equivalent coefficient K can be easily obtained from a relational expression representing the characteristics of the steering system mechanism 100.

<Viscosity correction amount calculation unit>
The viscosity correction amount calculation unit 25c includes a first correction amount ΔC1 that compensates for the difference between the expected stiffness and the actual stiffness, and a second correction that compensates for the change in the viscosity of the steering member due to the change in the stiffness equivalent coefficient K. The amount ΔC2 is obtained using the first map and the second map, respectively, and the added value is output as a viscosity correction amount ΔC (= ΔC1 + ΔC2).

  The first correction amount ΔC1 is generated by using the first map shown in FIG. 4A. The first correction amount ΔC1 is 0 when the stiffness value is 0, takes a positive value when the stiffness value is greater than 0, and the absolute value is the stiffness. Increases with increasing value. That is, the feeling of return caused by the increase in rigidity is set so as to be sensibly offset by increasing the viscosity.

  In other words, in human sensory characteristics, in order to more faithfully reproduce changes in sensory rigidity (feeling of rigidity), it is necessary to appropriately change not only the rigidity but also the viscosity in conjunction with the change in rigidity. The correction component for compensating for the shift is the first correction amount ΔC1. Therefore, the first map is set based on the measurement result of the sensory characteristics (perceptual characteristics related to force sense) of the driver.

  The second correction amount ΔC2 is generated using the second map shown in FIG. 4B, and takes a negative value when the stiffness value is 0, and a negative value when the stiffness value is greater than 0, and its absolute value is It becomes larger as the stiffness value increases.

  That is, as described above, when the stiffness coefficient is defined as a gain with respect to road load (equivalent stiffness coefficient K), the stiffness value of the steering member changes in proportion to the stiffness equivalent coefficient K as shown in FIG. As shown in FIG. 6, the viscosity value slightly fluctuates physically with the change in rigidity. The correction component for compensating for this physical variation is the second correction amount ΔC2. Therefore, the second map may be set based on the result of measuring the deviation of the viscosity value with respect to the change of the stiffness value, or a relational expression obtained mathematically from the steering system model between the stiffness value and the viscosity value. You may set using.

<Effect>
As described above, in the electric power steering system 1, the viscosity coefficient is corrected so as to compensate for the deviation between the expected steering feeling and the actual steering feeling in conjunction with the adjustment contents of the mechanical impedance stiffness coefficient. Yes.

  Therefore, according to the electric power steering system 1, a desired steering feeling (responsiveness when the steering wheel is turned, etc.) can be realized only by adjusting the stiffness coefficient. Adjustment work can be simplified, and as a result, labor required for adjustment work can be reduced.

<Other embodiments>
As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention can take a various form, without being limited to the said embodiment. For example, the functions of one component may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function.

  In the above embodiment, the driver power W that is the product of the steering torque Ts and the steering speed (motor speed ω) is used as a parameter for changing the mechanical impedance. However, the present invention is not limited to this. In addition to W, the vehicle speed V may be used, or the steering angle or the like may be used instead of the driver power W.

In the above embodiment, the viscosity correction amount ΔC is obtained by adding the first correction amount ΔC1 and the second correction amount ΔC2, but the second correction amount ΔC2 is obtained by calculating the basic torque Tf ^* and the stiffness adjustment torque Tk ^* . Since the change in viscosity caused by obtaining from the estimated load Tx instead of the steering angle is compensated, the second correction amount is obtained when the basic torque Tf ^* and the stiffness adjusting torque Tk ^* are obtained from the steering angle. It may be configured such that ΔC2 is omitted and the first correction amount ΔC1 is used as it is as the viscosity correction amount ΔC.

In the above embodiment, the load estimator 21 generates the estimated load Tx from the base assist command Tb ^* and the steering torque Ts, but the energization current Im detected by the current FB unit 42 instead of the base assist command Tb ^*. May be used.

In the above embodiment, the basic torque Tf ^* is generated from the estimated load Tx. However, the basic torque Tf ^* may be generated from the steering angle.
In the above embodiment, the basic torque Tf ^* and the mechanical impedance adjustment torques Tk ^* , Tc ^* , and Ti ^* are obtained separately and then added to generate the target steering torque Ts ^* . As described in Document 1, the present invention may be applied to a system configured to obtain a target steering torque Ts ^* from a steering angle using a reference steering model reflecting mechanical impedance.

DESCRIPTION OF SYMBOLS 1 ... Electric power steering system 15 ... ECU 20 ... Base assist part 21 ... Load estimator 22 ... Basic load amount calculating part 23 ... Driver work rate calculating part 24 ... Rigidity adjustment amount calculating part 24a ... Stiffness coefficient calculating part 24b, 25b, 26b ... multiplier 25 ... viscosity adjustment amount calculation unit 25a ... viscosity coefficient calculation unit 25c ... viscosity correction amount calculation unit,
25d ... Adder 26 ... Inertia adjustment amount calculation unit 26a ... Inertia coefficient calculation unit 27 ... Target calculation unit 28 ... Deviation calculation unit 29 ... Controller unit 30 ... Correction unit 41 ... Adder 42 ... Current FB unit 261 ... Differentiator

Claims (6)

A steering control device (15) for controlling steering characteristics by outputting an assist torque according to a steering torque applied to a steering shaft (3.5) coupled to a steering member (2) by a motor (6),
Stiffness adjustment torque generating means (24) for generating a stiffness adjustment torque that is a target value of the steering torque for adjusting a stiffness coefficient of a mechanical impedance that defines a relationship between a steering torque detected by the steering shaft and a steering angle; ,
Viscosity adjustment torque generating means (25) for generating a viscosity adjustment torque that is a target value of the steering torque for adjusting the viscosity coefficient of the mechanical impedance;
Command value generation means (27, 28, 29, 41, 42) for generating a command value for controlling the motor from the rigidity adjustment torque and the viscosity adjustment torque;
With
The viscosity adjustment torque generation means is linked to the adjustment contents of the rigidity adjustment torque generation means so that the difference between the rigidity feeling expected with respect to the change in the rigidity coefficient and the actually obtained rigidity feeling is compensated. And changing the viscosity coefficient. The viscosity adjusting torque generating means is
A viscosity coefficient calculating means (25a) for obtaining a viscosity coefficient from the steering state quantity;
A viscosity correction amount calculating means (25c) for obtaining a correction amount of the viscosity coefficient from the rigidity coefficient;
Correction amount reflecting means (25d) for reflecting the correction amount obtained by the viscosity correction amount calculating means to the viscosity coefficient obtained by the viscosity coefficient calculating means;
Torque calculating means (25b) for obtaining the viscosity adjustment torque by multiplying the output of the correction amount reflecting means by the steering speed;
The steering control device according to claim 1, further comprising:   The steering control device according to claim 2, wherein the correction amount includes a component that compensates for a change in the viscosity coefficient due to a change in the stiffness coefficient. Steering state quantity generating means (23) for generating a steering state quantity representing an operation applied to the steering member;
4. The rigidity adjusting torque generating means and the viscosity adjusting torque generating means generate the rigidity adjusting torque and the viscosity adjusting torque according to the steering state quantity, respectively. The steering control device described in 1.   The command value generating means generates a target steering torque including the rigidity adjustment torque and the viscosity adjustment torque, and the command value is for causing the steering torque to follow the target steering torque. The steering control device according to any one of claims 1 to 4.   The said rigidity coefficient is an adjustment gain with respect to the road surface load estimated from the said assist torque, The said viscosity coefficient is an adjustment gain with respect to steering speed, The any one of Claim 1 thru | or 5 characterized by the above-mentioned. The steering control device described.