Control unit for an electric power steering system

Abstract

Control unit for an electric power steering system, including: an input shaft (3) which is connected to a steering wheel (2) of a vehicle and rotates with the steering wheel (2); an input transmission device (100) that steers steered wheels (10) of the vehicle by transmitting a rotation of the input shaft (3) to the steered wheels (10); a steering torque detection device (4) which detects a steering torque (Ts) which is a torque applied to the input shaft (3) in an axis rotation direction; and a motor (6) which provides an assistive steering force for the input shaft (3) or the input transmission device (100) to assist an operation of turning the steering wheel (2) when the steered wheels (10) are steered by an operation of turning the steering wheel (2); wherein the control device for an electric power steering system, which controls the assisted steering force by controlling the motor (6), is provided in an electric power steering system (1), the control unit for an electric power steering system further includes: a basic support quantity generating device (20) which generates a basic support quantity (Tb*) to support the process of turning the steering wheel (2) on the basis of the steering torque (Ts) detected by the steering torque detection device (4) such that the detected steering torque (Ts) changes in accordance with a road surface force (Tx) transmitted from a road surface to the steered wheels (10); a support compensation variable generation device (30) that generates a support compensation variable (Tr) to modify the basic support variable (Tb*) calculated by the basic support variable generation device (20) such that an action of the steered wheels (10) responds to predetermined action characteristics; a support parameter modifier (41) that generates a modified support parameter (Ta) by modifying the basic support parameter (Tb*) generated by the basic support parameter generator (20) with the support compensation parameter (Tr) generated by the support compensation parameter generator (30); and a motor control device (42) that controls the motor (6) on the basis of the modified support parameter (Ta) from the support parameter modifying device (41); wherein the basic support quantity generating device (20) includes a road surface force estimating device (21) which estimates the road surface force (Tx) on the basis of the steering torque (Ts) detected by the basic support quantity (Tb*) and the steering torque (Ts) detected by the steering torque detection device (4), both of which are generated results of the basic support quantity generating device (20) itself; a target steering torque calculation device (22) calculates a target steering torque (Ts*) based on the estimated force, which is the road surface force (Tx) estimated by the road surface force estimation device (21), which is a desired value of the steering torque (Ts); and a basic support parameter calculation device (23, 24) calculates the basic support parameter (Tb*) for controlling the motor (6) such that the steering torque (Ts) detected by the steering torque detection device (4) matches the target steering torque (Ts*) calculated by the target steering torque calculation device (22).

Description

[0001] The invention relates to a control device for an electric power steering system, which controls an electric power steering system that assists a steering operation (steering) of a vehicle by means of a motor.

[0002] In order for a motor to generate a suitable assist steering force in accordance with a steering operation (a steering) of a vehicle, a control device (an electronic control unit or ECU) calculates the assist steering force based on various forces acting on a steering shaft through the driver's steering operation, such as steering torque and vehicle speed, and controls the motor based on the calculated assist steering force.

[0003] The well-known electric power steering system basically controls the motor in such a way that the assistive steering force supplied by the motor increases when the steering torque increases.

[0004] When the driver turns the steering wheel, the assistive steering force is generated in accordance with the applied steering torque, making the steering process easier.

[0005] However, it is difficult to give the driver a correct impression of the reaction between the road and the wheels simply by determining the assisting steering force based on the steering torque via the steering wheel.

[0006] In other words, it is difficult to configure a target steering torque in accordance with the road surface force and to generate the assisting steering force in accordance with the target steering torque (i.e., to realize the target steering torque in accordance with the road surface force) in order to convey to the driver the steering actuation feeling in accordance with the road surface force.

[0007] On the other hand, a technique that controls a motor based on a deviation of a target steering torque from an actual steering torque is disclosed in Japanese patent publication JP 2004-203089 A.

[0008] The technique disclosed in publication JP 2004-203089 A obtains a force (i.e., a road surface reaction) imparted to a tire by requesting an output torque from the sum of an actual steering torque (torque applied by the driver) and an assist torque (torque applied by the engine).

[0009] The target steering torque is then configured in accordance with the obtained output torque (the road surface reaction force).

[0010] This allows the target steering torque to be clearly determined.

[0011] Therefore, the target steering torque, the change of which (i.e., change in road surface reaction force) is compensated by the output torque, can be configured by taking into account the effects of friction and inertia superimposed on the steering torque when, for example, the steering wheel is turned abruptly, or by modifying it based on a vehicle motion condition.

[0012] Although in the technique disclosed in publication JP 2004-203089 A the target steering torque is configured taking into account the road surface reaction, the assist torque is generated on the basis of a torque applied to the steering wheel, which is fundamentally referred to as steering torque.

[0013] Although the required torque at the shaft can be suppressed (i.e., the steering process can be made easy), the convergence or steering of the vehicle, or bringing the vehicle's behavior into line with a desired behavior, cannot be guaranteed because the rotational speed of the engine (a rotational speed of the steering shaft) cannot be adequately controlled, for example, in a situation where a twist increases when the steering wheel is returned to a neutral position, or in a situation where the steering wheel returns to the neutral position with only a few turns when the driver's hands are released from the steering wheel after steering.

[0014] Although this is particularly satisfactory when, for example, the steering wheel is turned forcefully, the rotation of the shaft in a direction returning to the neutral position is accelerated because the twist of the shaft reverses when the steering wheel turns back, and thus the support torque also decreases, and therefore the stability and the convergence or steering behavior of the vehicle is worsened.

[0015] Although it is good for the driver to apply strong steering pressure, the vehicle's movement becomes sensitive and it becomes difficult to steer in the desired direction if the force applied to the steering wheel is reduced or the hands are released from the steering wheel, thus giving the driver a feeling of insecurity as the vehicle speed increases.

[0016] Therefore, ensuring the operational stability of the entire vehicle in a suitable manner (realizing the appropriate vehicle movement characteristics or properties) is not achieved with the technology disclosed in publication JP 2004-203089 A.

[0017] Therefore, the driver must respond to a vibration force transmitted to the steering wheel when the vehicle's movement is unstable, and there is therefore a possibility of interference with the driving process.

[0018] If damping is used to ensure convergence, resistance is conveyed when the steering wheel is returned or turned back, improving convergence; however, resistance is also conveyed when the steering wheel is turned far, thus worsening the steering feel for the driver.

[0019] If control actions are changed for the time of turning or turning the steering wheel back to avoid the aforementioned problem, the control processing can become very complicated, and achieving consistency between them can be difficult.

[0020] On the other hand, one of the technologies for adequately ensuring operational stability and for reducing a sudden sensation of return when the steering wheel is turned back, and increasing the convergence of the vehicle direction without impairing the sensation when turning the steering wheel, is known, for example, as a convergence control technology which calculates a basic support steering force (a basic support torque) based on the steering torque and the vehicle speed, calculates a modification torque to modify the basic support torque based on the steering torque and the engine speed (the angular velocity), and modifies the basic support torque with the modification torque (see, for example, Japanese Patent Publication JP 2010-264913 A).

[0021] That is, while steering torque is a physical value that reflects the operating state of the steering wheel by the driver, engine speed is a physical value that also reflects the influence of the road surface reaction in addition to the process of turning the steering wheel by the driver.

[0022] Therefore, based on the steering torque and the engine speed, a control mechanism can be built that can implement convergence control in such a way that the operating sensation is not affected when the steering wheel is turned, and the sudden feeling of the steering wheel returning to the neutral position due to the road surface reaction is reduced when the steering wheel is turned back.

[0023] Therefore, in the publication JP 2010-264913 A, based on the steering torque and the engine speed, suitable stability (suitable vehicle motion characteristics) of the entire vehicle is achieved by preventing the driver's steering perception from being impaired when the steering wheel is turned and returned, by generating the support compensation quantity in different ways when the steering wheel is turned and when it is returned, and by modifying the basic support torque by or with the support compensation quantity.

[0024] Various technologies for adequately ensuring operational stability are proposed, and a torque modification technology that aims to reduce frequent correction operations and reduce operating cycles by realizing a vehicle movement suitable for or corresponding to the driver's intention is disclosed, for example, in Japanese patent publication JP 2007-22373 A.

[0025] With this technology, a vehicle motion state is estimated based on a sum of the basic support torque and the steering torque, and a torque quantity modifying the basic support torque is generated so that the characteristics or properties are as desired.

[0026] Then, in order to achieve a realization of the steering response characteristics in accordance with the road surface response and a realization of the appropriate operational stability (appropriate vehicle movement characteristics) of the entire vehicle, consideration is given to attempting the combination of the technologies disclosed in, for example, the aforementioned publications JP 2004-203089 A and JP 2010-264913 A.

[0027] In detail, a can be like in Fig. The control mechanism shown in section 14 can be built.

[0028] At the in Fig. In the control mechanism shown in Figure 14, a current feedback section (feedback or FB section) 142 provides a support steering force to a steering shaft in accordance with a support torque command Ta by controlling a motor 110 by applying a control voltage Vd in accordance with a support torque command Ta supplied to the motor 110.

[0029] In a controlled object (a steering system mechanism) 100 from the steering shaft to the wheels, a motor speed ω, which is a rotational speed of the motor 110, and a steering torque Ts are detected.

[0030] The current feedback section 142 detects a current flowing into the motor 110 (a motor current Im) and executes a current feedback control (an FB control) such that the value of the current becomes a set current (a value that corresponds to the support torque command Ta).

[0031] Then, based on the detected motor current Im and the steering torque Ts, a force estimator or force estimating device 121 estimates a road surface force (a road surface reaction) and generates an estimated force Tx as an estimated value.

[0032] Then, a basic support section 120 generates a basic support command Tb* based on the estimated force Tx.

[0033] The basic support section 120 specifically includes a target generation section 122, which generates a target steering torque Ts* based on the estimated force Tx, a deviation calculation device 123, which calculates the difference (the torque deviation) between the steering torque Ts and the target steering torque Ts*, and a control device 124, which generates a basic support command Tb* to control the motor 110 (i.e., torque feedback control is performed) based on the torque deviation, so that the steering torque Ts matches the target steering torque Ts*.

[0034] Thus, by controlling the motor 110 using the received basic support command Tb*, it is possible to realize the characteristics of the steering response in accordance with the road surface response.

[0035] That is, the target generation section 122 configures the target steering torque Ts* in accordance with the road surface force relative to the road surface reaction estimated by the force estimating device 121.

[0036] The driver can then feel the response or reaction according to the road surface force, because the control unit 124 performs the torque feedback control in such a way that the actual steering torque Ts becomes equal to the target steering torque Ts*.

[0037] On the other hand, a modification section or modification section 130 has a torque modification section or modification section 131, which generates a torque modification command or modification command Tr based on the steering torque Ts and the motor speed ω, and implements the convergence control.

[0038] A certain composition and function of the torque modification section 131 are the same as those of a control device disclosed in the aforementioned publication JP 2010-264913 A.

[0039] Therefore, by modifying the basic support command Tb with the torque modification command Tr, which is obtained in the modification section 130 (here both are added with an adder 141), and if the modification result is given as the support torque command Ta to the current feedback section 142, it is currently possible to achieve the appropriate operational stability (appropriate vehicle motion characteristics) of the entire vehicle.

[0040] However, there is at least one major problem with the in Fig. Control mechanism shown in 14.

[0041] The problem is that the basic support section 120 cancels or reverses the modification process by the modification section 130.

[0042] That is, in the case of the Fig. In the control mechanism shown in 14, a force estimation is carried out with the force estimation device 121 on the basis of the motor current Im, which is finally supplied to the motor.

[0043] The motor current Im corresponds to, responds to, or reacts to the support torque command Ta, which is modified by the torque modification command Tr, generated by the modification section 130, to the basic support command Tb*, generated by the basic support section 120.

[0044] That is, the force estimation device 121 estimates the road surface force using the motor current Im as a result modified by the modification section 130.

[0045] In other words, if, for example, a steering wheel is subjected to strong steering input, the basic support command Tb* is modified so that the support steering force decreases through the convergence control in the modification section 130.

[0046] Then the motor current Im drops by the amount of the modification, and consequently the force value estimated by the force estimation device 121 (the estimated force Tx) also drops.

[0047] If the estimated force Tx decreases, then the target steering torque Ts* also decreases, and as a result, the basic support control command Tb* increases, i.e., the support steering force is controlled with a tendency to increase, so that the steering torque becomes small.

[0048] As a result, the convergence control is not reflected by the modifier section 130 (the convergence control is overridden by the basic support section 120).

[0049] Thus, the in Fig. 14 The control composition shown is incompatible with realizing the characteristics or properties of the steering response in accordance with the road surface response and with realizing the suitable operational stability (suitable vehicle motion characteristics) of the entire vehicle.

[0050] Therefore, it is difficult to increase the vehicle's driving performance, i.e., it is difficult to enable the driver to drive the vehicle intuitively and to feel safe while operating the vehicle.

[0051] In the context of the foregoing, furthermore, EP 2 251 245 B1, as a member of the patent family of the aforementioned JP 2010-264913 A, discloses a control device for an electric power steering system. The electric power steering system comprises an input shaft coupled to a vehicle's steering wheel to rotate with the steering wheel by means of a steering torque exerted when the steering wheel is turned, a rotation transmission section for transmitting rotation of the input shaft to the vehicle's moving wheels to steer the moving wheels, a torque sensor for measuring a steering torque due to torsion between the input shaft and the moving wheels, and an electric motor for generating an assistive steering force to support operation of the steering wheel to steer the moving wheels.The control device includes a basic support amount calculation section for calculating a basic support amount based on the steering torque measured by the torque sensor, a support compensation amount calculation section for calculating a support compensation amount, a support amount correction section for calculating a corrected support amount by correcting the basic support amount calculated by the basic support amount calculation section with the support compensation amount calculated by the support compensation amount calculation section, and a motor drive section for driving the electric motor according to the corrected support amount received from the support amount correction section to assist the operation of the steering wheel.The support compensation amount calculation section calculates the support compensation amount based on at least two signals of different types, each reflecting an operating state of the electric power steering system.The support compensation amount calculation section calculates the support compensation amount such that the following first specification (a) and the following second specification (b) are satisfied: (a) a first specification (a) such that a first relationship characteristic between an electric motor speed and the steering wheel torque is the same as a basic relationship characteristic where the electric motor is driven according to the basic support amount and is not corrected by the support compensation amount, and (b) a second specification (b) such that a second relationship characteristic between an electric motor speed and a road surface reaction force is such that the electric motor speed is damped compared to a case where the electric motor is driven according to the basic relationship characteristic.

[0052] In this respect, the document EP 2 251 245 B1, which is closest to the subject matter of the application, discloses a control device for an electric power steering system, comprising an input shaft connected to and rotating with the steering wheel of a vehicle, an input transmission device that steers the steered wheels of the vehicle by transmitting a rotation of the input shaft to the steered wheels, a steering torque detection device that detects a steering torque, which is a torque applied to the input shaft in an axial direction of rotation, and a motor that provides an assistive steering force to the input shaft or the input transmission device to assist an operation of turning the steering wheel when the steered wheels are steered by an operation of turning the steering wheel.The control unit for an electric power steering system, which controls the assisted steering force by controlling the motor, is provided in an electric power steering system and further includes a basic assist quantity generating unit that generates a basic assist quantity to support the process of turning the steering wheel based on the steering torque detected by the steering torque sensing unit.

[0053] The invention was made in light of the problems described above, and one of its objectives is to create a control device for an electric power steering system that can provide feedback to the driver about the reaction between the road and the vehicle, while ensuring suitable stability for the vehicle during its movement.

[0054] This problem is solved by a control device for an electric power steering system with the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0055] In a control device for an electric power steering system according to a first aspect, the control device for an electric power steering system includes an input shaft connected to and rotating with the steering wheel of a vehicle, an input transmission device that steers the steered wheels of the vehicle by transmitting a rotation of the input shaft to the steered wheels, a steering torque sensing device that detects a steering torque, which is a torque applied to the input shaft in an axial direction of rotation, and a motor that provides an assistive steering force to the input shaft or the input transmission device to assist an operation of turning the steering wheel when the steered wheels are steered by an operation of turning the steering wheel.

[0056] The control unit for an electric power steering system, which controls the assisted steering force by controlling the motor, is provided in an electric power steering system.

[0057] The control unit for an electric power steering system further includes a basic support parameter generator, which generates a basic support parameter to assist the steering wheel turning process based on the steering torque detected by the steering torque sensing device, such that the steering torque changes in accordance with a road surface force transmitted from a road surface to the steered wheels; a support compensation parameter generator, which generates a support compensation parameter to modify the basic support parameter calculated by the basic support parameter generator, such that an action of the steered wheels responds to predetermined action characteristics; and a support parameter modifier.which generates a modified support parameter by modifying the basic support parameter generated by the basic support parameter generator with the support compensation parameter generated by the support compensation parameter generator, and a motor control device that controls the motor based on the modified support parameter from the support parameter modification device.

[0058] The basic support variable generating device includes a road surface force estimating device, which estimates the road surface force based on the steering torque detected by the basic support variable and the steering torque detected by the steering torque detection device, both of which are generated results of the basic support variable generating device itself; a target steering torque calculation device, which calculates a target steering torque, which is a desired value of the steering torque, based on the estimated force, which is the road surface force, estimated by the road surface force estimating device; and a basic support variable calculation device, which calculates the basic support variable for controlling the motor such thatthat the steering torque detected by the steering torque detection device matches the target steering torque calculated by the target steering torque calculation device.

[0059] In accordance with the control unit for an electric power steering system as mentioned above, the function for configuring the target steering torque is closed within a loop (the basic support parameter calculation unit) in accordance with the force estimated by estimating the road surface force, and the function is separated from the support compensation parameter calculation unit in the present embodiment, so that interference or mutual influence between the basic support parameter calculation unit and the support compensation parameter generation unit can be minimized (or completely removed).

[0060] This allows the provision of a suitable steering response in accordance with the road surface force by the basic support parameter calculation unit and the realization of suitable operational stability (suitable vehicle motion characteristics) for the vehicle by the support compensation parameter generation unit to be harmonized, and therefore the driving performance of the vehicle can be improved.

[0061] In the control unit for an electric power steering system according to a second aspect, the road surface force estimation device extracts an element of a frequency band preconfigured from a sum of the basic assistance quantity and the steering torque, and outputs the component of the extracted frequency band as the estimated force.

[0062] Thus, by preserving the estimated force, for example, an unnecessary frequency component, such as a part of a band that the driver of the vehicle finds unpleasant, can be removed, and only a frequency component that is to be transmitted to the driver can be transmitted.

[0063] In the control unit for an electric power steering system, according to a third aspect, the frequency band is 10 Hz or less.

[0064] In the control unit for an electric power steering system according to a fourth aspect, the target steering torque calculation device calculates the target steering torque on the basis of the force estimated by the road surface force estimation device in such a way that the greater the estimated force becomes, the greater the target steering torque becomes.

[0065] By calculating the target steering torque in this way, the steering reaction force can be appropriately transferred to the side of the steering wheel (the driver's side) in accordance with the road surface force.

[0066] In the control unit for an electric power steering system according to a fifth aspect, the target steering torque calculation device calculates the target steering torque in such a way that the target steering torque changes logarithmically relative to the estimated force.

[0067] Generating the target steering torque in logarithmic form relative to the estimated force can be said, so to speak, that this is a technique based on a human perception model that shows the magnitude that the steering reaction force should have relative to the road surface force.

[0068] Therefore, by calculating the target steering torque in logarithmic form relative to the estimated force, the driver can be given a natural steering feel.

[0069] In the control device for an electric power steering system according to a sixth aspect, the electric power steering system has a speed detection device that detects the speed of a moving vehicle, and the target steering torque calculation device calculates the target steering torque on the basis of the vehicle speed detected by the speed detection device such that the faster the speed, the greater the target steering torque becomes.

[0070] In the control unit for an electric power steering system according to a seventh aspect, the target steering torque calculation device calculates the target steering torque in such a way that the target steering torque changes logarithmically relative to the vehicle speed.

[0071] Thus, by generating the target steering torque not only relative to the estimated force, but also relative to the vehicle speed, which changes logarithmically, even when the speed changes, the driver can be given a natural steering feel.

[0072] In the control unit for an electric power steering system according to an eighth aspect, the basic support quantity calculation unit includes a deviation calculation unit which calculates a torque deviation which is a difference between the steering torque detected by the steering torque sensing unit and the target steering torque calculated by the target steering torque calculation unit, and includes at least one basic command calculation unit which calculates a basic command corresponding to the basic support quantity such that the torque deviation calculated by the deviation calculation unit is configured to 0.

[0073] If more than one basic command calculation device is provided, a weighted sum of the basic commands calculated by each basic command calculation device is calculated as the basic support quantity, and the basic command calculation device is designed such that a transfer function of the basic support quantity to be output relative to the supplied torque deviation is greater than a predetermined level with a gain greater than 1 in the band below a predetermined frequency.

[0074] Thus, the steering torque can easily follow the target steering torque by calculating the basic command (consequently, the basic support quantity is calculated) using the basic command calculation device, which becomes more or larger or higher than a predetermined level or a predetermined level (high gain), where the gain in the band below a predetermined frequency is greater than 1.

[0075] Furthermore, if there is a plurality or multitude of basic command calculation units with different frequency characteristics or frequency curves, which calculate the basic support quantity using each basic command to generate a weighted sum, a transmission perception and a steering feel of the road surface force during a steering operation can be configured as the required characteristics or properties or curves by appropriately configuring the characteristics or properties or curves of each basic command calculation unit or each weight of each basic command.

[0076] In a control device for an electric power steering system according to a ninth aspect, the basic command calculation device has an integration device that integrates and outputs the supplied torque deviation, and is designed such that the basic command is calculated so that the torque deviation becomes 0.

[0077] Thus, the presence of such an integration device ensures that the transfer function of the gain of a basic instruction calculation device has characteristics or properties or curves that are higher at low frequencies, i.e., the gain increases as the frequency approaches 0.

[0078] Consequently, the steering torque follows the target steering torque more easily.

[0079] However, if the integration device is used, the integration value will increase rapidly if the actual steering torque continues to lag behind the target steering torque.

[0080] Then, if the integration value becomes too large, for example the steering support will be delayed under the influence of the large integration value when the steering wheel is turned.

[0081] In the control unit for an electric power steering system according to a tenth aspect, the integration device is designed such that the absolute value of the output integration value is limited to below a predetermined upper integration limit.

[0082] This means that even if the tracking towards the target value does not progress and the integration value continues to rise or fall, a maximum of the absolute value is configured in such a way that it is the upper integration limit or integration upper limit.

[0083] Thus, by configuring the maximum in the absolute value of the integration value, a blocking of the steering in one direction of changing the support direction as the integration value increases can be suppressed.

[0084] In a control device for an electric power steering system according to an eleventh aspect, the steering torque detected by the steering torque detection device, a rotation angle of the steering wheel, a rotation angle of the motor, or the basic support quantity generated by the basic support quantity generation device is used as a state variable for a configuration, and the upper integration limit is configured to be a larger value when the state variable for the configuration becomes larger.

[0085] This makes it possible to configure the appropriate upper integration limit in accordance with the state of the vehicle.

[0086] In the control unit for an electric power steering system according to a twelfth aspect, the predetermined frequency is 1 Hz.

[0087] In the control unit for an electric power steering system, according to a thirteenth aspect, the predetermined level is 10 times higher.

[0088] In the control device for an electric power steering system according to a fourteenth aspect, the basic support parameter calculation device has a plurality of basic command calculation devices with different frequency characteristics, and a calculation device for a first weighted sum is provided which calculates the weighted sum of the basic commands from the plurality of basic command calculation devices in accordance with a first weighting configuration command.

[0089] Thus, by using each basic command from a variety of basic command calculation devices with different frequency characteristics to produce a weighted sum, the transmission perception and steering feel of the road surface force during a steering operation can be configured more finely than the required characteristics.

[0090] In the control device for an electric power steering system according to a fifteenth aspect, a steering speed information receiving device is provided for obtaining steering speed information which directly or indirectly indicates a rotational speed of the motor, and the assistance quantity modifying device generates the assistance compensation quantity for converging a movement of the vehicle to the desired behavior on the basis of at least one of the steering speed information obtained by the steering speed information receiving device, the steering torque detected by the steering torque detection device and / or the road surface force estimated by the road surface force estimating device.

[0091] It can be said that the steering torque is the information relating to the steering wheel, the steering speed information is the information from the steering wheel and the road surface, and the road surface force (the estimated force) is the information from the road surface.

[0092] This allows the support compensation parameter to be suitable for converging and stabilizing the vehicle's motion by generating the support compensation parameter based on at least one of these, and the basic support parameter can be suitablely modified based on the support compensation parameter.

[0093] In the control device for an electric power steering system according to a sixteenth aspect, the support quantity modifying device includes at least one basic compensation quantity calculation device for calculating the basic compensation quantity according to the support compensation quantity for converging the motion of the vehicle, and, if there is more than one basic compensation quantity calculation device, a weighted sum of each compensation quantity calculated by each basic compensation quantity calculation device is calculated as the basic support quantity.

[0094] Consequently, if the support compensation parameter is designed to be calculated by specifying a weighted sum of each basic compensation parameter, when the multitude of basic compensation parameter calculation devices is provided, transition characteristics in converging and stabilizing the motion of the vehicle can be obtained as the required characteristics by appropriately configuring the characteristics of each basic compensation parameter calculation unit or the weight of each compensation parameter.

[0095] The attached drawings show: Fig. 1 a block diagram showing a schematic structure of an electric power steering system of an embodiment; Fig. 2 a block diagram showing a schematic structure of a control mechanism of an electronic control unit or ECU; Fig. 3. A block diagram showing a more detailed composition of the control mechanism of Fig. 2 shows; Fig. 4 a block diagram showing a schematic structure of a force estimation device or force estimator; Fig. 5A to Fig. 5D diagrams to explain a generation principle of a target torque; Fig. 6 a diagram showing a table for target steering torque generation, which is defined as a target value generation section; Fig. 7 a block diagram showing a specific composition of a section of a control device; Fig. 8 a characteristic diagram or characteristic curve diagram showing frequency characteristics or frequency curves of each modification filter from which the section of the control device is constructed; Fig. 9A to Fig. 9C Characteristic curves or characteristic diagrams showing the frequency characteristics of each modification filter that form the section of the control device; Fig. 10 a characteristic diagram showing transfer characteristics (frequency characteristics) of input and output of an entire section of the control device; Fig. 11 a characteristic diagram showing the transmission characteristics (frequency characteristics) of a steering torque relative to a steering wheel torque; Fig. 12A to Fig. 12D diagrams to explain examples of compositions of the support control device including an integrator; Fig. 13A to Fig. 13C Diagrams to explain the effects of a control mechanism of the present embodiment; and Fig. 14 a block diagram showing an example of a control mechanism considered to consist of a combination of conventional control mechanisms.

[0096] An embodiment of the invention is described in detail below with reference to the drawings.

[0097] As in Fig. As shown in Figure 1, an electric power steering system or a power steering system 1 of the present embodiment supports the operation of a steering wheel 2 by a user with a motor 6.

[0098] The steering wheel 2 is attached to one end of a steering shaft 3, one end of a torque sensor 4 is connected to another end of the steering shaft 3, and one end of an intermediate shaft 5 is connected to another end of the torque sensor 4.

[0099] Furthermore, in the following explanation, the entire axial unit from the steering shaft 3 via the torque sensor 4 to the intermediate shaft 5 is also collectively referred to as a steering wheel shaft.

[0100] The torque sensor 4 is a detection device for detecting a steering torque Ts. The torque sensor 4 corresponds to a steering torque detection device according to the invention.

[0101] Specifically, the torque sensor 4 has a torsion bar spring that connects the steering shaft 3 and the intermediate shaft 5, and detects the torque applied to the torsion bar spring based on a twist angle of the torsion bar spring.

[0102] The motor 6 serves to assist a steering force of the steering wheel 2, and a rotation of the motor 6 is transmitted to the intermediate shaft 5 via a speed reducer 6a.

[0103] The speed reducer 6a is formed by a worm drive located at the end of a rotating shaft of the motor 6 and a worm wheel located coaxially on the intermediate shaft 5 and meshing with the worm drive. The rotation of the motor 6 is transmitted to the intermediate shaft 5 via the speed reducer 6a.

[0104] In contrast, when the intermediate shaft 5 is rotated by the process of turning the steering wheel 2 or by a reaction from a road surface (a road surface reaction), the rotation is transferred to the motor 6 via the speed reducer 6a, so that the motor 6 is set in rotation.

[0105] Furthermore, the motor 6 is a brushless motor which is equipped internally with a rotation sensor, such as a rotary encoder, and is designed in such a way that, in the present embodiment, an output of a rotation state of the motor 6 is made possible.

[0106] The motor 6 of the present embodiment is constructed in such a way that at least one output of the motor speed ω (information showing the angular velocity) as a rotational state from the rotation sensor is made possible.

[0107] Another end of the intermediate shaft 5, which is an end opposite the end connected to the torque sensor 4, is connected to a steering gear housing or steering gear 7.

[0108] The steering gear 7 is constructed from a gear or transmission system consisting of a rack and pinion gear, and teeth of the rack engage with the pinion located at the other end of the intermediate shaft 5.

[0109] Therefore, the intermediate shaft 5 (i.e., the pinion rotates) then rotates when the driver turns the steering wheel 2, thereby moving the rack in a right-left direction.

[0110] The connecting rods or tie rods 8 are attached to both ends of the rack, and the connecting rods 8 move back and forth with the rack in the right-left direction.

[0111] As a result, each wheel or tire 10, which is a steered wheel or tire, changes its direction by means of the connecting rod 8, which pushes or pulls a tie rod lever arranged beyond the connecting rod 8.

[0112] Furthermore, a speed sensor 11 is arranged as a speed detection device for detecting a vehicle speed V at a predetermined position in the vehicle.

[0113] With such a composition, when the driver turns the steering wheel 2, the rotation is transmitted via the steering shaft 3, the torque sensor 4 and the intermediate shaft 5 to the steering gear 7.

[0114] Furthermore, the rotation of the intermediate shaft 5 is transmitted into a right-and-left movement of the connecting rods 8 in the steering gear 7, and both of the wheels 10 on each side of the vehicle are steered by the movement of the connecting rods 8.

[0115] An ECU 15 is provided, which operates using electrical power from a (not shown) battery in the vehicle.

[0116] The ECU 15 calculates an assist torque command Ta based on the steering torque Ts detected by the torque sensor 4, the motor speed ω, and the vehicle speed V detected by the speed sensor 11.

[0117] A support parameter of the force with which the driver turns the steering wheel 2 (therefore a force that steers both of the wheels 10) is controlled by applying a control voltage Vd to the motor 6 in accordance with the calculated result.

[0118] Since the motor 6 used in the present embodiment is a brushless motor, the control voltage Vd output (applied) to the motor 6 by the ECU 5 is in detail the control voltage VdU, VdV, and VdW from three phases (U, V, W).

[0119] The rotation of the motor 6 is controlled by applying the control voltage VdU, VdV and VdW of each phase (exciting a control current of each phase) from the ECU 15 to the motor 6.

[0120] Since a method for controlling a brushless motor using the three-phase control voltage (for example, a PWM control) or a control circuit that generates the control voltage of the three phases (for example, a bipolar 3-phase control circuit) is well known, a detailed explanation is omitted here.

[0121] Although the ECU 15 directly controls the motor 6 by controlling the control voltage Vd applied to the motor 6, it can be said that it controls a steering system mechanism 100 which is driven by the motor 6 as a result of controlling the motor 6, and therefore it can be said that a controlled object of the ECU 15 is the steering system mechanism 100.

[0122] Furthermore, the steering system mechanism 100 shows an overall mechanism in which in Fig. 1 system diagram shown with the exception of the ECU 15, i.e. the entire mechanism in which the steering force of the steering wheel 2 is transmitted from the steering wheel 2 to each wheel or tire 10.

[0123] Next, the schematic structure (the control mechanism) of the ECU 15 will be shown using the block diagrams of Fig. 2 and Fig. 3 explained.

[0124] Furthermore, among the control mechanisms of the ECU 15, shown in Fig. 2 and Fig. 3, in fact every section except a current feedback section (FB section) 42 and part of a function of the current feedback section 42 is realized when a (not shown) CPU with which the ECU 15 is equipped executes a predetermined control program.

[0125] That means the Fig. 2 and the Fig. Figure 3 shows different functions that are implemented by the central processing unit or CPU for each functional block.

[0126] However, this is just one example showing that the control mechanism depicted in each figure is implemented through software, and it goes without saying that the entire control mechanism, or part of it, shown in Fig. 2 shows, for example, that it can be implemented using hardware, such as a logic circuit.

[0127] The ECU 15 includes, as in Fig. Figure 2 shows a basic support section 20 that generates a basic support command Tb*, a modifier section 30 that generates a torque modifier command Tr, an adder 41 that generates a support torque command Ta by adding the basic support command Tb* and the torque modifier command Tr, and the current feedback section (FB section) 42 that controls the motor 6 by applying the control voltage Vd to the motor 6 based on the support torque command Ta.

[0128] The basic support section 20 is a block for realizing the characteristics or properties of a steering response (a steering torque) in accordance with a road surface response (a road surface force), that is, for realizing that the driver can easily perceive the conditions or states of the vehicle and the road surface by semi-regularly transmitting the response to the driver according to the road surface force. The basic support section 20 comprises a force estimator 21, a setpoint generation section 22, a deviation calculation unit 23, and a control unit 24.

[0129] That is, the basic support section 20 generates the basic support command Tb* to assist the process of turning the steering wheel 2 based on the steering torque Ts such that the steering torque Ts changes in accordance with the road surface force acting on each tire 10 emanating from the road surface.

[0130] The force estimation device 21 estimates the road surface force based on the basic support command Tb* and the steering torque Ts.

[0131] The target generation section 22 generates a target torque Ts*, which is a target value of the steering torque, based on the road surface force (the estimated force Tx) estimated by the force estimation device 21.

[0132] The deviation calculation device 23 calculates a torque deviation, which is a difference between the steering torque Ts and the target steering torque Ts*.

[0133] Furthermore, the section of a control device 24 generates the basic support command Tb* on the basis of the torque deviation, which indicates the support steering force (also referred to as support torque or support quantity), to generate the support steering force in accordance with the road surface force such that the torque deviation is set to 0.

[0134] Since the correspondingly generated basic support command Tb* is the torque command for generating the support steering force in accordance with the road surface force, it is also possible to realize at least the characteristics or properties of the steering response in accordance with the road surface force only by supplying the basic support command Tb* to the current feedback section 42.

[0135] On the other hand, modification section 30 is a block for realizing stable operation (vehicle motion characteristics) of the entire vehicle, that is, for shaping a movement of the vehicle (an action when each wheel 10 is steered) in such a way that it exhibits desired action characteristics (in particular, the vehicle converges appropriately) by suppressing unstable actions or behaviors (a vibration action, etc.) that are transmitted to the steering wheel by the action or behavior of the unstable vehicle. Modification section 30 includes a torque modification section 31.

[0136] The torque modification section 31 generates a torque modification command Tr to suppress (converge) the aforementioned unstable actions or behaviors based on the steering torque Ts and the engine speed ω.

[0137] Then the assist torque command Ta is generated by adding the basic assist command Tb*, which was generated in the basic assist section 20, and the torque modification command Tr, which was generated in the modification section 30, using the adder 41.

[0138] Then the current feedback section 42 applies the control voltage Vd to the motor 6 on the basis of the support torque command Ta, so that the torque (the support steering force) is directed to the steering shaft (in particular to the side of a tire 10 starting from the torque sensor 4) according to the support torque command Ta.

[0139] Specifically, a target current (one target current for each phase), which is to be excited or generated for each phase of the motor 6, is established on the basis of the support torque command TA.

[0140] The desired steering assistance force for the steering shaft is then generated by detecting and feeding back the excited current value Im in each phase and controlling the control voltage Vd (suppressing the excited current) such that the detected values ​​(the excited current Im in each phase) correspond to the target currents.

[0141] Compared with the one in Fig. As shown in Figure 14 of the control mechanism, it becomes clear that in the control mechanism of the present embodiment, the calculation of the estimated force Tx by the force estimation device 21 is not based on the motor current Im, but on the basis of the basic support command Tm*.

[0142] This means that the function of the basic support section 20, which generates the basic support instruction Tb*, is contained within the basic support section 20 and is independent of the various functions of other sections, such as the modifier section 30 or the current feedback section 42.

[0143] Therefore, interference and influence on the basic support command Tb* are minimized by the calculated value set in the modification section 30.

[0144] It proves advantageous that the control mechanism of the ECU 15 of the present embodiment, which is described in Fig. Figure 2 is simplified to explain the main composition and function of the control mechanism of the present embodiment, and the vehicle speed V is omitted.

[0145] Furthermore, the control mechanism of the present embodiment is indeed equipped with a functional block (a transmission system characteristic setting section 51, compare Fig. 3) provided which sets a transition characteristic or transition properties or transition curves (transmission system characteristics) relative to the road surface reaction in the basic support section 20 in accordance with the vehicle speed V and the basic support command Tb* in accordance with the transmission system characteristic as generated by the section of a control device 24.

[0146] Alternatively, the control mechanism of the present embodiment is actually connected to the functional block (the transmission system characteristic setting section 51, compare Fig. 3) provided which sets a transition characteristic or transition properties or transition curves (transmission system characteristics) relative to the road surface reaction in the basic support section 20 in accordance with the vehicle speed V, and the basic support command Tb* is generated in accordance with the transmission system characteristic by the section of a control device 24.

[0147] Furthermore, there is indeed another functional block (a vehicle motion characteristics setting section 52, compare Fig. 3) provided, which sets a transition characteristic (a vehicle motion characteristic) over a vehicle motion in the modification section 30 in accordance with the vehicle speed V and the torque modification command Tr in accordance with the vehicle motion characteristic as generated by the torque modification section 31.

[0148] Alternatively, the further functional block (the vehicle motion characteristics setting section 52, compare Fig. 3) provided, which sets a transition characteristic (a vehicle motion characteristic) over a vehicle motion in the modification section 30 in accordance with the vehicle speed V, and the torque modification command Tr is generated in accordance with the vehicle motion characteristic by the torque modification section 31.

[0149] This involves a more detailed control mechanism of the ECU 15 in Fig. 3 shown.

[0150] The in Fig. The control mechanism shown in Figure 3 is the more detailed control mechanism used in Figure 3. Fig. 2 is shown.

[0151] Specifically, each of the aforementioned functional blocks (the transmission system characteristic setting section 51 and the vehicle motion characteristic setting section 52) together with the setpoint generation section 22 in the basic support section 20 is grouped as a section for a human interface or HMI (Human Interface) interface 50, while each composition except the setpoint generation section 22 is grouped under the basic support sections 20 and is referred to as a transmission control calculation section 60, and the modification section 30 is referred to as a vehicle control calculation section 70.

[0152] Furthermore, the composition of the section for a control device 24 in the transmission control calculation section 60 and the torque modification section 31 in the vehicle control calculation section 70 are described in more detail.

[0153] The composition of the control mechanism of the present embodiment is described below using: Fig. 3 explained in more detail.

[0154] The power estimation device 21 shows, as in Fig. Figure 4 shows an adder 21b which adds the basic support command Tb* and the steering torque Ts, and a low-pass filter (LPF) 21b which extracts components from a band below a predetermined frequency from the addition result, and frequency components extracted by the low-pass filter 21b are output as the estimated force Tx.

[0155] Drivers predominantly control vehicles using steering response information of 10 Hz or less, and it is known that a frequency component higher than this, for example a vibration in the band(s) of about 10 Hz to 20 Hz due to unsprung parts or masses (circumferences of the wheels and the suspension), causes discomfort to drivers.

[0156] Therefore, the cutoff frequency of the low-pass filter 21b is set at approximately 10 Hz, so that such unpleasant vibrations are not transmitted to the drivers in the present embodiment, and the frequency component of 10 Hz or less is passed through (extracted), while a frequency component of more than 10 Hz is blocked.

[0157] Next, the target generation section 22 generates a target steering torque, which produces a heavy or light steering feel for the driver in accordance with the road surface reaction, and realizes an increasing degree (slope) of steering response (or steering torque) for the driver in accordance with an increase in the road surface reaction.

[0158] In the target generation section 22 of the present embodiment, the estimated force Tx and the target steering torque Ts* are actually mapped in a table or a characteristic map in accordance with the vehicle speed V, as shown in Fig. 6 is shown, and the target steering torque Ts* is generated on the basis of the table or the characteristic map.

[0159] Here, a derivation process (a resolution principle for generating the target steering torque) is described according to Fig. 6 explained.

[0160] From the composition of the power estimation device 21, which is in Fig. As shown in Figure 4, it is clearly evident that the main components of the estimated force Tx are based on the sum of the steering torque Ts and the basic support command Tb*.

[0161] That is, the estimated force Tx is a force that acts on the intermediate shaft 5 via the rack and pinion drive from the tires 10, and corresponds to the reaction received from the road surface when steering.

[0162] If the estimated force Tx is defined approximately as the road surface reaction, the road surface reaction will increase as the driver turns the steering wheel.

[0163] Then, when driving under steering, the road surface reaction force is proportional to a steering angle that is static in a linear vehicle zone (a sufficiently linear zone in which the tire's adhesion force does not reach saturation).

[0164] This assumes that assistance is provided in such a way that the steering torque becomes proportional to the road surface reaction, and that the steering torque increases proportionally or in relation to a steering angle of the steering wheel.

[0165] Then, although the driver feels that the steering torque is light or low near a neutral position, the driver tends to feel that the steering quickly becomes heavier when the steering wheel is turned sharply or far.

[0166] In accordance with Weber-Fechner's law, it is known that the perception of persons is often expressed by the logarithm of a physical stimulus, such as: perceived size = A log (size of stimulus) + B.

[0167] When people sense the rotating motion of a vehicle, the stimulus consists of the response, such as a steering torque transmitted to the hands, and a force and velocity, such as a lateral acceleration and yaw rate, acting on the human body.

[0168] In order to perceive a linear change in the feelings or sensations obtained through such a stimulus, it is suggested that the greater the intensity of the stimulus, the greater the change the stimulus must show.

[0169] If the steering wheel is turned at a fixed speed, and if the rate of change of a stimulus is constant, the driver feels that the wheel is not turning sufficiently and feels that the reaction increases too much compared to a feeling of turning as the degree or extent of turning (the stronger the stimulus) increases.

[0170] This is considered the reason why the driver tends to feel that steering quickly becomes difficult when the steering wheel is turned sharply.

[0171] Therefore, the present embodiments provide better feedback to the driver regarding the forces actually acting on the vehicle.

[0172] Lateral acceleration and yaw rate are proportional to the steering angle of the steering wheel, static like the road surface reaction in the linear range of the vehicle.

[0173] Therefore, in order to harmonize vehicle movement and steering “feel”, the steering torque must be logarithmically related to the road surface reaction.

[0174] This means that the steering torque Ts* must be predetermined for the estimated force Tx in the logarithmic function (in order to change logarithmically).

[0175] Specifically, for example, in | Tx | > 0 the target torque Ts* can be predetermined by the following formula (1). Ts*=sgn(Tx)×(A log (|Tx|)+B)

[0176] In the formula (), the target torque Ts* is obtained for the estimated force Tx if, for example, A = 0.8 and B = 0.5, and if Ts* = 0 in Tx = 0, as in Fig. 5 is shown.

[0177] The in Fig. The characteristic shown in 5A can be described as a model of human perception, showing a magnitude that the steering response should have over the road surface force.

[0178] Furthermore, when the target steering torque Ts* is generated, a value to compensate for the driver's perception is also added to the vehicle speed V.

[0179] A constant yaw rate γ for vehicle speed V and steering angle θs is given by the following formula (2). γ=V / (1+Ks×V2)×(θs / N / L)

[0180] In this context, N is a steering gear ratio, L is a wheelbase, and Ks is a stability factor.

[0181] Furthermore, a regular lateral acceleration Gy is obtained approximately by multiplying both sides of equation (2) by V as in the following formula (3) (cf. Fig. 5D). Gy=V2 / (1+Ks×V2)×(θs / N / L)

[0182] The relationship between the constant yaw rate γ and the vehicle speed V, and the example of the characteristic of the regular lateral acceleration Gy when the steering wheel is turned by one radian, are in Fig. 5B shown.

[0183] The example of the characteristic in Fig. Figure 5B shows that if the vehicle speed V increases, the vehicle movement will increase even if the steering angle is the same.

[0184] Although the constant yaw rate γ decreases from above a certain speed, some of γV can escape if the magnitude or extent of horizontal movements per unit time is used, so that it becomes the same as that of the regular lateral acceleration Gy, and results in a monotonic increase of the vehicle speed V.

[0185] If the driver perceives a stimulus such as lateral acceleration and the extent of horizontal movements at a unit steering angle as the steering torque (steering reaction), the magnitude or extent of the target steering torque Ts* can be determined by a logarithmic function to the vehicle speed V in order to maintain a consistent feeling, neither too light nor too heavy, even as the vehicle speed V increases.

[0186] This means that the final target steering torque Ts* can be generated by, for example, setting or adjusting a gain (a target steering torque gain) Kg, as shown in the following formula (4), and multiplying the target steering torque Ts* of formula (1) by a target steering torque gain Kg. Kg=C×log(V2 / (1+Ks×V2)×(1 / N / L))+D

[0187] In formula (4), when C = 0.25 and D = 1.5 are used as examples, the target steering torque gain Kg for the vehicle speed V is calculated as in Fig. 5C shown and received.

[0188] However, since the logarithm cannot be calculated when the vehicle is stationary (when the vehicle speed V is 0), the vehicle speed V is asymptotic to a fixed value, such as 1, as shown in Fig. 5C shown.

[0189] The target steering torque Ts*, which changes logarithmically with respect to the estimated force Tx and the vehicle speed V, can be generated by such a calculation.

[0190] However, if the target steering torque Ts* is actually calculated by the ECU 15, it is shown in a table as in Fig. 6 shown, so that fine-tuning may be possible.

[0191] Fig. Figure 6 shows a table that expresses the relationship between the estimated force Tx and the target steering torque Ts* for every 20 km / h when used in a real vehicle.

[0192] As in Fig. As shown in Figure 6, the target steering torque Ts* tends to increase logarithmically relative to the increase in the estimated force Tx, and to saturate with the increase in vehicle speed V (i.e., also to increase logarithmically relative to vehicle speed V).

[0193] Consequently, the driver can perceive a linear response because the change in the target steering torque Ts* is such that it is a logarithmic function relative to the change in the estimated force Tx.

[0194] Furthermore, certain numerical values, slope, etc., of the table are used. Fig. 6. Finely adjusted to suit the vehicle.

[0195] The target generation section 22 requests the estimated force Tx and the target steering torque Ts* relative to the vehicle speed V, which are supplied by linear interpolation based on the table.

[0196] Furthermore, although the table for Tx < 0 is not shown, it becomes a table with a form of origin symmetry to the table of Fig. 6.

[0197] Next, section 24 describes a control device for modifying a transmission sensation or steering sensation (a stiffness from the steering wheel to the tire) when a steering operation takes place. As in Fig. As shown in Figure 3, the section for a control unit 24 includes a support control unit 61, three modifying filters 62, 63, and 64, a transmission system planner 65, and a weighting section 66.

[0198] The more detailed composition of the section for a control device 24 is in Fig. 7 shown.

[0199] As in Fig. As shown in Figure 7, a torque deviation calculated by the deviation calculation device 23 is supplied to or entered into the support control device 61 and the three modifying filters 62, 63, and 64.

[0200] The support control unit 61 generates a basic command, which is used as a basis for the basic support command Tb*, which the section for a control unit 24 generates and outputs at the end.

[0201] The support control unit may or may not include an integrator as a component.

[0202] The frequency characteristic or frequency response curve of the support control unit 61, which does not include the integrator, is shown in Fig. 8 shown.

[0203] As in Fig. As shown in Figure 8, a gain characteristic of the support control device 61 is a high gain (10 times or more) in a low frequency wave or a low frequency band (generally 1 Hz or less).

[0204] To ensure the stability of the steering system mechanism 100, the gain above 1 Hz is slowly reduced, while the gain from 10 Hz to about 100 Hz is slowly increased by specifying a differentiation element.

[0205] In particular, the range of 1 to 20 Hz is the range that influences the steering feel when the steering wheel is operated.

[0206] For example, if there is a local minimum at 6 Hz, the connection from the steering wheel to the tire will feel harsh or have a harsh effect.

[0207] On the other hand, the steering feels soft if there is a local minimum around 6 Hz.

[0208] Furthermore, it has been experimentally confirmed that stiffness resulting from steering or stiffness resulting from tire grip on the road depends on the frequency.

[0209] In the present example, a basic control unit is used only as the support control unit 61, and the basic command that serves as a basis for the support control unit 61 is generated.

[0210] A variety of filters for modifying the basic command are prepared independently of the support control device 61, and a weighted sum is used to generate an overall modification value, after which the basic command is modified using the overall modification value.

[0211] In detail, as in Fig. Figure 7 shows that, with regard to a variety of filters, a first modifying filter 62 is provided for modifying (locally increasing) the gain of a 4 Hz band (4 Hz and its neighborhood), a second modifying filter 63 is provided for modifying (locally increasing) the gain of a 6 Hz band (6 Hz and its neighborhood), and a third modifying filter 64 is provided for modifying (locally increasing) the gain of a 12 Hz band (12 Hz and its neighborhood).

[0212] Examples of frequency characteristics or frequency response curves of each filter 62, 63, and 64 are in Fig. 9A to Fig. 9C shown.

[0213] Out of Fig. 9A to Fig. 9C clearly shows that the gain characteristic or gain curve of each filter 62, 63, and 64 increases locally in the corresponding frequency band (it has a local maximum).

[0214] On the other hand, the transmission system characteristic setting section 51 includes a table that calculates a transmission characteristic preset value P1 (within the limits of P1 = 0 - 1) relative to the vehicle speed V using the vehicle speed V as a parameter, as shown in Fig. 7 is shown.

[0215] Overall, the table shows a tendency for the transmission system characteristic preset value P1 to decrease with increasing vehicle speed V.

[0216] Furthermore, the transmission system characteristic preset value P1 serves to determine the weighting of the modification by the three modifying filters 62, 63, and 64 in accordance with the vehicle speed V.

[0217] The transmission system characteristic setting section 51 calculates the transmission characteristic preset value P1 based on the table relative to the input speed V, and supplies the transmission characteristic preset value P1 to the transmission system planner 65 in the section for a control device 24.

[0218] The transmission system planner 65 configures transmission system modification gains K1, K2, and K3, which show the severity and weight, respectively, of the modifying value from each of filters 62, 63, and 64, in accordance with the transmission system characteristic preset value P1 (i.e., responding to the vehicle speed V).

[0219] Specifically, the transmission system planner 65 includes a first planner 65a for configuring the first transmission system modification gain K1, which shows the weight of a first modifying value of the first modifying filter (4 Hz band modification) 62, a second planner 65b for configuring the second transmission system modification gain K2, which shows the weight of a second modifying value of the second modifying filter (6 Hz band modification) 63, and a third planner 65c for configuring the third transmission system modification gain K3, which shows the weight of a third modifying value of the third modifying filter (12 Hz band modification) 64.

[0220] Each planner 65a, 65b, and 65c is given as a table in the present embodiment, and each transmission system modification gain K1, K2, and K3 is calculated using a table according to the supplied transmission characteristic preset value P1.

[0221] The first planner 65a has the characteristic such that the first transmission system modification gain K1 increases from -1 to +1 when the transmission system characteristic preset value P1 increases from 0 to 1, as in Fig. 7 is shown.

[0222] This means that the lower the vehicle speed V, the greater the first transmission system modification gain K1 becomes, and the higher the vehicle speed V, the smaller the first transmission system modification gain K1 becomes.

[0223] The second planner 65b has the characteristic (trapezoidal characteristic) such that when the transmission system characteristic preset value P1 increases from 0 to 1, as in Fig. As shown in Figure 7, the second transmission system modification gain K2 ranges along a predetermined slope from -1 to +1, +1 is held for a while, and then K2 decreases along a predetermined slope from +1 to -1.

[0224] This means that the second transmission system modification gain K2 decreases when the vehicle speed V is in a low or high speed region, and the second transmission system modification gain K2 takes on a large value (+1) when the vehicle speed V is in a medium speed region.

[0225] As in Fig. As shown in Figure 7, the third planner 65c has a characteristic such that the third transmission system modification gain K3 decreases from +1 to -1 when the transmission system characteristic preset value P1 increases from 0 to 1.

[0226] This means that the lower the vehicle speed V, the smaller the third transmission system modification gain K3 becomes, and the faster the vehicle speed V, the larger the third transmission system modification gain K3 becomes.

[0227] As regards the size or extent of the first modification of the first modifying filter 62, the first transmission system modification gain K1 from the first planner 65a is integrated into the first integrator 66a.

[0228] As regards the size or extent of the second modification of the second modifying filter 63, the second transmission system modification gain K2 from the second planner 65a is integrated into the second integrator 66b.

[0229] Regarding the size or extent of the third modification of the third modifying filter 64, the third transmission system modification gain K3 from the third planner 65c is integrated into the third integrator 66c.

[0230] The full extent of the transmission system modification is obtained by adding each integrated value through the adder 66d.

[0231] That is, each modifying quantity from each modifying filter 62, 63, and 64 is given its weighted sum.

[0232] Consequently, the basic command is modified by adding the total extent of the transmission system modification, which is obtained by weighted addition to the basic command from the support control unit 61 with the adder 66e.

[0233] The modified result is output as the basic support command Tb*.

[0234] Here, assuming that each transmission system modifying gain K1, K2, and K3 is -1 (although such a case never occurs in the present embodiment), for example, a gain of each 4, 6, and 12 Hz zone in the input and output transmission characteristics of the entire section for a control device 24 falls, as in Fig. 10 is shown.

[0235] When such a modification is performed, the response of the steering torque Ts to a steering wheel torque (a torque added or applied by the driver) becomes part of the parameters defined in Fig. 11 characteristics or characteristic curves shown.

[0236] This means that the gain in a specific frequency band increases with the modification of each modifying filter 62, 63, and 64.

[0237] Although examples of modifying the basic command in three ranges (4, 6 and 12 Hz) are presented in the present embodiment, the steering torque signal increases more rapidly the higher the frequency component to which the modification is applied.

[0238] In other words, the steering response changes when the driver steers, according to the frequency of attention paid to it, or the gain on the transmission characteristic that is present. Fig. 11 is shown.

[0239] The faster the steering reaction and the greater the amplitude of the steering reaction, the more stiffness the driver feels in the steering system mechanism in conjunction with a transmission of force from the steering wheel to the vehicle body.

[0240] Conversely, the slower the steering response, the slower and less responsive the steering feel.

[0241] With regard to certain parts of the vehicle, 12 Hz creates the impression that a connection mechanism from the steering wheel to the tire is stiff, 6 Hz creates the impression that a shock absorber is hard, and 4 Hz creates the impression that the response of sprung parts of the vehicle body is good.

[0242] Since the range that contributes to such a perception is generally 1 to 20 Hz, it is preferred that modification be carried out in one or a plurality of frequency bands (three bands in the present embodiment) which are suitably distributed within the range of 1 to 20 Hz.

[0243] This allows for a characterization of the vehicles, such as deciding where a hard impression should be obtained, for example between the steering wheel, the tire and the vehicle body, to be carried out arbitrarily.

[0244] Furthermore, the type of impression obtained in each frequency band varies from vehicle to vehicle, so the aforementioned 4, 6, and 12 Hz are only examples.

[0245] In the present embodiment, each transmission system correction coefficient K1, K2 and K3 is configured separately by each planner 65a, 65b and 65c in accordance with the transmission system characteristic preset value P1, which is supplied to the transmission system planner 65.

[0246] This means that if the transmission system characteristic preset value P1 is 0, the planner 65a is mapped in such a way that the stiffness of the connection mechanism near the hands is improved mainly by adding the modification of the 12 Hz band.

[0247] Furthermore, when the transmission system characteristic preset value P1 is 1, the planner 65c is mapped in such a way that, mainly by adding the modification of the 4 Hz band, the response of the setup is perceived as increasing relatively far away from the hands.

[0248] Then, if the transmission system characteristic preset value P1 is a mean value between or from 0 to 1, the planner 65c is mapped in such a way that, mainly by adding the modification of the 6 Hz band, the stiffness of the shock absorbers is perceived as increasing.

[0249] Furthermore, a table in which the vehicle speed V and the transmission system characteristic preset value P1 correspond 1 to 1 is prepared in the transmission system characteristic preset section 51, so that the response of the vehicle body has a priority when the vehicle speed V is low, and produces a machine-like harshness and shows a consistent sensation when the vehicle speed V is high.

[0250] This means that the transmission system characteristic preset value P1 is configured larger at low speeds, and the transmission system characteristic preset value P1 is configured smaller at high speeds.

[0251] The transmission system characteristic setting section 51 calculates the transmission system characteristic preset value P1 relative to the vehicle speed V based on the table and outputs it.

[0252] Since each table of the transmission system characteristics setting section 51 and the transmission system planner 65 can be described as the parts that show the character of the vehicles, each table can be appropriately set or adjusted in accordance with a concept of a vehicle, etc.

[0253] Although the support control device 61 has been explained as operating without an integrator, a composition with an integrator that integrates the input or supplied torque deviation can be used.

[0254] An example of the composition of a support control unit that includes the integrator is in Fig. 12A to Fig. 12C shown.

[0255] A support tax facility 81 of Fig. 12 A indicates relative to the one in Fig. The support control unit 61 shown in 7 incorporates an integrator.

[0256] Therefore, the frequency characteristics of the support control device 81 change such that the lower the frequency, the greater the gain in a region of 10 Hz or less, shown as a solid line in Fig. 12D, increases.

[0257] The support control unit 81 has an integration element and generates the basic support command Tb* to control the motor 6 such that an input (a deviation of the target steering torque Ts* and the steering torque Ts) becomes 0.

[0258] Because of the integration element, it has a low-frequency characteristic like in Fig. As shown in Figure 12D, using the support control device 81, it is possible to follow the steering torque Ts to the target steering torque Ts* without a stability state error or steady state error.

[0259] However, if turning the steering requires assistance in the opposite direction, the integration element will apply the integration accumulated up to that point in the direction that blocks steering in the opposite direction.

[0260] To solve such problems, it is recommended to set up a support control unit in such a way that the integrator and the control unit are separate or provided separately.

[0261] Specifically, the integrator 82a and the control unit 82b can implement a series-connected structure such as the one shown in Fig. The support control unit shown in 12B is 82.

[0262] The control unit 82b is the one in which the integrator 82a is derived from the transmission control unit 81 (transmission function) of Fig. 12A has been removed.

[0263] Furthermore, the amplification K83a can be further increased from the control unit 82b of Fig. 12B removed and placed in front of the integrator 82a, as in the Fig. 12C shown support control device 83 to form a series connection of the amplifier K83a, the integrator 82a and the control device 83b.

[0264] Since the control unit 83b does not have the gain K83a and the integrator 82a, the frequency characteristics in Fig. 12D shown by a broken line.

[0265] Furthermore, the frequency characteristics of the series structure (K / s) of the amplifier K83a and the integrator 82a are shown in Fig. 12D shown with a long-and-short broken line.

[0266] Furthermore, the integrator 82a can have a composition such that an upper limit is applied to the absolute value of the integration output.

[0267] Specifically, the steering torque Ts is assigned to the integrator 82a as in Fig. 12B and Fig. 12C shown and supplied.

[0268] Furthermore, the integrator 82a has a suppression or limiting function, as a so-called limiter, such that the absolute value of its own integration output cannot exceed the predetermined times or frequencies (equivalent to the upper integration limit according to the invention) of the absolute value of the steering torque Ts.

[0269] Furthermore, a suitable decision can be made as to how the upper limit of the absolute value of the output of the integrator 82a is configured.

[0270] In addition to the steering torque Ts, the upper limit can be configured based on a state variable, such as a steering wheel rotation angle, a motor 6 rotation angle, or the basic support command Tb*, so that it increases as the state variable increases.

[0271] Thus, by providing the upper limit for the absolute value of the integration output, an accumulation of the integration value more than necessary due to steering rotation is eliminated, and the support in the steering direction decreases until the steering is turned without continuing, so that inhibition of the steering in the steering direction caused by the accumulation of the integration value can be suppressed.

[0272] The torque modification section 31 in the vehicle control calculation section 70 (the modification section 30) is described below using Fig. 3 explained.

[0273] The torque modification section 31 is a device for achieving suitable operational stability (suitable vehicle motion characteristics) of the entire vehicle.

[0274] The torque modification section 31 comprises a first vehicle motion control device 71, a second vehicle motion control device 72, a vehicle system planner 73 and a weighting section 74.

[0275] The first vehicle motion control device 71 serves to improve convergence by supplying signals of the steering torque Ts and the engine speed ω, and in particular the convergence control mechanism disclosed in publication JP 2010-264913 A can be applied.

[0276] This means that this is the technology for improving the convergence of the vehicle by reducing a sudden feeling of backsteering without deteriorating the operating feel when turning the steering wheel, and generates an initial modifier variable based on the steering torque Ts and the engine speed ω.

[0277] Since a specific method for generating a second modifier based on the steering torque Ts and the engine speed ω is disclosed in publication JP 2010-264913 A, a detailed explanation is omitted here.

[0278] Furthermore, the second vehicle motion control device 72 is a control device for modifying the motion characteristics of the sprung sections of the vehicle body, and in particular the torque modification technology can be applied in the control mechanism disclosed in document 373.

[0279] This means that the size or extent of the torque modification (a second compensation quantity) that modifies the basic support command Tb* to change the yaw response characteristic in early phases of steering is generated on the basis of the estimated force Tx, which shows the sum of the basic support command Tb* and the steering torque Ts.

[0280] Since a specific method of generating a second modifier on the basis of the estimated force Tx is disclosed in Publication '373, a detailed explanation is omitted here.

[0281] Furthermore, the torque modification command Tr is obtained by the weighted sum of each modification quantity from each vehicle motion control unit 71 and 72 in the weighting section 74.

[0282] The vehicle system planner 73 configures the weight of each modification parameter in accordance with the various vehicle motion characteristic preset values ​​supplied by the vehicle motion characteristic setting section 52.

[0283] The vehicle motion characteristic setting section 52 determines the vehicle motion characteristic preset value (for example, the yaw damping value ζ and a response speed (a stabilization time) R) relative to the vehicle speed V by a table calculation using the speed V as a parameter, and transfers the value to the vehicle system planner 73.

[0284] A table showing the weight distribution to achieve the yaw damping value ζ and the stabilization time R is configured in advance in the vehicle system planner 73 based on the results of function evaluations.

[0285] Then the vehicle system planner 73 calculates an initial gain to vary the damping of the yaw rate by tabular calculation in accordance with the vehicle motion characteristic preset value from the vehicle motion characteristic setting section 52.

[0286] The first amplification shows the weight of the first modifying quantity.

[0287] Although the constant yaw rate is explained in accordance with the vehicle speed V using formula (2) etc. in the above-mentioned functional explanation of the target generation section 22, it is known that this tends to show the increase in the resonance frequency and the damping drop together with the increase in the vehicle speed V if a transient or disturbance variable is included.

[0288] Since the damping drop causes discomfort when steering the vehicle, a desired damping is achieved by a convergence control through the first vehicle motion control device 71 in such a way that the damping does not drop.

[0289] The vehicle can easily feel familiar if the response to a process or operation is consistent with the driver's perception, such that the degree of damping remains the same even when the vehicle speed V changes, or if an adjustment time is set or adjusted so that it is the same when the hands are released from the state that has achieved a predetermined lateral acceleration.

[0290] Furthermore, the vehicle system planner 73 calculates the gain in accordance with the vehicle speed V or indices that show the response by spreadsheet in accordance with the vehicle motion characteristic preset value from the vehicle motion characteristic setting section 52 to obtain a second gain.

[0291] The second amplification shows the weight of the second modifier.

[0292] Furthermore, the first reinforcement from the vehicle system planner 73 is integrated into the weighting section 74 by the first vehicle motion control unit 71 onto the first modifier variable, and the second reinforcement from the vehicle system planner 73 is integrated into the second vehicle motion control unit 72 onto the second modifier variable.

[0293] The torque modifier command Tr, as a result of the weighted sum of each modifier quantity, is obtained by adding each result of the addition.

[0294] Convergence situations occur when the steering wheel is turned approximately 90° from a neutral position and the hands are released. Fig. 13A to Fig. 13C are shown as examples of the electric power steering system or the power steering 1 of the correspondingly constructed present embodiment.

[0295] In the Fig. 13A to Fig. 13C shows Fig. 13A shows a change in the steering wheel angle θs. Fig. 13B a ​​change to the torque modification command Tr, and shows Fig. 13C a change in steering torque Ts.

[0296] Furthermore, each signal waveform shows Fig. 13A to Fig. 13C a dotted line the change then when the basic support command Tb* from the basic support section 20 is controlled only taking into account the support torque command Ta (i.e. without modification by the modification section 30).

[0297] Furthermore, a long-and-short dashed line indicates the change when a control composition (that is, a simple combination of the printed documents JP 2004-203089 A and JP 2010-264913 A) is used in Fig. 14 is shown, it is controlled.

[0298] That is, although the torque modification is added, it is a control result in the control composition using the motor current Im, which corresponds to a final command value with the steering torque Ts to estimate the road surface force.

[0299] Furthermore, a solid line indicates the change when controlled by the ECU 15 of the present embodiment.

[0300] From the Fig. 13 A to Fig. 13 C it is clear that, since modification to stabilize vehicle movement is not carried out when only basic support (which does not include modification) is used, oscillation does not immediately subside and convergence takes time.

[0301] On the other hand, if the control composition, which is in Fig. As shown in 14, the time required for convergence is reduced compared to the case where no modification takes place.

[0302] However, since the control output is used as the modified result in the modification section 130, when the basic support section 120 uses the basic support command Tb* in the control composition of Fig. 14, as mentioned above, the basic support section 120 cancels, nullifies, or aborts the modification process by the modification section 130.

[0303] This means that the basic support and the torque modification interfere or negatively influence each other, so that sufficient convergence is not achieved.

[0304] On the other hand, in the control mechanism (the ECU 15) of the present embodiment, the basic support and the torque modification exist independently of each other, and since systems with two degrees of freedom, to which a mutual command value is added, are designed, there is virtually no influence of a disturbing influence or interference between the basic support and the torque modification, and therefore a rapid convergence is achieved.

[0305] As explained above, in accordance with the electric power steering system 1 (in particular the ECU 15) of the present embodiment, because the basic support section 20 generates the basic support command Tb* in accordance with the road surface force, the support appears to be in accordance with the response received from the road surface when a steering operation is performed, and the response in the steering wheel is entirely constant according to the force applied to the tire.

[0306] Therefore, it becomes easy to assess the condition of the vehicle and the condition of the road surface.

[0307] Furthermore, the unstable motion of the vehicle can be appropriately converged because the modification section 30 generates the torque modification command Tr, which can stably converge the vehicle.

[0308] Furthermore, the function for configuring the target steering torque Ts* in accordance with the estimated force Tx by estimating the road surface force within a loop or loop pass is closed or completed (basic support section 20), and in the present embodiment the function is separated from the modification section 30.

[0309] Therefore, interference between the two can be minimized (or completely removed).

[0310] This allows the characteristics of the steering response to be realized in accordance with the road surface force by the basic support section 20 and the suitable operational stability (a suitable vehicle motion characteristic) of the entire vehicle to be realized by the modification section 30, and therefore the driving performance of the vehicle can be improved.

[0311] It is noted that the steering shaft 3 in the present embodiment corresponds to an input shaft according to the invention.

[0312] An entire mechanism on the downward side (the side of the tire 10) of the steering shaft 3 in the steering system mechanism 100 corresponds to an input transmission device according to the invention.

[0313] The rotation sensor in the motor 6 corresponds to a steering speed information receiving device according to the invention.

[0314] The basic support section 20 corresponds to a basic support quantity generation device according to the invention.

[0315] The modification section 30 corresponds to a support compensation variable generation device according to the invention.

[0316] The eraser 41 corresponds to a support size modification device according to the invention.

[0317] The current feedback section 42 corresponds to a motor control device according to the invention.

[0318] The force estimation device 21 corresponds to a road surface force estimation device according to the invention.

[0319] The target generation section 22 corresponds to a target steering torque calculation device according to the invention.

[0320] A basic support parameter calculation device according to the invention is realized by the deviation calculation device 23 and the section of a control device 24, and the support control device 61 corresponds to a basic command calculation device according to the invention.

[0321] The weighting section 66 in the section of a control device 24 corresponds to a calculation device for a first weighted sum according to the invention.

[0322] The first vehicle motion control device 71 and the second vehicle motion control device 72 all correspond to a basic compensation parameter calculation device according to the invention.

[0323] Furthermore, the basic support command Tb* corresponds to a basic support quantity according to the invention.

[0324] The torque modification command Tr corresponds to the support compensation parameter according to the invention.

[0325] The support torque command Ta corresponds to a modified support parameter according to the invention.

[0326] The output from the support control unit 61 corresponds to a basic command according to the invention.

[0327] Each output from each vehicle motion control unit 71 and 72 corresponds to a basic compensation value according to the invention.

[0328] Each gain K1, K2, and K3 output by the transmission system planner 65 is equivalent to a first weighting configuration command according to the invention. [Modification]

[0329] Although the embodiment according to the invention has been explained above, further developments of the invention are not limited to the embodiment mentioned above, and it goes without saying that various forms can be used, as long as these are within the technical scope of the invention.

[0330] Although, for example, the cutoff frequency of the low-pass filter 21b in the Fig. The force estimation device 21 shown in section 4 is set to 10 Hz; this is merely an example, and which band is to be allowed through (which band is to be cut off) can be appropriately determined.

[0331] Furthermore, it is not necessary to use the low-pass filter itself, and as long as a desired frequency component can be allowed through (an unnecessary component is filtered out), the composition and the passband (cutoff frequency band) of a filter can be appropriately determined.

[0332] Furthermore, section 24, which is in Fig. Figure 7 shows the provision of the number of modifying filters with three (each modifying filter 62, 63, and 64), the provision of the number of planners that the transmission system planner 65 images, with three (each planner 65a, 65b, and 65c), the provision of the range of each gain K1, K2, and K3 to -1 to +1, and the provision of the range of the transmission system characteristic preset value P1 to 0 to 1; these are merely examples.

[0333] Furthermore, it is not necessary to perform a weighting configuration by each planner 65 and 73 in accordance with the vehicle speed V.

[0334] For example, the weighting configuration can be predetermined, or it can be configured in accordance with a different physical value and / or state variable than the vehicle speed V.

[0335] The assignment of each planner 65 and 73 to a type of output characteristic relative to the supplied characteristic preset value (that is, providing a table with a type of characteristic or characteristic curve) can also be appropriately decided.

[0336] Furthermore, the assignment of a type of output characteristic to the vehicle speed V can also be appropriately decided with regard to each characteristic setting section 51 and 52.

[0337] Furthermore, it is not necessary to provide each modifying filter 62, 63, and 64 in the section for a control unit 24, but the output from the support control unit 61 can simply be output as the basic support command Tb*.

[0338] Moreover, it is not necessary to include a large number of (in the present embodiment two) vehicle motion control devices in the torque modification section 31, which is described in Fig. 3 is shown, but three or more control devices with different characteristics or properties can be provided, or only one control device can be provided.

[0339] If only one vehicle motion control device is provided, an output from that single vehicle motion control device can simply be used to output the modifying torque Tr.

[0340] Furthermore, as in Fig. Figure 7 shows the section for a control unit 24 of the aforementioned embodiment as a composition of providing a support control unit 61, which is used as a base, and the output from the support control unit can be modified with any modifying parameter from the three modifying filters 62, 63, and 64.

[0341] However, such a composition is again only one example, and a large number of support control devices with different frequency characteristics or frequency response curves can be provided, for example, and outputs from the support control devices can be weighted or charged.

[0342] Thus, a control device with a performance capability equivalent to that of section 24 for a control device of the aforementioned embodiment can be realized by providing a plurality of support control devices even without providing the modifying filter(s).

[0343] Naturally, a variety of support control devices can be provided with the further addition of one or more modifying filters.

[0344] Furthermore, regarding the composition of the torque modification section 31, which is in Fig. Figure 3 is shown, this is only an example, and different compositions can be used.

[0345] For example, the combination can also be used with a vehicle motion control device for convergence control designed with a slow stabilization time and a vehicle motion control device for convergence control designed with a fast stabilization time.

[0346] In this case, the planner uses a table calculation to decide how much stabilization time R (s; seconds) is ultimately taken into account with the vehicle speed V, based on a table in which the speed and the stabilization time are aligned, and adds two outputs from vehicle motion control devices in what kind of distribution relative to the stabilization time R, and a single gain Ka is obtained for weighting.

[0347] Assuming that the output obtained by weighting to modify the stabilization time is set to Sb, Sb can be obtained, for example, by the following formula (5), if the outputs of the two vehicle motion control devices are set to S1 and S2, respectively. Sb=Ka×S1+(1−Ka)×S2

[0348] Furthermore, a damping level or damping factor ζ, which indicates how much yaw resonance of vehicles is suppressed at vehicle speed V (i.e., the damping strength), is calculated on the basis of a table in which the speed and the damping factor are aligned, and a single gain Kb is obtained for weighting by a table calculation by the designer that can achieve the damping factor ζ.

[0349] An output Sx of a final vehicle motion control device (here a convergence controller) can be obtained by multiplying the gain Kb by the aforementioned Sb.

[0350] In this example, it is preferred that the final stabilization time R is configured to be shorter, for example, to allow it to converge quickly when the vehicle speed V is low, and that the final stabilization time R is configured to be longer to some extent when the vehicle speed V is high.

[0351] This ensures that the steering wheel returns promptly at low speeds, which contributes to a reduction in the body's oscillation in one direction of travel through a quiet convergence action at high speeds.

[0352] Furthermore, the damping level can be configured as a large value to respond to vehicle yaw oscillation, which increases as the speed increases.

[0353] Furthermore, although the brushless DC motor is used as motor 6 in the exemplary embodiment, the use of the brushless DC motor is only an example, and this could be, for example, a DC motor with brushes or a different type of motor.

[0354] When the DC motor is used with brushes, the motor speed ω can be detected using a rotation sensor, such as an encoder, or estimated by estimating from results obtained from a terminal voltage and motor current of the motor.

[0355] Furthermore, although the motor 6 has the rotation sensor and the motor speed is to be detected by the rotation sensor in the present embodiment, this is only an example, and where the rotation sensor is placed and how the required information (the rotational state of the motor 6, such as the motor speed or rotational speed and the motor rotation angle) is detected can be appropriately decided.

[0356] Therefore, if the brushed DC motor is used as motor 6, for example a rotational state can be obtained using a method for assuming a rotational state based on the current flowing into motor 6, or the like.

[0357] Furthermore, as a system of the electric power steering system 1, a composition of supporting the rotation of the intermediate shaft 5 by the motor 6, or the so-called shaft support arrangement, is mentioned as an example and explained in the present embodiment.

[0358] However, this is also only one example, and the invention is applicable to the electric power steering system of various assistance or support systems, such as a system which supports the reciprocating movement of the linkage 8 (i.e. the reciprocating movement of the rack in the steering gear (housing) 7) by the motor, or the so-called rack and pinion support system.

Claims

[1] Control device for an electric power steering, comprising: an input shaft (3) connected to a steering wheel (2) of a vehicle and rotating with the steering wheel (2); an input transmission device (100) which steers steered wheels (10) of the vehicle by transmitting rotation of the input shaft (3) to the steered wheels (10); a steering torque detecting device (4) which detects a steering torque (Ts), which is a torque applied to the input shaft (3) in an axis rotation direction; and a motor (6) which provides an assist steering force to the input shaft (3) or the input transmission device (100) for assisting an operation of turning the steering wheel (2) when the steered wheels (10) are steered by an operation of turning the steering wheel (2); wherein the control device for an electric power steering, which controls the assist steering force by controlling the motor (6), is provided in an electric power steering system (1), wherein the control device for an electric power steering further comprises: a basic assistance amount generating means (20) that generates a basic assistance amount (Tb*) for assisting the operation of turning the steering wheel (2) on the basis of the steering torque (Ts) detected by the steering torque detecting means (4) such that the detected steering torque (Ts) changes in accordance with a road surface force (Tx) transmitted from a road surface to the steered wheels (10); an assistance compensation amount generating means (30) that generates an assistance compensation amount (Tr) for modifying the basic assistance amount (Tb*) calculated by the basic assistance amount generating means (20) such that an action of the steered wheels (10) responds to predetermined action characteristics; an assistance amount modifying means (41) that generates a modified assistance amount (Ta) by modifying the basic assistance amount (Tb*) generated by the basic assistance amount generating means (20) with the assistance compensation amount (Tr) generated by the assistance compensation amount generating means (30); and a motor control device (42) which controls the motor (6) on the basis of the modified assistance quantity (Ta) from the assistance quantity modifying device (41); wherein the basic assistance quantity generating means (20) comprises a road surface force estimating means (21) which estimates the road surface force (Tx) based on the steering torque (Ts) detected by the basic assistance quantity (Tb*) and the steering torque (Ts) detected by the steering torque detecting means (4), both of which are generated results of the basic assistance quantity generating means (20) itself; a target steering torque calculating means (22) calculates a target steering torque (Ts*) which is a desired value of the steering torque (Ts) based on the estimated force, which is the road surface force (Tx) estimated by the road surface force estimating means (21); and a basic assistance amount calculation device (23, 24) calculates the basic assistance amount (Tb*) for controlling the motor (6) such that the steering torque (Ts) detected by the steering torque detection device (4) agrees with the target steering torque (Ts*) calculated by the target steering torque calculation device (22). [2] An electric power steering control device according to claim 1, wherein said road surface force estimating means (21) extracts a member of a frequency band configured in advance from a sum of said basic assist amount (Tb*) and said steering torque (Ts), and outputs the member of the extracted frequency band as said estimated force. [3] An electric power steering control device according to claim 2, wherein the frequency band is 10 Hz or less. [4] An electric power steering control device according to claim 1, 2 or 3, wherein said target steering torque calculating means (22) calculates said target steering torque (Ts*) on the basis of the force estimated by said road surface force estimating means (21) such that the larger the estimated force becomes, the larger the target steering torque (Ts*) becomes. [5] An electric power steering control device according to claim 4, wherein said target steering torque calculating means (22) calculates said target steering torque (Ts*) such that said target steering torque (Ts*) changes logarithmically relative to said estimated force. [6] Control device for an electric power steering according to one of claims 1 to 5, in which the electric steering assistance system (1) has a speed detection device (11) which detects a speed of a moving vehicle, and the target steering torque calculating means (22) calculates the target steering torque (Ts*) on the basis of the vehicle speed detected by the speed detecting means (11) such that the faster the speed becomes, the greater the target steering torque (Ts*) becomes. [7] An electric power steering control device according to claim 6, wherein the target steering torque calculating means (22) calculates the target steering torque (Ts*) such that the target steering torque (Ts*) changes logarithmically relative to the vehicle speed. [8] A control device for an electric power steering according to any one of claims 1 to 7, wherein the basic assistance amount calculation means (23, 24) comprises a deviation calculation means which calculates a torque deviation which is a difference between the steering torque (Ts) detected by the steering torque detection means (4) and the target steering torque (Ts*) calculated by the target steering torque calculation means (22), and at least one basic command calculation device (61) which calculates a basic command corresponding to the basic assistance quantity (Tb*) such that the torque deviation calculated by the deviation calculation device is configured to 0, if more than one basic command calculating means (61) is provided, a weighted sum of the basic commands calculated by each basic command calculating means (61) is calculated as the basic assistance amount (Tb*), and the basic command calculating means (61) is constructed so that a transfer function of the basic assist amount (Tb*) to be output relative to the supplied torque deviation becomes more than a predetermined level with a gain greater than 1 in the band below a predetermined frequency. [9] Control device for an electric power steering according to claim 8, in which the basic command calculation means (61) comprises an integration means which integrates and outputs the supplied torque deviation, and which is designed in such a way that the basic command is calculated so that the torque deviation becomes 0. [10] An electric power steering control device according to claim 9, wherein the integrating means is constructed such that the absolute value of the outputted integration value is limited to below a predetermined upper integration limit. [11] The electric power steering control device according to claim 10, wherein the steering torque (Ts) detected by the steering torque detecting means (4), a rotation angle of the steering wheel (2), a rotation angle of the motor (6), or the basic assist amount (Tb*) generated by the basic assist amount generating means (20) is used as a state amount for a configuration, and the upper integration limit is configured to be a larger value as the state amount for the configuration becomes larger. [12] A control device for an electric power steering device according to any one of claims 8 to 11, wherein the predetermined frequency is 1 Hz. [13] An electric power steering control device according to any one of claims 8 to 12, wherein the predetermined level is 10 times. [14] Control device for an electric power steering according to one of claims 8 to 13, in which the basic support quantity calculation means (23, 24) comprises a plurality of basic command calculation means (61) having different frequency characteristics, and a first weighted sum calculating means (66) is provided which calculates the weighted sum of the basic commands from the plurality of basic command calculating means (61) in accordance with a first weight configuration command. [15] Control device for an electric power steering according to one of claims 1 to 14, in which a steering speed information obtaining device is provided for obtaining steering speed information directly or indirectly showing a rotational speed of the motor (6), and the assistance amount modifying means (41) generates the assistance compensation amount (Tr) for converging a movement of the vehicle to the desired behavior based on at least one of the steering speed information obtained by the steering speed information obtaining means, the steering torque (Ts) detected by the steering torque detecting means (4), and / or the road surface force (Tx) estimated by the road surface force estimating means (21). [16] The electric power steering control device according to claim 15, wherein the assist amount modifying means (41) comprises at least one basic compensation amount calculating means (71, 72) for calculating the basic compensation amount corresponding to the assist compensation amount (Tr) for converging the motion of the vehicle, and when there are more than one basic compensation amount calculating means (71, 72), a weighted sum of each compensation amount calculated by each basic compensation amount calculating means (71, 72) is calculated as the basic assist amount (Tb*).

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