Steering control device and steering control method

Abstract

The steering control device (40) is configured so as to execute an operation amount calculation process, a correction process, and an operation process. The operation amount calculation process is a process for calculating an operation amount for control using a steering torque as a control amount and using a target steering torque as a target value for the control amount. The correction process uses the steering torque and the operation amount as inputs, and corrects the operation amount on the basis of a correction amount corresponding to the difference between the steering torque assumed by a nominal model and the actual steering torque. The operation process is a process for operating a motor of the steering device so as to generate a torque corresponding to the operation amount corrected by the correction process.

Description

Technical Field

[0001] The present disclosure relates to a steering control device and a steering control method. Background Art

[0002] For example, Patent Document 1 below describes a device for operating a motor for steering a steering wheel according to an operation amount of feedback control using a steering torque as a control amount and a target value of the steering torque as a target value of the control amount. Specifically, the operation amount of feedback control is calculated based on an output value of a proportional element, an output value of a differential element, and an output value of an integral element.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-203089

[0004] However, when setting feedback gain and the like in order to satisfy the requirements such as improving the responsiveness of the feedback control, there is a possibility that the time required to determine the values ​​of the feedback control parameters to meet these requirements becomes excessive. Summary of the invention

[0005] In one embodiment of the present disclosure, a steering control device is provided. The steering control device is configured to perform an operation amount calculation process, a correction process, and an operation process, wherein the operation amount calculation process is a process of calculating an operation amount of control using a steering torque as a control amount and using a target steering torque as a target value of the control amount, the steering torque is a torque input to a steering device by a driver, and the target steering torque is a target value of the steering torque, the correction process is a process of using the steering torque and the operation amount as inputs, and is a process of correcting the operation amount according to a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque, and the operation process is a process of operating a motor of the steering device to generate a torque corresponding to the operation amount corrected by the correction process.

[0006] In another aspect of the present disclosure, a steering control method is provided. The steering control method has the steps of executing an operation amount calculation process, a correction process, and an operation process, wherein the operation amount calculation process is a process of calculating an operation amount of control using a steering torque as a control amount and using a target steering torque as a target value of the control amount, the steering torque being a torque input to a steering device by a driver, and the target steering torque being a target value of the steering torque, the correction process is a process of using the steering torque and the operation amount as inputs, and correcting the operation amount according to a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque, and the operation process is a process of operating a motor of the steering device to generate a torque corresponding to the operation amount corrected by the correction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a diagram showing the configuration of a steering control device and a steering device according to the first embodiment.

[0008] Figure 2 Yes means Figure 1 A block diagram of the processing performed by a steering control device.

[0009] Figure 3 This is a block diagram showing processing executed by the steering control device according to the second embodiment.

[0010] Figure 4 It is a diagram showing the configuration of a steering control device and a steering device according to a third embodiment.

[0011] Figure 5 Yes means Figure 4 A block diagram of the processing performed by a steering control device. DETAILED DESCRIPTION

[0012] <First embodiment>

[0013] Hereinafter, a first embodiment will be described with reference to the drawings.

[0014] "Premise"

[0015] like Figure 1 As shown in FIG. 1 , the steering device 10 includes a steering wheel 12. The steering wheel 12 is a member for transmitting the driver's steering intention. A transmission shaft 14 is connected to the steering wheel 12. Therefore, if the steering wheel 12 rotates, the transmission shaft 14 rotates integrally. The rotational power of the transmission shaft 14 is transmitted to the steering shaft 16. The steering shaft 16 is arranged in the vehicle width direction ( Figure 1The steering shaft 16 extends in the left-right direction. Steering wheels 20 are connected to both ends of the steering shaft 16 via steering tie rods 18.

[0016] The transmission shaft 14 is arranged to intersect with the steering shaft 16. Teeth that mesh with each other are formed on the transmission shaft 14 and the steering shaft 16. Moreover, by meshing these teeth with each other, power can be transmitted from the transmission shaft 14 to the steering shaft 16. That is, the rotational power of the transmission shaft 14 is converted into axial displacement power of the steering shaft 16. The axial displacement of the steering shaft 16 is transmitted to the steering wheel 20 via the steering tie rod 18. As a result, the steering angle of the steering wheel 20 is changed. In addition, the steering angle refers to the rotation angle of the tire.

[0017] In addition, the steering device 10 includes an auxiliary motor 30. The auxiliary motor 30 generates an auxiliary force, which is a force used to assist the driver's steering operation. The rotational power of the auxiliary motor 30 is given to the drive shaft 34. Teeth that mesh with each other are formed on the drive shaft 34 and the steering shaft 16. Moreover, by meshing these teeth with each other, power can be transmitted from the drive shaft 34 to the steering shaft 16. That is, the rotational power of the drive shaft 34 is converted into axial displacement power of the steering shaft 16. Thus, the rotational power of the auxiliary motor 30 is converted into axial displacement power of the steering shaft 16 via the drive shaft 34. In detail, as an example, the auxiliary motor 30 is a 3-phase brushless motor. In addition, the output voltage of the inverter 32 is applied to the terminals of the auxiliary motor 30.

[0018] The steering control device 40 controls the control amount of the steering device 10 as a control object. In order to control the control amount, the steering control device 40 refers to the steering torque Th input to the steering wheel 12. The steering torque Th is detected by the torque sensor 50. The torque sensor 50 is a sensor that detects the steering torque Th based on the degree of torsion of the torsion bar 52 that is a part of the transmission shaft 14. In addition, the steering control device 40 refers to the vehicle speed SPD detected by the vehicle speed sensor 54. In addition, the steering control device 40 refers to the rotation angle θa of the assist motor 30 detected by the rotation angle sensor 56. In addition, the steering control device 40 refers to the currents iu, iv, and iw flowing in the assist motor 30.

[0019] The steering control device 40 includes a PU 42 and a storage device 44. The PU 42 is a software processing device such as a CPU, a GPU, and a TPU. The storage device 44 includes a non-volatile memory that can be electrically rewritten, and a storage medium such as a magnetic disk medium. A steering control program 44a is stored in the storage device 44. The steering control device 40 controls the control amount by executing the steering control program 44a stored in the storage device 44 by the PU 42.

[0020] "Processing performed by the steering control device 40"

[0021] Figure 2 The processing executed by the steering control device 40 is shown. Figure 2 The processing shown is realized by the PU 42 repeatedly executing the steering control program 44 a at a predetermined cycle, for example.

[0022] The target steering torque calculation process M10 is a process for calculating the target steering torque Th* as the target value of the steering torque Th based on the axial force Fa. The axial force Fa is a force applied to the steering shaft 16. However, the axial force Fa is an amount converted into the torque of the transmission shaft 14. In addition, the target steering torque calculation process M10 includes a process for setting the target steering torque Th* to different values ​​according to the vehicle speed SPD even if the axial force Fa is the same. This is a setting intended to allow the driver to have the best steering feel corresponding to the vehicle speed SPD.

[0023] The open-loop operation amount calculation processing M12 is a processing for calculating the open-loop operation amount Mff. The open-loop operation amount Mff is the operation amount of open-loop control using the steering torque Th as the control amount and using the target steering torque Th* as the target value of the control amount. The open-loop operation amount calculation processing M12 is a processing for calculating the open-loop operation amount Mff by inputting the target steering torque Th*. The open-loop operation amount calculation processing M12 calculates the open-loop operation amount Mff according to the inverse model of the nominal model Pn. The nominal model Pn is a model that uses the auxiliary torque Ta as the torque of the auxiliary motor 30 as an input and outputs the estimated steering torque The as an estimated value of the steering torque Th. Here, the auxiliary torque Ta is a value converted into the torque of the transmission shaft 14. The inverse model is a model that uses the estimated steering torque The as an input and outputs the auxiliary torque Ta. In addition, the nominal model Pn will be described in detail later.

[0024] The deviation calculation process M14 is a process for calculating a deviation which is a value obtained by subtracting the target steering torque Th* from the steering torque Th.

[0025] The feedback operation amount calculation process M16 is a process for calculating the feedback operation amount Mfb using the deviation as an input. The feedback operation amount Mfb is an operation amount of feedback control using the steering torque Th as a control amount and using the target steering torque Th* as a target value of the control amount. The feedback operation amount Mfb is the sum of the output value of the proportional element using the deviation as an input and the output value of the differential element using the deviation as an input. In addition, the feedback operation amount Mfb is a value converted into the torque of the transmission shaft 14. In detail, the feedback operation amount calculation process M16 includes a process for changing at least one of the gain of the proportional element and the gain of the differential element according to the vehicle speed SPD.

[0026] The torque command value calculation process M20 is a process for calculating the assist torque Ta using the open-loop operation amount Mff, the feedback operation amount Mfb, and the estimated second disturbance torque de as inputs. In the torque command value calculation process M20, the value obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operation amount Mff and the feedback operation amount Mfb is substituted into the assist torque Ta.

[0027] The assist torque Ta is input to the axial force calculation process M22. The axial force calculation process M22 is a process of substituting the sum of the assist torque Ta and the steering torque Th into the axial force Fa.

[0028] The assist torque Ta is input to a disturbance observer M30. The disturbance observer M30 includes a steering torque estimation process M32, a first disturbance calculation process M34, and a second disturbance calculation process M36.

[0029] The steering torque estimation process M32 is a process of outputting an estimated steering torque The by inputting the assist torque Ta to the nominal model Pn. The estimated steering torque The is a steering torque assumed by the nominal model Pn.

[0030] The first interference calculation processing M34 is a processing for calculating the estimated first interference torque dhe. The estimated first interference torque dhe is the interference component in the steering torque Th in the actual control object. The estimated first interference torque dhe is the difference between the actual torque and the torque estimated from the nominal model Pn. In other words, the estimated first interference torque dhe is the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. In detail, the first interference calculation processing M34 is a processing for substituting the value obtained by subtracting the estimated steering torque The from the steering torque Th into the estimated first interference torque dhe.

[0031] The second disturbance calculation process M36 is a process for calculating the estimated second disturbance torque de using the estimated first disturbance torque dhe as an input. The estimated second disturbance torque de is a disturbance torque converted into the torque of the assist motor 30. The second disturbance calculation process M36 is a process for calculating the estimated second disturbance torque de using the inverse model of the nominal model Pn and the filter Hd.

[0032] The filter Hd is provided to reduce noise caused by differential operation included in the nominal model Pn. In the present embodiment, the filter Hd is a second-order low-pass filter as an example.

[0033] As described above, the assist torque Ta is a value obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operation amount Mff and the feedback operation amount Mfb. On the other hand, the estimated second disturbance torque de is a value obtained by converting the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th into the torque of the assist motor 30. This means that the estimated second disturbance torque de is a value corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. Therefore, the assist torque Ta is a value obtained by correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb according to the correction amount corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0034] The operation signal generation process M40 is a process of operating the inverter 32 by inputting the assist torque Ta. In detail, the operation signal generation process M40 includes a process of calculating an operation amount using the torque of the assist motor 30 as a control amount and using a value obtained by converting the assist torque Ta into the torque of the assist motor 30 as a target value of the control amount. The operation amount is calculated with reference to the rotation angle θa and the currents iu, iv, iw. In addition, the operation signal generation process M40 includes a process of operating the inverter 32 to obtain the operation amount. The operation amount may be, for example, a time ratio of the on operation time of the switching element of the inverter 32 to one cycle of the on / off operation. Figure 2 The operation signal MS for the inverter 32 is described. However, in reality, the operation signal MS is an individual operation signal for each switching element of the inverter 32 .

[0035] 「Nominal model Pn」

[0036] If the inertia coefficient Jh, the viscosity coefficient Ch and the steering angle θh are used, the steering torque Th is expressed by the following formula (c1). In addition, the inertia coefficient Jh represents the inertia of the first portion, which is a portion of the transmission shaft 14 that is closer to the steering wheel 12 than the torsion bar 52. In addition, the viscosity coefficient Ch represents the viscosity of the first portion of the transmission shaft 14. In addition, the steering angle θh is the rotation angle of the steering wheel 12.

[0037] -Th=(Jh·s·s+Ch·s)·θh…(c1)

[0038] On the other hand, using the rotation angle θ1 and the torsional rigidity coefficient Ktb of the torsion bar 52 , the following equation (c2) holds true. The rotation angle θ1 is the rotation angle of the second portion, which is the portion of the transmission shaft 14 farther from the steering wheel 12 than the torsion bar 52 .

[0039] Th=Ktb·(θh-θl)…(c2)

[0040] In addition, if the inertia coefficient J, the viscosity coefficient C and the elastic coefficient K are used, the following formula (c3) is established between the rotation angle θl and the auxiliary torque Ta and the steering torque Th. The inertia coefficient J represents the inertia of the second part of the transmission shaft 14. In addition, the viscosity coefficient C represents the viscosity of the second part of the transmission shaft 14. In addition, the elastic coefficient K represents the elasticity of the second part of the transmission shaft 14. In addition, the viscosity coefficient C and the elastic coefficient K actually reflect the influence of the steering shaft 16, the steering tie rod 18 and the steering wheel 20 on the transmission shaft 14.

[0041] Th+Ta=(J·s·s+C·s+K)·θl...(c3)

[0042] Here, if the steering torque Th is inputted so that the steering angle θh is zero, the steering angle θh is always zero. If the steering angle θh is set to zero, the transfer function from the assist torque Ta to the steering torque Th is calculated based on the above equations (c1) to (c3), and the following equation (c4) is obtained.

[0043] Th / Ta=(-Ktb) / {J·s·s+C·s+K+Ktb}…(c4)

[0044] In the above formula (c4), the differential operator s is used. The above formula (c4) is a nominal model Pn. In the above formulas (c1) to (c3), even if "θh" and "θl" are interpreted as follows, the above formula (c4) is valid.

[0045] θh: The phase difference between the rotation angle of the first portion of the transmission shaft 14 and the rotation angle of the steering wheel 12. It is always zero.

[0046] θl: a phase difference between the rotation angle of the second portion of the transmission shaft 14 and the rotation angle of the steering wheel 12 .

[0047] Therefore, the above-mentioned equation (c4) holds true for any steering angle θh.

[0048] <Functions and Effects of the Present Embodiment>

[0049] PU42 uses the estimated first disturbance torque dhe as input to calculate the estimated second disturbance torque de, which is the difference between the steering torque Th and the estimated steering torque The. The estimated second disturbance torque de represents the disturbance element of the torque of the second part of the transmission shaft 14. That is, it represents the disturbance element in the torque converted into the force that displaces the steering shaft 16.

[0050] PU42 uses the value obtained by correcting the open-loop operation amount Mff and the feedback operation amount Mfb according to the estimated second disturbance torque de as the auxiliary torque Ta. Moreover, PU42 operates the inverter 32 so that the torque of the auxiliary motor 30 is close to the auxiliary torque Ta. As a result, it is possible to perform control using the target steering torque Th* as the target value of the control amount while compensating for the disturbance factor, and the above-mentioned disturbance factor is the error between the nominal model Pn and the actual control object. In other words, it is possible to perform control using the target steering torque Th* as the target value of the control amount while compensating for the error of the nominal model Pn for the actual control object through the disturbance observer M30.

[0051] Since the error equivalent is immediately compensated in this manner, the responsiveness of the steering torque Th with respect to the target steering torque Th* can be improved.

[0052] In addition, compared with the case where the disturbance observer M30 is not used and the controller is designed according to the actual control target, the man-hours required for designing the controller can be reduced.

[0053] According to the present embodiment described above, the following actions and effects are further achieved.

[0054] (1-1) PU42 calculates the open-loop operation amount Mff by inputting the target steering torque Th* into the inverse model of the nominal model Pn. In addition, PU42 calculates the auxiliary torque Ta based on the open-loop operation amount Mff. Thus, it is possible to use the estimated second disturbance torque de as a compensation component for the error of the open-loop operation amount Mff in the control in which the target steering torque Th* is set as the target value of the control amount. Therefore, it is possible to perform pseudo-linear processing on the control object.

[0055] (1-2) The feedback operation amount Mfb is included in the assist torque Ta. Thus, the error equivalent amount of the designated second disturbance torque de can be compensated by the feedback operation amount Mfb. Therefore, the steering torque Th can be approximated to the target steering torque Th* with higher accuracy.

[0056] (1-3) The nominal model Pn includes not only the inertia coefficient J but also the viscosity coefficient C, the elastic coefficient K, and the torsional rigidity coefficient Ktb. Thus, the nominal model Pn can be a model that approximates the actual controlled object with high accuracy.

[0057] <Second embodiment>

[0058] Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

[0059] In this embodiment, the nominal model Pn is simplified.

[0060] Figure 3 FIG. 4 shows the processing performed by the steering control device 40 according to the present embodiment. Figure 3 The processing shown is Figure 2 The same reference numerals are used to denote corresponding processes shown in the drawings.

[0061] like Figure 3 As shown in the steering torque estimation processing M32a, in the present embodiment, the nominal model Pn is represented by the following equation (c5).

[0062] (-Ktb) / {J·s·s}…(c5)

[0063] That is, the nominal model Pn does not have the terms of the viscosity coefficient C and the elastic coefficient K. Here, the viscosity coefficient C and the elastic coefficient K need to be actually determined by estimation from the vehicle. In contrast, the inertia coefficient J is mostly determined by the inertia of the assist motor 30 and the attenuation ratio, which is the ratio of the rotation speed of the transmission shaft 14 in the steering device 10 to the rotation speed of the assist motor 30. In addition, the torsional rigidity coefficient Ktb is determined based on the characteristics of the torsion bar 52 of the torque sensor 50. Therefore, by omitting the terms of the viscosity coefficient C and the elastic coefficient K from the nominal model Pn, the man-hours involved in the design of the nominal model Pn can be reduced.

[0064] <Third embodiment>

[0065] Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

[0066] "Premise"

[0067] Figure 4 The structure of the steering control system according to the present embodiment is shown. Figure 4 For convenience, Figure 1 Corresponding parts are provided with the same reference numerals.

[0068] like Figure 4 As shown, in the steering device 10, the transmission shaft 14 is separated into an input shaft 14a connected to the steering wheel 12 and an output shaft 14b engaged with the steering shaft 16. In addition, in this embodiment, the output shaft 14b is not actually required. However, for the convenience of the following description, the output shaft 14b is provided.

[0069] The input shaft 14a is provided with a reaction force motor 70. The reaction force motor 70 is a motor for applying a reaction force to the steering wheel 12, and the reaction force is a torque in the opposite direction to the torque input by the driver. As an example, the reaction force motor 70 is a three-phase brushless motor. In addition, the output voltage of the inverter 72 is applied to the terminal of the reaction force motor 70.

[0070] The torque of the steering motor 80 is applied to the steering shaft 16 via the drive shaft 34 . As an example, the steering motor 80 is a three-phase brushless motor. In addition, the output voltage of the inverter 82 is applied to the terminal of the steering motor 80 .

[0071] The steering control device 40 controls the steering device 10. The steering control device 40 operates the inverter 72 to control the reaction force of the control amount as the control object. In addition, the steering control device 40 operates the inverter 82 to control the steering angle of the steering wheel 20 as the control amount as the control object.

[0072] The steering control device 40 refers to the rotation angle θs of the reaction force motor 70 detected by the rotation angle sensor 90 in order to control the reaction force as a control amount. In addition, the steering control device 40 refers to the currents ius, ivs, and iws flowing to the reaction force motor 70 in order to control the reaction force. In addition, the steering control device 40 refers to the rotation angle θt of the steering motor 80 detected by the rotation angle sensor 92 in order to control the steering angle as a control amount. In addition, the steering control device 40 refers to the currents iut, ivt, and iwt flowing in the steering motor 80 in order to control the steering angle.

[0073] "Processing performed by the steering control device 40"

[0074] Figure 5 FIG. 4 shows the processing performed by the steering control device 40. In other words, Figure 5 FIG. 2 shows the processing performed by the steering control device 40 in a state where the transmission of the power of the steering wheel 12 to the steering wheel 20 is cut off. Figure 5 For convenience, Figure 2 The same reference numerals are used to denote corresponding processes shown in the drawings.

[0075] like Figure 5As shown, the deviation calculation processing M14 is a processing for calculating the value obtained by subtracting the steering torque Th from the target steering torque Th*. The torque command value calculation processing M20 is a processing for outputting the reaction force command value Tr*. The torque command value calculation processing M20 is a processing for substituting the value obtained by subtracting the estimated second disturbance torque de from the sum of the open loop operation amount Mff and the feedback operation amount Mfb into the reaction force command value Tr*. The reaction force command value Tr* is a command value of the reaction force torque applied to the steering wheel 12. The reaction force command value Tr* is converted into the angle of the transmission shaft 14.

[0076] The steering operation signal generation process M40a is a process for operating the inverter 72 by inputting the reaction force command value Tr*. In detail, the steering operation signal generation process M40a includes a process for calculating the control operation amount using the torque of the reaction force motor 70 as the control amount and using the value obtained by converting the reaction force command value Tr* into the torque of the reaction force motor 70 as the target value of the control amount. The calculation of the operation amount refers to the rotation angle θs and the currents ius, ivs, and iws. In addition, the steering operation signal generation process M40a includes a process for operating the inverter 72 according to the operation amount. Figure 5 The operation signal MSs of the inverter 72 is described. In addition, in reality, the operation signal MSs is an individual operation signal for each switching element of the inverter 72.

[0077] The target angle calculation process M50 is a process for calculating the target angle θp* which is the target value of the rotation angle of the drive shaft 34. The rotation angle of the drive shaft 34 has a one-to-one correspondence with the steering angle. The target angle calculation process M50 may be, for example, a process for calculating the target angle θp* from the reaction force command value Tr* using a model of the steering device 10. In the model, for example, the reaction force command value Tr* may be regarded as a torque applied to the transmission shaft 14 assuming that the input shaft 14a and the output shaft 14b are mechanically connected.

[0078] The angle control process M52 is a process for calculating an operation amount for controlling the rotation angle of the drive shaft 34 to the target angle θp*. The operation amount is a steering torque command value Tt*, which is a command value of torque for the steering motor 80 .

[0079] The steering operation signal generation process M54 is a process for operating the inverter 82 by inputting the steering torque command value Tt*. The steering operation signal generation process M54 includes a process for calculating the control operation amount using the torque of the steering motor 80 as the control amount and using the amount obtained by converting the steering torque command value Tt* into the torque of the steering motor 80 as the target value of the control amount. The calculation of the operation amount refers to the rotation angle θt and the currents iut, ivt, and iwt. In addition, the steering operation signal generation process M54 includes a process for operating the inverter 82 according to the operation amount. Figure 5 The operation signal MSt of the inverter 82 is described. In addition, in reality, the operation signal MSt is an individual operation signal for each switching element of the inverter 82.

[0080] <Other embodiments>

[0081] In addition, the above-mentioned embodiments can be modified and implemented as follows. The above-mentioned embodiments and the following modified examples can be combined and implemented within the scope of no technical contradiction.

[0082] "Target steering torque calculation processing M10"

[0083] The target steering torque calculation process M10 does not necessarily calculate the target steering torque Th* based on the axial force Fa. For example, the target steering torque calculation process M10 may be a process for calculating the target steering torque Th* using the steering torque Th and the assist torque Ta as inputs.

[0084] The target steering torque calculation process M10 does not necessarily use the vehicle speed SPD as an input.

[0085] The input to the target steering torque calculation processing M10 is not limited to the above. For example, two or more sampled values ​​of the steering angle at different sampling times may be input to the target steering torque calculation processing M10. In this case, based on the input, the identification processing of when the steering wheel 12 is turned and when the steering wheel is returned can be realized. Therefore, for example, when turning the wheel, the absolute value of the target steering torque Th* may be set to a larger value than when returning the wheel.

[0086] 「Open loop operation amount calculation processing」

[0087] The open-loop operation amount calculation process M12 is not limited to the process using the target steering torque Th* as an input. For example, the open-loop operation amount calculation process M12 may also be a process using the axial force Fa as an input. In this case, the transfer function of the open-loop operation amount calculation process M12 is the product of the transfer function for calculating the target steering torque Th* based on the axial force Fa and the inverse model of the nominal model Pn.

[0088] 「Feedback operation amount calculation processing」

[0089] The feedback operation amount Mfb is not necessarily the sum of the output value of the proportional element using the deviation as input and the output value of the differential element using the deviation as input. For example, the feedback operation amount Mfb may be the sum of the output value of the proportional element using the deviation as input, the output value of the differential element using the deviation as input, and the output value of the integral element using the value corresponding to the deviation as input. In addition, for example, the feedback operation amount Mfb may be the sum of the output value of the proportional element using the deviation as input and the output value of the integral element using the value corresponding to the deviation as input. At this time, the gain of the integral element may also be changed according to the vehicle speed SPD.

[0090] In addition, the differential element is not limited to the deviation as input. For example, the differential element may use the steering torque Th as an input. In other words, the differential element may constitute a prior differential type controller.

[0091] The process of changing at least one of the gains of the elements constituting the feedback operation amount calculation process in accordance with the vehicle speed SPD is not essential.

[0092] 「Operation volume calculation processing」

[0093] For example, the feedback operation amount calculation process may not be provided, and the operation amount calculation process may be composed of only the open-loop operation amount calculation process. In addition, for example, the open-loop operation amount calculation process may not be provided, and the operation amount calculation process may be composed of only the feedback operation amount calculation process.

[0094] 「Nominal model Pn」

[0095] The nominal model Pn is not limited to the model exemplified in the above embodiment. For example, a model represented by the following equation (c6) may be used instead of the nominal model Pn used in the steering torque estimation process M32a.

[0096] (-Ktb) / {J·s·s+Ktb}…(c6)

[0097] That is, the polynomial in the denominator of the transfer function of the nominal model Pn may include a term of degree 0. In other words, the polynomial in the denominator of the transfer function of the nominal model Pn may include a term of degree 0 of the differential operator.

[0098] Furthermore, the degree of the polynomial of the denominator of the transfer function of the nominal model Pn is not necessarily quadratic.

[0099] "Correction Processing"

[0100] The correction processing is not limited to the processing including the steering torque estimation processing M32, the first disturbance calculation processing M34, the second disturbance calculation processing M36, and the torque command value calculation processing M20. For example, first, the estimated motor torque Tae can also be calculated by using the steering torque Th as the input of the combined processing of the inverse model of the nominal model Pn and the filter Hd. In this case, secondly, a difference calculation processing is performed to calculate the difference between the sum of the open-loop operation amount Mff and the feedback operation amount Mfb and the estimated motor torque Tae. Then, thirdly, the torque command value calculation processing M20 can also perform a processing of correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb using the output of the difference calculation processing. In this case, the correction processing is composed of the combined processing, the difference calculation processing, and the torque command value calculation processing M20. In addition, the output of the above-mentioned difference calculation processing is a quantity corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0101] "Operation Processing"

[0102] exist Figure 2 In the process shown, although the operation process is set as a process that uses the torque of the assist motor 30 as the control amount and uses the value obtained by converting the assist torque Ta into the torque of the assist motor 30 as the target value of the control amount, it is not limited to this. For example, the operation process may also include a process of calculating the target value of the rotation angle of the assist motor 30 based on the axial force Fa. In this case, the operation process is a process of operating the assist motor 30 based on the operation amount of feedback control using the rotation angle of the assist motor 30 as the control amount. In addition, here, the axial force Fa is the sum of the value obtained by correcting the operation amount determined by the open-loop operation amount Mff and the feedback operation amount Mfb based on the estimated second disturbance torque and the steering torque Th. Therefore, the operation process is a process of operating the inverter 32 based on the value obtained by correcting the operation amount determined by the open-loop operation amount Mff and the feedback operation amount Mfb based on the estimated second disturbance torque. This is a process of controlling the torque of the assist motor 30 so as to generate a torque corresponding to the value obtained by correcting the operation amount determined by the open-loop operation amount Mff and the feedback operation amount Mfb based on the estimated second disturbance torque.

[0103] In addition, as an example to which a change including the feedback control of the angle can be applied, it is not limited to Figure 2 For example, it can also be applied to Figure 3 as well as Figure 5 The embodiment shown.

[0104] Steering control device

[0105] exist Figure 4In the illustrated configuration, a device for operating the reaction force motor 70 and a device for operating the steering motor 80 may be independent.

[0106] The steering control device is not limited to one that includes the PU 42 and the storage device 44 and performs software processing. For example, a dedicated hardware circuit such as an ASIC may be provided that performs at least a portion of the processing performed in the above-mentioned embodiment. That is, the steering control device may include a processing circuit having any one of the following structures (a) to (c).

[0107] (a) A processing circuit including a processing device for executing all the above-mentioned processes according to a program and a program storage device such as a storage device for storing the program.

[0108] (b) A processing circuit including a processing device for executing part of the above-mentioned processing according to a program, a program storage device, and a dedicated hardware circuit for executing the remaining processing.

[0109] (c) A processing circuit having a dedicated hardware circuit for executing all of the above-mentioned processing.

[0110] Here, there may be multiple software execution devices including a processing device and a program storage device. In addition, there may be multiple dedicated hardware.

[0111] Steering control method

[0112] The subject that executes the above-mentioned various controls is not limited to the steering control device mounted on the vehicle. For example, part of the processing for controlling the target steering torque Th*, such as the disturbance observer M30, may be executed by the driver's mobile terminal.

[0113] 「Input section」

[0114] The input unit for inputting the steering torque is not limited to the steering wheel 12 .

[0115] "Power transmission cut-off state"

[0116] The structure for realizing the cut-off state of the power transmission between the input part for inputting the steering torque and the steered wheel 20 is not limited to Figure 4 For example, a clutch may be provided between the input shaft 14a and the output shaft 14b.

[0117] Steering control device

[0118] As an actuator for steering the steered wheel 20, for example, a device in which the assist motor 30 or the steering motor 80 is arranged coaxially with the steering shaft 16 may be adopted. In addition, for example, a device in which the power of the assist motor 30 or the steering motor 80 is transmitted to the steering shaft 16 via a belt speed reducer using a ball screw mechanism may be adopted.

[0119] The steering device capable of changing the relationship between the steering angle and the steering angle is not limited to the following. Figure 4 As shown in the example, the power transmission between the steering wheel 12 and the steering wheel 20 is cut off. For example, the gear that can transmit power between the steering wheel 12 and the steering wheel 20 can be set as a variable gear to form a steering device that can change the relationship between the steering angle and the steering angle.

Claims

1. A steering control device, wherein: The steering control device is configured to execute operation amount calculation processing, correction processing and operation processing, The operation amount calculation process is a process of calculating the operation amount of control using the steering torque as the control amount and using the target steering torque as the target value of the control amount. The steering torque is the torque inputted by the driver to the steering device. The target steering torque is a target value of the steering torque. The correction processing is a processing using the steering torque and the operation amount as inputs, and is a processing for correcting the operation amount according to a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque. The operation process is a process of operating the motor of the steering device so as to generate a torque corresponding to the operation amount corrected by the correction process.

2. The steering control device according to claim 1, wherein: The above-mentioned operation amount calculation process includes an open-loop operation amount calculation process. The above-mentioned open-loop operation amount calculation process is a process for calculating the open-loop operation amount. The open-loop operation amount is an operation amount of an open-loop control using the steering torque as the control amount and using the target value of the steering torque as the target value of the control amount. The correction process includes a steering torque estimation process. The steering torque estimation process is a process of estimating the steering torque as an output value of the nominal model using the operation amount corrected by the correction process as an input. The open-loop manipulated variable includes a process of calculating the open-loop manipulated variable based on an output value of an inverse model of the nominal model, the inverse model using the target steering torque as an input.

3. The steering control device according to claim 2, wherein: The operation amount calculation process includes feedback operation amount calculation process. The feedback operation amount calculation process is a process for calculating the feedback operation amount. The feedback operation amount is an operation amount of feedback control using the steering torque as the control amount and using the target steering torque as a target value of the control amount.

4. The steering control device according to claim 2, wherein: The degree of the polynomial of the numerator of the transfer function of the above nominal model is 0 and the degree of the polynomial of the denominator is 2.

5. The steering control device according to claim 4, wherein: The transfer function includes a quadratic term, a linear term, and a zero-order term in the polynomial in the denominator.

6. The steering control device according to claim 4, wherein: The first-order term of the polynomial of the denominator of the transfer function is zero.

7. The steering control device according to claim 1, wherein: The motor is a motor for steering the steering wheels of the vehicle.

8. The steering control device according to claim 1, wherein: The motor is a motor that applies torque to the input unit when power transmission between the steering wheels of the vehicle and the input unit for the steering torque is cut off.

9. A steering control method, wherein: It has the steps of executing operation amount calculation processing, correction processing and operation processing, The operation amount calculation process is a process of calculating the operation amount of control using the steering torque as the control amount and using the target steering torque as the target value of the control amount. The steering torque is the torque inputted by the driver to the steering device. The target steering torque is a target value of the steering torque. The correction processing is a processing using the steering torque and the operation amount as inputs, and is a processing for correcting the operation amount according to a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque. The operation process is a process of operating the motor of the steering device so as to generate a torque corresponding to the operation amount corrected by the correction process.

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