Steering control device and steering control method

Abstract

This steering control device (40) is configured to execute an operation-amount calculation process, a correction process and an operation process. In the operation-amount calculation process, an operation amount is calculated for control in which steering torque is used as a controlled amount and a target steering torque is used as a target value for the controlled amount. In the correction process, the steering torque and the operation amount are used as inputs, and the operation amount is corrected by a correction amount based on the difference between the steering torque as assumed by a nominal model and the actual steering torque. In the operation process, a motor of the steering device is operated so as to generate a torque based on the operation amount after being corrected by the correction process.

Description

[Technical Field]

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

[0002] For example, Patent Document 1 listed below describes a device that operates a motor for steering steered wheels in accordance with a feedback control operation amount that uses steering torque as a control amount and a target value of steering torque as a control amount target value. Specifically, the feedback control operation amount is calculated in accordance with an output value of a proportional element, an output value of a differential element, and an output value of an integral element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-203089 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when setting a feedback gain or the like in order to satisfy requirements such as improving the responsiveness of the feedback control, the amount of work required to adapt the parameter values ​​that determine the feedback control to those requirements may become excessively large. [Means for solving the problem]

[0005] One aspect of the present disclosure provides a steering control device configured to execute a manipulation amount calculation process, a correction process, and a manipulation process, wherein the manipulation amount calculation process calculates a manipulation amount for control using a steering torque as a control amount and 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 uses the steering torque and the manipulation amount as inputs and corrects the manipulation amount by a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque, and the manipulation process operates a motor of the steering device so as to generate a torque corresponding to the manipulation amount corrected by the correction process.

[0006] Another aspect of the present disclosure provides a steering control method, the steering control method including steps of executing an operation amount calculation process, a correction process, and an operation process, wherein the operation amount calculation process calculates an operation amount for control using a steering torque as a control amount and 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 using the steering torque and the operation amount as inputs and correcting the operation amount by 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 operating a motor of the steering device so as to generate a torque corresponding to the operation amount corrected by the correction process. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a diagram showing the configuration of a steering control device and a steering device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing the processing executed by the steering control device of FIG. 1. [Figure 3] FIG. 6 is a block diagram showing a process executed by a steering control device according to a second embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a steering control device and a steering device according to a third embodiment. [Figure 5] FIG. 5 is a block diagram showing the processing executed by the steering control device of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0008] First Embodiment The first embodiment will be described below with reference to the drawings. "Prerequisite configuration" As shown in FIG. 1, steering device 10 includes steering wheel 12. Steering wheel 12 is a means for transmitting steering instructions by the driver. A transmission shaft 14 is connected to steering wheel 12. Therefore, when steering wheel 12 rotates, transmission shaft 14 rotates integrally. The rotational power of transmission shaft 14 is transmitted to steering shaft 16. Steering shaft 16 extends in the vehicle width direction (left-right direction in FIG. 1). Steerable wheels 20 are connected to both ends of steering shaft 16 via tie rods 18.

[0009] Transmission shaft 14 is arranged so as to intersect with steered shaft 16. Transmission shaft 14 and steered shaft 16 have teeth formed thereon that mesh with each other. These teeth mesh with each other, enabling power to be transmitted from transmission shaft 14 to steered shaft 16. In other words, the rotational power of transmission shaft 14 is converted into power that displaces steered shaft 16 in the axial direction. The displacement of steered shaft 16 in the axial direction is transmitted to steered wheels 20 via tie rods 18. This changes the steering angle of steered wheels 20. The steering angle refers to the turning angle of the tires.

[0010] The steering device 10 also includes an assist motor 30. The assist motor 30 generates an assist force that assists the driver in steering. The rotational power of the assist motor 30 is applied to a drive shaft 34. The drive shaft 34 and the steered shaft 16 have teeth that mesh with each other. The meshing of these teeth enables power to be transmitted from the drive shaft 34 to the steered shaft 16. In other words, the rotational power of the drive shaft 34 is converted into displacement power in the axial direction of the steered shaft 16. As a result, the rotational power of the assist motor 30 is converted into displacement power in the axial direction of the steered shaft 16 via the drive shaft 34. More specifically, the assist motor 30 is, for example, a three-phase brushless motor. The output voltage of an inverter 32 is applied to the terminals of the assist motor 30.

[0011] The steering control device 40 controls the control amount of the steering device 10, which is the object to be controlled. 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 a torque sensor 50. The torque sensor 50 is a sensor that detects the steering torque Th according to the degree of torsion of a torsion bar 52, which is part of the transmission shaft 14. The steering control device 40 also refers to a vehicle speed SPD detected by a vehicle speed sensor 54. The steering control device 40 also refers to a rotation angle θa of the assist motor 30 detected by a rotation angle sensor 56. The steering control device 40 also refers to the currents iu, iv, and iw flowing through the assist motor 30.

[0012] 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 storage medium such as an electrically rewritable nonvolatile memory and a disk medium. A steering control program 44a is stored in the storage device 44. The steering control device 40 controls the control amount by having the PU 42 execute the steering control program 44a stored in the storage device 44.

[0013] "Processing Executed by Steering Control Device 40" Fig. 2 shows the processing executed by the steering control device 40. The processing shown in Fig. 2 is realized by the PU 42 repeatedly executing the steering control program 44a, for example, at a predetermined interval.

[0014] The target steering torque calculation process M10 is a process for calculating a target steering torque Th*, which is a target value of the steering torque Th, based on the axial force Fa. The axial force Fa is a force applied to the steered shaft 16. The axial force Fa is an amount converted into torque of the transmission shaft 14. The target steering torque calculation process M10 includes a process for setting the target steering torque Th* to a different value depending on the vehicle speed SPD, even if the axial force Fa is the same. This setting is intended to allow the driver to experience an optimal steering feel depending on the vehicle speed SPD.

[0015] The open-loop operation amount calculation process M12 is a process for calculating the open-loop operation amount Mff. The open-loop operation amount Mff is an operation amount for open-loop control that uses the steering torque Th as a control amount and the target steering torque Th* as a target value for the control amount. The open-loop operation amount calculation process M12 is a process for calculating the open-loop operation amount Mff by inputting the target steering torque Th*. The open-loop operation amount calculation process M12 calculates the open-loop operation amount Mff based on an inverse model of the nominal model Pn. The nominal model Pn is a model that uses the assist torque Ta, which is the torque of the assist motor 30, as an input and outputs an estimated steering torque The, which is an estimated value of the steering torque Th. Here, the assist 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 assist torque Ta. The nominal model Pn will be described in detail later.

[0016] 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. The feedback manipulated variable calculation process M16 is a process that uses the deviation as an input to calculate a feedback manipulated variable Mfb. The feedback manipulated variable Mfb is a manipulated variable of feedback control that uses the steering torque Th as a controlled variable and the target steering torque Th* as a controlled variable target value. The feedback manipulated variable Mfb is the sum of the output value of a proportional element that uses the deviation as an input and the output value of a derivative element that uses the deviation as an input. The feedback manipulated variable Mfb is a value converted into the torque of the transmission shaft 14. More specifically, the feedback manipulated variable calculation process M16 includes a process that changes at least one of the gain of the proportional element and the gain of the derivative element in accordance with the vehicle speed SPD.

[0017] The torque command value calculation process M20 is a process that calculates 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, 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 is substituted for the assist torque Ta.

[0018] The assist torque Ta is input to the axial force calculation process M22, which is a process for substituting the sum of the assist torque Ta and the steering torque Th for the axial force Fa. 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.

[0019] The steering torque estimation process M32 is a process for inputting the assist torque Ta to the nominal model Pn, thereby outputting the estimated steering torque The. The estimated steering torque The is the steering torque assumed by the nominal model Pn.

[0020] The first disturbance calculation process M34 is a process for calculating an estimated first disturbance torque dhe. The estimated first disturbance torque dhe is a disturbance component of the steering torque Th of the actual control object. The estimated first disturbance torque dhe is the difference between the torque estimated from the nominal model Pn and the actual steering torque Th. In other words, the estimated first disturbance torque dhe is the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. More specifically, the first disturbance calculation process M34 is a process for substituting the value obtained by subtracting the estimated steering torque The from the steering torque Th into the estimated first disturbance torque dhe.

[0021] The second disturbance calculation process M36 is a process that uses the estimated first disturbance torque dhe as an input and calculates the estimated second disturbance torque de. The estimated second disturbance torque de is disturbance torque converted into the torque of the assist motor 30. The second disturbance calculation process M36 is a process that calculates the estimated second disturbance torque de using an inverse model of the nominal model Pn and a filter Hd.

[0022] The filter Hd is provided to reduce noise caused by the differential operation included in the nominal model Pn. In this embodiment, the filter Hd is, for example, a second-order low-pass filter.

[0023] 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 an amount 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 an amount 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 an amount obtained by correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb according to a correction amount corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0024] The operation signal generation process M40 is a process for operating the inverter 32 by inputting the assist torque Ta. Specifically, the operation signal generation process M40 includes a process for 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 for the control amount. The calculation of the operation amount references the rotation angle θa and the currents iu, iv, and iw. The operation signal generation process M40 also includes a process for operating the inverter 32 so as to obtain the operation amount. The operation amount may be, for example, the time ratio of the ON operation time to one cycle of the ON / OFF operation of the switching elements of the inverter 32. FIG. 2 shows an operation signal MS for the inverter 32. However, in reality, the operation signal MS is a separate operation signal for each switching element of the inverter 32.

[0025] "Nominal Model Pn" The steering torque Th is expressed by the following equation (c1) using the inertia coefficient Jh, the viscosity coefficient Ch, and the steering angle θh. The inertia coefficient Jh indicates the inertia of a first portion of the transmission shaft 14, which is a portion closer to the steering wheel 12 than the torsion bar 52. The viscosity coefficient Ch indicates the viscosity of the first portion of the transmission shaft 14. The steering angle θh is the rotation angle of the steering wheel 12.

[0026] -Th=(Jh·s·s+Ch·s)·θh …(c1) On the other hand, the following equation (c2) is established using the rotation angle θl and the torsional rigidity coefficient Ktb of the torsion bar 52. Note that the rotation angle θl is the rotation angle of a second portion of the transmission shaft 14, which is a portion that is farther from the steering wheel 12 than the torsion bar 52.

[0027] Th=Ktb·(θh-θl) …(c2) Furthermore, using the inertia coefficient J, viscosity coefficient C, and elastic coefficient K, the following equation (c3) holds between the rotation angle θl and the assist torque Ta and steering torque Th. The inertia coefficient J represents the inertia of the second portion of the transmission shaft 14. The viscosity coefficient C represents the viscosity of the second portion of the transmission shaft 14. The elastic coefficient K represents the elasticity of the second portion of the transmission shaft 14. Note that the viscosity coefficient C and elastic coefficient K actually reflect the influences that the steered shaft 16, tie rod 18, steered wheels 20, etc. have on the transmission shaft 14.

[0028] Th+Ta=(J·s·s+C·s+K)·θl …(c3) Here, if the steering torque Th is input so that the steering angle θh is zero, the steering angle θh will always be zero. If the steering angle θh is set to zero and the transfer function from the assist torque Ta to the steering torque Th is calculated based on the above equations (c1) to (c3), the following equation (c4) is obtained.

[0029] Th / Ta=(-Ktb) / {J·s·s+C·s+K+Ktb} …(c4) In the above formula (c4), a differential operator s is used. The above formula (c4) is the nominal model Pn. The above formula (c4) also holds when "θh" and "θl" in the above formulas (c1) to (c3) are replaced as follows:

[0030] θh: Phase difference between the rotation angle of the first portion of the transmission shaft 14 and the rotation angle of the steering wheel 12. This is always zero. θl: Phase difference between the rotation angle of the second portion of the transmission shaft 14 and the rotation angle of the steering wheel 12.

[0031] Therefore, the above formula (c4) holds true for any steering angle θh. <Actions and Effects of This Embodiment> The PU 42 calculates an estimated second disturbance torque de using, as an input, an estimated first disturbance torque dhe, which is the difference between the steering torque Th and the estimated steering torque The. The estimated second disturbance torque de indicates the disturbance element of the torque of the second portion of the transmission shaft 14. In other words, it indicates the disturbance element of the torque converted into a force that displaces the steered shaft 16.

[0032] The PU42 uses the value obtained by correcting the open-loop control input Mff and the feedback control input Mfb with the estimated second disturbance torque de as the assist torque Ta. Then, the PU42 operates the inverter 32 so that the torque of the assist motor 30 approaches the assist torque Ta. This makes it possible to execute control using the target steering torque Th* as the target value of the controlled variable while compensating for disturbance elements such as the error between the nominal model Pn and the actual controlled object. In other words, the disturbance observer M30 makes it possible to execute control using the target steering torque Th* as the target value of the controlled variable while compensating for the error of the nominal model Pn with respect to the actual controlled object.

[0033] Since the amount equivalent to the error is immediately compensated for in this manner, the responsiveness of the steering torque Th to the target steering torque Th* can be improved. Furthermore, compared to the case where a controller is designed in accordance with an actual control target without using the disturbance observer M30, the number of steps required to design the controller can be reduced.

[0034] According to the present embodiment described above, the following further functions and effects are achieved. (1-1) The PU 42 calculates the open-loop control input Mff by inputting the target steering torque Th* to an inverse model of the nominal model Pn. The PU 42 also calculates the assist torque Ta according to the open-loop control input Mff. This makes it possible to use the estimated second disturbance torque de as a compensation component for the error in the open-loop control input Mff in control in which the target steering torque Th* is the target value of the control input. This allows the controlled object to be pseudo-linearized.

[0035] (1-2) The assist torque Ta includes the feedback control amount Mfb. Estimate The error equivalent of the second disturbance torque de can be compensated for by the feedback control input Mfb, and therefore the steering torque Th can be made to approximate the target steering torque Th* with higher accuracy.

[0036] (1-3) The nominal model Pn is configured to include not only the inertia coefficient J but also the viscosity coefficient C, elastic coefficient K, and torsional stiffness coefficient Ktb. This allows the nominal model Pn to be a model that closely approximates the actual controlled object.

[0037] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0038] In this embodiment, the nominal model Pn is simplified. Fig. 3 shows the processing executed by the steering control device 40 according to this embodiment. Of the processing shown in Fig. 3, the processing corresponding to the processing shown in Fig. 2 is denoted by the same reference numerals for convenience.

[0039] As shown in the steering torque estimation process M32a in FIG. 3, in this embodiment, the nominal model Pn is expressed by the following equation (c5). (-Ktb) / {J·s·s} …(c5) That is, the nominal model Pn does not have terms for the viscosity coefficient C and the elastic coefficient K. Here, the viscosity coefficient C and the elastic coefficient K need to be estimated and determined from an actual vehicle. In contrast, the inertia coefficient J is determined substantially by the inertia of the assist motor 30 and the damping ratio, which is the ratio of the rotational speed of the transmission shaft 14 to the rotational speed of the assist motor 30 in the steering device 10. Furthermore, the torsional stiffness coefficient Ktb is determined by the characteristics of the torsion bar 52 of the torque sensor 50. Therefore, by omitting the terms for the viscosity coefficient C and the elastic coefficient K from the nominal model Pn, the number of steps required to design the nominal model Pn can be reduced.

[0040] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0041] "Prerequisite configuration" The configuration of the steering control system according to this embodiment is shown in Fig. 4. In Fig. 4, members corresponding to those shown in Fig. 1 are denoted by the same reference numerals for convenience.

[0042] As shown in Fig. 4, 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 steered shaft 16. Note that in this embodiment, the output shaft 14b is not actually required. However, for convenience of the following explanation, the output shaft 14b is provided.

[0043] A reaction motor 70 is provided on the input shaft 14a. The reaction motor 70 is a motor for applying a reaction force, which is a torque in the opposite direction to the torque input by the driver, to the steering wheel 12. The reaction motor 70 is, for example, a three-phase brushless motor. The output voltage of an inverter 72 is applied to the terminals of the reaction motor 70.

[0044] Torque from steering motor 80 is applied to steering shaft 16 via drive shaft 34. As an example, steering motor 80 is a three-phase brushless motor. The output voltage of inverter 82 is applied to the terminals of steering motor 80.

[0045] The steering control device 40 controls the steering device 10. The steering control device 40 operates the inverter 72 to control the reaction force, which is the control variable of the control object. The steering control device 40 also operates the inverter 82 to control the steering angle of the steered wheels 20, which is the control variable of the control object.

[0046] Steering control device 40 refers to rotation angle θs of reaction force motor 70 detected by rotation angle sensor 90 in order to control the reaction force, which is a control variable. Steering control device 40 also refers to currents ius, ivs, iws flowing through reaction force motor 70 in order to control the reaction force. Steering control device 40 also refers to rotation angle θt of steering motor 80 detected by rotation angle sensor 92 in order to control the steering angle, which is a control variable. Steering control device 40 also refers to currents iut, ivt, iwt flowing through steering motor 80 in order to control the steering angle.

[0047] "Processing Executed by Steering Control Device 40" Fig. 5 shows the processing executed by the steering control device 40. In other words, Fig. 5 shows the processing executed by the steering control device 40 in a state where the transmission of power from the steering wheel 12 to the steered wheels 20 is interrupted. Note that in Fig. 5, the processing corresponding to the processing shown in Fig. 2 is denoted by the same reference numerals for convenience.

[0048] As shown in FIG. 5, deviation calculation processing M14 is processing for calculating a value obtained by subtracting the steering torque Th from the target steering torque Th*. Torque command value calculation processing M20 is processing for outputting a reaction force command value Tr*. Torque command value calculation processing M20 is processing for substituting 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 into the reaction force command value Tr*. The reaction force command value Tr* is a command value for the reaction torque to be applied to the steering wheel 12. The reaction force command value Tr* is converted into the angle of the transmission shaft 14.

[0049] The steering operation signal generation process M40a is a process for operating the inverter 72 by inputting the reaction force command value Tr*. Specifically, the steering operation signal generation process M40a includes a process for calculating a control operation amount using the torque of the reaction force motor 70 as a control amount and using a value obtained by converting the reaction force command value Tr* into the torque of the reaction force motor 70 as a target value for the control amount. The calculation of the operation amount refers to the rotation angle θs and the currents ius, ivs, and iws. The steering operation signal generation process M40a also includes a process for operating the inverter 72 in accordance with the operation amount. FIG. 5 shows an operation signal MSs for the inverter 72. Note that in reality, the operation signal MSs is a separate operation signal for each switching element of the inverter 72.

[0050] The target angle calculation process M50 is a process for calculating a target angle θp*, which is a target value for 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 a process for calculating the target angle θp* from the reaction force command value Tr* using, for example, a model of the steering device 10. In this model, for example, the reaction force command value Tr* may be regarded as a torque applied to the transmission shaft 14 when it is assumed that the input shaft 14a and the output shaft 14b are mechanically coupled.

[0051] The angle control process M52 is a process for calculating a manipulated variable for controlling the rotation angle of the drive shaft 34 to the target angle θp*. This manipulated variable is a steering torque command value Tt*, which is a torque command value for the steering motor 80.

[0052] Steering operation signal generation process M54 is a process for operating inverter 82 by inputting steering torque command value Tt*. Steering operation signal generation process M54 includes a process for calculating a control operation amount using the torque of steering motor 80 as a control amount and using a quantity obtained by converting steering torque command value Tt* into torque of steering motor 80 as a target value for the control amount. The calculation of the operation amount references rotation angle θt and currents iut, ivt, iwt. Steering operation signal generation process M54 also includes a process for operating inverter 82 in accordance with the operation amount. FIG. 5 shows an operation signal MSt for inverter 82. Note that in reality, operation signal MSt is a separate operation signal for each switching element of inverter 82.

[0053] <Other embodiments> The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0054] "About the target steering torque calculation process M10" It is not essential that the target steering torque calculation process M10 calculates the target steering torque Th* based on the axial force Fa. For example, the target steering torque calculation process M10 may be a process that calculates the target steering torque Th* using the steering torque Th and the assist torque Ta as inputs.

[0055] It is not essential that the target steering torque calculation process M10 uses the vehicle speed SPD as an input. The input to the target steering torque calculation process 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 process M10. In this case, a process for distinguishing between when the steering wheel 12 is turned and when it is returned to its original position can be realized in accordance with the input. Therefore, for example, the absolute value of the target steering torque Th* may be set to a larger value when the steering wheel 12 is turned to its original position than when it is returned to its original position.

[0056] "Open-loop operation amount calculation process" The open-loop manipulated variable calculation process M12 is not limited to a process that uses the target steering torque Th* as an input. For example, the open-loop manipulated variable calculation process M12 may be a process that uses the axial force Fa as an input. In that case, the transfer function of the open-loop manipulated variable calculation process M12 may be the product of a transfer function that calculates the target steering torque Th* from the axial force Fa and an inverse model of the nominal model Pn.

[0057] "Feedback manipulated variable calculation process" The feedback control input Mfb does not necessarily have to be the sum of the output value of a proportional element that uses the deviation as an input and the output value of a differential element that uses the deviation as an input. For example, the feedback control input Mfb may be the sum of the output value of a proportional element that uses the deviation as an input, the output value of a differential element that uses the deviation as an input, and the output value of an integral element that uses a value corresponding to the deviation as an input. Alternatively, the feedback control input Mfb may be the sum of the output value of a proportional element that uses the deviation as an input and the output value of an integral element that uses a value corresponding to the deviation as an input. In this case, the gain of the integral element may be variable depending on the vehicle speed SPD.

[0058] The differential element is not limited to one that receives a deviation as an input. For example, the differential element may use the steering torque Th as an input. In other words, the differential element may constitute a leading differential type controller.

[0059] The process of making at least one of the gains of the elements constituting the feedback manipulated variable calculation process variable in accordance with the vehicle speed SPD is not essential. "Operation volume calculation process" For example, the manipulated variable calculation process may be configured from only the open-loop manipulated variable calculation process without including the feedback manipulated variable calculation process.Further, for example, the manipulated variable calculation process may be configured from only the feedback manipulated variable calculation process without including the open-loop manipulated variable calculation process.

[0060] "About the nominal model Pn" The nominal model Pn is not limited to the model exemplified in the above embodiment. For example, instead of the nominal model Pn used in the steering torque estimation process M32a, a model expressed by the following equation (c6) may be used.

[0061] (-Ktb) / {J·s·s+Ktb} …(c6) That is, the polynomial in the denominator of the transfer function of the nominal model Pn may include a zeroth-order term. In other words, the denominator of the transfer function of the nominal model Pn may include a zeroth-order term of the differential operator.

[0062] It is not essential that the degree of the polynomial in the denominator of the transfer function of the nominal model Pn be quadratic. "About correction processing" The correction process is not limited to processes including the steering torque estimation process M32, the first disturbance calculation process M34, the second disturbance calculation process M36, and the torque command value calculation process M20. For example, first, the estimated motor torque Tae may be calculated by using the steering torque Th as an input to a combination process that combines an inverse model of the nominal model Pn with a filter Hd. In this case, second, a difference calculation process may be performed that calculates the difference between the estimated motor torque Tae and the sum of the open-loop control input Mff and the feedback control input Mfb. Third, the torque command value calculation process M20 may perform a process that corrects the sum of the open-loop control input Mff and the feedback control input Mfb using the output of the difference calculation process. In this case, the correction process is composed of the combination process, the difference calculation process, and the torque command value calculation process M20. Note that the output of the difference calculation process is an amount corresponding to the difference between the steering torque estimated by the nominal model Pn and the actual steering torque Th.

[0063] "About operation processing" In the process shown in FIG. 2 , the operation process uses the torque of the assist motor 30 as the control variable and the value obtained by converting the assist torque Ta into the torque of the assist motor 30 as the target value of the control variable. However, this is not limited to this. For example, the operation process may include a process of calculating a target value for the rotation angle of the assist motor 30 from the axial force Fa. In this case, the operation process is a process of operating the assist motor 30 in accordance with the operation variable of feedback control using the rotation angle of the assist motor 30 as the control variable. Note that the axial force Fa is the sum of the steering torque Th and a value obtained by correcting the operation variable determined from the open-loop operation variable Mff and the feedback operation variable Mfb with the estimated second disturbance torque de. Therefore, the operation process is a process of operating the inverter 32 in accordance with the value obtained by correcting the operation variable determined from the open-loop operation variable Mff and the feedback operation variable Mfb with the estimated second disturbance torque de. This is a process of controlling the torque of the assist motor 30 so as to generate a torque corresponding to a value obtained by correcting the operation amount determined from the open-loop operation amount Mff and the feedback operation amount Mfb according to the estimated second disturbance torque de.

[0064] Note that examples to which the modification including angle feedback control can be applied are not limited to the example shown in Fig. 2. For example, the modification may be applied to the examples shown in Figs. "About steering control devices" In the configuration shown in FIG. 4, the device that operates the reaction motor 70 and the device that operates the steering motor 80 may be separate devices.

[0065] The steering control device is not limited to one that includes the PU 42 and the storage device 44 and executes software processing. For example, it may include a dedicated hardware circuit such as an ASIC that executes at least part of the processing executed in the above embodiment. That is, the steering control device may include a processing circuit that has any one of the following configurations (a) to (c):

[0066] (a) A processing circuit comprising a processing device that executes all of the above processes according to a program, and a program storage device such as a memory device that stores the program. (b) A processing circuit comprising a processing device and a program storage device that execute part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing.

[0067] (c) A processing circuit having dedicated hardware circuitry for performing all of the above processes. Here, there may be a plurality of software execution devices each having a processing device and a program storage device, and there may also be a plurality of dedicated hardware circuits.

[0068] "About steering control methods" The entity that executes the various controls described above is not limited to a steering control device attached to the vehicle. For example, some of the processing for control to the target steering torque Th*, such as the disturbance observer M30, may be executed by a mobile terminal of the driver.

[0069] "About the input section" The input unit to which the steering torque is input is not limited to the steering wheel 12. "About the power transmission cutoff state" The configuration for interrupting the power transmission between the input section to which the steering torque is input and the steered wheels 20 is not limited to the configuration illustrated in Fig. 4. For example, a clutch may be provided between the input shaft 14a and the output shaft 14b.

[0070] "About the steering device" The actuator used to steer steered wheels 20 may be, for example, one in which assist motor 30 or steering motor 80 is arranged coaxially with steering shaft 16. Alternatively, for example, one in which the power of assist motor 30 or steering motor 80 is transmitted to steering shaft 16 via a belt-type reducer using a ball screw mechanism may be used.

[0071] The steering device capable of changing the relationship between the steering angle and the turning angle is not limited to a steering device in which the transmission of power between the steering wheel 12 and the steered wheels 20 is interrupted, as shown in Fig. 4. For example, a steering device capable of changing the relationship between the steering angle and the turning angle may be configured by using a variable gear as the gear that enables the transmission of power between the steering wheel 12 and the steered wheels 20.

Claims

1. configured to perform 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 of control using a steering torque as a control amount and a target steering torque as a target value of the control amount, The steering torque is a torque input by a driver to a steering device, the target steering torque is a target value of the steering torque, the correction process is a process that uses the steering torque and the operation amount as inputs, and corrects the operation amount by a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque, A steering control device, wherein the operation processing is processing for operating a motor of the steering device so as to generate torque according to the operation amount corrected by the correction processing.

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

3. The operation amount calculation process includes a feedback operation amount calculation process, the feedback manipulated variable calculation process is a process of calculating a feedback manipulated variable, 3. The steering control device according to claim 2, wherein the feedback manipulated variable is a manipulated variable of feedback control that uses the steering torque as the controlled variable and the target steering torque as a target value of the controlled variable.

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

5. 5. The steering control device according to claim 4, wherein the transfer function includes a second-order term, a first-order term, and a zeroth-order term in the polynomial of the denominator.

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

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

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

9. The method includes a step of performing 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 of control using a steering torque as a control amount and a target steering torque as a target value of the control amount, The steering torque is a torque input by a driver to a steering device, the target steering torque is a target value of the steering torque, the correction process is a process that uses the steering torque and the operation amount as inputs, and corrects the operation amount by a correction amount corresponding to a difference between the steering torque assumed by a nominal model and the actual steering torque, The steering control method, wherein the operation processing is processing for operating a motor of the steering device so as to generate torque according to the operation amount corrected by the correction processing.

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