Steering control device and steering control method

Abstract

A steering control device (10) executes 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 correction process is a process for correcting the operation amount on the basis of a correction amount corresponding to the difference between the actual steering torque and the steering torque assumed by the nominal model, using the steering torque and the operation amount as inputs. 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. The correction process includes an intermediate process repeatedly executed at a predetermined cycle, and the intermediate process sets a correction amount calculated at one sampling timing of the operation amount as an intermediate value of correction amounts virtually calculated using values of two adjacent sampling timings of the operation amount.

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, in order to meet the requirements such as improving the responsiveness of the feedback control, when setting the feedback gain, etc., there is a possibility that the time required to determine the value of the feedback control parameter to meet these requirements becomes too long. Summary of the invention

[0005] In one aspect of the present disclosure, a steering control device is provided. The steering control device is configured to execute 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 inputted by a driver to a steering device, 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, 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, the correction process is a process repeatedly executed at a predetermined cycle, and includes an intermediate process of setting the correction amount calculated at one sampling timing of the operation amount to an intermediate value of the correction amounts virtually calculated using the operation amounts obtained at two adjacent sampling timings.

[0006] In another aspect of the present disclosure, a steering control method is provided. The steering control method includes 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 inputted by a driver to a steering device, 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, 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, the correction process is a process repeatedly executed at a predetermined cycle, and includes an intermediate process of setting the correction amount calculated at one sampling timing of the operation amount to an intermediate value of the correction amounts virtually calculated using the operation amounts obtained at two adjacent sampling timings. 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 Yes means Figure 2 Block diagram of the performance of the disturbance observer in the s region.

[0010] Figure 4 Yes means Figure 2 Block diagram of the discrete representation of the disturbance observer in .

[0011] Figure 5 It is a diagram showing the configuration of a steering control device and a steering device according to a second embodiment.

[0012] Figure 6 Yes means Figure 5 A block diagram of the processing performed by a steering control device. DETAILED DESCRIPTION

[0013] <First embodiment>

[0014] Hereinafter, a first embodiment will be described with reference to the drawings.

[0015] "Premise"

[0016] 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 1 The 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.

[0017] 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 steering angle of the tire.

[0018] 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 the axial displacement power of the steering shaft 16. Thus, the rotational power of the auxiliary motor 30 is converted into the 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.

[0019] 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 through the assist motor 30.

[0020] 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.

[0021] "Processing performed by the steering control device 40"

[0022] 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.

[0023] 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 give the driver the best steering feel corresponding to the vehicle speed SPD.

[0024] 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 based on the inverse model of the nominal model Pn. The nominal model Pn is a model that uses the torque of the assist motor 30, that is, the assist torque Ta, as an input and outputs an estimated value of the steering torque Th, that is, the estimated steering torque The. 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. In addition, the nominal model Pn will be described in detail later.

[0025] 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.

[0026] The feedback operation amount calculation processing M16 is a processing that uses the deviation as an input and calculates the feedback operation amount Mfb. The feedback operation amount Mfb is the operation amount of feedback control using the steering torque Th as the control amount and the target steering torque Th* as the 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 processing M16 includes a processing of changing at least one of the gain of the proportional element and the gain of the differential element according to the vehicle speed SPD.

[0027] The torque command value calculation processing M20 is a processing for calculating the auxiliary 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 processing 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 auxiliary torque Ta.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 of the steering torque Th superimposed on the actual control object. The estimated first interference torque dhe is the difference between the actual torque and the torque estimated according to 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.

[0032] The second disturbance calculation process M36 is a process for calculating the estimated second disturbance torque de by taking 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.

[0033] 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, as an example, a third-order low-pass filter.

[0034] 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.

[0035] The operation signal generation process M40 is a process for operating the inverter 32 by inputting the assist torque Ta. In detail, the operation signal generation process M40 includes a process for calculating the operation amount using the torque of the assist motor 30 as the control amount and using 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. 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 for 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 .

[0036] 「Nominal Model Pn」

[0037] 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 of the transmission shaft 14, 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.

[0038] -Th=(Jh·s·s+Ch·s)·θh…(c1)

[0039] 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. The rotation angle θ1 is the rotation angle of the second portion of the transmission shaft 14 , which is the portion of the transmission shaft 14 farther from the steering wheel 12 than the torsion bar 52 .

[0040] Th=Ktb·(θh-θl)…(c2)

[0041] In addition, if the inertia coefficient J, the viscosity coefficient C, and the elastic coefficient K are used, the following equation (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, the steering wheel 20, etc. on the transmission shaft 14.

[0042] Th+Ta=(J·s·s+C·s+K)·θl...(c3)

[0043] 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 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.

[0044] Th / Ta=(-Ktb) / {J·s·s+C·s+K+Ktb}…(c4)

[0045] In addition, the differential operator s is used in the above-mentioned formula (c4). The above-mentioned formula (c4) is a nominal model Pn. In addition, even if "θh" and "θl" are interpreted as follows in the above-mentioned formulas (c1) to (c3), the above-mentioned formula (c4) is also established.

[0046] 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.

[0047] 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 .

[0048] Therefore, for any steering angle θh, the above-mentioned equation (c4) holds true.

[0049] 「Design of the Disturbance Observer M30」

[0050] Figure 3 The behavior in the s region of the disturbance observer M30 using the observer gains L1, L2, and L3 is shown.

[0051] like Figure 3 As shown, the addition process M50 is a process of calculating a value obtained by adding the estimated second disturbance torque de to the assist torque Ta.

[0052] The multiplication process M52 is a process of multiplying the output value of the addition process M50 by a value obtained by multiplying the torsional rigidity coefficient Ktb by “−1”.

[0053] The output value of the addition process M54 corresponding to the output value of the multiplication process M52 is input to the multiplication process M56. The multiplication process M56 is a process of multiplying the output value of the addition process M54 by the reciprocal of the inertia coefficient J.

[0054] The output value of the addition process M58 corresponding to the output value of the multiplication process M56 is input to the integration element M60.

[0055] The output value of the addition process M62 corresponding to the output value of the integration element M60 is output to the integration element M64. The output value of the integration element M64 is the estimated steering torque The.

[0056] The multiplication process M66 is a process of multiplying the output value of the integration element M60 by the viscosity coefficient C.

[0057] The multiplication process M68 is a process of multiplying the estimated steering torque The by "Ktb+K".

[0058] The addition process M54 is a process of subtracting the output value of the multiplication process M66 and the output value of the multiplication process M68 from the output value of the multiplication process M52.

[0059] The multiplication process M70 is a process of multiplying the estimated first disturbance torque dhe by the observer gain L3. The output value of the multiplication process M70 is input to the integration element M76. The output value of the integration element M76 is the estimated second disturbance torque de.

[0060] The multiplication process M72 is a process of multiplying the estimated first disturbance torque dhe by the observer gain L2. The addition process M58 is a process of adding the output value of the multiplication process M72 to the output value of the multiplication process M56.

[0061] The multiplication process M74 is a process of multiplying the estimated first disturbance torque dhe by the observer gain L1. The addition process M62 is a process of adding the output value of the multiplication process M74 to the output value of the integration element M60.

[0062] The actual device M80 is the actual control object.

[0063] In this embodiment, the filter Hd is the cube of "ω / (s+ω)". Therefore, the observer gains L1, L2, and L3 are designed so that Figure 3 The transfer function from the actual disturbance torque d to the estimated second disturbance torque de in is equal to the cube of "ω / (s+ω)". At this time, it is assumed that the above-mentioned nominal model Pn is equal to the actual device M80.

[0064] "Behavior of discrete systems"

[0065] The disturbance observer M30 is actually processed digitally.

[0066] Figure 4 The behavior of the discrete system of the disturbance observer M30 is shown. Figure 4 The processing shown is the processing actually performed by PU42. Figure 4 For the sake of convenience, Figure 3 The same parts in the processes shown are denoted by the same reference numerals.

[0067] like Figure 4 As shown, Figure 3 The integral elements M60, M64, and M76 are replaced by bilinear transformation processing M60a, M64a, and M76a. In the bilinear transformation "(T / 2)·(1+Z^(-1)) / (1-Z^(-1))", "T" is the sampling period. If a bilinear transformation is used, the intermediate value between the value obtained by approximating by the forward rectangular approximation "T·Z^(-1) / (1-Z^(-1))" and the value obtained by approximating by the backward rectangular approximation "T / (1-Z^(-1))" is calculated.

[0068] The use of bilinear transformation processing is intended to suppress actual performance deviations Figure 3Theoretical value in the continuous system shown. When bilinear transformation is used, the computational load is larger than when forward rectangular approximation or backward rectangular approximation is used. However, when bilinear transformation is used, the error accompanying discretization becomes smaller than when forward rectangular approximation or backward rectangular approximation is used. Therefore, the controllability of the control using the steering torque Th as the control amount can be improved.

[0069] in addition, Figure 4 The addition process M50 shown is a process of adding the estimated second disturbance torque de to the assist torque Ta. The delay process M92 is a process of outputting the value of the output value of the addition process M50 one sample ago. The addition process M94 is a process of adding the output value of the addition process M50 to the output value of the delay process M92. The multiplication process M96 is a process of multiplying the output value of the addition process M94 by "1 / 2". The output value of the multiplication process M96 is input to the multiplication process M52.

[0070] That is, the input of the multiplication process M52 is the average value of the assist torque Ta corrected based on the estimated second disturbance torque de obtained at two adjacent sampling timings. This is to reduce the error associated with discretization.

[0071] <Functions and Effects of the Present Embodiment>

[0072] 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.

[0073] PU42 uses the value obtained by correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb according to the estimated second disturbance torque de as the assist torque Ta. Moreover, PU42 operates the inverter 32 so that the torque of the assist motor 30 approaches the assist 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 disturbance factors such as the error between the nominal model Pn and the actual control object. In other words, through the disturbance observer M30, 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 between the nominal model Pn and the actual control object.

[0074] Since the error equivalent amount is immediately compensated in this way, the responsiveness of the steering torque Th with respect to the target steering torque Th* can be improved.

[0075] In addition, compared with the case where the controller is designed according to the actual control target without using the disturbance observer M30, the man-hours required for designing the controller can be reduced.

[0076] And, in Figure 3 When the expression in the s region shown in FIG. 1 is replaced with actual digital processing, PU42 uses the average value of the values ​​obtained at two adjacent sampling timings as the input of the disturbance observer M30. That is, PU42 calculates the estimated second disturbance torque de based on the value corresponding to the average value of the previous value and the current value of the sum of the open-loop manipulated variable Mff and the feedback manipulated variable Mfb. Thus, the estimated second disturbance torque de becomes the intermediate value of the values ​​obtained when the sum of the open-loop manipulated variable Mff and the feedback manipulated variable Mfb is used separately at the first timing and the second timing as two adjacent sampling timings.

[0077] That is, the second disturbance torque de is estimated to be a value intermediate between “de1” and “de2.” Here, “de1” and “de2” are the following values.

[0078] de1: The estimated second disturbance torque de calculated at the first timing using the open-loop operation amount Mff and the feedback operation amount Mfb.

[0079] de2: The estimated second disturbance torque de calculated at the second timing using the open-loop operation amount Mff and the feedback operation amount Mfb.

[0080] In the case of using only a single open-loop manipulated variable Mff and a single set of feedback manipulated variables Mfb that vary with a sampling period, it is possible that the estimated second disturbance torque de is greatly deviated from the value assumed by the continuous system. In contrast, by using a value intermediate between the value virtually calculated at the first timing and the value virtually calculated at the second timing as the estimated second disturbance torque de, the deviation from the value assumed by the continuous system can be reduced.

[0081] According to the present embodiment described above, the following actions and effects are further achieved.

[0082] (1-1) PU42 replaces the integral elements M60, M64, and M76 with bilinear transformation processes M60a, M64a, and M76a. This makes it possible to maintain the performance represented by the s-region representation as much as possible compared to the case where the forward rectangular approximation or the backward rectangular approximation is used.

[0083] In addition, when using the forward rectangular approximation or backward rectangular approximation, the value obtained at a single input timing is used for integration processing. In contrast, according to the bilinear transformation processing, the intermediate value of the values ​​obtained at two adjacent timings is used. This means that even if the bilinear transformation is not used, the value of the input timing is not used. Figure 4In the case of the delay process M92, the addition process M94, and the multiplication process M96 in , the estimated second disturbance torque de is also calculated as a value intermediate between "de1" and "de2".

[0084] (1-2) 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 with the target steering torque Th* as the control amount. Therefore, it is possible to pseudo-linearize the control object.

[0085] (1-3) 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 according to the feedback operation amount Mfb. Therefore, the steering torque Th can be approximated to the target steering torque Th* with higher accuracy.

[0086] (1-4) The nominal model Pn is configured to include not only the inertia coefficient J but also the viscosity coefficient C, the elastic coefficient K, and the torsional rigidity coefficient Ktb. This allows the nominal model Pn to be a model that accurately approximates the actual control target.

[0087] <Second embodiment>

[0088] Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

[0089] "Premise"

[0090] Figure 5 The structure of the steering control system according to the present embodiment is shown. Figure 5 For convenience, Figure 1 Corresponding parts are provided with the same reference numerals.

[0091] like Figure 5 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 connected to the steering shaft 16. In addition, in this embodiment, the output shaft 14b is actually not required. However, for the convenience of the following description, the output shaft 14b is provided.

[0092] 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.

[0093] 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 .

[0094] The steering control device 40 controls the steering device 10 as a control object. 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.

[0095] The steering control device 40 controls the reaction force as a control amount by referring to the rotation angle θs of the reaction force motor 70 detected by the rotation angle sensor 90. In addition, the steering control device 40 controls the reaction force by referring to the currents ius, ivs, iws flowing to the reaction force motor 70. In addition, the steering control device 40 controls the steering angle as a control amount by referring to the rotation angle θt of the steering motor 80 detected by the rotation angle sensor 92. In addition, the steering control device 40 controls the steering angle by referring to the currents iut, ivt, iwt flowing through the steering motor 80.

[0096] "Processing performed by the steering control device 40"

[0097] Figure 6 FIG. 4 shows the processing performed by the steering control device 40. In other words, Figure 6 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 6 For convenience, Figure 2 The same reference numerals are used to denote corresponding processes shown in the drawings.

[0098] like Figure 6As 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.

[0099] 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 6 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.

[0100] The target angle calculation process M100 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 M100 may also 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 the model, for example, the reaction force command value Tr* may also 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.

[0101] The angle control process M102 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 the torque for the steering motor 80 .

[0102] The steering operation signal generation process M104 is a process for operating the inverter 82 by inputting the steering torque command value Tt*. The steering operation signal generation process M104 includes a process for calculating the control operation amount using the torque of the steering motor 80 as the control amount and using the value converted from the steering torque command value Tt* to 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 M104 includes a process for operating the inverter 82 according to the operation amount. Figure 6 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.

[0103] <Other embodiments>

[0104] 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.

[0105] About intermediate processing

[0106] It is not necessary to replace the integral elements M60, M64, and M76 with bilinear transformation processing M60a, M64a, and M76a, respectively. For example, the integral elements M60 and M64 may be replaced with bilinear transformation processing M60a and M64a, respectively, while the integral element M76 adopts forward rectangular approximation or backward rectangular approximation.

[0107] It is also possible that none of the integral elements M60, M64, and M76 are replaced by bilinear transformation processing. Even in this case, if Figure 4 By performing the delay processing M92, the addition processing M94, and the multiplication processing M96 in the calculation method, the estimated second disturbance torque de can be set to a value intermediate between "de1" and "de2".

[0108] exist Figure 4 In the example shown, the simple average value of the output value of the addition process M50 is calculated by the delay process M92, the addition process M94, and the multiplication process M96, but the present invention is not limited to this. For example, a weighted average value may be calculated. That is, for example, the sum of the value obtained by multiplying the previous value of the output value by the weighting coefficient α and the value obtained by multiplying the current value of the output value by "1-α" may be calculated. Here, the value of the weighting coefficient α is an arbitrary value greater than "0" and less than "1".

[0109] use Figure 4The delay processing M92, the addition processing M94, and the multiplication processing M96 are not necessary. Even in this case, for example, by replacing at least one of the three processing of the integral elements M60, M64, and M76 with a bilinear transformation processing, the estimated second disturbance torque de can be set to a value between "de1" and "de2".

[0110] "Regarding the target steering torque calculation process M10"

[0111] The target steering torque calculation process M10 is not necessarily a process for calculating 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.

[0112] It is not essential that the target steering torque calculation process M10 uses the vehicle speed SPD as an input.

[0113] The input to the target steering torque calculation process M10 is not limited to the above. For example, two or more sample values ​​of the steering angle with different sampling timings may be input to the target steering torque calculation process M10. In this case, based on the input, the identification process of when the steering wheel 12 is turned and when it 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.

[0114] "About open loop operation amount calculation processing"

[0115] 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.

[0116] 「About feedback operation amount calculation processing」

[0117] 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 also 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. For another example, the feedback operation amount Mfb may also 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.

[0118] 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 be configured as a prior differential type controller.

[0119] 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.

[0120] 「About operation amount calculation processing」

[0121] 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. For another 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.

[0122] 「About the nominal model Pn」

[0123] The nominal model Pn is not limited to the model exemplified in the above embodiment, and may be, for example, a model expressed by the following equation (c6).

[0124] (-Ktb) / {J·s·s}…(c6)

[0125] That is, the polynomial in the denominator of the transfer function of the nominal model Pn may not include a first-order term and a zero-order term. Alternatively, "Ktb" may be added to the denominator of the above-mentioned formula (c6). In other words, the polynomial in the denominator of the transfer function of the nominal model Pn may include a zero-order term.

[0126] Furthermore, the degree of the polynomial of the denominator of the transfer function of the nominal model Pn is not necessarily quadratic.

[0127] "About Correction Processing"

[0128] The filter Hd does not necessarily have a transfer function whose denominator is a polynomial of degree 3 and whose numerator is a polynomial of degree 0. In other words, it is not necessary that the numerator of the transfer function of the inverse model combining the filter Hd and the nominal model Pn is of degree 2 and the denominator of the combined transfer function is of degree 3. For example, the filter Hd may be set to the square of "ω / (ω+s)". In addition, for example, the filter Hd may be set to the fourth power or higher of "ω / (ω+s)".

[0129] As a correction process, it is not limited to the process 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 can also be calculated by using the steering torque Th as the input of the combined process of the inverse model of the nominal model Pn and the filter Hd. In this case, secondly, a difference calculation process 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. In this case, thirdly, the torque command value calculation process M20 is a process of correcting the sum of the open-loop operation amount Mff and the feedback operation amount Mfb by the output of the difference calculation process. In this case, the correction process is composed of the combined process, the difference calculation process, and the torque command value calculation process M20. In addition, the output of the above-mentioned difference calculation process is a quantity corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0130] 「About operation processing」

[0131] exist Figure 2 In the process shown, the operation process is set as a process in which the torque of the assist motor 30 is used as the control amount and the value converted from the assist torque Ta to the torque of the assist motor 30 is used as the target value of the control amount, but 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.

[0132] 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 6 The embodiment shown.

[0133] 「About steering control device」

[0134] exist Figure 5 In the illustrated configuration, a device for operating the reaction force motor 70 and a device for operating the steering motor 80 may be independent.

[0135] The steering control device is not limited to a device that includes the PU 42 and the storage device 44 and executes software processing. For example, a dedicated hardware circuit such as an ASIC that executes at least a part of the processing executed in the above embodiment may be included. That is, the control device may also include a processing circuit having any one of the following structures (a) to (c).

[0136] (a) A processing circuit including a processing device for executing all the above-mentioned processing according to a program and a program storage device such as a storage device for storing the program.

[0137] (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.

[0138] (c) A processing circuit having a dedicated hardware circuit for executing all the above-mentioned processing.

[0139] 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 circuits.

[0140] Steering control method

[0141] The subject that executes the above-mentioned various controls is not limited to the steering control device mounted on the vehicle. For example, the disturbance observer M30 and other processing for controlling a part of the target steering torque Th* may be executed by the driver's mobile terminal.

[0142] 「Input section」

[0143] The input unit to which the steering torque is input is not limited to the steering wheel 12 .

[0144] "Power transmission cut-off state"

[0145] The structure for realizing the cut-off state of the power transmission between the input part to which the steering torque is input 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.

[0146] Steering control device

[0147] As an actuator for steering the steered wheel 20, for example, an assist motor 30 or a steering motor 80 may be disposed coaxially with the steering shaft 16. In addition, for example, a configuration may be adopted 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.

[0148] The steering device capable of changing the relationship between the steering angle and the steering angle is not limited to Figure 4 As shown in the example, the steering device cuts off the transmission of power between the steering wheel 12 and the steering wheel 20. 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 input by the driver into 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 to generate a torque corresponding to the operation amount corrected by the correction process. The correction process is a process repeatedly executed at a predetermined cycle, and includes an intermediate process of setting the correction amount calculated at one sampling timing of the operation amount to an intermediate value of the correction amounts virtually calculated using the operation amounts obtained at two adjacent sampling timings.

2. The steering control device according to claim 1, wherein: The intermediate processing includes a process of setting the operation amount used for calculating the correction amount to an average value of the operation amount obtained at two adjacent sampling timings.

3. The steering control device according to claim 1, wherein: The transfer function of the above correction process contains an integral element, The intermediate processing includes a process of discretizing the integral element by bilinear transformation.

4. The steering control device according to claim 1, wherein: The correction process includes a steering torque estimation process and a disturbance estimation process. The steering torque estimation process is a process of calculating an estimated steering torque using the nominal model, wherein the estimated steering torque is an estimated value of the steering torque corresponding to the operation amount. The disturbance estimation process is a process of estimating the disturbance torque by using an inverse model of the nominal model and a filter based on the difference between the estimated steering torque and the steering torque. The degree of the polynomial of the denominator of the transfer function synthesized by the inverse model and the filter is greater than the degree of the polynomial of the numerator of the transfer function.

5. The steering control device according to claim 4, wherein: The degree of the polynomial in the denominator of the transfer function of the above nominal model is 2, The degree of the polynomial of the denominator of the transfer function of the filter is 3 or more.

6. The steering control device according to claim 5, wherein: The polynomial in the denominator of the transfer function of the above-mentioned nominal model includes a first-order term and a zero-order term.

7. 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 open-loop operation amount calculation process is a process for calculating the open-loop operation amount by inputting the target steering torque into the inverse model of the nominal model. The open-loop operation amount is an operation amount of open-loop control using the steering torque as the control amount and using a target value of the steering torque as a target value of the control amount.

8. The steering control device according to claim 1, wherein: The above-mentioned 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.

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

10. 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.

11. 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 input by the driver into 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 to generate a torque corresponding to the operation amount corrected by the correction process. The correction process is a process repeatedly executed at a predetermined cycle, and includes an intermediate process of setting the correction amount calculated at one sampling timing of the operation amount to an intermediate value of the correction amounts virtually calculated using the operation amounts obtained at two adjacent sampling timings.

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