Steering control device and steering control method

Abstract

The steering manipulation control device (40) performs operation amount calculation processing, correction processing, and operation processing. The operation amount calculation processing is processing of calculating an operation amount of control using a steering manipulation torque as a control amount and using a target steering manipulation torque as a target value of the control amount. The correction processing is processing of correcting the operation amount according to a correction amount corresponding to a difference between a steering manipulation torque assumed by a nominal model and an actual steering manipulation torque, using the steering manipulation torque and the operation amount as inputs. The operation processing is processing of operating a motor of the steering manipulation device to generate a torque corresponding to the operation amount corrected by the correction processing. The correction processing includes intermediate processing repeatedly performed at a prescribed cycle, and the intermediate processing sets an intermediate value of correction amounts virtually calculated using values of adjacent two sampling timings of the operation amount to a correction amount calculated at one sampling timing of the operation amount.

Description

Technical Field

[0001] This disclosure relates to a steering control device and a steering control method. Background Technology

[0002] For example, Patent Document 1 describes a device for operating a motor that steers the steering wheel by means of an operating quantity controlled by feedback control, which uses the steering torque as the control quantity and a target value of the steering torque as the target value of the control quantity. Specifically, the operating quantity of the feedback control is calculated based on the output values ​​of the proportional element, the derivative element, and the 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 above-mentioned feedback control, when setting the feedback gain, it is possible that the time required to determine the value of the feedback control parameters to suit these requirements becomes too long. Summary of the Invention

[0005] In one aspect of this disclosure, a steering control device is provided. The steering control device is configured to perform operation quantity calculation processing, correction processing, and operation processing. The operation quantity calculation processing calculates a control operation quantity using steering torque as a control quantity and a target steering torque as a target value of the control quantity. The steering torque is the torque input to the steering control device by the driver, and the target steering torque is the target value of the steering torque. The correction processing uses the steering torque and the operation quantity as inputs and corrects the operation quantity based on a correction amount corresponding to the difference between the steering torque assumed by the nominal model and the actual steering torque. The operation processing operates the motor of the steering control device to generate a torque corresponding to the operation quantity corrected by the correction processing. The correction processing is a process that is repeatedly executed at a predetermined period and includes an intermediate process that sets the correction amount calculated at one sampling time of the operation quantity as an intermediate value of the correction amount virtually calculated using the operation quantities obtained at two adjacent sampling times.

[0006] In another aspect of this disclosure, a steering control method is provided. The steering control method includes steps of performing operation quantity calculation processing, correction processing, and operation processing. The operation quantity calculation processing calculates a control operation quantity using steering torque as a control quantity and a target steering torque as a target value of the control quantity. The steering torque is the torque input to the steering control device by the driver, and the target steering torque is the target value of the steering torque. The correction processing uses the steering torque and the operation quantity as inputs and corrects the operation quantity based on a correction amount corresponding to the difference between the steering torque assumed by the nominal model and the actual steering torque. The operation processing operates the motor of the steering control device to generate a torque corresponding to the operation quantity corrected by the correction processing. The correction processing is repeated at a predetermined period and includes an intermediate process of setting the correction amount calculated at one sampling time of the operation quantity to an intermediate value of the correction amount virtually calculated using the operation quantities obtained at two adjacent sampling times. Attached Figure Description

[0007] Figure 1 This diagram illustrates the steering control device and its configuration according to the first embodiment.

[0008] Figure 2 It means Figure 1 A block diagram of the processes performed by the steering control device.

[0009] Figure 3 It means Figure 2 A block diagram showing the behavior of the interference observer in the s region.

[0010] Figure 4 It means Figure 2 A block diagram illustrating the behavior of a discrete system with an interference observer.

[0011] Figure 5 This diagram illustrates the steering control device and its configuration according to the second embodiment.

[0012] Figure 6 It means Figure 5 A block diagram of the processes performed by the steering control device. Detailed Implementation

[0013] <First Implementation>

[0014] The first embodiment will now be described with reference to the accompanying drawings.

[0015] "Prerequisites"

[0016] like Figure 1 As shown, the steering control device 10 includes a steering wheel 12. The steering wheel 12 is a component that transmits steering input to the driver. A transmission shaft 14 is connected to the steering wheel 12. Therefore, if the steering wheel 12 rotates, the transmission shaft 14 rotates as a unit. The rotational power of the transmission shaft 14 is transmitted to the steering shaft 16. The steering shaft 16 is located along the vehicle width direction (…). Figure 1 It extends in the left and right direction. The steering wheels 20 are connected to both ends of the steering shaft 16 via the steering tie rod 18.

[0017] The transmission shaft 14 is configured to intersect with the steering shaft 16. Meshing teeth are formed on both the transmission shaft 14 and the steering shaft 16. Furthermore, through the meshing of these teeth, 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 changes. Furthermore, the steering angle refers to the tire steering angle.

[0018] Additionally, the steering control device 10 includes an auxiliary motor 30. The auxiliary motor 30 generates an auxiliary force to assist the driver in steering. The rotational power of the auxiliary motor 30 is supplied to the drive shaft 34. Meshing teeth are formed on the drive shaft 34 and the steering shaft 16. Furthermore, through the meshing of these teeth, power can be transmitted from the drive shaft 34 to the steering shaft 16. That is, the rotational power of the drive shaft 34 is converted into axial displacement power of the steering shaft 16. Thus, the rotational power of the auxiliary motor 30 is converted into axial displacement power of the steering shaft 16 via the drive shaft 34. Specifically, as an example, the auxiliary motor 30 is a three-phase brushless motor. Furthermore, the output voltage of the inverter 32 is applied to the terminals of the auxiliary motor 30.

[0019] The steering control unit 40 controls the control quantity of the steering control unit 10, which is the controlled object. To control the control quantity, the steering control unit 40 references 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, which is part of the transmission shaft 14. Additionally, the steering control unit 40 references the vehicle speed SPD detected by the vehicle speed sensor 54. Furthermore, the steering control unit 40 references the rotation angle θa of the auxiliary motor 30 detected by the rotation angle sensor 56. Additionally, the steering control unit 40 references the currents iu, iv, and iw flowing through the auxiliary motor 30.

[0020] The steering control unit 40 includes a PU 42 and a storage device 44. The PU 42 is a software processing device such as a CPU, GPU, or TPU. The storage device 44 includes a storage medium such as electrically rewritable non-volatile memory or a disk medium. The steering control program 44a is stored in the storage device 44. The steering control unit 40 executes the steering control program 44a stored in the storage device 44 via the PU 42 to control the control quantity.

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

[0022] Figure 2 The process performed by the steering control device 40 is shown. Figure 2 The processing shown is achieved by PU42 repeatedly executing steering control program 44a at a predetermined cycle, for example.

[0023] The target steering torque calculation process M10 calculates 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 the force applied to the steering shaft 16. However, the axial force Fa is a quantity converted into torque transmitted to the shaft 14. Furthermore, the target steering torque calculation process M10 includes a process that sets the target steering torque Th* to a different value according to the vehicle speed SPD, even if the axial force Fa is the same. This is a setting designed to give the driver the optimal steering feel corresponding to the vehicle speed SPD.

[0024] The open-loop operation quantity calculation process M12 is the process for calculating the open-loop operation quantity Mff. The open-loop operation quantity Mff is the operation quantity of open-loop control using the steering torque Th as the control quantity and the target steering torque Th* as the target value of the control quantity. The open-loop operation quantity calculation process M12 calculates the open-loop operation quantity Mff by inputting the target steering torque Th*. The open-loop operation quantity calculation process M12 calculates the open-loop operation quantity Mff based on the inverse model of the nominal model Pn. The nominal model Pn is a model that uses the torque of the auxiliary motor 30, i.e., the auxiliary torque Ta, as input and outputs an estimated value of the steering torque Th, i.e., the estimated steering torque The. Here, the auxiliary torque Ta is the value converted to the torque of the transmission shaft 14. The inverse model is a model that uses the estimated steering torque The as input and outputs the auxiliary torque Ta. Furthermore, the nominal model Pn will be described in detail later.

[0025] Deviation calculation processing M14 is the process for calculating deviation, which is the value obtained by subtracting the target steering torque Th* from the steering torque Th.

[0026] The feedback operation quantity calculation process M16 is a process that uses the deviation as input and calculates the feedback operation quantity Mfb. The feedback operation quantity Mfb is the operation quantity of feedback control that uses the steering torque Th as the control quantity and the target steering torque Th* as the target value of the control quantity. The feedback operation quantity Mfb is the sum of the output value of the proportional element using the deviation as input and the output value of the derivative element using the deviation as input. Furthermore, the feedback operation quantity Mfb is a value converted into the torque of the transmission shaft 14. Specifically, the feedback operation quantity 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 according to the vehicle speed SPD.

[0027] The torque command value calculation process M20 uses the open-loop operating quantity Mff, the feedback operating quantity Mfb, and the estimated second disturbance torque de as inputs to calculate the auxiliary torque Ta. In the torque command value calculation process M20, the value obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb is substituted into the auxiliary torque Ta.

[0028] The auxiliary torque Ta is input into the axial force calculation process M22. The axial force calculation process M22 is the process of substituting the sum of the auxiliary torque Ta and the steering torque Th into the axial force Fa.

[0029] The auxiliary torque Ta is input to the 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 outputs an estimated steering torque The by inputting the auxiliary torque Ta to the nominal model Pn. The estimated steering torque The is the steering torque assumed by the nominal model Pn.

[0031] The first disturbance calculation process M34 is the process of calculating and estimating the first disturbance torque dhe. The estimated first disturbance torque dhe is the disturbance component of the steering torque Th superimposed on the actual controlled object. The estimated first disturbance 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 disturbance torque dhe is the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. Specifically, the first disturbance calculation process M34 substitutes the value obtained by subtracting the estimated steering torque The from the steering torque Th into the process of estimating the first disturbance torque dhe.

[0032] The second interference calculation process M36 takes the estimated first interference torque dhe as input and calculates the estimated second interference torque de. The estimated second interference torque de is the interference torque converted into the torque of the auxiliary motor 30. The second interference calculation process M36 uses the inverse model of the nominal model Pn and the filter Hd to calculate the estimated second interference torque de.

[0033] The filter Hd is configured to reduce noise caused by the differential operations involved in the nominal model Pn. In this embodiment, as an example, the filter Hd is a third-order low-pass filter.

[0034] As described above, the auxiliary torque Ta is obtained by subtracting the estimated second disturbance torque de from the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb. On the other hand, the estimated second disturbance torque de is 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 auxiliary motor 30. This means that the estimated second disturbance torque de is the quantity corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th. Therefore, the auxiliary torque Ta is obtained by correcting the sum of the open-loop operating quantity Mff and the feedback operating quantity 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 operates the inverter 32 by inputting the auxiliary torque Ta. Specifically, the operation signal generation process M40 includes processing to calculate the operation quantity using the torque of the auxiliary motor 30 as the control quantity and using the value of the auxiliary torque Ta converted to the torque of the auxiliary motor 30 as the target value of the control quantity. The calculation of the operation quantity refers to the rotation angle θa and the currents iu, iv, and iw. Furthermore, the operation signal generation process M40 includes processing to operate the inverter 32 to obtain this operation quantity. The operation quantity can, for example, be the ratio of the on-time of the switching elements of the inverter 32 to the time of one cycle of on / off operation. Figure 2 The operating signal MS for inverter 32 is recorded. However, in reality, the operating signal MS is a separate operating signal for each switching element of inverter 32.

[0036] "Nominal model Pn"

[0037] If the inertia coefficient Jh, viscosity coefficient Ch, and steering angle θh are used, the steering torque Th is expressed by the following equation (c1). Furthermore, the inertia coefficient Jh represents the inertia of the first portion of the transmission shaft 14, which is the portion of the transmission shaft 14 closer to the steering wheel 12 than the torsion bar 52. Additionally, the viscosity coefficient Ch represents the viscosity of the first portion of the transmission shaft 14. Finally, 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, if the rotation angle θl and the torsional stiffness coefficient Ktb of the torsion bar 52 are used, then the following equation (c2) holds. Furthermore, the rotation angle θl is the rotation angle of the second part of the transmission shaft 14, which is the part of the transmission shaft 14 that is farther away from the steering wheel 12 than the torsion bar 52.

[0040] Th=Ktb·(θh-θl)…(c2)

[0041] Furthermore, if the inertia coefficient J, viscosity coefficient C, and elasticity coefficient K are used, then the following equation (c3) holds true between the rotation angle θl and the auxiliary torque Ta and steering torque Th. The inertia coefficient J represents the inertia of the second part of the transmission shaft 14. The viscosity coefficient C represents the viscosity of the second part of the transmission shaft 14. The elasticity coefficient K represents the elasticity of the second part of the transmission shaft 14. Moreover, the viscosity coefficient C and the elasticity coefficient K actually reflect the influence of the steering shaft 16, steering tie rod 18, and steering wheel 20 on the transmission shaft 14.

[0042] Th+Ta=(J·s·s+C·s+K)·θl...(c3)

[0043] Here, if the steering torque Th is input to make the steering angle θh zero, then the steering angle θh will always be zero. If the steering angle θh is set to zero, and the transfer function from the auxiliary torque Ta to the steering torque Th is calculated based on the above equations (c1) to (c3), then the following equation (c4) is obtained.

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

[0045] Furthermore, the differential operator s is used in equation (c4) above. Equation (c4) above is the nominal model Pn. Moreover, even if “θh” and “θl” are interpreted as follows in equations (c1) to (c3) above, equation (c4) above still holds.

[0046] θh: The phase difference between the rotation angle of the first part of the transmission shaft 14 and the rotation angle of the steering wheel 12. It is always zero.

[0047] θl: The phase difference between the rotation angle of the second part of the transmission shaft 14 and the rotation angle of the steering wheel 12.

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

[0049] Design of the Interference Observer M30

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

[0051] like Figure 3 As shown, the additive processing M50 is a process that calculates the value obtained by adding the estimated second disturbance torque de to the auxiliary torque Ta.

[0052] Multiplication processing M52 is the process of multiplying the output value of addition processing M50 by a factor of -1 of the torsional stiffness coefficient Ktb.

[0053] The output value of the addition process M54, corresponding to the output value of the multiplication process M52, is input into the multiplication process M56. The multiplication process M56 is the 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, which corresponds to the output value of the multiplication process M56, is input into the integration element M60.

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

[0056] Multiplication processing M66 is the process of multiplying the output value of the integral element M60 by the viscosity coefficient C.

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

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

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

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

[0061] Multiplication process M74 is the process of multiplying the estimated first disturbance torque dhe by the observer gain L1. Addition process M62 is the process of adding the output value of the integral element M60 to the output value of multiplication process M74.

[0062] The actual device M80 is the actual object being controlled.

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

[0064] "Performance of Discrete Systems"

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

[0066] Figure 4 The discrete system performance of the interference observer M30 is shown. Figure 4 The processing shown is the actual processing performed by PU42. Furthermore, in Figure 4 For convenience, the wording is consistent with... Figure 3 The parts that are processed in the same way are labeled with the same reference numerals.

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

[0068] The use of bilinear transform processing is intended to suppress actual performance deviations. Figure 3The theoretical values ​​in the continuous system are shown. Compared to using the forward rectangle approximation or the backward rectangle approximation, the computational load is larger when using the bilinear transformation. However, the accompanying discretization error is smaller when using the bilinear transformation compared to using the forward rectangle approximation or the backward rectangle approximation. Therefore, the controllability of the control using the steering torque Th as the control variable can be improved.

[0069] in addition, Figure 4 The addition process M50 shown is the process of adding the estimated second disturbance torque de to the auxiliary torque Ta. The delay process M92 is the process of outputting the value of the addition process M50 one sample before it is calculated. The addition process M94 is the 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 the 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 to the multiplication process M52 becomes the average of the values ​​of the auxiliary torque Ta, which is corrected based on the estimated second disturbance torque de, obtained at two adjacent sampling times. This is intended to reduce the error associated with discretization.

[0071] <The function and effects of this implementation method>

[0072] PU42 uses the estimated first disturbance torque dhe as input to calculate the estimated second disturbance torque de. The estimated first disturbance torque dhe 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 a force that displaces the steering shaft 16.

[0073] PU42 uses the value obtained by adjusting the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb based on the estimated second disturbance torque de as the auxiliary torque Ta. Furthermore, PU42 operates the inverter 32 to bring the torque of the auxiliary motor 30 close to the auxiliary torque Ta. Thus, while compensating for disturbance factors such as the error between the nominal model Pn and the actual controlled object, control using the target steering torque Th* as the target value of the control quantity can be performed. In other words, through the disturbance observer M30, control using the target steering torque Th* as the target value of the control quantity can be performed while compensating for the error between the nominal model Pn and the actual controlled object.

[0074] Since the error is compensated immediately, the responsiveness of the steering torque Th to the target steering torque Th* can be improved.

[0075] In addition, compared with designing a controller based on the actual controlled object without using the interference observer M30, the time required for controller design can be reduced.

[0076] Furthermore, in the case of Figure 3 When the performance in the s region shown is replaced by actual digital processing, PU42 uses the average value obtained from two adjacent sampling timings as the input to the interference observer M30. That is, PU42 calculates the estimated second interference torque de based on the value corresponding to the average of the previous and current values ​​of the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb. Thus, the estimated second interference torque de becomes the intermediate value obtained when the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb is used separately for the first and second timings, which are two adjacent sampling timings.

[0077] That is, the estimated second disturbance torque de is the value between "de1" and "de2". Here, "de1" and "de2" are the following values.

[0078] de1: The estimated second disturbance torque de is calculated using the open-loop operating quantity Mff and the feedback operating quantity Mfb in the first timing.

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

[0080] Using only a single set of open-loop operating quantities Mff and feedback operating quantities Mfb, which vary with the sampling period, it is possible to estimate the second disturbance torque de with a significant deviation from the value assumed by the continuous system. In contrast, by using the value arbitrarily calculated at the first timing and the value arbitrarily 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] Based on the above-described implementation method, the following functions and effects are further achieved.

[0082] (1-1) PU42 replaces the integral elements M60, M64, and M76 with bilinear transformations M60a, M64a, and M76a. Thus, compared to the cases using forward rectangle approximation or backward rectangle approximation, it can maintain the performance represented by the s region as much as possible.

[0083] Furthermore, when using either the forward rectangle approximation or the backward rectangle approximation, the value obtained at a single input timing is used for integration. In contrast, according to the bilinear transform, the intermediate value obtained at two adjacent timings is used. This means that even without using... Figure 4In the case of delay processing M92, addition processing M94, and multiplication processing M96, the estimated second disturbance torque de is also calculated as the value between "de1" and "de2".

[0084] (1-2) PU42 calculates the open-loop operating quantity Mff by inputting the target steering torque Th* into the inverse model of the nominal model Pn. Additionally, PU42 calculates the auxiliary torque Ta based on the open-loop operating quantity Mff. Therefore, the estimated second disturbance torque de can be used as a compensation component for the error in the open-loop operating quantity Mff in control where the target steering torque Th* is the control quantity. Thus, pseudo-linearization of the controlled object is possible.

[0085] (1-3) The auxiliary torque Ta includes the feedback operation amount Mfb. Therefore, the error in estimating the second disturbance torque de can be compensated based on the feedback operation amount Mfb. Thus, the steering torque Th can be approximated to the target steering torque Th* with higher accuracy.

[0086] (1-4) The nominal model Pn is constructed to include not only the inertia coefficient J, but also the viscosity coefficient C, the elastic coefficient K, and the torsional stiffness coefficient Ktb. Thus, the nominal model Pn can be set as a model that can approximate the actual control object with high accuracy.

[0087] <Second Implementation>

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

[0089] "Prerequisites"

[0090] Figure 5 The configuration of the steering control system according to this embodiment is shown. Furthermore, in Figure 5 For convenience, the following is used to describe the relationship between... Figure 1 The components shown are labeled with the same reference numerals as the corresponding components in the attached drawings.

[0091] like Figure 5 As shown, in the steering control device 10, the transmission shaft 14 is separated into an input shaft 14a connected to the steering wheel 12 and an output shaft 14b engaged with the steering shaft 16. Furthermore, the output shaft 14b is not actually required in this embodiment. However, it is provided for the convenience of the following explanation.

[0092] A reaction force motor 70 is provided on the input shaft 14a. The reaction force motor 70 is a motor used to apply a reaction force to the steering wheel 12, which is a torque in the opposite direction to the torque input by the driver. As an example, the reaction force motor 70 is a 3-phase brushless motor. Furthermore, the output voltage of the inverter 72 is applied to the terminals of the reaction force motor 70.

[0093] The torque of the steering motor 80 is supplied to the steering shaft 16 via the drive shaft 34. As an example, the steering motor 80 is a 3-phase brushless motor. In addition, the output voltage of the inverter 82 is applied to the terminals of the steering motor 80.

[0094] The steering control device 40 sets the steering control device 10 as the controlled object. The steering control device 40 operates the inverter 72 to control the reaction force of the control quantity as the controlled 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 quantity as the controlled object.

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

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

[0097] Figure 6 This illustrates the processing performed by the steering control device 40. In other words, Figure 6 This illustrates the processing performed by the steering control device 40 when the transmission of power from the steering wheel 12 to the steering wheel 20 is cut off. Furthermore, in Figure 6 For convenience, the following is used to describe the relationship between... Figure 2 The processing shown corresponds to the processing labeled with the same reference numerals in the attached figures.

[0098] like Figure 6As shown, deviation calculation process M14 calculates the value obtained by subtracting the steering torque Th from the target steering torque Th*. Torque command value calculation process M20 outputs the reaction force command value Tr*. Torque command value calculation process M20 substitutes 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 the command value of the reaction 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 of operating the inverter 72 by receiving a reaction force command value Tr*. Specifically, the steering operation signal generation process M40a includes a process of calculating the control quantity using the torque of the reaction force motor 70 as a control quantity and using the value of the reaction force command value Tr* converted into the torque of the reaction force motor 70 as the target value of the control quantity. The calculation of the control quantity refers to the rotation angle θs and the currents ius, ivs, and iws. Furthermore, the steering operation signal generation process M40a includes a process of operating the inverter 72 according to this control quantity. Figure 6 The operating signals MSs of inverter 72 are recorded. In addition, the operating signals MSs are actually individual operating signals for each switching element of inverter 72.

[0100] The target angle calculation process M100 is the process of calculating the target value of the rotation angle of the drive shaft 34, i.e., the target angle θp*. The rotation angle of the drive shaft 34 has a one-to-one correspondence with the steering angle. The target angle calculation process M100 can also be, for example, a process using the steering control device 10 model to calculate the target angle θp* based on the reaction force command value Tr*. In this model, for example, the reaction force command value Tr* can also be regarded as the 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 that calculates the operating amount used to control the rotation angle of the drive shaft 34 to the target angle θp*. This operating amount is the command value for the torque of the steering motor 80, i.e., the steering torque command value Tt*.

[0102] The steering operation signal generation process M104 is a process that operates the inverter 82 by receiving an input steering torque command value Tt*. The steering operation signal generation process M104 includes a process for calculating the control quantity using the torque of the steering motor 80 as the control quantity and using the value after converting the steering torque command value Tt* into the torque of the steering motor 80 as the target value of the control quantity. The calculation of the control quantity refers to the rotation angle θt and the currents iut, ivt, and iwt. Furthermore, the steering operation signal generation process M104 includes a process for operating the inverter 82 according to this control quantity. Figure 6 The operating signal MSt of inverter 82 is recorded. In addition, the operating signal MSt is actually a separate operating signal for each switching element of inverter 82.

[0103] <Other Implementation Methods>

[0104] Furthermore, the above embodiments can be modified as follows. The above embodiments and the following modifications can be combined and implemented to a extent that they are not technically contradictory.

[0105] Regarding intermediate processing

[0106] It is not necessary to replace the integral elements M60, M64, and M76 with bilinear transformations M60a, M64a, and M76a, respectively. For example, the integral elements M60 and M64 can also be replaced with bilinear transformations M60a and M64a, respectively. On the other hand, the integral element M76 can be approximated by either a forward rectangle approximation or a backward rectangle approximation.

[0107] Alternatively, none of the integration elements M60, M64, and M76 can be replaced with a bilinear transform. Even in this case, if... Figure 4 The delay processing M92, addition processing M94, and multiplication processing M96 in the process can set the estimated second disturbance torque de to the value between "de1" and "de2".

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

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

[0110] "Regarding the calculation and processing of target steering torque M10"

[0111] It is not mandatory for the target steering torque calculation process M10 to calculate the target steering torque Th* based on the axial force Fa. For example, the target steering torque calculation process M10 can also be a process that uses the steering torque Th and the auxiliary torque Ta as inputs to calculate the target steering torque Th*.

[0112] Using vehicle speed SPD as input is not mandatory for the target steering torque calculation processing M10.

[0113] The input to the target steering torque calculation process M10 is not limited to the above. For example, two or more sampled values ​​of steering angles with different sampling timings can be input to the target steering torque calculation process M10. In this case, based on this input, identification processing when the steering wheel 12 is turned and when it is returned to its original position can be achieved. Therefore, for example, when turning the wheel, the absolute value of the target steering torque Th* can be set to a larger value by comparing it with when returning to its original position.

[0114] Regarding the calculation and processing of open-loop operations.

[0115] The open-loop maneuvering calculation process M12 is not limited to using the target steering torque Th* as input. For example, the open-loop maneuvering calculation process M12 can also use the axial force Fa as input. In this case, the transfer function of the open-loop maneuvering calculation process M12 is the product of the transfer function of the target steering torque Th* calculated based on the axial force Fa and the inverse model of the nominal model Pn.

[0116] Regarding the calculation and processing of feedback operation volume

[0117] The feedback operation quantity Mfb is not necessarily the sum of the output values ​​of the proportional element (using the deviation as input) and the derivative element (using the deviation as input). For example, the feedback operation quantity Mfb can also be the sum of the output values ​​of the proportional element (using the deviation as input), the derivative element (using the deviation as input), and the integral element (using the value corresponding to the deviation as input). Alternatively, the feedback operation quantity Mfb can also be the sum of the output values ​​of the proportional element (using the deviation as input) and the integral element (using the value corresponding to the deviation as input). In this case, the gain of the integral element can be adjusted according to the vehicle speed SPD.

[0118] Furthermore, as a differential element, it is not limited to being input with a deviation. For example, the differential element can also use the steering torque Th as an input. In other words, the differential element can also be configured as a pre-differential type controller.

[0119] The processing of at least one element of the gain of the feedback operation quantity calculation processing based on the change of vehicle speed SPD is not necessary.

[0120] Regarding the calculation and processing of operational quantities

[0121] For example, it may be possible to omit feedback operation calculation processing and consist solely of open-loop operation calculation processing. Alternatively, it may omit open-loop operation calculation processing and consist solely of feedback operation calculation processing.

[0122] Regarding the nominal model Pn

[0123] The nominal model Pn is not limited to the model exemplified in the above embodiments. For example, it can also be a model represented by the following equation (c5).

[0124] (-Ktb) / {J·s·s}…(c5)

[0125] That is, the polynomial in the denominator of the transfer function of the nominal model Pn may not contain terms of degree 1 or degree 0. Alternatively, "Ktb" may be added to the denominator of equation (c5) above. In other words, the polynomial in the denominator of the transfer function of the nominal model Pn may also contain terms of degree 0.

[0126] Furthermore, it is not necessary for the polynomial in the denominator of the transfer function of the nominal model Pn to be of degree 2.

[0127] Regarding the correction process

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

[0129] The correction process is not limited to the process that includes steering torque estimation processing M32, first disturbance calculation processing M34, second disturbance calculation processing M36, and torque command value calculation processing M20. For example, firstly, the estimated motor torque Tae can be calculated by using the steering torque Th as the input to the combined processing of the inverse model of the nominal model Pn and the filter Hd. In this case, secondly, a difference calculation processing is performed to calculate the difference between the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb and the estimated motor torque Tae. In this case, thirdly, the torque command value calculation processing M20 corrects the sum of the open-loop operating quantity Mff and the feedback operating quantity Mfb using the output of the difference calculation processing. In this case, the correction process consists of the combined processing, the difference calculation processing, and the torque command value calculation processing M20. Furthermore, the output of the above-mentioned difference calculation processing is a quantity corresponding to the difference between the steering torque assumed by the nominal model Pn and the actual steering torque Th.

[0130] Regarding operational procedures

[0131] exist Figure 2 In the illustrated process, the operation process is set to use the torque of the auxiliary motor 30 as the control quantity and the target value of the control quantity is the value after converting the auxiliary torque Ta into the torque of the auxiliary motor 30, 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 auxiliary motor 30 based on the axial force Fa. In this case, the operation process is a process of operating the auxiliary motor 30 based on the operation quantity of feedback control using the rotation angle of the auxiliary motor 30 as the control quantity. Furthermore, here, the axial force Fa is the sum of the value obtained by correcting the operation quantity determined based on the open-loop operation quantity Mff and the feedback operation quantity Mfb based on the estimated second disturbance torque de, and the steering control torque Th. Therefore, the operation process is a process of operating the inverter 32 based on the value after correcting the operation quantity determined based on the open-loop operation quantity Mff and the feedback operation quantity Mfb based on the estimated second disturbance torque de. This is a process of controlling the torque of the auxiliary motor 30 to produce a torque corresponding to the value obtained by correcting the operation quantity determined based on the open-loop operation quantity Mff and the feedback operation quantity Mfb based on the estimated second disturbance torque de.

[0132] Furthermore, as an embodiment capable of applying changes including angle feedback control, it is not limited to... Figure 2 The illustrated embodiment. For example, it can also be applied to... Figure 6 The example shown.

[0133] Regarding the steering control system

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

[0135] The steering control device is not limited to a device that includes a PU42 and a storage device 44 and performs software processing. For example, it may also include dedicated hardware circuitry such as an ASIC that performs at least a portion of the processing performed in the above embodiments. That is, the steering control device may also include a processing circuit configured with any of the following (a) to (c).

[0136] (a) A processing circuit having a processing device that performs all of the above-mentioned processes according to a program, and a program storage device such as a storage device for storing the program.

[0137] (b) A processing circuit having a processing device that performs a portion of the above-described processing according to a program, a program storage device, and dedicated hardware circuitry for performing the remaining processing.

[0138] (c) A processing circuit with dedicated hardware circuitry to perform all of the above processes.

[0139] Here, there can be multiple software execution devices equipped with processing units and program storage units. In addition, there can also be multiple dedicated hardware circuits.

[0140] "Steering control method"

[0141] The entity that performs the various controls described above is not limited to the steering control device installed in the vehicle. For example, the processing of part of the interference observer M30 used to control the target steering torque Th* can also be performed by the driver's mobile terminal.

[0142] Input Section

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

[0144] "Power transmission interrupted state"

[0145] The configuration that achieves the disconnection of power transmission between the input unit for input steering torque and the steering wheel 20 is not limited to... Figure 5The configuration is illustrated. For example, a clutch may also be provided between the input shaft 14a and the output shaft 14b.

[0146] Steering control device

[0147] As an actuator to steer the steering wheel 20, for example, a device may be used in which an auxiliary motor 30 or a steering motor 80 is mounted coaxially on the steering shaft 16. Alternatively, for example, a configuration may be used in which the power of the auxiliary motor 30 or the steering motor 80 is transmitted to the steering shaft 16 via a belt reducer using a ball screw mechanism.

[0148] As a steering control device capable of changing the relationship between the steering angle and the steering control angle, it is not limited to... Figure 5 As illustrated, a steering control device that cuts off the power transmission between the steering wheel 12 and the steering wheel 20. For example, a steering control device capable of changing the relationship between the steering angle and the steering control angle can also be constructed by making the gear capable of transmitting power between the steering wheel 12 and the steering wheel 20 a variable gear.

Claims

1. A steering control device, wherein, The aforementioned steering control device is configured to perform operation quantity calculation processing, correction processing, and operation processing. The above-described operation quantity calculation process involves calculating the operation quantity for control that uses steering torque as the control quantity and a target steering torque as the target value of the control quantity. The aforementioned steering torque is the torque input by the driver to the steering control device. The aforementioned target steering torque is the target value of the aforementioned steering torque. The above-described correction process uses the steering torque and the operating amount as inputs, and corrects the operating amount based on the correction amount corresponding to the difference between the steering torque assumed by the nominal model and the actual steering torque. The above-described operation process involves operating the motor of the steering control device to generate torque corresponding to the operation amount corrected by the above-described correction process. The above correction process is a process that is repeatedly executed at a predetermined period, and includes an intermediate process that sets the correction amount calculated at one sampling time of the above operation amount as the intermediate value of the correction amount virtually calculated using the above operation amount obtained at two adjacent sampling times.

2. The steering control device according to claim 1, wherein, The intermediate processing described above includes setting the operation quantity used in calculating the correction amount to the average value of the operation quantity obtained at two adjacent sampling times.

3. The steering control device according to claim 1, wherein, The transfer function of the above-mentioned modified process includes an integral element. The intermediate processing described above includes discretizing the integral elements using a bilinear transformation.

4. The steering control device according to claim 1, wherein, The above correction process includes steering torque estimation processing and disturbance estimation processing. The above-described steering torque estimation process involves calculating and estimating the steering torque using the aforementioned nominal model. This estimated steering torque is a value corresponding to the aforementioned input input. The above-described interference estimation process involves estimating the interference torque based on the difference between the estimated steering torque and the original steering torque, using the inverse model of the nominal model and a filter. The degree of the polynomial in the denominator of the transfer function synthesized from the above inverse model and filter is greater than the degree of the polynomial in the numerator of the above transfer function.

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

6. The steering control device according to claim 5, wherein, The polynomial in the denominator of the transfer function of the above nominal model contains terms of degree 1 and terms of degree 0.

7. The steering control device according to claim 1, wherein, The above-mentioned operation quantity calculation and processing includes open-loop operation quantity calculation and processing. The above-described open-loop operation calculation process involves inputting the target steering torque into the inverse model of the nominal model to calculate the open-loop operation. The aforementioned open-loop operating quantity is an operating quantity for open-loop control that uses the aforementioned steering torque as the aforementioned control quantity and uses the target value of the aforementioned steering torque as the target value of the aforementioned control quantity.

8. The steering control device according to claim 1, wherein, The above-mentioned operation quantity calculation and processing includes feedback operation quantity calculation and processing. The above-described feedback operation quantity calculation process is the process of calculating the feedback operation quantity. The aforementioned feedback operation quantity is the operation quantity of feedback control that uses the aforementioned steering torque as the aforementioned control quantity and uses the aforementioned target steering torque as the target value of the aforementioned control quantity.

9. The steering control device according to claim 1, wherein, The motor mentioned above is the motor that steers the vehicle's steering wheels.

10. The steering control device according to claim 1, wherein, The motor described above is a motor that imparts torque to the input unit when the power transmission between the vehicle's steering wheel and the input unit for steering torque is cut off.

11. A steering control method, wherein, It has procedures for performing operation quantity calculation, correction, and operation processing. The above-described operation quantity calculation process involves calculating the operation quantity for control that uses steering torque as the control quantity and a target steering torque as the target value of the control quantity. The aforementioned steering torque is the torque input by the driver to the steering control device. The aforementioned target steering torque is the target value of the aforementioned steering torque. The above-described correction process uses the steering torque and the operating amount as inputs, and corrects the operating amount based on the correction amount corresponding to the difference between the steering torque assumed by the nominal model and the actual steering torque. The above-described operation process involves operating the motor of the steering control device to generate torque corresponding to the operation amount corrected by the above-described correction process. The above correction process is a process that is repeatedly executed at a predetermined period, and includes an intermediate process that sets the correction amount calculated at one sampling time of the above operation amount to the intermediate value of the correction amount virtually calculated using the above operation amount obtained at two adjacent sampling times.

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