Steering control device

Abstract

A steering control device (60) controls a steering device (10) including an electric motor (52). The steering control device (60) includes a control unit (62) configured to control operation of the steering device (10) by controlling the electric motor (52). The control unit (62) is configured to calculate a control value for controlling the electric motor (52), calculate a predetermined component indicating a characteristic of the steering device using a value of a variable associated with the control value as input, and determine whether a mechanical abnormality occurs in the steering device (10) based on the calculated predetermined component.

Description

Technical Field

[0001] This invention relates to a steering control device. Background Technology

[0002] For example, Japanese Unexamined Patent Application Publication No. 2019-131072 (JP2019-131072A) discloses an example of a so-called steer-by-wire steering device for a vehicle, which includes a steering wheel capable of shifting without transmitting power to the turning wheels. Summary of the Invention

[0003] Such steer-by-wire systems require even higher reliability. However, this high reliability requirement is not limited to steer-by-wire systems; it also applies to steering systems that include a steering wheel capable of shifting to transmit power to the turning wheels.

[0004] The present invention provides a steering control device capable of appropriately detecting mechanical abnormalities in the steering mechanism.

[0005] According to one aspect of the invention, a steering control device is provided that controls the steering of a vehicle's turning wheels and includes a steering mechanism with an electric motor. The steering control device includes: a control unit configured to control the operation of the steering mechanism by controlling the electric motor. The control unit is configured to perform: a control value calculation process that calculates a control value for controlling the electric motor; a predetermined component calculation process that calculates a predetermined component indicating the characteristics of the steering mechanism exhibited by the electric motor by using the values ​​of variables associated with the control value as input; and an abnormal state determination process that determines whether a mechanical abnormality has occurred in the steering mechanism based on the predetermined component calculated in the predetermined component calculation process.

[0006] According to this aspect, the characteristics of the steering mechanism exhibited by controlling the motor by using a predetermined component included in the control value calculated when controlling the motor can be detected. For example, when there is a mechanical abnormality in the steering mechanism, these characteristics exhibit different properties, such as excessively large or small viscous components, compared to when there is no mechanical abnormality in the steering mechanism. This is effective in a state prior to reaching the abnormality, such as a state in which no mechanical abnormality actually occurs in the steering mechanism and the abnormality cannot be determined even when directly monitoring the mechanical parts of the steering mechanism. That is, with this configuration, mechanical abnormalities of the steering mechanism can be detected indirectly based on the characteristics exhibited by the predetermined component, and abnormalities that cannot be detected even when directly monitoring the mechanical parts of the steering mechanism can be detected. Therefore, mechanical abnormalities of the steering mechanism, including their symptoms, can be appropriately detected before the steering mechanism becomes difficult to operate.

[0007] In this aspect, the predetermined component calculation process may include a disturbance torque calculation process, which uses the value of a variable associated with the torque output from the motor and the value of a state variable of the steering device that is changed by controlling the motor as the value of a variable associated with the control value, and calculates the torque component affecting the state variable other than the torque output from the motor as the disturbance torque.

[0008] With this configuration, the predetermined component can be calculated using disturbance torque calculation processing, taking into account the fact that the predetermined component is included in the torque component that affects the state variable of the steering device by controlling the motor, in addition to the torque output from the motor.

[0009] In this aspect, the predetermined component calculation process may include a filtering process that uses the disturbance torque as input and selectively transmits a specific frequency component of the disturbance torque, and the predetermined component calculation process may use the output of the filtering process as the predetermined component.

[0010] With this configuration, taking into account the fact that a predetermined component becomes significant at a predetermined frequency, the target component can be accurately calculated by adjusting a specific frequency component to a frequency at which the target component is particularly increased, using the output of the filtered process as the predetermined component.

[0011] In this aspect, the filtering process may include an intensity change process that, under the same input of the filtering process, changes the intensity of the output of the filtering process according to the temperature of the steering device.

[0012] The intensity of the predetermined component changes according to the temperature of the steering system. Therefore, even when the intensity change processing is not performed, unlike the aforementioned configuration, the intensity of the output of the filtering process changes according to the temperature of the steering system. In the aforementioned configuration, the intensity of the output of the filtering process is intentionally changed according to the temperature of the steering system. Therefore, compared to the case where intensity change processing is not used, using the abnormal state determination processing based on the output of the filtering process can easily improve the degree of freedom in determining accuracy.

[0013] In this aspect, the predetermined component calculation process may include a viscous component calculation process, which calculates the viscous component of the steering device as the predetermined component. With this configuration, taking into account the fact that the viscous component exhibits different characteristics when a mechanical abnormality exists in the steering device compared to the case where no abnormality exists, the viscous component is calculated using the values ​​of variables associated with the control values ​​of the electric motor as input. Therefore, mechanical abnormalities in the steering device can be appropriately detected.

[0014] In this aspect, the predetermined component calculation process may include a friction component calculation process, which calculates the friction component of the steering device as the predetermined component. With this configuration, taking into account the fact that the friction component exhibits different characteristics when a mechanical abnormality exists in the steering device compared to the case where no abnormality exists, the friction component is calculated using the values ​​of variables associated with the control values ​​of the electric motor as input. Therefore, mechanical abnormalities in the steering device can be appropriately detected.

[0015] In this aspect, the predetermined component calculation process may include an inertial component calculation process, which calculates the inertial component of the steering device as the predetermined component. With this configuration, taking into account the fact that the inertial component exhibits different characteristics when a mechanical anomaly exists in the steering device compared to the case where no anomaly is present, the inertial component is calculated using the values ​​of variables associated with the control values ​​of the motor as input. Therefore, mechanical anomalies of the steering device can be appropriately detected.

[0016] Mechanical abnormalities of the steering system can be properly detected by using a steering control device based on this aspect. Attached Figure Description

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which similar reference numerals denote similar elements, and in the drawings:

[0018] Figure 1 This is a diagram showing a steering device according to the first embodiment;

[0019] Figure 2 This is a block diagram illustrating the process performed by the steering control device according to the first embodiment;

[0020] Figure 3 This is a diagram showing the frequency response characteristics of the steering device according to the first embodiment;

[0021] Figure 4 This is a flowchart illustrating the processing routine executed by the steering control device according to the first embodiment;

[0022] Figure 5 This is a flowchart illustrating the processing routine executed by the steering control device according to the first embodiment;

[0023] Figure 6 This is a flowchart illustrating the processing routine executed by the steering control device according to the first embodiment;

[0024] Figure 7 This is a block diagram illustrating the process performed by the steering control device according to the second embodiment;

[0025] Figure 8 This is a block diagram illustrating the process performed by the steering control device according to the third embodiment;

[0026] Figure 9 This is a block diagram illustrating the process performed by the steering control device according to the fourth embodiment; and

[0027] Figure 10 This is a block diagram illustrating the process performed by the steering control device according to the fifth embodiment. Detailed Implementation

[0028] First Implementation Method

[0029] In the following description, a first embodiment of applying a steering control device to a steer-by-wire steering system will be described with reference to the accompanying drawings.

[0030] like Figure 1 As shown, the steering device 10 includes a steering mechanism 20, a steering actuator 50 for turning the steering wheel 42, and the steering wheel 42. The steering mechanism 20 includes a steering wheel 22, a drag force actuator 30 that applies a drag force as a force to resist the driver's operation of the steering wheel 22, a rack and pinion mechanism 27, and a clutch 24 between an input shaft 32 that rotates integrally with the steering wheel 22 and the rack and pinion mechanism 27.

[0031] The drag force actuator 30 includes an input shaft 32, a reduction gear 34, a steering-side motor 36, and an inverter 38, and applies power from the steering-side motor 36 to the input shaft 32 via the reduction gear 34. In this embodiment, a three-phase surface permanent magnet synchronous motor (SPMSM) is exemplified as the steering-side motor 36. The rack and pinion mechanism 27 includes a pinion shaft 26 and a rack shaft 28 mechanically connected to the input shaft 32 via a clutch 24, and converts the rotational force of the pinion shaft 26 into axial displacement of the rack shaft 28. The clutch 24 transmits power from the input shaft 32 to the pinion shaft 26 in the engaged state and disconnects the power transmission between the input shaft 32 and the pinion shaft 26 in the disengaged state. In the engaged state of the clutch 24, the rotational force of the steering wheel 22 is converted into axial displacement of the rack shaft 28, and this axial displacement is transmitted to the steering wheel 42 via tie rods 40 connected to both ends of the rack shaft 28, thereby changing the turning angle of the steering wheel 42.

[0032] On the other hand, the turning actuator 50 shares the rack shaft 28 with the steering mechanism 20, and the turning actuator 50 includes a turning-side motor 52, an inverter 54, a ball screw mechanism 56, and a belt reduction gear mechanism 58. The turning-side motor 52 is the power source for turning the turning wheel 42, and in this embodiment, a three-phase surface permanent magnet synchronous motor (SPMSM) is exemplified as the turning-side motor 52. The ball screw mechanism 56 is integrally attached to the rack shaft 28, and the belt reduction gear mechanism 58 transmits the rotational force of the output shaft 52a of the turning-side motor 52 to the ball screw mechanism 56. The rotational force of the output shaft 52a of the turning-side motor 52 is converted into a force for linearly moving the rack shaft 28 along its axial direction via the belt reduction gear mechanism 58 and the ball screw mechanism 56. The turning wheel 42 can be turned by applying an axial force to the rack shaft 28.

[0033] The steering control unit 60 operates the steering actuator 50 to control the turning angle, which is a control value of the steering unit 10. The steering control unit 60 operates the drag force actuator 30 to control the drag force, which is a control value of the steering unit 10, while the clutch 24 is held disengaged. The steering control unit 60 relates to the steering torque Th, detected by the torque sensor 70 and input by the driver via the steering wheel 22; the rotation angle θs of the rotation shaft of the steering-side motor 36, detected by the steering-side rotation angle sensor 72; or the vehicle speed V, detected by the vehicle speed sensor 74. The steering control unit 60 also relates to the temperature TS of the steering unit 10, detected by the temperature sensor 76, or the rotation angle θt of the output shaft 52a, detected by the rotation angle sensor 78. Here, the temperature TS can be the temperature of the steering-side motor 52, the temperature of the steering-side motor 36, the temperature of the inverter 54 or 38, the temperature of the ball screw mechanism 56, etc. The temperature TS can be the temperature of the ball screw mechanism 56 to account for the effects of grease-based viscosity. Most importantly, since the temperature sensor 76 is attached to the steering control unit 60 and the steering control unit 60 is located near the steering unit 10, the temperature of the steering control unit 60 can also be considered as the temperature of the steering unit 10. The steering control unit 60 also involves the currents ius, ivs, and iws flowing in the steering-side motor 36 or the currents iut, ivt, and iwt flowing in the turning-side motor 52. The currents ius, ivs, and iws can be detected using the voltage drop across the shunt resistor in the branch of the inverter 38, and the currents iut, ivt, and iwt can be detected using the voltage drop across the shunt resistor in the branch of the inverter 54.

[0034] The steering control device 60 operates the warning device 80 to warn the driver that a mechanical malfunction has occurred in the steering actuator 50. Here, the warning device 80 is located, for example, in the vehicle's dashboard. The warning device 80 is turned on or off to warn the driver. Mechanical malfunctions of the steering actuator 50 (hereinafter referred to as "mechanical malfunctions") include a state where smooth operation of the belt reduction gear mechanism 58 is difficult, for example, a symptom of the difficult smooth operation of the belt reduction gear mechanism 58 when left alone, in addition to states where teeth have fallen out, the belt has broken, or the rack shaft 28 has locked.

[0035] The steering control unit 60 includes a CPU 62, a ROM 64, and peripheral circuitry 66, which are communicatively connected to each other via a local network 68. The peripheral circuitry 66 includes circuitry for generating clock signals that define internal operations, a power supply circuit, and a reset circuit. In this embodiment, the CPU 62 is an example of a control unit.

[0036] Figure 2 This illustrates some of the processes performed by the steering control unit 60. This is achieved by having the CPU 62 execute a program stored in ROM 64. Figure 2 The processing is shown. Figure 2 The process shown is the process when clutch 24 is in the disengaged state.

[0037] The basic target torque calculation process M10 is a process that calculates the basic target torque Thb* based on the axial force Taf, which will be described later. This basic target torque Thb* is the basic value of the target steering torque Th* that the driver wants to input to the steering shaft 32 via the steering wheel 22. Here, the axial force Taf is the axial force applied to the rack shaft 28. Since the axial force Taf has a value corresponding to the lateral force acting on the steering wheel 42, the lateral force can be determined based on the axial force Taf. On the other hand, it is preferable to determine the torque that the driver wants to input to the input shaft 32 via the steering wheel 22 based on the lateral force. Therefore, the basic target torque calculation process M10 is a process that calculates the basic target torque Thb* based on the lateral force determined according to the axial force Taf.

[0038] Specifically, the basic target torque calculation process M10 calculates a smaller absolute value of the basic target torque Thb* compared to when the absolute value of the axial force Taf is the same and the vehicle speed V is lower. This can be achieved, for example, by having the CPU 62 perform a mapping calculation on the basic target torque Thb* while the mapping data is pre-stored in ROM 64, with the axial force Taf or the lateral acceleration and vehicle speed V determined based on the axial force Taf as input variables and the basic target torque Thb* as the output variable. Here, the mapping data consists of pairs of discrete values ​​of input variables and values ​​of output variables corresponding to the values ​​of the input variables. For example, the mapping calculation is performed such that when the value of an input variable matches one of the values ​​of the input variables in the mapping data, the corresponding output variable value of the mapping data is output as the calculation result; and when the value of an input variable does not match any of the input variables, the value obtained by interpolating the values ​​of multiple output variables included in the mapping data is output as the calculation result.

[0039] Additive processing M12 calculates the target steering torque Th* by adding the hysteresis correction Thys to the basic target torque Thb*. Hysteresis processing M14 calculates and outputs the hysteresis correction Thys, which is based on the pinion angle θp and is a convertible angle that can be converted into the turning angle of the turning wheel 42. Specifically, hysteresis processing M14 includes the following processes: identifying the turning and return steering of the steering wheel 22 based on changes in the pinion angle θp, etc., and calculating the hysteresis correction Thys such that the absolute value of the target steering torque Th* is greater during turning than during return steering. Specifically, hysteresis processing M14 includes setting the hysteresis correction Thys to be variable according to the vehicle speed V. The pinion angle θp is the rotation angle of the pinion shaft 26.

[0040] Steering operation calculation process M16 is the process for calculating the steering operation amount Ts*, which is the operation amount used to control the steering torque Th to become the target steering torque Th* through feedback control. The steering operation amount Ts* includes the operation amount used to control the steering torque Th to become the target steering torque Th* through feedback control, and may include feedforward terms. The steering operation amount Ts* is converted into the amount of torque that needs to be applied to the input shaft 32 in the feedback control of the steering torque Th to become the target steering torque Ts*.

[0041] The axial force calculation process M18 is a process that calculates the axial force Taf by adding the steering torque Th to the steering operation amount Ts*. Since the steering torque Th is the torque applied to the input shaft 32, the axial force Taf in this embodiment has a value obtained by converting the force applied axially to the rack shaft 28 into the torque applied to the input shaft 32 when the clutch 24 is in the engaged state.

[0042] The normative model calculating process M20 calculates the steering angle command value θh* based on the axial force Taf. θh* is the command value for the steering angle θh. Specifically, the normative model calculating process M20 uses the model formula represented by expression (c1) to calculate the steering angle command value θh*.

[0043] Taf=K·θh*+C·θh*'+J·θh*”…(c1)

[0044] The model represented by expression (c1) is a model of the value indicated by the steering angle θh when the clutch 24 is engaged and the same amount of torque as the axial force Taf is input to the input shaft 32. In expression (c1), the viscosity coefficient C is a model of the viscosity of the steering device 10, the inertia coefficient J is a model of the inertia of the steering device 10, and the elasticity coefficient K is a model of the specifications (e.g., suspension and wheel alignment) of the vehicle in which the steering device 10 is installed. This model is not a model that precisely represents the actual steering device 10, but rather a specification model designed to change the behavior of the steering angle to an ideal behavior in response to input. In this embodiment, the steering feel can be adjusted by designing a specification model.

[0045] Specifically, in subtraction process M22, the viscous term "C·θh*" and the elastic term "K·θh*" are subtracted from the axial force Taf. In inertia coefficient division process M24, the output of subtraction process M22 is divided by the inertia coefficient J to calculate the steering angle acceleration command value αh* (=θh*”). Then, in integration process M26 with the steering angle acceleration command value αh* as input, the steering angle velocity command value ωh* (=θh*) is calculated. In integration process M28 with the steering angle velocity command value ωh* as input, the steering angle command value θh* is calculated.

[0046] Viscosity coefficient multiplication processing M30 calculates the viscous term "C·θh*'" by multiplying the steering angle command value ωh* by the viscosity coefficient C. Elasticity coefficient multiplication processing M32 calculates the elasticity term "K·θh*" by multiplying the steering angle command value θh* by the elasticity coefficient K.

[0047] Steering angle calculation process M40 calculates the steering angle θh, which is the rotation angle of the steering wheel 22, based on the integration of the rotation angle θs. Driving force calculation process M42 calculates the command value of the torque of the steering-side motor 36 as the driving force command value Tr*. This torque command value is the operational quantity used to control the steering angle θh in a feedback manner to become the steering angle command value θh*. Operation signal generation process M44 generates an operation signal MSs for operating the inverter 38 and outputs the generated operation signal MSs to the inverter 38 to control the torque, which is the control value of the steering-side motor 36, to become the driving force command value Tr*. Specifically, operation signal generation process M44 uses the operational quantities used to control the currents ius, ivs, and iws flowing into the steering-side motor 36 in a feedback manner to operate the output line voltage of the inverter 38 to the current command value determined by the driving force command value Tr*.

[0048] Steering angle ratio change processing M46 sets an adjustment amount Δθa to change the steering angle ratio based on vehicle speed V. This steering angle ratio is the ratio of the pinion angle command value θp* to the steering angle command value θh*. Specifically, the adjustment amount Δθa is set such that when vehicle speed V is low, the change in the pinion angle command value θp is greater than the change in the steering angle command value θh** compared to when vehicle speed V is high. Addition processing M48 sets the pinion angle command value θp* by adding the adjustment amount Δθa to the steering angle command value θh*.

[0049] The pinion angle calculation process M50 is based on integrating the rotation angle θt of the turning-side motor 52 to calculate the pinion angle θp. When the pinion angle θp is "0", it indicates the forward driving direction, and whether the pinion angle θp is positive or negative indicates the right turn angle or the left turn angle.

[0050] The turning operation amount calculation process M60 is the process of calculating the turning operation amount Tt*, which is the operation amount used to control the pinion angle θp in a feedback manner to make it the pinion angle command value θp*. The turning operation amount Tt* is the amount corresponding to the torque required by the turning side motor 52 in the feedback control of the pinion angle θp to make it the pinion angle command value θp*, and it is the amount converted into the torque applied to the pinion shaft 26 under the assumption that the torque is applied to the pinion shaft 26 in this embodiment.

[0051] The turning operation amount calculation process M60 includes a disturbance torque calculation process M62. The disturbance torque calculation process M62 estimates the torque, other than the turning operation amount Tt*, that affects the pinion angle θp as a state variable of the steering device 10 and is changed by controlling the turning-side motor 52, as the disturbance torque. This estimated torque is set as the estimated disturbance torque Tlde. In this embodiment, the estimated disturbance torque Tlde is converted into the torque applied to the pinion shaft 26 assuming that the disturbance torque is applied to the pinion shaft 26.

[0052] The disturbance torque calculation process M62 uses the inertia coefficient Jp, pinion angle θp, steering operation amount Tt*, and a three-row, one-column matrix L to define the observer gains l1, l2, and l3 to calculate the estimated disturbance torque Tlde or the estimated value θpe using expression (c2). The inertia coefficient Jp is a model of the inertia of the steering device 10 and represents the actual inertia of the steering device 10 with a higher precision than that of the inertia coefficient J. In this embodiment, the disturbance torque calculation process M62 is an example of a predetermined component calculation process.

[0053]

[0054]

[0055] The differential calculation processing M64 calculates the pinion angular velocity command value by performing differential calculations on the pinion angle command value θp*.

[0056] The feedback term calculation process M66 is the process for calculating the feedback term Ttfb, which is the sum of the proportional term based on the difference between the pinion angle command value θp* and the estimated value θpe, and the differential term based on the difference between the first-order time derivative of the pinion angle command value θp* and the first-order derivative of the estimated value θpe.

[0057] The second-order differential processing M68 calculates the second-order time differential value of the pinion angle command value θp*. The feedforward term calculation processing M70 calculates the feedforward term Ttff by multiplying the output value of the second-order differential processing M68 by the inertia coefficient Jp. The two-degree-of-freedom maneuver calculation processing M72 calculates the turning maneuver Tt* by subtracting the estimated disturbance torque Tlde from the sum of the feedback term Ttfb and the feedforward term Ttff. In this embodiment, the turning maneuver calculation processing M60 is an example of control value calculation processing and predetermined component calculation processing.

[0058] The conversion process M80 is a process that converts the turning operation amount Tt* into a torque command value Tm*, which is the torque command value of the control value of the turning side motor 52, by dividing the turning operation amount Tt* by the reduction ratio Kt.

[0059] The operation signal generation process M82 generates and outputs an operation signal MSt for the inverter 54 to control the torque of the turn-side motor 52 to the torque command value Tm*. Specifically, the operation signal generation process M82 operates the output line voltage of the inverter 54 to the current command value determined by the torque command value Tm* by using the operating quantities of the currents iut, ivt, and iwt flowing into the turn-side motor 52 in a feedback manner. This operation signal MSt is actually the operation signal used for each arm of each branch of the inverter 54.

[0060] The filtering process M90 extracts specific frequency components from the estimated disturbance torque Tlde as input. The specific frequency components will be described below. Figure 3 The frequency response characteristics of the steering device 10 are shown. Specifically, when displacement, such as a change in turning angle, is used as the input to the steering device 10 and the torque of the turning-side motor 52, which is the force required for the same displacement, is used as its output, the horizontal axis represents frequency and the vertical axis represents gain G.

[0061] like Figure 3 As shown, the gain G increases when the frequency is between the lower limit frequency fL and the upper limit frequency fH. This is attributed to the stickiness of the steering mechanism 10. By controlling the steering-side motor 52, the gain G changes due to the stickiness within the assumed stickiness range of the steering mechanism 10, depending on the current state, and changes excessively or excessively beyond the assumed stickiness range when a mechanical malfunction occurs in the steering actuator 50.

[0062] When the frequency is below the lower limit frequency fL, the gain G is constant. This is attributed to the friction of the steering mechanism 10. By controlling the steering-side motor 52, the gain G changes due to friction within the assumed friction range of the steering mechanism 10, depending on the current state, and changes excessively or excessively beyond the assumed friction range when a mechanical abnormality occurs in the steering actuator 50.

[0063] When the frequency is greater than the upper limit frequency fH, the gain G decreases. This is attributed to the inertia of the steering device 10. By controlling the steering side motor 52, the gain G changes due to the inertia depending on the state at the time within the assumed inertia range of the steering device 10, and changes excessively or excessively beyond the assumed inertia range when a mechanical abnormality occurs in the steering actuator 50.

[0064] In the filtering process M90, the bandpass filter (BPF) extracts the viscous component of the steering device 10 and extracts the frequency characteristics between the lower limit frequency fL and the upper limit frequency fH to extract viscous-based characteristics. The low-pass filter (LPF) extracts the friction component of the steering device 10 and extracts the frequency characteristics below the lower limit frequency fL, which are less affected by viscosity or inertia, to extract friction-based characteristics. The high-pass filter (HPF) extracts the inertial component of the steering device 10 and extracts the frequency characteristics above the upper limit frequency fH to extract inertial-based characteristics. When extracting the viscous component, the center frequency transmitted by the bandpass filter (BPF) is preferably set to, for example, "7Hz to 9Hz". The bandwidth is preferably set to, for example, "4Hz to 6Hz". When extracting the friction component, the center frequency transmitted by the low-pass filter (LPF) is preferably set to less than, for example, "7Hz". When extracting the inertial component, the center frequency transmitted by the high-pass filter (HPF) is preferably set to greater than, for example, "9Hz". In this embodiment, the filtering process M90 is an example of a predetermined component calculation process, the bandpass filter BPF is an example of a viscous component calculation process, the low-pass filter LPF is an example of a friction component calculation process, and the high-pass filter HPF is an example of an inertial component calculation process.

[0065] Return to reference Figure 2 The abnormal state determination process M92 is a process that detects mechanical abnormalities in the steering actuator 50, which is an abnormality of the steering device 10, based on the viscous component Tc, friction component Tf, and inertial component Tj output from the filtering process M90. Specifically, the abnormal state determination process M92 is a process that generates and outputs a warning signal SIG for turning the warning device 80 on or off when a mechanical abnormality of the steering actuator 50 is detected.

[0066] Figure 4 , Figure 5 and Figure 6 The flowchart for the abnormal state determination process M92 is shown. In the following description, numbers prefixed with "S" indicate the step number of each process. Figure 4In the series of processes shown, CPU 62 first acquires the viscous component Tc (SA10). Then, CPU 62 determines whether at least one of the following conditions is met: the viscous component Tc is less than the short viscous determination value Tcth1 (Tc < Tcth1) and the viscous component Tc is greater than the overviscous determination value Tcth2 (Tc > Tcth2) (step SA12). This process is used to detect characteristics of the viscous component Tc indicating a mechanical abnormality in the steering actuator 50. In this embodiment, the short viscous determination value Tcth1 and the overviscous determination value Tcth2 are set to values ​​within a range that make it difficult to achieve a smooth operation of the belt reduction mechanism 58, for example, by experimentally acquiring values ​​such as through a durability test of the belt of the belt reduction gear mechanism 58. Specifically, the viscous component Tc changes based on the vehicle's driving state, such as vehicle speed V, and the minimum value experimentally acquired in this change is set as the short viscous determination value Tcth1, and the maximum value experimentally acquired is set as the overviscous determination value Tcth2. In this embodiment, CPU 62 is an example of a control unit.

[0067] If neither of the conditions in step SA12, namely, that the viscous component Tc is less than the short viscous determination value Tcth1 and that the viscous component Tc is greater than the overviscous determination value Tcth2, is met (step SA12: No), CPU 62 determines that no mechanical abnormality has occurred in the turning actuator 50. Thereafter, CPU 62 returns the processing flow to step SA10 and repeats the processing following step SA10.

[0068] On the other hand, when it is determined that at least one of the conditions of the viscous component Tc being less than the short viscous determination value Tcth1 and the viscous component Tc being greater than the overviscous determination value Tcth2 is met (step SA12: Yes), the CPU 62 executes the process of confirming the mechanical abnormality of the steering actuator 50 (step SA14). In step SA14, the CPU 62 controls the on state, causing the warning device 80 to be turned on or off to warn the driver that a mechanical abnormality of the steering actuator 50 has been detected. The CPU 62 records the abnormality information indicating that a mechanical abnormality of the steering actuator 50 has been detected in the ROM 64, thereby storing information indicating this fact. When a diagnostic tool is externally connected to the steering control device 60, the abnormality information recorded in the ROM 64 in this way is output to the diagnostic tool, which is not shown. In this embodiment, the ROM 64 has a diagnostic function. Thereafter, the CPU 62 executes the process of activating mechanical abnormality failsafe as a failsafe operation. In this embodiment, in mechanical abnormality failsafe, the process of safely stopping the vehicle while warning the driver is executed.

[0069] exist Figure 5In the series of processes shown, CPU 62 first acquires the friction component Tf (SB10). Then, CPU 62 determines whether at least one of the following conditions is met: the friction component Tf is less than the short friction determination value Tfth1 (Tf < Tfth1) and the friction component Tf is greater than the over-friction determination value Tfth2 (Tf > Tfth2) (step SB12). This process is used to detect characteristics of the friction component Tf that indicate a mechanical abnormality in the turning actuator 50. In this embodiment, the short friction determination value Tfth1 and the over-friction determination value Tfth2 are set to values ​​within a range that are experimentally acquired, for example, through a durability test of the belt of the belt reduction gear mechanism 58, making it difficult to achieve a state where the belt reduction mechanism 58 is difficult to operate smoothly. Specifically, the friction component Tf hardly changes throughout the entire frequency range, and even within the tolerance range, the minimum value experimentally acquired when it changes is set as the short friction determination value Tfth1, and the maximum value experimentally acquired is set as the over-friction determination value Tfth2.

[0070] If neither of the conditions in step SB12, namely, that the friction component Tf is less than the short friction determination value Tfth1 and that the friction component Tf is greater than the over-viscosity determination value Tfth2, is met (Step SB12: No), CPU 62 determines that no mechanical abnormality has occurred in the turning actuator 50. Thereafter, CPU 62 returns the processing flow to step SB10 and repeats the processing after step SB10.

[0071] On the other hand, when it is determined that at least one of the conditions being met—that the friction component Tf is less than the short friction determination value Tfth1 and that the friction component Tf is greater than the over-friction determination value Tfth2—is satisfied (step SB12: Yes), the CPU 62 performs processing to confirm the mechanical abnormality of the turning actuator 50 (step SB14). In step SB14, the CPU 62 performs various processes in the same manner as described in step SA14 above.

[0072] exist Figure 6In the series of processes shown, CPU 62 first acquires the inertial component Tj (SC10). Then, CPU 62 determines whether at least one of the following conditions is met: the inertial component Tj is less than the short inertial determination value Tjth1 (Tj < Tjth1) and the inertial component Tj is greater than the over-inertial determination value Tjth2 (Tj > Tjth2) (step SC12). This process is used to detect the characteristics of the inertial component Tj that indicate a mechanical abnormality present in the turning actuator 50. In this embodiment, the short inertial determination value Tjth1 and the over-inertial determination value Tjth2 are set to values ​​within a range that make it difficult to smoothly operate the belt reduction mechanism 58, for example, by experimentally acquiring values ​​such as through a durability test of the belt of the belt reduction gear mechanism 58. Specifically, the inertial component Tj changes based on the vehicle's driving state, such as vehicle speed V, and the minimum value experimentally acquired in this change is set as the short inertial determination value Tjth1, and the maximum value experimentally acquired is set as the over-inertial determination value Tjth2.

[0073] If neither of the conditions in step SC12, namely, that the inertial component Tj is less than the short inertia determination value Tjth1 and that the inertial component Tj is greater than the over-inertia determination value Tjth2, is met (step SC12: No), CPU 62 determines that no mechanical abnormality has occurred in the turning actuator 50. Thereafter, CPU 62 returns the processing flow to step SC10 and repeats the processing following step SC10.

[0074] On the other hand, when it is determined that at least one of the conditions being met—that the inertial component Tj is less than the short inertia determination value Tjth1 and that the inertial component Tj is greater than the over-inertia determination value Tjth2—is satisfied (step SC12: Yes), the CPU 62 performs processing to confirm the mechanical abnormality of the turning actuator 50 (step SC14). In step SC14, the CPU 62 performs various processes in the same manner as described in step SA14 above.

[0075] The operation of this embodiment will be described below. According to this embodiment, by acquiring the viscous component Tc, friction component Tf, and inertial component Tj in the estimated disturbance torque Tlde calculated simultaneously with controlling the torque output from the turning-side motor 52 via the filtering process M90, the characteristics of the steering device 10 represented by the control of the turning-side motor 52 can be detected. When a mechanical abnormality exists in the turning actuator 50, which operates in association with the operation of the turning-side motor 52, these characteristics exhibit different characteristics, i.e., the viscous component Tc, friction component Tf, or inertial component Tj is too large or too small compared to the case where no mechanical abnormality exists. This is also effective in a state where no abnormality has been reached, for example, a state where no mechanical abnormality has actually occurred in the turning actuator 50 and an abnormality cannot be determined even when the mechanical parts of the turning actuator 50 are directly monitored. That is, according to this embodiment, mechanical abnormalities of the turning actuator 50 can be detected indirectly based on the characteristics indicated by the viscous component Tc, friction component Tf, or inertial component Tj, and abnormalities that cannot be detected even when the mechanical parts of the turning actuator 50 are directly monitored can be detected.

[0076] The advantages of this embodiment will be described below. (1) In this embodiment, mechanical abnormalities of the steering actuator 50 can be detected based on characteristics indicated by the viscous component Tc, the friction component Tf, or the inertial component Tj included in the estimated disturbance torque Tlde. Therefore, mechanical abnormalities of the steering device, including their symptoms, can be detected more appropriately before the steering actuator 50 has reached a state where it is difficult to operate smoothly.

[0077] (2) In this embodiment, the disturbance torque calculation process M62 estimates the torque affecting the pinion angle θp, excluding the turning operation amount Tt*, as the disturbance torque, and calculates the detected disturbance torque as the estimated disturbance torque Tlde. According to this embodiment, considering that, in addition to the turning operation amount Tt*, the viscous component Tc, the friction component Tf, or the inertial component Tj is included in the disturbance torque affecting the pinion angle θp by controlling the turning side motor 52, the disturbance torque calculation process M62 can be used to calculate the viscous component Tc, the friction component Tf, or the inertial component Tj.

[0078] (3) In this embodiment, considering that the viscous component Tc, friction component Tf, or inertial component Tj becomes significant at a predetermined frequency, the outputs of the bandpass filter BPF, low-pass filter LPF, and high-pass filter HPF of the filtering process M90 are used as the viscous component Tc, friction component Tf, and inertial component Tj. Therefore, the target components can be calculated accurately.

[0079] (4) In this embodiment, considering that the viscous component Tc exhibits different characteristics when there is a mechanical abnormality in the turning actuator 50 compared to when there is no mechanical abnormality, the viscous component Tc is calculated based on the estimated disturbance torque Tlde, which affects the pinion angle θp in addition to the turning operation amount Tt*. Therefore, mechanical abnormalities in the turning actuator 50 can be appropriately detected.

[0080] (5) In this embodiment, considering that the friction component Tf exhibits different characteristics when there is a mechanical abnormality in the turning actuator 50 compared to when there is no mechanical abnormality, the friction component Tf is calculated based on the estimated disturbance torque Tlde, which affects the pinion angle θp in addition to the turning operation amount Tt*. Therefore, mechanical abnormalities in the turning actuator 50 can be appropriately detected.

[0081] (6) In this embodiment, considering that the inertial component Tj exhibits different characteristics when there is a mechanical abnormality in the turning actuator 50 compared to when there is no mechanical abnormality, the inertial component Tj is calculated based on the estimated disturbance torque Tlde, which affects the pinion angle θp in addition to the turning operation amount Tt*. Therefore, mechanical abnormalities in the turning actuator 50 can be appropriately detected.

[0082] Second Implementation Method

[0083] The second embodiment will now be described with reference to the accompanying drawings, focusing on the differences from the first embodiment.

[0084] Figure 7 The process performed by the steering control device 60 according to this embodiment is shown. Figure 7 For convenience, in the middle, and Figure 2 The corresponding processes shown will be indicated by the same reference numerals. For example... Figure 7 As shown, in this embodiment, the CPU 62 sets the filter characteristics of the bandpass filter BPF of the filtering process M90 such that they vary according to the temperature TS. Specifically, the intensity of the viscous component Tc is set to be greater at higher temperatures than at lower temperatures TS.

[0085] This is based on the fact that the hardness and viscosity of the lubricant, such as grease, in the steering system 10 increase. Since the output value of the bandpass filter BPF is set to be greater when the strength of the viscous component included in the estimated disturbance torque Tlde is high than when the strength of the viscous component is low, even if the filter characteristics are not set to variable, the strength of the viscous component Tc output from the bandpass filter BPF becomes greater at high temperatures TS than at low temperatures TS. On the other hand, in this embodiment, by setting the filter characteristics to be variable according to temperature TS, the strength of the viscous component Tc is set to be greater at low temperatures TS compared to not setting the filter characteristics to be variable. In this embodiment, the filtering process M90, i.e., the bandpass filter BPF, is an example of strength-changing processing.

[0086] According to this embodiment, in addition to the operations and advantages corresponding to those of the first embodiment, the following advantages can also be achieved. (7) In this embodiment, since the intensity of the viscous component Tc is set to be greater when the temperature TS is lower, the degree of freedom of the determination accuracy of the abnormal state determination process M92 can be easily improved based on the output of the filter process M90 compared to the case where the filtering characteristics of the bandpass filter BPF are not set to be variable.

[0087] Third Implementation Method

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

[0089] Figure 8 The process performed by the steering control device 60 according to this embodiment is shown. Figure 8 For convenience, in the middle, and Figure 2 The corresponding processes shown will be indicated by the same reference numerals. For example... Figure 8 As shown, in this embodiment, the filtering process M90 takes the drag force command value Tr* as input and outputs the viscous component, friction component, and inertial component included in the drag force command value Tr* as the viscous component Tc, friction component Tf, and inertial component Tj, respectively. The abnormal state determination process M92 detects mechanical abnormalities of the drag force actuator 30 based on the viscous component Tc, friction component Tf, or inertial component Tj included in the drag force command value Tr*. In this embodiment, the drag force calculation process M42 is an example of control value calculation processing and predetermined component calculation processing.

[0090] The operation of this embodiment will be described below. According to this embodiment, by acquiring the viscous component Tc, friction component Tf, and inertial component Tj included in the drag force command value Tr*, the characteristics of the steering device 10 represented by the control of the steering-side motor 36, which is calculated simultaneously with controlling the torque output from the steering-side motor 36 via the filter processing M90, can be detected. When a mechanical abnormality exists in the drag force actuator 30, which operates in association with the operation of the steering-side motor 36, these characteristics exhibit different characteristics, i.e., the viscous component Tc, friction component Tf, or inertial component Tj is too large or too small compared to the case where no mechanical abnormality exists. This is also effective in a state where no abnormality has actually occurred, for example, where no mechanical abnormality has actually occurred in the drag force actuator 30 and the abnormal state cannot be determined even when the mechanical parts of the drag force actuator 30 are directly monitored. That is, according to this embodiment, mechanical abnormalities of the drag force actuator 30 can be detected indirectly based on characteristics indicated by the viscous component Tc, the friction component Tf, or the inertial component Tj, and abnormalities that cannot be detected even when directly monitoring the mechanical parts of the drag force actuator 30 can be detected.

[0091] Fourth Implementation Method

[0092] The fourth embodiment will now be described with reference to the accompanying drawings, focusing on the differences from the first embodiment.

[0093] Figure 9 The process performed by the steering control device 60 according to this embodiment is shown. Figure 9 For convenience, in the middle, and Figure 2 The corresponding processes shown will be indicated by the same reference numerals. For example... Figure 9 As shown, in this embodiment, the filtering process M90a takes the estimated disturbance torque Tlde as input and outputs the viscous component, friction component, and inertial component included in the estimated disturbance torque Tlde as the viscous component Tca, friction component Tfa, and inertial component Tja, respectively. The abnormal state determination process M92a is a process that detects mechanical abnormalities of the turning actuator 50 based on the viscous component Tca, friction component Tfa, or inertial component Tja included in the estimated disturbance torque Tlde.

[0094] In this embodiment, the filtering process M90b takes the drag force command value Tr* as input and outputs the viscous component, friction component, and inertial component included in the drag force command value Tr* as the viscous component Tcb, friction component Tfb, and inertial component Tjb, respectively. The abnormal state determination process M92b is a process that detects mechanical abnormalities of the drag force actuator 30 based on the viscous component Tcb, friction component Tfb, or inertial component Tjb included in the drag force command value Tr*.

[0095] According to this embodiment, in the abnormal state determination process M92a, a mechanical abnormality of the steering actuator 50 can be detected by acquiring the characteristics of the steering device 10 represented by the operation of the steering-side motor 52. In the abnormal state determination process M92b, a mechanical abnormality of the drag force actuator 30 can be detected by acquiring the characteristics of the steering device 10 represented by the operation of the steering-side motor 36. That is, according to this embodiment, mechanical abnormalities of both the steering actuator 50 and the drag force actuator 30 can be detected.

[0096] Fifth Implementation Method

[0097] The fifth embodiment will now be described with reference to the accompanying drawings, focusing on the differences from the first embodiment.

[0098] Figure 10 The process performed by the steering control device 60 according to this embodiment is shown. Figure 10 For convenience, in the middle, and Figure 2 The corresponding processes shown will be indicated by the same reference numerals in the accompanying drawings.

[0099] In the steering device according to this embodiment, Figure 1 The clutch 24 is omitted, and the input shaft 32 is mechanically connected to the pinion shaft 26 via a transmission ratio changing mechanism with a variable transmission ratio. That is, the rotational force of the steering wheel 22 is converted into axial displacement of the rack shaft 28, and this axial displacement is transmitted to the steering wheel 42 via tie rods 40 connected to both ends of the rack shaft 28, thereby changing the turning angle of the steering wheel 42.

[0100] The steering control unit 60 performs control to turn the steering wheel 42 according to the operation of the steering wheel 22 by operating the steering device including the steering actuator 50, which applies an auxiliary force as a force to assist the operation of the steering wheel 22. In this embodiment, the rack-assisted electric power steering system is implemented by the steering actuator 50, and the steering control unit 60 controls the torque, which is a control value for the steering side motor 52, by operating the inverter 54 connected to the steering side motor 52. In this embodiment, the steering side motor 52 is an example of an auxiliary motor.

[0101] The standard model calculation process M100 calculates the pinion angle command value θp* based on the axial force Taf. The standard model calculation process M100 calculates the pinion angle command value θp* using the model formula represented by expression (c1).

[0102] Specifically, in subtraction process M102, the viscous term "C·θp*'" and the elastic term "K·θp*" are subtracted from the axial force Taf. In inertia coefficient division process M104, the output of subtraction process M102 is divided by the inertia coefficient J to calculate the turning angle acceleration command value αp* (=θp*”). Then, in integration process M106 with the turning angle acceleration command value αp* as input, the turning angle velocity command value ωp* (=θp*’) is calculated. In integration process M108 with the turning angle velocity command value ωp* as input, the pinion angle command value θp* is calculated.

[0103] The viscosity coefficient multiplication process M110 calculates the viscosity term "C·θp*'" by multiplying the turning angular velocity command value ωp* by the viscosity coefficient C. The elasticity coefficient multiplication process M112 calculates the elasticity term "K·θp*" by multiplying the pinion angle command value θp* by the elasticity coefficient K.

[0104] Additive processing M114 adds the steering operation amount Ts* to the steering operation amount Tt*, which is the output value of the two-degree-of-freedom operation amount calculation processing M72, and outputs the calculated steering operation amount Ts*. Conversion processing M80 converts the output value of additive processing M114 into the torque command value Tm* by dividing the output value of additive processing M114 by the reduction ratio Kt.

[0105] According to the foregoing embodiments, the operations and advantages corresponding to those of the first embodiment are achieved. This embodiment can be modified as follows. Unless there is a technical conflict, this embodiment and the following modification examples can be combined with each other.

[0106] In the first embodiment, the hardness component of the vehicle equipped with the steering device 10 is considered to be included in the frequency region for extracting the viscous component Tc. The hardness component changes depending on the air pressure state of the steering wheel 42 or the assembly state of the steering device 10 in the vehicle. Therefore, the viscous component Tc can be used to detect anomalies such as a tire blowout of the steering wheel 42 or a loose assembly of the steering device 10 in the vehicle. In this case, a short hardness determination value or an over-hardness determination value can be set for the viscous component Tc. This is the same in the second, fourth, and fifth embodiments, which are capable of detecting mechanical anomalies of the steering actuator 50.

[0107] In the first embodiment, at least one of the viscous component Tc, the friction component Tf, and the inertial component Tj is used only to detect mechanical abnormalities of the steering actuator 50, and these components can be appropriately modified, for example, using only the viscous component Tc or only the viscous component Tc and the friction component Tf. When using the viscous component Tc and the friction component Tf, mechanical abnormalities of the steering actuator 50 can be detected by comparing the difference between them with a predetermined value. When using only the viscous component Tc, characteristics including the range of the viscous component can be extracted using a low-pass filter LPF or a high-pass filter HPF. When the viscous component is extracted using a low-pass filter LPF, the extracted component includes the friction component. When the viscous component is extracted using a high-pass filter HPF, the extracted component includes the inertial component. This description applies to the second to fifth embodiments.

[0108] In the first embodiment, the method for determining the abnormal state determination process M92 can be appropriately modified, for example, to determine the previous and current values ​​or their changes within a predetermined sampling period using the viscous component Tc, the frictional component Tf, or the inertial component Tj. Furthermore, the determination method may include counting the number of times the determination result of steps SA12, SB12, and SC12 is "yes," and determining the counting result.

[0109] In the second embodiment, the filter characteristics can be modified so that the viscous component Tc at a lower temperature TS is less than the viscous component Tc at a higher temperature TS, and there are no particular limitations on the mode of changing the filter characteristics. In the second embodiment, in the process of changing the filter characteristics according to the temperature TS, the filter characteristics of the low-pass filter LPF or the high-pass filter HPF can be changed.

[0110] In a second embodiment, for example, the temperature estimated historically from the current flowing in the turning-side motor 52 or the steering-side motor 36 can be used as the input temperature when changing the filter characteristics. The temperature estimated historically from the current flowing in the components of the steering control device 60 can also be used. The detection value from a sensor that detects the outside air temperature can be used to estimate the temperature.

[0111] In the first embodiment, the disturbance torque calculation process M62 can be used to calculate the viscous component Tc, the friction component Tf, or the inertial component Tj, but cannot be used to calculate the turning operation amount Tt*. This applies to the second, fourth, and fifth embodiments, which can detect mechanical abnormalities in the turning actuator 50.

[0112] In the first embodiment, the disturbance torque calculation process composed of observers can use, for example, a nonlinear Kalman filter, such as an extended Kalman filter (EKF), an unscented Kalman filter (UKF), or an enumerated Kalman filter (EnKF). This applies to the second through fifth embodiments.

[0113] In the first embodiment, for example, when feedback control is performed on the pinion angle command value θp*, which is the command value, the viscous component Tc, friction component Tf, or inertial component Tj can be extracted by selectively transmitting a specific frequency component of the torque command value or current command value, such as the turning operation amount Tt*, as its operating amount. Considering the fact that the current is controlled to the command value, when feedback control is performed on the pinion angle command value θp*, which is the command value, the viscous component Tc, friction component Tf, or inertial component Tj can be extracted by selectively transmitting a specific frequency component of the current actually flowing into the turning-side motor 52. Furthermore, since the torque or current, which is the operating amount for angle feedback control of the turning angle, is the control value of the turning-side motor 52, its command value, in addition to the torque or current, is a variable associated with the control value of the turning-side motor 52. This applies to the second, fourth, and fifth embodiments where mechanical abnormalities of the turning actuator 50 can be detected.

[0114] In the third embodiment, for example, when the feedback control of the feedback control value is executed to make it a steering angle command value θh*, the viscous component Tc, friction component Tf, or inertial component Tj can be extracted by selectively transmitting the operation signal to generate a specific frequency component of the current command value in the process M44. Furthermore, since the torque or current, which is the operation quantity for angle feedback control of the steering angle, is the control value of the steering-side motor 36, its command value, in addition to the torque or current, is a variable associated with the control value of the steering-side motor 36. The drag force calculation process M42 can consist of processing for calculating feedforward and feedback terms, and processing for calculating disturbance torque, and the viscous component Tc, friction component Tf, or inertial component Tj can be extracted from the disturbance torque. The disturbance torque cannot be used to calculate the drag force command value Tr*, but the disturbance torque can be calculated to calculate the viscous component Tc, friction component Tf, or inertial component Tj. This applies to the fourth embodiment.

[0115] In the aforementioned embodiments, the feedforward term Ttff can be calculated, for example, based on the second-order time derivative of the pinion angle θp, or based on the second-order time derivative of the estimated value θpe.

[0116] In the aforementioned embodiments, a model can be used, for example, to calculate the feedforward term, in which the torque acting on the turning wheel 42 is balanced by the sum of the following two items: the torque proportional to the angular acceleration of the turning angle; and the viscosity of the torque proportional to the angular velocity of the turning angle. In this case, a model can be used to construct the disturbance torque calculation process M62, in which the torque acting on the turning wheel 42 is balanced by the sum of the following two items: the torque proportional to the angular acceleration of the turning angle; and the viscous component.

[0117] In the aforementioned embodiments, for example, the pinion angle θp or its time derivative, instead of the estimated value θpe or the first-order time derivative, can be used as the feedback control value for calculating the input of the M66 processing unit.

[0118] In the foregoing embodiments, for example, the feedback term calculation process M66 may output the output value of the proportional element or the output value of the differential element. Alternatively, the feedback term calculation process M66 may be a process that sums the output value of at least one of the proportional element and the output value of the differential element with the output value of the integral element. When the output value of the integral element is used, the disturbance torque calculation process M62 is preferably omitted. When the output value of the integral element is not used, using the disturbance torque calculation process M62 is not necessary.

[0119] In the aforementioned embodiments, the steering angle ratio change processing M46 and the addition processing M48 can be deleted, and the output of the standard model calculation processing M20 can be used as both the steering angle command value θh* and the pinion angle command value θp*.

[0120] In the aforementioned implementation, the steering angle command value θh* is calculated using expression (c1) with axial force Taf as input, but the logic (model) used to calculate the steering angle command value θh* is not limited to this.

[0121] In the aforementioned embodiment, the steering-side motor 36 can be controlled by deleting the drag force calculation process M42 and, for example, inputting the steering operation amount Ts* to the operation signal generation process M44.

[0122] In the foregoing embodiments, feedback control of the steering torque Th is not necessary, and for example, the auxiliary torque can be calculated based on the steering torque Th, the value obtained by correcting the auxiliary torque in various forms can be set as the steering operation amount Ts*, and the steering operation amount Ts* can be input to the operation signal generation process M44.

[0123] In the foregoing embodiments, for example, the turning angle of the turning wheel 42 can be used as a convertible angle for the turning angle of the turning-side motor 52. In the foregoing embodiments, for example, the rotation angle of the steering-side motor 36 can be used as a convertible angle for the rotation angle of the steering-side motor 36.

[0124] In the aforementioned embodiments, for example, the steering operation amount Ts* can be set to the torque of the steering-side motor 36. In this case, the sum of the value obtained by dividing the steering torque Th by the reduction ratio and the steering operation amount Ts* can be used as the axial force Taf, or the sum of the value obtained by multiplying the steering operation amount Ts* by the reduction ratio and the steering torque Th can be used as the axial force Taf.

[0125] In the aforementioned embodiments, the turning operation amount Tt* can be used, for example, as the torque of the turning-side motor 52. In the aforementioned embodiments, the processing of calculating the basic target torque Thb* based solely on the axial force Taf can be used as the basic target torque calculation processing M10.

[0126] In the aforementioned embodiments, the process of correcting the basic target torque Thb* using the hysteresis correction amount Thys is not necessarily performed. In the aforementioned embodiments, for example, motors 36 and 52 can be IPMSMs or induction motors. Alternatively, motors 36 and 52 can be brushed DC motors. In this case, an H-bridge circuit can be used as the drive circuit.

[0127] In the aforementioned embodiments, for example, a so-called double pinion type including a second pinion shaft can be used as a turning actuator 50, which transmits power from the turning-side motor 52 to the rack shaft 28 separately from the pinion shaft 26.

[0128] In the aforementioned embodiment, the rack shaft 28 is supported by a support mechanism (not shown) provided in the turning actuator 50, allowing it to move axially and be pressed against the pinion shaft 26. Therefore, the rack shaft 28 is movably supported, and its rotation in the circumferential direction is restricted. An alternative support mechanism can be provided that movably supports the rack shaft 28 without using the pinion shaft 26. In this case, the pinion shaft 26 can be omitted from the turning actuator 50.

[0129] In the aforementioned embodiments, when only one of the short viscosity determination value Tcth1 and the overviscosity determination value Tcth2 needs to be considered from the perspective of detecting mechanical anomalies in the target, the other determination value can be deleted, and the configuration can be modified appropriately. This applies to either the short friction determination value Tfth1 and the over friction determination value Tfth2, or the short inertia determination value Tjth1 and the over inertia determination value Tjth2.

[0130] In the aforementioned embodiments, for example, the warning given to the driver using the warning device 80 can be appropriately modified, as long as the driver is aware of the change in situation, for example, by using an audible alarm or by increasing the drag force to tighten the steering wheel 22 to warn the driver. In addition to warning the driver, for example, the vehicle's communication functions can be used to notify a shop that can perform vehicle maintenance, such as the nearest or most nearby dealership.

[0131] In the foregoing embodiments, the steering control device 60 is not limited to a device that includes a CPU 62 and a ROM 64 and performs software processing. For example, a dedicated hardware circuit (e.g., an ASIC) can be provided to perform at least a portion of the software processing executed in the foregoing embodiments in hardware. That is, the steering control device 60 may have at least one of the following configurations (a) to (c): (a) A processor that performs all processing according to a program and a program storage device, such as a ROM, that stores the program. (b) A processor that performs some processing according to a program, a program storage device, and dedicated hardware circuitry that performs other processing. (c) A dedicated hardware circuitry that performs all processing. Here, the number of software processing circuitry or dedicated hardware circuitry including the processor and program storage device may be two or more. That is, these processes are performed only by a processing circuitry that includes at least one side of one or more software processing circuitry and one or more dedicated hardware circuitry.

[0132] The following will add technical ideas that can be understood from the foregoing embodiments and modified examples. The steering device includes a steering wheel that can be moved without transmitting power to the turning wheels, and the electric motor is a turning-side electric motor that turns the turning wheels.

[0133] This configuration allows for the detection of mechanical abnormalities in the mechanism that transmits power to the steering wheels in the steering system. Therefore, in so-called steer-by-wire steering systems, mechanical abnormalities in the mechanism that transmits power to the steering wheels can be detected.

[0134] The steering system includes a steering wheel that can be moved without transmitting power to the turning wheels, and an electric motor that applies torque to the steering side to resist the movement of the steering wheel.

[0135] This configuration allows for the detection of mechanical abnormalities in the mechanism associated with the steering wheel within the steering system. Therefore, in so-called steer-by-wire steering systems, mechanical abnormalities in the mechanism associated with the steering wheel can be detected.

[0136] The steering system may include a steering wheel that can be moved to transmit power to the turning wheels, and the electric motor may be an auxiliary electric motor that applies torque to assist the operation of the steering wheel to turn the turning wheels.

[0137] With the aforementioned configuration, mechanical abnormalities of the steering system can be appropriately detected. Therefore, so-called mechanical abnormalities of the electric power steering system can be detected.

Claims

1. A steering control device (60) for controlling the turning wheels (42) of a vehicle and including a steering device (10) with an electric motor (52), the steering control device (60) being characterized in that it comprises: A control unit (62) is configured to control the operation of the steering device (10) by controlling the electric motor (52), wherein the control unit (62) is configured to perform: a control value calculation process that calculates a control value for controlling the electric motor (52); a predetermined component calculation process that calculates a predetermined component using the values ​​of variables associated with the control value as input, the predetermined component indicating the characteristics of the steering device (10) exhibited by controlling the electric motor (52); and an abnormal state determination process that determines whether a mechanical abnormality has occurred in the steering device (10) based on the predetermined component calculated in the predetermined component calculation process. The predetermined component calculation process includes a disturbance torque calculation process, which uses the value of a variable associated with the torque output from the motor (52) and the value of a state variable of the steering device (10) changed by controlling the motor (52) as the value of the variable associated with the control value, and calculates the torque component affecting the state variable other than the torque output from the motor (52) as the disturbance torque. The predetermined component calculation process includes a filtering process that uses the disturbance torque as input and selectively transmits a specific frequency component of the disturbance torque, and the predetermined component calculation process uses the output of the filtering process as the predetermined component.

2. The steering control device (60) according to claim 1, characterized in that, The filtering process includes an intensity change process, which changes the intensity of the output of the filtering process according to the temperature of the steering device (10) under the same input of the filtering process.

3. The steering control device (60) according to claim 1 or 2, characterized in that, The predetermined component calculation process includes a viscous component calculation process, which calculates the viscous component of the steering device (10) as the predetermined component.

4. The steering control device (60) according to claim 1 or 2, characterized in that, The predetermined component calculation process includes a friction component calculation process, which calculates the friction component of the steering device (10) as the predetermined component.

5. The steering control device (60) according to claim 1 or 2, characterized in that, The predetermined component calculation process includes an inertial component calculation process, which calculates the inertial component of the steering device (10) as the predetermined component.

Images