Steering Calculation Device

Abstract

To provide a steering calculation device capable of calculating a tilt angle.SOLUTION: A PU 52 calculates a rotation angle of a pinion shaft 22 on the basis of a rotation angle θm. The PU 52 acquires a steering angle θh through communication with an upper ECU 80. The PU 52 estimates a first knuckle and a second knuckle with the steering angle θh and the rotation angle of the pinion shaft 22 as input. The first knuckle is an angle formed by a shaft direction of a column shaft 14 and a shaft direction of an intermediate shaft 18. The second knuckle is an angle formed by the shaft direction of the intermediate shaft 18 and the shaft direction of the pinion shaft 22. The PU 52 calculates a tilt angle using the first knuckle and the second knuckle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a steering calculation device. [Background technology]

[0002] For example, Patent Document 1 listed below describes a device that can change the tilt angle that determines the axial direction of an input shaft connected to a steering wheel. The same document also describes a control device that executes control to assist the steering of steered wheels based on the detected value of a tilt angle sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-49992 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the case of the above control device, if a tilt angle sensor is not provided, desired control cannot be performed. [Means for solving the problem]

[0005] The means for solving the above problems and their effects will be described below. 1. A steering calculation device for calculating values ​​of state variables related to a steering device, the steering device comprising a steering wheel, an input shaft, an intermediate shaft, an output shaft, a first Cardan joint, a second Cardan joint, and steered wheels, the input shaft being connected to the steering wheel, the first Cardan joint being a member connecting the input shaft and the intermediate shaft, the second Cardan joint being a member connecting the intermediate shaft and the output shaft, the steered wheels receiving a steering torque input to the steering wheel being transmitted via the input shaft, the intermediate shaft, and the output shaft, the steering calculation device comprising a memory device and an execution device, the memory device storing a first bending angle, the steering calculation device stores mapping data that defines a mapping that takes the first bend angle and the second bend angle as input and outputs a tilt angle, the first bend angle is the angle between the input shaft and the intermediate shaft, and the second bend angle is the angle between the output shaft and the intermediate shaft; the execution device is configured to execute a bend angle acquisition process and a tilt angle calculation process, the bend angle acquisition process is a process for acquiring the first bend angle and the second bend angle, and the tilt angle calculation process is a process for calculating a tilt angle by inputting the first bend angle and the second bend angle into the mapping, and the tilt angle is a variable that indicates the angle between the axial direction of the input shaft and a reference direction.

[0006] As described above, when the input shaft, intermediate shaft, and output shaft are connected by a Cardan joint, a change in the tilt angle causes a change in the bending angle due to the Cardan joint. This means that the tilt angle can be determined from the first bending angle and the second bending angle. Therefore, with the above configuration, the tilt angle can be calculated from the first bending angle and the second bending angle using a mapping that contains relationship information between the first bending angle, the second bending angle, and the tilt angle.

[0007] 2. A steering calculation device as described in 1 above, wherein the mapping data includes data indicating vector components parallel to the reference direction, the mapping includes a position coordinate output mapping, a vector output mapping, and a tilt angle output mapping, the position coordinate of the wheel-side end portion and the position coordinate of the center of rotation of the first Cardan joint according to the first bending angle and the second bending angle, the vector output mapping is a mapping that outputs an input axis vector that is a vector determined from the position of the center of rotation of the first Cardan joint and the wheel-side end portion, the tilt angle output mapping is a mapping that receives as input the input axis vector and the parallel vector and outputs the tilt angle, and the wheel-side end portion is the end of the two ends of the input shaft that is closer to the steering wheel.

[0008] The direction connecting the rotation center of the first Cardan joint and the wheel-side end is the direction that determines the tilt angle. Therefore, with the above configuration, the tilt angle can be calculated by calculating the position coordinates of the rotation center of the first Cardan joint and the position coordinates of the wheel-side end.

[0009] 3. A steering calculation device as described in 2 above, wherein the position coordinate output mapping is a mapping that outputs the position coordinates as a solution to a system of simultaneous equations, the system of equations including a first bend angle relational expression and a second bend angle relational expression, the first bend angle relational expression being an expression that shows the relationship between the first bend angle and the inner product of a vector determined at the center of rotation of the first Cardan joint and the wheel-side end and a vector determined at the center of rotation of the first Cardan joint and the center of rotation of the second Cardan joint, and the second bend angle relational expression being an expression that shows the relationship between the second bend angle and the inner product of a vector determined at the center of rotation of the first Cardan joint and the center of rotation of the second Cardan joint and a predetermined vector.

[0010] The pair of dot products relates the lengths of the vectors to the first and second bend angles. The lengths of the vectors are determined by the unknown variables, the position coordinates of the wheel-side end and the position coordinates of the rotation center of the first Cardan joint. Therefore, the equations above relate the unknown variables to the first and second bend angles.

[0011] 4. A steering calculation device as described in 3 above, wherein the axial direction of the input shaft can be changed by rotating it around a predetermined location other than the first Cardan joint as the center of rotation, the intermediate shaft can expand and contract by changing the axial direction of the input shaft, the mapping data includes position coordinates of the predetermined location, and the simultaneous equations include an equation indicating the distance between the predetermined location and the center of rotation of the first Cardan joint.

[0012] In the above configuration, because the intermediate shaft is contractible, the distance between the center of rotation of the first Cardan joint and the center of rotation of the second Cardan joint varies. Therefore, it is difficult to create simultaneous equations using the distance between the centers of rotation of the first Cardan joint and the second Cardan joint. In contrast, in the above configuration, by using an equation that indicates the distance between a predetermined location and the center of rotation of the first Cardan joint, it is possible to obtain an equation that conditions the position coordinates of the center of rotation of the first Cardan joint.

[0013] 5. The execution device is configured to execute a steering angle variable acquisition process and an output shaft angle variable acquisition process, wherein the steering angle variable acquisition process is a process for acquiring the value of a steering angle variable that is a variable indicating the rotation angle of the steering wheel, the output shaft angle variable acquisition process is a process for acquiring the value of an output shaft angle variable that is a variable indicating the rotation angle of the output shaft, and the bend angle acquisition process is a process for acquiring the first bend angle and the second bend angle by calculating the first bend angle and the second bend angle using the value of the steering angle variable and the value of the output shaft angle variable as input. This is a steering calculation device described in any one of 1 to 4 above.

[0014] Since the relationship between the rotation angle of the output shaft and the steering angle depends on the bend angle between the input shaft and the intermediate shaft and the bend angle between the intermediate shaft and the output shaft, the pair of bend angles can be determined from the rotation angle of the output shaft and the steering angle. In view of this, the above configuration can calculate the first bend angle and the second bend angle using the steering angle variable value and the output shaft angle variable value as inputs.

[0015] 6. A steering calculation device as described in 5 above, wherein the steering angle variable acquisition process includes a process of acquiring a plurality of different values ​​of the steering angle variable, the output shaft angle variable acquisition process includes a process of acquiring values ​​of the output shaft angle variable synchronized with each of the plurality of values ​​of the steering angle variable, the storage device stores relationship specification data, the relationship specification data is data that specifies a relational equation, the relational equation is an equation that determines the relationship between the value of the steering angle variable, the value of the output shaft angle variable, and the first bend angle and the second bend angle, and the bend angle acquisition process includes a process of calculating the first bend angle and the second bend angle by the least squares method by inputting the plurality of different values ​​of the steering angle variable and the values ​​of the output shaft angle variable synchronized with each of the plurality of values ​​into the relational equation.

[0016] A physical relationship holds between the steering angle, the rotation angle of the output shaft, and the first and second bending angles. Therefore, in the above configuration, the first and second bending angles in the relationship can be calculated using the least squares method, with the first and second bending angles being unknown variables.

[0017] 7. The steering device is a steering calculation device described in any one of 1 to 6 above, wherein the steering device is equipped with an actuator that generates power to steer the steered wheels and is configured to perform operation processing and reflection processing, the operation processing being processing to operate the actuator in accordance with operation of the steering wheel, and the reflection processing being processing to reflect the tilt angle in the operation of the actuator.

[0018] The relationship between the steering angle and the rotation angle of the output shaft, and the relationship between the steering torque and the torque applied to the output shaft, can change depending on the tilt angle. Therefore, if the actuator is operated in response to the operation of the steering wheel without taking the tilt angle into account, there is a concern that the operation of the actuator may not be appropriate depending on the tilt angle. Therefore, with the above configuration, the tilt angle is reflected in the operation processing, making the operation processing more appropriate. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a configuration of a steering control system according to an embodiment. [Figure 2] 4A and 4B are diagrams showing the configuration of a first Cardan joint according to the embodiment. [Figure 3] FIG. 2 is a block diagram showing a process executed by a control device according to the embodiment. [Figure 4] 3 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Figure 5] 3 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Figure 6] 10 is a diagram defining coordinates used in the tilt angle calculation process according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of a steering calculation device will be described with reference to the drawings. System Configuration As shown in Figure 1, steering device 10 is a device that steers steered wheels 36 through cooperation between the steering torque input to steering wheel 12 by the driver and the power of steering actuator 40. Steering device 10 is an electric power steering device. Hereinafter, operation of steering wheel 12 to the right or left will be referred to as "steering."

[0021] The steering wheel 12 is fixed to a column shaft 14. The column shaft 14 is mechanically connected to an intermediate shaft 18 via a first Cardan joint 16. The intermediate shaft 18 has a known contractible structure. Of the two axial ends of the intermediate shaft 18, the end opposite to the end connected to the first Cardan joint 16 is connected to a pinion shaft 22 via a second Cardan joint 20.

[0022] FIG. 2 shows the configuration of the first Cardan joint 16. The first Cardan joint 16 includes a first yoke 16a, a second yoke 16b, and a cross shaft 16c. The cross shaft 16c has a cross shape. The cross shaft 16c rotatably connects the first yoke 16a and the second yoke 16b to each other. The first yoke 16a is fastened to the end of the column shaft 14 with a bolt. Alternatively, the first yoke 16a may be welded to the end of the column shaft 14. The second yoke 16b is fixed to the end of the intermediate shaft 18 by welding.

[0023] The configuration of the second Cardan joint 20 is similar to that of the first Cardan joint 16, and therefore a description thereof will be omitted. Returning to FIG. 1 , the pinion shaft 22 is disposed at a predetermined intersecting angle with the rack shaft 30. Rack teeth 30a formed on the rack shaft 30 mesh with pinion teeth 22a formed on the pinion shaft 22 to form a rack-and-pinion mechanism 32. Tie rods 34 are connected to both ends of the rack shaft 30. The ends of the tie rods 34 are connected to knuckles (not shown) to which steered wheels 36 are attached. The rack-and-pinion mechanism 32 converts the rotation of the steering wheel 12 into axial displacement of the rack shaft 30. This axial displacement is transmitted to the knuckle via the tie rods 34, thereby changing the steering angle of the steered wheels 36. The steering angle refers to the turning angle of the tires, which are the steered wheels 36.

[0024] Steering actuator 40 includes assist motor 42 as a drive source, transmission mechanism 44 that transmits the torque of assist motor 42, and ball screw mechanism 46. Ball screw mechanism 46 converts the torque of assist motor 42 transmitted via transmission mechanism 44 into a force that displaces rack shaft 30 in the axial direction. Assist motor 42 is, for example, a three-phase brushless motor. The output voltage of inverter 60 is applied to the terminals of assist motor 42.

[0025] The control device 50 operates the inverter 60 to control the control amount of the steered wheels 36, which are the control target. To control the control amount, the control device 50 refers to the rotation angle θm of the assist motor 42 detected by the rotation angle sensor 70. The control device 50 also refers to the currents iu, iv, iw output by the inverter 60. Note that the currents iu, iv, iw may be understood as voltage drops across shunt resistors provided in each leg of the inverter 60. The control device 50 also refers to the torque Trq applied to the steering wheel 12, which is detected by the torque sensor 72.

[0026] The control device 50 includes a PU 52 and a storage device 54. The PU 52 is a software processing device including at least one of a CPU, a GPU, a TPU, and the like. The host ECU 80 is an electronic control device that generates commands related to vehicle control at a higher level than the control device 50. The host ECU 80 refers to the steering angle θh detected by the steering angle sensor 82. The steering angle θh is the rotation angle of the steering wheel 12. In other words, it is the rotation angle of the column shaft 14.

[0027] The control device 50 and the host ECU 80 are capable of communicating with each other. The control device 50 can receive the steering angle θh acquired by the host ECU 80. However, the sampling period for the steering angle θh is longer than the sampling period for the rotation angle θm.

[0028] "About assist control" Fig. 3 shows the process executed by the control device 50. The process shown in Fig. 3 is realized by the PU 52 repeatedly executing an assist control program 54a stored in the storage device 54, for example, at a predetermined interval.

[0029] The pinion angle calculation process M10 is a process for calculating a pinion angle θp, which is the rotation angle of the pinion shaft 22, using the rotation angle θm as an input. The steering angle calculation process M12 is a process for calculating the steering angle θh using the pinion angle θp as an input. The steering angle calculation process M12 is a process for calculating the steering angle θh using a relational expression defined by the relational expression data 54b stored in the storage device 54 shown in FIG. 1. This relational expression is the following expression (c1). The relational expression uses the pinion angle θp as an independent variable and the steering angle θh as a dependent variable.

[0030]

number

[0031] The above formula (c1) is derived by applying to the first Cardan joint 16 and the second Cardan joint 20 a formula that defines the relationship between the rotation angle and bending angle of a pair of yokes of a Cardan joint.

[0032] That is, it is derived using the simultaneous equations (c2) and (c3) below. tanθ2=cosα1·tanθh …(c2) tan(θp´)=cosα2·tan(θ2+ψ) …(c3) Note that "θ2" above is the rotation angle of the intermediate shaft 18. Also, "θp'" indicates the phase difference of the pinion angle θp with respect to "θh." More specifically, the following equation (c4) can be determined from equations (c2) and (c3).

[0033] θp' =arctan(tan[arctan{tan(θh)·cos(α1)}+ψ]·cos(α2))…(c4) Therefore, the pinion angle θp is expressed by the following equation (c5).

[0034] θp=θp´-arctan{tan(ψ)·cos(α2)}…(c5) The above equation (c1) is derived by eliminating θp' from equations (c4) and (c5).

[0035] The compensation torque calculation process M20 is a process for calculating the steering torque Th by removing the effect of gravity from the torque Trq. That is, the center of rotation of the steering wheel 12 is shifted from the center of gravity of the steering wheel 12. Therefore, the torque Trq detected by the torque sensor 72 is the resultant force of gravity and the torque input to the steering wheel 12 by the driver. The compensation torque calculation process M20 is a process for calculating the steering torque Th by removing the gravity component included in the torque Trq.

[0036] Here, the magnitude of gravity contributing to the torque Trq changes periodically depending on the steering angle θh. Therefore, the compensation torque calculation process M20 is a process for calculating the steering torque Th using the steering angle θh as an input.

[0037] The column shaft 14 is rotatable around the tilt rotation center OT shown in Figure 1. This allows the position of the steering wheel 12 to be adjusted. However, when the tilt angle θtl, which is the amount of rotation around the tilt rotation center OT, changes, the magnitude of gravity contributing to the torque Trq changes even if the steering angle θh remains the same. For this reason, the compensation torque calculation process M20 is a process that calculates the steering torque Th using the tilt angle θtl as an input.

[0038] The assist torque calculation process M22 is a process that calculates the assist torque Ta using the steering torque Th as an input. That is, the assist torque calculation process M22 is a process that changes the magnitude of the assist torque Ta according to the magnitude of the steering torque Th so that the magnitude of the assist torque Ta is an appropriate magnitude according to the driver's steering intention. The assist torque calculation process M22 may be a process that sets the magnitude of the assist torque Ta when the magnitude of the steering torque Th is large to be equal to or greater than the magnitude of the assist torque Ta when the magnitude of the steering torque Th is small. Furthermore, the assist torque calculation process M22 may be a process that sets the assist torque Ta to different values ​​when steering back and when steering.

[0039] The operation signal output process M24 is a process that receives the assist torque Ta, the rotation angle θm, and the currents iu, iv, and iw as inputs, and generates and outputs an operation signal MS for the inverter 60 to control the torque of the assist motor 42 to the assist torque Ta. Note that the operation signal MS is actually an operation signal for each switching element of the inverter 60.

[0040] "On estimating tilt angles" As described above, the tilt angle θtl changes. When the tilt angle θtl changes, the first bending angle α1, the second bending angle α2, and the difference angle variable ψ also change. Therefore, in this embodiment, the first bending angle α1, the second bending angle α2, the difference angle variable ψ, and the tilt angle θtl are not values ​​that are uniquely determined by specifications, but are variables that change when the driver changes the tilt angle θtl.

[0041] The estimation process for these variables is described in detail below. The procedure of the estimation process is shown in Figures 4 and 5. The process shown in Figures 4 and 5 is realized by the PU 52 repeatedly executing an assist control program 54a stored in the storage device 54, for example, at predetermined intervals.

[0042] In the series of processes shown in Fig. 4, the PU 52 first determines whether the update flag F is "1" (S10). If the update flag F is "1", it indicates that the process for updating the above variables is being executed. If the update flag F is "0", it indicates that the process for updating the above variables is not being executed.

[0043] When the PU 52 determines that the update flag F is "0" (S10: NO), it determines whether the start switch has been switched from an OFF state to an ON state (S12). The start switch is a switch that puts the vehicle into a state where it can run. For example, if the thrust generating device of the vehicle is an internal combustion engine only, the start switch may be an ignition switch. Also, if the thrust generating device of the vehicle is equipped with a motor, the start switch may be a switch that opens and closes an electrical path between the motor and a battery.

[0044] When it is determined that the start switch has been switched to the ON state (S12: YES), the PU 52 assigns "1" to the update flag F (S14). The PU 52 acquires the pinion angle θp when the determination in the process of S10 is affirmative or when the process of S14 is completed (S16). The PU 52 also acquires the steering angle θh through communication with the host ECU 80 (S18). The PU 52 then stores a set of the pinion angle θp and the steering angle θh in the storage device 54 (S20). The pinion angle θp and the steering angle θh are synchronized data. This can be achieved, for example, by setting the cycle of the series of processes shown in FIG. 5 to the interval at which the steering angle θh is received.

[0045] Next, the PU 52 determines whether the difference between the maximum and minimum absolute values ​​of the steering angle θh stored by the process of S20 is equal to or greater than a predetermined value Δth (S22). If the PU 52 determines that the difference is equal to or greater than the predetermined value Δth (S22: YES), the PU 52 calculates the first bending angle α1, the second bending angle α2, and the difference angle variable ψ by the least squares method (S24).

[0046] That is, for each pair of pinion angle θp and steering angle θh stored by the processing of S20, the PU 52 calculates the square of the difference between the steering angle θh and the value obtained by substituting the pinion angle θp into the right-hand side of the above equation (c1).The PU 52 then searches for the first bend angle α1, the second bend angle α2, and the difference angle variable ψ that minimize the sum of the squared differences for the pair of pinion angle θp and steering angle θh stored by the processing of S20.

[0047] Next, the PU 52 updates the first bend angle α1, the second bend angle α2, and the difference angle variable ψ, which are defined by the relational definition data 54b (S26). Next, the PU 52 calculates the coordinates of points A and B shown in FIG. 6 (S28 in FIG. 5).

[0048] In FIG. 6, point A denotes the shaft center at the end of the column shaft 14 that is connected to the steering wheel 12. Point B is the center of the cross shaft 16c of the first Cardan joint 16. Point C is the center of the cross shaft of the second Cardan joint 20. Point D is a point on the central axis of rotation of the pinion shaft 22. Point D, together with point C, is introduced to define a vector parallel to the pinion shaft 22.

[0049] As described above, because intermediate shaft 18 expands and contracts, a change in tilt angle θtl causes a change in the distance between points B and C. On the other hand, because point B rotates around tilt rotation center OT, the distance between tilt rotation center OT and point B does not change with a change in tilt angle θtl. Similarly, the distance between tilt rotation center OT and point A does not change either. Taking these factors into consideration, the six unknowns, the coordinates (xa, ya, za) of point A and the coordinates (xb, yb, zb) of point B, are calculated using six simultaneous equations Eq1 to Eq6.

[0050] Here, equation Eq1 is an equation related to the square of the length between tilt rotation center OT and point A. This square of the length is a predetermined fixed value. The coordinates (xO, yO, zO) of tilt rotation center OT are also fixed values. Mapping data 54c stored in storage device 54 shown in FIG. 1 includes data related to the coordinates of tilt rotation center OT and data related to the square of the length.

[0051] Equation Eq2 is an equation obtained by substituting the coordinate components of point A into an equation that expresses the plane on which points A and B exist. This plane does not change with changes in tilt angle θtl. The mapping data 54c includes data that defines the equation that expresses the plane.

[0052] Equation Eq3 is an equation that expresses the dot product of a vector going from point B to point A using the first bending angle α1 and a vector going from point B to point C. The mapping data 54c includes data that defines the coordinates of point C.

[0053] Equation Eq4 is an equation related to the square of the length between the tilt rotation center OT and point B. This square of the length is a predetermined fixed value. The mapping data 54c includes data related to the square of the length.

[0054] Equation Eq5 is an equation obtained by substituting the coordinate components of point B into the equation that expresses the plane on which points A and B exist. Equation Eq6 expresses the dot product of the vector going from point C to point B and the vector going from point C to point D using the second bending angle α2.

[0055] Next, the PU 52 calculates a vector going from point B to point A using the coordinate components obtained by the process of S28 (S30). Then, the PU 52 calculates the tilt angle θtl (S32). The tilt angle θtl is quantified as an angle between the direction from the reference point B0 to the reference point A0 shown in FIG. 6 and the direction from the point B to the point A. The reference point B0 is the reference point for the point B. The reference point A0 is the reference point for the point A. When the steering wheel 12 is in the reference position, the point A coincides with the reference point A0. Furthermore, when the steering wheel 12 is in the reference position, the point B coincides with the reference point B0.

[0056] The PU 52 calculates the tilt angle θtl based on the dot product of a vector extending from the reference point B0 to the reference point A0 and a vector extending from point B to point A, the distance between the reference point B0 and the reference point A0, and the distance between point B and point A. The mapping data 54c includes data defining the vector extending from the reference point B0 to the reference point A0.

[0057] Then, the PU 52 assigns "0" to the update flag F (S34). When the process of S34 is completed or when a negative determination is made in the processes of S12 and S22, the PU 52 temporarily ends the series of processes shown in FIGS.

[0058] "Actions and Effects of the Present Embodiment" The PU 52 estimates the first bend angle α1, the second bend angle α2, and the difference angle variable ψ based on the above relational expression (c1) using time-series data of the steering angle θh and the pinion angle θp. The PU 52 then calculates the coordinate components of points A and B using the first bend angle α1, the second bend angle α2, and the difference angle variable ψ. The PU 52 then calculates the tilt angle θtl based on the coordinate components of points A and B. By using the tilt angle θtl, the PU 52 can accurately eliminate the influence of the gravity component on the torque Trq and determine the steering torque Th.

[0059] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the "Means for Solving the Problem" section above is as follows. Below, the correspondence is shown for each number of the means for solving the problem described in the "Means for Solving the Problem" section. [1] The steering calculation device corresponds to the control device 50. The input shaft corresponds to the column shaft 14. The output shaft corresponds to the pinion shaft 22. The bending angle acquisition process corresponds to the processes of S20 to S24. The tilt angle calculation process corresponds to the processes of S28 to S32. The mapping data corresponds to the mapping data 54c. The mapping corresponds to the mapping realized by the processes of S28 to S32. [2] The "center of rotation of the first Cardan joint" corresponds to point B. The "center of rotation of the second Cardan joint" corresponds to point C. The "vector parallel to the reference direction" corresponds to the vector proceeding from the reference point B0 to the reference point A0. The position coordinate output mapping corresponds to the mapping realized by the process of S28. The vector output mapping corresponds to the mapping realized by the process of S30. The tilt angle output mapping corresponds to the mapping realized by the processing of S32. [3] The first bend angle relational equation corresponds to equation Eq3. The second bend angle relational equation corresponds to equation Eq6. The predetermined vector corresponds to the vector going from point C to point D. [4] "The equation showing the distance between the predetermined point and the rotation center of the first Cardan joint" corresponds to equation Eq4. [5] The bend angle acquisition processing corresponds to the processing of S24. The steering angle variable acquisition processing corresponds to the processing of S18, which is repeated periodically until the determination in the processing of S22 is affirmative. The output shaft angle variable acquisition processing corresponds to the processing of S16, which is repeated periodically until the determination in the processing of S22 is affirmative. [6] The related specification data corresponds to the related specification data 54b. The relational equation corresponds to equation (c1). [7] The operation processing corresponds to the operation signal output processing M24. The reflection processing corresponds to the compensation torque calculation processing M20.

[0060] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0061] "On simultaneous equations" If the column shaft 14 does not expand or contract, an equation that specifies that the length between points A and B is a predetermined value may be used instead of the above equation Eq1.

[0062] If the intermediate shaft 18 does not expand or contract, an equation that specifies that the length between points B and C is a predetermined value may be used instead of the above equation Eq4. For example, if the tilt rotation center is the center of the cross shaft 16c of the first Cardan joint 16, the above equations Eq1 and Eq4 cannot be used in the simultaneous equations. In that case, equation Eq1 can be replaced with an equation that specifies that the length between points A and B will be a predetermined value, and equation Eq4 can be replaced with an equation that specifies that the length between points B and C will be a predetermined value. However, it is desirable to be able to ignore the expansion and contraction of the column shaft 14 and the intermediate shaft 18 due to changes in the tilt angle θtl.

[0063] In equation Eq6, a vector parallel to the axial direction of the pinion shaft 22 and proceeding from point C to point D is used, but this is not limiting. For example, a vector having a direction that is offset by a predetermined angle β from the axial direction of the pinion shaft 22 may also be used. In this case, the independent variable of the cosine function in equation Eq6 should be set to "α2 - β."

[0064] "About mapping data" The mapping data is not limited to data defining simultaneous equations. For example, it may be data defining a regression model with the first bending angle α1 and the second bending angle α2 as input variables and the tilt angle θtl as an output variable. That is, the mapping data may be data defining a trained model. Here, the regression model may be a linear regression model. The regression model may also be a neural network. Note that the trained model may be generated by, for example, generating various tilt angles θtl and the first bending angles α1 and second bending angles α2 that achieve those tilt angles θtl as training data.

[0065] "About output shaft angle variable acquisition process" The output shaft angle variable acquisition process is not limited to a process of acquiring a value calculated using the rotation angle θm of the assist motor 42 as an input. For example, a process may be performed in which a sensor is provided to detect the rotation angle of the pinion shaft 22 and the detected value is acquired. Alternatively, for example, a process may be performed in which a sensor is provided to detect the axial displacement of the rack shaft 30 and the detected value of the sensor is used as an input to acquire a value calculated.

[0066] "About relational expressions" The relational expression is not limited to an expression in which the pinion angle θp is an independent variable and the steering angle θh is an output variable. For example, it may be an expression in which the steering angle θh is an independent variable and the pinion angle θp is an output variable. The relational expression does not necessarily have to be a function-type expression. For example, it may be an expression in which the value calculated using the pinion angle θp and the steering angle θh is a constant such as "0."

[0067] "About the bending angle acquisition process" The process for obtaining the turning angles is not limited to processing using the least squares method using relational expression (c1). For example, a regression model may be used in which the steering angle θh and pinion angle θp are input and the first turning angle α1, the second turning angle α2, and the difference angle variable ψ are output. Here, the regression model as a trained model may be a linear regression model. The regression model may also be a neural network. The training data for the regression model can be the steering angle θh, the pinion angle θp, and the corresponding measured values ​​of the first turning angle α1, the second turning angle, and the difference angle variable ψ.

[0068] When the intermediate shaft 18 does not have a phase difference ε, or when the tolerance of the phase difference ε can be ignored, the angle ξ may be used as the difference angle variable to be estimated. If the intermediate shaft 18 does not have the phase difference ε, or if the tolerance of the phase difference ε can be ignored and the axial direction of the column shaft 14, the axial direction of the intermediate shaft 18, and the axial direction of the pinion shaft 22 are parallel to one plane, it is not necessary to estimate the difference angle variable ψ.

[0069] "About reflection processing" The reflection process is not limited to a process that includes the compensation torque calculation process M20. For example, the assist torque calculation process M22 may be implemented by inputting the steering angle θh, steering torque Th, and tilt angle θtl to calculate the assist torque Ta. In this case, the reflection process can be configured by the assist torque calculation process M22.

[0070] The reflection process is not limited to the process of compensating for the gravity component of the steering torque Th. "About the steering calculation device" The control device 50 is not limited to a device equipped with a PU 52 and a storage device 54 and executing software processing. For example, it may be equipped with a dedicated hardware circuit (e.g., ASIC, etc.) that performs hardware processing on at least a portion of the software processing performed in the above embodiment. That is, the steering calculation device may have any of the following configurations (a) to (c): (a) equipped with a processing device that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program; (b) equipped with a processing device and program storage device that executes part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing; or (c) equipped with a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software processing circuits equipped with a processing device and a program storage device, and multiple dedicated hardware circuits. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software processing circuits and one or more dedicated hardware circuits.

[0071] "About the steering device" The configuration is not limited to one in which the rotation shaft of the assist motor 42 and the rack shaft 30 are arranged parallel to each other. For example, a second rack and pinion mechanism may be provided in addition to the rack and pinion mechanism 32, and the torque of the assist motor 42 may be applied via the second rack and pinion mechanism.

[0072] "others" The factors that cause the bending angles α1 and α2 to change are not limited to changes in the tilt angle. For example, use of the telescopic function may also cause the bending angles α1 and α2 to change. [Explanation of symbols]

[0073] 10...Steering device 12...Steering wheel 14...Column axis 16...First cardan joint 16a...1st York 16b...Second York 16c…cross axis 18...Intermediate shaft 20...Second cardan joint 22...Pinion shaft 22a...Pinion teeth 30...Rack shaft 30a...rack teeth 32...Rack and pinion mechanism 34...Tie rod 36...Steering wheel 40...Steering actuator 42...Assist motor 44...Transmission mechanism 46...Ball screw mechanism 50...Control device

Claims

1. A steering calculation device that calculates values ​​of state variables related to a steering device, the steering device includes a steering wheel, an input shaft, an intermediate shaft, an output shaft, a first cardan joint, a second cardan joint, and steered wheels; The input shaft is connected to the steering wheel, the first Cardan joint is a member that connects the input shaft and the intermediate shaft, the second Cardan joint is a member that connects the intermediate shaft and the output shaft, A steering torque input to the steering wheel is transmitted to the steered wheels via the input shaft, the intermediate shaft, and the output shaft, a storage device and an execution device; the storage device stores mapping data that is data for defining a mapping that inputs the first bending angle and the second bending angle and outputs a tilt angle; the first bending angle is an angle formed between the input shaft and the intermediate shaft, the second bending angle is an angle formed between the output shaft and the intermediate shaft, the execution device is configured to execute a bending angle acquisition process and a tilt angle calculation process; the bend angle acquisition process is a process of acquiring the first bend angle and the second bend angle, the tilt angle calculation process is a process of calculating a tilt angle by inputting the first bending angle and the second bending angle into the mapping, the tilt angle is a variable indicating an angle between the axial direction of the input shaft and a reference direction, the mapping data includes data indicating vector components parallel to the reference direction; the mappings include a position coordinate output mapping, a vector output mapping, and a tilt angle output mapping; the position coordinate output map is a map that outputs a position coordinate of a wheel-side end portion and a position coordinate of a rotation center of the first Cardan joint in accordance with the first bending angle and the second bending angle, the vector output mapping is a mapping that outputs an input axis vector that is a vector determined from the position of the rotation center of the first Cardan joint and the wheel-side end portion, the tilt angle output mapping is a mapping that receives the input axis vector and the parallel vector as inputs and outputs the tilt angle, The wheel-side end portion of the steering calculation device is the end portion of the input shaft that is closer to the steering wheel than the other two ends of the input shaft.

2. the position coordinate output mapping is a mapping that outputs the position coordinates as a solution of a simultaneous equation; the simultaneous equations include a first bending angle relational expression and a second bending angle relational expression, the first bend angle relational expression is an expression that indicates the relationship between the dot product of a vector determined by the rotation center of the first Cardan joint and the wheel-side end portion, and a vector determined by the rotation center of the first Cardan joint and the rotation center of the second Cardan joint, and the first bend angle; 2. The steering calculation device according to claim 1, wherein the second bending angle relational expression is an expression that indicates the relationship between the second bending angle and an inner product of a vector determined by the rotation center of the first Cardan joint and the rotation center of the second Cardan joint and a predetermined vector.

3. the axial direction of the input shaft can be changed by rotating the input shaft around a predetermined position other than the first Cardan joint as a rotation center, The intermediate shaft can be extended or retracted by changing the axial direction of the input shaft, the mapping data includes position coordinates of the predetermined location; 3. A steering calculation device according to claim 2, wherein the simultaneous equations include an equation indicating the distance between the predetermined point and the center of rotation of the first Cardan joint.

4. A steering calculation device that calculates values ​​of state variables related to a steering device, the steering device includes a steering wheel, an input shaft, an intermediate shaft, an output shaft, a first cardan joint, a second cardan joint, and steered wheels; The input shaft is connected to the steering wheel, the first Cardan joint is a member that connects the input shaft and the intermediate shaft, the second Cardan joint is a member that connects the intermediate shaft and the output shaft, A steering torque input to the steering wheel is transmitted to the steered wheels via the input shaft, the intermediate shaft, and the output shaft, a storage device and an execution device; the storage device stores mapping data that is data for defining a mapping that inputs the first bending angle and the second bending angle and outputs a tilt angle; the first bending angle is an angle formed between the input shaft and the intermediate shaft, the second bending angle is an angle formed between the output shaft and the intermediate shaft, the execution device is configured to execute a bending angle acquisition process and a tilt angle calculation process; the bend angle acquisition process is a process of acquiring the first bend angle and the second bend angle, the tilt angle calculation process is a process of calculating a tilt angle by inputting the first bending angle and the second bending angle into the mapping, the tilt angle is a variable indicating an angle between the axial direction of the input shaft and a reference direction, the execution device is configured to execute a steering angle variable acquisition process and an output shaft angle variable acquisition process; the steering angle variable acquisition process is a process of acquiring a value of a steering angle variable that is a variable indicating a rotation angle of the steering wheel, the output shaft angle variable acquisition process is a process of acquiring a value of an output shaft angle variable that is a variable indicating a rotation angle of the output shaft, The steering calculation device, wherein the bend angle acquisition process is a process of acquiring the first bend angle and the second bend angle by calculating the first bend angle and the second bend angle using the value of the steering angle variable and the value of the output shaft angle variable as inputs.

5. the steering angle variable acquisition process includes a process of acquiring a plurality of different values ​​of the steering angle variable, the output shaft angle variable acquisition process includes a process of acquiring values ​​of the output shaft angle variable synchronized with each of the plurality of values ​​of the steering angle variable, The storage device stores related specification data, the relationship defining data is data defining a relational expression, the relational expression is an expression that defines a relationship between the value of the steering angle variable, the value of the output shaft angle variable, and the first bend angle and the second bend angle, 5. The steering calculation device according to claim 4, wherein the bend angle acquisition process includes a process of calculating the first bend angle and the second bend angle by a least squares method by inputting a plurality of different values ​​of the steering angle variable and values ​​of the output shaft angle variable synchronized with each of the plurality of values ​​into the relational expression.

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