Control device, control method, and control program for four-wheel steering steering vehicle

Abstract

This invention provides a control device, control method, and control program for a four-wheel steering vehicle. The control device sets commanded front wheel steering angles and commanded rear wheel steering angles, wherein the commanded front wheel steering angles are commanded values ​​for the front wheel steering angles, and the commanded rear wheel steering angles are commanded values ​​for the rear wheel steering angles. The control device acquires the aforementioned front wheel steering angles and rear wheel steering angles. Based on the commanded front wheel steering angles and the commanded rear wheel steering angles as input variables, the control device calculates an ideal yaw rate. Based on the aforementioned front wheel steering angles and the commanded rear wheel steering angles as input variables, the control device calculates an inferred yaw rate. The control device calculates the deviation between the ideal yaw rate and the inferred yaw rate. Based on the aforementioned deviation as an input variable, the control device corrects at least one of the commanded front wheel steering angles and the commanded rear wheel steering angles.

Description

Technical Field

[0001] This disclosure relates to a control device for a four-wheel steering vehicle, a control method for a four-wheel steering vehicle, and a control procedure for a four-wheel steering vehicle. Background Technology

[0002] Patent Document 1 describes a control device for a four-wheel steering vehicle. This control device, when the vehicle is in an emergency avoidance situation, performs in-phase control on the steering input of the rear wheels to stabilize the lateral movement of the vehicle body.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-74192

[0004] However, there are differences in dead time and response delay between the actuators that steer the front wheels and the actuators that steer the rear wheels. Therefore, if the timing of either the front or rear wheel steering is delayed relative to the timing of the other, there is a concern that the four-wheel steering maneuver may cause the vehicle to deviate from its intended driving trajectory. Summary of the Invention

[0005] In one aspect of this disclosure, a control device for a four-wheel steering vehicle is provided. The control device for a four-wheel steering vehicle is configured to perform a commanded steering angle setting process, an actual steering angle acquisition process, an ideal yaw rate calculation process, an inferred yaw rate calculation process, a deviation calculation process, and a correction process. The commanded steering angle setting process sets the commanded front wheel steering angle and the commanded rear wheel steering angle, where the commanded front wheel steering angle is a commanded value for the front wheel steering angle, and the commanded rear wheel steering angle is a commanded value for the rear wheel steering angle. The actual steering angle acquisition process acquires the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle. The ideal yaw rate calculation process calculates the ideal yaw rate based on the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle as input variables. The inferred yaw rate calculation process calculates the inferred yaw rate based on the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle as input variables. The deviation calculation process calculates the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process is based on the aforementioned deviation as an input variable, and corrects at least one of the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle.

[0006] In other aspects of this disclosure, a control method for a four-wheel steering vehicle is provided. The control method for a four-wheel steering vehicle includes the execution of a commanded steering angle setting process, the execution of an actual steering angle acquisition process, the execution of an ideal yaw rate calculation process, the execution of an inferred yaw rate calculation process, the execution of a deviation calculation process, and the execution of a correction process. The commanded steering angle setting process sets the commanded front wheel steering angle and the commanded rear wheel steering angle, where the commanded front wheel steering angle is a commanded value for the front wheel steering angle, and the commanded rear wheel steering angle is a commanded value for the rear wheel steering angle. The actual steering angle acquisition process acquires the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle. The ideal yaw rate calculation process calculates the ideal yaw rate based on the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle as input variables. The inferred yaw rate calculation process calculates the inferred yaw rate based on the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle as input variables. The above deviation calculation process calculates the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process corrects at least one of the commanded front wheel steering angle and the commanded rear wheel steering angle based on the above deviation as an input variable.

[0007] In other aspects of this disclosure, a control program for a four-wheel steering vehicle is provided. The control program for a four-wheel steering vehicle includes instructions that cause a computer to perform instruction steering angle setting processing, actual steering angle acquisition processing, ideal yaw rate calculation processing, inferred yaw rate calculation processing, deviation calculation processing, and correction processing. The instruction steering angle setting processing sets instruction front wheel steering angles and instruction rear wheel steering angles, where the instruction front wheel steering angle is an instruction value for the front wheel steering angle, and the instruction rear wheel steering angle is an instruction value for the rear wheel steering angle. The actual steering angle acquisition processing acquires the aforementioned front wheel steering angles and the aforementioned rear wheel steering angles. The ideal yaw rate calculation processing calculates the ideal yaw rate based on the aforementioned instruction front wheel steering angles and the aforementioned instruction rear wheel steering angles as input variables. The inferred yaw rate calculation processing calculates the inferred yaw rate based on the aforementioned front wheel steering angles and the aforementioned rear wheel steering angles as input variables. The above deviation calculation process calculates the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process corrects at least one of the commanded front wheel steering angle and the commanded rear wheel steering angle based on the above deviation as an input variable. Attached Figure Description

[0008] Figure 1 This is a diagram illustrating a control system for a four-wheel steering vehicle according to one embodiment.

[0009] Figure 2 It means Figure 1 The diagram shows the block diagram of the processes performed by the control device.

[0010] Figure 3 It means Figure 2 The flowchart shows the detailed steps of lateral motion control.

[0011] Figure 4 It means Figure 3 A block diagram showing details of a portion of the process.

[0012] Figure 5 This is an example of the application. Figure 3 A diagram showing the processing status.

[0013] Figure 6 This is a timing diagram illustrating the effects of the implementation method.

[0014] Figure 7 This is a graph representing the movement of the detected yaw rate.

[0015] Explanation of reference numerals in the attached figures

[0016] 10…Control device Detailed Implementation

[0017] Hereinafter, one embodiment will be described with reference to the accompanying drawings.

[0018] The structure of a control system for a four-wheel steering vehicle.

[0019] like Figure 1 As shown, the control unit 10 for a four-wheel steering vehicle includes a PU 12 and a storage device 14. The PU 12 is, for example, a processing unit that performs software processing, such as a CPU or GPU. The storage device 14 can be a non-volatile memory capable of electrical rewriting, or a storage medium such as a disk. The PU 12 performs various processes by executing programs stored in the storage device 14. In particular, a driving assistance program 14a is stored in the storage device 14. Driving assistance for the four-wheel steering vehicle is provided by executing the driving assistance program 14a through the PU 12.

[0020] The control device 10 refers to image data Di representing an external image captured by the camera 20. Additionally, the control device 10 refers to ranging point data Dmp output by the radar 22. The ranging point data Dmp is a signal generated based on the reception of reflected light when a laser beam is irradiated. The ranging point data Dmp is data that correlates information related to the distance up to the object reflecting the laser beam with the direction of laser irradiation. The control device 10 refers to position data Dgps output by the Global Positioning System (GPS 24). The control device 10 refers to the vehicle speed V of the four-wheel steering vehicle detected by the vehicle speed sensor 26. The control device 10 refers to the detection value Ssg detected by the sensor group 28. For convenience, the detection value Ssg is a value representing the sum of detection values ​​from multiple sensors. The detection value Ssg includes the detected values ​​of the front wheel tire angles (hereinafter referred to as front wheel steering angles), the detected values ​​of the rear wheel tire angles (hereinafter referred to as rear wheel steering angles), yaw rate, steering torque, etc. The steering torque is the torque input by the driver to the steering wheel. In addition, the detected value of the tire angle can also be calculated based on the cumulative value of the detected values ​​of the rotation angle of the motor that steers the wheel.

[0021] The drive unit 30 includes at least one of an internal combustion engine that serves as a thrust generating device for the vehicle and a rotary electric motor.

[0022] The brake actuator 32 is configured to provide braking force to the front and rear wheels of a four-wheel steering vehicle.

[0023] The front wheel steering control device 34 has an actuator that steers the front wheels of a four-wheel steering vehicle.

[0024] The rear-wheel steering control device 36 has an actuator that steers the rear wheels of a four-wheel steering vehicle.

[0025] Overview of Driver Assistance

[0026] exist Figure 2 This shows an overview of the processing related to driving assistance. This is achieved by executing driving assistance program 14a via PU12. Figure 2 The processing shown.

[0027] The situation determination process M10 determines the situation of a four-wheel steering vehicle based on image data Di, ranging point data Dmp, position data Dgps, vehicle speed V, and detection value Ssg as input signals. The situation determination process M10 includes determining whether there are obstacles, etc., ahead of the four-wheel steering vehicle's direction of travel. The situation determination process M10 includes predicting the risk of collision when obstacles, etc., are ahead of the four-wheel steering vehicle's direction of travel. The situation determination process M10 includes determining the likelihood of avoiding a collision when a collision risk is predicted.

[0028] The target track generation process M12 is a process that generates the target track for a four-wheel steering vehicle based on the conditions determined by the passage condition determination process M10.

[0029] The track tracking process M14 includes the setting of target values ​​for the state variables used to propel a four-wheel steering vehicle along a target trajectory. As an example, the target values ​​are the target vehicle slip angle β0* and the target yaw rate γ0*.

[0030] The target forward and backward G generation process M16 is the process of setting the target value of the acceleration in the forward and backward directions of a four-wheel steering vehicle.

[0031] Arbitration processing M18 is a process that arbitrates the output values ​​of trajectory tracking processing M14 and the output values ​​of target front and rear G generation processing M16.

[0032] The forward and backward motion control M20 is based on the output value of the arbitration process M18, which calculates the amount of operation used to control the forward and backward acceleration of the four-wheel steering vehicle.

[0033] Lateral motion control M22 is based on the target vehicle slip angle β* and target yaw rate γ* output by arbitration processing M18, and calculates the operating amounts for controlling the tire angles of the front and rear wheels of the four-wheel steering vehicle.

[0034] The operation signal generation and processing M24 processes the operation signals output by the drive unit 30, brake actuator 32, front wheel steering control device 34, and rear wheel steering control device 36 based on the aforementioned operation quantities as input variables.

[0035] Details of the lateral motion control M22

[0036] exist Figure 3 The steps of lateral motion control M22 and its associated operation signal generation and processing M24 are illustrated. This is achieved by PU12 repeatedly executing driving assistance program 14a, for example, at a predetermined cycle. Figure 3 The following describes a series of processes. Furthermore, the step numbers for each process are indicated below by numbers beginning with "S".

[0037] exist Figure 3 In the series of processes shown, PU12 first acquires the target vehicle slip angle β*, the target yaw rate γ*, the front wheel steering angle δf, the rear wheel steering angle δr detected by sensor group 28, and the vehicle speed V (S10). Based on the target vehicle slip angle β* and the target yaw rate γ* as input variables, PU12 sets the command front wheel steering angle δf* and the command rear wheel steering angle δr0* (S12).

[0038] exist Figure 4 The details of the S12 process are shown.

[0039] The commanded steering angle setting process M30 is a process that sets the commanded front wheel steering angle δf* and the commanded rear wheel steering angle base value δr1* based on the target vehicle slip angle β* and the target yaw rate γ* as input variables. Here, the commanded front wheel steering angle δf* is set based on the transfer function shown in equation (c1) below. In addition, the commanded rear wheel steering angle base value δr1* is set based on the transfer function shown in equation (c2) below.

[0040] δf*(s)={(Tfβ・s+1) / (Tβ・s+1)}・β*(s)+{Gfγ・(Tfγ・s+1) / (Tγ・s+1)}・γ*(s) …(c1)

[0041] δr1*(s)={(Trβ・s+1) / (Tβ・s+1)}・β*(s)+{Grγ・(Trγ・s+1) / (Tγ・s+1)}・γ*(s) …(c2)

[0042] In equations (c1) and (c2) above, Tfβ, Trβ, Tfγ, and Trγ are first-order lead time constants. Additionally, Tβ and Tγ are first-order lag time constants. Furthermore, Gfγ is the yaw rate gain of the front wheels, and Grγ is the yaw rate gain of the rear wheels.

[0043] Since the processing in S12 actually processes the variables of the discrete system, the transfer functions of equations (c1) and (c2) above are converted into the processing of the discrete system to determine the commanded front wheel steering angle δf* and the basic value of the commanded rear wheel steering angle δr1*. The denominator in the above transfer function is a first-order hysteresis filter. The numerator of the above transfer function represents the response determined according to the device model.

[0044] The delay processing M32 sets the commanded rear wheel steering angle δr0* by performing low-pass filtering and dead-time assignment processing on the base value δr1* of the commanded rear wheel steering angle, which is used as an input variable. The delay processing M32 is a countermeasure to the difference in response characteristics between the front wheel steering control device 34 and the rear wheel steering control device 36 of the four-wheel steering vehicle according to this embodiment. That is, in the four-wheel steering vehicle according to this embodiment, the responsiveness of the rear wheel steering control device 36 is sufficiently high compared to the responsiveness of the front wheel steering control device 34. Therefore, considering the response delay of the front wheel steering control device 34, the delay processing M32 is provided to synchronize the timing of the change in the commanded front wheel steering angle δf* reflecting the front wheel steering angle δf with the timing of the change in the commanded rear wheel steering angle δr0* reflecting the rear wheel steering angle δr.

[0045] Return to Figure 3 PU12 calculates the ideal yaw rate γa (S14) using the following equation (c3) based on the commanded front wheel steering angle δf* and commanded rear wheel steering angle δr0* as input variables.

[0046] γa=4・l・Kf・Kr・V・(δf*-δr0*) / {4・l^2・Kf・Kr-2・m・V^2・(lf・Kf-lr・Kr)} (c3)

[0047] This equation is derived using a two-wheel model of a four-wheel steering vehicle. In this two-wheel model, the first-order time derivatives of the yaw rate γ and the vehicle slip angle β are expressed by the yaw rate γ, the vehicle slip angle β, the front wheel steering angle δf, the rear wheel steering angle δr, and the vehicle speed V. Specifically, in this two-wheel model, the equation is derived by setting the first-order time derivatives of the yaw rate γ and the vehicle slip angle β to zero. Furthermore, in the above equation (c3), the wheelbase l, the front wheel lateral stiffness Kf, the rear wheel lateral stiffness Kr, the center of gravity distance between the front wheels lf, and the center of gravity distance between the rear wheels lr are used.

[0048] PU12 calculates the inferred yaw rate γe (S16) based on the front wheel steering angle δf and the rear wheel steering angle δr as input variables. In the processing of S16, the ideal yaw rate γa, the commanded front wheel steering angle δf*, and the commanded rear wheel steering angle δr0* in the above equation (c3) are replaced with the inferred yaw rate γe, the front wheel steering angle δf, and the rear wheel steering angle δr, respectively.

[0049] PU12 will substitute the value obtained by subtracting the inferred yaw rate γe from the ideal yaw rate γa into the deviation Δ (S18).

[0050] PU12 determines, based on the deviation Δ as an input variable, whether the four-wheel steering vehicle is moving in the opposite direction to the target lateral movement direction (S20). If it determines that the vehicle is moving in the opposite direction (S20: Yes), PU12 calculates the deviation Δfl by filtering the deviation Δ (S22). The filtering process uses a low-pass filter. The filtering process can also be a first-order hysteresis or second-order hysteresis filter.

[0051] PU12 calculates the correction amount Δrc (S24) of the commanded rear wheel steering angle δr0* based on the deviation Δfl as the input variable. In detail, PU12 substitutes the value obtained by multiplying the deviation Δfl by the proportional gain shown in the following equation (c4) into the correction amount Δrc.

[0052] [-1 / {1-m・V^2・(lf・Kf-lr・Kr) / 2・l^2・Kf・Kr}]・(V / l) …(c4)

[0053] The above formula represents the gain of the steering angle relative to the yaw rate during steady-state cornering in a two-wheel model of a four-wheel steering vehicle. PU12 calculates the proportional gain using the above formula (c4) based on the vehicle speed V as the input variable.

[0054] PU12 substitutes the value obtained by adding the correction amount Δrc to the commanded rear wheel steering angle δr0* into the commanded rear wheel steering angle δr* (S26).

[0055] PU12 substitutes the feedback control input, in which the front wheel steering angle δf is the control input and the target value of the commanded front wheel steering angle δf* is the control input, into the front wheel torque command value Trqf (S28). The front wheel torque command value Trqf is the command value for the torque of the motor provided by the front wheel steering control device 34.

[0056] PU12 substitutes the feedback control input, where the rear wheel steering angle δr is the control input and the target value of the commanded rear wheel steering angle δr* is the control input, into the rear wheel torque command value Trqr (S30). The rear wheel torque command value Trqr is the command value for the torque of the motor provided by the rear wheel steering control device 36.

[0057] PU12 outputs an operation signal MSf for the drive circuit of the motor of the front wheel steering control device 34 and an operation signal MSr for the drive circuit of the motor of the rear wheel steering control device 36 (S32).

[0058] On the other hand, if PU12 makes a negative determination in the process of S20, it substitutes the commanded rear wheel steering angle δr0* into the commanded rear wheel steering angle δr* (S34). If PU12 completes the process of S34, it moves to the process of S28.

[0059] In addition, PU12 temporarily terminates the process after completing S32. Figure 3 The following series of processes are shown. Additionally, the command steering angle setting process corresponds to process S12. The actual steering angle acquisition process corresponds to process S10. The ideal yaw rate calculation process corresponds to process S14. The inferred yaw rate calculation process corresponds to process S16. The deviation calculation process corresponds to process S18. The correction process corresponds to processes S22-S26. The vehicle speed acquisition process corresponds to process S10. The filtering process corresponds to process S22. The feedback process corresponds to processes S28 and S30. The decision process corresponds to process S20.

[0060] "The function and effects of this implementation method"

[0061] exist Figure 5 An example of driving assistance is shown in the image. Figure 5 The example shown illustrates a situation where a person, acting as an obstacle Oj, is positioned in front of the four-wheel steering vehicle Vc in its direction of travel. In this case, PU12 generates a target trajectory Tt within the drivable area that avoids the obstacle Oj. Figure 5 The example shown illustrates the generation of a target track Tt for a four-wheel steering vehicle Vc to turn right. PU12 enables the four-wheel steering vehicle Vc to turn by controlling the front wheels Wf and the rear wheels Wr in phase.

[0062] Here, in in-phase control, for example, in the case of a response delay in the front wheel Wf, there is concern that the yaw rate γ might become opposite to the target yaw rate γ* due to the rear wheel Wr steering being steered first. The deviation of the four-wheel steering vehicle's behavior from the desired behavior of the commanded front wheel steering angle δf* and the commanded rear wheel steering angle δr0* is determined based on the difference between the front wheel steering angle δf and the commanded front wheel steering angle δf*, and the difference between the rear wheel steering angle δr and the commanded rear wheel steering angle δr0*. However, this difference is difficult to handle directly. Therefore, PU12 quantifies the difference between the front wheel steering angle δf and the commanded front wheel steering angle δf*, and the difference between the rear wheel steering angle δr and the commanded rear wheel steering angle δr0*, using the deviation Δ between the ideal yaw rate γa and the inferred yaw rate γe. The deviation Δ is an appropriate parameter representing the behavior of the four-wheel steering vehicle. Then, PU12 corrects the commanded rear wheel steering angle δr0* based on the correction amount Δrc corresponding to the deviation Δ.

[0063] exist Figure 6 The upper side shows the case where no correction is made to the commanded rear wheel steering angle δr0* based on the correction amount Δrc. Figure 6On the upper side, the lateral position Lp of the four-wheel steering vehicle deviates significantly from the target lateral position Lp* specified according to the target track.

[0064] exist Figure 6 The lower part shows the case where the commanded rear wheel steering angle δr0* is corrected based on the correction amount Δrc. For example... Figure 6 As shown on the lower side, in this embodiment, the lateral position Lp of the four-wheel steering vehicle is displaced towards the target lateral position Lp*. Additionally, with... Figure 6 Compared to the upper side, the yaw angle φ will not deflect significantly to the opposite side.

[0065] Therefore, even if the response of the front wheel Wf is delayed in phase control as assumed above, the four-wheel steering vehicle Vc can still move away from the obstacle Oj.

[0066] Based on the above-described embodiment, the functions and effects described below can be further obtained.

[0067] (1) PU12 calculates the proportional gain used to calculate the correction amount Δrc based on the vehicle speed V as the input variable. Thus, a more appropriate proportional gain corresponding to the vehicle speed V can be calculated.

[0068] (2) The proportional gain used to calculate the correction amount Δrc based on the deviation Δfl is calculated using the steady-state turning formula expressed by equation (c4) above. This reduces the adaptation time of the proportional gain.

[0069] (3) PU12 replaces the proportional gain multiplied by the deviation Δ, while the proportional gain multiplies the deviation Δfl. This can suppress the influence of noise on the correction amount Δrc.

[0070] (4) PU12 uses a steady-state model obtained by setting the time derivatives of the vehicle slip angle and yaw rate in the two-wheel model of a four-wheel steering vehicle to zero to calculate the ideal yaw rate γa and the inferred yaw rate γe. Thus, the deviation Δ is the steady-state solution of the deviation between the ideal yaw rate γa and the inferred yaw rate γe. That is, the deviation Δ is the steady-state deviation resulting from maintaining the commanded front wheel steering angle δf*, front wheel steering angle δf, commanded rear wheel steering angle δr0*, and rear wheel steering angle δr at the current state. Therefore, based on the deviation Δ, it is possible to quickly and appropriately determine the extent to which the current state deviates from the desired vehicle behavior based on the commanded front wheel steering angle δf* and commanded rear wheel steering angle δr0*. Therefore, by using this deviation Δ, it is possible to quickly reduce the deviation from the desired vehicle behavior based on the commanded front wheel steering angle δf* and commanded rear wheel steering angle δr0*.

[0071] (5) PU12 corrects the commanded rear wheel steering angle δr0* only if the process of S20 makes a positive determination. This can minimize the possibility that the correction amount Δrc will become an interference factor in the feedback processing of S28 and S30.

[0072] Especially Figure 5 In the situation shown, even though a negative determination is made in the processing of S20, a correction is performed, which is concerned that the feedback processing may be interfered with even though the four-wheel steering maneuver of the vehicle Vc is moving away from the obstacle Oj. A correction is performed to suppress this movement away, even though the vehicle is moving away from the obstacle Oj.

[0073] (6) Instead of setting the deviation Δ as the difference between the ideal yaw rate γa and the detected yaw rate γ, it is set as the difference between the ideal yaw rate γa and the inferred yaw rate γe. In cases of strong deceleration, sharp turns, etc., of a four-wheel steering vehicle, which produce large sprung movements, the effect affects the yaw rate γ detected by the yaw rate sensor belonging to sensor group 28, causing it to deviate from the actual yaw rate.

[0074] exist Figure 7 An example is shown where the yaw rate γ becomes unstable. When the detected yaw rate γ produces an error, the judgment accuracy of the S20 process performed based on the deviation Δ is low when using the detected yaw rate γ to calculate the deviation Δ, and the correction amount Δrc will not be an appropriate value.

[0075] In contrast, by setting the deviation Δ as the difference between the ideal yaw rate γa and the inferred yaw rate γe, the state of a four-wheel steering vehicle can be accurately quantified by the deviation Δ.

[0076] (7) If in Figure 6 As the upper section represents the shifts in the front wheel steering angle δf, the commanded front wheel steering angle δf*, the rear wheel steering angle δr, and the commanded rear wheel steering angle δr*, in this embodiment, the responsiveness of the front wheel steering control device 34 is lower than that of the rear wheel steering control device 36. Therefore, PU12 uses the commanded rear wheel steering angle δr0* as the correction target based on the correction amount Δrc. This allows for a rapid reflection of the effect of the correction based on the correction amount Δrc.

[0077] (8) If in Figure 6As the upper section represents the shifts in the front wheel steering angle δf, the commanded front wheel steering angle δf*, the rear wheel steering angle δr, and the commanded rear wheel steering angle δr*, in this embodiment, the responsiveness of the front wheel steering control device 34 is lower than that of the rear wheel steering control device 36. Therefore, PU12 generates the commanded rear wheel steering angle δr0* by delaying the phase of the commanded rear wheel steering angle base value δr1* through delay processing M32. This compensates for the lower responsiveness of the front wheel steering control device 34 compared to the rear wheel steering control device 36. In other words, the relationship between the front wheel steering angle δf and the rear wheel steering angle δr can be matched with the relationship between the commanded front wheel steering angle δf* and the commanded rear wheel steering angle base value δr1*.

[0078] <Other Implementation Methods>

[0079] Furthermore, this embodiment can be modified as follows. This embodiment and the following modifications can be combined with each other within the scope of technical inconsistency.

[0080] "Command steering angle setting processing"

[0081] • Command steering angle setting processing is not mandatory Figure 4 The illustrated processing. For example, filtering processing may not be included in the command steering angle setting processing M30. Alternatively, for example, if the responsiveness of the actuator that steers the front wheels is higher than that of the actuator that steers the rear wheels, delay processing M32 may be applied to the command value of the front wheel steering angle δf.

[0082] • The input variables for the command steering angle setting process do not necessarily have to be the target yaw rate γ* and the target vehicle slip angle β*. The input variables for the command steering angle setting process can also be, for example, the torque input by the driver to the steering wheel, i.e., the steering torque, and the vehicle speed V.

[0083] "Ideal yaw rate calculation and processing, inferred yaw rate calculation and processing"

[0084] • The ideal yaw rate calculation process does not necessarily have to be a steady-state model that sets the first-order time derivative of the yaw rate γ and the first-order time derivative of the vehicle slip angle β to zero. For example, the yaw rate γ can also be calculated without ignoring the first-order time derivative. In this case, the inferred yaw rate calculation process is the same.

[0085] "Proportional elements"

[0086] • The gain of the proportional element does not necessarily have to be a value calculated using the formula described above, which is determined based on the steady-state turning formula. For example, it can also be a value obtained by performing a mapping operation using mapping data generated using the formula described above. Here, the mapping data is data where the vehicle speed V is the input variable and the gain is the output variable.

[0087] Here, mapping data refers to discrete values ​​of input variables and sets of output variable values ​​corresponding to those input variables. Furthermore, mapping operations are performed as long as the output variable of the corresponding mapping data is the result when any one of the input variable values ​​matches any one of the input variables in the mapping data. Alternatively, mapping operations are performed as the result when none of the input variable values ​​match any one of the input variables in the mapping data, obtained by interpolating the values ​​of the multiple output variables contained in the mapping data. Alternatively, instead of this process, mapping operations can be performed where, when none of the input variable values ​​match any one of the input variables in the mapping data, the output variable of the mapping data corresponding to the closest value among the multiple input variable values ​​contained in the mapping data is the result.

[0088] "Filtering"

[0089] • Filtering does not necessarily have to be a process where the deviation Δ is the input variable. Filtering can also be a process where the value obtained by multiplying the deviation Δ by the proportional gain is the input variable.

[0090] • Filtering is not always necessary for noise removal. For example, when a first-order lead model is used in both the ideal yaw rate calculation and the inferred yaw rate calculation, it is preferable to use a filter of first order or higher. Here, a first-order lead model, as described in the "Ideal Yaw Rate Calculation and Inferred Yaw Rate Calculation" section, is equivalent to not setting the first-order time derivative of the yaw rate γ and the first-order time derivative of the vehicle slip angle β to zero.

[0091] "Correction amount"

[0092] • The correction amount Δrc does not necessarily have to be the output value of the proportional element. For example, the correction amount Δrc can also be the deviation Δfl, which is the sum of the output values ​​of the proportional element and the derivative element of the input variable. Alternatively, the correction amount Δrc can also be the deviation Δfl, which is the sum of the output values ​​of the proportional element and the integral element of the input variable. Or, the correction amount Δrc can also be the deviation Δfl, which is the sum of the output values ​​of the proportional element, the integral element, and the derivative element of the input variable.

[0093] • The object of correction based on the correction amount does not necessarily have to be the commanded rear wheel steering angle δr0*. For example, if the responsiveness of the actuator that steers the front wheels is higher than that of the actuator that steers the rear wheels, the object of correction can also be the commanded front wheel steering angle.

[0094] • The object of correction based on the correction amount does not necessarily have to be either the commanded rear wheel steering angle or the commanded front wheel steering angle. The object of correction based on the correction amount can be, for example, both the commanded front wheel steering angle and the commanded rear wheel steering angle.

[0095] • It is not necessary to calculate the correction solely based on the deviation Δ between the ideal yaw rate γa and the inferred yaw rate γe. For example, the deviation between the ideal body slip angle βa and the inferred body slip angle βe can also be considered in the calculation. Here, for example, the ideal body slip angle βa and the inferred body slip angle βe can be calculated using the formula obtained through the derivation process of the model, which is used to calculate the ideal yaw rate γa and the inferred yaw rate γe.

[0096] "Correction Processing"

[0097] • It is not necessary to make a positive determination in the processing of S20 before correcting the commanded rear wheel steering angle δr0*. For example, it is also possible to... Figure 3 The illustrated process deletes S20 and S34.

[0098] • For correction processing, it is not necessary to include the logic for performing in-phase control to avoid obstacles in the control device.

[0099] "Judgment and processing"

[0100] • It can also replace the deviation Δ and make the input variable for the decision processing the deviation Δfl.

[0101] "Control device"

[0102] • The control device 10 does not necessarily have to be housed in a single housing. For example, the control device can also be configured by arranging multiple control units located at different positions in a four-wheel steering vehicle so that they can communicate with each other.

[0103] • The control device is not limited to a device that performs various processes via a PU. For example, it may include dedicated hardware circuits such as ASICs, which perform at least a portion of the processes performed in the above embodiments. That is, the control device may also include any of the following processing circuits (a) to (c): (a) A processing circuit including a processing device that performs all of the above processes according to a program, and a program storage device such as a storage device for storing the program. (b) A processing circuit including a processing device that performs a portion of the above processes according to a program, a program storage device, and dedicated hardware circuits that perform the remaining processes. (c) A processing circuit including dedicated hardware circuits that perform all of the above processes. Here, there may be multiple software execution devices and dedicated hardware circuits including processing devices and program storage devices.

[0104] "The entity that implements control"

[0105] ·implement Figure 2 The main body of the processing shown does not necessarily have to be a control device mounted on a four-wheel steering vehicle. For example, the status determination processing M10 and the target track generation processing M12 and S20 can also be performed by a mobile terminal held by the driver.

Claims

1. A control device for a four-wheel steering vehicle, wherein, It consists of the following steps: executing the steering angle setting command, acquiring the actual steering angle, calculating the ideal yaw rate, calculating the inferred yaw rate, calculating the deviation, and correcting the deviation. The above-described steering angle setting process involves setting the steering angles of the front and rear wheels. The aforementioned front wheel steering angle is the commanded value for the front wheel steering angle, and the aforementioned rear wheel steering angle is the commanded value for the rear wheel steering angle. The above-described actual steering angle acquisition process involves obtaining the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle. The above-described ideal yaw rate calculation process is based on the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle as input variables. The above-described inferred yaw rate calculation process is based on the aforementioned front wheel steering angle and rear wheel steering angle as input variables. The above deviation calculation process involves calculating the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process is based on the aforementioned deviation as an input variable, and corrects at least one of the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle.

2. The control device for a four-wheel steering vehicle according to claim 1, wherein, The above correction process includes calculating the correction amount based on the output value of the scale element, which is based on the value of the aforementioned deviation as an input variable.

3. The control device for a four-wheel steering vehicle according to claim 2, wherein, This is configured to perform vehicle speed acquisition processing. The above-described vehicle speed acquisition process describes the process of acquiring vehicle speed. The above correction process includes a process that variably sets the gain of the above proportional element based on the vehicle speed, which is an input variable.

4. The control device for a four-wheel steering vehicle according to claim 2, wherein, The gain of the aforementioned proportional element is set using the steady-state turning formula from the above-described four-wheel steering vehicle model.

5. The control device for a four-wheel steering vehicle according to claim 2, wherein, In addition to the aforementioned proportional element processing, the calculation of the correction amount in the above correction process also includes filtering processing.

6. The control device for a four-wheel steering vehicle according to claim 1, wherein, The above-described ideal yaw rate calculation process and the above-described inferred yaw rate calculation process include the use of a model to calculate the output value. This model is a formula with the front wheel steering angle and the rear wheel steering angle as input variables and yaw rate as the output variable. The above model is obtained by setting the time derivative value to zero in the formula that uses the yaw rate, the vehicle slip angle, the front wheel steering angle and the rear wheel steering angle to represent the first time derivative value of the yaw rate and the first time derivative value of the vehicle slip angle.

7. The control device for a four-wheel steering vehicle according to claim 1, wherein, It consists of execution feedback processing and decision processing. The aforementioned feedback processing includes: processing for operating the front wheel steering control device by feedback control using the aforementioned front wheel steering angle as the control variable and the aforementioned commanded front wheel steering angle as the target value of the control variable; and processing for operating the rear wheel steering control device by feedback control using the aforementioned rear wheel steering angle as the control variable and the aforementioned commanded rear wheel steering angle as the target value of the control variable. The above-described determination process is based on the aforementioned deviation as an input variable, and determines whether the four-wheel steering vehicle is moving in the opposite direction to the target driving direction. The above correction process is a process that corrects at least one of the above-commanded front wheel steering angle and the above-commanded rear wheel steering angle when it is determined that the movement is in the opposite direction.

8. The control device for a four-wheel steering vehicle according to claim 1, wherein, The above correction process corrects the rear wheel steering angle of the aforementioned command.

9. The control device for a four-wheel steering vehicle according to claim 8, wherein, The aforementioned command steering angle setting process includes: setting the commanded front wheel steering angle based on input variables; setting the commanded rear wheel steering angle base value based on the input variables; and setting the commanded rear wheel steering angle by delaying the phase of the commanded rear wheel steering angle base value.

10. A control method for a four-wheel steering vehicle, wherein, It includes the execution of command steering angle setting processing, actual steering angle acquisition processing, ideal yaw rate calculation processing, inferred yaw rate calculation processing, deviation calculation processing, and correction processing. The above-described steering angle setting process involves setting the steering angles of the front and rear wheels. The aforementioned front wheel steering angle is the commanded value for the front wheel steering angle, and the aforementioned rear wheel steering angle is the commanded value for the rear wheel steering angle. The above-described actual steering angle acquisition process involves obtaining the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle. The above-described ideal yaw rate calculation process is based on the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle as input variables. The above-described inferred yaw rate calculation process is based on the aforementioned front wheel steering angle and rear wheel steering angle as input variables. The above deviation calculation process involves calculating the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process is based on the aforementioned deviation as an input variable, and corrects at least one of the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle.

11. A control program for a four-wheel steering vehicle, wherein, It has instructions that cause the computer to perform the following processes: setting the instruction steering angle, acquiring the actual steering angle, calculating the ideal yaw rate, calculating the inferred yaw rate, calculating the deviation, and making corrections. The above-described steering angle setting process involves setting the steering angles of the front and rear wheels. The aforementioned front wheel steering angle is the commanded value for the front wheel steering angle, and the aforementioned rear wheel steering angle is the commanded value for the rear wheel steering angle. The above-described actual steering angle acquisition process involves obtaining the aforementioned front wheel steering angle and the aforementioned rear wheel steering angle. The above-described ideal yaw rate calculation process is based on the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle as input variables. The above-described inferred yaw rate calculation process is based on the aforementioned front wheel steering angle and rear wheel steering angle as input variables. The above deviation calculation process involves calculating the deviation between the ideal yaw rate and the inferred yaw rate. The above correction process is based on the aforementioned deviation as an input variable, and corrects at least one of the aforementioned commanded front wheel steering angle and the aforementioned commanded rear wheel steering angle.

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