Steering control device and electric power steering device

Abstract

The present application relates to a steering control device and an electric power steering device. A steering control device that controls steering of a vehicle that automatically drives or is assisted in driving includes: a reference steering angle operation section that operates a reference steering angle of the vehicle based on a target steering angle of the vehicle and a vehicle speed; and a compensation section that determines whether a deviation between the operated reference steering angle and the target steering angle becomes a prescribed value or more, and compensates the reference steering angle in a manner in which the operated reference steering angle follows the target steering angle in a case where it is determined that the deviation becomes the prescribed value or more.

Description

Technical Field

[0001] This invention relates to a steering control device that compensates for friction in the steering mechanism to control steering during autonomous or driver-assisted driving of a vehicle, thereby preventing drastic fluctuations in torque, and to an electric power steering device equipped with such a steering control device. Background Technology

[0002] As such a steering control device, a steering control device that compensates for the friction of the steering mechanism during vehicle driving assistance has been proposed (see Japanese Patent Application Publication No. 2005-343302).

[0003] However, according to the aforementioned Japanese Patent Application Publication No. 2005-343302, the following technical problem exists: when the direction of increase or decrease of the target lateral acceleration switches from increase to decrease or from decrease to increase, the requested torque relative to the target lateral acceleration fluctuates sharply with a lag, which may have an adverse effect on the steering feel. Summary of the Invention

[0004] The present invention was made in view of the above-mentioned technical problems, and its objective is to provide a steering control device and an electric power steering device having such a steering control device, which can suppress sharp fluctuations in the requested torque even when the direction of increase or decrease of the target lateral acceleration switches from increase to decrease or from decrease to increase in a vehicle performing autonomous driving or driving assistance.

[0005] To address the aforementioned issues, one aspect of the steering control device of the present invention is a steering control device that controls the steering of a vehicle performing autonomous driving or driver assistance, comprising: a reference rudder angle calculation unit that calculates a reference rudder angle of the vehicle based on a target rudder angle and the vehicle speed; and a compensation unit that determines whether the deviation between the calculated reference rudder angle and the target rudder angle is greater than or equal to a predetermined value, and if the deviation is determined to be greater than or equal to the predetermined value, compensates the calculated reference rudder angle by having the calculated reference rudder angle follow the target rudder angle.

[0006] To address the aforementioned issues, one embodiment of the electric power steering device of the present invention comprises: one embodiment of the steering control device of the present invention described above; and an electric actuator, wherein the steering control device controls the requested torque based on the compensated reference rudder angle.

[0007] According to one embodiment of the steering control device of the present invention, a reference steering angle of the vehicle is calculated by a reference steering angle calculation unit based on a target steering angle corresponding to the direction in which the vehicle should travel via autonomous driving or driver assistance and the vehicle speed. Next, the calculated reference steering angle (θ) is first determined by a compensation unit. tWhether the deviation between the target rudder angle (θ) and the target rudder angle (θ) exceeds a specified value (Δ), if it is determined that the deviation exceeds the specified value (Δ), then the calculated reference rudder angle (θ) is used as the result of compensation. t The reference rudder angle (θ) follows the target rudder angle. That is, in this case, through compensation, the reference rudder angle follows the target rudder angle (θ) with a separation less than a specified value (Δ). As a result, even when the direction of increase or decrease in the target lateral acceleration switches from increasing to decreasing or from decreasing to increasing, the effect of the compensated reference rudder angle (θ) can be suppressed. t The requested torque fluctuates sharply.

[0008] According to one embodiment of the electric power steering device of the present invention, which includes the steering control device of the present invention described above, it is possible to suppress sharp fluctuations in requested torque during automatic driving and driving assistance.

[0009] The effects achieved by the invention are further clarified by the following description of the embodiments of the invention. Attached Figure Description

[0010] Hereinafter, with reference to the accompanying drawings, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described, wherein the same reference numerals denote the same elements, wherein:

[0011] Figure 1 This is a block diagram showing the overall configuration of the electric power steering system of the vehicle according to the first embodiment.

[0012] Figure 2 It means Figure 1 The diagram shows the configuration of the driver assistance control unit in the electric power steering system.

[0013] Figure 3 It means Figure 2 The diagram shows the configuration of the friction compensation unit in the driver assistance control unit.

[0014] Figure 4 This is a characteristic graph showing the relationship between vehicle speed V and friction torque Tt in the first embodiment.

[0015] Figure 5 This is a flowchart illustrating the method for calculating the reference rudder angle in the steering control action of the first embodiment (in other words, the method for making the reference rudder angle appropriately follow the target rudder angle).

[0016] Figure 6 This indicates that in the first embodiment, the reference rudder angle θ is set during the steering control action. t Characteristic diagram of the case where the target rudder angle θ is followed.

[0017] Figure 7This is a characteristic diagram showing the friction compensation control amount Tc set for the target rudder angle θ during the steering control action in the first embodiment.

[0018] Figure 8A These are characteristic diagrams showing the time-varying target rudder angle and steering angle under the condition of no friction compensation, which are comparative examples of the first embodiment.

[0019] Figure 8B These are characteristic graphs showing the time-varying changes of the target rudder angle and steering angle under friction compensation according to the first embodiment.

[0020] Figure 9 This is a characteristic diagram showing an example of the trajectory of a vehicle turning and moving forward in the X-Y plane for simulation purposes in the first embodiment.

[0021] Figure 10A These respectively indicate that they were used as Figure 9 A simulation result of one example, showing the time variation of the steering angle under the first embodiment with and without friction compensation.

[0022] Figure 10B These respectively indicate that they were used as Figure 9 A partial enlarged view of the characteristic graph of the time variation of the steering angle under the first embodiment with and without friction compensation, representing a simulation result of an example.

[0023] Figure 11A It means as used Figure 9 A simulation result of one example, a characteristic graph of the time variation of friction generated in the steering mechanism under friction compensation according to the first embodiment.

[0024] Figure 11B It means as used Figure 9 A simulation result of an example, showing the time variation characteristic of the friction compensation control quantity Tcf under the condition of friction compensation according to the first embodiment.

[0025] Figure 12 It is the same as in the second embodiment. Figure 7 Feature diagrams with the same main content.

[0026] Figure 13 It is the same as in the second embodiment. Figure 5 Flowcharts with the same main content.

[0027] Figure 14 This is a flowchart illustrating an example of the calculation and processing of the friction compensation control quantity Tc in the second embodiment. Detailed Implementation

[0028] <First Implementation>

[0029] Reference Figures 1 to 11A , Figure 11B The first embodiment of the electric power steering device with a steering control device of the present invention will be described. The electric power steering device in the first embodiment is based on automatic driving or driving assistance.

[0030] like Figure 1 As shown, the electric power steering system is configured as follows: it includes a steering wheel 11, a torque sensor 15, a steering mechanism 20, an electric actuator 22, and an ECU (Electronic Control Unit) 80 with an operation stability control unit 82 and a driver assistance control unit 84.

[0031] The steering wheel 11 is turned by the driver when the driver performs steering operations or in a hands-free state during driving assistance or automatic driving, and outputs the steering angle and steering angular velocity to the ECU 80. The torque sensor 15 is a sensor that measures the torque applied to the steering wheel 11 when steering operations or turning actions are performed through the steering wheel 11, and the torque sensor value as the measurement result is output to the ECU 80.

[0032] The electric actuator 22 has an auxiliary motor or a rotation motor that rotates according to a torque input from the ECU 80. The steering mechanism 20 has a steering rack and is configured to perform steering actions in autonomous driving or driver assistance by torque applied from the electric actuator 22 and the steering wheel 11.

[0033] The ECU 80 includes a controller or processor, various memories, etc., and internally incorporates an operational stability control unit 82 and a driver assistance control unit 84, either in hardware or software. The ECU 80 is input with a target steering angle θ, vehicle speed V, and other vehicle information indicating various vehicle conditions or states (e.g., lateral acceleration, yaw rate, etc.). The operational stability control unit 82 is configured to perform existing operational stability control based on the information input to the ECU 80 as described above. The driver assistance control unit 84 is configured to take the target steering angle θ, vehicle speed V, and other vehicle information as input, calculate and output a compensated target torque based on a reference steering angle compensated in a manner that follows the target steering angle, as a torque input to the electric actuator 22 (i.e., a signal indicating a requested torque). Here, refer to... Figure 2 The driver assistance control unit 84 is described in detail.

[0034] like Figure 2As shown, the driver assistance control unit 84 includes a target torque calculation unit 86, a friction compensation unit 88, and an adder 90. The driver assistance control unit 84 is input to a target steering angle θ required for driving in the center of a sequentially set road using automatic driving or driver assistance, a vehicle speed V measured by a vehicle speed sensor, and other vehicle information, and outputs a target torque T required to move the steering rack of the steering mechanism 20. The driver assistance control unit 84 is configured to include, in addition to the existing target torque calculation unit 86, the friction compensation unit 88 of this embodiment. The friction compensation unit 88 is input to the target steering angle θ and the vehicle speed V, and the friction compensation control quantity Tcf (i.e., the friction compensation control quantity that has undergone low-pass filtering as described below) is added to the target torque T using the adder 90, which serves as an example of an "addition operation output unit," to obtain the compensated target torque Tm.

[0035] It should be noted that, in Figure 2 The addition operation is performed after the target torque calculation unit 86, but the location of the addition operation is arbitrary. Alternatively, the friction compensation control quantity Tc (without low-pass filtering) can be added to the target torque T instead of the friction compensation control quantity Tcf to obtain the compensated target torque Tm. Thus, in this embodiment, the driving assistance control unit 84, or particularly the friction compensation unit 88 therein, constitutes an example of a "steering control device". Here, refer to 3- Figure 7 The friction compensation unit 88 will be explained in further detail.

[0036] exist Figure 3 In this configuration, the friction compensation unit 88 is equipped with: a friction torque calculation unit 881, which calculates the friction torque Tt based on the vehicle speed V; and a reference rudder angle calculation unit 882, which calculates the reference rudder angle θ based on the friction torque Tt and the target rudder angle θ. t Subtractor 883 subtracts the reference rudder angle θ from the target rudder angle θ. t (that is, for -θ) t (Addition operation with +θ); Friction compensation control quantity calculation unit 884 calculates friction compensation control quantity Tc based on the subtraction result; and low-pass filter 885 performs low-pass filtering processing on the friction compensation control quantity Tc and outputs friction compensation control quantity Tcf.

[0037] Friction compensation unit 88 first calculates or sets the appropriate adjustment for steering mechanism 20 (see reference) based on the vehicle speed V input from the vehicle speed sensor. Figure 1 The compensated frictional torque Tt. Here, refer to... Figure 4 A preferred example of the calculation (or setting) method for the friction torque Tt will be explained. In the friction compensation unit 88, it is preferable to use, as shown in the example... Figure 4 The mapping diagram shown is used to calculate the friction torque Tt. Figure 4The diagram shows the curve of friction torque Tt when the horizontal axis is set to vehicle speed V and the vertical axis is set to friction torque Tt. This mapping is maintained in the memory of the ECU80 and updated as appropriate. It should be noted that the friction torque Tt determined here is precisely a physical quantity that only has magnitude; its compensation direction (i.e., sign) is determined in a later stage.

[0038] like Figure 4 As shown, when using this mapping, a smaller friction torque Tt is set at a higher vehicle speed (Vsmall) compared to a lower vehicle speed (Vsmall). This is because, from the perspective of improving stability, and due to the steering mechanism 20 (see reference 20) at high speeds... Figure 1 Friction decreases due to the reverse input vibration, therefore the compensation friction is relatively small. Furthermore, from a stability perspective, it can also be done as follows: Figure 4 Therefore, when the vehicle speed V is 0, the friction torque Tt is set to 0.

[0039] It should be noted that, in addition to vehicle speed V, the target rudder angle θ and steering torque (e.g., from...) can also be used in friction torque calculations. Figure 1 (The torque sensor value output by torque sensor 15). At this time, when the target rudder angle θ is large, from the perspective of improving stability, it is advisable to reduce the friction that should be compensated. Furthermore, to prevent a deterioration in steering feel, it is advisable to reduce the friction torque Tt when the steering torque is large.

[0040] Again, in Figure 3 In the friction compensation unit 88, following the above-mentioned calculation of friction torque Tt, the reference rudder angle θ is calculated or set by the reference rudder angle calculation unit 882. t Here, refer to Figure 5 Flowcharts and Figure 6 The characteristic diagram illustrates a preferred example of the reference rudder angle calculation method in the reference rudder angle calculation unit 882. It should be noted that... Figure 5 The processing routine shown can be executed in each specified operation cycle (e.g., 5 msec). Furthermore, in Figure 6 For ease of explanation, the reference rudder angle θ is used in the following text. t In the definition of positive and negative signs, the direction of rotation to the left from the neutral position (zero point) is set to positive.

[0041] exist Figure 5 First, determine the reference rudder angle θ. t Whether it has been initialized, that is, whether this cycle is the first cycle (step S100).

[0042] Here, at the reference rudder angle θ tIf it has not been initialized (step S100: No), proceed to step S102; otherwise, if this cycle is the first cycle, i.e. at the reference rudder angle θ, proceed to step S102. t If the previous cycle was initialized (step 100: Yes), proceed directly to step S104.

[0043] In step S102, the reference rudder angle θ is... t The initial value is set to the target rudder angle θ (the value for this cycle, the same below). That is, it is set to θ. t =θ. It should be noted that the reference rudder angle θ t The initial value can also be zero. When step S102 ends, proceed to step S104.

[0044] In step S104, the upper limit value of the deviation Δ is calculated. This upper limit value of the deviation Δ is obtained through the reference rudder angle θ of this embodiment. t Here's an example of a "prescribed value" used to determine the magnitude of the deviation from the target rudder angle θ. The upper limit of the deviation Δ is calculated using the friction torque Tt and gain K as described above, expressed as Δ = Tt / K. The gain K can be any fixed value determined considering steering feel and rudder angle following performance. It should be noted that Tt and K are positive values, therefore the upper limit of the deviation Δ is positive.

[0045] Next, in step S106, the target rudder angle θ, the upper limit of deviation Δ calculated in step S104 above, and the current reference rudder angle θ are determined. t Is it θ > θ? t The relationship between θ and Δ. That is, determining the relationship between θ and θ. t The deviation between (θ-θ) t Whether θ is greater than the upper limit of the deviation Δ, in other words, determine whether θ is greater than or equal to θ. t The deviation between (θ-θ) t Is it below the upper limit of the deviation Δ? As a result of this determination, when θ > θ t In the case of +Δ (step S106: yes), proceed to step S108; otherwise, in the case of θ≤θ t If +Δ is true (step S106: No), proceed to step S110.

[0046] In step S108, using the target rudder angle θ and the upper limit of deviation Δ calculated in step S104 above, the deviation is determined by θ. t The formula = θ - Δ will be used to calculate the reference rudder angle θ. t Change to the new value. That is, subtract the reference rudder angle θ from the target rudder angle θ. t The obtained deviation Δθ(=θ-θ) t When Δθ > Δ, the reference rudder angle θ t Change (update) to θt =θ-Δ.

[0047] On the other hand, in step S110, the target rudder angle θ (the value of this cycle), the upper limit of deviation Δ calculated in step S104 above, and the current reference rudder angle θ are determined. t Is θ < θ t The relationship between -Δ. That is, determining the relationship between θ and θ. t The deviation between (θ-θ) t Whether θ is less than the upper limit of the deviation - Δ, in other words, determining whether θ is less than or equal to θ'. t The deviation between (θ-θ) t Is it above the upper limit of deviation -Δ? The result of this determination is θ < θ t If -Δ is true (step S110: Yes), proceed to step S112.

[0048] In step S112, using the target rudder angle θ and the upper limit of deviation Δ calculated in step S104 above, the deviation is determined by θ. t The formula = θ + Δ will give the reference rudder angle θ t Change to the new value. That is, subtract the reference rudder angle θ from the target rudder angle θ. t The obtained deviation Δθ(=θ-θ) t When Δθ < -Δ, the reference rudder angle θ t Change (update) to θ t =θ + Δ. It should be noted that in step S110 above, θ ≥ θ. t In the case of -Δ (step 110: No), the processing of this cycle ends directly. Therefore, in this case, the current reference rudder angle θ is maintained. t Without making any changes. That is, subtracting the reference rudder angle θ from the target rudder angle θ. t The obtained deviation Δθ(=θ-θ) t When -Δ ≤ Δθ ≤ Δ, maintain the reference rudder angle θ. t Instead of making changes.

[0049] Figure 6 The scheme of representing the change of the target rudder angle θ through time series and the reference rudder angle θ t A diagram illustrating the relationship between the changing schemes. Figure 6 In the target rudder angle θ change scheme, the steering wheel 11 is turned left until time t1, and then turned right from time t1 onwards. Correspondingly, the reference rudder angle θ t Become θ>θ t The +Δ relationship continues until time t1, therefore, with θ t The relationship = θ - Δ is changed (refer to...) Figure 5Step S108). Furthermore, from time t1 to time t2, the reference rudder angle θ t Become θ≤θ t +Δ and θ≥θ t The relationship is -Δ, therefore the reference rudder angle θ is maintained. t Without making changes (see reference) Figure 5 Step S110: No). Furthermore, after time t2, the reference rudder angle θ t Become θ < θ t The relationship is -Δ, therefore, with θ t The relationship = θ + Δ is changed (refer to...) Figure 5 Step S112).

[0050] Again, in Figure 3 In the friction compensation control quantity calculation unit 884, the aforementioned reference rudder angle θ is then used. t The calculation is based on subtracting the reference rudder angle θ from the target rudder angle θ. t The friction compensation control quantity Tc is calculated or set using the subtraction result obtained through subtractor 883. In the definition of the positive and negative signs of the friction compensation control quantity Tc, the direction of the left-handed torque is set to positive.

[0051] Using the target rudder angle θ and the reference rudder angle θ calculated as described above. t And the gain K (=Tt / Δ), calculated using the formula Tc=K·Δθ, i.e. Tc=K(θ-θ t The friction compensation control quantity Tc is calculated using the formula. It should be noted that the gain K used here is the same as the gain K used in the aforementioned base rudder angle calculation (see [reference]). Figure 6 Step S104).

[0052] Here, refer to Figure 7 A preferred example of the calculation method for the friction compensation control quantity Tc in the friction compensation control quantity calculation unit 884 will be described. Figure 7 This is an explanatory diagram of the characteristics of the friction compensation control quantity Tc calculated as described above. Figure 7 In this model, the horizontal axis is set as the target rudder angle θ, and the vertical axis is set as the friction compensation control variable Tc. Figure 7 In the example, the cases where the friction torque Tt is Tt1 and Tt2 (< Tt1) calculated as described above are shown. That is, for example, the cases where the friction torque Tt1 is in the low-speed domain V1 or the medium-speed domain V2 and the cases where the friction torque Tt2 is in the high-speed domain V3 are shown. Furthermore, in... Figure 7 For ease of understanding, in either Tt1 or Tt2, a reference rudder angle θ is also assumed for convenience. tThe same, and does not change with variations in the target rudder angle θ. It should be noted that at the reference rudder angle θ... t In the event of changes, the corresponding curve is plotted only with the new reference rudder angle θ. t It moves parallel to the horizontal axis with the center as the center.

[0053] like Figure 7 As shown, the upper limit of deviation Δ is Δ = Tt / K. Therefore, the larger the friction torque Tt, the larger the upper limit of deviation Δ (for example, the upper limit of deviation Δ1 at Tt1 is larger than the upper limit of deviation Δ2 at Tt2). Furthermore, within the range of -Δ ≤ Δθ ≤ Δ, the reference rudder angle θ is maintained. t Without making any changes, according to Tc = K·Δθ, that is, Tc = K·(θ-θ) t The magnitude of the friction compensation control variable Tc increases proportionally to Δθ. Furthermore, within the range of Δθ > Δ and Δθ < -Δ, the reference rudder angle θ... t As described above, the magnitude of Δθ becomes a constant Δ, therefore, according to Tc=K·Δθ and Δ=Tt / K, the magnitude of the friction compensation control quantity Tc becomes a constant value corresponding to the magnitude of the friction torque Tt.

[0054] Again, in Figure 3 In the low-pass filter 885, following the aforementioned calculation of the friction compensation control quantity Tc, it is preferable to filter the friction compensation control quantity Tc using a low-pass filter. Here, the notation Tcf is used to denote the filtered friction compensation control quantity. The low-pass filter can be, for example, a first-order low-pass filter, or other forms (e.g., the order can be increased).

[0055] Tcf=1 / (fc·s+1)·Tc

[0056] Here, fc is the cutoff frequency. Ideally, fc should be a variable value to take into account steering feel and rudder angle vibration.

[0057] Thus, as Figure 2 As shown, the filter-processed friction compensation control quantity Tcf output from the friction compensation unit 88 and the target torque T output from the target torque calculation unit 86 are added by the adder 90. Then, the compensated target torque Tm output from the driving assistance control unit 84 is supplied to the steering rack of the steering mechanism 20 by the auxiliary motor of the electric actuator 22.

[0058] As referenced above Figures 1 to 7 As explained in detail, according to the first embodiment, in the friction compensation unit 88, an optimal magnitude / direction friction compensation control amount (Tc or Tcf) can be generated based on the vehicle speed V and the target rudder angle θ to compensate for the friction in the steering mechanism 20 (see reference). Figure 1The friction generated in the process. Therefore, the following performance of the steering angle can be improved relative to all target rudder angles θ, even with slight changes. In particular, such as... Figure 5 As shown, based on the target rudder angle θ and the reference rudder angle θ t The deviation causes the reference rudder angle θ t Appropriately change (in other words, make the reference rudder angle θ) t By appropriately following the target rudder angle θ, a friction compensation control quantity that is smooth, vibration-free, and closely approximates the actual friction characteristics can be generated. Furthermore, such as... Figure 5 As shown, based on the target rudder angle θ and the reference rudder angle θ t The deviation causes the reference rudder angle θ t By making appropriate changes, friction can be compensated at any turning position, not just in the neutral position (target rudder angle θ = 0).

[0059] Next, refer to Figure 8A , Figures 8B to 11A , Figure 11B Two simulation results illustrating the effects described above in the first embodiment will be explained. Hereinafter, friction compensation unit 88 (see reference 1) will be described with friction compensation (this embodiment) and without friction compensation (comparative example). Figure 2 The presence or absence of ).

[0060] Figure 8A , Figure 8B The first simulation is shown. Figure 8A , Figure 8B In the first simulation, friction compensation was used. Figure 8B This embodiment) and frictionless compensation ( Figure 8A In the case of the comparative example, the steering angle following performance was compared. In both cases, the vehicle speed was 40 km / h, and the same waveform was input as the target steering angle. The vehicle has a driver assistance control unit 84, which calculates the target torque relative to the target steering angle and controls the steering angle by rotating the steering rack via an actuator. Normally, the target steering angle changes constantly due to changes in vehicle behavior, but here, to evaluate steering angle following performance separately, the target steering angle is fixed. The dashed line represents the time-series waveform of the target steering angle, and the solid line represents the time-series waveform of the steering angle. The results show that with friction compensation, the steering angle following performance is improved compared to without friction compensation.

[0061] Next, in Figures 9-11A , Figure 11B The second simulation is shown in the figure. Figure 9 In the second simulation, unlike the first simulation described above, the target rudder angle is set to change constantly in a way that is the optimal value for following the lane based on the vehicle's state.

[0062] Figure 9This is a graph showing the coordinates of the route traveled in the second simulation (i.e., a top view of the road map on the ground), representing the task of entering a curve from a straight line at a speed of 80 km / h. The vehicle is equipped with a driver assistance control unit 84, which automatically follows the route without the need for driver steering.

[0063] Figure 10A It is a time series representing the change in steering angle. Figure 10B This is to make it easier to understand the behavior during steady-state turning. Figure 10A The graph shows a magnified view of the time from 5 seconds to 20 seconds. The dashed line represents the result without friction compensation, and the solid line represents the result with friction compensation. It can be seen that compared with the waveform without friction compensation, the waveform with friction compensation has less rudder angle fluctuation (i.e., a slight left-right sway relative to the center of the road). This is believed to be because friction compensation can compensate for the friction of the steering mechanism and allow for minute rudder angle control, thus improving straight-line stability.

[0064] Figure 11A It is a diagram of the actual friction generated in the steering mechanism, calculated using a detailed friction model when friction compensation is in place. Figure 11B This represents the time series showing the change of the friction compensation control quantity Tcf at this point. From this result, it can be seen that the friction compensation control quantity Tcf can generate a waveform similar to actual friction. That is, according to the first embodiment, it is known that an optimal magnitude / direction friction compensation control quantity Tcf can be generated relative to the target rudder angle θ.

[0065] <Second Implementation>

[0066] Reference Figures 12-14 A second embodiment of the steering control device of the present invention will be described. In the second embodiment, regarding the hardware configuration, ... Figure 1 The first embodiment shown is the same, mainly differing in the reference rudder angle θ. t The calculation of the friction compensation control quantity Tc differs from that of the first embodiment. Therefore, for the second embodiment, the following explanation addresses this difference, while the same reference numerals (reference symbols) are used for configurations and motion processing identical to those in the first embodiment. Figure 5 and Figure 13 ), and appropriately omit their descriptions.

[0067] In the second embodiment, the upper limit of the deviation Δ is a fixed value, and instead the gain K is set to a variable value. Figure 12 This is a graph showing the characteristics of the friction compensation control quantity Tc achieved through the second embodiment, which is equivalent to the first embodiment. Figure 7 The diagram. In the second embodiment, as shown... Figure 12As shown, the upper limit of deviation Δ is a fixed value, while the gain K is variable. It should be noted that, in the second embodiment, similar to the first embodiment, the relationship between the gain K and the upper limit of deviation Δ is Δ = Tt / K. Therefore, in the second embodiment, the gain K increases as the friction torque Tt increases. Thus, within the range of -Δ ≤ Δθ ≤ Δ, as the friction torque Tt increases, the change in the friction compensation control quantity Tc relative to the same Δθ increases. It should be noted that within the ranges of Δθ > Δ and Δθ < -Δ, the magnitude of the friction compensation control quantity Tc becomes the magnitude of the friction torque Tt and remains constant, as in the first embodiment. However, since the upper limit of deviation Δ is fixed, the ranges of Δθ > Δ and Δθ < -Δ are fixed regardless of the friction torque Tt, and within this range, the magnitude of the friction compensation control quantity Tc remains constant relative to the magnitude of the friction torque Tt.

[0068] It should be noted that, in the second embodiment, only the reference rudder angle θ t The calculation methods for the friction compensation control quantity Tc and the friction torque Tt differ from those in the first embodiment, but the calculation methods for the low-pass filter and the friction torque Tt can be the same. Hereinafter, only the reference rudder angle θ in the second embodiment will be discussed. t The calculation methods for the friction compensation control quantity Tc are explained.

[0069] Figure 13 This is a flowchart illustrating a preferred example of the reference rudder angle calculation method in the second embodiment. This reference rudder angle calculation method is similar to... Figure 5 The second embodiment differs from the first embodiment in that it lacks the processing step S104. That is, in the second embodiment, the upper limit of the deviation Δ is a predetermined fixed value, therefore it is not necessary to calculate the upper limit of the deviation Δ based on the friction torque Tt; this fixed value is used directly after step S106.

[0070] Figure 14 This is a flowchart illustrating an example of the calculation process for the friction compensation control quantity Tc in the second embodiment. In step S200, the gain K is calculated (set). The gain K is calculated as K = Tt / Δ using the friction torque Tt calculated as described above and the upper limit value of the deviation Δ (fixed value).

[0071] In step S202, the target rudder angle θ and the reference rudder angle θ are used. t The gain K set in step 200 above is calculated using the formula Tc = K·Δθ, i.e., Tc = K(θ - θ). t The calculation is performed using the formula.

[0072] According to the second embodiment described above, the same effects as the first embodiment described above can be obtained. However, in the second embodiment, vibration is prone to occur when the gain K is too large. Therefore, it is ideal to appropriately determine the upper limit value Δ of the deviation in a way that does not produce such vibration.

[0073] <Transformation Method>

[0074] In the first embodiment, the target steering angle θ required for following the lane is input to the driver assistance control unit 84, but lateral acceleration, yaw rate, etc., can also be used as the target value. In this case, the friction compensation unit 88 also replaces the target steering angle θ with other target values, and correspondingly replaces the reference steering angle with a reference value relative to the other target values, so that it can be used in the same logic, and its effect is the same as that of the first embodiment.

[0075] To improve steering feel, the friction torque Tt can also be set according to the steering wheel 11 (refer to...). Figure 1 The input driver steering torque is variable.

[0076] As a steering mechanism 20 (refer to) Figure 1 Due to the increased load on the steering rack, friction increases, so the friction torque Tt is set to be variable based on the steering angle, lateral acceleration, and rack axial force. Furthermore, in the case of a column-mounted EPS, friction increases due to the torque generated by the motor; therefore, the friction torque Tt can also be set based on the auxiliary amount (…). Figure 1 The torque input is variable.

[0077] The first embodiment produces a friction waveform that closely approximates the actual friction characteristics. However, to further consider static friction, the friction torque Tt can be set to be variable based on the target rudder angular velocity. This allows the generation of a friction compensation control quantity Tc that takes into account static friction, dynamic friction, and elastic friction gradients.

[0078] As detailed above, according to the embodiment, by providing a friction compensation unit 88 that outputs appropriate direction and magnitude friction compensation control amounts Tc or Tcf based on the target steering angle θ, vehicle speed V, etc., friction generated in the steering mechanism 20 is compensated during automatic driving or driver assistance, thereby improving steering angle following performance. This results in reduced swaying during straight-line driving and improved disturbance response.

[0079] Furthermore, even when a momentary torque fluctuation results in a lateral acceleration exceeding the vehicle's required level, it can suppress undesirable situations such as changes in the indicated target lateral acceleration itself or repeated reversals of the direction of increase or decrease in the target lateral acceleration, leading to amplified vibrations. When the direction of increase or decrease in the target lateral acceleration is switched, the requested torque is smoothly reduced or increased. Therefore, relative to small fluctuations in the target lateral acceleration, the friction compensation control quantity Tc or Tcf also fluctuates slightly, thereby reducing the amplitude of torque fluctuations.

[0080] Postscript

[0081] Regarding the implementation methods described above, the following notes are also disclosed.

[0082] [Postscript 1]

[0083] The steering control device described in Appendix 1 of this invention is a steering control device that controls the steering of a vehicle performing autonomous driving or driver assistance, characterized in that it includes: a reference rudder angle calculation unit that calculates the reference rudder angle (θ) of the vehicle based on the target rudder angle (θ) of the vehicle and the vehicle speed (V). t The compensation unit determines the calculated reference rudder angle (θ). t Whether the deviation between the target rudder angle (θ) and the target rudder angle (θ) exceeds a predetermined value (Δ), if the deviation is determined to exceed the predetermined value (Δ), the calculated reference rudder angle (θ) is used. t The calculated reference rudder angle (θ) is compensated by following the target rudder angle (θ). t ).

[0084] According to the steering control device described in Appendix 1, based on the target steering angle (θ) corresponding to the direction in which the vehicle should travel via autonomous driving or driver assistance and the vehicle speed (V), the reference steering angle calculation unit calculates the reference steering angle (θ) of the vehicle. t Next, the calculated reference rudder angle (θ) is determined first by the compensation unit. t Whether the deviation between the target rudder angle (θ) and the target rudder angle (θ) exceeds a specified value (Δ), if it is determined that the deviation exceeds the specified value (Δ), then as a compensation result, the calculated reference rudder angle (θ) is set as follows. t The target rudder angle (θ) is followed. That is, in this case, the reference rudder angle (θ) is calculated through compensation. t The target rudder angle (θ) is followed by a deviation less than a specified value (Δ) (in other words, it does not fluctuate beyond a specified value (Δ) from the target rudder angle (θ)). On the other hand, if the deviation does not exceed the specified value (Δ), the calculated reference rudder angle (θ) is... tThe calculated reference rudder angle (θ) will not be compensated, but in this case, even if the uncompensated state is maintained, the calculated reference rudder angle (θ) will still be calculated. t It is also set to follow the target rudder angle (θ) in the form of a separation less than a specified value (Δ).

[0085] Regarding the setting of the "prescribed value (Δ)," the threshold value at which fluctuations in the requested torque will not adversely affect steering feel or ride comfort can be determined through experimentation, experience, simulation, or machine learning. A margin is then added to this threshold value. This value can be preset as a predetermined value or updated appropriately during autonomous driving or driver assistance systems using machine learning. In either case, the predetermined value is set small enough to fall within the range of the reference steering angle (θ). t The value is determined by the degree to which the requested torque does not fluctuate drastically when oscillating towards the target steering angle (θ). Furthermore, regarding the "following" achieved by the compensation unit, it can be performed by adding a friction compensation control amount (Tc or Tcf) with appropriate direction and magnitude, calculated by the compensation unit based on the target steering angle and vehicle speed, to the target torque (T) corresponding to the target steering angle (θ). This compensates for the friction torque as the steering reaction force, thereby improving the following performance of the actual steering angle relative to the target steering angle (θ). By compensating for the friction generated in the vehicle's steering mechanism and improving steering angle following performance, it is also possible to reduce swaying during straight-line maneuvers and improve disturbance response.

[0086] The result is that even when the direction of increase or decrease of the target lateral acceleration switches from increase to decrease or from decrease to increase, the reference rudder angle is appropriately compensated, thus suppressing sharp fluctuations in the requested torque based on the compensated reference rudder angle in the electric actuator that performs the rotation of the steering mechanism or rotation assistance.

[0087] [Postscript 2]

[0088] The steering control device described in Appendix 2 is the same as the steering control device described in Appendix 1, characterized in that it further comprises a friction torque calculation unit, which calculates a friction torque value (Tt) to be compensated for the steering mechanism of the vehicle based on a parameter of a predetermined type representing the state of the vehicle including the vehicle speed (V), and the reference steering angle calculation unit calculates the reference steering angle (θ) based on the calculated friction torque value (Tt) and the target steering angle (θ) not based on the vehicle speed (V). t Alternatively, the reference rudder angle (θ) can be calculated based not only on the vehicle speed (V) but also on the calculated friction torque value (Tt) and the target rudder angle (θ). t ).

[0089] According to the steering control device described in Appendix 2, firstly, in the friction torque calculation unit, the friction torque value (Tt) to be compensated for the steering mechanism is calculated based on a specified type of parameters, including vehicle speed (V) (e.g., lateral acceleration, yaw rate, driver steering torque, etc., in addition to vehicle speed (V)). Next, in the reference rudder angle calculation unit, the reference rudder angle (θ) is calculated based on the friction torque value (Tt) thus calculated, not based on vehicle speed (V), and the target rudder angle (θ). t Alternatively, in addition to the vehicle speed (V), the reference rudder angle (θ) can be calculated based on the friction torque value (Tt) and the target rudder angle (θ). t Therefore, even when the direction of increase or decrease in the target lateral acceleration switches from increasing to decreasing or from decreasing to increasing, compensation can be performed in a form that reflects the vehicle's state, represented by parameters including vehicle speed (V), thereby allowing the requested torque to decrease or increase smoothly. Furthermore, the friction compensation control quantity can also fluctuate slightly relative to small fluctuations in the target lateral acceleration, thus reducing the amplitude of fluctuations in the requested torque. In this way, sharp fluctuations in the requested torque can be suppressed more effectively.

[0090] [Postscript 3]

[0091] The steering control device described in Appendix 3 is the steering control device described in Appendix 2, characterized in that the friction torque calculation unit calculates the friction torque value (Tt) to be compensated in such a way that the friction torque value (Tt) to be compensated when the vehicle speed (V) is a first vehicle speed value is smaller than the friction torque value to be compensated when the vehicle speed (V) is a second vehicle speed value less than the first vehicle speed value.

[0092] According to the steering control device described in Appendix 3, although the actual steering friction characteristics vary depending on the vehicle speed (V), a more suitable friction torque can be compensated based on the vehicle speed (V). For example, at high speeds, friction decreases due to the reverse input vibration of the steering mechanism, thus allowing for individual, specific adjustments to the actual steering mechanism, such as reducing the friction compensation control amount (Tc or Tcf).

[0093] [Postscript 4]

[0094] The steering control device described in Appendix 4 is the steering control device described in Appendix 2 or 3, characterized in that, as compensation for the calculated reference rudder angle, compared with the upper limit of the deviation set based on the calculated friction torque value (Tt), the calculated reference rudder angle (θ) t If the absolute value of the deviation between the reference rudder angle (θ) and the target rudder angle (θ) is large, the compensation unit changes the reference rudder angle (θ) in the direction that decreases the absolute value of the deviation. tIf the absolute value of the deviation is not large compared to the upper limit of the deviation, the compensation unit does not change the reference rudder angle (θ). t ).

[0095] According to the steering control device described in Appendix 4, the calculated reference rudder angle (θ) is compared with the upper limit of deviation set based on the calculated friction torque value (Tt). t If the absolute value of the deviation between the reference rudder angle (θ) and the target rudder angle (θ) is large, the compensation unit changes the reference rudder angle (θ) in the direction that reduces the absolute value of the deviation. t Conversely, if the absolute value of the deviation is not large compared to the upper limit of the deviation, the reference rudder angle (θ) is not changed. t ), that is, maintaining the reference rudder angle (θ) t Therefore, it can compensate for the frictional torque (Tt) that is close to the actual frictional characteristics, taking into account the elastic friction gradient. That is, it can avoid the frictional torque (Tt) to be compensated being excessive or insufficient, depending on the actual mobility of the steering mechanism.

[0096] [Postscript 5]

[0097] The steering control device described in Appendix 5 is the steering control device described in any one of Appendices 2 to 4, characterized in that the calculated reference rudder angle (θ) t The compensation unit compensates for the calculated reference rudder angle (θ) by using the calculated reference rudder angle (θ) t The friction compensation control quantity (Tc or Tcf) is calculated by multiplying the deviation between the target rudder angle (θ) and the target rudder angle (θ).

[0098] According to the steering control device described in Appendix 5, in the compensation unit, the calculated reference rudder angle (θ) is used as the reference rudder angle. t The friction compensation control amount (Tc or Tcf) is calculated by multiplying the deviation by a gain. Then, the calculated friction compensation control amount (Tc or Tcf) is added to the target torque (T) after further processing to set the compensated target torque (Tm). This allows for a simpler process: compensating the reference rudder angle.

[0099] [Postscript 6]

[0100] The steering control device described in Appendix 6 is the same as the steering control device described in Appendix 5, characterized in that it further comprises a low-pass filter, which performs low-pass filtering processing on the calculated friction compensation control quantity (Tc).

[0101] According to the steering control device described in Appendix 6, the compensated target torque (Tm) is set by adding the friction compensation control quantity (Tc) calculated as described in Appendix 6 after low-pass filtering (i.e., as the friction compensation control quantity (Tcf)) to the target torque (T). Therefore, the steering feel during manual operation can also be improved by a relatively simple process such as assigning an appropriate constant to the low-pass filter.

[0102] [Postscript 7]

[0103] The steering control device described in Appendix 7 is the steering control device described in Appendix 5 or 6, characterized in that, as compensation for the calculated reference rudder angle, the compensation unit sets an upper limit value (Δ) of deviation by dividing the calculated friction torque value (Tt) by the gain, and subtracts the calculated reference rudder angle (θ) from the target rudder angle (θ). t The deviation (θ-θ) obtained t If the calculated reference rudder angle (θ) is greater than the set upper limit value (Δ), the compensation unit will adjust the calculated reference rudder angle (θ). t The value (θ-Δ) is changed to the target rudder angle (θ) minus the set upper limit of deviation (Δ), and the calculated reference rudder angle (θ) is subtracted from the target rudder angle (θ). t The deviation (θ-θ) obtained t If the calculated reference rudder angle (θ) is smaller than the negative value (-Δ) of the set upper limit of deviation (Δ), the compensation unit will adjust the calculated reference rudder angle (θ). t The value (θ+Δ) is obtained by adding the set upper limit of deviation (Δ) to the target rudder angle (θ), and then subtracting the calculated reference rudder angle (θ). t The deviation (θ-θ) obtained t When the absolute value of ) is below the set upper limit of deviation (Δ), the compensation unit maintains the calculated reference rudder angle (θ). t (Without making any changes.)

[0104] According to the steering control device described in Appendix 7, the friction compensation control quantity (Tc or Tcf) can be arbitrarily designed to increase by a small change relative to the target steering angle (θ) by changing the value of the gain. For example, increasing the gain can improve responsiveness, reduce swaying during straight driving (or swaying relative to the center of a curved road), and improve responsiveness to disturbances such as crosswinds. Therefore, it is possible to compensate for friction torque (Tt) that is close to the actual friction characteristics taking into account the elastic friction gradient. That is, it is possible to avoid excessive or insufficient friction torque (Tt) to be compensated based on the actual mobility of the steering mechanism.

[0105] [Postscript 8]

[0106] The steering control device described in Appendix 8 is the steering control device described in any one of Appendices 1 to 7, characterized in that it further comprises: a target torque calculation unit that calculates the target torque (T) based on the target rudder angle (θ); and an addition operation output unit that outputs the calculated torque (T) based on the compensated reference rudder angle (θ). t The calculated friction compensation control quantity (Tc or Tcf) is added to the calculated target torque (T), thereby outputting the compensated target torque (Tm) to the electric actuator of the vehicle's steering mechanism.

[0107] According to the steering control device described in Appendix 8, when the target torque (T) is calculated by the target torque calculation unit based on the target steering angle (θ) or based on the target steering angle (θ) and vehicle speed (V), the addition calculation output unit compares the calculated target torque (T) with the compensated reference steering angle (θ). t The calculated friction compensation control quantity (Tc or Tcf) is added to the calculated target torque (T). This results in a compensated target torque (Tm) output to the electric actuator. Therefore, even when the direction of the target lateral acceleration changes from increasing to decreasing or from decreasing to increasing, the abrupt fluctuations in the requested torque of the electric actuator can be suppressed by adding the compensated target torque (Tm) to the target torque (T) with the friction compensation control quantity (Tc) either unchanged or after low-pass filtering.

[0108] [Postscript 9]

[0109] The electric power steering system described in Appendix 9 is an electric power steering system characterized by comprising: a steering control device as described in any one of Appendices 1 to 8; and an electric actuator that controls the requested torque based on the compensated reference rudder angle.

[0110] According to Appendix 9, the electric power steering device has the steering control devices described in the appendix above. Therefore, in autonomous driving and driver assistance, even when the direction of increase or decrease of the target lateral acceleration changes from increase to decrease or from decrease to increase, the requested torque of the electric actuator can be suppressed from fluctuating sharply.

[0111] The present invention may be modified appropriately without departing from the spirit or idea of ​​the invention as can be read from the claims and description in their entirety, and the steering control device or electric power steering device accompanying such modifications is also included in the technical concept of the present invention.

Claims

1. A steering control device for controlling the steering of a vehicle performing autonomous driving or driver assistance, the steering control device being characterized by comprising: The reference rudder angle calculation unit calculates the reference rudder angle of the vehicle based on the target rudder angle and the vehicle speed; The compensation unit determines whether the deviation between the calculated reference rudder angle and the target rudder angle exceeds a predetermined value. If the deviation exceeds the predetermined value, the calculated reference rudder angle is compensated by following the target rudder angle. The friction torque calculation unit calculates the friction torque value that should be compensated for to the vehicle's steering mechanism based on a specified type of parameter representing the state of the vehicle, including the vehicle speed. The reference rudder angle calculation unit calculates the reference rudder angle based on the calculated friction torque value and the target rudder angle, not based on the vehicle speed; or it calculates the reference rudder angle based on the calculated friction torque value and the target rudder angle in addition to the vehicle speed. The friction torque calculation unit calculates the friction torque value to be compensated in such a way that the friction torque value to be compensated when the vehicle speed is a first vehicle speed value is smaller than the friction torque value to be compensated when the vehicle speed is a second vehicle speed value that is less than the first vehicle speed value.

2. The steering control device according to claim 1, characterized in that, As compensation for the calculated reference rudder angle, if the absolute value of the deviation between the calculated reference rudder angle and the target rudder angle is large compared to the upper limit of the deviation set based on the calculated friction torque value, the compensation unit changes the reference rudder angle in the direction of decreasing the absolute value of the deviation; if the absolute value of the deviation is not large compared to the upper limit of the deviation, the compensation unit does not change the reference rudder angle.

3. The steering control device according to claim 1 or 2, characterized in that, As compensation for the calculated reference rudder angle, the compensation unit calculates the friction compensation control amount by multiplying the deviation between the calculated reference rudder angle and the target rudder angle by a gain.

4. The steering control device according to claim 3, characterized in that, It also features a low-pass filter that performs low-pass filtering on the calculated friction compensation control quantity.

5. The steering control device according to claim 3, characterized in that, As compensation for the calculated reference rudder angle The compensation unit sets the upper limit of the deviation by dividing the calculated friction torque value by the gain. If the deviation obtained by subtracting the calculated reference rudder angle from the target rudder angle is greater than the set upper limit of deviation, the compensation unit changes the calculated reference rudder angle to the value obtained by subtracting the set upper limit of deviation from the target rudder angle. If the deviation obtained by subtracting the calculated reference rudder angle is less than the negative value of the set upper limit of deviation, the compensation unit changes the calculated reference rudder angle to the value obtained by adding the set upper limit of deviation to the target rudder angle. If the absolute value of the deviation obtained by subtracting the calculated reference rudder angle is below the set upper limit of the deviation, the compensation unit maintains the calculated reference rudder angle without making any changes.

6. The steering control device according to claim 1 or 2, characterized in that, It also has: The target torque calculation unit calculates the target torque based on the target rudder angle; and The addition output unit adds the friction compensation control amount calculated corresponding to the compensated reference rudder angle to the calculated target torque, thereby outputting the compensated target torque to the electric actuator of the vehicle's steering mechanism.

7. An electric power steering device, characterized in that, have: The steering control device according to any one of claims 1 to 6; and An electric actuator controls the requested torque based on the compensated reference rudder angle.

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