Vehicle control device

Abstract

In the present invention, an ECU 10 comprises: a delay correction calculation unit 120 that calculates, as a delay correction amount α, an estimated increase / decrease amount of the vehicle velocity during a delay time occurring when acquiring a wheel velocity ωw via a wheel velocity sensor and CAN communication, such calculation being on the basis of the forward / backward acceleration X or an estimated vehicle body velocity V of an electric vehicle 1; an error correction unit 130 that calculates a corrected past estimated vehicle body velocity Vp´ obtained by correcting a past estimated vehicle body velocity Vp on the basis of an error ΔV between the past estimated vehicle body velocity Vp, which is the estimated vehicle body velocity V calculated earlier by the amount of the delay time, and a CAN vehicle body velocity Vs based on the wheel velocity ωw acquired by the CAN communication; and a vehicle body velocity calculation unit 140 that calculates the current estimated vehicle body velocity V by adding the corrected past estimated vehicle body velocity Vp´ to the delay correction amount α.

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device, and more particularly to a control device that estimates a vehicle speed. [Background technology]

[0002] Conventionally, there are known techniques for estimating the vehicle speed of a vehicle. For example, Patent Document 1 describes a vehicle speed estimation device that calculates an estimated vehicle speed value by performing a first-order lag filter process on wheel speeds, and then calculates a corrected estimated vehicle speed value by adding, to the calculated estimated vehicle speed value, a longitudinal acceleration multiplied by a transfer function and a time constant of the filter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-217934 Summary of the Invention [Problem to be solved by the invention]

[0004] In vehicles equipped with electric motors for traction, traction control that takes advantage of the high torque responsiveness of electric motors is expected to improve starting performance. Furthermore, vehicle wheel speeds are sometimes detected by sensors and transmitted from another controller to a motor controller via CAN (Controller Area Network) communication. Therefore, vehicle speed is estimated using wheel speeds from a time preceding a delay due to CAN communication delays and sensor detection delays. However, while the vehicle speed estimation device described in Patent Document 1 takes into account the delay caused by filtering, it is unable to obtain a vehicle speed that takes this delay into account. As a result, it may not be possible to execute control that fully utilizes the torque responsiveness of an electric motor.

[0005] The present invention has been made in consideration of these problems, and its purpose is to provide a vehicle control device that can more appropriately estimate vehicle speed by taking into account the delay time between detecting wheel speed by a sensor and obtaining it via CAN communication. [Means for solving the problem]

[0006] In order to achieve the above object, the vehicle control device of the present invention is a vehicle control device that calculates an estimated vehicle speed of a vehicle equipped with a driving electric motor, and is equipped with: a delay correction amount calculation unit that calculates an estimated increase / decrease in vehicle speed during a delay time that occurs when wheel speeds are obtained via sensors and CAN communication, as a delay correction amount based on either the longitudinal acceleration of the vehicle or the estimated vehicle speed; an error correction unit that calculates a corrected past estimated vehicle speed by correcting the past estimated vehicle speed based on the error between a past estimated vehicle speed, which is the estimated vehicle speed calculated the delay time ago, and a vehicle speed based on the wheel speed obtained via CAN communication; and a vehicle speed calculation unit that calculates the current estimated vehicle speed by adding the delay correction amount and the corrected past estimated vehicle speed.

[0007] With this configuration, the previous estimated vehicle speed calculated a delay time before due to CAN communication delays and sensor detection delays is corrected based on the wheel speeds acquired through CAN communication, thereby enabling accurate calculation of a base corrected previous estimated vehicle speed. The current estimated vehicle speed is calculated by adding a delay correction amount, which is the estimated increase or decrease in vehicle speed during the delay time, to the corrected previous estimated vehicle speed, thereby compensating for the vehicle speed for the delay time. Therefore, the vehicle speed can be more appropriately estimated by taking into account the delay time between when the wheel speed is detected by the sensor and when it is acquired through CAN communication.

[0008] Preferably, the delay correction amount calculation unit calculates the delay correction amount as an integrated value of the longitudinal acceleration of the vehicle during the delay time. With this configuration, the delay correction amount calculation unit can appropriately calculate the delay correction amount based on the longitudinal acceleration.

[0009] Preferably, the longitudinal acceleration is a value detected by an acceleration sensor mounted on the vehicle, and this configuration makes it possible to easily obtain the longitudinal acceleration.

[0010] Preferably, the longitudinal acceleration is a value calculated based on the wheel speed. With this configuration, the longitudinal acceleration can be obtained using only a wheel speed sensor for detecting the wheel speed, without using an acceleration sensor.

[0011] Preferably, the longitudinal acceleration is a value calculated based on the estimated vehicle speed. With this configuration, the longitudinal acceleration can be obtained without using an acceleration sensor or wheel speed sensor.

[0012] Preferably, the longitudinal acceleration is a value calculated based on the driving force and braking force of the vehicle. With this configuration, the longitudinal acceleration can be obtained without using an acceleration sensor or wheel speed sensor.

[0013] Preferably, the integrated value is an integrated value of corrected accelerations that have been corrected for disturbance components including road surface gradients. This configuration allows the integrated value to be calculated with higher accuracy.

[0014] Furthermore, it is preferable that when the previous estimated vehicle speed, which is the estimated vehicle speed calculated in the previous processing, is equal to or greater than a predetermined speed, the delay correction amount calculation unit sets the difference between the previous estimated vehicle speed and the past estimated vehicle speed as the delay correction amount, and when the previous estimated vehicle speed is less than the predetermined speed, sets the delay correction amount as an integrated value of the longitudinal acceleration of the vehicle during the delay time.

[0015] With this configuration, the delay correction amount calculation unit can accurately calculate the delay correction amount through simple calculations without using longitudinal acceleration in a speed range equal to or greater than the predetermined speed. Also, the delay correction amount calculation unit can appropriately calculate the delay correction amount based on longitudinal acceleration in a speed range below the predetermined speed. [Effects of the Invention]

[0016] In the vehicle control device of the present invention, a past estimated vehicle speed calculated a delay time before due to a CAN communication delay or a sensor detection delay is corrected based on the wheel speed obtained through CAN communication, and a delay correction amount, which is an estimated increase or decrease in vehicle speed during the delay time, is added to the corrected past estimated vehicle speed to calculate a current estimated vehicle speed. Therefore, the vehicle speed can be more appropriately estimated by taking into account the delay time between when the wheel speed is detected by the sensor and when it is obtained through CAN communication. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an electric vehicle equipped with an ECU as a control device according to an embodiment. [Figure 2] FIG. 2 is a schematic configuration diagram illustrating an example of an ECU. [Figure 3] FIG. 10 is an explanatory diagram showing a schematic diagram of the actual vehicle speed when the electric vehicle is traveling at a constant speed, the wheel speed acquired by the ECU through CAN communication, and the conventional estimated vehicle speed calculated based on the wheel speed. [Figure 4] FIG. 10 is an explanatory diagram showing the time-dependent changes in the actual vehicle speed when an electric vehicle is traveling at a constant speed in an extremely low speed range, the wheel speed acquired by the ECU through CAN communication, and the conventional estimated vehicle speed calculated based on the wheel speed. [Figure 5] FIG. 4 is a control block diagram showing an example of an estimated vehicle speed calculation unit. [Figure 6] FIG. 2 is a control block diagram showing an example of a traction control unit. [Figure 7] 10 is a flowchart illustrating an example of an estimated vehicle speed calculation process. [Figure 8] 10A and 10B are explanatory diagrams illustrating examples of experimental results in which an estimated vehicle speed is calculated by the estimated vehicle speed calculation process according to the embodiment. [Figure 9] 5 is an explanatory diagram showing a schematic diagram of changes over time in the reference rotation speed of the drive shaft and the wheel speed; FIG. [Figure 10] FIG. 2 is a control block diagram showing an example of the configuration of a traction control unit. [Figure 11] 10A and 10B are explanatory diagrams illustrating an example of experimental results in which an estimated drive shaft rotation speed is calculated by the ECU according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] (Electric vehicles) FIG. 1 is a schematic diagram showing an example of an electric vehicle equipped with an ECU as a control device according to an embodiment. The electric vehicle 1 is a front-wheel drive vehicle in which an electric motor 2 (electric traction motor) mounted as a power source for driving drives front wheels 3a, which are drive wheels among wheels 3. The output shaft of the motor 2 is connected to the left and right front wheels 3a via a speed reduction mechanism 4 incorporating a differential gear 4a and a drive shaft 5. The speed reduction mechanism 4 may also include a transmission mechanism. The motor 2 is connected to an inverter 6 via a power line, and the inverter 6 is connected to a battery 7. The inverter 6 performs a DC-AC conversion function. During powering control of the motor 2, the inverter 6 converts DC power supplied from the battery 7 into three-phase AC power and supplies it to the motor 2. During regenerative control of the motor 2, the inverter 6 converts regenerative power from the motor 2 into DC power and charges the battery 7.

[0020] (ECU) The electric vehicle 1 includes an ECU 10 (control device) as a motor controller that controls the drive of the motor 2. The ECU 10 includes input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and the like. FIG. 2 is a schematic diagram showing an example of the configuration of the ECU 10. Connected to the input side of the ECU 10 via a CAN are various sensors, including a motor rotation speed sensor 11 that detects the motor rotation speed ωm of the motor 2, a wheel speed sensor 12 that detects the wheel speeds ωw (ωw1 to ωw4) of the left and right front wheels 3a and the left and right rear wheels 3b, an accelerator sensor 13 that detects the accelerator operation amount, a brake sensor 14 that detects the brake operation amount, an acceleration sensor 15 that detects the longitudinal acceleration X of the electric vehicle 1, and a yaw rate sensor 16 that detects the yaw rate y of the electric vehicle 1. The motor rotation speed sensor 11 and the wheel speed sensor 12 may be well-known rotation sensors capable of detecting rotation speed, such as a rotary encoder. In this embodiment, the acceleration sensor 15 is a G sensor. An inverter 6 is connected to the output side of the ECU 10. The ECU 10 includes an estimated vehicle speed calculation unit 100 and a traction control unit 200.

[0021] (Estimated vehicle speed calculation section) First, the configuration and operation of the estimated vehicle speed calculation unit 100 will be described. Fig. 3 is an explanatory diagram that schematically shows how the actual vehicle speed VA when the electric vehicle 1 is traveling at a constant speed, the wheel speed ωw acquired by the ECU 10 through CAN communication, and the conventional estimated vehicle speed VB calculated based on the wheel speed ωw change over time. Fig. 4 is an explanatory diagram that schematically shows how the actual vehicle speed VA when the electric vehicle 1 is traveling at a constant speed in an extremely low speed range, the wheel speed ωw acquired by the ECU 10 through CAN communication, and the conventional estimated vehicle speed VB calculated based on the wheel speed ωw change over time. The conventional estimated vehicle speed VB, indicated by the two-dot chain line, is an estimated vehicle speed calculated using a conventional method, such as by filtering the wheel speed ωw using a low-pass filter.

[0022] As shown by the white circles in Fig. 3, the wheel speed ωw obtained through CAN communication is delayed from the actual vehicle speed VA by a delay time Δt1 due to the delay in CAN communication. Furthermore, the conventional estimated vehicle speed VB is further delayed from the actual vehicle speed VA by a delay time Δt2 due to filtering. 4, in the extremely low speed range, a detection delay occurs due to an insufficient number of teeth in the wheel speed sensor 12, such as a rotary encoder, which further lengthens the delay time Δt1, causing the wheel speed ωw and the conventional estimated vehicle speed VB to lag further behind the actual vehicle speed VA. In this way, when the conventional estimated vehicle speed VB is calculated with a delay from the actual vehicle speed VA, it may not be possible to fully expect the effect of improving starting performance through traction control that takes advantage of the high torque responsiveness of the motor 2. Therefore, in the ECU 10 of the electric vehicle 1 of this embodiment, the estimated vehicle speed calculation unit 100 attempts to more appropriately calculate the estimated vehicle speed of the electric vehicle 1.

[0023] 5 is a control block diagram showing an example of the estimated vehicle body speed calculation unit 100. The estimated vehicle body speed calculation unit 100 executes an estimated vehicle body speed calculation process to calculate an estimated vehicle body speed V of the electric vehicle 1. As shown in FIGS. 2 and 5, the estimated vehicle body speed calculation unit 100 includes a disturbance correction unit 110, a delay correction amount calculation unit 120, an error correction unit 130, and a vehicle body speed calculation unit 140.

[0024] (Acceleration disturbance correction section) The disturbance correction unit 110 acquires the longitudinal acceleration X of the electric vehicle 1 detected by the acceleration sensor 15 via CAN communication. The disturbance correction unit 110 also acquires the estimated vehicle speed V finally calculated by the estimated vehicle speed calculation unit 100, and calculates a derivative value dV / dt within the delay time Δt1 in a differentiation block 111. As described above, the delay time Δt1 is a delay time that occurs when the ECU 10 acquires the wheel speed ωw detected by the wheel speed sensor 12 due to a communication delay in CAN communication or an insufficient number of teeth in the wheel speed sensor 12, and has a value of approximately several milliseconds to several hundred milliseconds. The delay time Δt1 may be determined in advance using a map or the like based on experiments, analyses, or other factors, depending on the vehicle situation. The derivative value dV / dt is an estimated value of the longitudinal acceleration of the electric vehicle 1 during the delay time Δt1. Furthermore, the disturbance correction unit 110 calculates an estimated acceleration Xe by performing a predetermined low-pass filter process on the derivative value dV / dt in a low-pass filter block 112. The disturbance correction unit 110 then calculates the difference ΔX between the longitudinal acceleration X and the estimated acceleration Xe in the difference block 113, and calculates the disturbance component Xα based on the difference ΔX in the disturbance estimation unit 114. The disturbance component Xα is, for example, a disturbance component caused by a road surface gradient detected by the acceleration sensor 15, which is a G sensor. In this embodiment, the disturbance correction unit 110 calculates the difference ΔX as the disturbance component Xα of acceleration. Note that the disturbance component Xα may take into account a disturbance component other than the road surface gradient, and the disturbance correction unit 110 may calculate the disturbance component based on the difference ΔX using a well-known method. The disturbance correction unit 110 then calculates the corrected acceleration X' in the acceleration correction unit 115 by subtracting the disturbance component Xα from the longitudinal acceleration X.

[0025] (Delay correction amount calculation unit) The delay correction amount calculation unit 120 acquires the corrected acceleration X' from the disturbance correction unit 110, and the integrating unit 121 calculates an integrated value σX' by integrating the corrected acceleration X' during the delay time Δt1. The integrated value σX' is an estimated increase or decrease in the vehicle speed of the electric vehicle 1 during the delay time Δt1, and the delay correction amount calculation unit 120 sets the integrated value σX' as a delay correction amount α for the vehicle speed. In the following description, the integrated value σX' will be referred to as a first delay correction amount α1 where appropriate. The delay correction amount calculation unit 120 also calculates the delay correction amount α based on the amount of change in the estimated vehicle body speed V. Specifically, the delay correction amount calculation unit 120 acquires the previous estimated vehicle body speed Vn-1 calculated in the previous main process and the past estimated vehicle body speed Vp calculated the delay time Δt1 ago, from the estimated vehicle body speed V finally calculated by the estimated vehicle body speed calculation unit 100. The previous estimated vehicle body speed Vn-1 is used in place of the current estimated vehicle body speed V. The delay correction amount calculation unit 120 calculates the difference between the previous estimated vehicle body speed Vn-1 and the past estimated vehicle body speed Vp in a difference block 122, and sets the calculated difference as the delay correction amount α. In the following description, the difference between the previous estimated vehicle body speed Vn-1 and the past estimated vehicle body speed Vp will be referred to as a second delay correction amount α2 where appropriate.

[0026] After calculating and setting the delay correction amount α (first delay correction amount α1 and second delay correction amount α2) as described above, the delay correction amount calculation unit 120 determines which value to select from the first delay correction amount α1 and the second delay correction amount α2 using the vehicle speed weighting unit 123. Specifically, when the absolute value of the current vehicle body speed is less than a first predetermined speed V1 (predetermined speed), the first delay correction amount α1 is selected and output. On the other hand, when the absolute value of the current vehicle body speed is equal to or greater than the first predetermined speed V1, the second delay correction amount α2 is selected and output. Note that the current vehicle body speed here may be the previous estimated vehicle body speed Vn-1. That is, in a region where the current vehicle body speed has not reached a sufficient speed, the calculation accuracy of the estimated vehicle body speed V (described later) is relatively low compared to a region where the current vehicle body speed has reached a sufficient speed (see FIG. 8). Therefore, it is preferable to use the first delay correction amount α1, which is the integrated value σX' of the corrected acceleration X'. On the other hand, in a region where the current vehicle speed is sufficiently fast, the calculation accuracy of the estimated vehicle speed V, which will be described later, is relatively high (see FIG. 8), so a second delay correction amount α2, which is the difference between the previous estimated vehicle speed Vn-1 and the previous estimated vehicle speed Vp, can be used. Furthermore, the first predetermined speed V1 is, for example, preferably equal to or greater than 10 m / s and less than 70 m / s, more preferably equal to or greater than 20 m / s and less than 70 m / s, and even more preferably equal to or greater than 27 m / s and less than 70 m / s.

[0027] (Error correction section) The error correction unit 130 acquires the wheel speeds ωw1 to ωw4 from the wheel speed sensors 12 via CAN communication, and also acquires the yaw rate y of the electric vehicle 1 detected by the yaw rate sensor 16. The error correction unit 130 also acquires the previous estimated vehicle body speed Vn-1 instead of the current vehicle body speed. The error correction unit 130 calculates, in a center-of-gravity vehicle body speed estimation unit 131, center-of-gravity vehicle body speeds VG1, VG2, VG3, and VG4, which are the speeds at the center of gravity of the electric vehicle 1 when one of the wheels 3 is assumed to be the reference, for each wheel speed ωw1 to ωw4, based on the wheel speeds ωw1 to ωw4, the yaw rate y, the previous estimated vehicle body speed Vn-1, and the tread value of each wheel 3. Furthermore, the error correction unit 130 determines, in a reference wheel selector 132, which of the center-of-gravity vehicle body speeds VG1 to VG4 to select and output. In this embodiment, the error correction unit 130 sets and outputs the third highest value among the center-of-gravity vehicle body speeds VG1 to VG4 as the CAN vehicle body speed Vs based on the wheel speed ωw acquired through CAN communication. In other words, the CAN vehicle body speed Vs is a speed based on the actual measurement value of the wheel speed ωw before the delay time Δt1 in CAN communication.

[0028] When the CAN vehicle body speed Vs is calculated based on the actual measurement value before the delay time Δt1 as described above, the error correction unit 130 corrects the previous estimated vehicle body speed Vp calculated before the delay time Δt1 with the CAN vehicle body speed Vs. Specifically, the error correction unit 130 calculates the error ΔV between the previous estimated vehicle body speed Vp calculated before the delay time Δt1 in an error calculation block 133. Furthermore, the error correction unit 130 calculates a filtered CAN vehicle body speed Vsf by multiplying the CAN vehicle body speed Vs by a filter coefficient k as shown in equation (1) in a filter block 134. The filter coefficient k is a function of the CAN vehicle body speed Vs. The filter coefficient k is set to, for example, 0.5 when the absolute value of the CAN vehicle body speed Vs is equal to or greater than a second predetermined speed, and is set to, for example, 0 when the absolute value of the CAN vehicle body speed Vs is less than the second predetermined speed. The second predetermined speed is a speed, for example, 1 m / s, at which the wheel speeds ωw1 to ωw4 can be detected by the acceleration sensor 15. In this way, when the wheel speeds ωw1 to ωw4, which are actual measured values, cannot be detected, the filter coefficient k is set to 0, so that the error between the past estimated vehicle body speed Vp and the CAN vehicle body speed Vs based on the actual measured value is not taken into consideration.

[0029] Vsf=k·Vs …(1)

[0030] Furthermore, as shown in equation (2), the error correction unit 130 calculates an error correction value ΔVα, which is the product of the calculated error ΔV and the filtered CAN body speed Vsf, in the multiplication block 135. Therefore, the error correction value ΔVα increases as the error ΔV increases, and decreases as the error ΔV decreases. As described above, if the absolute value of the CAN body speed Vs is less than the second predetermined speed and the wheel speeds ωw1 to ωw4, which are actual measured values, cannot be detected, the filter coefficient k in equation (1) is zero, and therefore the filtered CAN body speed Vsf also becomes zero. Therefore, the error correction value ΔVα is also calculated as 0.

[0031] ΔVα=Vsf·ΔV …(2)

[0032] Then, as shown in equation (3), the error correction unit 130 adds the previous estimated vehicle body speed Vp and the error correction value ΔVα in the addition block 136 to calculate and output the corrected previous estimated vehicle body speed Vp' obtained by correcting the previous estimated vehicle body speed Vp. This allows the previous estimated vehicle body speed Vp to be corrected based on the error ΔV between it and the CAN vehicle body speed Vs, which is based on the actual measurement value. The corrected previous estimated vehicle body speed Vp' is a value obtained by greatly correcting the previous estimated vehicle body speed Vp so that it approaches the CAN vehicle body speed Vs, the larger the error ΔV between the CAN vehicle body speed Vs and the previous estimated vehicle body speed Vp.

[0033] Vp´=Vp+ΔVα …(3)

[0034] (Estimated vehicle speed calculation section) The vehicle speed calculation unit 140 calculates the current estimated vehicle speed V by adding the delay correction amount α (either the first delay correction amount α1 or the second delay correction amount α2) calculated by the delay correction amount calculation unit 120 to the corrected past estimated vehicle speed Vp' calculated by the error correction unit 130. That is, the current estimated vehicle speed V can be obtained by adding the delay correction amount α, which is the estimated increase or decrease in vehicle speed during the delay time Δt1, to the corrected past estimated vehicle speed Vp' before the delay time Δt1.

[0035] (Estimated vehicle speed calculation process) FIG. 6 is a flowchart showing an example of an estimated vehicle speed calculation process. The process shown in FIG. 6 is repeatedly executed by the estimated vehicle speed calculation unit 100 at a predetermined interval. The estimated vehicle speed calculation unit 100 acquires a delay time Δt1 from a map determined in advance depending on the vehicle situation (step S1). The estimated vehicle speed calculation unit 100 also acquires the wheel speeds ωw1 to ωw4, the longitudinal acceleration X, and the yaw rate y via CAN communication, as well as the previous estimated vehicle speed Vn-1 calculated in the previous process and the previous estimated vehicle speed Vp calculated before the delay time Δt1 (step S2). Next, the estimated vehicle speed calculation unit 100 sets the acquired wheel speeds ωw1 to ωw4 as the wheel speeds before the delay time Δt1, and the error correction unit 130 calculates the CAN vehicle speed Vs before the delay time Δt1 based on the wheel speeds ωw1 to ωw4, the yaw rate y, and the previous estimated vehicle speed Vn-1 (step S3).

[0036] Next, the estimated vehicle body speed calculation unit 100 determines whether the previous estimated vehicle body speed Vn-1 is less than the first predetermined speed V1 (step S4). When the estimated vehicle body speed calculation unit 100 determines that the previous estimated vehicle body speed Vn-1 is less than the first predetermined speed V1 (Yes in step S4), first, the disturbance correction unit 110 calculates a disturbance component Xα of the longitudinal acceleration X based on the longitudinal acceleration X and the differential value dV / dt of the estimated vehicle body speed V during the delay time Δt1 (step S5). Furthermore, the estimated vehicle body speed calculation unit 100 calculates a corrected acceleration X' by subtracting the disturbance component Xα from the longitudinal acceleration X (step S6). Next, the estimated vehicle body speed calculation unit 100 calculates an integrated value σX' by integrating the corrected acceleration X' during the delay time Δt1, sets this as a delay correction amount α (first delay correction amount α1) (step S7), and proceeds to the processing of step S9. On the other hand, if the estimated vehicle speed calculation unit 100 determines that the current vehicle speed is equal to or greater than the first predetermined speed V1 (No in step S4), it sets the difference between the previous estimated vehicle speed Vn-1 and the previous estimated vehicle speed Vp as the delay correction amount α (second delay correction amount α2) (step S8), skips steps S5 to S7, and proceeds to step S9.

[0037] Next, the estimated vehicle body speed calculation unit 100 compares the previous estimated vehicle body speed Vp from the delay time Δt1 before with the CAN vehicle body speed Vs from the delay time Δt1 before calculated in step S3, and determines whether or not there is an error ΔV (step S9). If the estimated vehicle body speed calculation unit 100 determines that there is an error ΔV between the previous estimated vehicle body speed Vp and the CAN vehicle body speed Vs from the delay time Δt1 before (Yes in step S9), the error correction unit 130 calculates an error correction value ΔVα based on the error ΔV according to the above equations (1) and (2) (step S10). Then, the estimated vehicle body speed calculation unit 100 adds the error correction value ΔVα to the previous estimated vehicle body speed Vp according to the above equation (3) to calculate a corrected previous estimated vehicle body speed Vp' (step S11), and proceeds to the processing of step S13. On the other hand, if the estimated vehicle speed calculation unit 100 determines that there is no error ΔV between the past estimated vehicle speed Vp and the CAN vehicle speed Vs before the delay time Δt1 (No in step S9), it sets the past estimated vehicle speed Vp to the corrected past estimated vehicle speed Vp' (step S12) and proceeds to processing in step S13. In other words, since the error ΔV becomes 0, the error correction value ΔVα calculated by the above equations (1) and (2) also becomes 0, and in the above equation (3), the value of the past estimated vehicle speed Vp is output as is as the corrected past estimated vehicle speed Vp'.

[0038] Next, the estimated vehicle speed calculation unit 100 adds the delay correction amount α (either the first delay correction amount α1 or the second delay correction amount α2) to the calculated corrected past estimated vehicle speed Vp' to calculate the current estimated vehicle speed V (step S13), and executes this routine again from step S1.

[0039] The behavior of the estimated vehicle body speed V calculated by the above-described estimated vehicle body speed calculation process will be described in detail with reference to Fig. 7. Fig. 7 is an explanatory diagram that schematically shows the behavior of the estimated vehicle body speed V by the estimated vehicle body speed calculation process according to the embodiment. Fig. 7 shows how the estimated vehicle body speed V (see the two-dot chain line) calculated by the estimated vehicle body speed calculation process, the wheel speed ωw (see the open circles) acquired by the ECU 10 via CAN communication, and the actual vehicle body speed VA (see the solid line) change over time.

[0040] First, immediately after the start of the electric vehicle 1, until time t1 when the wheel speed ωw is detected, the error correction unit 130 sets the filter coefficient k in the above equation (1) to 0, thereby setting the error correction value ΔVα in the above equation (2) to 0 and setting the corrected previous estimated vehicle speed Vp' to the previous estimated vehicle speed Vp. Then, as indicated by the solid white arrow in the figure, until time t1, the estimated vehicle speed V is calculated by adding the delay correction amount α to the previous estimated vehicle speed Vp. In other words, according to the configuration of this embodiment, it is possible to calculate the estimated vehicle speed V even until time t1 when the wheel speed ωw is detected. Note that, at the very beginning of the estimated vehicle speed calculation process, if the previous estimated vehicle speed Vp itself does not yet exist, both terms on the right side of the above equation (3) are 0, and therefore the corrected previous estimated vehicle speed Vp' is 0, and the value of the delay correction amount α becomes the estimated vehicle speed V.

[0041] When the wheel speed ωw starts to be detected at time t1, the error correction unit 130 calculates the error correction value ΔVα according to the above equations (1) and (2), and corrects the past estimated vehicle body speed Vp according to equation (3) to calculate the corrected past estimated vehicle body speed Vp'. Then, the estimated vehicle body speed V is calculated by adding the delay correction amount α to the corrected past estimated vehicle body speed Vp'. That is, as indicated by the white arrow in the figure, after time t1, the error correction value ΔVα is added to the past estimated vehicle body speed Vp in addition to the delay correction amount α. In other words, the corrected past estimated vehicle body speed Vp' corrected based on the actual measurement value of the wheel speed ωw becomes the reference value when calculating the estimated vehicle body speed V, and the delay correction amount α is added to this reference value. This improves the calculation accuracy of the estimated vehicle body speed V, and the estimated vehicle body speed V approaches the actual vehicle body speed VA.

[0042] 8 is an explanatory diagram showing an example of experimental results in which an estimated vehicle speed is calculated by the estimated vehicle speed calculation process according to the embodiment. FIG. 8 shows the behavior of time changes of the actual vehicle speed VA while the electric vehicle 1 is traveling, the conventional estimated vehicle speed VB calculated by a conventional method, and the estimated vehicle speed V calculated by the estimated vehicle speed calculation process according to the embodiment. Note that the actual vehicle speed VA here is a value detected by a GPS (Global Positioning System) device mounted on the electric vehicle 1. As shown in the figure, the estimated vehicle speed V calculated by the estimated vehicle speed calculation process according to the embodiment tracks the actual vehicle speed VA more closely than the conventional estimated vehicle speed VB, particularly in the extremely low speed range immediately after the electric vehicle 1 starts moving (the range where the actual vehicle speed VA is about 2 km / h). It is also shown that the estimated vehicle speed V tracks the actual vehicle speed VA more closely than the conventional estimated vehicle speed VB, even in the range where the actual vehicle speed VA is about 7 km / h or higher.

[0043] (Traction control unit) Next, a description will be given of the traction control unit 200. Here, Fig. 9 is an explanatory diagram that schematically shows how the reference rotation speed ωd of the drive shaft 5 and the wheel speed ωw change over time. 9 also shows the value of the estimated drive shaft rotation speed ωde, which will be described later. The reference rotation speed ωd is a value calculated by dividing the motor rotation speed ωm by the reduction ratio of the reduction gear mechanism 4. As shown in the figure, a deviation occurs between the reference rotation speed ωd and the wheel speed ωw due to torsion occurring in the drive shaft 5. Therefore, if the reference rotation speed ωd of the drive shaft 5 is used directly for traction control, it may lead to a deterioration in control accuracy. Therefore, in the ECU 10 of this embodiment, the traction control unit 200 more appropriately calculates the rotation speed of the drive shaft 5 and performs traction control.

[0044] FIG. 10 is a control block diagram showing an example of the configuration of traction control unit 200. As shown in FIGS. 2 and 10, traction control unit 200 includes required torque setting unit 210, target drive shaft rotation speed calculation unit 220, estimated drive shaft rotation speed calculation unit 230, and torque command value calculation unit 240. Note that delay block 310 in the diagram indicates that a control delay occurs due to a communication delay or the like. Also, plant block 320 in the diagram is a control block indicating that the electric vehicle 1 is drive-controlled using torque command value Tm* or the like, and FIG. 10 shows an example in which values ​​of motor rotation speed ωm, wheel speed ωw, and longitudinal acceleration X are output.

[0045] (Required torque setting section) The required torque setting unit 210 acquires the accelerator operation amount from the accelerator sensor 13 and also acquires the current estimated vehicle speed V from the estimated vehicle speed calculation unit 100. Based on the acquired accelerator operation amount and the current estimated vehicle speed V, the required torque setting unit 210 sets and outputs a required torque Tm1 to the motor 2 from a predetermined map.

[0046] (Target drive shaft rotation speed calculation section) The target drive shaft rotation speed calculation unit 220 acquires the current estimated vehicle speed V calculated by the estimated vehicle speed calculation unit 100. In the target drive shaft rotation speed calculation unit 220, a target slip ratio multiplication block 221 calculates a value Vλ* by multiplying the estimated vehicle speed V by the target slip ratio λ*. Furthermore, in the target drive shaft rotation speed calculation block 222, the target drive shaft rotation speed calculation unit 220 multiplies the estimated vehicle speed V by the value Vλ* to calculate the target slip speed V*, and outputs the calculated target slip speed V* as the target drive shaft rotation speed ωd*. Note that when the wheel 3 to be controlled is the front wheel 3a, the target slip ratio λ* is a target value for the slip ratio of the front wheel 3a, and is specified, for example, by a map in which values ​​are predetermined according to the estimated vehicle speed V.

[0047] (Drive shaft rotation speed calculation section) The estimated drive shaft rotation speed calculation unit 230 acquires a torque command value Tm* set by a torque command value calculation unit 240, which will be described later. The estimated drive shaft rotation speed calculation unit 230 also acquires a motor rotation speed ωm that is drive-controlled using the torque command value Tm*. The estimated drive shaft rotation speed calculation unit 230 then estimates a deviation Δωd between the reference rotation speed ωd and the wheel speed ωw of the front wheels 3a in accordance with a transfer function G(s) defined by the following equation (4) based on the acquired torque command value Tm* and vehicle specifications. The deviation Δωd is the deformation speed of the drive shaft 5. "Jall" on the right side of equation (4) is a value obtained by converting the inertia of the entire body of the electric vehicle 1 into the inertia of the front wheel 3a (hereinafter referred to as "body-side inertia Jall"), and "Jm" is the inertia of the motor 2 (hereinafter referred to as "motor inertia Jm"). Furthermore, "D" is the damping coefficient of the entire drive system including all power transmission mechanisms that transmit the output of the motor 2 to the front wheel 3a, and "K" is the spring coefficient of the entire drive system. These constants are values ​​that are set in advance as vehicle specifications of the electric vehicle 1. Note that equation (4) is based on the premise that the wheel 3 is in a state where it is gripping the road surface.

[0048] Δωd / Tm*=G(s)=Jall·s2 / (Jall·(Jm+D)·s2+(Jm·D+Jall·K)·s+Jm·K) …(4)

[0049] However, the inertia "Jall" of the entire vehicle body is calculated, for example, by the following equation (5). In equation (5), "Jw" is the inertia of the front wheels 3a, "r" is the effective radius of the front wheels 3a, "M" is the mass of the electric vehicle 1, and "λ" is the slip ratio of the front wheels 3a. The slip ratio λ is calculated, for example, by the following equation (6) based on the current estimated vehicle body speed V and the wheel speed ωw of the front wheels 3a. As shown in equation (5), the vehicle body inertia Jall becomes smaller as the slip ratio λ increases. Note that the vehicle body inertia Jall is not limited to being calculated based on equation (5), and may be corrected so that it becomes smaller as the slip ratio λ increases by multiplying the vehicle body inertia Jall, which is a predetermined vehicle specification, by a predetermined correction coefficient according to the slip ratio λ.

[0050] Jall=2·Jw+r2·M·(1-λ) …(5) λ=(V-ωw) / V …(6)

[0051] Then, the estimated drive shaft rotation speed calculation unit 230 calculates the reference rotation speed ωd of the drive shaft 5 by dividing the motor rotation speed ωm by the reduction ratio G of the speed reduction mechanism 4 in the reference rotation speed calculation unit 232. Furthermore, the estimated drive shaft rotation speed calculation unit 230 calculates the estimated drive shaft rotation speed ωde by subtracting the deviation Δωd, i.e., the component of the deformation speed due to torsion of the drive shaft 5, from the reference rotation speed ωd according to the following equation (7). The estimated drive shaft rotation speed calculation unit 230 outputs the calculated estimated drive shaft rotation speed ωde to the torque command value calculation unit 240.

[0052] ωde=ωd-Δωd …(7)

[0053] (torque command value calculation section) The torque command value calculation unit 240 acquires the target drive shaft rotation speed ωd* and the estimated drive shaft rotation speed ωde, and performs feedback control based on the target drive shaft rotation speed ωd* and the estimated drive shaft rotation speed ωde to calculate a torque command value Tm* for the motor 2. More specifically, the torque command value calculation unit 240 calculates the difference between the target drive shaft rotation speed ωd* and the estimated drive shaft rotation speed ωde, and outputs the difference to the PID control block 241. The PID control block 241 calculates a proportional term for the difference in a proportional term calculation unit 241p, a differential term for the difference in a differential term calculation unit 241d, and an integral term for the difference in an integral term calculation unit 241i. The torque command value calculation unit 240 adds together the proportional term, integral term, and differential term calculated in the PID control block 241 to calculate a feedback correction amount ΔTm. The feedback correction amount ΔTm is calculated as a correction amount for correcting the required torque Tm1 and setting the torque command value Tm* of the motor 2 so that the reference rotation speed ωd of the drive shaft 5 as an output value approaches the target drive shaft rotation speed ωd*. The torque command value calculation unit 240 obtains the required torque Tm1 from the required torque setting unit 210 in a difference block 242, and calculates the torque command value Tm* of the motor 2 by subtracting the feedback correction amount ΔTm from the required torque Tm1. As a result, the motor 2 is driven by the torque command value Tm*.

[0054] As described above, by subtracting the deviation Δωd from the reference rotation speed ωd, i.e., the component of the deformation speed due to torsion of the drive shaft 5, it is possible to accurately calculate the estimated drive shaft rotation speed ωde so that it follows the wheel speed ωw, as shown in FIG. 9. FIG. 11 is an explanatory diagram showing an example of experimental results in which the ECU 10 according to the embodiment calculates the estimated drive shaft rotation speed. FIG. 11 shows how the reference rotation speed ωd of the drive shaft 5, the estimated drive shaft rotation speed ωde, and the actual vehicle speed VA change over time. Note that the actual vehicle speed VA is the vehicle speed obtained by GPS, as described above. As shown in the figure, in the low-speed range, the estimated drive shaft rotation speed ωde behaves more closely to the actual vehicle speed VA than the reference rotation speed ωd.

[0055] (Effects of the embodiment) As described above, the ECU 10 (control device) of the electric vehicle 1 according to the embodiment is a control device that calculates the estimated vehicle speed V of the electric vehicle 1 that is equipped with the motor 2 (travel motor), and includes a delay correction amount calculation unit 120 that calculates an estimated increase or decrease in vehicle speed during the delay time that occurs when the wheel speed ωw is acquired via the wheel speed sensor 12 and CAN communication as a delay correction amount α based on either the longitudinal acceleration X of the electric vehicle 1 or the estimated vehicle speed V; an error correction unit 130 that calculates a corrected past estimated vehicle speed Vp' by correcting the past estimated vehicle speed Vp based on the error ΔV between the past estimated vehicle speed Vp, which is the estimated vehicle speed V calculated only the delay time Δt1 ago, and the CAN vehicle speed Vs, which is based on the wheel speed ωw acquired via CAN communication; and a vehicle speed calculation unit 140 that calculates the current estimated vehicle speed V by adding the delay correction amount α and the corrected past estimated vehicle speed Vp'.

[0056] With this configuration, the previous estimated vehicle speed Vp, which was calculated a delay time Δt1 due to a CAN communication delay and a detection delay of the wheel speed sensor 12, is corrected based on the wheel speed ωw acquired through CAN communication, thereby enabling accurate calculation of a base corrected previous estimated vehicle speed Vp'. Then, the current estimated vehicle speed V is calculated by adding the delay correction amount α, which is the estimated increase or decrease in vehicle speed during the delay time Δt1, to the corrected previous estimated vehicle speed Vp', thereby compensating for the vehicle speed for the delay time Δt1. Therefore, the ECU 10 according to the embodiment can more appropriately estimate the vehicle speed by taking into account the delay time Δt1 between when the wheel speed ωw is detected by the wheel speed sensor 12 and when it is acquired through CAN communication.

[0057] Furthermore, the delay correction amount calculation unit 120 calculates an integrated value σX' of the longitudinal acceleration X (corrected acceleration X' in this embodiment) of the electric vehicle 1 during the delay time Δt1 as the delay correction amount α (first delay correction amount α1). With this configuration, the delay correction amount calculation unit 120 can appropriately calculate the delay correction amount α based on the longitudinal acceleration X.

[0058] Further, the longitudinal acceleration X is a value detected by an acceleration sensor 15 mounted on the electric vehicle. With this configuration, the longitudinal acceleration X can be easily acquired. Note that, when the longitudinal acceleration X detected by the acceleration sensor 15 is used for this control, a communication delay may occur when the ECU 10 acquires the longitudinal acceleration X through CAN communication. Therefore, it is preferable that the ECU 10 uses the longitudinal acceleration X detected by the acceleration sensor 15 when the amount of change in the longitudinal acceleration X within a predetermined time is within a predetermined range. When the amount of change in the longitudinal acceleration X within a predetermined time is larger than the predetermined range, the ECU 10 may acquire the longitudinal acceleration X by another method described later.

[0059] The integrated value σX' is a value obtained by integrating the corrected acceleration X' after correcting the disturbance components including the road surface gradient. With this configuration, the integrated value σX' can be calculated with higher accuracy.

[0060] Furthermore, if the previous estimated vehicle body speed Vn-1 calculated in the previous processing is equal to or greater than the first predetermined speed V1 (predetermined speed), the delay correction amount calculation unit 120 sets the difference between the previous estimated vehicle body speed Vn-1 and the past estimated vehicle body speed Vp as the delay correction amount α (second delay correction amount α2), and if the previous estimated vehicle body speed Vn-1 is less than the first predetermined speed V1, it sets the integrated value σX' of the longitudinal acceleration X of the electric vehicle 1 during the delay time Δt1 as the delay correction amount α (first delay correction amount α1).

[0061] With this configuration, the delay correction amount calculation unit 120 can calculate the delay correction amount α with high accuracy through simple calculations in a speed range equal to or greater than the first predetermined speed V1, without using the longitudinal acceleration X. Furthermore, the delay correction amount calculation unit 120 can appropriately calculate the delay correction amount α based on the longitudinal acceleration X in a speed range less than the first predetermined speed V1. Note that the corrected previous estimated vehicle speed Vp' may be used instead of the previous estimated vehicle speed Vp.

[0062] (Variation) Although the description of the embodiment has been completed above, aspects of the present invention are not limited to this embodiment. For example, in this embodiment, the ECU 10 as the control device according to the embodiment is applied to an electrically powered vehicle 1 as an electric vehicle (BEV), but the ECU 10 is not limited to electric vehicles (BEVs), and may be applied to vehicles such as plug-in hybrid electric vehicles (PHEVs) or hybrid electric vehicles (HEVs) that can be externally charged or externally powered, as long as they are equipped with a traction motor.

[0063] Furthermore, in this embodiment, the longitudinal acceleration X is a value detected by the acceleration sensor 15. However, the longitudinal acceleration X may be a value calculated based on the wheel speed ωw. That is, a differential value over the delay time Δt1 may be calculated for the CAN vehicle speed Vs calculated based on the wheel speed ωw, and the calculated differential value may be used as the longitudinal acceleration X. With this configuration, the longitudinal acceleration X can be obtained using only the wheel speed sensor 12 for detecting the wheel speed ωw. Note that when the ECU 10 obtains the wheel speed ωw detected by the wheel speed sensor 12 through CAN communication, a delay time Δt1 occurs. Therefore, the ECU 10 may obtain the longitudinal acceleration X based on the wheel speed ωw in a situation where the delay time Δt1 is short, that is, in a region where the vehicle speed is greater than a predetermined value.

[0064] Furthermore, the longitudinal acceleration X may be a value calculated based on the estimated vehicle body speed V. That is, a derivative value dV / dt of the finally calculated estimated vehicle body speed V over the delay time Δt1 may be calculated, and the calculated derivative value dV / dt may be used as the longitudinal acceleration X. With this configuration, the longitudinal acceleration X can be obtained without using the acceleration sensor 15 or the wheel speed sensor 12.

[0065] Furthermore, the longitudinal acceleration X may be a value calculated based on the driving force and braking force of the electric vehicle 1. The driving force can be calculated based on the torque command value of the motor 2. The braking force can be calculated based on the brake operation amount detected by the brake sensor 14, the brake fluid pressure, and the like. The longitudinal acceleration X may be calculated based on the difference between the driving force and the braking force, for example, by dividing the vehicle weight by the difference between the driving force and the braking force. With this configuration, the longitudinal acceleration X can be obtained without using the acceleration sensor 15 or the wheel speed sensor 12.

[0066] Furthermore, the longitudinal acceleration X may be selected from the values ​​detected by the acceleration sensor 15, the values ​​calculated based on the wheel speed ωw, the values ​​calculated based on the estimated vehicle body speed V, and the values ​​calculated based on the driving force and braking force of the electric vehicle 1, so that the value that can be calculated most accurately is used depending on the vehicle situation.

[0067] In addition, the value of the differential value dV / dt of the estimated vehicle speed V used in the disturbance correction unit 110 may be calculated as either a value calculated based on the wheel speed ωw or a value calculated based on the driving force and braking force of the electric vehicle 1. [Explanation of symbols]

[0068] 1 Electric vehicle, 2 Motor, 3 Wheel, 3a Front wheel, 3b Rear wheel, 4 Reduction mechanism, 5 Drive shaft (drive axle), 10 ECU (controller), 11 Motor rotation speed sensor, 12 Wheel speed sensor, 15 Acceleration sensor, 100 Estimated vehicle speed calculation unit, 110 Disturbance correction unit, 120 Delay correction amount calculation unit, 130 Error correction unit, 140 Vehicle speed calculation unit, 200 Traction control unit, 210 Required torque setting unit, 220 Target drive shaft rotation speed calculation unit, 230 Estimated drive shaft rotation speed calculation unit, 231 Deviation calculation unit, 240 Torque command value calculation unit, Jall Vehicle side inertia, Jm Motor inertia, k Filter coefficient, Tm Torque command value, Tm1 Required torque, V Estimated vehicle speed, V1 First predetermined speed (predetermined speed), VA Actual vehicle speed, VB Conventional estimated vehicle speed, VG1, VG2, VG3, VG4 Center of gravity vehicle speed, Vn-1 Previous estimated vehicle speed, Vp Previous estimated vehicle speed, Vp´ Corrected previous estimated vehicle speed, Vs CAN vehicle speed, Vsf Filtered CAN vehicle speed, X Longitudinal acceleration, X´ Corrected acceleration, Xe Estimated acceleration, Xα Disturbance component, y Yaw rate, α Delay correction amount, α1 First delay correction amount, α2 Second delay correction amount, Δt1 Delay time, ΔTm Feedback correction amount, ΔV Error, ΔVα Error correction value, Δωd Deviation, λ* Target slip ratio, λ Slip ratio, σX Integrated value, ωd Reference rotation speed, ωd* Target drive shaft rotation speed, ωde Estimated drive shaft rotation speed, ωm Motor rotation speed, ωw, ωw1, ωw2, ωw3, ωw4 Wheel speed

Claims

1. A vehicle control device that calculates an estimated vehicle speed of a vehicle equipped with an electric motor for running, a delay correction amount calculation unit that calculates an estimated increase or decrease in vehicle speed during a delay time that occurs when acquiring wheel speeds via sensors and CAN communication, as a delay correction amount based on either a longitudinal acceleration of the vehicle or the estimated vehicle speed; an error correction unit that calculates a corrected past estimated vehicle speed by correcting the past estimated vehicle speed based on an error between the past estimated vehicle speed, which is the estimated vehicle speed calculated the delay time before, and a vehicle speed based on the wheel speed acquired via CAN communication; a vehicle speed calculation unit that calculates the current estimated vehicle speed by adding the delay correction amount and the corrected past estimated vehicle speed.

2. The vehicle control device according to claim 1 , wherein the delay correction amount calculation unit calculates, as the delay correction amount, an integrated value of longitudinal acceleration of the vehicle during the delay time.

3. 3. The vehicle control device according to claim 2, wherein the longitudinal acceleration is a value detected by an acceleration sensor mounted on the vehicle.

4. The vehicle control device according to claim 2 , wherein the longitudinal acceleration is a value calculated based on the wheel speed.

5. 3. The vehicle control device according to claim 2, wherein the longitudinal acceleration is a value calculated based on the estimated vehicle body speed.

6. 3. The vehicle control device according to claim 2, wherein the longitudinal acceleration is a value calculated based on a driving force and a braking force of the vehicle.

7. 7. The vehicle control device according to claim 2, wherein the integrated value is a value obtained by integrating corrected accelerations in which disturbance components including a road surface gradient have been corrected.

8. The delay correction amount calculation unit When the previous estimated vehicle speed calculated in the previous process is equal to or greater than a predetermined speed, the difference between the previous estimated vehicle speed and the past estimated vehicle speed is set as the delay correction amount; If the previous estimated vehicle speed is less than the predetermined speed, the integrated value of the longitudinal acceleration of the vehicle during the delay time is set as the delay correction amount. The vehicle control device according to any one of claims 2 to 6.

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