Vehicle state estimation device and control method for the operation of an active suspension system

Abstract

To provide a state estimation device for a vehicle, having improved calculation accuracy of a spring constant.SOLUTION: A state estimation device for a vehicle comprises: a physical quantity detection section which detects a physical quantity indicating vehicle behavior; a vehicle behavior estimation section which estimates current vehicle behavior on the basis of the physical quantity detected by the physical quantity detection section; a distance sensor which is provided on a vehicle body member of the vehicle and detects a value related to a distance between the vehicle body member and a measurement point on a road surface ahead of the vehicle and corresponding to at least a center part of a road surface contact part of a wheel; a distance calculation section which calculates a road surface distance, as the distance from the vehicle body member to the measurement point, on the basis of the detection value detected by the distance sensor; a spring constant calculation section which calculates a spring constant of at least part of an active type suspension device in a vehicle stopped state; and a suspension control section which controls operation of the active type suspension device on the basis of the spring constant, the road surface distance, and vehicle behavior information, as information indicating the current vehicle behavior estimated by the vehicle behavior estimation section.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a vehicle state estimation device and a method for controlling the operation of an active suspension system. [Background technology]

[0002] In recent years, there has been a surge in efforts to provide access to sustainable transportation systems that take into account vulnerable groups such as the elderly, people with disabilities, and children. To achieve this, we are focusing on research and development to further improve the safety and convenience of transportation through the development of vehicle behavior stability.

[0003] To improve the stability of vehicle behavior, vehicles equipped with active suspension have been proposed. For example, in the vehicle described in Patent Document 1, the vehicle is equipped with a vehicle body behavior estimation unit. The future speed and displacement of the front wheel suspension and the future speed and displacement of the rear wheel suspension are input to the vehicle body behavior estimation unit. Based on this input information, the damping coefficient of the dampers installed on each wheel and the spring constant of the suspension installed on each wheel are calculated. The estimated vehicle body behavior is then output to the suspension control unit. This makes it possible to realize a semi-active suspension or a stabilizer with adjustable rigidity. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-195323 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, in terms of vehicle behavior stability, it is necessary to more accurately understand vehicle specifications such as spring constants and reflect them in the control system. However, there is a challenge in that these specifications differ from the theoretical values ​​in the design due to errors and variations in vehicle parts and assembly, as well as the effects of deterioration and wear. In particular, there is a challenge in the accuracy of calculating spring constants, which hinders more accurate estimation of vehicle behavior.

[0006] This invention aims to provide a vehicle state estimation device with improved accuracy in calculating spring constants to solve the above-mentioned problems. Ultimately, this will contribute to the development of sustainable transportation systems. [Means for solving the problem]

[0007] (1) To solve the above problems, the vehicle state estimation device of the present invention is a vehicle state estimation device used in a vehicle equipped with an active suspension system and a suspension control device, comprising: a physical quantity detection unit that detects a physical quantity indicating the behavior of the vehicle; a vehicle behavior estimation unit that estimates the current behavior of the vehicle based on the physical quantity detected by the physical quantity detection unit; a distance sensor provided on a vehicle body member that constitutes the vehicle and that detects a value relating to the distance between the vehicle body member and a measurement point on the road surface in front of the vehicle that corresponds to at least the central part of the road contact portion of the wheel; a distance calculation unit that calculates a road surface distance, which is the distance from the vehicle body member to the measurement point, based on the detected value detected by the distance sensor; a spring constant calculation unit that calculates the spring constant of at least a part of the active suspension system when the vehicle is stopped; and a suspension control unit that controls the operation of the active suspension system based on the spring constant, the road surface distance, and vehicle behavior information, which is information indicating the current behavior of the vehicle estimated by the vehicle behavior estimation unit.

[0008] Such a vehicle state estimation device can provide a vehicle state estimation device with improved accuracy in calculating the spring constant. This is because it can calculate the spring constant with greater accuracy compared to calculating it while the vehicle is in motion.

[0009] (2) Furthermore, the vehicle state estimation device of the present invention includes a distance calculation unit which calculates the distance from the vehicle body member to the measurement point in front of the front wheel of the vehicle as the road surface distance, and a spring constant calculation unit which calculates the spring constant for the active suspension system corresponding to the front wheel.

[0010] This type of vehicle condition estimation device calculates the spring constant of the front wheels based on the distance to the road surface in front of the adjacent front wheels. Therefore, it is possible to calculate the spring constant with high accuracy. This is because it improves the measurement accuracy compared to calculating the spring constant of the rear wheels using the distance to the road surface in front of the front wheels, and consequently, the accuracy of the calculated spring constant is less likely to decrease.

[0011] (3) Furthermore, in the vehicle state estimation device of the present invention, the suspension control unit, when the vehicle is not in a stopped state, adopts a fixed value or the value used in the previous control as the spring constant to control the operation of the active suspension system.

[0012] Such a vehicle state estimation device can prevent the application of abnormally high spring constant values, because it only uses the spring constant calculated in a stationary state.

[0013] (4) Furthermore, in the vehicle state estimation device of the present invention, the suspension control unit uses the spring constant in at least one of the following calculations: correction of preview control, constant adjustment of skyhook control, and constant adjustment of damping control.

[0014] Such a vehicle condition estimation device can improve the accuracy of various controls in the suspension control system, even if there are individual differences or differences in conditions. This is because multiple suspension control modes are available.

[0015] (5) Furthermore, in the vehicle state estimation device of the present invention, the suspension control unit replaces the calculated spring constant of the member with the corresponding spring constant of the member in the formula for calculating the correction of the preview control.

[0016] According to such a vehicle state estimation device, even if there are individual differences or condition differences, the accuracy of various controls in the suspension control means can be improved. This is because it is possible to individually optimize a plurality of types of suspension control modes that are prepared.

[0017] (6) Further, in the vehicle state estimation device of the present invention, the calculated spring constant of the member is the spring constant of the tire, and in the mathematical formula for constant adjustment of the damping control in the suspension control unit, the larger the tire spring constant, the smaller the damper constant in the stroke speed × damper constant of the damping control.

[0018] According to such a vehicle state estimation device, even if there are individual differences or condition differences, the accuracy of various controls in the suspension control means can be improved. This is because it is possible to individually optimize a plurality of types of suspension control modes that are prepared.

[0019] (7) Further, in the vehicle state estimation device of the present invention, the calculated spring constant of the member is the spring constant of the tire, a tire pressure detection unit is provided, and the predicted value of the tire spring constant estimated based on the tire pressure detected by the tire pressure detection unit is compared with the calculated spring constant of the tire. When the difference is a certain value or more, a fixed value or the value used in the previous control is adopted as the spring constant to control the operation of the active suspension device.

[0020] According to such a vehicle state estimation device, the reliability of the calculated spring constant can be improved. By comparing the calculated spring constant with the spring constant obtained by a different method, it is possible to suppress the application of an abnormal value of the spring constant.

[0021] (8) To solve the above problems, a method for controlling the operation of the active suspension device of the present invention is a method for controlling the operation of the active suspension device in a vehicle equipped with the active suspension device and a suspension control device, the method comprising: a physical quantity detection step of detecting a physical quantity indicating the behavior of the vehicle; a vehicle behavior estimation step of estimating the current behavior of the vehicle based on the physical quantity detected in the physical quantity detection step; a distance detection step of detecting a value related to the distance between a vehicle body member constituting the vehicle and a measurement point on the road surface in front of the vehicle corresponding to at least the central portion of the road surface contact portion of the wheel; a distance calculation step of calculating a road surface distance, which is the distance from the vehicle body member to the measurement point, based on the detection value detected in the distance detection step; a spring constant calculation step of calculating at least a part of the spring constant of the active suspension device in a vehicle stop state; and a suspension control step of controlling the operation of the active suspension device based on the spring constant, the road surface distance, and vehicle behavior information, which is information indicating the current behavior of the vehicle estimated in the vehicle behavior estimation step.

[0022] According to such a method for controlling the operation of the active suspension device, it is possible to provide a method for controlling the operation of the active suspension device with improved accuracy in calculating the spring constant. This is because the spring constant can be calculated more accurately compared to the case of calculating the spring constant during running.

[0023] Note that the above (1) to (8) can be arbitrarily combined as necessary.

Effects of the Invention

[0024] According to the present invention, it is possible to provide a vehicle state estimation device with improved accuracy in calculating the spring constant.

Brief Description of the Drawings

[0025] [Figure 1] It is a block diagram showing an overview of a suspension system of a vehicle. [Figure 2] It is a side view of a vehicle showing an attachment structure of a distance sensor. [Figure 3]This diagram shows the configuration of the distance sensor, viewed from the front of the wheels. [Figure 4] This diagram shows the processing flow for estimating the spring constant of a tire. [Figure 5] This diagram shows the processing flow when estimating the spring constant of a suspension. [Figure 6] (a) shows the formula for calculating the preview control correction, and (b) is a diagram of the electric suspension model used to estimate the spring constant. [Modes for carrying out the invention]

[0026] (Suspension system) Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a diagram showing an overview of the suspension system 3 of a vehicle to which the preview road surface detection device 1 of this embodiment is applied.

[0027] The suspension system 3 includes a preview road surface detection device 1, a preview control unit 4, a suspension control unit 5, a vehicle body member 30, an active suspension D, and wheels W. The preview road surface detection device 1 also includes a distance calculation unit 12 and a distance sensor 11.

[0028] In the suspension system 3, the suspension control unit 5 controls the active suspension D so that the posture of the vehicle body member 30 is stable. This control is performed based on, for example, the skyhook theory.

[0029] (Road surface displacement) In the control of the active suspension D, first, the preview road surface detection device 1 acquires the road surface displacement L2 in front of the vehicle. Here, the road surface displacement L2 is the distance between the road surface R on which the wheel W is currently in contact and the measurement point P in the direction perpendicular to the road surface R. The road surface R refers to the ground on which the wheel W is in contact. The measurement point P refers to the point on the ground on which the distance sensor 11 measures the distance. The road surface displacement L2 is also called predictive information.

[0030] (Preview control unit) Next, the preview control unit 4 acquires the road surface displacement L2 from the preview road surface detection device 1. Then, based on the value of the road surface displacement L2, it controls the operation of the active suspension D to reduce body vibrations caused by road surface input. In this way, the suspension system 3 aims to improve the ride comfort of the vehicle.

[0031] (Vehicle configuration) The suspension system 3 will be explained in more detail, referring to Figure 2. Figure 2 is a side view of vehicle V showing the mounting mechanism of the distance sensor 11. Vehicle V comprises a body B and wheels W. The components constituting the body B include a body member 30. Wheels W are provided on the underside of the body member 30. Figure 2 shows the front wheels of the wheels W. The front wheels include the left wheel and the right wheel. Figure 2 shows the left wheel of the left and right wheels.

[0032] (Vibration model) The active suspension D and the tire portion of the wheel W absorb the irregularities of the road surface R. The suspension control unit 5 shown in Figure 2 controls the tire portion of the wheel W as a vibration model. This vibration model is a vibration model in which a spring W1 and a damper W2 are arranged in parallel.

[0033] (Active suspension) The active suspension D can control damping force using a suspension spring D1 and a hydraulic actuator. Alternatively, the active suspension D can be configured with a suspension spring D1 and a variable damper D2 arranged in parallel. The variable damper D2 is a damper whose damping force and thrust are controlled by electromagnetic force. The active suspension D is installed between the vehicle body member 30 and the wheel W.

[0034] (Suspension control unit) The suspension control unit 5 controls the variable damper D2 as the control target.

[0035] (Preview road surface detection device) The preview road surface detection device 1 is installed on the vehicle body member 30. The preview road surface detection device 1 includes a distance sensor 11 and a distance calculation unit 12.

[0036] (Distance sensor) The distance sensor 11 measures the distance between the vehicle body member 30 and the measurement point P on the road surface R. The distance between the vehicle body member 30 and the measurement point P on the road surface R is defined as the road surface distance L1. This measurement is performed using ultrasound, laser light, or millimeter-wave radar, etc.

[0037] (Distance calculation unit) The distance calculation unit 12 calculates the road surface displacement L2 in front of the wheel W based on the measurement value from the distance sensor 11. Specifically, the preview road surface detection device 1 calculates the road surface displacement L2 in front of the wheel W by subtracting the vehicle height L3 at the time of measurement from the road surface distance L1 calculated by the distance calculation unit 12. The vehicle height L3 is the distance between the vehicle body member 30 and the road surface R at the road contact point 41.

[0038] In other words, road surface distance L1 - vehicle height L3 = road surface displacement L2. Note that when calculating the road surface displacement L2, the vehicle height L3 can also be determined by referring to the value calculated by the suspension control unit 5 as a control variable.

[0039] (Time required to reach) The preview control unit 4 calculates the time required for the wheels W to travel to the measurement point P of the road surface displacement L2, based on the vehicle speed at the time the road surface displacement L2 was measured and the distance in the direction of travel of the vehicle V from the tire contact point to the measurement point P of the road surface displacement L2. This time required is defined as the arrival time. The distance in the direction of travel of the vehicle V from the tire contact point to the measurement point P of the road surface displacement L2 can also be determined by referring to information regarding the mounting position of the distance sensor 11.

[0040] (Predictive information) The preview road surface detection device 1 and the preview control unit 4 can periodically perform the aforementioned processing for determining the road surface displacement L2. This allows for obtaining predictive information about the road surface displacement L2. The predictive information, as described above, is information about the road surface condition in front of the wheel W that will pass after a predetermined time. The road surface condition includes the road surface displacement L2 and the state of unevenness of the road surface R.

[0041] The suspension control unit 5 controls the active suspension D based on predictive information of the road surface displacement L2. As a result, the suspension control unit 5 can improve the ride comfort of the vehicle V.

[0042] (Installation of preview road surface detection device) As described above, the preview road surface detection device 1 of this embodiment includes a distance sensor 11 and a distance calculation unit 12. Of these, the distance sensor 11 is installed on the vehicle body member 30. On the other hand, the distance calculation unit 12 is implemented in the ECU (Electronic Control Unit) of the vehicle V.

[0043] (Installation of distance sensor) The mounting of the distance sensor 11 will be explained in detail based on Figure 2. Note that the mounting structure of the distance sensor 11 described below, and the other structures of the vehicle V shown in Figure 2, have been simplified for the sake of clarity. Furthermore, the mounting of the distance sensor 11 is not limited to the method described below.

[0044] (Definition of direction) In this explanation, the direction of travel of vehicle V will be described as "forward," the direction of reversing as "rear," the vertical upward direction as "up," the vertical downward direction as "down," and the vehicle width direction as "left" and "right." Furthermore, the mounting structure of vehicle sensors such as the distance sensor 11 is, in principle, symmetrical. Therefore, in the following explanation, one side (left) will be mainly described, and the explanation of the other side (right) will be omitted as appropriate.

[0045] Figure 2 is a side view of vehicle V showing the mounting structure of the distance sensor 11. In Figure 2, the outer shape of vehicle V is shown by a dashed line. (Vehicle body) Vehicle V includes a vehicle body B as its main component. In addition to the vehicle body member 30, the vehicle body B includes an exterior member 20 and a distance sensor 11, etc. The distance sensor 11 is fixed to the vehicle body member 30.

[0046] Furthermore, the exterior member 20 is a component that forms the outer part of the vehicle V. The exterior member 20 forms the outer shell of the vehicle V. On the other hand, the distance sensor 11 is a device that detects the road surface condition.

[0047] (vehicle) Vehicle V is not particularly limited in form or type, as long as it is an automobile equipped with a body member 30, exterior member 20, and distance sensor 11 as described above. Vehicle V can be, for example, a passenger car, bus, truck, work vehicle, etc.

[0048] The following provides a more detailed explanation of each component. (Vehicle body components) The body member 30 has the function of supporting the exterior member 20. The body member 30 is also composed of a front side frame 31, an upper member 32, a bumper beam extension 33, and a bumper beam 34. The front side frame 31, upper member 32, and bumper beam 34 are sometimes referred to as frame members.

[0049] (Exterior components) The exterior components 20 include an engine hood 21, a front bumper 22, and a front fender 23. The front bumper 22 is sometimes simply referred to as the bumper.

[0050] The engine hood 21 is a panel member that covers the upper surface in front of the windshield. The front bumper 22 is located on the front side of the vehicle V and is made of a panel member made of, for example, synthetic resin. The front bumper 22 also has a front portion 22a on which air intakes and the like are provided, and a bottom portion 22b that extends rearward from the lower end of the front portion 22a. The front fender 23 is a panel member that covers the area around the wheels W.

[0051] (Installation of distance sensor) The distance sensor 11 is a sensor that detects the condition of the road surface R in front of the vehicle V. The distance sensor 11 is fixed to the upper member 32. As mentioned above, the upper member 32 is a component of the vehicle body member 30. The upper member 32 is positioned in front of the wheel W.

[0052] More specifically, the distance sensor 11 is mounted on the outer side of the upper member 32 in the vehicle width direction. Furthermore, the distance sensor 11 is located at the front end of the upper member 32 in the longitudinal direction.

[0053] (Distance sensor configuration) The distance sensor 11 of this embodiment is configured to detect the road surface distance L1 on the road surface R directly in front of the wheel W, as shown by arrow A1 in Figure 2. The road surface distance L1 is the distance between the vehicle body member 30 and the measurement point P on the road surface R. The distance sensor 11 can be appropriately selected from various types of sensors such as radar, camera, and laser. Furthermore, the distance sensor 11 does not need to be composed of a single type of sensor. The distance sensor 11 can also be configured by combining multiple types of sensors, such as a camera and a laser.

[0054] (Sensor element) Next, distance detection by the distance sensor 11 will be described based on Figure 3. Figure 3 shows the distance sensor 11 as viewed from the front of the vehicle towards the wheel W. The distance sensor 11 in this embodiment is equipped with a sensor element 11a. The sensor element is a component that detects distance. At least one sensor element is provided in the distance sensor 11. The method for detecting the distance of each sensor element is not particularly limited. Various methods can be used for detection, such as a method based on the principle of triangulation, a method that converts the reflected light intensity of emitted infrared light into distance, or a method that converts the time of flight of laser light into distance.

[0055] (Detection by sensor element) The detection of distance by the sensor element 11a will now be explained. As shown in Figure 3, the wheel W is in contact with the road surface R, specifically the ground surface S1 of the tire's contact point. As shown in Figure 1, the distance sensor 11, or more specifically, the distance sensor element 11a, detects the distance between the vehicle body member 30 and the measurement point P at a measurement point on the measurement surface S2 in front of the vehicle V (the position indicated by the arrow in Figure 3, shown as point P in Figure 1), which corresponds to the central part 43 of the wheel W's road contact width L4.

[0056] (Calculation of road surface distance) The distance calculation unit 12 (shown in Figure 1) of the preview road surface detection device 1 calculates the road surface distance based on the value detected by the distance sensor element 11a.

[0057] The active suspension D of vehicle V is controlled based on the condition of the road surface R detected by the distance sensor 11. Note that the condition of the road surface R may sometimes be simply referred to as the road surface condition.

[0058] (Other configurations) Figure 3 shows a configuration in which one distance sensor 11 is equipped with one distance sensor element 11a. However, the number of distance sensor elements equipped with one distance sensor 11 is not limited to one. One distance sensor 11 may be equipped with two or more distance sensor elements. For example, one distance sensor 11 may be equipped with three distance sensor elements. When multiple distance sensor elements are equipped, the road surface distance can be calculated based on the average value of the values ​​detected by, for example, three distance sensor elements. By using multiple distance sensor elements, the detection accuracy of road surface displacement can be improved.

[0059] (Overview of a vehicle condition estimation device) The suspension system 3 of this embodiment also functions as a vehicle state estimation device. In other words, the suspension system 3 includes a vehicle state estimation device in at least part of it. The vehicle state estimation device calculates the spring constant and controls the operation of the active suspension system based on the calculated spring constant. The active suspension system corresponds to, for example, the active suspension D.

[0060] (Configuration of a vehicle condition estimation device) As mentioned above, the vehicle state estimation device is part of the suspension system 3. The vehicle state estimation device includes a spring constant calculation unit 40, a physical quantity detection unit 51, and a vehicle behavior estimation unit 52. The spring constant calculation unit 40 is connected to the suspension control unit 5 in the suspension system 3. Similarly, the vehicle behavior estimation unit 52 is also connected to the suspension control unit 5. The physical quantity detection unit 51 is also connected to the vehicle behavior estimation unit 52. Through the cooperation of these units, the vehicle state estimation device corresponds to the part of the suspension system 3 that calculates the spring constant and controls the suspension based on the calculated spring constant.

[0061] (Spring constant calculation unit) The spring constant calculation unit 40 calculates the spring constants of at least a portion of the active suspension system. The spring constants of at least a portion of the active suspension system refer to, for example, the spring constant of the suspension and the spring constant of the tire. The spring constant of the suspension can be the combined spring constant of the suspension spring and the bush. In addition, the contribution of the bush can be approximated as zero in the spring constant of the suspension. In a single-wheel model of an active suspension D such as an electric suspension, the suspension spring is dominant in the characteristics of the active suspension D. Therefore, even if the bush is not considered, there will be no significant difference in the behavior of the suspension. Note that the spring constant is synonymous with the spring coefficient.

[0062] (Vehicle stopped) The spring constant calculation unit 40 calculates the spring constant when the vehicle is stopped. The vehicle is stopped when there is no vertical displacement of the active suspension system, when the vehicle V is started, and when the vehicle speed is 0. Note that when there is no vertical displacement of the active suspension system, it is synonymous with when there is no suspension displacement.

[0063] The spring constant calculated by the spring constant calculation unit 40 is not limited to the examples described above. For example, the spring constants of dampers and stabilizers directly or indirectly connected to the wheel W can also be used.

[0064] (Physical quantity detection unit) The physical quantity detection unit 51 is the part that detects physical quantities related to the vehicle V. These physical quantities include, for example, quantities that indicate the behavior of the vehicle V. The behavior of the vehicle V may include, for example, the vehicle V's speed, acceleration, direction of travel, and inclination. The physical quantity detection unit 51 also includes a tire pressure detection unit. The tire pressure detection unit is the part of the physical quantity detection unit 51 that detects the tire pressure. The tire pressure detection unit is also referred to as a TPM (Tire Pressure Monitoring System).

[0065] The physical quantity detection unit 51 is connected to the vehicle behavior estimation unit 52. The physical quantity detected by the physical quantity detection unit 51 is then input to the vehicle behavior estimation unit 52.

[0066] (Vehicle behavior estimation unit) The vehicle behavior estimation unit 52 estimates the current behavior of the vehicle V based on the physical quantities detected by the physical quantity detection unit 51. The vehicle behavior estimation unit 52 is also connected to the suspension control unit 5. The information indicating the current behavior of the vehicle V, estimated by the vehicle behavior estimation unit 52, is called vehicle behavior information. This vehicle behavior information is input to the suspension control unit 5.

[0067] (Suspension control unit) In this embodiment, the suspension control unit 5 functions as a suspension control unit. The suspension control unit 5 controls the operation of the active suspension D based on the spring constant calculated by the spring constant calculation unit 40, the road surface distance, and the vehicle behavior information estimated by the vehicle behavior estimation unit 52.

[0068] (Control using the front wheels) Preferably, the road surface distance L1 that the suspension control unit 5 uses as a basis when controlling the operation of the active suspension D is the road surface distance from the vehicle body member 30 to the measurement point P in front of the front wheel of the vehicle V. And preferably, the spring constant calculation unit 40 calculates the spring constant for the active suspension D corresponding to the front wheel.

[0069] (Process flow) The process for estimating the spring constant of the front tire will be explained based on Figure 4. Figure 4 is a flowchart showing the process for estimating the spring constant of the tire. (S1) Step 1 (S1) initiates the procedure for updating the tire spring constant.

[0070] (S2) In step 2 (S2), it is determined whether vehicle V is stationary. If vehicle V is stationary, the determination in step 2 (S2) is Yes. Then the process proceeds to step 3 (S3).

[0071] On the other hand, if it is not determined that vehicle V is in a stationary state, the determination in step 2 (S2) will be No. Then the process proceeds to step 11 (S11).

[0072] (S11) In step 11 (S11), it is determined that there is no update to the tire spring constant. This is because, in the vehicle state estimation device of this embodiment, the spring constant is calculated when the vehicle is stopped. Once it is determined in step 11 (S11) that there is no update to the tire spring constant, the flow proceeds to step 13 (S13). Then, in step 13 (S13), the procedure for updating the tire spring constant is completed.

[0073] (S3) If the determination in step 2 (S2) is Yes, the process proceeds to step 3 (S3). In step 3 (S3), the suspension stroke length and the detection value of the distance sensor 11 are acquired while the vehicle is stopped. In the example shown in Figure 4, a laser sensor is used as the distance sensor 11. Therefore, the acquired value is the laser sensor value.

[0074] (S4) The process proceeds from step 3 (S3) to step 4 (S4). In step 4 (S4), it is determined whether the suspension state has changed and subsequently transitioned to a stopped state. A change in the suspension state refers to a change in the suspension state, for example, due to people getting in or out of the vehicle.

[0075] If the suspension state changes and the vehicle then comes to a complete stop, the determination in step 4 (S4) will be Yes. The process then proceeds to step 5 (S5).

[0076] On the other hand, if it is not determined that the suspension state has changed and the vehicle has subsequently come to a stopped state, the determination in step 4 (S4) will be No. The process then proceeds to step 11 (S11). If it is determined in step 11 (S11) that there is no update to the tire spring constant, the process proceeds to step 13 (S13). In step 13 (S13), the procedure for updating the tire spring constant is completed.

[0077] As can be seen from Step 2 (S2) and Step 4 (S4), the spring constant is not estimated when the vehicle is not stationary. In this case, a fixed value or the value used in the previous control is adopted as the spring constant to control the operation of the active suspension system.

[0078] (S5) If the determination in step 4 (S4) is Yes, the process proceeds to step 5 (S5). In step 5 (S5), similar to step 3 (S3), the suspension stroke length and laser sensor values ​​can be obtained while the vehicle is stopped.

[0079] (S6) The process proceeds from step 5 (S5) to step 6 (S6). In step 6 (S6), the amount of change in vehicle weight is estimated by comparing the values ​​obtained before the suspension change with the values ​​obtained after the suspension change. The values ​​obtained before the suspension change refer to the values ​​obtained in step 3 (S3). The values ​​obtained after the suspension change refer to the values ​​obtained in step 5 (S5).

[0080] The calculation in step 6 (S6) is shown in formula F1. In formula F1, x s This indicates the suspension stroke length, K s indicates the spring constant of the suspension, and m indicates the vehicle weight.

[0081] (Single-wheel model) The single-wheel model of the electric suspension used to estimate the spring constant is described below. Figure 6(b) shows the single-wheel model of the electric suspension. As shown in Figure 6(b), in the single-wheel model, for one wheel W, the suspension is represented as a model in which a spring component and a damper component are connected in parallel, and the tire is represented as a model with only a spring component. Each mathematical formula mentioned in the description of the embodiment corresponds to the single-wheel model shown in Figure 6(b).

[0082] (S7) The process proceeds from step 6 (S6) to step 7 (S7). In step 7 (S7), the tire displacement is calculated from the suspension stroke length and the change in the laser sensor value.

[0083] The calculation in step 7 (S7) is shown in formula F2. In formula F2, x l This indicates the laser sensor value, x s x indicates the suspension stroke length, t This indicates the amount of tire displacement.

[0084] (S8) The process proceeds from step 7 (S7) to step 8 (S8). In step 8 (S8), the spring constant of the tire is estimated from the tire displacement and the change in vehicle weight. The tire displacement is the value obtained in step 7 (S7). The change in vehicle weight is the value obtained in step 6 (S6).

[0085] The calculation in step 8 (S8) is shown in formula F3. In formula F3, m represents the vehicle weight, and x t This indicates the amount of tire displacement, K t This indicates the spring constant of the tire.

[0086] (S9) The process proceeds from step 8 (S8) to step 9 (S9). In step 9 (S9), the value of the tire spring constant estimated in step 8 (S8) is compared with the value of the spring constant estimated from the value detected by the tire pressure sensor (TPM). It is then determined whether there is a significant difference between the two values.

[0087] If there is no significant difference between the two values, the judgment in step 8 (S8) is Yes. Then the process proceeds to step 10 (S10).

[0088] On the other hand, if it is determined that there is no significant difference between the two values, the judgment in step 8 (S8) is No. Then the process proceeds to step 12 (S12).

[0089] (S12) In step 12 (S12), the previous value is used as the tire spring constant. That is, the spring constant is not updated based on an estimate of the tire spring constant. Note that in step 12 (S12), the previous value is used as the tire spring constant as an example. In step 12 (S12), a fixed value can also be used as the tire spring constant instead of the previous value.

[0090] In this way, the calculated tire spring constant is compared with the value of the tire spring constant estimated based on the tire pressure detected by the tire pressure detection unit. If the difference is greater than a certain level, the value used in the previous control or a fixed value is adopted as the spring constant, and the operation of the active suspension system is controlled.

[0091] If it is decided in step 12 (S12) to use the previous value as the tire spring constant, the flow proceeds to step 13 (S13). Then, in step 13 (S13), the procedure for updating the tire spring constant is completed.

[0092] (S10) If the determination in step 9 (S9) is Yes, the process proceeds to step 10 (S10). In step 10 (S10), the estimated value of the tire spring constant is updated. After that, the process proceeds to step 13 (S13), and the procedure for updating the tire spring constant is completed.

[0093] (Suspension spring constant) Next, the procedure for updating the suspension spring constant will be explained based on Figure 5. Figure 5 is a flowchart showing the process for estimating the suspension spring constant. In the single-wheel model shown earlier in Figure 6(b), the suspension spring constant is K s This is shown. (S21) Step 21 (S21) initiates the procedure for updating the suspension spring constant.

[0094] (S22) In step 22 (S22), it is determined whether vehicle V is in a stationary state. If vehicle V is in a stationary state, the determination in step 22 (S22) is Yes. Then the process proceeds to step 23 (S23).

[0095] On the other hand, if it is not determined that vehicle V is in a stationary state, the determination in step 22 (S22) will be No. Then the process proceeds to step 27 (S27).

[0096] (S28) In step 27 (S27), it is determined that there is no update to the suspension spring constant. This is because, in the vehicle state estimation device of this embodiment, the spring constant is calculated when the vehicle is stopped. Once it is determined in step 27 (S27) that there is no update to the suspension spring constant, the flow proceeds to step 28 (S28). Then, in step 28 (S28), the procedure for updating the suspension spring constant is completed.

[0097] (S23) If the determination in step 22 (S22) is Yes, the process proceeds to step 23 (S23). In step 23 (S23), the suspension stroke length is obtained when the vehicle is stopped.

[0098] (S24) The step proceeds from step 23 (S23) to step 24 (S24). In step 24 (S24), a thrust is generated in the active suspension. And the change amount of the suspension stroke length at that time is obtained.

[0099] (S25) The step proceeds from step 24 (S24) to step 25 (S25). In step 25 (S25), the spring constant of the suspension is estimated from the change amount of the suspension stroke length and the thrust output by the active suspension.

[0100] The operation in step 25 (S25) is shown by mathematical formula F4. In mathematical formula F4, K s represents the spring constant of the suspension, x s represents the suspension stroke length, and F represents the thrust F output by the active suspension.

[0101] (S26) The step proceeds from step 25 (S25) to step 26 (S26). In step 26 (S26), the estimated value of the suspension spring constant is updated. The step then proceeds to step 28 (S28), and the update procedure for the suspension spring constant ends.

[0102] (Example of Suspension Control) An example of suspension control using the spring constant will be described. The suspension control unit 5 in the present embodiment can use the spring constant for at least one of the operations of preview control correction, skyhook control constant adjustment, and damping control constant adjustment.

[0103] (Preview Control) Preview control is to control the operation of the active suspension D according to the future behavior of the vehicle V based on the change amount of the road surface distance L1. Figure 6(a) shows a mathematical formula for determining correction in preview control. In the mathematical formula shown in Figure 6(a), F R is the thrust of the active suspension, C sThe damping coefficient of the suspension is K s C is the spring constant of the suspension. t The damping coefficient of the tire is K t M is the spring constant of the tire. t is the weight of the tire, x r is road surface displacement, x rR This indicates road surface displacement.

[0104] In preview control, the calculated spring constant can be substituted into the formula for calculating the preview control correction shown in Figure 6(a). That is, in the formula shown in Figure 6(a), the corresponding spring constant can be replaced with the calculated spring constant value.

[0105] (Skyhook control) The calculated spring constant can also be used for constant adjustment in skyhook control. Skyhook control is a control method that uses an electric suspension to reproduce the behavior of a vehicle where only the vehicle body B is equipped with a damping damper. Specifically, the feedback control in skyhook control is performed using the first integral of the acceleration of vehicle body B, that is, the velocity of vehicle body B multiplied by the skyhook gain, which is the damping coefficient. The calculated spring constant can be used when determining this value.

[0106] (Damping control) Furthermore, the calculated spring constant can also be used for constant adjustment in damping control. Damping control is a control that assists in the extension and compression of the suspension. In damping control, the value obtained is the suspension stroke speed multiplied by the damper constant c. Here, the stroke speed can be obtained as follows: That is, the stroke speed is obtained by the motor rotation sensor of the electric suspension. A resolver or encoder can be used as the motor rotation sensor. Alternatively, the stroke speed can also be obtained by the first stage of the stroke displacement sensor.

[0107] In damping control, the spring constant calculated in this embodiment is used as the spring constant of the tire, and the larger the tire's spring constant, the smaller the damper constant c in damping control can be.

[0108] (Method for controlling the operation of an active suspension system) Using the suspension system 3 of this embodiment, the following method for controlling the operation of the active suspension D can also be implemented. That is, a method for controlling the operation of the active suspension D in a vehicle V equipped with the active suspension D and a suspension control unit 5, comprising: a physical quantity detection step for detecting a physical quantity indicating the behavior of the vehicle V; a vehicle behavior estimation step for estimating the current behavior of the vehicle V based on the physical quantity detected in the physical quantity detection step; a distance detection step for detecting a value relating to the distance between a vehicle body member 30 constituting the vehicle V and a measurement point P on the road surface in front of the vehicle V that corresponds to at least the central part 43 of the road contact portion 41 of the wheel W; a distance calculation step for calculating a road surface distance L1, which is the distance from the vehicle body member 30 to the measurement point P, based on the detected value detected in the distance detection step; a spring constant calculation step for calculating the spring constant of at least a part of the active suspension D in a stopped state of the vehicle V; and a suspension control step for controlling the operation of the active suspension D based on the spring constant, the road surface distance L1, and vehicle behavior information which is information indicating the current behavior of the vehicle V estimated in the vehicle behavior estimation step.

[0109] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications, variations, and combinations are possible. [Explanation of Symbols]

[0110] 1. Preview road surface detection device 3. Suspension system (vehicle condition estimation device) 4. Preview Control Unit 5. Suspension Control Unit (Suspension Control System) 11. Distance Sensor 12 Distance Calculation Unit 20 Exterior components 30 Body components 40 Spring constant calculation unit 41 Road surface area 43 Central part 51. Physical quantity detection unit (tire pressure detection unit) 52 Vehicle behavior estimation unit B Body D Active suspension (active suspension system) D1 suspension spring D2 Variable Damper L1 road surface distance L2 Road surface displacement L3 ride height L4 Road surface width P measurement point R road surface V Vehicle W wheels W1 spring W2 Damper

Claims

1. A vehicle state estimation device used in a vehicle equipped with an active suspension system and a suspension control device, A physical quantity detection unit for detecting physical quantities that indicate the behavior of the vehicle, A vehicle behavior estimation unit estimates the current behavior of the vehicle based on the physical quantity detected by the physical quantity detection unit, A distance sensor is provided on a vehicle body member of the vehicle and detects a value relating to the distance between the vehicle body member and a measurement point on the road surface in front of the vehicle that corresponds to at least a portion of the part of the wheel that makes contact with the road. A distance calculation unit calculates the road surface distance, which is the distance from the vehicle body member to the measurement point, based on the detected value detected by the distance sensor. When there is no vertical displacement of the active suspension system, and it is determined that the vehicle is in a stopped state, which is either when the vehicle is starting or when the vehicle speed is 0, the stroke length of the suspension of the active suspension system is acquired, and when it is determined that the vehicle has returned to the stopped state after the stroke length has changed, the stroke length of the suspension of the active suspension system is acquired again, and the spring constant of at least a part of the active suspension system is calculated using the change in the acquired values ​​before and after the change in stroke length. A vehicle state estimation device comprising: a suspension control unit that controls the operation of the active suspension system based on the spring constant, the road surface distance, and vehicle behavior information which is information indicating the current behavior of the vehicle estimated by the vehicle behavior estimation unit.

2. The distance calculation unit calculates the distance from the vehicle body member to the measurement point on the front side of the front wheel of the vehicle as the road surface distance. The vehicle state estimation device according to claim 1, wherein the spring constant calculation unit calculates the spring constant for the active suspension system corresponding to the front wheel.

3. The suspension control unit is, The vehicle state estimation device according to claim 1 or 2, wherein when the vehicle is not in a stationary state, a fixed value or the value used in the previous control is adopted as the spring constant to control the operation of the active suspension device.

4. The vehicle state estimation device according to claim 1 or 2, wherein the suspension control unit uses the spring constant in at least one of the calculations for correction of preview control, constant adjustment of skyhook control, and constant adjustment of damping control.

5. The vehicle state estimation device according to claim 4, wherein the suspension control unit replaces the calculated spring constant with the spring constant of the corresponding member in the formula for calculating the correction of the preview control.

6. The calculated spring constant is the spring constant of the tire. The vehicle state estimation device according to claim 4, wherein the suspension control unit, in the formula for adjusting the damping control constant, reduces the damping constant in the stroke speed × damping constant of the damping control as the tire spring constant increases.

7. The calculated spring constant is the spring constant of the tire. It is equipped with a tire pressure detection unit. The vehicle state estimation device according to claim 1 or 2, wherein the predicted value of the tire spring constant estimated based on the tire pressure detected by the tire pressure detection unit is compared with the calculated tire spring constant, and if the difference is greater than a certain amount, a fixed value or the value used in the previous control is adopted as the spring constant to control the operation of the active suspension device.

8. A method for controlling the operation of an active suspension system in a vehicle equipped with an active suspension system and a suspension control device, A physical quantity detection step for detecting a physical quantity that indicates the behavior of the vehicle, A vehicle behavior estimation step in which the current behavior of the vehicle is estimated based on the physical quantity detected in the physical quantity detection step, A distance detection step for detecting a value relating to the distance between a vehicle body member constituting the vehicle and a measurement point on the road surface in front of the vehicle that corresponds to at least the central part of the part of the wheel that makes contact with the road, A distance calculation step which calculates the road surface distance, which is the distance from the vehicle body member to the measurement point, based on the detected value detected in the distance detection step, When there is no vertical displacement of the active suspension system, and it is determined that the vehicle is in a stopped state, which is either when the vehicle is starting or when the vehicle speed is 0, the stroke length of the suspension of the active suspension system is obtained, and when it is determined that the vehicle has returned to the stopped state after the stroke length has changed, the stroke length of the suspension of the active suspension system is obtained again, and the spring constant of at least a part of the active suspension system is calculated using the change in the obtained values ​​before and after the change in stroke length. A method for controlling the operation of an active suspension system, comprising: a suspension control step that controls the operation of the active suspension system based on the spring constant, the road surface distance, and vehicle behavior information which is information indicating the current behavior of the vehicle estimated in the vehicle behavior estimation step.

Images