Suspension control device for vehicle and suspension control method for vehicle

Abstract

The present application relates to a vehicle suspension control device and a vehicle suspension control method, which can effectively perform damping of a sprung structure. The vehicle suspension control device includes an actuator that applies a control force in a vertical direction between an unsprung structure and the sprung structure, and an electronic control unit that controls the actuator so as to generate the control force corresponding to a requested control amount requested for reducing vibration of the sprung structure. The requested control amount includes at least two control terms among a displacement term, a velocity term, and an acceleration term related to displacement, velocity, and acceleration of the sprung structure. The electronic control unit performs: a calculation process that calculates magnitudes of frequency components of a plurality of frequency bands included in road surface vibration information; and a gain determination process that determines control gains of the at least two control terms in a manner that varies based on the magnitudes of the frequency components of the plurality of frequency bands.

Description

Technical Field

[0001] This disclosure relates to a vehicle suspension control device and a vehicle suspension control method having an actuator that applies vertical control force between the unsprung structure and the sprung structure of the vehicle. Background Technology

[0002] Patent Document 1 discloses a suspension control device. This suspension control device includes an actuator that generates a control force capable of controlling the vertical travel of the wheels and the vehicle body, and controls the actuator to counteract vibration input transmitted from the unsprung portion of the suspension to the vehicle body. Furthermore, the suspension control device reduces control gain based on an increase in the input of the unsprung resonant frequency component.

[0003] Patent Document 1: Japanese Patent Application Publication No. 08-127213

[0004] The method described in Patent Document 1 is a method of reducing control gain in order to suppress the reduction of vibration damping effect caused by the execution of suspension control when the magnitude (level) of the frequency components in a specific frequency band is large.

[0005] Here, in order to reduce the vibration of the sprung structure, it is considered to utilize a requested control quantity having at least two of the displacement, velocity, and acceleration terms related to the displacement, velocity, and acceleration of the sprung structure. However, in the method described in Patent Document 1 (i.e., the method of only reducing control gain), it is not possible to properly adjust the balance of control gain among the above-mentioned at least two control terms. Therefore, it is difficult to effectively and flexibly utilize each control term for vibration reduction. Summary of the Invention

[0006] This disclosure was made in view of the aforementioned issues, and its purpose is to enable effective vibration reduction of the sprung structure by utilizing a request control quantity having at least two control items as described above.

[0007] The vehicle suspension control device disclosed herein includes an actuator and an electronic control unit. The actuator applies a vertical control force between the unsprung structure and the sprung structure of the vehicle. The electronic control unit controls the actuator to generate the control force corresponding to a requested control quantity requested to reduce vibration of the sprung structure. The requested control quantity includes at least two of the following control terms: displacement, velocity, and acceleration, which are related to the displacement, velocity, and acceleration of the sprung structure. The processing performed by the electronic control unit includes calculation processing and gain determination processing. The calculation processing is the processing of calculating the magnitude of the frequency components of multiple frequency bands included in road vibration information related to road surface input to the vehicle or vibration of the sprung structure caused by such road surface input. The gain determination processing is the processing of determining the control gain of each of the at least two control terms in a manner that varies based on the magnitude of the frequency components of the multiple frequency bands.

[0008] The frequency band with the largest frequency component among the aforementioned frequency bands is referred to as the specific frequency band. In the gain determination process, the electronic control unit can increase the control gain of at least two control items that have a vibration damping effect to suppress the vibration of the spring structure in the specific frequency band, and decrease the control gain of the control item that has a vibration excitation effect to promote the vibration of the spring structure in the specific frequency band.

[0009] When at least two control terms include displacement terms, the strength of the high-pass filter applied to the sprung state variables included in the displacement terms can be higher than the strength of the high-pass filter applied to the sprung state variables included in the other one or two control terms.

[0010] When at least two control terms include an acceleration term, the strength of the low-pass filter applied to the sprung state variables included in the acceleration term can be higher than the strength of the low-pass filter applied to the sprung state variables included in the other one or two control terms.

[0011] The aforementioned multiple frequency bands may include frequency bands that have a vibration reduction effect on each of the at least two control items with sprung structures.

[0012] The aforementioned multiple frequency bands may include frequency bands that have an excitation effect on each of the at least two control items with a spring structure.

[0013] The vehicle suspension control method disclosed herein controls an actuator that applies a vertical control force to the unsprung structure and the sprung structure of the vehicle to generate the control force corresponding to a requested control quantity requested to reduce vibration of the sprung structure. The requested control quantity includes at least two of the following control terms: displacement, velocity, and acceleration, related to the displacement, velocity, and acceleration of the sprung structure. The vehicle suspension control method includes a calculation process and a gain determination process. The calculation process calculates the magnitudes of frequency components of multiple frequency bands included in road vibration information related to road surface input to the vehicle or vibration of the sprung structure caused by such road surface input. The gain determination process determines the control gain of each of the at least two control terms in a manner that varies based on the magnitudes of the frequency components of the multiple frequency bands.

[0014] According to each of the vehicle suspension control device and vehicle suspension control method disclosed herein, the balance of control gains of at least two control items for reducing the vibration of the sprung structure is determined in a manner that varies based on the magnitude of the frequency components of the multiple frequency bands included in the road vibration information. Thus, vibration reduction of the sprung structure can be effectively performed based on the road vibration information. Attached Figure Description

[0015] Figure 1 This is a diagram that briefly illustrates an example of the structure of the vehicle involved in the embodiment.

[0016] Figure 2 This is a diagram that briefly illustrates an example of the structure of the suspension involved in the implementation method.

[0017] Figure 3 This is a flowchart illustrating the process related to FB control of the spring state variables involved in the implementation method.

[0018] Figure 4 It means in Figure 3 A diagram illustrating an example of multiple frequency bands B in step S104, where the magnitude of the frequency components is obtained.

[0019] Figure 5 This is a diagram illustrating an example of setting the control gain G1 to G3 based on a specific frequency band Bx.

[0020] Figure 6 This is a flowchart illustrating a variation of the gain determination process involved in the implementation method.

[0021] Explanation of reference numerals in the attached figures:

[0022] 1…Vehicle; 2…Wheel; 3…Suspension; 3A…Actuator; 4…Unsprung structure; 5…Sprung structure; 6…Body; 10…Electronic control unit (ECU); 12…Sensors; 14-1, 14-2, 14-3, 14-4…Sprung acceleration sensors; GC…Sprung center of gravity position. Detailed Implementation

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Where the number, quantity, amount, range, etc., of each element are mentioned in the embodiments shown below, the technical concept involved in this disclosure is not limited to the mentioned numbers, except where specifically stated or where the quantity can be clearly determined in principle.

[0024] 1. Vehicle structure

[0025] Figure 1 This is a diagram illustrating an example of the structure of the vehicle 1 according to the embodiment. The vehicle 1 includes wheels 2 and a body 6 (see figure). Figure 2The suspension 3 suspends the wheels 2. Wheel 2 includes a left front wheel 2FL, a right front wheel 2FR, a left rear wheel 2RL, and a right rear wheel 2RR. Suspension 3FL, 3FR, 3RL, and 3RR are respectively provided for these left front wheel 2FL, right front wheel 2FR, left rear wheel 2RL, and right rear wheel 2RR. In the following description, unless otherwise specified, each wheel will be referred to as wheel 2, and each suspension will be referred to as suspension 3.

[0026] Figure 2 This is a diagram illustrating a simplified example of the structure of the suspension 3 according to the embodiment. The suspension 3 is configured to connect the unsprung structure 4 and the sprung structure 5 of the vehicle 1. The unsprung structure 4 includes a wheel 2. The sprung structure 5 includes a body 6. The suspension 3 includes a spring 3S, a shock absorber 3D, and an actuator 3A. The spring 3S, the shock absorber 3D, and the actuator 3A are arranged side by side between the unsprung structure 4 and the sprung structure 5. The spring constant of the spring 3S is K. The damping coefficient of the shock absorber 3D is C. The actuator 3A applies a vertical control force Fc between the unsprung structure 4 and the sprung structure 5. Thus, the travel of the suspension 3 is controlled.

[0027] More specifically, as an example, actuator 3A is an electric or hydraulic active actuator (an actuator constituting a so-called fully active suspension). However, the "actuator" involved in this disclosure is not particularly limited as long as it can apply a vertical control force Fc between the unsprung structure 4 and the sprung structure 5. Specifically, the actuator may be, for example, an actuator that makes the damping force generated by the shock absorber 3D variable, or an actuator of an active stabilizer device. Furthermore, the actuator may be, for example, an actuator (e.g., an electric motor) that generates the vehicle's front-rear forces in a vehicle equipped with a suspension configured to convert the vehicle's front-rear forces (driving force and braking force) acting on the wheels into a control force F by utilizing suspension geometry. This electric motor may be, for example, an in-wheel motor (IWM) equipped on the wheel, or an electric motor capable of driving the wheel via the vehicle's drive axle.

[0028] Furthermore, vehicle 1 is equipped with an electronic control unit (ECU) 10. ECU 10 includes a processor, a storage device, and an input / output interface. The input / output interface acquires sensor signals from sensor class 12 installed in vehicle 1 and outputs operating signals to actuator 3A. The storage device stores various control programs for controlling actuator 3A. The processor reads the control programs from the storage device and executes them. Thus, suspension control utilizing actuator 3A can be achieved. Multiple ECUs 10 can be used.

[0029] Sensor type 12, for example, includes a sprung acceleration sensor that detects the vertical acceleration of the sprung structure 5. Figure 1In the example shown, four sprung acceleration sensors 14-i (i = 1 to 4) are provided. More specifically, sprung acceleration sensor 14-1 detects the sprung acceleration at position 1 on the right front wheel 2FR side as viewed from the sprung center of gravity position (GC position of the sprung structure 5). Sprung acceleration sensor 14-2 detects the sprung acceleration at position 2 on the left front wheel 2FL side as viewed from the sprung center of gravity position GC. Sprung acceleration sensor 14-3 detects the sprung acceleration at position 3 on the right rear wheel 2RR side as viewed from the sprung center of gravity position GC. Sprung acceleration sensor 14-4 detects the sprung acceleration at position 4 on the left rear wheel 2RL side as viewed from the sprung center of gravity position GC. That is, the values ​​of the symbol "i" 1 to 4 correspond to the right front wheel 2FR, left front wheel 2FL, right rear wheel 2RR, and left rear wheel 2RL, respectively. The distance from the sprung center of gravity position GC to each of the positions 1 to 4 is arbitrary. In addition, the sensor class 12 includes, for example, a lateral acceleration sensor, a suspension travel sensor, an unsprung acceleration sensor, and a wheel speed sensor disposed on each wheel 2.

[0030] 2. Suspension control

[0031] The suspension control executed by ECU10 includes feedback control based on a sky-hook control algorithm (hereinafter referred to as "FB control of sprung state variables" or simply "FB control") for reducing vibrations of the sprung structure 5. Furthermore, as an example, this FB control is performed on each of the four wheels 2 as an object, but it can also be performed, for example, on only the left and right front wheels 2F or only the left and right rear wheels 2R.

[0032] 2-1. Basic Example of FB Control for Sprout State Quantities

[0033] In this FB control, ECU10 controls actuator 3A to generate a control force Fc corresponding to the requested control amount X requested to reduce the vibration of the sprung structure 5. In one example described below, ECU10 calculates the requested control amount X as the requested control amount requested to suppress the vibration modes (up-down vibration (undulating vibration), roll vibration, and pitch vibration) at the sprung center of gravity position GC, namely the up-down requested control amount Fz, the roll requested control amount Mr, and the pitch requested control amount Mp.

[0034] Hereinafter, the detected values ​​of the sprung accelerations detected by each sprung acceleration sensor 14-i (i = 1 to 4) will be referred to as "detected acceleration Z". i The ECU10 calculates the acceleration in each mode (i.e., vertical acceleration Z) at the sprung center of gravity position GC based on the detected accelerations Z1” to Z4” detected by the four sprung acceleration sensors 14-1 to 14-4 respectively.g Lateral acceleration Φ g "and pitch acceleration Θ" g For example, ECU10 calculates the vertical acceleration Z according to the following formulas (1) to (4). g Lateral acceleration Φ g "and pitch acceleration Θ" g "Among them, the positions of each sprung acceleration sensor 14-i (i = 1~4) in the X direction (the direction of travel of vehicle 1) and the positions of each sprung acceleration sensor in the Y direction (the lateral direction of vehicle 1) are L." i and W i (Refer to Figure 1 The X-direction and Y-direction positions of the sprung center of gravity GC are L1 and L2, respectively. g and W g Obtain these parameters in advance (L) i W i L g and W g ), and stored in the storage device of ECU10.

[0035] [Formula 1]

[0036]

[0037]

[0038]

[0039]

[0040] By using the acceleration detected at four locations Z1″~Z4″, the vertical acceleration Z at the spring center of gravity GC can be calculated with high precision. g ", roll acceleration Φ g "and pitch acceleration Θ" g However, calculating the vertical acceleration Z at the spring-loaded center of gravity GC position... g ", Lateral acceleration Φ g "and pitch acceleration Θ" g The method is not limited to the one described above. For example, it is also possible to use only three on-spring accelerometers 14.

[0041] Next, ECU10 will measure the acceleration (vertical acceleration Z) in each mode. g ", Lateral acceleration Φ g "and pitch acceleration Θ" g Integrating the values ​​at the spring center of gravity GC position (vertical velocity Z) is performed to calculate the velocity in each mode (vertical velocity Z). g ′、lateral roll rate Φ g ′ and pitch speed Θg The vertical velocity Z of the center of gravity GC on the spring. g ′、lateral roll rate Φ g ′ and pitch speed Θ g ′ can be expressed by the following formulas (5) to (7).

[0042] [Formula 2]

[0043] Z′ g =∫Z″ g …(5)

[0044] Φ′ g =∫Φ″ g …(6)

[0045] Θ′ g =∫Θ″ g …(7)

[0046] Similarly, ECU10 controls the speed of each mode (vertical speed Z). g ′、lateral roll rate Φ g ′ and pitch speed Θ g Integrating is performed to calculate the displacements (vertical displacements Z and V) of each mode at the spring center of gravity position GC. g Φ (roll angle displacement) g And pitch angle (pitch angle displacement) Θ g The vertical displacement Z of the center of gravity GC on the spring. g Side roll angle Φ g and pitch angle Θ g They can be expressed by the following formulas (8) to (10).

[0047] [Formula 3]

[0048] Z g =∫Z′ g …(8)

[0049] Φ g =∫Φ′ g …(9)

[0050] Θ g =∫Θ′ g …(10)

[0051] Next, ECU10 calculates the up-down request control quantity F for suppressing the vibration modes (up-down, roll, and pitch) at the sprung center of gravity position GC. z Roll request control quantity M r And pitch request control quantity M p Here, let's assume the upper and lower request control quantities F are... zIt is positive when an upward control force is requested. Assume the roll control request amount is M. r The control torque is positive when the vehicle 1 is requested to descend on the right and ascend on the left. Assume the pitch control request is M. p It is positive when the control torque is requested to act in a manner that the front side of vehicle 1 descends and the rear side rises.

[0052] ECU10 uses the acceleration (vertical acceleration Z) of each mode obtained as described above. g Lateral acceleration Φ g "and pitch acceleration Θ" g (and speeds in each mode, including vertical speed Z) g ', roll rate Φ g 'and pitch speed Θ g ') and displacements of each mode (vertical displacement Z) g Side roll angle Φ g and pitch angle Θ g To calculate these uplink and downlink request control quantities F z Roll request control quantity M r And pitch request control quantity M p For example, the upper and lower request control quantities F are assigned by the following formulas (11) to (13) respectively. z Roll request control quantity M r And pitch request control quantity M p .

[0053] [Formula 4]

[0054] F z =G1 z ·Z g +G2 z ·Z′ g +G3 z ·Z″ g …(11)

[0055] M r =G1 r ·Φ g +G2 r ·Φ′ g +G3 r ·Φ″ g …(12)

[0056] M p =G1 p ·Θ g +G2 p ·Θ′ g +G3 p ·Θ″ g …(13)

[0057] In equations (11) to (13), G1 z G2 z G3 z G1 r G2 r G3 r G1 p G2 p and G3 p This refers to the control gain. In the following description, unless otherwise specified, each control gain will be referred to as control gain G. In this embodiment, each control gain G is determined by the "gain determination process" described later.

[0058] As shown in equations (11) to (13), the upper and lower request control quantities F z Roll request control quantity M r and pitch request control quantity M p Each has a displacement term, a velocity term, and an acceleration term related to the displacement, velocity, and acceleration of the spring-loaded structure 5.

[0059] Specifically, the up / down request control quantity F z It has vertical displacement Z g With control gain G1 z The product is the displacement term and the vertical velocity Z. g With control gain G2 z The product is the velocity term and the vertical acceleration Z. g "With control gain G3" z The product is also the acceleration term.

[0060] Similarly, the roll request control quantity M r With a roll angle Φ g With control gain G1 r The product is the displacement term and the roll velocity Φ. g With control gain G2 r The product is the velocity term and the roll acceleration Φ. g "With control gain G3" r The product is also the acceleration term.

[0061] Similarly, the pitch request control quantity M p With pitch angle Θ g With control gain G1 p The product is the displacement term, pitch velocity Θ g With control gain G2 p The product is the velocity term, pitch acceleration Θ. g "With control gain G3" p The product is also the acceleration term.

[0062] Next, ECU10 will request the control quantity F at the sprung center of gravity position GC. z M r and M p The requested control values ​​at the positions of each wheel 2 (2FR, 2FL, 2RR, and 2RL) are converted. The requested control values ​​at the positions of each wheel 2 are equivalent to the target control force Fct of the actuator 3A corresponding to each wheel 2.

[0063] The tread width of the front tire 2F is T. f The tread width of the rear wheel 2R is T. r The distance between the front axle and the sprung center of gravity GC is l. f The distance between the rear axle and the sprung center of gravity GC is l. r In this case, the target control force Fct(Fct) of each actuator 3A fr Fct fl Fct rr and Fct rl ) can be expressed by the following formula (14).

[0064] [Formula 5]

[0065]

[0066] ECU10 can use equation (14) to determine the requested control quantity F at the sprung center of gravity position GC. z M r and M p This is converted to the target control force Fct for each actuator 3A. Alternatively, ECU10 can refer to the requested control quantity F. z M r and M p The target control force Fct for each wheel 2 is calculated by mapping the target force Fct.

[0067] 2-2. Issues and countermeasures for FB control of spring state variables

[0068] The vibration of the sprung structure 5 of vehicle 1 is generated by the road input received by each wheel 2. Here, for ease of explanation, "information related to road input" and "information related to the vibration of the sprung structure 5 caused by road input" are collectively referred to as "road vibration information".

[0069] Specifically, the "information related to road surface input" in the former refers to information such as the magnitude of the road surface input or the magnitude of the road surface input velocity. For example, the vertical displacement of the road surface, i.e., the road surface displacement Z. r Or the vertical displacement of the unsprung structure 4 at the position of each wheel 2, i.e., the unsprung displacement Z. uThis is equivalent to road surface input. For example, road surface displacement Z. r The time derivative, i.e., the road surface displacement velocity Z r 'Or unsprung velocity Z' u This is equivalent to the road surface input speed. In addition, information related to the road surface input may include, for example, the road surface displacement velocity Z. r The time derivative of ' is also known as the road surface displacement acceleration Z'. r "or unsprung acceleration Z" u ".

[0070] For example, various sprung state quantities are equivalent to the latter's "information related to the vibration of the sprung structure 5 caused by road input." Specifically, for example, the sprung state quantities (sprung displacement Z) at the positions of each wheel 2. s Sponge velocity Z s 'or spring acceleration Z' s "), or the spring state quantity (vertical displacement Z) at the spring center of gravity position GC. g Vertical velocity Z g 'or vertical acceleration Z' g This information is equivalent to the given information. Among them, the road surface displacement Z... r Unsprung displacement Z u Spring displacement Z s and vertical displacement Z g The sign of is positive when pointing upwards and negative when pointing downwards.

[0071] The frequency characteristics of the road vibration information described above vary depending on the road surface on which vehicle 1 travels. On the other hand, in the case where the control quantity X is required to have at least two of the following control terms, such as displacement, velocity, and acceleration, as shown in the examples (11) to (13) above, the frequency band with a high vibration reduction effect on suppressing the vibration of the sprung structure 5 varies substantially depending on the control term. Similarly, the frequency band with an excitation effect that promotes the vibration of the sprung structure 5 also varies substantially depending on the control term. Therefore, if the control gain G of each control term is determined, for example, based on the balance of vehicle specifications, without considering that the frequency characteristics of the road vibration information vary depending on the road surface on which vehicle 1 travels, a situation may arise where the vibration reduction effect involved in this FB control cannot be sufficiently improved.

[0072] In view of the aforementioned issues, the processing performed by ECU10 for FB control in this embodiment includes the following "calculation processing" and "gain determination processing". Using the following... Figure 3 The flowchart shown illustrates specific examples of these processes, which are summarized below.

[0073] The calculation process involves calculating the magnitude (amplitude) of the frequency components of each of the multiple frequency bands B included in the aforementioned road vibration information. The gain determination process involves determining the control gain G of each of the three control terms (displacement, velocity, and acceleration) based on the magnitude of the frequency components of each of the multiple frequency bands B.

[0074] More specifically, in this embodiment, gain determination processing is performed as follows. Here, for ease of explanation, the frequency band with the largest frequency component among the plurality of frequency bands B is referred to as the "specific frequency band Bx". Gain determination processing is performed in such a way that the control gain G of the control item (displacement item, velocity item, and acceleration item) that has a vibration reduction effect in the specific frequency band Bx is increased, and the control gain G of the control item that has a vibration excitation effect in the specific frequency band Bx is decreased.

[0075] Figure 3 This is a flowchart illustrating the FB control process related to the sprung state variables involved in the implementation method. During the movement of vehicle 1, the processes in this flowchart are repeatedly executed according to a predetermined time step. Specifically, in... Figure 3 In this process, step S104 is equivalent to an example of the "calculation process" described above, and step S106 is equivalent to an example of the "gain determination process" described above.

[0076] <Step S100>

[0077] In step S100, ECU10 obtains the "sprung state quantity" used in calculating the requested control quantity X for reducing the vibration of the sprung structure 5. Each control term of the requested control quantity X is expressed as the product of the sprung state quantity and the control gain G. Therefore, if the control gain G increases, the value of the control term (control quantity), or in other words, the control force Fc, with that control gain G increases, resulting in a higher control effect (vibration reduction effect or vibration excitation effect).

[0078] As already explained, in this embodiment, as an example of the requested control quantity X, the up-down requested control quantity (fluctuation requested control quantity) F is used. z Roll request control quantity M r And pitch request control quantity M p (Refer to equations (11) to (13)). Therefore, in step S100, ECU10 obtains these requested control quantities F z M r and M p The sprung state variables used in the calculations are the accelerations of each mode (vertical acceleration Z). g Lateral acceleration Φ g "and pitch acceleration Θ" g(and speeds in each mode, including vertical speed Z) g ', roll rate Φ g and pitch speed Θ g '), and displacements of each mode (vertical displacement Z) g Side roll angle Φ g and pitch angle Θ g ).

[0079] In addition, the requested control quantity X in the FB control of the sprung state quantity only needs to be a requested control quantity that has at least two of the following control terms: displacement, velocity, and acceleration, expressed as the product of the sprung state quantity (displacement, velocity, acceleration) and the control gain G. Therefore, the requested control quantity X can be, for example, the sprung state quantity (sponge displacement Z) at the position of each wheel 2. s Sponge velocity Z s 'and sprung acceleration Z' s The product of the control gain and the control quantity F is used to replace the requested control quantity F used to suppress the vibration of each mode at the sprung center of gravity position GC. z M r and M p Furthermore, the sprung state variables used in the calculation of the requested control quantity X can be in-phase or out-of-phase components of the sprung state variables at positions 2F (left and right front wheels) or 2R (left and right rear wheels). Moreover, the acquisition of the sprung state variables is not limited to sensor measurements; for example, it can also be achieved using inferences from observers or models.

[0080] <Step S102>

[0081] Next, in step S102, ECU10 performs filtering. This filtering includes the sprung state quantity (Z) for each control term (displacement term, velocity term, and acceleration term) included in equations (11) to (13). g ”、Φ g ”、Θ g Z g '、Φ g '、Θ g '、Z g Φ g and Θ g The application of high-pass filter (HPF) and low-pass filter (LPF) for the spring state quantity.

[0082] The HPF described above is applied to remove the integral offset generated when calculating the mode velocity and mode displacement from the mode accelerations obtained using the detection values ​​of the sprung acceleration sensors 14-i (i = 1 to 4). In this step S102, the strength of the HPF varies among the control terms. Specifically, the strength of the HPF applied to the sprung state quantities (mode displacements) included in the displacement term is higher than the strength of the HPF applied to the sprung state quantities (mode velocities and mode accelerations) included in the other control terms, namely the velocity term and the acceleration term. The strength of the HPF can be increased, for example, by increasing the number of times the HPF is applied or by increasing the number of times the HPF is increased.

[0083] The LPF described above is applied to represent (simulate) the response delay of this FB control. In this step S102, the strength of the LPF varies among the control terms. Specifically, the strength of the LPF applied to the sprung state quantities (mode accelerations) included in the acceleration term is greater than the strength of the LPF applied to the sprung state quantities (mode displacements and mode velocities) included in the other control terms, namely the displacement and velocity terms. The strength of the LPF can be increased, for example, by increasing the number of times the LPF is applied or by increasing the number of times the LPF is increased.

[0084] Alternatively, unlike the examples above, only either HPL or LPF may be applied to the sprung state quantity of each control item. Furthermore, when at least one of HPL and LPF is applied to the sprung state quantity of each control item, unlike the process in step S102, the strength of at least one of HPF and LPF applied to the sprung state quantity of each control item can be the same across all control items.

[0085] <Step S104>

[0086] Next, in step S104, the ECU 10 performs a "calculation process" to calculate the magnitude of the frequency components of each of the multiple frequency bands B included in the aforementioned road vibration information. This calculation process is performed to obtain the magnitude of the frequency components used to evaluate the frequency characteristics of the road surface input to the moving vehicle 1. More specifically, the calculated magnitudes of the frequency components of each frequency band B are used to evaluate the differences in the magnitudes of the frequency components among the multiple frequency bands B of the judgment object (e.g., whether the road surface has more high-frequency components or more low-frequency components).

[0087] Specifically, for example, the “multiple frequency bands B” referred to here can be determined as follows. Figure 4 This is a diagram illustrating an example of multiple frequency bands B in step S104, where the magnitude of the frequency components is obtained. Figure 4 The example shows three frequency bands: B1, B2, and B3.

[0088] Frequency band B1 is the 0.5–1 Hz band, frequency band B2 is the 1–2 Hz band, and frequency band B3 is the 2–10 Hz band. Figure 4 In one example, frequency band B1 is the band where the displacement term has a vibration-damping effect, and the remaining velocity and acceleration terms have an excitation effect. Frequency band B2 is the band where the velocity term has a vibration-damping effect, and the remaining displacement and acceleration terms have an excitation effect. Furthermore, frequency band B3 is the band where the acceleration term has a vibration-damping effect, and the remaining displacement and velocity terms have an excitation effect.

[0089] By taking into account the characteristics of vehicle 1, the decision is made in advance. Figure 4 The multiple frequency bands B shown can be used to determine the frequency band with the largest frequency component among the multiple frequency bands B included in the road vibration information obtained during the driving of vehicle 1, that is, a specific frequency band Bx.

[0090] Next, we will use the examples of the three frequency bands B1 to B3 mentioned above to specifically explain the processing of step S104. Here, as an example of road vibration information, we will use the unsprung velocity Z. u The unsprung speed Z used u For example, the unsprung velocity Z of any one of the four wheels 2. u In the example where the requested control quantity X is calculated for each wheel 2, the unsprung velocity Z, as an example of road vibration information, can be obtained for each wheel 2. u Unsprung velocity Z u For example, by measuring the unsprung acceleration Z detected by the unsprung acceleration sensor u "This is obtained by integration. For example, the unsprung velocity Z is obtained at each time step." u The unsprung speed Z' is stored as time-series data in the storage device of ECU10. Furthermore, in the case of preview damping control based on road surface information in front of the vehicle as part of the suspension control of vehicle 1, road surface information (e.g., unsprung speed Z') obtained by a camera during vehicle movement or obtained in advance for this preview damping control can be used in this step S104. u ').

[0091] Based on this, in this step S104, ECU10 obtains the unsprung speed Z as described above. u The time-series data application uses the three frequency bands B1 to B3 as three bandpass filters (BPFs) for the passband. Furthermore, the ECU10 utilizes the unsprung speed Z obtained after applying these three BPFs with different passbands. uThe data is used to calculate the magnitude (e.g., signal strength) of the frequency components in each frequency band B1–B3. More specifically, for example, to calculate the unsprung speed Z after applying BPF. u The moving average or peak hold value of the data is used as the magnitude of the frequency component.

[0092] In addition, unlike this embodiment, in the example where the requested control quantity X has only any two of the displacement, velocity and acceleration terms, "multiple frequency bands B" can be two.

[0093] In addition, Figure 4 In the example of frequency bands B1 to B3 shown, if we focus on the displacement term, then frequency bands B2 and B3 correspond to the frequency bands that have an excitation effect on the displacement term. That is, in this example, as... Figure 4 As shown, the frequency bands with excitation effects for the displacement term are the same as those with damping effects for other control terms, namely frequency bands B2 and B3. However, this relationship is not always satisfied. Depending on the characteristics of the vehicle to which this FB control is applied, the frequency bands with excitation effects for the displacement term may differ from those with damping effects for other control terms. This is also true when considering other velocity or acceleration terms. Therefore, as explained here, when the frequency bands with excitation effects for a certain control term differ from those with damping effects for other control terms, "multiple frequency bands B" may include both the frequency bands with damping effects and the frequency bands with excitation effects for each control term.

[0094] <Step S106>

[0095] Next, in step S106, ECU10 performs gain determination processing. Specifically, in step S106, ECU10 first determines a specific frequency band Bx based on the calculation results of each frequency component in step S104. Thus, the frequency characteristics of the road surface on which vehicle 1 is currently traveling can be determined.

[0096] Based on this, ECU10 determines the control gain G of each control term according to which frequency band B1 to B3 the specific frequency band Bx belongs to. The control gain G1 of the displacement term will be explained below. z G1 r and G1 p This is also collectively referred to as "control gain G1". Similarly, the control gain G2 of the speed term... z G2 r and G2 p Also collectively referred to as "control gain G2", the control gain G3 of the acceleration term z G3 r and G3 p It is also collectively referred to as "control gain G3".

[0097] ECU10 has basic values ​​G1b, G2b, and G3b for control gains G1, G2, and G3, respectively. These basic values ​​G1b, G2b, and G3b are predetermined to achieve a balance among control terms that enable the FB control to achieve an appropriate vibration reduction effect under the frequency characteristics of a specified standard road surface.

[0098] Figure 5 This is a diagram illustrating an example of setting the control gains G1 to G3 based on a specific frequency band Bx. For example... Figure 5 As shown, the control gain G1 for the displacement term is determined to be greater than the basic value G1b (single-dot dash) when frequency band B1 is a specific frequency band Bx, and less than the basic value G1b when frequency bands B2 or B3 are specific frequency bands Bx. The control gain G2 for the velocity term is determined to be greater than the basic value G2b (single-dot dash) when frequency band B2 is a specific frequency band Bx, and less than the basic value G2b when frequency bands B1 or B3 are specific frequency bands Bx. Furthermore, the control gain G3 for the acceleration term is determined to be greater than the basic value G3b (single-dot dash) when frequency band B3 is a specific frequency band Bx, and less than the basic value G3b when frequency bands B1 or B2 are specific frequency bands Bx. The increase or decrease of control gains G1, G2, and G3 relative to the basic values ​​G1b, G2b, and G3b is determined, for example, by considering the characteristics of the vehicle 1 controlled by this FB.

[0099] The storage device of ECU10 stores Figure 5 The relationship shown is used as a mapping. ECU10 obtains control gains G1 to G3 corresponding to the specific frequency band Bx obtained from such a mapping.

[0100] Through this processing, the control gains G1, G2, and G3 can be increased or decreased from the basic values ​​G1b, G2b, and G3b determined as described above, based on the frequency characteristics of the road surface on which vehicle 1 is currently traveling.

[0101] In addition, Figure 4 In one example, the "multiple frequency bands B" are defined as frequency bands B1, B2, and B3, each containing a displacement, velocity, and acceleration term, respectively, which have a vibration reduction effect. Here, when the requested control quantity X has displacement, velocity, and acceleration terms, the frequency bands with vibration reduction effects for each control term are not necessarily clearly defined according to the characteristics of the vehicle to which this FB control is applied, as in the examples of frequency bands B1 to B3. Specifically, for example, sometimes a portion of the frequency bands with vibration reduction effects overlaps between any two control terms. Therefore, when there are two control terms with vibration reduction effects in frequency band B that conform to a specific frequency band Bx, the control gain G of those two control terms can be increased from their respective base values.

[0102] (Modified Example)

[0103] For example, the "gain determination process" described in this disclosure can be performed instead of the utilization decision, as follows. Figure 5 An example of a mapping of relationships as shown. Figure 6 This is a flowchart illustrating a modified example of the gain determination processing involved in the implementation. In this modified example, different first to third modes of balancing the control gain G between control terms are switched depending on which of the frequency bands B1 to B3 the specific frequency band Bx belongs to.

[0104] Specifically, in Figure 6 In step S200, ECU10 determines whether frequency band B1 is a specific frequency band Bx. If the determination is "yes", ECU10 selects the first mode in step S202. The first mode uses a control gain G1 (displacement term) larger than the basic value G1b, a control gain G2 (velocity term) smaller than the basic value G2b, and a control gain G3 (acceleration term) smaller than the basic value G3b.

[0105] On the other hand, if the determination result in step S200 is "no", ECU10 determines in step S204 whether frequency band B2 is a specific frequency band Bx. As a result, if the determination result is "yes", ECU10 selects the second mode in step S206. The second mode is a mode that uses a control gain G1 smaller than the basic value G1b, a control gain G2 larger than the basic value G2b, and a control gain G3 smaller than the basic value G3b.

[0106] Furthermore, if the determination result in step S204 is "No" (i.e., when frequency band B3 is a specific frequency band Bx), ECU10 selects the third mode in step S208. The third mode is a mode that uses a control gain G1 smaller than the basic value G1b, a control gain G2 smaller than the basic value G2b, and a control gain G3 larger than the basic value G3b.

[0107] <Step S108>

[0108] Next, in step S108, ECU10 calculates the upper and lower requested control quantities F corresponding to the requested control quantity X. z Roll request control quantity M r And pitch request control quantity M p Specifically, in the filtering process accompanying step S102... Figure 3 In the example of the processing shown, the values ​​of HPF and LPF after applying the above are used as the sprung state quantities (Z) substituted into equations (11) to (13). g ”、Φ g ”、Θ g Z g'、Φ g '、Θ g '、Z g Φ g and Θ g That is, ECU10 calculates each requested control quantity F based on the product of the sprung state quantities after applying HPF and LPF and the control gain G determined in step S106. z M r and M p .

[0109] <Step S110>

[0110] Next, in step S110, ECU10 controls actuator 3A to generate a control force Fc corresponding to the requested control quantity X calculated in step S108. Specifically, ECU10 calculates the control force Fc corresponding to the requested control quantity X (Fc) calculated in step S108 according to equation (14). z M r and M p The corresponding target control force Fct for each wheel 2 fr Fct fl Fct rr and Fct rl Furthermore, the ECU10 instructs the calculated target control force Fct to each actuator 3A corresponding to each wheel 2.

[0111] 3. Effects

[0112] As explained above, according to this embodiment, when calculating the requested control quantity X, the frequency components of each of the multiple frequency bands B included in the road vibration information are calculated. Furthermore, the control gain G of each of the three control terms (displacement, velocity, and acceleration) is determined in a manner that varies based on the magnitude of the calculated frequency components of each frequency band B. More specifically, the frequency band with the largest frequency component among the multiple frequency bands B, i.e., a specific frequency band Bx, is determined. Based on this, the control gain G of the control term (displacement, velocity, and acceleration) that has a vibration reduction effect in the specific frequency band Bx is increased, and the control gain G of the control term (excitation effect) that has a vibration reduction effect in the specific frequency band Bx is decreased (gain determination processing). In this way, the control gain G of each control term is not determined according to the balance of the ceiling control algorithm, but is determined to achieve an appropriate balance based on achieving a high vibration reduction effect relative to the frequency characteristics of the road surface on which the vehicle 1 is currently traveling. Therefore, based on the road vibration information, vibration reduction of the sprung structure 5 can be effectively performed. More specifically, the reduction in vibration reduction effect caused by the frequency characteristics of the road surface can be appropriately suppressed.

[0113] In addition, according to the gain determination process described above, the balance of the control gains G of each control item is determined such that the frequency components of frequency band B, which conforms to a specific frequency band Bx with the largest frequency component, are effectively reduced compared to the frequency components of other frequency bands. Here, according to the definition of the specific frequency band Bx described above, the magnitude of the frequency components of other frequency bands is smaller than the magnitude of the frequency components of the specific frequency band Bx. Therefore, although there is a possibility that the frequency components of these other frequency bands may increase as a trade-off in determining the balance of control gains G, it can be said that the impact of this trade-off is small. That is, by utilizing the gain determination process, the vibration reduction of the spring structure 5 can be improved even when viewed as a whole in the case of multiple frequency bands B.

[0114] Furthermore, according to the filtering process described above (refer to step S102), the HPF and LPF applied to each of the spring state variables used in the calculation of the requested control quantity X are different between control terms, rather than being the same between control terms.

[0115] Specifically, such as as frequency band B1 (refer to...) Figure 4 As illustrated, vibration reduction effects related to the displacement term can be obtained at low frequencies, but the value of the displacement term (control quantity) is inherently prone to being too large. Based on this additional issue A, according to this embodiment, the strength of the HPF applied to the sprung state quantities (displacements of each mode) included in the displacement term is increased compared to the strength of the HPF applied to the sprung state quantities (velocities of each mode and accelerations of each mode) included in the other control terms, namely the velocity and acceleration terms. Therefore, the balance between control terms can be adjusted to suppress the displacement term from becoming too large. Furthermore, considering the aforementioned additional issue A, the basic value of the control gain G for the displacement term can be determined in a smaller manner, using the balance of the basic values ​​of the control gains G among the control terms according to the ceiling control algorithm as a benchmark.

[0116] Additionally, as in frequency band B3 (refer to...) Figure 4As illustrated, vibration reduction effects related to the acceleration term are obtained at mid-to-high frequency levels, but the acceleration term can lead to increased vibration or control instability at higher frequency levels than the frequency band where vibration reduction effects can be obtained. In view of this additional problem B, according to this embodiment, the strength of the LPF applied to the sprung state quantities (mode accelerations) included in the acceleration term is increased compared to the strength of the LPF applied to the sprung state quantities (mode displacements and mode velocities) included in the other control terms, namely the displacement and velocity terms. Therefore, the balance between control terms can be adjusted to suppress increased vibration or control instability at higher frequency levels than the frequency band where vibration reduction effects can be obtained through the acceleration term. Furthermore, in view of the aforementioned additional problem B, the basic value of the control gain G for the acceleration term can be determined in a decreasing manner based on the balance of the basic values ​​of the control gain G among the control terms according to the ceiling control algorithm.

[0117] In the above-described embodiment, a "gain determination process" is performed to increase the control gain G of the control item that has a vibration reduction effect in a specific frequency band Bx, and to decrease the control gain G of the control item that has an excitation effect in the specific frequency band Bx, among the three control items (displacement, velocity, and acceleration). However, the "gain determination process" involved in this disclosure is not limited to the process that only considers the specific frequency band Bx to change the control gain G of each control item, as described above. It is acceptable as long as the process "determines the control gain of at least two control items in a manner that varies based on the magnitude of the frequency components of each of the multiple frequency bands".

[0118] Specifically, for example, when using the three frequency bands B1 to B3, the gain determination process does not only consider the specific frequency band Bx to change the control gain G of each control item, but can also consider the frequency band with the second largest frequency component among the three frequency bands B1 to B3 (hereinafter, for convenience, referred to as "second frequency band Bx2") to change the control gain G of each control item. Furthermore, the increase in the control gain G of the control item that has a vibration reduction effect in the second frequency band Bx2 can be set, for example, less than the increase in the control gain G of the control item that has a vibration reduction effect in the specific frequency band Bx. Similarly, the decrease in the control gain G of the control item that has an excitation effect in the second frequency band Bx2 can be set, for example, less than the decrease in the control gain G of the control item that has an excitation effect in the specific frequency band Bx.

[0119] Furthermore, the gain determination process can be performed, for example, as follows. That is, when using the three frequency bands B1 to B3, the gain determination process is not only focused on specific frequency bands Bx and the second frequency band Bx2 to change the control gain G of each control item, but can also focus on the frequency band with the smallest frequency component among the three frequency bands B1 to B3 (hereinafter, for convenience, referred to as "the third frequency band Bx3") to change the control gain G of each control item. Moreover, the increase in the control gain G of the control item with vibration reduction effect in the third frequency band Bx3 can be set, for example, less than the increase in the control gain G of the control item with vibration reduction effect in the second frequency band Bx2. Similarly, the decrease in the control gain G of the control item with excitation effect in the third frequency band Bx3 can be set, for example, less than the decrease in the control gain G of the control item with excitation effect in the second frequency band Bx2.

Claims

1. A suspension control device for a vehicle, comprising: an actuator that applies a control force in a vertical direction between an unsprung body and a sprung body of the vehicle; and an electronic control unit that controls the actuator so as to generate the control force corresponding to a requested control amount requested for reducing a vibration of the sprung body, characterized in that the requested control amount includes at least two control terms of a displacement term, a velocity term, and an acceleration term related to a displacement, a velocity, and an acceleration of the sprung body, a process executed by the electronic control unit includes: a calculation process that calculates magnitudes of frequency components of a plurality of frequency bands included in road surface vibration information related to a road surface input to the vehicle or a vibration of the sprung body caused by the road surface input; and a gain determination process that determines control gains of the at least two control terms in a manner that varies based on the magnitudes of the frequency components of the plurality of frequency bands.

2. The suspension control device for a vehicle according to claim 1, characterized in that a frequency band having a largest frequency component among the plurality of frequency bands is referred to as a specific frequency band, in the gain determination process, the electronic control unit increases a control gain of a control term of the at least two control terms that has a damping effect of suppressing a vibration of the sprung body in the specific frequency band, and decreases a control gain of a control term that has a vibration excitation effect of promoting a vibration of the sprung body in the specific frequency band.

3. The suspension control device for a vehicle according to claim 1 or 2, characterized in that the at least two control terms include the displacement term, and an intensity of a high-pass filter applied to a sprung state quantity included in the displacement term is higher than intensities of high-pass filters applied to sprung state quantities included in the remaining one or two control terms.

4. The suspension control device for a vehicle according to any one of claims 1 to 3, characterized in that the at least two control terms include the acceleration term, and an intensity of a low-pass filter applied to a sprung state quantity included in the acceleration term is higher than intensities of low-pass filters applied to sprung state quantities included in the remaining one or two control terms.

5. The suspension control device for a vehicle according to any one of claims 1 to 4, characterized in that the plurality of frequency bands include a frequency band having a damping effect of the sprung body for each of the at least two control terms.

6. The suspension control device for a vehicle according to any one of claims 1 to 5, characterized in that the plurality of frequency bands include a frequency band having a vibration excitation effect of the sprung body for each of the at least two control terms.

7. A suspension control method for a vehicle, which controls an actuator that applies a control force in a vertical direction between an unsprung body and a sprung body of the vehicle so as to generate the control force corresponding to a requested control amount requested for reducing a vibration of the sprung body, characterized in that ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The request control amount includes at least two control terms among a displacement term, a velocity term, and an acceleration term related to displacement, velocity, and acceleration of the sprung structure, The vehicle suspension control method includes: a calculation process that calculates magnitudes of frequency components of a plurality of frequency bands included in road surface vibration information related to a road surface input to the vehicle or vibration of the sprung structure caused by the road surface input; and a gain determination process that determines control gains of the at least two control terms in a manner that varies based on the magnitudes of the frequency components of the plurality of frequency bands.

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