Control Method and System

Abstract

The present invention relates to a control method, comprising the following steps: calculating a wheel dynamic load according to a vehicle body vertical acceleration and a wheel vertical acceleration; calculating a control variable according to the wheel dynamic load; determining a wheel vertical load requirement according to the control variable and a threshold value; and determining a control current according to the wheel vertical load requirement and a shock absorber state, the control current being adapted to control a shock absorber damping force.

Description

Technical Field

[0001] The present invention relates to the field of automobile braking, and in particular to a control method and system, which can effectively shorten the braking distance of an automobile. Background Art

[0002] In the automotive braking field, for vehicles equipped with an anti-lock braking system (ABS), maintaining an optimal slip ratio throughout the braking process is crucial to reducing braking distance and ensuring longitudinal safety. The slip ratio is affected by three factors: wheel braking torque, vertical wheel load, and peak road adhesion coefficient. While the ABS system can adjust wheel braking torque by setting wheel cylinder brake pressure, variations in vertical wheel load and peak road adhesion coefficient can also cause the slip ratio to deviate from the optimal value. For slip ratio fluctuations not caused by braking torque, the ABS controller lacks sufficient signals to identify the cause of the slip ratio fluctuation, resulting in a certain delay in the ABS system's response.

[0003] During vehicle braking, slip rate fluctuations caused by changes in vertical wheel load are inevitable, resulting in a certain gap between theoretical and actual braking distances. Further shortening vehicle braking distances has become a pressing issue in the industry. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a control method, which can effectively shorten the braking distance of a car.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is to provide a control method, comprising the following steps: calculating the wheel dynamic load based on the vehicle body vertical acceleration and the wheel vertical acceleration; calculating the control variable based on the wheel dynamic load; determining the wheel vertical load demand based on the control variable and a threshold; and determining a control current based on the wheel vertical load demand and the shock absorber state, wherein the control current is suitable for controlling the shock absorber damping force.

[0006] In one embodiment of the present invention, in the step of calculating the wheel dynamic load based on the vehicle body vertical acceleration and the wheel vertical acceleration, the calculation formula of the wheel dynamic load is: Among them, F z,dyn (t) is the wheel dynamic load, m u is the wheel mass, is the vertical acceleration of the vehicle body, m s For the body quality, is the vertical acceleration of the wheel.

[0007] In an embodiment of the present invention, in the step of calculating the control variable according to the wheel dynamic load, the calculation formula of the control variable is as follows: wherein, V WLC is the control variable, F z,dyn (t) is the wheel dynamic load, and v x (t) is the vehicle speed.

[0008] In an embodiment of the present invention, the step of determining the wheel vertical load demand according to the control variable and the threshold value includes: comparing the magnitudes of the control variable and the threshold value; and determining the wheel vertical load demand according to the magnitude relationship between the control variable and the threshold value; wherein, when the control variable is greater than the threshold value, the wheel vertical load demand is to increase the wheel vertical load, and the change amount of the wheel vertical load is a positive value; when the control variable is less than or equal to the threshold value, the wheel vertical load demand is to decrease the wheel vertical load, and the change amount of the wheel vertical load is a negative value.

[0009] In an embodiment of the present invention, the change amount of the wheel vertical load is suitable for controlling the change amount of the slip ratio of the vehicle.

[0010] In an embodiment of the present invention, the calculation formula for controlling the change amount of the slip ratio by the change amount of the wheel vertical load is as follows: wherein, Δλ B is the change amount of the slip ratio, μ is the braking force coefficient, r eff is the effective wheel radius, I w is the wheel moment of inertia, ΔF z is the change amount of the wheel vertical load, and v x is the vehicle speed.

[0011] In an embodiment of the present invention, the step of determining the control current according to the wheel vertical load demand and the shock absorber state includes: determining the shock absorber damping force setting according to the wheel vertical load demand and the shock absorber state; and determining the control current according to the shock absorber damping force setting; wherein, the shock absorber state is the relative movement speed of the shock absorber.

[0012] Another aspect of the present invention provides a control system, comprising: a first sensor configured to detect the vertical acceleration of the vehicle body; a second sensor configured to detect the vertical acceleration of the wheel; a third sensor configured to detect the state of the shock absorber; and a controller electrically connected to the first sensor, the second sensor and the third sensor, the controller being configured to calculate the wheel dynamic load according to the vertical acceleration of the vehicle body and the vertical acceleration of the wheel, calculate a control variable according to the wheel dynamic load, determine the wheel vertical load demand according to the control variable and a threshold value, and determine a control current according to the wheel vertical load demand and the state of the shock absorber, the control current being adapted to control the shock absorber damping force.

[0013] In an embodiment of the present invention, in the step of the controller calculating the wheel dynamic load according to the vertical acceleration of the vehicle body and the vertical acceleration of the wheel, the calculation formula of the wheel dynamic load is: wherein, F z,dyn (t) is the wheel dynamic load, m u is the wheel mass, is the vertical acceleration of the vehicle body, m s is the vehicle body mass, is the vertical acceleration of the wheel.

[0014] In an embodiment of the present invention, it further comprises a vehicle speed sensor configured to detect the vehicle speed. In the step of the controller calculating the control variable according to the wheel dynamic load, the calculation formula of the control variable is: wherein, V WLC is the control variable, F z,dyn (t) is the wheel dynamic load, v x (t) is the vehicle speed.

[0015] In an embodiment of the present invention, the step of the controller determining the wheel vertical load demand according to the control variable and the threshold value includes: comparing the magnitudes of the control variable and the threshold value; and determining the wheel vertical load demand according to the magnitude relationship between the control variable and the threshold value; wherein, when the control variable is greater than the threshold value, the wheel vertical load demand is to increase the wheel vertical load, and the change amount of the wheel vertical load is a positive value; when the control variable is less than or equal to the threshold value, the wheel vertical load demand is to decrease the wheel vertical load, and the change amount of the wheel vertical load is a negative value.

[0016] In an embodiment of the present invention, the change amount of the wheel vertical load is adapted to control the change amount of the slip ratio of the vehicle.

[0017] In an embodiment of the present invention, the calculation formula for controlling the change amount of the slip ratio by the change amount of the wheel vertical load is: wherein, ΔλB is the change amount of the slip ratio, μ is the braking force coefficient, and r eff is the effective wheel radius, and I w is the moment of inertia of the wheel, and ΔF z is the change amount of the vertical load of the wheel, and v x is the vehicle speed.

[0018] In an embodiment of the present invention, the step of the controller determining the control current according to the vertical load requirement of the wheel and the state of the shock absorber includes: determining the shock absorber damping force setting according to the vertical load requirement of the wheel and the state of the shock absorber; and determining the control current according to the shock absorber damping force setting; wherein, the state of the shock absorber is the relative movement speed of the shock absorber, and the third sensor is configured to detect the relative movement speed of the shock absorber.

[0019] Since the present invention adopts the above technical solutions, compared with the prior art, it has the following remarkable advantages: The control method of the present invention determines the control current according to the vertical load requirement of the wheel and the state of the shock absorber, and controls the shock absorber damping force through the control current, thereby effectively shortening the braking distance of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 is a flowchart of a control method according to an embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of a control method according to an embodiment of the present invention;

[0023] Figure 3A and Figure 3B are respectively schematic diagrams of the working damping characteristics of a damping adjustable shock absorber of a control method according to an embodiment of the present invention;

[0024] Figure 4A and Figure 4B are respectively schematic diagrams of the influence of the shock absorber damping force setting on the vertical load of the wheel of a control method according to an embodiment of the present invention;

[0025] Figure 5 is a schematic diagram of the braking pressure of a control method according to an embodiment of the present invention;

[0026] Figure 6 is a schematic diagram of the road surface input of a control method according to an embodiment of the present invention;

[0027] Figure 7 is a schematic diagram of the vehicle speed of a control method according to an embodiment of the present invention;

[0028] Figure 8 It is a schematic diagram of the braking distance of a control method according to an embodiment of the present invention;

[0029] Figure 9 It is a schematic diagram of the dynamic load of the left front wheel of a control method according to an embodiment of the present invention;

[0030] Figure 10 It is a schematic diagram of the dynamic load of the right rear wheel of a control method according to an embodiment of the present invention;

[0031] Figure 11 It is a schematic diagram of a control system according to an embodiment of the present invention. Detailed implementation manners

[0032] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention is provided in conjunction with the accompanying drawings.

[0033] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention may be implemented in other ways different from those described herein, and thus the present invention is not limited by the specific embodiments disclosed below.

[0034] As shown in this application and the claims, unless the context clearly indicates otherwise, words such as "a", "an", "one", and / or "the" are not specifically singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0035] When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure will be locally enlarged out of the general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions of length, width, and depth should be included.

[0036] For convenience of description, spatial relationship terms such as "below", "beneath", "lower", "under", "above", "on" and the like may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relationship terms are intended to encompass other orientations of the device in use or operation, in addition to the orientations depicted in the drawings. For example, if the device in the drawings is turned over, the orientation of an element described as "below" or "beneath" or "under" other elements or features will be changed to "above" the other elements or features. Thus, the exemplary terms "below" and "under" can encompass both an upper and a lower direction. The device may also have other orientations (rotated 90 degrees or at other orientations), and thus the spatial relationship descriptive terms used herein should be interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers.

[0037] In the context of the present application, the structure in which the first feature is "on" the second feature as described may include an embodiment in which the first and second features are formed in direct contact, and may also include an embodiment in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0038] It should be understood that when a component is referred to as being "on" another component, "connected to" another component, "coupled to" another component, or "in contact with" another component, it can be directly on, connected to, or coupled to, or in contact with the other component, or there can be intervening components. In contrast, when a component is referred to as being "directly on" another component, "directly connected to", "directly coupled to", or "in direct contact with" another component, there are no intervening components. Similarly, when the first component is referred to as being "electrically in contact with" or "electrically coupled to" the second component, there is an electrical path allowing current to flow between the first component and the second component. The electrical path can include capacitors, coupled inductors, and / or other components allowing current to flow, even if there is no direct contact between the conductive components.

[0039] The following embodiments of the present invention propose a control method that can effectively shorten the braking distance of an automobile.

[0040] It can be understood that the following description is merely exemplary, and those skilled in the art can make various changes without departing from the spirit of the present invention.

[0041] Figure 1 is a flowchart of a control method according to an embodiment of the present invention. Figure 2 is a schematic diagram of a control method according to an embodiment of the present invention. The following is combined with Figure 1 andFigure 2 Describe the steps of this control method.

[0042] A control method of the present invention includes the following steps: calculating the wheel dynamic load according to the vehicle body vertical acceleration and the wheel vertical acceleration; calculating the control variable according to the wheel dynamic load; determining the wheel vertical load demand according to the control variable and the threshold value; and determining the control current according to the wheel vertical load demand and the shock absorber state, and the control current is suitable for controlling the shock absorber damping force.

[0043] Step 110: Calculate the wheel dynamic load according to the vehicle body vertical acceleration and the wheel vertical acceleration.

[0044] Reference Figure 2 As shown, in an embodiment of the present invention, in the step of calculating the wheel dynamic load according to the vehicle body vertical acceleration and the wheel vertical acceleration, the calculation formula of the wheel dynamic load is:

[0045]

[0046] Wherein, F z,dyn (t) is the wheel dynamic load, m u is the wheel mass, is the vehicle body vertical acceleration, m s is the vehicle body mass, is the wheel vertical acceleration.

[0047] Step 120: Calculate the control variable according to the wheel dynamic load.

[0048] Reference Figure 2 As shown, in an embodiment of the present invention, in the step of calculating the control variable according to the wheel dynamic load, the calculation formula of the control variable is:

[0049]

[0050] Wherein, V WLC is the control variable, F z,dyn (t) is the wheel dynamic load, v x (t) is the vehicle speed.

[0051] The vehicle speed can be obtained from the vehicle speed signal. Exemplarily, the vehicle speed signal can come from the Controller Area Network (CAN) signal of the whole vehicle.

[0052] Step 130: Determine the wheel vertical load demand according to the control variable and the threshold value.

[0053] In an embodiment of the present invention, the step of determining the wheel vertical load demand according to the control variable and the threshold includes: comparing the magnitudes of the control variable and the threshold and determining the wheel vertical load demand according to the magnitude relationship between the control variable and the threshold.

[0054] Wherein, when the control variable is greater than the threshold, the wheel vertical load demand is to increase the wheel vertical load, and the change amount of the wheel vertical load is a positive value; when the control variable is less than or equal to the threshold, the wheel vertical load demand is to decrease the wheel vertical load, and the change amount of the wheel vertical load is a negative value.

[0055] Exemplarily, as shown in Figure 2 In the step of determining the wheel vertical load demand according to the control variable and the threshold, the following formula can be used to calculate the wheel vertical load demand:

[0056]

[0057] Wherein, F z,req is the wheel vertical load demand, V WLC is the control variable, V TH is the threshold. F z,req being equal to +1 indicates that it is necessary to increase the wheel vertical load, and F z,req being equal to -1 indicates that it is necessary to decrease the wheel vertical load.

[0058] In an embodiment of the present invention, the change amount of the wheel vertical load is suitable for controlling the change amount of the slip ratio of the vehicle. In some examples, the calculation formula for controlling the change amount of the slip ratio by the change amount of the wheel vertical load is:

[0059]

[0060] Wherein, Δλ B is the change amount of the slip ratio, μ is the braking force coefficient, r eff is the effective wheel radius, I w is the wheel moment of inertia, ΔF z is the change amount of the wheel vertical load, v x is the vehicle speed.

[0061] The following details the derivation process of the calculation formula (4) for controlling the change amount of the slip ratio Δλ z by the change amount of the wheel vertical load ΔF B .

[0062] For wheel rotation, its dynamic equation is:

[0063]

[0064] Wherein, I w is the wheel moment of inertia, is the angular acceleration of the wheel rotation, and F B is the braking force (from the ground), and r eff is the effective wheel radius, and M B is the braking torque.

[0065] Assume that the braking torque M B is a constant. A sudden change in the braking force F B will cause a sudden change in the angular acceleration of the wheel. Thus, the following relationship can be obtained:

[0066]

[0067] where is the change in the angular acceleration of the wheel, and ΔF B is the change in the braking force.

[0068] Integrating the relationship (6) with respect to time t, the calculation formula for the change in the angular velocity of the wheel can be obtained:

[0069]

[0070] where is the change in the angular velocity of the wheel.

[0071] Multiplying the formula (7) by the effective wheel radius r eff , the calculation formula for the change in the wheel speed can be obtained:

[0072]

[0073] where Δv w is the change in the wheel speed.

[0074] In the field of vehicle braking, the calculation formula for the braking slip ratio is:

[0075]

[0076] where λ B is the slip ratio, ω w is the angular velocity of the wheel, and v x is the speed of the wheel center (vehicle speed).

[0077] Generally, on a normal road surface, the maximum longitudinal deceleration of a vehicle can approach 10 m / s 2 . Due to a large braking torque M B acting on the wheel to cause a sharp deceleration, the wheel deceleration can often reach more than 10 times the vehicle acceleration. Assume that the change in the speed v x of the wheel center is less than the change in the wheel speed Δv w . According to the formula (9), the following relationship can be obtained:

[0078]

[0079] At the instant of braking of the vehicle, when the time interval is very small, v x (t2)≈v x (t1)=v x , thus further obtaining the calculation formula for the change in slip ratio Δλ B :

[0080]

[0081] It can be seen from formula (11) that the change in slip ratio Δλ B is proportional to the integral ∫ΔF B dt of the change in braking force ΔF B . The integral ∫ΔF B dt of the change in braking force ΔF B can play a role in low-pass filtering, so that high-frequency braking force oscillations will not affect the change in slip ratio Δλ B .

[0082] Assume that the braking torque M B and the peak road adhesion coefficient remain unchanged, and the change in wheel vertical load ΔF z and the change in braking force ΔF B will satisfy the following relationship:

[0083] ΔF B =μ·ΔF z (12)

[0084] where μ is the braking force coefficient.

[0085] From formula (11) and relationship (12), it can be further obtained that:

[0086]

[0087] Therefore, the change in slip ratio Δλ B is proportional to the integral ∫ΔF z dt of the change in wheel vertical load ΔF z . By changing the change in wheel vertical load ΔF z , the change in slip ratio Δλ B of the vehicle can be controlled.

[0088] Step 140, determine the control current according to the wheel vertical load demand and the shock absorber state. Among them, the control current is suitable for controlling the shock absorber damping force.

[0089] In an embodiment of the present invention, the steps of determining the control current according to the wheel vertical load demand and the shock absorber state include: determining the shock absorber damping force setting according to the wheel vertical load demand and the shock absorber state; and determining the control current I according to the shock absorber damping force setting d ; wherein, the shock absorber state is the relative movement speed v of the shock absorber d .

[0090] Reference Figure 2 As shown, in some other examples of the present invention, the control current I can also be directly determined according to the wheel vertical load demand F z,req and the relative movement speed v of the shock absorber d ; however, this application is not limited thereto d .

[0091] Table 1 shows the logical relationship between the shock absorber damping force (F d ) setting and the control current I d in a control method according to an embodiment of the present invention

[0092]

[0093] Table 1

[0094] Figure 3A And Figure 3B are respectively schematic diagrams of the working damping characteristics of a damping adjustable shock absorber in a control method according to an embodiment of the present invention. Referring to Table 1 and Figure 3A And Figure 3B shown, the shock absorber state (such as the compression state or the tension state) can be determined by the relative movement speed v of the shock absorber d .

[0095] When F z,req is equal to +1, it means that it is necessary to increase the wheel vertical load. At this time, if the shock absorber state is the compression state, it is necessary to increase the shock absorber damping force F d , and set the control current to the maximum value I d,max ; if the shock absorber state is the tension state, it is necessary to reduce the shock absorber damping force F d , and set the control current to the minimum value I d,min .

[0096] When F z,req is equal to -1, it means that it is necessary to reduce the wheel vertical load. At this time, if the shock absorber state is the compression state, it is necessary to reduce the shock absorber damping force F d , and set the control current to the minimum value I d,min ; if the shock absorber state is the tension state, it is necessary to increase the shock absorber damping force F d , and set the control current to the maximum value I d,max .

[0097] Figure 4A and Figure 4B are respectively schematic diagrams showing the influence of the shock absorber damping force setting on the wheel vertical load in an embodiment of the present invention. It should be noted that Figure 4A and Figure 4B only schematically show the influence of the shock absorber damping force setting on the wheel vertical load. In this example, the elastic element and the damping element are omitted.

[0098] Refer to Figure 4A and Figure 4B as shown. I d,min and I d,max respectively represent the minimum control current and the maximum control current of the shock absorber. F d (I d,min ) and F d (I d,max ) are respectively the minimum damping force and the maximum damping force of the shock absorber corresponding to the minimum control current and the maximum control current. F z,min and F z,max are respectively the minimum wheel vertical load and the maximum wheel vertical load corresponding to the minimum control current and the maximum control current. v s is the body vertical speed, and v u is the wheel vertical speed.

[0099] Refer to Figure 4A as shown. When the vehicle shock absorber (suspension) is stretched at a fixed speed (for example, the shock absorber has a given speed v d ), the shock absorber damping force F d generates a downward pulling force on the body and an upward pulling force on the wheel. If the control current is switched from the minimum I d,min to the maximum I d,max at this time, the corresponding shock absorber damping force F d increases, changing from the minimum shock absorber damping force F d (I d,min ) to the maximum shock absorber damping force F d (I d,max ). The upward pulling force on the wheel increases, and then the wheel vertical load F z will decrease, changing from the maximum wheel vertical load F z,max to the minimum wheel vertical load F z,min .

[0100] Refer to Figure 4B as shown. When the vehicle shock absorber (suspension) is compressed at a fixed speed (for example, when the relative movement speed of the shock absorber is v d ), the shock absorber damping force F d generates an upward pushing force on the body and a downward pressure on the wheel. If the control current is switched from the minimum I d,minSwitch to the maximum I d,max , the corresponding shock absorber damping force F d increases. From the minimum shock absorber damping force F d (I d,min ) it becomes the maximum shock absorber damping force F d (I d,max ). The downward pressure on the wheel increases, so the wheel vertical load F z will increase. From the minimum wheel vertical load F z,min it becomes the maximum wheel vertical load F z,max .

[0101] The change in the shock absorber damping force F d will cause a change in the wheel vertical load F z . The relationship between the shock absorber damping force F d and the wheel vertical load F z is shown in Table 2.

[0102]

[0103] Table 2

[0104] According to formula (4), it can be known that the change in slip ratio Δλ B is proportional to the integral ∫ΔF z dt of the change in wheel vertical load ΔF z . By changing the change in wheel vertical load ΔF z the change in slip ratio Δλ B of the vehicle can be controlled. And the setting of the shock absorber damping force (such as increasing the shock absorber damping force F d or decreasing the shock absorber damping force F d ) can affect the wheel vertical load F z . In this way, by controlling the current I d to change the magnitude of the shock absorber damping force F d , the change in wheel vertical load ΔF z can be changed, and further the change in slip ratio Δλ B of the vehicle can be controlled, thus effectively controlling the braking distance of the vehicle.

[0105] In some examples, the change in wheel vertical load ΔF z can be caused by the wheel dynamic load F z,dyn (t). The change in wheel vertical load ΔF z and the wheel dynamic load F z,dyn (t) satisfy the following relationship:

[0106] ΔF z (t) = -F z,dyn (t) (13)

[0107] The dynamic load F of a single wheel z,dyn (t) can be determined by the wheel stiffness and damping force:

[0108]

[0109] where k t is the vertical stiffness of the wheel, c t is the vertical damping coefficient of the wheel, z u (t) is the vertical displacement of the wheel, z g (t) is the vertical displacement of the road surface, is the vertical velocity of the wheel, is the vertical velocity of the road surface, is the vertical acceleration of the wheel, is the vertical acceleration of the vehicle body, m u is the mass of the wheel, m s is the mass of the vehicle body.

[0110] According to Equation (4) and Equation (13), integrate the wheel dynamic load F z,dyn (t), and then divide by the vehicle speed v x (t) as the control variable V WLC , the following relationship can be obtained:

[0111]

[0112] where V WLC is the control variable, ΔF z (t) is the change in the vertical load of the wheel, v x (t) is the vehicle speed.

[0113] Exemplarily, at a certain moment t, when the wheel jumps upward relative to the ground, the wheel dynamic load F z,dyn (t) is positive, the change in the vertical load of the wheel ΔF z is negative, and the vertical load of the wheel F z (t) decreases. According to the above relationship (15), it can be known that when the value of the control variable V WLC increases to a certain extent, it will necessarily cause an increase in the change in the slip ratio Δλ B . At this time, if it is necessary to prevent a large slip ratio oscillation, that is, to keep the change in the slip ratio Δλ B stable, then it is necessary to increase the vertical load of the wheel F z (t).

[0114] Conversely, at a certain moment t, when the wheel jumps downward relative to the ground, the wheel dynamic load F z,dyn (t) is negative, the change in the vertical load of the wheel ΔF z is positive, and the vertical load of the wheel F z(t) increases. At this time, if a large slip rate oscillation is to be prevented, that is, the change in slip rate Δλ B is to be kept stable, then the wheel vertical load F z (t) needs to be reduced.

[0115] Maintaining the optimal slip rate during vehicle braking can shorten the braking distance of the vehicle. Therefore, an appropriate (control variable) threshold V TH can be selected such that when the control variable V WLC is greater than or equal to the threshold V TH , the wheel vertical load demand F z,req is set to increase the wheel vertical load F z (t); when the control variable V WLC is less than the threshold V TH , the wheel vertical load demand F z,req is set to reduce the wheel vertical load F z (t).

[0116] Preferably, in the following embodiments of the present invention, the threshold V TH can be a positive value (i.e., V TH > 0). When the threshold V TH is a positive value, an increase in the control variable V WLC can cause a relatively large increase in the change in slip rate Δλ B . Moreover, when the threshold V TH is a positive value, it can also prevent the wheel vertical load demand F WLC from frequently switching between F z,req = +1 and F z,req = -1 when the control variable V z,req oscillates near zero.

[0117] Figure 5 is a schematic diagram of the braking pressure of a control method according to an embodiment of the present invention. Figure 6 is a schematic diagram of the road surface input of a control method according to an embodiment of the present invention. Figure 7 is a schematic diagram of the vehicle speed of a control method according to an embodiment of the present invention. Figure 8 is a schematic diagram of the braking distance of a control method according to an embodiment of the present invention. Figure 9 is a schematic diagram of the dynamic load of the left front wheel of a control method according to an embodiment of the present invention. Figure 10 is a schematic diagram of the dynamic load of the right rear wheel of a control method according to an embodiment of the present invention. The following is an illustration of an application example of the control method of the present invention in conjunction with Figures 5 to 10 .

[0118] Under the condition of straight-line driving, the damping force F of the shock absorber is verified by simulation dEffect on braking distance. Refer to Figure 5 and Figure 6 As shown, with a Class B road surface input, an initial vehicle speed of 120 km / h, when the time (t) is 5 s, brake pressures of 3 Mpa and 2.5 Mpa are applied to the wheel cylinders of the front (including the left front FL and the right front FR) and rear (including the left rear RL and the right rear RR) wheels respectively, and the total simulation time is 15 s, and a comparison is made with the ground shed damping control.

[0119] For ease of analysis and comparison, the results of the ground shed damping control are identified by A, and the control results of the control method of the present invention are identified by B. Refer to Figures 7 to 10 As shown, compared with the ground shed damping control, the vehicle speed of the control method of the present invention decreases faster, the braking distance is significantly shortened, and the change in the wheel dynamic load is also significantly reduced, so that the braking distance can be effectively shortened.

[0120] The control method of the present invention determines the control current according to the wheel vertical load demand and the shock absorber state, and controls the shock absorber damping force through the control current, thereby affecting the change in the wheel vertical load, reducing the fluctuation of the slip ratio during braking, and effectively shortening the braking distance of the vehicle. At the same time, it also avoids the frequent adjustment of the ABS system caused by the change in the wheel vertical load during braking, improving the stability and safety of vehicle braking.

[0121] It should be noted that the above embodiments use Figure 1 the flowchart shown to illustrate the steps / operations performed by the method according to the embodiments of the present application. It should be understood that the above steps / operations do not necessarily need to be precisely executed in sequence, but the order can be changed or various steps / operations can be processed simultaneously. At the same time, or other steps / operations can be added to these steps / operations, or one or several steps can be removed from these steps / operations.

[0122] Those skilled in the art can make corresponding adjustments to the priority order of the steps of the method determined according to actual needs, and the present invention is not limited thereto.

[0123] The above embodiments of the present invention propose a control method, which can effectively shorten the braking distance of a vehicle.

[0124] Another aspect of the present invention proposes a control system, which can effectively shorten the braking distance of a vehicle.

[0125] Figure 11 is a schematic diagram of a control system according to an embodiment of the present invention. The following will describe this control system in conjunction with Figure 11 It should be understood that the above control method of the present invention can be implemented in, for example, Figure 11 the control system 10 shown or its variants, but the present invention is not limited thereto.

[0126] Reference Figure 11 As shown, the control system 10 includes a first sensor 11, a second sensor 12, a third sensor 13, and a controller 14.

[0127] The first sensor 11 is configured to detect the vertical acceleration of the vehicle body. The second sensor 12 is configured to detect the vertical acceleration of the wheel. The third sensor 13 is configured to detect the state of the shock absorber. The controller 14 is electrically connected to the first sensor 11, the second sensor 12, and the third sensor 13. The controller 14 is configured to calculate the wheel dynamic load according to the vertical acceleration of the vehicle body and the vertical acceleration of the wheel, calculate the control variable according to the wheel dynamic load, determine the wheel vertical load demand according to the control variable and the threshold, and determine the control current according to the wheel vertical load demand and the state of the shock absorber. Among them, the control current is suitable for controlling the shock absorber damping force

[0128] Exemplarily, the first sensor 11 may be arranged at the upper hinge of the vehicle suspension and the vehicle body. The second sensor 12 may be arranged at the lower hinge of the vehicle suspension and the wheel.

[0129] In some examples, the third sensor 13 may be a suspension dynamic stroke sensor and is configured to measure the relative movement stroke of the suspension. The third sensor 13 is suitable for obtaining the shock absorber state information according to the relative movement stroke of the suspension. Preferably, the third sensor 13 may be arranged between the vehicle body and the wheel.

[0130] Preferably, the above control system 10 may be a damping adjustable semi-active suspension system.

[0131] In Figure 11 In one example shown, the unsprung mass may refer to the mass not supported by the elastic element in the suspension system, such as including the wheel, spring, shock absorber, and other related components, etc. The sprung mass may refer to the mass of the remaining part of the vehicle, such as including the frame, power system, transmission, occupants, etc.

[0132] Exemplarily, k s is the spring stiffness, k t is the wheel vertical stiffness, c s is the shock absorber damping coefficient, c t is the wheel vertical damping coefficient.

[0133] In an embodiment of the present invention, in the step of the controller 14 calculating the wheel dynamic load according to the vertical acceleration of the vehicle body and the vertical acceleration of the wheel, the calculation formula of the wheel dynamic load is:

[0134]

[0135] Among them, F z,dyn (t) is the wheel dynamic load, mu is the wheel mass, is the vehicle body vertical acceleration, m s is the vehicle body mass, is the wheel vertical acceleration.

[0136] In an embodiment of the present invention, a vehicle speed sensor (not shown in the figure) is further included, configured to detect the vehicle speed. In the step of calculating the control variable by the controller 14 according to the wheel dynamic load, the calculation formula of the control variable is:

[0137]

[0138] wherein, V WLC is the control variable, F z,dyn (t) is the wheel dynamic load, v x (t) is the vehicle speed.

[0139] In some other examples of the present invention, the vehicle speed can also be obtained through the Controller Area Network (CAN) signal of the whole vehicle.

[0140] In an embodiment of the present invention, the step that the controller 14 determines the wheel vertical load requirement according to the control variable and the threshold includes: comparing the magnitudes of the control variable and the threshold; and determining the wheel vertical load requirement according to the magnitude relationship between the control variable and the threshold.

[0141] wherein, when the control variable is greater than the threshold, the wheel vertical load requirement is to increase the wheel vertical load, and the change amount of the wheel vertical load is a positive value; when the control variable is less than or equal to the threshold, the wheel vertical load requirement is to decrease the wheel vertical load, and the change amount of the wheel vertical load is a negative value.

[0142] Exemplarily, in the step of determining the wheel vertical load requirement according to the control variable and the threshold, the following formula can be used to calculate the wheel vertical load requirement:

[0143]

[0144] wherein, F z,req is the wheel vertical load requirement, V WLC is the control variable, V TH is the threshold. F z,req equal to +1 indicates that it is necessary to increase the wheel vertical load, F z,req equal to -1 indicates that it is necessary to decrease the wheel vertical load.

[0145] Maintaining the optimal slip ratio during the vehicle braking process can shorten the braking distance of the vehicle. Therefore, a suitable threshold V of the (control variable) can be selected TH , such that when the control variable V WLC is greater than or equal to the threshold VTH When, set the wheel vertical load requirement F z,req To increase the wheel vertical load F z (t); When the control variable V WLC Is less than the threshold value V TH When, set the wheel vertical load requirement F z,req To decrease the wheel vertical load F z (t).

[0146] Preferably, in the following embodiments of the present invention, the threshold value V TH Can be a positive value (i.e., V TH > 0). When the threshold value V TH Is a positive value, the increase of the control variable V WLC Can cause a relatively large change in the slip ratio Δλ B Increase. Moreover, the threshold value V TH Being a positive value can also prevent the control variable V WLC When oscillating near zero, the wheel vertical load requirement F z,req At F z,req = +1 and F z,req = -1 and switch frequently.

[0147] In an embodiment of the present invention, the wheel vertical load change amount is suitable for controlling the slip ratio change amount of the vehicle. In some examples, the calculation formula for controlling the slip ratio change amount by the wheel vertical load change amount is:

[0148]

[0149] Wherein, Δλ B Is the slip ratio change amount, μ is the braking force coefficient, r eff Is the effective wheel radius, I w Is the wheel moment of inertia, ΔF z Is the wheel vertical load change amount, v x Is the vehicle speed.

[0150] In an embodiment of the present invention, the steps for the controller 14 to determine the control current according to the wheel vertical load requirement and the shock absorber state include: determining the shock absorber damping force setting according to the wheel vertical load requirement and the shock absorber state; and determining the control current I d ; Wherein, the shock absorber state is the shock absorber relative movement speed, and the third sensor 13 is configured to detect the shock absorber relative movement speed v d .

[0151] In some other examples of the present invention, the control current I can also be directly determined according to the wheel vertical load requirement F z,req And the shock absorber relative movement speed v d ​d , this application is not limited thereto.

[0152] According to formula (4), the change in slip ratio Δλ B is proportional to the integral ∫ΔF z of the change in wheel vertical load ΔF z with respect to time dt. By changing the change in wheel vertical load ΔF z , the change in slip ratio Δλ of the vehicle can be controlled. B . The setting of the shock absorber damping force (for example, increasing the shock absorber damping force F d or decreasing the shock absorber damping force F d ) can affect the wheel vertical load F z . Thus, by controlling the current I d to change the magnitude of the shock absorber damping force F d , the change in wheel vertical load ΔF z can be changed, and further the change in slip ratio Δλ of the vehicle can be controlled B , thereby effectively controlling the braking distance of the vehicle.

[0153] The control system of the present invention determines the control current according to the wheel vertical load demand and the state of the shock absorber, and controls the shock absorber damping force through the control current, thereby affecting the change in the wheel vertical load, reducing the fluctuation of the slip ratio during braking, and effectively shortening the braking distance of the vehicle. At the same time, it also avoids the frequent adjustment of the ABS system during braking due to the change in the wheel vertical load, improving the stability and safety of vehicle braking.

[0154] For other implementation details of the control system of this embodiment, reference can be made to Figures 1 to 10 the described embodiment, which will not be elaborated here.

[0155] The above embodiments of the present invention propose a control system, which can effectively shorten the braking distance of a vehicle.

[0156] It should be understood that the above-described embodiments are merely illustrative. The embodiments described herein can be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, and / or other electronic units designed to perform the functions described herein or a combination thereof.

[0157] The basic concepts have been described above. Obviously, for those skilled in the art, the above invention disclosure is only an example and does not constitute a limitation to this application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0158] Meanwhile, this application uses specific terms to describe the embodiments of this application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0159] The computer program codes required for the operations of various parts of this application can be written in any one or more programming languages, including object-oriented programming languages such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc., conventional procedural programming languages such as C language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages such as Python, Ruby, and Groovy, or other programming languages. This program code can run entirely on the user's computer, or run as an independent software package on the user's computer, or run partially on the user's computer and partially on a remote computer, or run entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer in any network form, such as a local area network (LAN) or a wide area network (WAN), or connected to an external computer (for example, via the Internet), or in a cloud computing environment, or used as a service such as software as a service (SaaS).

[0160] Further, unless otherwise specified in the claims, the order of the processing elements and sequences, the use of numerical letters, or the use of other names described in this application are not used to limit the order of the processes and methods of this application. Although some currently useful embodiments of the invention are discussed through various examples in the above disclosure, it should be understood that such details are only for illustrative purposes, and the appended claims are not limited to the disclosed embodiments. On the contrary, the claims are intended to cover all modifications and equivalent combinations that conform to the essence and scope of the embodiments of this application. For example, although the system components described above can be implemented by hardware devices, they can also be implemented only through software solutions, such as installing the described system on existing servers or mobile devices.

[0161] Similarly, it should be noted that, in order to simplify the description of the disclosure of this application and thus help the understanding of one or more embodiments of the application, in the previous description of the embodiments of this application, sometimes multiple features are merged into one embodiment, drawing, or description thereof. However, this method of disclosure does not mean that the features required by the subject matter of this application are more than those mentioned in the claims. In fact, the features of the embodiments are less than all the features of the individual embodiments disclosed above.

[0162] Although the present invention has been described with reference to the current specific embodiments, those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the spirit of the present invention, they will fall within the scope of the claims of this application.

Claims

1. A control method, comprising the following steps: Calculating a wheel dynamic load based on a vehicle body vertical acceleration and a wheel vertical acceleration; Calculating a control variable based on the wheel dynamic load; Determining a wheel vertical load requirement based on the control variable and a threshold value; And Determining a control current based on the wheel vertical load requirement and a shock absorber state, the control current being suitable for controlling a shock absorber damping force to change a wheel vertical load variation amount, the shock absorber state being a shock absorber relative movement speed; Wherein, the step of determining the wheel vertical load requirement based on the control variable and the threshold value includes: Comparing the magnitudes of the control variable and the threshold value; and Determining the wheel vertical load requirement based on the magnitude relationship between the control variable and the threshold value; Wherein, when the control variable is greater than the threshold value, the wheel vertical load requirement is to increase the wheel vertical load and the wheel vertical load variation amount is a positive value; when the control variable is less than or equal to the threshold value, the wheel vertical load requirement is to decrease the wheel vertical load and the wheel vertical load variation amount is a negative value; In the step of calculating the control variable based on the wheel dynamic load, the calculation formula of the control variable is: Among them, V WLC is the control variable, F z,dyn (t) is the dynamic wheel load, v x (t) is the vehicle speed; The wheel vertical load variation amount is suitable for controlling a vehicle slip ratio variation amount, and the calculation formula for controlling the slip ratio variation amount by the wheel vertical load variation amount is: Among them, Δλ B is the change amount of the slip ratio, μ is the braking force coefficient, r eff is the effective wheel radius, I w is the wheel moment of inertia, ΔF z is the change amount of the vertical load of the wheel, v x is the vehicle speed.

2. The control method according to claim 1, wherein In the step of calculating the wheel dynamic load based on the vehicle body vertical acceleration and the wheel vertical acceleration, the calculation formula of the wheel dynamic load is: Among them, F z,dyn (t) is the dynamic load of the wheel, m u is the wheel mass, is the vertical acceleration of the vehicle body, m s is the vehicle body mass, is the vertical acceleration of the wheel.

3. The control method according to claim 1, wherein The step of determining the control current based on the wheel vertical load requirement and the shock absorber state includes: Determining a shock absorber damping force setting based on the wheel vertical load requirement and the shock absorber state; and Determining the control current based on the shock absorber damping force setting.

4. A control system, comprising: A first sensor configured to detect a vehicle body vertical acceleration; A second sensor configured to detect a wheel vertical acceleration; A third sensor configured to detect a shock absorber state, the shock absorber state being a shock absorber relative movement speed; And A controller electrically connected to the first sensor, the second sensor, and the third sensor, the controller being configured to calculate a wheel dynamic load based on the vehicle body vertical acceleration and the wheel vertical acceleration, calculate a control variable based on the wheel dynamic load, determine a wheel vertical load requirement based on the control variable and a threshold value, and determine a control current based on the wheel vertical load requirement and the shock absorber state, the control current being suitable for controlling a shock absorber damping force to change a wheel vertical load variation amount; Wherein, the step in which the controller determines the wheel vertical load requirement based on the control variable and the threshold value includes: Comparing the magnitudes of the control variable and the threshold value; and Determining the wheel vertical load requirement based on the magnitude relationship between the control variable and the threshold value; Wherein, when the control variable is greater than the threshold value, the wheel vertical load demand is to increase the wheel vertical load, and the change amount of the wheel vertical load is a positive value; when the control variable is less than or equal to the threshold value, the wheel vertical load demand is to decrease the wheel vertical load, and the change amount of the wheel vertical load is a negative value; The control system further includes a vehicle speed sensor configured to detect the vehicle speed. In the step of calculating the control variable by the controller according to the wheel dynamic load, the calculation formula of the control variable is: Among them, V WLC is the control variable, F z,dyn (t) is the dynamic wheel load, v x (t) is the vehicle speed; The change amount of the wheel vertical load is suitable for controlling the change amount of the slip ratio of the vehicle. The calculation formula for controlling the change amount of the slip ratio by the change amount of the wheel vertical load is: where, Δλ B is the change amount of the slip ratio, μ is the braking force coefficient, r eff is the effective wheel radius, I w is the wheel moment of inertia, ΔF z is the change amount of the wheel vertical load, v x is the vehicle speed.

5. The control system according to claim 4, wherein In the step of calculating the wheel dynamic load by the controller according to the vehicle body vertical acceleration and the wheel vertical acceleration, the calculation formula of the wheel dynamic load is: Among them, F z,dyn (t) is the dynamic load of the wheel, m u is the wheel mass, is the vertical acceleration of the vehicle body, m s is the vehicle body mass, is the vertical acceleration of the wheel.

6. The control system according to claim 4, wherein The step of the controller determining the control current according to the wheel vertical load demand and the shock absorber state includes: Determining the shock absorber damping force setting according to the wheel vertical load demand and the shock absorber state; and Determining the control current according to the shock absorber damping force setting; Wherein, the third sensor is configured to detect the relative movement speed of the shock absorber.

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