Road surface detection system equipped with a hydraulic unit of an anti-lock braking system

Abstract

Road surface detection system. In one example, a system includes an antilock braking system hydraulic unit having a preload adjuster and a plurality of pressure sensors configured to generate pressure sensor data, and a controller configured to receive pressure sensor data from the plurality of pressure sensors, determine a target preload pressure level, calculate a pressure difference between the pressure sensor data and the target preload pressure level by comparing the pressure sensor data to the target preload pressure level, determine a road surface based on the calculated pressure difference, and adjust the preload adjuster to change pressure in the hydraulic unit based on the road surface.

Description

Technical Field

[0001] The embodiments, aspects, features, and examples described herein relate to road surface detection using a brake system pressure sensor.

Summary of the Invention

Means for Solving the Problems

[0002] [After the inventors have reviewed and approved the detailed description, claims, and provisional drawings, insert a summary of the independent claims in this section].

[0003] Other aspects, features, and examples will become apparent by considering the detailed description and the accompanying drawings.

Brief Description of the Drawings

[0004]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0005] Vehicles such as motorcycles and other wheeled vehicles often include a manual preload adjuster for adjusting the load level between two predetermined levels, such as a "soft level" and a "hard level" for example. It is desirable to adjust the preload level of a motorcycle to conform to a desired riding experience. For example, the desired preload level for a rough gravel road may differ from that for a smooth paved road. In some existing vehicles, the rider manually adjusts the preload level before operating the vehicle. For example, the rider may set the desired preload level by manually adjusting the mechanical collar of the preload adjuster to the desired load level according to the vehicle load or terrain type. Such preload adjustment is performed before operating the vehicle, and no further adjustment can be made during vehicle operation.

[0006] It is also desirable for the preload adjustment to automatically respond to dynamic changes in the road surface condition. To achieve this, some vehicles employ a semi-active damping control (SDC) system that includes, for example, an analog input that is a signal from one or more accelerometers to generate data indicating the road surface condition. In some examples, one accelerometer measures the vertical acceleration and generates and outputs a vertical acceleration signal. Another accelerometer measures the horizontal acceleration and generates and outputs a horizontal acceleration signal. A controller receives the vertical acceleration signal and the horizontal acceleration signal and generates a road surface roughness coefficient value used by the SDC algorithm. Then, the controller uses the SDC algorithm to command the shock absorber to perform shock adjustment, thereby corresponding to the changing road surface condition.

[0007] In addition to adjusting the preload level, the system may include ride “modes” that a rider can select. For example, the controller may include multiple suspension modes (e.g., sport, street, comfort, off-road, etc.) corresponding to different suspension characteristics. And the controller uses the selected mode in combination with the road surface roughness coefficient value so that the most comfortable ride experience for the rider is achieved through damping adjustment. As described above, these automatic adjustments are preferable to a manual adjustment system because they allow the rider to focus on the operation of the vehicle and the enjoyment of the ride experience.

[0008] The inventors have particularly discovered that it can be advantageous to utilize inputs other than those from the accelerometer for the automatic preload adjustment of the SDC.

[0009] FIG. 1 shows a system 100 for detecting a road surface. Instead of using information or signals provided by, for example, one or more accelerometers, the system 100 performs road surface detection based on pressure changes within a braking system. In the illustrated example, changes within the hydraulic unit of the ABS are detected. In the illustrated example, the system includes a controller 101. The controller 101 includes an electronic processor 102 (e.g., an electronic microprocessor), a memory 103, and an input / output interface 104. In some examples, the electronic processor 102 is implemented as a microprocessor having a separate memory such as the memory 103. In another example, the electronic processor 102 may be implemented as a microcontroller (having the memory 103 on the same chip). In another example, the electronic processor 102 may be implemented using a plurality of processors. Further, the electronic processor 102 may be partially or wholly implemented as, for example, an FPGA (field-programmable gate array), an ASIC (applications specific integrated circuit), etc., and thus the memory 103 may be unnecessary or may be correspondingly changed. In some examples detailed herein, the memory 103 includes a non-transitory computer-readable memory that stores instructions that the electronic processor 102 receives and executes in order to implement the methods described herein, including a road surface detection method. The memory 103 may include, for example, a program storage area and a data storage area. The program storage area and the data storage area may include a combination of different types of memories such as read-only memory and random access memory. The input / output interface 104 may include one or more input mechanisms and one or more output mechanisms (e.g., general-purpose input / output (GPIO), controller area network bus (CAN) bus interface, analog input, digital input, etc.).

[0010] In one example, system 100 includes one or more pressure sensors, and controller 101 is configured to receive a signal indicative of pressure information from the one or more pressure sensors. FIG. 1 schematically shows a plurality of pressure sensors 105. In the illustrated example, controller 101 is electrically and communicatively connected to the plurality of pressure sensors 105. In one example, the plurality of pressure sensors 105 are disposed within a motorcycle. In one example, for instance, one pressure sensor is disposed within each hydraulic shock absorber of the vehicle. In another case, one or more pressure sensors are disposed within an ABS hydraulic unit. Each of the plurality of pressure sensors 105 is configured to measure pressure and generate pressure sensor data (or a signal indicative of the pressure sensor). Controller 101 is configured to receive and interpret the pressure sensor data.

[0011] In some examples, the pressure sensor data includes the frequency response of the pressure sensor. This frequency response includes information that controller 101 interprets as information about the road surface condition or terrain type. For example, a high-frequency response may indicate a rough or uneven road surface such as a gravel road. A lower-frequency response may indicate a different type of road surface such as a flat paved road. Other road surfaces may have other frequency responses indicative of road surface conditions such as holes, off-road conditions, hillslopes, air-related events, etc. In some examples, the frequency response is interpreted directly within the ABS system and shared as an output to another vehicle system controller via CAN. Controller 101 is further configured to receive a target preload pressure level 110. In some examples, the target preload pressure level 110 is generated externally and stored in a non-transitory computer-readable storage medium such as memory 103 of controller 101. In some examples, the target preload pressure level 110 is set by the rider of the motorcycle.

[0012] The controller 101 is further electrically and communicatively connected to the hydraulic unit 115. The hydraulic unit 115 houses a preload adjuster 120. The preload adjuster 120 is configured to set the load level of the motorcycle. In some examples, the hydraulic unit 115 has a plurality of preload adjusters. For example, in one example, the hydraulic unit 115 has a preload adjuster 120 and a preload adjuster 125. A vehicle having a plurality of wheels may require a plurality of preload adjusters. For example, a motorcycle may have front fork shocks (for the front wheel) and rear shocks (for the rear wheel). In such an example, the preload adjuster 120 is configured to connect to the front shock, and the preload adjuster 125 is configured to connect to the rear shock. In some examples, the preload adjusters 120 and 125 are configured to be adjusted independently of each other by the controller 101. For example, the preload adjuster 120 may be associated with a target preload pressure level 110 that is different from the target preload pressure level of the preload adjuster 125.

[0013] The preload adjuster 120 is electrically and communicatively connected to a hydraulic pump 130. The hydraulic pump 130 is configured to be operatively coupled to a brake fluid reservoir tank. In some examples, the hydraulic pump 130 is configured to provide fluid from the brake fluid reservoir tank to the hydraulic shock and to adjust the pressure associated with the plurality of pressure sensors 105. In some examples, the preload adjuster 125 is further electrically and communicatively connected to a hydraulic pump 135. Similar to the hydraulic pump 130, the hydraulic pump 135 is configured to be operatively coupled to the brake fluid reservoir tank.

[0014] FIG. 2 shows a hydraulic system 200 for controlling a vehicle suspension system based on the detected road surface. In the illustrated example, the hydraulic system 200 includes a brake fluid storage tank 205 that holds the liquid used by the hydraulic unit 115. The hydraulic unit 115 includes a valve 210 connected to the brake fluid storage tank 205. The valve 210 is configured to open and close based on a control signal. In some examples, the controller 101 transmits a control signal to the valve 210 when a predetermined condition is satisfied. The valve 210 is connected to the preload adjuster 120 and provides liquid to the preload adjuster 120 in an open state. The preload adjuster 120 is operatively connected to the hydraulic pump 130. The hydraulic pump 130 is operatively connected to the vehicle suspension system 220. In some examples, the vehicle suspension system 220 includes a plurality of motorcycle shocks, such as front hydraulic shock absorbers and rear hydraulic shock absorbers. In some examples, the hydraulic unit 115 includes a plurality of valves, such as valves 210, 215, preload adjusters 120, 125, and hydraulic pumps 130, 135, a preload adjuster, and a hydraulic pump.

[0015] In some examples, the hydraulic system 200 adjusts the hydraulic compression threshold in one of the shocks of the vehicle suspension system 220 in response to the controller 101. For example, when the controller 101 determines that the road surface condition threshold is satisfied, the controller 101 controls the hydraulic pump 130 to control the preload pressure or hydraulic compression of the rear shock absorber. In such an example, the controller 101 may receive information indicating a road surface change, a terrain type change, etc. from the pressure sensor 105. In some examples, the hydraulic system 200 controls the extension side damping rate based on a change in the road surface condition.

[0016] Figure 3 shows a process 300 for road surface detection using a braking system. In the illustrated example, the braking system is an ABS. Process 300 is described as being executed by an electronic processor 102. However, in some examples, aspects of process 300 are executed by other devices. For example, process 300 can be executed by a processor other than electronic processor 102. In one example, process 300 begins at block 305, where the preload adjustment mode is activated. In some examples, the preload adjustment mode needs to be activated for the road surface detection system to operate. In some examples, the preload adjustment mode is automatically activated.

[0017] At block 310, a plurality of pressure sensors 105 send pressure sensor data to a controller, such as controller 101. In some examples, the plurality of pressure sensors 105 measure pressure changes in the hydraulic shock absorbers of a motorcycle. For example, when a motorcycle is traveling on a rough gravel road, the shock absorbers of the motorcycle move up and down, and the plurality of pressure sensors 105 convert this up and down movement into pressure sensor data. Then controller 101 receives the pressure sensor data.

[0018] At block 315, controller 101 obtains a target preload pressure level, such as target preload pressure level 110. Target preload pressure level 110 defines a desired preload pressure for a given riding experience. For example, a rider may prefer to vary the preload level for smooth road riding compared to rough or uneven road riding. Further, in some examples, the target preload level is different for front shock absorbers and rear shock absorbers. For example, in the case of a motorcycle with a heavy load attached to the rear saddlebag, the target preload level of the rear shock absorbers can be different from the target preload level of the front shock absorbers.

[0019] In block 320, the pressure sensor data is compared with the target preload pressure level. In some examples, the controller 101 compares the pressure sensor data obtained by the plurality of pressure sensors 105 with the target preload pressure level 110. The plurality of pressure sensors 105 detect the pressure change over time. In some examples, the controller 101 interprets this pressure change over time as a change in the characteristics of the terrain on which the motorcycle travels. For example, when the motorcycle moves from a smooth and flat road to a rough and uneven gravel road, the plurality of pressure sensors 105 generate pressure sensor data indicating both the flat road and the gravel road.

[0020] In block 325, the pressure difference between the pressure sensor data and the target preload pressure level is determined. In some examples, the controller further determines the pressure difference response. For example, when the motorcycle travels on a rough and uneven gravel road, the plurality of pressure sensors 105 generate pressure sensor data indicating the type of terrain. The controller 101 interprets the pressure sensor data to determine the pressure difference between the received pressure sensor data and the target preload pressure level 110. In some examples, the pattern of the pressure difference between the pressure sensor data and the target preload pressure indicates the type of terrain. In block 330, the road surface is determined based on the pressure difference determined in block 325. In some examples, the road surface is determined based on the pressure difference response. For example, a smooth and flat road generates a more stable pressure difference than the pressure difference generated by a rough and uneven gravel road. For example, when the motorcycle moves from a smooth flat road to a gravel road, the controller 101 determines that the pressure difference has changed from a more stable pressure difference to a more variable pressure difference. This change indicates the type of terrain.

[0021] In block 335, the preload adjuster adjusts the pressure within the hydraulic unit based on the pressure difference. For example, the controller 101 instructs the preload adjuster 120 to adjust the hydraulic pump 130 based on the pressure difference between the pressure sensor data and the target preload pressure level 110 until the pressure sensor data matches the target preload pressure level 110 or the pressure difference level reaches an acceptable threshold.

[0022] Figure 4 is a graph showing multiple responses in some aspects of the road surface detection system. Figure 4 includes a graph 400 that displays some of the control signals and response signals of some aspects of the road surface detection system. The graph 400 includes a preload mode trace 405 indicating that the preload mode is active, such as when the preload mode is activated at block 305 of process 300. In the illustrated example, the graph 400 includes a preload control activation flag trace 410 indicating the activity level of the road surface detection system. In some examples, the preload control activation flag trace 410 becomes active at a target preload pressure level of 2.5 bar or higher. In some examples, the target preload pressure level associated with the preload control activation flag trace 410 is a pressure level other than 2.5 bar.

[0023] Graph 400 includes a pressure leakage detection trace 415 that indicates an abnormal pressure drop within a hydraulic system. For example, in process 300, when it is determined that the pressure difference is -2.5 bar or less, the pressure leakage detection trace 415 becomes valid. In some examples, the determined pressure difference is a pressure level other than -2.5 bar. In some examples, the pressure leakage detection trace 415 indicates when a pressure change occurred within the hydraulic unit 115 when there is no difference between the target preload pressure level 110 and the pressure sensor data generated by the plurality of pressure sensors 105. For example, a sudden change in the pressure difference or pressure difference response may indicate a change in road surface conditions, such as a change from a smooth road to a rough gravel road. In this case, the pressure leakage detection trace 415 does not become valid. In another case, a gradual change in the pressure difference may indicate a leakage within the hydraulic system rather than a change in road surface conditions. In this case, the pressure leakage detection trace 415 becomes valid.

[0024] Graph 400 includes a target preload pressure level trace 420. In some examples, the target preload pressure level trace 420 is associated with the target preload pressure level 110. In some examples, there are a plurality of target preload pressure level traces 420 associated with a plurality of target preload pressure levels. For example, the target preload pressure level for the front hydraulic shock absorber has a first target preload pressure level trace, and the target preload pressure level for the rear hydraulic shock absorber has a second target preload pressure level trace. In some examples, the first target preload pressure level and the second target preload pressure level are the same. In some examples, the first target preload pressure level and the second target preload pressure level are different.

[0025] Graph 400 includes a measured pressure level trace 425 (also referred to as the actual pressure). In some examples, the measured pressure level trace 425 is associated with pressure level data provided by a plurality of pressure sensors 105. The measured pressure level trace 425 indicates pressure level data provided by at least one of the plurality of pressure sensors. In some examples, the measured pressure level trace indicates pressure level data from a plurality of sensors within the plurality of pressure sensors. For example, a front hydraulic shock absorber has a first measured pressure level trace associated with at least one of the plurality of pressure sensors of the front hydraulic shock absorber, and a rear hydraulic shock absorber has a second measured pressure level trace associated with at least one of the plurality of pressure sensors of the rear hydraulic shock absorber.

[0026] Graph 400 includes a pressure difference trace 430 (also referred to as delta P). The pressure difference trace indicates and is associated with a difference between a target pressure level, such as a pressure difference calculated at block 325 of process 300, and pressure sensor data. In some examples, the pressure difference trace is the difference between a target preload pressure level trace 420 and the measured pressure level trace 425. For example, during operation of the hydraulic unit 115, the pressure within the hydraulic unit changes. The pressure difference trace 430 indicates the difference between the target preload pressure level and the pressure sensor data, and this difference indicates the road surface condition and / or terrain type. In some examples, the pressure difference trace 430 indicates a pressure leakage condition.

[0027] Graph 400 further includes a target pump motor speed trace 435. The target pump motor speed trace 435 indicates a desired motor pump speed, such as a desired pump speed for hydraulic pumps 130 and 135. For example, at block 335 of process 300, the controller 101 adjusts a preload adjuster, such as preload adjuster 120, to change the pressure within the hydraulic unit 115. In this case, the target pump motor speed trace 435 indicates the desired pump speed to achieve the adjustment within the hydraulic unit.

[0028] Figure 5 is Table 500 showing the modes of the road surface detection system using the brake system. Table 500 includes a plurality of operating modes, a preload control mode, the build-up speed of the pump motor, and a rebuild target. Table 500 includes Mode 0 indicating that the system is off. In Mode 0, the preload control mode is not activated and the corresponding pump motor speed is none. In some examples, Mode 0 is associated with the preload mode trace 405. Table 500 includes Mode 1 in which the preload control mode is activated. In this case, the pump motor speed is set normally. In some examples, the normal pump motor speed is about 1500 revolutions per minute (RPM). In some examples, the normal pump motor speed is an RPM value other than 1500 RPM. In Mode 1, the rebuild target is on. In some examples, the rebuild target is -2.5 bar. Table 500 includes Mode 2 in which the preload control mode is activated. In this case, the pump motor speed exists, the pump motor speed is set normally, and the rebuild target is off. In Mode 2, the normal pump motor speed is 1500 RPM. Table 500 includes Mode 3 in which the preload control system is activated. In Mode 3, the pump motor speed is set high. In some examples, the high pump motor speed is 3000 RPM. In some examples, the high pump motor speed is an RPM value other than 3000 RPM. In Mode 3, the rebuild target is on. In some examples, the rebuild target is set to -2.5 bar.

[0029] Figure 6 shows a hydraulic system 600 for road surface detection using a braking system according to some embodiments. The hydraulic system 600 is similar to the hydraulic system 200 but is shown in more detail. Figure 6 shows the hydraulic system 600 in mode 0 with the preload mode not activated. The hydraulic system 600 includes a hydraulic unit 601. The hydraulic system 600 further includes a first valve 605 in a normally open state. The first valve 605 is operatively connected to a second valve 610. The second valve 610 is in a normally closed state. When the first valve 605 is open and the second valve 610 is closed, the liquid from the brake fluid storage tank 615 can flow through the first valve 605. In some examples, the brake fluid storage tank 615 is similar to the brake fluid storage tank 205. The liquid flow from the brake fluid storage tank 615, when flowing through the first valve 605, passes through a third valve 620, which is in a normally open state. The liquid then passes through a preload adjuster such as the preload adjuster 120 after being homogenized and at a low level.

[0030] In some examples, the hydraulic system 600 includes additional valves and pumps. The hydraulic system 600 further includes a pressure sensor 625. For example, the pressure sensor 625 measures the pressure within a vehicle suspension system, such as a rear shock absorber. In some examples, the pressure sensor 625 functions similarly to the pressure sensor 105. In some examples, the same hydraulic unit used for vehicle hold control functions is used for road surface condition detection. For example, according to some of the above examples, the hydraulic system 200 is coupled to the hydraulic unit 115 and the controller 101, and the controller 101 is configured to receive pressure data from the pressure sensor 105. Similarly, the hydraulic system 600 includes a hydraulic unit 601 and a pressure sensor 625, and is configured to be coupled to a controller such as the controller 101. In some examples, the pressure sensor 625 provides pressure sensor data indicating road surface conditions, terrain types, slope inclinations, air-related events, etc. to the controller. In this example, the pressure sensor 625 is the same as that used in the vehicle hold control function.

[0031] Figure 7 shows the hydraulic system 600 in a second state or mode. Figure 7, similar to Figure 6, shows the first valve 605, the second valve 610, the third valve 620, and the brake fluid storage tank 615. In this case shown in Figure 7, the hydraulic system is in mode 1 where the preload mode is activated. The first valve 605 transitions from an open state to a closed state, and the liquid flow from the brake fluid storage tank 615 is directed towards the second valve 610. The second valve 610 transitions from a closed state to an open state, allowing the liquid to pass towards the hydraulic pump 630. In some examples, the hydraulic pump 630 is similar to the hydraulic pumps 130, 135. The hydraulic pump 630 actively pumps the liquid from the brake fluid storage tank 615 through the third valve 620, thereby increasing the pressure within the hydraulic system 600.

[0032] In some examples, in response to a determination of a pressure differential, the hydraulic pump actively pumps fluid into and out of a vehicle suspension system 220 of the hydraulic system 200. The hydraulic system 600 includes a pressure sensor 625 configured to generate pressure sensor data. This pressure sensor data is used by the controller 101 to determine a pressure differential or a pressure differential response. For example, when the controller 101 determines a pressure differential, such as at block 325 of process 300, the controller 101 adjusts the hydraulic system 600 to close the first valve 605, adjusts the hydraulic system 600 to open the second valve 610, and controls the hydraulic pump 630 to adjust the pressure within a vehicle suspension system, such as a front or rear hydraulic shock absorber.

[0033] Thus, various implementations of the systems and methods described herein provide road surface determination techniques that use, among other things, a brake system pressure sensor. Other features and advantages of the present invention are set forth in the following claims.

[0034] In the foregoing specification, specific examples have been described. It will, however, be understood by those skilled in the art that various modifications and changes may be made without departing from the scope of the invention as set forth in the following claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a limiting sense, and it is intended that all such modifications be included within the scope of the present teachings.

[0035] None of the advantages, effects, problem-solving methods, further advantages, effects, or problem-solving methods that may be realized or made more prominent (one or more) elements should be construed as important, essential, or indispensable features or elements in any or all of the claims. The present invention is defined only by the appended claims, including any amendments made during the pendency of this application, and all equivalents of the scope of such claims as they existed at the time of filing.

[0036] Furthermore, terms used in this document to indicate relationships such as first and second, upper and lower, etc. may be used only to distinguish one entity or operation from another, and in so doing, do not necessarily require or imply any actual such relationship or order between those entities or operations. The terms "comprises", "comprising", "has", "having", "includes", "including", "contains", "containing", or any other form thereof, are intended to cover non-exclusive inclusion. That is, a process, method, article, or apparatus that comprises, has, includes, or contains the listed elements does not include only those elements, but may include elements not explicitly listed or other elements specific to such a process, method, article, or apparatus. Elements following "comprises", "has", "includes", or "contains" do not preclude the presence of additional, similar elements in the process, method, article, or apparatus that comprises, has, includes, or contains the said element, without imposing further restrictions. The terms "a" and "an" are defined as one or more, unless otherwise specified in this document. The terms "substantially", "essentially", "approximately", "about", or any other form thereof, are defined as being near, as understood by those skilled in the art, and in a non-limiting example, within 10%, in another example within 5%, in another example within 1%, and in another example within 0.5%. The term "coupled" as used in this document is defined as being connected, not necessarily directly and not necessarily mechanically. A device or structure "configured" in a certain way is at least configured in that way, but may also be configured in ways not listed.

Description of Reference Numerals

[0037] 100 System 101 Controller 102 Electronic Processor 103 Memory 104 Input / Output Interface 105,625 Pressure Sensor 115,601 Hydraulic Unit 120,125 Preload Adjuster 130,135,630 Hydraulic Pump 200,600 Hydraulic System 205,615 Brake Fluid Storage Tank 210,215 Valve 605 First Valve 610 Second Valve 620 Third Valve

Claims

1. A hydraulic unit of an antilock braking system having a preload adjuster, A plurality of pressure sensors disposed within a vehicle and configured to generate pressure sensor data respectively, A controller, comprising a road surface detection system, The controller, Receives the pressure sensor data from the plurality of pressure sensors, Determines a target preload pressure level, By comparing the pressure sensor data with the target preload pressure level, calculates a pressure difference between the pressure sensor data and the target preload pressure level, Determines a road surface based on the calculated pressure difference, A system configured to adjust the preload adjuster to change the pressure within the hydraulic unit based on the road surface.

2. The system according to claim 1, wherein the hydraulic unit further comprises a first preload adjuster and a second preload adjuster.

3. The controller is further configured to receive a preload mode control signal, and if the preload mode control signal is invalid, the controller ignores the determined road surface type, according to the system of claim 1.

4. The determined target pressure is based on a preset vehicle load level, according to the system of claim 1.

5. The determination of the road surface is based on the calculated pressure difference and the rate of change of the pressure sensor data, according to the system of claim 1.

6. The controller is further configured to control a pump to adjust the hydraulic compression of a shock absorber based on the calculated pressure difference, according to the system of claim 1.

7. The controller is further configured to control a pump to adjust the extension side damping rate of a shock absorber based on the calculated pressure difference, according to the system of claim 1.

8. The controller is further configured to adjust the preload adjuster to change the pressure within the hydraulic unit based on a mode indicated by a rider, according to the system of claim 1.

9. The controller is further configured to, By comparing the pressure sensor data with the target preload pressure level, calculates a pressure difference response, Determines a road surface based on the calculated pressure difference response, The system according to claim 1, configured to adjust the preload adjuster so as to change the pressure in the hydraulic unit based on the road surface.

10. The controller is further configured to adjust the first preload adjuster based on the calculated road surface and a first target preload pressure level, and to adjust the second preload adjuster based on the calculated road surface and a second target preload pressure level, wherein the first target preload pressure level is different from the second target preload pressure level. The system according to claim 2.

11. The preload adjuster has a hydraulic pump configured to change the hydraulic pressure in the hydraulic unit based on the road surface. The hydraulic pump is further configured to change the hydraulic pressure in the hydraulic unit with the rate of change of the pressure sensor data. The system according to claim 5.

12. A road surface detection method, comprising: Receiving pressure sensor data from each of a plurality of pressure sensors; Determining a target preload pressure level; Comparing, by a controller, the pressure sensor data with the target preload pressure level; Determining, by the controller, a pressure difference between the pressure sensor data and the target preload pressure level; Determining, by the controller, a road surface based on the pressure difference; Adjusting, by the controller, the preload adjuster so as to change the pressure in the hydraulic unit based on the road surface.

13. The method according to claim 12, further comprising adjusting, by the controller, a pump so as to adjust the hydraulic compression pressure of a shock absorber based on the calculated pressure difference.

14. The method according to claim 12, further comprising adjusting, by the controller, a pump so as to adjust the extension side damping rate of a shock absorber based on the calculated pressure difference.

15. Adjusting, by the controller, the first preload adjuster based on the calculated road surface and a first target preload pressure level; Adjusting, by the controller, the second preload adjuster based on the calculated road surface and a second target preload pressure level. The method according to claim 12, wherein the first target preload pressure level is different from the second target preload pressure level. **Claim 16** further comprising: adjusting a hydraulic pump by the controller to change the hydraulic pressure in the hydraulic unit based on the road surface; further comprising: adjusting the hydraulic pump by the controller to change the hydraulic pressure in the hydraulic unit with a rate of change of the pressure sensor data, the method according to claim 12. **Claim 17** further comprising: determining a road surface by the controller based on the pressure difference and a frequency response of the plurality of pressure sensors, the method according to claim 12. **Claim 18** determining, by the controller, a pressure difference response between the pressure sensor data and the target preload pressure level; determining, by the controller, a road surface based on the pressure difference response; further comprising: adjusting the preload adjuster by the controller to change the pressure in the hydraulic unit based on the road surface, the method according to claim 12.

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