A vehicle height dynamic adjustment control system and method for semi-active suspension

Abstract

The present invention discloses a vehicle height dynamic adjustment control system and method for a semi-active suspension, the control system includes an air pump motor, a relay switch group, an energy storage battery group, a controller, four air bags, four connecting valves and four charging / discharging valves; the four air bags are respectively arranged at the front left, front right, rear left and rear right of the vehicle, and the air pump motor realizes the inflation and deflation of the four air bags through the four charging / discharging valves; the relay switch group is arranged on the pipeline connecting the air pump motor and the air bag, and works in coordination with the charging / discharging valve; the four connecting valves are respectively arranged on the connecting pipeline between the two air bags on the same side and coaxially; the energy storage battery group is used to supply energy to the air pump motor; the controller is used to control the opening and closing of the four connecting valves and the four charging / discharging valves. The present invention can dynamically adjust the vehicle height to meet the driving conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle suspension control, and in particular to a vehicle height dynamic adjustment control system and method for a semi-active suspension. Background Art

[0002] In the actual driving process, the vehicle control system needs to make a comprehensive judgment based on the changes in vehicle speed and road conditions, as well as the driver's performance requirements and the dynamic update of the vehicle system status, so as to dynamically adjust the vehicle height under different driving conditions according to the specific working conditions, so as to achieve a smooth change in vehicle posture and comprehensive optimization of system performance according to control requirements. Among them, the vehicle height adjustment process involves the realization of functions and processes such as static vehicle start-up, smooth driving, high-altitude driving, off-road driving, and static side kneeling. At different stages, the specific adjustment target height of the vehicle is also different. Therefore, the control system needs to adjust the control target in real time according to the performance changes to ensure system safety and functional performance requirements.

[0003] However, the driving environment of vehicles is often different. In different environments, the performance requirements of vehicles are also different, and different performance requirements need to be met under different working conditions. At the same time, different performance requirements are often not single, and the satisfaction of a single performance will lead to the deterioration of the overall performance of the vehicle.

[0004] When traveling at high speed on the highway, the vehicle needs to lower the height of the vehicle body to reduce wind resistance, thereby improving grip performance and energy utilization efficiency, so as to ensure fuel economy and handling stability. When the vehicle is traveling in an off-road environment, because the road environment is relatively harsh and complex at this time, the vehicle needs to increase the height of the vehicle body to improve the off-road passing performance of the vehicle, and at the same time, the height must be adjusted to ensure the driver's riding comfort and the integrity of the cargo. When the vehicle turns, the vehicle needs to adjust the suspension stiffness to achieve the vehicle's anti-roll performance, and at the same time, the suspension stiffness needs to be adjusted to keep the wheels in contact with the ground, so as to ensure driving safety and handling stability during driving. Different performance requirements determine that the traditional passive suspension with fixed parameters cannot meet the actual performance requirements.

[0005] As a semi-active suspension system, the air suspension system can dynamically adjust the height of the vehicle by inflating / deflating the airbag. Figure 1 As shown, since the stiffness of the air bag is nonlinear, in the actual adjustment process, the stiffness of the vehicle suspension can be adjusted by briefly inflating / deflating the air bag, so as to quickly reach the ideal stiffness value and meet the actual performance requirements.

[0006] The traditional semi-active suspension height adjustment system divides the height adjustment system into different fixed gears according to the actual working conditions, which results in that the vehicle can only adjust the fixed height to meet specific functional requirements under the fixed gear. Although the semi-active suspension system can adjust the height at this time, it considers fewer external environmental factors. At this time, the system is closer to a passive suspension system with fixed parameters, which cannot meet the performance requirements of the actual vehicle. Summary of the invention

[0007] In view of this, the present invention provides a vehicle height dynamic adjustment control system and method for a semi-active suspension, which can dynamically adjust the vehicle height according to driving conditions.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A vehicle height dynamic adjustment control system for a semi-active suspension, comprising an air pump motor, a relay switch group, an energy supply battery group, a controller, four air bags, four connecting valves and four charging / discharging valves;

[0010] The four air bags are respectively arranged at the front left, front right, rear left and rear right of the vehicle, and the air pump motor realizes inflation and deflation of the four air bags through four charging / deflation valves; the relay switch group is arranged on the pipeline connecting the air pump motor and the air bags, and works with the charging / deflation valves; the four connecting valves are respectively arranged on the connecting pipelines between the front left air bag and the front right air bag, the rear left air bag and the rear right air bag, the front left air bag and the rear left air bag, and the front right air bag and the rear right air bag; the energy supply battery pack is used to supply energy to the air pump motor; the controller is used to control the opening and closing of the four connecting valves and the four charging / deflation valves.

[0011] Furthermore, when the height of the vehicle body rises, the air bags on both sides of the rear axle are inflated first, and the air bags on both sides of the front axle are inflated later; when the height of the vehicle body drops, the air bags on both sides of the front axle are deflated first, and the air bags on both sides of the rear axle are deflated later.

[0012] A method for dynamically adjusting the height of a semi-active suspension vehicle is provided, which adopts the above-mentioned vehicle height dynamic adjustment control system. The control method steps are as follows:

[0013] Step 1: When the vehicle speed v=0 km / h and the ignition device is turned off, the vehicle is stationary and the vehicle body does not move at this time; when the vehicle speed v=0 km / h and the ignition device is closed, the semi-active suspension is tested for vehicle system faults online. If a fault exists, troubleshooting is performed until the fault is cleared; if no fault is shown, the vehicle body height adjustment is performed;

[0014] Step 2: Open the connecting valves between the front left air bag and the front right air bag, and between the rear left air bag and the rear right air bag, so that the pressure of the air bags on both sides of the same axis is equal; inflate the four air bags, so that the rear axle of the vehicle body rises H r 、The front axle of the vehicle body rises H f ; After inflation is completed, open the connecting valve again to make the pressure of the air bags on both sides of the coaxial axis equal;

[0015]

[0016] Where A is the cross-sectional area of ​​the membrane air bag; n is the gas index, which ranges from [1, 1.40]; V0 is the initial volume of the air bag without compression or stretching; h if and h ir are the height change values ​​of the distance between the front and rear axles of the current vehicle in the initial state; H Pf and H Pr are the heights of the front and rear axles of the current vehicle respectively; P if and P ir are the internal pressures corresponding to the airbags on both sides of the front and rear axles of the current suspension; P If and P Ir are the internal pressure values ​​of the front and rear axle airbags after the semi-active suspension is highly stabilized; P I ' f and P I ' r They are the correction values ​​of the internal pressure of the front and rear axle airbags respectively;

[0017] Step 3: When the vehicle speed v∈(0km / h,20km / h], the vehicle height is increased by H in turn based on step 2. dr and H df , and the calculation formulas are:

[0018]

[0019] Where, χ is the height adjustment coefficient;

[0020] Step 4: When the vehicle speed v∈(20km / h, 60km / h], if the current road grade is not worse than the standard D-grade road, the vehicle height is raised by 20-30mm respectively on the basis of step 3, and the pressure of the coaxial airbags on both sides is self-balanced, and the vehicle enters the normal driving stage;

[0021] If the current road grade is worse than the standard D-grade road, the vehicle height is raised by 45-55mm on the basis of step 3, and the pressure of the coaxial airbags is adjusted to self-balance. At this time, the vehicle enters the off-road mode.

[0022] Step 5: When the vehicle speed v∈(60km / h,120km / h], and the current road grade is not worse than the standard C-grade road, if the vehicle height is in the normal driving stage of step 4, it is lowered by 15-25mm respectively; if the vehicle height is in the off-road mode driving stage of step 4, it is lowered by 65-75mm respectively, and the pressure of the coaxial airbags on both sides is self-balanced, and the vehicle enters the normal high-speed driving stage;

[0023] When the vehicle speed v∈(60km / h,120km / h], and the current road grade is worse than the standard C-grade road, if the vehicle height is in the normal driving stage of step 4, it will be increased by 45-55mm respectively; if the vehicle height is in the off-road mode driving stage of step 4, the vehicle height remains unchanged, and the vehicle height is still in the off-road mode driving stage;

[0024] Step 6: When the vehicle speed v>120km / h, and the current road grade is not worse than the standard B-grade road, if the vehicle body height is in the normal high-speed driving stage of step 5, it is lowered by 5-15mm respectively; if the vehicle body height is in the off-road mode driving stage of step 5, it is lowered by 75-87mm respectively, and the pressure of the coaxial airbags on both sides is self-balanced, and the vehicle enters the extreme high-speed driving stage;

[0025] When the vehicle speed v>120km / h and the current road grade is worse than the standard Class B road, if the vehicle body height is in the normal high-speed driving stage of step five, it will be increased by 25-35mm respectively, and the vehicle will enter the safety holding stage; if the vehicle body height is in the off-road mode driving stage of step five, the vehicle body height remains unchanged, and the vehicle height is still in the off-road mode driving stage.

[0026] Furthermore, when the height of the vehicle body rises, the air bags on both sides of the rear axle are inflated first, and the air bags on both sides of the front axle are inflated later; when the height of the vehicle body drops, the air bags on both sides of the front axle are deflated first, and the air bags on both sides of the rear axle are deflated later.

[0027] Furthermore, P I ' f and P I ' r They are:

[0028]

[0029] In the formula, γ f and γ r are the gas delay compensation coefficients of the front and rear axles of the vehicle respectively; ΔP is the rate of change of gas pressure inside the airbag; h f and h r The distances between the airbag pressure sensor installation positions on the front and rear axles and the middle of the airbag are measured from the airbag entrance and the middle position.f and h r is positive, and h is measured from the bottom and middle of the airbag f and h r is negative; q f and q r are the mass flow rates of the airbags at the front and rear axles respectively, and ρ is the gas density during the inflation / deflation process.

[0030] Furthermore, the calculation formula of ρ is as follows:

[0031]

[0032] t e is the ambient temperature.

[0033] Further,

[0034] n0 is the reference spatial frequency, G q (n0) is the power spectrum density of the road surface at frequency n0.

[0035] Furthermore, when the vehicle speed v = 0 km / h and the ignition device is closed, the driver manually selects the side kneeling function by pressing a button; when the side kneeling function is turned on, the connecting valves between the air bags on the left and right sides of the front and rear axles of the vehicle remain closed;

[0036] Kneeling on the left side: The front and rear air bags on the left side of the vehicle open their deflation valves first, and the height of the left side of the vehicle drops by H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the left side are closed, and then the inflation valves of the front and rear air bags on the right side of the vehicle are opened, and the height of the right side of the vehicle body rises by H SK_r ;

[0037] Kneeling on the right side: The front and rear air bags on the right side of the vehicle open their deflation valves first, and the height of the right side of the vehicle drops by H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the right side are closed, and then the inflation valves of the front and rear air bags on the left side of the vehicle are opened, and the height of the left side of the vehicle rises by H. SK_r ;

[0038] After the inflation valve is closed, the front and rear air bags on the same side of the vehicle body are opened respectively by opening the connecting valve between them, so as to achieve self-balancing of the pressure of the front and rear air bags on the same side.

[0039] Furthermore, if the side kneeling function is turned on on a horizontal ground, according to the vehicle wheelbase B and the vehicle body limit roll angle φ L , then H SK_l =H SK_r =0.45Bsinφ L ;

[0040] When the vehicle is at an inclination angle φ R On the road, if only the left kneeling function is available, the height of the left side of the vehicle will drop by a value of H SK_l and the right side height rise value H SK_r They are:

[0041]

[0042] If only the right side kneeling function exists, the height increase value of the left side of the vehicle body is H SK_l And the height drop value H of the right side of the vehicle SK_r They are:

[0043]

[0044] Beneficial effects:

[0045] 1. The present invention is based on a membrane air bag system. According to the vehicle speed, road condition changes and system status information, as well as the performance requirements of the driver and the control system, the four semi-active suspensions of the vehicle are adjusted in real time and dynamically, thereby realizing changes in the vehicle body height and posture under dynamic driving conditions. This can improve the vehicle's adaptability to changing environments and the system's superior comprehensive driving performance and experience.

[0046] 2. The present invention takes into account the influence of factors such as driving speed and road grade, and adapts to different system performance requirements according to different working conditions, thereby realizing dynamic adjustment of the vehicle body height to ensure the driver's excellent driving experience and safety performance.

[0047] 3. In order to ensure that the driver's field of vision and the headlights are always directed toward the ground ahead, the present invention follows the principle that the airbags on both sides of the rear axle are inflated first and the airbags on both sides of the front axle are inflated later when the vehicle body height rises; and follows the principle that the airbags on both sides of the front axle are deflated first and the airbags on both sides of the rear axle are deflated later when the vehicle body height drops.

[0048] 4. The present invention takes into account that the installation position of the air bag pressure sensor will affect the detection, calculation and adjustment of the actual air bag balance pressure. Therefore, the correction value of the air bag internal pressure value should be dynamically calculated according to the sensor installation position, which is more accurate.

[0049] 5. The present invention further realizes the static side kneeling function of the vehicle by adjusting the height of the suspension on the same side of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is the air bag stiffness characteristic curve.

[0051] Figure 2 It is a schematic diagram of the structure of the semi-active suspension of the present invention.

[0052] Figure 3Schematic diagram of dynamic height adjustment during vehicle driving.

[0053] Figure 4 This is a structural diagram of a membrane air bag.

[0054] Figure 5 The vehicle is stationary on a slope. Figure 5 (a) Figure 5 (b) The road conditions where only the left kneeling function and the right kneeling function exist respectively. DETAILED DESCRIPTION

[0055] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0056] The present invention provides a vehicle height dynamic adjustment control system for a semi-active suspension, such as Figure 2 As shown, it includes an air pump motor, a relay switch group, an energy supply battery group, a controller, four air bags, four connecting valves and four charging / discharging valves.

[0057] The four air bags are respectively arranged at the front left, front right, rear left and rear right of the vehicle, and the air pump motor realizes inflation and deflation of the four air bags through four charging / deflation valves; the relay switch group is arranged on the pipeline connecting the air pump motor and the air bags, and works with the charging / deflation valves; the four connecting valves are respectively arranged on the connecting pipelines between the front left air bag and the front right air bag, the rear left air bag and the rear right air bag, the front left air bag and the rear left air bag, and the front right air bag and the rear right air bag; the energy supply battery pack is used to supply energy to the air pump motor; the controller is used to control the opening and closing of the four connecting valves and the four charging / deflation valves.

[0058] When the air pump motor, relay switch group and charging / deflation valve work together, gas is filled into the airbag through the air pipe circuit by the air pump motor, the volume of the airbag expands, its internal pressure increases, and the height of the vehicle body increases synchronously; when the height of the vehicle body needs to be lowered, the passage between the air pump motor and the relay switch group is disconnected, and the gas in the airbag is discharged into the atmosphere through the air pipe circuit, charging / deflation valve and relay switch group. At this time, the volume of the airbag shrinks, its internal pressure decreases, and the height of the vehicle body is thereby lowered synchronously.

[0059] By opening and closing different connecting valves, different airbags can be connected to each other, so as to achieve self-balancing of pressure between different airbags, thereby ensuring the balance of the air spring system and the stability of the vehicle body posture during static and dynamic driving.

[0060] The opening and closing of different valves are controlled by current signals. When the controller outputs the rated current value I A When the current is lower than the rated value I AWhen , the valve port is closed.

[0061] On this basis, the dynamic adjustment process of the vehicle's height can be achieved by adjusting the changes in the vehicle's height according to the real-time changes in the vehicle system status, vehicle speed, and road driving conditions, and according to the control requirements of the driver and system safety. It involves the realization of functions and processes such as static starting, smooth driving, high-speed driving, off-road driving, and static side kneeling. Before performing the dynamic adjustment process of the vehicle's height, the adjustment control system first needs to perform a self-check on the vehicle system. After completion, it needs to calculate the vehicle's rising height during the normal starting phase based on the actual ambient temperature and sensor installation position. On this basis, the required rising height for the normal driving phase of the vehicle is further calculated according to different road conditions. After the vehicle enters the normal driving phase, the driver and the controller need to dynamically adjust the actual height changes of the vehicle in real time according to changes in the actual vehicle speed, road conditions, and vehicle status information. The specific dynamic adjustment process is as follows: Figure 3 shown.

[0062] The steps of dynamic adjustment control method are as follows:

[0063] Step 1: When the vehicle speed v = 0 km / h and the ignition device (key ON switch) is turned off, the vehicle is stationary. At this time, the controller does not function and the vehicle body does not move.

[0064] When the vehicle speed v=0km / h and the key ON switch is closed, the semi-active suspension system is subjected to online detection of vehicle system faults. If there is a fault in the system, troubleshooting is required until the fault is cleared; if the system does not show a fault, the next step of vehicle height adjustment is started.

[0065] Step 2: According to the test results of step 1, if the vehicle system has no fault display, adjust the vehicle height. To ensure that the driver's field of vision and the lights are always pointing toward the ground in front, when the vehicle height rises, the airbags on both sides of the rear axle are inflated first, and the airbags on both sides of the front axle are inflated later; when the vehicle height drops, the airbags on both sides of the front axle are deflated first, and the airbags on both sides of the rear axle are deflated later.

[0066] At this time, the airbags on the left and right sides of the front and rear axles of the vehicle are connected through the connecting valves on the front and rear axles for 2s, and the connecting valves are closed after 2s. At this time, the airbag pressure on the left and right sides of the front axle is P fl =P fr =P if , the airbag pressure P on the left and right sides of the rear axle rl =P rr =P irBased on step 1 and step 2, the air pump motor, rear left and rear right inflation valves are opened, and the airbags on the left and right sides of the rear axle of the vehicle body are inflated first to a height H r After the two inflation valves on the rear axle are closed, the inflation valves corresponding to the airbags on the left and right sides of the front axle are opened, the airbags begin to inflate, and the front axle of the vehicle body rises H f After the two inflation valves on the front axle are closed, the airbags on the left and right sides of the front and rear axles open their respective connecting valves to achieve self-balancing of the internal pressure of the airbags on both sides of the same axis. The connecting valves on the left and right sides are opened for 3 seconds and then closed. After completion, the vehicle enters the normal start-up stage.

[0067] Among them, the heights that the front and rear axles of the vehicle need to rise are H f and H r , the corresponding calculation formulas are:

[0068]

[0069] Where A is the cross-sectional area of ​​the membrane air bag; n is the gas index, which ranges from [1, 1.40]; V0 is the initial volume of the air bag without compression or stretching; h if and h ir are the height change values ​​of the distance between the front and rear axles of the current vehicle in the initial state; H Pf and H Pr are the heights of the front and rear axles of the current vehicle respectively; P if and P ir are the internal pressures corresponding to the airbags on both sides of the front and rear axles of the current suspension; P If and P Ir are the internal pressure values ​​of the front and rear axle airbags after the semi-active suspension is highly stabilized; P I ' f and P I ' r are the correction values ​​of the internal pressure of the front and rear axle airbags, which are equal to P If and P Ir Functions related to value size.

[0070] Since the installation position of the air bag pressure sensor will affect the detection, calculation and adjustment of the actual air bag balance pressure, the corresponding size of its dynamic calculation process should be dynamically calculated according to the installation position of the sensor. If and P Ir Correction is made, then the correction value P I ' f and P I ' r They are:

[0071]

[0072] In the formula, γ f and γ r are the gas delay compensation coefficients of the front and rear axles of the vehicle respectively; ΔP is the rate of change of gas pressure inside the airbag; h f and h r They are the distances between the installation positions of the airbag pressure sensors on the front and rear axles and the middle position of the airbag, respectively. Figure 4 As shown, h is measured from the airbag entrance and the middle position. f and h r is positive, and h is measured from the bottom and middle of the airbag f and h r is negative; q f and q r are the mass flow rates of the airbags at the front and rear axles respectively, and ρ is the gas density during the inflation / deflation process.

[0073] ρ and ambient temperature t e The calculation formula is as follows:

[0074]

[0075] Step 3: When the vehicle speed v∈(0km / h,20km / h], the vehicle height is raised in the order of the rear axle and the front axle based on the step 2. dr and H df , and the calculation formulas are:

[0076]

[0077] Where χ is the height adjustment coefficient, which is related to the road grade, that is, the road roughness coefficient G q (n0) is related, and its value range is as follows:

[0078]

[0079] n0 is the reference spatial frequency; G q (n0) is the power spectrum density of the road surface at the frequency n0, that is, the road roughness coefficient.

[0080] After the height of the front and rear axles of the vehicle is raised, the vehicle enters the normal speed transition stage.

[0081] Step 4: When the vehicle speed v∈(20km / h,60km / h], if the current road grade is not worse than the standard D-grade road, that is, the road roughness coefficient G q(n0)≤1024, the vehicle height is further increased by 20-30mm in the order of the rear axle and the front axle based on step 3, and is 25mm in this embodiment. After the airbag inflation and the pressure self-balancing adjustment process of the coaxial airbags are completed, the vehicle enters the normal driving stage.

[0082] If the current road grade is worse than the standard D-grade road, that is, the road roughness coefficient G q (n0)>1024, to ensure the vehicle's passability, the vehicle height is further increased by 45-55mm in the order of the rear axle and the front axle based on step 3, and 50mm in this embodiment. After the airbag inflation and the pressure self-balancing adjustment process of the coaxial airbags are completed, the vehicle enters the off-road mode driving stage.

[0083] Step 5: When the vehicle speed v∈(60km / h,120km / h], and the current road grade is not worse than the standard C-grade road, that is, the road roughness coefficient G q (n0)≤256, in order to ensure the fuel economy and road adhesion performance of the vehicle, if the vehicle height is in the normal driving stage described in step 4, then the front axle and the rear axle are lowered by 15-25mm in sequence, which is 20mm in this embodiment; if the vehicle height is in the off-road mode driving stage described in step 4, then the front axle and the rear axle are lowered by 65-75mm in sequence, which is 70mm in this embodiment. After the airbag deflation and the coaxial two-side inflated airbag pressure self-balancing adjustment process are completed, the vehicle enters the normal high-speed driving stage.

[0084] When the vehicle speed v∈(60km / h,120km / h], and the current road grade is worse than the standard C-grade road, that is, the road roughness coefficient G q (n0)>256. In order to ensure the good passability of the vehicle in adverse environments, if the vehicle body height is in the normal driving stage described in step four, the height is raised by 45-55mm in the order of the rear axle and the front axle, and is 50mm in this embodiment; if the vehicle body height is in the off-road mode driving stage described in step four, the vehicle body height remains unchanged. At this time, the vehicle height is still in the off-road mode driving stage.

[0085] Step 6: When the vehicle speed v>120km / h, and the current road grade is not worse than the standard B-grade road, that is, the road roughness coefficient G q(n0)≤64, in order to ensure the handling stability and driving safety of the ultra-high-speed vehicle, if the vehicle height is in the normal high-speed driving stage described in step 5, the front axle and the rear axle are lowered by 5-15mm in sequence, and 10mm in this embodiment; if the vehicle height is in the off-road mode driving stage described in step 5, the front axle and the rear axle are lowered by 75-87mm in sequence, and 80mm in this embodiment. After the airbag deflation and the coaxial two-side inflated airbag pressure self-balancing adjustment process are completed, the vehicle enters the extreme high-speed driving stage.

[0086] When the vehicle speed v>120km / h, and the current road grade is worse than the standard B-grade road, that is, the road roughness coefficient G q (n0)>64. In order to ensure the safety of the vehicle and the driving experience, if the vehicle body height is in the normal high-speed driving stage described in step five, the height is raised by 25-35 mm in the order of the rear axle and the front axle, and is 30 mm in this embodiment. At this time, the vehicle enters the safety holding stage; if the vehicle body height is in the off-road mode driving stage described in step five, the vehicle body height remains unchanged, and the vehicle height is still in the off-road mode driving stage.

[0087] In addition, by adjusting the height of the suspension on the same side of the vehicle, the static side kneeling function of the vehicle is further realized.

[0088] When the vehicle speed v = 0km / h and the ignition device (key ON switch) is closed, the driver manually selects the side kneeling function by pressing a button; the vehicle's side kneeling function includes two functions: left kneeling and right kneeling. When the side kneeling function is turned on, the connecting valve between the air bags on the left and right sides of the front and rear axles of the vehicle remains closed. The specific control method is as follows:

[0089] Kneeling on the left side: The front and rear air bags on the left side of the vehicle open their deflation valves first, and the height of the left side of the vehicle drops by H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the left side are closed, and then the inflation valves of the front and rear air bags on the right side of the vehicle are opened, and the height of the right side of the vehicle body rises by H SK_r .

[0090] Kneeling on the right side: The front and rear air bags on the right side of the vehicle open their deflation valves first, and the height of the right side of the vehicle drops by H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the right side are closed, and then the inflation valves of the front and rear air bags on the left side of the vehicle are opened, and the height of the left side of the vehicle rises by H. SK_r .

[0091] If the side kneeling function is turned on on a level ground, according to the vehicle's wheelbase B and the vehicle's maximum roll angle φ L , then H SK_l =HSK_r =0.45Bsinφ L ; When the vehicle is at an inclination angle φ R When on a road with a tilt angle, the specific left and right airbag inflation / deflation height values ​​need to be calculated based on the road inclination. Figure 5 If the road conditions are as follows Figure 5 (a), then only the left kneeling function exists, and the height drop value H of the left side of the vehicle body SK_l and the right side height rise value H SK_r They are:

[0092]

[0093] If the road conditions are Figure 5 (b) shows that only the right kneeling function exists at this time, and the height increase value H of the left side of the vehicle body SK_l And the height drop value H of the right side of the vehicle SK_r They are:

[0094]

[0095] After the inflation / deflation process of the side kneeling function is completed and the inflation / deflation valves are closed successively, the front and rear air bags on the same side of the vehicle body are opened through the connecting valves between them respectively to achieve self-balancing of the pressure of the front and rear air bags on the same side. The connecting valves are closed after opening for 5 seconds. After all valve bodies are closed, the vehicle realizes the expected side kneeling function.

[0096] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for dynamically adjusting vehicle height of a semi-active suspension, characterized in that: A vehicle height dynamic adjustment control system is adopted, including an air pump motor, a relay switch group, an energy supply battery group, a controller, four air bags, four connecting valves and four charging / discharging valves; the four air bags are respectively arranged at the front left, front right, rear left and rear right of the vehicle, and the air pump motor realizes the inflation and deflation of the four air bags through the four charging / discharging valves; the relay switch group is arranged on the pipeline connecting the air pump motor and the air bags, and works in coordination with the charging / discharging valves; the four connecting valves are respectively arranged on the connecting pipelines between the front left air bag and the front right air bag, the rear left air bag and the rear right air bag, the front left air bag and the rear left air bag, and the front right air bag and the rear right air bag; the energy supply battery group is used to supply energy to the air pump motor; the controller is used to control the opening and closing of the four connecting valves and the four charging / discharging valves; the control method steps are as follows: Step 1: When the vehicle speed v =0km / h and the ignition device is turned off, the vehicle is stationary and the vehicle body does not move; v =0km / h and the ignition device is closed, the semi-active suspension is tested for vehicle system faults online. If a fault exists, troubleshooting is performed until the fault is cleared; if no fault is displayed, the vehicle height adjustment is performed; Step 2: Open the connecting valves between the front left air bag and the front right air bag, and the rear left air bag and the rear right air bag, so that the pressure of the air bags on both sides of the same axis is equal; inflate the four air bags, so that the rear axle of the vehicle body rises. H r , the front axle of the vehicle body rises H f ; After inflation is completed, open the connecting valve again to make the pressure of the air bags on both sides of the coaxial axis equal; In the formula, A is the cross-sectional area of ​​the membrane air bag; n is the gas index, ranging from [1, 1.40]; V 0 is the initial volume of the air bag without compression or stretching; h if and h ir They are the height change values ​​of the distance between the front and rear axles of the current vehicle in the initial state; H Pf and H Pr They are the heights of the front and rear axles of the current vehicle respectively; P if and P ir They are the internal pressures corresponding to the airbags on both sides of the front and rear axles of the current suspension; P If and P Ir They are the internal pressure values ​​of the front and rear axle airbags after the semi-active suspension height is stabilized; and They are the correction values ​​of the internal pressure of the front and rear axle airbags respectively; Step 3: When the vehicle speed v ∈(0km / h, 20km / h], the vehicle height is based on step 2, and the height is increased in sequence H dr and H df , and the calculation formulas are: In the formula, is the height adjustment coefficient; Step 4: When the vehicle speed v ∈(20km / h, 60km / h], if the current road grade is not worse than the standard D-grade road, the vehicle height is raised by 20-30mm on the basis of step 3, and the pressure of the coaxial airbags is self-balanced, and the vehicle enters the normal driving stage; If the current road grade is worse than the standard D-grade road, the vehicle height is raised by 45-55mm on the basis of step 3, and the pressure of the coaxial airbags is adjusted to self-balance. At this time, the vehicle enters the off-road mode. Step 5: When the vehicle speed v ∈(60km / h, 120km / h], and the current road grade is not worse than the standard C-grade road, if the vehicle body height is in the normal driving stage of step 4, it is lowered by 15-25mm respectively; if the vehicle body height is in the off-road mode driving stage of step 4, it is lowered by 65-75mm respectively, and the pressure of the coaxial airbags on both sides is self-balanced, and the vehicle enters the normal high-speed driving stage; When the speed v ∈(60km / h, 120km / h], and the current road grade is worse than the standard C-grade road, if the vehicle height is in the normal driving stage of step 4, it is raised by 45-55mm respectively; if the vehicle height is in the off-road mode driving stage of step 4, the vehicle height remains unchanged, and the vehicle height is still in the off-road mode driving stage; Step 6: When the vehicle speed v >120km / h, and the current road grade is not worse than the standard B-grade road, if the vehicle height is in the normal high-speed driving stage of step 5, it will be lowered by 5-15mm respectively; if the vehicle height is in the off-road mode driving stage of step 5, it will be lowered by 75-87mm respectively, and the pressure of the coaxial airbags on both sides will be self-balanced, and the vehicle will enter the extreme high-speed driving stage; When the speed v >120km / h, and the current road grade is worse than the standard Class B road, if the vehicle body height is in the normal high-speed driving stage of step five, it will be increased by 25-35mm respectively, and the vehicle will enter the safety holding stage; if the vehicle body height is in the off-road mode driving stage of step five, the vehicle body height remains unchanged, and the vehicle height is still in the off-road mode driving stage.

2. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 1, characterized in that: When the height of the vehicle body rises, the air bags on both sides of the rear axle are inflated first, and the air bags on both sides of the front axle are inflated later; when the height of the vehicle body descends, the air bags on both sides of the front axle are deflated first, and the air bags on both sides of the rear axle are deflated later.

3. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 1, characterized in that: and They are: In the formula, γ f and γ r are the gas delay compensation coefficients of the front and rear axles of the vehicle respectively; ∆ P is the rate of change of gas pressure inside the airbag; h f and h r The distances between the airbag pressure sensor installation positions on the front and rear axles and the middle of the airbag are measured from the airbag entrance and the middle position. h f and h r Positive, measured from the bottom and middle of the airbag h f and h r It is negative; q f and q r are the mass flow rates of the airbags at both ends of the front and rear axles, ρ is the gas density during the filling / deflating process.

4. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 3 is characterized in that: ρ The calculation formula is as follows: t e is the ambient temperature.

5. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 1, characterized in that: n0 is the reference spatial frequency, G q ( n 0) is the power spectrum density of the road surface at frequency n0.

6. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 1, characterized in that: When the speed v =0km / h, and the ignition device is closed, the driver manually selects the side kneeling function by pressing a button; when the side kneeling function is turned on, the connecting valve between the air bags on the left and right sides of the front and rear axles of the vehicle remains closed; Kneeling on the left side: The front and rear air bags on the left side of the vehicle open their deflation valves first, and the height of the left side of the vehicle drops. H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the left side are closed, and then the inflation valves of the front and rear air bags on the right side of the vehicle are opened, and the height of the right side of the vehicle body rises. H SK_r ; Kneeling on the right side: The front and rear air bags on the right side of the vehicle open their deflation valves first, and the height of the right side of the vehicle drops. H SK_l After deflation is completed, the deflation valves corresponding to the two air bags on the right side are closed, and then the inflation valves of the front and rear air bags on the left side of the vehicle are opened, and the height of the left side of the vehicle body rises. H SK_r ; After the inflation valve is closed, the front and rear air bags on the same side of the vehicle body are opened respectively by opening the connecting valve between them, so as to achieve self-balancing of the pressure of the front and rear air bags on the same side.

7. The vehicle height dynamic adjustment control method of the semi-active suspension according to claim 6, characterized in that: If the side kneeling function is turned on on level ground, according to the vehicle's wheelbase B and the body's maximum roll angle φ L , then H SK_l = H SK_r =0.45Bsin φ L ; When the vehicle is at an inclination φ R On the road, if only the left kneeling function is available, the height of the left side of the vehicle will drop by H SK_l and the right side height rise value H SK_r They are: If only the right side kneeling function exists, the height increase value of the left side of the vehicle body H SK_l And the height drop value of the right side of the vehicle H SK_r They are:

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