Control system and method for coordinated control of air suspension and pneumatic braking in autonomous vehicles

Abstract

This invention provides a coordinated control system and method for air suspension and pneumatic braking in autonomous vehicles, including an air supply unit, a braking unit, and an adjustment unit mounted on the vehicle chassis. The air supply unit supplies air to the braking unit and the adjustment unit. The braking unit brakes the vehicle, and the adjustment unit adjusts the vehicle's driving posture. The braking unit and the adjustment unit share the same air supply unit. The advantages of this invention are: the air spring arrangement structure is simple, lightweight, small in size and space, and has a wide range of applications; the air spring and pneumatic braking arrangement structure uses a single air tank, reducing the number of air tanks in the vehicle and significantly lowering the failure rate, saving resources and reducing costs; the coordinated control algorithm for air springs and pneumatic braking improves handling stability while ensuring the safety and effectiveness of braking in the event of a system failure.

Description

Technical Field

[0001] This invention belongs to the automotive field, and in particular relates to a coordinated control system and method for air suspension and pneumatic braking in autonomous vehicles. Background Technology

[0002] Air springs have nonlinear characteristics and can be designed with a relatively ideal elastic characteristic curve according to the vehicle's vibration performance; they can make the natural frequencies of empty and loaded vehicles almost equal; when used with a height control valve, they can keep the vehicle floor level from the rail surface constant under different loads; and they have good performance in absorbing high-frequency vibrations.

[0003] Pneumatic braking utilizes compressed air generated by an air pump to push the brake shoes, achieving the purpose of braking. Pneumatic braking mainly uses shoe-shaped brakes and drum brakes. Due to the large air flow and high pressure, the stroke generated on the brake pump is relatively large. Moreover, pneumatic braking has a rapid response, abrupt braking, and strong braking force.

[0004] Lightweight and simplified installation of air brake and air spring components is of paramount importance. Nowadays, most vehicles have an urgent need for new configurations of air brake and air spring, but due to factors such as large weight, size, and complex structure, they are not conducive to installation. Summary of the Invention

[0005] In view of this, the present invention aims to provide a coordinated control system and method for air suspension and pneumatic braking of autonomous vehicles, so as to solve at least one of the problems in the background art.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] An autonomous vehicle air suspension and pneumatic braking coordinated control method includes an air supply unit, a braking unit and an adjustment unit installed on the vehicle chassis. The air supply unit is used to supply air to the braking unit and the adjustment unit. The braking unit is used to brake the vehicle and the adjustment unit is used to adjust the vehicle's driving posture.

[0008] The regulating unit includes an air spring, and the air supply unit includes an air tank;

[0009] The braking unit and the regulating unit share the same air supply unit;

[0010] A first valve is installed on the air supply line from the air supply unit to the braking unit, and a second valve is installed on the air supply line from the air supply unit to the regulating unit.

[0011] During normal vehicle operation, the first valve is closed and the second valve is open, and the gas in the air tank is only used by the air springs to adjust the overall vehicle posture.

[0012] When the vehicle is braking, there are two situations: the braking behavior when the air supply is normal is set as the normal braking state, and the braking behavior when the air supply is abnormal is set as the emergency braking state.

[0013] When the vehicle is under normal braking, when the vehicle needs to brake, the first valve opens and the second valve opens. Part of the gas in the air tank is used for braking, and the other part is used for the air spring to adjust the overall vehicle attitude.

[0014] When the vehicle is under emergency braking, the first valve opens and the second valve closes, and the gas in the air tank is used only for air brake braking.

[0015] Furthermore, when the air supply is normal, the braking unit and the regulating unit control the valves separately in a decoupled manner to achieve the air supply to the braking unit and the regulating unit. The decoupling means that when the air supply is normal, the air spring and the air brake do not have priority or mutual constraints in the control of the whole vehicle, and the amount and duration of air supply can be freely adjusted as needed.

[0016] Furthermore, in the event of abnormal air supply, the air spring and pneumatic brake failure control method is implemented;

[0017] The method for controlling the failure of the air spring and pneumatic brake is as follows: the gas in the air tank is distributed to the braking unit and the regulating unit using a fuzzy algorithm.

[0018] Furthermore, if the air supply unit is not supplying air properly and the current vehicle speed is high, resulting in a large braking demand, the gas in the air tank will be allocated only to the braking unit.

[0019] Furthermore, when the air supply unit is not supplying air properly and the braking intention is relatively mild, and the vehicle body posture needs to be adjusted, the gas in the air tank is distributed to the braking unit and the adjustment unit through a fuzzy algorithm, thereby improving the vehicle's handling stability while ensuring the braking effect.

[0020] Secondly, this solution discloses a control system for a coordinated control method of air suspension and pneumatic braking for autonomous vehicles. The air supply unit also includes an air compressor, which is equipped with a regulating valve, and the air storage tank is equipped with a safety valve and a drain valve.

[0021] The air tank supplies air to the braking unit through an air supply pipeline.

[0022] Furthermore, the braking unit includes a brake chamber and a brake pedal. The brake pedal is located between the air tank and the air supply line, and the braking operation of the brake chamber is controlled by the brake pedal.

[0023] Furthermore, the braking unit includes a drum brake, which is connected to the brake chamber.

[0024] Compared with the prior art, the autonomous vehicle air suspension and pneumatic braking coordinated control system and method of the present invention have the following advantages:

[0025] 1. The novel pneumatic braking and air spring arrangement structure of the present invention has the advantages of simple structure, light weight, small size and space occupation, and wide applicability;

[0026] 2. The novel air pressure brake and air spring arrangement structure of the present invention uses a single air tank for both the air spring and the air pressure brake, which reduces the number of air tanks in the vehicle and also greatly reduces the failure rate, saving resources and thus reducing costs.

[0027] 3. The air spring and pneumatic brake coordination control algorithm of the present invention improves the handling stability while ensuring the safety and effectiveness of braking when the system fails. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a schematic diagram of the air suspension and pneumatic braking coordinated control system for autonomous vehicles according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic flowchart of the coordination control algorithm described in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of stiffness adjustment based on fuzzy control algorithm according to an embodiment of the present invention;

[0032] Figure 4 , Figure 5 This is a schematic diagram of the failure control based on fuzzy algorithm according to an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the membership degree of the fuzzy variable E as described in an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the membership degree of the fuzzy variable EC as described in an embodiment of the present invention;

[0035] Figure 8 This is a schematic diagram of the membership degree of the fuzzy variable U as described in an embodiment of the present invention;

[0036] Figure 9 This is a diagram illustrating the coordinated control valve status as described in an embodiment of the present invention.

[0037] Figure 10This is a detailed flowchart of the coordination control described in an embodiment of the present invention;

[0038] Figure 11 This is a schematic diagram of the fuzzy algorithm reasoning mechanism.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1-Air compressor; 2-Air tank; 3-Brake pedal; 4-Brake chamber; 5-Air spring; 6-Drum brake. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0042] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, the novel pneumatic brake and air spring combined working configuration provided by this solution includes a brake pedal 3, a brake chamber 4, a drum brake 6, an air spring 5, an air tank, and other devices.

[0044] The new air pressure brake and air spring 5 working configuration is that the air pressure brake and air spring 5 share an air tank and a compressor that pumps in fresh air in the working airflow circuit, providing sufficient air volume and pressure for the entire circuit to ensure the normal operation of the air spring 5 and the air pressure brake. When the vehicle load changes, in order to keep the vehicle height above the road constant, the compressed air in the rubber bladder of the air spring 5 is adjusted through the height adjustment valve between the vehicle body and the bogie, so that the vehicle floor is basically level regardless of the number and uneven distribution of passengers in the vehicle. When braking is required, the driver connects the air inlets of the upper and lower chambers of the brake valve to the air outlets of the chambers respectively, so that the air in the front and rear chambers of the air tank enters the front and rear brake chambers 4 through the upper and lower chambers of the brake valve, thereby promoting the brake to engage.

[0045] This combined working configuration ensures that the air spring 5 and the air brake work normally while sharing a single air tank, while also reducing the number of components used and making the car lighter.

[0046] Meanwhile, this solution discloses a control method based on the above structure, which uses a shared air tank and a compressor for pumping fresh air in the working airflow circuit, and implements braking and attitude adjustment functions through relevant algorithms to ensure the normal operation of the air spring 5 and the air pressure brake.

[0047] PID control utilizes the relative control error target value to determine the controlled object's operation through three actions: proportional, integral, and derivative of the controlled variable. For height adjustment, the control variable must first be determined. Following the principle of determining the surface from three points, a method is chosen where the two rear air springs (5) are controlled separately, while the two front air springs (5) are controlled together. The height signals from the two rear controllers are taken from the lengths of the two rear air springs (5), while the height signal from the one front controller is the average height of the two front air springs (5). The operating length signals of each spring are compared with the set standard length signal to obtain the height error signal, which is then input to the controller for adjustment.

[0048] The fuzzy control strategy for stiffness adjustment in this invention is based on adjusting the opening and closing time of the solenoid valve according to the root mean square value of the acceleration of the spring mass in the vertical direction, thereby achieving the purpose of adjusting the spring stiffness. The difference between the root mean square value of the acceleration of the spring mass in the vertical direction and the root mean square value of the acceleration of the reference model is selected as the controller input variable e, the rate of change of the difference is selected as another input, and the spring stiffness is selected as the output variable u. The algorithm is then constructed, and the fuzzy linguistic values ​​are as follows:

[0049] E={NB, NM, NULL, PS, PM, PB}

[0050] EC={NB,NS,NULL,PS,PB}

[0051] U = {NB, NS, NULL, PS, PB}

[0052] The purpose of the failure control fuzzy control strategy is to ensure that, in the event of an interruption in energy supply, the valve openings of the brakes and air springs 5 ​​are rationally allocated, so as to improve the vehicle's handling stability and comfort as much as possible while ensuring braking safety.

[0053] This combined working configuration and control algorithm can ensure normal operation of the air spring 5 and the air brake when they share a common air tank. At the same time, it can reduce the use of components, reduce the failure rate, and make the car lighter.

[0054] This solution also discloses a method for coordinated control of air suspension and pneumatic braking in autonomous vehicles, such as... Figure 9 and Figure 10 :

[0055] 1. The vehicle is driving normally.

[0056] The first valve is closed, the second valve is open, and the gas in the air tank is only used by the air springs to adjust the vehicle's attitude.

[0057] 2. Vehicle braking and driving

[0058] i. During normal braking, the first valve opens and the second valve opens. Part of the gas in the air tank is used for braking, and the other part is used by the air springs to adjust the vehicle's attitude.

[0059] ii. In case of emergency braking, the first valve is closed and the second valve is opened. The gas in the air tank is used only for air brake braking.

[0060] "0" represents the valve open state, "1" represents the valve closed state, and "a0" represents the braking intensity threshold. The value of a0 is generally 0.7, but its specific value can also be adjusted according to different driving conditions such as specific vehicle models, urban road conditions, and mountain road conditions, to coordinate and control the valve state. Figure 9 While ensuring vehicle safety, the overall vehicle attitude was adjusted to greatly improve energy efficiency. The specific control flowchart is as follows: Figure 10 .

[0061] Finally, it should be noted that the fuzzy algorithm mentioned in this solution is a fuzzy control strategy, an intelligent control method based on human experience. It does not require a precise mathematical model of the controlled object, therefore involves very few mathematical operations. It can be implemented in conjunction with the vehicle control system. Please refer to [link / reference needed] for details. Figure 11 Adjustments are made based on experience using vehicle speed and pedal signals;

[0062] The values ​​of vehicle speed and pedal signal are converted into fuzzy values ​​using the following equation:

[0063] 1. If the vehicle speed is high and the braking demand is large, the gas in the air tank will be distributed only to the braking unit.

[0064] 2. The braking intention is relatively mild, and the vehicle body posture needs to be adjusted, while the braking force is distributed to the braking unit and the air spring;

[0065] 3. The braking intention is relatively mild, the vehicle body posture is good, and the braking unit is allocated accordingly.

[0066] Those skilled in the art will recognize that the units and method steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0067] In the several embodiments provided in this application, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the division of units described above is merely a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. The aforementioned units may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention according to actual needs.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for coordinated control of air suspension and pneumatic braking in autonomous vehicles, characterized in that: It includes an air supply unit, a braking unit, and an adjustment unit installed on the vehicle chassis. The air supply unit is used to supply air to the braking unit and the adjustment unit. The braking unit is used to brake the vehicle, and the adjustment unit is used to adjust the vehicle's driving posture. The regulating unit includes an air spring (5), and the air supply unit includes an air tank (2); The braking unit and the regulating unit share the same air supply unit; A first valve is installed on the air supply line from the air supply unit to the braking unit, and a second valve is installed on the air supply line from the air supply unit to the regulating unit. During normal vehicle operation, the first valve is closed and the second valve is open, and the gas in the air tank is only used by the air springs to adjust the overall vehicle posture. When the vehicle is braking, there are two situations: the braking behavior when the air supply is normal is set as the normal braking state, and the braking behavior when the air supply is abnormal is set as the emergency braking state. When the vehicle is under normal braking, when the vehicle needs to brake, the first valve opens and the second valve opens. Part of the gas in the air tank is used for braking, and the other part is used for the air spring to adjust the overall vehicle attitude. When the vehicle is under emergency braking, the first valve opens and the second valve closes, and the gas in the air tank is only used for air brake braking. When the gas supply is normal, the braking unit and the regulating unit control the valves separately in a decoupled manner to achieve gas supply to the braking unit and the regulating unit.

2. The method according to claim 1, characterized in that: If the air supply unit is not supplying air properly and the current vehicle speed is high, the braking demand will be large. In this case, the air in the air tank will be allocated only to the braking unit.

3. A control system based on the method according to any one of claims 1-2, characterized in that: The air supply unit also includes an air compressor (1), which is equipped with a regulating valve, and an air storage tank (2) is equipped with a safety valve and a drain valve; The air tank (2) supplies air to the braking unit through the air supply pipeline.

4. The control system according to claim 3, characterized in that: The braking unit includes a brake chamber (4) and a brake pedal (3). The brake pedal (3) is located between the air tank (2) and the air supply line. The braking operation of the brake chamber (4) is controlled by the brake pedal (3).

5. The control system according to claim 4, characterized in that: The braking unit includes a drum brake (6), which is connected to the brake chamber (4).

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