Vehicle downhill constant-speed control method and system based on hydraulic retarder and storage medium

Abstract

The invention relates to the field of vehicle control, in particular to a vehicle downhill constant-speed control method and system based on a hydraulic retarder and a storage medium. According to the ramp information and the state information of the vehicle, fitting wind resistance and road resistance coefficients of the vehicle based on a least square method; according to the wind resistance and road resistance coefficient and ramp information of the vehicle, first target brake pressure of a hydraulic retarder controller and second target brake pressure of a hydraulic retarder are calculated; calculating a proportional valve control input value, wherein the hydraulic retarder controls the vehicle speed based on the proportional valve control input value; the first target brake pressure and the second target brake pressure of the hydrodynamic retarder are calculated by fitting the wind resistance coefficient of the vehicle and the road resistance coefficient, the pressure of the working cavity is adjusted through the input value of the pressure closed-loop control proportional valve, and the precision and stability of vehicle downhill constant-speed control are remarkably improved; and it is ensured that the vehicle can still rapidly and stably maintain the target vehicle speed when the gradient changes, and the driving safety and comfort are greatly optimized.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control, and in particular to a method, system and storage medium for controlling a vehicle downhill at a constant speed based on a hydraulic retarder. Background Art

[0002] When heavy-load commercial vehicles are traveling on long downhill sections, they need to use the braking system for a long time to maintain the vehicle within a safe and appropriate speed range. Currently, the hydraulic retarder is the most widely used and effective braking device for long downhill sections. After the hydraulic retarder is turned on in constant speed mode, it will monitor the vehicle speed in real time and apply corresponding braking force to the vehicle based on the deviation between the actual vehicle speed and the target speed, so as to maintain the vehicle speed at the target speed as much as possible. The braking force applied by the hydraulic retarder to the vehicle is directly adjusted by adjusting the amount of oil filled in the retarder working chamber by adjusting the input current of the proportional valve, thereby indirectly controlling the braking torque of the retarder. The larger the control input current, the higher the filling rate, and the greater the braking force generated at the same vehicle speed. The existing technology calculates the PID closed-loop torque through the deviation between the target vehicle speed and the actual vehicle speed and provides it to the retarder as a control input to achieve speed control. In order to avoid excessive vehicle speed and speed up the control response speed, the existing technology calculates the vehicle weight according to the vehicle's current road slope, pre-stored fixed rolling resistance coefficient, vehicle weight, and tire radius information to generate a component torque along the vehicle's driving direction as a pre-control driving torque. Finally, the PID closed-loop torque and the pre-control torque are summed as the control input to achieve constant vehicle speed control.

[0003] However, the existing technology has the following problems when controlling the vehicle at a constant speed: 1. Only the rapidity of control response was considered to prevent dangerous excessive speeds, without ensuring the accuracy and stability of speed control during the control process. This resulted in low speed control accuracy, a long time for the vehicle to reach the target speed on roads with a fixed slope, and slight changes in the road slope, causing the vehicle speed to fluctuate repeatedly around the target speed, resulting in a poor driving experience. 2. The pre-braking torque is calculated from the component of the vehicle's weight along the direction of travel and the vehicle's rolling resistance. However, the actual vehicle rolling resistance coefficient varies with factors such as the moisture content of the road surface material. Furthermore, the vehicle is also affected by loads such as wind resistance and the back-drag of the transmission system, resulting in poor results in improving control response speed.

[0004] 3. The actual braking torque generated by using the calculated sum of the PID closed-loop torque and the pre-braking torque as the control input of the retarder for braking often deviates greatly from the calculated sum. Different retarders have differences in installation and manufacturing. In addition, the relationship between the control input and the corresponding torque may change significantly due to long-term wear, aging, or when the solenoid valve core is stuck by impurities. Figure 2As shown in Figure 2, when the valve core is stuck, there is a large control dead zone between the control input and the braking torque. Figure 3 As shown in FIG, when the braking torque is used as the control input current for closed-loop control, the braking torque rise time is long, which will lead to a large speed control deviation and the actual speed oscillating around the target speed. Summary of the Invention

[0005] In response to the problems mentioned in the prior art, the present invention proposes a method, system and storage medium for controlling a constant speed of a vehicle going downhill based on a hydraulic retarder. By constructing a dynamic equation, the wind resistance and road resistance coefficients in the dynamic equation are calculated. The first target braking pressure of the retarder controller and the second target braking pressure of the retarder are calculated based on the wind resistance and road resistance coefficients. According to the first target braking pressure and the second target braking pressure, vehicle speed control is achieved through closed-loop control of the pressure. In order to achieve the above object, the present invention adopts the following technical solutions: The present invention proposes a method for controlling a vehicle's downhill constant speed based on a hydraulic retarder, comprising the following steps: Get the vehicle's slope information and status information; Fit the vehicle's wind resistance and road resistance coefficients based on the vehicle's slope information and state information; Calculating a first target braking pressure and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and vehicle slope information; A proportional valve control input value is calculated according to the first target brake pressure, the second target brake pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

[0006] As a further improvement of the present invention, the vehicle's slope information includes the vehicle's current road slope and future road slope; The vehicle status information includes engine status parameters, transmission status parameters and vehicle status parameters.

[0007] As a further improvement of the present invention, fitting the wind resistance and road resistance coefficient of the vehicle includes: Construct the kinetic equation:

[0008] Where: It is the driving force of the tire; The braking torque output by the engine; is the engine output shaft speed; is the vehicle weight item; The force generated by the retarder brake; 、 、 Indicates the wind resistance and road resistance coefficient; is the transmission ratio from the engine to the drive wheels; is the tire radius; Fitting and updating wind resistance and road resistance coefficients 、 、 , so that the equation satisfies:

[0009] As a further improvement of the present invention, calculating the first target braking pressure of the hydraulic retarder controller includes: Calculation of Steady-State Braking Torque of Hydraulic Retarder , the calculation formula is as follows:

[0010]

[0011] Where: is the engine output shaft speed; 、 、 Indicates wind resistance and road resistance coefficient; The force generated by the retarder brake; Indicates the transmission ratio of the current gear; It is the driving force of the tire; is the braking torque value output by the engine; is the vehicle's gravity; is the road slope value obtained; is the future road slope; is the transmission ratio from the engine to the drive wheels; is the tire radius; Based on the steady-state braking torque of the hydraulic retarder, the first target braking pressure is calculated according to the following formula: :

[0012] Where: and It is the torque-pressure conversion parameter obtained through experiments.

[0013] As a further improvement of the present invention, the calculating the second target braking pressure of the hydraulic retarder includes: Get speed difference; According to the first target braking pressure and the speed difference, the second target braking pressure is calculated according to the following formula: ;

[0014] Where: is the preset maximum permissible speed difference; is the braking pressure corresponding to the maximum braking torque of the retarder; It is the speed difference; is the first target brake pressure.

[0015] As a further improvement of the present invention, calculating the proportional valve control input value includes: The proportional valve control input value is calculated by the following formula :

[0016] Where: is the controller parameter; For actual work pressure; for ; is the difference between the total target brake pressure and the actual working pressure; i For the current moment.

[0017] A vehicle downhill constant speed control system based on a hydraulic retarder, comprising: An acquisition module, used to obtain the vehicle's slope information and status information; An updating module, used to fit the vehicle's wind resistance and road resistance coefficients based on the vehicle's slope information and state information; a calculation module, configured to calculate a first target braking pressure and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and slope information of the vehicle; The control module is configured to calculate a proportional valve control input value based on the first target braking pressure, the second target braking pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

[0018] As a further improvement of the present invention, the acquisition module includes an environment perception sensor, a state sensor and vehicle internal storage data.

[0019] As a further improvement of the present invention, the acquisition module and the update module are applied to a vehicle controller. The present invention provides a computer-readable storage medium for storing a computer program, wherein when the computer program is executed by a processor, the method for controlling a vehicle downhill at a constant speed based on a hydraulic retarder as described above is implemented.

[0020] Compared with the prior art, the present invention has achieved the following technical effects: The present invention proposes a method for controlling a constant speed of a vehicle going downhill. By fitting the vehicle's wind resistance and road resistance coefficient, the actual resistance condition of the vehicle when traveling is sensed, and the first target braking pressure and the second target braking pressure of the hydraulic retarder are calculated in real time according to the actual resistance condition, wherein the first target braking pressure can be the steady-state braking force required to maintain the target vehicle speed, which can effectively avoid a surge in vehicle speed inertia; the second target braking pressure can dynamically adjust the vehicle speed according to the road condition, so that the vehicle speed is guaranteed to be within a safe range; the working chamber pressure can be directly adjusted by adopting a pressure closed-loop control proportional valve input value, which significantly improves the accuracy and stability of the vehicle's constant speed control when going downhill. The method effectively overcomes the vehicle speed oscillation problem caused by fixed resistance parameters and torque control deviation in traditional technologies. Even when the slope changes, the vehicle can quickly and smoothly maintain the target speed, greatly optimizing driving safety and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of a method flow in an embodiment of the present invention; Figure 2 This is a diagram showing the relationship between control input and retarder torque in the prior art; Figure 3 This is a schematic diagram of the pressure change of the closed-loop working chamber controlled by the prior art; Figure 4 This is the relationship between pressure and torque in the retarder bench test of an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0023] See also Figure 1 The present invention proposes a method for controlling a vehicle's downhill constant speed based on a hydraulic retarder, comprising the following steps: Get the vehicle's slope information and status information; According to the vehicle's slope information and state information, the vehicle's wind resistance and road resistance coefficients are fitted based on the least squares method; Calculating a first target braking pressure of the hydraulic retarder controller and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and vehicle slope information; A proportional valve control input value is calculated according to the first target brake pressure, the second target brake pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

[0024] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments: Step 1: Obtain the vehicle's slope information and status information. Specifically, obtain the vehicle's future road slope through the vehicle environment perception sensor, obtain the vehicle's current road slope through the vehicle status sensor, and obtain engine status parameters, transmission status parameters, vehicle status parameters and other data through the CAN bus and internal storage data.

[0025] Step 2: While the vehicle is moving, the parameters to be calculated in the vehicle dynamics equation are updated in real time based on the data obtained in step 1, as follows: According to the vehicle dynamics equation, the driving force at the vehicle tire is calculated as follows:

[0026] Where: is the driving force at the vehicle tires; is the tire radius; It is the transmission ratio from the engine to the drive wheels; is the vehicle mass; is the engine's moment of inertia.

[0027] The total dynamic equation for calculating the vehicle is as follows:

[0028] Where: is the total resistance experienced by the vehicle; is the braking torque value output by the engine; is the vehicle drag coefficient; is the frontal area of ​​the vehicle; is the air density; is the engine output shaft speed; is the road resistance coefficient; is the vehicle's gravity; is the road slope; is the retarder braking torque; is the gear ratio of the transmission's current gear.

[0029] make is the headwind resistance term; is the road resistance term, It is the vehicle weight item; is the force generated by the retarder braking, so formula (2) can also be expressed as:

[0030] When the vehicle is driving steadily, the driving force at the vehicle tires Equal to the total resistance experienced by the vehicle , so substituting into formula (1) and formula (2) we get: (3) Because the parameters and It changes with time and cannot be measured in real time by sensors. When the parameters change, It will also change accordingly.

[0031] Therefore, this embodiment first and Combined into a quadratic polynomial, as follows:

[0032] Combining with formula (3), we get: (4) When the retarder is not working, , so formula (4) can be transformed into: =

[0033] In the formula: At this time, 、 、 、 Real-time measurement, right is a known quantity.

[0034] By collecting multiple groups in real time and D, and the parameters are obtained by online fitting using the least squares method 、 and .

[0035] Step 3: When the driver turns on the hydraulic retarder constant speed control switch, the first target braking pressure of the hydraulic retarder controller is calculated according to formula (5):

[0036]

[0037] Where: is the engine output shaft speed; 、 、 Indicates the wind resistance and road resistance coefficient; The force generated by the retarder brake; Indicates the transmission ratio of the current gear; It is the driving force of the tire; It is the torque value output by the engine to the transmission input shaft; is the vehicle's gravity; is the road slope value obtained; It is the future road slope.

[0038] Based on the steady-state braking torque of the hydraulic retarder, the first target braking pressure is calculated according to the following formula: :

[0039] Where: is the retarder torque; is the control input relation parameter.

[0040] Step 4: When the driver turns on the hydraulic retarder constant speed control switch, the vehicle's current speed Set as the target speed, the real-time speed obtained by the vehicle sensor is , the speed difference can be calculated , calculate the second target brake pressure according to the following formula ;

[0041] Where: is the preset maximum permissible speed difference; is the braking pressure corresponding to the maximum braking torque of the retarder; It is the speed difference; is the first target brake pressure.

[0042] Step 5. Calculate the proportional valve control input value using the following formula: :

[0043] Where: is the controller parameter; For actual work pressure; for ; is the difference between the total target brake pressure and the actual working pressure; i For the current moment.

[0044] Based on the same inventive concept, an embodiment of the present invention further provides a vehicle downhill constant speed control system based on a hydraulic retarder. Since the principle of solving the problem of the vehicle downhill constant speed control system based on the hydraulic retarder is similar to the aforementioned vehicle downhill constant speed control method based on the hydraulic retarder, the implementation of the vehicle downhill constant speed control system based on the hydraulic retarder can refer to the implementation of the vehicle downhill constant speed control method based on the hydraulic retarder, and the repeated parts are not repeated here.

[0045] In specific implementation, the vehicle downhill constant speed control system based on the hydraulic retarder provided in the embodiment of the present invention specifically includes: An acquisition module, used to obtain the vehicle's slope information and status information; An updating module, configured to fit the wind resistance and road resistance coefficients of the vehicle based on the least squares method according to the slope information and state information of the vehicle; a calculation module, configured to calculate a first target braking pressure of the hydraulic retarder controller and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and slope information of the vehicle; The control module is configured to calculate a proportional valve control input value based on the first target braking pressure, the second target braking pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

[0046] In the embodiment, the acquisition module is specifically applied to the vehicle controller, and is mainly used to collect and acquire the signals and data required by other modules, mainly including acquiring the future road slope of the vehicle through the vehicle environment perception sensor, acquiring the current road slope of the vehicle through the vehicle status sensor, and acquiring engine status parameters, transmission status parameters, vehicle status parameters and other data through the Can bus and internal storage data.

[0047] The update module is used to calculate the wind resistance and road resistance coefficient of the vehicle online based on the acquisition module and the vehicle dynamics equation. In the embodiment, the update module is specifically applied to the vehicle controller.

[0048] The calculation module is used to accurately calculate the steady-state braking torque of the retarder under the target vehicle speed condition by using the wind resistance and road resistance coefficient after the driver activates the retarder constant speed control switch, and convert it into the first target braking pressure of the retarder controller; by obtaining the target control vehicle speed deviation, according to the pre-set maximum allowable speed deviation and the pre-acquired bench test data, the target control vehicle speed deviation is converted into the second target braking pressure of the retarder.

[0049] The control module is used to obtain the first target braking pressure, the second target braking pressure and the actual pressure in the retarder working chamber according to the calculation module, establish a pressure closed-loop control, and thus achieve constant speed control of the vehicle.

[0050] Accordingly, an embodiment of the present invention further provides a computer-readable storage medium for storing a computer program, wherein when the computer program is executed by a processor, the vehicle downhill constant speed control method based on a hydraulic retarder as provided in an embodiment of the present invention is implemented.

[0051] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. References to the same or similar portions of the various embodiments will be sufficient. The systems, devices, and storage media disclosed in the embodiments are described briefly because they correspond to the methods disclosed in the embodiments. For relevant details, refer to the method descriptions.

[0052] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0053] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0054] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0055] The above is a detailed introduction to the vehicle downhill constant speed control method, system and storage medium based on the hydraulic retarder provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for controlling a vehicle's constant speed when descending a slope based on a hydraulic retarder, characterized in that: The following steps are involved: Get the vehicle's slope information and status information; Fit the vehicle's wind resistance and road resistance coefficients based on the vehicle's slope information and state information; Calculating a first target braking pressure and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and vehicle slope information; A proportional valve control input value is calculated according to the first target brake pressure, the second target brake pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

2. A method for controlling a vehicle's downhill constant speed based on a hydraulic retarder according to claim 1, characterized in that: The vehicle's slope information includes the vehicle's current road slope and future road slope; The vehicle status information includes engine status parameters, transmission status parameters and vehicle status parameters.

3. The method for controlling a vehicle's downhill constant speed based on a hydraulic retarder according to claim 1, characterized in that: Fitting the vehicle's wind resistance and road resistance coefficients, including: Construct the kinetic equation: Where: It is the driving force of the tire; The braking torque output by the engine; is the engine output shaft speed; is the vehicle weight item; The force generated by the retarder brake; 、 、 Indicates wind resistance and road resistance coefficient; is the transmission ratio from the engine to the drive wheels; is the tire radius; Fitting and updating wind resistance and road resistance coefficients 、 、 , so that the equation satisfies: 。 4. The method for controlling a vehicle's downhill constant speed based on a hydraulic retarder according to claim 1, characterized in that: Calculating a first target braking pressure of a hydraulic retarder controller includes: Calculation of Steady-State Braking Torque of Hydraulic Retarder , the calculation formula is as follows: Where: is the engine output shaft speed; 、 、 Indicates wind resistance and road resistance coefficient; The force generated by the retarder brake; Indicates the transmission ratio of the current gear; It is the driving force of the tire; is the braking torque value output by the engine; is the vehicle's gravity; is the road slope value obtained; is the future road slope; is the transmission ratio from the engine to the drive wheels; is the tire radius; Based on the steady-state braking torque of the hydraulic retarder, the first target braking pressure is calculated according to the following formula: : Where: and It is the torque-pressure conversion parameter obtained through experiments.

5. The method for controlling a vehicle's downhill constant speed based on a hydraulic retarder according to claim 1, characterized in that: The calculating the second target braking pressure of the hydraulic retarder includes: Get speed difference; According to the first target braking pressure and the speed difference, the second target braking pressure is calculated according to the following formula: ; Where: is the preset maximum permissible speed difference; is the braking pressure corresponding to the maximum braking torque of the retarder; It is the speed difference; is the first target brake pressure.

6. The method for controlling a vehicle's downhill constant speed based on a hydraulic retarder according to claim 1, characterized in that: Calculates proportional valve control input values, including: The proportional valve control input value is calculated by the following formula : Where: is the controller parameter; For actual work pressure; for ; is the difference between the total target brake pressure and the actual working pressure; i For the current moment.

7. A vehicle downhill constant speed control system based on a hydraulic retarder, characterized in that: include: An acquisition module, used to obtain the vehicle's slope information and status information; An updating module, used to fit the vehicle's wind resistance and road resistance coefficients based on the vehicle's slope information and state information; a calculation module, configured to calculate a first target braking pressure and a second target braking pressure of the hydraulic retarder according to wind resistance and road resistance coefficients and slope information of the vehicle; The control module is configured to calculate a proportional valve control input value based on the first target braking pressure, the second target braking pressure, and the acquired actual working pressure of the hydraulic retarder, and the hydraulic retarder controls the vehicle speed based on the proportional valve control input value.

8. A vehicle downhill constant speed control system based on a hydraulic retarder according to claim 7, characterized in that: The acquisition module includes an environment perception sensor, a state sensor and vehicle internal storage data.

9. A vehicle downhill constant speed control system based on a hydraulic retarder according to claim 7, characterized in that: The acquisition module and the update module are applied to the vehicle controller.

10. A computer-readable storage medium, characterized in that Used to store a computer program, wherein when the computer program is executed by a processor, the vehicle downhill constant speed control method based on a hydraulic retarder is implemented as described in any one of claims 1 to 6.

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