A drum brake braking force detection method, system, device and readable storage medium

Abstract

The present invention discloses a drum brake braking force detection method, system, equipment and readable storage medium. According to a drum brake temperature model, a relationship between the braking force work and temperature during the braking process of the drum brake is established, thereby deducing the relationship between the braking force work and the vehicle speed and brake temperature. The braking force of the drum brake is calculated according to the vehicle speed and the brake temperature. The present invention utilizes the principle that the temperature of the drum brake changes with time during the braking process, and uses the monitored brake temperature to predict the braking force of the brake, thereby providing a basis for the formulation of a braking strategy, improving the accuracy of the vehicle control braking strategy, and avoiding the inaccuracy of the braking force deduced due to local deformation, assembly error, and uneven wear of the vehicle brake. The present invention can accurately obtain the size of the vehicle braking force without being affected by the deformation of the vehicle brake, providing accurate feedback data for vehicle braking, and greatly improving the safety of vehicle operation.

Description

Technical Field

[0001] The invention belongs to the technical field of downhill braking of heavy-duty trucks and relates to a method, system, equipment and a readable storage medium for detecting the braking force of a drum brake. Background Art

[0002] During vehicle braking, the braking force is difficult to measure directly through sensors. Previous methods for solving the braking force of drum brakes mainly include: forward deduction to solve the braking force (theoretical model or empirical model), regression equation to derive the braking force. However, in the actual working process of drum brakes, due to local deformation, assembly error, uneven wear and other problems, the braking force error obtained by the above methods is large, and the brake force cannot be effectively responded to. At present, the braking control of the car mainly relies on the driver's experience during driving, and it is impossible to effectively record and feedback the braking effect data of the vehicle drum brake. Summary of the invention

[0003] The object of the present invention is to provide a drum brake braking force detection method, system, device and readable storage medium to overcome the deficiencies of the prior art.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] A drum brake braking force detection method comprises the following steps:

[0006] S1, based on the heat transfer and tribology theory, establish the drum brake temperature model;

[0007] S2. According to the drum brake temperature model, the relationship between the braking force work and the temperature during the drum brake braking process is established, and the relationship between the braking force work and the vehicle speed and brake temperature is derived. The drum brake braking force is calculated according to the vehicle speed and brake temperature.

[0008] Furthermore, the expression of the temperature change of the friction working surface during the braking process of the drum brake with time is specifically expressed as:

[0009]

[0010] λ i is the thermal conductivity of the brake material; b i is the effective thickness of the friction pair component involved in heat absorption, in m; τ N is the friction power ratio, τ N =2(1-τ),τ W is the ratio of friction work to braking work, τ W =2τ-τ 2 , τ N is the time ratio, F oi is the Fourier number at a certain point on the drum brake; φ vi is the heat influence coefficient; S ai is the actual friction area during braking, in m 2 ;t T is the continuous braking time, in seconds; F oi is the Fourier number of point i on the drum brake; a Tni is the thermal field distribution coefficient, a Tn1 +a Tn2 =1;W Tn is the braking work, the unit is J; further, assuming that the initial temperature of the brake is T, the actual temperature change during braking is expressed as:

[0011] T Z =T+T * (2)

[0012] The drum brake temperature change prediction model is converted into a braking force prediction model.

[0013] The integral of the braking work with respect to time is:

[0014]

[0015] v is the data of the heavy truck speed changing with time during braking.

[0016] Furthermore, the relationship between the braking force of the drum brake and the speed and temperature during the braking process is expressed as:

[0017]

[0018] Furthermore, the longitudinal dynamic equation of the vehicle driving downhill is established as:

[0019] F t +F i =F f +F w +F j (5)

[0020] Among them, F t The driving force of the vehicle, T tq is the engine torque, i g is the transmission ratio of the transmission, i0 is the transmission ratio of the main reducer, η T is the mechanical efficiency of the transmission system, r is the wheel radius;

[0021] F i is the component of gravity down the ramp, F i =Gsinα;

[0022] F f is the rolling resistance, F f =Gf cosα, f is the rolling resistance coefficient;

[0023] F w is the air resistance, C D is the air resistance coefficient, A is the frontal area of ​​the car, u a is the vehicle speed;

[0024] F j is the acceleration resistance, δ is the rotation mass conversion factor, m is the vehicle mass, is the vehicle acceleration.

[0025] Furthermore, the dynamic equation of a heavy truck going downhill is expressed as:

[0026] F i =F f +F w +F j +F b +F b_con (6)

[0027] Among them, F b Total braking force of the main brake, F b_con Provides engine braking force.

[0028] A drum brake braking force detection system, comprising:

[0029] Model building module, used to build and store drum brake temperature model based on brake material properties, heat transfer and tribology theory;

[0030] The temperature detection module is used to collect the temperature change value during the braking process of the drum brake and transmit the temperature change value to the braking force calculation module;

[0031] The speed detection module is used to collect the vehicle's driving speed and transmit the vehicle's driving speed to the braking force calculation module;

[0032] The braking force calculation module is used to establish the relationship between the braking force work and the temperature during the braking process of the drum brake according to the drum brake temperature model, and calculate the braking force of the drum brake according to the vehicle speed and the brake temperature.

[0033] A terminal device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of a drum brake braking force detection method when executing the computer program.

[0034] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the drum brake braking force detection method are implemented.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] The invention discloses a drum brake braking force detection method. Based on the heat transfer and tribology theories, a drum brake temperature model is established. According to the drum brake temperature model, the relationship between the braking force work and the temperature in the drum brake braking process is established, thereby the relationship between the braking force work and the vehicle speed and the brake temperature is derived. The braking force of the drum brake is calculated according to the vehicle speed and the brake temperature. The invention utilizes the principle that the temperature of the drum brake changes with time in the braking process, and utilizes the monitored brake temperature to predict the braking force of the brake, thereby providing a basis for the formulation of a braking strategy, improving the accuracy of the vehicle control braking strategy, and avoiding the inaccuracy of the braking force deduced due to the local deformation, assembly error and uneven wear of the vehicle brake. The invention can accurately obtain the braking force of the vehicle without being affected by the deformation of the vehicle brake, and provide accurate feedback data for vehicle braking. The invention is particularly suitable for unmanned vehicle control braking, and greatly improves the safety of vehicle operation.

[0037] Furthermore, the accuracy of the observer is verified by the change of braking deceleration using the established dynamic model of a heavy-loaded truck going downhill.

[0038] Furthermore, the ratio of the heat absorbed by the brake drum to the total heat generated during braking is called the heat distribution coefficient, which can accurately obtain the relationship between the temperature of the friction working surface of the drum brake during braking and the time change, thereby improving the calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a simulation model diagram in an embodiment of the present invention.

[0040] Figure 2 The present invention is a flow chart of the drum braking force observer design in an embodiment of the present invention.

[0041] Figure 3 1 is a temperature variation curve of the second-axle brake drum in an embodiment of the present invention.

[0042] Figure 4 1 is a temperature variation curve of the three-axis brake drum in an embodiment of the present invention.

[0043] Figure 5 This is a test verification of the braking process in the embodiment of the present invention.

[0044] Figure 6 4 is a diagram showing the simulation results of the two-axis braking force in an embodiment of the present invention.

[0045] Figure 7 4 is a diagram of the simulation results of the three-axis braking force in an embodiment of the present invention.

[0046] Figure 8 2 is a diagram of brake pedal displacement in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0048] Part 1: The temperature of the drum brake process is related to the material properties of the brake. Using this feature, a suitable temperature field model is established based on the basic theories of heat transfer and automotive tribology, thereby deducing the relationship between the braking force and the heat of the brake drum. By measuring the vehicle speed, braking time, braking distance, brake drum surface temperature, etc., and referring to the manual to obtain the material properties of the brake, the braking force can be solved.

[0049] A drum brake braking force detection method comprises the following steps:

[0050] S1, based on the heat transfer and tribology theory, establish the drum brake temperature model;

[0051] The drum brake temperature model, which is derived based on heat transfer and tribology theories, is a temperature change model of the brake during braking. The brake drum temperature in this model is related to the work done by the braking force.

[0052] S2. According to the drum brake temperature model, the relationship between the braking force work and the temperature during the drum brake braking process is established, and the relationship between the braking force work and the vehicle speed and brake temperature is derived. The drum brake braking force is calculated according to the vehicle speed and brake temperature.

[0053] A drum brake braking force observer and a vehicle longitudinal dynamics simulation model were established. The braking force of the brake was predicted by monitoring the brake temperature to provide a basis for formulating braking strategies. Considering that the actual braking force cannot be obtained directly, the speed was obtained from the braking test for comparison, and the accuracy of the model was never verified.

[0054] Specifically, the mathematical expression of the drum brake temperature model is derived using the heat transfer and tribology theories;

[0055] First, a simple temperature field model is established:

[0056]

[0057] r is the brake drum radius, T i is the braking temperature, t is the braking time, α iis the thermal diffusion coefficient, i=1 represents the brake drum, and i=2 represents the brake shoe.

[0058] The temperature T of point i on the drum brake can be calculated using the following formula:

[0059]

[0060] ε i is the radial coordinate value of the drum brake temperature field model and b i The ratio of Tni is the thermal field distribution coefficient, W Tn is the braking work, the unit is J; t T is the continuous braking time, in seconds; b i The effective thickness of the friction pair component participating in heat absorption during braking, in m, can be calculated by:

[0061]

[0062] ρ i is the density of the brake material; c i is the specific heat capacity of the brake material; i is the thermal conductivity of the brake material; F oi is the Fourier number at point i of the drum brake:

[0063]

[0064] α i is the thermal diffusion coefficient of the brake material; φ vi is the heat influence coefficient, which can be numerically calculated using the following formula:

[0065]

[0066] b iφ It is the actual thickness of the friction pair component.

[0067] During the braking process, the mechanical energy of a heavy truck generates a large amount of heat after intense friction with the drum brake. In a short period of time, without considering the heat dissipation of the drum brake, the heat generated during braking is absorbed by the brake drum and brake shoe. The ratio of the heat absorbed by the brake drum (or brake shoe) to the total heat generated during braking is called the heat distribution coefficient, and the heat distribution coefficient can be calculated using the following formula:

[0068]

[0069]

[0070]

[0071] a Tn2 +a Tn1 =1 (12)

[0072] Since the temperature sensor can only measure the temperature of the friction surface of the drum brake when measuring the temperature in the road test, the parameter ε in the formula is i The value of ε i =0.

[0073] So at this time, we can get the expression of the temperature change of the friction working surface with time during the braking process of the drum brake, which is specifically expressed as:

[0074]

[0075] ε i is the ratio of the radial coordinate value of the drum brake temperature field model to R0; r i F is the effective thickness of the friction pair components involved in heat absorption during braking, in m; oi is the Fourier number at point i of the drum brake; φ vi is the heat influence coefficient; S ai is the actual friction area during braking, in m 2 ;t T is the continuous braking time, in seconds; W τn is the braking work;

[0076] Assuming the initial temperature of the brake is T, the actual temperature change during braking is expressed as:

[0077] T Z =T+T * (2)

[0078] The drum brake temperature change prediction model is converted into a braking force prediction model to complete the derivation of the drum brake braking force observer model;

[0079] In the actual braking process, the braking force is a constantly changing process. Using calculus, the braking work W τn It can be expressed by the following formula:

[0080] W τn =F b *S=∫F b ds (13)

[0081] Convert the braking work into an integral over time:

[0082]

[0083] Considering that the speed changes with time during braking, the relationship between braking work and speed change with time is obtained:

[0084]

[0085] Combining the above formula, the relationship between the braking force of the drum brake and the speed and temperature during braking is expressed as:

[0086]

[0087] v is the data of the heavy truck speed changing with time during braking.

[0088] A drum brake braking force observer simulation model was built. Considering that the braking force cannot be obtained directly, the established dynamic model of a heavy-loaded truck going downhill was used to verify the accuracy of the observer through changes in braking deceleration.

[0089] The longitudinal dynamic equation of a car driving downhill is:

[0090] F t +F i =F f +F w +F j (5)

[0091] Among them, F t The driving force of the vehicle, T tq is the engine torque, i g is the transmission ratio of the transmission, t0 is the transmission ratio of the main reducer, η T is the mechanical efficiency of the transmission system, r is the wheel radius;

[0092] F i is the component of gravity down the ramp, F i =Gsinα;

[0093] F f is the rolling resistance, F f =Gf cosα, f is the rolling resistance coefficient;

[0094] F w is the air resistance, C D is the air resistance coefficient, A is the frontal area of ​​the car, u a is the vehicle speed;

[0095] F j is the acceleration resistance, δ is the rotation mass conversion factor, m is the vehicle mass, is the vehicle acceleration.

[0096] The dynamic equation of a heavy truck going downhill is expressed as:

[0097] F i =F f +F w +F j +F b +F b_con (6)

[0098] Among them, F b Total braking force of the main brake, F b_con Provides engine braking force.

[0099] The temperature signal wireless acquisition and transmission module, VGPS speed and distance acquisition module and other modules are used to collect data on the test road. Then, typical drum brake temperature rise section data is selected for simulation to obtain the braking force change curve.

[0100] The actual speed change of the vehicle can be expressed by the following formula:

[0101]

[0102] In one embodiment of the present invention, a terminal device is provided, the terminal device includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor adopts a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), off-the-shelf programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the drum brake braking force detection method.

[0103] A drum brake braking force detection system, comprising:

[0104] Model building module, used to build and store drum brake temperature model based on brake material properties, heat transfer and tribology theory;

[0105] The temperature detection module is used to collect the temperature change value during the braking process of the drum brake and transmit the temperature change value to the braking force calculation module;

[0106] The speed detection module is used to collect the vehicle's driving speed and transmit the vehicle's driving speed to the braking force calculation module;

[0107] The braking force calculation module is used to establish the relationship between the braking force work and the temperature during the braking process of the drum brake according to the drum brake temperature model, and calculate the braking force of the drum brake according to the vehicle speed and the brake temperature.

[0108] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. The computer-readable storage medium includes a built-in storage medium in the terminal device, which provides a storage space and stores the operating system of the terminal, and may also include an extended storage medium supported by the terminal device. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here may be a high-speed RAM memory, or a non-volatile memory (Non-volatile memory), such as at least one disk memory. The processor may load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the drum brake braking force detection method in the above embodiment.

[0109] Example

[0110] The test section is: the left line of the Ya'an-Xichang section of the Beijing-Kunming Expressway: K174-K25 (Psonggang Service Area-Yingjing Service Area) downhill section.

[0111] The vehicle parameters are:

[0112]

[0113] like Figure 1 Simulation model diagram, the inputs are three-axis temperature (H), two-axis temperature (T), speed (U), and the outputs include temperature, braking force, and vehicle braking deceleration distribution coefficient, etc. Figure 2 It is the design flow chart of drum brake force observer.

[0114] In order to verify the accuracy of the model, a braking test was conducted. The initial braking speed was 78km / h and the final speed was 58km / h. The simulation and actual speeds were as follows: Figure 5 , with a maximum error of 3%. The verification results show that the established model can truly reflect the speed change characteristics of the vehicle during braking. It proves that the observer based on the material properties of the drum brake can be used to observe the actual output braking force during continuous braking during a long downhill section when the speed and brake drum temperature are measured. For this purpose, a simulation calculation of a long downhill section was carried out. Figure 3 and Figure 4To measure the temperature variation curve of the brake drum of two axes and three cycles, the calculation results are as follows Figure 6 , Figure 7 and Figure 8 The change trend of the braking force of the second and third axes is consistent with the action of the brake pedal. The accuracy of the observer is verified by the change of braking deceleration using the established dynamic model of a heavy-duty truck going downhill.

Claims

1. A drum brake braking force detection method, characterized in that: The following steps are involved: S1, based on the heat transfer and tribology theory, establish the drum brake temperature model; S2. Establishing the relationship between the braking force work and the temperature during the braking process of the drum brake according to the drum brake temperature model, deriving the relationship between the braking force work and the vehicle speed and the brake temperature, and calculating the drum brake braking force according to the vehicle speed and the brake temperature; The expression of the temperature change of the friction working surface with time during the braking process of the drum brake is specifically expressed as: λ i is the thermal conductivity of the brake material; b i is the effective thickness of the friction pair component involved in heat absorption, in m; τ W is the ratio of friction work to braking work, τ W =2τ-τ 2 , τ N is the time ratio, F oi is the Fourier number at point i of the drum brake; φ vi is the heat influence coefficient; S ai is the actual friction area during braking, in m 2 ; t T is the continuous braking time, in seconds; F oi is the Fourier number of point i on the drum brake; a Tni is the thermal field distribution coefficient; W τn is the braking work, the unit is J; Assuming the initial temperature of the brake is T, the actual temperature change during braking is expressed as: T Z =T+T * Convert the drum brake temperature change prediction model into a braking force prediction model; Using calculus, the braking work W τn It is expressed as follows: W τn =F b *S=∫F b ds F b Provides braking force for the brakes; Convert the braking work into an integral over time: The relationship between the braking force of the drum brake and the speed and temperature during braking is expressed as: v is the data of the heavy truck speed changing with time during braking.

2. A drum brake braking force detection method according to claim 1, characterized in that: The longitudinal dynamic equation of a car driving downhill is established as: F t +F i =F f +F w +F j Among them, F t The driving force of the vehicle, T tq is the engine torque, i g is the transmission ratio of the transmission, i0 is the transmission ratio of the main reducer, η T is the mechanical efficiency of the transmission system, r is the wheel radius; F i is the component of gravity down the ramp, F i =Gsinα; F f is the rolling resistance, F f =Gfcosα, f is the rolling resistance coefficient; F w is the air resistance, C D is the air resistance coefficient, A is the frontal area of ​​the car, u a is the vehicle speed; F j is the acceleration resistance, δ is the rotation mass conversion factor, m is the vehicle mass, is the vehicle acceleration.

3. A drum brake braking force detection method according to claim 2, characterized in that: The dynamic equation of a heavy truck going downhill is expressed as: F i =F f +F w +F j +F b +F b_con Among them, F b is the braking force, F b_con Provides engine braking force.

4. A drum brake braking force detection system, characterized in that: include: Model building module, used to build and store drum brake temperature model based on brake material properties, heat transfer and tribology theory; The temperature detection module is used to collect the temperature change value during the braking process of the drum brake and transmit the temperature change value to the braking force calculation module; The speed detection module is used to collect the vehicle's driving speed and transmit the vehicle's driving speed to the braking force calculation module; A braking force calculation module is used to establish the relationship between the braking force work and the temperature during the braking process of the drum brake according to the drum brake temperature model, and calculate the braking force of the drum brake according to the vehicle speed and the brake temperature; The expression of the temperature change of the friction working surface with time during the braking process of the drum brake is specifically expressed as: λ i is the thermal conductivity of the brake material; b i is the effective thickness of the friction pair component involved in heat absorption, in m; τ W is the ratio of friction work to braking work, τ W =2τ-τ 2 , τ N is the time ratio, F oi is the Fourier number at point i of the drum brake; φ vi is the heat influence coefficient; S ai is the actual friction area during braking, in m 2 ; t T is the continuous braking time, in seconds; F oi is the Fourier number of point i on the drum brake; a Tni is the thermal field distribution coefficient; W Tn is the braking work, the unit is J; Assuming the initial temperature of the brake is T, the actual temperature change during braking is expressed as: T Z =T+T * Convert the drum brake temperature change prediction model into a braking force prediction model; Using calculus, the braking work W τn It is expressed as follows: W τn =F b *S=∫F b ds F b Provides braking force for the brakes; Convert the braking work into an integral over time: The relationship between the braking force of the drum brake and the speed and temperature during braking is expressed as: v is the data of the heavy truck speed changing with time during braking.

5. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 3 are implemented.

6. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 3 are implemented.

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