Brake pressure estimation method based on time-frequency domain characteristics and redundant brake system

Abstract

The invention relates to a brake pressure estimation method based on time-frequency domain characteristics and a redundant brake system. The method comprises the following steps: estimating the rotating speed of a motor based on the time-frequency characteristics; pressure estimation based on the motor current; pressure estimation based on the motor speed; pressure estimation based on multi-method fusion; the system comprises a main braking system, an energy accumulator, a two-way one-way valve, a normally open valve, a pressure release valve, a pump, an oil can and an ECU (Electronic Control Unit), the main braking system is connected with the braking mechanism; the normally-open valve, the energy accumulator and the pump are connected in series and then connected with the pressure release valve in parallel to form an energy accumulator working oil way, one end of the energy accumulator working oil way is connected with the oil can, and the other end is connected with the two-way one-way valve. Two inlets of the two-way one-way valve are respectively connected with an energy accumulator working oil path and a main braking system, and an outlet is connected with a brake wheel cylinder; and the redundant braking system is controlled to be in three working states of normal braking, redundant braking applying and redundant braking removing through the ECU. The method and the system are easy to implement, small in application limitation, wide in application range and high in reliability and safety.

Description

Technical Field

[0001] The present invention relates to the field of braking technology, and in particular to a braking pressure estimation method based on time-frequency domain characteristics and a redundant braking system. Background Art

[0002] Braking system redundancy is a key feature of autonomous vehicles, preventing braking failure due to failure of one braking system. In addition to providing redundant execution capabilities (i.e., brake application capabilities), redundant braking systems also require redundant sensing capabilities (primarily pressure sensing). However, the probability of a redundant braking system being triggered is very low, and equipping the system with a separate pressure sensor would significantly increase system cost, making it extremely uneconomical. Furthermore, the primary function of a redundant braking system is to ensure vehicle safety and provide braking force, which may not require precise control of the braking system. Therefore, using an estimation algorithm to achieve redundant pressure sensing is an effective method for improving safety and reducing costs. Furthermore, by using different sensing methods, redundancy can also be achieved between the sensing methods. Patent CN117786852A discloses a master cylinder pressure estimation method for an electro-hydraulic brake system based on an EKF algorithm. This method proposes estimating pressure based on vehicle kinematics (the main logic of the method is that greater brake pressure indicates greater vehicle deceleration, or greater brake pressure on a particular wheel indicates greater wheel slip). This method integrates vehicle dynamics information with actuator operating instructions to obtain a more critical pressure estimate. Such methods rely on vehicle dynamics information and cannot be used once the vehicle is stationary or the vehicle dynamics information is unavailable. Summary of the Invention

[0003] The object of the present invention is to provide a brake pressure estimation method and a redundant brake system based on time-frequency domain characteristics, which are easy to implement, have few application restrictions, a wide range of applications, and high reliability and safety.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a brake pressure estimation method based on time-frequency domain characteristics, comprising the following steps:

[0005] Step A: Motor speed estimation based on time-frequency characteristics:

[0006] A1) Set the motor current sampling frequency and use FIR filter to filter the current signal;

[0007] A2) Find the extreme point in the filtered current signal and record the amplitude and occurrence time of the extreme point;

[0008] A3) Eliminate misidentified peak points;

[0009] A4) calculating the original speed of the motor based on the time interval between adjacent peak points;

[0010] A5) Perform phase compensation on the calculated original speed to correct the phase difference introduced by current filtering;

[0011] A6) performing fixed-period linear interpolation on the non-uniformly sampled motor speed to obtain a uniformly sampled estimated speed;

[0012] Step B: Pressure estimation based on motor current:

[0013] B1) using the current signal filtered in step A, calculating the extreme value point of the current;

[0014] B2) Based on the balance between the motor output torque and the load torque, combined with the motor torque coefficient, pump outlet pressure, pump area and pump resistance, calculate the estimated pressure value

[0015] Step C: Pressure estimation based on motor speed:

[0016] C1) calculating the total output power of the motor within a certain period, wherein the total output power is determined based on the motor output efficiency, input voltage, collected current, and motor internal resistance;

[0017] C2) calculating the pressure output power within the same cycle, wherein the pressure output power is determined based on the pump displacement coefficient and the motor speed estimated in step A;

[0018] C3) Calculate the estimated pressure value based on the balance between the total power output of the motor and the pressure output power

[0019] Step D: Pressure estimation based on multi-method fusion:

[0020] Introducing at least The weights of the pressure estimates are calculated by fuzzy function, and then the final pressure estimate is obtained by weighted fusion.

[0021] Furthermore, in step A, for a system in which the plunger pump operates N times per one rotation, the calculated rotation speed needs to be divided by N.

[0022] Furthermore, in step A1), the sampling frequency is higher than the motor rotation frequency f m More than twice the pass frequency of the filter f pass Higher than the motor rotation frequency f m , cutoff frequency f stop Higher than the passing frequency f pass ;

[0023] In step A2), the sampling point where the current value is greater than the signals on its left and right sides is recorded as the extreme point;

[0024] In step A3), if the amplitude of a peak point changes suddenly compared with the amplitude of the previously identified peak point, or the interval between a peak point and the previous peak point changes suddenly compared with the previous peak interval, the peak point is determined to be a misidentified peak point and is removed.

[0025] Furthermore, the specific implementation method of step D is:

[0026] D1) Setting a fuzzy function, wherein the fuzzy function includes the following logic:

[0027] D101) Calculate the i-th pressure estimate Distance D to other pressure estimates i :

[0028]

[0029] in, represents the jth pressure estimate, and n is the number of pressure estimates;

[0030] Then define the i-th pressure estimate The first weight is: Distance D i The larger the first weight F a,i The lower;

[0031] D102) Calculate the signal standard deviation σ within a certain period of time i :

[0032]

[0033] Among them, N represents the total number of sampling points within the set time. represents the estimated pressure value at time τ before the current time t;

[0034] Then define the i-th pressure estimate The second weight is: Standard deviation σ i The larger the second weight F b,i The lower;

[0035] D103) If the deviation between the current pressure estimate and the previous pressure estimate is greater than the preset maximum deviation, then define the i-th pressure estimate The third weight is F c,i =0.5, otherwise the third weight is the normal record F c,i =1;

[0036] D104) If the pressure estimate If the preset maximum limit is exceeded, the i-th pressure estimate is defined The fourth weight is F d,i =1, if there is no braking status Or the brake is already in place If the value is less than the preset threshold, the fourth power is reset to F. d,i =0.5;

[0037] D2) Calculate the i-th pressure estimate The total weight F i :

[0038] F i =K a F a,i +K b F b,i +K c F c,i +K d F d,i

[0039] Among them, K a , K b , K c , K d is the preset weight coefficient;

[0040] D3) Obtain the final pressure estimate by weighted fusion of multiple estimated pressure values:

[0041]

[0042] in, It represents the final pressure estimation value obtained by weighted fusion of n pressure estimation values ​​obtained by n different pressure estimation methods.

[0043] The present invention also provides a redundant braking system, comprising a main braking system, an accumulator, a two-way one-way valve, a normally open valve, a pressure relief valve, a pump, an oil pot and an ECU control unit; the main braking system is connected to a braking mechanism; the normally open valve, accumulator and pump are connected in series and in parallel with the pressure relief valve to form an accumulator working oil circuit, one end of the accumulator working oil circuit is connected to the oil pot, and the other end is connected to the two-way one-way valve; the two inlets of the two-way one-way valve are respectively connected to the accumulator working oil circuit and the main braking system, and the outlet is connected to the brake wheel cylinder; springs are provided on both sides of the valve core of the two-way one-way valve, and the springs are configured such that when the pressure difference between the outlet and any inlet is less than a preset value, the valve core is in a middle position and neither inlet is closed; when the pressure difference between the outlet and one inlet is greater than the preset value, the valve core moves toward the other inlet under the action of the pressure difference and thereby closes the corresponding inlet;

[0044] The redundant braking system is controlled by the ECU control unit in the following three working states:

[0045] 1) Normal braking state: At this time, the normally open valve is energized and the pressure relief valve is de-energized. If the brake mechanism is activated at this time, the high-pressure oil generated by the main brake system pushes the valve core of the two-way check valve toward the accumulator working oil circuit, closing the inlet connected to the accumulator working oil circuit. At this time, high-pressure oil enters the brake cylinder to brake. In the normal braking state, the ECU control unit intermittently determines whether the pressure in the accumulator is sufficient. If the pressure is insufficient, it controls the pump to increase the pressure in the accumulator.

[0046] 2) Redundant brake application state: When a vehicle malfunctions and the normal braking state fails, the ECU controls the redundant brake system to switch to the redundant brake application state. At this time, the normally open valve and the pressure relief valve are both de-energized. The high-pressure oil in the accumulator pushes the valve core of the two-way check valve toward the main brake system, closing the inlet connecting to the main brake system. At this time, the high-pressure oil enters the brake cylinder to apply the brake.

[0047] 3) Redundant brake release state: When the vehicle completes braking, the ECU controls the redundant brake system to switch to the redundant brake release state; at this time, the normally closed valve is controlled to be intermittently energized to prevent the pressure difference between the outlet and inlet of the two-way one-way valve from being too large and closing the valve core. At this time, high-pressure oil flows to the oil tank through the pressure relief valve; when the redundant brake release is completed, the ECU controls the redundant brake system to switch to the normal braking state.

[0048] Furthermore, under normal braking conditions, when the brake mechanism is actuated to brake the wheel cylinder and then released, the pressure of the brake mechanism will not drop suddenly at this time. As long as the reduced oil pressure is still greater than the preset value, the high-pressure oil generated by the main brake system can return to the master brake cylinder of the main brake system, thereby releasing the brake.

[0049] Furthermore, the pump is driven by a motor.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. The present invention can be applied to most occasions without adding pressure sensors, effectively reducing costs. In systems with existing pressure sensors, the present method can also be used to estimate pressure, which can serve as a redundant method for obtaining pressure. This method can be used to diagnose pressure sensor failures and can also provide a reference value for pressure when a pressure sensor fails.

[0052] 2. The redundant braking system based on the method proposed in the present invention can realize automatic braking after power failure, which greatly improves the safety of both manned and unmanned vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a flow chart of a brake pressure estimation method based on time-frequency domain characteristics provided by an embodiment of the present invention;

[0054] Figure 2 Schematic diagram of the structure of a redundant braking system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0056] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0057] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0058] like Figure 1 As shown, this embodiment provides a brake pressure estimation method based on time-frequency domain characteristics, and its specific implementation steps are as follows.

[0059] Step A: Motor speed estimation based on time-frequency characteristics

[0060] This method is mainly used to estimate the speed of a pump driven by a brushless motor. Since the operation of a plunger pump has periodic characteristics, taking a system in which the plunger pump works reciprocatingly once the motor rotates one circle as an example, it performs oil suction and oil pumping actions once within a circle. When pumping oil, the load pressure is large, and the corresponding motor current is also large. Therefore, the system speed is indirectly calculated through the periodic characteristics of the motor current. The main steps are as follows.

[0061] A1) Set the motor current sampling frequency and use FIR filter to filter the current signal.

[0062] Specifically, the sampling frequency of the motor current is set to be higher than the motor rotation frequency f m More than twice the current, usually the motor speed is below 6000rpm (ie the frequency is 100Hz), set the current sampling frequency to f s =1000Hz, the FIR (finite impulse response filter) filter is used to filter the current signal, and the filter pass frequency f pass Slightly higher than the motor rotation frequency f m , cutoff frequency f stop Slightly higher than the pass frequency, here the pass frequency and cutoff frequency are set to 125Hz and 130Hz respectively.

[0063] A2) Find the maximum point (or minimum point) in the filtered current signal and record the amplitude and occurrence time of the maximum point (or minimum point).

[0064] Specifically, the sampling point where the current value is greater than (or less than) the signal on its left and right sides is recorded as the maximum point (or minimum point), and the amplitude and occurrence event of the maximum point are recorded.

[0065] A3) Eliminate misidentified peak points.

[0066] Specifically, points mistakenly identified as peaks are eliminated using predefined logical rules, including: ① a peak point's amplitude undergoes a sudden change compared to the amplitude of a previously identified peak point; ② the interval between a peak point and the previous peak point undergoes a sudden change compared to the interval between the previous peaks. If either of these two rules is met, the peak point is considered a mistakenly identified peak point and should be eliminated.

[0067] A4) Calculate the original speed of the motor based on the time interval between adjacent peak points.

[0068] Calculate the original rotation speed and the time interval T between two adjacent peaks s (t), after obtaining the time interval, the motor speed can be calculated as

[0069] A5) performs phase compensation on the calculated original speed to correct the phase difference introduced by the current filtering.

[0070] Phase compensation is used for current filtering, which will introduce phase difference. Therefore, the speed obtained in the previous step should be corrected by phase compensation. The corrected speed is ω6(t)=ω5(tt pha ), where t pha is the phase difference, which can be obtained through testing.

[0071] A6) performing fixed-period linear interpolation on the non-uniformly sampled motor speed to obtain a uniformly sampled estimated speed.

[0072] The signal is resampled to handle the non-uniform sampling of the estimated speed, which is triggered by events. That is, the speed is calculated only when the current peak occurs. Considering that the motor speed does not change suddenly, a fixed-period linear interpolation is performed on the non-uniformly sampled motor speed to obtain the uniformly sampled estimated speed ω.

[0073] For a system where the plunger pump operates N times per rotation, the calculated speed must be divided by N.

[0074] Step B: Pressure estimation based on motor current (hereinafter referred to as pressure estimation method 1)

[0075] B1) Using the current signal filtered in step A, calculate the current minimum point according to the same logic, denoted as I m .

[0076] B2) Based on the balance between the motor output torque and the load torque, combined with the motor torque coefficient, pump outlet pressure, pump area and plunger pump resistance, calculate the estimated pressure value

[0077] As the motor current reaches its minimum point, the motor torque increases to pump oil out. At this time, the motor speed remains essentially unchanged. The motor output torque is K t I m (K t is the torque coefficient of the motor), the load on the motor is P p S p +f p (where P p is the pump outlet pressure, S p is the pump action area, f p is the resistance of the plunger pump, including friction resistance and damping force), so the pressure can be estimated as P p =(K t I m -f p ) / S p .

[0078] Step C: Pressure estimation based on motor speed (hereinafter referred to as pressure estimation method 2)

[0079] The estimation method based on motor speed mainly realizes pressure estimation by balancing the motor power output and pressure output power.

[0080] C1) Calculate the total output power of the motor within a certain period, which is determined based on the motor output efficiency, input voltage, collected current and motor internal resistance. The specific calculation formula is:

[0081]

[0082] Where η e is the output efficiency of the motor, U is the input voltage of the motor (in the vehicle, it is the battery voltage, usually 12V or 24V, which is a known quantity), I e is the collected current of the motor, R e is the internal resistance of the motor.

[0083] C2) Calculate the pressure output power within the same cycle, where the pressure output power is determined based on the pump displacement coefficient and the motor speed estimated in step A. The specific calculation formula is:

[0084] W p=∫(P p ωK p )dt

[0085] Where K p The pump displacement coefficient represents the conversion relationship between motor speed and pump displacement, where ω is the motor speed (estimated using the aforementioned method).

[0086] C3) Calculate the estimated pressure value based on the balance between the total power output of the motor and the pressure output power

[0087] The motor power output and pressure output power should be balanced, that is, W p =η p W e , that is, the motor works according to the efficiency η p (is a known parameter) is converted into pressure output work, then the pressure is approximately calculated as Repeat the above steps at regular intervals to estimate the pressure.

[0088] Step D: Pressure estimation based on multi-method fusion (achieving high redundancy of pressure)

[0089] Introducing at least The weights of the pressure estimates are calculated by fuzzy function, and then the final pressure estimate is obtained by weighted fusion.

[0090] The pressure estimation value obtained by pressure estimation method 1 is The pressure estimation value obtained by pressure estimation method 2 is The pressure estimate obtained based on other methods (such as dynamic methods) is recorded as This method presents a method for fusing multiple pressure signals to obtain a pressure estimate.

[0091] D1) Setting a fuzzy function, wherein the fuzzy function includes the following logic:

[0092] D101) If a value is far away from other values, then the value has a low weight. The specific processing method is as follows:

[0093] Calculate the i-th pressure estimate Distance D to other pressure estimates i :

[0094]

[0095] in, represents the jth pressure estimate, and n is the number of pressure estimates.

[0096] Then define the i-th pressure estimate The first weight is: Distance D i The larger the first weight F a,i The lower.

[0097] D102) If the signal noise of a certain value is large, the weight of this value is low. The specific processing method is as follows:

[0098] Calculate the signal standard deviation σ within a certain period of time i :

[0099]

[0100] Among them, N represents the total number of sampling points within the set time. It represents the estimated pressure value at time τ before the current time t.

[0101] Then define the i-th pressure estimate The second weight is: Standard deviation σ i The larger the second weight F b,i The lower.

[0102] D103) If a value suddenly exceeds the threshold, the weight of this value is low. The specific processing method is as follows:

[0103] If the deviation between the current pressure estimate and the previous pressure estimate is greater than the preset maximum deviation, the i-th pressure estimate is defined as The third weight is F c,i =0.5, otherwise the third weight is the normal record F c,i =1.

[0104] D104) If a value exceeds the limit, the weight of the value is low, and the specific processing method is as follows:

[0105] If the pressure estimate If the preset maximum limit is exceeded, the i-th pressure estimate is defined The fourth weight is F d,i =1, if there is no braking status Or the brake is already in place If the value is less than the preset threshold, the fourth power is reset to F. d,i =0.5.

[0106] D2) Calculate the i-th pressure estimate The total weight F i :

[0107] F i =K a F a,i +K b F b,i +K c Fc,i +K d F d,i

[0108] Among them, K a , K b , K c , K d is the preset weight coefficient.

[0109] D3) Obtain the final pressure estimate by weighted fusion of multiple estimated pressure values:

[0110]

[0111] in, It represents the final pressure estimation value obtained by weighted fusion of n pressure estimation values ​​obtained by n different pressure estimation methods.

[0112] Based on the above pressure estimation method, the estimated value of the pressure can be obtained without a pressure sensor, which is very suitable for redundant braking applications. To this end, this embodiment proposes a redundant braking system. Figure 2 As shown, the redundant braking system includes a main braking system 1, an accumulator 2, a two-way check valve 3, a normally open valve 4, a pressure relief valve 5, a pump 6, an oil tank 7, and an ECU control unit. The main braking system 1 is connected to a braking mechanism (in this embodiment, a brake pedal 8, but may also be other braking sources capable of braking the vehicle). The normally open valve 4, accumulator 2, and pump 6 are connected in series and in parallel with the pressure relief valve 5 to form an accumulator working oil circuit. One end of the accumulator working oil circuit is connected to the oil tank 7, and the other end is connected to the two-way check valve 3. The two inlets of the two-way check valve 3 are respectively connected to the accumulator working oil circuit and the main braking system 1, and the outlet is connected to the brake wheel cylinder 9. Springs are provided on both sides of the valve core of the two-way check valve 3. The springs are configured such that when the pressure differential between the outlet and either inlet is less than a preset value, the valve core is in an intermediate position and does not close either inlet. When the pressure differential between the outlet and one inlet is greater than a preset value, the valve core moves toward the other inlet under the action of the pressure differential, thereby closing the corresponding inlet.

[0113] The redundant braking system is controlled by the ECU control unit in the following three working states:

[0114] 1) Normal braking state: At this time, the normally open valve 4 is controlled to be energized and the pressure relief valve 5 is de-energized; if the pedal 8 is pressed at this time, the high-pressure oil generated by the main brake system will push the valve core of the two-way check valve 3 to the side of the accumulator working oil circuit, closing the inlet connected to the accumulator working oil circuit. At this time, the high-pressure oil enters the brake wheel cylinder 9 to form braking; when the pedal 8 is released, since the pressure of the brake pedal 8 will not drop suddenly at this time, as long as the reduced oil pressure is still greater than the preset value, the brake fluid can return to the brake master cylinder 10 of the main brake system 1, and the brake is released.

[0115] When the pedal is pressed or not, the ECU control unit intermittently determines whether the pressure in the accumulator 2 (estimated by the above pressure estimation method) is sufficient. If the pressure is insufficient, the pump 6 is controlled to work to increase the pressure in the accumulator 2.

[0116] 2) Redundant brake application state: When the vehicle fails and the normal braking state fails, the ECU controls the redundant brake system to switch to the redundant brake application state; at this time, the normally open valve 4 and the pressure relief valve 5 are both de-energized, and the high-pressure oil in the accumulator 2 pushes the valve core of the two-way check valve 3 to the side of the main brake system, closing the inlet connected to the main brake system 1. At this time, the high-pressure oil enters the brake wheel cylinder 9 to form braking.

[0117] 3) Redundant brake release state: When the vehicle completes braking, the ECU controls the redundant brake system to switch to the redundant brake release state; at this time, the normally open valve 4 is controlled to be intermittently energized to prevent the pressure difference between the outlet and the two inlets of the two-way check valve 3 from being too large and closing the valve core. At this time, the high-pressure oil flows to the oil tank 7 through the pressure relief valve 5; when the redundant brake release is completed, the ECU controls the redundant brake system to switch to the normal braking state.

[0118] In this embodiment, the pump 6 is driven by a motor whose rotation speed is estimated by the above-mentioned pressure estimation method.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A brake pressure estimation method based on time-frequency domain characteristics, characterized in that: The following steps are involved: Step A: Motor speed estimation based on time-frequency characteristics: A1) Set the motor current sampling frequency and use FIR filter to filter the current signal; A2) Find the extreme point in the filtered current signal and record the amplitude and occurrence time of the extreme point; A3) Eliminate misidentified peak points; A4) calculating the original speed of the motor based on the time interval between adjacent peak points; A5) Perform phase compensation on the calculated original speed to correct the phase difference introduced by current filtering; A6) performing fixed-period linear interpolation on the non-uniformly sampled motor speed to obtain a uniformly sampled estimated speed; Step B: Pressure estimation based on motor current: B1) using the current signal filtered in step A, calculating the extreme value point of the current; B2) Based on the balance between the motor output torque and the load torque, combined with the motor torque coefficient, pump outlet pressure, pump area and pump resistance, calculate the estimated pressure value Step C: Pressure estimation based on motor speed: C1) calculating the total output power of the motor within a certain period, wherein the total output power is determined based on the motor output efficiency, input voltage, collected current, and motor internal resistance; C2) calculating the pressure output power within the same cycle, wherein the pressure output power is determined based on the pump displacement coefficient and the motor speed estimated in step A; C3) Calculate the estimated pressure value based on the balance between the total power output of the motor and the pressure output power Step D: Pressure estimation based on multi-method fusion: Introducing at least The weights of the pressure estimates are calculated by fuzzy function, and then the final pressure estimate is obtained by weighted fusion.

2. The brake pressure estimation method based on time-frequency domain characteristics according to claim 1, characterized in that: In step A, for a system where the plunger pump operates N times per rotation, the calculated speed must be divided by N.

3. The brake pressure estimation method based on time-frequency domain characteristics according to claim 1, characterized in that: In step A1), the sampling frequency is higher than the motor rotation frequency f m More than twice the pass frequency of the filter f pass Higher than the motor rotation frequency f m , cutoff frequency f stop Higher than the passing frequency f pass ; In step A2), the sampling point where the current value is greater than the signals on its left and right sides is recorded as the extreme point; In step A3), if the amplitude of a peak point changes suddenly compared with the amplitude of the previously identified peak point, or the interval between a peak point and the previous peak point changes suddenly compared with the previous peak interval, the peak point is determined to be a misidentified peak point and is removed.

4. The brake pressure estimation method based on time-frequency domain characteristics according to claim 1, characterized in that: The specific implementation method of step D is: D1) Setting a fuzzy function, wherein the fuzzy function includes the following logic: D101) Calculate the i-th pressure estimate Distance D to other pressure estimates i : in, represents the jth pressure estimate, and n is the number of pressure estimates; Then define the i-th pressure estimate The first weight is: Distance D i The larger the first weight F a,i The lower; D102) Calculate the signal standard deviation σ within a certain period of time i : Among them, N represents the total number of sampling points within the set time. represents the estimated pressure value at time τ before the current time t; Then define the i-th pressure estimate The second weight is: Standard deviation σ i The larger the second weight F b,i The lower; D103) If the deviation between the current pressure estimate and the previous pressure estimate is greater than the preset maximum deviation, then define the i-th pressure estimate The third weight is F c,i =0.5, otherwise the third weight is the normal record F c,i =1; D104) If the pressure estimate If the preset maximum limit is exceeded, the i-th pressure estimate is defined The fourth weight is F d,i =1, if there is no braking status Or the brake is already in place If the value is less than the preset threshold, the fourth power is reset to F. d,i =0.5; D2) Calculate the i-th pressure estimate The total weight F i : F i =K a F a,i +K b F b,i +K c F c,i +K d F d,i Among them, K a , K b , K c , K d is the preset weight coefficient; D3) Obtain the final pressure estimate by weighted fusion of multiple estimated pressure values: in, It represents the final pressure estimation value obtained by weighted fusion of n pressure estimation values ​​obtained by n different pressure estimation methods.

5. A redundant braking system, characterized in that: The accumulator comprises a main brake system, an accumulator, a two-way check valve, a normally open valve, a pressure relief valve, a pump, an oil tank and an ECU control unit; the main brake system is connected to the brake mechanism; the normally open valve, accumulator and pump are connected in series and in parallel with the pressure relief valve to form an accumulator working oil circuit, one end of which is connected to the oil tank and the other end is connected to the two-way check valve; the two inlets of the two-way check valve are respectively connected to the accumulator working oil circuit and the main brake system, and the outlet is connected to the brake wheel cylinder; springs are provided on both sides of the valve core of the two-way check valve, and the springs are configured such that when the pressure difference between the outlet and any inlet is less than a preset value, the valve core is in the middle position and neither inlet is closed; when the pressure difference between the outlet and one inlet is greater than the preset value, the valve core moves toward the other inlet under the action of the pressure difference and thus closes the corresponding inlet; The redundant braking system is controlled by the ECU control unit in the following three working states: 1) Normal braking state: At this time, the normally open valve is energized and the pressure relief valve is de-energized. If the brake mechanism is activated at this time, the high-pressure oil generated by the main brake system pushes the valve core of the two-way check valve toward the accumulator working oil circuit, closing the inlet connected to the accumulator working oil circuit. At this time, high-pressure oil enters the brake cylinder to brake. In the normal braking state, the ECU control unit intermittently determines whether the pressure in the accumulator is sufficient. If the pressure is insufficient, it controls the pump to increase the pressure in the accumulator. 2) Redundant brake application state: When a vehicle malfunctions and the normal braking state fails, the ECU controls the redundant brake system to switch to the redundant brake application state. At this time, the normally open valve and the pressure relief valve are both de-energized. The high-pressure oil in the accumulator pushes the valve core of the two-way check valve toward the main brake system, closing the inlet connecting to the main brake system. At this time, the high-pressure oil enters the brake cylinder to apply the brake. 3) Redundant brake release state: When the vehicle completes braking, the ECU controls the redundant brake system to switch to the redundant brake release state; at this time, the normally closed valve is controlled to be intermittently energized to prevent the pressure difference between the outlet and inlet of the two-way one-way valve from being too large and closing the valve core. At this time, high-pressure oil flows to the oil tank through the pressure relief valve; when the redundant brake release is completed, the ECU controls the redundant brake system to switch to the normal braking state.

6. The redundant braking system according to claim 5, characterized in that Under normal braking conditions, when the brake mechanism is actuated to brake the wheel cylinder and then released, the pressure of the brake mechanism will not drop suddenly at this time. As long as the reduced oil pressure is still greater than the preset value, the high-pressure oil generated by the main brake system can return to the master brake cylinder of the main brake system, thereby releasing the brake.

7. The redundant braking system according to claim 5, characterized in that: The pump is driven by an electric motor.

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