A method for diagnosing switch faults in commercial vehicles and a switch circuit.

Abstract

This invention relates to switch diagnostic technology and discloses a switch fault diagnosis method and switch circuit for commercial vehicles. The switch circuit includes a power supply unit, a switch unit, a protection unit, and a main control unit. The power supply unit provides power to the main control unit. The switch unit includes a hill start assist switch, a parking switch, a release switch, and an autohold switch. The protection unit provides current limiting protection for the switch unit, and the main control unit receives the switch signals from the switch unit. The circuit designed in this invention is compatible with both pull-up resistor switch signals and pull-down resistor switch signals, has diagnostic functions, and meets the switch signal processing circuit requirements of GB / T28046.2-2019. The switch circuit designed in this invention has low hardware cost, a simple sampling circuit, and reduces the consumption of microcontroller port resources.

Description

Technical Field

[0001] This invention relates to switch diagnostic technology, and more particularly to a method and circuit for diagnosing switch faults in commercial vehicles. Background Technology

[0002] Commercial vehicles operate in harsh environments, and the signal input connectors are exposed to air for extended periods, causing the outer casing to gradually age and break, and the metal connection points to corrode. This can lead to short circuits between connection points, or open circuits caused by wear and tear on the connecting wires. These conditions can easily result in open circuits or short circuits to the power supply in the AD signal input circuit.

[0003] For example, in the prior art, patent document 1: CN201920173924.X, a control switch circuit for an automotive electronic parking system EPB; patent document 2: CN201410107102.3; the prior art cannot meet the test requirements of Section 4.10 "Short Circuit Protection" of "GB / T28046.2-2019 Environmental Conditions and Tests for Electrical and Electronic Equipment of Road Vehicles Part 2: Electrical Loads"; and cannot be compatible with both signal processing at the same time. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies in meeting the test requirements outlined in Section 4.10, "Short Circuit Protection," of GB / T28046.2-2019 "Environmental Conditions and Tests for Electrical and Electronic Equipment of Road Vehicles - Part 2: Electrical Loads," and in the inability to simultaneously handle two signal processing methods. It provides a method for diagnosing switch faults in commercial vehicles and a switch circuit.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A switching circuit for a commercial vehicle includes a power supply unit, a switching unit, a protection unit, and a main control unit; the power supply unit provides power to the main control unit; its protection unit provides current limiting protection for the switching unit; and the main control unit receives the switching signals from the switching unit.

[0007] The designed switching circuit has low hardware cost and is compatible with different sampling circuit modes, making it highly adaptable.

[0008] Preferably, the main control unit includes EBS main control unit MCU1 and EPB main control unit MCU2.

[0009] Preferably, the switch unit includes a hill start assist switch, a parking switch, a release switch, and an autohold switch;

[0010] The protection unit includes a power supply protection unit, a ramp assist switch protection unit, a parking switch protection unit, a release switch protection unit, and an autohold switch protection unit; the power supply unit is connected to the EBS main control unit MCU1 through the power supply protection unit; the ramp assist switch is connected to the EBS main control unit MCU1 through the ramp assist switch protection unit.

[0011] The parking switch is connected to the EPB main control unit MCU2 via the parking switch protection unit;

[0012] The release switch is connected to the EPB main control unit MCU2 via the release switch protection unit;

[0013] The autohold switch is connected to the EPB main control unit MCU2 via the autohold switch protection unit.

[0014] Preferably, the hill start assist switch and parking switch are pull-up resistor switches; the release switch and autohold switch are pull-down resistor switches.

[0015] Preferably, the power protection unit, the ramp assist switch protection unit, the parking switch protection unit, the release switch protection unit, and the autohold switch protection unit all include a current limiting unit, a voltage divider unit, and a filtering unit; the switch current signal is current limited by the current limiting unit, the current-limited voltage signal is voltage divided by the voltage divider unit, and then filtered by the filtering unit; and the filtered voltage signal is transmitted to the main control unit.

[0016] To address the aforementioned technical problems, this invention also provides a method for diagnosing switch faults in commercial vehicles. The switch states include a normal inactive state, a normal active state, a fault open circuit state, a fault power supply short circuit state, and a fault ground short circuit state. The method is characterized by including a switch circuit and comprising:

[0017] Obtain the voltage values ​​at the input terminals of the main control unit MCU1, namely V0a and V1a;

[0018] Obtain the voltage V2 output from the ramp assist start switch and the voltage VDD from the power supply unit; and transmit VDD to the CAN bus;

[0019] Obtain the voltages for the normal invalid state, normal valid state, fault open circuit state, and fault power supply short circuit state, which are respectively V21 for normal invalid state, V22 for normal valid state, V23 for fault open circuit state, and V24 for fault power supply short circuit state.

[0020] The switch status is determined based on the voltage V24 of the normal invalid state V21, the normal valid state V22, the fault open circuit state V23, and the fault power supply short circuit state, as well as the voltage acquisition error value.

[0021] Preferably, the voltage VDD of the power supply unit is calculated using the symbol V0a from the real-time voltage value acquired by the AD acquisition port AD0 of the main control unit MCU1.

[0022] Preferably, the voltage values ​​of the voltages V24 in the normal invalid state V21, normal valid state V22, fault open circuit state V23, and fault power supply short circuit state are obtained by the voltage VDD of the power supply unit.

[0023] This invention, by adopting the above technical solutions, has significant technical effects:

[0024] I. The switching circuit designed in this invention has low design cost and is compatible with sampling circuits of different modes, making it highly applicable.

[0025] Second, the circuit designed in this invention can detect the switch status in real time and can promptly detect switch malfunctions, thus ensuring good safety.

[0026] Third, the circuit designed in this invention is compatible with both pull-up resistor switch signals and pull-down resistor switch signals, and also has diagnostic functions. It also meets the test requirements of Section 4.10 "Short Circuit Protection" of "GB / T28046.2-2019 Environmental Conditions and Tests for Electrical and Electronic Equipment of Road Vehicles Part 2: Electrical Loads". In addition, the hardware cost of the switch circuit design is low, the sampling circuit is simpler, and the consumption of microcontroller port resources is reduced. Attached Figure Description

[0027] Figure 1 This is the circuit diagram of the present invention.

[0028] Figure 2 This is a flowchart of the present invention.

[0029] Figure 3 This is a flowchart of the present invention. Detailed Implementation

[0030] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Example 1

[0032] A switching circuit for a commercial vehicle includes a power supply unit, a switching unit, a protection unit, and a main control unit; the power supply unit provides power to the main control unit; its protection unit provides current limiting protection for the switching unit; and the main control unit receives the switching signals from the switching unit.

[0033] The designed switching circuit has low design cost and is compatible with sampling circuits of different modes, making it highly applicable.

[0034] The main control unit includes EBS main control unit MCU1 and EPB main control unit MCU2.

[0035] The switch unit includes a hill start assist switch, a parking switch, a release switch, and an autohold switch;

[0036] The protection unit includes a power supply protection unit, a ramp assist switch protection unit, a parking switch protection unit, a release switch protection unit, and an autohold switch protection unit; the power supply unit is connected to the EBS main control unit MCU1 through the power supply protection unit; the ramp assist switch is connected to the EBS main control unit MCU1 through the ramp assist switch protection unit.

[0037] The parking switch is connected to the EPB main control unit MCU2 via the parking switch protection unit;

[0038] The release switch is connected to the EPB main control unit MCU2 via the release switch protection unit;

[0039] The autohold switch is connected to the EPB main control unit MCU2 via the autohold switch protection unit.

[0040] The hill start assist switch and parking switch are pull-up resistor switches; the release switch and autohold are pull-down resistor switches.

[0041] The power protection unit, ramp assist switch protection unit, parking switch protection unit, release switch protection unit, and autohold switch protection unit all include a current limiting unit, a voltage divider unit, and a filtering unit. The switch current signal is current limited by the current limiting unit, the current-limited voltage signal is divided by the voltage divider unit, and then filtered by the filtering unit. The filtered voltage signal is then transmitted to the main control unit.

[0042] In the appendix Figure 1 In the diagram, when harness 2 is short-circuited to ground, the current-limiting effect of R1E prevents the harness from burning out. Harness 3 is the same as harness 2. When harness 5 is short-circuited to the power supply, the current-limiting effect of R3F prevents the harness from burning out. Harness 7 is the same as harness 5. For harness 2, R1A, R1B, and R1C are voltage divider resistors, R1D is a current-limiting resistor, and C1 is a filter capacitor. For harness 3, R2A, R2B, and R2C are voltage divider resistors, R2D is a current-limiting resistor, and C2 is a filter capacitor. For harness 5, R3A, R3B, and R3C are voltage divider resistors, R3D is a current-limiting resistor, and C3 is a filter capacitor. For harness 7, R4A, R4B, and R4C are voltage divider resistors, R4D is a current-limiting resistor, and C4 is a filter capacitor.

[0043] Example 2

[0044] Based on Embodiment 1, this embodiment provides a method for diagnosing switch faults in commercial vehicles. The switch states include a normal inactive state, a normal active state, a fault open circuit state, a fault power supply short circuit state, and a fault ground short circuit state. The method includes a switch circuit and comprises:

[0045] Obtain the voltage values ​​at the input terminals of the main control unit MCU1, namely V0a and V1a;

[0046] Obtain the voltage V2 output from the ramp assist start switch and the voltage VDD from the power supply unit; and transmit VDD to the CAN bus;

[0047] Obtain the voltages for the normal invalid state, normal valid state, fault open circuit state, and fault power supply short circuit state, which are respectively V21 for normal invalid state, V22 for normal valid state, V23 for fault open circuit state, and V24 for fault power supply short circuit state.

[0048] The switch status is determined based on the voltage V24 of the normal invalid state V21, the normal valid state V22, the fault open circuit state V23, and the fault power supply short circuit state, as well as the voltage acquisition error value.

[0049] The voltage VDD of the power supply unit is calculated using the symbol V0a from the real-time voltage value acquired by the AD acquisition port AD0 of the main control unit MCU1.

[0050] The voltage values ​​of V24 in the normal invalid state V21, normal valid state V22, fault open circuit state V23, and fault power supply short circuit state are obtained through the voltage VDD of the power supply unit.

[0051] The operating voltage of the MCU used in commercial vehicle automotive electronics is represented by VCC, which is typically 5V or 3.3V. Commercial vehicles commonly use 12V and 24V power systems. When the vehicle power supply is 24V, the supply voltage range is generally 18V to 32V; when the vehicle power supply is 12V, the supply voltage range is generally 8V to 16V.

[0052] The vehicle power supply is connected to the EBS module via a 5A fuse and wiring harness 1. The voltage input to the EBS terminal is represented by the symbol VDD. The fuse resistance is negligible and is equivalent to the vehicle power supply. The upper limit of the vehicle power supply is represented by the symbol VDDmax, and the lower limit is represented by the symbol VDDmin. In the vehicle power supply voltage sampling circuit, the values ​​of resistors R0B, R0C, and R0D are determined by the minimum current that the AD0 port of MCU1 can recognize. The values ​​of resistors R0B and R0C are also determined by VDDmax and the power rating of the resistors, while the value of resistor R0D is determined by the sink current allowed by MCU1 and the power rating of the resistors. Resistors R0B and R0C satisfy the following two inequalities;

[0053] VDD*R0C / (R0B+R0C)≤VCC*0.95 (1);

[0054] VDD*R0C / (R0B+R0C)≥VCC*0.10 (2);

[0055] Taking the MCU's operating voltage VCC = 5V as an example, in order to be compatible with 12V and 24V power systems, VDDmax = 32V and VDDmin = 8V in the design. Substituting VDDmax and VCC into inequality (1), and VDDmin and VCC into inequality (2), we have:

[0056] 32*R0C / (R0B+R0C)≤4.75;

[0057] 8*R0C / (R0B+R0C)≥0.5;

[0058] Therefore, the relationship between R0B and R0C can be derived as follows:

[0059] R0B / R0C ≥ 5.7368;

[0060] R0B / R0C≤15;

[0061] The slope assist start switch signal voltage sampling circuit, the values ​​of resistors R1A, R1B, R1C and R1D are determined by the minimum current that the AD1 port of MCU1 can recognize, and need to take into account the short circuit of wiring harness 2 to the vehicle power supply and the short circuit to the vehicle ground. The values ​​of resistors R1A, R1B and R1C are also determined by VDDmax and the power of the resistors. The value of resistor R1D is also determined by the sink current allowed by MCU1 and the power of the resistors. Resistors R1A, R1B and R1C satisfy the following two inequalities;

[0062] VDD*R1C / (R1B+R1C)≤VCC*0.95 (3);

[0063] VDD*R1C / (R1A+R1B+R1C)≥VCC*0.10 (4);

[0064] To better achieve the diagnostic function, resistors R1C, R1E, ​​and R1F satisfy the following three inequalities;

[0065] R1F / R1E≤0.70 (5);

[0066] R1F / R1E≥0.30 (6);

[0067] R1F≥R1C (7);

[0068] The real-time voltage value acquired by the AD acquisition port AD0 of MCU1 is represented by the symbol V0a. Then the vehicle power supply voltage VDD = V0a*(R0B+R0C) / R0C (8);

[0069] The EBS module transmits the collected vehicle power supply voltage value to the vehicle's CAN bus via the CAN bus interface. The hill start assist switch uses a pull-up resistor switch signal; we will analyze this as an example.

[0070] The real-time voltage value acquired by the AD acquisition port AD1 of MCU1 is represented by the symbol V1a, and the actual voltage on the harness 2 is represented by the symbol V2. Then the relationship between V2 and V1a satisfies Equation 9.

[0071] V2=V1a*(R1B+R1C) / R1C (9);

[0072] The voltage on harness 2 is analyzed and compared to distinguish the five states of the ramp assist start switch.

[0073] When the ramp assist start switch is in the normal inactive state, the theoretical voltage on harness 2 is represented by the symbol V21, and the relationship between V21 and VDD satisfies equation 10:

[0074] V21=VDD*(R1B+R1C) / ((R1B+R1C+(R1A*R1E) / (R1A+R1E))(10);

[0075] When the ramp auxiliary start switch is in normal and effective condition, the theoretical voltage on harness 2 is represented by the symbol V22, and the relationship between V22 and VDD satisfies equation 11:

[0076] V22=VDD*((R1B+R1C)*R1F / (R1B+R1C+R1F)) / (((R1B+R1C)*R1F / (R1B+R1C+R1F))+((R1A*R1E) / (R1A+R1E))) (11);

[0077] When the ramp auxiliary start switch is in an open-circuit fault state, the theoretical voltage on harness 2 is represented by the symbol V23, and the relationship between V23 and VDD satisfies equation 12:

[0078] V23=VDD*(R1B+R1C) / (R1B+R1C+R1A) (12);

[0079] When the ramp assist start switch fails and the power supply is short-circuited, the theoretical voltage on harness 2 is represented by the symbol V24. The relationship between V24 and VDD satisfies equation 13:

[0080] V24 = VDD(13);

[0081] When the ramp auxiliary start switch is in a faulty ground short-circuit state, the theoretical voltage on harness 2 is represented by the symbol V25, and V25 satisfies equation (14): V25=0(14);

[0082] With R1A = 20K, R1B = 60K, R1C = 10K, R1E = 10K, and R1F = 10K, the theoretical voltages on wire harness 2 under various conditions when VDD is 32V, 24V, 18V, 12V, and 8V are shown in the table below:

[0083] Table 1

[0084]

[0085] The voltage acquisition error value is represented by the symbol Ve. Based on the calculation results in the table above, Ve = 0.3V can be set.

[0086] Example 3

[0087] Based on the above embodiments, unlike Embodiment 2, this embodiment diagnoses the state of the release switch.

[0088] The real-time voltage value acquired by the AD acquisition port AD3 of MCU2 is represented by the symbol V3a, and the actual voltage on the wire harness 5 is represented by the symbol V5. Then the relationship between V5 and V3a satisfies Equation 9.

[0089] V5=V3a*(R3B+R3C) / R3C (9);

[0090] When the input / output port corresponding to the release switch is not open-circuited, short-circuited to the vehicle power supply, or short-circuited to the vehicle ground, and the release switch is in the normally open state, we call it the normal ineffective state of the release switch. When the release switch is in the closed state, we call it the normal effective state of the release switch. When the input / output port corresponding to the release switch is open-circuited, we call it the fault open-circuit state of the release switch. When the input / output port corresponding to the release switch is short-circuited to the vehicle power supply, we call it the fault power supply short-circuit state of the release switch. When the input / output port corresponding to the release switch is short-circuited to the vehicle ground, we call it the fault ground short-circuit state of the release switch. The five states of the release switch are distinguished by analyzing and comparing the voltage on wiring harness 5.

[0091] When the release switch is in a normal inactive state, the theoretical voltage on harness 5 is represented by the symbol V51, and the relationship between V51 and VDD satisfies equation 20:

[0092] V51=VDD*((R3B+R3C)*R3F / (R3B+R3C+R3F)) / (((R3B+R3C)*R3F / (R3B+R3C+R3F))+R3A) (20);

[0093] When the release switch is in a normal and effective state, the theoretical voltage on wire harness 5 is represented by the symbol V52, and the relationship between V52 and VDD satisfies equation 21:

[0094] V52=VDD*((R3B+R3C)*R3F / (R3B+R3C+R3F)) / (((R3B+R3C)*R3F / (R3B+R3C+R3F))+((R3A*R3E) / (R3A+R3E))) (21);

[0095] When the release switch is in an open-circuit fault state, the theoretical voltage on harness 5 is represented by the symbol V53, and the relationship between V53 and VDD satisfies equation 22:

[0096] V53=VDD*(R3B+R3C) / (R3B+R3C+R3A) (22);

[0097] When the release switch fails and the power supply is short-circuited, the theoretical voltage on harness 5 is represented by the symbol V54. The relationship between V54 and VDD satisfies equation 23:

[0098] V54 = VDD (23);

[0099] When the release switch is in a fault ground short-circuit state, the theoretical voltage on harness 5 is represented by the symbol V55, and V55 satisfies equation 24:

[0100] V55 = 0 (24);

[0101] For example, if R3A = 20K, R3B = 60K, R3C = 10K, R3E = 10K, and R3F = 10K, the theoretical voltages on wire harness 2 under various states when VDD is 32V, 24V, 18V, 12V, and 8V are shown in Table 2.

[0102] Table 2

[0103]

[0104] The voltage acquisition error value is represented by the symbol Ver. Based on the calculation results in the table above, Ver = 0.5V is set.

Claims

1. A method for diagnosing switch faults in a commercial vehicle, wherein the switch states include normal inactive state, normal active state, fault open circuit state, fault power supply short circuit state, and fault ground short circuit state, and includes a power supply unit, a switch unit, a protection unit, and a main control unit; the power supply unit provides power to the main control unit; The protection unit provides current-limiting protection for the switching unit, and the main control unit receives the signal from the switching unit after the current-limiting protection is applied. The methods include: Obtain the voltage values ​​at the input terminals of the main control unit MCU1, namely V0a and V1a; Obtain the voltage V2 output from the ramp assist start switch and the voltage VDD from the power supply unit; and transmit VDD to the CAN bus; Obtain the voltages for the normal invalid state, normal valid state, fault open circuit state, and fault power supply short circuit state, which are respectively V21 for normal invalid state, V22 for normal valid state, V23 for fault open circuit state, and V24 for fault power supply short circuit state. The switch status is determined based on the voltage V24 of the normal invalid state V21, the normal valid state V22, the fault open circuit state V23, and the fault power supply short circuit state, as well as the voltage acquisition error value.

2. The method for diagnosing switch faults in a commercial vehicle according to claim 1, characterized in that: The voltage VDD of the power supply unit is calculated using the symbol V0a from the real-time voltage value acquired by the AD acquisition port AD0 of the main control unit MCU1.

3. The method for diagnosing switch faults in commercial vehicles according to claim 1, characterized in that: The voltage values ​​of V24 in the normal invalid state V21, normal valid state V22, fault open circuit state V23, and fault power supply short circuit state are obtained through the voltage VDD of the power supply unit.

4. The method for diagnosing switch faults in a commercial vehicle according to claim 1, characterized in that, The main control unit includes EBS main control unit MCU1 and EPB main control unit MCU2.

5. A method for diagnosing switch faults in a commercial vehicle according to claim 4, characterized in that, The switch unit includes a hill start assist switch, a parking switch, a release switch, and an autohold switch; The protection unit includes a power supply protection unit, a hill start assist switch protection unit, a parking switch protection unit, a release switch protection unit, and an autohold switch protection unit; The power supply unit is connected to the EBS main control unit MCU1 via the power protection unit; The ramp auxiliary switch is connected to the EBS main control unit MCU1 through the ramp auxiliary switch protection unit; The parking switch is connected to the EPB main control unit MCU2 via the parking switch protection unit; The release switch is connected to the EPB main control unit MCU2 via the release switch protection unit; The autohold switch is connected to the EPB main control unit MCU2 via the autohold switch protection unit.

6. The method for diagnosing switch faults in a commercial vehicle according to claim 5, characterized in that, The hill start assist switch and parking switch are pull-up resistor switches; the release switch and autohold switch are pull-down resistor switches.

7. A method for diagnosing switch faults in a commercial vehicle according to claim 6, characterized in that, The power protection unit, ramp assist switch protection unit, parking switch protection unit, release switch protection unit, and autohold switch protection unit all include a current limiting unit, a voltage divider unit, and a filtering unit. The switch current signal is current limited by the current limiting unit, the current-limited voltage signal is divided by the voltage divider unit, and then filtered by the filtering unit. The filtered voltage signal is then transmitted to the main control unit.

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