Oxygen sensor signal simulation device

Abstract

The invention provides an oxygen sensor signal simulation device. The oxygen sensor signal simulation device comprises a control module, a heating current measuring module, a pump unit control module, an internal resistance adjusting module, a fault injection module, a DAC output module, a relay driving module, a CAN bus receiving and transmitting module and a hardware interface. The invention aims to provide the simulation device which is high in universality and can simulate signals of the wide-domain oxygen sensor and the narrow-domain oxygen sensor at the same time. The device can output various signals, such as real tail gas oxygen content, covering high and low temperature conditions, simulating short circuit, open circuit and the like, which are matched with the actual running environment of a real vehicle in a virtual test environment.

Description

Technical Field

[0001] The invention relates to a signal simulation device, in particular to an oxygen sensor signal simulation device. Background Art

[0002] The engine hardware-in-the-loop test system is designed to simulate the operation of the real engine hardware through a real-time simulation system model, and at the same time connect the real control unit (i.e., engine electronic control unit, ECU) to the real-time simulation system through the input and output (IO) interface to build a closed-loop system. In this system, the mutual conversion between physical signals and electrical signals is used to achieve the purpose of verifying the function of the control unit. It is worth noting that since the test system does not need to be equipped with real engine hardware, it can create special environmental conditions that are difficult to achieve in a real test environment before the actual vehicle is installed, and then conduct testing work for extreme working conditions, and implement comprehensive testing and verification of the fault diagnosis and safety handling functions of the real control unit.

[0003] As a key component of automobile engine fuel feedback control, oxygen sensor plays an extremely important role. The real control unit will accurately control the air-fuel ratio based on the signal fed back by the oxygen sensor, and the accuracy of the air-fuel ratio is directly related to the engine's emission level, combustion efficiency, and economic performance. It can be seen that the simulation of oxygen sensor signals has become an indispensable part of the engine controller hardware-in-the-loop test system.

[0004] Oxygen sensors can be specifically divided into two types: narrow-band oxygen sensors and wide-band oxygen sensors. Among them, the narrow-band oxygen sensor is a switch-type oxygen sensor, which can only reflect whether the mixture is in a rich or lean state, but cannot accurately present the specific degree of the mixture. The wide-band oxygen sensor is based on the narrow-band type, with an additional pump oxygen element, which is used to adjust the oxygen content in the exhaust gas. During actual operation, the real control unit will apply a control current to the pump oxygen element. In this way, the Nernst output voltage of the pump oxygen element can be maintained at a voltage value corresponding to the theoretical air-fuel ratio, and the size and direction of the applied pump current can accurately reflect the actual air-fuel ratio of the mixture.

[0005] As emission and economy requirements become increasingly stringent, emission after-treatment systems usually use a combination of wide-band and narrow-band oxygen sensors. Specifically, a wide-band oxygen sensor is configured before the three-way catalyst to feed back the precise air-fuel ratio in the exhaust gas to the real control unit, thereby achieving closed-loop control; and a narrow-band oxygen sensor is set after the three-way catalyst to detect the working status of the three-way catalyst. In view of this, the market urgently needs a universal simulation device that can simulate the signals of wide-band and narrow-band oxygen sensors at the same time, so that it can provide various signals that are consistent with the actual vehicle environment, such as the actual exhaust gas oxygen content, high and low temperatures, short circuits, open circuits, etc. in a virtual test environment, thereby providing a more complete test environment for the real control unit product during the development process.

[0006] As far as the existing patents involving oxygen sensors are concerned, they mainly focus on the parameter identification of wide-range oxygen sensors and the simulation design of control systems related thereto, and when performing related operations, it is necessary to connect a real wide-range oxygen sensor, and then carry out simulation design work for the real control unit controller connected thereto. However, there are few patents in the field of oxygen sensor signal simulation for real control unit hardware-in-the-loop testing. For example, a wide-range oxygen sensor simulator disclosed in the patent document with publication number CN104977920A is mainly used to discretely simulate the signals of the wide-range oxygen sensor in various normal working conditions and fault conditions, so as to carry out functional testing of the real control unit under specific test conditions. However, the simulator does not perform corresponding signal simulation on some inherent physical properties of the wide-range oxygen sensor, such as temperature-internal resistance characteristics, pump oxygen element characteristics, etc., so it cannot be applied to the hardware-in-the-loop testing of the real control unit of the engine under various operating conditions. For another example, the patent document with publication number CN110672331A discloses a wide-band oxygen sensor signal simulator, whose working principle is to offset the Nernst output voltage based on the collected real oxygen sensor signal. It can only simulate the richness of the mixture, but cannot simulate other core performance parameters of the oxygen sensor, such as the temperature-internal resistance characteristics and pump oxygen element characteristics. Moreover, it needs to be connected to a real oxygen sensor when working. It is not a universal signal simulator designed based on the intrinsic physical characteristics of the oxygen sensor. Summary of the invention

[0007] The purpose of the present invention is to provide a simulation device with strong versatility and capable of simulating wide-band and narrow-band oxygen sensor signals at the same time. The device can output various signals that match the actual operating environment of a real vehicle, such as the real exhaust oxygen content, high and low temperature conditions, and simulated short circuits and open circuits, in a virtual test environment.

[0008] The present invention provides an oxygen sensor signal simulation device, comprising a control module, a heating current measurement module, a pump unit control module, an internal resistance adjustment module, a fault injection module, a DAC output module (digital-to-analog conversion output module), a relay drive module, a CAN (controller area network) bus transceiver module and a hardware interface.

[0009] The control module performs CAN interactive communication with the engine hardware-in-the-loop test system and collects signals from the heating current measurement module. The control module also controls the pump unit control module, the internal resistance adjustment module and the fault injection module.

[0010] The heating current measurement module simulates the oxygen sensor heating resistor.

[0011] The pump unit control module includes an instrument amplifier and a voltage follower. The pump unit control module performs equivalent simulation on the electrical characteristics of the pump oxygen element and the electrical characteristics of the oxygen concentration difference battery, and outputs the oxygen sensor Nernst voltage signal according to the air-fuel ratio control signal.

[0012] The internal resistance adjustment module simulates the actual operating temperature of the oxygen sensor by outputting a variable oxygen concentration difference battery internal resistance.

[0013] The fault injection module injects output signal faults into the Nernst voltage output terminal and the virtual ground terminal of the oxygen sensor diaphragm.

[0014] The DAC output module converts the digital command value of the control module for the air-fuel ratio control signal into an accurate analog output.

[0015] The relay driving module improves the output driving capability of the IO pin of the control module, converts the relay control instruction output by the control module into a current signal to drive the relay to operate.

[0016] The CAN bus transceiver module realizes bidirectional conversion between the CAN bus physical differential voltage signal and the digital signal, and transmits the digital signal to the control module.

[0017] The hardware interface includes a CAN bus interface, a calibration terminal for a calibrated resistor, a pump current signal terminal, a virtual ground terminal, an oxygen sensor diaphragm Nernst voltage output terminal, and a heating current acquisition terminal, and the hardware interface is connected to a real control unit of the engine.

[0018] In one embodiment, the control module sends the sampling results of the heating current measurement module to the engine hardware-in-the-loop test system through the CAN bus interface, and receives air-fuel ratio, oxygen sensor internal resistance and fault injection control instructions from the engine hardware-in-the-loop test system, and converts the instructions into control signals to control the pump unit control module, internal resistance adjustment module and fault injection module.

[0019] In one embodiment, the input end of the heating current measurement module is connected to the heating current acquisition end of the hardware interface, and the output end is connected to the control module, so as to transmit the PWM (pulse width modulation) control signal of the real control unit for heating the oxygen sensor to the control module.

[0020] In one embodiment, the pump unit control module has a first instrument amplifier and a second instrument amplifier, the positive input terminal of the first instrument amplifier is connected to the virtual ground terminal, the negative input terminal is connected to the pump current signal terminal, the negative input terminal is also connected to one end of the calibration resistor, and the other end of the calibration resistor is connected to the calibration terminal of the calibration resistor, and the two ends of the pump unit resistor are connected between the positive and negative input terminals of the first instrument amplifier; the output of the first instrument amplifier is connected to the negative input terminal of the second instrument amplifier, the positive input terminal of the second instrument amplifier is connected to the output terminal of the voltage follower, the output terminal of the DAC output module is connected to the positive input terminal of the voltage follower as an air-fuel ratio control signal, and the air-fuel ratio control signal is connected to the positive input terminal of the voltage follower; the output terminal of the second instrument amplifier is connected to the input terminal of the internal resistance adjustment module as the Nernst voltage signal of the oxygen sensor.

[0021] In one embodiment, the input end of the internal resistance adjustment module is connected to the output end of the pump unit control module, and the output end of the internal resistance adjustment module is connected to the Nernst voltage output end of the oxygen sensor diaphragm.

[0022] In one embodiment, the internal resistance adjustment module is composed of a discrete resistor array and a photorelay array, and each discrete resistor is connected in parallel with a photorelay switch.

[0023] In one embodiment, the fault injection module is composed of four relays, three of which are used to perform fault injection on the Nernst voltage output terminal of the oxygen sensor diaphragm to achieve signal disconnection, short circuit to ground and short circuit to power supply at the Nernst voltage output terminal of the oxygen sensor diaphragm; and one relay is used to perform output signal fault injection on the virtual ground terminal to achieve signal disconnection at the virtual ground terminal.

[0024] In one embodiment, the DAC output module is connected to the control module via an SPI communication interface (serial peripheral communication interface), and the output end is connected to the positive input end of the voltage follower in the pump unit control module, so as to transmit the PWM control signal of the real control unit for heating the oxygen sensor to the control module.

[0025] In one embodiment, the relay driving module is composed of a Darlington transistor.

[0026] In one embodiment, the CAN bus interface can be connected to the engine hardware-in-the-loop test system for two-way communication. The control module sends the sampling results of the heating current measurement module to the engine hardware-in-the-loop test system, and the engine hardware-in-the-loop test system transmits the air-fuel ratio, oxygen sensor internal resistance and fault injection control instructions calculated thereby to the oxygen sensor signal simulation device through the CAN bus; the calibration resistance calibration terminal, pump current signal terminal, virtual ground terminal, oxygen sensor diaphragm Nernst voltage output terminal and heating current acquisition terminal are used to connect to the real control unit of the engine, and can send the simulation signal of the oxygen sensor to the real control unit of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of an oxygen sensor signal simulation device of the present invention;

[0028] Figure 2 It is a schematic diagram of a DAC output module and a heating current measurement module of an oxygen sensor signal simulation device of the present invention;

[0029] Figure 3 It is a schematic diagram of a pump unit control module of an oxygen sensor signal simulation device of the present invention;

[0030] Figure 4 It is a schematic diagram of a resistance recovery module of an oxygen sensor signal simulation device of the present invention;

[0031] Figure 5 It is a fault injection module of an oxygen sensor signal simulation device of the present invention;

[0032] Figure 6 The present invention discloses a software control flow chart of an oxygen sensor signal simulation device.

[0033] Reference numerals:

[0034] Control module-1;

[0035] Virtual ground end_1-11;

[0036] Heating current measurement module-2;

[0037] Pump unit control module-3;

[0038] Instrument amplifier-31;

[0039] First Instrument Amplifier-311;

[0040] Second instrument amplifier-312;

[0041] Voltage follower-32;

[0042] Internal resistance adjustment module-4;

[0043] Fault injection module-5;

[0044] DAC output module-6;

[0045] Relay driver module-7;

[0046] CAN bus transceiver module-8;

[0047] Hardware interface-9;

[0048] Calibration resistance calibration terminal -91;

[0049] Pump current signal terminal -92;

[0050] Virtual ground end - 93;

[0051] Oxygen sensor diaphragm Nernst voltage output terminal -94;

[0052] Heating current collection terminal 95. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0054] In addition, it should be noted that, unless otherwise clearly specified and limited, the words "installed", "connected", "connected" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. Technical personnel in the field can understand their specific meanings in this application according to the specific circumstances.

[0055] Figure 1 It is a schematic diagram of the structure of the present invention, such as Figure 1 The present invention provides an oxygen sensor signal simulation device, including a control module 1, a heating current measurement module 2, a pump unit control module 3, an internal resistance adjustment module 4, a fault injection module 5, a DAC output module 6, a relay drive module 7, a CAN bus transceiver module 8 and a hardware interface 9.

[0056] The control module 1 performs CAN interactive communication with the engine hardware-in-the-loop test system, collects signals from the heating current measurement module 2, and the control module 1 also controls the pump unit control module 3, the internal resistance adjustment module 4, and the fault injection module 5. Preferably, the control module 1 sends the sampling results of the heating current measurement module 2 to the engine hardware-in-the-loop test system through the CAN bus interface, and receives control instructions for the air-fuel ratio, the internal resistance of the oxygen sensor, and the fault injection from the engine hardware-in-the-loop test system, and converts the instructions into control signals to control the pump unit control module 3, the internal resistance adjustment module 4, and the fault injection module 5.

[0057] Figure 2 Schematic diagram of a DAC output module and a heating current measurement module of an oxygen sensor signal simulation device of the present invention. Figure 2 As shown, the heating current measuring module 2 simulates the oxygen sensor heating resistor. Preferably, the input end of the heating current measuring module 2 is connected to the heating current acquisition end of the hardware interface, and the output end is connected to the control module, so as to transmit the PWM control signal of the real control unit for heating the oxygen sensor to the control module 1.

[0058] like Figure 2 As shown, the DAC output module 6 converts the digital command value of the air-fuel ratio control signal of the control module 1 into an accurate analog output. Preferably, the DAC output module 6 is connected to the control module 1 through an SPI communication interface, and the output end is connected to the positive input end of the voltage follower 32 in the pump unit control module 3, and the PWM control signal of the real control unit for heating the oxygen sensor is transmitted to the control module 1. The DAC output module adopts a 16-bit AD sampling chip AD5764. Figure 2 In the figure, AGND indicates analog ground, DGND indicates digital ground, and VOUTA, VOUTB, VOUTC, VOUTD corresponding to SPI_SCK, SPI_MOSI, SPI_MISO, LDAC, CLR, SDIN, SDO, SYNC, BIN / 2's COMP, AGND, DGND, VREF, VDD, RESET, DAC1 AD5764RBSUZ, and KL87, PE9 are the pins of chip AD5764. For the specific function of each pin, please refer to the instruction manual of chip AD5764.

[0059] Figure 3 This is a schematic diagram of a pump unit control module of an oxygen sensor signal simulation device of the present invention, such as Figure 3As shown, the pump unit control module 3 includes an instrument amplifier 31 and a voltage follower 32. The pump unit control module 3 performs equivalent simulation on the electrical characteristics of the pump oxygen element and the electrical characteristics of the oxygen concentration difference battery, and outputs the oxygen sensor Nernst voltage signal according to the air-fuel ratio control signal. Preferably, the pump unit control module 3 has a first instrument amplifier 311 and a second instrument amplifier 312. The positive input terminal of the first instrument amplifier 311 is connected to the virtual ground terminal _111, and the negative input terminal is connected to the pump current signal terminal 92. The negative input terminal is also connected to one end of the calibration resistor R1, and the other end of the calibration resistor R1 is connected to the calibration resistor calibration terminal 91. The two ends of the pump unit resistor R4 are connected between the positive and negative input terminals of the first instrument amplifier 311; the output of the first instrument amplifier 311 is connected to the negative input terminal of the second instrument amplifier 312, and the positive input terminal of the second instrument amplifier 312 is connected to the output terminal of the voltage follower 32. The output terminal of the DAC output module 6 is connected to the positive input terminal of the voltage follower 32 as an air-fuel ratio control signal, and the air-fuel ratio control signal is connected to the positive input terminal of the voltage follower 32; the output terminal of the second instrument amplifier 312 is connected to the input terminal of the internal resistance adjustment module 4 as an oxygen sensor Nernst voltage signal. The output terminal V of the first instrument amplifier 311 1o With positive and negative input terminals The equivalent relationship is The output terminal V of the second instrument amplifier 312 2o With positive and negative input terminals The equivalent relationship is Therefore, according to the signal simulation requirements of the characteristics of each model series of mainstream manufacturers, appropriate R2 and R3 resistor values ​​can be selected to adjust the output gain of instrument amplifiers 1 and 2. Make the oxygen sensor Nernst voltage signal V 2o The reference voltage is equal to the theoretical air-fuel ratio. At this time, the real control unit has no pump current signal output, and the output voltage of the first instrument amplifier 311 is 0V. When rich mixture needs to be simulated, increase the air-fuel ratio control signal Then the output voltage V of the second instrument amplifier 312 is 2o The real control unit detects that the Nernst voltage of the oxygen sensor diaphragm increases, and determines that the mixed gas is too rich, so it outputs a negative pump current signal, which flows from the virtual ground end from bottom to top through the resistor R4, and a positive voltage is formed between the positive and negative input terminals of the first instrument amplifier 311, so the first instrument amplifier 311 will output a positive voltage. Make V 2o Gradually decrease until the reference voltage is equal to the theoretical air-fuel ratio again. Conversely, by reducing the air-fuel ratio control signal Make V2o The reduction can simulate a lean mixture, allowing the real control unit to output a positive pump current signal, which flows from the pump current signal terminal 92 from top to bottom through the resistor R4, and the first instrument amplifier 311 outputs a negative voltage Make V 2o It gradually increases until it reaches the reference voltage when it is equal to the theoretical air-fuel ratio again. The real control unit will determine the actual air-fuel ratio of the mixture at this time based on the size and direction of the output pump current. It can be seen that in the process of adjusting the air-fuel ratio control signal, the first instrument amplifier 311 and the second instrument amplifier 312 can respectively realize ideal equivalent simulation of the electrical characteristics of the pump oxygen element and the oxygen concentration difference battery, so that the real control unit can dynamically adjust the direction and size of the pump current signal according to the simulated Nernst voltage of the oxygen sensor diaphragm, thereby realizing the simulation of the air-fuel ratio signal. Since the narrow-band oxygen sensor does not have a pump oxygen element unit, when simulating the narrow-band oxygen sensor signal, the calibration end of the calibration resistor and the pump current signal end can be left floating. At this time The output of the first instrument amplifier 311 will always be 0V, and the air-fuel ratio control signal To directly control the output voltage (V 2o ) to simulate the narrow-band oxygen sensor signal. The instrument amplifier uses the INA128 chip and the voltage follower uses the OP07 chip. Figure 3 In the figure, GND indicates grounding. For the specific functions of INA128's RG pin (RG pin corresponding to instrumentation amplifier 1 and instrumentation amplifier 2 respectively), V-in pin (inverting input pin corresponding to the two instrumentation amplifiers respectively), V+ pin (non-inverting input pin corresponding to the two instrumentation amplifiers respectively), Vo pin (output pin corresponding to the two instrumentation amplifiers respectively), and Ref pin (reference pin corresponding to the two instrumentation amplifiers), please refer to the instruction manual of the chip INA128.

[0060] Figure 4 This is a schematic diagram of a resistance recovery module of an oxygen sensor signal simulation device of the present invention, such as Figure 4As shown, the internal resistance adjustment module 4 simulates the actual working temperature of the oxygen sensor by outputting a variable oxygen concentration difference battery internal resistance. Preferably, the internal resistance adjustment module 4 is composed of a discrete resistor array and a photorelay array, and a photorelay switch is connected in parallel to each discrete resistor. The input end of the internal resistance adjustment module 4 is connected to the output end of the pump unit control module 3, and the output end of the internal resistance adjustment module 4 is connected to the Nernst voltage output end 94 of the oxygen sensor diaphragm, and its function is to simulate the actual working temperature of the oxygen sensor by outputting a variable oxygen concentration difference battery internal resistance. The internal resistance adjustment module 4 is composed of a discrete resistor array (R5~R20) and a photorelay array (RE1~RE16). The discrete resistor array is composed of four groups of discrete resistors connected in series, which respectively represent the units, tens, hundreds and thousands of the output resistance. Each group of discrete resistors is composed of four discrete resistors connected in series, and the distribution is arranged in one, two, three and four. A photorelay switch is connected in parallel to each discrete resistor. Any value from 0 to 9 can be achieved through different photorelay switch state combinations. The principle is that the photorelay switch is disconnected by default. When the photorelay switch is closed, the corresponding discrete resistor is short-circuited. In this way, through a total of sixteen different state combinations of photorelay switches, the series connection of resistors with different resistance values ​​can be controlled, thereby realizing the variable output resistance value of the corresponding channel. The photorelay switch state is driven and controlled by the output terminal signal of the relay drive module 7. The specific process is as follows:

[0061] Resistors R5 to R8 are used to represent the units of the output resistance, and the resistance values ​​are 1 ohm, 2 ohms, 3 ohms, and 4 ohms respectively. Any value between 0 ohms and 10 ohms can be achieved by controlling the state of the photorelay switches (RE1 to RE4);

[0062] Resistors R9 to R12 are used to represent the tens digit of the output resistance, and the resistance values ​​are 10 ohms, 20 ohms, 30 ohms, and 40 ohms respectively. By controlling the states of the photorelay switches (RE5 to RE8), any integer resistance value between 10 ohms and 100 ohms can be achieved. If all switches are closed, 0 ohms can also be represented.

[0063] Resistors R13 to R16 are used to represent the hundreds place of the output resistance, and the resistance values ​​are 100 ohms, 200 ohms, 300 ohms, and 400 ohms respectively. By controlling the state of the photorelay switches (RE9 to RE12), any integer resistance value between 100 ohms and 1000 ohms can be achieved. If all the switches are closed, 0 ohms can also be represented.

[0064] Resistors R17 to R20 are used to represent the thousandths of the output resistance, and the resistance values ​​are 1k ohm, 2k ohm, 3k ohm, and 4k ohm respectively. By controlling the state of the photorelay switches (RE13 to RE16), any integer thousandth resistance value between 1k ohm and 10k ohm can be achieved. If all switches are closed, 0 ohm can also be represented.

[0065] Through the series connection of the above four groups of resistors and the combination of the switch states of the photorelay, it is theoretically possible to achieve continuous adjustment of any resistance value between 0 ohm and 11.11k ohms, with an adjustment step of 1 ohm.

[0066] The relay driving module 7 improves the output driving capability of the IO pin of the control module 1, converts the relay control instruction output by the control module 1 into a current signal to drive the relay action of the internal resistance adjustment module 4 and the fault injection module 5. Preferably, the relay driving module 7 is composed of a Darlington transistor.

[0067] Figure 5 is a fault injection module of an oxygen sensor signal simulation device of the present invention, such as Figure 5 As shown, the fault injection module 5 performs output signal fault injection on the oxygen sensor diaphragm Nernst voltage output terminal 94 and the virtual ground terminal 93. Preferably, the input terminal of the fault injection module 5 is connected to the virtual ground terminal 93 of the hardware interface 9 and the oxygen sensor diaphragm Nernst voltage_1 of the internal resistance adjustment module 4. Its function is to inject output signal fault into the oxygen sensor diaphragm Nernst voltage output terminal 94 and the virtual ground terminal 93. It is mainly composed of four (FIU_RE1~FIU_RE4) relays, among which the FIU_RE1 relay is used to enable fault injection into the oxygen sensor diaphragm Nernst voltage output terminal signal. When the FIU_RE1 relay is disconnected, the oxygen sensor diaphragm Nernst voltage output terminal is not injected with faults, and the output end oxygen sensor diaphragm Nernst voltage_1 signal of the internal resistance adjustment module 4 is connected to the oxygen sensor diaphragm Nernst voltage output terminal. When the FIU_RE1 relay is closed, the fault signal is connected to the oxygen sensor diaphragm Nernst voltage output terminal; the FIU_RE2 relay is used to inject a circuit breaker signal fault into the oxygen sensor diaphragm Nernst voltage output terminal signal. When the FIU_RE2 relay is disconnected, the circuit breaker fault signal is connected to the oxygen sensor diaphragm Nernst voltage output terminal. When the FIU_RE2 relay is closed, the circuit breaker fault signal is connected to the oxygen sensor diaphragm Nernst voltage output terminal. When the U_RE2 relay is closed, the short-circuit to ground or short-circuit to power fault signal is connected to the Nernst voltage output terminal of the oxygen sensor diaphragm; the FIU_RE3 relay is used to inject a short-circuit to ground or short-circuit to power fault into the signal at the Nernst voltage output terminal of the oxygen sensor diaphragm. When the FIU_RE3 relay is disconnected, the short-circuit to power fault signal is connected to the Nernst voltage output terminal of the oxygen sensor diaphragm. When the FIU_RE3 relay is closed, the short-circuit to ground fault signal is connected to the Nernst voltage output terminal of the oxygen sensor diaphragm. The FIU_RE4 relay is used to enable fault injection of the virtual ground terminal 93 signal. When the FIU_RE4 relay is disconnected, the virtual ground terminal 93 signal is not fault injected, and the virtual ground terminal 93 signal is connected to the virtual ground terminal_111 of the pump unit control module 1. When the FIU_RE4 relay is closed, the open circuit fault signal is connected to the virtual ground terminal_111 of the pump unit control module 1.

[0068] The CAN bus transceiver module 8 realizes bidirectional conversion between the CAN bus physical differential voltage signal and the digital signal, and transmits the digital signal to the control module 1. Preferably, the CAN bus interface can be connected to the engine hardware-in-the-loop test system for bidirectional communication, and the control module 1 sends the sampling result of the heating current measurement module 2 to the engine hardware-in-the-loop test system, and the engine hardware-in-the-loop test system transmits the air-fuel ratio, oxygen sensor internal resistance and fault injection control instructions calculated thereby to the oxygen sensor signal simulation device through the CAN bus; the calibration resistance calibration terminal 91, the pump current signal terminal 92, the virtual ground terminal 93, the oxygen sensor diaphragm Nernst voltage output terminal 94 and the heating current acquisition terminal 95 are used to connect to the real control unit of the engine, and can send the simulation signal of the oxygen sensor to the real control unit of the engine. The CAN bus is one of the field buses widely used in the field of industrial communication control. The use of the CAN bus can make the present invention very convenient to expand and apply to any industrial equipment and system with a CAN interface, and is easy to expand. The CAN bus transceiver module 8 adopts TJA1050.

[0069] The hardware interface 9 includes a CAN bus interface, a calibration terminal 91 for a calibrated resistor, a pump current signal terminal 92, a virtual ground terminal 93, an oxygen sensor diaphragm Nernst voltage output terminal 94, and a heating current acquisition terminal 95. The hardware interface 9 is connected to the real control unit of the engine. Preferably, the CAN bus interface can be connected to the engine hardware-in-the-loop test system for two-way communication. The control module 1 sends the sampling result of the heating current measurement module 2 to the engine hardware-in-the-loop test system. The engine hardware-in-the-loop test system transmits the air-fuel ratio, oxygen sensor internal resistance, and fault injection control instructions calculated therefrom to the oxygen sensor signal simulation device through the CAN bus; the calibration terminal 91 for a calibrated resistor, a pump current signal terminal 92, a virtual ground terminal 93, an oxygen sensor diaphragm Nernst voltage output terminal 94, and a heating current acquisition terminal 95 are used to connect to the real control unit of the engine, and can send the simulation signal of the oxygen sensor to the real control unit of the engine. If you need to simulate a narrow-band oxygen sensor, you only need to connect the virtual ground terminal 93, the oxygen sensor diaphragm Nernst voltage output terminal 94 and the heating current acquisition terminal 95 to the real control unit of the engine, and leave the calibration resistor calibration terminal 91 and the pump current signal terminal 92 unconnected.

[0070] Figure 6The software flow chart of the system of the present invention is shown in FIG. 1. The control module 1 of the system of the present invention will enter the initialization program when powered on, mainly performing clock configuration, IO port configuration, interrupt configuration, PWM sampling configuration, CAN module configuration, etc., and then enter the standby mode to wait for receiving CAN bus information. When the CAN bus transceiver module 8 receives a valid CAN physical signal from the outside world, it will transmit the converted digital signal to the control module 1. After the control module 1 recognizes the valid CAN signal, it will enter the CAN interrupt program and put the valid CAN data into the RxMessage (receive message) message. In the interrupt program, the control module 1 will extract the ID and data information. When the extracted ID is consistent with the preset ID in the control module 1, it will enter the data processing program, otherwise it will ignore this CAN message information, enter the standby mode, and continue to wait for the next interrupt. In the data processing program, control module 1 first collects the PWM heating control signal of the real control unit for the oxygen sensor, encapsulates the extracted frequency and duty cycle signals into the TxMessage (send message) message and sends it to the engine hardware-in-the-loop test system, and then extracts the air-fuel ratio control signal, oxygen sensor internal resistance and fault injection command signal from the RxMessage message, and determines whether the command signal is consistent with the current output value. If they are consistent, the CAN message information is ignored and the standby mode is entered. If they are inconsistent, the latest command signal is output.

[0071] The present invention has the following beneficial effects:

[0072] 1. High simulation accuracy: The present invention designs the circuit based on the physical properties of the oxygen sensor, deeply studies and utilizes the relationship between the key physical properties of the oxygen sensor, such as the Nernst voltage, pump current and internal resistance, and the actual working state. Through the precise simulation and adjustment of these physical parameters, the signal characteristics of the oxygen sensor under different working conditions can be accurately reproduced, and a highly realistic oxygen sensor signal simulation is provided for the engine hardware-in-the-loop test system, which effectively improves the accuracy and reliability of the test and ensures that the real control unit of the engine can be tested and optimized in an oxygen sensor signal environment close to the real one during the development and verification process.

[0073] 2. Flexible and controllable parameters: The present invention can adjust the core performance parameters of the oxygen sensor, such as the Nernst voltage, pump current and internal resistance of the oxygen sensor. The air-fuel ratio signal is precisely controlled by the DAC output module, combined with the equivalent simulation of the electrical characteristics of the pump oxygen element and the oxygen concentration difference battery by the pump unit control module, and the flexible adjustment of the internal resistance of the oxygen concentration difference battery by the internal resistance adjustment module. According to different test requirements and oxygen sensor model characteristics, various parameter combinations can be freely set to accurately and effectively simulate the various models of products of mainstream manufacturers on the market. This high degree of flexibility enables the equipment of the present invention to adapt to diverse testing needs, whether it is for the research and development testing of new oxygen sensors or the batch testing and verification of various existing models of oxygen sensors. It can provide a customized simulation environment, which greatly improves the versatility and practicality of the equipment.

[0074] 3. High integration: The present invention integrates a fault injection function, which can inject output signal faults into the Nernst voltage output terminal and virtual ground terminal of the oxygen sensor diaphragm. Through the combination of multiple relays, it is possible to fully simulate various fault conditions that may occur in the actual use of the oxygen sensor. In the development process of the real control unit of the engine, it is necessary not only to verify its performance during normal operation, but also to test its fault handling capabilities. The fault injection function of the present invention provides a convenient and comprehensive means for testing and verifying the fault diagnosis and safety handling functions of the real control unit, thereby improving the integrity and effectiveness of the test system.

[0075] 4. Good general practicability: The present invention can flexibly switch simulation modes according to different test requirements and application scenarios, whether simulating the complex characteristics of wide-band oxygen sensors, such as pump oxygen element characteristics, precise air-fuel ratio feedback, etc., or simulating the relatively simple mixture rich-lean judgment signal of narrow-band oxygen sensors, it can be accurately realized. This enables the present invention to play an important role in the testing of various engine types and different emission control strategies, reducing the cost and complexity of developing test equipment for different types of oxygen sensors.

[0076] 5. Easy to expand: The present invention adopts CAN bus as the communication method, which is widely used in the field of industrial communication control. This enables the present invention to be easily connected to any industrial equipment and system with a CAN interface, thereby greatly expanding its scope of application. Whether it is integrated in the existing industrial test system or used in the newly developed related equipment system in the future, it has strong adaptability and compatibility and can be easily integrated into a larger and more complex industrial automation network architecture.

[0077] The above-described embodiments are only further explanations of the present invention, and are not intended to limit the present invention in other forms. The present invention may also have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding modifications and changes according to the present invention, but these corresponding modifications and changes should all fall within the protection scope of the present invention.

[0078] In the description of the present application, 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. For ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0079] It should be noted that, in the present application, the terms "comprises", "includes" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. It should also be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0080] The above embodiments are provided for persons familiar with the art to implement or use the present application. Personnel familiar with the art can make various modifications or changes to the above embodiments without departing from the application concept of the present application. Therefore, the protection scope of the present application is not limited to the above embodiments, but should be the maximum scope of the innovative features mentioned in the claims.

Claims

1. An oxygen sensor signal simulation device, characterized in that: include: A control module, wherein the control module performs CAN interactive communication with the engine hardware-in-the-loop test system and collects signals from the heating current measurement module. The control module also controls the pump unit control module, the internal resistance adjustment module, and the fault injection module; A heating current measurement module, wherein the heating current measurement module simulates the oxygen sensor heating resistor; A pump unit control module, including an instrument amplifier and a voltage follower, the pump unit control module performs equivalent simulation on the electrical characteristics of the pump oxygen element and the electrical characteristics of the oxygen concentration difference battery, and outputs the Nernst voltage signal of the oxygen sensor according to the air-fuel ratio control signal; The internal resistance adjustment module simulates the actual working temperature of the oxygen sensor by outputting a variable oxygen concentration difference battery internal resistance; A fault injection module, wherein the fault injection module performs output signal fault injection on the Nernst voltage output terminal and the virtual ground terminal of the oxygen sensor diaphragm; A DAC output module, wherein the DAC output module converts the digital command value of the air-fuel ratio control signal of the control module into an accurate analog output; A relay driving module, which improves the output driving capability of the IO pin of the control module, converts the relay control instruction output by the control module into a current signal to drive the relay to operate; A CAN bus transceiver module, which realizes bidirectional conversion between the CAN bus physical differential voltage signal and the digital signal, and transmits the digital signal to the control module; The hardware interface includes a CAN bus interface, a calibration terminal for a calibrated resistor, a pump current signal terminal, a virtual ground terminal, an oxygen sensor diaphragm Nernst voltage output terminal, and a heating current acquisition terminal. The hardware interface is connected to a real control unit of the engine.

2. The oxygen sensor signal simulation device according to claim 1, characterized in that: The control module sends the sampling results of the heating current measurement module to the engine hardware-in-the-loop test system through the CAN bus interface, and receives control instructions for the air-fuel ratio, oxygen sensor internal resistance and fault injection from the engine hardware-in-the-loop test system, and converts the instructions into control signals to control the pump unit control module, internal resistance adjustment module and fault injection module.

3. The oxygen sensor signal simulation device according to claim 1, characterized in that: The input end of the heating current measurement module is connected to the heating current acquisition end of the hardware interface, and the output end is connected to the control module, so as to transmit the PWM control signal of the real control unit for heating the oxygen sensor to the control module.

4. The oxygen sensor signal simulation device according to claim 1, characterized in that: The pump unit control module comprises a first instrument amplifier and a second instrument amplifier, wherein the positive input terminal of the first instrument amplifier is connected to the virtual ground terminal, the negative input terminal is connected to the pump current signal terminal, the negative input terminal is also connected to one end of the calibration resistor, the other end of the calibration resistor is connected to the calibration terminal of the calibration resistor, and the two ends of the pump unit resistor are connected between the positive and negative input terminals of the first instrument amplifier; the output of the first instrument amplifier is connected to the negative input terminal of the second instrument amplifier, the positive input terminal of the second instrument amplifier is connected to the output terminal of the voltage follower, the output terminal of the DAC output module is connected to the positive input terminal of the voltage follower as an air-fuel ratio control signal, and the air-fuel ratio control signal is connected to the positive input terminal of the voltage follower; the output terminal of the second instrument amplifier is connected to the input terminal of the internal resistance adjustment module as the Nernst voltage signal of the oxygen sensor.

5. The oxygen sensor signal simulation device according to claim 1, characterized in that: The input end of the internal resistance adjustment module is connected to the output end of the pump unit control module, and the output end of the internal resistance adjustment module is connected to the Nernst voltage output end of the oxygen sensor diaphragm.

6. The oxygen sensor signal simulation device according to claim 1, characterized in that: The internal resistance adjustment module is composed of a discrete resistor array and a photorelay array, and each discrete resistor is connected in parallel with a photorelay switch.

7. The oxygen sensor signal simulation device according to claim 1, characterized in that: The fault injection module is composed of four relays, three of which are used to perform fault injection on the Nernst voltage output end of the oxygen sensor diaphragm to achieve signal disconnection, short circuit to ground and short circuit to power supply at the Nernst voltage output end of the oxygen sensor diaphragm; and one relay is used to perform output signal fault injection on the virtual ground end to achieve signal disconnection at the virtual ground end.

8. The oxygen sensor signal simulation device according to claim 1, characterized in that: The DAC output module is connected to the control module via an SPI communication interface, and the output end is connected to the positive input end of the voltage follower in the pump unit control module, so as to transmit the PWM control signal of the real control unit for heating the oxygen sensor to the control module.

9. The oxygen sensor signal simulation device according to claim 1, characterized in that: The relay driving module is composed of a Darlington transistor.

10. The oxygen sensor signal simulation device according to claim 1, characterized in that: The CAN bus interface can be connected to the engine hardware-in-the-loop test system for two-way communication. The control module sends the sampling results of the heating current measurement module to the engine hardware-in-the-loop test system. The engine hardware-in-the-loop test system transmits the air-fuel ratio, oxygen sensor internal resistance and fault injection control instructions calculated thereby to the oxygen sensor signal simulation device through the CAN bus; the calibration resistance calibration terminal, pump current signal terminal, virtual ground terminal, oxygen sensor diaphragm Nernst voltage output terminal and heating current acquisition terminal are used to connect to the real control unit of the engine, and can send the simulation signal of the oxygen sensor to the real control unit of the engine.

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