JP2019211381A - Electronic control device - Google Patents

Abstract

To obtain an electronic control device with which it is possible to detect circuit abnormality at low cost without adding a redundant circuit.SOLUTION: There is provided an electronic control device 1 equipped with a microprocessor 6 having an AD conversion unit 10, for transferring a voltage signal inputted from the outside from input terminals 9a-9n of the microprocessor 6 to the AD conversion unit 10 via low-pass filters 5a-5n. The electronic control device 1 detects open abnormality in the input terminals 9a-9n of the microprocessor 6 and/or the low-pass filters 5a-5n by comparing a change speed of the AD conversion value with a threshold Sth for an AD change speed calculated using the circuit constants of the low-pass filters 5a-5n.SELECTED DRAWING: Figure 1

Description

  The present application relates to an electronic control device that AD-converts a voltage signal input from the outside using a microprocessor.

  In a system using an electronic control unit that AD-converts a voltage signal input from an external sensor or the like by a microprocessor, if an open abnormality occurs in the input terminal of the microprocessor or the preceding circuit as a transmission path There is a problem that the voltage at the input terminal of the microprocessor becomes unstable depending on where the abnormality occurs.

  As a technique for detecting the occurrence of this open abnormality, for example, there is a technique disclosed in Patent Document 1. In Patent Document 1, a test capacitor connected to a voltage signal input terminal is provided in an IC that performs AD conversion, and the test capacitor is charged to 5 V or 0 V at the time of initialization or sampling in AD conversion. The switch connects the voltage signal input terminal and the inspection capacitor. When the AD conversion value is a value close to 5V or 0V, it is determined that there is a possibility that an open abnormality of the voltage signal input terminal has occurred.

JP 2012-145411 A

  However, in the technique disclosed in Patent Document 1, it is necessary to provide a test capacitor and a test switch for connecting the test capacitor to the voltage signal input terminal. In addition, there is a problem that a complicated processing load for charging the inspection capacitor or executing the switching control of the inspection switch occurs. Furthermore, there is a problem that an IC chip for installing a test capacitor and a test switch is required, and the area of the substrate is required.

  The present application discloses a technique for solving the above-described problems, and an object thereof is to provide an electronic control device capable of detecting a circuit abnormality at a low cost without adding a redundant circuit. .

An electronic control device disclosed in the present application includes a microprocessor having an AD conversion unit, and transmits a voltage signal input from the outside to the AD conversion unit from an input terminal of the microprocessor via a voltage signal input circuit, An electronic control device for calculating an AD conversion value,
The open abnormality of at least one of the input terminal of the microprocessor and the voltage signal input circuit is compared with the threshold value of the voltage change rate calculated using the circuit constant of the voltage signal input circuit and the change rate of the AD conversion value. It is characterized by detecting.

  According to the electronic control device disclosed in the present application, it is possible to detect a circuit abnormality at low cost without adding a redundant circuit by monitoring the voltage change speed of the AD conversion value and whether or not the original conversion value converges. There is.

1 is a block configuration diagram of an electronic control device according to Embodiment 1. FIG. 4 is a flowchart of abnormality determination by the electronic control device according to the first embodiment. It is a figure which shows the mode of the state of AD conversion by the electronic controller which concerns on Embodiment 1, and the mode of calculating the absolute value of AD change speed.

Embodiment 1.
FIG. 1 is a block configuration diagram of the electronic control device according to the first embodiment. In FIG. 1, a first sensor 3 a to an nth sensor 3 n provided outside the electronic control device 1 are connected to a plurality of connectors 2 a to 2 n of the electronic control device 1, respectively. The first sensor 3a to the nth sensor 3n are sensors such as a water temperature sensor or an accelerator position sensor that detects the amount of depression of the accelerator. The first sensor 3a to the nth sensor 3n correspond to the detected temperature or operation amount from the first sensor 3a to the nth sensor 3n. In general, a voltage signal obtained by removing the voltage range for failure determination from 0 to 5V is output. The voltage signals of the first sensor 3a to the nth sensor 3n input to the electronic control device 1 via the connectors 2a to 2n are potential fixing resistors 4a to 4n for detecting an open abnormality of the connectors 2a to 2n. And voltage signal input circuits 5a to 5n. The voltage signal input circuits 5a to 5n are generally configured by a low-pass filter that removes noise. In the following description, the voltage signal input circuit is described as a low-pass filter.

  The low-pass filters 5a to 5n are connected to the series resistors 7a to 7n connected in series between the first sensor 3a to the nth sensor 3n and the microprocessor 6, and between the series resistors 7a to 7n and the microprocessor 6, and to the GND. And capacitors 8a to 8n connected to each other. That is, the voltage signals output from the first sensor 3a to the nth sensor 3n outside the electronic control device 1 are subjected to noise removal by the low-pass filters 5a to 5n via the connectors 2a to 2n of the electronic control device 1. The signal is transmitted from the input terminals 9a to 9n of the microprocessor 6 to the AD conversion unit 10, and after AD conversion by the AD conversion unit 10, it is stored in the RAM 11 and used for control.

  That is, the first external load 13a to the nth external load 13n, which are loads such as an injector connected to the outside of the electronic control unit 1 or an ignition coil, according to the AD conversion value stored in the RAM 11 and the program written in the ROM 12. Is controlled via output I / F circuits 14a to 14n provided in the electronic control unit 1.

  Here, when an open abnormality occurs in the connectors 2a to 2n of the electronic control unit 1, the voltage applied to the input terminals 9a to 9n of the microprocessor 6 is the potential fixed by the resistors 4a to 4n for fixing the potential. Failure detection is possible by AD-converting this fixed potential that is input. However, when an open abnormality occurs due to a solder crack or the like in the series resistors 7a to 7n constituting the low-pass filters 5a to 5n or the input terminals 9a to 9n of the microprocessor 6, it is applied to the AD conversion unit 10 of the microprocessor 6. The voltage is indefinite because the potential cannot be fixed.

  Therefore, even when an open abnormality occurs in the input terminals 9a to 9n and the series resistors 7a to 7n of the microprocessor 6, it is necessary to detect that the open abnormality has occurred.

FIG. 2 is a flowchart for explaining a method of detecting the possibility that an open abnormality has occurred when an open abnormality occurs in the input terminals 9a to 9n and the series resistors 7a to 7n of the microprocessor 6.
In FIG. 2, first, processing is started in step S20. Next, in step S21, an AD change speed absolute value Cn described later is calculated.

  Next, in step S22, it is determined whether or not the AD change speed absolute value Cn exceeds a preset AD change speed threshold value Sth. The threshold value Sth of the AD change rate is set to about 90% of the absolute value of the AD change rate when the input terminals 9a to 9n of the microprocessor 6 or the series resistors 7a to 7n of the low-pass filters 5a to 5n are actually opened. However, the following formula (1) may be used as the AD change speed threshold value Sth.

That is, the voltage applied to the input terminals 9a to 9n of the microprocessor 6 is V, Δt is the AD conversion period of the microprocessor 6, and C is the capacitance value [F] of the capacitors 8a to 8n of the low-pass filters 5a to 5n. , R is the resistance value [Ω] of the series resistors 7a to 7n of the low-pass filters 5a to 5n, and v is the voltage [V] across the capacitors 8a to 8n.
V = RCΔv / Δt + v, and when converted,
RCΔv / Δt = V−v, and Δv / Δt = (V−v) / (RC).
When V = 0 to 5 [V] and v = 0 to 5 [V], the AD change speed threshold value Sth is expressed by the following equation (1).
Sth = | ΔV / Δt | ≦ 5 / RC (1)

  If a negative determination is obtained in step S22, the process proceeds to step S23, where it is determined that there is no possibility of abnormality, and the process ends. If an affirmative determination is obtained in step S22, the process proceeds to step S24 to set a return determination voltage upper limit LU, a return determination voltage lower limit LD, which will be described later, and a return determination time Tt, which will be described later. The return determination time Tt is set longer than the time until the voltage fluctuation due to the transient noise superimposition converges.

  In the subsequent step S25, it is determined whether or not the AD conversion value is between the return determination voltage upper limit LU and the return determination voltage lower limit LD within the return determination time Tt. If an affirmative determination is obtained, the process proceeds to step S23, where it is determined that there is no possibility of abnormality, and the process ends.

  On the other hand, if a negative determination is obtained in step S25, the process proceeds to step S26, where it is determined that there is a possibility of abnormality, and the process ends.

  Next, an open abnormality detection method will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A shows the state of AD conversion in the AD conversion unit 10 of the microprocessor 6. The conversion cycle of AD conversion is Δt, and the AD conversion value at a certain time tn is Vn. The time before one sample is tn-1, the AD conversion value is Vn-1, the time before the sample is tn-2, and the AD conversion value is Vn-2. Similarly, the AD conversion value at time tn + 1 is Vn + 1, the AD conversion value at time tn + 2 is Vn + 2, and the AD conversion value at time tn + 3 is Vn + 3.

FIG. 3B shows how to calculate the absolute value of the AD change speed from the AD conversion value of FIG. The AD conversion speed absolute value Cn at time tn is expressed by the following equation (2) using the AD conversion value Vn at time tn, the AD conversion value Vn-1 at time tn−1, and the conversion cycle Δt. be able to.
Cn = | ((Vn) − (Vn−1)) / Δt | (2)
Similarly, the AD conversion speed absolute value Cn-1 at time tn-1 can be expressed as the following formula (3).
Cn−1 = | ((Vn−1) − (Vn−2)) / Δt | (3)
Further, the AD conversion speed absolute value Cn + 1 at the time tn + 1 can be expressed by the following equation (4) using the AD conversion value Vn + 1 at the time tn + 1, the AD conversion value Vn at the time tn, and the conversion cycle Δt. The AD conversion speed absolute value Cn + 2 at time tn + 2 can be expressed by the following expression (5), and the AD conversion speed absolute value Cn + 3 at time tn + 3 can be expressed by the following expression (6). it can.
Cn + 1 = | ((Vn + 1) − (Vn)) / Δt | (4)
Cn + 2 = | ((Vn + 2) − (Vn + 1)) / Δt | (5)
Cn + 3 = | ((Vn + 3) − (Vn + 2)) / Δt | (6)

  At time tn + 1, after the AD conversion value rapidly increases from Vn to Vn + 1 and exceeds the threshold value Sth of the AD change speed, at time tn + 2, between the return determination voltage upper limit LU and the return determination voltage lower limit LD, as Vn + 2. If it is within the range, it can be determined that there is no possibility of an open abnormality. Note that ΔVt between the return determination voltage upper limit LU and the return determination voltage lower limit LD is the return determination voltage value, and this return determination voltage value ΔVt is the AD conversion value immediately before exceeding the threshold Sth of the AD change speed. Set based on.

  Here, the return determination voltage upper limit value LU and the return determination voltage lower limit value LD are respectively LU = Vn + ΔVt with reference to the AD conversion value Vn one sample before the time when the AD conversion value exceeds the threshold value Sth of the AD change speed. / 2, LD = Vn−ΔVt / 2. In the case of noise, since it generally returns to the same AD value as before the noise is superimposed, ΔVt = 0 may be set, but ± 5% to 10% based on the value Vn immediately before exceeding the threshold Sth of the AD change speed. You may give the width of.

  Furthermore, the return determination time Tt may be set to be equal to or less than the time taken to actually open and return the input terminals 9a to 9n of the microprocessor 6.

  Here, also at time tn + 3, which is the end point of the return determination time Tt, if the AD conversion value becomes V′n + 3 indicated by the plot ○ in FIG. 3, it is determined that there is a possibility of an open abnormality. become. In FIGS. 3A and 3B, the AD change rate absolute value is calculated for each AD conversion sample time Δt, and it is determined whether or not the AD change rate threshold value Sth is exceeded. In order to reduce the processing load on the microprocessor 6, it is possible to determine whether or not there is an open abnormality by executing the processing from step S20 to step S23 shown in FIG.

  As described above, the voltages of the input terminals 9a to 9n of the microprocessor 6 are input through the voltage signal input circuit constituted by the low-pass filters 5a to 5n, but the open abnormality is detected in the input terminals 9a to 9n of the microprocessor 6. When this occurs, the AD conversion value calculated by the microprocessor 6 is a fluctuation exceeding the threshold Sth of the AD change speed calculated from the circuit constants of the voltage signal input circuit generally constituted by the low-pass filters 5a to 5n. Become. By detecting this variation, it is possible to detect that there is a possibility of an open abnormality of the input terminals 9a to 9n of the microprocessor 6 or the low-pass filters 5a to 5n that are the transmission paths thereof.

  However, even when noise is superimposed on the input terminals 9a to 9n of the microprocessor 6 or its transmission path, the threshold value Sth of the AD change speed may be exceeded. For this reason, it is necessary to distinguish between noise superposition and circuit open abnormality. When noise superposition is the cause, when noise superposition disappears, it returns to the same AD conversion value as before noise superposition, whereas when the input terminals 9a to 9n of the microprocessor 6 or the transmission path is open abnormally, It takes time until the AD conversion value is the same as that before the occurrence of the abnormality.

  Therefore, as in the electronic control device 1 according to the first embodiment, the return determination time Tt is set longer than the time until the voltage fluctuation due to the transient noise superposition converges, and exceeds the AD change speed threshold value Sth. When the time until the AD change rate returns to the AD conversion value before exceeding the threshold value Sth exceeds a preset return determination time Tt, it is determined that there is a possibility of a circuit failure, and thus noise superimposition and circuit It becomes possible to distinguish abnormalities.

  As described above, according to the electronic control device 1 according to the first embodiment, after the AD conversion value exceeds the preset AD change speed threshold value Sth, the AD change occurs within the preset return determination time Tt. When the value does not return to the value immediately before exceeding the speed threshold value Sth, it is determined that there is a possibility of a circuit abnormality including terminal open rather than noise superimposition. In other words, when a circuit abnormality occurs that causes a terminal to open, the voltage of the AD conversion value generally changes beyond the filter constant of the input circuit and does not converge to the original value, or even if it converges, it takes time. By paying attention to the above, by monitoring the voltage change speed of the AD conversion value and whether or not it converges to the original value, it is possible to detect a circuit abnormality at low cost without adding a redundant circuit.

Although this application has described exemplary embodiments, the various features, aspects, and functions described in the embodiments are not limited to the application of a particular embodiment, but can be used alone or in various ways. The present invention can be applied to the embodiments in various combinations.
Accordingly, innumerable modifications not illustrated are envisaged within the scope of the technology disclosed in the present application. For example, the case where at least one component is modified, the case where it is added, or the case where it is omitted are included.

1 electronic control unit, 2a, 2n connector, 3a first sensor, 3n n sensor, 4a, 4n resistor, 5a, 5n voltage signal input circuit (low-pass filter), 7a, 7n series resistor, 8a, 8n capacitor, 9a, 9n input terminal, 10 AD converter, 11 RAM, 12 ROM, 13a first external load, 13n n external load, 14a, 14n output I / F circuit, Cn AD conversion speed absolute value, threshold of Sth AD change speed, LU recovery determination voltage upper limit value, LD recovery determination voltage lower limit value, Tt recovery determination time.

An electronic control device disclosed in the present application includes a microprocessor having an AD conversion unit, and transmits a voltage signal input from the outside to the AD conversion unit from an input terminal of the microprocessor via a voltage signal input circuit, An electronic control device for calculating an AD conversion value,
The open abnormality of at least one of the input terminal of the microprocessor and the voltage signal input circuit is compared with the threshold value of the voltage change rate calculated using the circuit constant of the voltage signal input circuit and the change rate of the AD conversion value. detected,
When the AD conversion value returns to the return determination voltage value within the return determination time after exceeding the voltage change speed threshold, it is determined that the open abnormality is not detected.

Claims (5)

An electronic control device that includes a microprocessor having an AD conversion unit, transmits a voltage signal input from the outside to the AD conversion unit from the input terminal of the microprocessor via a voltage signal input circuit, and calculates an AD conversion value. There,
The open abnormality of at least one of the input terminal of the microprocessor and the voltage signal input circuit is compared with the threshold value of the voltage change rate calculated using the circuit constant of the voltage signal input circuit and the change rate of the AD conversion value. An electronic control device for detecting.   2. When the change rate of the AD conversion value exceeds the threshold value of the voltage change rate and returns to the return determination voltage value within the return determination time, it is determined that the open abnormality is not present. The electronic control apparatus as described in.   The electronic control device according to claim 2, wherein the return determination voltage value is set based on the AD conversion value immediately before exceeding the threshold value of the voltage change speed.   The electronic control device according to claim 2, wherein the return determination voltage value is a voltage value between a return determination voltage upper limit value and a return determination voltage lower limit value.   5. The electronic control device according to claim 2, wherein the return determination time is set longer than a time until voltage fluctuation due to transient noise superimposition converges.

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