WO1995011435A1

WO1995011435A1 - Measuring bench for automobile diagnosis

Info

Publication number: WO1995011435A1
Application number: PCT/FR1994/001174
Authority: WO
Inventors: Yannick Vernier; Christian Marchais
Original assignee: Souriau Diagnostic Electronique
Priority date: 1993-10-21
Filing date: 1994-10-07
Publication date: 1995-04-27
Also published as: FR2711795B1; EP0676044A1; FR2711795A1

Abstract

The measuring bench for automobile diagnosis is characterised in that it comprises a main element (1) having a central unit (3), measuring modules (31, 32, 33, 34) each having a measuring circuit (25, 26, 27, 28) for at least one measuring device (41, 42 ... 50) and a microprocessor (21, 22, 23, 24), the measuring circuit (25 ... 28) generating measuring signals; a first asynchronous link (10) between the main element (1) and each of the measuring modules (31, 32, 33, 34) and conveying the measuring signals between the modules (31 ... 34); and a second asynchronous link (20) between the measuring modules (31 .. 34). The first asynchronous link (10) has a first communication protocol which sets at least one module in an emission mode and the second asynchronous link (20) having a second protocol which conveys synchronisation transitions generated by the measuring modules (31 ... 34) between said modules (31 ... 34).

Description

MEASURING BENCH FOR AUTOMOTIVE DIAGNOSIS

The present invention relates to a measurement bench for automotive diagnostics.

There are already known measurement benches for automobile diagnostics, using a microprocessor (for example of the PC type) controlling several measurement takes to carry out an overall diagnosis on a vehicle.

Such test benches have specialized circuits for each of the measurements to be carried out on the vehicle, and therefore have a complicated structure which is less and less suited to the multiplicity and to the complexity of the tests to be carried out on motor vehicles.

It will be noted in particular that for a motor vehicle, the measurements to be carried out relate to sensors (Hall effect probes, electromagnetic probes, lambda probes) of the actuators (injectors, solenoid valves for example for idling regulation), measurements of the signals coming from the ignition (coil), temperature (thermocouple) or pressure signals, or vehicle beam tests.

The subject of the present invention is a measurement bench for automobile diagnostics which has a modular structure capable of simplifying the design and / or production thereof relative to known measurement benches.

The invention thus relates to a measurement bench for automobile diagnostics, characterized in that it comprises:

- a main element comprising a central unit

- measurement modules each having a measurement circuit for at least one measurement device and a microprocessor, the measurement circuit generating measurement signals

a first asynchronous link between the main element and each of the measurement modules and conveying the measurement signals between the modules and a second asynchronous link between the measurement modules, the first asynchronous link presenting a first communication protocol making it possible to put at least one module in transmission mode and the second asynchronous link presenting a second protocol making it possible to convey between the modules event transitions generated by the measurement modules.

This architecture makes it possible to simplify the communication protocol, in that only one module at a time is capable of transmitting towards the central unit, while the logical synchronization information, which concerns the inter-module dialogue, is conveyed by a bus connecting the microprocessor of the modules.

The central unit of the main element advantageously comprises a means for downloading the microprocessor programs from the measurement modules.

Such an architecture thus allows standardization of modules. These can thus be at least partly identical.

The first protocol can be used to program each module either in transmission mode, in reception mode, or in high impedance mode.

According to a preferred mode, the first protocol comprises means for programming a single module in transmission mode on the second asynchronous link.

The measurement bench according to the invention can be characterized in that the measurement circuit of at least one module comprises a measurement unit having a single input for at least two measurement devices. The measuring devices can be sensors and / or actuators of a motor vehicle.

The invention also relates to a measurement unit (or card) comprising

- an input stage for at least two measuring devices

- at least two amplifier stages arranged in parallel and whose input is coupled to the output of the input stage and whose output is coupled to as many inputs of a multiplexer - said multiplexer whose output is coupled to the input of a filtering circuit

- an analog-digital converter having an input coupled to the output of the filtering circuit

the multiplexer and the filtering circuit being controlled by said microprocessor so as to select a range of measurements as a function of the measurement device coupled to the input stage.

According to an advantageous variant, the measurement unit comprises a digital-analog converter controlled by the microprocessor and the output of which is connected to an input of an offset voltage control circuit disposed between the filtering circuit and the analog-to-converter. digital.

The input stage may include a calibration circuit allowing its inputs to be grounded, the calibration circuit being controlled by the microprocessor.

The measurement unit can also include a threshold discrimination circuit having an input coupled to the output of the filtering circuit and having at least one output producing said synchronization transitions.

The above circuit (or measurement card) can be incorporated into the measurement circuit of at least one module.

Other characteristics and advantages of the invention will appear better on reading the description which follows, given by way of nonlimiting example, in conjunction with the drawings which represent:

FIG. 1, a measurement bench having an architecture according to the invention,

- Figure 2, an automatic switching measurement card to receive as input the signals from different types of sensors or actuators.

According to FIG. 1, a main element designated by the general reference 1 consists of a measurement carriage having a central processing unit 3 with a microcomputer, for example of the PC type, and a screen 2 for displaying signals. It is connected by an asynchronous serial bus 10 to measurement modules 31, 32, 33 and 34 each having a microprocessor respectively 21, 22, 23 and 24 and one or more measuring devices (respectively 25, 26, 27 and 28 connected to sensors, actuators, or to generators of measurement signals, referenced 41, 42 and 43 for module 31, 44 and 45 for module 32, 46 for module 33 and 47, 48, 49 and 50 for module 34.

An asynchronous serial bus 20 also connects the microprocessors 21 to 24 together, but is not connected to the central unit 3 of the main element 1.

Bus 10 can be of the RS485 type operating, for example, under the ISO 8802-30 protocol which is a simplified version of the CSMA / CRCD protocol with deterministic collision resolution.

The bus 10 makes it possible to retransmit the measurement signals between the modules 31 to 34 and the main element 1 and to select the operating mode of the bus 20.

Bus 20, using for example the physical RS485 medium, is governed by a protocol, reduced to transmission reception, of logic signals representative of transitions of physical events, the transmission speed and format of which are not pre-defined. The bus 20 therefore makes it possible to broadcast to all the modules 21 to 24 signals representing logic levels or transitions characteristic of vehicle events and which are used for measurement triggering purposes.

The course of a motor vehicle diagnosis can then be as follows:

When the installation is powered up, the central unit 3 downloads via the bus 10, as in itself, the programs of the microprocessors 21 to 24.

For the course of the measurement sequence, the central unit ("master") which is capable, by the protocol adopted, of configuring any of the microprocessors 22 to 24 in one of three modes on the bus 20 , namely the transmission mode, the reception mode and the high impedance (or inactive) mode, programs one of the microprocessors ("slaves"), for example the one referenced 22 and it alone, in transmission mode on the bus 20. This selects the module 32, and only it, to send transitions which are sent on the bus 20 for the other modules. Bus 20, the operating mode of which, once initialized by the central unit 3, is independent of this allows logic information to flow between the microcomputers 21 to 24 of the modules 31 to 34.

On detection of one or more transitions, one or more of the modules 31 to 34 trigger measurements and transmit them to the central unit 3 by the bus 10 (interactive mode). There is also an independent mode where one or more modules carry out measurements and retransmit them to the central unit 3. One or more modules can operate in interactive mode at the same time as one or more other modules operate in independent mode.

Indeed, suppose that the measurement of the sensor 44 of the selected module 32 is only significant when the signal delivered by the sensor 49 of the module (not selected) 34 has reached a certain high H or low B threshold, and that it must not therefore be sent on bus 10 only when this threshold is reached.

In this case, when said threshold is reached, the microprocessor 24 sends the corresponding logic signal (or transition) on the bus 20 to all the other modules. The microprocessor of an active module detects this transition and then begins to transmit on bus 10 the signals from a sensor. The logic signal therefore fulfills the function of a trigger synchronization signal for the signals from this sensor. The microprocessor 22 can also transmit said transition on the bus 10 to the central unit 3.

Note that, since the modules 31 to 34 are controlled by the central unit 3, there is no need for the microprocessor 22 to identify the origin of the transition, since, by definition, in the given configuration only the sensor 43 is capable of generating a logic signal.

According to FIG. 2, an automatic switching measurement card designated by the general reference 60 has a single differential input for different sensors and / or actuators, for example for a sensor (lambda probe for measuring oxygen content in a catalytic converter) and two actuators (injector and idle control solenoid valve). These probes and actuators deliver very different signals as to their level (low or high), their frequency spectrum. For example, an injector has voltage peaks of up to 80 V, while a lambda probe delivers very low frequency signals of low level. The measurement card comprises two input resistors R \ and R2 of high value, and an input stage with differential amplifier AQ mounted so as to produce an attenuation (for example in a ratio 100) (resistors R3 to R7).

In series between the resistors R \ and R2 and the input resistors respectively R3 and R4 of the amplifier AQ is disposed a relay switch C controlled by the internal bus 50 to the microprocessor MP and which allows, in a position to connect in series R \ to R3 and R2 to R4 to make a measurement, and in the other position, ground the inputs of the amplifier AQ to adjust the overall offset voltage of the measurement card .

The output of the amplifier AQ attacks in parallel the input of three amplifiers A \, A2, A3 counter-reacted (respectively Rg, Rj]; R9 Rj2 and RlO _. R13) To obtain gains in stages for example 1 for A \, 10 for A2 and 100 for A3.

The output of amplifiers Ai to A3 drives a multiplexer MUX controlled by the bus 50 of the microprocessor MP. This multiplexer can be of the type

MAX 508 or MAX 509 from MAXIM Inc.

Depending on the type of sensor to which the differential input (El, E2) is connected, the bus 50 can automatically route the output of the most suitable amplifier among Ai, A2 and A3 to the output of the multiplexer MUX.

This can be done either because the microprocessor MP knows positively what type of sensor it is, or by an automatic range detection procedure, then automatic determination of the measurement range by successive approximations allowing obtain the greatest dynamics without signal clipping ("auto-ranging").

The output of the multiplexer MUX drives a filtering circuit F, here of the low-pass type, the cut-off frequency of which can be programmed between 2 Hz and 25 kHz for example, by the microprocessor MP via the bus 50. The circuit F can for example be of the MAX 291 to 296 type from the company MAXIM Inc.

The output of the filter F drives an input of a differential amplifier A6 of unity gain (Ri 4, Ri 5, Ri 6) the other input of which receives from a multiple DAC digital-analog converter controlled by the bus 50, a signal adjustable offset voltage. The output of filter F also attacks an input of a differential amplifier A4 (comparator) and a differential amplifier A5 (comparator), the other input of which receives one of two threshold signals generated by the DAC converter controlled by bus 50. This gives the output of A4 a high threshold signal H and a low threshold signal B at the output of A5. The DAC converter can be of the MAX 528 type from the company MAXIM Inc.

An OR gate receives the H signals at its inputs and makes it possible to generate the T transitions. The H and L signals and the T transitions are introduced into logic inputs of the microprocessor MP.

The logic card of FIG. 2 can be incorporated into one or more modules of FIG. 1, in which case the microprocessor MP is constituted by the corresponding microprocessor 21, 22, 23 and / or 24 of the corresponding module. Since the modules 31 to 34 are configurable by the central unit 3, it is possible to use modules 31 to 34 which are wholly or partly identical.

The output of amplifier A drives an input from an analog-to-digital converter ADC for digitizing the measurement signals. The output of the ADC converter is delivered to the microprocessor MP.

Claims

1. Measuring bench for automobile diagnostics, characterized in that it comprises:

- a main element (1) comprising a central unit (3)

- measurement modules (31, 32, 33, 34) each having a measurement circuit (25, 26, 27, 28) for at least one measurement device (41, 42 ... 50) and a microprocessor (21 , 22, 23, 24), the measurement circuit (25 .... 28) generating measurement signals

a first asynchronous link (10) between the main element (1) and each of the measurement modules (31, 32, 33, 34) and conveying the measurement signals between the modules (31 ... 34) and

- a second asynchronous link (20) between the measurement modules (31 ... 34) ,.

the first asynchronous link (10) presenting a first communication protocol making it possible to put at least one module in transmission mode and the second asynchronous link (20) presenting a second protocol making it possible to convey between the modules (31 ... 34) event transitions generated by the measurement modules (31 ... 34).

2. Measuring bench according to claim 1, characterized in that the central unit (3) of the main element (1) comprises a means for downloading the microprocessors from the programs of the measurement modules (31 ... 34).

3. Measuring bench according to claim 1, characterized in that the first protocol includes a means for programming each module (31 ... 34) either in transmission mode or in reception mode, or in high impedance mode.

4. Measuring bench according to claim 1, characterized in that the first protocol comprises means for programming a single module in transmission mode on the second asynchronous link (20).

5. Measuring bench according to one of the preceding claims, characterized in that the measuring circuit (25 ... 28) of at least one module (31 ... 34) comprises a measuring unit (60) having an input unique for at least two measuring devices (41 ... 50).

6. Measuring bench according to claim 5, characterized in that the measuring devices (41 ... 50) are sensors and / or actuators of a motor vehicle.

7. Measuring bench according to one of claims 5 or 6, characterized in that the measuring unit comprises:

- an input stage (A) for at least two measuring devices (41 ... 50)

- at least two amplifier stages (Aj, A2 _. A3) arranged in parallel and whose input is coupled to the output of the input step (AQ) and whose output is coupled to as many inputs of a multiplexer (MUX)

- said multiplexer (MUX) whose output is coupled to the input of a filtering circuit (F)

- an analog-digital converter (ADC) having an input coupled to the output of the filtering circuit (F)

- the multiplexer (MUX) and the filtering circuit (F) being controlled by said microprocessor (MP) so as to select a range of measurements according to the measuring device (41 ... 50) coupled to the stage of Entrance

8. Measuring bench according to claim 7, characterized in that the measurement unit has a digital-analog converter (DAC) controlled by the microprocessor (MP) and whose output is connected to an input of a control circuit offset voltage (A6) arranged between the filtering circuit (F) and the analog-digital converter (ADC).

9. Measuring bench according to one of claims 7 or 8, characterized in that the input stage (A _υ ) of the measurement unit comprises a calibration circuit (C) allowing its inputs to be grounded, the calibration circuit (C) being controlled by the microprocessor (MP).

10. Measuring bench according to one of claims 7 to 9, characterized in that the input stage (An) is an attenuator stage.

11. Measuring bench according to one of claims 7 to 10, characterized in that the measuring unit (60) comprises a threshold discrimination circuit (A4, A5) having an input coupled to the output of the filtering circuit (F ) and having at least one output producing said synchronization transitions (T).