GB1596191A

GB1596191A - Process and apparatus for testing the operation of a brake antilocking control system

Info

Publication number: GB1596191A
Application number: GB720/78A
Authority: GB
Original assignee: Wabco Fahrzeugbremsen GmbH
Current assignee: Wabco Fahrzeugbremsen GmbH
Priority date: 1977-01-13
Filing date: 1978-01-09
Publication date: 1981-08-19
Also published as: FR2377308B1; JPS5388490A; DE2701159B2; DE2701159A1; JPH0141536B2; SE437499B; FR2377308A1; DE2701159C3; SE7800222L

Description

(54) PROCESS AND APPARATUS FOR TESTING THE OPERATION OF A BRAKE ANTI-LOCKING CONTROL SYSTEM (71) We, WABCO FAHRZEUG BREMSEN G.m.b.H,, formerly Wabco Westinghouse G.m.b.H., a Company organised according to the laws of the Federal Republic of Germany, of 3000 Hannover 91, Postfach 91 12 80, Federal Republic of Germany; do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a process and apparatus for testing the operation of a brake anti-locking control system.

The braking of a motor vehicle with a brake anti-locking control system can result in very dangerous situations if a fault occurs in the electronic arrangement of the antilocking control system. Therefore, it is necessary to provide monitoring circuits which, when faults occur, serve to detect them and to prevent potentially dangerous and unreliable control situations developing by correction or cut-out signals. It is therefore necessary to test the operational ability and reliability of the electronic switching devices, which serve the purpose of energising pressure control valves of the brake system. Such testing may be performed occasionally or preferably at given intervals of time, and the testing may be carried out continuously under different operational conditions of the vehicle.

A testing device of this type has been described in which a simulated control signal is produced by short-circuiting a wheel revolution rate transmitter or sensor, and the system is then tested to discover whether it reacts to this signal. The disadvantage is that once the sensor is shortcircuited, it is no longer possible to recognise at what instant the short-circuit should be terminated, which means there is the danger that an unspecific remainder of the duration of the short-circuit be measured and evaluated and thus for a short time excessively high speed values are determined.

Another testing device has been proposed in which it is possible to test the satisfactory function of the anti-lock control system only before starting off, that is, when the vehicle is stationary.

It is an object of the present invention so to improve a process and an apparatus of this type that the disadvantages of the known processes and apparatus are at least partially avoided and that it is possible in particular to test at any time prior to and during operation whether the brake antilocking control system can produce control signals and whether the magnets of the braking pressure control valves are actuated.

According to one aspect of the present invention there is provided a process for testing the operation of an anti-lock control system, which has wheel speed sensors, brake pressure control valves, a plurality of similar control circuits each capable of producing control signals suitable for use in controlling the brake pressure control valves, the process including the application of the same testing signal to at least two of the control circuits, comparing control signals generated by the control circuits in response to the testing signal and producing an error signal when the control signals generated by two control circuits in response to the same testing signal differ.

According to a second apsect of the present invention there is provided apparatus for testing the operation of a brake anti-locking control system having wheel speed sensors, and a plurality of similar control circuits each able to produce control signals by means of which magnetic brake pressure control valves can be energised and actuated, the apparatus including a device for producing testing signals, means for applying the testing signals to at least two control circuits, and at least one comparator, which is connected to receive control signals produced in response to the testing signals from two of the at least two control circuits, and the output of which is connected to a fault displaying device to produce an indication of malfunctioning when the control signals produced by the two control circuits differ.

One advantage of the present invention is that it is possible to carry out testing to ascertain whether a control process can or cannot operate correctly irrespective of the driving conditions. The comparison with a reference signal produced in response to the same testing signal has the advantage that, as regards the circuit, it is not necessary to prescribe the points in time at which the output signals to be tested appear.

In an advantageous further development of the invention, a testing pulse is also produced and applied to an output amplifier connected to drive a magnetic valve, the output of which amplifier is scanned and compared with the testing pulse. This makes possible the advantage that the testing of the final stages, including the energisability of the magnets, does not result in any excitation of the magnets, which means that testing can be carried out even when the vehicle is in motion.

After scanning of the output signal of the output amplifier and after interrupting the energisation of the magnetic valve, testing signals having a simulated wheel speed sensor frequency are produced and fed to at least one control circuit of the control system, the output signals of which circuit are compared with associated reference signals. These reference signals are produced by a separate reference signal control circuit or by a control circuit associated with another wheel.

A safety circuit may be integrated in a single unit or in two separate units. The integration into a single unit has the advantage of involving little expenditure in terms of construction, while the arrangement in two separate units correspondingly increases the likelihood of detecting faults.

In order that the invention may be fully understood and readily carried into effect embodiments of the invention will now be explained in greater detail with reference to the accompanying drawings, of which: Figure 1 shows a first embodiment of an apparatus for testing the function of a brake anti-locking control system; Figure 2 shows a second embodiment of apparatus according to the invention with a testing and safety circuit which is arranged in a unit separate from that of the control channels; Figure 3 shows the apparatus of Figure 2, but in which the testing and safety circuit is integrated with the control circuit in one unit; and Figure 4 shows basically the construction of the testing circuit according to Figures 2 and 3.

Figure 1 will firstly be considered. In this Figure, a sensor 2 supplies signals representing a wheel rotation rate via a logic circuit 4, including AND-gates 32 and 34 and OR-gate 36, to a control channel 6 of a brake anti-locking control system. In order to stimulate the sensor signals for testing purposes, a generator 8 is provided. A control device 10 controls the testing operations.

A testing operation takes place as follows.

After initiation of a testing operation, there firstly appears at output 12 of the control device 10 a signal which is fed by means of a lead 14, an OR-gate 16 and an AND-gate 18 to an amplifier 20 and from the amplifier 20 the amplified signals are applied to magnet 22 of a magnetic valve. The further output 24 of the control device 10 is "low" at this time. The signal at the output 12 of the control device 10 is also fed to an input of a comparator 28 via a lead 26, which comparator receives via a lead 30 at its other input the output signal of the amplifier 20.

If the signal chain from the OR-gate 16 to the magnet 22 is working correctly, the amplifier 20 produces an output signal. The output signal of the amplifier 20 is compared by the comparator 28 with the testing pulse or the testing signal produced by the control device 10. If no fault is detected, the control device can interchange the outputs on the conductors 12 and 24, so that the output 12 becomes "low" and the output 24 becomes "high". The "high" signals at the output 24 interrupts firstly the energisability of the final stage (amplifier 20 and magnet 22) by blocking the AND-gate 18 and also enables a signal from the generator 8, which signal simulates the wheel speed signal from the sensor 2, to be fed via the AND-gate 34 and the OR-gate 36 to the control channel 6 which is to be tested instead of the signal from the sensor 2, the gate 32 being closed. The output signal from the generator 8 is also fed to a reference control channel 38 which produces a reference signal, which signal is compared in a comparator 40 with the output signal from the wheel control channel 6. The output signal of the generator 8 is regulated by means of an output 42 of the control device 10. If no fault is detected, the testing cycle is complete and the control device 10 is reset.

If a fault is detected during testing of the final stage and of the magnet 22 by comparison of the associated signals in the comparator 28, a fault displaying device 48 is energised by an output signal of the comparator 28 transmitted via an OR-gate 50 and an AND gate 52, so as to indicate the fault. At the same time, by means of a re-set lead, not shown, the control device 10 is reset, as a result of which simulated wheel signals are no longer produced and testing is discontinued.

If a fault is detected during testing of the control channel 6, there appears at the output of the comparator 40 a difference signal which is likewise fed to the fault displaying device 48 by means of the gates 50 and 52. In this case, too, the control device 10 is reset by means of a reset lead, not shown, and with this the testing process is ended.

It is an advantage and also important that testing be stopped when braking is initiated.

For this, as illustrated by way of example, a lead passes from a brake light switch to an input 54 of the control device 10 by means of which lead in this case the control device 10 is reset and thus a testing programme that is already in progress is interrupted.

Instead of a separate reference signal channel 38, it is also possible for another control channel associated with another wheel to be taken as a reference channel. In this case, it would likewise be necessary for the energising of the magnet valves to be interrupted.

In the case of four-wheel brake antilocking control, four steps would be necessary for complete testing of the control channels. In this case, firstly all final stages are tested; if these are found to be sound, then all channels of the anti-lock control system receive the simulated wheel frequency and are compared with one another. In this manner, complete and reliable testing of the anti-lock control system as a whole is possible.

Figure 2 will now be considered; this Figure shows one connection of a testing and safety circuit, in which the safety circuit is arranged in a switching circuit of its own, separate from the wheel control circuits.

A control circuit 62 is allocated to a first wheel sensor 60 and a control circuit 66 is allocated to a further wheel sensor 64. The control circuit 62 has output amplifiers 68 and 70, and also magnets 72 and 74 of an outlet and inlet valve respectively; to outputs of the control circuit 66 are connected corresponding output amplifiers 76 and 78 and also magnets 80 and 82 of an outlet and inlet valve.

A safety circuit 84 has two safety circuit channels 86 and 88 which are arranged in one unit, these channels producing testing signals which are transmitted in each case by means of leads 90 and 92 and OR-gates 94 and 96 respectively to the control circuits 62 and 66. The output of the testing signals of the two safety circuit channels 86 and 88 is so controlled that the signals are produced successively.The output signals of the control circuits 62 and 66, that is, the output signals of the threshold value stages for acceleration, retardation and slip, are transmitted by means of leads 98 and 100, in each case on to both safety circuit channels and are compared in a redundant manner, that is, in each safety circuit channel the output signals of both control circuits are compared; as a result, testing and detection of faults will occur, even if one safety circuit channel is defective.

If the magnets 72, 74, 80 and 82 of the magnetic valves are in order, it is possible for the output amplifers 68, 70, 76 and 78 to drive them, and the output signals of the amplifiers are transmitted by means of leads 102, 104, 106 and 108 respectively to both safety circuit channels 86 and 88 and are compared in a manner analogue to that described above for the control signals.

Along a lead 110 the supply voltage of a source of voltage 112 is applied to both safety circuit channels for the voltage to be tested against a reference value in a redundant manner. If one of the above tests indicates a defective control circuit, a damaged magnet, a fault in a chain of signals or a defective supply voltage, corresponding error signals are fed to a fault displaying device 118 along a conductor 114 and/or a conductor 116.

In Figure 3, which is to be considered now, there is shown a testing and safety circuit with two separate safety circuit channels 130, 132, which in contrast to the embodiment according to Figure 2, together with the control circuits 134 and 136 allocated to them, are integrated in a single unit 137. In addition, the safety circuit channels are so switched in this circuit that it is possible for each to test its own control circuit and the other control circuit.

The apparatus according to Figure 3 operates in principle in the same manner as that according to Figure 2. The testing signals from both safety circuit channels 130, 132 are fed to both control circuit 134 and 136 by means of leads 138 and 140 and OR-gates 142 and 144. The output signals of the control circuits and the output signals of output amplifiers 146, 148, 150 and 152 which are connected to drive magnets 154,.

156, 158 and 160 of associated outlet and inlet valves, are returned to the safety circuit channels where, as already described for the apparatus according to Figure 2, they are compared in a redundant manner.

Monitoring of the supply voltage is likewise provided by unit 162. If faults are found, corresponding error signals are transmitted along leads 164 and 166 or directly from the unit 162, to a fault displaying device 168.

In Figure 4, the basic construction of a testing circuit according to Figure 2 and 3 is shown. Along a lead 170 a signal of a specific pulse repetition frequency is fed in, which signal is fed by means of an ANDgate 172 to a multi-stage counter or frequency divider 174. The AND-gate 172 is opened in response to the setting of a store 176 by means of a priming input 178. In the counter 174 there is carried out a multistage division of the frequency of the signals in order to stimulate specific wheel behaviour. A multiplexer 179 is energised successively by means of the individual signals tapped at the stages of the counter and thereby signals of different frequencies fl, . . ., fn are successively switched on to the output of the multiplexer 179 and fed to the control circuits.

The output signals of the output amplifiers, connected to drive the magnets of the control valves, are also fed to connections 180, 181, 183, 184, 185,186 and 187, in the present case there being taken to be four control circuits in each case with one outlet and one inlet valve, in which arrangement the connections 180 to 183 are allocated to the outlet valves and the connections 184 to 187 are assigned to the inlet valves. The output signals of the final stages, which signals are synchronised in time and are fed to the connections 180 to 183, are combined in an exclusive OR-gate 188 and the output signals fed to the connections 184 to 187 are combined in an exclusive OR-gate 190. The outputs of these gates 180 and 190 and the output 192 of other monitoring devices, for example, devices for monitoring the threshold value stages, are applied to an OR-gate 194.If a signal does not occur, a fault is indicated by a "high" signal appearing at the output of the associated exclusive OR-gate, which "high" signal sets a fault store 196 via the OR-gate 194. The Q-output of the store 196 serves to energise a fault displaying device 201 via an OR-gate 198, it being possible to apply to the said OR-gate 198 outputs 200 of other testing circuits.

The store 176 is automatically reset via a lead 202 from the Q output of the final stage of the counter 174. The fault store 196 can be reset and erased by means of a connection 204.

Although the invention has been described with reference to specific embodiments it will be appreciated that modifications can be made to the embodiments without departing from the invention.

WHAT WE CLAIM IS: 1. A process for testing the operation of an anti-lock brake control system, which has wheel speed sensors, brake pressure control valves, a plurality of similar control circuits each capable of producing control signals suitable for use in controlling the brake pressure control valves, the process including the application of the same testing signal to at least two of the control circuits, comparing control signals generated by the control circuits in response to the testing signal and producing an error signal when the control signals generated by two control circuits in response to the same testing signal differ.

2. A process according to claim 1, wherein the testing signal is a simulated wheel speed sensor output signal.

3. A process according to claim 1 or 2 wherein one of the control circuits is a reference control circuit and the control signals from the other control circuits are compared with the control signals from the reference control circuit.

4. A process according to claim 3, wherein the reference control circuit is a control circuit additional to those used for controlling brake pressure control valves.

5. A process according to claim 3, wherein the reference control circuit is also used to control the braking of a wheel.

6. A process according to any one of the preceding claims, wherein when an error signal is produced, the testing process is interrupted.

7. A process according to any preceding claim, wherein prior to the application of the testing signal to the control circuits a pulse signal is applied to output amplifiers driving the magnetic valves and the response of the amplifiers is compared with a reference pulse.

8. A process for testing a brake antilocking control system substantially as described herein with reference to Figure 1, or Figure 2 or 3 with or without Figure 4, of the accompanying drawings.

9. Apparatus for testing the operation of a brake anti-locking control system having wheel speed sensors, and a plurality of similar control circuits each able to produce control signals by means of which magnetic brake pressure control valves can be energised and actuated, the apparatus including a device for producing testing signals, means for applying the testing signals to at least two control circuits, and at least one comparator, which is connected to receive control signals produced in response to the testing signals from two of the at least two control circuits, and the output of which is connected to a fault displaying device to produce an indication of malfunctioning when the control signals produced by the two control circuits differ.

10. Apparatus according to claim 9, wherein one of the control circuits is a reference control circuit and the control

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. testing circuit according to Figure 2 and 3 is shown. Along a lead 170 a signal of a specific pulse repetition frequency is fed in, which signal is fed by means of an ANDgate 172 to a multi-stage counter or frequency divider 174. The AND-gate 172 is opened in response to the setting of a store 176 by means of a priming input 178. In the counter 174 there is carried out a multistage division of the frequency of the signals in order to stimulate specific wheel behaviour. A multiplexer 179 is energised successively by means of the individual signals tapped at the stages of the counter and thereby signals of different frequencies fl, . . ., fn are successively switched on to the output of the multiplexer 179 and fed to the control circuits. The output signals of the output amplifiers, connected to drive the magnets of the control valves, are also fed to connections 180, 181, 183, 184, 185,186 and 187, in the present case there being taken to be four control circuits in each case with one outlet and one inlet valve, in which arrangement the connections 180 to 183 are allocated to the outlet valves and the connections 184 to 187 are assigned to the inlet valves. The output signals of the final stages, which signals are synchronised in time and are fed to the connections 180 to 183, are combined in an exclusive OR-gate 188 and the output signals fed to the connections 184 to 187 are combined in an exclusive OR-gate 190. The outputs of these gates 180 and 190 and the output 192 of other monitoring devices, for example, devices for monitoring the threshold value stages, are applied to an OR-gate 194.If a signal does not occur, a fault is indicated by a "high" signal appearing at the output of the associated exclusive OR-gate, which "high" signal sets a fault store 196 via the OR-gate 194. The Q-output of the store 196 serves to energise a fault displaying device 201 via an OR-gate 198, it being possible to apply to the said OR-gate 198 outputs 200 of other testing circuits. The store 176 is automatically reset via a lead 202 from the Q output of the final stage of the counter 174. The fault store 196 can be reset and erased by means of a connection 204. Although the invention has been described with reference to specific embodiments it will be appreciated that modifications can be made to the embodiments without departing from the invention. WHAT WE CLAIM IS:

1. A process for testing the operation of an anti-lock brake control system, which has wheel speed sensors, brake pressure control valves, a plurality of similar control circuits each capable of producing control signals suitable for use in controlling the brake pressure control valves, the process including the application of the same testing signal to at least two of the control circuits, comparing control signals generated by the control circuits in response to the testing signal and producing an error signal when the control signals generated by two control circuits in response to the same testing signal differ.

signals from the other control circuits are compared with the control signals from the reference control circuit.

11. Apparatus according to claim 10 wherein the reference control circuit is additional to the control circuits allocated to the control of wheel brakes.

12. Apparatus according to claim 10, wherein the reference control circuit is also used to control vehicle wheel brakes.

13. Apparatus according to any of claims 9 to 12 including means for applying pulses to an output amplifier driving a magnetic brake pressure control valve and means for comparing the response of the amplifier with a reference pulse.

14. Apparatus according to any one of the claims 8 to 11, including a safety circuit with two safety circuit channels, which channels each apply testing signals to control circuits of the system and the outputs of the control circuits of the system are connected to be applied to both the safety circuit channels, each of which channels has a comparator in which the output signals of the control circuits of the system are compared in a redundant manner.

15. Apparatus according to claim 14, wherein the safety circuit channels are integrated in a single unit or in two separate units.

16. Apparatus for testing the operation of a brake anti-locking control system substantially as described herein with reference to Figure 1, to Figure 2 or 3 with or without Figure 4 of the accompanying drawings.