Vehicle safety system equipped with microcomputer

• US 5,602,736 A
• Filed: 12/20/1994
• Issued: 02/11/1997
• Est. Priority Date: 12/27/1993
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd., Bosch Automotive Systems Corporation (Robert Bosch GmbH)
• Original Assignee: Airbag Systems Company Limited, Nissan Motor Co., Ltd.
• Inventors: Ogawa, Akira, Kaneko, Hideyuki, Odashima, Masaru, Toya, Takaaki, Fujishima, Tetsuo, Fukuzumi, Shuzo, Ando, Junichi
• Primary Examiner(s): Park, Collin W.
• Assistant Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/359,993
• Time in Patent Office: 784 Days
• Field of Search: 364/424.05, 364/424.03, 364/424.04, 364/554, 180/268, 280/735, 307/10.1, 307/9.1
• US Class Current: 701/45
• CPC Class Codes: B60R 21/0132 responsive to vehicle motion parameters , e.g. to vehicle longitudinal or transversal deceleration or speed value
• CPC Class Codes: B60R 21/0173 Diagnostic or recording means therefor

Abstract

A vehicle safety system is equipped with a microcomputer for reliably detecting whether or not programs for controlling activation of passenger protection devices are being properly executed and, based on this detection, preventing problems from occurring in the control operations of the programs. According to one aspect of the invention, the system monitors a program executed on an interrupt basis at prescribed regular time intervals, a repeatedly executed program, and the operations of these programs, synchronously with the execution of the programs, and resets the microcomputer if an error is detected in the execution of either program. According to another, at the time of moving to a subroutine a code peculiar to the subroutine is saved at the entry portion and the saved code is compared with the code peculiar to the executed subroutine at the exit portion for detecting occurrence of error and if error is detected the microcomputer is reset.

Claims

1. A vehicle safety system having a sensor for detecting vehicle acceleration and a microcomputer for processing the sensor output and in which the microcomputer executes a collision discrimination program on an interrupt basis at prescribed regular time intervals based on the sensor output for discriminating whether or not a collision has occurred and repeatedly executes a background program for processing prescribed background jobs, thereby controlling activation of the vehicle safety devices, the system further comprising:

first monitoring means for monitoring whether or not the collision discrimination program is being properly executed based on whether or not the time for executing one program cycle of the collision discrimination program is longer than a prescribed value,

a second monitoring means for monitoring whether or not the background program is being properly executed based on whether or not the time for executing one program cycle of the background program is longer than a prescribed value, and

reset means for resetting the microcomputer when at least one of the first and second monitoring means detects an error in program execution.

2. A system as claimed in claim 1, wherein the first monitoring means comprises means for outputting a first timer reset signal at the execution of each program cycle of the collision discrimination program and first timer means operative in response to the first timer reset signal for outputting a first reset signal when the time for executing one program cycle of the collision discrimination program becomes longer than a prescribed value.

3. A system as claimed in claim 2, wherein the first timer means is a watchdog timer.

4. A system as claimed in claim 2, wherein the reset means is a means provided in the microcomputer for resetting the microcomputer in response to a signal from outside and is supplied with the first reset signal.

5. A system as claimed in claim 2, wherein the reset means is a means provided in the microcomputer for resetting the microcomputer in response to a signal from outside and is supplied with the second reset signal.

6. A system as claimed in claim 1, wherein the second monitoring means comprises means for outputting a second timer reset signal at the execution of each program cycle of the background program and second timer means operative in response to the second timer reset signal for outputting a second reset signal when the time for executing one program cycle of the background program becomes longer than a prescribed value.

7. A system as claimed in claim 6, wherein the second timer means is a monitoring timer means having a timer period slightly longer than the time for executing one program cycle of the background program.

8. A vehicle safety system having a sensor for detecting vehicle acceleration and a microcomputer for processing the sensor output and in which the microcomputer executes a collision discrimination program on an interrupt basis at prescribed regular time intervals based on the sensor output for discriminating whether or not a collision has occurred and repeatedly executes a background program for processing prescribed background jobs, thereby controlling activation of the vehicle safety devices, the system further comprising:

means for outputting a first timer reset signal at the execution of each program cycle of the collision discrimination program,

first timer means operative in response to the first timer reset signal for outputting a first reset signal when the time for executing one program cycle of the collision discrimination program becomes longer than a prescribed value,

means for outputting a second timer reset signal at the execution of each program cycle of the background program,

second timer means operative in response to the second timer reset signal for outputting a second reset signal when the time for executing one program cycle of the background program becomes longer than a prescribed value, and

reset means responsive to the first and second reset signals for resetting the microcomputer when the time for executing one program cycle of the collision discrimination program becomes longer than the prescribed value or when the time for executing one program cycle of the background program becomes longer the prescribed value.

9. A method of controlling a vehicle safety system having a sensor for detecting vehicle acceleration and a microcomputer for processing the sensor output and in which the microcomputer executes a collision discrimination program on an interrupt basis at prescribed regular time intervals based on the sensor output for discriminating whether or not a collision has occurred and repeatedly executes a background program for processing prescribed background jobs, thereby controlling activation of the vehicle safety devices, the method comprising:

a first monitoring step for monitoring whether or not a collision discrimination program is being properly executed based on whether or not the time for executing one program cycle of the collision discrimination program is longer than a prescribed value,

a second monitoring step for monitoring whether or not a background program is being properly executed based on whether or not the time for executing one program cycle of the background program is longer than a prescribed value, and

a step for resetting the microcomputer when at least one of the first and second monitoring steps detects an error in program execution.

10. A vehicle safety system having a sensor for detecting vehicle acceleration and a microcomputer for processing the sensor output and in which the microcomputer executes a collision discrimination program on an interrupt basis at prescribed regular time intervals based on the sensor output for discriminating whether or not a collision has occurred and repeatedly executes a background program for processing prescribed background jobs, thereby controlling activation of the vehicle safety devices, the system further comprising:

means for at the entry portion of the subroutine of each data processing program executed in the microcomputer saving to memory a code peculiar to the subroutine concerned,

comparing means for at the exit portion of each subroutine comparing the code of the executed subroutine with the saved code,

checking means responsive to the comparing means for checking whether or not the data processing program was properly executed, and

reset means for resetting the microcomputer in accordance with the result of the check by the checking means.