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Periodic rate sensor self testRelated Patent Categories: Data Processing: Vehicles, Navigation, And Relative Location, Vehicle Control, Guidance, Operation, Or Indication, Vehicle Diagnosis Or Maintenance Indication, Detection Of Faulty SensorPeriodic rate sensor self test description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070150136, Periodic rate sensor self test. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not Applicable BACKGROUND OF THE INVENTION [0002] This invention relates in general to motion sensors and in particular to a method for periodically testing the operation of such sensors. [0003] Vehicle electronically controlled brake systems are becoming increasing sophisticated to include the capability to correct vehicle directional movement upon detection of an undesired vehicle motion, such as, for example, loss of directional control on a low mu surface or potential vehicle roll over. Such detection typically involves motion sensors, to include accelerometers and/or angular rate sensors and also usually includes input from other vehicle operating parameter sensors, such as, for example, wheel speed sensors and a steering angle sensor. Vehicle brake control systems typically include an Electronic Control Unit (ECU) that receives the various sensor output signals. A microprocessor within the ECU that is controlled by a stored algorithm monitors the received sensor signals. The microprocessor is operative, upon detection of a potential vehicle directional stability problem, to selectively apply the vehicle brakes and/or vary engine torque to correct the problem. [0004] The motion sensors utilized by the brake control system are also becoming increasingly miniaturized and sophisticated to include signal conditioning circuits. Multiple motion sensors with associated signal conditioning circuits for the sensor outputs may be included on a single sensor chip. The signal conditioning circuits also may include a self testing capacity for monitoring the sensor output signal to detect a malfunctioning sensor. Typically, the self test is carried out during initial vehicle start-up and will generate an error code if the signal conditioning circuit determines that the senor output signal exceeds a predetermined threshold Additionally, upon detecting a malfunctioning sensor, the self test capability may disable the sensor output so an erroneous signal is not sent to the ECU. [0005] However, because vehicles are operated for increasingly lengthy periods of time, the operational time of motion sensors between self tests also has increased. As a result, if motion sensors begin to malfunction the problem may not be detected in a timely fashion. Accordingly, it would be desirable to provide a periodic self test method for the motion sensors that would occur while the vehicle is in operation. BRIEF SUMMARY OF THE INVENTION [0006] This invention relates to a method for periodically testing the operation of motion sensors. [0007] The present invention contemplates a method for verifying proper operation of a motion sensor that includes injecting a test signal into the motion sensor and then, after a predetermined delay, measuring the output of the sensor. The measured sensor output is then compared to an acceptable range of output values and, upon determining that the output is either above or below the acceptable range of output values, a fault is declared and an error signal generated. Additionally, the present invention contemplates that the test signal is a periodic signal and that the error signal is generated only after a predetermined number of consecutive faults have been detected. Furthermore, the invention also contemplates that the output of the sensor is blocked for a period of time following the injection of each test single. In the preferred embodiment, the test signal comprises a series of pulses of one millisecond duration. The pulses may all be positive, all negative, alternately positive and negative or selected or random combinations of positive and negative pulses. [0008] Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0009] FIG. 1 is a block diagram of a portion of a control circuit for an electronic vehicular brake control system that includes motion sensors and that is in accordance with the invention. [0010] FIG. 2 is a graph of typical voltage waveforms produced by the accelerometer shown in FIG. 1. [0011] FIG. 3 is a graph of a periodic test voltage that is injected into the accelerometer shown in FIG. 1. [0012] FIG. 4 is a graph of the accelerometer voltage waveform produced by the accelerometer shown in FIG. 1 after the test voltage shown in FIG. 3 has been injected. [0013] FIG. 5 is an enlarged graph that illustrates the response of the acceleration sensor to the test voltage shown in FIG. 3. [0014] FIG. 5A is a graph of waveform shown in FIG. 4 after digital filtering. [0015] FIG. 6 is a flow chart of a method of testing the accelerometer shown in the circuit shown in FIG. 1 that is in accordance with the invention. [0016] FIG. 7 is a flow chart for a subroutine included in the method illustrated in FIG. 6. [0017] FIG. 8 is a graph of typical voltage waveforms produced by the yaw sensor shown in FIG. 1. [0018] FIG. 9 is graph of a periodic test voltage that is injected into the yaw sensor shown in FIG. 1. [0019] FIG. 10 is a graph of the yaw sensor voltage waveform produced by the yaw sensor shown in FIG. 1 after the test voltage shown in FIG. 9 has been injected. [0020] FIG. 11 is an enlarged graph that illustrates the response of the yaw sensor to the test voltage shown in FIG. 9. Continue reading about Periodic rate sensor self test... Full patent description for Periodic rate sensor self test Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Periodic rate sensor self test patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Periodic rate sensor self test or other areas of interest. ### Previous Patent Application: Device and method for central on-board diagnosis for motor vehicles Next Patent Application: Apparatus and method for tracking vehicle travel and expenditures Industry Class: Data processing: vehicles, navigation, and relative location ### FreshPatents.com Support Thank you for viewing the Periodic rate sensor self test patent info. 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