Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1998-07-02
2001-11-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S001000, C303S113200
Reexamination Certificate
active
06317674
ABSTRACT:
The present invention relates to a method and an arrangement for the acquisition and evaluation of safety-critical measured quantities. These quantities include more particularly the measured quantities representative of yaw angle motions of the automotive vehicle which are required as input quantities of an automotive vehicle control system. The control systems of this type mainly include all driving stability control systems (DSC or ASMS, i.e., automatic stability management systems), but also anti-lock systems (ABS), traction slip control systems (TCS), and other systems.
Methods and arrangements for monitoring and limiting undesirable vehicle yaw motions, namely movements about the vertical vehicle axis, are known in the art. In such systems, the steering angle, the accelerator pedal position, the braking pressure and the rotational behavior of the individual vehicle wheels is measured by sensors. The driver's wish is concluded from these measured values, and the nominal yaw motion or yaw rate of the vehicle is calculated. Simultaneously, the transverse acceleration acting on the vehicle and the yaw rate is determined by further sensors. If the difference between the actual yaw motion of the vehicle and the nominal yaw motion exceeds a predetermined value which jeopardizes driving stability, stabilizing intervention is effected by the system by way of a controlled brake management and/or engine management, and the yaw motion is limited to allowable values.
A high degree of safety and reliability in operation is basically demanded from vehicle control systems, such as driving stability control systems, because malfunctions, for example, brake operation or braking pressure reduction at the wrong time, may cause dangerous situations. The same demands with respect to safety and reliability in operation are also placed on sensors which supply the input signals for control systems of this type. Wrong, insecure, or inexact input signals make a reliable, safe and effective control impossible. Therefore, it is necessary to permanently monitor the operation of the sensors, to signal defects or disconnect the control upon the occurrence of defects to prevent at least control in the wrong direction, e.g., erroneous braking pressure reduction.
Yaw rate sensors are required especially for driving stability control systems (DSC, ASMS). In this example of application, the sensors supply data or measured quantities which are critical with respect to safety because brake management caused by a wrong signal would naturally bear a risk for the vehicle. The prior art yaw rate sensors appropriate for use in such control systems are complicated and relatively expensive because they must satisfy the requirements of a high degree of measuring accuracy, great precision and reliability in operation. The identification of malfunctions also involves difficulties because no defined vehicle movement, which would cause a yaw velocity appropriate for calibrating the system and the sensor, can be produced. Only a possible deviation from zero point during standstill of the vehicle can be detected and corrected.
An object of the present invention is to limit or even reduce the effort and structure required for the acquisition and evaluation of such safety-critical measured quantities and to maintain or increase the safety in operation in addition.
It has been found that this object can be achieved by the method described in the accompanying main claim, the special features of the method including that the measured quantities are produced by way of two or more measuring channels which are independent of each other, one of the measuring channels covering the entire range being measured and the other measuring channel(s) covering partial measuring ranges. For error detection, the output quantities of the measuring channels are logically combined, and correlation of the measured quantities in the measuring range covered by several measuring channels and/or plausibility of the measured quantities or measurement results is checked. An arrangement for implementing the method and some favorable embodiments of this arrangement are also described in the claims.
Thus, the concept underlying the present invention is that, with respect to the example of yaw rate measurement for driving stability control, by means of one single yaw rate sensor or yaw rate measuring channel, it is impossible to achieve a sufficient degree of safety and reliability in operation because, even with maximum effort and structure in manufacture, ‘stealthy’ errors may occur due to certain component defects which are not identifiable. Defects of this type can be due to defective capacitors, open high-ohmic semiconductor inputs, intermittent contacts, etc. The identification of these errors must be effected indirectly by indicia which are produced from auxiliary quantities and causalities or plausibility criteria which are more or less indirectly related to the yaw action. The identification mechanism, due to its principle, therefore reacts with reduced resolution and increased inertia compared with a direct comparison method. To compensate this disadvantage, it is necessary to measure with a correspondingly still greater precision. This necessitates employing a still more exact yaw rate sensor which must satisfy the requirements of a large measuring range and increased resolution and a high degree of precision in the range of small and medium yaw rates. The relation between technical efforts and attainable accuracy, however, rises overproportionally. Despite the high amount of effort and structure, it cannot be avoided that malfunctions of the sensor remain undetected. To avoid any danger caused by erroneous data and control actions, the control system must be deactivated instantaneously in the case of a suspected malfunction already. The system behavior is indefinite when such an error occurs during a control action. Maximum requirements of reliability of the components and self-test functions of the sensor are needed to minimize the probability of such malfunctions occurring.
A redundant yaw rate measurement with two identical measuring channels or yaw rate sensors and comparison of the measuring results for correlation permits only partly minimizing the technical shortcomings of prior art systems. Immediate system activation is imperative when minor discrepancies occur. Both yaw rate sensors must cover the entire measuring range with a high degree of precision. Yaw rate sensors of this type are very costly.
Therefore, the present invention aims at a different solution. Two (or more) complete, independent measuring channels are used. only one of the channels is set to the entire measuring range, while the other channel covers only part of the range being measured, however, with a significantly higher resolution.
A great number of advantages are achieved by the method of the present invention and the corresponding order. Initially, all advantages of redundant yaw rate measurement are used by the parallel operation of two measuring channels. Mutual monitoring of the two independent measuring channels is rendered possible, and the degree of correlation of the synchronously acquired yaw rate measuring values can be assessed as a direct parameter of the operational safety of the yaw rate sensors. This monitoring action can be permanent. It permits directly and reliably identifying slowly progressing component defects in any one of the two sensors or measuring channels. System deactivation is immediate in certain situations, e.g. outside a control operation, and in the presence of defined errors. In other situations, for example, when one of the two measuring channels is subject to a defined total failure, the control system may also be operated with the remaining measuring channel alone for an emergency-operation period.
Further important advantages are due to the different design or configuration of the two measuring channels. One measuring channel covers the entire measuring range. However, because the other measuring channel observes only pa
Burghardt Roland
Lohberg Peter
Cuchlinski Jr. William A.
Donnelly Arthur D.
ITT Manufacturing Enterprises Inc.
Rader & Fishman & Grauer, PLLC
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