Duplicate rate sensor and inertial rate sensing method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates broadly to inertial rate sensors, and more particularly to rate sensors with built-in redundancy for use in automotive stability control systems.

【0002】

[Conventional technology]

Automotive stability control systems and other applications where safety is important may use redundancy to increase reliability. This duplication is now somewhat limited in automotive braking systems, which use two completely independent devices and compare the outputs of these two devices for proper matching. .. This provides a system that is more tolerant of sensor errors than a system that has only one sensor.

【0003】

Redundancy itself is not a new concept in applications that require high reliability, and prior art redundant systems are, for example, U.S. Pat. Nos. 3,551,776, 3,663,879, 3,813,990. Found in Nos. 3,881,670, and 4,105,900. In these systems, the output of multiple sensors (typically three), each independent and identical, is an integral part of the duplicate system to ensure that the primary sensors work. Compared by control system.

【0004】

[Problems to be Solved by the Invention]

Using a large number of independent sensors to achieve duplication causes some inconvenience. Each sensor requires a separate mounting location, a separate mounting procedure, and separate cabling that must reach a specific mounting location. In cost-sensitive applications such as automobiles, it is generally forbidden to increase costs by providing additional sensors, multiple mounting positions, additional mounting procedures, and additional cabling.

【0005】

An object of the present invention is, broadly speaking, to provide new and improved rate sensors and methods with built-in duplication.

【0006】

Another object of the present invention is to provide a rate sensor and method having the above characteristics, which is particularly suitable for use in an automobile stability control system.

【0007】

Another object of the present invention is to provide a rate sensor and method having the above-mentioned characteristics, which eliminates the limitation and inconvenience of the above-mentioned overlapping sensor.

【0008】

[Means for solving problems]

These and other objectives are based on the present invention in which the inertial rate is monitored using multiple vibration sensitive elements within a single enclosure and the signals from these sensory elements are processed. By providing overlapping rate sensors and methods such that separate rate output signals are obtained for each sensing element and these separate rate output signals are transmitted to connectors accessible from outside the enclosure. , Achieved.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, the rate sensor has a relatively flat, overall rectangular housing 11, which housing 11 is between the upper section 12 and the sensor and the structure on which the sensor is mounted. Includes a lower section 13 with a rubber mount 14 that is flexible at the corners of the housing to provide mechanical separation.

【0010】

A set of vibrating rate sensing elements in the form of vibrating tuning forks 16 and 17 are mounted on both sides of the printed circuit board 18 inside the housing, with the tuning fork input axes 19 and 21 parallel to each other. .. The circuit for processing the signal from the tuning fork is included in the integrated circuits 22 and 23 mounted next to the tuning fork on the circuit board, and a separate integrated circuit is provided for each of the tuning forks. .. These circuits provide separate rate output signals for each of the sensing elements.

【0011】

The connector assembly 24 is mounted on top of the housing with pins accessible from the outside of the housing. The connection to the integrated circuit is made via connector pins. Such connections typically include power and calibration connections as well as output signals for the two sensors.

【0012】

The system supplies two separate rate output signals, one signal for each sensor. These outputs are approximately identical in all respects and are compared to ensure proper operation of the system. This comparison is generally performed by electronic control units in the braking system or by signal processors elsewhere in the vehicle. Including such capabilities within the sensor package does not provide any further benefits.

【0013】

Other elements, such as power regulation circuits that act as both channels of the rate sensor, can be included in the housing.

【0014】

As shown in FIG. 2, the sensing elements 16 and 17 take the form of a double ended tuning fork. Each of these tuning forks is made of a single crystalquartz material and has an H-shape with a drive tines 26 at one end and a pick-up tines 27 at the other end. Have. The branches of each pair are arranged symmetrically with respect to the input axes 19 and 21 of the tuning fork.

【0015】

The exciting branch is excited and vibrates in the plane of the tuning fork at the natural frequency of the tuning fork. Different excitation frequencies are used for the two tuning forks to prevent unnecessary cross-coupling between the two sensing elements and the associated circuitry. Excitation frequencies are typically separated at about 1 KHz. When the tuning fork undergoes a rotation about its vertical axis, the Coriolis force causes the branches to distort from the plane of the tuning fork, stimulating a pick-up mode of vibration. The excitation and pull signals are connected to the branches by a conventional method using electrodes (not shown), the excitation signals stimulate the mechanical vibrations of the branches by the piezoelectric effect, and the pull signals are due to the Coriolis force. It takes the form of the charge generated by the inverse piezoelectric effect according to the strain generated.

【0016】

With some tuning forks, the pull-up frequency is separated from the excitation frequency, and an erroneous signal can typically occur while the unit vibrates as a result of rotational inputs at the separation frequency. Different frequency separations can be used for different sensing elements within the unit to increase the likelihood of detecting such errors. So, for example, one sensor in one unit may have a separation of about 340 Hz between its excitation frequency and its pull frequency, and another sensor may have a separation of about 280 Hz. These values are not important and any suitable separation can be used.

【0017】

The use of overlapping sensors and different frequency separations for the sensors within the sensor significantly reduces the possibility that vibration induced errors will not be detected. This is because it is highly unlikely that equal vibration induction errors will occur at the same time at the separation frequencies of both sensors.

【0018】

Although the sensing element has been described as a double-ended tuning fork, other types of vibration sensing elements can be utilized, including a single ended tuning fork, if desired.

【0019】

At each channel in the rate sensor, the pull-up signal from the tuning fork passes through the preamplifier 29 via the charge amplifier 28 and then reaches the demodulator 31. When the signal from this demodulator passes through the low-pass filter 32 and then reaches the output amplifier 33, the rate output signal appears as a baseband signal in the output section of the output amplifier.

【0020】

The excitation signal can be, for example, of the type shown in 09 / 663,742 filed on September 15, 2000, the disclosure of which is incorporated herein by reference, by an excitation circuit 34. Supplied to the branches.

【0021】

The output of the output amplifier 33, which has two channels, is connected to a separate pin in the output connector 24, and operating power is also supplied to the two channels via the connector in the housing and the power adjustment circuit. Overlapping (separate) power regulation circuits may be used as an option to improve reliability.

【0022】

In situations where additional duplication is desired, additional sensing elements and processing circuits can be included within the unit. This requires the housing to be properly sized, but its size package will still remain significantly smaller than a three-dimensional independent unit.

【0023】

In another embodiment, a rate sensing output with two degrees of freedom can be provided for overlap on one or more axes. In these embodiments, three or more sensing elements are mounted in one package, and at least one of these elements is second so that the axis of that element is perpendicular to the axis of the remaining elements. Oriented to sense rotation about the axis of. Output duplication is obtained by multiple sensing elements placed along one or both of these axes in this device.

【0024】

Thus, for example, in the embodiment shown in FIG. 3, the sensing elements 38, 39 are arranged along axes 41, 42 that are orthogonal to each other, and for each of these sensing elements, the sensing elements 43, 44. Is given duplication. Similar to the first embodiment, separate processing circuits provide separate rate output signals for each of the sensing elements in these embodiments.

【0025】

In another embodiment, one overlap sensing element is shared between two or more sensors mounted orthogonally. In this embodiment, the input axes of the overlapping sensing elements are arranged at an angle to the input axes of the other sensing elements so as to detect rotational components about the input axes of the other sensing elements.

【0026】

For example, in the embodiment shown in FIG. 4, two non-redundant rate sensing elements 46, 47 are mounted such that their axes 48, 49 are orthogonal to each other. Both, overlap signals are given by the sensing element 51 having an input axis 52 oriented at an angle of 45 degrees with respect to the axes of the two non-overlapping rate sensing elements. Use a sensing element oriented at 45 degrees with respect to the two major sensing axes as a check on the performance of the major sensing element by comparing its output with the appropriate vector sum of the other two outputs. Can be done. Here again, separate processing circuits provide separate rate output signals for each of the sensing elements.

【0027】

In the embodiment shown in FIG. 5, the three sensing elements 54, 56, 57 have their input axes 58, 59, 61 orthogonal to each other, and the fourth sensing element 62 senses its input axis 63. Since it is parallel to the input axis of element 54, it gives overlap to the sensing element.

【0028】

In the embodiment shown in FIG. 6, the three sensing elements 64, 66, 67 have their input axes 68, 69, 71 orthogonal to each other, and the fourth sensing element 72 is the other three sensing elements. It has its input axis 73 at an angle not orthogonal to the input axis of at least two of the sensing elements. With this arrangement, the fourth sensing element provides overlap for two or three sensing elements whose axes are not orthogonal.

【0029】

The present invention has many important features and effects. The two sensing channels share a common printed circuit board, power conditioning circuit, one housing and a common mechanical separation, so the overall cost of the two channels of rate output is two separate rates. It is substantially smaller than the cost of the sensor unit. In addition, since duplicate sensors are used in one package, only one mounting location, one set of connection cables, one set of mounting bolts, and one mounting procedure are required.

【0030】

Moreover, with overlapping sensors, it is acceptable to reduce the accuracy level of overlapping channels. This is because the channel is only used to verify that the output of the main channel is valid. This will increase production during production. This is because not all rate sensing elements need to meet the stringent performance requirements of major channels. This will also improve the performance of the main channels. This is because the best performing sensing element can be used in its primary channel. The ultimate effect is that by improving the reliability of duplication, performance can be improved while reducing costs.

【0031】

The algorithm used to handle duplicate outputs involves combining two duplicate outputs, for example both sum and difference signals. The sum signal can be used as the primary output for automotive stability control or other purposes, while the difference signal can be used to establish the effectiveness of that output. Sensing elements that work significantly better than a specified requirement can be aligned with a requirement that is somewhat worse than that requirement. The sum of these signals, or more effectively their mean, is still kept within the original specification error limit. However, if the difference signal exceeds a predetermined value, the system detects an error and the erroneous braking operation is not executed.

【0032】

It is clear from the disclosures described above that new and improved overlap rate sensors and methods are provided. Although only the most preferable embodiments at present are specifically described, those skilled in the art can make changes and modifications without departing from the scope of the invention specified by the separate claims. Will be clear.

[Simple explanation of drawings]

[Figure 1]

An isometric exploded view showing an embodiment of the overlapping rate sensor according to the present invention. [Figure 2]

A block diagram briefly showing the overlap rate sensor according to the embodiment shown in FIG. [Fig. 3]

The figure which shows another embodiment of the overlap rate sensor which concerns on this invention. [Fig. 4]

The figure which shows another embodiment of the overlap rate sensor which concerns on this invention. [Fig. 5]

The figure which shows another embodiment of the overlap rate sensor which concerns on this invention. [Fig. 6]

The figure which shows another embodiment of the overlap rate sensor which concerns on this invention. [Explanation of symbols]

11 Housing 12 Upper section 13 Lower section 14 rubber mount 16, 17 Vibrating tuning fork 18 Circuit board 19, 21 Input axis 22, 23 integrated circuits 24 connector assembly