Measuring and testing – Instrument proving or calibrating – Speed – velocity – or acceleration
Patent
1997-06-27
1999-03-30
Chapman, John E.
Measuring and testing
Instrument proving or calibrating
Speed, velocity, or acceleration
7350413, G01P 2100
Patent
active
058891935
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a device for ascertaining a rate of rotation.
The use of rotation rate sensors, which function for instance on the principle of a vibration gyrometer, in conjunction with systems for regulating the driving dynamics of motor vehicles is already known. Such sensors evaluate the effect of the Coriolis acceleration, which serves as a measure of the actual yaw speed of the vehicle.
Such a rotation rate sensor is described for instance by U.S. Pat. No. 4,759,220. In that patent, the typical construction of such a sensor and the associated evaluation circuit are described in further detail. Essentially, this sensor is a thin-walled hollow cylinder of elastic material. A plurality of piezoelectric sensor elements are mounted on the cylinder wall, with two sensor elements at a time facing one another. These sensor elements are set into constant mechanical drive oscillations with the aid of an oscillator loop. The Coriolis effect, together with a rotary speed coupled in vertically to the drive oscillation, brings about a Coriolis acceleration, which causes a deflection of the drive oscillation in the Coriolis direction. This deflection is a measure for the coupled-in rate of rotation. The resultant output voltage is ascertained with the aid of a detector circuit and finally is utilized to determine the rate of rotation.
The sensor along with the associated evaluation circuit known from U.S. Pat. No. 4,759,220 has the disadvantage that a malfunction cannot readily be detected. If such a sensor is used in conjunction with systems relevant to safety in a motor vehicle, then it is necessary that the operability be monitored.
SUMMARY OF THE INVENTION
The device according to the invention for ascertaining a rate of rotation has the advantage over the known version that a malfunction of the sensor is reliably detected. An especially advantageous aspect is that only little additional expense is required, and as a consequence of the reliable sensor monitoring, the expense for redundant sensors can be markedly reduced.
The advantages are attained in that an offset signal is coupled, correctly in-phase, into the compensation loop of the evaluation circuit, thus mistuning the compensation loop. A superposition of the rotation rate and offset is then indicated at the output of the sensor or evaluation circuit, and from this indication the operability is detectable directly.
Further advantages of the invention are attained with the aid of the provisions recited in the dependent claims. It is especially advantageous that the offset can be imposed by actuating a test input, thus making the sensor testable, given a known mistuning. A more-extensive test is possible, since the test function, because of the loop arrangement, tests both the evaluation electronics and the sensor element itself for malfunction. The coupling-in of an interference variable, a so-called BITE function, that corresponds to a fixedly set rotation rate has the advantage that the sensor output, because of the interference variable, is independent of the sensitivity calibration.
BRIEF DESCRIPTION OF THE DRAWING
The invention is shown in the drawing and described in further detail in the ensuing description. Specifically, FIG. 1 shows a sensor arrangement together with an evaluation circuit of the kind known from U.S. Pat. No. 4,759,220, and FIG. 2 shows the exemplary embodiment of an evaluation circuit according to the invention, which permits monitoring of the operability of both the sensor and the evaluation circuit itself.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, the sensor is identified by reference numeral 10. The hollow cylinder 11 of the sensor 10 carries the individual measuring elements A, A', B, B', C, C' and D, D'. The deformations that the hollow cylinder 11 can assume as a result of oscillations are shown in dashed lines.
The measuring elements A, B, C, D are connected to blocks 12, 13, 14 of the electronics; 12 indicates the oscillator loop (drive circuit), which sets a suita
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patent: 4654582 (1987-03-01), Ito
patent: 4759220 (1988-07-01), Burdess et al.
patent: 5426970 (1995-06-01), Florida et al.
patent: 5652374 (1997-07-01), Chia et al.
Artzner Johannes
Bauer Wolfram
Erhardt Rainer
Pfaff Georg
Chapman John E.
Robert & Bosch GmbH
Striker Michael J.
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