EP0786073A1

EP0786073A1 - Device and process for the simultaneous measurement of a rate of rotation and transverse acceleration

Info

Publication number: EP0786073A1
Application number: EP95930398A
Authority: EP
Inventors: Manfred Rothley; Erich Zabler; Jörg WOLF
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-10-12
Filing date: 1995-09-15
Publication date: 1997-07-30
Also published as: KR970706481A; JPH10507520A; DE4436396A1; WO1996012163A1

Abstract

The proposal is for a device and a process for the simultaneous determination of a rate of rotation W and an acceleration atr transverse to the axis of rotation. Said device has at least one acceleration sensor (1, 2) on each of at least two sections (3, 4) fitted in such a way that its axis (Z1, Z2) sensitive to accelerations (ac1, ac2, atr) does not lie in the plane formed by the axis of rotation (D) and the velocity component (v) of the oscillation. In implementing the process, the device is rotated about the axis (D) at a rotation speed corresponding to the speed W to be determined, and simultaneously the device is caused to oscillate at at least two sections (3, 4) with a velocity component (v1, v2) perpendicular to the axis of rotation (D). With the symmetrical fitting of identical acceleration sensors (1, 2) to the device, the rate of rotation W and the transverse acceleration atr can be obtained in a simple manner by adding or substracting the measurement signals detected in the acceleration sensors (1, 2).

Description

Device and method for the simultaneous measurement of a rotation rate and a transverse acceleration

STATE OF THE ART

The invention relates to a device and a method for the simultaneous measurement of a rotation rate and a transverse acceleration perpendicular to the associated rotation axis.

In recent years, the need for inexpensive sensors for measuring yaw rate and linear acceleration has increased. These sensors for measuring rotation rate and acceleration are e.g. in electronic navigation systems, systems for direction detection and stabilizer devices for robots. The present invention is of particular interest as a cost-effective solution for driving dynamics control.

For example, it is known from EP-B-0 161 049 to use a vibrating element to determine the angular velocity or rate of rotation of a structure to which the vibrating element is attached. The underlying measuring principle is based on the detection of the so-called Coriolis force. If an element moves at a speed v in a reference system rotating with the rotation rate W, a Coriolis acceleration a _c = 2v x W occurs which can be measured in the rotating reference system. This Coriolis acceleration is perpendicular to the plane spanned by the speed vector v and the rotation rate vector W. This principle is used, for example, in a tuning fork rotation rate sensor. Here, a tuning fork is attached to a rotatable object, the rotational speed of which is to be determined, the axis of symmetry of the tuning fork coinciding with the axis of rotation about which the object rotates. The tuning fork then rotates at the rotation rate to be determined. In addition, the tuning fork is set into a resonance oscillation with a constant speed amplitude by a suitable drive. The above-mentioned Coriolis acceleration then occurs at the ends of the prongs of this tuning fork. This Coriolis acceleration at the swinging ends of the tines can be detected by acceleration sensors fitted in this area. If the speed vector v is known, the rotation rate W can then be determined by suitable measurements by measuring a _c .

A quartz tuning fork rotation rate sensor, which can be used to measure both rotation rate and acceleration, was developed by Systron Donner as a so-called university sensor. In this case, one of the prongs of the tuning fork is designed as an acceleration sensor by suitable shaping, and additional electrodes are required on the tuning fork, the space requirement of which has a disadvantageous effect.

Combined sensors are also known, in which a rotation rate sensor and, in addition to the transverse acceleration measurement, a separate acceleration sensor are accommodated in a common housing. However, these combined sensors are complex and also require additional space.

ADVANTAGES OF THE INVENTION

The device according to the invention with the characterizing features of the main claim and the method according to the invention with the characterizing features of claim 10 have the advantage that in addition to the yaw rate, an acceleration transverse to the axis of rotation can be measured simultaneously without an additional acceleration sensor. All that is required for this is additional electronics, and in addition to the measuring output for the yaw rate, another measuring output is used for the transverse acceleration. The transverse acceleration signal can be obtained with a single-axis as well as with a multi-axis rotation rate sensor. The number of measuring axes for the acceleration corresponds to the number of axes of the rotation rate sensor.

The measures listed in the subclaims enable advantageous further developments and improvements of the device specified in the main claim or of the method specified in claim 10.

The device for measuring the rate of rotation and the acceleration transverse to it is advantageously of axially symmetrical design, the axis of symmetry of the device coinciding with the axis of rotation. The device is expediently set into vibration during the measurement such that the two sections of the device, on which the acceleration sensors are mounted, oscillate in phase opposition to one another. This simplifies the evaluation of the measurement.

In order to receive a signal of maximum strength from the acceleration sensors mounted in each case on the two sections, these are expediently mounted in such a way that their sensitive axis runs perpendicular to the plane spanned by the axis of rotation and the speed component of the vibration. In this way, the entire amount of the Coriolis acceleration acting perpendicular to this spanned plane is recorded at all times.

In a further advantageous embodiment of the invention, the device for measuring the rotation rate and the acceleration transverse thereto is in the form of a tuning fork, the first section being the first prong and the symmetrical second section being the second prong of the tuning fork. This makes use of the tried and tested, well-defined vibration properties of tuning forks. This is important because precise knowledge of the speed vector v of the vibration is necessary for determining the rotation rate W. A particularly simple detection of the rotation rate W and the transverse acceleration a _tr is made possible by the fact that the acceleration sensors mounted both on the first section and on the second section are identical to one another. The acceleration sensors are expediently mounted on one side of the tuning fork so that their sensitive axes are aligned parallel to one another and in the same orientation perpendicular to this surface of the tuning fork. Alternatively, it is possible that one of the two identical acceleration sensors is mounted on one side and the second of the two acceleration sensors on the opposite side, the sensitive axis of which is oriented opposite to that of the first acceleration sensor. As a result, the signs of the measurement signals output by the second acceleration sensor are reversed.

It is particularly advantageous if the device has a natural frequency w that is significantly greater than the rotation rate W.

In the method for the simultaneous determination of the rotation rate W and the transverse acceleration a _tr perpendicular to it, a measurement signal a- _j is measured by the first acceleration sensor and a measurement signal a2 by the second acceleration sensor, wherein

a-, = k-, (a _{c 1} + a _tr ) = k ₁ (2v ₁ W + a _tr ) (1) and a ₂ = ^k 2 ^a c2 ^{+ a} tr ' ⁼ 2 (2v2W + a _tr ) ( 2).

Here, k ^ and k _{2 are} known calibration factors of the two acceleration sensors and v- _j and the speeds of the vibration of the respective sections on which the acceleration sensors are mounted. In principle, the two unknowns W and a _{tr to} be determined can be determined from these two equations (1) and (2).

This determination is particularly simple if, in the case of a symmetrical device, such as, for example, a tuning fork, two identical arranges acceleration sensors on the same side of the tuning fork, whereby -1 = v = -V2 and ki = k2 = 1, which results in a simplification of equations (1) and (2), namely

a-, = 2vW + a _tr (V) and a ₂ = -2vW + a _tr (2 ').

Now the rotation rate W can be determined simply by forming the difference between the measurement signals a ^ and a2 to W = (a- _j ^ l v. In a similar way, the sum of the measurement signals ai and a2 gives the transverse acceleration a _tr = ( a ^ + a2) / 2.

If the second of the two identical acceleration sensors is arranged on the side of the tuning fork opposite the first acceleration sensor, its sensitive axis is oriented opposite to that of the first acceleration sensor. Here, too, the tuning fork v - _j = v = - 2 and k - _j = - k2 = 1 result from reasons of symmetry, which gives two similar simplified equations as before, namely a, = 2vW + a _tr (1 ") and a ₂ = 2vW - a _tr (2 ").

The yaw rate is now obtained from this by summing the measurement signals a-i and a2

W = (a- _| + a2) / 4v and the transverse acceleration a _tr by forming the difference between the measurement signals a < _j and a to a _tr = (a-ι -a2 «/ 2.

The signal obtained by forming the difference or adding the sum, depending on the attachment of the acceleration sensors, is expediently processed further in a lock-in amplifier to determine the rotation rate W. The signal obtained for determining the transverse acceleration a _tr by forming the sum or difference is used to remove an interference component which is based on the fundamental oscillation frequency of the tuning fork due to the cross sensitivity of the acceleration sensors given a low pass filter. The interference component is a periodic signal with the oscillation frequency w of the resonance oscillation of the tuning fork. In almost all applications, this is greater than the rotation rate W, which enables their removal by the low-pass filter.

It can be seen that, depending on the arrangement of the acceleration sensors, either the rotation rate component or the transverse acceleration component is made possible by simple summation or difference formation of the two measurement signals of the acceleration sensors. By using two measuring sensors, the measuring sensitivity is doubled both for the yaw rate and for the transverse acceleration.

DRAWING

Further advantages, features and possible uses of the present invention result from the following description of a preferred exemplary embodiment in conjunction with the drawing. It shows:

Fig. 1 shows a device with acceleration sensors for measuring yaw rate and transverse acceleration, and

FIG. 2 shows a block diagram of a circuit for evaluating the quantities measured in FIG. 1.

DESCRIPTION OF AN EMBODIMENT

1 shows a device for simultaneously measuring yaw rate W and transverse acceleration a _tr , which is designed as a steel tuning fork, in which a first Si acceleration sensor 1 on its first prong 3 and a second one on its second prong 4 Si acceleration sensor 2 is mounted. By means of a suitable drive, this tuning fork is converted into a resonance oscillation of frequency w with constant speed amplitude excited while rotating at the rotation rate W to be determined. If v denotes the speed vector of a vibrating tine and W the rotation rate vector, the Coriolis acceleration a _c = 2v x W occurs on the tine. This Coriolis acceleration occurring on the tines 3 and 4 extends perpendicular to the plane spanned by the speed vector v and the rotation rate vector W. When the tuning fork resonates with its fundamental frequency or an upper frequency, the two prongs 3, 4 always oscillate in opposite directions to one another, ie in opposite phases. In the arrangement of the Si acceleration sensors 1, 2 shown in FIG. 1, the sensitive axes Z- _j , Z2 of which are perpendicular to their planar extent, measured values a- _j and a- _| are thus obtained on the Si acceleration sensors, which have an opposite sign at all times. If the two Si acceleration sensors 1, 2 are two identical sensors, then the two measured signals a _c and a _C 2 are always of the same amount, but are opposite in sign.

If the steel tuning fork is now additionally subjected to a linear acceleration which has a component which extends perpendicular to the axis of rotation, this component a _tr can also be detected by the two Si acceleration sensors 1, 2. These transverse accelerations a _tr - _| and a _tr 2 on the Si acceleration sensors 1 and 2 always act in phase on the two sensors and also produce a measurement signal a _tr - _j = a _tr 2 = a _tr with the same amount and sign at every moment, provided that it is identical Si acceleration sensors 1 and 2. The two Si acceleration sensors 1, 2 thus each measure a signal a1 or a2 composed of Coriolis acceleration and transverse acceleration, whereby

a- _j = 2vW + a _tr and a ₂ = -2vW + a _tr . The yaw rate W is now obtained from this by forming the difference between the two signals a ₁ and a ₂ . and you get

W = (a _r a ₂ ) / 4v.

By forming the difference, the portions of the transverse accelerations a _tr that act in phase on both acceleration sensors 1 and 2 are eliminated.

If, on the other hand, instead of forming the difference, the two signals a- _j and a2 are summed, the components vW and -vW cancel each other out and the transverse acceleration a _tr = (a ₁ + a ₂ ) / 2 is obtained.

Due to the symmetrical arrangement and the use of identical acceleration sensors 1 and 2, the rotation rate W and the transverse acceleration a _tr can be determined in a simple manner. In addition, the use of zeier acceleration sensors doubles the measurement sensitivity both for the rotation rate W. and for the transverse acceleration a _tr .

2 illustrates in a block diagram the evaluation principle just described for determining the rotation rate W and the transverse acceleration a _tr . The measurement signals a- _{j of} the acceleration sensor 1 and a2 of the acceleration sensor 2, which are composed of the rotation rate component and the transverse acceleration component, are either subtracted from one another or added to one another. The difference signal that occurs is fed to a lock-in amplifier 5 for further processing, while the sum signal is fed to a low-pass filter 6. The low-pass filter 6 is necessary in order to eliminate a noise component in the transverse acceleration signal a _tr . This interference component is a periodic signal, the frequency of which is equal to the tuning fork resonance frequency w used in the measurement, and it results from the cross sensitivity of the acceleration sensors 1 and 2 used. The transver¬ sale acceleration signal a _tr is also a periodic signal with rotational frequency W, since when measuring the transverse acceleration a _tr only the projection of the acceleration vector on the sensitive axes Z- _j , 2 are effective at any moment. As a rule, however, the tuning fork frequency w is much greater than the rotation rate W to be determined, so that only the high-frequency interference signal is blocked by a suitable low-pass filter 6, while the periodic signal relevant to the measurement of the transverse acceleration a _{tr is} passed at the rotation frequency W. becomes.

Reference list

Accelerometer 1, 2

Axis of rotation D

Yaw rate W transverse acceleration ^a tr

Section 3, 4

Velocity component V sensitive axis zz ₂

Axis of symmetry S

Pages A, B, C, D, E, F

Lock-in amplifier 5

Low pass filter 6

Claims

Device and method for the simultaneous measurement of a rotation rate and a transverse acceleration claims

1 . Device with acceleration sensors (1, 2) for measuring a rate of rotation W about a certain axis of rotation (D) and an acceleration a _tr transverse to the axis of rotation by rotating the device at a rate of rotation corresponding to the rate of rotation (W) to be determined about the axis of rotation ( D) with simultaneous generation of an oscillation on at least two sections (3, 4) of the device, each with a speed component (vj, V2> perpendicular to the turning axis (D), characterized in that on the at least two sections (3, 4) in each case at least one acceleration sensor (1, 2) is mounted in such a way that its axis (Z- _j , Z2) sensitive to occurring accelerations ( _ac - _j , _ac2 , a _tr ) does not move in the direction defined by the axis of rotation (D) and the velocity component (vj, V2) of the plane formed lies.

2. Device according to claim 1, characterized in that the device is axially symmetrical, the axis of symmetry (S) coinciding with the axis of rotation (D).

3. Apparatus according to claim 2, characterized in that the Vor¬ direction has two sections (3, 4) which can be set in vibration in opposite phase to each other. 4. Device according to one of the preceding claims, characterized ge indicates that the at least one acceleration sensor (1, 2) on the at least two sections (3,

4) is mounted in such a way that its sensitive axis (Z- _j , Z2) runs perpendicular to the plane spanned by the axis of rotation (D) and the speed component (v- _j , V2) of the vibration.

5. Device according to one of the preceding claims, characterized ge indicates that it is designed as an oscillation gyrometer, the first section (3) being a first oscillation element and the second section (4) being a second oscillation element coupled to it.

6. The device according to claim 5, characterized in that it has the shape of a tuning fork, wherein the first section (3) of the first prongs and the second section (4) is the second prong of the tuning fork.

7. Apparatus according to claim 5 or 6, characterized in that the acceleration sensors (1, 2) mounted both on the first section (3) and on the second section (4) are identical to one another.

8. The device according to claim 7, characterized in that the two identical acceleration sensors (1, 2) are mounted on one side (A) of the tuning fork.

9. The device according to claim 7, characterized in that the first of the two identical acceleration sensors (1) on one side (A) and the second of the two acceleration sensors (2) on the opposite side ge (B) is mounted, wherein the sensitive axis (Z2) of the second acceleration sensor (2) is oriented opposite to that (Z ^) of the first acceleration sensor (1).

10. Device according to one of the preceding claims, characterized ge indicates that the vibration of the device is a resonance vibration excited with a natural frequency w of the device, where w> W.

1 1. Method for the simultaneous determination of rotation rate W about a certain rotation axis (D) and a transverse acceleration a _tr perpendicular to the rotation axis (D) with the device of claim 1, the sections (3, 4) of which oscillate with constant amplitude, characterized in that at least two acceleration sensors (1, 2) each measure an acceleration a- _j or a2, which is composed of a Coriolis acceleration component a _c - _| or a _C 2 and a transverse _{acceleration component} a _tr1 or a _tr 2, where ^a tr1 ^{= a} tr2 ^{= a} tr

and a- _j = k ^ a _c - _| + k ^ a _tr = 2k ₁ v- _| W + k ^ a ^ (1) or a2 = ^ 2 ^a c2 ⁺ ' ^c 2 ^a tr ⁼ 2k2 2W + k2a _tr ⁽ 2 ⁾ , where k ^ and k2 depend on the orientation of the acceleration sensors (1, 2) on the The device and its sensitivity are dependent, known calibration factors and v- _j or V2 is the magnitude of the respective, also known speed vector of the vibration of the respective sections (3, 4) with the acceleration sensors (1, 2), and from ( 1) and (2) the rotation rate W and the transverse acceleration a _{tr are} calculated.

12. The method according to claim 1 1 and with the device according to claim 7, characterized in that v ₁ = v = -v ₂ and ki = k = 1 and thus a- _| = 2fw + a _tr (V) or a ₂ = -2vW + a _tr (2 '), and that of (V) and (2'), the rotation rate W essentially by Differenz¬ of the measurement signals forming a- and a _j ₂ emerges according to W = (a- _j - a ₂ ) / 4v, while the transverse acceleration a _tr jm essentially arises from the sum of the measurement signals a ^ and a2 according to a _tr = (a- _j + a2> / 2 .

13. The method according to claim 1 1 and with the device according to claim 8, characterized in that v ₁ = v = - V2 and k- _j = - k-2 = 1 and thus a-] = 2vW + a _tr (1 " ) or a ₂ = 2vW - a _tr (2 "), and that from (1") and (2 ") the rotation rate W essentially by summing the measurement signals a ₁ and a2 according to W = (a ₁ + a2> 4v proceeds, while the transverse acceleration a _{* r} essentially results from the formation of a difference between the measurement signals a- _j and a2 according to a _tr = (a- _j - θ2> 2.

14. The method according to claim 12, characterized in that the difference signal a- _j - a for determining the rotation rate W is further processed in a lock-in amplifier (5).

15. The method according to claim 12, characterized in that the

Sum signal a ^ + a2 for determining the transverse acceleration a _{tr is given} to a low-pass filter (6).

16. The method according to claim 13, characterized in that the sum signal a ^ + a2 for determining the rotation rate W in a lock-in amplifier (5) is further processed.

17. The method according to claim 13, characterized in that the difference signal a- _j - a for determining the transverse acceleration a _{tr is given} to a low-pass filter (6).