EP1044353A1

EP1044353A1 - Device for determining a rotational speed

Info

Publication number: EP1044353A1
Application number: EP99965356A
Authority: EP
Inventors: Klaus Miekley; Manfred Abendroth
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-08-06
Filing date: 1999-07-08
Publication date: 2000-10-18
Also published as: JP2002522753A; WO2000008416A1; DE19835578A1; US6427518B1

Abstract

The invention relates to a device for determining a rotational speed which comprises an oscillating body (11) on which a plurality of electromechanical transducers (A, A', B, B', C, C', D, D') are mounted. At least one first transducer (A, A') is moved in mechanical oscillations by an electric driver signal (UF,O) which is generated in a first circuit (12). In addition, at least one second transducer (D, D') is moved in mechanical oscillations by an electric damping signal (UF,D) which is generated in a second circuit (13). At least one third transducer (C, C') emits an electric sensor damping signal (US,D) which corresponds to the oscillation of the body (11) in the position at which the at least third transducer (D, D') is mounted. The damping sensor signal (US,D) is sent back to the input of the second circuit (13). In addition, a voltage divider (31) is provided with which the signal (UF,D) generated in the second circuit (13) can be reduced.

Description

Device for determining a rotation rate

The invention relates to a device for determining a rotation rate according to the preamble of claim 1, with an oscillatable body, on which a plurality of electromechanical transducers are attached, of which at least a first transducer by means of an electrical driver signal generated in a first circuit arrangement and at least a second Converter is set into mechanical vibrations by means of an electrical damping signal generated in a second circuit arrangement, and at least one third transducer emits an electrical sensor damping signal which corresponds to the vibration of the body at the point at which the at least third transducer is attached, the sensor damping signal being fed back to the input of the second circuit arrangement.

Such a device, which works regularly on the principle of a vibrating gyrometer, is known for example from DE-44 47 005 AI. The electromechanical transducers present in the device, which are regularly piezoelectric elements, evaluate the effect the Coriolis acceleration, which serves as a measure of a rotation rate at which the vibrating body rotates. ^'The known device is therefore very good to use in conjunction with systems for vehicle dynamics control in motor vehicles, since the detected

Coriolis acceleration can be used as a measure of the current yaw rate of the vehicle.

In the known device, the vibratable body is designed as a thin-walled hollow cylinder made of an elastic material. Eight piezo elements are spaced 45 degrees apart on the cylinder wall. The piezo elements arranged for example in the positions 0 degrees, 90 degrees, 180 degrees and 270 degrees work together with an oscillator stage. The piezo elements arranged in the positions 45 degrees, 135 degrees, 225 degrees and 315 degrees work together with a damping stage. The piezo elements arranged in the 0 and 180 degree positions are set in mechanical oscillations by an oscillator driver stage. The piezo elements arranged in positions 90 and 270 degrees emit a signal which corresponds to the oscillation of the hollow cylinder at the point at which the piezo elements are attached. The signal emitted by the piezo elements arranged in the positions 90 degrees and 270 degrees is fed back to the input of the circuit arrangement for generating the electrical oscillator driver signal in such a way that an oscillator results which oscillates at its resonance frequency.

The hollow elements are set in vibration by the piezo elements arranged in the 0 and 180 degree positions, which are set in mechanical vibrations by the oscillator driver stage. The hollow cylinder swings in such a way that in the steady state, nodes form 45 degrees, 135 degrees, 225 degrees and 315 degrees. If a rotation rate acts on the hollow cylinder from the outside, the steady state of the hollow cylinder is disturbed due to the Coriolis acceleration. The system is detuned in such a way that the position of the nodes shifts. As a result, the hollow cylinder vibrates at the previous locations of the nodes.

The piezo elements arranged in the 45 degree and 225 degree positions can be set into mechanical vibrations by means of a damping driver stage. The piezo elements arranged in the positions 135 degrees and 315 degrees emit a signal which corresponds to the vibration of the hollow cylinder at the point at which they are attached. The signal emitted by the piezo elements arranged in the positions 135 degrees and 315 degrees is thus provided to the input of the excitation of the piezo elements arranged in the positions 45 degrees and 225 degrees

Circuit arrangement fed back that the vibrations at the positions 135 degrees and 315 degrees are compensated for approximately zero.

The voltage fed back to the input of the circuit arrangement for excitation of the piezo elements arranged in the positions 45 degrees and 225 degrees represents a measure of the detuning of the hollow cylinder caused by the action of a rotation rate on the oscillating hollow cylinder. This signal can thus be a measure of the rotation rate be used.

To adapt to a circuit arrangement which processes the signal further, in the known device there is a Adjustable gain amplifier provided. Although the output signal of the known device can also be set by the amplifier, the known device has the disadvantage that there is no possibility of adjusting the circuit with regard

Tolerances of the components is provided. This is particularly disadvantageous if, as provided in the known circuit arrangement, there is a possibility of applying an interference signal, by means of which the proper functioning of the circuit arrangement is checked as a so-called self-test.

To carry out the self-test, the signal emitted by the piezo elements arranged in positions 90 degrees and 270 degrees and fed back to the input of the oscillator driver stage is fed to an amplifier and, via a switch, to the input to excite the signals in positions 45 Degrees and 225 degrees arranged piezo elements provided damping driver stage. As a result, the system is detuned in the same way as when a rotation rate is applied. Since the size of the self-test signal is determined, the output signal must reach a certain size due to the detuning when the device is operating correctly. If this is not the case, this indicates that the device is not working correctly.

Since the output signal generated on the basis of the interference signal should correspond to a predetermined yaw rate and should be independent of the adaptation carried out by the output amplifier, the gain of the amplifier for generating the self-test signal can also be adjusted. The independence of the output signal from the adjustment made by the output amplifier achieved in that the inputs of the amplifier are coupled to each other for adjusting the gain and operate in opposite directions ^".

However, component tolerances cannot be compensated for by adapting the self-test signal by means of the amplifier, which can be adjusted in the gain. In particular, the setting of the self-test signal cannot compensate for differences between the transmission behavior of the piezo elements of the damping stage and the piezo elements of the oscillator stage.

A flawless function of the known circuit arrangement with regard to the self-test is only guaranteed if the transmission behavior is the same, so that they cancel each other out. Since this is not the case in practice, an incorrect self-test value is obtained. In order to remedy this, a correspondingly large amount of circuitry must be carried out. An adaptation of the transmission behavior on an integrated circuit, as the known circuit arrangement is designed regularly, is overlaid by the process parameters in semiconductor manufacture and is therefore difficult to carry out with the desired accuracy. In the known circuit arrangement, there is therefore a systematic correction by means of two differently dimensioned capacitive voltage dividers on the hybrid circuit following the circuit arrangement. However, this is disadvantageous since this measure has a temperature response which consists of the transmission behavior and the capacitive voltage divider. It is an object of the present invention to design a device mentioned at the outset in such a way that it can be compared in a simple manner.

This object is achieved from the features of the characterizing part of claim 1. Advantageous further developments of the invention result from the subclaims.

According to the invention, a voltage divider is provided, by means of which the signal generated in the second circuit arrangement can be reduced. It has been shown that the transmission behavior of the piezo elements of the damping stage is always greater than that of the piezo elements of the oscillator stage. The signal decoupled from the oscillator stage for generating the self-test signal must therefore be compensated for by a typically smaller output signal from the damping driver stage. The output signal of the circuit arrangement obtained on the basis of the self-test signal therefore always deviates downward from the true value.

If the signal given to the piezo elements of the damping stage arranged in the 45 degree and 225 degree positions is now reduced, the circuit arrangement provided for generating the signal required to excite the piezo elements arranged in the 45 degree and 225 degree positions must supply a greater output voltage than it does this would have to be done if the signal was not reduced. As a result, the output signal of the invention

Circuit arrangement raised so that its value corresponds to the injected self-test signal. It is thus possible to adapt the output signal of the device for determining a rotation rate to the self-test signal by changing the signal provided to excite the damping stage. It is particularly favorable that the adaptation can be carried out by means of an ohmic voltage divider. This has a very favorable effect on the temperature response of the device. Furthermore, it is very advantageous that the voltage divider is in the low-resistance driver circuit and not in the high-resistance sensing circuit. Since the adaptation takes place over the entire circuit arrangement, all tolerances that affect the self-test signal can be compensated for in this way. The voltage is divided in a particularly advantageous manner by means of a potentiometer.

In a special embodiment of the invention, circuit elements are provided, by means of which an interference signal is conducted to the input of the second circuit arrangement. The interference signal can advantageously be used to carry out a self-test of the device according to the invention. It is particularly advantageous in the circuit according to the invention that the output signal generated on the basis of the interference signal can be adjusted in a simple manner by means of the voltage divider.

In a further embodiment of the device according to the invention, at least a fourth electromechanical transducer is provided, which emits a sensor driver signal which corresponds to the vibration of the body at the point at which the at least fourth transducer is attached, the sensor driver signal is fed back to the input of the first circuit arrangement and the interference signal to a part or a large number of the sensor driver driver which is attributed to the input of the first circuit arrangement Signal corresponds. Since the interference signal is obtained from the oscillator circuit, its frequency always matches the frequency at which the vibrating body vibrates. It can therefore be optimally adapted to the input of the second circuit arrangement in a simple manner.

Further advantages of the present invention result from the following description of a particular exemplary embodiment with reference to the drawing.

It shows :

Figure 1 is a block diagram of a device according to the invention and

Figure 2 shows the arrangement shown in Figure 1 broken down block diagram.

In Figure 1, the sensor is designated 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 due to vibrations are shown in dashed lines.

The piezo elements A, B, C, D are connected to the blocks 12, 13, 14 of the electronics, 12 denotes the oscillator loop (drive circuit), which sets the associated piezo element in a constant mechanical drive oscillation. At 13 is one

Damping circuit designated and 14 represents the detector circuit at the output of the measurement signal U _M , which is still filtered in the filter 15 in a suitable manner, so that the actual output signal Uout is obtained. The signal output from the damping circuit 13 is divided down by means of a potentiometer 31. Piezo elements A ', B', C, D 'are internally connected to elements A, B, C, D, respectively.

The yaw rate or yaw rate of a vehicle can be determined with the sensor arrangement shown in FIG. 1, including the electronics of a yaw rate sensor, which works on the principle of a vibration gyrometer. The Coriolis effect, together with a rotational speed coupled in perpendicular to the drive vibration, brings about a Coriolis acceleration, which results in deflection of the drive vibration in the Coriolis direction. This deflection is ultimately a measure of the coupled yaw rate and should be measured.

The evaluation circuit of a device according to the invention is shown in FIG. With this arrangement, the sensor and the associated electronics are coupled to one another. The arrangement shown comprises essentially four blocks. The first block 16 is the so-called BITE block, the oscillator loop is designated 17, the damping loop is 18 and the output stage bears the reference number 19.

The blocks 16 to 19 contained in FIG. 2 are in turn divided into further blocks. The interactions between the individual blocks are indicated by corresponding connecting lines, if necessary by indicating the direction of action by corresponding arrows. Specifically, the BITE block 16 includes a variable gain amplifier 20 in which the BITE function is generated. This function is symbolized by the expression k _BITE / v _s . It is forwarded to point 22 via BITE switch 21 as BITE disturbance variable U _BITE when a test BITE test is triggered.

This point 22 stands with the blocks 23, 24 of the

Steaming loop 18 in connection. Block 23 designates the mechanical coupling (of the cylinder and the measuring elements, for example the piezo elements). The transfer function of the sensor element is designated k _{Z / D.}

Block 24 represents an electronic damping loop with phase control from the AFC and constant gain. The associated transfer function of the electronic damping loop is denoted by k _{e / D.} The electrical zero point adjustment takes place in point 22. The voltage at point 22 is designated U _{S / D.}

Two blocks 25, 26 of the oscillator loop 17 are shown, which interact with one another. Block 25 in turn denotes the mechanical coupling between the cylinder and the piezo elements. The transfer function of the sensor element is k _Zι0 . The voltage is denoted by U _s , ₀ . This is the voltage of the oscillator loop, i.e. the voltage of the excitation of the system.

Block 26 denotes the electronic excitation loop with phase controller (AFC) and amplitude controller (AGC). The associated transfer function of the oscillator loop is designated k _e , ₀ .

The drive voltage or force or drive voltage is located at the connection point between blocks 25 and 26 U _{F # 0} which is supplied to block 27 for phase rectification and constant amplification of output stage 19. Block 27 also receives the voltage U _FD from the damping loop 18. The transfer function of block 27 is designated k _BM * k ₀ . A point 28 is entered at the output of block 27, at which the offset adjustment takes place. At point 28 there is an amplifier 29 with variable gain, the gain is denoted by v _s . The yaw _rate output voltage U _rate , which is a measure of the yaw _rate actually present, can be tapped off at the output of the amplifier 29.

The mechanical zero point adjustment takes place at point 30. For this zero point adjustment, a voltage U _{cor is} fed in as the electrical equivalent of the Coriolis effect.

The voltage supplied to the block 23 for exciting the piezo elements is divided down by means of a potentiometer 31. Since blocks 23 and 24 form a control loop, block 24 must therefore output a greater output voltage U _{S, D} than it would have to do with a signal which is not divided down. The higher transfer function k _{Z # D} of block 23 can therefore be compensated for by the potentiometer 31.

With the arrangement shown as a block diagram in FIG. 2, the yaw rate sensor can be evaluated and, at the same time, the proper functioning of the sensor and the evaluation circuit itself can be checked.

If a suitable sensor element is set in a constant mechanical drive oscillation by the amplitude-controlled oscillator loop, the Coriolis effect together with one that is perpendicular to the drive oscillation coupled torsional vibration a Coriolis acceleration, which results in a deflection of the drive vibration in the Coriolis direction. As a result of these effects, the hollow cylinder on which the piezo elements serving as measuring elements are arranged is additionally vibrated. The hollow cylinder therefore fluctuates between the limits shown in dashed lines in FIG. 1.

Is used to evaluate the deflection, which, as already mentioned, is a measure of the coupled rotation rate

Compensation loop used, for example a servo loop, then the resulting manipulated variable is a measure of the rotation rate to be measured. If this compensation loop is detuned with an offset signal that is coupled in with the correct phase, the output of the sensor will indicate the superposition of the yaw rate and offset. This offset is generated in the BITE block. The offset can be activated, for example, by actuating the BITE switch 21, since the sensor can be tested if the detuning is known. Since the test function by the loop arrangement both the

Both the evaluation electronics and the sensor element can be tested for malfunction.

The derivation of the voltage U _rate occurring at the output of the sensor when the BITE function is activated corresponds to the derivation described in DE-44 47 005 AI. Reference is therefore expressly made to DE-44 47 005 AI; it is incorporated into the present invention in its entirety.

The assumption made in DE 44 47 005 AI that the transfer function k _{z, D is the} same size as the transfer function k _{Z 0} of block 25 is realized in the present invention in that the block 23 supplied voltage is reduced by means of the potentiometer 31. The prerequisite for the derivation made in DE 44 47 005 AI is thus created by the potentiometer 31.

Claims

PATENT CLAIMS

1. Device for determining a rotation rate, with a vibratable body (11) on which a plurality of electromechanical transducers (A, A ', B, B', C, C, D, D ') are attached, at least a first transducer (A, A ') by means of an electrical driver signal (U _{F; 0} ) generated in a first circuit arrangement (12, 26) and at least one second converter (D, D') by means of a in a second circuit arrangement (13, 24) generated electrical damping signal (U _FD ) in mechanical

Vibrations are set and at least one third transducer (C, C) emits an electrical sensor damping signal (U _S , _D ) which corresponds to the vibration of the body (11) at the point at which the at least third transducer (D, D ') is attached, wherein the damping sensor signal (U _{S / D} ) is fed back to the input of the second circuit arrangement (13, 24), characterized in that a voltage divider (31) is provided by means of which the second circuit arrangement (13, 24) generated signal (U _{F (D} ) can be reduced.

2. Device according to claim 1, characterized in that the voltage divider (31) is a potentiometer.

3. Apparatus according to claim 1 or 2, characterized in that circuit elements (16) are provided, by means of which an interference signal (U _BITE ) on the input of the second circuit arrangement (13, 24) is performed.

4. The device according to claim 3, characterized in that at least a fourth electromechanical transducer (B,

B ') is provided, which emits a sensor driver signal (U _{s, 0} ), which indicates the vibration of the body (11)

Corresponds to the point at which the at least fourth converter (B, B ') is attached, the sensor driver signal (U _{S / 0} ) being fed back to the input of the first circuit arrangement (12, 26) and the interference signal (U _BITE ) part or multiples of the receipt of the first

Circuit arrangement (12, 26) returned sensor driver signal (U _s , ₀ ) corresponds.