Device for determining the rotational speed

• US 6,249,754 B1
• Filed: 06/24/1998
• Issued: 06/19/2001
• Est. Priority Date: 12/19/1996
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Lamprecht, Dirk, Neul, Reinhard
• Primary Examiner(s): ASSOUAD, PATRICK J
• Application Number:
  US09/091,912
• Time in Patent Office: 1,091 Days
• Field of Search: 702/145, 702/147, 735/040.2, 735/040.4
• US Class Current: 702/145
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Abstract

A device for determining a rotation rate can be employed in conjunction with a rotation rate sensor which furnishes one or two output signals that among other things are a measure for the Coriolis acceleration and thus also for the rotation rate. The device includes an arrangement for signal processing, with which both digital subtraction of the output signals and an ensuing digital multiplication by a carrier signal shifted in a digital phase shifter are accomplished. The digital multiplication is followed by a digital/analog conversion and low-pass filtration, which in the final analysis furnishes an output signal (DR) that is equivalent to the rotation rate.

Claims

1. A device for determining a rotation rate, having a rotation rate sensor which outputs one or two output signals (A or A and B), which among other things are a measure for the Coriolis acceleration and thus also for the rotation rate, characterized in that the output signals (A, B) are delivered in the form of pulse width modulated signals or sigma-delta signals to a digital evaluation circuit, which includes digital means for subtraction and multiplication of the signals and a digital phase shifter, to which the carrier signal (T₁) that induces the rotation rate sensor to oscillate is delivered, wherein the digital phase shifter puts the carrier signal (T₁) in phase with the Coriolis acceleration components, and the associated signal (T₂) is delivered to the means for multiplication, whose output signal is delivered to a digital/analog converter and low-pass filter (13), at whose output the rotation rate signal (DR) is available.

2. The device for determining a rotation rate of claim 1, characterized in that the rotation rate sensor includes an oscillatable body, which is set into constant oscillation by means of an oscillator, having one or more sensor elements, which are disposed on the oscillatable body and output the output signals (A or A and B).

3. The device for determining a rotation rate of claim 1, characterized in that the digital subtraction and the digital multiplication means are effected with the aid of a common Boolean switching network, to which the signals (A, B, T₂) are delivered, and that from this the items of information in the form of a positive switching signal (S_p), negative switching signal (S_n) for the D/A conversion and analog low-pass filtration, or a sign (V) and data bit (D) for further digital processing are formed.

4. The device for determining a rotation rate of claim 3, characterized in that the Boolean switching network includes solely means for complement formation (14) and NAND gates (15).

5. The device for determining a rotation rate of claim 1, characterized in that the Boolean switching network comprises only EXOR gates (27) and AND gates (28).

6. The device for determining a rotation rate of claim 3, characterized in that the Boolean switching network is the conversion of a truth table with the aid of logical means.

7. The device for determining a rotation rate of claim 1, characterized in that the digital/analog converter and low-pass filter has switches (16, 16a), which are built up in the form of CMOS outputs of gates and that apply the inputs of a downstream operational amplifier circuit (17) either to ground or to a reference voltage (V_ref).

8. The device for determining a rotation rate of claim 1, characterized in that the digital/analog converter and low-pass filter has semiconductor switches (29, 29a), which switch the current into the following operational amplifier circuit (30).

9. The device for determining a rotation rate of claim 1 characterized in that the low-pass filter (22) or (31) is of an order that is adapted to the desired frequency requirements.

10. The device for determining a rotation rate of claim 1, characterized in that the phase shifter (12) effects a phase rotation that compensates for the phase rotations occurring in the acceleration sensors, in order from the carrier signal (T₁) to generate a carrier signal (T₂) that is in phase with the Coriolis acceleration components that act on the sensor elements.

11. The device for determining a rotation rate of claim 1, characterized in that the phase shifter (12) includes at least one counter, and the phase displacement is set digitally via the starting value of the counter.

12. The device for determining a rotation rate of claim 1, characterized in that the phase shifter includes a phase locked loop (PLL), which generates a clock signal (T₂) that couples in rigid phase to the carrier frequency (T₁).

13. The device for determining a rotation rate of claim 1, characterized in that the phase shifter (12) includes an RC member with a variable resistor and a gate with a Schmitt trigger input or a comparator with a comparison voltage at half the supply voltage, and the carrier signal (T₁) is delivered via the resistor, and the phase-shifted carrier signal (T₂) occurs at the output of the gate or of the comparator.