GB2047885A

GB2047885A - Method of and Circuit Arrangement for Dynamic Measurement of Motions

Info

Publication number: GB2047885A
Application number: GB8010512A
Authority: GB
Original assignee: Carl Zeiss Jena GmbH
Current assignee: Jenoptik AG
Priority date: 1979-03-30
Filing date: 1980-03-28
Publication date: 1980-12-03
Also published as: DE3004464A1; JPS55134358A; DD141866A1

Abstract

The invention, to produce instantaneous values of speeds (velocities) and accelerations, uses two periodic basic signals (1,2) phase shifted relative to each other and multipliers each of them in respective multipliers (5,6) by a differential signal of the other basic signal produced in differentiators (3,4) and the two products are either added or subtracted. The resulting signals (8) are suitable for use in control operations. The invention permits the measurement of very low velocities or accelerations. <IMAGE>

Description

SPECIFICATION Method of and Circuit Arrangement for Dynamic Measurement of Motions The invention relates to a method of and a circuit arrangement for dynamic measurement of motions, particularly velocities or accelerations, derived from two periodic basic signals phase shifted relative to each other.

The basic signals are produced, for example, in incremental measuring systems. The invention can be employed both for dynamic measurement of motions and for deriving signals to control motion processes.

Several methods of and devices for speed measurements are known operating on the ground of two 900 phase shifted basic signals derived from the respective motion.

It is common use to reduce the speed measurement to a measurement of the clock-pulse repetition frequency by means of incremental measuring systems.

The DE patent applications laid open Nos. 2 616 972 and 2 601 800 describe, for example, that the speed measurements are carried out by time measurements of two subsequent pulses derived from a sine voltage and by pulse counting, repectively.

Said methods are suitable neither for measuring low speeds nor for control applications since in those events the measurements are subject to a speed dependent dead time and only a mean speed over a time interval can be measured rather than the instantaneous speed as required.

Acceleration measurements can only be performed by this method via speed measurements and involve the same disadvantages.

Furthermore, the DE-patent applications laid open Nos. 2326660 and 2 513688 disclose circuit arrangements which digitally or, after DA (digital to analogue) conversion, permit differentiation of the output signal from incremental measuring systems for speed measurements.

These arrangements also involve the disadvantage that the speed cannot be measured as an instantaneous value within the time interval from one increment up to the subsequent one.

Furthermore, methods are known which differentiate, rectify and filter one of the basic signals.

Said methods also have great time constants and are disadvantageous concerning control applications.

It is an object of the present invention to obviate the above disadvantages.

It is a further object of the present invention to provide a method of and an arrangement for measuring low rate motions at a low technical expenditure.

It is still a further object of the invention to provide a method of and a circuit arrangement for producing signals out of two basic signals which contain the entire primary informations of a motion and which are proportional to the instantaneous values of typical motion processes, particularly of extremely low speeds and accelerations, apart from being suitable for control applications, that is, being free of dead times and delay times.

The invention relates to a method for dynamic measurement of motions, comprising for example, an incremental measuring system for producing two basic signals phase shifted relative to each other and indicative of a motion process wherein, in a first step, each of the two basic signals is multiplied by a transformed signal obtained from the other basic signal, and, in a second step, the two products resulting are subtracted.

Further motion values may be derived from a further transformation of both motion values previously obtained by subtraction of one product from the other.

The transformation of the basic signal can consist of a first or a second differentiation, from which speeds and accelerations, respectively, can be obtained as motion values.

The above method is realised by a circuit arrangement comprising a first transmitting member to the input of which one of the two basic signals is applied, and a second transmitting member to the input of which the second basic signal is applied, a first multiplier connected to the first transmitting member, and a second multiplier connected to the second transmitting member, the second basic signal is applied to a further input of the first multiplier and the first basic signal to a further input of the second multiplier, the outputs of the first and the second multiplier are connected to a difference former the output signal of which may be applied to the input of a third transmitting member.

The output of the difference former delivers a signal proportional to speed in the event of the first differentiation performed by the first and the second transmitting member, and a signal proportional to acceleration when a first and second differentiation is performed.

When a speed value is already at hand, a signal proportional to the acceleration simultaneously produced by a further differentiation, is derived from the output of the third transmitting member.

In order that the invention may be more readily understood reference is made to the accompanying drawing which illustrates diagrammatically and by way of example one embodiment thereof and where the sole Figure shows a block scheme of the inventional arrangement.

Two basic sine signals 1 and 2 which are phase shifted relative to each other by 900 are derived, for example, from a (not shown) laser path measuring system.

The basic signal 1 is transformed, in a differentiating and transmitting member 3 and the basic signal 2 in a differentiating and transmitting member 4.

The transmitting members 3 and 4 can be embodied by a feed-back operation amplifier in the event that they perform a first differentiation.

The output signal from the transmitting member 3 and the basic signal 2 are combined in a multiplier 5 and likewise the output signal from the transmitting member 4 and the basic signal 1 in a multiplier 6.

The output signals from the multipliers 5 and 6 are subtracted from each other in a difference forming member 7.

The resulting difference signal 8 can be subject to a second differentiation in a further differentiating and transmitting member 9: thus the output signal 10 is obtained.

In the event that the transmitting members 3, 4 and 9 perform a first differentiation, the signal 8 is proportional to a measured speed and the output signal 10 to an acceleration, both signals being simultaneously obtained.

When a second differentiation is performed in the transmitting members 3 and 4 the resulting signal 8 is proportional to the acceleration.

The signals 8 and 10 do not contain any periodical components when the two basic signals are sinoidal ones and 900 phase shifted relative to each other.

The time constants of the measurement is only determined by the time constants of real differentiating members. The measuring range can be varied by selection of the differentiating constants in the transmitting members 3, 4 and 9.

Claims

1. Method of dynamic measurement of motions, comprising a measuring system for producing two periodic basic signals phase shifted relative to each other and indicative of a motion process, wherein each of the two basic signals is multiplied by a transformed signal of the other basic signal, and that the two resulting products are subtracted.

2. Method as claimed in claim 1, wherein further motion values are derived from the signals obtained by subtraction of both products in executing a further transformation.

3. Method as claimed in claim 1 or claim 2, wherein the transformation of the basic signal consists in a first differentiation thereof.

4. Method as claimed in claim 1, wherein the transformation of each basic signal consists in two successive differentiations.

5. Circuit arrangement for performing a dynamic measurement of motions by the method claimed in claims 1 to 4, comprising a first transmitting member to the input of which the first basic signal is applied, and a second transmitting member to the input of which the second basic signal is applied, wherein the output of said first transmitting member is connected to a first multiplier, and the output of said second transmitting member is connected to a second multiplier, that the second basic signal is applied to a further input of the first multiplier and the first basic signal is applied to a further input of the second multiplier, and in that the outputs of the first and the second multipliers are connected to a difference former, the output signals of which represent a function of an instantaneous motion value.

6. A circuit arrangement as claimed in claim 5, wherein the first and second transmitting members are constituted to effect a differentiation of the input signals thereto.

7. A circuit arrangement as claimed in claim 6, wherein the first and second transmitting members are constituted to effect a double differentiation of the input signals thereto.

8. A circuit arrangement as claimed in claim 5 or 6, wherein a third transmitting member is connected to the output of the difference former to produce output signals representing a further function of an instantaneous speed value.

9. A circuit arrangement as claimed in claim 8 as dependent on claim 6, wherein the third transmitting member is constituted to effect a differentiation of the input signal thereto.

10. A method of dynamic measurement of motions, substantially as hereinbefore described with reference to the accompanying drawing.

11. A circuit arrangement for performing a dynamic measurement of motions, substantially as hereinbefore described with reference to the accompanying drawing.