SE513392C2 - Method and device for contactless detection via modulation of electromagnetic signal by measuring magnitude controlled mechanical resonance - Google Patents

Abstract

A method for contactless detection of preferably mechanic measuring quantities such as torque, force or pressure, characterised in that a measuring quantity actuates a mechanic resonance in a string shaped element and that said resonance is excited by naturally appearing vibrations or movements in the vicinity of the sensor. The sensor is radiated with for instance microwave energy and a modulation of the microwave signal caused by the mechanic oscillation of the string element of the sensor. The distance between the sensor and the microwave transceiver can be > 10 m.

Description

15 20 25 30 513 392 2 “vibrating string” principle. Through a trivial mechanical arrangement, the pressure which it is desired to measure is converted into a corresponding mechanical stress in a string which is excited at its resonant frequency. Measurement of this resonant frequency takes place locally within the pressure sensor housing by e.g. inductive technology.

By a combination of mechanical HF modulation and the already known "vibration rating string" pressure sensor principle, a new pressure sensor for remote detection can be constructed, namely (Fig. 1) consisting of: a pressure sensing element (eg a diaphragm bellows) connected to a mechanical resonant element whose frequency is thereby controlled (eg a guitar string) a mechanical excitation signal for excitation of the mechanical resonant oscillation (eg vibrations from roadway and motor vehicle in the tire pressure sensor application) a radio transmitter / receiver with amplitude demodulator and subsequent signal conversion from AM to pressure.

An identical method can now also be used for measuring torque (Fig. 2). A string element is applied between two points along a main voltage line on the shaft whose torque is desired to be measured. The string is applied freely over the shaft surface so that it can be brought into resonant oscillation - e.g. by naturally occurring vibrations in the shaft or by an impact excitation by the rotation of the shaft.

The string is given a mechanical bias so that its resonant frequency can be controlled up or down depending on tensile or compressive stresses along the selected elongation line.

By applying your strings to the same shaft in different elongation directions and tuned to different frequency bands (by giving them different lengths, bias levels, mass loads, etc.), the complete mechanical stress state of the shaft can be sensed without contact and at a considerable distance. .

By utilizing an element whose mechanical shape changes with its temperature and by, according to the method described above, coupling this for controlling a mechanical resonant frequency, a telemetric temperature sensor can also be manufactured according to the new principle described here.

Measurement and monitoring of mechanical vibrations is a significant area of technology. Here, the new radio technology offers a variety of possibilities. A vibrating object can be directly irradiated with electromagnetic signals and the modulation introduced by the mechanical movement is analyzed. Alternatively, e.g. antenna-shaped wire elements are applied to a vibrating structure at particularly interesting measuring points.

An acoustic signal which sets a simple diaphragm in oscillation allows, according to the new principle, in itself a microphone function.

For stringed instruments, again with the guitar example, a new method is offered for conversion from mechanical / acoustic to electrical signal for further processing and distribution in sound system systems.

For i.a. In the torque and tire pressure measurement applications, an additional effect can be used in order to increase the detection reliability and to obtain additional information such as speed and angular course. When the oscillating string sensor is also caused to rotate, its antenna aspect changes relative to the transmitting / receiving antennas of the detection system, which results in a superimposed modulation of the total strength of the electromagnetic signal from the oscillating string. This means that the spectral line from the string in the amplitude-modulated spectra of the HF signal, whose frequency position corresponds to a certain tire pressure or torque, now varies in strength depending on the rotation of the sensor. Thereby 513 392 4 information is also obtained about e.g. tire speed and angular course. This Information can e.g. is used to distinguish the tire signals coming from the own vehicle (which are normally all rotationally synchronized) from signals originating from other vehicles in the vicinity of the own vehicle and equipped with the same measuring system for tire pressure measurement.

Further exploitation and analysis of the new principle described here and its utilization in a measurement system is of course possible and is therefore considered to be covered by this invention. il

Claims (1)

A method for detecting a measured quantity of an object, characterized in that an oscillating element connected to the object is irradiated with a microwave signal, said measuring quantity controlling a mechanical oscillating movement occurring at the oscillating element, the oscillating movement as a modulation of the microwave signal from the oscillating element, the mechanical oscillating motion is excited by naturally occurring mechanical energy available in its immediate vicinity. Method according to Claim 1, characterized in that the measured quantity controls a mechanical resonant frequency. Method according to claims 1 and 2, characterized in that the measured quantity is a gas or liquid pressure. Method according to claims 1 and 2, characterized in that the measured quantity is a torque. Method according to claims 1 and 2, characterized in that the measured quantity is a temperature. _ _ A method according to claim 2, characterized in that ät your measured quantities are simultaneously detected by the resonance frequencies controlled by these not coinciding. The method according to claim 1, characterized by the variation in the intensity of the microwave signal from the oscillating element is used to detect a rotation of the oscillating element. Method according to claims 1 and 7, characterized in that such intensity variations are used to relate rot your rotating oscillating elements next to each other. Device for detecting a measured quantity of an object, characterized by a microwave transmitter, is arranged for irradiating an oscillation element connected to the object with a microwave signal, the oscillation element is connected to the object, so that said measuring quantity controls an oscillation element mechanical oscillation movement, means are provided for receiving a microwave signal from the oscillation element and for detecting a modulation of the received microwave signal introduced by the oscillation movement, the oscillation element is mechanically arranged to be excited by the naturally occurring mechanical energy available in the immediate vicinity of the oscillating element. Device according to claim 9, wherein the pivoting element is string-shaped. Device according to claim 10, wherein the strand-shaped element is arranged to perform a transverse resonant oscillation. Device according to claim 9, wherein the strand-shaped element is mechanically prestressed.