Communications: electrical – Continuously variable indicating – Condition responsive
Patent
1997-10-23
1999-09-07
Horabik, Michael
Communications: electrical
Continuously variable indicating
Condition responsive
340680, 340681, 34087023, 324754, 324756, 33558, 33561, G08B 2100
Patent
active
059493526
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a system for the wireless signal transmission between a checking probe and a remote receiver, comprising a sensor located in the probe, for detecting a change in the state of the probe and providing an associated checking signal, a signal generator, connected to the sensor and adapted for generating a signal comprising information about the state of the probe, and a timing generator connected to the signal generator.
Furthermore, the invention relates to a method for the wireless transmission of a signal between a checking probe and a remote receiver, the probe having sensor for detecting a change of state of the probe and a transmitter section, the method comprising the steps of generating and transmitting, by the transmitter section, a signal comprising information regarding the state of the probe, detecting the change of state of the probe, and modifying said signal to change said information about the state of the probe.
BACKGROUND ART
Measuring systems are known, for use on numerical control machines, for determining the position and/or the dimensions of mechanical workpieces, for example by means of contact detecting probes, mounted on the machine, that wireless transmit signals to remote receiver units, displace, in the course of the measuring cycles, with respect to the workpiece, contact the surface to be checked by means of a stylus, and, in consequence of the contact, modify some features of the wireless transmitted signals. Each receiver unit is connected in its turn, by means of an interface unit, with the associated numerical control unit that, by processing other signals relating to the spatial position of the probe, achieves information about the position of the workpiece surfaces.
Probes can be equipped with electric batteries for the power supply of contact detecting circuits and transmission devices. The wireless transmission can occur, for example, by sending electromagnetic signals of optical or radio-frequency type.
A contact detecting probe including a wireless infrared transmission system is disclosed in patent U.S. Pat. No. 4,509,266, according to which the information about the contact between the stylus of the probe and a workpiece is represented by a shift in the frequency of the optical signal transmitted.
In order to identify with a suitable amount of accuracy the instant when contact occurs, it is necessary that the delays--that necessarily arise in the course of the transmission of the state of the probe--be sufficiently short and repeatable.
A method for achieving a good repeatability, in systems of digital type, is that of utilizing a serial transmission of asynchronous type: in this case a message, consisting of a definite bit sequence, is immediately sent, in an asynchronous way with respect to the sequence of the serial signal, the moment when the probe detects the change of state. The information indicating the exact moment when there occurs the change in the state of the probe is implicitly given by the message end.
However, since for the asynchronous transmission there must be employed a receiver that is extremely quick in synchronising with the received signal, such method is rather sensitive to noise. Especially in the case of radio-frequency transmission, a synchronous transmission is undoubtedly preferable since, owing to the fact that it is possible to extract in the receiver a signal of synchronism of remarkable stability, it assures a major immunity against noise.
Every transmission of electromagnetic signals of synchronous type sets the need for a time resolution given by the bit period, so necessarily introducing an inaccuracy, of an equal entity, in the delay time.
In order to minimize the aforementioned inaccuracy, one could envisage the use of a sufficiently high bit rate, in other terms bit periods as short as possible. However, this would mean the employing of broad transmission bandwidths and their use may not be in compliance with the radio communication regulations, or limiting the total number of
REFERENCES:
patent: 4175253 (1979-11-01), Pitegoff
patent: 4509266 (1985-04-01), Cusack
patent: 4864294 (1989-09-01), Fukuhisa
patent: 5182543 (1993-01-01), Siegel
patent: 5279042 (1994-01-01), Gonzalez et al.
Patent Abstracts of Japan from the European Patent Office for publication No. JP61023449, publication date Jan. 31, 1986, entitled "Transmission System" by Matsumoto Masahiro.
Edwards, Jr. Timothy
Horabik Michael
Marposs Societa'per Azioni
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