WO2002030803A1

WO2002030803A1 - Arrangement for detection of a contact

Info

Publication number: WO2002030803A1
Application number: PCT/FI2001/000875
Authority: WO
Inventors: Raimo Sepponen
Original assignee: Increa Oy
Current assignee: Increa Oy
Priority date: 2000-10-09
Filing date: 2001-10-09
Publication date: 2002-04-18
Anticipated expiration: 2003-04-09
Also published as: FI20002219A0; FI20002219L; FI109625B

Abstract

The invention is related to an arrangement for detecting a mechanical contact between two objects moving in respect each other. The arrangement includes one or several transmission line (PSTL) to transfer electrical, acoustical or mechanical energy and a contact of said objects in that area, where said transmission line (PSTL) is, cause a change in properties of energy transfer of said transmission line (PSTL) and this change is detected by the means of the arrangement (RECEIVER, PROCESSOR) either as a reflection of energy or as a change of energy transmission capability or as both.

Description

ARRANGEMENT FOR DETECTION OF A CONTACT

The invention relates to an arrangement for detection of a contact between two objects and to perform the eventual following measures. The arrangement of the invention is especially applicable as a safety edge for doors and moving parts of equipment.

An automatic closing of doors may include a safety risk. A part of a body of a person or an animal may stay between moving parts of an opening or closing door. Also a piece of clothing, strap of a backpack, or other corresponding item may stay compressed. The situation may be very dangerous for example in the case of doors of a bus. If the driver do not notice the situation the bus starting to move may pull the person with fateful consequences.

Because of this reason one has developed different types of safety solutions. The most common of these are various limit switches, which are activated by a contact. The switch may be mechanical or switching may be actuated via pneumatic or hydraulic transmission. In addition there are pietsoresistive and capacitive switches, whose operation is based on the changes in resistance or capacitance due to compression. In addition to these there exist also optical arrangements, in which an object breaking the light path give rise the precautionary measures. All these solutions are able to recognize also a static compression due to the object staying between.

Problems with the mechanical solutions are related to mechanics and electrical contacts. Optical solutions are sensitive to contamination. The pietsoresistive or capacitive solutions are usually not very sensitive for small objects. One may not be able to detect the location of the compression and the material changes that occur slowly further reduce the sensitivity or the threshold level of electronics must be set at so high level that there will not be false alarms at disturbing numbers.

The piezoelectric solutions are exploiting materials, which by changing their shapes change also the distribution of internal charges. This change may be de- tected with metal electrodes attached on the surface of the material. These solutions are very sensitive to detect the dynamical phases of compression but a static compression is very difficult if not impossible to detect. In addition the electric impedance of a transducer realized in this way is high so the solution is very sensitive to electric interference. If the area to be protected is large it must be divided in many different parts which must be equipped dedicated preamplifiers in order to reach sensitivity high enough. This adds the complexity of the system and hence the sensitivity to malfunctions.

Similar safety problems are present among others with doors, windows and hatches of buses, trains, buildings, elevators and equipment.

Provisions, which must be filled by the proper solution, are:

1) A reliable detection of dangerous situation

2) A minimal number of false alarms

3) An high reliability of operation 4) An easy installation and implementation

5) An easy serviceability

6) Low initial and operation costs.

With the solution of the invention one may eliminate the problems of the present technology and one may realize an arrangement according to the requirements to improve the safety of doors, windows, machine parts etc..

Objects of the invention are accomplished by what is set forth in more detail in claim 1 and in the subclaims.

The invention is described in following with reference to the attached drawings, wherein:

- Figure 1 shows one implementation of the invention at the level of block diagram of the principle.

- Figure 2 shows pulses to be sent and received in transmission line

- Figure 3 shows an arrangement of the invention as a safety edge of doors - Figure 4 shows a transmission line of the invention

- Figure 5 shows another transmission line of the invention

- Figure 6 shows a transmission line generated by contacting transmission lines

In figure 1 there is a block diagram describing the operation of an arrangement of the invention. The arrangement includes a pulse generator PULSE GENERATOR and a receiver RECEIVER both controlled by a processor PROCESSOR which additionally performs some signal processing and to which there has been connected control means, which has not been shown in the figure and which are used to control the operation of the equipment. There are also display means DISPLAY for e.g. to show the location of a contact and an alarm signal ALARM, which may be used to control the means for alarm.

PROCESSOR may be connected directly or indirectly to means for transfer of information, which may be used for transmitting information related to the state of PROCESSOR means and information processed by these means via wired or wireless connection and possibly make connection to a local network or to wider networks such as telephone network or to the Internet.

PULSE GENERATOR is connected to a transmission line PSTL (Pressure Sensitive Transmission Line), which has been realized in such a way, that its electric properties will change when an external pressure has been applied on it. PSTL includes conductors TLC1 (Transmission Line Conductor) and TLC2 and insulator DEM (DiElectric Material) between them.

PROCESSOR controls operation of PULSE GENERATOR and RECEIVER blocks among other things by SYNC control, which activates PULSE GENERA- TOR block to send a short pulse TRP (Transmission Pulse) in the transmission line PSTL as shown in the Figure 2.

As TRP proceeds in the transmission line PSTL it finally reaches the termination

TERM of PSTL. If the impedance of TERM differs from the inherent impedance of

PSTL a reflection is generated. The strength of the reflection depends on the mismatch of the impedances. As known the reflection coefficient is p = (ZPDTL - ZTERM)/(ZPDTL+ZTERM), where ZPDTL is the inherent impedance of the transmission line and ZTERM is the impedance of the termination TERM.

If there is not other impedance mismatches in PSTL the reflection RCP2 (Re- Ceived Pulse) arrives after a delay TD2 (Time Delay), which corresponds to the propagation speed v of the pulse, i.e. TD2=2*L/v, where L is the length of PSTL.

When RECEIVER detects the reflected signal it sends a strobe signal DETECTED. If there is some other impedance mismatch a reflection reaches RE- CEIVER after a delay TD1. Obviously TD1<TD2. The distance of the impedance mismatch from the starting point of the pulse is L1=TD1*v/2. This information may be exploited for example in such a way, that the bus driver has at his disposal display means DISPLAY, which indicates a location of compression. This helps a fast evaluation and clearing of the situation.

The display means may include a line of light emitting diodes, which by brightness of the light source, temporal variation or a combination of these indicates the location of the detected compression. The display means may be realized using any known technology, these include among others liquid crystal, gas discharge, plastic, electroluminesence, electro- chromats, cathode ray tube, mechanical indicator or light projector. In addition to the display means or without them the compression may be indicated using sound indicators, such as buzzer, speaker, bell or some other sound generating means. Synthesized speech or prerecorded speech is also considered here as sound indicators.

In some cases it may be beneficial that a detection of compression leads also to stopping or to change in the direction of the movement of an object, such as a door.

A reflection, which arrives after certain delay, may be exploited in monitoring of a condition of a transmission line. If any reflection is not detected the transmission line or the connected electronics is faulty.

The transmission line may also serve as a resonator. Then a frequency of an oscillator attached to it is at lowest level when the delay is long (e.g. TD2) and at highest level when the delay (TD1) is short. If there is not any reflection the os- cillator will cease to oscillate or oscillates at a random frequency.

Transmission lines, PSTL1 and PSTL2 may be placed as shown in Figure 3 on the both contacting surfaces. These may be used to monitor the doors DOOR1 and DOOR2. To these transmission lines one may connect dedicated electronics units EU1 and EU2. In this way one may get an improved reliability, because each system alone may detect the contact.

In addition the two contacting surfaces may create a transmission line as shown in Figure 6. In this case the contacting surfaces may include three transmission lines PSTL1 , PSTL2 and PSTL3. If needed one may layer several transmission lines and improve the reliability of the detection compared to the reliability, which may be reached, with a smaller number or transmission lines. As the detection is based on a change of impedance when the transmission line is compressed it is beneficial to realize the transmission line in such a way that the properties of the conductor and/or of the insulator are to be changed significantly. Due to the compressing effect of an object OTBD (Object To Be De- tected) the bending conductor of the transmission line may be broken as shown in figure 4.

The insulator of the transmission line may change its properties when compressed. A solution like this is shown in Figure 5 where the permittivity of the dielectrics DEMS increases when compressed. In this case the gas bubbles inside the dielectrics are compressed or gas give way the compression. In this way the dielectric coefficient increases.

A change in the dielectric property of the layer DEMS may be arranged to be taking place in such a way that the dielectric substance is in liquid from and is compressed out from the space between the conductors. When the electromagnetic interference is considered it is beneficial in may cases to connect the outer conductor to he electronics ground or to the body of the bus. This connection may be galvanic or capacitive e.g. in order to avoid low frequency currents or inductive to limit high frequency currents. With the arrangement described one may suppress e.g. interference caused by mobile phones. In order to minimize unnecessary alarms PROCESSOR means may expect more than one strobe signal DETECTED to be arrived corresponding to the essentially successive TRP pulses. If the repetition frequency of TRP pulses is e.g. 10 kHz then within one second one may register up to 10 000 events and a number exceeding a certain threshold value (e.g. 80 %) leads to arrivals of the DETECTED pulses, which indicates an event of an contact, sends PROCESSOR the corresponding information to the display means DISPLAY and eventually an alarm signal ALARM

The system may also adapt to the slow changes in the surroundings and the equipment. These changes are such as a gradual change of the material of the transmission line or an accumulation of dirt on the contact surfaces. This may assume digital processing of signal and adaptive filters. Fuzzy logic may be used to generate at least partially this adaptive capability, in this adaptive system an exceptional event may be detected clearly because of stronger contact than because of slow changes. In the system one may realize with several ways confirmation and monitoring of the operation of the system. This is possible by connecting two or more parallel transmission lines to the electronics. In the same object to be observed one may implement two or more transmission lines. For example the door halves closing and facing each other there may be independent arrangements of transmission lines. In addition the opposing transmission lines PSTL1 and PSTL2 in Figure 6 may create a third transmission line PSTL3, which may be monitored. In this way one may improve the reliability of the system.

Although an electric transmission line is beneficial in many cases the transmission line may also be acoustic. Such a transmission line is a tube where sound waves are progressing. A transmission line carrying surface waves is also usable or it may be a vibrating wire, to which a contact will lead a change of oscillation. The invention is not limited to the above embodiments but a plurality of modifications can be considered plausible within the scope of the annexed claims.

Claims

PATENT CLAIMS

1. An arrangement to detect a contact between two in respect each other moving mechanical objects characterized in that it includes one or several transmission line (PSTL) to transfer electrical, acoustical or mechanical energy and that contact between said objects in that area where said transmission line (PSTL) is , causes a change in energy transfer properties of said transmission line (PSTL) and this change is detected by means of the arrangement (RECEIVER, PROCESSOR) either as a reflection of energy or as change in energy transfer capability or as both.

2. Arrangement of claim 1 characterized by that said energy is directed in transmission line (PSTL) as one or several pulses which are limited by time.

3. Arrangement set forth in any of the claims above character^'! zed by that said energy is directed in transmission line (PSTL) as essentially continuous oscillation.

4. Arrangement set forth in any of the claims above characterized by that information about location of said contact may be obtained through temporal information related to progress of energy such as for example time of registration of reflection of energy (RCP) in relation to time of sending or length of oscillation period of energy.

5. Arrangement set forth in any of the claims above characterized by that said transmission line (PSTL) is attached on the first object (DOOR1), such as for example on a door of a vehicle and a contact of some other object, such as a part of body of a person, a part of a piece of clothing, a part of backbag, with said object (DOOR1) on that part where said transmission line (PSTL) is, will be registered and said registration leads to measure, such as for example alarm or stopping of movement of said first object or change in the direction of movement.

6. Arrangement set forth in any of the claims above characterized by that transmission line (PSTL) is an electric transmission line, which dielectric ma- terial near conductors has been arranged to change it's dielectric property as a result of a contact, for example in such a way, that dielectric material in- eludes at least partially compressible material such as gas.

7. Arrangement set forth in any of the claims above characterized by that transmission line (PSTL) is an electric transmission line, which dielectric material near conductors has been arranged to be displaced by contact.

8. Arrangement set forth in any of the claims above characterized by that it includes one or several transmission line (PSTL), means to supply energy in transmission line (PULSE GENERATOR) and means to receive energy (RE- CEIVER) and means to control these (PROCESSOR) and means to indicate state of signal means and possibly to indicate site of contact (DISPLAY) and indicate event of contact (ALARM).

9. Arrangement set forth in any of the claims above characterized by that information about event of contact has been arranged to transmitted forward for example partially via data network or data networks using either wired or wireless communication path.

10. Arrangement set forth in any of the claims above characterized by that signal reflecting from termination (TERM) of transmission line is used to evaluate function of equipment.