Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
1999-07-12
2002-12-10
Bui, Bryan (Department: 2663)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
C702S153000, C367S099000
Reexamination Certificate
active
06493649
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a detection system for determining information concerning the location of objects, and which can be extended go determine movement and orientation and even physical parameters such as shape of objects in a specified environment. The invention can be applied to people and animals as well as inanimate objects such as furniture, machines, vehicles, equipment and the like, and in this connection object is intended to include any movable entity.
BACKGROUND TO THE INVENTION
Location systems are known which allow the presence or absence of an object in a specified environment (such as a room) to be confirmed or denied, and relative to one or more reference points to identify where in the environment the object is located.
EP 0485879 describes a system for locating vehicles in automatic guidance transport systems. Ultrasound is employed as a distance measuring medium whilst an infra-red link allows communication between vehicles.
WO95/14241 describes a tracking system which enables a spotlight to follow a person on a stage carrying a transponder. Again infra-red signals are used to instigate ultrasonic transmissions to determine the position of the transponder and therefore the person. The spotlight is moved accordingly.
EP 0591899 describes another spotlight controlling system for tracking a moving target (actor on a stage) carrying a transponder. Here radio transmissions establish the communication link and ultrasound transmissions are employed to determine distance and position.
These systems do not measure characteristics other than position and are limited with regard to the number of objects which can be tracked due to the length of time needed for each ultrasound transmission to die away, which is inherent in any such system, and it is an object of the present invention to provide a detection system capable of track-in more objects, which can be modified to allow orientation, rotational movement and linear movement to be determined and tracked and will further allow for control of operable devices on or associated with the object.
THE INVENTION
A system embodying the invention enables the position of each of a plurality of labelled objects in a specified environment to be determined by determining the transit time of slowly propagating energy transmitted from a transmitter on each labelled object, to a plurality of receivers positioned at fixed points in or around the specified environment, and computing therefrom the actual distance of the transmitter from the receivers, wherein the transmission of the slowly propagating energy is initiated by a burst of high speed propagating energy from a master transmitter located so as to cause transmitted bursts of such high speed energy to enter the said environment, and the transmitter is associated with a receiver adapted to respond to an appropriately encoded burst of such high speed energy, to thereby initiate a burst of slowly propagating energy therefrom, (each said transmitter/receiver combination being referred to as a transponder) and in order to allow the system to adapt to different numbers of transponders and differing demands for service (eg frequency of position determination per transponder or object), a coordinating control system is provided for determining the order in which the object mounted transmitter/receiver combinations are to be addressed and triggered by the transmissions from the master transmitter, in response to updatable information relating to the objects and related service demands.
Preferably each of the said plurality of receivers is adapted also to be responsive to said burst of high speed energy, so as to identify the beginning of a window of time within which a slow speed energy burst may arise and be received thereby. The burst may be the same burst as is sent to trigger one of the transmitter/receiver units transponders to transmit a slowly propagating wave, for time measurement.
Alternatively the said plurality of receivers may be connected by a network of cables and the reset signals and the polling of the time values may be achieved via the network.
Preferably the receivers include a latch to retain information about the time at which the beginning of a burst of slow speed energy is received after the beginning of each said time window.
Preferably the receivers are scanned (ie polled) so as to recover the time information and reset the latches.
Preferably computing means is provided to associate the time information with the receiver from which the times have been obtained, and generate a transmit time for each receiver.
Preferably the computing means is programmed to convert the transit time into distance values and using position data relating to the receivers stored in a memory, to compute therefrom the position of the object mounted transponder from each of the receivers, and therefore, by geometry its position relative to one or more fixed points defining the specified environment.
By encoding the high speed energy transmission, so a plurality of different slow speed signal transmitters all located in the same specified environment, can be triggered in turn, so that during a sequence of time windows, position data relating to each of the slow speed signal transmitters in the environment can be obtained, the data in each window relating specifically to one only of the object mounted transponders.
Typically the slow speed signals are acoustic or ultrasonic signals and the high speed signals are electric currents or voltage or visible or invisible electromagnetic radiation such as IR, UV or radio signals.
Encoding of the high speed signals may be by way of frequency or amplitude or phase modulation or pulse coding or any combination thereof.
Preferably digital encoding techniques are employed, if only to ensure adequate signal to noise ratios can be achieved.
Background Theory to Position Determining Systems
Such systems are based on the principle or location by multilateration. For each object that is to be located, the straight-line distances are measured from a point on that object to a number of other points in the environment whose positions (in some frame of reference) are already known. Given enough distances, and a suitable geometry of the endpoints between which they are measured, it is possible to derive a position for the object.
To determine the distances between objects and points in the environment, transmitters and receivers are placed on them and measurements are made of the times of signal pulses being generated and received. The system can be used to measure round trip delays, or alternatively can give the difference in the one-way delays for signal pulses sent simultaneously (or with known time offsets). If the one-way delay in two media are dt
1
and dt
2
, then
D=dt
1
−dt
2
,
and
if the (predictable) velocities of propagation in the two media are v
1
and v
2
, and the distance between transmitter and receiver is R, then
R=D
/(1
/v
1
−1
/v
2
).
It may be seen that if v
2
is much greater than v
1
, then the range calculation can be approximated by
R=Dv
1
.
Thus, if, for example, radio and ultrasonic signals are transmitted simultaneously through space then the equation R=Dv
1
will give sufficiently accurate results for the limited range of distance likely to occur in an indoor environment, such as a typical house, room, office or even small factory unit or warehouse.
It is not necessary to transmit both fast and slow speed signals simultaneously. A radio pulse for example, can be treated as if its travel time is zero (i.e. independent of range), and it can thus simply be used as a trigger signal. However the flight times of the slow signal pulses (e.g. ultrasonic pulses) can be accurately measured by synchronising the transmitter and receiver units, as by a timing pulse generated by a suitable controller.
Reflections from other objects in the transmitter's environment may cause multiple signals to arrive at a receiver. Any direct-path signal from the transmitter to the receiver
Jones Alan Henry
Ward Andrew Martin Robert
AT&T Laboratories - Cambridge Limited
Bui Bryan
Lee Mann Smith McWilliams Sweeney & Ohlson
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