WO2006095368A1

WO2006095368A1 - A system for localization inside tunnels using satellite signals

Info

Publication number: WO2006095368A1
Application number: PCT/IT2005/000128
Authority: WO
Inventors: Franco Mazzenga; Antonio Saitto; Gino Di Mambro
Original assignee: Franco Mazzenga; Antonio Saitto; Gino Di Mambro
Priority date: 2005-03-10
Filing date: 2005-03-10
Publication date: 2006-09-14
Also published as: CN101203771B; CN101203771A; EP1861730A1

Abstract

This invention concerns a system for localization of objects, persons, vehicles, etc. inside tunnels using satellite signals commonly deployed for outdoor localization. The proposed system can operate with every satellite radio-localization systems actually operating, GPS/GLONASS, and of next generation, GALILEO. The proposed system is composed of two independent parts: one system for the radiation of satellite signals inside tunnels and one processor, hardware, software, or hardware and software, which is added to a generic satellite receiver used for localization in order to process the information gathered from the tunnel reirradiated satellite signals in order to determine the position of the object, person, vehicle etc. inside the tunnel.

Description

A SYSTEM FOR LOCALIZATION INSIDE TUNNELS USING SATELLITE SIGNALS

The invention allows to measure the position of an object inside a tunnel by means of the satellite signals commonly deployed for outdoor localization. The proposed system allows to determine the position of the object and its velocity inside the tunnel with measurement errors in the order of tens of metres. The proposed system is composed of two distinct and inter-operating parts, indicated in the following as sub-systems, whose characteristics are now detailed.

1. The first sub-system includes all the necessary functions that are required to irradiate the satellite signals inside the tunnel.

2. The second sub-system is a processor, to be inserted in a generic satellite receiver used for localization, which implements all the functions required to calculate the position of the object inside the tunnel from the information contained in the satellite signals that have been re-irradiated inside the tunnel by the sub-system described in the previous point 1.

Depending on the specific application, the sub-system used for the radiation of satellite signals into the tunnel can operate in accordance to two different modes: direct radiation and guided radiation. For each operating mode we can have different implementations of the radiation sub-system.

The scheme of the direct-radiation subsystem to be used for radiation inside the tunnel is shown in FIG.l. The signals transmitted by the visible satellites are received by a suitably steered antenna which is located outside the tunnel and in the proximity of the tunnel entrance. These signals are then amplified by the sub-system AMP, and are sent by means of a transmission line LT to an electromagnetic radiator RAD located at the entrance or inside the tunnel.

The scheme of the guided-radiation sub-system, subject of this invention, which is used for the radiation inside the tunnel is shown in FIG.2. The signals transmitted by the visible satellites are received by the antenna located outside the tunnel and in the proximity of the tunnel entrance. Then these signals are amplified by the sub-system AMP in FIG.2 and are given in input, by means of a transmission line LT, to the electro-optical converter E/O in FIG.2 whose main task is to retranmit them on one or more optical fibers FO with different lengths. Each FO is terminated on an optical-electrical converter O/E and the recovered electric signal is used as input to the electromagnetic radiator RAD. Radiators RAD are arbitrarily positioned or can be regularly spaced along the gallery profile with distance step d. The FOs follow the longitudinal extension of the tunnel.

The satellite signals reirradiated in the tunnel in direct or guided mode experience the same tunnel propagation delay. The value of this additional delay directly depends on the distance between the tunnel entrance and the satellite receiver located inside the tunnel. The additional delay due to propagation inside the tunnel directly adds to the propagation delays associated to each path from satellite to the tunnel entrance.

Starting from this consideration it can be observed that the overall path from satellite to the receiver inside the tunnel can be conveniently decomposed into two parts:

1. the path between the satellite and the antenna located outside the tunnel in the proximity of the tunnel entrance;

2. the path in the tunnel extending from the receiving antenna to the satellite receiver in the tunnel. The additional delay due to propagation inside the tunnel introduces an additional error in the measure of the distance between the generic satellite and the receiver, indicated as pseudorange. This additional error can be accounted for in the pseudorange equations by introducing a novel unknown representing the distance covered by the signals reirradiated in the tunnel, curvilinear coordinate. Indicating with s the curvilinear coordinate, the pseudorange equation for the generic satellite can be rewritten as:

R_k = ^χ -χ_kΫ + (y - y_k Ϋ + (z - z_k γ + s + C_b , k=1 ,2 N_s

where (xyέ) are the coordinates of the tunnel entrance; (x^y^k) k=\,2,...,N_s, are the coordinates of the N_s visible satellites; s is the distance of the satellite receiver from the tunnel entrance and Q is the clock bias whose behavior with time can be predicted by means of known and very accurate mathematical models. When the satellite receiver is outside the tunnel _v=0.

Conventional satellite receivers used for localization are not equipped with processing hardware/software sub-systems able to extract the value of s contained in the overall clock bias error i.e. s+C_b- As a consequence s appears to a conventional satellite receiver as an additional noise that introduces significant errors in the position estimation and leads to a block of the receiver operations when its value increases beyond a threshold.

In order to avoid this inconvenient it is necessary to insert in the conventional or modern satellite receiver a novel processor P, subject of this invention, as shown in FIG.3.

From the scheme in FIG.3, the signals transmitted by the satellites, that have been reirradiated in the tunnel, are received by the satellite receiver antenna ANT-RIC. Signals are then demodulated and processed by the conventional subsystem RCS in order to obtain the pseudorange and phase measurements. These data are the given as input to the processing subsystem ELAB whose main task is to determine the pseudorange and/or phase data and the overall clock bias C_b+s.

Pseudorange and overall clock bias data at the output of ELAB are given as input to the novel processor P whose main task is the calculation of the receiver position inside the tunnel starting from the measured overall clock bias i.e. Cb+s.

The processor P can be realized using hardware, software or hardware and software technologies. The functions of the processor P can be illustrated by introducing two distinct sub-processors Pl and P2 in FIG.4. Both Pl and P2 interface with the subsystems of the generic satellite receiver as illustrated in FIG.4 and their tasks are now detailed.

The sub-processor Pl determines weather the receiver is inside or outside the tunnel by using the overall clock bias data measured by the ELAB subsystem. When the receiver is outside the tunnel the pseudorange and/or phase data are directly passed to the PRES subsystem, following the arrow with label NO, for the calculation of the receiver position and the presentation of this information to the final user.

When the receiver is inside the tunnel data from ELAB are sent in input to the sub-processor P2, following the arrow with label YES. The task of P2 is to correct the pseudorange and/or phase data in accordance to the estimated curvilinear coordinate s which is directly proportional to the distance between the antenna at the tunnel entrance and the position of the receiver inside the tunnel. The updated data are then sent to the PRES sub-system for the calculation of the receiver position and the presentation of this information to the final user.

Either Pl and P2, implement algorithms that are based on the overall clock bias information s+C_b provided by the ELAB subsystem.

Claims

1. A system for localization of an object inside tunnels based on the signals transmitted by satellite systems for navigation characterized by one subsystem radiating the satellite signals inside the tunnel, in accordance to a direct or a guided radiation mode, and by a second subsystem P, for the processing of the data obtained by the signals radiated in the tunnel which is inserted in a generic satellite receiver between the subsystem for pseudorange/phase measurements ELAB and the subsystem for the calculation of the position PRES to determine the position of the receiver inside the tunnel.

2. A system as in CLAIM 1 , characterized by a sub-system for the direct radiation of satellite signals in the tunnel which is composed by a receiving antenna ANT-RIC, an amplifier AMP and one electromagnetic radiator (RAD) in the tunnel and joined by means of a cable, a guide or an optical fiber whose length is comparable with the accuracy of the desidered measurement.

3. A system as in CLAIM 1, characterized by a sub-system for the guided radiation of the satellite signals inside the tunnel including a receiving antenna ANT-RIC outside the tunnel which receives the satellite signals, an amplifier AMP, if necessary, a transmission line LT to send the signals in input to an electro-opical E/O converter that send the set of signals on a number of optical fibers FO each of them connected first to an optical-electrical O/E converter and then to an electromagnetic radiator RAD.

4. A system as in CLAIM 1 , characterized by the sub-system P that, when inserted in a satellite receiver used for localization, uses the information contained in the satellite signals reirradiated in the tunnel to establish if the receiver is inside or outside the tunnel using algorithms implemented in the Pl sub-processor, and to evaluate the position of the receiver when it is inside the tunnel using the algorithms implemented in the sub-processor P2.

5. A system as in CLAIM 1, characterized by a sub-system Pl that, when inserted in a satellite receiver used for localizzation, uses the overall clock bias information obtained from the received satellite signals to establish if the receiver is inside or outside the tunnel.

6. A system as in CLAIM 1 , characterized by a sub-system P2 that, when inserted in a satellite receiver used for localizzation uses the overall clock bias information obtained from the satellite signals radiated in the runnel by subsystems in CLAIM 2 or CLAIM 3, to calculate the position of the receiver inside the tunnel.