Patent Description:
The centralized or de-centralized control system stores the location and speed information for guideway mounted vehicles within a control zone. Based on this stored location and speed information, the centralized or de-centralized control system generates movement instructions for the guideway mounted vehicles.

When communication between the guideway mounted vehicle and the centralized or de-centralized control system is interrupted, the guideway mounted vehicle is braked to a stop to await a manual driver to control the guideway mounted vehicle. Communication interruption occurs not only when a communication system ceases to function, but also when the communication system transmits incorrect information or when the CTBC rejects an instruction due to incorrect sequencing or corruption of the instruction. The documents <CIT> and <CIT> disclose solutions relative to the location and speed information for guideway mounted vehicles within a control zone. However these solutions do not provide optimal vehicle detection.

One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout. It is emphasized that, in accordance with standard practice in the industry various features may not be drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features in the drawings may be arbitrarily increased or reduced for clarity of discussion.

The invention relates to a system according to claim <NUM> and a method according to claim <NUM>. The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are examples and are not intended to be limiting.

<FIG> is a diagram of a vehicle localization system <NUM>, in accordance with one or more embodiments. Vehicle localization system <NUM> is associated with a vehicle <NUM> having a first end <NUM> and a second end <NUM>. Vehicle localization system <NUM> comprises a controller <NUM>, a memory <NUM>, a first set of sensors including a first sensor 110a and a second sensor 110b (collectively referred to herein as the "first set of sensors <NUM>") on the first end <NUM> of the vehicle <NUM>, and a second set of sensors including a third sensor 112a and a fourth sensor 112b (collectively referred to herein as the "second set of sensors <NUM>") on the second end <NUM> of the vehicle. In some embodiments, though described as a set of sensors, one or more of the first set of sensors <NUM> or the second set of sensors <NUM> includes only one sensor.

The controller <NUM> is electrically coupled with the memory <NUM>, the sensors of the first set of sensors <NUM> and with the sensors of the second set of sensors <NUM>. The controller <NUM> is on-board the vehicle <NUM>. If on-board, the controller <NUM> is a vehicle on-board controller ("VOBC"). In some embodiments, one or more of the controller <NUM> or the memory <NUM> is off- board the vehicle <NUM>. In some embodiments, the controller <NUM> comprises one or more of the memory <NUM> and a processor (e.g., processor <NUM> (shown in <FIG>)).

Vehicle <NUM> is configured to move along a guideway <NUM> in one of a first direction <NUM> or a second direction <NUM>. In some embodiments, guideway <NUM> includes two spaced rails. In some embodiments, guideway <NUM> includes a monorail. In some embodiments, guideway <NUM> is along a ground. In some embodiments, guideway <NUM> is elevated above the ground. Based on which direction the vehicle <NUM> moves along the guideway <NUM>, one of the first end <NUM> is a leading end of the vehicle <NUM> or the second end <NUM> is the leading end of the vehicle <NUM>. The leading end of the vehicle <NUM> is the end of the vehicle <NUM> that corresponds to the direction of movement of the vehicle <NUM> along the guideway <NUM>. For example, if the vehicle <NUM> moves in the first direction <NUM> (GD0), then the first end <NUM> is the leading end of the vehicle <NUM>. If the vehicle <NUM> moves in the second direction <NUM> (GD1), then the second end <NUM> is the leading end of the vehicle <NUM>. In some embodiments, the vehicle <NUM> is capable of being rotated with respect to the guideway <NUM> such that the first end <NUM> is the leading end of the vehicle <NUM> if the vehicle <NUM> moves in the second direction <NUM>, and the second end <NUM> is the leading end of the vehicle <NUM> if the vehicle <NUM> moves in the first direction <NUM>.

As the vehicle <NUM> moves in the first direction <NUM> or in the second direction <NUM> along the guideway <NUM>, the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are each configured to detect at least one marker of a set of markers 120a- 120n, where n is a positive integer equal to or greater than <NUM>. At least one marker of the set of markers 120a-120n are collectively referred to herein as "marker(s) <NUM>. " The sensors of the first set of sensors <NUM> and the sensor of the second set of sensors <NUM> are each configured to generate corresponding sensor data based on a detected marker <NUM>. Markers <NUM> are part of system <NUM>.

A marker <NUM> is, for example, a static object such as a sign, a shape, a pattern of objects, a distinct or sharp change in one or more guideway properties (e.g. direction, curvature, or other identifiable property) which can be accurately associated with a specific location, or some other suitable detectable feature or object usable to determine a geographic location of a vehicle. The markers <NUM> include one or more of the metasurface plates <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> as described in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. In some embodiments, markers <NUM> of the present disclosure are synonymous with the term "metasurface plate". One or more of the markers <NUM> are on the guideway <NUM>. In some embodiments, one or more of the markers <NUM> are on a wayside of the guideway <NUM>. In some embodiments, all of the markers <NUM> are on the guideway. In some embodiments, all of the markers <NUM> are on the wayside of the guideway. In some embodiments, the markers <NUM> comprise one or more of rails installed on the guideway <NUM>, sleepers or ties installed on the guideway <NUM>, rail baseplates installed on the guideway <NUM>, garbage catchers installed on the guideway <NUM>, boxes containing signaling equipment installed on the guideway <NUM>, fence posts installed on the wayside of the guideway <NUM>, signs installed on the wayside of the guideway <NUM>, other suitable objects associated with being on the guideway <NUM> or on the wayside of the guideway <NUM>. In some embodiments, at least some of the markers <NUM> comprise one or more different objects or patterns of objects compared to other markers <NUM>. For example, if one marker <NUM> comprises a garbage catcher, a different marker <NUM> comprises a railroad tie.

Consecutive markers <NUM> are spaced apart by a distance d. In some embodiments, the distance d between consecutive markers <NUM> is substantially equal between all of the markers <NUM> of the set of markers 120a-120n. In some embodiments, the distance d between consecutive markers <NUM> is different between a first pair of markers <NUM> and a second pair of markers <NUM>. The memory <NUM> comprises data that includes information describing the markers <NUM>, a geographic position of the markers <NUM>, and a unique RF signature of the markers <NUM> and/or a unique additional signature of the markers <NUM>. In some embodiments, based on the detection of a marker <NUM>, controller <NUM> is configured to query the memory <NUM> for the information describing the detected marker <NUM> such that the detected marker <NUM> has a location that is known to the controller <NUM>. In some embodiments, the markers <NUM> generate at least a unique RF signature or another signature that are known by the controller <NUM>, and the controller <NUM> is able to determine the position of the vehicle <NUM> from the corresponding unique RF signature, from information associated with the corresponding unique RF signature, the corresponding unique another signature or from information associated with the corresponding unique another signature.

Each of the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> is positioned on the first end <NUM> of the vehicle <NUM> or the second end of the vehicle <NUM> at a corresponding distance L from the markers <NUM>. The distance L is measured in a direction perpendicular to the direction of movement of the vehicle <NUM>, between each sensor of the first set of sensors <NUM> and each sensor of the second set of sensors <NUM> as the vehicle <NUM> moves past a same marker <NUM>. For example, if the vehicle <NUM> is moving in the first direction <NUM>, the first sensor 110a is positioned a distance L1 from marker 120a, and second sensor 110b is positioned a distance L2 from marker 120a. Similarly, as the vehicle <NUM> passes marker 120a, third sensor 112a is a distance L3 from marker 120a, and fourth sensor 112b is a distance L4 from marker 120a. The corresponding distances L1, L2, L3 and L4 are not shown in <FIG> to avoid obscuring the drawing.

The first sensor 110a has a first inclination angle α1 with respect to the detected marker <NUM>. The second sensor 110b has a second inclination angle α2 with respect to the detected marker <NUM> different from the first inclination angle α1. The third sensor 112a has a third inclination angle β1 with respect to the detected marker <NUM>. The fourth sensor 112b has a fourth inclination angle β2 with respect to the detected marker <NUM> of different from the fourth inclination angle β1. In some embodiments, the discussed inclination angles α1, α2, β1 and β2 are measured with respect to a corresponding horizon line that is parallel to the guideway <NUM>. The corresponding horizon line for each sensor of the first set of sensors <NUM> and each sensor of the second set of sensors <NUM> is separated from the marker <NUM> by the corresponding distance L of each sensor of the first set of sensors <NUM> or each sensor of the second set of sensors <NUM>.

In some embodiments, inclination angle α1 is substantially equal to inclination angle B1, and inclination angle α2 is substantially equal to inclination angle β2. If the markers <NUM> are on the guideway, then the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are directed toward the guideway <NUM>. In some embodiments, if the vehicle <NUM> is configured to move over the guideway <NUM>, and the markers <NUM> are on the guideway, then the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are directed downward toward the guideway <NUM>. If the markers <NUM> are along the guideway <NUM> on the wayside of the guideway <NUM>, then the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are directed toward the wayside of the guideway <NUM>.

Each of the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> has a corresponding field of view. Sensor 110a has a field of view 122a that is based on the position of sensor 110a on the first end <NUM> of the vehicle <NUM> and inclination angle α1. Sensor 110b has a field of view 122b that is based on the position of sensor 110b on the first end <NUM> of the vehicle <NUM> and inclination angle α2. Sensor 112a has a field of view 124a that is based on the position of sensor 112a on the second end <NUM> of the vehicle <NUM> and inclination angle β1. Sensor 112b has a field of view 124b that is based on the position of sensor 112b on the second end <NUM> of the vehicle <NUM> and inclination angle β2.

Field of view 122a overlaps with field of view 122b, and field of view 124a overlaps with field of view 124b. In some embodiments, one or more of field of view 122a and field of view 122b are non-overlapping, or field of view 124a and field of view 124b are non-overlapping. The position and inclination angle of each sensor <NUM> of the first set of sensors <NUM> is such that a detected marker <NUM> enters one of the field of view 122a or 122b, first, based on the direction the vehicle <NUM> moves along the guideway <NUM>. Similarly, the position and inclination angle of each sensor <NUM> of the second set of sensors <NUM> is such that a detected marker <NUM> enters one of the field of view 124a or 124b, first, based on the direction the vehicle <NUM> moves along the guideway <NUM>. In some embodiments, the markers <NUM> are spaced along the guideway <NUM> such that only one of the markers <NUM> is within field of view 122a or 122b at a time. Similarly, in some embodiments, the markers <NUM> are spaced along the guideway <NUM> such that only one of the markers <NUM> is within field of view 124a or 124b at a time. In some embodiments, the markers <NUM> are spaced along the guideway <NUM> such that only one of the markers <NUM> is within field of view 122a, 122b, 124a or 124b at a time. In some embodiments, markers <NUM> are spaced along the guideway <NUM> such that only one marker <NUM> is detected by the sensors of the first set of sensors <NUM> or the sensors of the second set of sensors <NUM> at a time. In other words, in some embodiments, a marker <NUM> is within field of view 122a and 122b, or within field of view 124a and 124b.

In some embodiments, the markers <NUM> are separated by a distance d that results in there being non-detection time between consecutive marker <NUM> detections as the vehicle <NUM> moves along the guideway <NUM>.

In some embodiments, the distance d between consecutive markers <NUM> is set based on the frequency of the RADAR sensor of first set of sensors <NUM> or second set of sensors <NUM>. For example, as the bandwidth or frequency of the radar increases, the minimum distance between each consecutive marker <NUM> decreases, and the consecutive markers <NUM> can be spaced closer to each other (<FIG>). Similarly, as the bandwidth or frequency of the radar decreases, the minimum distance between consecutive markers <NUM> increases, and the consecutive markers <NUM> are spaced further from each other (<FIG>). In some embodiments, if the consecutive markers <NUM> are not separated by a sufficient minimum distance, then the radar sensor of first set of sensors <NUM> or second set of sensors <NUM> may not be able to accurately discern or detect one or more retro reflecting or absorbing elements within marker <NUM> which would affect the determination of the position of marker <NUM>.

In some embodiments, the distance d between consecutive markers <NUM> is set based on one or more of the velocity of the vehicle <NUM>, processing time and delays of the controller <NUM>, field of view 122a, 122b, 124a and/or 124b, the inclination angles α1, α2, β1, and/or β2, the separation distances L1, L2, L3 and/or L4 between the sensors and the markers <NUM>, and/or a width of each marker <NUM> measured in the direction of movement of the vehicle <NUM>.

First sensor 110a of the first set of sensors <NUM> and third sensor 112a of the second set of sensors <NUM> include one or more radio detection and ranging ("RADAR") sensors configured to detect an object or pattern of objects such as markers <NUM>. In some embodiments, the RADAR sensor is configured to capture information in a microwave spectrum. The RADAR sensor is capable of identifying the presence of an object as well as unique identifying characteristics of a detected object similar to an optical sensor (described below). In some embodiments, first sensor 110a and/or second sensor 110b includes a microwave emitter configured to emit electromagnetic radiation which is reflected off objects along the guideway or the wayside of the guideway. In some embodiments, first sensor 110a or third sensor 112a are configured to detect an RF signature of markers <NUM>. In some embodiments, the RF signature includes one or more of a distance from the first sensor 110a or third sensor 112a to the markers <NUM>, a relative velocity of vehicle <NUM> between the first sensor 110a or third sensor 112a and markers <NUM>, an angular position of the first sensor 110a or third sensor 112a relative to markers <NUM> or a signal to noise ratio (SNR) of the echo signal received by first sensor 110a or third sensor 112a from markers <NUM>.

Second sensor 110b of the first set of sensors <NUM> and fourth sensor 112b of the second set of sensors <NUM> include one or more of laser imaging detection and ranging ("LIDAR") sensors, cameras, infrared-based sensors, or other suitable sensors configured to detect an object or pattern of objects such as markers <NUM>. In some embodiments, second sensor 110b or fourth sensor 112b is configured to detect another signature of markers <NUM>. In some embodiments, the another signature includes one or more of a relative velocity of vehicle <NUM> between the second sensor 110b or fourth sensor 112b and markers <NUM>, an angular position of the second sensor 110b or fourth sensor 112b relative to markers <NUM> or a signal to noise ratio (SNR) of the echo signal received by second sensor 110b or fourth sensor 112b from markers <NUM>.

In some embodiments, second sensor 110b and/or fourth sensor 112b is an optical sensor configured to capture information in a visible spectrum. In some embodiments, second sensor 110b and/or fourth sensor 112b includes a visible light source configured to emit light which is reflected off objects along the guideway or the wayside of the guideway. In some embodiments, the optical sensor includes a photodiode, a charged coupled device (CCD), or another suitable visible light detecting device. The optical sensor is capable of identifying the presence of objects as well as unique identification codes associated with detected objects. In some embodiments, the unique identification codes include barcodes, quick response (QR) codes, alphanumeric sequences, pulsed light sequences, color combinations, images, geometric representations or other suitable identifying indicia.

In some embodiments, second sensor 110b and/or fourth sensor 112b includes a thermal sensor configured to capture information in an infrared spectrum. In some embodiments, second sensor 110b and/or fourth sensor 112b includes an infrared light source configured to emit light which is reflected off objects along the guideway or the wayside of the guideway. In some embodiments, the thermal sensor includes a Dewar sensor, a photodiode, a CCD or another suitable infrared light detecting device. The thermal sensor is capable of identifying the presence of an object as well as unique identifying characteristics of a detected object similar to the optical sensor.

In some embodiments, second sensor 110b and/or fourth sensor 112b includes a laser sensor configured to capture information within a narrow bandwidth. In some embodiments, second sensor 110b and/or fourth sensor 112b includes a laser light source configured to emit light in the narrow bandwidth which is reflected off objects along the guideway or the wayside of the guideway. The laser sensor is capable of identifying the presence of an object as well as unique identifying characteristics of a detected object similar to the optical sensor.

One or more sensors in first set of sensors <NUM> and/or second set of sensor <NUM> are capable of identifying an object without additional equipment such as a guideway map or location and speed information. The ability to operate without additional equipment decreases operating costs for first set of sensors <NUM> and second set of sensors <NUM> and reduces points of failure for system <NUM>.

The above description is based on the use of four sensors, first sensor 110a, second sensor 110b, third sensor 112a or fourth sensor 112b, for the sake of clarity. One of ordinary skill in the art would recognize that other number of sensors are able to be incorporated into the first set of sensors <NUM> and second set of sensors <NUM> without departing from the scope of the invention as defined in the appended claims. In some embodiments, redundant sensors which are a same sensor type as first sensor 110a, second sensor 110b, third sensor 112a or fourth sensor 112b are included in system <NUM>.

In some embodiments, locations of first sensor 110a and second sensor 110b of the first set of sensors <NUM> are swapped with each other. Similarly, in some embodiments, locations of third sensor 112a and fourth sensor 112b of the second set of sensors <NUM> are swapped with each other.

In some embodiments, first sensor 110a or third sensor 112a are configured to detect a corresponding first RF signature or a corresponding second RF signature of markers <NUM> that is known by controller <NUM>. In some embodiments, the first RF signature is equal to the second RF signature. In some embodiments, the first RF signature is not equal to the second RF signature.

In some embodiments, the first RF signature includes one or more of a distance from the first sensor 110a to the markers <NUM>, a relative velocity of vehicle <NUM> between the first sensor 110a and markers <NUM>, an angular position of the first sensor 110a relative to markers <NUM> or an SNR of the echo signal received by first sensor 110a from markers <NUM>.

In some embodiments, the second RF signature includes one or more of a distance from the third sensor 112a to the markers <NUM>, a relative velocity of vehicle <NUM> between the third sensor 112a and markers <NUM>, an angular position of the third sensor 112a relative to markers <NUM> or an SNR of the echo signal received by third sensor 112a from markers <NUM>.

The controller <NUM> is configured to determine a first position (e.g., Pvehicle in <FIG>) of vehicle <NUM> on guideway <NUM> or a first distance from the position of vehicle <NUM> to a stopping location along guideway <NUM> based on at least the first RF signature received from the first sensor 110a.

The controller <NUM> is configured to determine a second position (e.g., Pvehicle in <FIG>) of vehicle <NUM> on guideway <NUM> or a second distance from the position of vehicle <NUM> to a stopping location along guideway <NUM> based on at least the second RF signature received from the third sensor 112a.

In some embodiments, controller <NUM> is configured to perform consistency checks between the first distance and the second distance by comparing the first distance with the second distance. In some embodiments, controller <NUM> determines that first sensor 110a and third sensor 112a are not faulty, if the first distance does not differ by more than a predefined tolerance from the second distance. In some embodiments, controller <NUM> determines that first sensor 110a and third sensor 112a are not faulty, if the first distance differs by more than the predefined tolerance from the second distance.

In some embodiments, controller <NUM> is configured to perform consistency checks between the first position and second position by comparing the first position with the second position. In some embodiments, controller <NUM> determines that first sensor 110a and third sensor 112a are not faulty, if the first position does not differ by more than a predefined tolerance from the second position. In some embodiments, controller <NUM> determines that first sensor 110a and third sensor 112a are faulty, if the first position differs by more than a predefined tolerance from the second position.

In some embodiments, second sensor 110b or fourth sensor 112b are configured to detect a corresponding first another signature or a corresponding second another signature of markers <NUM> that is known by controller <NUM>. In some embodiments, the first another signature is equal to the second another signature. In some embodiments, the first another signature is not equal to the second another signature.

In some embodiments, the first another signature includes one or more of a distance from the second sensor 110b to the markers <NUM>, a relative velocity of vehicle <NUM> between the second sensor 110b and markers <NUM>, an angular position of the second sensor 110b relative to markers <NUM> or an SNR of the echo signal received by second sensor 110b from markers <NUM>.

In some embodiments, the second another signature includes one or more of a distance from the fourth sensor 112b to the markers <NUM>, a relative velocity of vehicle <NUM> between the fourth sensor 112b and markers <NUM>, an angular position of the fourth sensor 112b relative to markers <NUM> or an SNR of the echo signal received by fourth sensor 112b from markers <NUM>.

The controller <NUM> is configured to determine a third position (e.g., Pvehicle in <FIG>) of vehicle <NUM> on guideway <NUM> or a third distance from the position of vehicle <NUM> to a stopping location along guideway <NUM> based on at least the first another signature received from the second sensor 110b.

The controller <NUM> is configured to determine a fourth position (e.g., Pvehicle in <FIG>) of vehicle <NUM> on guideway <NUM> or a fourth distance from the position of vehicle <NUM> to a stopping location along guideway <NUM> based on at least the second another signature received from the third sensor 112a.

In some embodiments, controller <NUM> is configured to perform consistency checks between the third distance and the fourth distance by comparing the third distance with the fourth distance. In some embodiments, controller <NUM> determines that second sensor 110b and fourth sensor 112b are not faulty, if the third distance does not differ by more than a predefined tolerance from the fourth distance. In some embodiments, controller <NUM> determines that second sensor 110b and fourth sensor 112b are faulty, if the third distance differs by more than a predefined tolerance from the fourth distance.

In some embodiments, controller <NUM> is configured to perform consistency checks between the third position and fourth position by comparing the third position with the fourth position. In some embodiments, controller <NUM> determines that second sensor 110b and fourth sensor 112b are not faulty, if the third position does not differ by more than a predefined tolerance from the fourth position. In some embodiments, controller <NUM> determines that second sensor 110b and fourth sensor 112b are faulty, if the third position differs by more than a predefined tolerance from the fourth position.

In some embodiments, controller <NUM> is configured to perform consistency checks between the first distance and the third distance by comparing the first distance with the third distance. In some embodiments, controller <NUM> determines that first sensor 110a and second sensor 110b are not faulty, if the first distance does not differ by more than a predefined tolerance from the third distance. In some embodiments, controller <NUM> determines that first sensor 110a and second sensor 110b are faulty, if the first distance differs by more than a predefined tolerance from the third distance.

In some embodiments, controller <NUM> is configured to perform consistency checks between the second distance and the fourth distance by comparing the second distance with the fourth distance. In some embodiments, controller <NUM> determines that third sensor 112a and fourth sensor 112b are not faulty, if the second distance does not differ by more than a predefined tolerance from the fourth distance. In some embodiments, controller <NUM> determines that third sensor 112a and fourth sensor 112b are not faulty, if the second distance differs by more than a predefined tolerance from the fourth distance.

The controller <NUM> is configured to determine which of the first end <NUM> or the second end <NUM> of the vehicle <NUM> is the leading end of the vehicle <NUM> as the vehicle <NUM> moves along the guideway <NUM>, determine a position of the leading end or trailing end of the vehicle <NUM> with respect to a detected marker <NUM>, determine a position of the vehicle <NUM> with respect to a detected marker <NUM>, and determine a velocity of the vehicle <NUM> as the vehicle <NUM> moves along the guideway <NUM>.

In some embodiments, the controller <NUM> is configured to use one or more of the sensor data generated by the first sensor 110a or the second sensor 110b of the first set of sensors <NUM> as the sensor data for determining the leading end of the vehicle <NUM>, the position of the leading end of the vehicle <NUM>, the velocity of the vehicle <NUM>, the velocity of the leading end of the vehicle <NUM>, the length of the vehicle <NUM>, the position of the trailing end of the vehicle <NUM>, and/or the velocity of the trailing end of the vehicle <NUM>. Similarly, the controller <NUM> is configured to use one or more of the sensor data generated by the third sensor 112a or the fourth sensor 112b of the second set of sensors <NUM> as the sensor data for determining the leading end of the vehicle <NUM>, the position of the leading end of the vehicle <NUM>, the velocity of the vehicle <NUM>, the velocity of the leading end of the vehicle <NUM>, the position of the trailing end of the vehicle <NUM>, and/or the velocity of the trailing end of the vehicle <NUM>.

In some embodiments, the controller <NUM> is configured to determine a start point of makers <NUM> based on a sequence of symbols associated with a first portion of the markers <NUM>, and determine an end point of the markers <NUM> based on the sequence of symbols associated with a second portion of the markers <NUM>.

In some embodiments, the controller <NUM> is configured to determine a leading end of vehicle <NUM> and a trailing end of vehicle <NUM> based on an order of the sequence of symbols associated with the first portion of markers <NUM> or the second portion of markers <NUM>.

In some embodiments, to determine the position of the vehicle <NUM>, the controller <NUM> is configured to query the memory <NUM> for information describing a detected marker <NUM>. For example, the memory <NUM> includes location information describing the geographic location of the detected marker <NUM>. In some embodiments, the memory <NUM> includes location information describing the distance d between marker <NUM> and a previously detected marker <NUM>. The controller <NUM> uses the location information to calculate a position of the leading end of the vehicle <NUM> based on the sensor data generated by one or more of the first sensor 110a or the second sensor 110b. For example, the controller <NUM> is configured to calculate the position of the leading end of the vehicle <NUM> based on the distance d between marker 120a and marker 120b. In some embodiments, consecutive markers <NUM> are pairs of markers separated by a distance d stored in memory <NUM>.

In some embodiments, the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are configured to determine a distance between the sensor and the detected marker <NUM> in the field of view of the sensor along the line of sight of the sensor. In some embodiments, the controller <NUM> is configured to use the distance between the sensor and the detected marker <NUM> to calculate the position of the vehicle <NUM>.

In some embodiments, the controller <NUM> is configured to determine a relative velocity VRELATIVE between the sensors of the first set of sensors <NUM> and/or the sensors of the second set of sensors <NUM> and the detected marker <NUM>.

The controller <NUM> is configured to perform consistency checks to compare the determinations or calculations that are based on the sensor data generated by the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM>.

In some embodiments, the controller <NUM> is configured to determine if a leading end determination based on the sensor data generated by the sensors of the first set of sensors <NUM> matches a leading end determination based on the sensor data generated by the sensors of the second set of sensors <NUM>. In some embodiments, the controller <NUM> is configured to determine if a position or distance traveled calculation based on the sensor data generated by the sensors of the first set of sensors <NUM> matches a corresponding position or distance traveled calculation based on the sensor data generated by the sensors of the second set of sensors <NUM>.

The controller <NUM> is configured to identify one or more of the first sensor 110a, the second sensor 110b, the third sensor 112a or the fourth sensor 112b as being faulty based on a determination that a mismatch between one or more of the calculated leading end of the vehicle <NUM>, the calculated position of the vehicle <NUM>, the calculated distance the vehicle <NUM> traveled, or the calculated velocity of the vehicle <NUM> results in a difference between the calculated values that is greater than a predefined threshold. The controller <NUM>, based on a determination that at least one of the sensors is faulty, generates a message indicating that at least one of the sensors is in error. In some embodiments, the controller <NUM> is configured to identify which sensor of the first set of sensors <NUM> or the second set of sensors <NUM> is the faulty sensor based on the sensor that has position data that is different from the position data from the other sensors.

Similarly, in some embodiments, the controller <NUM> is configured to generate an alarm if the position of the leading end of the vehicle <NUM> calculated based on the sensor data generated by one of more of the first sensor 110a or the second sensor 110b differs from the position of the leading end of the vehicle <NUM> calculated based on the sensor data generated by one or more of the third sensor 112a or the fourth sensor 112b by more than a predefined threshold.

In some embodiments, if the calculated position of the leading end of the vehicle <NUM> based on the sensor data generated by the first set of sensors differs from the position of the leading end of the vehicle based on the sensor data generated by the second set of sensors by more than the predefined threshold, the controller <NUM> is configured to cause the vehicle <NUM> to be braked to a stop via an emergency brake actuated by the controller <NUM> or to increase or decrease the speed of the vehicle <NUM>.

The sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are positioned on the first end <NUM> or the second end <NUM> of the vehicle <NUM> independent of any wheel and/or gear of the vehicle <NUM>. As a result the calculated velocity of the vehicle <NUM>, position of the vehicle <NUM>, distance traveled by the vehicle <NUM>, or the determination of the leading end of the vehicle <NUM> are not sensitive to wheel spin or slide or wheel diameter calibration errors, making the calculations made by the system <NUM> more accurate than wheel- based or gear-based velocity or position calculations. In some embodiments, the system <NUM> is capable of calculating the speed and/or the position of the vehicle <NUM> to a level of accuracy greater than wheel-based or gear-based techniques, even at low speeds, at least because the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> make it possible to calculate a distance traveled from, or a positional relationship to, a particular marker <NUM> to within about +/- <NUM> centimeters (cm).

Additionally, by positioning the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> away from the wheels and gears of the vehicle, the sensors of the first set of sensors <NUM> and the sensors of the second set of sensors <NUM> are less likely to experience reliability issues and likely to require less maintenance compared to sensors that are installed on or near a wheel or a gear of the vehicle <NUM>.

In some embodiments, system <NUM> is capable of detecting markers <NUM> from relatively long distances (><NUM>) resulting in greater accuracy of the position of vehicle <NUM> than wheel-based or gear-based techniques.

<FIG> is a diagram of a metasurface plate <NUM>, in accordance with one or more embodiments.

Metasurface plate <NUM> is a flat plate including one or more of a set of diffused elements <NUM>, a set of retro reflecting elements <NUM> or a set of absorbing elements <NUM>. In some embodiments, metasurface plate <NUM> is not flat.

Set of diffused elements <NUM> includes two or more of diffused elements 202a, 202b, 202c, 202d, 202e or 202f. Set of retro reflecting elements <NUM> includes two or more of retro reflecting elements <NUM>, <NUM> or <NUM>. Set of absorbing elements <NUM> includes one or more of absorbing elements <NUM> or <NUM>.

At least a diffused element of the set of diffused elements <NUM> is positioned between at least two elements from the set of retro reflecting elements <NUM> or the set of absorbing elements <NUM>. For example, diffused element 202b is between retro reflecting element <NUM> and absorbing element <NUM>. Diffused element 202c is between absorbing elements <NUM> and <NUM>. Diffused element 202d is between absorbing element <NUM> and retro reflecting element <NUM>. Diffused element 202e is between retro reflecting element <NUM> and retro reflecting element <NUM>.

Diffused element 202a is on a first end of metasurface plate <NUM>, and diffused element <NUM> is on a second end of metasurface plate <NUM>. In some embodiments, the second end of metasurface plate <NUM> is opposite from the first end of metasurface plate <NUM>.

In some embodiments, one or more of retro reflecting elements <NUM>, <NUM> or <NUM> includes at least a metal or a metal compound. In some embodiments, one or more of retro reflecting elements <NUM>, <NUM> or <NUM> includes at least aluminum, iron, steel, or the like.

In some embodiments, at least one retro reflecting element of the set of retro reflecting elements <NUM> is configured to reflect an incident electromagnetic wavefront back along a vector that is parallel to, but opposite in direction from the wave's source.

In some embodiments, one or more of absorbing elements <NUM> or <NUM> includes at least a foam material, a foam compound, or the like. In some embodiments, one or more of absorbing elements <NUM> or <NUM> includes at least a foam material inside a plastic box.

In some embodiments, one or more of diffused elements 202a, 202b, 202c, 202d, 202e or 202f includes at least a ballast, a sleeper, a concrete material, or the like. In some embodiments, one or more of diffused elements 202a, 202b, 202c, 202d, 202e or 202f includes at least a material or structure capable of generating an SNR profile, similar to that shown in <FIG>, relative to that of set of retro reflecting elements <NUM> or set of absorbing elements <NUM>.

Metasurface plate <NUM> has a width in the Y direction, and a length in the X direction. Each of the elements (202a, <NUM>,. , 202f) of metasurface plate <NUM> has a corresponding length (e.g., L1, L2,. , L11) in the X direction.

In some embodiments, the length L1, L3, L5, L7, L9 and L11 of corresponding diffusion elements 202a, 202b, 202c, 202d, 202e and 202f are used to ensure sufficient separation distance Dmin (<FIG>) is between the elements of metasurface plate <NUM> allowing the radar sensor of set of sensors <NUM> or <NUM> to properly discriminate between the different elements as discussed in <FIG>.

In some embodiments, the area or size of one or more elements within metasurface plate <NUM> is determined by at least the radar emitted power, the power of the echo signal, or the environment the metasurface plate <NUM> is installed. In some embodiments, metasurface plate <NUM> is configured to generate an SNR profile similar to that shown in <FIG> or <NUM>.

For example, the area of metasurface plate <NUM> is equal to the length L multiplied by the width W. The signal to noise ratio (SNR) of the echo signal or the amount of power reflected by metal surface plate <NUM> is proportional to the area of metasurface plate <NUM>. For example, as the area of metasurface plate <NUM> increases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> increases. For example, as the area of metasurface plate <NUM> decreases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> decreases.

For example, as the length (e.g., L2, L8 or L10) or width W of retro reflecting elements <NUM>, <NUM> or <NUM> in metasurface plate <NUM> increases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> increases. Similarly, as the length (e.g., L2, L8 or L10) or width W of retro reflecting elements <NUM>, <NUM> or <NUM> in metasurface plate <NUM> decreases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> decreases.

For example, as the length (e.g., L4 or L6) or width W of absorbing elements <NUM> or <NUM> in metasurface plate <NUM> increases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> decreases. Similarly, as the length (e.g., L4 or L6) or width W of absorbing elements <NUM> or <NUM> in metasurface plate <NUM> decreases, the SNR of the echo signal or the amount of power reflected by metasurface plate <NUM> increases.

In some embodiments, if the areas of the metasurface elements are not large enough, then the echo signal detected by the radar sensor of first sensor 110a or third sensor 112a may not be large enough to accurately discern or detect one or more metasurface elements within metasurface plate <NUM> which would affect the RF signature of metasurface plate <NUM> detected by system <NUM>.

In some embodiments, metasurface <NUM> creates a unique RF signature detected by the radar of set of sensors <NUM> or <NUM> to localize vehicle <NUM> on guideway <NUM>, and to provide a landmark vehicle <NUM> is should aligned with if located at the platform (not shown) where vehicle <NUM> is expected to stop at.

In some embodiments, the unique RF signature includes the echo received from the metasurface plate <NUM>. In some embodiments, the echo received from the set of retro reflecting elements <NUM> has a sufficient SNR margin (><NUM> dB) with respect to the echo received from the set of diffused elements <NUM>. In some embodiments, the echo received from the set of absorbing elements <NUM> has a sufficient SNR margin (<<NUM> dB) with respect to the echo received from the set of diffused elements <NUM> such that there is a difference of at least <NUM> dB between the SNR of the echo signal received from the set of retro reflecting elements <NUM> and the set of absorbing elements <NUM>. Other SNR values of echo signals received from elements within the set of diffused elements <NUM>, set of retro reflecting elements <NUM> or set of absorbing elements <NUM> are within the scope of the present disclosure.

In some embodiments, the SNR's of each element in metasurface plate <NUM> are associated with a corresponding identification symbol or corresponding plate element that is used by controller <NUM> to identify a location of metasurface plate <NUM>.

Other quantities, configurations or order of elements within the set of diffused elements <NUM>, set of retro reflecting elements <NUM> or set of absorbing elements <NUM> are within the scope of the present disclosure.

<FIG> is a diagram of a metasurface plate, in accordance with one or more embodiments.

Metasurface plate <NUM> includes a metasurface portion <NUM> and a metasurface portion <NUM>. Metasurface portion <NUM> corresponds to metasurface plate <NUM> of <FIG>, and similar detailed description is therefore omitted.

In some embodiments, metasurface plate <NUM> is installed horizontally on the track bed as shown in <FIG> and <FIG> or vertically on a sign post as shown in <FIG>.

Metasurface portion <NUM> is integrated with metasurface portion <NUM> in forming metasurface plate <NUM>. Metasurface plate <NUM> creates an RF signature and another signature. For example, metasurface portion <NUM> generates an RF signature, and metasurface portion <NUM> generates another signature. In some embodiments, a size of metasurface plate <NUM> is about <NUM> by <NUM>. In some embodiments, a high bandwidth radar (e.g. bandwidth > <NUM>) is used to detect an RF signature of metasurface plate <NUM>.

Metasurface portion <NUM> includes one or more retro reflecting elements 312a, 312b or 312c (collectively referred to as "set of retro reflecting elements <NUM>") embedded in metasurface plate <NUM> to form a barcode, a quick response (QR) code, an image, or the like. In some embodiments, the image of metasurface portion <NUM> or the set of retro reflecting elements <NUM> are associated with a corresponding identification symbol that is used by controller <NUM> to identify a location of the metasurface plate <NUM>.

In some embodiments, metasurface plate <NUM> creates two unique signatures (e.g., RF signature and another signature) detected by at least two sensors in the set of sensors <NUM> and <NUM> to localize vehicle <NUM> on guideway <NUM>, and to provide a landmark vehicle <NUM> is aligned with if located at the platform (not shown) where vehicle <NUM> is expected to stop at.

In some embodiments, metasurface portion <NUM> generates an RF signature that can be detected by first sensor 110a or third sensor 112a, such as RADAR. In some embodiments, metasurface portion <NUM> generates another type of signature that can be detected by second sensor 110b or fourth sensor 112b, such as a camera or LiDAR.

In some embodiments, the corresponding signatures of metasurface portion <NUM> and metasurface portion <NUM> have corresponding identification symbols stored in a database of memory <NUM> that are each used to identify the position of metasurface plate <NUM>.

In some embodiments, radar of first sensor 110a or third sensor 112a is configured to measure the range or distance to metasurface portion <NUM>, and the camera or LiDAR of second sensor 110b or fourth sensor 112b is configured to detect the another signature of metasurface portion <NUM>. In some embodiments, the another signature includes the range to metasurface portion <NUM> or the type of image. In some embodiments, the another signature is used to identify the metasurface plate <NUM> or the position of metasurface plate <NUM>.

In some embodiments, the distance to the retroreflective element in metasurface plate <NUM> is determined by the radar of first sensor 110a or third sensor 112a, while second sensor 110b or fourth sensor 112b (e.g. camera, LiDAR or IR) are used to determine the identification symbol of the metasurface portion <NUM> with the range to metasurface portion <NUM> being calculated based on the image of metasurface portion <NUM>.

In some embodiments, one or more of the size of the QR code, the size of the barcode, the camera's sensor resolution (e.g., pixels matrix) or the camera's lens field of view (FOV) are known by system <NUM>. In these embodiments, controller <NUM> is configured to calculate the distance to metasurface portion <NUM>, which is compared with the distance measured by the radar of sensors 110a, 112a.

In some embodiments, by combining metasurface portions <NUM> and <NUM> into metasurface plate <NUM>, the corresponding generated or reflected signatures are used to increase the confidence in the range determination calculation and position determination of vehicle <NUM>. In this embodiment, diverse detection is created decreasing the probability of a false positive or a false negative for detecting metasurface plate <NUM>.

Other quantities, configurations or order of elements within metasurface plate <NUM> are within the scope of the present disclosure.

<FIG> is a side view of a guideway mounted vehicle <NUM>, in accordance with one or more embodiments. Vehicle <NUM> comprises the features discussed with respect to vehicle <NUM> (<FIG>). Vehicle <NUM> includes vehicle localization system <NUM> (<FIG>), and is configured to move over guideway <NUM>. Guideway <NUM> is a two-rail example of guideway <NUM> (<FIG>). Markers 420a-420n, where n is an integer greater than <NUM>, corresponding to markers <NUM> (<FIG>). Markers 420a-420n are on the wayside of the guideway <NUM>. In this example embodiment, markers 420a-420n are posts on the wayside of the guideway <NUM> separated by the distance d. In some embodiments, one or more of the markers 420a-420n or posts include metasurface plate <NUM>, metasurface plate <NUM> or <NUM> or plate <NUM>.

<FIG> is a top-side view of vehicle <NUM>, in accordance with one or more embodiments. Vehicle <NUM> is configured to travel over guideway <NUM>. Markers 420a-420n are on the wayside of the guideway <NUM>. First sensor 410a corresponds to first sensor 110a (<FIG>). First sensor 410a is positioned on the first end of vehicle <NUM> at a distance L from the markers 420a-420n. First sensor 410a is directed toward markers 420a-420n. Accordingly, first sensor 410a has an inclination angle γ that corresponds to inclination angle α1 (<FIG>) of the first sensor 110a. First sensor 410a has a field of view FOV that corresponds to field of view 122a (<FIG>). Based on the inclination angle γ, the field of view FOV, and the distance L, first sensor 410a has a detection span I. One of ordinary skill would recognize that the sensors of the first set of sensors <NUM> (<FIG>) and the sensors of the second set of sensors <NUM> (<FIG>) have properties similar to those discussed with respect to sensor 410a that vary based on the position of the sensor on the vehicle <NUM>.

<FIG> is a top-side view of a guideway mounted vehicle <NUM>, in accordance with one or more embodiments. Vehicle <NUM> comprises the features discussed with respect to vehicle <NUM> (<FIG>). Vehicle <NUM> includes vehicle localization system <NUM> (<FIG>), and is configured to move over guideway <NUM>. Guideway <NUM> is a two-rail example of guideway <NUM> (<FIG>). Markers 520a-520n, where n is an integer greater than <NUM>, corresponding to markers <NUM> (<FIG>). Markers 520a-520n are on the guideway <NUM>. In this example embodiment, markers 520a-520n are railroad ties separated by the distance d. In some embodiments, one or more of the markers 520a-520n include metasurface plate <NUM>, metasurface plate <NUM> or <NUM> or plate <NUM>.

<FIG> is a side view of vehicle <NUM>, in accordance with one or more embodiments. Vehicle <NUM> is configured to travel over markers 520a-520n. First sensor 510a corresponds to first sensor 110a (<FIG>). First sensor 510a is positioned on the first end <NUM> of vehicle <NUM> at a distance L' from the guideway <NUM>. First end <NUM> is first end <NUM> of vehicle <NUM>, and second end <NUM> is second end <NUM> of vehicle <NUM>. First sensor 510a is directed toward the guideway <NUM> to detect markers 520a-520n. Accordingly, first sensor 510a has an inclination angle γ that corresponds to inclination angle α1 (<FIG>) of the first sensor 110a. First sensor 510a has a field of view FOV that corresponds to field of view 122a (<FIG>). Based on the inclination angle γ, the field of view FOV, and the distance L', first sensor 510a has a detection span I. One of ordinary skill would recognize that the sensors of the first set of sensors <NUM> (<FIG>) and the sensors of the second set of sensors <NUM> (<FIG>) have properties similar to those discussed with respect to sensor 510a that vary based on the position of the sensor on the vehicle <NUM>.

<FIG> is a side view of a system <NUM>, in accordance with one or more embodiments. <FIG> is a top-side view of system <NUM>, in accordance with one or more embodiments. <FIG> is a view of a curve <NUM>, in accordance with one or more embodiments.

<FIG> is a variation of <FIG>, and <FIG> is a variation of <FIG>, in accordance with some embodiments.

In comparison with system <NUM> of <FIG>, system <NUM> of <FIG> includes a single marker (e.g., metasurface plate <NUM>), and the sensor 510a is on the second end <NUM> of vehicle <NUM>. For example, metasurface plate <NUM> replaces one of the markers of markers 520a- 520n.

Vehicle <NUM> is configured to move over guideway <NUM> and metasurface plate <NUM>. First sensor 510a is positioned on the second end <NUM> of vehicle <NUM>. First sensor 510a is directed toward the guideway <NUM> to detect metasurface plate <NUM>. Metasurface plate <NUM> is in the field of view FOV of first sensor 510a.

Vehicle <NUM> is separated from metasurface plate <NUM> by a distance D. In some embodiments, distance D is determined by controller <NUM> based on radar ranging information received from first sensor 110a or third sensor 112a. Metasurface plate <NUM> has a position Pplate relative to the guideway <NUM>. In some embodiments, the position Pplate of metasurface plate <NUM> is determined based on the numerical value of metasurface plate <NUM> stored in a database (e.g., memory <NUM>).

Vehicle <NUM> or first sensor 510a has a position Pvehicle relative to the metasurface plate <NUM> that is calculated by equation <NUM> based on the position Pplate of metasurface plate <NUM> relative to the guideway <NUM> and distance D. Vehicle <NUM> or first sensor 510a has a position Pvehicle relative to the metasurface plate <NUM>, as calculated by equation <NUM>:
<MAT>.

In some embodiments, if metasurface plate <NUM> is located at a stopping location along the guideway <NUM>, then distance D corresponds to the distance from the position Pvehicle of vehicle <NUM> to the stopping location along guideway <NUM>.

In some embodiments, if metasurface plate <NUM> is not located at a stopping location along the guideway <NUM>, then distance D and the position of the position Pplate of metasurface plate <NUM> are used by controller <NUM> to determine the distance from the position Pvehicle of vehicle <NUM> to the stopping location along guideway <NUM>.

Meta-surface <NUM> corresponds to meta-surface plate <NUM> or <NUM>. Metasurface plate <NUM> includes the features discussed with respect to metasurface plate <NUM> or <NUM> (<FIG>).

Metasurface plate <NUM> is on the guideway <NUM>. In some embodiments, metasurface plate <NUM> is on the wayside of guideway <NUM> similar to <FIG>, but is not described herein for brevity.

In some embodiments, metasurface plate <NUM> includes at least one railroad tie. In some embodiments, metasurface plate <NUM> is positioned on a single railroad tie. In some embodiments, metasurface plate <NUM> is positioned on more than a single railroad tie.

Metasurface plate <NUM> includes n elements (collectively "metasurface elements E"), where n is an integer corresponding to the number of elements in metasurface plate <NUM>. Metasurface elements E include two or more retro reflecting elements (e.g., E1 and E3 in <FIG>) that alternate with one or more absorbing elements (e.g., E2 in <FIG>). Metasurface plate <NUM> also includes diffused elements between adjacent absorbing elements and reflecting elements, but are not labeled for ease of illustration. In some embodiments, adjacent means directly next to.

Each of the metasurface elements E are separated from each other by at least a minimum distance Dmin. Minimum distance Dmin is dependent upon the bandwidth and frequency of the radar as shown in <FIG> is a view of a curve <NUM> of bandwidth versus discrimination distance in centimeters (cm), in accordance with one or more embodiments. For example, as shown in <FIG>, as the bandwidth or frequency of the radar increases, the discrimination or minimum distance Dmin decreases, and the metasurface elements E can be spaced closer to each other. Similarly, as the as shown in <FIG>, as the bandwidth or frequency of the radar decreases, the minimum distance Dmin increases, and the metasurface elements E are spaced further from each other. In some embodiments, if the metasurface elements are not separated by the minimum distance Dmin, then the radar sensor of first sensor 510a may not be able to accurately discern or detect one or more metasurface elements within metasurface plate <NUM> which would affect the determination of the position of metasurface plate <NUM>.

<FIG> is a view of an SNR profile <NUM> generated by a metasurface plate <NUM>, in accordance with one or more embodiments.

Metasurface plate <NUM> or <NUM> corresponds to metasurface plate <NUM>, <NUM> or <NUM> (<FIG>), and similar detailed description is therefore omitted.

Metasurface plate <NUM> includes diffused element 710a, retro reflecting element 710b, diffused element 710c and retro reflecting element 710d.

Metasurface plate <NUM> includes diffused element 720a, absorbing element 720b and diffused element 720c.

In some embodiments, metasurface plate <NUM> or <NUM> creates a unique RF signature detected by the radar of set of sensors <NUM> or <NUM>. In some embodiments, the unique RF signature includes at least the SNR of the echo received from metasurface plate <NUM> or <NUM>.

In some embodiments, the echo received from the retro reflecting element 710b has an SNR margin with respect to the echo received from diffused elements 710a and 710c. In some embodiments, the echo received from the retro reflecting element <NUM> has an SNR margin with respect to the echo received from diffused elements 710a and 710c.

In some embodiments, the echo received from absorbing element 720b has an SNR margin with respect to the echo received from diffused elements 720a and 720c.

In some embodiments, based on the SNR margin, the retro reflecting element or the absorbing element is associated with a corresponding symbol.

In some embodiments, if the SNR margin of the echo received from retro reflecting element 710b with respect to diffused elements 710a and 710c is greater than <NUM> DB and less than <NUM> DB, then the corresponding element of metasurface plate <NUM> is associated with a symbol having a logical value of "<NUM>". Thus, in these embodiments, retro reflecting element 710b is associated with a symbol having a logical value of "<NUM>".

In some embodiments, if the SNR margin of the echo received from retro reflecting element 710d with respect to diffused elements 710a and 710c is greater than <NUM> DB and less than <NUM> DB, then the corresponding element of metasurface plate <NUM> is associated with a symbol having a logical value of "<NUM>". Thus, in these embodiments, retro reflecting element 710d is associated with a symbol having a logical value of "<NUM>".

In some embodiments, if the SNR margin of the echo received from diffused elements 720a and 720c with respect to absorbing element 720b is greater than <NUM> DB, then the corresponding element of metasurface plate <NUM> is associated with a symbol having a logical value of "<NUM>". Thus, in these embodiments, absorbing element 720b is associated with a symbol having a logical value of "<NUM>".

In some embodiments, the logical values of symbols is based upon multilevel signaling. Other values of symbols or types of signaling are within the scope of the present disclosure.

In some embodiments, the echo received from retro reflecting elements 710b and 710d has an SNR margin (>20dB) with respect to the echo received from absorbing element 720b, which is a sufficient margin for system <NUM> to accurately determine whether an absorbing element or a retro reflecting element was detected by first sensor 110a or third sensor 112a.

In some embodiments, based on the SNR margin detected by first sensor 110a or third sensor 112a of system <NUM>, controller <NUM> can identify a location of metasurface plate <NUM> or <NUM>.

In some embodiments, based on the SNR margin detected by first sensor 110a or third sensor 112a of system <NUM>, controller <NUM> determines the corresponding symbols associated with the corresponding SNR margins, and then determines the position of metasurface plate <NUM> or <NUM> from the symbols or a numerical value calculated from the symbol.

In some embodiments, each metasurface plate <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> of system <NUM> can be identified based on an order of a sequence of symbols. In some embodiments, the order of the sequence of symbols is unique.

In some embodiments, based on the SNR margin, the retro reflecting element and the absorbing element are associated with corresponding symbols. In some embodiments, the symbol values are a design choice based on the number of elements in metasurface plates in system <NUM>. For example, as the number of unique metasurface plates increases, the number of symbols also increases. Similarly, as the number of unique metasurface plates decreases, the number of symbols also decreases.

In some embodiments, the SNR's of each element in metasurface plate <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> are associated with a corresponding identification symbol or corresponding plate element that is used by controller <NUM> to identify a location of metasurface plate <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>.

Other SNR values of echo signals received from elements within the set of diffused elements <NUM>, set of retro reflecting elements <NUM> or set of absorbing elements <NUM> are within the scope of the present disclosure.

<FIG> is a variation of <FIG>, in accordance with some embodiments.

Metasurface plate <NUM> corresponds to metasurface plate <NUM>, <NUM> or <NUM> (<FIG>), and similar detailed description is therefore omitted.

Metasurface plate <NUM> includes diffused element 730a, retro reflecting element 730b, diffused element 730c, absorbing element 730d and diffused element 730e.

In some embodiments, metasurface plate <NUM> creates a unique RF signature (shown in <FIG>) detected by the radar of set of sensors <NUM> or <NUM>. In some embodiments, the unique RF signature includes at least the SNR of the echo received from metasurface plate <NUM>.

In some embodiments, the unique RF signature of <FIG> is used to identify a start position or an end position of a metasurface plate (e.g., metasurface plate <NUM>, <NUM> or <NUM>).

In some embodiments, controller <NUM> is configured to determine which of the first end <NUM> or the second end <NUM> of vehicle <NUM> is the leading end of vehicle <NUM> as vehicle <NUM> moves along guideway <NUM>.

For example, in some embodiments, controller <NUM> is configured to receive SNR values (as shown in <FIG>) from first sensor 110a or third sensor 112a. In some embodiments, from the SNR values, controller <NUM> is configured to determine a sequence of symbols or a sequence of elements within metasurface plate <NUM>. In some embodiments, from the sequence of symbols, controller <NUM> is configured to determine or a sequence of elements within metasurface plate <NUM>. In some embodiments, from one or more of the order of SNR values, order of the sequence of symbols or order of the sequence of elements within metasurface plate <NUM>, controller <NUM> is configured to determine the leading end of vehicle <NUM> or trailing end of vehicle <NUM> as vehicle <NUM> moves along guideway <NUM>.

For example, if vehicle <NUM> is moving in the GD0 or first direction <NUM>, controller <NUM> would expect to sense metasurface <NUM> to have corresponding SNRs of diffused element 730a, retro reflecting element 730b, diffused element 730c, absorbing element 730d and diffused element 730e. Thus, based on a determination by controller <NUM> that the metasurface sequence is "diffused element 730a-retro reflecting element 730b-diffused element 730c-absorbing element 730d-diffused element 730e", controller <NUM> determines that the first end <NUM> of vehicle <NUM> is the leading end of vehicle <NUM>.

In some embodiments, if vehicle <NUM> is moving in the GD0 or first direction <NUM>, controller <NUM> would expect to sense a sequence of symbols in order "<NUM>" and "<NUM>". Thus, based on a determination by controller <NUM> that the symbol sequence is "<NUM>", controller <NUM> determines that the first end <NUM> of vehicle <NUM> is the leading end of vehicle <NUM>.

For example, if vehicle <NUM> is moving in the GD1 or second direction <NUM>, controller <NUM> would expect to sense metasurface <NUM> to have corresponding SNRs of diffused element 730e, absorbing element 730d, diffused element 730c, retro reflecting element 730b and diffused element 730a. Thus, based on a determination by controller <NUM> that the metasurface sequence is "diffused element 730e-absorbing element 730d-diffused element 730c-retro reflecting element 730b-diffused element 730a," controller <NUM> determines that the first end <NUM> of vehicle <NUM> is the leading end of vehicle <NUM>.

In some embodiments, if vehicle <NUM> is moving in the GD1 or second direction <NUM>, controller <NUM> would expect to sense a sequence of symbols in order "<NUM>" and "<NUM>". Thus, based on a determination by controller <NUM> that the symbol sequence is "<NUM>", controller <NUM> determines that the second end <NUM> of vehicle <NUM> is the leading end of vehicle <NUM>.

In some embodiments, the elements of metasurface <NUM> are used to identify a start position and an end position of each metasurface plate. In other words, metasurface plate <NUM> is used to identify a beginning portion (e.g., portion <NUM>) and an end portion (e.g., portion <NUM>) of each metasurface plate (e.g., metasurface plate <NUM>) in system <NUM>.

In some embodiments, the order of the elements within metasurface plate <NUM>, the order of SNR values associated with the corresponding elements of metasurface plate <NUM>, or the order of the sequence of symbols associated with the corresponding elements of metasurface plate <NUM> of <FIG> is used to identify a start position or an end position of each metasurface plate (e.g., metasurface plate <NUM>, <NUM> or <NUM>) in system <NUM>.

Other SNR sequences, symbol sequences or metasurface element sequences to identify a start position or an end position of each metasurface plate are within are within the scope of the present disclosure.

<FIG> is a view of fields of data associated with a metasurface plate <NUM>, in accordance with one or more embodiments.

Metasurface plate <NUM> corresponds to metasurface plate <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, and similar detailed description is therefore omitted.

Metasurface plate <NUM> includes a portion <NUM>, portion <NUM> and portion <NUM>. Portion <NUM> is positioned between portion <NUM> and <NUM>. In some embodiments, at least portion <NUM> or portion <NUM> corresponds to metasurface plate <NUM>, and similar detailed description is therefore omitted. Portion <NUM> is used by controller <NUM> to identify a beginning portion of metasurface plate <NUM>. Portion <NUM> is used by controller <NUM> to identify an end portion of metasurface plate <NUM>.

In some embodiments, controller <NUM> is configured to determine a start point of the metasurface plate <NUM> based on a sequence of symbols <NUM> associated with portion <NUM> of metasurface plate <NUM>, and determine an end point of the metasurface plate <NUM> based on the sequence of symbols <NUM> associated with portion <NUM> of metasurface plate <NUM>.

In some embodiments, the controller <NUM> is configured to determine a leading end of vehicle <NUM> and a trailing end of vehicle <NUM> based on an order of the sequence of symbols <NUM> associated with portion <NUM> of metasurface plate <NUM> or portion <NUM> of metasurface plate <NUM>.

In some embodiments, portion <NUM> is used by controller <NUM> to identify a corresponding position of metasurface plate <NUM> on guideway <NUM>.

Portion <NUM> is used by controller <NUM> to identify a start or end position of metasurface plate <NUM> dependent upon the travel direction of vehicle <NUM>.

Portion <NUM> includes a set of metasurface elements (not shown) similar to metasurface plate <NUM>. Portion <NUM> is associated with corresponding set of SNRs <NUM>.

Set of SNRs <NUM> includes one or more of SNR 820a, 820b, 820c, 820d or 820e. In some embodiments, each of the metasurface elements (not shown) within portion <NUM> is associated with corresponding SNR 820a, 820b, 820c, 820d or 820e.

Set of SNRs <NUM> is associated with set of symbols or plates <NUM>. Set of symbols or plates <NUM> includes one or more of symbols or plates 830a, 830b, 830c, 830d or 830e. In some embodiments, each of SNR 820a, 820b, 820c, 820d or 820e of the set of SNRs <NUM> has a corresponding sequence of symbols or plates 830a, 830b, 830c, 830d or 830e. In some embodiments, set of symbols <NUM> is similar to a header or a footer of a sequence of data.

In some embodiments, from the set of symbols or plates <NUM>, controller <NUM> is configured to determine vehicle travel direction <NUM>. In some embodiments, vehicle travel direction <NUM> corresponds to the leading end of vehicle <NUM> or trailing end of vehicle <NUM> as vehicle <NUM> moves along guideway <NUM>.

Set of SNRs <NUM> includes one or more of SNR 822a, 822b, 822c, 822d or 822e. In some embodiments, each of the metasurface elements (not shown) within portion <NUM> is associated with corresponding SNR 822a, 822b, 822c, 822d or 822e.

Set of SNRs <NUM> is associated with set of symbols or plates <NUM>. Set of symbols or plates <NUM> includes one or more of symbols or plates 832a, 832b, 832c, 832d or 832e. In some embodiments, each of SNR 822a, 822b, 822c, 822d or 822e of the set of SNRs <NUM> has a corresponding sequence of symbols or plates 832a, 832b, 832c, 832d or 832e. In some embodiments, set of symbols <NUM> is similar to a header or a footer of a sequence of data.

In some embodiments, from the set of symbols or plates <NUM>, controller <NUM> is configured to determine vehicle travel direction <NUM>. In some embodiments, vehicle travel direction <NUM> corresponds to the leading end of vehicle <NUM> or trailing end of vehicle <NUM> as vehicle <NUM> moves along guideway <NUM>. Vehicle travel direction <NUM> is equal to vehicle travel direction <NUM>.

Portion <NUM> includes a set of metasurface elements (not shown) similar to metasurface plate <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Portion <NUM> is associated with corresponding set of SNRs <NUM>.

Set of SNRs <NUM> includes one or more of SNR 824a, 824b, 824c, 824d or 824e. In some embodiments, each of the metasurface elements (not shown) within portion <NUM> is associated with corresponding SNR 824a, 824b, 824c, 824d or 824e.

Set of SNRs <NUM> is associated with set of symbols <NUM>. Set of symbols <NUM> includes one or more of symbols 834a, 834b, 834c, 834d or 834e. In some embodiments, each of SNR 824a, 824b, 824c, 824d or 824e of the set of SNRs <NUM> has a corresponding sequence of symbols 834a, 834b, 834c, 834d or 834e.

Set of symbols <NUM> is associated with a numerical value <NUM>. In some embodiments, controller <NUM> is configured to calculate the numerical value <NUM> associated with portion <NUM> of metasurface plate <NUM> based on the set of symbols <NUM>, with the least significant element as the first element in the GD<NUM> direction and the most significant element as the last element in the GD<NUM> direction.

For example, if vehicle <NUM> is moving in the GD1 direction, and <NUM> elements are sequentially detected with the following logical values: E1=<NUM>, E2=<NUM>, E3=<NUM>, E4=<NUM>, E5=<NUM>. In this example, controller <NUM> calculates numerical value <NUM> as: <MAT>.

For example, if vehicle <NUM> is moving in the GD<NUM> direction, and <NUM> elements are sequentially detected with the following logical values: E1=<NUM>, E2=<NUM>, E3=<NUM>, E4=<NUM>, E5=<NUM>. In this example, controller <NUM> calculates numerical value <NUM> as: <MAT>.

Therefore, in this example, the numerical value <NUM> calculated by controller <NUM> is not sensitive to the direction of travel. Other approaches to determining numerical value <NUM> are within the scope of the present disclosure.

Plate position <NUM> is associated with numerical value <NUM>. In some embodiments, controller <NUM> is configured to determine plate position <NUM> based on numerical value <NUM> stored in the database (e.g., memory <NUM>).

In some embodiments, based on the numerical value <NUM> of metasurface plate <NUM>, the plate reference position <NUM> on guideway <NUM> is determined by controller <NUM> according to a database (e.g., memory <NUM>).

In some embodiments, the plate reference position <NUM> is Pplate of equation <NUM>. In some embodiments, the plate reference position <NUM> corresponds to the position of the end retro reflective element in portion <NUM> or portion <NUM>.

In some embodiments, the vehicle reference position Pvehicle on guideway <NUM> is determined based on the plate reference position <NUM>. In some embodiments, the vehicle reference position Pvehicle on guideway <NUM> is determined by controller <NUM>, and is expressed by equation <NUM>.

<FIG> is a flowchart of a method <NUM> of determining a position of a vehicle on a guideway and a distance from the position of the vehicle to a stopping location along the guideway, in accordance with one or more embodiments. In some embodiments, one or more steps of method <NUM> is implemented by a controller such as controller <NUM> (<FIG>).

In step <NUM>, the vehicle moves from a start position such as a known or a detected marker in one of a first direction or a second direction.

In step <NUM>, one or more sensors generate sensor data based on a detection of a marker of a set of markers using a set of sensors on the first end or on the second end of the vehicle. Each sensor of the set of sensors on the first end or the second end of the vehicle is configured to generate corresponding sensor data. In some embodiments, the sensors detect a pattern of objects on a guideway along which the vehicle moves, and the controller recognizes the pattern of objects as the detected marker of the set of markers based on data stored in a memory comprising information describing the detected marker of the set of markers.

In some embodiments, step <NUM> further includes at least step 903a or step 903b.

In some embodiments, step 903a includes detecting, by a first sensor, an RF signature of at least a marker. In some embodiments, the first sensor is on a first end <NUM> of the vehicle <NUM> along the guideway <NUM>, and is a radar detection device. In some embodiments, the marker is a metasurface plate <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> including at least a first retroreflector element.

In some embodiments, step 903a further includes transmitting an RF signal from the first sensor towards the metasurface plate, and receiving, by the first sensor, a reflected RF signal from the metasurface plate. In some embodiments, the reflected RF signal has the corresponding RF signature that identifies the position of the vehicle.

In some embodiments, step 903b includes detecting, by a second sensor, another signature of at least the marker. In some embodiments, the another signature of at least the marker is another RF signature. In some embodiments, the second sensor is on the first end <NUM> of the vehicle <NUM> or the second end <NUM> of the vehicle <NUM> opposite from the first end <NUM> of the vehicle <NUM>. In some embodiments, the second sensor is another radar detection device, a camera, a LIDAR device or an IR sensor detection device.

In some embodiments, step 903b further includes transmitting another signal from the second sensor towards the metasurface plate, and receiving, by the second sensor, a reflected another signal from the metasurface plate. In some embodiments, the another signature has a corresponding signature that identifies the position of the vehicle.

In step <NUM>, the controller <NUM> determines the leading end of the vehicle, and the trailing end of the vehicle. In some embodiments, determining the leading end of the vehicle or the trailing end of the vehicle of step <NUM> is similar to the description in at least <FIG> or <FIG>, and similar detailed description is therefore omitted.

In some embodiments, step <NUM> further includes the controller <NUM> determining a start point of the metasurface plate <NUM> based on a sequence of symbols associated with a first portion <NUM> of the metasurface plate, and determining an end point of the metasurface plate <NUM> based on the sequence of symbols associated with a second portion <NUM> of the metasurface plate <NUM>. In some embodiments, determining the starting point or end point of the vehicle of step <NUM> is similar to the description in at least <FIG> or <FIG>, and similar detailed description is therefore omitted.

In step <NUM>, the controller determines a position of the vehicle on the guideway based on information received from at least the first sensor or the second sensor. In some embodiments, the information includes the RF signature and the another signature.

In some embodiments, step <NUM> includes the controller determining a distance from the position of the vehicle to a stopping location along the guideway based on the information received from the first sensor or the second sensor, the marker being located at the stopping location.

In some embodiments, calculating a position of the vehicle of step <NUM> includes calculating one or more of a position of the leading end of the vehicle based on the sensor data generated by one or more of the first sensor or the second sensor, or calculating a position of the end of the vehicle that is other than the leading end of the vehicle based on the position of the leading end of the vehicle and a length of the vehicle.

In some embodiments, step <NUM> further includes measuring a set of SNRs (<NUM>, <NUM> and <NUM>) based on the corresponding received RF signal from the metasurface plate <NUM>, determining a symbol sequence (<NUM>, <NUM>, <NUM>) of the corresponding metasurface plate from the set of SNRs (<NUM>, <NUM> and <NUM>) of the corresponding metasurface plate <NUM> (e.g., <NUM>, <NUM>, <NUM>), identifying a beginning portion <NUM> of the metasurface plate <NUM> and an end portion <NUM> of the metasurface plate <NUM> based on the symbol sequence (<NUM>, <NUM>, <NUM>) of the corresponding metasurface plate, determining a numerical value <NUM> of a middle portion <NUM> of the metasurface plate <NUM> based on the corresponding symbol sequence <NUM> of the middle portion <NUM> of the metasurface plate <NUM>, determining a metasurface reference position <NUM> based on the numerical value <NUM> of the corresponding middle portion <NUM> of the metasurface plate <NUM>, determining a distance D (equation <NUM>) from the first sensor or the second sensor to the metasurface plate <NUM>, and determining the position Pvehicle of the vehicle from the metasurface reference position <NUM> and the distance D (equation <NUM>) from the first sensor or the second sensor to the metasurface plate.

In some embodiments, if metasurface plate <NUM> is located at the stopping location, then distance D (equation <NUM>) of step <NUM> corresponds to the distance from the stopping location.

In some embodiments, step <NUM> is similar to the description in at least <FIG> or <FIG>, and similar detailed description is therefore omitted.

In step <NUM>, the controller determines a length of the vehicle from the speed of the vehicle and a time value T.

In some embodiments, the length LV of the vehicle is equal to the speed Vvehicle of the vehicle multiplied by time value T, as expressed by equation <NUM>.

In some embodiments, the time value T is the difference between time T1 when the sensor installed on the vehicle's leading end passes the starting point of the metasurface plate <NUM>, and time T2, when the sensor installed on the vehicle's trailing end passes the starting point of metasurface plate <NUM>. In some embodiments, the time value T is the difference between time T1 when the sensor installed on the vehicle's leading end passes the end point of the metasurface plate <NUM>, and time T2, when the sensor installed on the vehicle's trailing end passes the end point of metasurface plate <NUM>.

In some embodiments, the speed Vvehicle of the vehicle is determined by radar sensor of the first set of sensors were the second set of sensors.

<FIG> is a block diagram of a vehicle on board controller ("VOBC") <NUM>, in accordance with one or more embodiments. VOBC <NUM> is usable in place of one or more of controller <NUM> (<FIG>), alone or in combination with memory <NUM> (<FIG>). VOBC <NUM> includes a specific-purpose hardware processor <NUM> and a non-transitory, computer readable storage medium <NUM> encoded with, i.e., storing, the computer program code <NUM>, i.e., a set of executable instructions. Computer readable storage medium <NUM> is also encoded with instructions <NUM> for interfacing with vehicle <NUM>. The processor <NUM> is electrically coupled to the computer readable storage medium <NUM> via a bus <NUM>. The processor <NUM> is also electrically coupled to an I/O interface <NUM> by bus <NUM>. A network interface <NUM> is also electrically connected to the processor <NUM> via bus <NUM>. Network interface <NUM> is connected to a network <NUM>, so that processor <NUM> and computer readable storage medium <NUM> are capable of connecting to external elements via network <NUM>. The processor <NUM> is configured to execute the computer program code <NUM> encoded in the computer readable storage medium <NUM> in order to cause controller <NUM> to be usable for performing a portion or all of the operations as described in method <NUM>.

In some embodiments, the processor <NUM> is a central processing unit (CPU), a multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), and/or a suitable processing unit.

In some embodiments, the computer readable storage medium <NUM> is an electronic, magnetic, optical, electromagnetic, infrared, and/or a semiconductor system (or apparatus or device). For example, the computer readable storage medium <NUM> includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or an optical disk. In some embodiments using optical disks, the computer readable storage medium <NUM> includes a compact disk-read only memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital video disc (DVD).

In some embodiments, the storage medium <NUM> stores the computer program code <NUM> configured to cause system <NUM> to perform method <NUM>. In some embodiments, the storage medium <NUM> also stores information needed for performing method <NUM> as well as information generated during performing the method <NUM> such as a sensor information parameter <NUM>, a guideway database parameter <NUM>, a vehicle location parameter <NUM>, a vehicle speed parameter <NUM>, a vehicle leading end parameter <NUM>, and/or a set of executable instructions to perform the operation of method <NUM>.

In some embodiments, the storage medium <NUM> stores instructions <NUM> to effectively implement method <NUM>.

VOBC <NUM> includes I/O interface <NUM>. I/O interface <NUM> is coupled to external circuitry. In some embodiments, I/O interface <NUM> includes a keyboard, keypad, mouse, trackball, trackpad, and/or cursor direction keys for communicating information and commands to processor <NUM>.

VOBC <NUM> also includes network interface <NUM> coupled to the processor <NUM>. Network interface <NUM> allows VOBC <NUM> to communicate with network <NUM>, to which one or more other computer systems are connected. Network interface <NUM> includes wireless network interfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wired network interface such as ETHERNET, USB, or IEEE-<NUM>. In some embodiments, method <NUM> is implemented in two or more VOBCs <NUM>, and information such as memory type, memory array layout, I/O voltage, I/O pin location and charge pump are exchanged between different VOBCs <NUM> via network <NUM>.

VOBC <NUM> is configured to receive sensor information. The information is stored in computer readable medium <NUM> as sensor information parameter <NUM>. VOBC <NUM> is configured to receive information related to the guideway database through I/O interface <NUM> or network interface <NUM>. The information is stored in computer readable medium <NUM> as guideway database parameter <NUM>. VOBC <NUM> is configured to receive information related to vehicle location through I/O interface <NUM> or network interface <NUM>. The information is stored in computer readable medium <NUM> as vehicle location parameter <NUM>. VOBC <NUM> is configured to receive information related to vehicle speed through I/O interface <NUM> or network interface <NUM>. The information is stored in computer readable medium <NUM> as vehicle speed parameter <NUM>.

During operation, processor <NUM> executes a set of instructions to determine the location and speed of the guideway mounted vehicle, which are used to update vehicle location parameter <NUM> and vehicle speed parameter <NUM>. Processor <NUM> is further configured to receive LMA instructions and speed instructions from a centralized or de-centralized control system. Processor <NUM> determines whether the received instructions are in conflict with the sensor information. Processor <NUM> is configured to generate instructions for controlling an acceleration and braking system of the guideway mounted vehicle to control travel along the guideway.

An aspect of this description relates to a system. The system comprises a first sensor on a first end of a vehicle and an on-board controller coupled to the first sensor. The first sensor is configured to detect a radio frequency (RF) signature of a marker along a guideway. The first sensor is a radar detection device. The on-board controller is configured to determine a first position of the vehicle on the guideway or a first distance from the position of the vehicle to a stopping location along the guideway based on at least the RF signature received from the first sensor. The marker is a metasurface plate comprising a first diffused element, a first retroreflector element, a first absorbing element and a second diffused element between the first retroreflector element and the first absorbing element.

Another aspect of this description relates a system. The system comprises a marker along a guideway, a first sensor, a second sensor and an on-board controller.

The marker includes a metasurface plate comprising a first portion having a first retroreflector element, a second portion having a second retroreflector element and a third portion having a third retroreflector element. The first sensor is on a first end of a vehicle, and configured to detect a radio frequency (RF) signature of the marker. The first sensor is a radar detection device. The second sensor is on the first end of the vehicle, and configured to detect another signature of the marker. The second sensor is a camera, a LIDAR device or an IR sensor detection device. The on-board controller is coupled to the first sensor and the second sensor, and configured to determine a position of the vehicle on the guideway or a distance from the position of the vehicle to a stopping location along the guideway based on information received from the first sensor and the second sensor. The information includes the RF signature and the another signature.

Yet another aspect of this description relates to a method comprising detecting, by a first sensor, a radio frequency (RF) signature of at least a marker, the first sensor being on a first end of a vehicle along a guideway, and being a radar detection device, and the marker being a metasurface plate including at least a first retroreflector element. The method further includes detecting, by a second sensor, another signature of at least the marker, the second sensor being on the first end of the vehicle or a second end of the vehicle opposite from the first end of the vehicle, and the second sensor being another radar detection device, a camera, a LIDAR device or an IR sensor detection device. The method further includes determining, by an on-board controller, at least a position of the vehicle on the guideway based on information received from at least the first sensor or the second sensor, or a distance from the position of the vehicle to a stopping location along the guideway based on the information received from the first sensor or the second sensor, the marker being located at the stopping location, the information including the RF signature and the another signature.

Claim 1:
A system (<NUM>) comprising:
a marker (<NUM>) along a guideway (<NUM>);
a first sensor (110a) adapted to be placed on a first end (<NUM>) of a vehicle (<NUM>), and configured to detect a radio frequency, RF, signature of the marker (<NUM>) along the guideway (<NUM>), wherein the first sensor (110a) is a radar detection device; and
an on-board controller (<NUM>) coupled to the first sensor (110a), and configured to determine a first position of the vehicle (<NUM>) on the guideway (<NUM>) or a first distance from the position of the vehicle (<NUM>) to a stopping location along the guideway (<NUM>) based on at least the RF signature received from the first sensor (110a);
characterized in that the marker (<NUM>) is a metasurface plate (<NUM>, <NUM>, <NUM>) comprising:
a first diffused element (202a);
a first absorbing element (<NUM>);
a second diffused element (202b); and
a first retroreflector element (<NUM>) between the first diffused element (202a) and the second diffused element (202b),
the second diffused element (202b) being between the first retroreflector element (<NUM>) and the first absorbing element (<NUM>).