Patent Application
20190114911
Vehicles are increasingly equipped with navigation systems that rely on knowledge about a vehicle's location in order to provide navigation services to the driver. Further, newer and future generations of vehicles include various levels of autonomous driving capabilities that depend on accurate vehicle location information. While global navigation satellite system (GNSS) services may frequently be used to determine a vehicle's location, there are various situations in which alternative methods and systems for determining a vehicles location are preferable or necessary, for example, when GNSS signals are not available or weak, or when higher accuracy than GNSS position determination is needed.
In general, in one aspect, the invention relates to a method for determining a location of a vehicle. The method includes obtaining, by a marker reader of the vehicle, a first marker location from a signal emitted by a first marker located in a vicinity of the vehicle, wherein the first marker location is provided relative to a known reference point; obtaining a first vehicle location information relative to the first marker using at least one sensor disposed in the vehicle; and obtaining an estimate of the vehicle location relative to the known reference point, using the first marker location and the first vehicle location information.
In general, in one aspect, the invention relates to a system for determining a location of a vehicle. The system includes a marker reader installed in the vehicle and configured to obtain a first marker location from a signal emitted by a first marker that is placed in a vicinity of the vehicle, wherein the first marker location is provided relative to a known reference point; at least one vehicle sensor configured to obtain a first vehicle location information relative to the first marker; and a vehicle location estimator, configured to obtain an estimate of the vehicle location relative to the known reference point, using the first marker location and the first vehicle location information.
In general, in one aspect, the invention relates to a non-transitory computer-readable storage medium storing a program, which when executed on a processor, performs instructions comprising: obtaining, by a marker reader of the vehicle, a first marker location from a signal emitted by a first marker located in a vicinity of the vehicle, wherein the first marker location is provided relative to a known reference point; obtaining a first vehicle location information relative to the first marker using at least one vehicle sensor disposed in the vehicle; and obtaining an estimate of the vehicle location relative to the known reference point, using the first marker location and the first vehicle location information.
Specific embodiments of the invention will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. Like elements may not be labeled in all figures for the sake of simplicity.
In the following detailed description of embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.
Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as an adjective for an element (i.e., any noun in the application). The use of ordinal numbers does not imply or create a particular ordering of the elements or limit any element to being only a single element unless expressly disclosed, such as by the use of the terms “before,” “after,” “single,” and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element may encompass more than one element and succeed (or precede) the second element in an ordering of elements.
In the following description of
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a horizontal beam” includes reference to one or more of such beams.
Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
It is to be understood that, one or more of the steps shown in the flowcharts may be omitted, repeated, and/or performed in a different order than the order shown. Accordingly, the scope of the invention should not be considered limited to the specific arrangement of steps shown in the flowcharts.
Although multiple dependent claims are not introduced, it would be apparent to one of ordinary skill that the subject matter of the dependent claims of one or more embodiments may be combined with other dependent claims.
While global navigation satellite system (GNSS) services such as the global positioning system (GPS) may frequently be used to determine a vehicle's location, there are various situations in which alternative methods and systems for determining a vehicles location are preferable or necessary, for example, when GNSS signals are not available. This may apply in particular in parking structures, tunnels, in the vicinity of tall buildings, etc. Frequently, vehicle navigation systems, therefore, rely on GPS-based location determination systems, supplemented by inertial measurement units (IMUs). An IMU may use inertial sensors such as gyroscopes and acceleration sensors, velocity sensors, steering angle sensors, etc. to estimate or predict the location of a vehicle, even in absence of GPS signals. If these location estimates are updated as the vehicle moves, location estimates are continuously available, over time. However, due to various inaccuracies, e.g., measurement and modeling errors, such an estimated vehicle location may have limited accuracy. While the accuracy may be high initially, e.g., immediately after GPS signals have been lost, the accuracy may deteriorate over time and may, thus, become sufficiently inaccurate to prevent use of the location estimate for the purpose of navigation and/or autonomous driving. Accordingly, such estimates may require periodic correction, using actual location information. In situations in which GPS signals are not available or when their accuracy is degraded, alternative location signal sources, different from the IMU, may, thus, be relied upon in order to accurately determine vehicle location, in accordance with one or more embodiments of the invention.
Turning to
In one or more embodiments of the invention, the vehicle location detection system (120) relies on a marker reader (112) and a vehicle sensor (114) to identify the location of the vehicle, using the marker (152), as subsequently described.
In one or more embodiments of the invention, the marker (152) emits a marker location signal (154) that identifies the exact location of the marker (152). Any type of coordinate system, such as a geographic coordinate system that enables the location of the marker (152) on earth to be specified using a set of numbers, letters and/or symbols, may be used to describe the absolute marker location, e.g., in a global reference frame. The location of the marker may alternatively be provided in relative coordinates, e.g., relative to a geographic landmark, an entrance of a building, another marker, etc. In one or more embodiments of the invention, the marker location signal (154) accurately provides the marker location, with a tolerance of for example, a few decimeters or a few centimeters. The marker location information may have been programmed into the marker, prior to, during, or after the installation of the marker.
In one or more embodiments of the invention, the marker location signal (154) is emitted using a radio frequency (RF) signal. The RF signal may be a Bluetooth, Bluetooth Low Energy (BLE), Wi-Fi or any other type of RF signal suitable for transmitting the marker location. The marker may operate as a beacon, capable of only transmitting but not receiving, or it may have transmitting and receiving capabilities. The emitted marker location signal (154) may be picked up by the marker reader (112) of the vehicle (100), when in the vicinity of the marker (152). Depending on the type of RF signal that is used for the emission of the marker location, the range in which the marker location signal (154) can be received by the marker reader (112) may be limited. For example, the range may be limited to 10 m or 100 m away from the marker. Those skilled in the art will appreciate that the range of the RF signal may be limited to any range, and may further be influenced by other factors such as marker location, environmental conditions, the types of antennas and signal conditioning being used, etc., without departing from the invention.
In one or more embodiments of the invention, the marker reader (112) in the vehicle (100) is configured to receive the marker location signal(s) (154) of one or more markers in the vicinity of the vehicle (100), and to forward the marker location(s) extracted from the marker location signal(s) to a vehicle location estimator (118), further described below. Depending on the type of RF signal that is used by the marker(s) (152), the marker reader (112) includes the proper RF signal receiver, such as a BLE or Wi-Fi receiver.
In one or more embodiments of the invention, the vehicle (100) is further equipped with a vehicle sensor (114). A detection of the marker location(s), in accordance with one or more embodiments of the invention, performed by the vehicle sensor (114), is relative to the vehicle (100). The marker location information, obtained by performing the detection, may include a distance of the marker(s) from the vehicle and/or one or more marker angles. Depending on the data included in the marker location information, a unique point in space may be identified as the location of a marker (e.g., when marker distance and marker angles are included in the marker location information), or a direction of the marker in space may be identified (e.g., when only marker angles are obtained), or a radius of a circle or sphere on which the marker may be located may be identified (e.g., when only the marker distance is obtained). In one or more embodiments of the invention, the marker location information is provided to the vehicle location estimator (118), where it is used to estimate the vehicle's location, as further described below.
In one or more embodiments of the invention, the marker detection is performed using optical sensing. The optical sensing is performed by a vehicle sensor (114) that may be a light detection and ranging (LiDAR) sensor, a stereoscopic camera or a non-stereoscopic camera. While LiDAR sensors and stereoscopic cameras may provide angle and distance information, non-stereoscopic monochrome or color cameras may provide angle information. Additionally or alternatively, non-optical sensing techniques may be employed. For example, the RF signal emitted by the marker (152) may be suitable to determine distance using a time of flight (ToF) identification. Further, a relative received signal strength (RSSI) may be used to determine the distance of the marker. In one or more embodiments of the invention, multiple vehicle sensors (114) may be installed in the vehicle (100). For example, the vehicle (100) may include multiple cameras that are oriented differently to cover a wide range of angles. Any combination of sensors may be used as the vehicle sensor (114). For example, combinations of a LiDAR sensor and one or more optical cameras may be used. Further a radar sensor may be used alone or in combination with other sensors to obtain marker distance and/or marker angle. Functionally, some sensors may be used merely to detect the presence of a marker, other sensors may be used to obtain a marker distance, and other sensors may further be used to obtain a marker angle. Alternatively, sensors that perform a combination of these functions may be used.
The type of sensing performed by the vehicle sensor (114) may determine possible marker placement locations and/or the appearance of the marker(s) (152). If the vehicle sensor (114) is an optical sensor, direct line-of-sight may be needed between the vehicle sensor (114) and the marker(s) (152). Further, depending on the detection method being used (e.g., if image processing is used on one or more video frames obtained by a camera), the marker (152) may be required to have certain visual characteristics. These visual characteristics may include, but are not limited to, a particular geometry, color and/or pattern, etc. In contrast, if non-optical sensing methods are used, direct line-of-sight contact may not be necessary. For example, if the marker location sensing is based on ToF or RSSI methods, the marker(s) (152) may not need to be visible. This may allow the marker(s) (152) to be embedded in other structures such as in a floor, wall or ceiling, without preventing the obtaining marker location information by the vehicle sensor (114).
Using the marker location obtained by the marker location signal (154), by the marker reader (112), and the marker location relative to the vehicle, obtained by the vehicle sensor (114), the location of the vehicle (100) may be estimated by the vehicle location estimator (118), as further described below.
Turning to
In one or more embodiments of the invention, the use of multiple markers (152) for determining the location of the vehicle may also provide redundancy. Assume, for example, that in example 1 of
Those skilled in the art will recognize that the invention is not limited to the scenarios introduced in
The vehicle location estimator (118) may include a computing device configured to perform one or more of the steps described below with reference to
The vehicle location estimator (118) may interface with one or more vehicle electronic control units (ECU) (not shown). The vehicle ECU is a processing unit that may support one or more of the vehicle's functionalities. The vehicle ECU may also include, for example, an input/output interface for the vehicle's instrument cluster, the vehicle's navigation system, etc. The vehicle location estimate, provided by the vehicle location estimator (118) may thus be made available to those vehicle components that require location information. This may be, for example, the vehicle's navigation system or an autonomous driving unit.
Turning to
The BLE beacon transmitting unit (202), as previously described, is configured to emit a location signal that precisely specifies the location of the marker (200). The BLE beacon transmitting unit may periodically emit the location data, and may permit one-way communication only. The communication range of the BLE beacon may be anywhere between, for example, 5 and 15 meters. The location signal may be emitted frequently enough to enable vehicles entering the communication range to receive the location signal before moving out of range when traversing the zone in which the location signal is receivable. For example, if a vehicle moves at 10 m/s, then emitting the location signal at 10 Hz may be frequent enough to allow receiving of the location signal even if the vehicle only traverses a distance of 1 m within the communication range of the BLE beacon transmitting unit.
The marker reader (112) of the vehicle (100) may, thus, merely need to listen to the location information that is advertised by the BLE beacon transmitting unit (202), thereby not requiring time and power consuming protocol negotiations and two-way communication. Because the use of the BLE protocol enables marker advertisement while using limited power only, the marker (200) may be powered by a battery, e.g., a lithium-ion battery (206). Alternative power sources may be used, without departing from the invention. For example, the marker may be equipped with other types of batteries, solar panels, etc. Further, any other wireless communication protocol may be used to transmit the marker location information, without departing from the invention. For example, Wi-Fi, Zigbee, radio frequency identification (RFID), or cellular communication protocols may be used.
In one or more embodiments of the invention, the LoRa modem (204) is used to enable communication between the marker (200) and a gateway. The range of the LoRa signal may be, for example, 100 meters. This range may be increased or decreased by adjusting transmission power. Communication with the marker may be performed to update the marker's software over the air, modify configuration parameters, activate or deactivate the marker, to obtain a health status, battery level, and/or other such information. To conserve energy, the time interval between status transmissions may be fairly long, e.g., status transmission may be performed only once per day. Communication protocols other than LoRa may be relied upon. For example, LTE-M, SigFox, or any other protocol may be used, without departing from the invention.
Turning to
In one or more embodiments of the invention, one or more of the steps shown in
In Step 300, the marker location relative to a known reference point is obtained from the marker. The marker location, in accordance with one or more embodiments of the invention, may be obtained from a radio transmission of the marker location, emitted by the marker. The marker location is provided in an absolute reference frame, e.g., in a globally valid geographic coordinate system or in a locally valid reference frame, e.g., relative to a landmark, a physical structure, etc. If multiple markers are in the vicinity of the vehicle, the marker locations of these multiple markers may be obtained.
In Step 302, vehicle location information, relative to one or more markers, is obtained. The information may describe the vehicle's location relative to the marker(s) using distance between the vehicle and one or more markers, and/or one or more angles between the direction of movement of the vehicle and an imaginary line between the vehicle and the marker. The details of Step 302 are provided in
In Step 304, an estimate of the vehicle's location is determined relative to the known reference point, using the data obtained in Steps 300 and 302. The details of Step 304 are provided in
In one or more embodiments of the invention, one or more of the steps described in
Turning to
In Step 400, a marker is detected using a vehicle sensor. Depending on the type of the vehicle sensor and the type of marker being present in the vicinity of the vehicle, the presence of the marker may be detected optically or based on an RF signal emitted by the marker. The optical detection of the marker (e.g., using a LiDAR sensor or a camera) may be performed using three-dimensional or two-dimensional image processing methods that are capable of recognizing a particular shape, color and/or pattern that identify the marker. If the marker detection is based on RF signals, the marker may be invisible and therefore may be detected merely by the presence of the RF signal. If multiple markers are present in the vicinity of the vehicle, Step 400 may be performed for one or more markers.
In Step 402, information about the marker location relative to the vehicle is obtained. The information that describes the marker location may depend on the type of marker and the type of vehicle sensor being used for obtaining the marker location information. More specifically, if a marker is optically detected, using, for example, a LiDAR sensor or a stereoscopic camera, the marker location may be obtained relative to the vehicle in all three dimensions. In other words, the marker location information may describe a point in space that identifies the marker. One skilled in the art will appreciate that various representations may be used to identify the location of the marker. For example, x, y and z coordinates may specify the location of the marker relative to the vehicle. Alternatively, various distance/angle formats may be used to describe the marker location. Alternatively, if the marker is optically detected using a non-stereoscopic camera, one or more angles describing the marker location relative to the vehicle may be obtained. Similarly, if the marker location is obtained using the analysis of the marker's RF signal, e.g., using time-of-flight methods, a marker distance may be obtained. In general, information about location of the marker relative to the vehicle may be gathered from one or more sensors and fused together to determine the relative location of the marker with respect to the vehicle. If multiple markers are present in the vicinity of the vehicle, Step 402 may be performed for one or more markers.
In Step 404, vehicle location information is obtained relative to the marker. Step 404 may be performed in various ways, depending on the marker location information obtained in Step 402. If a complete description of the marker location relative to the vehicle was obtained in Step 404, the vehicle location relative to the marker may be directly obtained through the inverse geometric relationship. Further, if complete descriptions of marker locations relative to the vehicle were obtained for multiple markers, the obtained data may be fused to obtain a higher-accuracy vehicle location estimate. The fusion may be performed using optimization methods that minimize a location error, e.g., using a least-squares method.
In one embodiment, marker location information obtained for multiple markers may be used. As an example, if only distance information for different markers is available, at least three of these distances may be combined to obtain vehicle location information, relative to one of the markers. Error minimization methods may be used to obtain a high-accuracy vehicle location estimate. Similarly, if only angle information is available, a vehicle location estimate may also be obtained by combining angle information obtained for multiple markers.
Regardless of the type of marker location information obtained in Step 402, the use of location information of additional markers may result in a higher-accuracy estimates of the vehicle location.
Turning to
In Step 500, the vehicle location is obtained using the marker location relative to the known reference point obtained from the marker location signal, and the vehicle location information relative to the marker. The vehicle location may be obtained relative to the known reference point by geometrically combining the vehicle location information relative to the marker, with the marker location relative to the known reference point. Intuitively, this geometric combination may be understood as an addition of a vector that describes the vehicle location relative to the marker and a vector that describes the marker location relative to the known reference point. Although, depending on the geometric representation used to describe marker and vehicle location, these operations may be performed in different ways, the result is the estimated vehicle location relative to the known reference point, in accordance with one or more embodiments of the invention. A similar operation may be performed if multiple markers were relied upon to determine the vehicle location, relative to the markers. In such a scenario, an optimized estimated vehicle location may be obtained using least squares optimization, or any other error minimization approach.
In Step 502, a continuous estimation of the vehicle location, for example once every second, may be performed using vehicle or other sensors such as a camera, a laser scanner, etc. While the estimation is optional, it may be useful to maintain an accurate vehicle location as the vehicle is moving, in particular when the vehicle goes in and out of communication ranges of markers. Consider, for example, a scenario in which markers are spaced at far distance from each other, for example every 100 meters. In this scenario, without estimation, no location information may be available when the vehicle is in a region without any markers in the vicinity. In order to consistently obtain location information, which may be critical to perform navigation and/or autonomous driving functions, the vehicle location is estimated, even in absence of a current marker location estimate, as subsequently described.
In one embodiment of the invention, a Kalman filter may be used to recursively perform a forward prediction. The Kalman filter may include a basic model of the vehicle dynamics, enabling the forward prediction. While contact with one or more markers is available, the location information, e.g., the location estimate obtained in Step 500, may serve as an input to the Kalman filter. The Kalman filter may further obtain other inputs. Specifically, signals obtained from the vehicle's inertial measurement unit (IMU) may be considered. These signals may include gyroscope data, but also wheel sensor data such as steering angle, velocity, etc. In one or more embodiments of the invention, these signals are available even when no markers are in the vicinity of the vehicle and may thus be used to estimate vehicle location in absence of a marker-based location estimate. Once the vehicle reaches a location in which markers are, again, available, the available markers may be considered for the estimation of the vehicle location.
In one or more embodiments of the invention, IMU data and/or GPS data may be relied upon to supplement the location information obtained using the marker(s) even while the vehicle is in the vicinity of markers. This may enable further increasing location estimation accuracy in comparison to the use of marker information only. A Kalman filter or other sensor data fusion methods such as the least squares method, may be used for this data fusion.
In one or more embodiments of the invention, if multiple signals are available that are suitable to be used to estimate vehicle location, the contribution of these signals is weighted to improve estimation accuracy. A signal that is less likely to improve accuracy may be considered to a lesser degree in comparison to a signal that is more likely to improve accuracy.
Further, regardless of whether the estimation is based on marker information, IMU data and/or GPS data, the estimation may be performed for various location variables including vehicle position, vehicle speed and/or vehicle heading. Vehicle speed and heading may be obtained, using the change between vehicle location estimates obtained at different points in time, e.g., using subsequently obtained vehicle location estimates.
Various embodiments of the invention have one or more of the following advantages. A vehicle location may be determined, using methods and systems in accordance with one or more embodiments of the invention, in the absence of GPS signals. This may enable navigation and or autonomous driving features that would otherwise be unreliable or not available, e.g., in a covered parking structure. Embodiments of the invention enable estimation of a vehicle position, a vehicle speed and/or a vehicle heading. Forward prediction may further improve accuracy and/or may enable continued location estimation even when markers are temporarily not in the vicinity of the vehicle.
While the technology has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the technology as disclosed herein. Accordingly, the scope of the technology should be limited only by the attached claims.
