Vehicle guidance using an IMU and radar with reflective targets on or near a driving surface

Abstract

An apparatus guides a land vehicle along a pathway on which there are one or more side targets with different radar reflectivity characteristics compared to the pathway. The apparatus comprises a radar sensor, a processor, and an inertial measurement unit (IMU). The radar sensor is mounted to the vehicle and configured to radiate to the pathway one or more signals having a main beam pattern center aimed toward the ground and sideways from the vehicle. The radar sensor is further configured to detect one or more reflection signals from one or more of the side targets along the pathway. The processor is configured to determine based on a reflection signal a lateral distance between the vehicle and a side target as the vehicle passes or first encounters the side target. The IMU is configured to determine a change of lateral position of the vehicle between side targets.

Description

VEHICLE GUIDANCE USING AN IMU AND RADAR WITH REFLECTIVE TARGETS ON OR NEAR A DRIVING SURFACERELATED APPLICATIONS

[0001] This application claims priority to the following United States provisionalpatent applications: (1) No. 63 / 543,444 filed October 10, 2023, entitled “Radar-Based andIMU-Based Vehicle Guidance using Radar Reflectors Embedded in Pavement Markers on aDriving Surface”; (2) No. 63 / 605,500 filed December 2, 2023, entitled “Radar-Based andIMU-Based Vehicle Guidance using Radar Reflectors Embedded in Pavement Markers on aDriving Surface”; and (3) No. 63 / 683,882 filed August 16, 2024, entitled “Radar-BasedVehicle Guidance Using Reflectivity of Targets on or Near the Driving Surface.” The entiredisclosures of each of the foregoing priority patent applications are hereby incorporated byreference herein.

[0002] The subject matter of this application also relates to the following patentapplications filed by the Applicant: (1) International Patent Appl. No. PCT / US2023 / 028710,entitled “Radar-Based Vehicle Guidance Using Radar Reflectors Embedded in PavementMarkers on a Driving Surface,” filed July 26, 2023, which claims priority to each of thefollowing United States provisional patent applications: (a) No. 63 / 474,257, filed August 1,2022, entitled “Vehicle Guidance System”; (b) No.63 / 474,383, filed August 10, 2022, entitled“Vehicle Guidance System”; (c) No. 63 / 576,322, filed Jan. 30, 2023, entitled “Short-RangeRadar for use in Vehicle Lateral Guidance and Control”; (d) No.63 / 576,323, filed January 30,2023, entitled “Vehicle Guidance System”; (e) No. 63 / 454,669, filed March 25, 2023, entitled“Radar-Based Vehicle Guidance System Using Dihedral Corner Reflector Embedded inPavement Marker”; (f) No. 63 / 464,532, filed May 5, 2023, entitled “Vehicle GuidanceSystem”; (g) No. 63 / 464,527, filed May 5, 2023, entitled “Short-Range Radar for Use inVehicle Lateral Guidance and Control”; (h) No. 63 / 466,612, filed May 15, 2023, entitled“Vehicle Guidance System”; and (i) No. 63 / 469,920, filed May 31, 2023, entitled “Radar-Based Vehicle Guidance Using Corner Reflectors Embedded in Pavement Markers on aDriving Surface”; and (2) International Patent Appl. No. PCT / US2024 / 027899, entitled“Radar-Based Vehicle Guidance Using Arrays of Reflectors Embedded in or Under a RoadLine on a Driving Surface,” filed May 4, 2023, which claims priority to, inter alia, United States50066 / 0402 Page 1 of 55provisional patent application No. 63 / 470,102, filed May 31, 2023, entitled “Radar-BasedVehicle Guidance Using Array of Corner Reflectors Embedded in or Under a Line on a DrivingSurface.” The entire disclosures of each of the foregoing patent applications are herebyincorporated by reference herein.TECHNICAL FIELD

[0003] The field of this disclosure relates generally to control of an automobile orsimilar land vehicle. More specifically, this disclosure relates to the use of radar (radiodetection and ranging) reflectivity of targets on or near a roadway or other driving surfaceto control or assist in controlling a vehicle, especially its lateral positioning.BACKGROUND INFORMATION

[0004] Radar has been used with automobiles for various purposes such as blind-spotdetection and forward collision warning. However, radar is not conventionally used toperform or assist in performing lateral steering of an automobile. Instead, electronic lateralsteering or steering assistance systems typically collect and process visual data. Thatapproach is complicated and limited or unusable in inclement weather (e.g., rain, snow, ice,fog), smoke, and darkness.

[0005] Road lines and pavement markers are commonly deployed on or near adriving surface to demark road or lane boundaries. Curbs, concrete barriers, and otherroadside objects also sometimes demark the edge of a road or lane.SUMMARY OF THE DISCLOSURE

[0006] This disclosure relates generally to the use of a radar sensor or transceiver andinertial measurement unit (IMU) on or in a land vehicle to perform lateral steering or toassist in performing lateral steering, such as, for example, lane-based ADAS functions. Atleast one radar sensor is mounted on a vehicle and oriented to transmit radar signalsdownward and laterally sideways from the vehicle and to receive return reflection signalsfrom side targets on or near the side of the road or lane. Such side targets may be, forexample, conventional pavement markers, improved pavement markers with enhancedradar reflectivity, curbs, concrete barriers, sign posts, etc. Round-trip time-of-flight of radarsignals to and from the side targets can provide accurate lateral distance measurements and50066 / 0402 Page 2 of 55therefore lateral vehicle position information for steering, steering assistance, or lateralposition checking, as the vehicle passes each target. Between intermittently spaced sidetargets, various types of information from the IMU can be used to determine lateral positioninformation for the vehicle. In this way, the combination of the radar sensor and the IMU canprovide continuous or approximately continuous lateral vehicle position information alonga road or lane having intermittent radar-reflective side targets.

[0007] According to one embodiment, an apparatus guides a land vehicle along apathway on which there are one or more side targets with different radar reflectivitycharacteristics compared to the pathway. The apparatus comprises a radar sensor, aprocessor, and an IMU. The radar sensor is mounted to the vehicle and aimed downwardand to the side of the vehicle. The radar sensor is configured to radiate to the pathway, viaat least one transmitter, one or more signals having a main beam pattern center aimedtoward the ground and sideways from the vehicle. The radar sensor is further configured todetect via one or more receiving antennas one or more reflection signals from one or moreof the side targets along the pathway. The processor is operatively connected to the radarsensor. The processor is configured to determine based on a reflection signal a lateraldistance between the vehicle and a side target as the vehicle passes or first encounters theside target. The IMU is configured to determine a change of lateral position of the vehiclebetween side targets.

[0008] Optionally, the radar sensor operates within a frequency range from about 300MHz to about I THz or a frequency range from about 77 GHz to about 81 GHz.

[0009] Optionally, the radar sensor is a frequency-modulated continuous wave radartransceiver, an ultra wideband impulse radar transceiver, or of a type selected from a groupconsisting of two-frequency phase difference radar, multiple-frequency radar, multiple-frequency phase radar, orthogonal frequency division multiplex radar, frequency shiftkeying radar, digital code modulation radar, phase-modulated continuous wave radar,multiple-input-multiple-output radar, polarimetric radar, dual-polarimetric radar,monopulse radar, noise radar, and interferometric synthetic aperture radar.

[0010] The radar sensor may be, for example, monostatic or bi-static. 50066 / 0402 Page 3 of 55

[0011] Optionally, the radar sensor comprises an antenna array, is configured totransmit a polarized radar signal, is configured to detect the reflection signal based on itspolarization, is configured to be placed on or within a front bumper of the vehicle, and / or ispackaged within a vehicle light assembly.

[0012] Optionally, the processor is configured to process just a portion of a reflectionsignal received in a window corresponding to an expected range of a reflection target orconfigured to perform a frequency transform of the reflection signal.

[0013] Optionally, the side targets are selected from a group consisting of raisedpavement markers, raised pavement markers with dihedral corner reflectors, snow-plowable pavement markers, snow-plowable pavement markers with dihedral cornerreflectors, grooves in the road, slots in the pathway, sign posts, mail boxes, curbs, concretebarriers, guardrails, lamp posts, fire hydrants, trees, and pathway edges.

[0014] Optionally, the IMU comprises an accelerometer that provides a lateralacceleration, which is integrated twice to provide a change in lateral position of the vehiclebetween targets,

[0015] Optionally, the IMU comprises a gyroscope that provides a yaw rate, and whichis integrated once to provide a change of heading of the vehicle, and the changes of headingare used to determine a change in lateral position of the vehicle between targets.

[0016] Optionally, the IMU comprises a magnetometer that provides a direction of thevehicle, and the direction is used to determine a change in lateral position of the vehiclebetween targets.

[0017] Optionally, the lateral distance from the radar sensor and the change of lateralposition from the IMU are combined using a complimentary filter or a Kalman filter.

[0018] According to another embodiment, a vehicle is designed for use on a roadalong which are a plurality of side targets. Each of the side targets is characterized by a radarreflectivity. The vehicle comprises a first lateral side, a radar transceiver mounted to thevehicle, a processor, and an IMU. The radar transceiver is characterized by a main beampattern having a center aimed downward and sideways from the vehicle such that areflection is detected from the radar reflectivity of the side target as the vehicle moves50066 / 0402 Page 4 of 55forward by the side target on the first lateral side of the vehicle. The processor is operativelycoupled to the radar transceiver and configured to determine, based on the reflection, a pathlength from the radar transceiver to the side target. The IMU is configured to determine achange of lateral position of the vehicle between side targets.

[0019] Optionally, the vehicle further comprises a second lateral side opposite thefirst lateral side, and said main beam pattern is a first main beam pattern having a first centeraimed downward in a first sideways direction from the vehicle, said side target is a first sidetarget on the first lateral side of the vehicle, and the radar transceiver is further characterizedby a second main beam pattern having a second center aimed downward and in a secondsideways direction from the vehicle such that a reflection is detected from a second radarreflector embedded in a second side target as the vehicle moves by the second side target.The second sideways direction is horizontally approximately opposite the sidewaysdirection, and the second side target is on the second lateral side of the vehicle.

[0020] Optionally, said radar transceiver is a first radar transceiver, said main beampattern is a first beam pattern having a first center aimed downward in a first sidewaysdirection from the vehicle, and said side target is a first side target on the first lateral side ofthe vehicle, and the vehicle further comprises a second radar transceiver mounted to thevehicle. The second radar transceiver is characterized by a second main beam patternhaving a second center aimed downward and in a second sideways direction from the vehiclesuch that a reflection is detected from a radar reflectivity from a second side target as thevehicle moves forward by the second side target by on the vehicle’s first lateral side.

[0021] Optionally, the vehicle further comprises an exterior light assembly, and theradar transceiver is located on or within the exterior light assembly.

[0022] Optionally, the vehicle further comprises a front bumper, and the radartransceiver is located on or within the front bumper.

[0023] Optionally, the processor is configured to perform or assist performing one ormore of a lane departure warning function, a lane keeping function, and a lane centeringassistance function based on the path length from the radar transceiver to the side target.50066 / 0402 Page 5 of 55

[0024] Optionally, the vehicle further comprises a lateral positioning systemindependent of the radar transceiver, wherein the radar transceiver and the processor forma redundant lateral positioning system.

[0025] Optionally, the vehicle is at least partially autonomous, and lateral positioningof the vehicle is performed based at least in part on the path length from the radartransceiver to the side target.

[0026] Optionally, the radar transceiver is also configured to perform blind-spotdetection or cross traffic detection.

[0027] According to another embodiment, a method determines a lateral position ofa land vehicle along a pathway. The pathway has side targets with different radar reflectivitycharacteristics compared to the pathway. The side targets are arranged along the pathwayin a direction of vehicle travel. The method transmits downward and sideways a radartransmit signal from the land vehicle towards side targets mounted on or near the pathwayas the vehicle passes a side target. The method receives at the land vehicle a radar reflectionsignal from the side target as the vehicle passes by the side target. The method determines,based on the radar transmit signal and the radar reflection signal, a distance between theland vehicle and the side target. The method determines, based on one or more inertialmeasurements, a change of lateral position of the vehicle between side targets. The methoddetermines, based on the change of lateral position and the distance between the land vehicleand a passed side target, an approximate lateral position of the vehicle between side targets.

[0028] Optionally, the steps of transmitting the radar signal, receiving a radarreflection signal, and determining the distance are repeated for substantially every radar-reflective side target that the vehicle passes.

[0029] Optionally, the transmitting step is repeated periodically at a period selectedfrom a range from about 0.5 milliseconds to about 1 second.

[0030] Optionally, the side targets are distributed along one side of the vehicle as thevehicle travels along the pathway.

[0031] Optionally, the pathway is one lane of a multi-lane road, and the side targetsare pavement markers that are distributed along a line demarking one side of the pathway.50066 / 0402 Page 6 of 55

[0032] Optionally, the pathway is one lane of a multi-lane road, and wherein the sidetargets are pavement markers distributed along a line demarking one side of a lane adjacentto a lane corresponding to the pathway of the vehicle.

[0033] Optionally, the method also filters the radar reflection signal based on a rangeof expected distances between the land vehicle and the side target.

[0034] Optionally, the method also performs a frequency transform on the radarreflection signal.

[0035] Optionally, the method also uses the distance to guide or assist steering thevehicle laterally to follow the pathway.

[0036] Optionally, the method provides a warning to a driver of the vehicle and / orexternal to the vehicle either if the distance exceeds a maximum threshold or is less than aminimum threshold or if the approximate lateral position is outside of an acceptable range,.The warning external to the vehicle may comprise, for example, flashing a blinker.

[0037] Optionally, the method also performs one or more of a lane-centeringassistance function and a lane-keeping function based on the distance between the landvehicle and a side marker.

[0038] Optionally, the vehicle comprises a lateral positioning system independent ofthe method described above, and the method further uses the distance in conjunction withthe independent lateral positioning system to improve lateral position determination. Thelateral positioning system may comprise one or more of, for example, a global navigationsatellite system, a vision system viewing painted lines along the pathway, or a lidar systemviewing painted lines along the pathway, recorded targets along the pathway.

[0039] According to another embodiment, a set of one or more radar transceivers isconfigured to be installed in or on a land vehicle for continuously viewing radar-reflectiveside targets along a pathway along which the land vehicle can travel. The set comprises aradar transmitter and a radar receiver. The radar transmitter is configured to transmit radarsignals from multiple transmission antennas installed horizontally along a lateral side of thevehicle. The antennas have transmission beam patterns having center directions ofmaximum transmission. The radar receiver is configured to receive radar return reflection50066 / 0402 Page 7 of 55signals at one or more of multiple reception antennas installed horizontally along the lateralside of the vehicle. The antennas are configured to have reception beam patterns havingcenter directions of maximum reception. The radar transceiver is configured to be installedin or on the land vehicle so that the center directions of maximum transmission aredownward and sideways from the land vehicle and so that the center directions of maximumreception are upward and sideways toward the land vehicle when the set is installed on orin the land vehicle. The multiple transmission antennas are spaced apart longitudinallyalong the vehicle so that every side target is within a transmission beam pattern of at leastone transmission antenna, and the multiple reception antennas are spaced apartlongitudinally along the vehicle so that every side target is within a reception beam patternof at least one antenna as the vehicle passes the side target.

[0040] Optionally, the multiple transmission antennas and the multiple receptionantennas are the same, and each antenna is a transmission / reception antenna.

[0041] According to another embodiment, a vehicle is designed for use on a roadalong which a plurality of side targets have been installed. Each of the side targets ischaracterized by an RF reflectivity. The vehicle comprises a first radar transceiver, a secondradar transceiver, and a processor. The first radar transceiver mounted on or near the frontof the vehicle, wherein the first radar transceiver is characterized by a first main beampattern having a first center aimed downward and sideways from the vehicle such that areflection is detected from the RF reflectivity of the side target as the vehicle moves forwardby the side target on the vehicle’s side. The second radar transceiver mounted on or nearthe rear of the vehicle, wherein the second radar transceiver is characterized by a secondmain beam pattern having a second center aimed towards downward and sideways from thevehicle such that a reflection is detected from the RF reflectivity of the side target as thevehicle moves forward by the side target on the vehicle’s side. The processor is operativelycoupled to the radar transceivers and configured to determine, based on the reflections fromthe two radar transceivers, path length from each radar transceivers to the side targets.

[0042] Optionally, the processor is further configured to determine vehicle headinginformation and lateral deviation along the road with respect to the side targets.50066 / 0402 Page 8 of 55BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1A is a front-view diagram of a vehicle equipped with two radartransceivers interacting with side targets, including another vehicle, on a driving surface andalong the side of the road, according to one embodiment.

[0044] Figure 1B is a front-view diagram of a vehicle equipped with a dual-directionradar transceiver interacting with side targets, including another vehicle, on a drivingsurface and along the side of the road, according to another embodiment.

[0045] Figure 2 is a top view of a vehicle equipped with radar transceivers and inertialmeasurement units on a road having pavement markers, according to one embodiment.

[0046] Figure 3 is a block diagram of a system that combines multiple detection,guidance, and / or control systems, including a radar-based lateral positioning system,according to one embodiment.

[0047] Figure 4A is an isometric diagram of a conventional pavement marker.

[0048] Figure 4B is a top view of a segment of a road on which conventional pavementmarkers have been placed.

[0049] Figure 5A is a front view of a pavement marker illustrating a reflection from / toa radar transceiver, according to one embodiment.

[0050] Figure 5B is a front view of another pavement marker illustrating a reflectionfrom / to a radar transceiver, according to one embodiment.

[0051] Figure 6A is an isometric diagram of a dihedral corner reflector.

[0052] Figure 6B is an isometric diagram of a pavement marker augmented with twodihedral corner reflectors, according to one embodiment.

[0053] Figure 6C is a top view of the pavement marker of Figure 6B.

[0054] Figure 6D is a side view of the pavement marker of Figure 6B.

[0055] Figure 7A is a cross-section view of a cavity in or below a driving surface,according to one embodiment.50066 / 0402 Page 9 of 55

[0056] Figure 7B is a top view of a section of a road in which cavities of Figure 7A havebeen arranged, according to one embodiment.

[0057] Figure 7C is a top view of a section of a road in which long cavities of Figure7A have been arranged, according to another embodiment.

[0058] Figure 8A is a cross-section view of a pavement marker in a cavity below adriving surface illustrating a reflection from / to a radar transceiver, according to oneembodiment.

[0059] Figure 8B is a top view of a section of a road in which pavement markers ofFigure 8A have been arranged, according to one embodiment.

[0060] Figure 8C is a top view of a section of a road in which pavement markers ofFigure 8A have been arranged, according to another embodiment.

[0061] Figure 9 is an isometric view of a snow-plowable pavement marker, accordingto one embodiment.

[0062] Figure 10A is an isometric view of a curb illustrating a reflection from / to aradar transceiver, according to one embodiment.

[0063] Figure 10B is a diagram illustrating a curb illustrating a reflection from / to aradar transceiver, according to one embodiment.

[0064] Figure 10C is a front view of concrete barrier illustrating a reflection from / toa radar transceiver, according to one embodiment.

[0065] Figure 10D is a diagram illustrating pavement markers and roadsidevegetation, according to one embodiment.

[0066] Figure 10E is a diagram illustrating pavement markers and a roadside sign,according to one embodiment.

[0067] Figure 10F is a diagram illustrating street curbs, according to oneembodiment.

[0068] Figure 10G is a side view of concrete barrier illustrating a reflection from / to aradar transceiver, according to one embodiment.50066 / 0402 Page 10 of 55

[0069] Figure 11A is a top-view diagram of two vehicles equipped with radartransceivers, illustrating range-based gating interacting with radar-reflective pavementmarkers and other target structures on a multi-lane road, according to one embodiment.

[0070] Figure 11B is a top-view diagram of two vehicles equipped with radartransceivers, illustrating range-based gating with vehicle dynamics modelling interactingwith radar-reflective pavement markers and other target structures on a multi-lane road,according to one embodiment.

[0071] Figure 11C is a top-view diagram of two vehicles equipped with radartransceivers illustrating time-based gating interacting with radar-reflective pavementmarkers and other target structures on a multi-lane road, according to one embodiment.

[0072] Figure 12A is a plot of a received radar distance vs. time, illustratingamplitude-based and range-based gating, according to one embodiment.

[0073] Figure 12B is a plot of a received radar amplitude vs. time, illustratingamplitude-based and range-based gating, according to one embodiment.

[0074] Figure 12C is a plot of filtered received distance vs. time, illustratingamplitude-based and range-based gating, according to one embodiment.

[0075] Figure 13 is a block diagram of a radar-based LDW / LKA / LKS system for avehicle, according to one embodiment.

[0076] Figure 14 is a block diagram of a radar transceiver combined with othersensors using a complimentary filter, according to one embodiment.

[0077] Figure 15 is a block diagram of a radar transceiver combined with othersensors using a complimentary filter, according to another embodiment.

[0078] Figure 16 is a block diagram of a radar transceiver combined with othersensors using a Kalman filter, according to one embodiment.

[0079] Figure 17A is timing diagram showing the lateral distance from a radartransceiver, which is mounted on the moving vehicle, to side targets along a road, accordingto one embodiment.50066 / 0402 Page 11 of 55

[0080] Figure 17B is a diagram showing the lateral distance from a radar transceiverfused with an IMU, which are mounted on the moving vehicle, to side targets along a road,according to one embodiment.

[0081] Figure 18 is a block diagram of a radar-based LDW / LKA / LKS system for avehicle, according to one embodiment.

[0082] Figure 19 is a block diagram of a radar transceiver combined with othersensors using a Kalman filter, according to one embodiment.

[0083] Figure 20 is a top view of a vehicle traveling along a roadway, illustratingvehicle-roadway geometry and the use of multiple radars, according to one embodiment.

[0084] Figure 21 is a top view of a vehicle traveling along a roadway, illustrating thevehicle-roadway geometry and the use of a single radar, according to one embodiment.

[0085] Figure 22 is a block diagram of a radar-based LDW / LKA / LKS system for avehicle, according to one embodiment.

[0086] Figure 23 is a block diagram of a radar-based autonomous lateral controlsystem for a vehicle, according to one embodiment.

[0087] Figure 24 is a block diagram of a radar-based autonomous lateral controlsystem for a vehicle, according to another embodiment.

[0088] Figure 25 is a top-view diagram of two vehicles equipped with radartransceivers interacting with radar-reflective pavement markers on a multi-lane road,according to one embodiment.

[0089] Figure 26 is a top-view diagram of a vehicle equipped with radar transceiversinteracting with radar-reflective pavement markers on a curved road, according to oneembodiment.

[0090] Figure 27 is a top-view diagram of a vehicle equipped with radar transceiversinteracting with radar-reflective pavement markers on a curved road, according to anotherembodiment50066 / 0402 Page 12 of 55

[0091] Figure 28 is a top-view diagram of a vehicle equipped with side-looking radartransceivers having multiple antennas on a road with radar-reflective pavement markers,according to one embodiment.

[0092] Figure 29 is a top-view diagram of a vehicle equipped with side-looking radartransceivers on a road with radar-reflective pavement markers, according to one anotherembodiment.

[0093] Figure 30 is a diagram of an array of radar transceivers, according to oneembodiment.

[0094] Figure 31 is a block diagram of a radar transceiver with multipletransmit / receive antennas, according to one embodiment.

[0095] Figure 32 is a block diagram of a radar transceiver with multipletransmit / receive antennas, according to another embodiment.

[0096] Figure 33 is a block diagram of a multiple radar transceivers, according to oneembodiment.

[0097] Figure 34 is a timing diagram of the output of the radar transceiver withmultiple transmit / receive antennas, according to one embodiment.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTSPreliminary Notes

[0098] Example embodiments are described below with reference to theaccompanying drawings. Unless otherwise expressly stated, the sizes, positions, etc., ofcomponents, features, elements, etc., as well as any distances therebetween, in the drawingsare not necessarily to scale, and may be disproportionate and / or exaggerated for clarity.

[0099] The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As used herein, the singularforms “a,” “an” and “the” are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It should be recognized that the terms “comprise,” “comprises,”“comprising,” “include,” “includes,” “including,” “has,” “have,” and “having,” when used in thisdocument, specify the presence of stated features, integers, steps, operations, elements,50066 / 0402 Page 13 of 55and / or components, but do not preclude the presence or addition of one or more otherfeatures, integers, steps, operations, elements, components, and / or groups thereof. Unlessotherwise specified, a range of values, when recited, includes both the upper and lower limitsof the range, as well as any sub-ranges therebetween. Unless indicated otherwise, termssuch as “first,” “second,” etc., are only used to distinguish one element from another and notto imply any relative order, placement, or ranking. For example, one element could betermed a “first element” and similarly, another element could be termed a “second element,”or vice versa. The section headings used herein are for organizational purposes only and arenot to be construed as limiting the subject matter described.

[0100] Unless indicated otherwise, the terms “about,” “thereabout,” “substantially,”“generally,” “approximately,” etc., mean that amounts, sizes, formulations, parameters, andother quantities and characteristics are not and need not be exact, but may be approximateand / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off,measurement error, and the like, and other factors known to those of skill in the art.

[0101] Spatially relative terms, such as “right,” “left,” “forward,” “rearward,” “below,”“beneath,” “lower,” “above,” and “upper,” and the like, may be used herein for ease ofdescription to describe one element’s or feature’s relationship to another element or feature,as illustrated in the drawings. It should be recognized that the spatially relative terms areintended to encompass different orientations in addition to the orientation depicted in thedrawings. For example, if an object in the figures is turned over, elements described as“below” or “beneath” other elements or features would then be oriented “above” the otherelements or features. Thus, the term “below” can, for example, encompass both anorientation of above and below. An object may be otherwise oriented (e.g., rotated 90° or atother orientations) and the spatially relative descriptors used herein may be interpretedaccordingly.

[0102] The terms “RF” and “radio” are used herein to refer to or implyelectromagnetic radiation in the frequency range that can be detected and processedelectronically. For example, the RF spectrum includes very low frequencies (VLF, e.g., about3 kHz) and may extend to just below infrared (e.g., about 300 THz). The RF spectrumincludes VLF, low frequency (LF), medium frequency (MF), high frequency (HF), very high50066 / 0402 Page 14 of 55frequency (VHF), ultra high frequency (UHF), super high frequency (SHF), and extremelyhigh frequency (EHF) bands. The RF spectrum also includes microwave and millimeter-wave bands.

[0103] The concepts and innovations described herein with reference to RF or radioradiation and / or radar can also be practiced with other types of radiation or waves,including, for example, infrared, visible, ultraviolet, laser, lidar, and sonar, with suitablemodifications to the transceivers and reflectors.

[0104] Unless clearly indicated otherwise, all connections and couplings may bedirect (without intermediaries) or indirect (with one or more intermediaries). All operativeconnections and couplings, unless clearly indicated otherwise, may be electronic viahardware or logical via software. Similarly, unless clearly indicated otherwise, all physicalconnections and couplings may be rigid or non-rigid, permanent or detachable.

[0105] Like numbers refer to like elements throughout. Thus, the same or similarnumbers may be described with reference to other drawings even if they are neithermentioned nor described in the corresponding drawing. Also, even elements that are notdenoted by reference numbers may be described with reference to other drawings.Additionally, the drawings may include non-essential elements that are included only for thesake of thoroughness. These non-essential elements may be removed entirely or left only inoutline form if drawing changes are desired to create greater clarity.

[0106] The embodiments described herein are merely examples, set forth by way ofillustration only and not limitation. Those skilled in the art will recognize in light of theteachings herein that there are alternatives, variations and equivalents to the exampleembodiments described herein and their component parts. For example, otherembodiments are readily possible, variations can be made to the embodiments describedherein, and there may be equivalents to the components, parts, or steps that make up thedescribed embodiments.

[0107] For the sake of clarity and conciseness, certain aspects of components or stepsof certain embodiments are presented without undue detail where such detail would be50066 / 0402 Page 15 of 55apparent to those skilled in the art in light of the teachings herein and / or where such detailwould obfuscate an understanding of more pertinent aspects of the embodiments.

[0108] The foregoing is illustrative of embodiments of the invention and is not to beconstrued as limiting thereof. Although a few specific example embodiments have beendescribed, those skilled in the art will readily appreciate that many modifications to thedisclosed example embodiments, as well as other embodiments, are possible withoutmaterially departing from the novel teachings and advantages of the invention. Accordingly,all such modifications are intended to be included within the scope of the invention asdefined in the claims. For example, skilled persons will appreciate that the subject matter ofany sentence or paragraph can be combined with subject matter of some or all of the othersentences or paragraphs, except where such combinations are mutually exclusive.

[0109] It will be clear to those having skill in the art that many changes may be madeto the details of the above-described embodiments without departing from the underlyingprinciples of the inventions described herein.Downward Side-Looking Radar(s) with IMU(s) and Other Sensors

[0110] Figure 1A shows two vehicles 180 and 182 on a typical roadway 300. Thevehicle 180 has side radar transceivers 116 and 117 to detect targets on the road, e.g.,pavement markers, slots in the road, grooves in the road, other vehicles, and roadsidestructures such as, for example, street curbs, road signs, concrete barriers, guardrails,mailboxes, trees, fire hydrants, lamp posts, etc. As illustrated, the radar transceiver 117 onthe vehicle 180 looks downward and to the side to see the street curb 1420 and lookssideways to view the road sign 1306.

[0111] The radar transceiver 116 on the same vehicle 180 views the pavementmarkers 445 in the center of the roadway 300 and also views the vehicle 182 along its side.The radar transceivers 116 uses a radar beam 1108 to view the pavement marker and aradar beam 1106 to view the vehicle 182, as illustrated. Similarly, the radar transceiver 117uses a radar beam 1109 to view the street curb and a radar beam 1107 to view the road sign1306. Alternatively, the radar transceiver 116 may have a single wider beam that sees bothvehicle 182 and the pavement marker 445, and the radar transceiver 117 may have a single50066 / 0402 Page 16 of 55wider beam that encompasses both the beam 1107 and the beam 1109. Whether the radartransceivers 116 and 117 have single beams or multiple beams and their beamwidths areparameters that those skilled in the art can select as desired.

[0112] The radar beams 1106, 1107, 1108, and 1109 may be fixed looking to the sidesand downward, may alternatively view the targets, may be steered between the differenttargets, or may be adjusted according to a database of roadside targets. The radartransceiver 116 and 117 may view many different roadside targets and track themsimultaneously or effectively simultaneously on or near the road via looking downward andto the side, near the side of the road via looking downward and to the side, and near the sideof the road via looking only to the side. The radar transceiver 116 on the vehicle 180 mayalso facilitate determination of a lateral distance 1811 between the vehicles 180 and 182when the vehicle 180 passes the vehicle 182. The vehicle 182 would typically block the viewof the radar transceiver 116 on the vehicle 180 from viewing far roadside targets, e.g., aconcrete barrier. The lateral distance 1811 information, when available, in addition toviewing fixed roadside targets, can provide a more robust control system.

[0113] Figure 1A also shows other sensors such as IMUs (Inertial Measurement Units)907, a GNSS (Global Navigation Satellite System) receiver 901, and vision sensors 903. Thesesensors can provide lateral and longitudinal distance information when the radartransceivers 116 and 117 do not view a target for lateral or longitude distance information.

[0114] Figure 1B illustrates the mounting of a radar transceiver 119 in the centerfront of the vehicle 180 to view the road and roadside targets from two antennas viewingboth directions (i.e., opposite lateral directions, right and left or driver-side and passenger-side). In this embodiment, the radar transceiver 119 uses radar beams 1106-1109 similarto those in Figure 1A to view the targets. Two advantages of this mounting scheme overmounting separate radar transceivers 116 and 117 on the front sides are that (1) having onlyone unit saves costs and (2) the viewing distances allows the vehicle 180 to cross a target(e.g., pavement marker 445) on or in or in-line with a lane-boundary line while still trackingthe target.50066 / 0402 Page 17 of 55

[0115] Figure 2 shows another embodiment in which multiple radar transceivers 117along with IMUs 907 can be installed at several places on the left side of the vehicle 180 andsimilarly one or more radar transceivers 116 along with IMUs 907 can be installed on theright side the vehicle 180. The radar transceivers 116 and 117 can be installed in sidemarker lights, headlights, fog lights, daytime running lights, or turn signals on the vehicle, orunder covers or within enclosures for the same, for example, for minimum impact on theexterior design. The radar transceivers 116 and 117 can be mounted on or in a bumper (e.g.,front bumper) of the vehicle 180. The radar transceivers 116 and 117 can be mountedbehind the vehicle 180 body exterior (e.g., behind a body panel) made of RF-transparentmaterial typically plastic and / or fiberglass. In another embodiment, one or more radartransceivers 117 would see pavement markers 1284 on the left and one or more radartransceivers 116 would see pavement markers 284 on the right. Also, a radar transceiver119 along with an IMU 907 can be mounted in the center front of the vehicle 180 and see inboth directions, right and left side of the vehicle 180, in view of pavement markers 284 and1284. These additional radar transceivers can provide redundancy, heading angleinformation, and more timely distance measurements. There can be many othercombinations of mounting one or more radar transceivers on the vehicle 180 to provide formore robust lateral guidance control.

[0116] The IMUs 907 around the vehicle 180 can be part of the radar transceivers116, 117, and 119 or separate standalone units. A separate IMU is also shown in the centerof the vehicle 180. The IMUs 907 can provide a change in distance measurements from thelast side target that the radar transceivers viewed. Therefore, when IMU information (i.e.,inertial measurements) is fused with the radar transceiver information, a distancemeasurement between side targets, e.g., pavement markers 284 and 1284, can becontinuously, quasi-continuously, or approximately continuously determined or determinedat discrete points between side targets. As used herein, the phrase “inertial measurement”refers to any data that an IMU can produce. Examples of inertial measurements includeacceleration, yaw rate, heading, and changes of the foregoing.

[0117] For redundancy and / or higher reliability, the radar guidance techniquesdescribed herein can be combined with other guidance techniques based on other50066 / 0402 Page 18 of 55technologies. For example, the radar transceivers 116 and 117 can be integrated with othersensors such as, for example, a GNSS receiver 901, lidar sensor 902, vision sensor 903,forward-looking radar 904, IMU 907, steering wheel angle sensor 8028, vehicle speed sensor8008, or other location sensors 905, as shown in Figure 3. As another example, theprocessing of signals from a variety of sensors, including the radar sensors described herein,can be performed by a common processor or computer (which may have multipleprocessors). Joint processing of the various sensor types can improve the performance ofany one sensor type alone. For example, the output of an onboard processor 437 using, forexample, one or more Kalman filters can provide more reliable location information 914,steering information 912, and speed information 918.Targets On the Road Surface and on the Side of Road

[0118] Figures 4A and 4B shows typical pavement markers 445 that are currentlyused on today’s roads. The pavement marker 445 shown in Figure 4A is rectangular, butpavement markers come in many different shapes and sizes. The pavement marker 445 canbe placed on top of the pavement surface, in which case they are called raised pavementmarkers (RPMs), or can be installed at or slightly below the pavement surface level (e.g.,snow-plowable markers), or below the roadway surface 300 in cut grooves, divots, or slots.The pavement markers 445 are typically installed along or in-line with lane-boundary lines,such as painted lines 305, 307, and 309 on the roadway 300, as shown in Figure 4B. Thepainted line 307 is typically a yellow center line and the painted white lines 305 and 309mark the sides of the road. The primary function of the pavement marker 445 is to reflectlight waves so that the vehicle headlights or sunlight is reflected back to the driver of thevehicle in order for the driver to visually see the location of the road lines, especially ininclement weather. The pavement markers have a visible reflector 275 on one or more sidesas shown in Figure 4A. Also, the raised pavement reflectors may act as a rumble guard whenthe vehicle crosses the roadway lines or pavement markers 445 since the marker 445 aretypically 25 mm above the roadway surface and causes the vehicle tires to impact the raisedpavement marker. The raised pavement markers 445 have had many modifications over theyears with various visible reflective properties such as cat’s eye, LED (light emitting diode)lights, lidar reflection patterns, etc. The pavement markers 445 are very reflective to visible50066 / 0402 Page 19 of 55light, and they may or may not be reflective to radio frequency (RF) radiation coming fromradar transceivers though they have traditionally not been purposefully designed for RFreflectivity. The pavement markers are used typically on roadways, but also in parking lots,shipping yards, shipping docks, and other paved and non-paved areas.

[0119] Figures 5A-5B is a front view of pavement markers, 445 and 447, respectively,illustrating the radar transceiver 116 transmitting a RF signal 1119 and receiving a RF signal1118 which is a reflection from pavement markers, 445 and 447. Figure 5A shows the radartransceiver with pavement marker 445, and Figure 5B shows another type of pavementmarker 447 with curved sides. Both pavement markers 445 and 447 contain an opticalreflector 275.

[0120] Figures 6B-6D illustrate a pavement marker 284 in which is embedded a typeof radar reflector called a dihedral corner reflector 287, as shown in Figure 6A. The dihedralcorner reflector 287 (and 286) consists of two plane reflectors intersecting along an axiswhere a dihedral angle is formed. The dihedral angle may be 90° or approximately 90° (i.e.,at a right angle, orthogonal, perpendicular, or normal). Incident waves entering the apertureso formed with a direction of incidence perpendicular to the edge (i.e., at a direction ofincidence that bisects the 90° angle between the two planes), are returned parallel to theirdirection of incidence.

[0121] Figure 6B is an isometric view of the pavement marker 284 with dihedralcorner reflectors 286 and 287 on opposite sides of the pavement marker 284. The dihedralcorner reflectors 286 and 287 can be constructed in a variety of manners. For example, thedihedral corner reflector 287 may be molded or extruded and cut into segments. Thedihedral corner reflector 287 may be, for example, formed by welding or otherwiseconnecting two slats or flat plats together, or by bending a flat plate.

[0122] Figure 6B shows the incorporation of the dihedral corner reflectors 286 and287 within a pavement marker 284 which also has an optical reflector 275 for human vision,cameras, and lidar. In this embodiment, the dihedral corner reflectors 286 and 287 areattached to the sides of the pavement marker 284 with the dihedral corner reflector 286 and287 substantially parallel to the direction of vehicle travel. The method of attachment of the50066 / 0402 Page 20 of 55dihedral corner reflector 286 and 287 to the central body portion of the pavement marker284 may be, for example, glue, adhesive, snap fit, friction fit, fasteners (e.g., screws, rivets,nails, staples), etc. Optionally, the pavement marker 284 may have a bottom plate (notshown).

[0123] A dihedral corner reflector is a passive device used to reflect radio waves backtoward the emission source directly. The dihedral corner reflectors 286 and 287 can be aright-angle metal such as aluminum, galvanized steel, copper, brass, magnesium, steel, etc.or any other RF-reflective material. The dihedral corner reflectors 286 and 287 can alsoconsist of metallic or other RF-reflective paint on a non-metallic surface, a metallic or otherRF-reflective foil, or electroplating a conductive other RF-reflective material on a non-metallic or non-RF-reflective surface such as plastic. A dihedral corner reflector can also beformed with one side being a roadway surface (e.g., asphalt, concrete), and other side beinga metallic surface, as the road surface may be sufficiently reflective to RF radiation. Forexample, when a radar signal is transmitted toward the dihedral corner reflectors 287downward from the side (right, as illustrated in Figure 6A), and the radar signal is directedat a downward angle less than 45°, e.g., 25° (where perfectly horizontal toward the horizonis considered 0° and vertical straight into the ground is 90°), and the radar source mountedlow from the ground, e.g., 0.3 m, the ground surface acts like a smooth reflective surface tothe RF waves and the road surface acts as one side for the dihedral corner reflector. Theroad surface is more reflective when wet.

[0124] The reflectivity of the road surface can be enhanced by coating portions of theroad surface with an RF-reflective adhesive (e.g., conductive epoxy) or RF-reflective paint,(e.g., copper, carbon, nickel, and silver conductive paint) below and / or around the pavementmarker. For example, MG Chemicals 841AR is an acrylic nickel conductive paint and MGChemicals 841ER is a nickel conductive epoxy. An RF-reflective adhesive may also be usedto adhere the pavement marker, which contains the other surface of the dihedral cornerreflector, to the road surface. A dihedral corner reflector can also be formed by painting orcoating pertinent sides of an existing pavement marker with perpendicular or nearlyperpendicular sides and the road surface near sides with an RF-reflective coating. A dihedral50066 / 0402 Page 21 of 55corner reflector can also be formed by painting milled grooves, divots, or cutouts in aroadway surface with RF-reflective coating.

[0125] The pavement marker 284 has an optical reflector 275 similar to currentpavement markers to provide optical reflections on the front side facing oncoming vehicles.These optical reflectors in the pavement marker can be used by vision cameras or lidarsensors for further redundancy for lateral guidance.

[0126] Figures 6C and 6D show the top and side view of the pavement marker 284.Typical dimensions of a current raised pavement markers that are installed on the roadwaysare typically 100 mm x 100 mm x 25 mm. Using these dimensions, the dihedral cornerreflectors 286 and 287 can be around 25 mm x 25 mm x 100 mm. These dimensions are fortypical current raised pavement markers; longer or higher raised pavement markers can beconstructed and installed on the roadways which can have higher radar cross-section (RCS).

[0127] The pavement marker 284 (and the other pavement markers describedherein) may be affixed to any driving surface for any vehicle, including roadways such asone-way, bidirectional or multi-lane roads, highways, thoroughfares, lanes, avenues,boulevards, parkways, pathways, byways, streets, paths, trails, and the like, as well as onbridges, in tunnels, parking lots, parking structures, shipping yards, shipping docks,transportation depots, loading / unloading bays, warehouse lots or yards, etc., whether paved(e.g., asphalt, concrete, brick, stone) or unpaved. The pavement marker 284 (and the otherpavement markers described herein) are preferably affixed to the surface so that thelongitudinal axis of a dihedral corner reflector within the pavement marker 284 is generallyparallel to the direction of vehicle travel and along one or both sides of the path of travel ofthe vehicle.

[0128] Figures 7A-7C and 8A-8C illustrate embodiments of pavement markers thatmay be mounted below the surface in rumble strips, parallel cut slots, or grooves. Figure 7Aillustrates a front side view of a rumble strip 310 which is a cut groove formed in the roadsurface 300 to produce a sound when a tire rides over the rumble strip 310 to alert thedriver. The radar transceiver 116 transmits a signal 1119 and receives a returned signal1118 from the side of the rumble strip 310. In this configuration, the side and bottom of the50066 / 0402 Page 22 of 55rumble strip form a dihedral corner reflector but with less return than a metallic cornerreflector since the pavement material is typically non-metallic.

[0129] Figure 8A shows a pavement marker 394 placed inside a rumble strip 310. Inthis embodiment, the returned radar signal 1118 will be altered by the presence of thepavement marker 394. The radar return-signal characteristics for this arrangement aredifferent than an empty rumble strip 310.

[0130] Figure 7B shows a top view of rumble strips 310 along a roadway with apainted line 910. Figure 8B shows a top view of the pavement marker 394 installed inrumble strips 310 along a roadway with a painted line 910. Figure 7C shows the top view ofslots 312 cut in the highway. Here, the radar transceiver 116 views the slots 312 for moretime, thus allowing the onboard controller to determine the lateral position and / or thevehicle heading based on taking many lateral distance measurements from the long slot 312.Figure 8C shows another embodiment where the pavement marker 394 is installed in theslots 312 where existing pavement markers are installed so that snow plows or otherequipment will not tear them off the roadway surface. To improve the reflectivity of theseslots, rumble strips, or grooves, the milled rumble strips may be made to form dihedralcorner reflectors by use of sprayed conductive paint. Figure 7A shows the milled rumblestrip 310, having coated sides and bottom with conductive paint to increase the reflectivityof the rumble strip. The longer length milled highway slots 312 as shown in Figure 7C canbe painted with conductive paint along the entire length of the rumble strip 312 to providea larger RCS for a radar transceiver to view.

[0131] Figure 9 shows a front view of an installed snow-plowable pavement marker1290 and the radar transceiver 116. A snow plow rides on the top of sides 1206 and 1208which are typically metal. An optical reflector 1275, which is typically made of plastic, isinstalled in the middle of the frame of the snow-plowable pavement marker 1290 so thatdrivers or vision sensors can see the marker 1290. The radar transceiver 116 transmitssignals 1119 to the metal surface 1285 and receives signals 1118 back to a radar transceiver116 from one side of the pavement marker 1290. The radar return signal 1118 is strongerfor the pavement marker 1295 than the other raised pavement markers described earliersince the pavement marker 1295 is made of metal and the some of the sides are at right50066 / 0402 Page 23 of 55angles. Snow-plowable markers 1290 may be mounted in a center or interior lane line to beviewed by radar sensors mounted on vehicles in two different lanes. The snow-plowablemarker 1290 is usually mounted in an interior road line. When the snow plowable marker1290 is covered with snow, the marker 1290 is not visible to the human eye, cameras, orlidar. However, the marker 1290 is visible to the radar transceiver 116 despite beingcovered with snow.Concrete Barriers, Curbs, Streets, Road Edges, and Signs

[0132] Figures 10A-10F illustrate other structures along a roadside. Figure 10Ashows a sidewalk 1422 and a curb 1420 next to a road surface 300. The radar transceiver116 transmits signals 1119 to the curb 1420 and receives signals 1118 from the curb 1420.The curb 1420 acts like a dihedral corner reflector but has lower reflectivity than a metallicsurface. The reflectivity is greater if the concrete is wet.

[0133] Figure 10B shows another surface of the concrete curb 1424. In oneembodiment, the radar transceiver 116 could alter its beam pattern and its beam angle todetect the distance from an inside curb surface. For example, transmit signals 1119 areaimed at bottom of the concrete curb 1424, the top of the concrete curb 1424, and at thecenter of the concrete curb 1424 to get the best reflective return signals 1118.

[0134] Figure 10C shows a front view of a concrete barrier 1426 and the radartransceiver 116. In this embodiment, the radar transceiver 116 can treat the concretesurface as either an angle reflector along the bottom of the concrete barrier 1426 or as a sidereflector along the flat side surfaces or both. The radar transceiver can adjust the height andbeam angle at 45 degrees for the bottom angle of the concrete barrier 1426 and then changethe beam angle to 90 degrees to see side the surface of the concrete barrier 1426.

[0135] Figure 10D shows the roadway 300 with pavement markers 284 on one sideand a road edge 305 and off-road surface 1305 on the other side. In this embodiment, a radartransceiver can transmit a certain angle with a certain beamwidth to detect the road edge.Figure 10E is similar to Figure 10D, but here the bottom of a sign post 1306 can be detectedby the radar transceiver. Figure 10F shows an isometric view of a center curb 1928 and astreet side curb 1420. The radar transceiver 116 (not shown in the figure) may view the50066 / 0402 Page 24 of 55structures as corner reflectors to receive strong return signals. Figure 10G shows a side viewof a guardrail 1432 that can be easily detected by the radar transceiver 116 if the radartransceiver is aimed approximately directly at the metallic guardrail 1432.

[0136] There can be many items or markers along the roadside that have certainradar characteristics that allows an onboard controller to classify or recognize marker-basedfactors such as return signal strength, the number of markers, and previously recorded data(e.g., in a database) for those markers (e.g., approximate location, distance, expected RCScharacteristics, etc.).Processing Radar Transceiver Signal With IMU Information

[0137] Range-based gating, time-gating, amplitude gating, and other (e.g., Kalman)filtering can be employed to ignore reflection signals from objects that are not side targetsof interest. These are several methods of gating or filtering the received signal that can beutilized to detect the pavement markers or other target structures 284 as shown in Figures11A-11C.

[0138] In Figure 11A, a range gate 3030 is illustrated, and the range is gated based onthe expected width of roads and lanes in a database. Lanes are typically 2.7 to 4.6 m (9 to15 ft.) wide. The vehicles 180 and 182 with radar transceivers 116 and 117 view thepavement markers and other target structures 284 and 284’ (a marker structure) which isdenoted in each lane, but only labeled for the top lane. Recorded data along with locationinformation (e.g., GPS-based or GNSS-based) can be used to determine an approximatelocation of a vehicle in terms of street, lane, etc. With this information and the expected lanewidth or expected distance to the target structure, a suitable range gate can be determined,as illustrated in Figure 11A.

[0139] In Figure 11B, a Kalman filter tracks the pavement markers and targetstructures based on a vehicle lateral movement model, vehicle speed, and expected targetstructure spacings from a navigational database. The range gate 3030 can be smallerbecause of the known vehicle model and the Kalman filter, and more filtering of other roaddebris can therefore be achieved.50066 / 0402 Page 25 of 55

[0140] In Figure 11C, a time gating 3083 on the expected pavement marker 284 orother target structure 284’ is based on the vehicle speed and known spacings of the targetstructures from a database.

[0141] Figure 12A-12C illustrate radar transceiver processing and filtering of bothreceived signal amplitude (denoted in dB) and range to the target to obtain a more reliabledistance to the target structure, and no distance if there is no marker visible to the radartransceiver. Figure 12A shows the radar-measured distance vs. time to the strongest targetswith clutter from a vehicle to the side targets on the side of the road while the vehicle ismoving along the roadway. The side targets include three RF-reflective markers 1100, 1102,and 1104. Figure 12B shows the radar amplitude vs. time for the same setup. The three RF-reflective markers 1100, 1102, and 1104 are the highest returned signal strength as seen onthe Figure 12B. An amplitude threshold 1106 can be set for filtering of the radar markerdata from the clutter. With both amplitude filtering and range gating, Figure 12C shows theresults where the radar distance to the three markers 1100, 1102, and 1104 are clearly notedwith the clutter removed.

[0142] These techniques can have static range gating and amplitude threshold valuesor the thresholds and range can be dynamic (e.g., determined from previously collected radardata). The range, time, and amplitude can be updated with proper gates. Range gates aretypically based on the road width, lane widths, and the number of lanes. A map database canprovide that information based on the location of the vehicle using GPS, GNSS, or othernavigational sensor. Time gating between pavement markers can be based on the markerspacing and vehicle speed where time = marker spacing / vehicle speed. The received signalstrength (amplitude) gate can be based on the average received signal strength overprevious (e.g., the last few) target passings plus a pre-determined threshold value.

[0143] Figure 13 is a block diagram of a lateral guidance system 1850 that can warnthe driver if the vehicle is leaving its lane with visual, audible, and / or haptic warnings. If nocorrective response is taken by the driver, the system 1850 may automatically take steps tomaintain the vehicle in its lane. This embodiment represents a Lane Departure Warning(LDW), Lane Keeping Assist (LKA / LKS), or Lane Centering Assist (LCA) system. The radartransceiver 116 transmits signals 1119 in the direction of the side target, e.g., pavement50066 / 0402 Page 26 of 55marker 284, and receives signals 1118 reflected back from the side target. The distance dRbetween the side target and the radar transceiver 116 is measured by the radar transceiver116 using well known radar techniques and provided to a lateral guidance controller 830, asshown in Figure 13. In addition to the radar input, the guidance controller 830 may haveadditional inputs from a vehicle speed sensor 8008, a steering wheel angle sensor 8028, andthe IMU 907. The vehicle speed sensor 8008 provides forward vehicle velocity. The IMU907 provides the vehicle body’s acceleration, angular rate, and sometimes the orientation ofthe body, using a combination of accelerometer, gyroscope, and sometimes a magnetometer.If the vehicle 180 travels too close to or too far away from the side target, indicating a lanedeparture, the guidance controller 830 may transmit a sound signal to a speaker 824 (orplural speakers) to alert the driver on a lane departure and / or cause a display 826 to alertthe driver of the lane departure visually and / or cause vibration or other haptic stimulationto the driver. If no driver response is detected, the controller 830 may control the steeringmechanism 802 to control the wheels 804 to keep the vehicle in the lane. The guidancecontroller 830 may not generate an alert or take action if a turn signals 822 is turned on tosignal a lane change or turn in the direction of the detected lane departure. Anotherembodiment similar to the system shown in Figure 13 can implement Lane Centering Assist(LCA). An LCA system controls steering of the vehicle 180 to keep the vehicle in the lanewithout the driver’s effort, but the system can be overridden by the driver.

[0144] Figures 14-16 show an IMU 907, which measures the acceleration in x, y, andz directions and the yaw, pitch and roll rates. One or more IMUs 907 can be mounted on thevehicle 180. The IMU 907 may also contain a magnetometer to measure the orientation ofthe vehicle 180 related to Earth’s magnetic poles. One IMU 907 mounted near the radartransceiver measures the yaw rate ψ(dt) and lateral acceleration aX of the vehicle’smovement. The IMU 907 also measures pitch and roll of the vehicle’s movement, which aretaken into account for lateral acceleration measurements. When the vehicle 108 passes aside target, the side-looking radar transceiver 116 on the vehicle provides lateralmeasurements to the side targets with a designated RF-reflectivity. When the vehicle passesno side targets (targets that are lower than a designated RF-reflectivity) or between side50066 / 0402 Page 27 of 55targets, the IMU 907 provides changes to the lateral movement of the vehicle by measuringvehicle’s lateral acceleration aX and yaw rate ψ(dt).

[0145] Figure 14 shows an embodiment for combining the radar measurement dXfrom the radar transceiver 116 and the yaw rate from the IMU 907 using a complementaryfilter. In Figure 14, sensor fusion for combining sensor data uses a complementary filter1908. The yaw rate from a gyroscope in the IMU 907 is integrated via an integrator 909 toprovide a yaw angle and high-pass filtered via HPF 1157. The outputs of the radartransceiver 116 at two timed intervals, tR apart, are dx1 and dx2. The two values aresubtracted from each other (dx1 – dx2) to form an estimated vehicle deviation angle ψ(radar)relative to side targets that represent the path trajectory. The output from this subtractionis divided by the side target spacing, converted to an estimated vehicle deviation angle ψ indegrees, and low-pass filtered by the low-pass filter (LPF) 1159. The complementary filter1908 combines the yaw rate from the IMU 907 with the radar-measured deviation angle.The complementary filter 1908 takes the high-frequency updates of the yaw rate with thelow-frequency updates of the radar-measured vehicle deviation angle relative to the sidetargets, e.g., the pavement markers 284, and provides a more accurate vehicle deviationangle (i.e., vehicle heading error), the output of the complementary filter 1908. Thecomplementary filter 1908 has a transfer function of the form:ψ = [1 − G(s)] ∗ (ψ(dt)s) + G(s) ∗ ψ(radar)where ψ(dt) / s is thethe yaw rate and whereψ(radar) is the measured vehicle deviation angle by the radar transceiver 116. Theintegrator blocks 909 are represented as “1 / s” in the Laplace format. The LPF 1159 withtransfer function G(s) = (Kp*s + Kl) / (s2+ Kp*s+ Kl) filters out the radar measured yaw angle.The high-pass filter (HPF) 1157 with transfer function 1-G(s) filters out the integrated yawrate (ψ(dt) / s). In the complementary filter 1908, the final estimated deviation angle ψ ofthe vehicle relative to the side targets is computed by adding the low-frequency componentof116 measurements and the high-frequency componentinertial sensor IMU 907. If the vehicle deviation angle is estimated as zero, then the vehicleis parallel to the pavement markers.50066 / 0402 Page 28 of 55

[0146] Another embodiment (not shown) combines two radar measurements dx1 anddx2 from the front and rear radar transceivers 116 and 1016, respectively, shown in Figure20, and the yaw rate from the IMU 907 using a complementary filter. The samecomplementary filter may be used as shown in Figure 14, but the two radar transceivers areused to provide the vehicle heading error instead of using the same radar transceiver 116.

[0147] Figure 15 shows how an IMU 907 can be combined with the radar transceiver116 to provide a continuous side distance measurement using a complementary filter withina controller or computer. The IMU 907 provides fast updates, while the radar transceiver(s)116 provides updates when passing side targets, and combining the two sensors provides acontinuous or nearly continuous lateral measurement between the vehicle 180 and sidetargets.

[0148] In a curve, there is centrifugal acceleration which is taken into account withinthe block diagram of Figure 15. The centrifugal acceleration in a curve on the vehicle 180 isac = (vehicle velocity)2 / R. The radius R of the curvature of the road is equal to the vehiclevelocity divided by the yaw rate or R = v / ψ(dt). The centrifugal acceleration ac is equal tovehicle velocity multiplied by the yaw rate or ac = v * ψ(dt). The lateral acceleration axc isequal to the measured lateral acceleration minus acceleration or axc = ax – ac.The lateral distance dX from the RF-reflective pavement markers at any time is equal to theradar measurement dR plus the distance changes based on lateral acceleration axc during theradar measurement updates: dx = d0 + vx * Δt + 0.5 * axc * (Δt)2 where vx is derived from theaxc integration and Δt is time between samples. The radar transceiver measurement d0 takesinto account the geometry of the radar transceiver mounting angle and distance from theground, and the lateral distance dX between the RF-reflective pavement markers 284 and theradar transceiver 116 is derived from the radar transceiver 116 measurement updates d0and the changes in lateral distance based on the measurements in the IMU 907 during thespacing between the side targets. The changes in the lateral distance are based on theintegration of the lateral acceleration twice as shown in Figure 15 with integrator units 909.The complementary filter uses constants K1, K2, and K3 and the integrators 909 to fuse theradar distance d0 with the corrected acceleration axc. The IMU 907 also measures yaw rateangle ψ(dt). Integrating the yaw rate angle gives the change in vehicle deviation angle λ. In50066 / 0402 Page 29 of 55a curve, the vehicle deviation angle λ may be changing, but the outcome of the control systemmaintains the vehicle a constant or approximately constant distance from the pavementmarkers 284.

[0149] Figure 16 shows a block diagram of one embodiment for combining the radartransceiver 116 measurements, from different roadside targets, at about the same time withdata from other sensors such as a vehicle speed sensor 8008, IMU 907 and a wheel anglesensor 8028 using a Kalman filter within a processor 830. The inputs to the processor 830are the vehicle forward velocity, v, from the vehicle speed sensor 8008, acceleration and yawrate ψ(dt) values from the IMU 907, wheel angle δ from the wheel angel sensor 8028, andradar distance measurements from the radar transceiver 116. The output of the processor830 is the lateral distance x to the roadside targets, e.g., RF-reflective pavement markers 284.

[0150] Figure 17A-17B show the output of the radar transceiver 116 measuringlateral distance from the vehicle 180 to the side targets, e.g., pavement markers 284, withand without the IMU 907. In this embodiment, the side targets are spaced on a side of theroad surface. Figure 17A shows the radar transceiver 116 measuring the distance from thevehicle 180 to the side targets or zero when no substantial target is passed. In Figure 17B,using the complementary filter as shown in Figure 15 or the Kalman filter as shown in Figure16, the output from the filters is a continuously lateral measurement from the vehicle 180 tothe roadside targets or anticipated future targets.

[0151] Figures 18-19 illustrate several embodiments of lateral guidance andnavigation schemes. Figure 18 is a block diagram of a guidance / navigation system 850 thatwarns the driver if the vehicle leaves its lane with visual, audible, haptic, and / or vibrationwarnings and also provides navigational guidance information to the driver. Thisembodiment represents a Lane Departure Warning (LDW) and Lane Keeping Assist(LKA / LKS) systems integrated with a navigational system using radar-based targets todefine an absolute navigational point. The radar transceiver 116 transmits a signal 1119 inthe direction of a side target 284 and receives a signal 1118 reflected back from the targetstructure 284. The distance between the target structure 284 and the radar transceiver 116is measured by the radar transceiver 116 using well known radar techniques and providedto the lateral guidance controller 830 shown in Figure 18. The radar transceiver 11650066 / 0402 Page 30 of 55measures the distance dR from the target structure 284. The actual lateral distance from thevehicle to the pavement marker 284 is related the radar’s measured distance dR and thegeometry of the mounting of the radar transceiver 116 attached to the vehicle. The radartransceiver 116 distance can be fused with a GNSS sensor 901, IMU 907, and a markerdatabase 8006. The marker database 8006 contains the coordinates (e.g., GNSS) of thelocation of the marker 284 and, optionally, the marker’s radar characteristics. When theradar transceiver 116 passes the marker 284, the radar sensor will know the distance dR tothe marker 284. The controller 820 is programmed to use the current GNSS sensor 901 andIMU 907 information on the current vehicle location and select the nearest marker in thedatabase 8006 or the nearest marker that acceptably matches the radar characteristic andlocation information provided by the radar transceiver 116 and the GNSS sensor 901,respectively. Once a match is found, the exact location information from the database 8006is used to update the navigation information. The guidance controller 830 fuses thesesensors (GNSS 901, IMU 907, vehicle speed 8008, and radar 116) using, for example, anextended Kalman filter 830 as shown in Figure 19. The output of the extended Kalman filter830 is more accurate position and speed information under many external conditions, e.g.,blockage of navigation / positioning satellites when in the tunnel. If the global positioning(e.g., GNSS) satellites are blocked, the IMU sensor 901 can provide relative information onthe vehicle location and the radar transceiver 116 would provide absolute information everytime the vehicle passes a marker 284.

[0152] With the fusion of these types of sensors, the controller 830 in Figure 18 canprovide an early warning if the vehicle leaves the lane. If the vehicle travels too close to ortoo far away from the target 284, indicating a lane departure, the guidance controller 830can cause a sound to be emitted by a speaker 824 (or plural speakers) to alert the driver ofthe lane departure, cause the display 826 to alert the driver of the lane departure visually,and / or cause vibration of the driver seat, steering wheel, or other vehicle part. The guidancecontroller 830 can disable lane-departure alerts if a turn signal 822 is turned on signaling anintent by the driver to initiate a lane change or turn in the direction of the detected lanedeparture. Whether or not lane-departure alerts are enabled or disabled by a prior turnsignal can be a configurable setting set by the driver, factory, or service technician. The50066 / 0402 Page 31 of 55guidance controller 830 can also be configured to activate the turn signal indicator (e.g.,blinker) on the side of the vehicle corresponding to the detected lane departure when a lanedeparture is detected. That can serve as a warning to other drivers, vehicles, pedestrians,cyclists, etc. that a lane departure is occurring or might occur even if the driver has notactuated a turn signal. In this way, safety can be enhanced for others as compared to the casein which no lane-change indication is provided.

[0153] Figure 18 also shows a navigational display 888 to provide the driverinformation regarding the road the vehicle is travelling on and instructions to follow to getto the driver’s destination. The guidance system 850 can warn the driver if the vehicle isleaving its lane with visual, audible, and / or haptic warning, and, if no corrective response istaken by the driver, the system 850 can automatically take steps to maintain the vehicle inits lane. The database 8006 in Figure 18 can be upgraded via the Internet 500 to keep thedatabase 8006 current with updates reflecting road changes and maintenance.

[0154] Figure 19 shows one embodiment of the extended Kalman filter (EKF) that canbe used in the guidance controller 830 for determining guidance information to be providedto a driver. The IMU 907, vehicle speed 8008, radar transceiver 116, GNSS 901, and database8006 are filtered together using the EKF, which may be incorporated in the guidancecontroller 830, to provide vehicle location information x and y.Front and Rear Radars for Lateral Distance and Vehicle Heading from Side Targets

[0155] Figure 20 is a top view of diagram illustrating a vehicle 180 travelling along aroad 300. The dynamics of the vehicle 180 shows that the vehicle 180 is travelling in the ydirection along a lane with a velocity of v. The wheel angle δ of the front wheels 804 is shownfrom the vehicle 180 going straight ahead. The x direction is the lateral movement of thevehicle 180. The yaw angle of the vehicle 180 is nonzero travelling around a curve ascompared to straight ahead. The vehicle 180 has a radar transceiver 116 mounted on theside of the vehicle 180 measuring a distance dx1 between one RF-reflective pavement marker284 and the radar transceiver 116. The spacing 194 of the RF-reflective pavement markers284 is denoted as a distance dm. Thus, the radar transceiver 116 measures the passing RF-reflective pavement markers 284 every time the vehicle 180 passes a marker 284.50066 / 0402 Page 32 of 55

[0156] Figure 20 also shows another radar transceiver 1016 mounted similarly as theradar transceiver 116 but on the rear of the vehicle 180 on the same side as radar transceiver116. Likewise, two radar sensors can be mounted on the other sides and measuring distancefrom the RF-reflective pavement markers (not shown). Radar transceiver 116 measuresdistance dx1from one of the RF-reflective pavement markers 284, and at a similar time or assoon as it passes a RF-reflective pavement 284, the radar transceiver 1016 measures thedistance dx2 to the another of the RF-reflective pavement markers 284. Besides providingthe distances from radar sensor to the RF-reflective pavement markers 284, a vehicleheading angle relative to the RF-reflective pavement markers can be derived by the formula:ψ= tan-1((dx1-dx2) / L)where dx1 is radar measurement taken from the radar transceiver 116, where dx2 is the radarmeasurement taken from radar transceiver 1016 at about the same time, and where L is thelength between the radar transceivers 116 and 1016. The lateral distance dx1 and theestimated vehicle heading angle ψ of the vehicle 180 can be determined from these two radardistance measurements. One embodiment has two radar transceivers spaced the same ormultiple lengths of the pavement markers 284 separation distance dm 194 so that the radartransceiver 116 passes a pavement marker 284 at about the same time radar transceiver1016 passes another pavement marker 284. This specific radar transceivers spacing Lminimizes concerns that vehicle motion might cause issues in measuring the vehicle headingangle ψ. For instance, if the pavement markers separation distance 194 is 1.5 meters apart,then the radar transceivers should be spaced at 1,5, 3.0, 4.5 or 6.0 meters apart for both radartransceivers to view pavement markers 284 at approximately the same time.

[0157] The Stanley controller uses the vehicle heading angle ψ and the position errore(t) (desired distance -radar measured lateral distance dx1) at the front of the vehicle tocontrol the steering wheel angle δ. The formula for the Stanley controller is as follows: δ(t)=ψ(t)+tan-1(ks*e(t) / (ksv+vy(t))where δ(t) is the steering wheel angle command a certain time t, ψ(t) is the vehicle headingangle related to the path trajectory, e(t) is the position error related to desired path, vy(t) is50066 / 0402 Page 33 of 55the vehicle velocity, and ks and ksv are constants that can be tuned for desired performance.There are enhancements to the Stanley controller, e.g., preview information, that can providebetter performance. Those enhancements are also possible with the radar transceiver andRF-reflective pavement markers described herein.

[0158] Figure 21 is a top view of another embodiment illustrating a vehicle 180travelling along the road 300. The dynamics of the vehicle 180 shows that the vehicle 180 istravelling in the y direction along the lane with a velocity of v. The wheel angle δ of the frontwheels 804 is shown from the vehicle 180 going straight ahead. The x direction is the lateralmovement of the vehicle 180. The yaw angle of the vehicle 180 is nonzero travelling aroundthe curve versus straight ahead. The vehicle 180 has a radar transceiver 116 mounted onthe side of the vehicle measuring a distance dx2 between one RF-reflective pavement marker284 or side target and the radar transceiver 116. The spacing 194 of the RF-reflectivepavement markers 284 is denoted as a distance dm and stored in a database for side targetsthat are not spaced equally. The radar transceiver 116 measures the passing RF-reflectivepavement markers 284 every time the radar transceiver 116 passes a marker 284. The timetR between pavement markers is derived from the set marker 284 separation distance dmstored in a database divided by the average vehicle velocity v during the transition betweenpavement markers 284: tR = dm / v(average). For example, if the vehicle 180 is travelling ata constant velocity of 25 m / s, and the distance between markers is 3 m, the update time ofthe radar transceiver distance measurements tR is (3 m / (25 m / s)) or 120 ms.

[0159] Figure 21 also shows the forward movement of the vehicle 180 from oneposition to another position 180’ shown in the dash lines. The same radar sensor 116’ a time(tR) later will measure the lateral distance dx1 to the next pavement marker 284. Besidesproviding the distances from radar sensor to the pavement markers 284, a deviation anglebe derived by the formula: ψ= sin-1((dx1-dx2) / dm)where dx2 is radar measurement taken at tR, the time between pavement markers, before dx1,measurement, where dx2 is the radar measurement taken at current time, and where dm isspacing of the pavement markers. The lateral distance dx of the vehicle 180 and the vehicle50066 / 0402 Page 34 of 55deviation angle ψ relative to the pavement markers 284 can be determined from takingmultiple radar distance measurements from a number of pavement markers 284.

[0160] The distances dx1 and dx2 between the pavement markers 284 and the radartransceivers 116 and 1016 are measured by the radar transceivers 116 and 1016,respectively, using well known radar techniques and provided to a lateral guidancecontroller 830, as shown in Figure 22. The radar transceivers 116 and 1016 or an associatedprocessor (which may be a general-purpose processor, signal processor, digital signalprocessor (DSP) or the like and which may implement its processing in software, hardware,firmware, or some combination of the foregoing) measures the distances dx1 and dx2,respectively, from the pavement markers 284. The actual lateral distance from the vehicle180 to the pavement marker 284 is related the radar’s measured distance dx1 and geometryof the mounting of the radar transceivers attached to the vehicle 180. The desired controlleddistance dC to maintain the vehicle 180 in the center of the lane or at any predetermineddistance from the pavement marker 284 and the radar-measured distances dx1 and dx2 areinputs to a lateral guidance controller 830. In addition to the radar input, the guidancecontroller 800 has additional inputs from the vehicle speed sensor 8008 and the IMU 907.The vehicle speed sensor 8008 provides forward vehicle velocity. The IMU 907 provides thevehicle body’s acceleration, angular rate, and the orientation of the body, using acombination of accelerometer, gyroscope, and sometimes a magnetometer. In thisembodiment, the lateral guidance controller 830 accepts the radar measurements andgyroscope readings to obtain position error relative to the pavement markers, the angularvehicle deviation of the vehicle relative to pavement markers, the yaw rate, and vehiclespeed. The lateral guidance controller can accept other sensor information, e.g., lateralacceleration and compass direction to provide for a robust lateral guidance controller. Thelateral guidance controller 800 sends a signal to the steering motor or controlled device inthe steering mechanism 802. The steering mechanism 802 controls the steering wheels 804.The steering wheels 804 and steering mechanism 802 are for road vehicles, but the vehiclecould be an off-road vehicle and the controller could utilize hydraulic actuators. The desiredlateral distance the vehicle 180 maintains from the reflector pavement marker 284 is50066 / 0402 Page 35 of 55maintained by controlling the steering wheels 804. Note that in some cases there could bejust a single steerable wheel, e.g., bike, trike, three-wheeled vehicle, etc.

[0161] The radar transceivers 116 and 1016 may generate a continuous radartransmission signal and / or monitor continuously for a reflection, or the radar transceivers116 and 1016 may periodically and repeatedly transmit a discrete radar signal (e.g., a pulse)and monitor for reflections, depending on the type of radar techniques employed. The radartransmission signal is generally directed partially downward and sideways from the vehicle180, and the pavement marker 284 is designed to reflect the incident radar signal partiallyupward and sideways back toward the radar signal source (i.e., the transceiver 116 and / or1016) on the vehicle 180.

[0162] The radar transceivers 116 and 1016 and / or the lateral guidance controller830 may filter reflections based on range and / or magnitude to distinguish the target fromother objects. The targets (e.g., pavement markers 284) are typically within a known rangefrom the vehicle. Since the radar cross section of the dihedral corner reflector 286 is largefor automotive frequencies and since the pavement marker 284 is in close range of the radartransceivers 116 and 1016, the magnitude of the returned signal is typically notably highcompared to the road surface and other road objects, e.g., dead animals, cardboard, rocks,beverage cans, etc. when a dihedral-corner-reflector enhanced pavement marker is used.

[0163] Figure 22 is a block diagram of a lateral guidance system 950 designed tofollow lane markings with no human driver (i.e., fully autonomous steering). The radartransceivers 116 and 1016 are mounted on a side of the vehicle near the front and rear ofthe vehicle 180, respectively. In this example, the side target is a dihedral-corner-reflector-augmented pavement marker 284 mounted on the roadway lane marking or within a setdistance from the lane marking on the roadway 300. The pavement marker 284 can be araised pavement markers or installed at or below the pavement level. The radar transceiver116 transmits a signal 1119 in the direction of the pavement marker 284 and receives asignal 1118 reflected back from the pavement marker 284 via its dihedral corner reflectortherein. The orientation of the pavement marker 284 is such that its dihedral cornerreflector(s) is(are) approximately parallel to the lane markings and the direction of the50066 / 0402 Page 36 of 55vehicle travel. This orientation provides the maximum returned signal when the radartransceiver 116 and 1016 passes by the pavement markers 284.

[0164] Other radar processing techniques, besides filtering on magnitude and range,can be used to distinguish the pavement markers from the road surface and other objects.For example, polarization can distinguish a dihedral corner reflector from the road surfaceand other objects on or near the road. Also, fixed or approximately fixed spacing of thepavement markers can be used to filter out false signals based on time. For example, areflection arriving between two pavement markers may be excluded as a probable falsetarget. As described above, Kalman filter, complimentary filer, or other known filteringtechniques can filter out reflection signals based on the fixed spacing / time of the pavementmarkers and / or other known or predictable attributes of the pavement markers. Thepavement markers 284 are therefore distinguishable from other objects, and the manypavement markers 284 on a driving surface may be uniformly identical or similar withsimilar dihedral corner reflectors and similar RCSs.

[0165] Figure 23 is a block diagram of a lateral guidance control system 970 thatcontrols the steering of the vehicle to keep the vehicle in its lane. This embodimentrepresents an autonomous lateral control system. The front and rear radar transceivers1160 and 1016, respectively, transmit signals in the direction of targets and receive signalsreflected back from the targets. The distances dx1 and dx2 between the targets and the radartransceivers 1160 and 1016 are measured by the radar transceivers 1160 and 1016,respectively, using well known radar techniques. The output of the radar transceiver 1160,which also has the IMU 907 as an input sensor, provides the lateral guidance controller 8004the measured distance dx and the vehicle deviation angle ψ relative to the target-defined pathtrajectory. The radar transceiver 1160 in Figure 23 (or associated processor(s)) computethe lateral distance dX and yaw angle ψ relative to the pavement markers using inputs fromthe IMU 907, radar transceiver 1016, vehicle speed 8008, and wheel angle 8020. The desiredcontrol distance dC from the target is subtracted from the radar measured distance dX todetermine an error dERROR, which is input to the lateral guidance controller 8004. In additionto distance from the target, the deviation angle ψ of the vehicle relative to the targets is alsodetermined and sent to the lateral guidance controller 8004. Vehicle speed 8008 and road50066 / 0402 Page 37 of 55geometry preview information 8006 are also sent to the lateral guidance controller 8004.There may be other sensors, e.g., other IMUs, GPS, vision cameras, laser radar, etc. (notshown) that can be used to augment the lateral control system 970.

[0166] The output of the guidance controller 8004 controls a steering mechanism8020 via a desired steering wheel command dCMD, which controls the angle of the wheelsand, along with the vehicle dynamics 8040, controls the lateral position, dXACT, of the vehiclein the lane in relation to the targets. The lateral guidance controller system 970 can employone or more of many different control algorithms to control the steering of the vehicle alongthe pavement markers. The desired control distance dC from the target may be apredetermined distance based on assumed lane width, vehicle width, and radar transceiverlocation on the vehicle. Alternatively, the desired control distance dC from the target may bedependent on the approximate location of the vehicle to account for different lane widthsand / or different target locations on different roads. For example, a database may store a setof desired control distances for different roads or geographic locations, and the databasemay be queried based on the geographic location of the vehicle, such as determined, forexample, by GPS, sufficient to determine which road or set of nearby roads the vehicle istraveling on. Additionally, the desired control distance dC from the target may be dependenton the vehicle’s direction of travel, which may be determined from compass sensors and / orGPS measurements, as lane widths and / or target locations may not be the same in differentdirections on the same road. The desired control distance dC may be offset from the true lanecenter or varied slightly (e.g., with a small random component) to distribute tire wear acrossthe lane more evenly.

[0167] Figure 24 is a block diagram of a lateral guidance control system 960 whichcontrols steering of the vehicle to keep the vehicle in its lane. This embodiment representsan autonomous lateral control system. The radar transceivers 116 and 1016, mounted onthe front and rear of the vehicle, respectively, transmit signals in the direction of targetstructures and receive signals reflected back from the target structures. The distancesbetween the target structures and the radar transceivers 116 and 1016 are measured by theradar transceiver using well known radar techniques and provided to the lateral guidancecontroller 8004 shown in Figure 24. The radar transceiver 116, which is mounted on the50066 / 0402 Page 38 of 55front of the vehicle, measures the distance dx1 from a target structure. The radar transceiver1016 measures the distance dX2 from a different target structure. The desired controldistance dC from the target structure is subtracted by the radar measured distance dX1 todetermine the cross-track error, dERROR, which is inputted in the lateral guidance controller8004. Vehicle speed 8008, location and radar characteristic database 8006, IMU 907, visionsensor 903, GPS sensor 901, and wheel angle 8028 may be sent to the lateral guidancecontroller 8004. There may be additional sensors, e.g., multiple IMUs, RTK-GPS ( Real-TimeKinematic Global Precision System), multiple vision cameras, laser radar, etc. (not shown)that can be used to augment the lateral control system 960.

[0168] The output of the guidance controller 8004 controls a steering mechanism8020, which controls the angle of the wheels and, along with the vehicle dynamics 8040,controls the lateral position of the vehicle in the lane in relation to the pavement markers.The two radar transceivers 116 and 1016 provide cross-track error, dERROR, and headingangle error based on the front and rear distance measurements to the markers. The lateralguidance controller system 960 can have many different embodiments for controlalgorithms to control the steering of the vehicle along the pavement markers. Someexamples are fuzzy control algorithms, proportional integral derivative (PID) controlalgorithms, adaptive PID control algorithms, Stanley control algorithms, model predictivecontrol (MPC) control algorithms, neural network control algorithms, modified sliding modecontrol algorithms, multi-rate control algorithms, and linear quadratic regulator (LQR)control algorithms.

[0169] The desired control distance dC from the target structure may be apredetermined distance based on assumed lane width, vehicle width, and radar transceiverlocation on the vehicle. Alternatively, the desired control distance dC from the targetstructure may be dependent on the approximate location of the vehicle to account fordifferent lane widths and / or different target structure locations on different roads. Forexample, a database may store a set of desired control distances for different roads orgeographic locations, and the database may be queried based on the geographic location ofthe vehicle, such as determined, for example, by GPS, sufficient to determine which road orset of nearby roads the vehicle is traveling on. Additionally, the desired control distance dC50066 / 0402 Page 39 of 55from the target structure may be dependent on the vehicle’s direction of travel, which maybe determined from compass sensors and / or GPS measurements, as lane widths and / ortarget structure locations may not be the same in different directions on the same road. Asnoted above, the desired control distance dC may be offset or varied to distribute tire wearon the road in a less concentrated way.

[0170] In another embodiment, the desired control distance dC may be dynamicallydetermined as the vehicle travels down the road by measuring distances to different,laterally displaced target structures. For example, the lane width can be indirectly measuredby (a) measuring distance(s) to target structures marking an adjacent lane boundary on agiven side of the vehicle, (b) measuring distance(s) to target structures marking the next laneboundary on the same side of the vehicle, (c) subtracting those measured distances tocalculate the adjacent lane width, and assuming that the vehicle’s current lane width is thesame.

[0171] If the vehicle is equipped with right-looking and left-looking radartransceivers, two desired control distances (right and left) can be used, and the controlstrategy can be to equalize the two distances (e.g., using a zero difference between the rightand left distances as the nominal setpoint) so that the vehicle is centered in its lane. Also,the desired control distance dC may be offset or varied from the true lane center for differentvehicles so that the tire pattern does not wear out the pavement in the same area.

[0172] Figures 25-27 show top views of different configurations of distanceseparation of pavement markers. Figure 25 is a top view of a multi-lane highway 3000 withtwo vehicles 180 and 182 in the highway lanes between the painted lines 304 and pavementmarkers 284 and 1284. The separation distance 190 between pavement markers 284 canbe constant or variable. The separation distance 190 may be small (e.g., 0.3 m or continuous)or large (e.g., 22.4 m). Current (conventional) markers are typically spaced 6.1 m, 12.2 m, or22.4 m on straight roadways and gradual curves depending on the type of roadway. Current(conventional) pavement markers are typically spaced 0.3-6.1 m around sharp curves. On astraight highway as shown in Figure 25 the pavement markers 284 may be separated by aconstant distance but offset by half of the separation every other lane. Providing radartransceivers 116, 1016, 117, and 1017 on both sides of the vehicle 180 allows the radar50066 / 0402 Page 40 of 55transceivers to track pavement markers 284 and 1284 on both sides and allows for largerseparation distance 190 of the pavement markers 284 on each side. If, for example, thelateral controller 830 (in Figure 22) needs a minimum pavement marker separation ofapproximately 4 m for good lateral control, similar controller performance can be obtainedwith 8 m of separation pavement markers 284 or 1284 offset on both sides of the lane. Aseparation distance 190 from about 0.3 m to about 8.0 m between pavement markers canwork well for the lateral controller 830 (in Figure 22) without any augmented sensors (e.g.,GPS, IMU, camera, or lidar). Lateral controllers with inputs from other sensors (e.g., GPS, andIMU) may achieve good performance with larger separation distance 190 (e.g., about 12.2m) similar to currently prevalent pavement marker spacing. In one embodiment, radartransceivers 116 and 1016 on the vehicle 180 sees the pavement markers 284 on the rightside of the vehicle 180. The radar transceiver 117 on the same vehicle 180 sees thepavement markers 1284 in the far-left lane with the radar beam 1107. So, the onboardlateral guidance controller in the vehicle 180 can decide to stay in the same highway laneand follow the pavement markers 284 on the right side of the vehicle or make a lane-changemaneuver and follow the pavement markers 1284 on the far-left side of the vehicle 180. Thevehicle 182 with similar radar transceivers 116 and 117 can follow the same strategy.Another sensor, not shown, e.g., radar, vision, ultrasonic, or lidar, or the same radartransceivers 116, 1016, 117 and 1017 with vehicle detection capabilities (in addition toproviding lateral distance), can determine if there is another vehicle in the left or right laneand allow such a lane-changing maneuver. If the antennas on the radar transceivers 116 and1016 on the vehicles 180 and 182 are left-hand circular polarized and antennas on the radartransceivers 117 and 1017 on all vehicles 180 and 182 are right-hand circular polarized, thenradar signals from the radar transceivers 116 and 1016 on the vehicle 180 will not interfere,because of the different polarizations, with radar signals from the radar transceivers 117and 1017 on the vehicle 182 as the vehicle 180 passes by the vehicle 182.

[0173] In another embodiment, Figure 26 shows the separation distance 194between pavement markers 284 may be smaller in a turn on the roadway 301 to allow moreradar distance measurements from the radar transceivers 116 and 117 to correct the50066 / 0402 Page 41 of 55steering of the vehicle 180 more often to stay in the middle of the lane. When on a straightsection or coming out of the curve, a larger separation distance 192 can be used.

[0174] In another embodiment, Figure 27 shows an arrangement of pavementmarkers 285 in the beginning of the curve section and at the end of the curve section of theroadway 301. This arrangement of pavement makers 285, which will be referred to as a“coded section,” allows for radar transceiver to pick up additional (preview) information toinform a lateral controller (e.g., controller 8004 in Figure 23) that a certain road geometrywill be forthcoming. For example, the lateral controller could take action upon receiving thisinformation from the coded section to minimize lateral errors coming into and leaving acurve section. The coded section 285 can be used to communicate current or upcoming roadgeometry (e.g., curves or straight sections, narrow lanes), intersections, hazards, roadconditions, school zones, hospital zones, construction zones, railroad crossing, road changes,no-stopping areas, speed limits, speed limit changes, or other information. The distance 192between pavement markers 284 may be smaller in the highway turns 301 to allow moreradar distance measurements from the radar transceivers 116 and 117 to correct thesteering of the vehicle 180 more often to stay in the middle of the lane. When on a straightsection or coming out of the curve, a larger separation distance can be used.Multiple Radar Sensors for Continuous Monitoring

[0175] Another embodiment shown in Figures 28 and 29 utilizes multiple radartransceivers or multiple transmit / receive antennas using the same radar transceiver 1165and 1175 attached to the right and left side of the vehicle 180. As shown in Figure 28,multiple radar transceivers 1175 on the left side of the vehicle 180 see the pavementmarkers 1284 continuously as the vehicle 180 moves in the forward direction. Likewise,multiple radar transceivers 1175 on the left side of the vehicle 180 see the pavementmarkers 1284 continuously on the left side or driver’s side of the vehicle 180. The spacingbetween the pavement makers 1284 is at a distance dm as shown in Figure 29. The array ofradar transceivers or antennas 1165 and 1175 cover a distance dtotal on the vehicle 180. Ifthe array of radar transceivers 1165 and 1175 spacing dtotal is the same as or greater thanthe spacing dm of the pavement markers 284 and 1284, respectively, then the lateral distancecan be measured continuously or quasi-continuously (discrete measurements taken50066 / 0402 Page 42 of 55frequently enough to adequately approximate a continuous measurement) between thevehicle radars and the pavement markers.

[0176] Interferometric synthetic aperture radar (InSAR) and synthetic apertureradar (SAR) are processing techniques to determine the lateral distance using radar imagesof a target collected by multiple radar transceivers or multiple receive / transmit antennas.InSAR and SAR can be applied to pavement markers and other target structures. Multipleradar images of the same area that collected at different times from similar locations as thevehicle passes the pavement marker can be compared against each other. Movement of thevehicle toward or away from the pavement markers can be measured during the timebetween the images.

[0177] The multi-radar / multi-antenna embodiment illustrated in Figure 28 canutilize a lateral controller the same as or similar to ones that have already demonstratedsatisfactory control using a continuous marking reference along the roadway. As shown inFigure 28, the spacing of the pavement markers 284 and 1284 alternate in distance such thatthe right-side pavement marker 284 are seen by multiple radar transceivers or antennas1165 half the time and the left-side pavement markers 1284 are seen by the multiple radartransceivers or antennas 1175 the other half of the time. With alternate spacing like this, thenumber of radars in the radar array is reduced by half. In addition, this embodiment showsan IMU 907 mounted on the front center of the vehicle 180. One or more IMUs 907 can belocated on the vehicle 180 in different areas or even within the multiple radar transceiverarrays 1165 or 1175. The IMU(s) 907 can be combined with the radar transceivers array1165 or 1175 to provide for the lateral distance measurements, as described above. WithIMUs 907, the radar transceiver array 1165 and 1175 may be reduced in length and stillprovide an accurate lateral distance measurement continuously.

[0178] Figure 29 shows an embodiment with an array of radar transceivers 1175 onone side of the entire length of the vehicle viewing the pavement markers 1284 spaced adistance dm apart. Not only can the distances d1 and d2 to the pavement markers 1284 bemeasured, but a vehicle heading angle with reference to the pavement markers 1284 can becalculated from two offset (e.g., rear and front) distance measurements.50066 / 0402 Page 43 of 55

[0179] Figure 30 shows an array of radar transceivers 4400 having six TX / RX antennacombinations. Each combination is formed by a reception antenna 4306 and a transmissionantenna 4308. The antennas are mounted in an array 4302 to form a multiple-antenna arrayof radars. Also, vehicle speed sensor 8008 and an IMU 907 are included. Other sensors mayalso be added for further redundancies. The vehicle speed can be used along with receivedsignals to determine when to transmit a power signal based on when a TX antenna 4308 isexpected to be over a target. The IMU 907 may complement the radar distancemeasurements using a Kalman or complementary filter, for example. The spacing betweenadjacent ones of the six TX / RX combos is at a distance dant, which may be the same length asthe width PW of the target. For example, if the width PW of a pavement marker is 0.1 m, thenthe distance dant may be the same as or less than 0.1 m. If the pavement marker separationdm is 3.0 m, then the total array length dtotal may be 3.0 m or longer. If using alternate spacingmarkers as shown in Figure 28, the array length dtotal would be 1.5 m or longer. With a 3.0m array length, then 30 (dtotal / dant = 3.0 m / 0.1 m) TX / RX combos would be needed toprovide continuous lateral distance for the pavement marker.

[0180] Figure 31 shows a schematic diagram of a radar sensor 4500 with multipletransmit / receive antennas. This embodiment can be used with the array of radartransceivers 1165 and / or 1175 (Figure 28). A radar processor 4260 starts a frequencysynthesizer 4160 to provide a suitable FMCW (frequency-modulated continuous wave)signal, which may be amplified by power amplifier / phase shifters 4130 and transmitted tomultiple transmit antennas set up in an array of paired antennas spaced at a distance dantapart. The receive antennas may be part of a paired antenna TX / RX (transmit / receive)combination array 4300 and receive return signals, which may be amplified by low noiseamplifiers (LNAs) 4150. The received signals are mixed with the transmit signal viamodulators 4180. The signals output from the modulators 4180 are filtered via the filterblock 4190 to provide the beat or immediate frequency from the modulator 4180. Thefiltered signals are sampled by the A / D converters 4120 and sent to the radar processor4260 to compute the measured distance, velocity, phase, and / or amplitude. Figure 31 showsonly six TX / RX pairs but many more pairs can be created. If only one pair is provided, thenmore radar transceivers can provide the array 1165 and / or 1175. The radar processor 426050066 / 0402 Page 44 of 55can control the power amplifier / phase shifters 4130 to turn on various antennas in timesequence to minimize interference between antenna pairs.

[0181] Figure 32 shows a schematic diagram of a radar sensor 4510 with multipletransmit / receive antennas. This embodiment can be used with an array of radartransceivers 1165 and / or 1175 (Figure 28). The radar processor 4260 starts a frequencysynthesizer 4160 to provide a suitable FMCW signal, which may be amplified by poweramplifier / phase shifters 4130 and transmitted to multiple transmit antennas set up in anarray of paired antennas spaced at a distance dant apart. However in this embodiment, thereis a gated power amplifier 4165 for each antenna pair, and the vehicle speed 8088 isprovided to the radar processor 4260. The radar processor 4260 can determine which pairof antennas received the distance measurement from a pavement marker 284 or 1284. Oncethe pavement marker 284 or 1284 is determined relative to which radar antenna pair, theradar processor 4260 can anticipate when the pavement marker will be at the next antennapair based on vehicle speed 8008 and turn on the next gated power amplifier 4165 totransmit and receive signals from that pair. In this embodiment, each antenna pair is firedin a sequence to track the pavement marker and to measure the lateral distance. In otherembodiments, other sequences can be employed. This minimizes RF interference andreduces total power transmitted versus transmitting power from all pairs simultaneously.The time tant to the next antenna pair is the antenna pair separation dant divided by the vehiclespeed: tant = dant / v. Similarly, as in Figure 31, the receive antennas may be part of a pairedantenna TX / RX (transmit / receive) combination array 4300 and receive return signals,which may be amplified by low noise amplifiers (LNA) 4150. The received signals are mixedwith the transmit signal via modulators 4180. The signal output of the modulator 4180 isfiltered via the filter block 4190 to provide the beat frequency from the modulator 4180. Thefiltered signal is sampled by the A / D converter 4120 and sent to the radar processor 4260to compute the measured distance, velocity, phase, and / or amplitude. The radar processor4260 can control the frequency synthesizers 4160 to turn on various antennas in timesequence to minimize interference between antenna pairs.

[0182] Figure 33 illustrates another embodiment 4600 which has separate radartransceivers 116 that are synchronized by a radar controller unit 4360. With this50066 / 0402 Page 45 of 55embodiment, one can use current off-the-shelf components, e.g., Texas InstrumentsAWR1843AOP as the radar transceiver 116 and a microcontroller as the radar controllerunit 4360.

[0183] Figure 34 shows a diagram of the output (vehicle lateral distance from thetargets vs. vehicle distance traveled down the roadway) for the array of radar TX / RXantennas 4400 shown in Figure 30 or array of radar transceivers 4600 shown in Figure 33when the targets are spaced within a vehicle’s length. The lateral distance between thevehicle 180 and the targets is shown as constant to illustrate that each TX / RX antenna orradar transceivers will provide the same lateral distance and, therefore, a continuous lateralmeasurement.CONCLUSION

[0184] The foregoing embodiments, descriptions, and terms are set forth by way ofillustration and example only and are not meant as limitations. For example, the while theforegoing description often refers to a pavement marker as a specific example of a radar-reflective road side target, that is just an example for the same of illustration. The principlespresented herein are equally applicable to other types of side targets, and other any radar-reflective side target can be used in place of a pavement marker in the examples presentedabove. The scope of the invention should be determined only by the following claims, claimspresented in a continuing patent application or a post-issuance proceeding, and equivalentsto such claims.50066 / 0402 Page 46 of 55

Claims

CLAIMS1. An apparatus for guiding a land vehicle along a pathway on which there are one ormore side targets with different radar reflectivity characteristics compared to the pathway,the apparatus comprising:a radar sensor mounted to the vehicle and aimed downward and to the side of thevehicle, wherein the radar sensor is configured to radiate to the pathway, via at least onetransmitter, one or more signals having a main beam pattern center aimed toward theground and sideways from the vehicle, wherein the radar sensor is further configured todetect via one or more receiving antennas one or more reflection signals from one or moreof the side targets along the pathway;a processor operatively connected to the radar sensor, wherein the processor isconfigured to determine based on a reflection signal a lateral distance between the vehicleand a side target as the vehicle passes or first encounters the side target; andan inertial measurement unit configured to determine a change of lateral position ofthe vehicle between side targets.

2. An apparatus according to claim 1, wherein the radar sensor operates within afrequency range from about 300 MHz to about I THz.

3. An apparatus according to claim 2, wherein the radar sensor operates within afrequency range from about 77 GHz to about 81 GHz.

4. An apparatus according to claim 1, wherein the radar sensor is a frequency-modulated continuous wave radar transceiver.

5. An apparatus according to claim 1, wherein the radar sensor is an ultra widebandimpulse radar transceiver.

6. An apparatus according to claim 1, wherein the radar sensor is of a type selected froma group consisting of two-frequency phase difference radar, multiple-frequency radar,50066 / 0402 Page 47 of 55multiple-frequency phase radar, orthogonal frequency division multiplex radar, frequencyshift keying radar, digital code modulation radar, phase-modulated continuous wave radar,multiple-input-multiple-output radar, polarimetric radar, dual-polarimetric radar,monopulse radar, noise radar, and interferometric synthetic aperture radar.

7. An apparatus according to claim 1, wherein the radar sensor is monostatic.

8. An apparatus according to claim 1, wherein the radar sensor is bi-static.

9. An apparatus according to claim 1, wherein the radar sensor comprises an antennaarray.

10. An apparatus according to claim 1, wherein the radar sensor is configured to transmita polarized radar signal.

11. An apparatus according to claim 10, wherein the radar sensor is configured to detectthe reflection signal based on its polarization.

12. An apparatus according to claim 1, wherein the radar sensor is configured to beplaced on or within a front bumper of the vehicle.

13. An apparatus according to claim 1, wherein the radar sensor is packaged within avehicle light assembly.

14. An apparatus according to claim 1, wherein the processor is configured to processjust a portion of a reflection signal received in a window corresponding to an expected rangeof a reflection target.

15. An apparatus according to claim 1, wherein the processor is configured to perform afrequency transform of the reflection signal.50066 / 0402 Page 48 of 5516. An apparatus according to claim 1, wherein the side targets are selected from a groupconsisting of raised pavement markers, raised pavement markers with dihedral cornerreflectors, snow plowable pavement markers, snow plowable pavement markers withdihedral corner reflectors, grooves in the pathway, slots in the pathway, sign posts, mailboxes, curbs, concrete barriers, guardrails, and pathway edges.

17. An apparatus according to claim 1, wherein the inertial measurement unit comprisesan accelerometer that provides a lateral acceleration, and wherein the lateral acceleration isintegrated twice to provide a change in lateral position of the vehicle between targets.

18. An apparatus according to claim 1, wherein the inertial measurement unit comprisesa gyroscope that provides a yaw rate, and wherein the yaw rate is integrated once to providea change of heading of the vehicle, and wherein the changes of heading are used to determinea change in lateral position of the vehicle between targets.

19. An apparatus according to claim 1, wherein the inertial measurement unit comprisesa magnetometer that provides a direction of the vehicle, and wherein the direction is used todetermine a change in lateral position of the vehicle between targets.

20. An apparatus according to claim 1, wherein the lateral distance from the radar sensorand the change of lateral position from the inertial measurement unit are combined using acomplimentary filter.

21. An apparatus according to claim 1, wherein the lateral distance from the radar sensorand the change of lateral position from the inertial measurement unit are combined using aKalman filter.

22. A vehicle for use on a road along which are a plurality of side targets, each of the sidetargets being characterized by a radar reflectivity, the vehicle comprising:a first lateral side;50066 / 0402 Page 49 of 55a radar transceiver mounted to the vehicle, wherein the radar transceiver ischaracterized by a main beam pattern having a center aimed downward and sideways fromthe vehicle such that a reflection is detected from the radar reflectivity of the side target asthe vehicle moves forward by the side target on the first lateral side of the vehicle;aprocessor operatively coupled to the radar transceiver and configured to determine,based on the reflection, a path length from the radar transceiver to the side target; andan inertial measurement unit configured to determine a change of lateral position ofthe vehicle between side targets.

23. A vehicle according to claim 22, further comprising:a second lateral side opposite the first lateral side,wherein said main beam pattern is a first main beam pattern having a first centeraimed downward in a first sideways direction from the vehicle, wherein said side target is afirst side target on the first lateral side of the vehicle, wherein the radar transceiver is furthercharacterized by a second main beam pattern having a second center aimed downward andin a second sideways direction from the vehicle such that a reflection is detected from asecond radar reflector embedded in a second side target as the vehicle moves by the secondside target, wherein the second sideways direction is horizontally approximately oppositethe sideways direction, and wherein the second side target is on the second lateral side ofthe vehicle.

24. A vehicle according to claim 22, wherein said radar transceiver is a first radartransceiver, said main beam pattern having said center aimed downward and sideways fromthe vehicle is a first beam pattern having a first center aimed downward and in a firstsideways direction from the vehicle, wherein said side target is a first side target on the firstlateral side of the vehicle, the vehicle further comprising:asecond radar transceiver mounted to the vehicle, wherein the second radartransceiver is characterized by a second main beam pattern having a second center aimeddownward and in a second sideways direction from the vehicle such that a reflection isdetected from a radar reflectivity from a second side target as the vehicle moves forward bythe second side target by on the vehicle’s first lateral side.50066 / 0402 Page 50 of 5525. A vehicle according to claim 22, further comprising:an exterior light assembly, wherein the radar transceiver is located on or within theexterior light assembly.

26. A vehicle according to claim 22, further comprising:afront bumper, wherein the radar transceiver is located on or within the frontbumper.

27. A vehicle according to claim 22, wherein the processor is configured to perform orassist in performing one or more of a lane departure warning function, a lane keepingfunction, and a lane centering assistance function based on the path length from the radartransceiver to the side target.

28. A vehicle according to claim 22, further comprising:a lateral positioning system independent of the radar transceiver, wherein the radartransceiver and the processor form a redundant lateral positioning system.

29. A vehicle according to claim 22, wherein the vehicle is at least partially autonomous,and wherein lateral positioning of the vehicle is performed based at least in part on the pathlength from the radar transceiver to the side target.

30. A vehicle according to claim 22, wherein the radar transceiver is also configured toperform blind-spot detection.

31. A vehicle according to claim 22, wherein the side targets are selected from a groupconsisting of raised pavement markers, raised pavement markers with dihedral cornerreflectors, snow plowable pavement markers, snow plowable pavement markers withdihedral corner reflectors, grooves in the road, slots in the road, sign posts, mail boxes, curbs,concrete barriers, guardrails, and road edges.50066 / 0402 Page 51 of 5532. A method for determining a lateral position of a land vehicle along a pathway, thepathway having side targets with different radar reflectivity characteristics compared to thepathway, the side targets being arranged along the pathway in a direction of vehicle travel,the method comprising:transmitting downward and sideways a radar transmit signal from the land vehicletowards side targets mounted on or near the pathway as the vehicle passes a side target;receiving at the land vehicle a radar reflection signal from the side target as thevehicle passes by the side target;determining, based on the radar transmit signal and the radar reflection signal, adistance between the land vehicle and the side target;determining, based on one or more inertial measurements, a change of lateralposition of the vehicle between side targets; anddetermining, based on the change of lateral position and the distance between theland vehicle and a passed side target, an approximate lateral position of the vehicle betweenside targets.

33. A method according to claim 32, wherein the steps of transmitting the radar signal,receiving a radar reflection signal, and determining the distance are repeated forsubstantially every radar-reflective side target that the vehicle passes.

34. A method according to claim 32, wherein the transmitting step is repeatedperiodically at a period selected from a range from about 0.5 milliseconds to about 1 second.

35. A method according to claim 32, wherein the side targets are distributed along oneside of the vehicle as the vehicle travels along the pathway.

36. A method according to claim 32, wherein the pathway is one lane of a multi-lane road,and wherein the side targets are pavement markers that are distributed along a linedemarking one side of the pathway.50066 / 0402 Page 52 of 5537. A method according to claim 32, wherein the pathway is one lane of a multi-lane road,and wherein the side targets are pavement markers that are distributed along a linedemarking one side of a lane adjacent to a lane corresponding to the pathway of the vehicle.

38. A method according to claim 32, further comprising:filtering the radar reflection signal based on a range of expected distances betweenthe land vehicle and the side target.

39. A method according to claim 32, further comprising:performing a frequency transform on the radar reflection signal.

40. A method according to claim 32, further comprising:using the distance to guide or assist steering the vehicle laterally to follow thepathway.

41. A method according to claim 32, further comprising:providing a warning to a driver of the vehicle either if the distance exceeds amaximum threshold or is less than a minimum threshold or if the approximate lateralposition is outside of an acceptable range.

42. A method according to claim 41, further comprising:providing a warning external to the vehicle either if the distance exceeds a maximumthreshold or is less than a minimum threshold or if the approximate lateral position isoutside of an acceptable range.

43. A method according to claim 42, wherein the warning external to the vehiclecomprises flashing a blinker.

44. A method according to claim 32, further comprising:performing one or more of a lane-centering assistance function and a lane-keepingfunction based on the distance between the land vehicle and a side marker.50066 / 0402 Page 53 of 5545. A method according to claim 32, wherein the vehicle comprises a lateral positioningsystem independent of the method of claim 1, the method further comprising:using the distance in conjunction with the independent lateral positioning system toimprove lateral position determination.

46. A method according to claim 45, wherein the lateral positioning system comprises aglobal navigation satellite system.

47. A method according to claim 45, wherein the lateral positioning system comprises avision system viewing painted lines along the pathway.

48. A method according to claim 45, wherein the lateral positioning system comprises alidar system viewing painted lines along the pathway, recorded targets along the pathway,or both.50066 / 0402 Page 54 of 55

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