Vehicle control scheme for autonomous vehicle system

Abstract

To provide a method of navigating a plurality of vehicles along a roadway.SOLUTION: A method of navigating a plurality of vehicles along a roadway, includes the following steps of: at a first vehicle, navigating along a section of a roadway by following a first moving position-target, the first moving position-target determined in accordance with a first tracking function defining a position along the section of the roadway as a function of time; and, a second vehicle, navigating along the section of the roadway by following a second moving position-target, the second moving position-target determined in accordance with a second tracking function defining a position along the section of the roadway as a function of time. When the first vehicle and the second vehicle navigate along the section of the roadway, a distance between the first vehicle and the second vehicle may change.SELECTED DRAWING: Figure 2B

Description

[Technical field]

[0001] This Patent Cooperation Treaty patent application claims priority to U.S. Provisional Patent Application No. 62 / 992,739, filed March 20, 2020, the entire contents of which are incorporated herein by reference.

[0002] The described embodiments relate generally to vehicles, and more particularly to a vehicle control scheme for controlling the operation of an autonomous vehicle along a roadway. [Background technology]

[0003] Vehicles, such as cars, trucks, vans, buses, and streetcars, are widespread in modern society. Cars, trucks, and vans are frequently used for personal transportation, carrying relatively small numbers of occupants, while buses, streetcars, and other larger vehicles are frequently used for public transportation. Vehicles may also be used for freight transportation or other purposes. Such vehicles may be operated on roads, which may include surface roads, bridges, highways, overpasses, or other types of vehicle rights-of-way. Unmanned or autonomous vehicles may eliminate the need for individuals to manually operate a vehicle when transportation is required. Summary of the Invention [Means for solving the problem]

[0004] A method of navigating multiple vehicles along a road may include navigating, at a first vehicle, along a section of road by following a first moving position target, the first moving position target being determined according to a first tracking function that defines a position along the section of road as a function of time, and navigating, at a second vehicle, along the section of road by following a second moving position target, the second moving position target being determined according to a second tracking function that defines a position along the section of road as a function of time. As the first and second vehicles navigate along the section of road, the distance between the first and second vehicles may change. A time interval between the first and second vehicles may be maintained above a specified minimum.

[0005] As the first and second vehicles navigate along a section of road, a time interval between the first and second vehicles may remain constant. The time interval between the first and second vehicles at a given time may be defined by a first tracking function and a second tracking function, and the distance between the first and second vehicles at a given time may be defined by the first tracking function and the second tracking function.

[0006] As the first vehicle navigates along the section of road, the first vehicle may calculate a first movement position target, and as the second vehicle navigates along the section of road, the second vehicle may calculate a second movement position target. The first vehicle may include a first clock synchronized to a reference clock, and the first vehicle may calculate the first movement position target using time from the first clock, and the second vehicle may include a second clock synchronized to the reference clock, and the second vehicle may calculate the second movement position target using time from the second clock.

[0007] The transportation system may include a plurality of vehicles configured to autonomously navigate along a road by following a moving position target defined for the road. The transportation system may include a vehicle presence detector configured to detect a presence or absence of a vehicle at a location upstream of a merging area of ​​the road, where absence of the vehicle at the location for a predetermined time indicates an available vehicle location along the road. The transportation system may also include the vehicle. The vehicle may include a drive system configured to advance the vehicle, a steering system configured to steer the vehicle, and a vehicle controller configured to receive information from the vehicle presence detector indicative of an available vehicle location, select a tracking function associated with the available vehicle location from a plurality of candidate tracking functions in response to receiving the information indicative of the available vehicle location, cause the drive system and the steering system to merge the vehicle into the road at the available vehicle location, and cause the drive system and the steering system to navigate the vehicle along the road according to the selected tracking function.

[0008] At least two of the plurality of candidate tracking functions may define a variable distance between the two vehicles along a road and a fixed time interval between the two vehicles. The vehicle presence detector may wirelessly communicate with the vehicle to transmit information indicative of an available vehicle position. The information indicative of the available vehicle position may include coordinates of the available vehicle position and a time.

[0009] The act of selecting a tracking function may include selecting a tracking function that correlates the available vehicle position to a time at which the available vehicle position was detected. The vehicle controller may further include a first clock synchronized to the reference clock, and the vehicle presence detector may include a second clock synchronized to the reference clock.

[0010] The transportation system may further include a plurality of additional vehicles navigating along the road, each additional vehicle navigating according to a different respective tracking function of the plurality of candidate tracking functions, each tracking function of the plurality of candidate tracking functions may define a position along the road as a function of time, and the vehicle and each additional vehicle may store the plurality of candidate tracking functions.

[0011] The transportation system may include a plurality of vehicles configured to autonomously navigate along a road having a first segment associated with a first vehicle control scheme and a second segment associated with a second vehicle control scheme. The transportation system may include a vehicle including a drive system configured to propel the vehicle forward, a steering system configured to steer the vehicle, and a vehicle controller. The vehicle controller may be configured to detect a transition from the first segment of the road to a second segment of the road, the first segment of the road associated with a platooning scheme and the second segment of the road associated with a moving position target vehicle control scheme. The vehicle controller may also be configured to determine a time at which the vehicle enters the second segment of the road from the first segment of the road, select a tracking function from a plurality of candidate tracking functions associated with the time at which the vehicle enters the second segment of the road and a starting position of the second segment of the road, and cause the drive system and the steering system to navigate the vehicle along the second segment of the road according to the selected tracking function.

[0012] The vehicle may be a first vehicle, and the vehicle controller may be further configured to navigate the first vehicle along the first segment of the road in accordance with a platooning scheme prior to entering the second segment of the road. Navigating the first vehicle in accordance with a platooning scheme may include detecting a change in a speed of a second vehicle in front of the first vehicle, and altering a speed of the first vehicle in response to detecting the change in speed of the second vehicle.

[0013] The vehicle controller may maintain the vehicle at a position dictated by the selected tracking function using closed-loop position control. The vehicle may store information indicative of a location of a transition from a first segment of road to a second segment of road, and the vehicle controller may detect a transition from the first segment of road to the second segment of road based at least in part on the location of the vehicle and the stored information indicative of the location of the transition.

[0014] The transportation system may further include a detectable component indicating a transition from the first segment of the road to the second segment of the road, and the vehicle may include a sensor, and the act of detecting the transition from the first segment of the road to the second segment of the road may include detecting the detectable component with the sensor. The detectable component may be embedded in the road.

[0015] The present disclosure can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which like reference numbers indicate like structural elements and in which: [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 shows a portion of an example road. [Figure 2A] FIG. 1 illustrates a portion of an example road employing a moving position target control method. [Figure 2B] 2B shows a portion of the road of FIG. 2A at a given time illustrating an example of vehicle positions on the road. [Figure 2C] 2B shows a portion of the road of FIG. 2A at another time, illustrating an example of vehicle positions on the road. [Figure 2D] 2B shows a portion of the road of FIG. 2A at yet another time illustrating an example of vehicle positions on the road. [Figure 3A] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 3B] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 3C] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 3D] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 3E] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 3F] FIG. 1 illustrates an example road junction and associated vehicle control strategy. [Figure 4A]FIG. 2 illustrates an example plot of a tracking function that defines a vehicle's position along a road segment versus time. [Figure 4B] FIG. 2 illustrates an example plot of a tracking function that defines a vehicle's position along a road segment versus time. [Diagram 5] FIG. 2 is a diagram showing a portion of an example road illustrating an example of inter-vehicle distance in a moving position target control scheme. [Figure 6A] FIG. 1 illustrates the operation of an example platooning strategy that may be used on a segment of a road. [Figure 6B] FIG. 1 illustrates the operation of an example platooning strategy that may be used on a segment of a road. [Figure 6C] FIG. 1 illustrates the operation of an example platooning strategy that may be used on a segment of a road. [Figure 7A] FIG. 1 illustrates an example of a vehicle. [Figure 7B] FIG. 1 illustrates an example of a vehicle. [Figure 8A] FIG. 7C shows the vehicle of FIGS. 7A-7B with the doors open. [Figure 8B] FIG. 7C shows the vehicle of FIGS. 7A-7B with the doors open. [Figure 9] FIG. 2 is a partially exploded view of an example vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Reference will now be made in detail to the exemplary embodiments, as illustrated in the accompanying drawings. It is to be understood that the following description is not intended to limit the embodiments to a single preferred embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the described embodiments as defined by the appended claims.

[0018] Examples herein are generally directed to transportation systems in which a number of vehicles may be operated autonomously to transport passengers and / or cargo along roads. For example, a transportation system or service may provide a fleet of vehicles operating along roads to pick up and drop off passengers at either pre-set locations or stops or dynamically selected locations (e.g., selected by a person via a smartphone). The term "road" as used herein may refer to a structure that supports moving vehicles.

[0019] However, autonomous operation of vehicles is a complex task, and the particular techniques or strategies adopted by vehicles on a road can significantly affect the operation of not only individual cars but also the system as a whole. For example, some vehicle control strategies may be susceptible to the occurrence or propagation of traffic congestion or other disturbances that adversely affect the operation and / or efficiency of the system. Thus, prescribing one or more vehicle control strategies appropriate for a road can help ensure smooth and efficient operation of the system.

[0020] One example of a vehicle control scheme described herein defines a virtual position target (referred to herein as a moving position target or simply a position target) that moves along a road and serves as a target (or position set point) for an autonomous vehicle. As a vehicle travels along a road segment utilizing this type of control scheme, the vehicle may be assigned or otherwise associated with a particular moving position target, and the vehicle may adjust its speed and / or heading to minimize the error between its actual position and the position of the moving position target. Each vehicle on the road segment may be assigned or otherwise associated with a different moving position target, and the moving position targets may be predetermined (e.g., by a function relating position along the road to time) so that the vehicles keep a safe distance from each other. In this manner, the location of individual vehicles on the road and the overall flow of vehicles along the road segment may be tightly controlled, thereby reducing the risk of traffic congestion, collisions, and the like. A vehicle control scheme in which a vehicle navigates by following moving position targets may be referred to as a moving position target vehicle control scheme as used herein.

[0021] However, roads in the transportation systems described herein may be large and complex, and may benefit from employing different vehicle control strategies along different segments of the system. For example, along some segments of the roads, a first vehicle control strategy may be employed in which vehicles are configured to autonomously form a platoon or group of multiple vehicles, and along other segments of the roads, a second vehicle control strategy, such as a moving position target vehicle control strategy, may be employed. Examples of such vehicle control strategies, as well as techniques for transitioning between various different vehicle control strategies at intersections, mergers, junctions, and the like, are described herein.

[0022] The transportation systems described herein may include or be operated with a dedicated type of vehicle (or several dedicated types of vehicles) that may be configured to operate independently according to a particular vehicle control scheme defined for a particular road segment, and may be subject to direct control or guidance by a transportation system controller that may issue commands to or otherwise control components of the transportation system (e.g., the vehicles within the transportation system). A vehicle control scheme, as used herein, may be performed by the vehicles, by the transportation system controller, by a combination of the vehicles and the transportation system controller, or using any other suitable components, computers, servers, controllers, or combinations thereof.

[0023] FIG. 1 illustrates a section of road 100 for an autonomous vehicle 108 according to embodiments described herein. The section of road illustrated in FIG. 1 is shown on the ground in a typical urban or suburban environment, but this is not meant to be limiting. In practice, the road may be located in any environment or location, including rural areas, fully or partially within a building, off the road, on an elevated structure, underground, etc. The road 100 is shown with a number of four-wheeled vehicles 108 navigating along the road 100. The vehicles 108 may be autonomous or semi-autonomous vehicles specifically designed for use on the road 100. Although one exemplary type of vehicle for use on the road 100 is described with reference to FIGS. 7A-9B, other types of vehicles may be driven along the road 100 instead of or in addition to the vehicles described herein. The section of road 100 illustrated in FIG. 1 may be only a small portion, and the road 100 may include multiple segments including straight roads, turns, intersections, bridges, tunnels, boarding areas, parking facilities, etc. Different vehicle control strategies may be used on different segments to facilitate efficient vehicle operation. For example, along highways, a moving position target vehicle control strategy may be employed, while along on-ramps, boarding areas, etc., a platooning (or other) strategy may be employed.

[0024] 2A illustrates an example of a portion of a road 200 that employs a moving position target control scheme along at least a portion of the road 200. The portion of the road 200 may include a first segment 208 and a second segment 210 that merges with the first segment 208 at a merge area 212. The first segment 208 may be associated with a moving position target control scheme and the second segment 210 may be associated with a moving position target control scheme, a platooning scheme, or any other suitable vehicle control scheme.

[0025] In the moving position target control scheme, vehicles on a road are configured to follow virtual position targets 202 (e.g., 202-1, ..., 202-n) that virtually move along a road 200. For example, the virtual position targets 202 (also referred to simply as position targets herein) may be conceptualized as virtual containers that move along the road, and the vehicles will attempt to stay "inside" the virtual container as they navigate along the road. In this manner, the manner in which the position targets 202 move along the road may be predefined for the road, and any vehicles traveling along the road according to the position target moving control scheme will move in a predictable, predefined manner (e.g., at a position, speed, heading, etc. predefined by the position target). This control scheme also helps avoid traffic jams or other unpredictable traffic situations, since the vehicles are configured to stay within the "virtual container" that provides a predefined vehicle flow / pattern. As shown in FIG. 2A, the position targets 202 move along a direction indicated by the arrow 204.

[0026] As described herein, the position targets need not have a fixed speed or fixed separation distance across a road segment. Rather, such parameters may vary to accommodate different needs of the transportation system. For example, the speed of the position targets may change (e.g., decrease) around turns in the road segment, and the distance between the position targets may also change (e.g., decrease) around turns. Even if the speed and / or following distance change in a moving position target control scheme, the flow rate of vehicles may remain constant along that segment of the road, thus enabling steady-state operation of the system and avoiding backup or other non-steady-state conditions.

[0027] The position target 202 may be defined in any suitable manner. For example, as described herein with respect to Figures 4A-4B, the position target 202 may be defined by a function that defines a position along a road as a function of time. Each vehicle may store or otherwise access the function such that each vehicle may independently determine the location of the position target at a given time. In this manner, the vehicles may independently determine the location of the position target they are attempting to follow without having to transmit the location of the position target from a remote source (e.g., a remote server or remote controller). As another example, the position target 202 may be defined by a waveform (e.g., a traveling wave), with minimum and / or maximum values ​​of the waveform defining the position target.

[0028] A vehicle that "follows" a virtual position target, as used herein, refers to a vehicle that attempts to maintain the position of the vehicle at (or at a fixed offset from) a virtual position target, and does not necessarily have to be behind the position target. For example, a vehicle may "follow" a position target by using a closed-loop position controller that attempts to minimize the error between the actual position of the vehicle and the position of the position target. Thus, as the position target moves (virtually) along the road, the vehicle will steer itself forward to keep the vehicle approximately aligned with the position target. As expected in closed-loop position control, the actual position of the vehicle may deviate slightly from the set point (here the position target), so that during normal operation of the system, the actual position and the set point may not be exactly equivalent. Thus, following a position target, tracking a position target, or otherwise maintaining alignment with a position target is understood to include the possibility of such accidental position errors.

[0029] Furthermore, the vehicle's position and the position of the virtual position target may be defined in any suitable manner. In one example, the position target may be defined by a one-dimensional point, and the vehicle's position may correspond to a one-dimensional point at a fixed location on the vehicle (e.g., at the geometric center of the vehicle, the center of gravity of the vehicle after unloading, the front-most point of the vehicle, etc.). In another example, the position target may be defined by a two-dimensional shape corresponding to the shape of the vehicle in the transportation system, and the vehicle's position may be defined as the perimeter or outer boundary of the vehicle. In such a case, the vehicle may be configured to follow the position target by attempting to keep the perimeter of the vehicle within the two-dimensional shape (e.g., a rectangle) of the position target. Other techniques for defining the vehicle's position and the position target may also be contemplated.

[0030] 2B illustrates a portion of road 200 at time t0 with vehicles 214-1, 214-2, 214-3, and 214-4 traveling along road 200. As illustrated in FIG. 2B, each vehicle is aligned with a respective position target (e.g., vehicle 214-1 is aligned with position target 202-1, and vehicle 214-2 is aligned with position target 202-2). The vehicles may be configured to follow their respective position targets as the position targets move in direction 204 along road 200. For example, as described above, vehicle 214 may implement a closed-loop position control scheme in which the position of position target 202 is used as a position setpoint for the vehicle, and vehicle 214 follows position target 202 by attempting to minimize or reduce the error between the position target and the vehicle's actual position.

[0031] As described in more detail herein, the location of the position target may be absolute position coordinates (e.g., latitude and longitude coordinates), or any other suitable type of variable. In some cases, the vehicle may store a map or other representation of the road, and the location of the position target may be expressed as a distance or length parameter. This technique may allow the vehicle to at least partially decouple steering control from speed control, thereby simplifying operation to follow the position target. For example, the closed-loop position controller may control the speed of the vehicle independently of the steering system (e.g., via the vehicle's drive system) to minimize the error between a set point and the vehicle position. Meanwhile, the steering system may control the angle of the vehicle's wheels (or otherwise steer the vehicle) based on where the vehicle is on the road and according to the map of the road. In this manner, the closed-loop position controller does not need to calculate a new path between its current position and its position target, since the path is already defined by the map of the road.

[0032] FIG. 2C illustrates a portion of road 200 at time t1 where vehicles 214-1, 214-2, 214-3, and 214-4 have progressed along the road in accordance with the movement of the position targets. For example, vehicle 214-1 is progressing in coordination with position target 202-1. FIG. 2C also illustrates a new position target 216, which represents a position target that is immediately behind position target 202-1 (shown in FIG. 2A and occupied by vehicle 214-1). Notably, because the vehicles are following the position targets, the vehicles do not converge on each other as they progress along the road. For example, the available vehicle positions (position targets 218) between vehicles 214-3 and 214-4 remain available and unoccupied while these vehicles navigate along the road (e.g., trailing vehicle 214-3 does not attempt to catch up with leading vehicle 214-4 and remains associated with its associated position target).

[0033] 2C also shows a vehicle 214-5 on a second segment of road 210. The vehicle 214-5 may be preparing to enter the first segment of road 208. The second segment 210 may not be associated with a mobile position target control scheme, and the vehicle 214-5 must safely merge onto the first segment 208 and begin following the appropriate mobile position targets.

[0034] To merge safely, the vehicle 214-5 must select an unoccupied location target to follow (e.g., location target 218 that is unoccupied and therefore represents an available vehicle position). Once an unoccupied location target is identified, the vehicle 214-5 may enter the first segment 208 and begin following the selected location target.

[0035] Vehicle 214-5 may determine available vehicle locations in any suitable manner. In some cases, the transportation system may include a vehicle presence detector configured to detect the presence or absence of a vehicle on a roadway. For example, vehicle presence detector 206 may detect whether a vehicle is present or absent at the location. As shown, vehicle presence detector 206 is located upstream of merge area 212. Thus, vehicle presence information from vehicle presence detector 206 may be used by vehicles attempting to merge at merge area 212 to identify available vehicle locations. Vehicle presence detector 206 may be or include any suitable system and / or component capable of sensing the presence or absence of a vehicle at a location on a roadway. For example, vehicle presence detector 206 may be or employ optical sensors, cameras, magnetic sensors, ultrasonic sensors, weight-based sensors, etc. to determine whether a vehicle is present or absent at a given location.

[0036] The vehicle presence detector 206 may transmit information regarding the presence or absence of a vehicle at its location directly to nearby vehicles and / or to an overall transportation system controller. The vehicle presence detector 206 may transmit or otherwise provide various types of information. For example, in some cases, the vehicle presence detector 206 transmits simple presence / absence data. In such cases, the vehicle and / or transportation system controller may then use the presence / absence data from the sensor, time, and location to determine which location targets are occupied and which are not. The time and location from the sensor may be transmitted by the sensor itself or may be retrieved by a receiving vehicle or computer system using the sensor's unique identifier (which may be transmitted by the sensor along with the presence / absence data). In some cases, the vehicle presence detector 206 (and / or any associated computer system) may determine whether the location target is occupied or not occupied and transmit the occupancy status of the location target to the vehicle and / or transportation system controller.

[0037] Although the vehicle presence detector 206 may determine the presence or absence of a vehicle at a given location, that information alone may not be sufficient to determine whether and how a vehicle, such as vehicle 214-5, can merge onto a roadway. For example, vehicles on directly adjacent location targets have a gap between them, but there is no valid location target between them. Thus, it must be determined whether the gap between the vehicles encompasses or corresponds to a valid location target, thereby constituting an available vehicle position. This determination may be made in a variety of ways. For example, an available vehicle position may be identified in response to detecting a gap of a certain distance or duration between the vehicles (e.g., a gap large enough to encompass a valid, unoccupied location target). As another example, an available vehicle position may be identified in response to detecting the absence of a vehicle on the roadway for a predetermined period of time. As yet another example, an available vehicle position may be identified in response to detecting the absence of a vehicle when a known location target passes by the vehicle presence detector 206. In such instances, the act of detecting the presence and / or absence of a vehicle may be performed using vehicle presence detector 206, and the act of determining whether the absence of a vehicle corresponds to or indicates an available vehicle location may be performed by vehicle presence detector 206, one or more vehicles, a transportation system controller, or any other suitable device or system. Other techniques for determining and / or identifying available vehicle locations are also contemplated.

[0038] If the vehicle presence detector 206 is configured to transmit not only presence or absence data but also information regarding available vehicle location, the vehicle presence detector 206 may store or otherwise access a function that defines a location target to determine whether the location target is occupied or unoccupied.

[0039] In some cases, a computer system (e.g., a centralized or distributed transportation system controller) may track the location of vehicles along a roadway and may broadcast the vehicle's position on the roadway and available vehicle positions on the roadway to one or more vehicles in the system. The computer system may also assign position targets to vehicles entering road segments that employ a moving position target control scheme. The computer system may track the location of vehicles using sensors in or along the roadway (e.g., optical sensors, cameras, magnetic sensors, ultrasonic sensors, weight-based sensors), by receiving location information from the vehicles themselves (e.g., each vehicle self-reports its location to the computer system), or using any other suitable tracking technique.

[0040] In some cases, a vehicle on a roadway and operating under a moving location target control scheme transmits its own location, the location target it is following, the locations of other nearby vehicles, the presence or absence of vehicles at adjacent location targets, etc. to other vehicles and / or to a system controller of the transportation system. In some cases, such information is shared directly between vehicles. For example, referring to FIG. 2C, vehicle 214-4 may transmit information to vehicle 214-5 indicating its location and the absence of a vehicle at location target 218.

[0041] Once an available vehicle position is identified, the joining vehicle 214-5 may select a tracking function associated with the available vehicle position from a number of candidate tracking functions. For example, as described herein, the available vehicle position may correspond to a location target, which may be defined by or associated with a unique tracking function that defines the location of the location target with respect to time. Thus, as described herein, the joining vehicle 214-5 may use information such as the location where the available vehicle position was detected and the time it was detected to determine a tracking function that corresponds to the available vehicle position. Once a tracking function is selected (and if it is safe to do so), the joining vehicle 214-5 may join the first segment 208 of the road at the available vehicle position. Once joined, the vehicle 214-5 navigates along the road according to the selected tracking function.

[0042] FIG. 2D illustrates vehicle 214-5 as it merges into first leg 208 of road 200 and begins to follow position target 218. As shown in FIG. 2D, merging into first leg 208 may include vehicle 214-5 initiating a closed-loop position control scheme to accelerate vehicle 214-5 to an appropriate merge speed to converge on position target 218. Maneuvering into the first segment as part of the merging operation may be performed in a similar manner to maneuvering along other segments of the road. For example, vehicle 214-5 may store a map or other representation of the road (including first segment 208 and second segment 210) and may be configured to steer along a path consistent with the map and the vehicle's location. In another example, vehicle 214-5 may determine a path (including heading, steering angle, speed, acceleration, or other parameters) that will lead vehicle 214-5 from its position on second segment 210 to position target 218 while remaining within specified road boundaries.

[0043] During a merge, the vehicle 214-5 may use various techniques to ensure a safe merging operation. For example, the vehicle 214-5 may determine the location of other vehicles, the distance between itself and the other vehicles, the approaching speed and / or direction of other nearby vehicles, etc. The vehicle 214-5 may use such information to accelerate, decelerate, or change heading or position to maintain a safe clearance between itself and the other vehicles, approaching speed, etc. during a merge. The vehicle 214-5 may detect or determine such parameters using on-board sensors (e.g., LIDAR, radar, ultrasonic sensors, optical sensors, cameras, infrared sensors, etc.).

[0044] Roads in a transportation system may require various different types of junctions between road segments. For example, roads may include on-ramps, off-ramps, segments where vehicle speeds increase or decrease, areas where two traffic flows must merge, etc. To facilitate smooth and efficient operation of the system, control strategies may be defined for various types of junctions in the road. More specifically, the design and operation of roads may be facilitated by predefining how vehicles, and more specifically, the mobile position target control strategies, behave at junctions.

[0045] 3A-3F show some examples of junctions that may be used in a transportation system. For example, FIG. 3A shows an on-ramp junction 300 where a second segment 304 merges with a first segment 302. The first segment 302 may be associated with a moving position target control scheme, and the second segment 304 may be associated with a control scheme other than the moving position target control scheme (e.g., a platooning scheme). When a vehicle encounters an on-ramp junction, the vehicle operates according to a predetermined routine. For example, a vehicle on the first segment 302 operates according to a moving position target control scheme (indicated by a moving position target 306 moving in a direction 308), and a vehicle on the second segment 304 transitions to the moving position target control scheme when merging with the first segment 302. Such behavior may be predetermined, so that under normal operating conditions, each vehicle in the system can expect the other vehicles to operate according to their behavior.

[0046] FIG. 3B illustrates an exit ramp junction 310 where a second segment 314 is merging out from a first segment 312. The first segment 312 may be associated with a moving position target control scheme, and the second segment 314 may be associated with a control scheme other than the moving position target control scheme (e.g., a platooning scheme). When a vehicle encounters an exit ramp junction, the vehicle operates according to a predetermined routine. For example, a vehicle on the first segment 312 operates according to a moving position target control scheme (indicated by a moving position target 316 moving in a direction 318), and a vehicle exiting the first segment 312 transitions from the moving position target control scheme to a different vehicle control scheme as it exits the first segment 312 and enters the second segment 314. In some instances, while in the process of exiting the first segment 312, the exiting vehicle may attempt to maintain the same distance between the leading vehicle and the trailing vehicle until the exiting vehicle is completely out of the flow of traffic along the first segment 312.

[0047] 3C illustrates a junction 320 where a first segment 324 joins with a second segment 325, and the vehicular flow from the first segment 324 and the second segment 325 continues (moving in a direction 327) along a third segment 322. The first segment 324, the second segment 325, and the third segment 322 may all be associated with a moving position target control scheme. To couple together the vehicular flow from the first segment 324 and the vehicular flow from the second segment 325 without causing stagnation or other non-steady state flow conditions, the flow rate of the third segment 322 may need to be substantially equal to the combined flow rate of the first segment 324 and the second segment 325. In other words, the vehicular flow rate of the first segment 324 may be half of the vehicular flow rate of the third segment 322, and the vehicular flow rate of the second segment 325 may also be half of the vehicular flow rate of the third segment 322. 3C, this condition is illustrated by the first segment 324 having a position target 326 with sufficient clearance to accommodate the position target 328 of the second segment 325. In this manner, the vehicular flows of the first and second segments can merge without stalling or slowing down. Furthermore, the speeds of the vehicles on the first segment 324 and the second segment 325 can remain the same after the vehicular flows are joined and they are navigating along the third segment 322.

[0048] The position targets 326 and 328 may be staggered such that the position target 326 of the first segment 324 accommodates the position target 328 of the second segment 325 into an existing gap between the position targets 326. Because the vehicle control strategy for all segments of the junction 320 is predetermined, including the positions and speeds of the position targets 326, 328, and 329, a continuous and uninterrupted merging of the vehicle flow may be continuously maintained (without the need for vehicles to significantly slow or accelerate to effect the merge).

[0049] 3D-3F show transition junctions 330, 340, and 350 where two segments with different vehicle control strategies are adjacent. At these junctions, the vehicle transitions from one vehicle control strategy to another when the vehicle crosses the boundary from one segment to the next. For example, FIG. 3D shows transition junction 330 where a first segment 332 is associated with a vehicle control strategy other than a moving position target control strategy and a second segment 334 is associated with a moving position target control strategy as indicated by position target 336 (moving in direction 338 along the road). As the vehicle approaches boundary 339 between first segment 332 and second segment 334, the vehicle anticipates transitioning to the moving position target control strategy. For example, in some instances, when the vehicle comes within a threshold distance of boundary 339, the vehicle determines the position targets and associated tracking functions that will be available and preferred when crossing boundary 339. When the vehicle crosses the boundary, the vehicle begins operating according to the moving position target control scheme and follows the moving position target defined by the selected tracking function. In some cases, the vehicle does not transition to the moving position target scheme until there are no other vehicles between the vehicle and the boundary 339. If such vehicles are present, the vehicle must slow down and / or stop until they enter the second segment. A vehicle presence detector (as described above) or other techniques may be used to determine which position targets and / or tracking functions are available and facilitate a safe and efficient transition to the second segment 334. The boundary between segments may be or may include a detectable component, such as a detectable substance in or along the road (e.g., a magnet, metal, a light signal or beacon, a sign, etc.).

[0050] 3E illustrates a transition junction 340 where a first segment 342 is associated with a moving position target control scheme (as shown by a position target 346 moving in a direction 348 along a road) and a second segment 344 is associated with a vehicle scheme other than the moving position target control scheme (e.g., a platooning scheme). As the vehicle approaches a boundary 349 between the first segment 342 and the second segment 344, the vehicle anticipates a transition from the moving position target control scheme. For example, as the vehicle crosses the boundary 349, the vehicle stops following the position target of the tracking function and begins navigating according to a different control scheme, such as by attempting to maintain a following distance or headway behind a leading vehicle up to a maximum speed limit.

[0051] FIG. 3F illustrates a transition junction 350 in which a first segment 352 and a second segment 354 are associated with a moving position target control scheme, but each has different vehicle motion parameters (e.g., different speeds). For example, FIG. 3F illustrates a first segment 352 having a position target 355 moving in a direction 357 at a first speed, and a second segment 354 having a position target 356 moving in a direction 358 at a second speed different (e.g., faster) than the first speed. When the vehicle comes within a threshold distance to a boundary 359, the vehicle determines the position targets and associated tracking functions that will be available and preferred when crossing the boundary 359. Once the vehicle crosses the boundary, the vehicle begins operating according to the second moving position target control scheme and follows the moving position targets defined by the selected tracking function. To avoid holdups, traffic jams, or other unsteady-state operating conditions, the vehicle control strategies for the first and second segments of transition junction 350 (as well as other similar transition junctions) may be configured to have the same vehicle flow rates. In other cases, the vehicle flow rates may vary so long as the vehicle flow rates only increase along the downstream direction (e.g., the flow rate only increases as the vehicle progresses along the road until it exits the road or the road ends).

[0052] As noted above, a vehicle may use a tracking function to identify the location of a moving position target that the vehicle is following. A tracking function may be defined in a number of ways. FIGS. 4A-4B show examples of tracking functions and how they define the relative positions of multiple vehicles on a roadway. As noted above, a vehicle may be assigned a given tracking function. The assignment of a tracking function to a vehicle may be done by the vehicle itself, a transportation system controller, another vehicle, or in any other suitable manner.

[0053] FIG. 4A illustrates a plot 400 of length versus time along a section of road. For ease of understanding, the y-axis of plot 400 represents length position along the road, rather than absolute position (e.g., latitude and longitude coordinates). Thus, the plot illustrated in FIG. 4A may be associated with a tracking function used in conjunction with a map or other representation of a road to provide steering and acceleration instructions to a vehicle. Other types of tracking functions, such as tracking functions that correlate absolute position to time, may also be used.

[0054] Plot 400 is a plot of a first tracking function F t1 , the second tracking function F t2 , and a third tracking function F t3 . The non-linearity of the tracking function indicates the variation in the vehicle's speed along the represented section of the road. Thus, the tracking function may define a more complex speed profile than a simple constant speed profile. This may be particularly useful in complex road situations that include features such as turns of different radii and / or banking angles, hills, tunnels, merge zones or other road junctions. In such cases, the constant speed tracking function may be unsafe and / or inefficient, since the speed of the constant speed tracking function needs to be set to the slowest speed required for the road. (For example, if a turn in the road requires a very slow speed for safety reasons, the constant speed function cannot exceed that slow speed even for sections where it is safe to do so).

[0055] The tracking function may be predefined for a road segment such that each vehicle on that segment follows a separate tracking function. In this manner, the tracking function defines and predetermines the gap between the vehicles, thus helping to avoid collisions or other interactions between the vehicles. For example, at time t1, the vehicle-following function F t1 is at the length position L1, and the vehicle following function F t2 is at the length position L2, and the vehicle following function F t3 is at length position L3. By using the tracking function as an input to or a set point for a position controller (e.g., a closed loop position controller), the vehicle can maintain its position at the position dictated by its assigned tracking function.

[0056] As mentioned above, the tracking function may not maintain a fixed distance between adjacent vehicles. Rather, the tracking function may maintain a fixed time between adjacent vehicles. In other words, the vehicles may remain, for example, 2 seconds apart from each other, regardless of the speed of the vehicles. Under such conditions, the distance between the vehicles increases as the speed increases. Defining the gap between the vehicles using a fixed (or at least a predetermined) time interval rather than a distance interval contributes to the efficiency of the overall system. More specifically, a fixed distance-based interval would require selecting the maximum safe gap size required along the road, ultimately resulting in unnecessarily large gaps between vehicles on low-speed sections of the road. As described herein, for safety, the time interval between the vehicles may be maintained above a threshold or a prescribed minimum value.

[0057] FIG. 4B illustrates how the time interval between adjacent tracking functions can remain constant while the distance between the vehicles can change. For example, the equal length or size of representative time intervals 402, 404, 406, 408, and 410 demonstrates that the time interval between tracking functions can be fixed or constant over the length of the road (or at least a segment of the road). The different sizes of distance intervals D1 and D2 (at times t1 and t2, respectively) indicate that the distance between adjacent vehicles can change as the vehicles progress along the road. In other words, the two tracking functions can define a variable distance between the two vehicles as they progress along the road according to the two tracking functions.

[0058] In some cases, the tracking function of a road may be changed or adjusted in real time. This may be done, for example, when there is a change in weather or road conditions, traffic conditions, etc. For example, a time interval between vehicles that is safe in dry weather conditions may not be sufficient in wet weather conditions. Thus, in a transportation system, a vehicle may need to modify its tracking function in response to detecting a condition (or change in condition) that affects the transportation system, such as a change in weather conditions, road conditions, or the presence of debris, people, or other objects on the road. In some cases, multiple sets of tracking functions are predefined, and the vehicle may be instructed (e.g., by a transportation system controller) to change from one set to another set depending on the detected condition. In other cases, the vehicle may be instructed (e.g., by a transportation system controller) to modify the vehicle's existing tracking function (e.g., by changing the value of a constant in the tracking function) to increase or decrease the time interval between vehicles. Other techniques for changing the tracking function associated with a road are also possible.

[0059] In some cases, the transportation system has a prescribed minimum for the time interval between two vehicles. For example, the minimum time interval between two vehicles may be about 1 second, about 2 seconds, about 5 seconds, or any other suitable value. The prescribed minimum time interval may be defined at least in part based on characteristics of the components of the transportation system, including, but not limited to, vehicle braking performance, vehicle available traction, road design (e.g., road radius of curvature and road slope, etc.), etc. The prescribed minimum time interval may be system-wide. In some cases, instead of or in addition to a system-wide prescribed minimum time interval, local and / or temporary minimum time intervals may be defined. For example, certain sections of roads may have different minimum time intervals (e.g., different sections of roads may have different weather or road surface conditions, different road layouts, etc., and therefore may have different minimum time intervals). As another example, certain circumstances may impose different minimum time intervals system-wide (e.g., a system-wide weather event may result in a larger prescribed minimum time interval for safety or other reasons).

[0060] Changes to the tracking function may be configured to occur at road junctions (e.g., when the vehicle crosses certain boundaries between road segments) so that the vehicle can adapt to the new tracking function in an orderly (e.g., sequential) manner without causing traffic congestion, collisions, or other problems.

[0061] To ensure that all vehicles on the road are accurately tracking position targets, all vehicles must operate using a synchronized clock system. For example, if two vehicles' clocks do not have the same time, the vehicles may not be in the correct position for their tracking function. Thus, vehicles may each include a clock that is synchronized with the clocks of other vehicles and / or with a reference clock (which may be associated with a transportation system controller, a central server, a publicly accessible clock service, etc.).

[0062] FIG. 5 illustrates a road segment 500 illustrating how the physical distance between vehicles may vary while the time interval between the vehicles remains constant. For example, distance 502 between target location 508 and target location 510 may represent a two second time interval due to the speed of target location 508 and target location 510 at their locations along the straight portion of the road. As the target location approaches and enters a turn in the road, the target location may slow down to maintain occupant comfort and / or vehicle safety during the turn. As the speed of the vehicles decreases, the physical distance between the vehicles may also decrease while maintaining a constant time interval. Thus, for example, distance 504 between target location 512 and target location 514 may represent the same two second time interval even if distance 504 is shorter than distance 502. Similarly, distance 506 between target location 516 and target location 518 may represent the same two second time interval even if distance 506 is shorter than distances 502 and 504. As the vehicles exit the corner and begin to accelerate, the physical distance between the target locations may increase again to maintain a constant time interval between the target locations. As mentioned above, maintaining a constant time interval allows vehicles to be packed closer together along the roadway compared to maintaining a constant physical distance, since the physical distance may be more closely tailored to how fast the vehicles are traveling.

[0063] A mobile position target vehicle control strategy may be used along some segments of a road, but may not be suitable for all segments of the road. For example, some segments may require the ability to handle non-steady-state traffic flow. Examples may include on-ramps where vehicles may need to wait for an available vehicle position, and boarding areas where vehicle flow may be unpredictable and / or driven by user demand. For these or other reasons, some segments of the road may be configured to operate according to another vehicle control strategy, such as a platooning strategy.

[0064] In some cases, the same segment of road may transition between vehicle control strategies in response to certain conditions being detected or otherwise met. For example, a segment of road may transition from a mobile position target control strategy to a platooning strategy in response to certain road conditions being detected (e.g., wet or slippery conditions, debris on the road, unexpected vehicles or other traffic on the road, etc.). When such a condition occurs, the transportation system may change the vehicle control strategy of one or more segments (e.g., transition from a mobile position target control strategy to a platooning control strategy).

[0065] 6A-6C show the operation of an example of a platooning scheme that may be used on a road segment. The platooning scheme in these figures represents a technique where vehicles self-organize into a platoon (e.g., a group of vehicles traveling together, where the following vehicles react to the actions of the preceding vehicle). In one example, the self-organization into a platoon is achieved by prescribing a rule that smaller platoons of vehicles travel faster than larger platoons. In this way, the smaller platoons (including single vehicle platoons) always tend to reduce the separation distance from the larger platoons that are further along the road, and catch up with the larger platoons if the road is long enough. Furthermore, grouping into larger platoons tends to create more and larger gaps along the road, allowing more opportunities for other vehicles to merge into the traffic flow.

[0066] Figure 6A shows a segment of road 600 with three platoons: a first platoon 602 with one vehicle, a second platoon 604 with three vehicles, and a third platoon 606 with five vehicles. Figure 6A shows the platoons at time t0. As noted above, the smaller platoon may travel faster than the larger platoon so that the smaller platoon can catch up and join the larger platoon. Thus, the first, second, and third platoons may travel at speeds (e.g., speeds) V1, V2, and V3, respectively, where V1 is greater than V2, which is greater than V3.

[0067] FIG. 6B illustrates the road segment 600 at time t1, showing how the first platoon 602 catches up with and joins the second platoon 604 due to the relative speeds of the platoons. Upon joining, the first platoon 602 changes its speed to match the speed (e.g., V2) of the second platoon 604. FIG. 6B also shows that the second platoon 604 has closed the distance to the third platoon 606 due to the higher speed V2. FIG. 6C illustrates the road segment 600 at t2, showing how the second platoon 604 catches up with and joins the third platoon 606. Once the second platoon 604 joins, all vehicles proceed according to the speed V3 of the third platoon 606.

[0068] In one example, the speed of a platoon with n vehicles is calculated using the equation

number

[0069] The above equations may only apply to vehicles with a platoon size of a given number of vehicles, with larger platoons traveling at a different speed (which may be set to a specific value or defined by a different equation or set of considerations). In some cases, the above equations apply to platoons with five or fewer vehicles, while platoons with six or more vehicles travel at a prescribed minimum platoon speed. However, the minimum platoon speed may be v because vehicles traveling in a platoon need to retain the ability to slow down somewhat during normal operation to accommodate changes in the lead vehicle's speed that may occur during normal operation. min For example, a vehicle may experience a large impact on the road under normal driving conditions. min However, the formation can be configured to maintain a speed greater than v min If the leading vehicle happens to slow down (e.g., due to an obstacle on the road or for some other reason), the following vehicle (already min Since the vehicle is moving at a speed of 100 km / h, and further deceleration is limited by the program, it may not be possible to decelerate any further. min If set above, vehicles can slow down when in a platoon and exceed the prescribed minimum vehicle speed v min This mitigates this problem by ensuring that the .

[0070] The platooning strategy may also prescribe or define a maximum platoon size. For example, a platoon may be limited to a maximum of 10 vehicles, 6 vehicles, 5 vehicles, or any other suitable size. In some cases, the maximum platoon size may change based on the situation and / or environment. For example, different sections of roads may have different maximum platoon sizes. As another example, changing weather conditions may cause a transportation system to change the maximum platoon size. If the platoon size is larger than the maximum platoon size, the platoon may split into multiple platoons, each of which is equal to or smaller than the maximum platoon size. The vehicles may communicate among themselves to determine which vehicles should split into different platoons. Alternatively or additionally, the system controller may send instructions to the vehicles indicating which vehicles should split into different platoons. If a smaller (and therefore faster) platoon catches up with a larger platoon that is already at the maximum platoon size, the smaller platoon may slow down to the speed of the leading platoon (and may maintain a constant separation distance between the smaller and larger platoons).

[0071] The platooning strategy may also define a target spacing between platoons (referred to as target platoon spacing) (which may be used as a minimum spacing) and a target spacing between vehicles within the platoon (referred to as target vehicle spacing). The target vehicle spacing between vehicles within the platoon may be defined as a distance spacing (e.g., 10 feet, 30 feet, or any other suitable value) or a time spacing (e.g., 1 second, 2 seconds, 3 seconds, or any other suitable value). Using a time spacing may help maximize the number of vehicles that can safely navigate a road at one time. The target platoon spacing may be defined as a certain multiple of the target spacing between vehicles within the platoon. For example, the target platoon spacing between platoons may be approximately 1.5 times the target vehicle spacing, 1.8 times the target vehicle spacing, 2.0 times the target vehicle spacing, 3.0 times the target vehicle spacing, or any other suitable value.

[0072] As described above, vehicles operating according to a platooning scheme may communicate with each other to determine whether to join the platoon or form a new platoon. For example, each vehicle may be configured to communicate with the vehicle directly in front of it on the roadway. The vehicles may include wireless vehicle-to-vehicle communication systems that facilitate communication, such as optical communication systems, radio-based communication systems, and the like. Vehicle-to-vehicle communication may be direct communication from one vehicle to another vehicle, or messages may be relayed via one or more other servers, computers, controllers, communication systems or providers, and the like.

[0073] Each vehicle may be configured to request information about the number of vehicles ahead of it from the next vehicle, and the queried vehicle may be configured to respond to such requests. For example, a following vehicle directly behind a leading vehicle may query the leading vehicle for the number of vehicles ahead of it that are a certain time interval (e.g., a target vehicle spacing) away from the next vehicle. If the leading vehicle reports a number that is higher than the maximum platoon size, the following vehicle will slow down its speed and increase its distance to the leading vehicle. In some cases, the following vehicle will slow down its speed until it is at the target platoon spacing, and then attempt to maintain the spacing at the target platoon spacing until the number of vehicles in the platoon ahead changes.

[0074] If a trailing vehicle receives more than the maximum platoon size from the leading vehicle, it may immediately begin responding to similar inquiries from further trailing vehicles by reporting the value zero (indicating that there are no cars immediately ahead and that it is effectively the head of the platoon). This may occur immediately after the trailing vehicle detects that a new platoon should begin, even if the trailing vehicle has not yet physically extended the separation distance to the platoon spacing. If the trailing vehicle did not report the value zero immediately after determining that it is the head of the new platoon, each of the further trailing vehicles may attempt to slow down at substantially the same time (each determining that there are too many vehicles immediately ahead), which may potentially result in unnecessary slowdowns or gaps in the system.

[0075] In some cases, instead of (or in addition to) sending a query to the vehicle ahead, a query can be sent to the following or following vehicles. For example, instead of (or in addition to) the following vehicle querying the leading vehicle for the number of vehicles ahead, the leading vehicle may query the following vehicle for the number of vehicles behind the leading vehicle that are a certain time interval (e.g., a target vehicle spacing). Upon receiving one or more responses from the following vehicles, the lead vehicle may adjust its speed accordingly. For example, if the leading vehicle receives a response indicating that the number is greater than the maximum platoon size, the lead vehicle may adjust its speed (e.g., increase its speed) to allow the lead vehicle (and, optionally, some following vehicles) to form a new platoon.

[0076] Such communication may also be used to facilitate the leading vehicle in determining its speed through a road. For example, as described above, a platoon may proceed at different speeds based on the number of vehicles in the platoon. In such cases, the leading vehicle may adjust its speed based on the response to a query regarding the number of following vehicles. For example, if the number of following vehicles is less than the maximum platoon size, the leading vehicle may proceed at a speed faster than the minimum platoon speed, and if the number of following vehicles is the maximum platoon size, the leading vehicle may proceed at the minimum platoon speed. The leading vehicle may respond to changes in the number of following vehicles by accelerating or decelerating its speed according to an equation relating platoon size to platoon speed (as described above).

[0077] The vehicle control strategies described herein may be used with or by a transportation system in which a number of vehicles may operate autonomously to transport passengers and / or cargo along a road. For example, a transportation system or transportation service may provide a fleet of vehicles operating along a road. Vehicles in such a transportation system may be configured to operate autonomously according to one or more vehicle strategies described herein (e.g., platooning, moving location targeting, etc.). The term "autonomous" as used herein may refer to a mode or manner in which a vehicle may operate without continuous manual control by a human operator. For example, an unmanned vehicle may navigate along a road using an automated system of drive and steering systems that control the speed and direction of the vehicle. In some cases, a vehicle may not require control of steering, speed, or direction by an occupant and may eliminate controls such as accelerator and brake pedals, steering wheels, and other manual controls that are accessible to the occupant. In some cases, a vehicle may include manual drive controls that may be used for maintenance, emergency override, etc. Such controls may be hidden, stored, or otherwise not directly accessible to a user during normal vehicle operation. For example, they may be designed to be accessible only to trained operators, maintenance personnel, and the like.

[0078] Autonomous operation need not exclude all human or manual operation of a vehicle or the entire transportation system. For example, a human operator may be able to intervene in the operation of the vehicle for safety, convenience, testing, or other purposes. Such intervention may be local to the vehicle, such as when a human driver controls the vehicle, or remote, such as when an operator sends commands to the vehicle via a remote control system. Similarly, some aspects of the vehicle may be controlled by the vehicle occupant. For example, the vehicle occupant may select a target destination, a route, a speed, control the operation of doors and / or windows, etc. Thus, it will be understood that the terms "autonomous" and "autonomous operation" do not necessarily exclude all human intervention or operation of individual vehicles or the entire transportation system.

[0079] Vehicles in a transportation system may include various sensors, cameras, communication systems, processors, and / or other components or systems that help facilitate autonomous operation. For example, the vehicles may include a sensor array that detects magnets or other markers embedded in the roadway that help the vehicles determine their location, position, and / or orientation on the roadway. The vehicles may also include wireless vehicle-to-vehicle communication systems, such as optical communication systems, that allow the vehicles to inform each other of operating parameters, such as vehicle braking status, the number of vehicles ahead in the platoon, acceleration status, the vehicle's next maneuver (e.g., right turn, left turn, planned stop), and the number or type of vehicle payload (e.g., people or cargo). The vehicles may also include wireless communication systems that facilitate communication with a transportation system controller that has administrative command and control authority over the transportation system.

[0080] Vehicles within a transportation system may be designed to enhance the operation and convenience of the transportation system. For example, a primary objective of a transportation system may be to provide comfortable, convenient, fast, and efficient personal transportation. To provide personal comfort, the vehicles may be designed for easy occupant ingress and egress and may have a comfortable seating arrangement with ample leg and headroom. To help position and level the vehicle at a convenient height, and to ensure a comfortable ride over the full range of varying load weights, the vehicles may also have advanced suspension systems that provide a comfortable ride and dynamically adjustable parameters.

[0081] Conventional personal automobiles are primarily designed to operate in only one direction. This is due in part to the fact that the driver faces the forward direction and it is generally not safe or necessary to drive long distances in reverse. However, in an autonomous vehicle where a human does not have direct real-time control over the vehicle's operation, it may be advantageous for the vehicle to be able to operate in both directions. For example, the vehicles in the transportation systems described herein may be substantially symmetrical, such that the vehicle does not have a visually or mechanically distinct front or rear. Furthermore, the wheels may be controlled independently enough that the vehicle can operate substantially the same regardless of which end of the vehicle is facing the direction of travel. This symmetrical design provides several advantages. For example, the vehicle may be able to operate in a tighter space, as it may not be necessary to make a U-turn or other maneuver to redirect the vehicle so that it faces the "forward direction" before beginning a journey.

[0082] 7A and 7B are perspective views of an example four-wheeled road vehicle 700 (referred to herein simply as a "vehicle") that may be used in the transportation system described herein. FIGS. 7A-7B illustrate the symmetry and bidirectionality of the vehicle 700. Specifically, the vehicle 700 defines a first end 702, shown at the forefront of FIG. 7A, and a second end 704, shown at the forefront of FIG. 7B. In some examples, as shown, the first end 702 and the second end 704 are substantially identical. Furthermore, the vehicle 700 may be configured to be driven with either end pointing in the direction of travel. For example, when the vehicle 700 is traveling in the direction indicated by arrow 714, the first end 702 is the front end of the vehicle 700, and when the vehicle 700 is traveling in the direction indicated by arrow 712, the second end 704 is the front end of the vehicle 700.

[0083] The vehicle 700 may also include wheels 706 (e.g., wheels 706-1 through 706-4). The wheels 706 may be paired depending on their proximity to an end of the vehicle. Thus, wheels 706-1, 706-3 are located proximate a first end 702 of the vehicle and may be referred to as a first pair of wheels 706, and wheels 706-2, 706-4 are located proximate a second end 704 of the vehicle and may be referred to as a second pair of wheels 706. Each pair of wheels may be driven by at least one motor (e.g., an electric motor that may be a drive system or part of a drive system of the vehicle), and each pair of wheels may be capable of steering the vehicle. Because each pair of wheels is capable of rotating to steer the vehicle, the vehicle may have similar driving and handling characteristics regardless of the direction of travel. In some cases, the vehicle may operate in a two-wheel steering mode in which only one pair of wheels steers the vehicle 700 at a given time. In such cases, a change in direction of travel may change the particular wheel pairs that steer the vehicle 700. In other cases, the vehicle may operate in a four-wheel steering mode in which the wheels work in concert to steer the vehicle. In four-wheel steering mode, the wheel pairs may turn in either the same or opposite directions depending on the steering maneuver being performed and / or the speed of the vehicle.

[0084] The vehicle 700 may also include doors 708, 710 that open to allow passengers and other loads (e.g., luggage, baggage, cargo) to be placed inside the vehicle 700. The doors 708, 710, described in more detail herein, may extend over the top of the vehicle such that each of the doors defines two opposing side sections. For example, each door defines a side section on a first side of the vehicle and another side section on a second opposing side of the vehicle. Each door also defines a roof section that extends between the side sections and defines a portion of the roof (or top surface) of the vehicle. In some instances, the doors 708, 710 resemble an inverted "U" shape in cross section and may be referred to as a canopy door. The side and roof sections of the door may be formed as a rigid structural unit such that all components of the door (e.g., the side and roof sections) move in coordination with one another. In some cases, the doors 708, 710 include a one-piece shell or door chassis formed from a monolithic structure, which may be formed from composite sheets or structures including, for example, fiberglass, carbon composite, and / or other lightweight composite materials.

[0085] The vehicle 700 may also include a vehicle controller that controls the operation of the vehicle 700 and the vehicle's systems and / or subsystems. For example, the vehicle controller may control the vehicle's drive systems (e.g., motors, motor controllers, gearboxes, transmissions, etc.), steering systems, suspension systems, doors, etc. to facilitate vehicle operation, including navigating the vehicle along roads according to one or more vehicle control strategies. The vehicle controller may also be configured to communicate with other vehicles, transportation system controllers, vehicle presence detectors, or other components of the transportation system. For example, the vehicle controller may be configured to receive information from other vehicles regarding their vehicle's position in the platoon, speed, approaching speed or direction changes, etc. The vehicle controller may also be configured to receive information regarding available vehicle positions from the vehicle presence detectors. The vehicle controller may include a computer, processor, memory, circuitry, or any other suitable hardware components and may interconnect with other systems of the vehicle to facilitate the operations described herein and other vehicle operations.

[0086] 8A and 8B are side and perspective views of the vehicle 700 with the doors 708, 710 open. Because the doors 708, 710 define two opposing side sections and a roof section, respectively, an uninterrupted interior space 802 may be revealed when the doors 708, 710 are open. In the example shown in FIG. 8A and 8B, when the doors 708, 710 are open, an open section may be defined between the doors 708 and 710 that extends from one side of the vehicle 700 to the other. This may allow unhindered access to and egress from the vehicle 700 by occupants on both sides of the vehicle 700. The lack of overhead structure when the doors 708, 710 are open may allow occupants to walk across the vehicle 700 without overhead clearance limitations.

[0087] Vehicle 700 may also include seats 804, which may be located at either end of vehicle 700 and face each other. As shown, vehicle includes two seats 804, although other numbers of seats and other seating arrangements are possible (e.g., 0 seats, 1 seat, 3 seats, etc.). In some cases, seats 804 may be removed, folded up, or stowed so that wheelchairs, strollers, bicycles, or luggage may be more easily placed in vehicle 700.

[0088] Vehicles such as vehicle 700 for use in the transportation system described herein may be designed for safe and comfortable operation as well as ease of manufacture and maintenance. To achieve these benefits, the vehicle may be designed with a frame structure that contains many of the vehicle's structural and operational components (e.g., motor, suspension, battery, etc.) and is located low to the ground. The body structure may be attached or fixed to the frame structure. FIG. 9 shows a partial exploded view of a vehicle that may be an embodiment of vehicle 700, illustrating an example of the frame structure and body structure configuration. As described below, the combination of the frame structure and the relatively lightweight body structure at a low position results in a vehicle with a very low center of gravity, which improves the safety and handling of the vehicle. For example, a low center of gravity reduces the risk of the vehicle rolling over when the vehicle encounters an inclined road surface, wind loads, sharp turns, etc., and reduces the vehicle's body roll during turns or other maneuvers. Additionally, manufacturing and repairs may be simplified by locating many of the vehicle's operating components, such as the motor, battery, vehicle controller, and sensors (e.g., sensors that detect magnets or other markers attached to the road), on a frame structure (e.g., frame structure 904 in FIG. 9 ).

[0089] 9 is a partially exploded view of a vehicle 900, which may be an embodiment of vehicle 700. Details of vehicle 700 may be equally applicable to vehicle 900 and will not be repeated here. Vehicle 900 may include a body structure 902, which may include doors (e.g., doors 708, 710 described above) and other body components, and a frame structure 904 to which body structure 902 is mounted.

[0090] The frame structure 904 may include drive, suspension, and steering components of the vehicle. For example, the frame structure 904 may include a wheel suspension system (represented as points 912 in FIG. 9, which may define or include wheel mounts, axles, or hubs), a steering system, a drive motor, and optionally a motor controller. The wheels may be attached to the wheel suspension system via wheel mounts, axles, hubs, etc. The drive motor may include one or more drive motors that drive the wheels independently or in coordination with one another. The drive motors may receive power from a power source (e.g., a battery) attached to the frame structure 904. Motor controllers for the drive motors may also be attached to the frame structure 904.

[0091] The suspension system may be any suitable type of suspension system. In some cases, the suspension system includes an independent suspension system for each wheel. For example, the suspension system may be a double wishbone torsion bar suspension system. The suspension system may also be dynamically adjustable, such as to control ride height, suspension preload, damping, or other suspension parameters while the vehicle is stationary or moving. Other suspension systems, such as swing axle suspension, sliding pillar suspension, MacPherson strut suspension, etc., are also contemplated. Additionally, the spring and damping functions may be provided by any suitable components or systems, such as coil springs, leaf springs, air springs, hydropneumatic springs, magnetorheological shock absorbers, etc. The suspension system may be configured to operate in conjunction with undulations of the road surface (e.g., roads as described above) to maintain a desirable experience for the occupants.

[0092] The frame structure 904 may also include a steering system that allows the wheels to rotate to steer the vehicle. In some cases, the wheels may be independently steerable or may be linked (e.g., via a steering rack) to always point in substantially the same direction during normal operation of the vehicle. This further allows the vehicle to use a four-wheel steering scheme and to alternate between two-wheel and four-wheel steering schemes.

[0093] The frame structure 904 may include components such as batteries, motors, and mechanisms for opening and closing the vehicle doors, a control system (including a computer or other processing unit), and the like.

[0094] FIG. 9 shows an example configuration of a vehicle and frame structure. However, other configurations are possible. Also, the frame structure and body structure shown in FIG. 9 are intended as schematic representations of these components, which may include other structures omitted from FIG. 9 for clarity. Additional structural connections and integrations may occur between the body structure and the frame structure beyond those explicitly depicted in FIG. 9. For example, components of a door mechanism that opens and closes a door on the body structure may be joined to both the door and the frame structure.

[0095] In the foregoing description, certain terminology has been used for purposes of explanation to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that specific details are not required to practice the described embodiments. Thus, the foregoing description of the specific embodiments described herein has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one skilled in the art that many modifications and variations are possible in light of the above teachings. For example, while methods or processes disclosed herein have been described and illustrated with reference to certain operations performed in a particular order, these operations can be combined, sub-divided, or rearranged to form equivalent methods or processes without departing from the teachings of the disclosure. Furthermore, structures, features, components, materials, steps, processes, etc. described herein with respect to one embodiment may be omitted from that embodiment or incorporated in other embodiments. Furthermore, although the term "road" is used herein to refer to a structure that supports moving vehicles, the roads described herein do not necessarily conform to definitions, standards, or requirements as may be used in laws, regulations, transportation rules, etc. that may be associated with the term "road." Thus, the roads described herein need not (and in fact may not) provide the same characteristics and / or structure as a conventional “road.” Of course, the roads described herein may comply with any and all applicable laws, safety regulations, or other rules for the safety of occupants, bystanders, operators, construction workers, maintenance personnel, and the like.

Claims

1. 1. A method of navigating a plurality of vehicles along a road, comprising: In the vehicle, navigating along a first segment of a road according to a first vehicle control strategy; in response to crossing a boundary between a first segment of the road and a second segment of the road, transitioning from navigating according to the first vehicle control scheme to navigating according to a second vehicle control scheme different from the first vehicle control scheme, the second vehicle control scheme corresponding to a vehicle control scheme of a moving position target; The step of transitioning from navigating according to the first vehicle control strategy to navigating according to the second vehicle control strategy includes: selecting, from a plurality of candidate tracking functions, a tracking function associated with a time at which the vehicle enters the second segment of the road; responsive to crossing the boundary, causing the vehicle to follow a moving position target defined by the selected tracking function; A method comprising:

2. 2. The method of claim 1 , wherein the first vehicle control strategy is a platooning vehicle control strategy in which the vehicle is configured to change a speed of the vehicle in response to detecting a change in a speed of a downstream vehicle.

3. The plurality of candidate tracking functions are stored in the vehicle; The method of claim 1 , wherein the act of selecting the tracking function is performed by a vehicle controller of the vehicle.

4. The method of claim 1 , wherein the act of selecting the tracking function is performed by a transportation system controller.

5. The method of claim 4 , wherein the transportation system controller transmits the tracking function to the vehicle.

6. the vehicle is a first vehicle, The method comprises: determining whether a second vehicle is located between the first vehicle and the boundary; based on a determination that a second vehicle is located between the first vehicle and the boundary, stopping the first vehicle in front of the boundary until the second vehicle enters the second segment of the road; The method of claim 1 further comprising:

7. The vehicle control method of the moving position target is a vehicle control method of a first moving position target, the first vehicle control method corresponds to a vehicle control method of a second moving position target different from a vehicle control method of the first moving position target; The method of claim 1 , wherein a first vehicle flow rate defined by a vehicle control strategy of the first moving position target is the same as a second vehicle flow rate defined by a vehicle control strategy of the second moving position target.

8. 1. A transportation system including a plurality of vehicles configured to autonomously navigate along roads, The vehicle is configured to navigate along a first segment of a road according to a first vehicle control strategy; configured to transition from navigating according to the first vehicle control scheme to navigating according to a second vehicle control scheme different from the first vehicle control scheme in response to crossing a boundary between the first segment of the road and a second segment of the road, the second vehicle control scheme corresponding to a vehicle control scheme of a moving position target; Transitioning from navigating according to the first vehicle control strategy to navigating according to the second vehicle control strategy includes: selecting, from a plurality of candidate tracking functions, a tracking function associated with a time at which the vehicle enters the second segment of the road; responsive to crossing the boundary, causing the vehicle to follow a moving position target defined by the selected tracking function; , including, transportation systems.

9. 10. The transportation system of claim 8, wherein the first vehicle control strategy is a platooning vehicle control strategy in which the vehicle is configured to change a speed of the vehicle in response to detecting a change in a speed of a downstream vehicle.

10. The vehicle is a drive system configured to propel the vehicle; a steering system configured to steer the vehicle; a vehicle position controller configured to control the steering system and the drive system to maintain the vehicle at a travel position target defined by the selected tracking function; The transportation system of claim 8 .

11. The plurality of candidate tracking functions are stored in the vehicle; The transportation system of claim 8 , wherein the act of selecting the tracking function is performed by a vehicle controller of the vehicle.

12. The act of selecting the tracking function is performed by a transport system controller; The transportation system of claim 8 , wherein the transportation system controller transmits the tracking function to the vehicle.

13. The transportation system of claim 8 , further comprising a detectable component located at the boundary and detectable by the vehicle.

14. 14. The transportation system of claim 13, wherein the vehicle begins navigating according to the second vehicle control strategy in response to detecting the detectable component.

15. 1. A method of navigating a plurality of vehicles along a road, comprising: In a transport system controller, detecting that a vehicle is approaching a boundary between a first segment of a road associated with a first vehicle control scheme and a second segment of a road associated with a second vehicle control scheme different from the first vehicle control scheme, the second vehicle control scheme corresponding to a vehicle control scheme of a moving position target; in response to detecting the vehicle approaching the boundary, selecting from a plurality of candidate tracking functions a tracking function associated with a time at which the vehicle enters the second segment of the road; transmitting the tracking function to the vehicle, the vehicle being configured to follow a moving position target defined by the selected tracking function when the vehicle enters the second segment of the road; A method comprising:

16. In the vehicle, receiving the tracking function; detecting when the vehicle enters the second segment of the road; in response to detecting that the vehicle has entered the second segment of the road, beginning to follow the moving position target defined by the selected tracking function; The method of claim 15 further comprising:

17. 16. The method of claim 15, wherein the first vehicle control strategy is a platooning vehicle control strategy in which the vehicle is configured to change a speed of the vehicle in response to detecting a change in a speed of a downstream vehicle.

18. The vehicle control method of the moving position target is a vehicle control method of a first moving position target, The method of claim 15 , wherein the first vehicle control strategy corresponds to a vehicle control strategy of a second moving position target that is different from a vehicle control strategy of the first moving position target.

19. In the transportation system controller, selecting a modified tracking function for the vehicle in response to changes in at least one of weather conditions, road conditions, and traffic conditions; transmitting the modified tracking function to the vehicle; transitioning, at the vehicle, in response to receiving the modified tracking function, from following the moving position target defined by the selected tracking function to following a new moving position target defined by the modified tracking function; The method of claim 15 further comprising:

20. 20. The method of claim 19, wherein the vehicle detects changes in at least one of the weather conditions, the road conditions, and the traffic conditions and transmits information about the detected changes to the transportation system controller.

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