Braking and signaling schemes for autonomous vehicle system

Abstract

To provide A robust and safe braking operation for an autonomous vehicle in a transport system.SOLUTION: A method of decelerating a plurality of vehicles along a roadway may include, at a first vehicle, receiving, from an adjacent downstream vehicle, a first braking initiation signal and a first deceleration value indicating a deceleration rate of the adjacent downstream vehicle, determining a first distance to the adjacent downstream vehicle, and determining, based at least in part on the first distance, a second deceleration value configured to prevent the first vehicle from colliding with the adjacent downstream vehicle. The method may further include in accordance with a determination that the second deceleration value is greater than or equal to an upper deceleration value, decelerating at the upper deceleration value, and, in accordance with a determination that the second deceleration value is less than the upper deceleration value and greater than a lower deceleration target, decelerating at the second deceleration value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This Patent Cooperation Treaty patent application claims priority to U.S. Provisional Patent Application No. 63 / 041,513, filed on June 19, 2020, entitled "Braking and Signaling Schemes for Autonomous Vehicle System", the content of which is hereby incorporated by reference in its entirety.

[0002] The embodiments described generally relate to vehicles, and more particularly, to braking and signaling schemes for autonomous vehicles in an autonomous vehicle system.

Background Art

[0003] Vehicles such as cars, trucks, vans, buses, and streetcars are present everywhere in modern society. Cars, trucks, and vans are often used for personal transportation to transport a relatively small number of passengers, while buses, streetcars, and other large vehicles are often used for public transportation. Vehicles can also be used for carrying goods or other purposes. Such vehicles may be driven on roads, which may include paved roads, bridges, highways, overpasses, or other types of vehicle rights - of - way. Driverless or autonomous vehicles can relieve individuals of the need to manually operate a vehicle for their transportation needs.

Summary of the Invention

[0004] A method for decelerating a plurality of vehicles along a road can include, at a first vehicle, receiving, from a downstream vehicle in the vicinity, a first braking start signal and a first deceleration value indicating a deceleration rate of the downstream vehicle in the vicinity; determining a first distance to the downstream vehicle in the vicinity; and determining a second deceleration value set to prevent a collision with the downstream vehicle in the vicinity of the first vehicle, at least partially based on the first distance. The method can further include decelerating at an upper deceleration value in accordance with a determination that the second deceleration value is greater than or equal to the upper deceleration value, and decelerating at the second deceleration value in accordance with a determination that the second deceleration value is less than the upper deceleration value and greater than a lower deceleration target value. The second deceleration value can further be at least partially based on the speed of the first vehicle, the speed of the downstream vehicle in the vicinity, and the first deceleration value. The upper deceleration value can correspond to a maximum deceleration value that the first vehicle can withstand without skidding.

[0005] The method can further include transmitting, to an upstream vehicle in the vicinity, the second braking start signal and the upper deceleration value in accordance with a determination that the second deceleration value is greater than or equal to the upper deceleration value. The method can further include transmitting, to an upstream vehicle in the vicinity, the second braking start signal and the second deceleration value in accordance with a determination that the second deceleration value is less than the upper deceleration value and greater than the lower deceleration target value.

[0006] The method can further include maintaining the speed of the vehicle in accordance with a determination that the first deceleration value is less than or equal to the lower deceleration target value, detecting a deceleration rate of a downstream vehicle in the vicinity after maintaining the speed of the vehicle for a certain period of time, and decelerating at the lower deceleration target in response to detecting the deceleration rate of the downstream vehicle in the vicinity.

[0007] A nearby downstream vehicle may include an optical input / output system configured to transmit information, and the first vehicle may include an optical sensing system configured to receive the information transmitted by the optical input / output system. The first braking start signal may be transmitted via the optical output system of the nearby downstream vehicle and may also be received by the optical sensing system of the first vehicle. The first deceleration value may be transmitted as an encoded signal via the optical output system of the nearby downstream vehicle.

[0008] The vehicle includes a drive system configured to move the vehicle forward, a braking system configured to decelerate the vehicle, a steering system configured to steer the vehicle, and a vehicle control unit. The vehicle control unit is configured to receive, from a nearby downstream vehicle, a first braking start signal and a first deceleration value indicating the deceleration rate of the nearby downstream vehicle, to determine a first distance to the nearby downstream vehicle, and at least partially based on the first distance, to determine a second deceleration value set to prevent a collision with the nearby downstream vehicle of the vehicle. In accordance with a determination that the second deceleration value is greater than or equal to an upper deceleration value, the vehicle control unit can decelerate the vehicle at the upper deceleration value using the braking system. In accordance with a determination that the second deceleration value is less than the upper deceleration value and greater than a lower deceleration target value, the vehicle control unit can decelerate the vehicle at the second deceleration value using the braking system. The vehicle may further include an optical output system configured to transmit deceleration information to a nearby upstream vehicle and an optical sensing system configured to receive the first braking start signal and the first deceleration value.

[0009] The vehicle control unit may further be configured to determine a second deceleration value based at least in part on the speed of the vehicle and the speed of a downstream vehicle in the vicinity. The vehicle control unit may further be configured to transmit deceleration information to an upstream vehicle in the vicinity according to a determination that the second deceleration value is greater than or equal to an upper deceleration value, where the deceleration information includes a second braking start signal and the upper deceleration value. The vehicle control device may further be configured to transmit deceleration information to an upstream vehicle in the vicinity in response to a determination that the second deceleration value is less than a higher deceleration value, where the deceleration information includes a second braking start signal and the second deceleration value.

[0010] A method for decelerating a plurality of vehicles along a road may include, at a first vehicle, receiving from a downstream vehicle in the vicinity a first braking start signal and a first deceleration value indicating a deceleration rate of the downstream vehicle in the vicinity, and determining a second deceleration value set to prevent the first vehicle from colliding with the downstream vehicle in the vicinity. The method may include transmitting, according to a determination that the second deceleration value is greater than or equal to an upper deceleration value, a second braking start signal and the upper deceleration value to a second vehicle, and decelerating at the upper deceleration value. The method may further include, at the second vehicle, receiving the second braking start signal and the upper deceleration value from the first vehicle, and determining a third deceleration value configured to prevent the second vehicle from colliding with the first vehicle. The method may further include transmitting, according to a determination that the third deceleration value is less than the upper deceleration value and greater than a lower deceleration target value, a third braking start signal and the third deceleration value to an upstream vehicle in the vicinity, and decelerating at the third deceleration value.

[0011] The method may further include, at the second vehicle, transmitting, according to a determination that the third deceleration value is greater than or equal to the upper deceleration value, the third braking start signal and the upper deceleration value to the vehicle in the vicinity, and decelerating at the upper deceleration value.

[0012] A method for determining the deceleration rate of a vehicle within a group of vehicles may include, at each vehicle within the group, determining a respective distance to each upstream vehicle in its vicinity, determining a respective deceleration value based on at least a portion of each distance, and receiving, at a vehicle within the group traveling at a certain speed and related to the first deceleration value, a braking instruction of the upstream vehicle in the vicinity and a second deceleration value of the next braking event of the upstream vehicle in the vicinity. The method may further include decelerating at an upper deceleration value according to a determination that the first deceleration value is greater than or equal to the upper deceleration value, decelerating at the first deceleration value according to a determination that the first deceleration value is less than the upper deceleration value and greater than the lower deceleration target value, and maintaining the vehicle at its speed according to a determination that the first deceleration value is less than or equal to the lower deceleration target value.

[0013] The method may further include, at each vehicle within the group, determining the speed of each upstream vehicle in its vicinity, and the respective deceleration values may be determined based at least in part on the speed of each upstream vehicle in its vicinity.

[0014] The method may further include, at the vehicle, detecting the deceleration of the upstream vehicle in the vicinity after maintaining the vehicle at the speed, and decelerating at the lower deceleration target. The upper deceleration value corresponds to the maximum deceleration value that the vehicle can withstand without skidding, and the lower deceleration target value may be 2.0 m / s 2 as follows.

Brief Description of the Drawings

[0015] The present disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings. Here, like reference numerals indicate like structural elements.

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DETAILED DESCRIPTION OF THE INVENTION

[0025] Detailed Description Hereinafter, a representative embodiment illustrated in the accompanying drawings will be described in detail. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the described embodiments as defined by the appended claims.

[0026] Embodiments of the present specification generally relate to a transportation system in which a number of vehicles may be autonomously operated to transport passengers and / or cargo along a road. For example, a transportation system or service can provide a fleet of vehicles that operate along a road to pick up and drop off passengers at either a preset location or stop, or at a dynamically selected location (e.g., selected by a person via a smartphone). As used herein, the term "road" can refer to a structure that supports moving vehicles.

[0027] However, the autonomous operation of vehicles is a complex task, and the specific techniques or methods employed by vehicles on the road can have a dramatic impact on both the comfort and safety of passengers and / or cargo within the vehicles as well as the overall operation of the system. One important aspect for the safe operation of a transportation system is braking. For example, to maximize the efficiency and throughput of a transportation system, it is advantageous to minimize the distance between vehicles. However, as vehicles get closer, it becomes more important that a following vehicle can stop safely in the event that the leading vehicle unexpectedly decelerates, such as to avoid an obstacle on the road. Thus, the safety and efficiency of a transportation system can be enhanced by providing a robust braking system as follows, i.e., a braking system in which a leading vehicle can quickly transmit information about upcoming braking events that will occur in the near future, a following vehicle can quickly respond to the information received from the leading vehicle, and on the other hand, can propagate information about upcoming braking events to further following vehicles.

[0028] Described herein are various techniques and systems for providing robust and safe braking operations for autonomous vehicles in a transportation system. One aspect of such techniques and systems relates to an optical communication system that enables vehicles to communicate with each other in a reliable manner at high speeds. For example, as described herein with respect to FIGS. 2A and 2B of FIG. 2, vehicles may each include an optical output system and an optical input system, which facilitate the transmission and reception of braking information such as braking instructions (e.g., warnings indicating an imminent or active braking event), as well as information regarding a braking event (e.g., the deceleration rate of a vehicle during an imminent or active braking event). Such a system enables braking event information to quickly pass through a population of vehicles, such that each vehicle can initiate deceleration at an appropriate speed even before the deceleration of a downstream vehicle is detected. As used herein, deceleration means a decrease in speed. It will be understood that a deceleration rate or deceleration value may also be characterized as a negative acceleration rate or negative acceleration value. For purposes of the calculations or evaluations described herein, either sign convention may be used.

[0029] The vehicle can operate according to a braking control scheme, which defines how vehicles in a group should react to braking events and attempts to minimize the number of vehicles that have to implement high deceleration values that may be uncomfortable for passengers. For example, as described herein with respect to FIGS. 4-5, the vehicle can be configured to monitor the speed and distance of nearby upstream vehicles (e.g., the vehicle immediately ahead) and continuously determine the deceleration rate required to prevent a collision with the nearby upstream vehicle. If a nearby upstream vehicle has to decelerate in an emergency to avoid a collision with an object or other obstacle in the road, the nearby upstream vehicle can transmit information about the next braking event, such as a planned deceleration rate, to the downstream vehicle. The downstream vehicle can then determine how to react based on the planned deceleration rate of the upstream vehicle as well as its own safe deceleration rate. The downstream vehicle may also provide information to further upstream (e.g., following) vehicles, such that they can each determine how to react based on the planned deceleration rate of the downstream vehicle and their respective own safe deceleration rates. As described herein, this system enables the vehicle to start decelerating earlier than would be possible if the vehicle simply reacted to the detected deceleration of the downstream vehicle and can also reduce the number of vehicles in the group (or otherwise in proximity to each other) that have to decelerate beyond a comfortable level.

[0030] As used herein, "downstream" refers to an object (e.g., a vehicle) that is in front of a position in a particular vehicle or traveling direction, and "upstream" refers to an object (e.g., a vehicle) that is behind a position in a particular vehicle or traveling direction. Thus, for example, within a group of vehicles moving from west to east, the easternmost vehicle in the group is considered to be downstream of all other vehicles in the group. Similarly, the westernmost vehicle in the group is considered to be upstream of all other vehicles in the group. Further, unless otherwise specified, the terms "preceding" and "following" are used to indicate relative positions rather than absolute positions. Accordingly, a preceding vehicle can be any vehicle that is ahead of or downstream of another vehicle, and a following vehicle can be any vehicle that is behind or upstream of another vehicle.

[0031] Vehicles within the system can share braking information and / or deceleration information using optical communication technology and / or an optical communication system. For example, each vehicle can include an optical sensing system and an optical output system. The optical output system can be configured to transmit or output information such as a braking start signal (e.g., an indication that a braking event is imminent or active), a planned deceleration value, etc. The optical output system may include a plurality of lights that are selectively illuminated to convey the information. The optical output from one vehicle can be detected by the (plural) optical sensing systems of other vehicles.

[0032] FIG. 1 illustrates a portion of a road 100 for an autonomous vehicle 108 according to an embodiment described in the specification. The portion of the road shown in FIG. 1 is shown at ground level in a typical urban or suburban environment, but this is not limiting. In fact, the road may be deployed in any environment or location, including rural areas, inside buildings, in whole or in part, away from roads, elevated structures, underground, etc. Road 100 is shown with a plurality of four-wheeled vehicles 108 navigating along road 100. Vehicle 108 may be an autonomous or semi-autonomous vehicle specifically designed for use with road 100. An example of the type of vehicle for use with road 100 is described in connection with FIGS. 7-9, but other types of vehicles may be driven along road 100 in place of, or in addition to, the vehicles described herein. Road 100, of which only a small portion is shown in FIG. 1, can include a plurality of segments, including straightaways, turns, intersections, bridges, tunnels, boarding zones, parking facilities, etc. To facilitate safe and efficient vehicle operation, vehicles 108 on road 100 can use a braking control scheme, whereby information regarding braking events is rapidly propagated between vehicles and the vehicles can make intelligent decisions about the rate at which they should decelerate in order to maintain both safety and comfort.

[0033] FIG.A and FIG.2B of FIG. 2 show an exemplary vehicle 108. As described herein, the vehicle 108 can be configured for bidirectional operation. Thus, the vehicle 108 can include optical communication systems 200 (e.g., optical communication systems 200-1, 200-2) at each end of the vehicle. Each optical communication system can include an optical output system 201 (e.g., optical output systems 201-1, 201-2) configured to transmit information to other vehicles, and an optical sensing system 204 (e.g., optical sensing systems 204-1, 204-1) configured to detect and / or receive information from other vehicles (e.g., from the optical output systems of other vehicles). This configuration provides several advantages. For example, the vehicle can receive information from a preceding vehicle and transmit information to a following vehicle regardless of which end of the vehicle is acting as the "front" of the vehicle. Also, having both an optical output system and an optical sensing system at both ends of the vehicle enables bidirectional communication (e.g., the vehicle can communicate with both upstream and downstream vehicles).

[0034] The optical output system 201 can include a plurality of light sources 202. The optical output system 201 can transmit information via the light sources 202 by selectively illuminating the light sources according to an encoding scheme. For example, the optical output system 201 can be configured to transmit various types of information, including deceleration information, to other vehicles (and the corresponding optical sensing system to receive it). The deceleration information can include a braking start signal and / or a deceleration value. As used herein, the deceleration value can refer to a deceleration rate, and these terms can be used interchangeably unless otherwise specified. Other types of information that can be transmitted and received by the optical communication system 200 can include the number of vehicles ahead in the group, acceleration events and / or deceleration events that are scheduled or likely to occur soon, information regarding upcoming maneuvers (e.g., right turn, left turn, scheduled stop), the number or type of payloads in the vehicle (e.g., humans or cargo), etc., but are not limited thereto.

[0035] The braking start signal can indicate that the vehicle transmitting the signal is under a deceleration event or a braking event, and the deceleration value can indicate the rate at which the vehicle is decelerating or attempting to decelerate. Other information, such as the time when a deceleration event is expected or predicted to occur soon, a steering event that will occur soon (e.g., when and how much the leading vehicle will turn), an acceleration that will occur soon, etc., can also be transmitted.

[0036] The following vehicle can receive information from the optical output system 201 of the leading vehicle (e.g., via the optical sensing system 204 of the following vehicle described herein) and react according to a braking control scheme. For example, upon receiving deceleration information from the leading vehicle, the following vehicle can determine whether to initiate deceleration, what deceleration rate to use for that deceleration, and what information to transmit to the following vehicles.

[0037] The optical output from one vehicle can be detected and / or received by the optical sensing system 204 of the other vehicle. The optical sensing system 204 can include components such as lenses, image sensors, processors, memories, imaging software and / or firmware, and / or other suitable components that facilitate the capture and / or analysis of images and, optionally, the decoding of the captured information. The optical sensing system 204 can have optical characteristics (e.g., focal length, field of view, resolution) and can be designed such that the optical output system 201 of a nearby vehicle is optically detectable by the optical sensing system 204.

[0038] As described above, the information transmitted by the optical communication system 200 may be in an encoded format. For example, if the optical output system 201 includes a plurality of light sources as shown in FIGS. A and 2B of FIG. 2, each light source can convey 1 bit of information (e.g., a light source that is off conveys a value of 0, and a lit light source conveys a value of 1). Thus, for example, an optical output system 201 including 8 light sources 202 can facilitate an 8-bit information channel. More or fewer light sources can be used to provide an appropriate amount of information transfer between vehicles.

[0039] In some cases, some of the light sources are used for binary or other encoded communication, while other light sources are used to convey information on a dedicated single-bit channel. For example, in the optical output system 201 shown in FIGS. A and 2B of FIG. 2, one light source can be reserved as a brake indicator that conveys a brake start signal (e.g., the light source is on and thus braking and the resulting deceleration are currently active, the light source is off and braking is not active), while the remaining 7 light sources can be used as a 7-bit channel to convey information such as deceleration values associated with a braking event (or an impending braking event). The 7-bit channel can also be used to convey other information such as vehicle speed, impending maneuvers (e.g., turns, accelerations, decelerations), type of cargo within the vehicle (e.g., packages, passengers), etc.

[0040] The optical communication system 200 can be used for the propagation of rapid deceleration information between vehicles, and more particularly, to upstream vehicles. As described above, the information can include not only the fact that the leading vehicle is actively braking, but also the actual deceleration value at which the leading vehicle is braking or the actual deceleration value at which it will brake. Further, the use of optical communication can enable vehicles further upstream to prepare (or initiate) a braking operation even before they can detect the actual deceleration of vehicles in the immediate downstream vicinity.

[0041] FIG.A to FIG.3C of FIG. 3 show a top view of a road 302 along which a plurality of vehicles 300 (300-1 to 300-7) are traveling in the traveling direction 301. FIG.A to FIG.3C of FIG. 3 show how deceleration information such as a deceleration value can be propagated upstream through a group of vehicles or other groups. More specifically, FIG.A to FIG.3C of FIG. 3 show how deceleration information moves faster through a group of vehicles 300 than a physical braking event.

[0042] FIG.A of FIG. 3 shows the road at time t0. At this time, vehicle 300-1 needs to detect an obstacle on the road or otherwise start a braking event. When vehicle 300-1 starts a braking event (or optionally, before starting a braking event), vehicle 300-1 can start braking (as indicated by the enclosed x symbol) and transmit a deceleration value 305 indicating the deceleration rate of vehicle 300-1 to the upstream vehicle 300-2 in the vicinity. Vehicle 300-1 may also transmit a braking start signal (for example, indicating that braking is occurring). At time t0 shown in FIG.A of FIG. 3, both the wavefront of the deceleration value 305 and the wavefront of the actual braking operation are at position 304.

[0043] Due to the speed of optical communication, the wavefront of the deceleration value information may propagate quickly through a group of vehicles 300. For example, FIG.B of FIG. 3 shows the road at time t1. At this time, vehicles 300-2, 300-3, 300-4 are in a state of receiving a deceleration value from an upstream vehicle, even though only vehicles 300-1 and 300-2 have actually started decelerating. Therefore, the wavefront of the deceleration value has moved further upstream (for example, to position 308) than the wavefront of the physical braking operation (for example, to position 306).

[0044] FIG.C in FIG. 3 shows road 302 at time t2. At this time, vehicles 300-2, 300-3, 300-4, 300-5, 300-6, and 300-7 are receiving deceleration values from upstream vehicles even though only vehicles 300-1, 300-2, 300-3, and 300-4 have actually started to decelerate. Therefore, the wavefront of the deceleration value has moved further upstream (e.g., up to position 314) than the wavefront of the physical braking operation (e.g., up to position 312).

[0045] FIG.A to FIG. 3C in FIG. 3 show how information regarding an impending braking event can be transmitted earlier than if vehicles simply reacted to the detection of the actual physical deceleration of immediately neighboring upstream vehicles through a group of vehicles. Since upstream vehicles have information about how immediately neighboring downstream vehicles are going to decelerate, there is a possibility that upstream vehicles can make decisions about their own braking parameters before they actually have to start the deceleration operation.

[0046] A plurality of vehicles are traveling within a group or a cluster. When the leading vehicle has to execute a deceleration operation (e.g., due to an unexpected obstacle or danger that appears on the road), the leading vehicle may have to decelerate quite rapidly to avoid a collision with the obstacle or the danger. In some cases, the leading vehicle has to decelerate at an upper deceleration value that can correspond to the maximum deceleration value that the vehicle can withstand without skidding (e.g., without the wheels locking up and without causing a continuous slide or skid between the vehicle's tires and the road). However, such a rapid deceleration is uncomfortable for the passengers and may also increase mechanical wear and stress on the vehicle. Therefore, it is advantageous to reduce the number of vehicles that need to decelerate at that speed within the vehicle group. For example, instead of each vehicle decelerating at the same maximum rate, if it is safe to do so as follows, each vehicle can make an independent determination regarding its own deceleration speed according to a scheme that results in the upstream vehicle decelerating at a slower rate (e.g., a lower deceleration value) than the downstream vehicle. The optical communication system of the vehicle helps to facilitate such a scheme because each vehicle can evaluate its own deceleration requirement considering the actual deceleration rate of the vehicle in front of it.

[0047] In one example of a braking control scheme, each vehicle continuously (e.g., periodically) determines a minimum deceleration rate, which would be necessary to prevent a collision with an immediately neighboring upstream vehicle (which may be referred to herein as the vehicle's base deceleration rate). Next, when the vehicle receives information that an immediately neighboring upstream vehicle is about to start braking, it can evaluate its base deceleration rate using the deceleration rate notified by the immediately neighboring upstream vehicle and determine which deceleration rate to use for its own braking event and whether to notify or transmit the deceleration rate to a following vehicle. This braking control scheme may be configured such that, when it is safe to do so, an upstream vehicle decelerates at a lower rate than a downstream vehicle. FIGS. 4 through 6 illustrate an example of a braking control scheme, where an example of the braking control scheme results in an even more upstream vehicle decelerating at a lower deceleration value than a downstream vehicle, thereby reducing the overall impact that a braking event (particularly an emergency braking event) has on other vehicles on the road.

[0048] As described above, each vehicle within a transportation system may be configured to continuously or periodically determine a minimum deceleration rate necessary to prevent a collision with an immediately neighboring upstream vehicle. FIG. 4 shows two exemplary vehicles, vehicle A 400 and vehicle B 402, traveling in the same direction (e.g., to the right). Vehicle A 400 may be traveling at speed V A and vehicle B 402 may be traveling at speed V BIt may be traveling, and vehicle B is separated from vehicle A by a distance d behind vehicle A. Each vehicle may include sensors that allow the vehicle to determine these values. For example, each vehicle may have a speedometer, as a result, it can determine its own speed, and may also have an additional sensor system, which enables the additional sensor system to determine the distance d and speed of the downstream vehicle in the immediate vicinity. Such a sensor system may include proximity sensors (e.g., optical, ultrasonic), radar (radio detection and ranging), lidar (Light Detection and Ranging), imaging systems, or any other suitable type of sensing system, as well as any related circuitry, processors, memory, hardware, software, firmware, etc. that facilitate the sensing function. In some cases, the subsequent vehicle (e.g., vehicle B 402) may determine the speed of the nearby vehicle (e.g., vehicle A 400) based on its own speed (measured, for example, by a speedometer, GPS, or other system) and, if any, the change in distance d.

[0049] When these values are provided, JPEG2025093933000002.jpg52163As described above, each vehicle can calculate its base deceleration value continuously or periodically, so that in the event of an unexpected braking event, the accurate base deceleration value can be maintained.

[0050] When vehicle B 402 receives a braking start signal from the optical communication system of an immediately neighboring upstream vehicle (e.g., vehicle A 400) and a deceleration value used by the immediately neighboring upstream vehicle (e.g., vehicle A 400) during a braking event occurring nearby, vehicle B 402 can evaluate its base deceleration rate with respect to the received deceleration value of vehicle A 400 and take one or more actions based on that evaluation. For example, vehicle B 402 can determine whether its base deceleration rate is greater than or equal to an upper deceleration value (e.g., the maximum deceleration value that vehicle B 402 can withstand without skidding). In response to a determination that the base deceleration rate is greater than or equal to the upper deceleration value, vehicle B 402 decelerates at the upper deceleration value (e.g., by decelerating the vehicle in the vehicle's braking system). This determination and the corresponding action reflect the fact that vehicle B 402 must decelerate at the maximum safe rate when attempting to avoid a collision with vehicle A 400.

[0051] On the other hand, when vehicle B 402 determines that its base deceleration rate is less than the upper deceleration value and greater than a lower deceleration target value, vehicle B may decelerate at its base deceleration rate (e.g., by decelerating the vehicle in the vehicle's braking system). The lower deceleration target value can correspond to a deceleration rate selected based on being comfortable for the vehicle's occupants or, otherwise, on safety, comfort, the occupants' preferences, or any other suitable factor. For example, the lower deceleration target value can be about 1.5 m / s 2 , 2.0 m / s 2 , 2.5 m / s 2 , 3.0 m / s 2 , or any other suitable value.

[0052] When vehicle B 402 determines that its base deceleration rate is less than or equal to the lower deceleration target value, vehicle B 402 may maintain its speed for at least the duration before starting deceleration. This operation may be due to the fact that emergency braking (e.g., exceeding the lower deceleration target value) and immediate braking response (e.g., before detecting the actual deceleration of a downstream vehicle in the vicinity) are not necessary to avoid a collision. Rather, vehicle B 402 can drive according to the normal operation mode, in which when it detects the actual deceleration rate of a downstream vehicle in the vicinity, it is at the lower deceleration target value. Thus, for example, after maintaining its speed for that duration, vehicle B 402 may immediately detect the actual deceleration rate of a downstream vehicle in the vicinity (vehicle A 400) by, for example, determining a decrease in the distance between the vehicles, and in response to detecting the deceleration rate of the downstream vehicle in the vicinity, may start decelerating at the lower deceleration target (e.g., by causing the vehicle to decelerate in the vehicle's braking system).

[0053] To continue the propagation of information through the group of vehicles, vehicle B 402 may also transmit information to an upstream vehicle in the vicinity, and the specific information transmitted may be based, at least in part, on a deceleration value selected based on information from a downstream vehicle. For example, in response to a determination that the base deceleration rate is greater than or equal to an upper deceleration value, vehicle B may transmit a braking start signal and the upper deceleration value to an upstream vehicle in the vicinity. On the other hand, in response to a determination that the base deceleration rate is less than the upper deceleration value and greater than the lower deceleration target value, vehicle B 402 may transmit a second braking start signal and the base deceleration rate to an upstream vehicle in the vicinity.

[0054] The information transmitted from vehicle B402 to the upstream vehicle notifies the upstream vehicle that vehicle B402 has started its braking event and also indicates the deceleration value that vehicle B402 intends to use. Thus, the immediately adjacent upstream vehicle can make its own determination as to which deceleration rate to use by applying the same or a similar operation as that described for vehicle B402. This scheme facilitates the rapid transmission of braking information and also results in a natural attenuation of braking aggressiveness through the group of vehicles, such that no given vehicle need use a greater deceleration rate than is necessary for comfort and / or safety. Put another way, each vehicle determines whether, given factors such as its speed, the distance to the downstream vehicle, and the impending deceleration rate of the downstream vehicle, it is possible to decelerate at a rate less severe than that of the downstream vehicle. If it is possible and safe to decelerate at the lower deceleration rate, it will do so, and that rate will in turn enable the still more upstream vehicle to decelerate at an even lower rate.

[0055] Figures 5 - 6 illustrate how the above braking and communication scheme results in an attenuation or decrease of the deceleration rate towards the upstream vehicles within a group of vehicles. For example, Figure 5 shows a plot 500 using the deceleration rate (y-axis: DECLERATION RATE) for six exemplary vehicles (VEHICLE on the x-axis). Vehicle 1 could be the first vehicle within the group to encounter an obstacle or have a need to perform an emergency braking operation. In this example, vehicle 1 determines that it must decelerate at the upper deceleration rate 502 (e.g., the maximum deceleration value that vehicle 1 can withstand without skidding) in order to avoid a collision or other problem (or increase the chance of avoidance). As described above, vehicle 1 will transmit a braking start signal and its deceleration rate (e.g., the maximum value) to the immediately adjacent upstream vehicle (vehicle 2).

[0056] At plot 500, vehicle 2 can evaluate its own deceleration rate (e.g., calculated by Equation 1) against the deceleration rate received from vehicle 1 to determine how to decelerate (and what information to provide to vehicle 3). In the example shown in FIG. 5, the deceleration rate calculated by vehicle 2 itself (from Equation 1) is below the upper deceleration rate but above the lower deceleration target value 504. As described above, in this situation, vehicle 2 will decelerate at the deceleration rate it calculated itself.

[0057] Next, vehicle 3 determines its own deceleration rate (e.g., as calculated by Equation 1), receives a braking start signal and the deceleration rate of vehicle 2 from vehicle 2, and evaluates its own deceleration rate against the deceleration rate received from vehicle 2 to determine how to decelerate (and what information to provide to vehicle 4). In the illustrated example, the deceleration rate calculated by vehicle 3 itself (from Equation 1) is also lower than the upper deceleration rate 502 but above the lower deceleration target value 504. As described above, in this situation, vehicle 3 will decelerate at its own calculated deceleration rate rather than at the upper deceleration rate 502 or the lower deceleration target value 504.

[0058] In the example of FIG. 5, vehicle 4 is the first vehicle that can safely decelerate at the lower deceleration target value 504. In particular, vehicle 4 determines its own deceleration rate (e.g., as calculated by Equation 1), receives a braking start signal and the deceleration rate of vehicle 3 from vehicle 3, and evaluates its own deceleration rate against the deceleration rate received from vehicle 3 to determine how to decelerate (and what information to provide to vehicle 5). Since the deceleration rate calculated by vehicle 4 itself (from Equation 1) is below or equal to the lower deceleration target value 504, vehicle 4 may delay deceleration until it detects the deceleration of vehicle 3, and at that point, start decelerating at the lower deceleration target value 504.

[0059] Vehicle 4 also transmits the actual deceleration rate of vehicle 4 (here, the lower deceleration target value 504) and a braking start signal to vehicle 5. Accordingly, vehicle 5 can determine that its own deceleration rate is also equal to or less than the lower deceleration target value 504. In this way, once vehicle 5 detects vehicle 4 that is actually decelerating, it can decelerate at the lower deceleration target value 504. Vehicle 6 can operate in the same manner as vehicle 5.

[0060] Plot 500 in FIG. 5 shows that the braking control scheme described in the present specification results in the attenuation of the deceleration rate through the vehicle group. More specifically, since each vehicle determines its own safe deceleration rate and is given the authority to select its own deceleration rate if that is safe, the system can prioritize both safety and comfort while, on the other hand, minimizing or reducing traffic flow disruption.

[0061] One reason why an upstream vehicle can decelerate at a lower deceleration rate than a downstream vehicle is that the vehicles can be configured to maintain a fixed (or at least a predetermined) time interval between vehicles. In other words, the vehicles can stay, for example, two seconds apart from each other regardless of speed. Under these conditions, the inter-vehicle distance will increase as the speed increases and decrease as the speed decreases. The ability of a vehicle to reduce the physical distance between vehicles enables an upstream vehicle within a group of vehicles to use a gradually lower deceleration value, as explained with respect to FIG. 5.

[0062] FIG. 6 further shows how maintaining a time interval between vehicles (rather than a fixed or predetermined distance interval) facilitates a progressively decreasing deceleration value in a group of vehicles. In particular, FIG. 6 shows a first vehicle 602, a second vehicle 604, and a third vehicle 606, all of which are traveling towards the right side of the page. At time t0, the gap 608 between neighboring vehicles may represent equal time intervals (e.g., 2 seconds, 3 seconds, 4 seconds, or any other suitable time), and each vehicle may move at the same or a similar speed.

[0063] At time t0, the first vehicle 602 may determine that it must perform a braking operation. For example, the first vehicle 602 may detect an object 600 (e.g., an obstacle) on or in the path of the first vehicle 602, and as a result, determine that it needs to decelerate. The object 600 is shown as a simple square, but this simply represents any obstruction, location, object, or indeed anything that the vehicle may encounter and should avoid. It includes, but is not limited to, holes, potholes, curbs, animals, other vehicles, chemicals or other spills on the road, lighting poles, intersections, stop signs, red lights, rocks, puddles, unidentified objects, road debris, construction signs, bollards, buildings, etc.

[0064] The first vehicle 602 can determine the deceleration value required to avoid colliding with or otherwise interacting with the object 600. The deceleration value can be based at least in part on the speed of the first vehicle 602, the distance to the object 600, the motion characteristics of the object 600 (e.g., speed, direction of motion, acceleration, etc.), the upper deceleration value (e.g., the maximum deceleration value that the first vehicle 602 can withstand without skidding), the existing road conditions, and the current tire conditions. Other factors may be used to determine the deceleration value of the first vehicle 602.

[0065] Time t1 shows an example of the relative positions of vehicles 602, 604, and 606 during a braking event that starts when the first vehicle 602 begins braking. As shown at t1, the first vehicle 602 is decelerating at a relatively high rate, as illustrated by a deceleration intensity indicator (e.g., deceleration intensity indicator 618). The thickness of the deceleration intensity indicator can represent and / or indicate the relative intensity of the deceleration value employed by that vehicle. As shown in the figure, from t0 to t1, the first vehicle 602 decelerates over distance 612. On the other hand, the second vehicle 604 was able to decelerate over a distance 614 that is greater than distance 612. The greater distance 614 available to the second vehicle 604 may at least partially result from the fact that it can reduce the physical distance between the vehicles at a slower speed while maintaining the target time interval. For example, even if the physical distances of gaps 608, 610 are different (e.g., gap 610 is smaller than gap 608), the time intervals between the vehicles at time t0 and time t1 can be the same. Returning to the second vehicle 604, since it was able to decelerate over a distance 614 that is greater than distance 612, it was able to use a lower deceleration value, as indicated by the thinner deceleration intensity indicator 620. Similarly, the third vehicle 606 can reduce its distance to the second vehicle 604 while braking (while maintaining the same safe time interval represented by gaps 608 and 610), so the third vehicle 606 can decelerate over a distance 616 that is greater than distance 614. Thus, the third vehicle 606 can apply an even lower deceleration value, as indicated by the thinnest deceleration intensity indicator 622.

[0066] As described above, the vehicles in FIG. 6 may communicate with each other to provide deceleration values and braking start signals. For example, each of the following vehicles may receive the deceleration value of the immediately neighboring downstream vehicle, whereby the following vehicle can calculate its own deceleration value (e.g., using Equation 1 above), compare those calculated deceleration values with the upper deceleration value and the lower deceleration target value, and determine how to decelerate based on the result of the comparison.

[0067] In this application, the term "braking" can refer to any action that results in the deceleration of a vehicle and is not limited to a particular mechanism or technology for decelerating the vehicle. For example, braking may be achieved using a braking system that uses mechanical friction to resist the rotation of the wheels (e.g., disc brakes, drum brakes, etc.), a motor (e.g., electric, internal combustion, etc.) that applies torque to the wheels to oppose the rotation, an aerodynamic braking system (e.g., parachute, movable fins, wings, or other objects), an external friction-based system (e.g., bars, boards, or other objects that are forced into contact with the ground, rails, or other objects), a forced air system (e.g., rockets, turbines, fans, etc.), or any other suitable system (or a combination of the foregoing systems or other systems).

[0068] The braking control scheme described in this specification may be used with, or by, a transportation system that autonomously operates a number of vehicles to transport passengers and / or cargo along a road. For example, the transportation system or service may provide a fleet of vehicles operating along a road. Vehicles within such a transportation system may be configured to operate autonomously according to one or more vehicle control schemes. As used herein, the term "autonomous" can refer to a mode or scheme in which a vehicle can operate without continuous manual control by a human operator. For example, a driverless vehicle can navigate along a road using an automated driving system and a steering system that control the speed and direction of the vehicle. In some cases, the vehicle may not require steering, speed, or direction control from a passenger, and may also exclude control devices such as an accelerator and brake pedal, a steering wheel, and other manual control devices accessible to the passenger. In some cases, the vehicle may include a manual drive control device that can be used for maintenance, emergency override, etc. Such control devices may be hidden, stored, or otherwise made inaccessible to the user during normal vehicle operation. For example, they may be designed to be accessible only by trained operators, maintenance personnel, etc.

[0069] The autonomous operation does not necessarily need to exclude all human or manual operations of the vehicle or the entire transportation system. For example, a human operator may be able to intervene in the operation of the vehicle for purposes such as safety, convenience, testing, or others. Such an intervention may be local to the vehicle, as when a human driver takes control of the vehicle, or may be remote, 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's passengers. For example, it is advisable that the vehicle's passengers be able to select a target destination, select a route, select a speed, control the operation of doors and / or windows, etc. Therefore, it should be understood that the terms "autonomous" and "autonomous operation" do not necessarily exclude all human interventions or operations of an individual vehicle or the overall transportation system.

[0070] Vehicles within a transportation system may include various sensors, cameras, communication systems, processors, and / or other components or systems that help facilitate autonomous operation. For example, a vehicle may include a sensor array that detects magnets or other markers embedded in the road and that helps the vehicle determine its location, position, and / or direction on that road. The vehicle may similarly include a wireless vehicle-to-vehicle communication system, such as an optical communication system (e.g., optical communication system 200, FIGS. A and 2B of FIG. 2), that enables vehicles to notify each other of operating parameters such as deceleration information (e.g., braking start signal, deceleration value, etc.), the number of vehicles ahead in a group, acceleration state, maneuvers occurring near them (e.g., right turn, left turn, planned stop), and the number and type of their payloads (e.g., people, cargo). The vehicle may similarly include a wireless communication system to facilitate communication with a transportation system control unit that has monitoring commands and control authority on the transportation system (e.g., using cellular, Wi-Fi (registered trademark), or other suitable wireless communication technologies).

[0071] Vehicles within a transportation system may be designed to enhance the operation and convenience of the transportation system. For example, the primary purpose of the transportation system may be to provide comfortable, convenient, fast, and efficient personal transportation. To provide for the comfort of individuals, the vehicle may be designed to allow passengers to easily enter and exit, and may have a comfortable seating arrangement with sufficient legroom and headroom. Additionally, the vehicle may have a sophisticated suspension system that provides a comfortable ride, dynamically adjustable parameters, assists in maintaining a vehicle level positioned at a convenient height, and ensures a comfortable ride over the entire range of variable load weights.

[0072] Conventional personal automobiles are designed primarily for operation in only one direction. This is due in part to the fact that the driver faces forward and it is generally not safe or necessary to operate in the reverse direction for long distances. However, in an autonomous vehicle where a human is not directly controlling the operation of the vehicle in real time, it may be advantageous for the vehicle to be able to operate bidirectionally. For example, the vehicles within the transportation system described herein may be substantially symmetric such that the vehicle lacks a visually or mechanically distinct front or rear. Further, the wheels may be sufficiently independently controlled such that the vehicle operates substantially identically regardless of which end of the vehicle is facing the direction of travel. This symmetric design provides several advantages. For example, the vehicle may be maneuvered in a smaller space by potentially eliminating the need to perform a U-turn or other maneuvers to turn the vehicle so that it faces “forward” before starting to move.

[0073] FIG. 7A and FIG. 7B of FIG. 7 are perspective views of an exemplary four-wheeled road vehicle 700 (hereinafter simply referred to as "vehicle") that can be used in the transportation system described herein. Vehicle 700 may be an embodiment of vehicle 108 (FIGS. 1 and 2) or any other vehicle described herein. FIG. 7A and FIG. 7B of FIG. 7 show the symmetry and bidirectionality of vehicle 700. In particular, vehicle 700 defines a first end 702 shown at the front in FIG. 7A of FIG. 7 and a second end 704 shown at the front in FIG. 7B of FIG. 7. In some examples, and as illustrated, the first end 702 and the second end 704 are substantially identical. Also, vehicle 700 may be configured to be able to travel with either end facing the direction of travel. For example, when vehicle 700 is traveling in the direction indicated by arrow 714, the first end 702 is the leading portion of vehicle 700, while when vehicle 700 is traveling in the direction indicated by arrow 712, the second end 704 is the leading portion of vehicle 700.

[0074] Vehicle 700 may also include wheels 706 (e.g., wheels 706-1 to 706-4). The wheels 706 may be paired in response to an approach to an end of the vehicle. Thus, wheels 706-1, 706-3 can be disposed near the first end 702 of the vehicle and can be referred to as the first pair of wheels 706, and wheels 706-2, 706-4 can be disposed near the second end 704 of the vehicle and can be referred to as the second pair of wheels 706. The wheels may be driven by a drive system, which may include a motor, an engine, a motor control unit, a speed control unit, a computer, a processor, and any other suitable components, systems, subsystems, etc. that facilitate propulsion (and optionally braking or deceleration) of the vehicle. Each pair of wheels can be driven by at least one motor (e.g., an electric motor), and each pair of wheels can steer the vehicle. Since each pair of wheels can turn to steer the vehicle, the vehicle can have similar driving and handling characteristics regardless of the direction of travel. In some cases, the vehicle may be operated in a two-wheel steering mode, in which case only one pair of wheels steers the vehicle 700 at a given time. In such a case, the particular pair of wheels that steers the vehicle 700 can change as the direction of travel changes. In other cases, the vehicle may be operated in a four-wheel steering mode, in which case the wheels are operated in cooperation to steer the vehicle. In the four-wheel steering mode, the pairs of wheels can turn in the same direction or in opposite directions depending on the steering operation being performed and / or the speed of the vehicle.

[0075] Vehicle 700 may also include doors 708, 710 that open to enable occupants and other payloads (e.g., packages, luggage, cargo) to be positioned inside vehicle 700. Doors 708, 710, which will be described in more detail herein, may extend along the upper portion of the vehicle such that each defines two opposing side segments. For example, each door defines a side segment at a first side of the vehicle and another side segment at a second side of the vehicle. Further, each door defines a roof segment that extends between the side segments and defines a portion of the roof (or upper side) of the vehicle. In some cases, doors 708, 710 may resemble an upside-down "U" in cross-section and may be referred to as canopy doors. The side segments and upper segment of the door may be formed as a rigid structural unit such that all of the door components (e.g., the side segments and upper segment) move in concert with each other. In some cases, doors 708, 710 include an integral shell or door chassis formed from a monolithic structure. The integral shell or door chassis may be formed from a composite sheet or composite structure that includes, for example, glass fibers, carbon composites, and / or other lightweight composites.

[0076] Vehicle 700 may include a vehicle control unit that controls the operation of vehicle 700 and the vehicle's systems and / or subsystems. For example, the vehicle control unit controls the vehicle's drive system, braking system, steering system, suspension system, doors, etc., to facilitate vehicle operation in accordance with one or more vehicle control schemes and navigate the vehicle along a road, and controls the operation of the braking system in accordance with one or more braking control schemes described herein. The vehicle control device may also be configured to communicate with other vehicles, a transportation system control unit, and / or other components of the transportation system (e.g., via optical communication system 200). For example, the vehicle control device may be configured to receive information from other vehicles regarding their positions, speeds, upcoming speed or direction changes, upcoming brake events, etc. within the group. The vehicle control unit may include a computer, a processor, a memory, a circuit, or any other suitable hardware component, and may also be interconnected with other systems of the vehicle to facilitate the operations described herein, similar to other vehicle operations.

[0077] Figures 8A and 8B are side and perspective views of vehicle 700 with doors 708, 710 in the open position. Since doors 708, 710 each define two opposing side segments and a roof segment, an unobstructed interior space 802 may be revealed when doors 708, 710 are opened. In the example depicted in Figures 8A and 8B, when doors 708, 710 are open, an open interval extending from one side of vehicle 700 to the other may be defined between doors 708, 710. This can enable unobstructed entry into and exit from vehicle 700 by passengers on both sides of vehicle 700. The absence of an overhead structure when doors 708, 710 are open may allow passengers to walk across vehicle 700 without restrictions on overhead clearance.

[0078] Vehicle 700 may also include seats 804, which may be disposed at both ends of the vehicle 700 and may face each other. As shown in the figure, the vehicle includes two seats 804, but other numbers of seats and other seat arrangements are also possible (e.g., 0 seats, 1 seat, 3 seats, etc.). In some cases, the seats 804 may be removable, foldable, or storable, so that wheelchairs, strollers, bicycles, or luggage can be more easily placed within the vehicle 700.

[0079] Vehicles used in the transportation systems described herein, such as vehicle 700, can be designed considering ease of manufacture and maintenance in addition to safe and comfortable operation. To achieve these advantages, the vehicle may be designed to have a frame structure that includes many of the vehicle's structural and operational components (e.g., motors, suspensions, batteries, etc.) and is in a low position relative 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, which may be an embodiment of vehicle 108, 700 (or any other vehicle described herein) and shows an example of the configuration of the frame structure and the body structure. As will be described later, a combination of the low position of the frame structure and a relatively lightweight body structure results in a vehicle with a very low center of gravity, thereby enhancing the safety and handling of the vehicle. For example, the low center of gravity reduces the risk of the vehicle tipping over when the vehicle encounters a sloping road surface, wind load, sharp turn, etc., and also reduces the body roll of the vehicle during turning or other maneuvers. Further, by positioning many of the vehicle's operational components, such as motors, batteries, vehicle control units, sensors (e.g., sensors that detect magnets or other markers installed on the road), etc., on the frame structure (e.g., frame structure 904, FIG. 9), manufacture and repair can be simplified.

[0080] FIG. 9 is a partially exploded view of a vehicle 900, which may be an embodiment of the vehicle 700. Details of the vehicle 700 are similarly applicable to the vehicle 900 and will not be repeated here. The vehicle 900 can include a body structure 902 that may include doors (e.g., the aforementioned doors 708, 710) and other body components, and a frame structure 904 to which the body structure 902 is attached.

[0081] The frame structure 904 may include drive components, suspension components, and steering components of the vehicle. For example, the frame structure 904 can include a wheel suspension system, a steering system, a drive system (e.g., a motor, an engine, etc.), a brake system (e.g., a disc brake, a drum brake, etc.), and optionally a motor control unit, which can define or include (a wheel mount, an axle, or a hub, represented as point 912 in FIG. 9). The wheels may be attached to the wheel suspension system via a wheel mount, an axle, a hub, etc. The drive motor may include one or more drive motors that drive the wheels independently or in cooperation with each other. The drive motor may receive power from a power source (e.g., a battery) attached to the frame structure 904. The motor control unit for the drive motor may also be attached to the frame structure 904.

[0082] The suspension system may be any suitable type of suspension system. In some cases, the suspension system includes a suspension system independent for each wheel. For example, the suspension system may be a double-wishbone torsion-bar suspension system. Also, the suspension system may be dynamically adjustable to control ride height, suspension preload, damping, or other suspension parameters while the vehicle is stationary or while the vehicle is moving. Other suspension systems such as swing axle suspension, sliding pillar suspension, MacPherson strut suspension, etc. are also conceivable. Further, the spring function and the damping function may be provided by any suitable component or device such as coil springs, leaf springs, pneumatic springs, hydropneumatic springs, magneto-rheological shock absorbers. The suspension system may be configured to operate in conjunction with the profile of the road surface (such as the road described above) to maintain the desired experience of the occupants.

[0083] The frame structure 904 may include a steering system that enables the wheels to be turned to steer the vehicle. In some cases, the wheels may be steerable independently, or they may be connected (e.g., via a steering rack) such that they always point in substantially the same direction during normal operation of the vehicle. Further, this enables the vehicle to use a four-wheel steering scheme and to alternate between a two-wheel steering scheme and a four-wheel steering scheme.

[0084] The frame structure 904 can include components such as a battery, a motor, a mechanism for opening and closing a vehicle door, and a control system (including a computer or other processing unit).

[0085] FIG. 9 shows an exemplary configuration of a vehicle and a frame structure. However, other configurations are possible. Further, the frame structure and the body structure shown in FIG. 9 are intended to schematically represent these components, and these components may include other structures omitted from FIG. 9 for clarity. Additional structural connections and integrations may be formed between the body structure and the frame structure than those explicitly shown in FIG. 9. For example, components of a door mechanism for opening and closing a door of the body structure may be connected to both the door and the frame structure.

[0086] The foregoing description has used specific terms for purposes of explanation to provide a complete understanding of the embodiments being described. However, it will be apparent to those skilled in the art that specific details are not required to practice the described embodiments. Accordingly, the foregoing description of specific embodiments described herein is presented for purposes of illustration and explanation. They are not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to those skilled in the art that many modifications and variations are possible in light of the above teachings. For example, the methods or processes disclosed herein are described and shown with reference to specific operations performed in a particular order, but these operations can be combined, subdivided, or reordered to form equivalent methods or processes without departing from the teachings of the present disclosure. Further, the structures, features, components, materials, steps, processes, etc. described herein with respect to one embodiment can be omitted from that embodiment or incorporated into other embodiments. Additionally, although the term "roadway" is used herein to refer to a structure that supports a moving vehicle, the roadways described herein do not necessarily conform to any definition, standard, or requirement associated with the term "roadway" as might be used in laws, regulations, transportation codes, etc. Thus, the roadways described herein do not necessarily (and in fact may not) provide the same characteristics and / or the same structure as a conventional "roadway". Of course, the roadways described herein can conform to any or all applicable laws, safety rules, or other regulations for the safety of passengers, bystanders, drivers, constructors, maintainers, etc.

Claims

1. 1. A method of slowing a plurality of vehicles along a roadway, comprising: In the first vehicle, From a nearby downstream vehicle a first braking initiation signal; and a first deceleration value indicative of a deceleration rate of the adjacent downstream vehicle; receiving the determining a first distance to the nearby downstream vehicle; determining a second deceleration value based at least in part on the first distance, the second deceleration value configured to prevent a collision of the first vehicle with the adjacent downstream vehicle; decelerating at an upper deceleration value in response to a determination that the second deceleration value is equal to or greater than an upper deceleration value; and decelerating at the second deceleration value in response to a determination that the second deceleration value is less than the upper deceleration value and greater than a lower deceleration target value; The method includes:

2. 2. The method of claim 1, pursuant to determining that the second deceleration value is greater than or equal to the upper deceleration value, To nearby upstream vehicles, a second braking initiation signal; and The upper deceleration value, The method further comprising:

3. 3. The method of claim 2, further comprising: instructing the adjacent upstream vehicle to: the second braking initiation signal, and The second deceleration value, The method further comprises transmitting.

4. 2. The method of claim 1, maintaining a velocity of the vehicle in accordance with a determination that the first deceleration value is less than or equal to the lower deceleration target value; After maintaining the speed of the vehicle for a period of time, detecting a deceleration of the adjacent downstream vehicle; and decelerating at a lower deceleration target value in response to detecting deceleration of the nearby downstream vehicle; The method further comprises:

5. 2. The method of claim 1, wherein the second deceleration value is further determined, at least in part, by: the speed of the first vehicle; the speed of the nearby downstream vehicle; and The first deceleration value, Based on,method.

6. 2. The method of claim 1, wherein the upper deceleration value corresponds to a maximum deceleration value that the first vehicle can withstand without skidding.

7. 2. The method of claim 1, the adjacent downstream vehicle includes an optical output system configured to transmit information; and the first vehicle including an optical sensing system configured to receive information transmitted by the optical output system; method.

8. 8. The method of claim 7, wherein the first brake initiation signal is transmitted via the optical output system of the adjacent downstream vehicle and received by the optical sensing system of the first vehicle.

9. 8. The method of claim 7, wherein the first deceleration value is transmitted as a coded signal via the optical output system of the adjacent downstream vehicle.

10. A vehicle, a drive system configured to propel the vehicle; a braking system configured to decelerate the vehicle; a steering system configured to steer the vehicle; and A vehicle control unit, the vehicle control unit comprising: From a nearby downstream vehicle, a first braking initiation signal; and a first deceleration value indicative of a deceleration rate of the adjacent downstream vehicle; To receive, determining a first distance to the nearby downstream vehicle; determining a second deceleration value based at least in part on the first distance, the second deceleration value being configured to prevent a collision of the vehicle with the adjacent downstream vehicle; responsive to determining that the second deceleration value is greater than or equal to an upper deceleration value, causing the brake system to decelerate the vehicle at the upper deceleration value; and in response to determining that the second deceleration value is less than the upper deceleration value and greater than a lower deceleration target value, causing the brake system to decelerate the vehicle at the second deceleration value. It is composed of vehicle.

11. 11. The vehicle of claim 10, wherein the vehicle control unit is further configured to determine the second deceleration value based, at least in part, on a speed of the vehicle and a speed of the adjacent downstream vehicle.

12. 12. The vehicle according to claim 11, wherein the vehicle control unit is further configured to transmit deceleration information to a nearby upstream vehicle in response to a determination that the second deceleration value is equal to or greater than the upper deceleration value, and the deceleration information is a second braking initiation signal; and The upper deceleration value, Including, vehicles.

13. 13. The vehicle according to claim 12, wherein the vehicle control unit is further configured to transmit the deceleration information to the nearby upstream vehicle in response to a determination that the second deceleration value is less than the upper deceleration value, and the deceleration information is the second braking initiation signal, and The second deceleration value, Including, vehicles.

14. 14. The vehicle of claim 13, further comprising: an optical output system configured to transmit the deceleration information to the adjacent upstream vehicle; an optical sensing system configured to receive the first braking initiation signal and the first deceleration value; A vehicle equipped with:

15. 1. A method of slowing a plurality of vehicles along a roadway, comprising: In the first vehicle, From nearby downstream vehicles, a first braking initiation signal; a first deceleration value indicating a deceleration rate of the adjacent downstream vehicle; receiving the determining a second deceleration value configured to prevent the first vehicle from colliding with the adjacent downstream vehicle; in response to determining that the second deceleration value is greater than or equal to an upper deceleration value, To the second car, a second braking initiation signal; and the upper deceleration value; Sending decelerating at said upper deceleration value; In the second vehicle, From the first vehicle, the second braking initiation signal; the upper deceleration value; receiving the determining a third deceleration value configured to prevent the second vehicle from colliding with the first vehicle; In response to a determination that the third deceleration value is smaller than the upper deceleration value and is greater than a lower deceleration target value, To nearby upstream vehicles, a third braking initiation signal; and the third deceleration value; and and decelerating at the third deceleration value; A method comprising:

16. 16. The method of claim 15, further comprising: in response to a determination that the third deceleration value is greater than or equal to the upper deceleration value, to the nearby upstream vehicle, the third braking initiation signal; and the upper deceleration value; and decelerating at said upper deceleration value; The method further comprising:

17. 1. A method for determining a deceleration rate of a vehicle in a fleet of vehicles, comprising: In each vehicle in the group, determining a respective distance to a respective nearby upstream vehicle; and determining a respective deceleration value based at least in part on the respective distances; and a vehicle in the fleet traveling at a speed associated with a first deceleration value; From a nearby upstream vehicle, Braking instructions and a second deceleration value of a next braking event of the adjacent upstream vehicle; receiving the in response to a determination that the first deceleration value is equal to or greater than an upper deceleration value, decelerating at the upper deceleration value; decelerating at the first deceleration value in accordance with a determination that the first deceleration value is less than the upper deceleration value and greater than a lower deceleration target value; maintaining the vehicle at the speed pursuant to determining that the first deceleration value is less than or equal to the lower deceleration target value; A method comprising:

18. 18. The method of claim 17, further comprising: determining, at each vehicle in the fleet, a speed of each of the adjacent upstream vehicles; the respective deceleration values ​​are determined based at least in part on the speed of the respective adjacent upstream vehicles. method.

19. 20. The method of claim 17, further comprising: After maintaining the vehicle at the speed, Detecting the deceleration of the nearby upstream vehicle; and decelerating at the lower deceleration target value; The method further comprises:

20. 20. The method of claim 19, further comprising: the upper deceleration value corresponds to a maximum deceleration that the vehicle can withstand without skidding; and The lower deceleration target value is 2.0 m / s ２ Below is the method.

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