Patent Description:
Low latency of the communication link between a remotely operated vehicle and the remote operation station is a key enabling factor for remote driving or monitoring. Safe operation of the vehicle requires that the latency is low enough to allow the remote operator to perceive and react to what is happening in the surrounding of the vehicle in real time. Contributing factors to the total latency of the system include communication delays, video processing delays, and mechanical delays.

A critical safety feature of remotely driven or monitored vehicles is the ability to perform an emergency stop, should the operator for example identify a problem with the steering of the vehicle. A maximum communications latency threshold for operating the vehicle is typically set to ensure that the vehicle can perform an emergency stop within a certain maximum distance. Above this threshold, remote driving of the vehicle may not be allowed. For example, <CIT> discloses disabling remote driving and performing vehicle braking in response to the vehicle speed and network delay both being above respective thresholds.

In wireless communication links, such as cellular networks, used for remote driving, interruptions due to e.g. lost packets causing retransmission or cell tower handover, occur regularly. Latencies for an LTE cellular link are commonly around <NUM> to <NUM>, while latency spikes of <NUM> are not uncommon. Therefore, the maximum communications latency threshold for operating the vehicle is normally set above this range of commonly occurring latency, to avoid too frequent interruption of the operation of the vehicle. In turn this limits the maximum speed at which the vehicle can be allowed to operate, to ensure that an emergency stop can be performed within the maximum distance.

<CIT> describes a method for remote operation of a robot, preferably including: recording a set of sensor streams; transmitting a transmission stream; selecting a received stream for display; and/or displaying the selected stream. A system, preferably including a robot and a remote operation system connected to the robot by one or more communication networks.

<CIT> describes a remote driving system and a safety protection method and module thereof. The safety protection method comprises the steps of SI obtaining a first parameter and a second parameter, enabling the first parameter to be correlated with the driving condition of a vehicle, and enabling the second parameter to be correlated with the network delay of the vehicle for receiving a remote driving instruction; S2 calculating a danger index of current remote driving of the vehicle according to the first parameter and the second parameter; and S3 when the danger index is greater than a first threshold value, correcting a remote driving instruction received by the vehicle so as to control the vehicle speed through the corrected remote driving instruction.

<CIT> describes methods, systems, computer-readable media, and apparatuses forblended control of remote operation of vehicles. The sensors of automated vehicles can detect conditions for which there is no preprogrammed response. In these situations, automated vehicles can engage a remote operator mode. Remote operation of vehicles can be difficult. These techniques can use the automated driving system of the vehicle to monitor the driving commands from a remote operator and the sensor information of the vehicle.

It is an object of the present disclosure to alleviate at least some of the above-mentioned drawbacks, and to provide a more effective and safe method of controlling a remotely operated vehicle.

The invention is defined by the appended independent claims, with embodiments being set forth in the appended dependent claims, in the following description, and in the drawings.

According to a first aspect of the inventive concept, there is provided a method of controlling a remotely operated vehicle, said vehicle being operated from a remote operation station via a communication link between said vehicle and said remote operation station, the method comprising the steps of: monitoring a latency of said communication link, requesting an emergency stop manoeuvre of the vehicle, in response to said latency exceeding a predetermined threshold, determining whether the communication link is recovered within a brake reaction time period starting when the emergency stop manoeuvre is requested, and cancelling said requested emergency stop manoeuvre, in response to said communication link being recovered within a brake reaction time period, wherein said steps of monitoring (S1) a latency of said communication link, requesting (S2) an emergency stop manoeuvre of the vehicle, determining whether the communication link is recovered within a brake reaction time period (A), and cancelling (S3) said requested emergency stop manoeuvre are performed by the vehicle.

The present disclosure is at least partly based on the realization that commonly observed brake reaction times are in the same order of magnitude as common latencies of the communication link. By ensuring that a requested emergency stop manoeuvre is cancelled, should the communication link be recovered within a time period corresponding to the brake reaction time, the latency threshold can be set lower, without increasing the number of performed emergency stops. In other words, the latency threshold can be set low, within the range of common latencies, without causing frequent interruptions in the operation of the vehicle.

An additional advantage, in cases when the communication link is not recovered, is that the lower latency threshold means that the brakes are engaged earlier than with a higher latency threshold. This creates an additional margin for stopping the vehicle in the emergency stop manoeuvre, which can be used to increase the maximum allowed speed of the vehicle without increasing the stopping distance of the emergency stop manoeuvre.

According to an embodiment, the predetermined threshold may be dynamic, such that the predetermined threshold can vary depending on a current driving scenario.

In some embodiments, the latency threshold may be set depending on external parameters such the traffic environment, current visibility conditions, etc. Such a driving scenario may encompass the current traffic environment, the current weather conditions, the current visibility conditions, the type of cargo transported by the vehicle, and/or the type of road driven on, e.g. open road or private fenced area. Setting the latency threshold may be done automatically by the vehicle or manually by a remote operator. It may additionally or alternatively be set by a fleet manager or a fleet management system, if the vehicle is part of a fleet of vehicles. The latency threshold may be set for a particular trip, or may be changed during a trip, for example in response to changing traffic environment or visibility conditions.

Alternatively, the latency threshold may be static, i.e. fixed for the vehicle being operated. For example, it may be set as a predetermined vehicle parameter from the factory. Additionally, or alternatively, the latency threshold may be later updated, for example as part as a software update of the vehicle.

According to an embodiment, said requested emergency stop manoeuvre is cancelled before said vehicle starts decelerating.

This ensures continuous operation of the vehicle without any adverse effects due to normal fluctuations of the communication link. No sudden movement is experienced in the vehicle, avoiding possible risks for cargo transported by the vehicle and improving the comfort of any passengers present in the vehicle. Additionally, it avoids an unpredictable movement of the vehicle that could surprise drivers of other vehicles present in the surroundings, which improves the safety of the vehicle.

According to an embodiment, the brake reaction time period corresponds to a delay between the moment the emergency stop manoeuvre is requested and the moment a brake system of the vehicle start slowing the vehicle down. For example, in air or pneumatic brake systems, which are used for most heavy-duty trucks, the delay is related to the time required for sufficient pressure to build up for the brake to engage. The brake reaction time period is generally static for a vehicle, but can differ between different vehicles and brake systems.

According to an embodiment, the method further comprises continuing the requested emergency stop manoeuvre, in response to said communication link not being recovered within the brake reaction time period.

This provides a safe course of action. If the communication link is not recovered, there is no guarantee that a remote operator of the vehicle has control over the vehicle.

According to an embodiment, the requested emergency stop manoeuvre continues to stop the vehicle until the vehicles is stationary. Stopping the vehicle in its lane may be the safest option.

According to an embodiment, the method further comprises: cancelling said requested emergency stop manoeuvre, in response to said communication link being recovered within a second time period following the brake reaction time period, wherein the second time period corresponds to a delay between the moment a brake system of the vehicle starts slowing the vehicle down and the moment the brake system reaches full braking power.

This may allow the vehicle to be operated with fewer interruptions in the presence of if higher latency peaks in the communication link. The requested emergency stop manoeuvre being cancelled only after the moment the brake system of the vehicle starts slowing the vehicle means that a deceleration will be felt, at least to some extent, by passengers or cargo present in the vehicle. On the other hand, the requested emergency stop manoeuvre is more likely to be cancelled, i.e. operation of the vehicle is more likely to be continued without performing a full emergency stop manoeuvre. In other words, a trade-off can be chosen between comfort of the passengers/safety of the cargo and continuity of operation of the vehicle.

In the context of this application, full braking power means that the maximum air pressure has been achieved in the air brake system and/or that the maximum deceleration of the vehicle has been achieved.

According to an embodiment, said predetermined threshold is in the range of <NUM>-<NUM>, such as about <NUM>.

This allows the vehicle to be effectively operated with communication links exhibiting a wide range of latencies.

According to an embodiment, said brake reaction time period is in the range of <NUM>-<NUM>, such as about <NUM>.

According to an embodiment, requesting an emergency stop manoeuvre includes a control unit of the vehicle sending a request for an emergency stop manoeuvre to a brake system of the vehicle.

The request for an emergency stop manoeuvre is thus made from within the vehicle, independently of the remote operation station. The communication between the control unit of the vehicle sending a request for an emergency stop manoeuvre and the brake system is not affected by the latency of the communication link between the vehicle and the remote operation station.

According to an embodiment, said communication link is recovered when said latency falls below said predetermined threshold.

In other words, monitoring a latency of the communication link may comprise determining if the latency is above the predetermined threshold or below the predetermined threshold. The latency being above the predetermined threshold indicates at least an interruption of the communication link long enough that it cannot be guaranteed that the remote operator has control over the vehicle. The latency subsequently falling below the predetermined threshold indicates that interruptions of the communication link are short enough to consider operation of the vehicle safe.

According to an embodiment, wherein the communication link is wireless, wherein the latency is round-trip latency, and/or wherein the latency is continuously monitored in the vehicle.

The communication link may be through a cellular network, such as e.g. an LTE or <NUM> network. The communication link may alternatively be through Wi-Fi or radio. The latency may be based on the age of the last acknowledged packet.

According to an embodiment, said step continuing the requested emergency stop manoeuvre is performed by the vehicle.

Thus, the steps of the method may be performed by the vehicle, independently of the remote operation station. This ensures that the steps of the method can be performed even when the communication link between the vehicle and the remote operation station is interrupted or lost.

According to an embodiment, the vehicle is at least one of: capable of autonomous driving and remote driving, capable of fully electric propulsion, and a road vehicle.

According to an embodiment, operating the vehicle from a remote operation station includes at least one of: an operator of the remote operation station remotely driving the vehicle and an operator of the remote operation station remotely monitoring the vehicle.

A remotely operated vehicle may at certain times be remotely driven and at other times be remotely monitored. One trip of a remotely operated vehicle may include segments in which the vehicle is remotely driven, segments in which the vehicle is remotely monitored, or a combination thereof. The predetermined latency threshold may be the same when the vehicle is remotely driven and when the vehicle is remotely monitored. Alternatively, the predetermined latency threshold may be different when the vehicle is remotely driven and when the vehicle is remotely monitored.

According to a second aspect of the invention, there is provided a (remotely operated) vehicle configured to be operated from a remote operation station via a communication link between said vehicle and said remote operation station, said vehicle having a control unit comprising at least one processor, which control unit is configured to: monitor a latency of said communication link, request an emergency stop manoeuvre, in response to said latency exceeding a threshold, and cancel said requested emergency stop manoeuvre, in response to said communication link being recovered within a brake reaction time period starting when the emergency stop manoeuvre is requested.

The remotely operated vehicle may be suitable to be controlled by a method for controlling a remotely operated vehicle as described in connection with the first aspect of the inventive concept. It should be understood that any steps and embodiments of the first aspect may, as far as is compatible with the remotely operated vehicle, be implemented in the remotely operated vehicle according to the second aspect of the inventive concept, and vice versa. Any advantages described in connection to the first aspect thus also apply to the remotely operated vehicle of the second aspect.

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing exemplary embodiments of the present invention.

Embodiments of the invention will now be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Even though in the following description, numerous details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention. The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.

<FIG> illustrates a remotely operated vehicle <NUM> which is operated from a remote operation station <NUM> via a wireless communication link <NUM> (e.g. LTE, <NUM>, radio, WiFi). Remotely operating the remotely operated vehicle <NUM> may comprise remotely driving the remotely operated vehicle <NUM>, wherein a human teleoperator <NUM> remotely drives the remotely operated vehicle <NUM> from the remote operation station <NUM>, and/or remotely monitoring the remotely operated vehicle <NUM>, wherein a (human) teleoperator <NUM> remotely monitors and/or confirms otherwise autonomous driving of the remotely operated vehicle <NUM>. Accordingly, the vehicle <NUM> may also be capable of autonomous driving. As such, the vehicle <NUM> could be denoted an autonomous/remotely operated vehicle <NUM>.

The remotely operated vehicle <NUM> has at least one control unit <NUM>, and wireless communication means <NUM> to communicate with the remote operation station <NUM> via the wireless communication link <NUM>. Various sensors <NUM> may detect surroundings of the remotely operated vehicle <NUM>. The remotely operated vehicle <NUM> may be an all-electric vehicle, propelled by at least one electric motor <NUM> powered by a battery <NUM>. The remotely operated vehicle <NUM> also comprises a (service) brake system <NUM>, which may be e.g. an air or pneumatic brake system. Furthermore, the remotely operated vehicle <NUM> may be a transport vehicle, such as a box truck or a tractor trailer combination, for transporting pallets, timber, perishable goods, etc (not shown in <FIG>). Alternatively, the remotely operated vehicle <NUM> may be a passenger vehicle, a bus, mini-bus or similar. The remotely operated vehicle <NUM> may also be devoid of driver's cab or driver's seat, such that it cannot be driven manually by a driver in the vehicle <NUM>.

The remote operation station <NUM> comprises wireless communication means <NUM> for communication with the remotely operated vehicle <NUM> via the wireless communication link <NUM>, as well as equipment <NUM> for remotely operating the vehicle <NUM>. The equipment can comprise e.g. at least one screen for displaying the surroundings of the remotely operated vehicle <NUM> as detected by the sensors <NUM>, a steering wheel, throttle, braking means, etc..

One exemplary embodiment of a method for controlling a remotely operated vehicle (e.g. remotely operated vehicle <NUM>) according to the present disclosure is illustrated in the flow chart of <FIG>. Step S1 consists in monitoring a (round-trip) latency of the communication link <NUM> between the remotely operated vehicle <NUM> and the remote operation station <NUM>. In one alternative, monitoring the latency is performed by a control unit of the vehicle <NUM>, e.g. control unit <NUM>. This step may advantageously be performed continuously and in parallel with subsequent steps of the method. If the latency exceeds a predetermined threshold (step D1), a request for an emergency stop manoeuvre is made in step S2. Typically, this comprises a control unit of the vehicle <NUM>, e.g. control unit <NUM>, sending a request for an emergency stop manoeuvre to a brake system of the vehicle <NUM>, e.g. brake system <NUM>.

The latency threshold may be set in the range of <NUM>-<NUM>, such as about <NUM>. This range is appropriate when the communication link <NUM> between the remotely operated vehicle <NUM> and the remote operation station <NUM> is an LTE cellular link, for instance, which commonly has latencies around <NUM>-<NUM>, with latency peaks of approximately <NUM>. The skilled person realizes that other thresholds may be appropriate for other types of communication links.

It should be noted that the remotely operated vehicle <NUM> does not start decelerating instantly when the request for an emergency stop manoeuvre is made. For example, in vehicles using air brake systems, sufficient air pressure has to build up in the system before the brakes can engage, causing a delay between the request and the start of the braking action. According to the example embodiment of <FIG>, if the communication link is recovered within this brake reaction time period (step D2), the requested emergency stop manoeuvre is cancelled in step S3. Operation of the vehicle <NUM> may then continue according to the method, i.e. the vehicle <NUM> keeps or resumes monitoring the latency of the communication link (step S1) and requests another emergency stop manoeuvre (step S2) in response to the latency exceeding the predetermined threshold (step D1), etc..

The embodiment of <FIG> is exemplified in <FIG>, which shows an example plot of the latency L of the communication link <NUM> between the remotely operated vehicle <NUM> and the remote operation station <NUM> as a function of time t. The predetermined threshold T is marked by a horizontal dashed line. In the first part of the plot, to the left of arrow <NUM>, the latency fluctuates but stays under the threshold T. At the moment indicated by arrow <NUM>, the latency rises above the threshold T, corresponding to step D1 of <FIG>. For the purpose of operating the remotely operated vehicle <NUM>, the communication link <NUM> between the vehicle <NUM> and the remote operation station <NUM> is considered lost. As a result, an emergency stop manoeuvre is requested according to step S2. A brake reaction time period A starting when the emergency stop manoeuvre is requested is marked by the hatched area between two vertical dashed lines. Here, the latency L falls back below the threshold T within this brake reaction time period, as in step D2, i.e. the plot of the latency L crossed the horizontal dashed line at the moment indicated by arrow <NUM>. In other words, the communication link <NUM> between the remotely operated vehicle <NUM> and the remote operation station <NUM> is recovered within the brake reaction time period A starting when the emergency stop manoeuvre is requested. As a result, the requested emergency stop manoeuvre is cancelled according to step S3.

<FIG> illustrates at least one other exemplary embodiment of the method for controlling a remotely operated vehicle (e.g. remotely operated vehicle <NUM>) according to the present disclosure. The method may comprise five major steps S1-S5 and seven decision points steps D10, D21, D22, D31, D32, D41, D42 which determine the order in which the major steps are performed. Steps D41 and D42 are optional.

Similarly to the embodiment illustrated in <FIG>, step S1 consists in monitoring a (round-trip) latency of the communication link <NUM> between the remotely operated vehicle <NUM> and the remote operation station <NUM>. In one alternative, monitoring the latency is performed by a control unit of the vehicle <NUM>, e.g. control unit <NUM>. This step may advantageously be performed continuously and in parallel with subsequent steps of the method. Step S2 consists in requesting an emergency stop manoeuvre, e.g. a control unit of the vehicle1 <NUM>, e.g. control unit <NUM>, sending a request for an emergency stop manoeuvre to a brake system of the vehicle <NUM>, e.g. brake system <NUM>. Step S3 consists in cancelling the requested emergency stop manoeuvre.

The method thus starts in step S1. Step D10 answers the question "is the latency above the predetermined threshold?", i.e. latency > T?. The latency threshold may be set according to the same considerations as detailed above in connection with <FIG>. If the latency is not above the predetermined threshold, the method continues toward step D21; if the latency is above the predetermined threshold, the method continues toward step D22. In both steps D21 and D22, the path forward is determined by whether there is a current request for an emergency stop manoeuvre. By current emergency stop manoeuvre, it is meant a request for an emergency stop manoeuvre that has neither been cancelled not fully carried out. In other words, if there is a current request for an emergency stop manoeuvre, the vehicle <NUM> is in the process of performing an emergency stop manoeuvre. Importantly, if there is a current request for an emergency stop manoeuvre, the brakes of the vehicle <NUM> may or may not have engaged and/or the vehicle <NUM> may or may not have started decelerating, depending on the time elapsed since the emergency stop manoeuvre was requested.

After step D21, if there is no current request for an emergency stop manoeuvre, the method goes back to step S1, where the latency of the communication link <NUM> is monitored. This corresponds to "normal" operation of the remotely operated vehicle <NUM>, i.e. the latency is under the predetermined threshold and no emergency stop manoeuvre is requested. Conversely, after step D22, if there is no current request for an emergency stop manoeuvre, an emergency stop manoeuvre is requested at step S2.

If there is a current request for an emergency stop manoeuvre at steps D21 and D22, the method continues to steps D31 and D32, respectively. Here, the path forward depends on whether the time elapsed since the emergency stop manoeuvre was requested is below the brake reaction time. If at D31, where the latency is below the predetermined threshold and there is a current request for an emergency stop manoeuvre, the time elapsed since the request is below the brake reaction time, the method goes to step S3, in which the request for an emergency stop manoeuvre is cancelled. Thereafter, the method returns to step S1. If at D32, where the latency is above the predetermined threshold and there is a current request for an emergency stop manoeuvre, the time elapsed since the request is below the brake reaction time, the method returns to step S1.

If at steps D31 and D32, the time elapsed since the request is not below the brake reaction time, the method may go to optional steps D41 and D42, respectively, or directly to step S4, in which the requested emergency stop manoeuvre is continued, followed by step S5, in which the requested emergency stop continues to stop the vehicle <NUM> until the vehicle <NUM> is stationary.

Optional steps D41 and D42 are similar to steps D31 and D32, except that the time elapsed since the request is compared to the brake reaction time period A plus a second time period B (shown in <FIG>) corresponding to a delay between the moment the brake system <NUM> of the vehicle <NUM> starts slowing the vehicle down and the moment the brake system reaches full braking power. If, at step D41, the time elapsed is below this combined time period (brake reaction time period A plus second time period B), i.e. the communication link <NUM> is recovered within the second time period B following the brake reaction time period A, the method goes to step S3, in which the request for an emergency stop manoeuvre is cancelled. Thereafter, the method returns to step S1. Conversely, if, at step D42, the time elapsed is below the combined time period, the method returns to step S1.

If at steps D41 and D42, the time elapsed since the request is not below the combined time period (brake reaction time plus second time period), the method goes to step S4, in which the requested emergency stop is continued. In other words, the requested emergency stop manoeuvre is continued in response to the communication link <NUM> not being recovered within the second time period B following the brake reaction time period A.

Returning to <FIG>, the plot also exemplifies a possible scenario according to the method described in relation to <FIG>. In the first part of the plot, the method is in a loop comprising steps S1-D10-D21-S1, i.e. the latency is below the predetermined threshold T and there is no current request for an emergency stop manoeuvre. At the moment indicated by arrow <NUM>, the method goes to S2 following the steps: S1-D10-D22-S2 and an emergency stop manoeuvre is requested. Thereafter, until the moment indicated by arrow <NUM>, the method is in the loop S1-D10-D22-D32-S1, i.e. the latency is above the predetermined threshold and there is a current request for an emergency stop manoeuvre. At arrow <NUM>, the method goes through steps S1-D10-D21-D31. Here, since the latency crossed below the threshold T within the brake reaction time period A, the requested emergency stop manoeuvre is cancelled in step S3 and the method thereafter goes back to step S1.

<FIG> shows another example plot of the latency L as a function of time t. Here, analogous to <FIG>, the latency crossed the predetermined threshold T at the moment indicated by arrow <NUM>. However, the latency stays above the predetermined threshold T throughout the brake reaction time period A, i.e. the plot exits the hatched area above the horizontal dashed line, at the moment indicated by arrow <NUM>. This corresponds to the method following steps S1-D10-D22-D32-S4 in <FIG>, i.e. the requested emergency stop manoeuvre is continued, in response to the communication link <NUM> not being recovered within the brake reaction time period A (step D42 being absent from this scenario).

A scenario in which the communication link <NUM> is recovered within the aforementioned second time period B following the brake reaction time period A is shown in <FIG>. As mentioned above, time period B corresponds to a delay between the moment the brake system <NUM> of the vehicle <NUM> starts slowing the vehicle <NUM> down and the moment the brake system <NUM> reaches full braking power. After an emergency stop manoeuvre has been requested (step S2 of <FIG>) at the moment indicated by arrow <NUM>, the plot within the brake reaction time period A corresponds to the method following a loop with steps S1-D1 <NUM>-D22-D32-S1 of <FIG>. After crossing into the second time period B, the method initially follows a loop with steps S1-D1 <NUM>-D22-D32-D42-S1. At the moment indicated by arrow <NUM>, i.e. when the latency falls back below the predetermined threshold T, the method follows steps S1-D10-D21-D31-D41-S3 and the requested emergency stop manoeuvre is cancelled. The method then goes back to step S1.

<FIG> shows a scenario in which the communication link <NUM> is neither recovered within the brake reaction time period A nor within the second time period B following the brake reaction time period A. After an emergency stop manoeuvre has been requested (step S2 of <FIG>) at the moment indicated by arrow <NUM>, the plot within the brake reaction time period A corresponds to the method following a loop with steps S1-D10-D22-D32-S1 of <FIG>. After crossing into the second time period B, the method follows a loop with steps S1-D10-D22-D32-D42-S1. At the moment indicated by arrow <NUM>, the plot exits the second time period B with the latency L still above the predetermined threshold T. The communication link <NUM> is thus not recovered within the second time period B (and obviously was not recovered within the brake reaction time period A). Here, the method goes to step S4 and the emergency stop manoeuvre is continued. In step S5, the requested emergency stop manoeuvre continues to stop the vehicle <NUM> until the vehicle <NUM> is stationary.

Claim 1:
A method of controlling a remotely operated vehicle (<NUM>), said vehicle being operated from a remote operation station (<NUM>) via a communication link (<NUM>) between said vehicle and said remote operation station, the method comprising the steps of:
monitoring (S1) a latency (L) of said communication link,
requesting (S2) an emergency stop manoeuvre of the vehicle, in response to said latency exceeding a predetermined threshold (T),
determining whether the communication link is recovered within a brake reaction time period (A) starting when the emergency stop manoeuvre is requested, and
cancelling (S3) said requested emergency stop manoeuvre, in response to said communication link being recovered within a brake reaction time period (A),
wherein said steps of monitoring (S1) a latency of said communication link, requesting (S2) an emergency stop manoeuvre of the vehicle, determining whether the communication link is recovered within a brake reaction time period (A), and cancelling (S3) said requested emergency stop manoeuvre are performed by the vehicle.