VWGoA - Ex. 1003
`Volkswagen Group of America, Inc., Petitioner
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`US. Patent
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`May 28, 1996
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`Sheet 1 of 3
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`5,521,579
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`US. Patent
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`May 28, 1996
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`Sheet 2 of 3
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`5,521,579
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`US. Patent
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`May 28, 1996
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`Sheet 3 of 3
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`1
`METHOD FOR PROVIDING GUIDING
`ASSISTANCE FOR A VEHICLE IN
`CHANGING LANE
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`BACKGROUND AND SUMMARY OF THE
`INVENTION
`
`The invention relates to a process for providing guidance
`assistance for a vehicle in changing lanes from a current lane
`to an adjacent lane. In particular, the method according to the
`invention assists the driver of the motor vehicle when
`changing lanes (for example entering or exiting a motorway
`or passing a slower vehicle) by taking over, at least partially,
`certain monitoring requirements for this maneuver, and by
`evaluating the data acquired during the monitoring to help
`determine whether a risk-free lane change is possible.
`German Patent Document DE 40 05 444 Al discloses, for
`example, an arrangement in which the space behind the
`vehicle is monitored for the presence of objects, (principally,
`vehicles travelling behind) and the distance and speed of any
`such objects are determined. From this information,
`the
`deceleration which would have to be performed by a trailing
`vehicle when the driver’s own vehicle changes lanes, and an
`associated evaluation index is formed. Incremental values of
`this index are displayed to provide the driver with audible or
`visual information on the effect of a possible lane change on
`the traffic behind. Alaser-impulse distance measuring device
`serves to monitor the space behind.
`In addition to ultrasonic and infrared systems (see for
`example DE 38 32 720 Al), the use of radar devices as
`monitoring detectors is also known. In addition to their use
`for monitoring the so-called blind-spot area (see for example
`DE 39 02 852 Al),
`the latter are also widely used for
`measuring distances from vehicles travelling ahead, such as
`for example for driving with automatic distance control (see
`F. Ackermann, Distance Control Using Radar, Spektrum d.
`Wiss., June 1980, pp. 25 et seq.) or for making recommen-
`dations with respect to passing, such as in the case of DE 36
`22 447 C1 (monitoring of space in front by radar).
`DE 36 22 091 Al discloses a lane change warning system
`in which a monitoring detector can be switched between
`monitoring of a blind-spot area and monitoring of a space in
`front. Monitoring of the blind spot behind is selected during
`a lane change warning mode of operation, and monitoring of
`the space in front is selected in a distance warning operation
`mode, coupled to the switching of a fog lamp.
`DE 30 28 077 C2 discloses a device for warning the
`vehicle driver of a vehicle travelling ahead of him in the
`current lane. In this arrangement, the space in front in the
`current lane is monitored by means of a radar device to
`detect the presence of a vehicle travelling ahead, and to
`determine its distance from the driver’s own vehicle and its
`relative speed. As a function of these parameters and the
`speed of the driver’s own vehicle (and,
`if appropriate,
`further parameters such as the state of the carriageway and
`brakes), a safe distance between the two vehicles is calcu-
`lated and compared with the measured distance. If the
`measured distance is smaller than the safe distance, a
`warning signal is produced and/or the risk of an impact is
`displayed on a visual display panel.
`In a variant of this known device, additional provision is
`made for detecting the risk of a collision in changing lanes,
`by monitoring the respective space behind in adjacent lanes
`as well as the space in front in the current lane. The detected
`data are evaluated in a manner analogous to that for the
`vehicle travelling ahead in the current lane. Thus, this device
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`only takes into account the current situation in the space
`behind in a possible target lane.
`The object of the present invention is to provide a process
`for assisting the operator of a motor vehicle when changing
`lanes, which process is capable of deciding automatically as
`to the advisability of a present or future lane change, and
`largely relieves the driver of the task of observing the
`surroundings and estimating distances and speeds.
`This problem is achieved according to the invention by
`monitoring in the target lane both the spaces behind and in
`front of the driver’s own vehicle, by determining the dis—
`tance and speed of such objects (vehicles), and taking into
`account risk-preventing safety distances to be observed.
`This method is capable of detecting whether a suflicient gap
`is present in the target lane for a desired lane change. Thus,
`the driver does not need to observe the space behind or the
`space in front in the target lane, nor does he need to estimate
`the distances and speeds of the vehicles in it. Instead, he is
`informed by appropriate warning indications and/or instruc-
`tions
`from the computer-controlled guiding assistance
`method of the presence of a sufficient gap in the target lane
`to accommodate a desired lane change.
`According to the invention it is also possible to detect
`whether, if not in the current vehicle situation, a gap which
`is potentially suitable for lane change is possible in the target
`lane. That is, it is possible to detect the presence of a gap,
`permitting a lane change, in the target lane obliquely in front
`of, or obliquely behind the driver’s own vehicle, and to
`indicate this to the driver. The driver can then attempt by
`means of suitable maneuvers (acceleration or deceleration of
`his vehicle) to align his vehicle with the gap and carry out
`the lane change. This relieves the driver of the vehicle in a
`particularly advantageous manner of the tasks of observing
`and evaluating the driving situation in the space in front and
`behind in the target lane.
`In another embodiment of the invention, vehicles in the
`lane in which the driver’s own vehicle is located before a
`lane change, are also included as factors to be considered.
`The search for a gap in this embodiment detects not only
`whether a suitable gap is present in the target lane, but also
`whether the position of the driver’s own vehicle in the
`current lane (relative to vehicles which may be located there
`in the space in front or behind) permits him to reach such a
`gap, so that
`the driver is also relieved of the task of
`evaluating the driving situation in the current lane.
`Advantageously, the question as to whether a detected
`gap, in the target lane, which is in principle suflicient for a
`lane change, can in practice even be reached by the driver
`maneuvering his car can also be taken into account. Thus, in
`another embodiment of the invention, possible future driv-
`ing behavior for reaching the gap is analyzed in a computer
`simulation and tested as to whether the gap is actually
`reachable.
`In a further embodiment
`the acceleration or
`deceleration values necessary to accomplish a reachable lane
`change are displayed to the driver; or, alternatively,
`to
`further increase driving comfort, such information is passed
`on directly to a longitudinal movement controller device,
`which device is capable of automatically controlling the
`movement of the vehicle in the direction of travel without
`the intervention by the driver.
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`A particularly high level of driving comfort with respect
`to the control of the vehicle can be achieved by signaling to
`a device for controlling transverse movement of the vehicle
`that a gap which permits a lane change has been reached.
`The transverse movement control device can then automati-
`cally cause the vehicle to move into the gap in the target lane 5
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`without the driver having to perform steering movements
`himself. In conjunction with a longitudinal movement con-
`trol device which is actuated simultaneously, a method for
`completely autonomous vehicle control including possible
`lane changes is realized without need of controlling inter-
`vention by the driver.
`features of the
`Other objects, advantages and novel
`present invention will become apparent from the following
`detailed description of the invention when considered in
`conjunction with the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a flow chart which shows a computer-controlled
`guiding assistance method for a lane change according to the
`invention;
`FIGS. 2 to 6 show different vehicle situations in order to
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`illustrate the guiding assistance method; and
`FIG. 7 shows a diagrammatic illustration of the monitored
`areas used by the method according to the invention.
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`DETAILED DESCRIPTION OF THE DRAWINGS
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`In the illustrations in FIGS. 2 to 7, which depict the lanes
`of a highway, in each case a vehicle 0 is shown in a current
`lane 8, with a vehicle 2 travelling ahead in this current lane
`8 and a vehicle 4 following, as well as a front vehicle 3 and
`a rear vehicle 1 in a target lane 9. The direction of travel is
`indicated in each case by the arrow 25. In FIG. 2,
`the
`respective distances s01, s02, s03, $04 of the driver’s own
`vehicle 0 from the four other vehicles 1, 2, 3, 4 are shown.
`In FIG. 7, it can be seen that the driver’s own vehicle 0
`has a rear-mounted radar device (HR) for monitoring the
`space 23 behind in the current lane 8, a distance radar device
`(AR) for monitoring the space 24 in front in the current lane
`8, a blind—spot radar device (TWR) for monitoring the space
`21 behind in the adjacent target lane 9, and a forward-
`directed radar device (VR) for monitoring the space 22 in
`front in the target lane 9. These devices detect the presence
`of objects in the respective area covered by them, and also
`permit the distance from the object to be determined. (The
`term object here includes both other vehicles and stationary
`obstacles which may be encountered, for example at the end
`of a lane.) The blind—spot radar and the forward-directed
`radar (TWR, VR) are integrated in the exterior mirrors. The
`angle of the radar lobe is sufficiently large to reduce the blind
`spot. The monitoring of the space behind requires that the
`blind-spot radar have a range in the longitudinal direction of
`at least approximately 100 m.
`The mode of operation of the method according to the
`invention for computer-assisted guiding assistance for a
`driver’s motor vehicle 0 when changing from the current
`lane 8 to the adjacent target lane 9 (which in the case shown
`constitutes a passing lane located to the left of the current
`lane 8 in the direction of travel) is explained in detail below
`with reference to the program sequence plan of FIG. 1.
`The method is initiated in step 10 by activation of a travel
`direction indicator lever, which also simultaneously triggers
`a travel direction indicator. Alternatively, the system may be
`activated simply by tapping a travel direction indicator lever
`without the travel direction indication being triggered so that
`the operators of adjacent vehicles are not confused by the
`intention of a possibly imminent but not yet realizable lane
`change. In the latter case, a travel direction indication is not
`issued until a gap is detected for a possible lane change and
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`the driver’s own vehicle has reached the position required
`for the lane change.
`Actuation of the system is preferably cancelled if it has
`not been possible to find a gap within a predetermined time,
`after which the driver is requested to repeat the command if
`he still intends to change lane. If, on the other hand, the
`operators of adjacent vehicles are informed of the imminent
`intention to make a lane change by the immediate lighting of
`the travel direction indicator, the other operators may react
`differently, either by leaving space for a sufficient gap or else
`by closing a gap which may be present, thus making a lane
`change impossible.
`In an alternative embodiment of the invention, the system
`remains continuously activated and only the data output to
`corresponding display devices or vehicle movement-con-
`trolling devices is actuated in each case by the request for an
`indication of a change in travel direction. In this embodi-
`ment,
`the computer and the data lines are continuously
`occupied and ready. If, on the other hand, the system is
`activated only in response to the request for a travel direction
`indication, it can be used in the meantime for other purposes.
`It is to be noted at this point that the method can be carried
`out by means of a customary vehicle-mounted computer
`system, such as is known for example for the purpose of
`automatic distance-controlled driving, for which reason a
`detailed description of the system components is dispensed
`with here.
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`The request for activation of the travel direction indicator
`can be communicated to the driver,
`if desired, by the
`forward-directed monitoring in the current lane 8 if it is
`detected during this process that there is an object 2 in this
`area 24 in front which is moving more slowly in the
`direction of travel than the driver’s own vehicle 0.
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`After activation of the system, in step 11, the distances
`s01, s02, 503, s04 to the objects 1 to 4 are detected in the
`monitored areas 21 to 24, and their relative speeds with
`respect to the driver’s own vehicle 0 are measured by means
`of the radar devices. (The driver’s own speed vO is deter-
`mined by means of the speedometer.) In order to retain the
`data for these variables, the raw data from the radar devices
`are preprocessed according to their purpose, faults (for
`example due to signal reflections) are filtered out, and
`sufficient plausibility tests are carried out. For example, the
`objects 1 to 4 detected when cornering are assigned to the
`respective lane by means of the steering angle. If the relative
`speed of an object is equal and opposite to that of the driver’s
`own vehicle, the object is interpreted as a stationary obstacle
`or the end of a lane, for example a merge lane. If contra-
`dictory signals occur which cannot be evaluated, this fact is
`indicated to the driver if he has actuated the travel direction
`indicator. Vehicles travelling in the opposite direction on an
`oncoming carriageway can be blanked out or a warning
`signal can be triggered when the travel direction indicator is
`actuated.
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`In step 12, the safety distances sw01, sw02, sw03, sw04
`are calculated from the distance and speed data acquired in
`the previous step. For this purpose, initially the absolute
`speeds v1, v2, v3, v4 of the other vehicles and detected
`objects 1 to 4 are calculated from the relative speeds and the
`vehicle’s own speed v0. Subsequently, the safety distances
`are determined in each case as the sum of a reaction distance,
`a residual distance, a braking distance differential and a
`distance for coasting to a standstill.
`The reaction distance is obtained from the product of a
`reaction time and the speed of a trailing vehicle. (A cus-
`tomary driver’s reaction time of approximately 1.8 s, for6
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`example, can be used for this purpose.) When starting a
`distance control, the shortest system reaction time can be
`used. The residual distance constitutes a safety margin,
`which is typically set at approximately 5 m. Braking dis-
`tance differential
`is the difference between the braking
`distances for full braking of the two vehicles (between
`which the safety distance has just been detected), the maxi-
`mum braking deceleration, for example typically 3 rn/s2
`being specified or, if the driver’s own vehicle 0 has appro-
`priate devices, being determined automatically by means of
`the coefficient of friction dependent on the state of the road.
`Finally, the distance for coasting to a standstill is obtained
`from non—driven rolling of the vehicles with a reasonable
`deceleration which is typically 1 m/sZ. With these specified
`parameters (of which, incidentally, the residual distance and
`the reaction time can be matched by means of an adaptive
`control), the system computer calculates the safety distances
`sw01 to sw04 of the driver’s own vehicle 0 from each of the
`detected objects or vehicles 1 to 4.
`In step 13, the measured distances $01 to s04 are com-
`pared with the calculated safety distances sw01 to sw04 to
`determine whether the safety distances have all been main-
`tained. If the driver’s own vehicle 0 has a distance controller
`device, for example in conjunction with a speed control, the
`safety distance sw02 from the vehicle 2 travelling ahead in
`the current lane 8 is automatically maintained and it is
`necessary only to check the other distances. If the computer
`determines that all the measured distances are at least as
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`great as the respectively associated calculated safety dis-
`tances, it signals that a lane change can be made in the
`current situation and indicates this to the driver appropri-
`ately. He can then carry out the lane change in a following
`step 14, after which the system returns again to the point A
`before the actuation of the system.
`When carrying out this step it may be advantageous not to
`use precisely calculated values for the safety distance but
`rather, in particular during a lane change, to determine the
`distance boundaries according to a plausibility test some-
`what imprecisely or to provide them with hysteresis prop-
`erties. Furthermore, the inclusion of acceleration processes,
`which have already been started, of individual vehicles in
`the calculation of the safety distances can be useful to the
`flow of traffic.
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`If, on the other hand, the computer has calculated that one
`of the measured distances is smaller than the associated
`safety distance, a current lane change is not possible. In such
`case, in step 15 the method according to the invention then
`searches for a gap in the target lane suflicient to permit a lane
`change, even though it is not already adjacent to the driver’s
`own vehicle 0. (Such a gap may possibly be located, for
`example, obliquely in front of or obliquely behind the
`driver’s vehicle 0 and is basically also accessible to the
`driver’s vehicle 0.) For this purpose, the following measured
`distances and calculated safety distances are summed and
`compared by the computer. First, the sum s01+503 of the
`measured distances to the vehicles 1, 3 in the target lane 9
`and the sum sw01+sw03 of the associated calculated safety
`distances are calculated. The computer compares both sums
`and detects the presence of a gap in the target lane 9 if the
`sum of the measured distances is greater than the sum of the
`calculated safety distances. Second, it calculates the sum
`s01+s02 of the measured distances between the vehicle 1
`behind in the target lane 9 and the vehicle 2 which is
`travelling ahead in the current lane 8, and likewise in turn
`calculates the associated sum sw01+sw02 of the calculated
`safety distances. The same process is carried out as a third
`step with the distances of the two other vehicles 3, 4. Both
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`sums s01+s02, s03+504 of the measured distances are then
`in turn compared in each case with the associated sum of the
`calculated safety distances, and if it is detected in both cases
`that the sum of the measured distances is greater than the
`sum of the associated calculated safety distances,
`it
`is
`determined to mean that space is available for the driver’s
`own vehicle 0 to accelerate or decelerate, as a result of which
`it may be possible to reach the detected gap in order to
`change lanes.
`If,
`in one or more of the three comparisons of this
`interrogation step 16, the sum of the measured distances is
`smaller than the sum of the calculated safety distances, it is
`determined to mean that under the set parameters (for
`example reaction time, safety margin, residual distance, the
`driver’s acceleration or deceleration and reasonable decel-
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`eration of the other vehicles), a lane change is not possible.
`In consequence, in a following step 17, the instruction to
`stay in lane is issued to the driver. The system then returns
`to point B before the measurement step 11 and the process
`is repeated, during which new measurement data, which
`may arise from possible changes in the positions or speeds
`of the vehicles, are acquired.
`If, on the other hand, in step 16 for all three comparisons
`the measured distances is greater than that of the calculated
`safety distances, it is determined that a gap is currently
`available for a lane change, and can be reached after suitable
`vehicle maneuvers have first been carried out (in particular,
`an acceleration or deceleration). This can be signalled to the
`driver by the system, for example by means of an LED.
`The method according to the invention provides extensive
`assistance to the driver in determining suitable maneuvers
`by which his own vehicle 0 can reach the gap which is
`present in the target lane 9. For the latter purpose, after a
`positive response in the preceding interrogation step 16, a
`computer simulation step 18 determines whether a gap was
`basically present, taking into account possible future actions
`(for example accelerations, declarations or lane changes) of
`each of the vehicles 0—4 during the period until the gap is
`reached.
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`This is a highly non-linear problem, since a change in the
`vehicle’s own speed means at the same time a change in the
`calculated safety distances. Even when the speed of the other
`vehicles remains constant, such an increase in the vehicle’s
`own speed v0 can occur that even though the gap remains
`the same size, the safety distances from the vehicles trav-
`elling ahead may no longer be maintained, or that
`the
`specified acceleration is not sufficient to carry out the change
`in position within a period in which the change in traflic
`situation permits a lane change. In both cases, an initiated
`passing process would have to be aborted. Thus, the simu—
`lation which is calculated in advance in the time accelerator
`is appropriate at this point. For this purpose,
`the radar
`devices according to FIG. 7 detect the current traffic situa-
`tion,
`including the distances and speeds of the other
`vehicles, and on the basis of this information, it is deter-
`mined in the simulation whether, and by means of which
`activities, it may become possible for the driver to enter the
`gap which has been found.
`In this simulation, a negative acceleration value (that is, a
`deceleration) is prescribed if the calculated safety distances
`from the vehicles 1, 4 behind can both be maintained. If, on
`the other hand, the safety distances from .the two front
`vehicles 2, 3 are satisfied by the measured distances, a
`positive acceleration value is prescribed. Thus, the traffic
`behavior is simulated in advance, specifically in the longest
`case until, when accelerating, the distance from the vehicle 7
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`2 travelling ahead in the current lane 8 or, when decelerating,
`the distance from the vehicle 4 following in the current lane
`8, drops below the respective associated safety distance. If
`the existing gap is not reached by this time, when acceler-
`ating a new simulation cycle with an incrementally
`increased acceleration value is carried out. The interrogation
`step 19 as to a possible lane change, on accelerating, is not
`ultimately answered negatively (and the driver in turn given
`the instruction in step 17 to stay in lane) until it has been
`determined that it is not possible to reach the gap after a set
`upper limit for the acceleration value (which results for
`example from the smallest value of the engine output
`threshold, the threshold of the coeflicient of friction or an
`individual comfort threshold) has been reached or after a
`prescribed maximum speed has been reached.
`On the other hand, for reasons of driving comfort the
`deceleration in the simulation is not increased incrementally
`in the manner described above, but is set right at
`the
`beginning to a value which is still advantageous for comfort.
`If the gap is not reached after the single deceleration
`simulation cycle, the instruction to stay in lane is issued to
`the driver again.
`If, on the other hand, it is determined by the simulation in
`the interrogation step 19 that a lane change is possible by
`means of a simulated vehicle maneuver, the data determined
`for such change, relating to the vehicle acceleration or
`deceleration, are output, for example, to a display device for
`the driver, who can subsequently set the required accelera-
`tion or deceleration value and perform the maneuver to
`reach the gap in the target lane under his own control. This
`realization of the previously simulated vehicle maneuver is
`shown in step 20 of the positioning in the flow chart in FIG.
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`the vehicle has a longitudinal
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`movement control device for automatic movement of the
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`vehicle in the longitudinal direction, the data can be output
`to such longitudinal movement control which automatically
`moves the vehicle onto the acceleration or deceleration
`value detected in the simulation. The system then returns to
`point B before the measurement step 11 and the process is
`repeated to detect that the sufficient gap has been reached
`and to be able to perform the desired lane change.
`A completely autonomous vehicle control, including lane
`changes without need of any intervention of the driver, is
`possible if the vehicle also has a transverse movement
`control device. In such case, when it is detected that a lane
`change is possible,
`this information is signalled to the
`transverse movement control device, and the lane change is
`carried out automatically by the longitudinal movement
`controller and transverse movement controller of
`the
`vehicle, possibly after an appropriate request from the
`driver.
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`The process according to the invention is explained below
`with respect to different traffic situations according to FIGS.
`1 to 6.
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`FIG. 2 shows an example in which it is presumed that all
`the safety distances are maintained. The execution of the
`method described above detects the gap in the adjacent (here
`left—hand)
`target
`lane 9, and thus the possibility of an
`immediate lane change.
`In the case in FIG. 3, the required safety distance from the
`vehicle 1 behind in the target lane 9 is not satisfied, and the
`system thus detects that an instantaneous lane change is not
`possible. However, the gap search step 15 detects a suitable
`gap located obliquely in front of the driver’s own vehicle 0.
`The measured distance from the vehicle 2 travelling ahead
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`in the current lane 8 allows sufiicient distance for accelera-
`tion. In the subsequent simulation, it is determined whether
`it is possible to position the vehicle in this gap at a safe
`distance from all the other vehicles; and if so, with what
`acceleration.
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`In the trafiic situation in FIG. 4, the safety distance from
`the vehicle 3 travelling ahead in the target lane 9 is not
`suflicient, and the system detects in turn that an immediate
`lane change is not possible. The subsequent search for a gap
`in step 15 (FIG. 1) determines that a suitable gap is located
`obliquely behind the driver’s own vehicle 0. The measured
`distance from the vehicle 4 travelling behind in the current
`lane 8 turns out to be considerably greater than the calcu-
`lated safety distance, so that sufiicient distance is available
`for deceleration. In the subsequent simulation, it is deter-
`mined whether it is possible to position the vehicle in the gap
`at a safe distance from the other vehicles by means of the
`preselected deceleration or simply by waiting.
`In the case in FIG. 5, as in the case in FIG. 3, the presence
`of a suitable gap is detected obliquely in front of the driver’s
`own vehicle 0. The distance to the vehicle 2 travelling ahead
`in the current lane 8 corresponds, however, approximately to
`the calculated safety distance, so that there is insufficient
`distance available for acceleration, and a safe lane change is
`not possible (step 19). In this case, an instruction to stay in
`the current lane 8 is issued to the driver.
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`In the situation in FIG. 6, as in FIG. 4, the presence of a
`suitable gap is detected obliquely behind the driver’s own
`vehicle 0. However, the measured distance from the vehicle
`4 travelling behind in the current lane 8 corresponds already
`approximately to the calculated safety distance, so that there
`is insufficient distance available for deceleration, and the
`question of a possible lane change is again answered nega-
`tively. In this case the vehicle also has to stay in the current
`lane 8.
`
`The method can of course, as to a certain extent already
`indicated, he used in conjunction with distance-controlled
`driving and a speed controller. In the same way as for
`changing into a left-hand target lane, a lane change to the
`right-hand target lane can be brought about by the method if
`the driver’s own vehicle has appropriate radar detection
`devices on the right—hand side, the actuation then taking
`place in response to the request for an indication of a change
`in travel direction to the right. Usually, the speeds of the
`vehicles in the right-hand target lane are lower, and the
`computer simulation is therefore modified so that a decel-
`eration is preselected if the current speed of the driver’s own
`vehicle is higher than the speed preselected on a speed
`controller.
`
`It is also possible, on multi-lane roads such as for example
`highways in the USA. on which passing on the right is
`permitted, for the method to detect, by means of the simu-
`lation via the computer, the lane which is currently most
`suitable for passing, and to propose this to the driver or to
`the transverse movement controller device of the vehicle
`which may be present.
`Although the invention has been described and illustrated
`in detail, it is to be clearly understood that the same is by
`way of illustration and example, and is not to be taken by
`way of limitation. The spirit and scope of the present
`invention are to be limited only by the terms of the appended
`claims.
`What is claimed is:
`
`1. Method of assisting a motor vehicle in changing from
`a current lane in which the vehicle is operated, to a target
`lane adjacent thereto, comprising the steps of:
`
`8
`
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`9
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`10
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`5,521,579
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`monitoring a space behind and a space in front of said
`vehicle in at least the target lane, to detect presence of
`objects therein;
`
`determining speeds of detected objects in said target lane
`and of said vehicle;
`
`determining distances of the detected objects in said target
`lane from said vehicle;
`
`calculating for each detected object in said target lane a
`safety distance from said vehicle based on determined
`speed of said object, a predetermined reaction time and
`a predetermined deceleration value;
`comparing the determined distance of each detected
`object
`in said target
`lane with the safety distance
`calculated therefor;
`
`if at least the determined distance of each detected object
`in said target
`lane is greater than or equal
`to the
`calculated safety distance for said object, activating a
`signal to a driver of said vehicle, indicating that a lane
`change is possible; and
`if the determined distance of at least one detected object
`in said target lane is smaller than the calculated safety
`distance for said object, performing the additional steps
`of:
`
`comparing at least a first sum of the determined distances
`of said detected objects in said target lane with a first
`corresponding sum of the safety distances calculated
`for said detected objects;
`if said at least a first sum of said determined distances is
`greater than said first corresponding sum of calculated
`safety distances, activating a signal
`to said driver,
`indicating that a lane change is possible; and
`if at least the determined distance of any detected object
`in the target lane is less than the calculated safety
`distance for said object, and if said at least a first sum
`of determined distances is not greater than the first
`corresponding sum of calculated safety distances, acti-
`vating a signal indicating that a lane change is not
`possible.
`2. Method according to claim 1 further comprising the
`steps of
`monitoring a space behind and a space in front of said
`vehicle in said current lane to detect presence of objects
`therein;
`
`determining speeds of detected objects in said current
`lane;
`
`determining distances of detected objects in said current
`lane from said vehicle; and
`
`calculating for each detected object in said current lane a
`safety distance from said vehicle based on the deter-
`mined speed of said object, a predetermined reaction
`time and a predeterrnine deceleration value;
`wherein said second comparing step further comprises the
`steps of:
`comparing a second sum of said determined distances of
`an object detected in the space behind said vehicle in
`the t