Method for controlling loading dock equipment and associated control device

Abstract

A control device for a piece of loading dock equipment (3) (1) that is mobile between a non-use position and a loading / unloading position is proposed. The device comprises: - first detection means (10) located on the loading dock, - transmission means (8) located on the dock, - reception means (9) located on the dock, - dock control means (6), - a human-machine interface (13), - second detection means (11), - manually operated control means (4). Figure for the abstract: Fig 1

Description

Title of the invention: Method for controlling loading dock equipment and associated control device

[0001] The present invention relates to the field of road vehicles for transporting goods, such as semi-trailers, trailers or carriers, and more particularly to a device for controlling equipment of a loading dock and an associated method.

[0002] Conventionally, a road vehicle for transporting goods is docked at a loading dock of a warehouse to load or unload goods contained in the road vehicle.

[0003] During these operations, a loader tranships the goods between the road vehicle and the warehouse.

[0004] In order to prevent the loader from falling between the loading dock and the vehicle during loading and unloading operations, it is necessary to prevent any possible movement of the road vehicle and to validate its position.

[0005] For this purpose, it is possible to actuate means for immobilizing the road vehicle when a curtain of the loading dock has been raised for these goods loading / unloading operations. For further details, reference may be made, for example, to patent application FR 3 111 340 (Chéreau).

[0006] In this prior solution, the loading dock is equipped with transmission means, and the vehicle is equipped with means for controlling the immobilization means.

[0007] The transmission means emit an electromagnetic activation signal when the platform curtain opens, and upon receipt of this signal the control means immobilize the vehicle.

[0008] However, with this prior solution, the loading dock curtain rises independently of the presence of a vehicle docked at the dock and also requires the road vehicle to be equipped with means for controlling the immobilization means interacting with the dock emission means.

[0009] If the road vehicle is not equipped with control means, the road vehicle is likely to be moved when the platform curtain is open.

[0010] Therefore, an operator can fall from the loading dock if no vehicle is docked or when the road vehicle is moving.

[0011] The present invention aims to remedy these drawbacks.

[0012] The invention relates to a method for controlling loading dock equipment which is movable between a non-use position and a use position. loading / unloading.

[0013] The method comprises:

[0014] - a step of detecting a road vehicle for transporting goods by first detection means placed on the loading dock.

[0015] The method further comprises:

[0016] - a step of transmitting an initialization signal by transmitting means placed on the platform when the road vehicle is detected by the detection means,

[0017] - a step of transmitting a first signal by means of controlling the die placement of the equipment arranged on the platform when reception means arranged on the platform do not receive an identification signal emitted by the vehicle in response to the initialization signal for a predetermined duration which begins upon the emission of said initialization signal,

[0018] - after reception of the first signal by a human-machine interface, a step manual immobilization of the vehicle,

[0019] - an emission of a blocking signal by second detection means when the vehicle is immobilized,

[0020] - a step of manually actuating manually actuated control means to control the movement of the equipment from the non-use position to the loading / unloading position, and

[0021] - a step of moving the equipment to the loading / unloading position loading during manual actuation of the control means, only if a blocking signal is received by the dock control means and if the minimum distance between the vehicle and the dock determined by the detection means is less than or equal to a predetermined detection distance.

[0022] By "minimum distance between the vehicle and the dock" is meant the smallest distance that exists between the dock and the vehicle, this distance generally being between the dock and the vehicle's docking rollers or buffers.

[0023] With the method of the invention, the movement of the equipment to its loading / unloading position is carried out only if a road goods transport vehicle is present in front of the dock and if this vehicle is immobilized. Thus, the probability of the operator falling from the dock is greatly reduced.

[0024] Furthermore, the opening of the curtain is possible while the road vehicle is not equipped with control means interacting with the control means of the platform.

[0025] Advantageously, the initialization signal is emitted by the emission means arranged on the platform when, in addition to the minimum distance determined by the detection means, it is less than or equal to the predetermined detection distance.

[0026] According to a first design, the manual immobilization step comprises inserting the vehicle's start key into a key box placed on the platform, closing the key box and emitting the locking signal by the second detection means incorporated in the key box when the key is inside the key box and the key box is locked.

[0027] The key may comprise an electronic card or a physical key having notches.

[0028] According to a second design, the manual immobilization step comprises mounting at least one chock against wheels of the vehicle, and emitting the blocking signal by the second detection means arranged on said chock when the chock is in contact with said wheel.

[0029] According to a third design, the manual immobilization step comprises the insertion of at least one hook fixed to the dock on an anti-underrun bar of the vehicle and the emission of the blocking signal by the second detection means arranged on said hook when the hook is attached to the anti-underrun bar.

[0030] According to a fourth design, the manual immobilization step comprises the arrangement of a bar between two wheels of the vehicle, and the emission of the blocking signal by the second detection means arranged on said axle bar when the axle bar is arranged between the two wheels.

[0031] According to a fifth design, the manual immobilization step comprises mounting the vehicle start key on a hook arranged on the equipment and emitting the blocking signal by the second detection means arranged on the hook when the key is mounted on the hook.

[0032] Advantageously, the detection means deliver an alarm signal when the absolute value of the time derivative of the distance between the vehicle docked at the quay and immobilized is greater than a predetermined alarm threshold.

[0033] Preferably, the detection means continuously determine the minimum distance between the vehicle and the platform.

[0034] The loading dock equipment may comprise a curtain for closing access to the mobile loading dock between an open loading / unloading position and a closed, lowered, non-use position.

[0035] Alternatively, the loading dock equipment comprises a loading bridge movable between a lowered horizontal loading / unloading position and a raised, stowed, non-use position.

[0036] The invention also relates to a device for controlling loading dock equipment which is movable between a non-use position and a loading / unloading position.

[0037] The device comprises:

[0038] - first detection means arranged on the loading dock and configured to detect a road freight vehicle and the dock,

[0039] - transmission means arranged on the platform and configured to transmit a signal initialization when the road vehicle is detected by the detection means,

[0040] - reception means arranged on the platform,

[0041] - means for controlling the movement of the equipment which are arranged on the dock and configured to emit a first signal when the reception means arranged on the dock do not receive an identification signal emitted by the vehicle in response to the initialization signal for a predetermined duration which begins upon emission of said initialization signal,

[0042] - a human-machine interface configured to receive the first signal and interact with a dock operator,

[0043] - second detection means configured to emit a blocking signal when the vehicle is immobilized,

[0044] - manually operated control means arranged on the platform and configured to control the movement of the equipment from the non-use position to the loading / unloading position,

[0045] - the means for controlling the movement of the equipment being further configured to make operational the manual actuation of the control means to move the equipment from the non-use position to the loading / unloading position, when the blocking signal has been received by the dock control means and if the minimum distance between the vehicle and the dock determined by the detection means is less than or equal to a predetermined detection distance.

[0046] The present invention will be better understood upon studying the detailed description of embodiments taken as non-limiting examples and illustrated by the appended drawings, in which:

[0047] [Fig. 1] schematically illustrates an exemplary embodiment of a road vehicle for transporting goods during docking according to the invention;

[0048] [Fig.2]

[0049] [Fig.3] schematically illustrates a method of controlling a curtain for closing access to the loading dock according to the invention;

[0050] [Fig.4] schematically illustrates a second example of blocking means of a road vehicle for transporting goods according to the invention;

[0051] [Fig.5] schematically illustrates a third example of means for blocking a road vehicle for transporting goods according to the invention;

[0052] [Fig.6] schematically illustrates a fourth example of means for blocking a road vehicle for transporting goods according to the invention; and

[0053] [Fig.7] schematically illustrates a fifth example of blocking means of a road vehicle for transporting goods according to the invention.

[0054] [Fig.l] schematically illustrates a road vehicle for transporting goods when docking said vehicle at a loading bay 1.

[0055] The road vehicle here is a semi-trailer 2a connected to a tractor 2b.

[0056] Alternatively, the road vehicle could be a single semi-trailer, a trailer or a carrier.

[0057] The loading dock 1 is equipped with a closing curtain 3 for access to the loading dock, which is movable between a lowered closed position and a raised open position for loading and unloading. The fully open or partially open position of the curtain 3 corresponds to a loading / unloading position, and the closed position of the curtain corresponds to a non-use position. In [Fig.l], the curtain 3 is in the closed position.

[0058] The loading dock 1 also comprises manually operated control means 4 for controlling the movement of the curtain 3. In a manner known per se, the curtain 3 is equipped with a drive means (not shown), for example an electric motor to enable it to move between the loading / unloading position and the non-use position, and vice versa. A control unit 5 is also provided for controlling the drive means of the curtain 3.

[0059] The control means 4 of the curtain may for example be provided on the inside of the warehouse equipped with the loading dock 1. The control means 4 may for example comprise a first push button 4a so that the user of the dock can control the opening of the curtain 3, and a second push button 4b to control the closing of the latter. The control means 4 may for example be in the form of a box positioned on a wall of the warehouse or in the form of a remote control.

[0060] The loading dock 1 further comprises control means 6 comprising a counter 7. The control means 6 are further connected to the control means 4 and to the control unit 5.

[0061] The loading dock 1 further comprises transmission means 8 and reception means 9 connected to the control means 6, and first detection means 10 connected to the control means 6.

[0062] The control means 6 are connected to the command means 4 by a connection which is for example of the wired or radioelectric type or even made via a communication bus.

[0063] The control means 6 comprise for example a processing unit.

[0064] The transmission means 8 and reception means 9 can be produced in the form of two separate boxes as shown or a single box.

[0065] The first detection means 10 are capable of detecting the presence of the semi-trailer 2. In the illustrated embodiment, the detection means 10 are also capable of determining the minimum distance between the semi-trailer 2a and the dock. 1.

[0066] The first detection means 10 comprise for example an ultrasonic radar.

[0067] The first detection means 10 can detect and determine the distance minimal from other technologies by implementing optical technologies implementing for example a laser.

[0068] The transmission means 8 arranged on the platform 1 are capable of transmitting an initialization signal Sinit when a road vehicle is detected by the detection means 10.

[0069] As will be described in more detail below, the control means 6 arranged on the platform 1 are capable of rendering inoperative the manual actuation of the control means 4 when a blocking signal Sb has not been received by the control means 6 of the platform 1 or when the minimum distance between the semi-trailer 2a and the platform 1 determined by the detection means 10 is greater than a predetermined detection distance.

[0070] The predetermined detection distance is chosen according to the configuration of platform 1 and can for example be equal to 40 cm, 50 cm or one meter.

[0071] In [Fig.l], the semi-trailer 2 is shown in a docking position relative to the loading dock 1. The distance between the nearest end of the semi-trailer 2 and the dock 1 is referenced Dp. This distance Di is the minimum distance between the semi-trailer 2 and the dock 1.

[0072] As will also be described in more detail later, the control means 6 arranged on the platform 1 are further capable of delivering, after actuation of the control means 4, a control signal for moving the equipment 3 from the non-use position to the loading / unloading position only if the blocking signal Sb has been received by the control means 6 of the platform 1 and if the minimum distance between the semi-trailer 2a and the platform 1 determined by the detection means 10 is less than or equal to the predetermined detection distance.

[0073] In this embodiment, means 11 for ensuring the immobilization of the semi-trailer 2a are arranged on the platform 1.

[0074] These means 11 comprise second detection means capable of emitting a blocking signal when the semi-trailer 2a is immobilized.

[0075] The means 11 comprise for example a key box 12 arranged on the platform 1.

[0076] The key box 12 comprises the second detection means 12a capable of emitting the blocking signal Sb when the second detection means 12a detect the presence of a key inside said box and said box is locked so that the key cannot be removed from said box 12.

[0077] The platform further comprises a man-machine interface 13 capable of receiving a first signal emitted by the control means 6 and of interacting with an operator OP. from platform 1.

[0078] The human-machine interface 13 comprises, for example, an indicator light 13a.

[0079] The control means 6, the transmission means 8, the reception means 9, the first detection means 10, the human-machine interface 13, the second detection means 12a and the manually actuated control means 4 form a device for controlling the curtain 3 of the loading dock 1.

[0080] The transmission means 8 of the platform 1 comprise, for example, a transmission device of the RFID radio frequency identification type and the reception means 9 of the platform 1 comprise, for example, a reception device of the RFID radio frequency identification type.

[0081] The initialization signal Sinit is for example of the radio type.

[0082] Of course, the transmission means 8 and the reception means 9 can implement another communication protocol.

[0083] We will now describe with reference to figures 2 and 3, the method of controlling the curtain 3 for closing access to the loading dock 1.

[0084] The first detection means 10 of the dock, which operate permanently, detect the presence of the semi-trailer 2 and determine the minimum distance between it and the dock 1. This minimum distance is permanently determined by the detection means 10 during the process.

[0085] The curtain 3 is in the closed position in the non-use position preventing access to the loading dock 1.

[0086] It is assumed that the semi-trailer 2 is approaching the loading dock 1.

[0087] When the first detection means 10 detect the presence of the semi-trailer 2a near the quay 1, the detection means 10 determine the distance Di (step 20).

[0088] If the determined distance Di is greater than the predetermined detection distance (step 21), the method continues to step 20.

[0089] When the first detection means 10 determine that the distance Di is less than or equal to the predetermined detection distance (step 21), the method continues with a step 22 during which the transmission means 8 of the platform 1 transmit the initialization signal Sinit and the control means 6 trigger the counter 7.

[0090] If the road vehicle does not include means for receiving the initialization signal Sinit or if the means for receiving the initialization signal Sinit are faulty, the vehicle does not emit any signal in response to the emission of the initialization signal Sinit.

[0091] When the counter 7 reaches a predetermined duration starting from the emission of the initialization signal Sinit and the reception means 9 do not receive a signal emitted by the vehicle in response to the initialization signal Sinit, the control means 6 emit a first signal SI during a step 23. The predetermined duration is for example equal to thirty seconds.

[0092] The first signal SI is transmitted to the human-machine interface 13 to inform the operator OP that the road vehicle is not able to communicate with the transmission 8 and reception 9 means.

[0093] For example, upon receipt of the first signal SI, the indicator light 13a changes color.

[0094] During a step 24, when the operator OP detects that the human-machine interface 13 has received the first signal SI, for example by the change in color of the indicator light 13a, the operator OP manually immobilizes the road vehicle.

[0095] The operator OP inserts the starting key 14 of the tractor 2b of the road vehicle into the key box 12 of the platform 1, and then closes it.

[0096] During a step 25, when the second detection means 12a detect that the ignition key 14 is inside the key box 12 and the key box is locked, the detection means 12a emit the blocking signal Sb representative of the immobilization of the vehicle.

[0097] In this case, when the detection means 12a of the box 12 detect the presence of the key 14 inside the locked box 12 so that the key 14 cannot be removed from the key box 12, said means 12a deliver the blocking signal Sb.

[0098] The second detection means 12a comprise, for example, a sensor for detecting the presence of a key.

[0099] As the ignition key 14 is no longer accessible, it is not possible to start the tractor 2b so that the road vehicle is considered to be immobilized.

[0100] During a step 26, an operator OP actuates the control means 4 by pressing the first button 4a to control the opening of the curtain 3.

[0101] A signal to control the opening of the curtain is transmitted to the control means 6 of platform 2.

[0102] If the blocking signal Sb has not been received by the control means 6 of the platform 1, or if the minimum distance is no longer less than or equal to the predetermined detection distance (step 27), the method stops and the curtain 3 remains closed.

[0103] If the control means 6 of the platform 1 have received the blocking signal Sb (step 27) and if the minimum distance is still less than or equal to the predetermined detection distance, during a step 28, the control means 6 transmit the manual control order from the operator OP via the actuation of the control means 4 to the control unit 5 for the opening of the curtain 3. As indicated previously, the determination of the minimum distance between the semi-trailer and the platform 1 is determined, in this method, continuously by the detection means 10 during the method. Alternatively, it could be possible to provide a first determination of the minimum distance in step 20 and a second determination of the minimum distance at step 27, the detection means 10 being inactive between steps 20 and 27.

[0104] The curtain 3 is moved to the loading / unloading position only if the control means 6 of the platform 1 have received the blocking signal Sb and if the minimum distance is still less than or equal to the predetermined detection distance.

[0105] At the end of the loading / unloading operations (step 29), when the operator OP actuates the second button 4b of the control means 4 for closing the curtain 3, the control means 4 emit a signal controlling the closing of the curtain which is transmitted to the control means 6 of the platform 1.

[0106] Upon receipt of the control signal for closing the curtain 3, the control means 6 of the platform 1 emit a control signal which is delivered to the control unit 5 to control the closing of the curtain 3.

[0107] When the curtain 3 is in the closed position, the control means 6 of the platform 2 emit an unlocking signal Sdev authorizing the opening of the key box 12.

[0108] Furthermore, when the curtain 3 is in the open position, the detection means 9 always measure the distance Dp

[0109] If the absolute value of the time derivative of the distance between the semi-trailer 2 docked at the quay 1 and immobilized is greater than a predetermined alarm threshold, the detection means 9 deliver an alarm signal to the control means 6 of the quay 1.

[0110] The control means 6 of the platform 1 control the human-machine interface 13 to inform the operators present near the platform 1 that the semi-trailer 2 is no longer immobilized.

[0111] The movement of the equipment to its loading / unloading position is carried out only if the minimum distance between the semi-trailer 2a and the dock determined by the detection means is less than or equal to the predetermined detection distance, if the blocking signal representative of the immobilization of the vehicle is received by the control means 6 of the dock 1, and if the manually actuated control means are actuated. Thus, the probability of the operator falling from the dock is greatly reduced.

[0112] Furthermore, the opening of the curtain 3 is possible while the road vehicle is not equipped with control means interacting with the control means of the platform 1.

[0113] In the example which has just been described, during step 20, the detection means detect the presence of the semi-trailer 2 and determine the minimum distance between it and the platform 1. Alternatively, in step 20, the first detection means 10 could detect only the presence of the semi-trailer 2a near the platform 1 in step 20, and the method could continue directly to step 22 without perform step 21, and then continue as described previously from step 22.

[0114] [Fig.4] schematically illustrates a second example of the means 11 for ensuring the immobilization of the vehicle.

[0115] The means 11 comprise at least one wedge 30 comprising second detection means 31.

[0116] The second detection means 31 comprise for example a pressure sensor.

[0117] When the wedge is mounted by the operator OP against one of the wheels of the road vehicle, the second detection means 31 detect a variation in pressure exerted by the wheel on the wedge 30 and emit the blocking signal Sb.

[0118] The operator OP can mount several wedges 30, each wedge being mounted against a different wheel of the road vehicle.

[0119] [Fig.5] schematically illustrates a third example of the means 11.

[0120] The locking means 11 comprise a hook 32 comprising a base 33 fixed to the platform 1 and second detection means 34.

[0121] The hook 32 is connected to the base 33 by a pivot connection and is intended to be inserted on an anti-underrun bar 35 of the road vehicle.

[0122] When the hook 32 is inserted onto the anti-underrun bar 35 of the road vehicle, the second detection means 34 emit the blocking signal Sb.

[0123] The second detection means 34 comprise, for example, a contactor closing when the hook 32 is inserted onto the anti-embed bar.

[0124] [Fig.6] schematically illustrates a fourth example of the means 11.

[0125] The means 11 comprise a bar 36 comprising second detection means 37.

[0126] When the axle bar 36 is mounted between two wheels of the road vehicle, the detection means 37 emit the locking signal Sb. The second detection means 37 comprise, for example, a contactor which closes when the bar is inserted between the two wheels. The bar can be mounted manually or be part of an automatic wheel locking system fitted to the dock.

[0127] [Fig.7] schematically illustrates a fifth example of the means 11.

[0128] The means 11 comprise a hook 38 arranged on the curtain 3 and comprising second detection means 39.

[0129] When the starting key 14 of the road vehicle is mounted on the hook 38, the second detection means 39 emit the blocking signal Sb.

[0130] The second detection means 39 comprise, for example, a force sensor detecting the force exerted by the ignition key 14 on the hook 38.

[0131] In the illustrated embodiments, the equipment of platform 1 is a curtain sliding. Alternatively, the equipment may be a mobile mounted gangway rotatable relative to the dock between a vertical non-use position and a lowered horizontal loading / unloading position.

Claims

Claims

1. Method for controlling equipment (3) of a loading dock (1) which is movable between a non-use position and a loading / unloading position, the method comprising: - a step of detecting a road vehicle (2a, 2b) for transporting goods by first detection means (10) arranged on the loading dock, - a step of transmitting an initialization signal (Sinit) by transmission means (8) arranged on the dock when the road vehicle is detected by the detection means (10), - a step of transmitting a first signal (SI) by means (6) for controlling the movement of the equipment arranged on the dock when reception means arranged on the dock do not receive an identification signal transmitted by the vehicle in response to the initialization signal (Sinit) for a predetermined duration which begins at the transmission of said initialization signal,- after receiving the first signal (SI) by a human-machine interface (13), a step of manually immobilizing the vehicle, - an emission of a blocking signal (Sb) by second detection means (12a; 31; 34; 39) when the vehicle is immobilized, - a step of manually actuating manually actuated control means (4) to control the movement of the equipment (3) from the non-use position to the loading / unloading position, and - a step of moving the equipment (3) to the loading / unloading position upon manual actuation of the control means, only if the blocking signal (Sb) is received by the control means (6) of the dock and if the minimum distance between the vehicle and the dock determined by the detection means (10) is less than or equal to a predetermined detection distance.,

2. Method according to claim 1, in which the initialization signal (Sinit) is emitted by the emission means (8) arranged on the platform when, in addition to the minimum distance determined by the detection means (10), it is less than or equal to the predetermined detection distance.

3. A method according to claim 1 or 2, wherein the step of manually immobilizing comprises inserting the ignition key (14) of the vehicle in a key box (12) arranged on the platform (1), closing the key box, and emitting the blocking signal (Sb) by the second detection means (12a) incorporated in the key box (12) when the key is inside the key box and the key box is locked.

4. Method according to claim 1 or 2, wherein the manual immobilization step comprises mounting at least one chock (30) against one of the wheels of the vehicle, and emitting the blocking signal (Sb) by the second detection means (31) arranged on said chock when said chock is in contact with said wheel.

5. Method according to claim 1 or 2, wherein the manual immobilization step comprises inserting at least one hook (32) fixed to the dock (1) on an anti-underrun bar (35) of the vehicle, and emitting the blocking signal (Sb) by the second detection means (34) arranged on said hook when the hook is hooked to the anti-underrun bar.

6. A method according to claim 1 or 2, wherein the manual immobilization step comprises arranging a bar (36) between two wheels of the vehicle, and emitting the blocking signal (Sb) by the second detection means (37) arranged on said bar when said axle bar is arranged between the two wheels.

7. A method according to claim 1 or 2, wherein the manual immobilization step comprises mounting the ignition key (14) of the vehicle (2a, 2b) on a hook (38) arranged on the equipment (3), and emitting the blocking signal (Sb) by the second detection means (39) arranged on the hook when the key is mounted on the hook.

8. Method according to one of claims 1 to 7, in which the detection means (10) deliver an alarm signal when the absolute value of the time derivative of the distance between the vehicle (2a, 2b) docked at the quay and immobilized is greater than a predetermined alarm threshold.

9. Method according to one of claims 1 to 8, in which the detection means (10) continuously determine the minimum distance between the vehicle and the platform.

10. Method according to one of claims 1 to 9, in which the equipment of the loading dock (1) comprises a curtain (3) for closing access to the mobile loading dock between an open loading / unloading position and a lowered closed non- use.

11. Method according to one of claims 1 to 9, in which the equipment of the loading dock (1) comprises a loading bridge movable between a lowered horizontal loading / unloading position and a raised, stowed position for non-use.

12. Device for controlling equipment (3) for a loading dock (1) which is movable between a non-use position and a loading / unloading position, the device comprising: - first detection means (10) arranged on the loading dock and configured to detect a road vehicle for transporting goods (2a, 2b), - transmission means (8) arranged on the dock and configured to transmit an initialization signal (Sinit) when the road vehicle is detected by the detection means (10), - reception means (9) arranged on the dock, - means (6) for controlling the movement of the equipment which are arranged on the dock and configured to transmit a first signal (SI) when the reception means (9) arranged on the dock do not receive an identification signal transmitted by the vehicle in response to the initialization signal for a predetermined duration which begins at the transmission of said initialization signal,- a human-machine interface (13) configured to receive the first signal (SI) and interact with an operator (OP) of the dock, - second detection means (12a; 31; 34; 39) configured to emit a blocking signal (Sb) when the vehicle is immobilized, - manually actuated control means (4) arranged on the dock and configured to control the movement of the equipment (3) from the non-use position to the loading / unloading position, - the control means (6) for the movement of the equipment being further configured to make the manual actuation of the control means (4) operative to move the equipment (3) from the non-use position to the loading / unloading position, when the blocking signal has been received by the control means of the dock and if the minimum distance between the vehicle and the dock determined by the detection means (10) is less than or equal to a predetermined detection distance.,

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