SYSTEM AND METHOD FOR ASSISTING A VEHICLE OPERATOR TO PARALLEL PARK A VEHICLE

[0001] The invention generally relates to a system and method for assisting a vehicle operator to parallel park a vehicle, and more particularly relates to a system and method for finding a suitable parallel parking place and providing parallel parking assistance using only a single proximity sensor.

[0002] Some vehicles are equipped with parallel parking guidance or parallel parking assistance systems to either autonomously operate the steering and braking of the vehicle to parallel park the vehicle, or to provide the vehicle operator with audible and/or visual cues to assist the vehicle operator to parallel park the vehicle. However such systems are equipped with cameras and/or multiple sensors, and correspondingly complex controllers that undesirably increase the cost of such systems.

[0003] In accordance with one embodiment of this invention, a method for assisting a vehicle operator to parallel park a vehicle is provided. The method includes the step of determining parallel parking space requirements based on a travel path defined by a vehicle length, a vehicle width, a minimum turning radius, and a minimum arc radius of a front corner of the vehicle. The method further includes the step of providing a single proximity sensor configured to output a clearance signal indicative of a clearance distance beside the vehicle. The method also includes the step of providing a controller configured to perform a plurality of steps. The steps performed by the controller include storing the parallel parking space requirements. The steps performed by the controller further include receiving the clearance signal from the single proximity sensor and detecting a parallel parking space suitable for parallel parking the vehicle based on the clearance signal. The steps performed by the controller also include indicating when to start a first backing maneuver, indicating when to start a second backing maneuver, and indicating when to end the second backing maneuver.

[0004] In another embodiment of the present invention, a vehicle parallel parking system for assisting a vehicle operator to parallel park a vehicle is provided. The system includes a single proximity sensor and a controller. The single proximity sensor is configured to output a clearance signal indicative of a clearance distance beside the vehicle. The controller is configured to store parallel parking space requirements based on a vehicle length, a vehicle width, a minimum turning radius, and a minimum arc radius of a front corner of the vehicle. The controller is further configured to receive the clearance signal from the single proximity sensor and detect a parallel parking space suitable for parallel parking the vehicle based on the clearance signal. The controller is also configured to indicate when to start a first backing maneuver, indicate when to start a second backing maneuver, and indicate when to end the second backing maneuver.

[0005] In yet another embodiment of the present invention, a controller for a vehicle parallel parking system that assists a vehicle operator to parallel park a vehicle is provided. The controller includes a memory device, an input, and a processor. The memory device is configured to store parallel parking space requirements that are based on a vehicle length, a vehicle width, a minimum turning radius, and a minimum arc radius of a front corner of the vehicle. The input is configured to receive the clearance signal from the single proximity sensor that is configured to output a clearance signal indicative of a clearance distance beside the vehicle. The processor is configured to detect a parallel parking space suitable for parallel parking the vehicle based on the clearance signal. The processor is also configured to indicate when to start a first backing maneuver, indicate when to start a second backing maneuver, and indicate when to end the second backing maneuver.

[0006] Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of the preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.

[0015] FIG. 1 illustrates a travel path 8 for a vehicle 10 when the vehicle is moved and a steering angle of the steering wheels 12 is held constant at the steering angle illustrated. The four innermost circles illustrate a path for the steering wheels 12 and the non-steering wheels. In this non-limiting example illustrated, two of the four vehicle wheels have variable steering angles, and the other two have fixed steering angles and so are characterized as non-steering wheels. The description below is generally directed to the steering wheels being at the front of the vehicle, but it will be appreciated that the teachings herein could be applied to vehicles with rear steering. Alternatively, the vehicle 10 could be equipped with four-wheel steering and so all four wheels would have variable steering angles. The outer circle illustrates an arc radius 14 of a path traveled by a front corner 16 of the vehicle. Accordingly, any object located within the travel path 8, e.g.—inside the arc radius 14 and outside of the innermost circle 18, may come into contact with the vehicle 10 if the vehicle moves in the travel path 8 illustrated. As described in more detail below, the vehicle 10 may be equipped with a vehicle parallel parking system 50 (FIG. 5) for assisting a vehicle operator 52 with the task of parallel parking the vehicle 10. FIG. 1 may be useful for determining parallel parking space requirements so that it can be determined if a parallel parking space is large enough to accommodate the vehicle 10. The parallel parking space requirements may be based on a vehicle length 20, a vehicle width 22, a minimum turning radius corresponding to the innermost circle 18 when the steering wheels 12 are at a maximum steering angle relative to a straight ahead travel steering angle, and a minimum arc radius 14 of a front corner 16 of the vehicle corresponding to the arc radius traced by the front corner 16 when the steering wheels 12 are at a maximum steering angle relative to a straight ahead travel steering angle.

[0016] FIG. 2 illustrates a vehicle 10 equipped with a single proximity sensor 24. As used herein, a proximity sensor is a device suitable to measure a distance or range to an object, for example the distance from the proximity sensor 24 to a first other vehicle 30 or a second other vehicle 32 located alongside the vehicle 10, or a distance to a curb 34 alongside the vehicle 10. Suitable devices for the single proximity sensor 24 include, but are not limited to, radar based range sensing devices, ultrasonic based range sensing devices, and laser based range sensing devices. Furthermore, cameras and other such optical imaging devices that create a two dimensional map of a scene are not within the meaning of a proximity sensor as used herein. Such optical imaging devices are specifically excluded from the list of devices suitable to use as the single proximity sensor 24 as such devices require complicated signal processing to determine a distance to an object, and so undesirably increase the cost and complexity of the vehicle 10.

[0017] In general, the single proximity sensor 24 is configured to output a clearance signal 54 (FIG. 5) indicative of a clearance distance beside the vehicle 10. The vehicle 10 is equipped with only the single proximity sensor 24 because, as will become apparent in the description below, the method for assisting a vehicle operator to parallel park a vehicle, and the vehicle parallel parking system for assisting a vehicle operator to parallel park a vehicle, only requires a single proximity sensor to operate. The vehicle 10 may also be equipped with a controller 26 configured to receive the clearance signal 54 from the single proximity sensor 24. The controller 26 may also be configured to store the parallel parking space requirements described above, and receive and send signals to other vehicle systems such as a braking system 56 and a steering system 58 (FIG. 5) as will be described in more detail below. Signals to and from the controller 26 may be sent through a vehicle wiring harness as is well known, or may be communicated wirelessly.

[0018] The method of parallel parking the vehicle 10 may be generally divided into two distinct processes for reasons of simplifying an explanation of the method. Those distinct processes may be generally defined as a) determining that a parallel parking space is suitable, i.e.—large enough for the vehicle 10, and b) parallel parking the vehicle 10. It should be appreciated that the two processes are generally practiced together. However, it will also be appreciated that determining if a parallel parking space is suitable may be repeated multiple times on multiple parallel parking spaces found to be unsuitable until a suitable parallel parking space is actually found, and then executing the process of parallel parking the vehicle 10.

[0019] FIGS. 2A-2D illustrate a progression of the vehicle 10 moving in the direction indicated by arrow 28 to detect a parallel parking space 36 suitable for parallel parking the vehicle 10 based on the clearance signal 54. FIG. 6 illustrates a method 600 that describes steps that may be taken by the vehicle parallel parking system 50 that generally correspond to FIGS. 2A-2D. Step 610, MOVE VEHICLE FORWARD, may include moving the vehicle 10 in a direction substantially parallel to the parallel parking space 36 while the controller 26 performs the steps described below. As used herein, substantially parallel to the parallel parking space 36 means that a first distance between the vehicle 10 and the first other vehicle 30 illustrated in FIG. 2A is about equal to a second distance between the vehicle 10 and the second other vehicle 32 illustrated in FIG. 2D, for example the first distance and the second distance differing by less than 0.5 meters. If the first distance and the second distance differ by more than 0.5 meters, then it may indicate that the parking space is not parallel to the path traveled when the vehicle 10 moved from the location illustrated in FIG. 2A to the location illustrated in FIG. 2D. A similar determination of the path traveled by the vehicle 10 may be based on a steady change in the distance to the curb 34 when the vehicle is moving forward.

[0020] When the single proximity sensor 24 is mounted on the front corner 16 of the vehicle 10, it is preferable that detecting the parallel parking space 36 be initiated when the vehicle is at or behind the location beside the first other vehicle 30 illustrated in FIG. 2A. By starting at this location, when a suitable parallel parking space is detected, the vehicle 10 will then be near the location beside the second other vehicle 32 from where parallel parking can be initiated. Initiating the process of detecting the parallel parking space 36 may include the vehicle operator 52 pressing a button or issuing a voice command to activate the vehicle parallel parking system 50.

[0021] Step 620, DETECT REAR BOUNDARY, may include the controller 26 detecting a rear boundary 38 of the parallel parking space 36 when the clearance signal 54 indicates a clearance distance 40 greater than a predetermined depth threshold, for example greater than 2.5 meters. It will be appreciated that the depth threshold may be adjusted based on the vehicle width, and/or a typical vehicle width for the region or country in which the vehicle parallel parking system 50 is being used. The clearance distance 40 may be a distance from the single proximity sensor 24 to the curb 34 as illustrated, or in the case where no curb or other object is present, the clearance distance 40 recorded by the controller 26 may be limited to some value relative to the distance between the vehicle 10 and the first other vehicle 30.

[0022] Step 630, DETECT PARKING SPACE DEPTH, may include the controller 26 recording a number of clearance signal 54 values as the vehicle moves forward so that at a later time a minimum parking space depth value can be determined. By way of example and not limitation, if no curb 34 is present and a tree or fire hydrant is present alongside the parallel parking space 36 (not shown), then these objects may determine the minimum parking space depth value.

[0023] Step 640, DETECT FRONT BOUNDARY, may include the controller 26 receiving a clearance signal 54 indicating that the clearance distance is less than the depth threshold. As illustrated in FIG. 2D, a front boundary 42 may be indicated by an abrupt decrease in the clearance distance corresponding to the back end of the second other vehicle 32. Alternatively, the change in clearance distance may be gradual, for example caused by an angled section of the curb 34, or the second other vehicle 32 being parked at an angle. Also, if the second other vehicle is not present and the curb 34 continues straight as illustrated, the vehicle parallel parking system 50 may be configured to designate a location as the front boundary 42 after the vehicle 10 has moved a distance greater than a minimum parallel parking space length.

[0024] Step 650, DETERMINE PARALLEL PARKING SPACE DEPTH, may include determining a parallel parking space depth 43 based on a minimum clearance distance detected in step 630 above while the clearance distance 40 is greater than the depth threshold. Alternatively, if no curb 34 or other objects are detected in step 630, the vehicle parallel parking system 50 may be configured to set the parallel parking space depth 43 to a predetermined value based on the vehicle width 22 (FIG. 1).

[0025] Step 660, DETERMINE PARALLEL PARKING SPACE LENGTH, may include determining a parallel parking space length 44 based on a distance traveled by the vehicle 10 between detecting the rear boundary 38 and the front boundary 42 of the parallel parking space 36.

[0026] Step 670, STOP THE VEHICLE, may be performed by the vehicle operator 52 in response to a signal from the controller 26, or may be performed by the controller 26 if the vehicle parallel parking system 50 is equipped for autonomous parallel parking.

[0027] Step 680, SUITABLE PARALLEL PARKING SPACE?, may include the controller processing data received from the clearance signal 54 and a wheel rotation sensor 70, and determining if the parallel parking space 36 is large enough for parallel parking the vehicle 10. If the parallel parking space is not suitable, for example not large enough to accommodate the vehicle 10, then the method 600 may start again to search for a parallel parking space 36 that is suitable by moving the vehicle 10 forward past the second other vehicle 32 in search of another parallel parking space. If the parallel parking space 36 is suitable, then step 680 may include activating an audible indication such as a tone or voice announcement, or may include illuminating an indicator to indicate that the parallel parking space 36 is large enough for parallel parking the vehicle 10. The suitability is generally based on the parallel parking space length 44 and the parallel parking space depth 43. Then vehicle operator 52 or the controller 26, depending on the configuration of the vehicle parallel parking system 50, may proceed with the process of parallel parking the vehicle 10 by proceeding to method 700 (FIG. 7) to parallel park the vehicle.

[0028] FIG. 3 illustrates a first travel path 8A for a vehicle 10A when the vehicle 10A is moved and the steering angle of the steering wheels is held constant at the steering angle illustrated for vehicle 10A. FIG. 3 also illustrates a second travel path 8B for a vehicle 10B when the vehicle 10B is moved and the steering angle of the steering wheels is held constant at the steering angle illustrated for vehicle 10B. By overlapping the first travel path 8A and the second travel path 8B, the location where the steering angle should be changed to parallel park the vehicle 10 should be evident.

[0029] FIG. 7 illustrates a method 700 that assumes that the vehicle 10 is starting near the location suggested in FIG. 4A. FIG. 4A-4D illustrate the progressive motion of the vehicle 10 during parallel parking into the parallel parking space 36. While not specifically illustrated, it will be appreciated that the progressive motion of the vehicle 10 may also include moving the vehicle 10 forward within the parallel parking space 36 so as to center the vehicle 10 within the parallel parking space 36. Centering the vehicle 10 may be performed by the operator or by the vehicle 10 if so equipped.

[0030] Step 710, START FIRST BACKING MANEUVER, may occur following step 680 (FIG. 6) as described above, and may include notifying the vehicle operator 52 that the vehicle 10 is about to start parallel parking if the vehicle parallel parking system 50 is configured for autonomous parallel parking of the vehicle 10, and so may include instructing the vehicle operator 52 to release the brake pedal 62 and/or shift a transmission 64 (FIG. 5) into a specific gear.

[0031] Step 720, OPERATE STEERING MECHANISM TO FIRST POSITION, may include instructing the vehicle operator 52 to rotate the steering wheel 60 (FIG. 5) in a direction until the steering system 58 indicates that the steering system 58 has been operated to a first position, such as illustrated in FIG. 4A. If the vehicle parallel parking system 50 is equipped for autonomous operation, the vehicle operator 52 may be instructed to release control of the steering wheel, for example by instructing the vehicle operator 52 to remove the operator's hands from the steering wheel 60 so the controller 26 can operate the steering system 58 to the first position.

[0032] Step 730, BACK THE VEHICLE, may include the vehicle operator 52 or the controller 26 operating the braking system 56 to control the speed of the vehicle 10 while backing.

[0033] Step 740, ABORT PARALLEL PARKING?, may include the controller 26 determining that the vehicle operator 52 did not hold the steering system 58 in the first position, and so it will not be possible to properly parallel park the vehicle 10. This determination is indicated by the YES response indicating that the operator should not continue to try and parallel park the vehicle, as illustrated by END PARKING. If the parallel parking maneuver is aborted, the vehicle operator may return the vehicle to a location near that indicated in FIG. 4A and attempt parallel parking the vehicle 10 again. It will be appreciated that step 740 may be repeated throughout the method 700 and is illustrated here as a non-limiting example.

[0034] Step 750, END FIRST BACKING MANEUVER?, is generally based on determining when the vehicle 10 has backed far enough with the steering system in the first position. The distance that the vehicle 10 has backed may be indicated by the wheel rotation sensor 70 (FIG. 5) and communicated to the controller 26. If NO, the vehicle continues to back-up and the vehicle 10 is monitored to see if parking should be aborted. If YES, the vehicle 10 may be stopped in preparation for step 760.

[0035] After the vehicle 10 backs to a location similar to that shown in FIG. 4B, an embodiment of the method 700 may include a step of indicating when to start the second backing maneuver, followed a step of operating a steering mechanism such as a steering wheel 60 or a steering system 50 to a second position, and then actually backing the vehicle 10 as describe below. Depending on the configuration of the vehicle parallel parking system 50, the steps of operating the steering mechanism to a second position and then backing the vehicle may be performed by the vehicle operator 52, or the controller 26.

[0036] Step 760, OPERATE STEERING MECHANISM TO SECOND POSITION, may include the vehicle operator 52 or the controller 26 operating the steering system 58 so the steering wheels are at a second position corresponding to that illustrated in FIG. 4B. Operating the steering mechanism may also include adjusting vehicle speed based on the rate at which the steering is being adjusted. For example, stop the vehicle 10 if the steering mechanism is not operating or move the vehicle 10 slowly if steering is operating slowly. Method 700 may be continued by executing step 770, BACK THE VEHICLE, to continue to move the vehicle into the parallel parking space 36.

[0037] Step 780, MINIMUM ARC RADIUS CLEARS FRONT BOUNDARY?, may include the controller 26 monitoring the clearance signal to determine if the front corner 16 of the vehicle 10 will clear the second other vehicle 32, as illustrated in FIG. 4C. If NO, parallel parking may be stopped, and may include moving the vehicle 10 forward to a location similar to that illustrated in FIG. 4A so parallel parking of the vehicle 10 may be attempted again. If YES, parallel parking may continue and so the vehicle 10 continues to back. In one embodiment, the controller 26 may determine that the minimum arc radius will clear the front boundary of the parallel parking space, and that determination may include the controller 26 determining that the clearance signal 54 indicates a clearance distance greater than a clearance threshold, for example a clearance distance greater than 0.2 meters.

[0038] Step 790, ABORT PARALLEL PARKING?, may be similar to step 740 described above and may stop or end the parallel parking process if, for example, it is determined that the vehicle operator 52 did not hold the steering mechanism in the second position. If YES, then END PARKING stops the parallel parking process. If NO, then the parallel parking process may continue.

[0039] Step 800, END SECOND BACKING MANEUVER?, may include the controller 26 determining that the vehicle has backed far enough while the steering system 58 is in the second position. If NO, then the vehicle 10 continues to back. If YES, then the second backing maneuver is completed.

[0040] Step 810, CENTER THE VEHICLE, is an optional step that may be performed so a first separation between the vehicle 10 and the first other vehicle 30 and a second separation between the vehicle 10 and the second other vehicle 32 may be about the same. Depending on the configuration of the vehicle parallel parking system 50, centering the vehicle may be performed by the vehicle operator 52 or the controller 26. By centering the vehicle 10 in the parallel parking space 36, it may make it more convenient for the first other vehicle 30 and/or the second other vehicle 32 to exit their respective parallel parking spaces without contacting the vehicle 10.

[0041] FIG. 5 illustrates an embodiment of the vehicle parallel parking system 50 for assisting a vehicle operator 52 to parallel park a vehicle 10. In one embodiment, the vehicle parallel parking system 50 may include a single proximity sensor 24 configured to output a clearance signal 54 indicative of a clearance distance beside the vehicle 10. The vehicle parallel parking system 50 may include a controller 26 configured to store parallel parking space requirements based on a vehicle length 20 (FIG. 1), a vehicle width 22, an innermost circle 18 or a minimum turning radius 18, and a minimum arc radius of a travel path 8 of a front corner 16 of the vehicle 10. The controller 26 may also be configured to receive the clearance signal 54 from the single proximity sensor 24, detect a parallel parking space 36 suitable for parallel parking the vehicle 10 based on the clearance signal 54.

[0042] Continuing to refer to FIG. 5, the controller 26 may also be configured to indicate when to start a first backing maneuver based on a suitable parallel parking space 36 being detected. An example of the first backing maneuver is illustrated as beginning with the vehicle 10 in a position illustrated in FIG. 4A and backing to a position illustrated in FIG. 4B. The controller 26 may also be configured to indicate when to stop or finish the first backing maneuver which may be followed or temporally coincident with indicating to start a second backing maneuver. An example of a second backing maneuver is illustrated as beginning with the vehicle in a position illustrated in FIG. 4B, backing through a position illustrated in FIG. 4C, and backing to a position illustrated in FIG. 4D. The controller 26 may also be configured to indicate when to end the second backing maneuver, for example when the vehicle 10 reaches the position illustrated in FIG. 4D. The indications provided by the controller 26 may include activating an audible tone or voice command to notify the vehicle operator 52. For case where the vehicle parallel parking system 50 is configured to autonomously parallel park the vehicle 10, the indications provided by the controller may be signals to the steering system 58 and or the braking system 56 to control movement of the vehicle 10

[0043] In one embodiment of the vehicle parallel parking system 50, the single proximity sensor 24 may is preferably mounted on a front corner 16 of the vehicle 10, as this location is particularly convenient for typical situations where the vehicle 10 is traveling forward while searching for a parallel parking space 36 that is suitable.

[0044] An embodiment of the vehicle parallel parking system 50 may also include a transmission 64 configured to receive a gear selection signal 66 from the controller 26 for controlling vehicle direction, and a brake system 56 configured to receive a brake signal 68 from the controller 26 for stopping the vehicle. The vehicle parallel parking system 50 may also include a distance traveled sensing means for measuring a distance traveled by the vehicle 10. A non-limiting example of distance traveled sensing means is a wheel rotation sensor 70, as illustrated in FIG. 5. Alternatively, the distance traveled sensing means may be a GPS system or a system that determines vehicle motion based on inertial guidance. The vehicle parallel parking system 50 may also include a steering angle sensor within the steering system 58 configured to output a steering angle signal 72 indicative of a steering angle of the steering wheels 12 of the vehicle 10.

[0045] While not specifically illustrated, the controller 26 may a memory device to store parallel parking space requirements and an input configured to receive the clearance signal 54 from the single proximity sensor 24. The controller may also include a processor configured to detect a parallel parking space 36 suitable for parallel parking the vehicle 10, indicate when to start a first backing maneuver, indicate when to stop or end the first backing maneuver followed by or coincident with indicating when to start a second backing maneuver, and indicate when to end the second backing maneuver.

[0046] Accordingly, a vehicle parallel parking system 50, a controller 26 for the vehicle parallel parking system 50, and a method 600,700 for assisting a vehicle operator to parallel park a vehicle 10 is provided. The system and method relies on only a single proximity sensor 24 to detect a suitable parallel parking space 36 and parallel park the vehicle 10. The single proximity sensor 24 only need indicate distance or range, and as such cameras and other such devices that add undesirable complexity and cost to the vehicle are avoided. Detecting a suitable parking space 36 and parallel parking the vehicle 10 may have the vehicle operator 52 operate the vehicle 10 relying on the vehicle parallel parking system 50 provide indications of when to change steering wheel angle and back the vehicle 10, or may be an autonomous system that controls the vehicle 10 without any intervention on the part of the vehicle operator 52.

[0047] While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.