Parking zone detection device and control method thereof

Abstract

A parking zone detection device for detecting a parking zone based on transmission / reception signals transmitted and received by an ultrasonic sensor (10) installed in a vehicle, the parking zone detection device comprising: an electronic control unit (20) configured to detect a surrounding target object in a parking zone as a tall object in the case of a double echo condition in which a distance of a second echo signal is twice as large as a distance of a first echo signal and to determine an available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responding to the transmission signal transmitted by the ultrasonic sensor (10), the electronic control unit (20) comprising: a receiving unit (21) configured to receive the echo signals responding to the transmission signal sent toward the vicinity of the parking zone by the ultrasonic sensor (10); a calculation unit (22) configured to calculate a first echo distance to the surrounding target object in the parking zone based on the first echo signal among the received echo signals that exceeds a predetermined threshold for the first time, and to calculate a second echo distance to the surrounding target object in the parking zone based on the second echo signal among the received echo signals that exceeds the predetermined threshold for the second time; and an available parking zone determination unit (23) configured to determine whether the double echo condition is satisfied, the double echo condition being a condition in which the calculated second echo distance is twice the first echo distance, accurately discriminate the surrounding target object in the parking zone as a tall object or a parked vehicle based on the determination result, and determine the available parking zone based on the recognition result.

Description

BACKGROUND OF THE INVENTIONField of the InventionThe present invention relates to a parking zone detection apparatus and a control method thereof, and more particularly, to a parking zone detection apparatus and a control method thereof that detect a surrounding target object in the parking zone as a tall object when a double echo condition is satisfied, that is, when a distance of a second echo signal is twice as large as a distance of a first echo signal, thereby accurately obtaining an actually available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responsive to transmission signals transmitted by an ultrasonic sensor.Description of the Prior ArtAn existing parking assist system recognizes a parking zone by detecting an object (obstacle) around the parking zone in which a vehicle is to be parked using a sensor such as an ultrasonic sensor mounted on the vehicle, and performs a parking assist control function by using recognition result information on the parking zone.In order to stably and accurately park a vehicle using the parking assist control system, it is necessary to be able to correctly recognize a parking zone.However, existing parking zone recognition technology cannot distinguish between a parked vehicle and a pillar or wall which is an object higher than the parked vehicle in a parking zone. As a result, an error may occur between an actual parking zone (an actual place where a vehicle can be stably parked) and a detected parking zone, thereby making it impossible to accurately detect the actual parking zone.In particular, when a pillar is erroneously recognized as a parked vehicle in a perpendicular parking situation, a vehicle may be parked close to the pillar, or when the vehicle is parked between the pillar and the parked vehicle, the vehicle may be parked close to the parked vehicle, thereby raising a risk of collision, respectively. The post may often be recognized as the parked vehicle, and thus the available parking zone may not be recognized. Therefore, there is a need for an improved parking zone recognition device capable of distinguishing between a pillar and a parked vehicle and accurately recognizing an actual parking zone.Many applications (for example, Korean Patent Publication No. 10-2012-0091603 published on Aug. 20, 2012) disclose parking zone detection devices.The parking zone recognition device disclosed in Korean Patent Publication No. 10-2012-0091603 includes an upper sensor, a lower sensor, and a recognition processor that recognizes a parking zone by identifying whether an object is a parked vehicle or a pillar based on detection data detected by the two sensors.However, the parking zone detection device described above needs to have both the upper sensor and the lower sensor in order to distinguish between the pillar and the parked vehicle. Therefore, manufacturing costs may increase and product implementation may be difficult.LIST OF CITED DOCUMENTSPATENT LITERATURE(Patent Literature 1) Korean Patent Application Publication No. 10-2012-0091603 (20.08.2012), entitled "PARKING ZONE RECOGNIZING METHOD AND APPARATUS" (parking zone recognition method and apparatus)KR 10 2014 0 063 169 A describes a method and a device for classifying obstacles in order to assist a parking process of a vehicle.SUMMARY OF THE INVENTIONAn aspect of the present invention is directed to a parking zone detection apparatus and a control method thereof that detect a surrounding target object in a parking zone as a tall object when a double echo condition is satisfied, that is, when a distance of a second echo signal is twice as large as a distance of a first echo signal, thereby accurately obtaining an actually available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responding to transmission signals transmitted by an ultrasonic sensor.According to an embodiment of the present invention, there is provided a parking zone detection apparatus for detecting a parking zone based on transmission / reception signals transmitted and received by an ultrasonic sensor installed in a vehicle, the parking zone detection apparatus comprising: an electronic control unit configured to detect a surrounding target object of a parking zone as a high object in the case of a double echo condition in which a distance of a second echo signal is twice as large as a distance of a first echo signal, and determine an available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responding to the transmission signal transmitted by the ultrasonic sensor.The electronic control apparatus may include: a receiving unit configured to receive the echo signals responding to the transmission signal transmitted toward the vicinity of the parking zone by the ultrasonic sensor; a calculating unit configured to calculate a first echo distance to the surrounding target object of the parking zone based on the first echo signal exceeding a predetermined threshold for the first time among the received echo signals, and calculate a second echo distance to the surrounding target object of the parking zone based on the second echo signal exceeding the predetermined threshold for the second time among the received echo signals; An available parking zone determination unit configured to determine whether the dual echo condition is satisfied, the dual echo condition being a condition in which the calculated second echo distance is twice as large as the first echo distance, discriminately recognize the surrounding target object of the parking zone as a tall object or a parked vehicle based on the determination result, and determine the available parking zone based on the recognition result.The available parking zone determination unit may calculate the number of double echoes of the echo signals reflected back from a front and edges of the surrounding target object during a predetermined sampling period, recognize the surrounding target object of the parking zone as a pillar when a double echo rate calculated based on the number of double echoes from the front and edges of the surrounding target object is greater than a predetermined reference rate, and recognize the surrounding target object of the parking zone as a parked vehicle when the double echo rate is less than the reference rate.When only the tall object is disposed as the surrounding target object of the parking zone, the available parking zone obtaining unit may obtain an available parking zone from a position spaced apart from the tall object by a predetermined distance.When the tall object and the parked vehicle are present as the surrounding target object of the parking zone, the available parking zone determination unit may determine an available parking zone between the tall object and the parked vehicle, the determined available parking zone being closer to the tall object.When a double echo signal is continuously received from the ultrasonic sensor for a predetermined time, the electronic control device may recognize the surrounding target object of the vehicle as a tall object.According to another embodiment of the present invention, there is provided a method of controlling a parking zone detection apparatus for detecting a parking zone on the basis of transmission / reception signals transmitted and received by an ultrasonic sensor installed in the vehicle, the method comprising the steps of: performing control for detecting a surrounding target object of a parking zone as a tall object; and determining an available parking zone in the case of a double echo condition in which a distance of a second echo signal is twice as large as a distance of a first echo signal, wherein the first echo signal and the second echo signal are determined from echo signals responding to the transmission signal transmitted by the ultrasonic sensor.The determining of the controller may include the steps of: receiving the echo signals responding to the transmission signal transmitted toward the vicinity of the parking zone by the ultrasonic sensor; calculating a first echo distance to the surrounding target object of the parking zone based on the first echo signal exceeding a predetermined threshold for the first time among the received echo signals; and calculating a second echo distance to the surrounding target object of the parking zone based on the second echo signal exceeding the predetermined threshold for the second time among the received echo signals; determining whether the dual echo condition is satisfied, wherein the dual echo condition is a condition in which the calculated second echo distance is twice as large as the first echo distance, accurately discriminating the surrounding target object of the parking zone as a tall object or a parked vehicle based on the determination result, and determining the available parking zone based on the determination result.The calculating the first and second distances may include calculating the number of double echoes of the echo signals reflected back from a front and edges of the surrounding target object during a predetermined sampling period, and calculating a double echo rate from the calculated number of the double echoes from the front and edges of the surrounding target object, and the determining the available parking zone may include recognizing the surrounding target object of the parking zone as a pillar when the calculated double echo rate is greater than a predetermined reference rate and recognizing the surrounding target object of the parking zone as a parked vehicle when the double echo rate is less than the reference rate.If only the tall object is located as the surrounding target object of the parking zone, then the available parking zone may be determined from a position spaced from the tall object by a predetermined distance.If the tall object and the parked vehicle are located as the surrounding target of the parking zone, then the available parking zone between the tall object and the parked vehicle may be determined with the determined available parking zone being closer to the tall object.If a double echo signal can be continuously received by the ultrasonic sensor over a predetermined time, then the target object of the vehicle located in the environment is recognized as a tall object.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a block diagram of a parking zone recognition apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart of a method for controlling a parking zone recognition apparatus according to an embodiment of the present invention. FIGS. 3A and 3B are schematic diagrams for describing a method of determining an available parking zone at the time of parking when pillars are disposed in a parking zone. FIGS. 4A and 4B are schematic diagrams for describing a method of determining an available parking zone at the time of parking between a pillar and a parked vehicle. FIGS. 5A and 5B are schematic diagrams for describing a method for correctly recognizing a pillar and determining an available parking zone. FIGS. 6A to 6F are diagrams illustrating planes of a pillar and a parked vehicle on which a transmission signal is incident, and graphs illustrating reception signals measured by the planes of the pillar and the parked vehicle. FIGS. 7A to 7C are diagrams for describing a first echo signal and a second echo signal.DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTSExemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.FIG. 1 is a block diagram of a parking zone recognition apparatus according to an embodiment of the present invention.Referring to FIG. 1, the parking zone detection apparatus according to the embodiment of the present invention includes an ultrasonic sensor 10 and an electronic control unit 20 connected to the ultrasonic sensor 10 for detecting an available parking zone in a parking zone.The ultrasonic sensor 10 may measure a distance between a vehicle and a surrounding target object (for example, a parked vehicle, a pillar, a wall, or other obstacles installed in the parking zone) located in the vicinity of the vehicle in the parking zone.The ultrasonic sensor 10 transmits a transmission signal to the surrounding target object in the parking zone and receives an echo signal responding to the transmission signal in the parking zone. The ultrasonic sensor 10 receives echo signals which are sent back after the transmission signal impinges on a front and edges of the target object located in the environment. Based on characteristics of the ultrasonic sensor 10, the ultrasonic sensor 10 acquires a first echo signal and a second echo signal from the received signals on the basis of a threshold value set according to a minimum detection distance, for example, 30 cm. The first echo signal is an echo signal exceeding the predetermined threshold for the first time, and the second echo signal is an echo signal exceeding the predetermined threshold for the second time.The electronic control device 20 is connected to the ultrasonic sensor 10 through, for example, a local interconnect network (LIN). The electronic control unit 20 receives the transmission signal and the echo signals and determines the first echo signal and the second echo signal from the received echo signals. The electronic control unit 20 calculates distances of the first and second echo signals and determines whether a double echo condition is satisfied, that is, whether the calculated distance of the second echo signal is twice as large as the calculated distance of the first echo signal.If the double echo condition is fulfilled, then the electronic control unit 20 recognizes the target object located in the environment as a tall object. If the double echo condition is not fulfilled, then the electronic control unit 20 recognizes the target object located in the environment as a parked vehicle. Then, the electronic control device 20 determines an available parking zone based on the detected information. The tall object includes a pillar, a wall, and the like located in the parking zone.In addition, when a double echo signal is received from the ultrasonic sensor 10 for a predetermined time, the electronic control device 20 can recognize the surrounding target object as a tall object. The double echo signal refers to a signal satisfying the above-described double echo condition, that is, a signal whose distance is twice (twice the distance of the first echo signal) among second echo signals.The electronic control device 20 has a receiving unit 21, a calculating unit and a unit 23 for determining an available parking zone.The receiving unit 21 receives echo signals that are returned after the transmission signal transmitted from the ultrasonic sensor 10 impinges on the surrounding target object located in the parking zone, and detects the first echo signal that exceeds the predetermined threshold for the first time among the echo signals and the second echo signal that exceeds the predetermined threshold for the second time among the echo signals.Referring to an environment illustrated in FIG. 7A, the first echo signal refers to an echo signal that impinges on a front side of an object T and faces the object T at the closest distance and that has a voltage exceeding the predetermined threshold Th. The second echo signal refers to an echo signal having a voltage exceeding the predetermined threshold Th among signals incident on edges of the object T and returning to the ultrasonic sensor 10. In addition to the first and second echo signals, third and fourth echo signals are present. However, since the voltages of the third and fourth signals are lower than the threshold value Th, only the first and second echo signals are considered in the present invention.FIG. 7B is a graph of a transmission signal 1 transmitted toward a low object such as a parked vehicle by the ultrasonic sensor 10 and echo signals 2 and 3 responding to the transmission signal 1; and FIG. 7C is a graph of a transmission signal 1 transmitted toward a high object such as a pillar by the ultrasonic sensor 10 and echo signals 2 and 3 responding to the transmission signal 1. Referring to FIGS. 7B and 7C, a low object such as a parked vehicle does not satisfy the double echo condition because a distance calculated from the second echo signal 3 is not twice as large as the distance calculated from the first echo signal 2. However, a tall object such as a pillar satisfies the double echo condition because a distance calculated from the second echo signal 3 is twice as large as a distance calculated from the first echo signal 2.Therefore, the electronic control unit 20 determines whether the distance calculated from the second echo signal is twice as large as the distance calculated from the first echo signal by using the first and second echo signals from the echo signals received by the ultrasonic sensor 10. When the double echo condition is satisfied, the electronic control device 20 recognizes the surrounding target object of the parking zone as a pillar that is a tall object.The calculation unit 22 calculates a first echo distance to a target object located in the parking zone corresponding to the first echo signal determined based on the echo signals received by the reception unit 21. In addition, the calculation unit 22 calculates a second echo distance to the target object located in the parking zone corresponding to the second echo signal determined based on the echo signals received by the reception unit 21.The available parking zone determination unit 23 determines whether the double echo condition is satisfied, that is, whether the second echo distance calculated by the calculation unit 22 is twice as large as the first echo distance calculated by the calculation unit 22. The double echo condition includes a condition in which the second echo distance is twice as large as the first echo distance, or a condition defined by Formula 1 below. In this case, 30 cm is a fixed value, and another value may be applied according to the characteristics of the ultrasonic sensor 10 installed in the vehicle. In the present embodiment, it is assumed that the ultrasonic sensor 10 of the parking zone detection device installed in the vehicle has a minimum detection distance of 30 cm.When the second echo distance is twice as large as the first echo distance, or when the above-mentioned formula 1 is satisfied, the available parking zone determination unit 23 recognizes the target object of the parking zone as a tall object (for example, a pillar or a wall). Otherwise, the available parking zone determination unit 23 recognizes the target object of the parking zone as a parked vehicle.In order to improve recognition reliability, the available parking zone determination unit 23 may calculate a double echo rate by Formula 2 below, and recognize the target object as a tall object or a parked vehicle according to whether or not the calculated double echo rate is greater than a predetermined reference rate, for example 50%.As illustrated in FIGS. 6A and 6D, in the above-mentioned formula 2, R is the total number of rising-edge double echoes, and N is the total number of non-edge double echoes, and F is the total number of falling-edge double echoes.FIG. 6B is a graph of echo signals received with respect to rising edges and falling edges when the surrounding target object is the parked vehicle as illustrated in FIG. 6A, and FIG. 6C is a graph of echo signals received with respect to non-edges. It will be seen from FIGS. 6B and 6C that echo signals are received that do not meet a double echo condition.FIG. 6E is a graph of echo signals received with respect to rising edges and falling edges when the surrounding target object is a pillar as illustrated in FIG. 6D, and FIG. 6F is a graph of echo signals received with respect to non-edges. As can be seen from FIGS. 6E and 6F, the double echo condition is not satisfied in the rising edges and the falling edges, but is satisfied in the non-edges.As described above, the double echo condition in which the distance of the second echo signal is twice as large as the distance of the first echo signal is not generated in most cases in the rising and falling edges of the parked vehicle.When only a tall object (for example, the pillar) as the target object is located in the parking zone at the time of parking, the available parking zone determination unit 23 determines an available parking zone having a predetermined vehicle width at a position spaced apart from the tall object by a predetermined distance. When a height of the target object in the parking zone is between a height of a tall object and a height of a parked vehicle, the available parking zone determination unit 23 determines an available parking zone having a predetermined vehicle width at a position close to the tall object. In addition, the vehicle-accessible parking zone determination unit 23 may determine, as an available parking zone, a zone that has not been determined as an available parking zone in the past because a tall object is not frequently recognized as a parked vehicle and is recognized as the tall object such as the pillar or the wall.Therefore, it is possible to solve the problem of not recognizing an available parking zone because a tall object and a parked vehicle are recognized in a parking zone quite accurately in distinction. In addition, it is possible to determine an available parking zone such that a vehicle is parked so as to be parked close to or apart from a tall object when only the tall object is located there, and determine a central zone between the tall object and the parked vehicle as an available parking zone in a space between the tall object and the parked vehicle at the time of parking, thereby determining, as the available parking zone, a parking zone that has not been recognized as an available parking zone yet because the tall object is frequently recognized as the parked vehicle.A method of controlling the parking zone recognition device having the above-described configuration will be described with reference to FIG. 2.FIG. 2 is a flowchart of the method for controlling the parking zone recognition device according to an embodiment of the present invention.Referring to FIG. 2, in step S 11, the ultrasonic sensor 10 included in the parking zone detection device transmits a predetermined transmission signal to a surrounding target object around a vehicle in a parking zone.In step S 13, the ultrasonic sensor 10 receives echo signals that are returned after the transmission signal impinges on the front and the edges of the target object located in the surroundings.In step S 15, the electronic control device 20 acquires a first echo signal exceeding a predetermined threshold for the first time and a second echo signal exceeding the predetermined threshold for the second time from echo signals received by the ultrasonic sensor 10, and calculates a first echo distance and a second echo distance to a target object with respect to the first echo signal and the second echo signal.In step S 17, the electronic control unit 20 determines whether a double echo condition is satisfied, that is, whether the calculated second echo distance is twice as large as the first echo distance. The double echo condition may be a condition in which the second echo distance is twice as large as the first echo distance, or may be a condition defined by the above-mentioned formula 1.In step S 20, when it is determined in step S 17 that the double echo condition is not satisfied, the electronic control device 20 recognizes the target object as a parked vehicle.In step S 19, when it is determined in step S 17 that the double echo condition is satisfied, the electronic control device 20 calculates a double echo rate during one sampling period. The double echo rate can be calculated by the above-mentioned formula 2. Although step S 19 has been described as being performed when the double echo condition is satisfied, the electronic control device 20 may proceed to step S 19 even when a double echo signal is continuously received for a predetermined time in the case of satisfying the double echo condition.In step S 21, the electronic control device 20 determines whether the calculated double echo rate is greater than a predetermined reference rate (for example, 50%).In step S 23, when it is determined in step S 21 that the calculated double echo rate is greater than the reference rate, the electronic control device 20 recognizes the target object as a tall object.If it is determined in step S 21 that the calculated double echo rate is less than the reference rate, then the electronic control device 21 proceeds to step S 20 and recognizes the target object as a parked vehicle.As described above, it is possible to find out an available parking zone even in the environments illustrated in FIGS. 3 to 5 by accurately recognizing a parked vehicle and an object higher than the parked vehicle in a parking zone.Referring to FIG. 3A, an existing parking zone recognition device in the past determines an available parking zone larger than a vehicle width from a position spaced apart from the pillar when only a tall object (hereinafter referred to as a "pillar") is in the parking zone. Referring to FIG. 3B, the parking zone recognition apparatus according to the present invention correctly recognizes a pillar located in the parking zone, and detects an available parking zone as large as a vehicle width from a position spaced from the pillar by a predetermined distance. Therefore, it is possible to detect an available parking zone at a position spaced apart from the pillar by a predetermined distance when only one pillar is in a parking zone, thereby obtaining many available parking zones as compared with the existing parking zone recognition device.Referring to FIG. 4A, the existing parking zone recognition device determines a zone close to a parked vehicle as an available parking zone in a space between a pillar and the parked vehicle in a parking zone at the time of parking. Referring to FIG. 4B, the parking zone recognition apparatus according to the present invention correctly recognizes the pillar and determines a central zone between the pillar and the parked vehicle as an available parking zone. Therefore, it is possible to reduce a collision risk occurring when a vehicle is parked close to the parked vehicle at the time of parking between the pillar and the parked vehicle.Referring to FIG. 5A, the existing parking zone recognition device erroneously recognizes a pillar as a parked vehicle and hardly determines an available parking zone. Referring to FIG. 5B, the parking zone recognition apparatus according to the present invention correctly recognizes the pillar and easily detects an available parking zone. Accordingly, it is possible to easily find out an available parking zone in an actual parking zone.According to the embodiments of the present invention, it is possible to recognize a surrounding target object of a parking zone as a tall object when a double echo condition is satisfied, that is, when a distance of a second echo signal is twice as large as a distance of a second echo signal, thereby accurately obtaining an actual available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responding to a transmission signal transmitted by an ultrasonic sensor. In particular, it is possible to solve a problem occurring when a target object located in a parking zone is erroneously recognized not as a tall object but as a parked vehicle.In accordance with embodiments of the present invention, the number of double echoes of echo signals reflected back from a front and edges of the surrounding target object during a predetermined sampling period is calculated. When a double echo rate calculated based on the number of double echoes from the front and the edges of the surrounding target object is greater than a predetermined reference rate, the surrounding target object of the parking zone is recognized as a pillar. If the double echo rate is less than the reference rate, then the target object located in the environment around the parking zone is recognized as a parked vehicle. Therefore, the detection reliability can be improved.Although the embodiments of the present invention have been described with reference to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention as defined in the following claims.BRIEF DESCRIPTION OF REFERENCE NUMERALS10 Ultrasonic sensor 20 Electronic control device 21 Receiving unit 22 Calculation unit 23 Unit for ascertaining an available parking zone

Claims

A parking zone detection apparatus for detecting a parking zone based on transmission / reception signals transmitted and received by an ultrasonic sensor (10) installed in a vehicle, the parking zone detection apparatus comprising: an electronic control device (20) configured to detect a surrounding target object in a parking zone as a high object in the case of a double echo condition in which a distance of a second echo signal is twice as large as a distance of a first echo signal, and determine an available parking zone, wherein the first echo signal and the second echo signal are determined from echo signals responsive to the transmission signal transmitted by the ultrasonic sensor (10), the electronic control device (20) comprising: a reception unit (21) configured to receive the echo signals, responding to the transmission signal transmitted toward the vicinity of the parking zone by the ultrasonic sensor (10); a calculation unit (22) configured to calculate a first echo distance to the surrounding target object in the parking zone based on the first echo signal among the received echo signals exceeding a predetermined threshold value for the first time, and calculate a second echo distance to the surrounding target object in the parking zone based on the second echo signal among the received echo signals exceeding the predetermined threshold value for the second time; An available parking zone determination unit (23) configured to determine whether the dual echo condition is satisfied, wherein the dual echo condition is a condition in which the calculated second echo distance is twice as large as the first echo distance, recognize the surrounding target object in the parking zone quite accurately as a tall object or a parked vehicle based on the determination result, and determine the available parking zone based on the recognition result.The parking zone detection device according to claim 1, wherein the available parking zone obtaining unit (23) calculates the number of double echoes of the echo signals reflected back from a front and edges of the surrounding target object during a predetermined sampling period, detects the surrounding target object in the parking zone as a pillar when a double echo rate calculated based on the number of double echoes from the front and edges of the surrounding target object is greater than a predetermined reference rate, and detects the surrounding target object in the parking zone as a parked vehicle when the double echo rate is less than the reference rate.The parking zone recognition device according to claim 1, wherein when only the tall object is disposed in the parking zone as the surrounding target object, the available parking zone determination unit (23) determines an available parking zone from a position spaced apart from the tall object by a predetermined distance.The parking zone recognition device according to claim 1, wherein when the tall object and the parked vehicle are located in the parking zone as the surrounding target object, the available parking zone determination unit (23) determines an available parking zone between the tall object and the parked vehicle, the determined available parking zone being closer to the tall object.The parking zone detection apparatus according to claim 1, wherein when a double echo signal is continuously received from the ultrasonic sensor (10) for a predetermined time, the electronic control unit (20) detects the target object around the vehicle as a tall object.A method of controlling a parking zone detection apparatus for detecting a parking zone based on transmission / reception signals transmitted and received by an ultrasonic sensor (10) installed in a vehicle, the method comprising the steps of: performing control for detecting a surrounding target object in a parking zone as a tall object; and determining an available parking zone in the case of a double echo condition in which a distance of a second echo signal is twice as large as the distance of a first echo signal, wherein the first echo signal and the second echo signal are determined from echo signals responding to the transmission signal transmitted by the ultrasonic sensor (10), wherein performing the control comprises the steps of: receiving (S13) the echo signals responding to the transmission signal, transmitting toward the vicinity of the parking zone by the ultrasonic sensor (10); calculating (S15) a first echo distance to the surrounding target object in the parking zone based on the first echo signal exceeding a predetermined threshold value for the first time among the received echo signals, and calculating a second echo distance to the surrounding target object in the parking zone based on the second echo signal exceeding the predetermined threshold value for the second time among the received echo signals; determining (S 17) whether the dual echo condition is satisfied, wherein the dual echo condition is a condition in which the calculated second echo distance is twice as large as the first echo distance, accurately discriminatingly recognizing the surrounding target object in the parking zone as a tall object or a parked vehicle based on the determination result, and determining (S 25) the available parking zone based on the recognition result.The method of claim 6, wherein the calculating the first and second distances comprises calculating the number of double echoes of the echo signals reflected back from a front and edges of the surrounding target object during a predetermined sampling period, and calculating (S19) a double echo rate from the calculated number of double echoes from the front and edges of the surrounding target object, and wherein the determining (S25) the available parking zone comprises recognizing the surrounding target object in the parking zone as a pillar when the calculated double echo rate is greater than a predetermined reference rate and recognizing the surrounding target object in the parking zone as a parked vehicle when the double echo rate is less than the reference rate.The method according to claim 6, wherein when only the tall object is located in the parking zone as the surrounding target object, the available parking zone is determined from a position spaced apart from the tall object by a predetermined distance.The method of claim 6, wherein when the tall object and the parked vehicle are located in the parking zone as the surrounding target object, the available parking zone between the tall object and the parked vehicle is determined, the determined available parking zone being closer to the tall object.The method according to claim 6, wherein when a double echo signal is continuously received from the ultrasonic sensor (10) for a predetermined time, the target object around the vehicle is recognized as a tall object.

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