Method and device for determining ultrasonic detecting cycle

A method for determining an ultrasonic detecting cycle is provided. Firstly, an initial detecting cycle T is set. Then, a first sensing wave is generated. Then, a first time-of-flight value is calculated corresponding to the first sensing wave. After the first sensing wave has been generated for the initial detecting cycle T, a second sensing wave is generated. Then, a second time-of-flight value is calculated corresponding to the second sensing wave. Afterwards, the second time-of-flight value is compared with the first time-of-flight value. If a difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value, the initial detecting cycle T is determined as the ultrasonic detecting cycle.

FIELD OF THE INVENTION

The present invention relates to a method and a device for detecting ultrasonic wave, and more particularly to a method and a device for determining an ultrasonic detecting cycle.

BACKGROUND OF THE INVENTION

An ultrasonic sensing device is widely used for measuring a relative distance or detecting whether an object is within the sensing range of the ultrasonic sensing device. According to the measuring or detecting result, further actions will be performed.

Generally, when the ultrasonic sensing device is activated, a sensing wave is generated to detect whether any object is within the sensing range of the ultrasonic sensing device. In a case that an object enters the sensing range of the ultrasonic sensing device, the sensing wave is reflected by the object and the reflected sensing wave (also referred as an echo signal) is returned back to the ultrasonic sensing device. When the echo signal is received, the ultrasonic sensing device will calculate the time interval between generation of the sensing wave and receipt of the echo signal, thereby acquiring a time of flight (TOF). According to the time of flight (TOF), the ultrasonic sensing device could estimate the distance between the ultrasonic sensing device and the object. Alternatively, according to the time of flight (TOF), further actions will be performed.

FIG. 1Ais a schematic diagram illustrating a conventional ultrasonic sensing device. As shown inFIG. 1A, the ultrasonic sensing device10is mounted on a supporting object21(e.g. a ceiling or a vehicle). A reference object22(e.g. a floor, a desk surface or a wall) is within the sensing range of the ultrasonic sensing device10. The ultrasonic sensing device10could be used to detect whether a foreign object enters the range between the ultrasonic sensing device10and the reference object22, thereby performing further actions. The operating principles of the ultrasonic sensing device10will be illustrated in more details as follows with reference toFIG. 1.

First of all, the reference object22is detected by the ultrasonic sensing device10. Generally, after the ultrasonic sensing device10is activated, the sensing wave is generated, the echo signal from the reference object22is detected, and the time interval between generation of the sensing wave and receipt of the echo signal is calculated. As such, a reference time of flight is acquired. Next, the ultrasonic sensing device10periodically generates the sensing wave and receives the echo signal. If the time of flight of the echo signal received by the ultrasonic sensing device10is equal to the reference time of flight, the ultrasonic sensing device10will discriminate that the echo signal is reflected by the reference object22. Under this circumstance, no action is done. On the other hand, in a case that a foreign object enters the range between the ultrasonic sensing device10and the reference object22, the sensing wave11generated by the ultrasonic sensing device10will be reflected back by the foreign object. As such, the time of flight of the echo signal received by the ultrasonic sensing device10is not equal to the reference time of flight. Meanwhile, the ultrasonic sensing device10discriminates that a foreign object enters the sensing range of the ultrasonic sensing device10, and further actions are performed.

As known, in a case that the undesired noise is received, erroneous discrimination of the ultrasonic sensing device occurs. In order to prevent from erroneous discrimination, a boundary value is usually predetermined in the ultrasonic sensing device. Once the intensity of the echo signal is greater than the predetermined boundary value, the ultrasonic sensing device will record the time of receiving the echo signal. According to the time of receiving the echo signal, the time of flight will be calculated.

Moreover, after the reference object is detected and the reference time of flight is recorded, the ultrasonic sensing device is in a detecting status. Once the ultrasonic sensing device is operated in the detecting status, the ultrasonic sensing device periodically generates a sensing wave in a predetermined detecting cycle, receives a corresponding effective echo signal, and calculates the time of flight. In such way, the ultrasonic sensing device could determine whether any foreign object enters the sensing range of the ultrasonic sensing device. However, if a multiple reflection effect of the sensing wave occurs, the ultrasonic sensing device fails to actually discriminate whether any foreign object enters the sensing range of the ultrasonic sensing device.

FIG. 1Bis a schematic timing waveform diagram of the sensing wave once the multiple reflection effect occurs. After the sensing wave11is generated by the ultrasonic sensing device10, a main echo signal12is reflected by the reference object22and then received by the ultrasonic sensing device10at the time t0. During the main echo signal12is returned back to the ultrasonic sensing device10, the main echo signal12also hits the supporting object21. The main echo signal12is reflected by the supporting object21, moved downwardly to hit the reference object22, and reflected back to the ultrasonic sensing device10again. Consequently, at the time t1, a first reflected echo signal13is received by the ultrasonic sensing device10. During the first reflected echo signal13is returned back to the ultrasonic sensing device10, the first reflected echo signal13also hits the supporting object21. The first reflected echo signal13is reflected by the supporting object21, moved downwardly to hit the reference object22, and reflected back to the ultrasonic sensing device10again. Consequently, at the time t2, a second reflected echo signal14is received by the ultrasonic sensing device10. Similarly, a third reflected echo signal15is received by the ultrasonic sensing device10at the time t3, and a fourth reflected echo signal16is received by the ultrasonic sensing device10at the time t4.

As known, the intensity of the reflected echo signal is gradually decreased. As shown inFIG. 1B, the intensities of the third reflected echo signal15and the fourth reflected echo signal16are lower than the boundary value, so that the third reflected echo signal15and the fourth reflected echo signal16are ignored by the ultrasonic sensing device10. Since the intensities of the first reflected echo signal13and the second reflected echo signal14are still greater than the boundary value, the first reflected echo signal13and the second reflected echo signal14are deemed as effective echo signals. Since the reflected echo signals having the intensity greater than the predetermined boundary value of the ultrasonic sensing device10are deemed as effective echo signals, the ultrasonic sensing device10may erroneously discriminate that a foreign object enters the sensing range.

FIG. 2is a schematic timing waveform diagram illustrating occurrence of an erroneous discrimination of the ultrasonic sensing device. During the process of detecting a foreign object by the ultrasonic sensing device, the ultrasonic sensing device continuously generates the sensing wave in a detecting cycle T. After a first sensing wave111has been generated by the ultrasonic sensing device for the detecting cycle T, a second sensing wave121is generated by the ultrasonic sensing device. When the first sensing wave111hits the reference object22, a first main echo signal112is reflected by reference object22and then received by the ultrasonic sensing device. Due to occurrence of the multiple reflection effect, the first main echo signal112results in a first reflected echo signal113, a second reflected echo signal114, a third reflected echo signal115and a fourth reflected echo signal116. Since the intensities of the third reflected echo signal115and the fourth reflected echo signal116are lower than the predetermined boundary value of the ultrasonic sensing device, the third reflected echo signal115and the fourth reflected echo signal116are ignored. Since the intensities of the first reflected echo signal113and the second reflected echo signal114are still greater than the boundary value, the first reflected echo signal113and the second reflected echo signal114are deemed as effective echo signals. Similarly, when the second sensing wave121hits the reference object22, a second main echo signal122is reflected by reference object22and then received by the ultrasonic sensing device. Due to occurrence of the multiple reflection effect, the second main echo signal122results in the reflected echo signals123and124.

Generally, the time of flight is calculated according to the effective echo signal first received after the sensing wave is generated. As shown inFIG. 2, the first main echo signal112is the effective echo signal first received after the first sensing wave111is generated, and the second reflected echo signal114is the effective echo signal first received after the second sensing wave121is generated. In reality, the actual effective echo signal of the second sensing wave121is the second main echo signal122, rather than the second reflected echo signal114. In other words, since the time interval between generation of the second sensing wave121and receipt of the second reflected echo signal114is shorter than the actual time interval, the time of flight is erroneously calculated. Under this circumstance, the ultrasonic sensing device may erroneously discriminate that a foreign object enters the sensing range.

SUMMARY OF THE INVENTION

The present invention provides a method and a device for determining an ultrasonic detecting cycle in order to avoid erroneous discrimination due to the multiple reflection effect.

In accordance with an aspect of the present invention, there is provided a method for determining an ultrasonic detecting cycle. Firstly, an initial detecting cycle T is set. Then, a first sensing wave is generated. Then, a first time-of-flight value is calculated corresponding to the first sensing wave. After the first sensing wave has been generated for the initial detecting cycle T, a second sensing wave is generated. Then, a second time-of-flight value is calculated corresponding to the second sensing wave. Afterwards, the second time-of-flight value is compared with the first time-of-flight value. If a difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value, the initial detecting cycle T is determined as the ultrasonic detecting cycle.

In accordance with another aspect of the present invention, there is provided a device for determining an ultrasonic detecting cycle. The device includes a microprocessor and an ultrasonic transducer. The microprocessor is used for setting an initial detecting cycle T, and generating a first emitting signal and a second emitting signal. The ultrasonic transducer is used for generating a first sensing wave and a second sensing wave corresponding to the first emitting signal and the second emitting signal, respectively. Furthermore, the microprocessor calculates a first time-of-flight value corresponding to the first emitting signal, calculates a second time-of-flight value corresponding to the second emitting signal, and compares the second time-of-flight value with the first time-of-flight value. If a difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value, the initial detecting cycle T is determined as the ultrasonic detecting cycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3is a schematic functional block diagram illustrating an exemplary ultrasonic sensing device of the present invention. As shown inFIG. 3, the ultrasonic sensing device comprises a microprocessor40, an emitting circuit50, an ultrasonic transducer60and a receiving circuit70. The microprocessor40generates an emitting signal41to the emitting circuit50. When the emitting signal41is received by the emitting circuit50, the emitting signal41is converted into a driving signal51by the emitting circuit50. The driving signal51is transmitted to the ultrasonic transducer60. According to the driving signal51, the ultrasonic transducer60generates a sensing wave. Once the sensing wave hits an object, the sensing wave is reflected by the object and the reflected sensing wave (also referred as an echo signal) is returned back to the ultrasonic transducer60. When the echo signal is received by the ultrasonic transducer60, the ultrasonic transducer60generates a vibrating signal61, which is transmitted to the receiving circuit70. According to the vibrating signal, the receiving circuit70generates a receiving signal71, which is transmitted to the microprocessor40. According to the receiving signal71, the microprocessor40will calculate the time of flight (TOF) between the ultrasonic sensing device and the object.

Moreover, a detecting cycle for generating the sensing wave by the ultrasonic sensing device is predetermined in the microprocessor40. According to the predetermined detecting cycle, the microprocessor40generates the emitting signal41. In other words, the ultrasonic sensing device generates the sensing wave according to the predetermined detecting cycle. Moreover, a boundary value is also predetermined in the microprocessor40. For initially ignoring the adverse influence of undesired noise, the microprocessor40will discriminate whether the receiving signal71is effective according to the predetermined boundary value. In an embodiment, the predetermined boundary value is equal to 50% or 60% of the magnitude of the maximum receiving signal71. Alternatively, the predetermined boundary value is equal to the average of several successive receiving signals71. The procedure of predetermining the boundary value is known in the art, and is not redundantly described herein.

FIG. 4Ais a flowchart illustrating a method for determining an ultrasonic detecting cycle according to a first embodiment of the present invention. After the ultrasonic sensing device is activated (Step S100), the microprocessor40sets an initial detecting cycle T, a time increment ΔT and a variable integer n, where n=0 (Step S110). Next, the ultrasonic sensing device generates a first sensing wave (Step S120). When the first sensing wave hits the reference object, an echo signal is reflected by reference object and then received by the ultrasonic sensing device. Next, according to the effective echo signal first received after the first sensing wave is generated, the microprocessor40calculates a first time-of-flight value (1stTOF) (Step S130). After the initial detecting cycle T, the microprocessor40generates an emitting signal and thus the ultrasonic sensing device generates a second sensing wave (Step S140). Similarly, when the second sensing wave hits the reference object, an echo signal is reflected by reference object and then received by the ultrasonic sensing device. Next, according to the effective echo signal first received after the second sensing wave is generated, the microprocessor40calculates a second time-of-flight (2ndTOF) value (Step S150).

Next, the microprocessor40compares the second time-of-flight value with the first time-of-flight value, and discriminates whether the difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value (e.g. 1 ms) (Step S160). If the difference between the second time-of-flight value and the first time-of-flight value is smaller than the threshold value, the initial detecting cycle T is determined as the ultrasonic detecting cycle (Step S170). After the ultrasonic detecting cycle is determined, the microprocessor40will periodically generates the emitting signal in every ultrasonic detecting cycle. Since the sensing wave is periodically generated by the ultrasonic sensing device in every ultrasonic detecting cycle, the ultrasonic sensing device is capable of discriminating whether a foreign object enters the sensing range.

On the other hand, if the difference between the second time-of-flight value and the first time-of-flight value is greater than the threshold value, the variable integer n is adjusted to be (n+1) (Step S180). Next, the microprocessor40adjusts the initial detecting cycle T to be T+n×ΔT (Step S181). After the second sensing wave has been generated for the updated initial detecting cycle T, the microprocessor40generates an emitting signal and thus the ultrasonic sensing device generates a third sensing wave (Step S182). Similarly, when the third sensing wave hits the reference object, an echo signal is reflected by reference object and then received by the ultrasonic sensing device. Next, according to the effective echo signal first received after the third sensing wave is generated, the microprocessor40calculates a third time-of-flight value (Step S183). Next, the microprocessor40compares the third time-of-flight value with the first time-of-flight value, and discriminates whether the difference between the third time-of-flight value and the first time-of-flight value is smaller than the threshold value (Step S184). If the difference between the third time-of-flight value and the first time-of-flight value is smaller than the threshold value, the updated initial detecting cycle T is determined as the ultrasonic detecting cycle (Step S170). On the other hand, if the difference between the third time-of-flight value and the first time-of-flight value is greater than the threshold value, the variable integer n is continuously adjusted to be (n+1) (Step S180).

FIG. 4Bis a schematic timing waveform diagram illustrating the related signal processed by the method according to the first embodiment of the present invention. After a first sensing wave111is generated by the ultrasonic sensing device, the first sensing wave111hits the reference object22, and thus a first main echo signal112is reflected by reference object22and then received by the ultrasonic sensing device. Due to occurrence of the multiple reflection effect, the first main echo signal112results in a first reflected echo signal113, a second reflected echo signal114, a third reflected echo signal115and a fourth reflected echo signal116. Since the intensities of the third reflected echo signal115and the fourth reflected echo signal116are lower than the predetermined boundary value of the ultrasonic sensing device, the third reflected echo signal115and the fourth reflected echo signal116are ignored. Since the intensities of the first reflected echo signal113and the second reflected echo signal114are still greater than the boundary value, the first reflected echo signal113and the second reflected echo signal114are deemed as effective echo signals.

As shown inFIG. 4B, the first main echo signal112is the effective echo signal first received after the first sensing wave111is generated. When the first main echo signal112is received, the microprocessor40will calculate the time interval between generation of the first sensing wave111and receipt of the first main echo signal112, thereby acquiring a first time-of-flight (1stTOF) value.

After a first sensing wave111has been generated by the ultrasonic sensing device for the initial detecting cycle T, an emitting signal is generated by the microprocessor40and thus a second sensing wave121is generated by the ultrasonic sensing device. Similarly, when the second sensing wave121hits the reference object22, a second main echo signal122is reflected by reference object22and then received by the ultrasonic sensing device. Due to occurrence of the multiple reflection effect, the second main echo signal122results in the reflected echo signals123and124. The echo signals122,123and124are all effective echo signals.

In reality, the actual effective echo signal of the second sensing wave121is the second main echo signal122. However, as shown inFIG. 4B, the second reflected echo signal114of the first main echo signal112is the effective echo signal first received after the second sensing wave121is generated. When the second reflected echo signal114is received, the microprocessor40will calculate the time interval between generation of the second sensing wave121and receipt of the second reflected echo signal114, thereby acquiring a second time-of-flight (2ndTOF) value. Due to occurrence of the multiple reflection effect, the second time-of-flight value is shorter than the first time-of-flight value.

After the second time-of-flight value is calculated, the microprocessor40will compare whether the difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value. If the difference between the second time-of-flight value and the first time-of-flight value is smaller than the threshold value, it is meant that the effective echo signals first received after the first sensing wave and the second sensing wave are respective main echo signals. Under this circumstance, the initial detecting cycle T is determined as the ultrasonic detecting cycle by the microprocessor40. After the ultrasonic detecting cycle is determined, the microprocessor40will periodically generates the emitting signal in every ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device.

Please refer toFIG. 4Bagain. Since the difference between the second time-of-flight value and the first time-of-flight value is greater than the threshold value, the microprocessor40adjusts the variable integer n and the initial detecting cycle T to be (n+1) and T+n×ΔT, respectively, wherein the initial value of the variable integer n is 0, and ΔT is the time increment. After the updated initial detecting cycle T, the ultrasonic sensing device generates a third sensing wave131. In reality, the actual effective echo signal of the third sensing wave131is the third main echo signal132. As shown inFIG. 4B, the reflected echo signal124of the second main echo signal122is the effective echo signal first received after the third sensing wave131is generated. When the reflected echo signal124is received, the microprocessor40will calculate the time interval between generation of the third sensing wave131and receipt of the reflected echo signal124, thereby acquiring a third time-of-flight (3rdTOF) value.

After the third time-of-flight value is calculated, the microprocessor40will compare whether the difference between the third time-of-flight value and the first time-of-flight value is smaller than a threshold value. If the difference between the third time-of-flight value and the first time-of-flight value is smaller than the threshold value, the updated initial detecting cycle T is determined as the ultrasonic detecting cycle by the microprocessor40. After the ultrasonic detecting cycle is determined, the microprocessor40will periodically generates the emitting signal in every ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device. Since the difference between the third time-of-flight value and the first time-of-flight value is greater than the threshold value, the microprocessor40adjusts the variable integer n and the initial detecting cycle T to be (n+1) and T+n×ΔT, respectively. After the updated initial detecting cycle T, the ultrasonic sensing device generates a next sensing wave and a next time-of-flight value is calculated. The above procedure is repeatedly done until the difference between the calculated time-of-flight value and the first time-of-flight value is smaller than the threshold value, and thus the updated initial detecting cycle T is determined as the ultrasonic detecting cycle by the microprocessor40. After the ultrasonic detecting cycle is determined, the microprocessor40will periodically generates the emitting signal in every ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device.

FIG. 5Ais a flowchart illustrating a method for determining an ultrasonic detecting cycle according to a second embodiment of the present invention. After the ultrasonic sensing device is activated (Step S100), the microprocessor40sets an initial detecting cycle T (Step S110′). Next, the ultrasonic sensing device generates a first sensing wave (Step S120). According to the effective echo signal first received after the first sensing wave is generated, the microprocessor40calculates a first time-of-flight (1stTOF) value (Step S130). After the initial detecting cycle T, the ultrasonic sensing device generates a second sensing wave (Step S140). According to the effective echo signal first received after the second sensing wave is generated, the microprocessor40calculates a second time-of-flight (2ndTOF) value (Step S150).

Next, the microprocessor40will compare whether the difference between the second time-of-flight value and the first time-of-flight value is smaller than a threshold value (Step S260). If the difference between the second time-of-flight value and the first time-of-flight value is smaller than the threshold value, the initial detecting cycle T is determined as the ultrasonic detecting cycle by the microprocessor40(Step S270). After the ultrasonic detecting cycle is determined, the microprocessor40will periodically generates the emitting signal in every ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device. On the other hand, if the difference between the second time-of-flight value and the first time-of-flight value is greater than the threshold value, the sum of the initial detecting cycle T and the second time-of-flight value is determined as the ultrasonic detecting cycle by the microprocessor40(Step S280). After the ultrasonic detecting cycle is determined, the ultrasonic sensing device will periodically generates the sensing wave in every ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device.

FIG. 5Bis a schematic timing waveform diagram illustrating the related signal processed by the method according to the second embodiment of the present invention. As described inFIG. 4B, the first main echo signal112is the effective echo signal first received after the first sensing wave111is generated. When the first main echo signal112is received, the microprocessor40will calculate the time interval between generation of the first sensing wave111and receipt of the first main echo signal112, thereby acquiring a first time-of-flight (1stTOF) value. As described inFIG. 4B, the second reflected echo signal114of the first main echo signal112is the effective echo signal first received after the second sensing wave121is generated. When the second reflected echo signal114is received, the microprocessor40will calculate the time interval between generation of the second sensing wave121and receipt of the second reflected echo signal114, thereby acquiring a second time-of-flight (2ndTOF) value. Due to occurrence of the multiple reflection effect, the second time-of-flight value is not equal to the first time-of-flight value. If the difference between the second time-of-flight value and the first time-of-flight value is greater than the threshold value, the sum of the initial detecting cycle T and the second time-of-flight value is determined as the ultrasonic detecting cycle by the microprocessor40. Next, the ultrasonic detecting cycle generates a third sensing wave131according to the updated ultrasonic detecting cycle in order to determine whether a foreign object enters the sensing range of the ultrasonic sensing device.

As shown inFIG. 5B, since the time of emitting the third sensing wave131is substantially consistent with the time of receiving the reflected echo signal124of the second main echo signal122, the third main echo signal132is the effective echo signal first received after the third sensing wave131is generated. Under this circumstance, the adverse influence of the multiple reflection effect is minimized.

The method for determining the ultrasonic detecting cycle according to the present invention could be performed once the ultrasonic detecting device is activated. Alternatively, the method for determining the ultrasonic detecting cycle according to the present invention could be periodically performed or adjusted according to the practical applications or environments. The method could be controlled by firmware without any additional component. As a consequence, the method for determining the ultrasonic detecting cycle according to the present invention is cost-effective and is capable of avoiding erroneous discrimination due to the multiple reflection effect.