JP4287315B2 - Position detection device using ultrasonic waves - Google Patents

Description

  The present invention relates to a position detection apparatus using an ultrasonic wave that is used in a virtual reality, a training system, and the like and is suitable for detecting a human position in a limited space. The position detection apparatus according to the present invention is suitable for constructing an inexpensive and compact system, not a high-precision, high-function, and high-cost system.

  A three-point position detection method is often used as a method for detecting a position in a two-dimensional plane using an ultrasonic element.

  Hereinafter, the principle of the three-point position detection method will be described with reference to FIG.

  As shown in FIG. 2, consider X-axis coordinates and Y-axis coordinates that are orthogonal to each other through the origin. In this case, the origin is the reference position. It is assumed that there is a detection target (not shown) at a position away from the origin, and the transmitting ultrasonic element 21 is attached to this detection target. In the example shown in FIG. 2, the transmitting ultrasonic element 21 is at the position (X1, Y1) in the XY coordinates. In the three-point position detection method, the XY coordinate position (X1, Y1) of the transmitting ultrasonic element 21 is obtained as follows.

  That is, the first receiving ultrasonic element 22 and the second receiving ultrasonic element 23 are arranged facing the transmitting ultrasonic element 21. The first receiving ultrasonic element 22 and the second receiving ultrasonic element 23 are arranged apart from each other by a distance 2D along the Y-axis direction with the origin as the center. That is, the first receiving ultrasonic element 22 is arranged at the XY coordinate position (0, D) separated by a distance D in the positive direction of the Y axis, and the second receiving ultrasonic element 23 is negative in the Y axis. It is arranged at the XY coordinate position (0, -D) that is separated by a distance D in the direction.

  As shown in FIG. 2, the first reception ultrasonic element 22 is separated from the transmission ultrasonic element 21 by a first distance R1, and the second reception ultrasonic element 23 is a transmission ultrasonic element. 21 is a second distance R2.

In such a situation, it is assumed that an ultrasonic wave is transmitted from the transmitting ultrasonic element 21 at the 0th time t0. In this case, the first receiving ultrasonic element 22 receives the ultrasonic wave at the first time t1 when a first time T1 proportional to the first distance R1 has elapsed from the zero time t0. Similarly, the second receiving ultrasonic element 23 receives an ultrasonic wave at a second time t2 after a second time T2 that is proportional to the second distance R2 from the zero time t0. Accordingly, the first time (from the 0th time t0 when the ultrasonic wave is transmitted from the transmitting ultrasonic element 21 to the first time t1 when the first receiving ultrasonic element 22 receives the ultrasonic wave ( By measuring (time difference) T1, the first distance R1 can be determined. Similarly, the second time from the 0th time t0 when the ultrasonic wave is transmitted from the transmitting ultrasonic element 21 to the second time t2 when the second receiving ultrasonic element 23 receives the ultrasonic wave. By measuring (time difference) T2, the second distance R2 can be determined. On the other hand, from the Pythagorean theorem, the following equations 1 and 2 are established.

Equation 2 is subtracted from Equation 1 (Equation 1 -Equation 2), and the Y-axis coordinate position Y1 of the transmitting ultrasonic element 21 is obtained as shown in Equation 3 and Equation 4 below.

  By substituting the Y-axis coordinate position Y1 of the transmitting ultrasonic element 21 into the above equation 1, the X-axis coordinate position X1 of the transmitting ultrasonic element 21 is also obtained.

  In the above, the method for detecting the position in the two-dimensional plane using the ultrasonic element has been described. However, in order to further expand in three dimensions, the receiving ultrasonic element is moved in the vertical direction (Z-axis direction). And the time in the vertical direction (time difference) may be detected.

  However, when the above method is used, since there is a squared distance term, the detection error is also squared. As a result, there is a problem that the position detection accuracy deteriorates with respect to the distance detection accuracy. In addition, since the receiving ultrasonic elements 22 and 23 are arranged at positions away from the origin (reference position), the range in which all the receiving ultrasonic elements can receive ultrasonic waves is within the range of individual receiving ultrasonic waves. There is also a problem that it becomes narrower than the detection range of the element. Furthermore, since the receiving ultrasonic elements 22 and 23 must be arranged apart to some extent, there is a problem that the apparatus becomes large.

  The present invention is intended to solve the problems of the position detection apparatus using the ultrasonic wave, and has a position detection accuracy equivalent to the distance detection accuracy and is ideal as a more compact system without narrowing the position detection range. A position detection apparatus using a typical ultrasonic wave is provided.

That is, the position detection device according to the present invention is a position detection device using an ultrasonic wave that detects the position of a detection target based on a reference position in a two-dimensional or three-dimensional space. At least two transmitting ultrasonic elements that are attached and transmit ultrasonic signals and at least two that are arranged close to each other at a reference position away from the detection target and receive ultrasonic waves transmitted from the transmitting ultrasonic elements, or and three receiving ultrasonic transducer, a transmission drive apparatus for driving the transmitting ultrasonic transducer, receiving detects that any one of at least two or three of the receiving ultrasonic transducer receives the ultrasonic detection The apparatus, a time difference detecting means for detecting a time difference from when the ultrasonic wave is transmitted until it is received, and a distance between the transmitting ultrasonic element and the receiving ultrasonic element are calculated from the time difference detected by the time difference detecting means. Distance performance And means, which is detected from the phase difference detecting device and the distance calculating means at the detected distance and the phase difference detector for detecting a phase difference between the ultrasonic wave received by at least two or three of the receiving ultrasonic transducer a position detecting apparatus using ultrasonic waves that Yusuke and position calculating means for calculating a position of the transmission credit ultrasonic element relative to the phase difference Toka RaHajime reference position, and the phase difference detection device is at least Addition is performed between a phase delay device that delays one phase of ultrasonic waves received by two or three receiving ultrasonic elements and ultrasonic waves received by at least two or three receiving ultrasonic elements. Subtraction between the adder and the ultrasonic waves received by at least two or three receiving ultrasonic elements, and the ultrasonic wave received by the receiving ultrasonic element whose phase is not delayed by the phase delay apparatus Reduction between output of phase delay device A position detecting device comprising: a subtracting device that performs a subtracting operation; an amplitude detecting device that detects an amplitude of an output waveform of the adding device and the subtracting device; and a phase difference calculating means that calculates a phase difference from the output of the amplitude detecting device. It is .

  The transmitting ultrasonic element is preferably a cylindrical ultrasonic element capable of transmitting non-directional ultrasonic waves in the horizontal direction.

  Further, the position detection device includes a posture angle detection device and an acceleration detection device attached to the detection target, a minute position calculation means for calculating a position moved in a minute time from the output of the posture angle detection device and the acceleration detection device, It is preferable to further include position correction calculation means for calculating a position by combining the outputs of the position calculation means and the minute position calculation means.

  In the present invention, two or more receiving ultrasonic elements are arranged close to each other at the reference position, and the transmitting ultrasonic element is calculated from the distance and phase difference between the receiving ultrasonic element and the transmitting ultrasonic element. Since the phase difference type position detection method for calculating the position of the position is used, the problems of the conventional three-point position detection method can be solved, and a highly accurate, inexpensive and compact position detection apparatus can be obtained. it can. Furthermore, the data update speed can be improved by combining the attitude angle detection device and the acceleration detection device. With this system, an ideal position detection device using ultrasonic waves can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 shows an example of use of the position detection apparatus using the ultrasonic wave of the present invention in virtual reality. A user 31 wears an HMD (head mounted display) 32 on the head. As a result, the user 31 can see the video displayed on the HMD 32.

  The transmitting ultrasonic element 33, a posture angle detection device (head tracker) (not shown), and an acceleration detection device (not shown) are attached to the top of the HMD 32 together. Therefore, the head of the user 31 is the detection target.

  The posture angle detection device (not shown) detects the tilt and direction of the head and transmits the detection result to the personal computer 34. As a result, the HMD 32 displays an image that matches the angle.

  On the other hand, the receiving ultrasonic unit 35 is disposed on the display 36 so as to receive an ultrasonic signal and detect the position of the head (detection target) of the user 31. The position where the receiving ultrasonic unit 35 is disposed is the reference position (origin). The transmitting ultrasonic element 33 is a cylindrical vibrator and has no directivity in the horizontal direction, and transmits an ultrasonic signal that is uniform by 360 degrees. This is so that the reception ultrasonic unit 35 can receive ultrasonic waves even when the user 31 faces in various directions.

  FIG. 1 is a diagram for explaining the principle of a phase difference type position detection method of a position detection apparatus using ultrasonic waves according to the present invention. First, the two-dimensional case will be described.

  Consider X and Y axis coordinates that are orthogonal to each other through the origin. In this case, the origin is the reference position. There is a detection object (that is, the head of the user 31 in the example of FIG. 3) at a position away from the origin. The transmitting ultrasonic element 11 is attached to this detection object. The transmission ultrasonic element 11 corresponds to the transmission ultrasonic element 33 of FIG.

  In the example shown in FIG. 1, the transmitting ultrasonic element 11 is at the position (X1, Y1) in the XY coordinates.

  Two first receiving ultrasonic elements 12 and two second receiving ultrasonic elements 13 are arranged adjacent to each other so as to face the transmitting ultrasonic element 11. The first receiving ultrasonic element 12 and the second receiving ultrasonic element 13 are arranged apart from each other by a distance L around the origin along the Y-axis direction. That is, the first receiving ultrasonic element 12 is arranged at the XY coordinate position (0, L / 2) separated by a distance of L / 2 in the positive direction of the Y axis, and the second receiving ultrasonic element 13 is It is arranged at the XY coordinate position (0, -L / 2) separated by a distance of L / 2 in the negative direction of the Y axis.

  As shown in FIG. 1, the first receiving ultrasonic element 12 is separated from the transmitting ultrasonic element 11 by a first distance R1, and the second receiving ultrasonic element 13 is a transmitting ultrasonic element. 11 is a second distance R2.

  In such a situation, it is assumed that an ultrasonic wave is transmitted from the transmitting ultrasonic element 11 at the 0th time t0. In this case, the first receiving ultrasonic element 12 receives the ultrasonic wave at the first time t1 when a first time T1 proportional to the first distance R1 has elapsed from the zero time t0. Similarly, the second receiving ultrasonic element 13 receives an ultrasonic wave at a second time t2 after a second time T2 that is proportional to the second distance R2 from the zero time t0. Accordingly, the first time (from the 0th time t0 when the ultrasonic wave is transmitted from the transmitting ultrasonic element 11 to the first time t1 when the first receiving ultrasonic element 12 receives the ultrasonic wave ( By measuring (time difference) T1, the first distance R1 can be determined. Similarly, the second time from the 0th time t0 when the ultrasonic wave is transmitted from the transmitting ultrasonic element 11 to the second time t2 when the second receiving ultrasonic element 13 receives the ultrasonic wave. By measuring (time difference) T2, the second distance R2 can be determined. However, as described above, since the first receiving ultrasonic element 12 and the second receiving ultrasonic element 13 are arranged close to each other, the first distance R1 and the second distance R2 Are almost the same and can be approximated to the distance R.

Similar to the above-described three-point position detection method, the following formulas 5 and 6 are established from the Pythagorean theorem.

By subtracting Equation 6 from Equation 5 (Equation 5-Equation 6) and approximating the first distance R1 and the second distance R2 to R1 = R2 = R, the following Equation 7 and Equation 8 As shown in Equation 9, the Y-axis coordinate position Y1 of the transmitting ultrasonic element 11 is obtained.

On the other hand, the minute difference D between the first distance R1 and the second distance R2 is expressed by the wavelength λ and the phase difference θ, and the wavelength λ can be expressed by the sound speed c and the frequency f. That is, the Y-axis coordinate position Y1 of the transmitting ultrasonic element 11 is expressed by the following equation (10).

  By substituting the Y-axis coordinate position Y1 of the transmitting ultrasonic element 11 into the above equation 5, the X-axis coordinate position X1 of the transmitting ultrasonic element 11 is obtained.

  Thus, by measuring the distance R and the phase difference θ, the XY coordinate position (X1, Y1) of the transmitting ultrasonic element 11 can be detected.

  In order to expand in three dimensions, another receiving ultrasonic element may be added in the vertical direction (Z-axis direction) to detect the phase difference in the vertical direction.

  Since there is no square term in the equation (10), the position detection error is not significantly worse than the distance detection error. Further, considering that the phase difference θ varies between ± π / 2, it can be seen that the detection range in the Y-axis direction becomes wider as the value of c / fL is larger. In practice, c / fL cannot be increased so much due to the limitations on the characteristics of the receiving ultrasonic element. In this example, since f = 25 kHz and L = 14 mm, c / fL is 0.97, and the detection range is ± 55 degrees.

  FIG. 4 shows a block diagram of a position detection apparatus using ultrasonic waves according to the present invention. Hereinafter, with reference to FIG. 4, the flow of each signal or output and the procedure of position detection will be described.

  The illustrated position detection apparatus includes a transmission ultrasonic element 401, a transmission drive unit 402, a time difference detection unit 403, a distance calculation unit 404, first to third reception ultrasonic elements 405, 406, and 407. A reception detection device 408, a phase difference detection device 409, a position calculation means 415, a position correction calculation means 416, an attitude angle detection device 417, an acceleration detection device 418, and a minute position calculation means 419. The transmitting ultrasonic element 401 is attached to the detection target as described above. As described above, the first to third receiving ultrasonic elements 405 to 407 are arranged close to each other around the reference position (origin).

  The phase difference detection device 409 includes a phase delay device 410, an addition device 411, a subtraction device 412, a phase difference calculation unit 413, and an amplitude detection device 414.

  The transmission drive device 402 sends a drive signal to the transmission ultrasonic element 401 at the 0th time t0. In response to this drive signal, the transmitting ultrasonic element 401 transmits an ultrasonic wave at the 0th time t0. At the same time, the transmission drive device 402 notifies the time difference detection means 403 that “ultrasonic wave has been transmitted”.

  The time difference detection means 403 has a timer (not shown). Upon reception of the “transmission of ultrasonic waves” at the 0th time t0, the time difference detection means 403 starts counting the timer.

  On the other hand, the ultrasonic wave transmitted from the transmitting ultrasonic element 401 at the 0th time t0 propagates in the air, and soon the first receiving ultrasonic element 405, the second receiving ultrasonic element 406, and the third Are received almost simultaneously by the receiving ultrasonic element 407. More specifically, the first receiving ultrasonic element 405 receives an ultrasonic wave at a first time t1 that has passed a first time T1 from the zero time t0. The second receiving ultrasonic element 406 receives the ultrasonic wave at the second time t2 after the second time T2 has elapsed from the zero time t0. The third receiving ultrasonic element 407 receives the ultrasonic wave at the third time t3 after the third time T3 has elapsed from the zero time t0. As described above, the first to third reception ultrasonic elements 405 to 407 are arranged close to each other around the reference position, so that the first to third times t1 to t3 are substantially the same time. It is.

  The reception detection device 408 detects that the first reception ultrasonic element 405 has received the ultrasonic wave at the first time t1, and notifies the time difference detection means 403 that “the ultrasonic wave has been received”. Upon receiving “the fact that an ultrasonic wave has been received”, the time difference detection means 403 stops counting the timer at the first time t1. Then, the time difference detection unit 403 outputs the count value, that is, the time difference Δt between transmission and reception, to the distance calculation unit 404. This time difference Δt is equal to the first time T1.

  The distance calculation unit 404 multiplies the time difference Δt by the speed of sound c to obtain the distance R between the transmitting ultrasonic element 401 and the first receiving ultrasonic element 405. The distance calculation means 404 outputs the obtained distance R to the position calculation means 415.

  On the other hand, the ultrasonic waves received by the first reception ultrasonic element 405, the second reception ultrasonic element 406, and the third reception ultrasonic element 407 are the first reception signal Out1 and the second reception. The signals are converted into electrical signals of the signal Out2 and the third reception signal Out3 and output to the phase difference detection device 409. The phase of the first received signal Out1 is delayed by the phase delay device 410 to become a delayed signal Out1 '.

  The adder 411 adds the first reception signal Out1 and the second reception signal Out2, and outputs a first addition result signal 1 + 2. Further, the adding device 411 adds the first reception signal Out1 and the third reception signal Out3, and outputs a second addition result signal 1 + 3.

  The subtracting device 412 includes a first subtraction result signal 1-2, a second subtraction result signal 1− from the first reception signal Out1, the second reception signal Out2, the third reception signal Out3, and the delayed signal Out1 ′. 3. The third subtraction result signal 1′-2 and the fourth subtraction result signal 1′-3 are output. Specifically, the subtracting device 412 subtracts the second received signal Out2 from the first received signal Out1, and outputs a first subtraction result signal 1-2. The subtracting device 412 subtracts the third reception signal Out3 from the first reception signal Out1, and outputs a second subtraction result signal 1-3. The subtracting device 412 subtracts the second received signal Out2 from the delayed signal Out1 'and outputs a third subtraction result signal 1'-2. The subtracting device 412 subtracts the third reception signal Out3 from the delay signal Out1 'and outputs a fourth subtraction result signal 1'-3.

  The six electric signals 1 + 2, 1 + 3, 1-2, 1-3, 1′-2, and 1′-3 output from the adder 411 and the subtractor 412 are respectively amplified by the amplitude detector 414. The six converted voltage values are output to the phase difference calculation means 413. Based on these six converted voltage values, the phase difference calculation means 413 calculates the first phase difference θ1 between the first received signal Out1 and the second received signal Out2, the first received signal Out1, and the first received signal Out1. 3 is calculated, and the first and second phase differences θ 1 and θ 2 are output to the position calculating means 415.

  The position calculation means 415 calculates a temporary position (X1, Y1, Z1) on the XYZ coordinates of the transmitting ultrasonic element 410 with reference to the reference position, based on the first and second phase differences θ1 and θ2. Then, the temporary position (X1, Y1, Z1) is output to the position correction calculation means 416.

  The posture angle detection device 417 detects the posture angle (α, β, γ) and outputs the detected posture angle (α, β, γ) to the minute position calculation means 419. The acceleration detection device 418 detects the acceleration (Ax, Ay, Az) and outputs the detected acceleration (Ax, Ay, Az) to the minute position calculation means 419. The posture angle detection device 417 and the acceleration detection device 418 are sampled and updated at a higher speed because there is no time loss for propagating in the air like ultrasonic waves in detecting the posture angle and acceleration. The minute position calculating means 419 calculates the minute position (ΔX, ΔY, ΔZ) based on the posture angle (α, β, γ) and the acceleration (Ax, Ay, Az), and obtains the obtained minute position (ΔX, ΔY, ΔZ) is output to the position correction calculation means 416. Finally, the position correction calculation means 416 calculates the position output (X, Y, Z) corrected from the temporary position (X1, Y1, Z1) and the minute position (ΔX, ΔY, ΔZ), and obtains it. The corrected position output (X, Y, Z) is output.

  Next, the transmission drive device 402 and the reception detection device 408 will be described. FIG. 5 shows an ultrasonic transmission waveform 52 and an ultrasonic reception waveform 51. When a rectangular wave having a voltage of ± 12 V and a frequency of 25 kHz is output from the transmission driving device 402, the transmission ultrasonic element 301 resonates with this signal and transmits a 25 kHz ultrasonic wave. Shortly after this ultrasonic transmission, the receiving ultrasonic element receives the ultrasonic wave and a 25 kHz reception signal is detected. The reception detection device 408 is configured to detect an output exceeding a certain level.

  Next, the phase difference detection device 409 will be described. Originally, the phase difference detection device 409 is configured to output the first received signal Out1, the second received signal Out2, and the third received signal Out3 received by the first to third receiving ultrasonic elements 405 to 407. It suffices if all the signals can be read and the phase difference can be examined. However, in order to read three electrical signals with a frequency of 25 kHz as data whose phase is known, A / D conversion must be performed with a sampling period of at least several μs. If accuracy is required, A / D conversion must be performed with a sampling period shorter than 1 μs. This is not easy even if a high-spec microcomputer is used. Therefore, in this embodiment, the phase difference is accurately detected by converting the phase difference into another output. Details will be described below.

  The phase delay device 410 is a circuit that changes only the phase without changing the amplitude of a signal having a frequency of 25 kHz. In this embodiment, the phase delay device 410 is composed of an active bandpass filter shown in FIG. The active bandpass filter shown in the figure has a phase delay of a design value of 138 degrees, but actually the phase is delayed by 130 degrees.

  The illustrated phase delay device 410 includes a signal input terminal 410a that inputs a first received signal Out1, a signal output terminal 410b that outputs a delayed signal Out1 ′, and a reference input terminal 410c that is supplied with a 2V reference voltage. Have. The phase delay device 410 includes an operational amplifier 601 having an inverting input terminal, a non-inverting input terminal, and an output terminal, first and second capacitors 606 and 607, and first and second resistors 611 and 612. Have. The first capacitor 606 and the first resistor 611 are connected in series between the signal input terminal 410 a of the phase delay device 410 and the inverting input terminal of the operational amplifier 601. The second capacitor 607 and the second resistor 612 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 601. The non-inverting input terminal of the operational amplifier 601 is connected to the reference input terminal 410c, and the operational amplifier 601 is supplied with a power supply voltage of 4V. The output terminal of the operational amplifier 601 is connected to the signal output terminal 410 b of the phase delay device 410.

  In this embodiment, the capacitance value of the first capacitor 606 is 5100 pF, the resistance value of the first resistor 611 is 1.3 kΩ, the capacitance value of the second capacitor 607 is 100 pF, The resistance value of the resistor 612 is 1.8 kΩ.

  The adder 411 includes the adder circuit shown in FIG. More specifically, the adder 411 adds a first reception signal Out1 and a second reception signal Out2, and outputs a first addition result signal 1 + 2, and a second reception. It consists of two addition circuits, a second addition circuit that adds the signal Out1 and the third reception signal Out3 and outputs the second addition result signal 1 + 3.

  Here, the first adder circuit will be described, but the second adder circuit has the same configuration.

  The first adder circuit includes a first signal input terminal 411a for inputting the first reception signal Out1, a second signal input terminal 411b for inputting the second reception signal Out2, and a first addition result signal 1 It has a signal output terminal 411c for outputting +2 and a reference input terminal 411d to which a 2V reference voltage is supplied. The first adder circuit includes an operational amplifier 701 having an inverting input terminal, a non-inverting input terminal, and an output terminal, first to third resistors 706, 707, and 708, and a capacitor 711. The first resistor 706 is connected between the first signal input terminal 411 a of the first adder circuit and the inverting input terminal of the operational amplifier 701. The second resistor 707 is connected between the second signal input terminal 411 b of the first adder circuit and the inverting input terminal of the operational amplifier 701. The third resistor 708 and the capacitor 708 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 701. The non-inverting input terminal of the operational amplifier 701 is connected to the reference input terminal 411d, and the operational amplifier 701 is supplied with a power supply voltage of 4V. The output terminal of the operational amplifier 701 is connected to the signal output terminal 411c of the first adder circuit.

  In this embodiment, each of the resistance values of the first to third resistors 706 to 708 is 2 kΩ, and the capacitance value of the capacitor 711 is 100 pF.

  The subtracting device 412 includes a subtracting circuit shown in FIG. More specifically, the subtracting device 412 subtracts the second received signal Out2 from the first received signal Out1 and outputs a first subtraction result signal 1-2, and a first received signal. A second subtraction circuit that subtracts the third reception signal Out3 from Out1 and outputs a second subtraction result signal 1-3, and a third subtraction by subtracting the second reception signal Out2 from the delayed signal Out1 ′ A third subtracting circuit for outputting the result signal 1′-2, and a fourth subtracting circuit for subtracting the third reception signal Out3 from the delayed signal Out1 ′ to output a fourth subtraction result signal 1′-3. It consists of four subtracting circuits.

  Here, the first subtraction circuit will be described, but the second to fourth subtraction circuits have the same configuration.

  The first subtraction circuit includes a first signal input terminal 412a for inputting the first reception signal Out1, a second signal input terminal 412b for inputting the second reception signal Out2, and a first subtraction result signal 1 A signal output terminal 412c that outputs -2 and a reference input terminal 412d to which a 2V reference voltage is supplied. The first subtracting circuit includes an operational amplifier 801 having an inverting input terminal, a non-inverting input terminal, and an output terminal, first to fourth resistors 806, 807, 808, and 809, and first and second capacitors. 811 and 812.

  The first resistor 806 is connected between the first signal input terminal 412a of the first subtraction circuit and the inverting input terminal of the operational amplifier 801. The second resistor 807 is connected between the second signal input terminal 412b of the first subtraction circuit and the non-inverting input terminal of the operational amplifier 801. The third resistor 808 and the first capacitor 811 are connected in parallel between the inverting input terminal and the output terminal of the operational amplifier 801. The fourth resistor 809 and the second capacitor 812 are connected in parallel between the reference input terminal 412a and the non-inverting input terminal of the operational amplifier 801. A power supply voltage of 4V is supplied to the operational amplifier 801.

  In the present embodiment, each of the first to fourth resistors 806 to 809 has a resistance value of 2 kΩ, and each of the first and second capacitors 811 and 812 has a capacitance value of 100 pF.

  The amplitude detector 414 includes a peak hold circuit shown in FIG. 9 and an A / D converter that reads an output voltage. The peak hold circuit is composed of first to sixth peak hold circuits corresponding to the outputs of the first and second adder circuits and the first to fourth subtractor circuits, and is proportional to the amplitude of each. Has been converted. The reset switch of the peak hold circuit is turned on after the A / D conversion is completed until the next ultrasonic wave is transmitted, and the held voltage is reset.

  Hereinafter, the first peak hold circuit will be described, but the second to sixth peak hold circuits have the same configuration.

  The first peak hold circuit includes a signal input terminal 414a that inputs the first addition result signal 1 + 2 from the first addition circuit of the adder 411, and a voltage output terminal 414b that outputs the first peak hold voltage. And have. The first peak hold circuit includes a first operational amplifier 901 having an inverting input terminal, a non-inverting input terminal, and an output terminal, and a second operational amplifier 902 having an inverting input terminal, a non-inverting input terminal, and an output terminal. A diode 906, a capacitor 907, and a reset switch 909.

  The signal input terminal 414a of the first peak hold circuit is connected to the non-inverting input terminal of the first operational amplifier 901. The output terminal of the first operational amplifier 901 is connected to the anode of the diode 906. The cathode of the diode 906 is connected to the inverting input terminal of the first operational amplifier 901 and grounded via the capacitor 907. The cathode of the diode 906 is connected to the non-inverting input terminal of the second operational amplifier 902. A non-inverting input terminal of the second operational amplifier 902 is grounded via a reset switch 909. The inverting input terminal and the output terminal of the second operational amplifier 902 are directly connected to each other. A power supply voltage of 4 V is supplied to the first operational amplifier 901 and the second operational amplifier 902. The output terminal of the second operational amplifier 902 is connected to the voltage output terminal 414b of the first peak hold circuit. The voltage output terminal 414b of the first peak hold circuit is connected to the input terminal of an A / D converter (not shown).

  The phase difference calculation means 413 is a circuit that calculates the phase difference from the value read by the amplitude detection device 414 by A / D conversion.

The waveforms of the first reception signal Out1 and the second reception signal Out2 are assumed to be Asin ωt and Asin (ωt + θ ₁ ). In this case, when the first phase difference theta ₁ between a first received signal Out1 and the second reception signal Out2 is 0, the amplitude of the first addition result signal 1 + 2 is maximized at 2A, the The amplitude of the 1 subtraction result signal 1-2 is 0 at the minimum. Conversely, when the first phase difference θ ₁ is ± π [rad], the amplitude of the first addition result signal 1 + 2 is 0 and the minimum, and the amplitude of the first subtraction result signal 1-2 is the maximum. 2A. When the amplitudes of the first addition result signal 1 + 2, the first subtraction result signal 1-2, and the third subtraction result signal 1′-2 are expressed by the expression of the _first phase difference θ ₁ , respectively, It is expressed by Equation 11, Equation 12, and Equation 13.

Similarly, when the second phase difference between the first received signal Out1 and third received signals Out3 and theta _2, the second addition result signals 1 + 3, the second subtraction result signal 1-3 , And the fourth subtraction result signal 1′-3 are expressed by the following formula 14, formula 15, and formula 16, respectively.

From the above formulas 11 and 12, the absolute value | 2A | that is twice the amplitude A of the waveform and the absolute value | θ ₁ | of the first phase difference θ ₁ are expressed by the following formulas 17 and 18, respectively. It is represented by

Therefore, the first phase difference θ1 is obtained by the following equation (19), but the sign is unknown.

On the other hand, | θ ₁ −130π / 180 | is expressed by the following equation (20) from the above equations (13) and (17).

Therefore, the first phase difference θ ₁ is obtained by the following equation (21).

  The two solutions of the equation (21) are compared with the two solutions of the equation (19). In fact, it contains errors and does not match, so the closest combination is the correct solution.

The second phase difference θ ₂ is also obtained in the same manner from the above formulas 14 to 16.

Next, the position calculation means 415 will be described. Based on the above formula 10, the temporary position Y1 on the Y coordinate and the temporary position Z1 on the Z coordinate of the transmitting ultrasonic element 401 are obtained by the following formula 22 and formula 23, respectively.

Further, the temporary position X1 on the X coordinate of the transmitting ultrasonic element 401 is obtained by the following equation (24).

  Next, the attitude angle detection device 417, the acceleration detection device 418, and the minute position calculation means 419 will be described.

  Position detection by ultrasonic waves requires time for ultrasonic waves to propagate, and it takes about 10 ms for a detection range of several meters. Including other signal processing, arithmetic processing, averaging processing, etc., a time of several tens to several hundreds of ms is required.

  On the other hand, in order to use the user comfortably without feeling a time delay due to virtual reality or the like, it is necessary to update data of 100 Hz or more. Therefore, in this embodiment, the posture angle detection device 417, the acceleration detection device 418, and the minute position calculation means 419 are used to compensate for the time delay of position detection by ultrasonic waves.

  The posture angle detection device 417 is preferably an autonomous posture angle detection device using an inertial sensor such as a gyro, which does not require an additional device around it. In this embodiment, as the posture angle detection device 417, an NEC TOKIN 3D motion sensor MDP-A3U9 that is an autonomous posture angle detection device and can output a posture angle and acceleration is used.

First, the minute position calculation means 419 calculates an acceleration output (Ax ′) expressed by the following equation (25) that combines the position detection device and the coordinate axis from the output of the posture angle (α, β, γ) and acceleration (Ax, Ay, Az). , Ay ', Az').

  Next, the minute position calculation means 419 integrates the acceleration output (Ax ′, Ay ′, Az ′) twice in time, and calculates the position (ΔX, ΔY, ΔZ) moved in the minute time. Normally, the integration calculation accumulates errors, and if the integration is performed twice, a considerably high accuracy is required. However, in this example, the errors are not accumulated due to the integration of a minute time.

Finally, the position correction calculation means 416 will be described. When the ultrasonic processing is not completed and there is no output from the position calculation means 415, the position correction calculation means 416 calculates the previously calculated XYZ coordinate positions (X (n-1), Y (n-1), Z ( The output (ΔX, ΔY, ΔZ) of the minute position calculating means 419 is added to n-1)). When there is an output (X1, Y1, Z1) of the position calculation means 415, the position correction calculation means 416 uses the constant k equal to or less than 1 and the current XYZ coordinate position (X (n), Y (n), Z (n)) is calculated.

It is a figure explaining the principle of the phase difference position detection method in this invention. It is a figure explaining the principle of a three-point type position detection method. It is a figure explaining an example of use of a position detection device using an ultrasonic wave in the present invention. It is a block diagram of the position detection apparatus using the ultrasonic wave in this invention. It is a figure of the ultrasonic wave transmission waveform and ultrasonic wave reception waveform in this invention. FIG. 5 is a circuit diagram illustrating a configuration example of the phase delay device illustrated in FIG. 4. FIG. 5 is a circuit diagram illustrating a configuration example of an adder circuit configuring the adder illustrated in FIG. 4. FIG. 5 is a circuit diagram showing a configuration example of a subtracting circuit constituting the subtracting device shown in FIG. 4. FIG. 5 is a circuit diagram illustrating a configuration example of a peak hold circuit that configures the amplitude detection device illustrated in FIG. 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transmission ultrasonic element 12 1st reception ultrasonic element 13 2nd reception ultrasonic element 31 User 32 HMD (head mounted display)
33 Transmission ultrasonic element 34 Personal computer 35 Reception ultrasonic unit 36 Display 401 Transmission ultrasonic element 402 Transmission drive unit 403 Time difference detection means 404 Distance calculation means 405 First reception ultrasonic element 406 Second reception use Ultrasonic element 407 Third receiving ultrasonic element 408 Reception detection device 409 Phase difference detection device 410 Phase delay device 411 Addition device 412 Subtraction device 413 Phase difference calculation means 414 Amplitude detection device 415 Position calculation means 416 Position correction calculation means 417 Attitude angle detection device 418 Acceleration detection device 419 Fine position calculation means

Claims (3)

A position detection apparatus using ultrasonic waves for detecting a position of a detection target with reference to a reference position in a two-dimensional or three-dimensional space,
An ultrasonic element for transmission that is attached to the detection object and transmits an ultrasonic signal;
At least two or three receiving ultrasonic elements that are arranged close to each other at the reference position away from the detection object and receive ultrasonic waves transmitted from the transmitting ultrasonic elements;
A transmission drive device for driving the transmission ultrasonic element;
A reception detection device for detecting that any of the at least two or three reception ultrasonic elements has received an ultrasonic wave;
A time difference detecting means for detecting a time difference from when an ultrasonic wave is transmitted until it is received;
Distance calculating means for calculating the distance between the transmitting ultrasonic element and the receiving ultrasonic element from the time difference detected by the time difference detecting means;
A phase difference detecting device for detecting a phase difference between ultrasonic waves received by the at least two or three receiving ultrasonic elements;
Position calculating means for calculating the position of the ultrasonic element for transmission based on the reference position from the distance detected by the distance calculating means and the phase difference detected from the phase difference detecting device ;
The phase difference detection device includes a phase delay device that delays one phase of ultrasonic waves received by the at least two or three reception ultrasonic elements, and the at least two or three reception ultrasonic elements. One that does not delay the phase by the addition device that adds between the received ultrasonic waves, the subtraction between the ultrasonic waves received by the at least two or three receiving ultrasonic elements, and the phase delay device A subtractor for subtracting between the ultrasonic wave received by the receiving ultrasonic element and the output of the phase delay device, the adder and an amplitude detector for detecting the amplitude of the output waveform of the subtractor, and And a phase difference calculating means for calculating a phase difference from an output of the amplitude detecting device. The position detecting device according to claim 1 , wherein the transmitting ultrasonic element is a cylindrical ultrasonic element capable of transmitting non-directional ultrasonic waves in a horizontal direction. A posture angle detection device and an acceleration detection device attached to the detection object, a minute position calculation means for calculating a position moved in a minute time from outputs of the posture angle detection device and the acceleration detection device, and the position calculation means The position detection apparatus according to claim 1 , further comprising position correction calculation means for calculating a position by combining the output of the minute position calculation means.

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