JP5454475B2 - Position detection system, transmission device, reception device, position detection method, position detection program - Google Patents

Description

  The present invention relates to a position determination system that determines the position of a moving body using ultrasonic signals, and in particular, a position detection system that makes it possible to accurately and stably determine the position of a moving body using ultrasonic waves, The present invention relates to a transmission device, a reception device, a position detection method, and a position detection program.

  As an example of a related technique of a device that performs distance measurement based on the propagation time of an ultrasonic wave, an ultrasonic object measurement device is described in Patent Document 1. The ultrasonic object measuring apparatus described in Patent Document 1 performs transmission by performing frequency spread modulation on a tone burst wave generated from a tone burst wave generator using a pseudo noise signal from a pseudo noise signal generator by a frequency spread modulator. To do.

  The cross-correlator obtains the cross-correlation between the signal received by the reflected wave and demodulated by the frequency spread signal demodulator and the pseudo noise signal used for frequency spreading. Further, from the correlation level obtained by the correlation level detector 9, the presence or absence of reception of the reflected signal at the object is determined, and the distance is further measured.

  In addition, a transmission tone burst wave is transmitted using a frequency spread modulation signal in which a plurality of pseudo noise signals are sequentially switched and distinguished, and the plurality of tone burst waves are distinguished and discriminated.

Japanese Patent Laid-Open No. 7-104063

Satoshi Kashiki “M series and its application” (March 25, 1996, Shosodo)

  Since the ultrasonic signal transmitted from the ultrasonic transmission source uses a frequency that is higher than the audible band that cannot be heard by humans, it is necessary that the ultrasonic signal be at least 20 kHz. As a means for generating a signal in this frequency band with a sufficient sound pressure, a so-called speaker is known which electromagnetically drives a small and highly rigid diaphragm. However, it is difficult to mount on a small mobile body because it is difficult to reduce the size and power consumption is large because of current driving. For this reason, voltage-driven piezoelectric elements are widely used as ultrasonic transmission sources.

  Since this piezoelectric element is a voltage-driven type and generally consumes little power, it is often used in combination with a resonator having a low acoustic impedance in order to ensure sufficient sound pressure. However, when the resonance phenomenon is used, ultrasonic waves can be transmitted with a constant phase, frequency, and gain, but the transmission gain at other frequencies is considerably low, and a modulation method having wideband frequency characteristics such as frequency spread modulation is used. Difficult to do.

  In addition, even in a single piezoelectric element, since the mechanical Q is high and the residual vibration is prolonged, it is difficult to transmit an ultrasonic wave that accurately follows the modulated wave regardless of the modulation method.

  This is ideal when a transmitter with a lot of residual vibration is used for such an ultrasonic transmitter, or when the bandwidth of the transmitter is insufficient compared to the frequency band required for transmission / reception of frequency-spread modulated ultrasonic waves. Since it is difficult to transmit a modulated wave, there is a problem that it is difficult to suppress a secondary correlation peak caused by non-pseudo noise.

(Object of invention)
It is an object of the present invention to receive an ultrasonic wave transmitted from a transmitter at a receiver, measure the propagation time of the ultrasonic wave, and detect the distance between the transmitter and the transmitter or the position of the transmitter in each measurement cycle. The position detection system, transmitter, receiver, position that can reduce the influence of the reflected wave of the ultrasonic wave transmitted in the previous period and accurately measure the propagation time of the direct wave that reaches the earliest The object is to provide a detection method and a position detection program.

  A position detection system according to the present invention includes a moving body including a transmission unit that transmits an ultrasonic signal modulated based on a pseudorandom signal with high autocorrelation, and a pseudorandom signal that receives the ultrasonic signal and is the same as the pseudorandom signal. A model waveform of the ultrasonic wave modulated by the above is generated, a correlation value is obtained with the received ultrasonic signal, and a correlation value that appears when the ultrasonic signal partially matches the pseudo-random signal model waveform A receiving unit that selects a plurality of corresponding pseudo-random signals from the smaller secondary peak, and the transmitting unit simultaneously transmits an electromagnetic wave signal and an ultrasonic signal modulated based on the selected pseudo-random signal. The reception unit specifies the arrival time of the ultrasonic signal by executing correlation processing between the ultrasonic signal and the ultrasonic model waveform modulated by the pseudo-random signal. The position of the moving body is determined based on the time of arrival of the electromagnetic wave signal and the specified arrival time, the ultrasonic wave propagation time, and the calculated ultrasonic wave propagation time and the distance between the ultrasonic wave reception means. And a transmission unit uses a pseudo-random signal that is different for each transmission cycle.

  A transmission device according to the present invention is a transmission device of a position detection system that receives an ultrasonic signal transmitted from a transmission device by a reception device and detects the position of the transmission device, and is based on a pseudo-random signal having high autocorrelation. Means for transmitting the modulated first ultrasonic signal, means for simultaneously transmitting the electromagnetic wave signal indicating the transmission timing, and the second ultrasonic signal modulated based on the pseudo-random signal selected by the receiver. Including a different pseudo-random signal for each transmission cycle.

  A receiving device according to the present invention is a receiving device of a position detection system that receives an ultrasonic signal transmitted from a transmitting device and detects the position of the transmitting device, and has high autocorrelation transmitted from the transmitting device. The first ultrasonic signal modulated by the pseudo-random sequence data is received, the model waveform of the ultrasonic wave modulated by the same pseudo-random signal as the pseudo-random signal is generated, and the correlation with the received ultrasonic signal is generated. Means for selecting a plurality of corresponding pseudo-random signals from the smaller secondary peak of the correlation value that appears when the ultrasonic signal partially matches the pseudo-random signal model waveform; The second ultrasonic signal modulated based on the electromagnetic wave signal to be transmitted and the pseudo random signal selected by the receiving device is received, and the second ultrasonic signal and the pseudo random signal are received. The arrival time of the ultrasonic signal is specified by executing correlation processing with the ultrasonic model waveform modulated by, and the propagation time of the ultrasonic wave is calculated from the arrival time of the electromagnetic wave signal and the specified arrival time Means, and means for calculating the position of the moving body based on the calculated ultrasonic propagation time and the interval length between the ultrasonic receiving means.

  In the position detection method according to the present invention, a) a step of transmitting an ultrasonic signal modulated based on a pseudorandom signal having a high autocorrelation from a transmission unit of a moving body, and b) a reception unit receiving the ultrasonic signal, Generating a model waveform of an ultrasonic wave modulated by a pseudo-random signal, executing correlation processing between the model waveform and the received ultrasonic signal, and detecting a correlation waveform; c) for different pseudo-random signals, A step of detecting a plurality of correlation waveforms, and selecting a plurality of corresponding pseudo-random signals from the smaller secondary peak appearing in each correlation waveform when the model waveform and the received ultrasonic signal partially match, and d) step An electromagnetic wave including an ultrasonic signal modulated based on the pseudo-random signal selected in (c), a trigger signal indicating transmission timing, and data defining the pseudo-random signal And e) transmitting an ultrasonic model waveform modulated by a pseudo-random signal from data that receives the electromagnetic wave signal and defines a pseudo-random signal included in the electromagnetic wave signal; Generating step, f) receiving an ultrasonic signal, calculating a correlation value between the received ultrasonic signal and the ultrasonic model waveform generated in step (e), and g) the calculated ultrasonic wave. And calculating the position of the moving body based on the propagation time and the interval length between the ultrasonic receiving means, and step (d) uses a pseudo-random signal that is different for each transmission period.

  The position detection program according to the present invention executes a process of transmitting an ultrasonic signal modulated based on a pseudo-random signal having high autocorrelation from a transmission unit of a mobile body to a computer constituting a transmission device provided in the mobile body. Then, the computer constituting the receiving apparatus receives the ultrasonic signal, generates an ultrasonic model waveform modulated by the pseudo-random signal, and performs correlation processing between the model waveform and the received ultrasonic signal. When the correlation waveform is detected and multiple correlation waveforms are detected for different pseudo-random signals and the model waveform and the received ultrasound signal partially match, the secondary peak that appears in each correlation waveform is smaller And processing for selecting a plurality of corresponding pseudo-random signals from the computer, and the computer constituting the transmission apparatus performs modulation based on the selected pseudo-random signals. A computer that constitutes a receiving apparatus by executing a process of simultaneously transmitting an ultrasonic signal, a trigger signal indicating transmission timing, and an electromagnetic wave signal including data defining the pseudo-random signal from a moving body at regular intervals A process of generating an ultrasonic model waveform modulated by a pseudo random signal from data defining the pseudo random signal included in the electromagnetic wave signal and receiving the ultrasonic signal, and receiving the ultrasonic signal And a process for calculating the position of the moving body based on the calculated ultrasonic propagation time and the interval length between the ultrasonic receiving means. In the transmission of the ultrasonic signal from the transmission device, a different pseudo random signal is used for each transmission cycle.

  According to the present invention, it is possible to accurately calculate the propagation time of the direct wave that reaches the earliest from the ultrasonic wave transmission source without being affected by the reflected wave of the ultrasonic signal.

It is a block diagram which shows the structure of the transmission part of the position detection system by the 1st Embodiment of this invention, and a receiving part. It is a figure which shows the example of the ultrasonic M series data modulated by the phase modulation which allocated 1 period per bit. It is a figure which shows the example of the received ultrasound waveform stored in the memory of the receiving part of the position detection system by the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the transmission part of the M sequence selection mode in the position detection system by the 1st Embodiment of this invention. It is a flowchart which shows operation | movement of the transmission part in ultrasonic propagation measurement mode. It is a flowchart which shows operation | movement of the receiving part in the position detection system by the 1st Embodiment of this invention. It is a figure which shows a correlation value waveform in case M series is "100010011010111" in M series selection mode. It is a figure which shows a correlation value waveform in case M series is "000100110101111" in M series selection mode. It is a figure which shows a correlation value waveform in case M series is "100110101111000" in M series selection mode. It is a figure explaining the position calculation method of the electronic pen in the position detection system by the 1st Embodiment of this invention in two dimensions. It is a figure which shows operation | movement of the receiving part 200 in the ultrasonic propagation time measurement mode in the position detection system by the 1st Embodiment of this invention. It is a figure which shows the hardware structural example of the transmission part and receiving part in the position detection system by the 1st Embodiment of this invention.

Next, a first embodiment according to the present invention will be described in detail with reference to FIGS.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a position detection system according to a first embodiment of the present invention. In the following embodiments, a case where the position detection system according to the present invention is applied to an electronic pen system will be described.

  In FIG. 1, a position detection system using ultrasonic propagation time measurement according to the first embodiment of the present invention includes an electronic pen 10 as a movable object on which a transmitter 100 is mounted, and a predetermined position away from the electronic pen 10. A receiving device 20 including a receiving unit 200 installed in the device is provided. In this position detection system, selection of an M sequence to be used prior to measurement of ultrasonic propagation time (hereinafter referred to as an M sequence selection mode) is performed.

  The transmission unit 100 of the electronic pen 10 includes a control circuit 101, an M sequence generation circuit 102, an ultrasonic drive circuit 103, an ultrasonic transmitter 104, a reception trigger drive circuit 105, and a reception trigger transmitter 106.

The M series generated by the M series generation circuit 102 is a series generated by a characteristic polynomial, and is obtained by defining the characteristic polynomial and initial conditions. Details of the M series are described, for example, in Non-Patent Document 1 (Maki Satoshi, “M series and its application” (March 25, 1996, Shogodo)). For example, a data string having a sequence length of 15 bits generated by a fourth-order characteristic polynomial f (x) = x ⁴ + x + 1 is used. By changing the initial conditions, 15 different data strings in which the data sequence is cyclically shifted can be obtained.

  In the M-sequence selection mode, the control circuit 101 determines an M-sequence initial condition based on a characteristic polynomial determined in advance in each transmission cycle, and this initial condition is driven by the M-sequence generation circuit 102 and the reception trigger in a fixed transmission cycle. This is transmitted to the circuit 105.

  The M-sequence generation unit 102 generates an M-sequence coded bit string that is different for each transmission period in accordance with the initial condition sent from the control circuit 101.

  The ultrasonic drive circuit 103 supplies the M series data generated by the M series generation means 102 to the ultrasonic transmitter 104 as a drive signal for ultrasonic modulation.

  The ultrasonic transmitter 104 modulates an ultrasonic wave using the drive signal from the ultrasonic drive circuit 103 as a modulation signal, and sends an M-sequence modulated ultrasonic signal to space. In a preferred embodiment, a phase modulation method is used for ultrasonic modulation.

  On the other hand, the control circuit 101 instructs the reception trigger driving circuit 105 to generate a trigger pulse, and then supplies the reception trigger driving circuit 105 with initial condition data that encodes the above-described M-sequence initial conditions.

  In synchronization with the transmission timing of the ultrasonic transmitter 104, the reception trigger transmitter 106 is driven by the output of the reception trigger drive circuit 105 and sends a reception trigger signal from the electronic pen 10 to the space. This reception trigger signal is transmitted as an infrared signal which is an electromagnetic wave signal, for example.

  As will be described later, the M sequence is selected in the M sequence selection mode. In the subsequent ultrasonic propagation time measurement mode, the control circuit 101 determines the M-sequence initial condition in order for each transmission period from among a plurality of initial conditions determined in the M-sequence selection mode based on the M-sequence characteristic polynomial. Then, this initial condition is transmitted to the M-sequence generation circuit 102 and the reception trigger drive circuit 105.

  The M sequence generation unit 102 generates M sequence data according to the initial condition. The ultrasonic drive circuit 103 supplies the M series data to the ultrasonic transmitter 104 as a drive signal for ultrasonic modulation. The ultrasonic transmitter 104 modulates the ultrasonic wave using this drive signal as a modulation signal, and sends the M-sequence modulated ultrasonic signal to space.

  FIG. 2 shows an example of a waveform of a modulated wave phase-modulated by the M sequence as an example of encoding by the M sequence. Here, the waveform of an ultrasonic signal obtained by phase-modulating an ultrasonic wave having a constant frequency with a 15-bit M-sequence “100010011010111” is shown. The waveform shown in FIG. 2 corresponds to one cycle of the fundamental wave per bit (for example, 40 kHz), and is “0” in phase inversion and “1” in phase modulation. The wave has a length of 15 fundamental waves.

  On the other hand, the control circuit 101 instructs the reception trigger driving circuit 105 to generate a reception trigger signal, and then supplies the selected M-sequence initial condition data to the reception trigger driving circuit 105.

  In synchronization with the transmission timing of the ultrasonic transmitter 104, the reception trigger transmitter 106 is driven by the output of the reception trigger drive circuit 105 and sends a reception trigger signal from the electronic pen 10 to the space.

  The receiving unit 200 of the receiving device 20 includes one or more ultrasonic receivers 201, one or more sampling circuits 202 corresponding to the ultrasonic receiver 201, a reception trigger receiver 203, and a detection circuit 204. A memory 205 and a data processing circuit 206.

  The reception trigger receiver 203 receives a reception trigger signal from the electronic pen 10 and converts the reception trigger signal into an electric signal.

  When detecting the reception trigger signal from the output of the reception trigger receiver 203, the detection circuit 204 stores the arrival time of the reception trigger signal in the memory 205, and then detects M-sequence initial condition data and stores it in the memory 205. To do.

  The ultrasonic receiver 201 receives an ultrasonic signal transmitted from the electronic pen 10 and converts the ultrasonic signal into an electrical signal of an M-sequence code.

  The sampling circuit 202 samples the output of the ultrasonic receiver 201 at a constant sampling interval (ΔT), and sequentially stores the sampled ultrasonic waveform data in the memory 205. Further, the sampling circuit 202 performs filter processing for the purpose of noise removal as necessary.

  FIG. 3 shows an example of a waveform when an ultrasonic wave phase-modulated by a 15-bit M-sequence data string “100010011010111” is received. Here, the received waveform of the ultrasonic wave stored in the memory 205 with the sampling interval (ΔT) being 1/16 of the fundamental wave period of the ultrasonic wave is shown. The horizontal axis indicates the time when the reception trigger signal is received as “0”. When an ultrasonic wave having a fundamental frequency of 20 kHz is used, the basic period of the ultrasonic wave is 50 μsec, and the sampling interval is 3.125 μsec. The ultrasonic reception waveform (FIG. 3) stored in the memory 205 is a synthesized wave in which a direct wave or a reflected wave of the transmitted ultrasonic wave and noise are mixed.

  When the data indicating the arrival time of the reception trigger signal is stored in the memory 205, the data processing circuit 206 reads M-sequence initial condition data, and based on this initial condition (further characteristic polynomial if necessary), the M-sequence model A waveform is generated, and correlation processing is performed with the ultrasonic reception waveform stored in the memory 205.

  In the M-sequence selection mode, the reception trigger signal and the ultrasonic signal are repeatedly sent from the electronic pen 10. At that time, a different M sequence is used for each transmission. The data processing circuit 206 checks the degree of correlation of the ultrasonic wave with the M-sequence model waveform for each reception based on a plurality of secondary peaks generated when the shapes partially coincide with each other to check the optimum degree of the M-sequence. . The optimality of the M series having a smaller maximum secondary peak value is evaluated higher. The M series corresponding to the order of the largest secondary peak value is selected from all M series.

  In the ultrasonic wave propagation measurement mode, a reception trigger signal and an ultrasonic signal generated based on the selected M series are transmitted and correlation processing is performed. When the data processing circuit 206 detects the first peak of the correlation value, the elapsed time from the arrival time of the reception trigger signal to the time when the peak is detected, that is, the propagation time of the ultrasonic signal from the electronic pen 10 to the receiving unit 200. Is calculated.

(Operation of the embodiment)
Next, the operation of the control circuit 101 of the transmission unit 100 in the first embodiment of the present invention will be described with reference to the flowcharts of FIGS. The operation of the data processing circuit 206 of the receiving unit 200 will be described with reference to the flowchart of FIG.

  First, the case of the M-sequence selection mode will be described. In FIG. 4, the control circuit 101 selects an arbitrary M sequence from a plurality of M sequences different from each other, and determines an initial condition of the selected M sequence (step 301).

  The control circuit 101 supplies the determined initial condition to the M-sequence generation circuit 102 (step 302).

  When the control circuit 101 determines the M-sequence initial condition, the control circuit 101 instructs the reception trigger drive circuit 105 to generate a trigger pulse, and supplies initial condition data in which the initial condition is encoded. (Step 303).

  The M-sequence generation circuit 102 generates M-sequence data based on the initial conditions set by the control circuit 101 (step 304) and supplies it to the ultrasonic drive circuit 103.

  The ultrasonic drive circuit 103 generates a drive signal (modulation signal) for modulating ultrasonic waves from the M-sequence data supplied from the M-sequence generation circuit 102 (step 305).

  The reception trigger drive circuit 105 generates a reception trigger drive signal in response to a trigger pulse generation instruction from the control circuit 101 (step 306).

  When both drive signals are generated in steps 303 and 304, the reception trigger transmitter 106 and the ultrasonic transmitter 104 are simultaneously driven by the outputs of the reception trigger drive circuit 105 and the ultrasonic drive circuit 103, respectively. The ultrasonic signal modulated by the M series is transmitted from the electronic pen 10 to the space (step 307).

  When step 307 is executed, the control circuit 101 determines whether or not all M-sequence initial conditions have been checked in determination step 308. If transmission of all M sequences has not been completed, the control circuit 101 returns to step 301 and sets initial conditions for the next M sequence.

  Therefore, steps 301 to 307 are sequentially executed until transmission of all M sequences is completed, and a plurality of ultrasonic signals modulated by different M sequences are sequentially transmitted.

  Simultaneously with the transmission of each ultrasonic signal, initial condition data that encodes these M-sequence initial conditions and a plurality of reception trigger signals modulated by the trigger pulse are sequentially transmitted. In the case of the ultrasonic signal phase-modulated with the 15-bit M-sequence shown in FIG. 2, the processing of steps 301 to 307 is repeated 15 times to check 15 types of M-sequence data.

  When transmission of all M sequences ends (step 308), an M sequence to be used is selected from all M sequences (step 309).

  Next, the case of the ultrasonic propagation time measurement mode will be described. In FIG. 5, first, when the electronic pen 10 starts to operate (step 311), the control circuit 101 sequentially starts from the M-sequence initial conditions corresponding to the M-sequence selected in the M-sequence selection mode for each transmission cycle. One is determined (step 312), and the determined initial condition is supplied to the M-sequence generation circuit 102 (step 313).

  Further, when determining the M-sequence initial condition, the control circuit 101 supplies the trigger pulse and the M-sequence initial condition data to the reception trigger drive circuit 105 and instructs the generation of the reception trigger signal (Step 314).

  The M-sequence generation circuit 102 generates M-sequence data based on the supplied initial conditions (Step 315) and supplies it to the ultrasonic drive circuit 103.

  The ultrasonic drive circuit 103 generates a drive signal (modulation signal) for modulating ultrasonic waves from the M-sequence data supplied from the M-sequence generation circuit 102 (step 316).

  The reception trigger drive circuit 105 generates a reception trigger drive signal (step 317).

  When both drive signals are generated in steps 316 and 317, the reception trigger transmitter 106 and the ultrasonic transmitter 104 are simultaneously driven by the outputs of the reception trigger drive circuit 105 and the ultrasonic drive circuit 103, respectively. The ultrasonic signal modulated by the series is sent from the electronic pen 10 to the space (step 318).

  When step 318 is executed, the control circuit 101 drives a timer for determining the transmission cycle (step 319). When the control circuit 101 detects the next transmission time (step 320), it determines whether or not the operation of the electronic pen 10 has been completed (step 321). If the operation is in operation, the control circuit 101 returns to step 312. The initial condition of the M sequence is determined again at the start of the next transmission cycle, and the above operation is repeated.

  When the operation of the electronic pen 10 is completed, the control circuit 101 returns from step 321 to step 311.

  In the receiving unit 200, before the data processing circuit 206 executes the processing according to the flowchart of FIG. 6, the sampling circuit 202 samples the ultrasonic signal received by the ultrasonic receiver 201 at a constant sampling interval. Ultrasonic waveform data is stored in the memory 205. On the other hand, the detection circuit 204 detects a trigger detection signal and M-sequence initial condition data from the reception trigger signal received by the reception trigger receiver 203, and stores it in the memory 205.

  When reading the trigger detection signal from the memory 205, the data processing circuit 206 sets the value “t” (sampling time) of the sampling counter to “0” (step 401).

The M-sequence initial condition is set to the initial condition stored in the memory (step 402), and an M-sequence model waveform by phase modulation as shown in FIG. 2 is generated based on the initial condition (step 403). If the M sequence is being selected (step 404), the data processing circuit 206 sets the correlation start time (t _s ) (step 405), and proceeds to the correlation value calculation step 406.

In step 406, first, N received ultrasonic waveform data are read from the memory 205, and correlation calculation is performed with the model waveform generated in step 403, and the correlation value C is calculated based on the following equation (1). (T) is calculated and stored in the memory.

  In Equation 1, i is an integer value and the sampling time is a variable, N is the number of samplings of the model waveform, r (i) is the value of the model waveform at the sampling time i, and f (i + t) is the reception of the sampling time (i + t). The value of the waveform.

  It is determined whether or not a predetermined time has elapsed since the start of the correlation process (step 407). If not, the sampling time t is advanced by the unit amount 1 in step 408, and the process returns to step 406. This correlation calculation is executed until a predetermined time elapses, and a plurality of correlation values are stored in the memory 205.

When a predetermined time has elapsed from the start of correlation, it is determined whether or not the M series is being selected (step 409). If the M series is being selected, the maximum correlation value (primary value) is selected from the correlation values stored in the memory 205. A peak) is detected, and the time of occurrence is set as the ultrasonic arrival time (t _e ) (step 410).

における最大の相関値を検出する。

In step 411, the data processing circuit 206, based on the following equation (2), a period from the correlation start time to immediately before the ultrasonic wave arrival time, that is,

The maximum correlation value at is detected.

)の相関値C(t)の最大値を表す。例えば、この期間は到来した超音波の形状がモデル波形と部分的に一致する期間であり、この結果現れる相関値を副次ピークと称する。t_sおよびt_eは限定するものではなく、任意に定めてもよい。検出された最大副次ピークはメモリ２０５に格納される。Here, P (n) is a period before the ultrasonic arrival time of an initial condition n of a certain M series (

) Represents the maximum value of the correlation value C (t). For example, this period is a period in which the shape of the incoming ultrasonic wave partially matches the model waveform, and the correlation value that appears as a result is referred to as a secondary peak. t _s and t _e are not limited and may be arbitrarily determined. The detected maximum secondary peak is stored in the memory 205.

  Next, the ultrasonic data and all correlation values stored in the memory 205 are erased in step 412, and preparations for storing the next incoming ultrasonic data, trigger detection signal, and M-sequence initial condition data are made.

  The data processing circuit 206 determines whether or not the selection of all M sequences has been completed (step 413), and if not completed, returns to step 401 to detect the arrival of the next reception trigger signal and ultrasonic signal. The memory 205 is monitored and the trigger detection signal is read.

  If the selection of all M series has been completed, the data processing circuit 206 proceeds to step 414, and uses the M series corresponding to the secondary peak in ascending order of all secondary peaks stored in the memory 205. Select as the M series, end the M series selection mode, and return to step 401.

  As another embodiment of the present invention, when an M-sequence initial condition is determined by the control circuit 101 on the transmission side, an M-sequence bit string is automatically determined by a preset characteristic polynomial. It is also possible to make an array shifted by 1 bit without changing the.

  FIG. 7 shows the correlation value between the above-mentioned ultrasonic reception waveform and the 15-bit M-sequence model waveform of FIG. 2, and shows that the maximum secondary peak is detected at the point of the arrow in step 410.

  FIG. 8 shows a correlation value when using a 15-bit M-sequence data string shifted by 1 bit in the 15-bit M-sequence of FIG. 2, that is, an ultrasonic wave phase-modulated by “000100110101111”, and the maximum secondary peak is an arrow. It is detected at the point.

  FIG. 9 shows a correlation value when an ultrasonic wave phase-modulated by a 15-bit M-sequence data string “100110101111000” is used, and shows that the maximum secondary peak is detected at the point of the arrow.

  7 to 9, in all cases, the time point when the trigger pulse is received is “0”, and the sampling interval is 3.125 μsec. As long as the transmitter 100 and the receiver 200 are kept at a constant distance, the correlation value peak (main peak) at the time of arrival of the ultrasonic wave appears at the same time.

  Since the ultrasonic signal is attenuated depending on the propagation distance, it is necessary to set the number of necessary M sequences in consideration of how many cycles before the reception unit 200 may receive the ultrasonic signal.

  For example, when there is a possibility of receiving an ultrasonic signal up to three cycles before, it is necessary to obtain at least four different M sequences, and the possibility of receiving an ultrasonic signal up to one cycle before If there is, at least two different M sequences must be obtained. When two different M sequences are selected, the M sequences “000100110101111” and “100110101111000” having the smallest maximum secondary peak are selected as M sequences to be used in FIGS.

  Furthermore, as yet another embodiment of the present invention, a plurality of different codes (or indexes) are allocated corresponding to a plurality of different M sequences, and these codes and the corresponding M sequence initial conditions and characteristic polynomials are assigned. It is possible to provide the receiving unit 200 with an associated mapping table.

  In the M sequence selection mode, the transmitting unit 100 transmits a code (index) assigned to this M sequence by a reception trigger signal when transmitting one M sequence, and the receiving unit 200 receives the reference by referring to the mapping table. The M-sequence initial condition and the characteristic polynomial associated with the code are read out.

  By this method, the M-sequence initial condition and the characteristic polynomial can be transmitted to the receiving side with a small amount of information. Different M-sequence bit strings may be assigned corresponding to the mapping table.

  The M-sequence initial conditions determined as described above are set in the control circuit 101 of the transmission unit 100 and used in the ultrasonic propagation time measurement mode. Therefore, the transmission unit 100 cyclically changes the set plurality of M sequences for each transmission cycle, generates a reception trigger signal and an ultrasonic signal based on the M sequences, and sends them to the reception unit 200.

  In the ultrasonic propagation time measurement mode, when the reception trigger signal and the ultrasonic signal generated based on the selected M series are transmitted from the transmission unit 100, the data processing circuit 206 stores the trigger detection signal in the memory 205 in step 401. In step 402, the M-sequence initial condition is set to the initial condition stored in the memory, and an M-sequence model waveform is generated (step 403).

  Since it is not in the M-sequence selection mode, the data processing circuit 206 skips step 405 and proceeds to step 406 to read M-sequence ultrasonic data for one sample from the memory 205 as described above, and generate the M-sequence model generated in step 403. Correlation calculation with the waveform is executed, and a correlation value C (t) is calculated based on the equation (1) and stored in the memory 205.

  The data processing circuit 206 executes step 406 until a predetermined time elapses, and proceeds from step 407 to step 409. In step 409, since the M-sequence selection mode has already been completed, the processing from step 415 is executed.

  In step 415, the data processing circuit 206 selects a correlation value greater than or equal to a predetermined value greater than the value of the secondary peak from all correlation values calculated within a predetermined time, and detects a leading peak from the correlation value.

The sampling time (t _f ) at the time when the first peak is detected is set as the first peak detection time (step 416), and the ultrasonic wave propagation time (t _f
× ΔT) is calculated (step 417). Next, in step 418, all data is erased from the memory 205.

  Hereinafter, an example of processing by the data processing circuit 206 that detects the position of the electronic pen 10 as a moving body from the ultrasonic propagation time measured as described above will be described.

  FIG. 10 is a diagram illustrating a two-dimensional position calculation method between the electronic pen 10 and the ultrasonic receivers 201-1 and 201-2. In FIG. 10, P is the position coordinate value (x, y) in the xy coordinates on the drawable range of the electronic pen 10, and S1 and S2 are the positions of the ultrasonic receiving units 201-1 and 201-2, respectively. Yes.

  Further, d1 is a distance from the electronic pen 10 to the ultrasonic receiver 201-1 and d2 is a distance from the electronic pen 10 to the ultrasonic receiver 201-2. D is the distance from the origin when the center of the ultrasonic receivers 201-1 and 201-2 is the origin of the xy coordinates. Moreover, (alpha) has shown the angle which the straight line which connects the electronic pen 10 and the ultrasonic receiver 201-1 makes with an x-axis.

  Here, the ultrasonic propagation times calculated based on the ultrasonic signals received by the ultrasonic receivers 201-1 and 201-2 are t1 and t2, respectively, and the sound velocity is A.

  The distances d1 and d2 can be calculated as d1 = A × t1 and d2 = A × t2. Since the relationship shown in FIG. 10 is established between the distance (2D) between the ultrasonic receivers 201-1 and 201-2 and the distances d1 and d2, the position (x, y) of the electronic pen 10 is established. ) Can be obtained by calculation.

  In addition, it is possible to specify a three-dimensional position by using three or more ultrasonic receivers.

  FIG. 11 is a diagram for explaining the operation of the receiving unit 200 in the ultrasonic propagation time measurement mode. In each measurement period, the reflected wave of the previous period is also received in addition to the direct wave, but the reflected wave of the previous period and the M series of the current period can be obtained by using M-sequence ultrasonic waves having a small secondary peak. Even if the peak of the cross-correlation value with the model waveform overlaps with the secondary peak, the peak of the direct wave can be detected.

  On the other hand, in the M-sequence selection mode, each time the reception device 20 receives the reception trigger signal and the ultrasonic signal, the correlation value between all the M-sequence model waveforms used for the ultrasonic signal is obtained. Check the cross-correlation value. At that time, M-sequence data with a smaller cross-correlation value peak value is evaluated higher, and the M-sequence (initial stage) that forms a combination of M-sequences with respect to the cross-correlation value from the smaller cross-correlation value peak of all M sequences. Condition) may be assigned as the M sequence to be used.

  Further, a combination having a low cross-correlation value may be selected from the M sequences having a small secondary peak and assigned as the M sequence to be used.

(Effects of the first embodiment)
According to the first embodiment described above, by using M-sequence ultrasound with a small secondary peak, the peak of the cross-correlation value between the reflected wave of the previous cycle and the M-sequence model waveform of the current cycle Since it is possible to detect the peak of the direct wave even if the secondary peaks overlap, the propagation time of the direct wave that reaches the earliest from the ultrasonic wave source can be reduced without being affected by the reflected wave of the ultrasonic signal. It is possible to calculate accurately.

  Here, a hardware configuration example of the transmission unit 100 of the electronic pen 10 and the reception unit 200 of the reception device 20 will be described with reference to FIG.

Referring to FIG. 12, the transmission unit 100 and the reception unit 200 can be realized by a hardware configuration similar to that of a general computer device. Main components such as a CPU (Central Processing Unit) 401 and a RAM (Random Access Memory) are provided. A main memory unit 402 used as a data work area and a temporary data save area, a communication unit 403 functioning as a transmitter and receiver of electromagnetic wave signals and ultrasonic signals, an input device 405, an output device 406, and a memory An input / output interface unit 404 that is connected to the apparatus 407 and transmits / receives data, and a system bus 408 that connects the above-described components to each other are provided. The storage device 407 is, for example, a ROM (Read
Only Memory), a hard disk device including a non-volatile memory such as a magnetic disk and a semiconductor memory.

  In the position detection system according to the present embodiment, a circuit component that is a hardware component such as an LSI (Large Scale Integration) in which a position detection program that realizes the function of each unit shown in FIG. As a matter of course, the operation is realized in hardware, the position detection program is stored in the storage device 407, and the program is realized by loading the program into the main storage unit 402 and executing it by the CPU 401. It is also possible to do.

  The present invention has been described above with reference to preferred embodiments and examples. However, the present invention is not necessarily limited to the above embodiments and examples, and various modifications can be made within the scope of the technical idea. Can be implemented.

  In each of the above embodiments, the case where the present invention is applied to an electronic pen system has been described. However, the present invention can be applied to a robot system. The position of the robot in the space can be detected by installing the transmitter on the robot and installing the receiver on the ceiling or wall of a certain space. By grasping the position of the robot in space, the robot can be controlled and used for collision avoidance.

  On the other hand, by installing the transmission device on a person or the like and installing the reception device on the ceiling or wall of a certain space, it can also be applied to uses such as flow line detection and position tracking in the space.

  So far, modulation by M sequence has been described, but it is not limited to M sequence as long as it is a pseudo-random signal having high autocorrelation and low cross-correlation with other sequences such as Gold sequence, for example. .

This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2008-191880 for which it applied on July 25, 2008, and takes in those the indications of all here.

Claims (42)

A moving body including a transmitter that transmits an ultrasonic signal modulated based on a pseudorandom signal having high autocorrelation;
Receiving the ultrasonic signal, generating an ultrasonic model waveform modulated by the same pseudo-random signal as the pseudo-random signal , executing correlation processing between the model waveform and the received ultrasonic signal, and generating a correlation waveform It detects, for different pseudo-random signal, the correlation waveform plurality detects, from the corresponding more sub following peaks that appear in the correlation waveform is small when the model waveform and the reception ultrasonic signal is partially coincident A receiver for selecting a plurality of the pseudo-random signals,
The transmitter is
Means for simultaneously transmitting an ultrasonic signal modulated based on the selected pseudo-random signal, a trigger signal representing transmission timing, and an electromagnetic wave signal including data defining the pseudo-random signal at regular intervals ;
The receiver is
The arrival time of the ultrasonic signal is specified by performing correlation processing between the ultrasonic signal and the ultrasonic model waveform modulated by the pseudo-random signal, and the arrival time specified as the arrival time of the electromagnetic wave signal Means for calculating the propagation time of the ultrasonic wave from the time,
Means for calculating the position of the moving body based on the calculated ultrasonic propagation time and the interval length between the ultrasonic receiving means;
The position detecting system characterized in that the means for simultaneously transmitting an ultrasonic signal and an electromagnetic wave signal at a constant cycle uses a pseudo-random signal that is different for each transmission cycle.   The position detection system according to claim 1, wherein the pseudo-random signal is an M series. The transmitter is
Transmitting an ultrasonic signal modulated by M-sequence data generated based on data defining an arbitrary M-sequence selected from a plurality of different M-sequences, and an electromagnetic wave signal including the data defining the M-sequence. The position detection system according to claim 2. The transmitter is
Electromagnetic wave transmission means for determining data for defining a transmission timing and an M-sequence for each transmission cycle, and transmitting an electromagnetic wave signal including a trigger signal indicating the transmission timing and data for defining the M-sequence to a space;
An ultrasonic transmission means for generating an M-sequence waveform based on data defining an M-sequence determined for each transmission period, and transmitting an ultrasonic signal of the M-sequence waveform to the space simultaneously with the electromagnetic wave signal;
The receiver is
Ultrasonic receiving means for receiving the transmitted ultrasonic signal and outputting an M-sequence waveform;
Detecting means for detecting data defining the trigger signal and the M-sequence from the received electromagnetic wave signal;
A storage circuit for storing data defining the M-sequence detected by the detection means and an M-sequence waveform output by the ultrasonic reception means;
The data defining the M series is read from the storage circuit, the M series model waveform is generated, the stored M series waveforms are sequentially read out, the correlation value is calculated with the M series model waveform, and the calculated correlation value The first correlation peak value is detected, the ultrasonic propagation time is determined from the time when the trigger signal is received and the detection time of the correlation peak value, and the interval length between the ultrasonic propagation time and the ultrasonic receiving means is determined. The position detection system according to claim 2, further comprising: a data processing circuit that calculates a position of the moving body based on the position. The position detection system according to claim 3 or 4, wherein the data defining the M series included in the electromagnetic wave signal is M series initial condition data. The position detection system according to claim 3 or 4, wherein the data defining the M series included in the electromagnetic wave signal includes an M series characteristic polynomial and initial condition data.   The position detection system according to claim 2, wherein the ultrasonic signal is phase-modulated by M-sequence data.   The position detection system according to claim 1, wherein infrared light is transmitted as the electromagnetic wave signal.   The position detection system according to claim 1, wherein the moving body is an electronic pen.   The position detection system according to claim 1, wherein the moving body is a robot. A transmitter for transmitting an ultrasonic signal modulated based on a pseudorandom signal having high autocorrelation; and receiving the ultrasonic signal, generating a model waveform of an ultrasonic wave modulated by the pseudorandom signal, and Correlation processing is performed between the waveform and the received ultrasonic signal to detect the correlation waveform, and multiple correlation waveforms are detected for different pseudo-random signals, and the model waveform and the received ultrasonic signal partially match And a receiving device that selects a plurality of the corresponding pseudo-random signals from the smaller secondary peak that appears in each correlation waveform when the transmitting device of the position detection system,
Means for simultaneously transmitting an ultrasonic signal modulated based on the selected pseudo-random signal, a trigger signal representing transmission timing, and an electromagnetic wave signal including data defining the pseudo-random signal at regular intervals ;
The transmitting device characterized in that the means for simultaneously transmitting an ultrasonic signal and an electromagnetic wave signal at a constant cycle uses a pseudo-random signal that differs at each transmission cycle.   The transmission apparatus according to claim 11, wherein the pseudo-random signal is an M sequence.   Transmitting an ultrasonic signal modulated by M-sequence data generated based on data defining an arbitrary M-sequence selected from a plurality of different M-sequences, and an electromagnetic wave signal including the data defining the M-sequence. The transmission device according to claim 12, characterized in that: The transmission apparatus according to claim 13 , wherein the data defining the M series included in the electromagnetic wave signal is M series initial condition data. 14. The transmission apparatus according to claim 13 , wherein the data defining the M series included in the electromagnetic wave signal includes an M series characteristic polynomial and initial condition data.   The transmission apparatus according to any one of claims 12 to 15, wherein the ultrasonic signal is phase-modulated by M-sequence data. The transmission device according to claim 13, wherein infrared light is transmitted as the electromagnetic wave signal. The reception device of the position detection system that receives an ultrasonic signal transmitted from a transmission device by a reception device and detects the position of the transmission device,
Receiving said ultrasonic signal modulated by the data of high pseudo-random sequence of autocorrelation transmitted from the transmission device to generate the pseudo random signal ultrasonic waves modulated by the same pseudo-random signal and a model waveform, Correlation processing is executed between the model waveform and the received ultrasonic signal to detect a correlation waveform, a plurality of correlation waveforms are detected for different pseudo-random signals, and the model waveform and the received ultrasonic signal are partially means for selecting a plurality of corresponding said pseudo-random signals from more sub following peaks that appear in the correlation waveform is small when the match,
The transmitting device uses the pseudo random signal which is different for each transmission cycle from the simultaneously transmitted at fixed intervals, and the modulated ultrasound signal on the basis of the pseudo random signal said selected trigger signal and said representative of the transmission timing receiving an electromagnetic wave signal including data defining a pseudo-random signal, the arrival of the ultrasonic signal by performing a correlation process with the ultrasonic model waveform modulated by the pseudo random signal and the ultrasonic signal Means for specifying time, and calculating the propagation time of the ultrasonic wave from the arrival time of the electromagnetic wave signal and the specified arrival time;
A receiving apparatus comprising: means for calculating a position of the transmitting apparatus based on the calculated ultrasonic propagation time and an interval length between the ultrasonic receiving means.   The receiving apparatus according to claim 18, wherein the pseudo-random signal is an M sequence.   An ultrasonic signal modulated by M sequence data generated based on data defining an arbitrary M sequence selected from a plurality of different M sequences from the transmitter, and an electromagnetic wave signal including data defining the M sequence The receiving apparatus according to claim 19, wherein: 21. The receiving apparatus according to claim 20 , wherein the data defining the M series included in the electromagnetic wave signal is M series initial condition data. 21. The receiving apparatus according to claim 20 , wherein the data defining the M series included in the electromagnetic wave signal includes an M series characteristic polynomial and initial condition data.   The receiving apparatus according to any one of claims 19 to 22, wherein the ultrasonic signal is phase-modulated by M-sequence data.   The receiving device according to any one of claims 18 to 23, wherein infrared rays are transmitted as the electromagnetic wave signal. a) transmitting an ultrasonic signal modulated based on a pseudo-random signal having a high autocorrelation from a transmitter of the moving body;
b) The reception unit receives the ultrasonic signal, generates an ultrasonic model waveform modulated by the pseudo-random signal, executes correlation processing between the model waveform and the received ultrasonic signal, and generates a correlation waveform Detecting steps,
c) For a plurality of different pseudo-random signals, a plurality of the correlation waveforms are detected, and when the model waveform and the received ultrasonic signal partially match, the corresponding pseudo-random ones corresponding to the smaller secondary peaks appearing in the correlation waveforms. Selecting a plurality of signals;
d) An ultrasonic signal modulated based on the pseudo-random signal selected in the step (c), a trigger signal indicating transmission timing, and an electromagnetic wave signal including data defining the pseudo-random signal are transmitted at fixed transmission cycles. Simultaneously sending from the mobile;
e) receiving the electromagnetic wave signal and generating an ultrasonic model waveform modulated by the pseudo random signal from data defining a pseudo random signal included in the electromagnetic wave signal;
f) receiving the ultrasonic signal, and determining the arrival time of the ultrasonic signal by executing a correlation process between the received ultrasonic signal and the ultrasonic model waveform generated in step (e). Calculating the propagation time of the ultrasonic wave from the arrival time of the electromagnetic wave signal and the identified arrival time ;
g) calculating the position of the moving body based on the calculated ultrasonic propagation time and the interval length between the ultrasonic receiving means,
Step (d) uses a different pseudo-random signal for each transmission cycle.   The position detection method according to claim 25, wherein the pseudo-random signal is an M series. The transmitter is
Transmitting an ultrasonic signal modulated by M-sequence data generated based on data defining an arbitrary M-sequence selected from a plurality of different M-sequences, and an electromagnetic wave signal including the data defining the M-sequence. The position detection method according to claim 26, characterized in that: 28. The position detection method according to claim 27 , wherein the data defining the M series included in the electromagnetic wave signal is M series initial condition data. 28. The position detection method according to claim 27 , wherein the data defining the M series included in the electromagnetic wave signal includes an M series characteristic polynomial and initial condition data.   30. The position detection method according to claim 26, wherein the ultrasonic signal is phase-modulated with M-sequence data.   31. The position detection method according to claim 25, wherein infrared rays are transmitted as the electromagnetic wave signal.   32. The position detection method according to claim 25, wherein the moving body is an electronic pen.   32. The position detection method according to claim 25, wherein the moving body is a robot. In a computer constituting a transmission device provided in a moving body,
A process of transmitting an ultrasonic signal modulated based on a pseudo-random signal having a high autocorrelation from a transmission unit of a mobile object is executed.
To the computer that configures the receiver,
Receiving the ultrasonic signal, generating an ultrasonic model waveform modulated by the pseudo-random signal, executing correlation processing between the model waveform and the received ultrasonic signal, and detecting a correlation waveform; ,
A plurality of the correlation waveforms are detected for different pseudo-random signals, and the corresponding pseudo-random signals corresponding to the smaller secondary peak appearing in each correlation waveform when the model waveform and the received ultrasonic signal partially coincide with each other. Process to select multiple,
In the computer constituting the transmission device,
A process of simultaneously transmitting an ultrasonic signal modulated based on the selected pseudo-random signal, a trigger signal indicating transmission timing, and an electromagnetic wave signal including data defining the pseudo-random signal from the moving body at regular intervals And execute
In a computer constituting the receiving device,
Processing for receiving the electromagnetic wave signal and generating an ultrasonic model waveform modulated by the pseudo random signal from data defining a pseudo random signal included in the electromagnetic wave signal;
Receiving the ultrasonic signal , specifying the arrival time of the ultrasonic signal by executing a correlation process between the received ultrasonic signal and the generated ultrasonic model waveform, and the arrival time of the electromagnetic wave signal A process of calculating the propagation time of the ultrasonic wave from the identified arrival time ,
Based on the calculated ultrasonic propagation time and the distance between the ultrasonic receiving means, a process for calculating the position of the moving body is executed,
A position detection program that uses a pseudo-random signal that is different for each transmission period in the process of simultaneously transmitting an ultrasonic signal and an electromagnetic wave signal for every predetermined period .   The position detection program according to claim 34, wherein the pseudo-random signal is an M series. A computer constituting the transmitting device is
Transmitting an ultrasonic signal modulated by M-sequence data generated based on data defining an arbitrary M-sequence selected from a plurality of different M-sequences, and an electromagnetic wave signal including the data defining the M-sequence. 36. The position detection program according to claim 35, wherein: 37. The position detection program according to claim 36 , wherein the data defining the M series included in the electromagnetic wave signal is M series initial condition data. 37. The position detection program according to claim 36 , wherein the data defining the M series included in the electromagnetic wave signal includes an M series characteristic polynomial and initial condition data.   The position detection method according to any one of claims 35 to 38, wherein the ultrasonic signal is phase-modulated by M-sequence data.   40. The position detection program according to claim 34, wherein infrared rays are transmitted as the electromagnetic wave signal.   41. The position detection program according to claim 34, wherein the moving body is an electronic pen.   41. The position detection program according to claim 34, wherein the moving body is a robot.

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