JP2667980B2 - Video output type pressure distribution sensor using high-speed scanning method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video output type pressure distribution sensor capable of observing a pressure distribution state as a picture image in real time by a video monitor or the like by using a high speed scanning method. It is a thing.

[Prior Art] Conventionally, in order to measure a pressure distribution, pressure detectors are two-dimensionally arranged, and measurement is performed by sequentially scanning each pressure detector. An example is shown in FIGS. 2A and 2B. Figure A
In this pressure distribution sensor, a large number of elongated electrodes 11, 12, ... And 21, 22, ... Are arranged on the upper and lower surfaces of the pressure-sensitive conductive rubber 10 whose resistance value changes according to pressure. Thus, the pressure-sensitive conductive rubber 10 is arranged as a pressure detector at each intersection of the upper and lower electrodes arranged in a matrix. FIG. 2B shows a circuit equivalent to the structure of the pressure distribution sensor.

Just arranging the pressure detectors as in such a pressure distribution sensor causes interference from a point other than the target measurement point. This will be described with reference to FIG. 2B above.

Now, assume that it is desired to measure the resistance between the upper and lower electrodes at point A at the time of scanning. However, when this is measured as the resistance between the electrode 12 and the electrode 22, an unnecessary path (wraparound) occurs as shown by a dotted line in FIG. 2B, and three points B ₁ , B ₂ , and B ₃ are pressed. Then, even if the point A is not pressed, the resistance between the electrode 12 and the electrode 22 decreases through the dotted path. Such a phenomenon occurs not only in the pressure-sensitive conductive rubber but also in other methods such as a pressure capacity converter.

As a basic method for preventing such wraparound, there is a method of inserting diodes 31 at all measurement points. The outline is shown in FIG. This method is used when possible paths B ₂ are cut in Figure 2 B, wraparound can be prevented. However, leakage resistance between the electrodes such as the electrodes 11 and 12 and between the electrodes 21 and 22 remains.

There is also a method in which each measurement point is completely independent to eliminate the leakage resistance between the electrodes. This circuit is shown in FIG. In this method, only one point becomes active at a certain time using the FET 32. In addition, there is a simple method that does not require the use of a diode or FET at each point.

FIG. 5 shows a method called a voltage mirror method.
This method uses an analog switch 33 to make a drive line not involved in a target measurement point (point Rs in FIG. 5) equipotential with an output voltage, thereby eliminating current due to sneak and leakage resistance. This method requires a circuit for generating an equipotential, and the response speed becomes slow due to this circuit.

There is a zero potential method as a method similar to the above method. This method is shown in FIG. This method is characterized in that the output circuit of the equipotential method is changed so that the potential applied to the scanning electrode becomes zero. In this case, it is sufficient to lower the zero potential instead of generating the equal potential, and the circuit is simplified. An analog switch 34 is arranged in each column to select a target column. However, the ON resistance Ron of the analog switch inserted in each column is several tens to several hundreds of ohms. Therefore, the current flowing through the measurement resistor Rs causes a voltage to be generated at the point A, which causes a measurement error. FIG. 7 shows the equivalent circuit. The resistors other than the measurement points in the selected column are connected to the ground, and R 'indicates the combined resistance. The output Vout is
Equation (1) is obtained.

From the equation (1), it is clear that the output is affected by the combined resistance R '. Since the combined resistance R' changes depending on the pressure distribution state, the resistance of the target measurement point can be accurately determined. I can't get the value. It is clear from equation (1) that there is no effect if the ON resistance of the analog switch is zero.

[Problems to be Solved by the Invention] The technical problem of the present invention is to realize accurate and high-speed measurement as compared with the conventional circuit system as described above.
Along with this, there is a need to obtain a video output type pressure distribution sensor that converts pressure distribution information into a video signal so that it can be observed in real time as an image on a video monitor or the like.

[Means for Solving the Problems] A video output type pressure distribution sensor according to the present invention for solving the above problems includes m × n pressure detectors whose electric resistance or capacitance is changed by pressure in m rows and n columns. Arranged at each intersection of the matrix electrodes, sending horizontal scanning signal and vertical scanning signal to the above electrodes, sequentially scanning each pressure detector at high speed, and outputting the pressure data of the pressure detector as an image image. In order to make the timing of the video signal, in the pressure distribution sensor, the inverting operational amplifier is connected to the scanning circuit of each column and the FET switch is connected to the operational amplifier to make the column selectable The vertical scanning signal and the horizontal scanning signal are sent to the high-speed scanning unit, and the pressure data extracted from the pressure detector selected by both scanning signals is converted into a video signal and output. It is characterized in further comprising a video signal converter for.

[Operation] According to the pressure distribution sensor described above, the pressure detectors arranged at the respective intersections of the matrix electrodes are sequentially scanned at high speed, and the mutual pressure detectors generated by the sneak of the current between the pressure detectors. The measured value from the pressure detector can be taken out accurately and at high speed while eliminating interference, and the pressure distribution information according to the magnitude of the electric resistance or capacitance changing in the pressure detector is converted into a video signal, The pressure distribution state can be observed in real time as an image image without image fluctuation on a monitor or the like.

[Embodiment] In the embodiment of the present invention shown in FIG. 1, the high-speed scanning section uses the zero-potential method as its basic principle, but the circuit system to be realized is different from the above-mentioned zero-potential method. This makes it possible to realize accurate and high-speed measurement as compared with the conventional various methods described above.

In the pressure distribution sensor shown in the figure, m × n pressure detectors 1 whose electric resistance or capacitance changes according to pressure are provided.
Is arranged at each intersection of matrix electrodes of m rows and n columns, and the measurement value from the pressure detector is scanned at high speed while eliminating mutual interference between the pressure detectors caused by the current sneak between the pressure detectors. I take it out by the method.

That is, the scanning circuit in the row direction is the same as the conventional one, but the inversion type operational amplifier 2 is connected to the scanning circuit in each column, and the input potential to this operational amplifier becomes virtually zero potential.
The conditions of the zero potential method are satisfied. Therefore, the analog switch as described in FIG. 6 is not required, and the same effect as the analog switch ON resistance in FIG. 6 is zero. Then, the FET switch 3 is arranged after the inverting operational amplifier,
By this, each column is selected.

According to such a method, scanning can be performed at high speed and with high accuracy. By the way, in the sensor with 64 × 64 matrix detectors prototyped to confirm the operation state this time, the scanning time available for each pressure detector is 500nse
Although the time is as short as c, it has been confirmed that high-speed and accurate scanning can be performed using this method without any practical problems.

The pressure distribution sensor of the present invention includes a video signal converter together with such a high-speed scanning unit.

The video signal conversion unit sends a vertical scanning signal and a horizontal scanning signal to the high-speed scanning unit in order to generate the timing of the video signal, and the pressure data extracted from the pressure detector selected by both scanning signals is converted into a video signal. It is converted to and output.

In the high-speed scanning unit, scanning synchronized with the vertical synchronization signal and the horizontal synchronization signal of the video signal is performed based on the signal from the video signal conversion unit.

For example, assume that the i-th row and the j-th column are selected. Then, the electrode potential Vi of the selected row becomes V, and the potentials of the other row electrodes become zero potential. Since the electrode potential in the column direction is always zero, there is no current flowing into the input side of the inverting operational amplifier in the j-th column other than that flowing from the electrode of the electrode potential Vi via r _ij , and the amount of current is Vi / r _ij . Since the input of the inverting operational amplifier is amplified so as to be virtually at zero potential, the output voltage Vj of the inverting operational amplifier in the j-th column is −
(Rf / r _ij ) × Vi, and the resistance value in the i-th column and the j-th row can be measured without interference with other portions. Since the resistance value r _ij and the pressure have a functional relationship, the pressure value can be easily calculated back from Vj. Further, since Vj is connected to the FET switch which is opened / closed by the scanning signal synchronized with the vertical synchronizing signal, only the measured voltage of Vj corresponding to the magnitude of the electric resistance changing in the pressure detector 1 is selected. This Vj is guided to the video signal converter via the buffer 4.

According to the above-described pressure distribution sensor, pressure distribution information can be observed with a video monitor, and the pressure distribution state can be observed easily and at high speed, and recording can be performed for a long time using a general household video recorder.

Further, in the conventional method of inserting a diode (Fig. 3), the diode is inserted in each pressure detector, and the detection surface cannot be made flexible, or if it is possible, it is a little. If a pressure-sensitive conductive rubber or the like is used as a pressure detector, the detection section can be made flexible and thin, and therefore, not only can the body pressure distribution of a chair, a bed or the like be measured, but the pressure distribution sensor can be used in an automobile. It is possible to load the video recorder and observe the pressure distribution between the driver's seat and the human body in the actual driving state.

As described above, the pressure distribution sensor can be effectively used in many fields where pressure distribution measurement is required.

[Advantages of the Invention] According to the video output type pressure distribution sensor of the present invention described in detail above, it is possible to realize accurate and high-speed measurement as compared with the conventional circuit system, and the electric resistance which changes in the pressure detector. Alternatively, the pressure distribution information corresponding to the size of the capacity is converted into a video signal, and the pressure distribution state can be observed in real time as an image image without image fluctuation on a video monitor or the like.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a video output type pressure distribution sensor according to the present invention, FIGS. 2A and 2B are perspective views showing a structure of a conventional pressure distribution sensor, and a circuit diagram equivalent to the structure of the pressure distribution sensor. FIG. 3 is a circuit diagram of a conventional example in which a diode is inserted in each pressure detector, FIG. 4 is a circuit diagram of a conventional example in which each pressure detector is completely independent, and FIG. 5 is called a voltage mirror system. FIG. 6 is a circuit diagram of a conventional example called a zero potential method, and FIG. 7 is an equivalent circuit diagram of a main part in the circuit diagram of FIG. 1 ... pressure detector, 2 ... inverting operational amplifier, 3 ... FET switch.

Claims (1)

(57) [Claims] 1. A m × n pressure detector whose electric resistance or capacitance changes depending on pressure is arranged at each intersection of matrix electrodes of m rows and n columns, and a horizontal scanning signal and a vertical scanning signal are applied to the electrodes. In the pressure distribution sensor that sends out a signal and sequentially scans each pressure detector at high speed and outputs the pressure data of the pressure detector as an image image, an inverting operational amplifier is connected to the scanning circuit of each column,
A high-speed scanning unit that connects a FET switch to the operational amplifier to make it possible to select a column, and sends a vertical scanning signal and a horizontal scanning signal to the high-speed scanning unit to make the timing of the video signal. A video output type pressure distribution sensor using a high-speed scanning method, comprising: a video signal conversion unit that converts pressure data taken out from a selected pressure detector into a video signal and outputs the video signal.