阅读说明：本技术 压力检测信号处理装置、发动机控制系统及程序 (Pressure detection signal processing device, engine control system, and program ) 是由 藤崎悟 福井克彦 于 2018-11-19 设计创作，主要内容包括：本发明的课题在于以简单的结构去除压电元件的漂移,而获得精度良好的压力检测信号。压力检测信号处理装置200包括：电荷放大器210,蓄积根据受压而由压电元件35产生的电荷,并输出对应的电压信号；漂移分量提取部230、240,通过对电压信号实施微分处理,而提取压电元件35的漂移分量；以及漂移校正部250,基于提取出的漂移分量生成用于去除所述漂移分量的校正信号,并反馈至电荷放大器的输入侧。(The invention aims to obtain a pressure detection signal with good precision by eliminating the drift of a piezoelectric element with a simple structure. The pressure detection signal processing device 200 includes: a charge amplifier 210 that accumulates the charge generated by the piezoelectric element 35 in response to the voltage applied thereto and outputs a corresponding voltage signal; drift component extraction units 230 and 240 that extract a drift component of the piezoelectric element 35 by performing differential processing on the voltage signal; and a drift correction unit 250 that generates a correction signal for removing the drift component based on the extracted drift component and feeds the correction signal back to the input side of the charge amplifier.)

1. A pressure detection signal processing device for performing signal processing on an output signal of a pressure sensor including a piezoelectric element that generates a charge corresponding to a pressure applied thereto, the pressure detection signal processing device comprising:

a charge amplifier that accumulates the charge and outputs a corresponding voltage signal;

a drift component extraction unit that extracts a drift component of the piezoelectric element by performing a differential process on the voltage signal; and

and a drift correction unit that generates a correction signal for removing the extracted drift component and feeds the correction signal back to the input side of the charge amplifier.

2. The pressure detection signal processing apparatus according to claim 1, said apparatus being characterized in that,

the drift component extraction section includes:

a differential processing unit that performs differential processing on the voltage signal; and

and a low-pass filter for extracting a predetermined low-frequency band component of the signal subjected to the differentiation processing.

3. The pressure detection signal processing device according to claim 1 or 2, characterized in that,

the drift correction unit includes:

a first difference calculation unit that obtains a first difference between a first target value set in advance and the extracted drift component; and

and a correction processing unit that generates the correction signal corresponding to the first difference and feeds the correction signal back to the input side of the charge amplifier.

4. The pressure detection signal processing apparatus according to claim 3, characterized by further comprising:

a second low-pass filter that extracts a signal representing a predetermined low-frequency band component of the voltage signal;

a second difference calculation unit that obtains a second difference between a preset second target value and the signal extracted by the second low-pass filter; and

a ratio processing unit for outputting a ratio signal obtained by performing a ratio process on the second difference

The correction processing unit generates the correction signal corresponding to an addition signal obtained by adding the proportional signal and the first difference, and feeds the correction signal back to the input side of the charge amplifier.

5. The pressure detection signal processing apparatus according to claim 4, characterized by further comprising:

a third difference calculation unit that obtains a third difference between the second target value and the signal extracted by the second low-pass filter; and

an integration processing unit for outputting an integration signal obtained by integrating the third difference

The correction processing unit generates the correction signal corresponding to an addition signal obtained by adding the first difference, the proportional signal, and the integral signal, and feeds the correction signal back to the input side of the charge amplifier.

6. The pressure detection signal processing device according to any one of claims 1 to 5, characterized in that,

a slice section is provided in a stage preceding the differential processing section and/or a stage preceding the second low-pass filter, and the slice section suppresses an input signal exceeding a predetermined value to the predetermined value.

7. The pressure detection signal processing apparatus according to claim 1, said apparatus being characterized in that,

the drift component extraction section includes:

a low-pass filter that extracts a signal representing a predetermined low-frequency band component of the voltage signal; and

a differential processing unit for outputting a differential signal obtained by applying differential processing to the signal extracted by the low-pass filter, and

the drift correction unit includes:

a first difference calculation unit that obtains a first difference between a preset first target value and the differential signal; and

a correction processing section that generates the correction signal and feeds back the correction signal to an input side of the charge amplifier,

the device comprises:

a second difference calculation unit that obtains a second difference that is a difference between a preset second target value and the signal extracted by the low-pass filter;

a ratio processing unit that outputs a ratio signal obtained by performing a ratio process on the second difference; and

an integration processing unit that outputs an integrated signal obtained by integrating the second difference,

the correction processing unit generates the correction signal based on an addition signal obtained by adding the first differential signal, the proportional signal, and the integral signal.

8. The pressure detection signal processing device according to any one of claims 1 to 7, characterized in that,

the charge amplifier includes an operational amplifier connected through a parallel circuit including a resistor and a capacitor, or through negative feedback of a capacitor.

9. An engine control system comprising:

the pressure detection signal processing device according to any one of claims 1 to 8; and

and a control unit for controlling the engine based on the output signal from the pressure detection signal processing device.

10. The pressure detection signal processing device according to any one of claims 2 to 8, characterized in that,

the digital signal processing unit changes a cutoff frequency of a low-pass filter constituting the drift component extracting unit according to a rotation speed of the engine.

11. A program for causing a pressure detection signal device to perform an extraction function and a correction function, the pressure detection signal device performing signal processing on an output signal of a pressure sensor including a piezoelectric element generating a charge corresponding to a pressure,

the extracting function is a function of extracting a drift component of the piezoelectric element by performing a differential process on the voltage signal from a charge amplifier that accumulates the electric charge and outputs a corresponding voltage signal,

the correction function is a function of generating a correction signal for removing the extracted drift component and feeding back to the input side of the charge amplifier.

12. The program according to claim 11, wherein

The correction function includes:

a difference calculation function of obtaining a difference between a preset target value and the drift component extracted by the extraction function; and

and a correction processing function of feeding back a correction signal corresponding to the difference to an input side of the charge amplifier.

Technical Field

The present invention relates to a pressure detection signal processing device, an engine control system, and a program for performing signal processing on a pressure detection signal from a pressure sensor including a piezoelectric element.

Background

Conventionally, a configuration has been proposed which includes a charge amplifier as a signal processing circuit for a pressure detection signal from a pressure sensor using a piezoelectric element that outputs a charge corresponding to the intensity of pressure. The charge amplifier is configured to: a feedback resistor and a feedback capacitor are connected in parallel to the operational amplifier to be connected in a negative feedback manner to the operational amplifier.

In the signal processing circuit, since the leakage current of the piezoelectric element becomes a drift of the pressure detection signal, a correction circuit or the like for removing the drift that is an influence of the drift is required.

As an example of the correction circuit, a circuit for removing the influence of the drift by a reset signal synchronized with the rotation signal of the crankshaft has been proposed (for example, see patent document 1). However, the reset timing detecting unit included in the correction circuit determines whether or not the predetermined reset timing is present in the intake stroke based on the output of the crank angle sensor, and outputs a reset signal to reset the output of the charge amplifier to zero when the predetermined reset timing is present. Therefore, the circuit system of the pressure detection signal processing circuit is complicated. Further, if the output accuracy of the crank angle sensor is not ensured, the resetting cannot be performed with high accuracy.

Therefore, a circuit structure in which a dc insulator is interposed between the piezoelectric element and the charge amplifier has been proposed. The dc insulator blocks a dc component and passes a pressure detection signal, and is configured by a capacitor (see, for example, patent document 2). That is, the leakage current of the piezoelectric element acts as a drift, but can be regarded as a dc component having a stable magnitude even for a relatively long time, and therefore the dc component is blocked by the capacitor.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2002-242750 (pages 3-6, FIG. 10)

Patent document 2: japanese patent laid-open publication No. 2009-115484 (pages 2-7, FIG. 1)

Disclosure of Invention

Problems to be solved by the invention

However, according to the structure of patent document 1, the capacitance of the capacitor as a dc insulator depends on the magnitude of the impedance of the piezoelectric element. Therefore, when the impedance of the piezoelectric element is small, there is a problem that the capacitance of the capacitor becomes large. Further, when the capacitance of the capacitor is increased, there is a problem that the mounting area of the capacitor on the surface of the electronic substrate is increased.

The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a pressure detection signal processing device, an engine control system, and a program, which can remove drift of a piezoelectric element with a simple configuration and obtain a pressure detection signal with high accuracy.

Means for solving the problems

In order to achieve the above object, a pressure detection signal processing device according to an embodiment of the present invention is a device that performs signal processing on an output signal of a pressure sensor including a piezoelectric element that generates an electric charge corresponding to a pressure applied thereto, and includes:

a charge amplifier that accumulates charges and outputs a corresponding voltage signal;

a drift component extraction unit that extracts a drift component of the piezoelectric element by performing differential processing on the voltage signal; and

and a drift correction unit that generates a correction signal for removing the extracted drift component and feeds the correction signal back to the input side of the charge amplifier.

In addition, the drift component extraction section may include:

a differential processing unit that performs differential processing on the voltage signal; and

and a low-pass filter for extracting a predetermined low-frequency band component of the signal subjected to the differentiation processing. The charge amplifier may be an operational amplifier connected in a parallel circuit including a resistor and a capacitor, or connected in negative feedback by a capacitor.

In addition, the drift correction section may include:

a first difference calculation unit that obtains a first difference between a first target value set in advance and the extracted drift component; and

and a correction processing unit that generates the correction signal corresponding to the first difference and feeds the correction signal back to the input side of the charge amplifier.

Further, the method for performing P control further includes:

a second low-pass filter for extracting a signal representing a predetermined low-frequency band component of the voltage signal;

a second difference calculation unit that calculates a second difference between a preset second target value and the signal extracted by the second low-pass filter; and

a ratio processing unit for outputting a ratio signal obtained by performing a ratio process on the second difference

The following structure may be adopted: the correction processing unit generates the correction signal corresponding to an addition signal obtained by adding the proportional signal and the first difference, and feeds the correction signal back to the charge amplifier output on the input side of the charge amplifier.

Further, the method further includes, for the I control:

a third difference calculation unit that calculates a third difference between the second target value and the signal extracted by the second low-pass filter; and

an integration processing unit for outputting an integration signal obtained by integrating the third difference

The following structure may be adopted: the correction processing unit generates the correction signal corresponding to an addition signal obtained by adding the first difference, the proportional signal, and the integral signal, and feeds the correction signal back to the input side of the charge amplifier.

A slice section for dividing an input signal exceeding a predetermined value into the predetermined value may be provided in a stage preceding the differential processing section and/or a stage preceding the second low-pass filter.

In addition, in order to perform proportional-Integral-derivative (PID) control,

the drift component extraction unit may include:

a low-pass filter for extracting a signal representing a predetermined low-frequency band component of the voltage signal; and

a differential processing unit for outputting a differential signal obtained by differentiating the signal extracted by the low-pass filter, and

the drift correction unit includes:

a first difference calculation unit that obtains a first difference between a preset first target value and the differential signal; and

a correction processing section for generating a correction signal and feeding it back to the input side of the charge amplifier,

the pressure detection signal processing device includes:

a second difference calculation unit that calculates a second difference that is a difference between a preset second target value and the signal extracted by the low-pass filter;

a ratio processing unit that outputs a ratio signal obtained by performing a ratio process on the second difference; and

an integration processing unit for outputting an integrated signal obtained by integrating the second difference,

the correction processing unit generates a correction signal based on an addition signal obtained by adding the first difference signal, the proportional signal, and the integral signal.

Further, in order to perform engine control using the pressure detection signal, an engine control system may be configured, the engine control system including: a pressure detection signal processing device; and a control unit for controlling the engine based on the output signal from the pressure detection signal processing device. The digital signal processing unit may change the cutoff frequency of the low-pass filter according to the engine speed.

A program according to another embodiment of the present invention is a program for causing a pressure detection signal device, which performs signal processing on an output signal of a pressure sensor including a piezoelectric element that generates a charge corresponding to a pressure applied,

the extracting function is a function of extracting a drift component of the piezoelectric element by performing a differential process on the voltage signal from a charge amplifier that accumulates charges and outputs a corresponding voltage signal,

the correction function is a function of generating a correction signal for removing the extracted drift component and feeding back to the input side of the charge amplifier.

Additionally, the correction function may include: a difference calculation function that calculates a difference between a target value set in advance and the drift component extracted by the extraction function; and a correction processing function of feeding back a correction signal corresponding to the difference to the input side of the charge amplifier.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided a pressure detection signal processing device capable of obtaining a pressure detection signal with high accuracy by eliminating drift of a piezoelectric element with a simple configuration, an engine control system, and a program.

Drawings

Fig. 1 is a schematic explanatory diagram showing the structure of an engine control system 300.

Fig. 2 is a functional configuration diagram of the ECU 100.

Fig. 3 shows the structure of the pressure detection signal processing device 200.

Fig. 4 is a schematic structural view of the pressure sensor 30.

Fig. 5 is a structural diagram of the charge amplifier 210.

Fig. 6 is a configuration diagram of the digital signal processing section 220 of the first embodiment.

Fig. 7 is a configuration diagram of the correction processing unit 252.

Fig. 8 is a structural diagram of the digital signal processing section 220 of the second embodiment.

Fig. 9 is a block diagram of another embodiment of the correction processing unit 252.

Fig. 10 is a structural diagram of a digital signal processing section 220 of the third embodiment.

Fig. 11 is a schematic explanatory diagram of PID control.

Fig. 12 is an explanatory diagram of the operation of the pressure detection signal processing device 200.

Fig. 13 is a graph showing a conventional example and a comparative example of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments of the present invention described below are examples, and the present invention is not limited to the embodiments described below, and various modifications and changes can be made to the embodiments described below.

(outline of the Engine control System 300)

Fig. 1 is a schematic configuration diagram of an engine Control system 300 including an engine 1 and an Electronic Control Unit (ECU) 100. The engine control system 300 performs engine control using the pressure detection signal obtained by the signal processing performed by the pressure detection signal processing device 200. The "pressure detection signal" is an output signal from the pressure sensor 30. In fig. 1, the spark plug is not shown for the sake of easy understanding.

The engine 1 includes a cylinder 2 and a piston 3 fitted in the cylinder 2 so as to be slidable in the vertical direction. One end side of a connecting rod 4 is connected to the piston 3, and the other end side of the connecting rod 4 is connected to a crankshaft 5. The flywheel 7 is rotatably coupled to an end portion of the crankshaft 5 on the transmission side, not shown. A magnet-resistive rotor 20, which is a protrusion made of a magnetic material, is formed in a predetermined angular region of the outer periphery of the flywheel 7.

The electromagnetic pickup 22 disposed opposite the crankshaft 5 outputs a pulse of a positive voltage when the reluctance rotor 20 is close, and outputs a pulse of a negative voltage when the reluctance rotor 20 is far. When pulse shaping is performed using a known pulse shaping circuit so that one rectangular pulse is output based on pulse signals of positive and negative polarities, one rectangular pulse is output every time the flywheel 7 rotates.

Therefore, in one cycle of "intake → compression → combustion → exhaust", the crankshaft 5 rotates 720 °, and thus a rectangular signal (engine rotation signal) of two pulses is output from the electromagnetic pickup 22 in one cycle. In this way, the electromagnetic pickup 22 serves as a crank angle sensor that detects the rotation angle of the crankshaft 5.

As a result, the rotation speed of the engine 1 can be obtained based on the engine rotation signal from the electromagnetic pickup 22. Further, the formation position of the reluctance rotor 20 on the outer periphery of the flywheel 7 is set to an appropriate angular region, and an ignition control signal is applied to the ignition plug based on the engine rotation signal from the electromagnetic pickup 22, whereby the timing of fuel ignition can be set to a desired timing. The desired timing is a timing corresponding to a Top Dead Center (TDC), a more advanced than Top Dead Center (BTDC) side, or a retarded Angle (ATDC) side.

An intake pipe 8 and an exhaust pipe 9 are connected to a cylinder head (cylinder head) above the cylinder 2. The inside of the intake pipe 8 becomes an intake passage for introducing fresh air from the outside into the combustion chamber 15. Further, an air cleaner (air cleaner)6 for removing dust and the like of fresh air, a throttle valve 24 for adjusting an intake amount of fresh air, an injector 40 for performing fuel injection, and the like are arranged in the intake passage from the upstream side. The timing of introducing the fresh air into the combustion chamber 15 is controlled by the opening and closing operations of the intake valve 12 biased in the valve closing direction by a spring, not shown.

The pressure sensor 30 detects a combustion pressure, which is a pressure in the combustion chamber 15, and outputs a pressure detection signal indicating the detected combustion pressure. The pressure sensor 30 is disposed on the top of the cylinder head in a posture in which the front end surface faces the inside of the combustion chamber. The mounting position of the pressure sensor 30 is not limited to the position shown in fig. 1. Similarly, a spark plug, not shown, is also disposed at an appropriate position of the cylinder head in a posture in which the tip end face thereof faces into the combustion chamber. The pressure sensor 30 may be provided integrally with the inside of the spark plug, or the pressure sensor 30 may be provided separately from the spark plug.

On the other hand, the inside of the exhaust pipe 9 serves as an exhaust passage for discharging the exhaust gas from the combustion chamber 15. The timing of the exhaust gas discharged from the combustion chamber 15 is controlled by the opening and closing operations of the exhaust valve 10 biased in the valve closing direction by a spring, not shown.

Signals from the electromagnetic pickup 22, the pressure sensor 30, and the like are input to the ECU 100 that controls the operation of the engine 1. A rectangular pulse signal corresponding to the engine rotation is input from the electromagnetic pickup 22. A pressure detection signal is input from the pressure sensor 30. On the other hand, the ECU 100 controls fuel injection of the injector 40, and controls ignition of the ignition plug.

Then, the pressure detection signal from the pressure sensor 30 is subjected to signal processing by the pressure detection signal processing device 200. The ECU 100 performs fuel injection control (injection amount, injection timing) by the injector 40 and ignition timing control by the spark plug based on the engine rotation signal and the pressure detection signal subjected to signal processing by the pressure detection signal processing device 200.

The reciprocating motion of the piston 3 in the vertical direction in the cylinder 2 is converted into the rotational motion of the crankshaft 5. The rotational motion of the crankshaft 5 is transmitted to the drive wheels via the transmission, and the vehicle (two wheels, four wheels) is advanced by repeating the stroke of "intake → compression → combustion → exhaust".

Fig. 1 shows an example of the configuration of the engine 1 and the ECU 100 that controls the engine 1, and for example, the ECU 100 may control the engine 1 by referring to the intake air temperature, the cooling water temperature, the oxygen concentration in the exhaust gas, the throttle opening, and the like of the engine 1 in addition to the engine rotation signal and the pressure detection signal.

(functional Structure of ECU 100)

Fig. 2 is a functional configuration diagram showing the functions of the ECU 100. The ECU 100 includes: memory unit 130, engine control unit 150, and pressure detection signal processing device 200. The storage unit 130 includes: a program 132, a table 134, a non-volatile storage area 136, and a work area 138. The work area 138 is a temporary storage area for temporarily storing various parameters during operation or the like, and the nonvolatile storage area 136 is a storage area for nonvolatile storage of various parameters or the like used for operation.

The engine control unit 150 obtains the fuel injection amount based on the pressure detection signal or the like output from the pressure detection signal processing device 200, and controls the injector 40 at the timing based on the engine rotation signal from the electromagnetic pickup 22 by using the fuel injection signal corresponding to the obtained fuel injection amount. Thereby, the injector 40 injects fuel in a fuel injection amount corresponding to the control from the engine control portion 150.

The engine control section 150 determines the ignition timing based on the engine rotation signal from the electromagnetic pickup 22, and controls the spark plug. In addition to the engine rotation signal from the electromagnetic pickup 22, the engine control unit 150 may control the ignition timing based on the pressure detection signal from the pressure detection signal processing device 200.

The functional structure of the ECU 100 shown in fig. 2 is merely an example. The ECU 100 may have a functional configuration other than this. The signal-processed pressure detection signal output from the pressure detection signal processing device 200 can be applied not only to fuel injection control and ignition timing control but also to detection and control of various parameters such as knock detection, misfire detection, and combustion speed calculation.

(construction of pressure detection Signal processing device 200)

Fig. 3 is a block diagram of the pressure detection signal processing device 200. The pressure detection signal processing device 200 includes a charge amplifier 210 and a digital signal processing unit 220. The digital signal processing section 220 includes: the Analog-to-Digital (AD) converter 205, the differential processor 230, the low-pass filter 240, and the drift corrector 250 are configured such that a correction signal from the drift corrector 250 is fed back to the input side of the charge amplifier 210. The output of the charge amplifier 210 is an output signal to the digital signal processing unit 220.

Fig. 4 is a schematic structural view of the pressure sensor 30. A diaphragm 32 receiving a pressure signal P and a piezoelectric element 35 sandwiched between a pair of electrodes 36 and 37 are built in a cylindrical case 31 of the pressure sensor 30. One of the electrodes 36 is used to connect a lead wire connected to ground, and the other electrode 37 is connected to a lead wire for transmitting a pressure detection signal Ps of the pressure sensor 30 to the next stage. The piezoelectric element 35 generates and outputs electric charges corresponding to the pressure intensity. The piezoelectric element 35 is made of a dielectric material such as zinc oxide (ZnO), for example.

When the diaphragm 32 applies pressure to the piezoelectric element 35 in accordance with the pressure intensity, the piezoelectric element 35 generates electric charge corresponding to the applied pressure, and outputs the electric charge to the charge amplifier 210 of the next stage. Thus, the electric charge corresponding to the pressure P is transferred to the charge amplifier 210 as the pressure detection signal Ps.

Fig. 5 is a structural diagram of the charge amplifier (current amplifier) 210. The charge amplifier 210 is configured to: a parallel circuit in which a resistor 212 having a resistance value R1 is connected in parallel with a capacitor 214 having a capacitance value C1 is connected to the operational amplifier 211 in negative feedback. The non-inverting terminal of the operational amplifier 211 is grounded and becomes a virtual ground state. In addition, the charge amplifier 210 may be configured such that only the capacitor 214 is negatively fed back and connected to the operational amplifier 211.

Since the input impedance of the operational amplifier 211 is ideally infinite, the charge from the piezoelectric element 35 is accumulated in the capacitor 214, and a voltage corresponding to the accumulated charge is generated across the capacitor 214. In this manner, the charge amplifier 210 accumulates the charge generated by the piezoelectric element 35 and outputs a corresponding voltage signal V (Q ═ C1 · V ("Q" is charge and "V" is output voltage).

The AD converter 205 shown in fig. 3 receives an analog output signal from the charge amplifier 210 and converts the received signal into a digital signal. The differentiation processing unit 230 performs differentiation processing on the digital signal subjected to analog-digital conversion by the AD conversion unit 205. The differentiation process performed by the differentiation process section 230 sequentially obtains the slope of the signal input to the differentiation process section 230.

When the digital sampling period by the AD converter 205 is "T" and the signals of "T, 2 · T, 3 · T, …, (n-1) · T, n · T" over time are "y (1), y (2), y (3), …, y (n-1), and y (n)", the differentiation process is realized by obtaining "y (2) -y (1)," y (3) -y (2), "…," and "y (n) -y (n-1)". That is, the differentiation process performed by the differentiation processing unit 230 corresponds to sequentially obtaining the difference of the digital signals.

The low-pass filter unit 240 extracts a drift component of the differential signal obtained by the differentiation processing performed by the differentiation processing unit 230. The low pass filter section 240 may be implemented by a low pass filter that extracts a drift component that slowly changes in the differentiated signal. As an example of the low-pass filter, a "moving average filter" may be used. When the digital sampling period is "T" and signals with time "T, 2 · T, 3 · T, …, (n-1) · T, n · T" are "y (1)," y (2), "y (3)," …, "y (n-2)," y (n-1), "y (n) (" y (1) + y (2) + y (3))/3), "…," "y (n-2) + y (n-1) + y (n))/3" are obtained, the "moving average filter" is realized. In this way, the differentiation processing unit 230 and the low-pass filter unit 240 cooperate with each other to function as a drift component extraction unit that extracts a drift component of the piezoelectric element 35.

That is, the moving average filter sequentially obtains the average value of n (n is an integer of 3 or more) digital signals before and after the digital signal of interest. When the value of n is set to a large value, the cutoff frequency can be lowered. For example, by linearly changing the value of n of the moving average filter according to the engine speed, stable signal processing can be realized regardless of the peak value.

More specifically, the engine speed and n may be set to be proportional, for example. Further, the following structure may be adopted: the engine speed is obtained from the combustion pressure indicated by the pressure detection signal obtained by the pressure detection signal processing device 200 performing signal processing. Further, the following configuration may be adopted: the engine speed is obtained from the engine control unit 150 by inputting an engine speed signal obtained by the engine control unit 150 to the pressure detection signal processing device 200.

The drift correction section 250 outputs a correction signal to be fed back to the input side of the charge amplifier 210. More specifically, the drift correction unit 250 performs the following feedback control: a voltage signal corresponding to a difference between a preset target value and the extraction signal of the low-pass filter unit 240 is subjected to digital-to-analog conversion, and a current signal corresponding to the analog voltage signal after the digital-to-analog conversion is applied to the input side of the charge amplifier 210 as a correction signal.

("digital signal processing section of first embodiment")

Fig. 6 shows a first embodiment of the digital signal processing unit 220. In the first embodiment, the following aspects are characterized: the drift is removed only by the differential control (D control). In the following description, the AD conversion unit 205 arranged at the previous stage of the digital signal processing unit 220 described with reference to fig. 6, 8, and 9 is not shown.

The digital signal processing section 220 shown in fig. 6 includes: a differentiation processing unit 230, a low-pass filter unit 240, a difference calculating unit 251, and a correction processing unit 252. The drift correction unit 250 shown in fig. 3 corresponds to the difference calculation unit 251 and the correction processing unit 252.

The low-pass filter unit 240 outputs an extracted signal, which is obtained by extracting a drift component from the differential signal output from the differential processing unit 230, to the difference calculating unit 251. The difference calculation unit 251 calculates the difference between the first target value set in advance and the extraction signal, and outputs the difference to the correction processing unit 252.

Fig. 7 is a configuration diagram of the correction processing unit 252 according to the first embodiment. The correction processing unit 252 includes a Digital to Analog (DA) conversion unit 254 and a Voltage and Current (VI) conversion unit 255. The DA converter 254 performs digital-to-analog conversion on the differential signal output from the differential calculator 251, and outputs the converted signal to the VI converter 255. The VI conversion section 255 performs voltage-current conversion (VI conversion) on the digital-analog converted differential signal, and applies the voltage-current converted current signal as a correction signal to the input side of the charge amplifier 210.

That is, the differential signal is digital-to-analog converted by the DA conversion section 254, and the VI conversion section 255VI converts the differential signal into a current signal corresponding to the digital-converted voltage signal and outputs to the charge amplifier 210.

In this way, the digital signal processing unit 220 according to the first embodiment shown in fig. 6 performs feedback control under Differential control (D control) by the Differential processing unit 230, the difference calculating unit 251, and the correction processing unit 252.

("digital signal processing section of second embodiment")

Fig. 8 shows a second embodiment of the digital signal processing unit 220. In the second embodiment, the following aspects are characterized: the PID control using the differential control (D control), the Proportional control (P control: Proportional control), and the Integral control (I control: Integral control) removes the drift and keeps the base line constant.

The digital signal processing unit 220 shown in fig. 8 further includes, in the first embodiment shown in fig. 6: low-pass filter unit 260, difference calculation unit 280, difference calculation unit 281, proportional processing unit 270, and integral processing unit 271.

The low-pass filter unit 260 outputs a signal obtained by extracting a component of a predetermined low frequency band of the voltage signal output from the charge amplifier 210. The difference calculating unit 280 calculates a difference between the preset second target value and the output signal of the low-pass filter unit 260, and outputs a difference signal indicating the calculated difference to the proportional processing unit 270. Similarly, the difference calculation unit 281 calculates the difference between the preset second target value and the output signal of the low-pass filter unit 260, and outputs a difference signal indicating the calculated difference to the integration processing unit 271. The differentiation processing unit 230, the low-pass filter 240, and the difference calculating unit 251 shown in fig. 8 are not changed from the differentiation processing unit 230, the low-pass filter unit 240, and the difference calculating unit 251 shown in fig. 6.

The proportional processing unit 270 outputs a signal obtained by multiplying the difference signal output from the difference calculating unit 280 by a proportional constant to the correction processing unit 252. The integration processing unit 271 outputs an integrated signal obtained by integrating the difference signal output from the difference calculating unit 281 to the correction processing unit 252. The output of the difference calculation unit 280 may be input to the integration processing unit 271 or the output of the difference calculation unit 281 may be input to the proportional processing unit 270. In this case, only one of the difference calculation unit 280 and the difference calculation unit 281 may be provided.

Fig. 9 is a configuration diagram of the correction processing unit 252 according to the second embodiment. The correction processing section 252 includes: an adding section 253, a DA conversion section 254, and a VI conversion section 255. The adder 253 adds the input signals to obtain an added signal, and the DA converter 254 performs digital-to-analog conversion on the added signal and outputs the converted signal to the VI converter 255. The VI conversion section 255 performs voltage-current conversion (VI conversion) on the addition signal subjected to the digital-analog conversion, and applies the current signal subjected to the voltage-current conversion to the input side of the charge amplifier 210 as a correction signal.

The correction processing unit 252 adds the signals from the difference calculating unit 251, the proportional processing unit 270, and the integral processing unit 271 to obtain an addition signal, performs digital-to-analog conversion on the obtained addition signal, and feeds back a current signal obtained by VI-converting the digital-to-analog converted signal to the input side of the charge amplifier 210 as a correction signal.

When the digital sampling period is "T" and the signals with time lapse "T, 2 · T, 3 · T, …, (n-1) · T, n · T" are "y (1), y (2), y (3), …, y (n-1), y (n)", the integration processing is realized by obtaining "y (1) · T, y (1) · T + y (2) · T, y (1) · T + y (2) · T + y (3) · T, …, y (1) · T + y (2) · T + y (3) · T + … + y · n · T". That is, the integration processing performed by the integration processing unit 271 corresponds to sequentially obtaining the total sum of the digital signals.

In this manner, the digital signal processing unit 220 of the second embodiment shown in fig. 8 is configured to: in addition to the feedback control in the differential control (D control), the feedback control in the proportional control (P control) and the integral control (I control) is performed by the proportional processing unit 270, the integral processing unit 271, the difference calculating unit 280, the difference calculating unit 281, and the correction processing unit 252. Therefore, since the proportional control (P control) and the integral control (I control) are performed in addition to the derivative control (D control), convergence to the target value is fast, and controllability can be further improved.

The "ac fluctuation" constituted by the differentiation processing unit 230 and the difference calculating unit 251 has an action of removing a drift component of the ac fluctuation from the application circuit system, "and the" reference voltage holding circuit system "constituted by the proportional processing unit 270, the integral processing unit 271, the difference calculating unit 280, and the difference calculating unit 281 has an action of: a baseline of the voltage as a reference of the pressure detection signal is maintained.

("third embodiment" digital Signal processing section)

Fig. 10 shows a third embodiment of the digital signal processing unit 220. The third embodiment is characterized by the following aspects: the signal processing is performed by one low-pass filter section 240. The digital signal processing section 220 shown in fig. 10 includes: low-pass filter unit 240, differentiation processing unit 230, difference calculating unit 251, difference calculating unit 280, difference calculating unit 281, proportional processing unit 270, integral processing unit 271, and correction processing unit 252. In the configuration of fig. 10, the output of the difference calculation unit 280 may be input to the integration processing unit 271, or the output of the difference calculation unit 281 may be input to the proportional processing unit 270. In this case, only one of the difference calculation unit 280 and the difference calculation unit 281 may be provided.

The low-pass filter unit 240 outputs an extraction signal obtained by extracting the drift component based on the voltage signal of the charge amplifier 210. The differential processing unit 230 outputs a differential signal obtained by performing differential processing on the extracted signal to the difference calculating unit 251. Further, the proportional control unit 270 outputs a proportional signal obtained by multiplying the input signal by a proportional constant to the correction processing unit 252. The integration processing unit 271 outputs an integrated signal obtained by integrating the input signal to the correction processing unit 252.

The difference calculating unit 251 calculates a difference between a preset first target value and the output signal of the differential processing unit 230, and outputs a difference signal indicating the calculated difference to the correction processing unit 252. Similarly, difference calculation unit 280 calculates a difference between a preset second target value and the output signal of low-pass filter unit 240, and outputs a difference signal indicating the calculated difference to proportional processing unit 270. The difference calculation unit 281 calculates a difference between a preset second target value and the output signal of the low-pass filter unit 240, and outputs a difference signal indicating the calculated difference to the integration processing unit 271.

The addition unit 253 of the correction processing unit 252 shown in fig. 9 obtains an addition signal obtained by adding the three signals output from the difference calculation unit 251, the proportion processing unit 270, and the integration processing unit 271, the DA conversion unit 254 performs digital-to-analog conversion on the addition signal, and the VI conversion unit 255 feeds back the current signal obtained by VI-converting the addition signal subjected to digital-to-analog conversion to the input side of the charge amplifier 210 as a correction signal.

In this way, by a simple configuration using one low-pass filter, feedback control such as differential control (D control), proportional control (P control), and integral control (I control) can be performed for the extraction of the drift component and the extraction of the base line.

Fig. 11 is an explanatory diagram illustrating an outline of PID control applied to the present invention. The output signal of the charge amplifier 210 is subjected to respective processes of proportional, integral, and differential by the P control unit 310, the I control unit 320, and the D control unit 330. The P control unit 310 outputs a proportional signal obtained by performing a proportional process on the difference between the second target value and the output signal of the charge amplifier 210 to the addition unit 340.

Similarly, the I control unit 320 outputs an integrated signal obtained by integrating the difference between the second target value and the output signal of the charge amplifier 210 to the addition unit 340, and the D control unit 330 outputs a differential signal indicating the difference between the first target value and a differential signal obtained by differentiating the output signal of the charge amplifier 210 to the addition unit 340. The adder 340 adds the respective signals, and outputs an addition signal indicating the addition result to the VI conversion unit 350.

Then, the VI conversion section 350 feeds back the current signal obtained by VI-converting the addition signal to the input side of the charge amplifier 210 as a correction signal. By performing the differential control, the drift component can be removed, and by performing the proportional control and the integral control, the pressure detection signal can be obtained in which the base line is maintained constant regardless of the atmospheric pressure, for processing in the ECU 100 and the like. In this way, by the PID control, a highly accurate pressure detection signal can be obtained.

In the P control unit 310, a multiplication signal obtained by multiplying the difference between the output of the charge amplifier 210 and the second target value by the proportional control gain (Kp) is output to the addition unit 340. Similarly, the following structure may be adopted: the I control unit 320 and the D control unit 330 multiply the corresponding integrated signal and differential signal by an integral gain (Ki) and a differential gain (Kd) and output the result to the addition unit 340. In this case, "Ki" and "Kd" may be constants other than "1.0". In order to improve controllability such as responsiveness of a control system, the "integral gain: ki "," differential gain: kd ". The gain adjustment method may be, for example, a Ziegler-nicols (Ziegler-Nichols) limit sensitivity method.

(operation)

Next, the operation of the digital signal processing unit 220 will be described with reference to fig. 12. Fig. 12(a) is an output signal from the charge amplifier 210 (signal at the position of symbol "a" of fig. 3). The output signal of the charge amplifier 210 is mixed with the integrated drift component and varies with the passage of time. (Signal at the position of symbol "a" of FIG. 3)

Then, the differential processing unit 230 performs differential processing on the signal shown in fig. 12 a to obtain a signal shown in fig. 12 b (a signal at the position of the symbol "b" in fig. 3). The differential processing section 230 functions to extract the drift component. That is, by performing the differentiation processing, the drift component before integration can be extracted.

Then, the low-pass filter unit 240 attenuates the frequency components higher than the cutoff frequency in the signal shown in fig. 12 b, and obtains a signal that varies with an extremely small alternating current around the base line (see fig. 12 c and the signal at the position of symbol "c" in fig. 3).

Then, the difference calculation unit 251 extracts the drift component as the difference between the first target value and the signal shown in fig. 12 (c). Here, for example, "0V" is set as the first target value. Next, fig. 12(d) shows a signal (signal at the position of symbol (d) in fig. 3) when the correction processing section 252 obtains a correction signal for feedback control based on the extraction signal indicating the drift component and feeds back the obtained correction signal to the input side of the charge amplifier 210. From the signal shown in fig. 12(d), it is known that the drift component has been removed.

In the proportional processing performed by the proportional processing unit 270 and the integral processing performed by the integral processing unit 271, the baseline voltage of the output signal from the charge amplifier 210 is corrected so as to be the set second target value. For example, when the second target value is set to "0.5 (V)", the base line voltage of the output signal from the charge amplifier 210 becomes "0.5 (V)". The parameters required for PID control, such as the first target value and the second target value, are stored in the nonvolatile memory 136 in advance, for example, in a nonvolatile manner.

According to the embodiment described above, the charge amplifier 210 accumulates the electric charges generated by the pressure applied to the piezoelectric element 35 and outputs a corresponding voltage signal, and the differential processing unit 230 outputs a differential signal obtained by performing differential processing on the voltage signal. Further, the low-pass filter section 240 extracts a drift component based on the differential signal.

Further, the drift correction unit 250 obtains a correction current signal for reducing the extracted drift component, and feeds back the obtained current signal as a correction signal to the input side of the charge amplifier 210, so that the drift of the piezoelectric element 35 can be removed, and a pressure detection signal with high accuracy can be obtained.

Fig. 13 is a comparative example of a pressure detection signal of a conventional example and a pressure detection signal subjected to signal processing of the present invention. Fig. 13(a) is a graph showing an output signal from the conventional pressure sensor 30, where "horizontal axis" represents time (sec) and "vertical axis" represents combustion pressure (Mpa). As is clear from fig. 12(a), the conventional pressure detection signal has a drift of the piezoelectric element 35, and thus the baseline changes with time.

On the other hand, fig. 13(b) is a graph showing the pressure detection signal subjected to the signal processing of the present invention, and the "horizontal axis" represents time (sec) and the "vertical axis" represents combustion pressure (Mpa). As can be seen from fig. 13(b), the baseline to which the pressure detection signal of the present invention is applied does not change with time. That is, a pressure detection signal in which the drift component is removed and the baseline is maintained at a certain high accuracy can be obtained. The pressure detection signal to which the present invention is applied facilitates various signal processing in the subsequent steps of the ECU 100 and the like.

As an example, the pressure detection signal processing Device 200 described above can be realized by a Programmable Logic Device (PLD) such as a Field Programmable Gate Array (FPGA). The CPU can also function as the digital signal processing unit 220 by executing the program 132 stored in the storage unit 130.

In addition, the following has been confirmed: if a slice section having a slice function of suppressing a signal exceeding a predetermined level when an input exceeds the predetermined level is provided between the charge amplifier 210 and the preceding stage of the "differentiation processing section 230 and the low-pass filter section 260", stable drift extraction can be performed regardless of the peak value. The slice portion may be realized by a circuit element such as a Zener diode (Zener diode), or may be realized by a program or the like that performs a clipping process.

Further, according to the pressure detection signal processing device 200 of the present invention, since the pressure detection signal in the ECU 100 or the like can be processed with high accuracy, the engine can be controlled with high accuracy based on the output signal from the pressure detection signal processing device 200.

The configuration of the correction processing unit 252 and the like described above are merely examples. For example, the difference and the current value corresponding thereto may be registered in advance in the table 134 in association, and the correction processing section 252 includes a current control section. Further, the following structure and the like may be adopted: the current control unit reads out the current values corresponding to the differences calculated by the difference calculation units 251, 280, and 281 from the table 134, and feeds back a correction signal, which is the read current values, to the input side of the charge amplifier, thereby controlling the operation of one or more variable current sources. In this case, the table 134 may be constructed for each difference calculation unit. Further, the added value and the current value corresponding thereto may be registered in advance in the table 134 in association with each other, and the current control section may feed back a correction signal, which is the current value corresponding to the added value indicated by the addition signal from the addition section 253, to the input side of the charge amplifier. Further, the following configuration may be adopted: the difference or added value is registered in advance in the table 134 in association with the voltage value, and the current control section reads out the voltage value corresponding to the difference or added value from the table 134 and outputs a voltage signal as the read voltage value to the DA conversion section 254.

Further, in the above description, the configuration example of the pressure detection signal indicating the pressure in the combustion chamber of the engine 1 is particularly shown, but the present invention is applicable not only to a gas but also to a pressure detection signal for another pressure receiving medium such as a fluid. Further, the following structure is provided: in engine control system 300 of fig. 1, pressure detection signal processing device 200 is provided in ECU 100, but the following system configuration may be adopted: the ECU 100 is provided separately from the pressure detection signal processing device 200, and the pressure detection signal is supplied to the ECU 100.

In the above description, the configuration example including the low pass filter units 240 and 260 has been described, but the present invention is not limited thereto, and a configuration not including the low pass filter units 240 and 260 may be adopted. However, it is preferable to have a configuration including the low-pass filter units 240 and 260 as described above, and by removing the high-frequency components related to the pressure fluctuation, the drift voltage and the baseline voltage can be extracted with higher accuracy, and feedback control with higher accuracy can be performed.

The processing function, the extraction function, the correction function, the difference calculation function, the correction processing function, and the like are realized by executing a program by a Processor such as a CPU or a Digital Signal Processor (DSP). Further, the present invention may provide a non-transitory recording medium on which the program is recorded. Examples of the non-transitory recording medium on which the program is recorded include semiconductor devices such as Read Only Memories (ROMs), optical devices such as Compact Discs (CDs) and Digital Versatile Discs (DVDs), and magnetic devices such as magnetic disks. As the recording medium, as long as it can be executed on a computer by reading a program stored in the recording medium by a reading unit, the kind and the like thereof are not limited.

Description of the symbols

1: engine

15: combustion chamber

30: pressure sensor

32: diaphragm

35: piezoelectric element

36. 37: electrode for electrochemical cell

100：ECU

200: pressure detection signal processing device

210: charge amplifier

211: operational amplifier

212: resistance (RC)

214: capacitor with a capacitor element

205: AD converter

220: digital signal processing unit

230: differential processing unit

240: low pass filter unit

250: drift correction unit

251: difference calculating part

252: correction processing unit

260: low pass filter unit

270: ratio processing section

271: integration processing unit

300: engine control system