JPH06260891A - Signal processor - Google Patents

Abstract

PURPOSE:To provide a signal processor which improves S/N without attenuating or abandoning a signal. CONSTITUTION:The output of a sensor 11 is delayed by time delay elements 2i (1<=i<=N) having a unit time T. Outputs of respective delay elements and the sensor output are added by adding elements 3i (1<=i<=N) to become the output of the signal processor. If the sensor output is a periodic signal and noise is a random signal, the result of the signal processing S/N ratio is improved by 10X(logi) dB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device, and more particularly to a signal processing device capable of improving the S / N ratio.

[0002]

2. Description of the Related Art In addition to signals, noise such as an ignition signal is usually superimposed on the output of a sensor mounted on a signal generating source, for example, a knocking sensor for detecting knocking of an internal combustion engine mounted on an automobile. In general, a filter having a coil and a capacitor as main elements is used to remove a noise component.

[0003]

However, if the selectivity Q is increased in order to improve the S / N ratio, ringing may occur and the S / N ratio may deteriorate.
Although a processing device using a wide-range resonance type sensor has been proposed to solve this problem, the signal itself is also attenuated.

Further, a processing device has been proposed in which the input of the output from the sensor is interrupted for a certain period at the timing when the signal generation source generates noise, but the signal itself was also discarded during the interruption. The present invention has been made in view of the above problems, and an object thereof is to provide a signal processing device capable of improving the S / N ratio without attenuating or discarding the signal.

[0005]

A signal processing device according to a first aspect of the present invention is a sensor for detecting a signal of a specific frequency, and a unit for which the signal detected by the sensor is an integral multiple of the reciprocal of the sensor's self-resonant frequency. A delay element for delaying time,
A first-stage signal processing element including an addition element that adds the output of the delay element and the signal detected by the sensor, a delay element that delays the output of the delay element by a unit time, and an output of the delay element And an output of the addition element of the previous stage, and an N-stage signal processing element that is a natural number of 2 or more and is cascade-connected and that is an N-th stage. A signal processing device that uses the output of the addition element of the eye as its output.

In the signal processing device according to the second aspect of the present invention, the delay time of the delay element is set to an integral multiple of the operating state quantity having the periodicity of the signal generation source to which the sensor is attached. In the signal processing device according to the third aspect of the present invention, the subtraction element that subtracts the output of the delay element from the output of the sensor is used instead of the addition element in the signal processing element of the first stage.

In the signal processing device according to the fourth aspect of the present invention, the number of stages of the signal processing devices to be cascade-connected is changed according to the operating state of the signal generating source.

[0008]

In the signal processing device according to the first invention,
The signal is multiplied by (N squared) by adding the signal that has been made into a periodic signal by delaying the sensor output by a unit delay time that is an integral multiple of the reciprocal of the self-resonant frequency of the sensor and the signal that has not been subjected to delay processing. However, the noise is N
Since it is only multiplied, the S / N ratio is improved by (10 × log N) dB by cascade-connecting the signal processing elements in N stages.

In the signal processing device according to the second aspect of the invention, the delay processing is performed in accordance with the noise generation timing of the signal generation source. In the signal processing device according to the third aspect of the invention, it is possible to reduce the delay time to half and improve the responsiveness. In the signal processing device according to the fourth aspect of the invention, the number of stages of the signal processing element is changed according to the operating state of the signal generation source, and the delay of the signal is reduced when the noise is small.

[0010]

1 is a block diagram of an embodiment of a signal processing device according to the present invention, which is used as a signal processing device for a knocking sensor mounted on an internal combustion engine of an automobile, and the processing device itself serves as a microcomputer system. Composed. That is, the knocking sensor 11 is directly attached to the internal combustion engine and detects the vibration of the cylinder block of the internal combustion engine when knocking occurs.

The output of the knocking sensor 11 is input to the signal processing unit 12 which is configured as a microcomputer system. The signal processing unit 12 is composed of a CPU 122, a memory 123, and an A / D converter 124 around a bus 121. The signal from the knocking sensor 11 is converted into digital information by the A / D converter 124, and the CP is converted according to the program stored in the memory 123.
It is processed in U122. Then, a known ignition angle control for suppressing knocking is executed based on the processed knocking signal.

FIG. 2 is a functional diagram of the first embodiment,
The output of the knocking sensor 11 is delayed by a delay element 2i (1 ≦ i ≦ N) cascade-connected to N stages. In the delay element 2i, the resonance frequency f _{0 of the} knocking sensor 11
The input signal is delayed by a unit time T that is an integral multiple (m / f ₀ ) of the reciprocal of Hz. That is, T = m / f ₀ is established.

In the addition element 3i (1≤i≤N),
The output of the delay element 2i and the addition element 3 (i-1) at the preceding stage are added. Here, the output signal of the knocking sensor 11 is x
_{If s} (t), the power Px _s of the signal is expressed by equation (1).

[0014]

[Equation 1]

Output signal x _{s of the} knocking sensor 11
A signal obtained by adding (t) i times for each cycle T, that is, an addition element 3i
The output of y _si (t) is expressed by equation (2).

[0016]

[Equation 2]

Here, the output signal x of the knocking sensor 11
_{Since s} (t) is a periodic function of the period T, the formula (3) holds.

[0018]

[Equation 3]

Therefore, the equation (2) can be transformed into the equation (4).

[0020]

[Equation 4]

Therefore, the power P _ysi of the output y _si (t) of the adder element 3i can be expressed by the equation (5).

[0022]

[Equation 5]

On the other hand, if the noise is x _n (t), the power P _xn of the noise can be expressed by equation (6).

[0024]

[Equation 6]

The mutual power R _xn of the noise itself is expressed by the equation (7)
If the noise is white noise, its value is “0”.

[0026]

[Equation 7]

Further, the noise x _n (t) is added i times in every cycle T, that is, the output of the adder element 3i is y _{ni as} expressed by equation (8).
It is represented by.

[0028]

[Equation 8]

Therefore, the power P _yni of the output y _ni (t) of the adder element 3i can be expressed by the equation (9).

[0030]

[Equation 9]

That is, according to the configuration of FIG. 2, as is clear from the equations (5) and (9), the power of the signal is multiplied by the square of the number of delay stages, whereas the power of the noise is only multiplied by the number of delay stages. In other words, the so-called S / N ratio is improved by the number of delay stages. Here, the delay time T of the delay element i is set to an integral multiple of the ignition cycle or the rotation cycle of the internal combustion engine, and the post-processing signal y _si (t) is subtracted from the output signal x _s (t) of the knocking sensor 11. It is possible to reliably remove the noise at the time of ignition, which is the largest noise.

FIG. 3 is a functional diagram of the second embodiment,
This is a signal processing device in which delay elements are connected in three stages. Figure 2
The difference is that the delay time of the delay element 2i is set to T / 2, and the subtraction element 311 is used instead of the addition element 31.
The point is to use. According to this configuration, the subtraction element 311
The same waveform as that of the output of the adder element 31 in FIG. 2 can be obtained as the output of the above, and since the delay time can be half, the rounding amount of the waveform by the time delay element can be reduced.

FIG. 4 is a frequency characteristic diagram of the second embodiment, in which the horizontal axis represents frequency and the vertical axis represents gain. That is, if the delay elements 2i are cascade-connected to 2 k power stages (two stages here), at least a frequency of 2 (n-1) f ₀ (n = 1, 2, 3 ...) That is, a resonance frequency f of the knocking sensor _{Since the} gain becomes zero at a frequency that is an even multiple of ₀ , it is possible to reliably block even-order harmonics and frequency noise components included in the knocking sensor output.

Here, a is a delay element in two stages (k = 1), b
Is four delay elements (k = 2), c is eight delay elements (k = 2)
3 is a frequency characteristic diagram when = 3). In addition, when the frequency characteristic diagram is expressed in more detail by using an equation, 2 (n−1) f ₀ ± f ₀ · L / 2 ^k−1 (k = 1, 2, 3, ..., L is 2 ^k It becomes a natural number up to ^-1 ).

Further, a changeover switch 41 is additionally provided, and the output of the signal processing device is changed to the subtracting element 311, the first and second adding elements 32 and 33 according to the operating state of the internal combustion engine.
By switching between the two, the number of stages of delay elements used is increased to improve the S / N ratio when a lot of noise is generated, and the number of stages of delay elements used is reduced to pass the delay elements when a lot of noise is generated. It is also possible to reduce the effect of time delay due to. In the present embodiment, the application of the knocking sensor to the signal processing device has been described above, but it is clear that the present invention is also applicable to the signal processing device of another type of sensor used in an environment where periodic noise is superimposed. Is.

[0036]

According to the signal processor of the first aspect of the present invention, the power ratio of the sensor output, which is a periodic signal, and the noise, which is a random signal, that is, the S / N ratio, is improved according to the number of stages of time delay. Is possible. According to the signal processing device of the second aspect of the present invention, the delay time of the time delay element is determined according to the operating state amount of the signal generating source, thereby reliably removing noise generated in synchronization with the operating state. Is possible.

According to the signal processing device of the third invention, not only the delay time of the delay element can be halved and the rounding amount of the signal can be reduced, but also the even harmonics. It is also possible to reduce noise. According to the signal processing device of the fourth aspect of the present invention, it is possible to improve the S / N ratio and reduce the time delay amount by switching the number of stages of the delay elements used according to the operating state.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment.

FIG. 2 is a functional diagram of the first embodiment.

FIG. 3 is a functional diagram of the second embodiment.

FIG. 4 is a frequency characteristic diagram of the second embodiment.

[Explanation of symbols]

 11 ... Sensor 12 ... Microcomputer 2i (1≤i≤N) ... Delay element 3i (1≤i≤N) ... Addition element 311 ... Subtraction element 41 ... Switch

Claims (4)

[Claims] 1. A sensor that detects a signal of a specific frequency, a delay element that delays the signal detected by the sensor by a unit time that is an integral multiple of the reciprocal of the self-resonant frequency of the sensor, and an output of the delay element. A first stage signal processing element including an adding element for adding a signal detected by the sensor, a delay element for delaying the output of the preceding delay element by the unit time, and an output of the delay element A signal processing device comprising an adder element for adding the output of an adder element in the preceding stage, and an N-stage signal processing element that is a natural number of 2 or more and is cascade-connected Signal processing device whose output is the output of the adding element of. 2. The signal processing device according to claim 1, wherein the delay time of the delay element is an integral multiple of an operating state quantity having a periodicity of a signal generation source to which the sensor is attached. 3. The signal processing device according to claim 1, wherein a subtracting element that subtracts the output of the delay element from the output of the sensor is used instead of the adding element in the signal processing element of the first stage. 4. The signal processing device according to claim 1, wherein the number of stages of the signal processing devices to be cascade-connected is changed according to an operating state of the signal generation source.