JPH06201401A - Noise eliminator for sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] A small-scale digital circuit should be able to remove noise from sensors such as encoders. An output signal from a sensor is input to a shift register 4, and the input signal is incremented by using a time-up signal T of a timer 2 as a clock signal. The coincidence determination circuit 6 inputs the output signal of each stage of the shift register 4 and outputs the output terminal O
₂ , O ₃ and O ₄ determine the coincidence of the input signals D _{1 to} D ₃ .
For example, the output terminal O ₃ updates to the input signal of the input terminal D ₀ which is the latest sensor output signal when all the input signals of the input terminals D ₀ , D ₁ and D ₂ match, and outputs it. At this time, the previous output signal from the output terminal O ₃ is held and output continues. The selector 8 selects one of the signals according to the designated number of coincidence determinations and outputs it as the sensor value Sd. This sensor value Sd becomes a sensor value with noise removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for removing noise from output signals of sensors, which is generally realized by a digital circuit, like a noise removing device for an encoder in a digital LSI circuit.

[0002]

2. Description of the Related Art An encoder output signal is a pulse signal obtained by shaping an analog signal of a light receiving element into a rectangular wave with a reference voltage of a voltage comparator. At this time, when noise is present in the output of the light receiving element, a phenomenon occurs in which a rectangular wave pulse is broken by the noise. The present invention can be utilized, for example, to prevent such encoder output signals from pulse cracking. Regarding such an encoder in which pulse cracking occurs, generally, a low-pass filter by CR (capacitance and resistance) or a low-pass filter by DSP in a digital circuit is inserted to remove pulse cracking noise. Regarding common-mode noise (line noise, etc.), a circuit is provided to remove the common-mode noise by receiving the encoder output with a differential amplifier.

[0003]

A circuit using a CR or a differential amplifier is an analog circuit and is not suitable for an LSI. A circuit using a DSP also has a drawback that an AD converter is required and the circuit becomes large in scale. Therefore,
An object of the present invention is to make it possible to remove the noise of general sensors such as encoders with a small-scale digital circuit.

[0004]

SUMMARY OF THE INVENTION A noise removing device of the present invention is provided with a timer for outputting a time-up signal at each set time and an output signal of a sensor, and a time-out output signal of the timer as a clock signal. As an input signal, the output signal of each stage of the shift register is used as an input signal, the output signal of each stage is compared with the output signal of each stage of the shift register The signal is updated to the signal of the first stage when the signals of all the corresponding stages match, and in other cases, the match determination means that holds the output signal up to the previous time and the output signal of each output terminal of the match determination means And a selection unit for selecting and outputting the output signal of the specified number of comparison stages.

In a preferred mode, the timer is provided with means for changing the timer value, and the timer value is changed according to the noise condition of the sensor. In a further preferred aspect, it is further provided with control means for discriminating the presence or absence of noise detection from the output of the shift register with respect to the set timer value and shortening the timer set value until noise is detected. This noise removing device is preferably integrated and formed on a one-chip semiconductor substrate.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment. A timer value is set in the timer 2 so that the time-up signal T can be output at intervals at which noise can be detected, and the time-up signal T is output when the set timer value is reached. An output signal from a sensor such as a linear encoder is input to the shift register 4, and the input signal is incremented by using the time-up signal T of the timer 2 as a clock signal. The coincidence determination circuit 6 inputs the output signal of each stage of the shift register 4. For example, the first stage of the output signal of the shift register 4 to an input terminal D _0, that is, enter the latest value of the sensor output signal, to the input terminal D ₁ enter the next stage of the output signal of the shift register 4, input terminal D The output signal of the next stage of the shift register 4 is input to ₂ and the shift register 4 is input to the input terminal D _3.
Input the output signal of the next stage. Output terminals O _2, O _3, O ₄ of the match determining circuit 6 performs a matching determination of the input signal D ₁ to D _3. The output terminal O ₂ is an output terminal indicating that the number of coincidences for outputting the result of comparing the input signals of the input terminals D ₀ and D ₁ is 2 times, and both input signals of the input terminals D ₀ and D ₁ When they match, the input signal of the input terminal D ₀ which is the latest sensor output signal is updated and output, and the input terminals D ₀ and D ₁ are output.
When the input signals of ₂ and 3 do not match, the previous output signal of the output terminal O ₂ is held and output continues. The output terminal O ₃ is an output terminal that indicates that the number of coincidences that outputs the result of comparing the input signals of the input terminals D ₀ , D ₁ and D ₂ is 3, and that the input terminals D ₀ , D ₁ and When all the input signals of D ₂ match, the latest sensor output signal is updated to the input signal of the input terminal D ₀ and output, otherwise, the previous output signal of the output terminal O ₃ is held. And continue to output. The output terminal O ₄ is an output terminal that indicates that the number of coincidences that outputs the result of comparing the input signals of the input terminals D ₀ , D ₁ , D ₂ and D ₃ is 4, and the input terminal D ₀ , D ₁ , D ₂ and D ₃
When all the input signals of are matched, the latest sensor output signal is updated to the input signal of the input terminal D ₀ and output, otherwise, the previous output signal of the output terminal O ₄ is held and output. Keep doing

The selector 8 which is a selection means inputs the latest input signal from the shift register 4 and the output signals of the output terminals O ₂ , O ₃ and O ₄ of the coincidence judging circuit 6 and makes a designated coincidence. One of the signals is selected according to the number of determinations, and the selected signal is output as the sensor value Sd. The sensor value Sd is a sensor value with noise removed.

A noise removing operation according to the embodiment shown in FIG. 1 will be described with reference to FIG. The sensor output signal S is a shaped pulse signal, and it is assumed that the noise N causes a pulse breakup due to noise. The timer value is set so that the time-up signal T from the timer 2 is output at an interval at which the noise N can be detected. In the selector 8, among the output signals of the output terminals O ₂ , O ₃ , and O ₄ of the match determination circuit 6,
For example, it is assumed that the output signal of the output terminal O ₂ is set to be selected and output. Time-up signal T is T
Assuming that the sensor output signal S does not have noise until reaching ₁ , the latest sensor output signal input to the shift register 4 is adopted and output as the sensor value Sd. Since the noise N is input to the time-up signal T _{2 and} the output signal of the first-stage shift register output terminal D ₀ becomes a noise component, the match determination circuit 6 does not match the input signals of the input terminals D ₀ and D ₁ As the value Sd, the previous output is held and continues to be output. When the time-up signal T becomes T ₃ , the sensor output signal without noise is input to the shift register 4, but in the match determination circuit 6, the input signals of the input terminals D ₀ and D ₁ do not match, so the sensor value As the output Sd, the output signal of the previous two times, which is also held, is output. The sensor output signal without noise is input also in the time-up signal T ₄ , and in the coincidence determination circuit 6, the input signals of the input terminals D ₀ and D ₁ coincide, and the latest sensor output signal is adopted as the sensor value Sd. It

It is desirable that the timer value of the timer 2 be set to an appropriate value according to the noise situation. So timer 2
FIG. 3 shows the timer portion of the embodiment provided with the timer value preset register 10 for making the setting of the timer value variable, and FIG. 4 shows the timer value changing operation according to the embodiment of FIG. In FIG. 3, the timer value preset register 10 is loaded with the timer value to be changed so that the timer value preset register 10 can be dealt with when the noise situation changes. As a result, the timer 2 loads the new timer value using the time-up signal T as a load signal, and thereafter outputs the time-up signal T according to the changed timer value. In this way, when the timer value is variable, it is possible to remove noise according to the type and nature of noise.

FIG. 5 shows the noise eliminator of FIG. 1 in which the setting of the timer value is variable as shown in FIG.
12 shows an embodiment in which a memory device 14 such as a RAM 12 and a RAM is provided to remove noise as programmed in advance or to cause the CPU 12 to determine the noise condition and change the timer value. The CPU 12 sets the timer value and the number of coincidence determinations in the noise removing device 16, and the set value is also stored and held in the memory 14. The address signal of the CPU 12 is supplied to the noise eliminator 16 as a load signal for changing the timer value of the noise eliminator 16 and for changing the number of coincidence determinations, and as a read signal for fetching an output signal from the sensor.
4 is used as an address signal when writing data to or reading data from the memory 14.
Will also be supplied. The read / write signal from the CPU 12 is supplied to the noise removing device 16 and the memory 14.

The operation for changing the timer value according to the noise condition in the embodiment of FIG. 5 will be described with reference to FIG. First, a predetermined number of coincidence determinations and a timer value are set in the noise removing device 16. The output signal of the sensor is read in the reference state, and it is determined whether or not noise in the sensor output signal can be detected according to the set number of coincidence determinations and the timer value. When noise is not detected, the timer value of the noise eliminator 16 is changed so that the timer value is set to be long and the timer value is shortened.
The sensor value is read again by the changed timer value, and noise detection determination is performed. This operation is repeated so as to shorten the timer value until noise is detected, and when the noise is detected, the timer value is changed assuming that the timer value is properly set. After that, the actual detection by the sensor is performed.

FIG. 7 shows the operation of changing the timer value. In order to detect the noise N on the sensor output signal S _{0 in} the reference state for setting the timer value, noise is repeatedly detected by the time-up signal T (1) according to the initially set timer value. Done. T
In the case of (1), when the noise N is not reliably detected, the detection of the noise N is repeated by changing it to the time-up signal T (2) which shortens the interval of generation of the time-up signal. Further, when noise is not reliably detected even at T (2), the time-up signal T (3) is changed. Assuming that the noise N can be reliably detected by repeating the time-up signal T (3), the timer value is changed and set to the value at that time. In the operation of the embodiment, only the change of the timer value is explained, but the number of coincidence determinations can be changed so that noise can be detected appropriately.

[0013]

Since the noise eliminator of the present invention employs a digital circuit, the structure is simple and the integration is easy. Since the timer value and the number of coincidence determinations can be freely set, the present invention can be applied to any type of sensor noise. In addition, by making the timer value and the number of matching judgments programmable, and enabling them to be set automatically according to the noise situation, the range of application for various sensor noises will be further expanded, and the self-determination function will be improved. The noise removing device may be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment.

FIG. 2 is a waveform chart showing the operation of the embodiment.

FIG. 3 is a block diagram showing a timer portion of an embodiment in which setting of a timer value is variable.

FIG. 4 is a waveform diagram showing a timer value changing operation according to the embodiment of FIG.

FIG. 5 is a block diagram showing an embodiment in which a timer value can be automatically set according to a noise condition.

FIG. 6 is a flowchart showing an operation of setting a timer value in the embodiment of FIG.

7 is a waveform diagram showing an operation of setting a timer value in the embodiment of FIG.

[Explanation of symbols]

 2 timer 4 shift register 6 match determination circuit 8 selector 10 timer value preset register 12 CPU 14 memory device 16 noise eliminator

Claims (4)

[Claims] 1. A timer for outputting a time-up signal every set time, a shift register for inputting an output signal of a sensor, and stepping the input signal using the time-up output signal of the timer as a clock signal, The output signal of each stage of the shift register is used as an input signal, the signal of the first stage and the signal of the latter stage are compared, each output stage has an output terminal, and the output signal of each output terminal is the same for all the corresponding stages. When it is updated to the first stage signal, otherwise, the coincidence determination means that holds the output signal up to the previous time and the output signal of each output terminal of the coincidence determination means are input, and the output signal of the designated comparison stage number is input. A noise removing device for a sensor, comprising: selecting means for selecting and outputting. 2. The noise eliminator according to claim 1, wherein the timer is provided with means for changing a timer value, and the timer value is changed according to a noise condition of the sensor. 3. A control means is further provided for discriminating the presence or absence of noise detection from the output of the shift register with respect to the set timer value, and shortening the timer set value of the timer until noise is detected. The noise removing device according to claim 2. 4. The noise eliminator according to claim 1, wherein the noise eliminator is integrated and formed on a one-chip semiconductor substrate.