JP4006610B2 - Bump suppression filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the redundant control system in which a plurality of sensors having the same function are provided on the same object and a failure occurs, the present invention is applied to a redundant system control system that reduces fluctuation (this is called a bump) that occurs at the time of switching. Regarding filters.
[0002]
[Prior art]
Redundant control systems are used in devices that can lead to major accidents due to a single sensor failure, such as aircraft engines. As an example of this, there is a system in which a plurality of sensors having the same function are provided on the same object, and if one fails, the system is switched to another sensor.
[0003]
FIG. 4 shows a conventionally used sensor switching method. A switch connected to a plurality of sensors is switched by a selection signal, and a measurement value of one sensor is output. However, although each sensor has the same function, the measured values of the sensors all have different values because of some variation in output and different mounting positions of the sensors. For this reason, the measured value fluctuates at the moment of switching the sensor signal to be taken into the control loop. This leads to unwanted fluctuations (bumps) in the control. In particular, when the control element has a differential element, significant fluctuation occurs. This bump may be a problem in terms of control performance and safety of the control system.
[0004]
[Problems to be solved by the invention]
Therefore, as shown in FIG. 5, a low-pass filter LPF is connected to the switch, and a high-frequency component generated at the time of switching is cut and output as a gentle signal. However, if a normal LPF (for example, a first-order lag filter) is used, the filter works even when the sensor is not switched, so that a delay occurs in the measurement system, making it difficult to speed up the control. .
[0005]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a bump suppression filter that operates a filter only when a sensor is switched.
[0006]
[Means for Solving the Problems]
In the reference example, a plurality of sensors having the same function for measuring the same object, an input side switch for selecting one of the plurality of sensors, a first line for taking out an output of the input side switch, and an input side switch A second line for extracting the output of the output through a low pass filter, an output side switch for selecting the first line and the second line, and when the input side switch is switched, the output side switch is changed from the first line to the second line. A switch control unit that switches the output side switch from the second line to the first line when the output difference between the first line and the second line falls within a predetermined value.
[0007]
The sensor is switched and the output of the second line through the low-pass filter is taken out. At the same time as switching, the difference between the output of the first line without the low-pass filter and the output of the second line with the low-pass filter is taken, and the output of the first line is taken out when this difference is within the fluctuation tolerance. As a result, the low-pass filter is used only during the period when the fluctuation at the time of sensor switching is large and the low-pass filter is not used during the other periods, so that the influence of bumps due to sensor switching can be reduced.
[0008]
In the invention of claim 1 , a plurality of sensors having the same function of measuring the same object, an input side switch for selecting one of the plurality of sensors, a first line for taking out an output of the input side switch, A first subtracter that subtracts the output of the selection switch from the output of the input switch, a second line that is output by applying a first-order lag element to the output of the first subtractor, and an output of the second line from the output of the first line And a switch control unit for controlling the selection switch. The selection switch selects the output A of the input side switch and the output B of one sampling before the second subtractor. The switch control unit switches the selection switch from A to B when the input side switch is switched, and switches the selection switch from B to A when the difference between A and B falls within a predetermined value.
[0009]
When the sensor is not switched, the output of the selection switch is the output A of the input switch, so the first subtracter takes the difference between the outputs A of the input switches and the output is zero. . As a result, the output of the second line becomes 0, and the output of the second subtractor becomes the output A of the input side switch. When the sensor is switched, the output of the selection switch is the output B one sampling before the second subtractor, so the output of the first subtracter is the difference between A and B, that is, the fluctuation, and this fluctuation. A value obtained by subtracting the value obtained by multiplying the first delay element from the output A of the input side switch is output from the second subtractor. As a result, a value with reduced fluctuation is output when the sensor is switched, and the value from the sensor is output as it is at other times.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Reference examples and embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a bump suppression filter of a reference example . A plurality of sensors having the same function for measuring the same object, such as sensor L, sensor M, sensor N,..., Are connected to the input switch 1, and one of these is selected by a selection signal from the selection signal line 7. The Connected to the output side of the input side switch 1 are a first line 2 that outputs the output of the input side switch 1 as it is and a second line 4 that outputs it via a low-pass filter 3. The low-pass filter 3 may be of any type. The first line 2 and the second line 4 are connected to the output side switch 5, and either output is output to the control system. The switching logic 6 (switch control unit) controls switching of the output side switch 5, and is connected to the selection signal line 7, the first line 2 and the second line 4, and the second line when the sensor is switched by the selection signal. 4 is connected, the difference between the output value a of the first line 2 and the output value b of the second line 4 is taken, and the output side switch 5 is controlled to switch back to the first line 2 when the difference falls within the allowable value. To do.
[0011]
Next, the operation will be described. It is assumed that the sensor L is connected to the incoming switch 1 and the first line 2 is connected to the outgoing switch 5. At this time, a selection signal is output from the selection signal line 7, and the input side switch 1 is switched to the sensor M. At the same time, the switching logic 6 switches the output side switch 5 from the first line 2 to the second line 4 and outputs a value through which the fluctuation due to the difference in sensor is reduced through the low-pass filter 3. At the same time, the difference between the output a of the first line 2 that does not pass through the low-pass filter and the output b of the second line 4 that passes through the filter is obtained, and when this difference falls within an allowable value, the first line 2 is connected to the output side switch 5 again. Connect and output the output of the sensor M as it is. As a result, the influence of the fluctuation can be reduced by using the low-pass filter only during the period when the fluctuation of the sensor switching is large.
[0012]
Next, an embodiment of the present invention will be described. FIG. 2 is a diagram illustrating a bump suppression filter according to an embodiment of the present invention . A plurality of sensors having the same function for measuring the same object, such as sensor L, sensor M, sensor N,..., Are connected to the ingress switch 11, and one of these is selected by a selection signal from the selection signal line 19. The The output A of the ingress switch 11 is output to the first line 12. The output of the second subtractor 18 that is the output of the bump suppression filter is temporarily stored in the latch 13. The sensor output is output at every sampling interval. The latch 13 holds the value immediately before the current sampling. The selection switch 14 switches between the output A of the ingress switch 11 and the output B of the latch 13. The first subtracter 15 subtracts the output of the selection switch 14 from the output A of the ingress switch 11. This value is naturally 0 when the selection switch 14 selects A. Further, when the sensor is switched while B is selected, a fluctuation value (bump) is obtained. The second line 17 is a line that multiplies the output of the first subtractor 15 by the first-order lag element exp (−Δt / τ) by the multiplier 16 and outputs the value, and the first-order lag element is a high frequency from the output of the first subtractor 15. The component is removed and the low frequency component is output. Note that Δt of the first-order lag element represents a sampling interval, and τ represents a time constant. The second subtracter 18 subtracts the output of the multiplier 16 from the output of the first line 11 to obtain the output of the bump suppression filter. The switch control unit 20 switches the selection switch 14 to the output B of the latch 13 in response to a selection signal from the selection signal line 19, and switches the selection switch 14 from B to A when the difference between A and B is within an allowable value. The selection switch 14 is instructed.
[0013]
Next, the operation will be described. Assume that the sensor L is connected to the ingress switch 11. At this time, a selection signal is output from the selection signal line 19 and the input side switch 11 is switched to the sensor M. At the same time, the switch controller 20 switches the selection switch 14 from A to B. B is the value of the sensor L before switching and is the value before the change, and the output A of the input side switch is the value that caused the change when switching to the sensor M. For this reason, the output of the first subtractor 15 is a fluctuation value (bump). By applying a first-order lag element to the fluctuation value, a gentle component of the fluctuation value is extracted, and the second subtractor 18 outputs the first line. Subtracted from A. As a result, the output of the sensor M with less fluctuation is output from the second subtracter 18. The switch control unit 20 examines the difference between A and B by the selection signal and switches the selection switch 14 to A when the difference is less than the allowable value. As a result, when the sensor is switched, the sensor value obtained by substantially subtracting the fluctuation value is output. In other cases, the sensor output is output as it is.
[0014]
FIG. 3 is a diagram showing the configuration of a commonly used primary filter. Implementation of the invention shown in Figure 2 so as to operate the primary filter to provide a selection switch 14 and the switch control section 20, the switch control unit 20 in synchronization with the selection signal for controlling the ingress switching 11.
[0015]
【The invention's effect】
As is clear from the above description, the present invention reduces fluctuations occurring at the time of sensor switching by using a low-pass filter, but if the fluctuations are within an allowable value, a sensor output that does not pass through the filter can be output as it is. .
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a bump suppression filter of a reference example .
FIG. 2 is a diagram illustrating a bump suppression filter according to an embodiment of the present invention .
FIG. 3 is a circuit of a primary filter.
FIG. 4 is a conventional sensor switching circuit.
FIG. 5 is a sensor switching circuit using a conventional low-pass filter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Input side switch 2 1st line 3 Low pass filter 4 2nd line 5 Output side switch 6 Switching logic 7 Selection signal line 11 Input side switch 12 1st line 13 Latch 14 Selection switch 15 1st subtractor 16 Multiplier 17 2nd Line 18 Second subtractor 19 Selection signal line 20 Switch control unit

Claims (1)

Select from a plurality of sensors having the same function to measure the same object, an input side switch for selecting one of the plurality of sensors, a first line for extracting the output of the input side switch, and an output of the input side switch A first subtracter for subtracting the output of the switch; a second line for outputting the output of the first subtractor by applying a first-order lag element; and a second subtractor for subtracting the output of the second line from the output of the first line And a switch control unit for controlling the selection switch, wherein the selection switch selects the output A of the input side switch and the output B of one sampling before the second subtractor, and the switch control unit includes: A bump suppression filter, wherein the selection switch is switched from A to B when the input side switch is switched, and the selection switch is switched from B to A when the difference between A and B falls within a predetermined value.

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