JPH11301833A - Electromagnetic feeder, measuring device and combination measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a circuit constitution for performing feedback control and to facilitate reproducing of amplitude control in accordance with an article, in an electromagnetic feeder. SOLUTION: Acceleration detected by an acceleration sensor 10 mounted in an electromagnetic feeder 3 is converted into a digital amount by an A/D converter 12, amplitude of a conveying part 37 is obtained to be based on this converted digital amount, the amplitude is compared with target amplitude Tf, a deviation between both the amplitudes is obtained, and by controlling drive energy of vibration in the next time input to an electromagnetic coil 39 from an excitation power source 18 based on the deviation, and thereby amplitude in the next time is feedback controlled so as to approach the target amplitude.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic feeder, a weighing device, and a combination weighing system.

[0002]

2. Description of the Related Art A combination weighing system collects a plurality of various articles such as confectionery, fruits, vegetables and the like, each having a different weight, to obtain a target weight or a target number. In order to improve the weighing accuracy of such a combination weighing system, it is very important to stabilize the supply amount from an electromagnetic feeder provided upstream of the weighing device. But,
Conventionally, feedback control based on a measured value of a weighing hopper provided downstream of the electromagnetic feeder is employed. That is,
After the electromagnetic feeder vibrates a plurality of times and the articles are supplied to the weighing hopper, the supply amount is fed back. Therefore, the response of the electromagnetic feeder is delayed.

Therefore, it is conceivable to perform feedback control on the amplitude of the electromagnetic feeder itself. As disclosed in Japanese Patent Application Laid-Open No. 63-134413, an acceleration sensor is attached to the transport section, the amplitude of the transport section is detected by the sensor, and the detected amplitude signal of the analog amount is used as the electromagnetic feeder. There has been proposed a system adopting a feedback control method for controlling the amplitude of the transport unit to approach a target amplitude by making a feedback input to a feeder controller.

[0004]

However, in the above-mentioned conventional electromagnetic feeder, since the amplitude signal fed back to the controller is an analog signal, an integration circuit is provided at a stage preceding the feeder controller which feeds back the detected amplitude signal. Or a vibration level setting circuit for setting a reference signal to be compared with the detected amplitude signal, and for controlling charging and discharging of a capacitor so as to obtain a pulse control signal based on a difference signal obtained by comparing the two signals. Many analog processing circuits, such as a switching circuit and a trigger pulse generation circuit, are required, and the circuit configuration becomes complicated accordingly, and the feedback system becomes expensive. Such a problem occurs not only in the combination weighing system but also in other devices, that is, a problem relating to the electromagnetic feeder itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an electromagnetic feeder, a weighing device, and a combination weighing system that can simplify a circuit configuration and configure an entire feedback system at low cost. .

[0006]

In order to achieve the above object, an electromagnetic feeder according to the present invention includes an electromagnetic coil connected to an excitation power supply, and a transport unit that is supported so as to be able to vibrate and transports an article. An electromagnetic feeder that vibrates a conveyance unit by the electromagnetic coil to supply an article downstream and controls an amplitude of the conveyance unit to control a supply amount to the downstream. A sensor for detecting a displacement, an A / D converter for converting an acceleration or a displacement detected by the sensor into a digital amount, an amplitude calculating means for obtaining an amplitude of the transport unit based on the converted digital amount, By controlling the driving energy of the next vibration input to the electromagnetic coil based on the deviation obtained by comparing the amplitude calculated by the means with the target amplitude, the next amplitude approaches the target amplitude. And it is characterized in that it comprises a feedback control circuit for controlled so.

According to the present invention, the acceleration or displacement of the transport unit detected by the sensor is first discretized by an A / D converter and converted into a digital value, and the digital signal is fed back to a feedback control circuit. A simple circuit that uses only one sensor and an A / D converter and provides a minimum preprocessing circuit that does not require an integrating circuit or many analog circuits. A digitized feedback signal is obtained by the configuration, and the entire feedback system can be configured at low cost. In particular, in the case of a combination weighing device or the like using a digital circuit such as a microcomputer as a main control circuit, the analog signal detected by the sensor is converted into a digital signal in advance, so that the feedback system can be controlled by the microcomputer. With this configuration, the cost can be reduced.

Further, since a digitized feedback signal is obtained, not only can it be used for predetermined amplitude control, but also data processing such as reading of maximum and minimum values and calculation of an average value can be easily performed. Then, it is easy to construct a learning system for storing a pattern for each article to be conveyed, thereby making it possible to easily read out a pattern for each article and reproduce appropriate feedback control.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a conceptual diagram of a combination weighing system including a plurality of sets of weighing devices including an electromagnetic feeder according to the present invention. In FIG. 1A, the conveyor 100 drops an article M to be weighed to a central portion of the dispersion feeder 2. A number of electromagnetic feeders (supply troughs) 3i are provided on the periphery of the dispersion feeder 2. The dispersion feeder 2 and each of the electromagnetic feeders 3i vibrate by driving the vibrating device.
The upper item (object to be weighed) M is supplied to a large number of pool hoppers 4i provided downstream of each electromagnetic feeder 3i. Each of the pool hoppers 4i is provided with a gate 5i, and temporarily stores the articles M supplied and received from the electromagnetic feeders 3i. A measuring hopper 6i is provided downstream of each pool hopper 4i. Each of these weighing hoppers 6i
Is provided with a weight detector 7i for detecting the weight of the article M input from the pool hopper 4i to the weighing hopper 6i, and a gate 8i. A large collecting discharge chute 9 is provided below the gate 8i, and as described later, by combining the weights of the articles M detected by the respective weight detectors 7i, the articles M are collectively set to a target value. Alternatively, a value close to the target value is set.

As shown in FIG. 2, the electromagnetic feeder 3 is supported by a plurality of coil springs 32.
, A pair of leaf springs 34 attached to the feeder base 33, a connecting member 35 for connecting the upper ends of the leaf springs 34, and supported on the connecting member 35. A feeder main body (conveying section) 37 configured to be swingable (vibrating) and an electromagnetic coil 39 installed on the feeder base 33 and applying an electromagnetic force to a magnetic body 38 attached to the connecting member 35. Have. When the electromagnetic feeder 3 is intermittently energized from the excitation power supply 18 (FIG. 3) to the electromagnetic coil 39, the leaf spring 3
4, the magnetic body 38 is pulled in the direction of the arrow a against the elastic force of 4, and the feeder body 37 is displaced in the direction of the arrow a while sinking downward, and then the feeder body 37 is displaced in the direction of the arrow b while floating upward. Then, the feeder body 3
7 repeatedly vibrates in the directions of arrows ab. The supply operation is performed once by vibrating the feeder main body 37 a plurality of times, and the articles M on the feeder main body 37 are supplied to the pool hopper 4.

Next, the combination control of the present combination weighing system will be described. In FIG. 1B, each weight detector 7i outputs the detected weight to the multiplexer 70 as an analog signal. The multiplexer 70 outputs each weighing signal to the first A / D converter 71 when a predetermined synchronization signal is applied. The first A / D converter 71 converts each weighing signal into a weighing value Wh composed of a digital signal and outputs the weighing value Wh to the microcomputer 1. The microcomputer 1 includes a combination control unit 40 and a supply amount control unit 50.

The combination control means 40 has a combination target storage section 41 for storing a combination target value Tc preset for each article M. The combination control means 40 calculates a combination calculation value Wc obtained by combining one or more of the measurement values Wh.
And calculates the combination calculation value Wc as the combination target value T.
c, the combination target value Tc of the combinations whose combination calculation value Wc is equal to or close to the combination target value Tc
1 (a) corresponding to the combination is opened, and the articles M are combined and discharged from the weighing hopper 6i to the collecting chute 9.

The supply amount control means 50 shown in FIG.
The feed amount of the article M supplied from the electromagnetic feeder 3i to the pool hopper 4i is feedback-controlled by a plurality of vibrations (one supply operation) of the electromagnetic feeder 3i in FIG. 1B for storing the supply target value Th of FIG. 1B, and the previous target amplitude (the target amplitude of the previous supply operation) T of the electromagnetic feeder 3i.
and a previous target amplitude storage unit 53 for storing f1. The supply amount control means 50 includes a first A / D converter 71
Is compared with the target supply value Th to determine the deviation Δh of the target value Th from the target value Th. The deviation Δh is input to the target amplitude calculation means 55, and the target amplitude calculation means 55 calculates the target amplitude Tf of the present time (current supply operation) by increasing or decreasing the previous target amplitude Tf1 according to the deviation Δh. Output to the amplitude control means 51. For example, the supply amount control means 50
The weighing value Wh detected by the weight detector 7i is equal to the supply target value T.
If the measured value Wh is smaller than the supply target value Th, the target amplitude Tf is increased.

The target amplitude calculating means 55 updates and stores the newly obtained target amplitude Tf in the previous target amplitude storage section 53. The target amplitude Tf is calculated, for example, by adding a value obtained by multiplying the deviation Δh by a constant to the previous target amplitude Tf1.

The amplitude control means 5 of the supply amount control means 50
1 indicates that the amplitude of the electromagnetic feeder 3i is equal to the target amplitude Tf.
The feedback control is performed so as to approach.
Hereinafter, the amplitude control means 51 will be described.

An acceleration sensor (an example of a sensor) 10 for detecting the acceleration of the trough body 37 is attached to the connecting member 35 of each electromagnetic feeder 3 shown in FIG. The acceleration signal detected by the acceleration sensor 10 is passed through an amplifier 11 and amplified, and then the second A / D
The signal is input to the converter 12, subjected to a discretization process, and converted into a digital acceleration signal. The acceleration signal converted into the digital amount is passed through a low-pass filter (LPF) 13 to remove noise, and is modulated by a sampling circuit 14 into a pulse wave signal at a constant period. An example of the means) is input to 15 and is multiplied by a constant according to a preset constant. Here, as shown in FIG. 3B, the acceleration G and the displacement X are generally expressed as X = −C · G
Since (C is a positive constant), by multiplying the acceleration signal by a constant, the acceleration signal is converted into an amplitude of the feeder body 37 in the electromagnetic feeder 3i, that is, a digital amplitude signal.

The digital amplitude signal is supplied to an amplitude control means 5.
1 the maximum allowable value Ma of the amplitude stored in the maximum value storage unit 80
x and a discrimination circuit 81, and as a result, if the amplitude is smaller than the allowable maximum value Max, the switching circuit 82
When the digital amplitude signal is turned on,
Is output to The digital amplitude signal and amplitude control means 5
After comparing the target amplitude Tf stored in the storage unit 1 with the comparison circuit 16 to calculate the difference Δf between the two, the difference signal is sent to a first feedback control circuit (hereinafter referred to as FB controller) 17. Is entered. On the other hand, the electromagnetic coil 39 is connected to an excitation power supply (commercial power supply) 18 via an electromagnetic contactor 19. The first FB controller 17 turns on and off the electromagnetic contactor 19 via the firing angle driver 20 by outputting a main control signal based on the deviation Δf. As a result, the excitation power supply 18
By controlling the power supplied from the
By controlling the firing angle αi in FIG.
By controlling the vibration energy ΔEi indicated by the hatched portion in (b), control is performed so that the amplitude of the trough body 37 in each supply operation approaches a predetermined target amplitude Tf. Note that half-wave driving may be performed with each voltage zero cross as the starting point of the firing angle.

That is, when the acceleration detected by the acceleration sensor 10 is small, the amplitude control means 51 in FIG. 3 determines that the amplitude (transport capacity) calculated by the constant multiplying circuit 15 is smaller than the target amplitude Tf. 4, the vibration energy Ei is increased to control the next amplitude to approach the target amplitude Tf, while the acceleration detected by the acceleration sensor 10 in FIG. 3 is large. In
Since the amplitude calculated by the constant multiplying circuit 15 is larger than the target amplitude Tf, the vibration energy Ei is reduced by increasing the firing angle αi in FIG. 4 so that the next amplitude approaches the target amplitude Tf. Control. In other words, the amplitude control means 51 of FIG. 3 controls the vibration energy Ei of each vibration of the electromagnetic feeder 3 based on the output of the acceleration sensor 10 so that the amplitude of the trough body 37 approaches the target amplitude Tf.

In the above configuration, during one supply operation, the supply amount of the article M from the dispersion feeder 2 of FIG. 1 to the electromagnetic feeder 3i changes abruptly, and the amplitude of the trough body 37 becomes the target amplitude Tf. The electromagnetic feeder 3i
Since the amplitude of the next vibration is feedback-controlled based on the previous amplitude, the next amplitude approaches the target amplitude Tf. Therefore, when the state of the article M on the feeder body 37 changes, the article M can be supplied to the pool hopper 4 in accordance with the target amplitude Tf without delay in response. As a result, the pool hopper 4 is less likely to be under-supplied or over-supplied, and there is no possibility that the combination will not be established.

In this feedback control system, the acceleration signal detected by the acceleration sensor 10 is input to the second A / D converter 12 and converted into a digital acceleration signal. , A digitized feedback signal can be obtained with a simple circuit configuration that does not require an integrating circuit or the like and only requires a minimum preprocessing circuit. Therefore, the entire feedback system can be configured at low cost. In particular, in a system originally having a digital control circuit such as the present combination weighing system, the feedback control circuit can be configured at low cost.

By the way, the electromagnetic feeder 3 having the feedback control system for performing the above-described firing angle control can make the amplitude of the feeder body 37 substantially coincide with the target amplitude at the time of steady oscillation in one supply operation. It is. However, in the initial stage of the vibration when the spring system is started, the target amplitude Tf is changed due to a well-known transient response as shown by a dotted line in FIG.
An overshoot that oscillates at a larger amplitude occurs. As a result, a greater load is applied to the leaf spring 34 of FIG. 2 than in the steady state for each supply operation, so that the durability of the leaf spring 34 needs to be increased. In particular, in the weighing device, fine adjustment of the supply amount may be difficult due to the overshoot. On the other hand, in order to suppress the increase in the supply amount due to such a transient response, it is conceivable to suppress the amplitude control output at the initial stage of the vibration to a value lower than the output of the target amplitude, but in this case, until the output reaches the steady amplitude. It takes time.

Therefore, in the present invention, the above-mentioned feedback control system includes a feedforward control means (hereinafter referred to as an FF controller) 60 and a second FB controller (a second feedback control circuit: It is preferable to provide a controller 17A.
Hereinafter, the FF controller 60 and the second FB controller 17A will be described.

The FF controller 60 has a target amplitude T
The apparatus includes a steady-state response control unit 61 and a transient response control unit 62 that receive f as an input. The steady-state response control unit 61 includes:
A map of the ignition angle αi with respect to the amplitude when there is no article M in the electromagnetic feeder 3 is stored. Therefore, when the target amplitude Tf is determined, the firing angle αi when the object is empty is determined.
On the other hand, the transient response control unit 62 monitors the change in the target amplitude Tf, and when the target amplitude Tf fluctuates, reduces the response of the first FB controller 17 to the change (deviation) in the target amplitude Tf. To control. Here, it is considered that the overshoot in the transient response occurs because the differentiator of the first FB controller 17 excessively responds to the change in the target amplitude Tf. Therefore, during the transient response in which the target amplitude Tf fluctuates, The FF controller 60 outputs a correction control signal, and controls the ON-OFF signal output from the firing angle driver 20 to the electromagnetic contactor 19 by adding the correction control signal to the main control signal from the first FB controller 17. Thus, the driving energy is reduced to suppress the overshoot amount as shown by the solid line in FIG. As described above, in the present embodiment, the excessive reaction of the first FB controller 17 in FIG.
Since the transient response of the feeder body 37 is reduced and the amplitude at the initial stage of vibration is suppressed from overshoot as shown by the solid line in FIG. 5, fine adjustment of the supply amount becomes easy, and
It is possible to quickly approach steady vibration.

The amplitude control means 51 shown in FIG.
Has the maximum value storage section 80 for storing the maximum allowable value Max of the amplitude, the discriminating circuit 81 and the second FB controller 17A as described above, and the amplitude output from the constant multiplying circuit 15 is equal to the maximum allowable value. If not less than Max, the switching circuit 82 is held in the OFF state and the first F
The B controller 17 does not work, and the second FB controller 17A works instead. That is, when the calculated amplitude is equal to or larger than the allowable maximum value Max, the discrimination circuit 81 outputs an amplitude suppression signal to the second FB controller 17A, and the second FB controller 17A outputs a sub-control signal. 4 through the firing angle driver 20.
So that the firing angle αi of
The electromagnetic contactor 19 (FIG. 3) is turned on and off, thereby reducing the vibration energy Ei. Therefore, it is possible to suppress the amplitude from becoming larger than the allowable maximum value Max. Here, as described above, since the amplitude increases to near the allowable maximum value Max generally during a transient response, the amplitude can be prevented from becoming larger than the allowable maximum value Max during the transient response, and the amplitude can be quickly increased. It can approach steady vibration.

The present invention can be applied to an electromagnetic feeder that does not constitute a weighing device. In the above-described embodiment, the acceleration sensor 10 is used as a sensor for controlling the amplitude of the feeder main body 37. However, a sensor for detecting the displacement of the feeder main body 37 may be used instead. However, when using an optical displacement sensor to detect the amplitude,
There is a problem of performance degradation due to the adhesion of dust and the like, and in the case of using an electromagnetic displacement sensor, not only magnetic shielding is required, but also the use of a high-frequency transmission circuit makes it susceptible to environmental temperature, and However, there is a problem that fine adjustment is required to increase the detection accuracy. On the other hand, if the acceleration sensor 10 is used, such a problem does not occur. In addition, the maximum value storage unit 80 stores the allowable maximum acceleration or displacement instead of the allowable maximum value Max of the amplitude, and compares the allowable maximum acceleration or displacement with the acceleration or displacement from the sensor to prevent the maximum allowable value from being exceeded. Is also good.

[0026]

As described above, according to the present invention,
Since the acceleration or displacement of the transport unit detected by the sensor is converted into a digital amount and the digital signal is fed back to a feedback control circuit to perform a predetermined amplitude control, one sensor and an A / D converter are used. It is possible to obtain a digitized feedback signal with a simple circuit configuration requiring only a minimum pre-processing circuit without using an integrating circuit or the like by only using it, and the entire feedback system can be configured at low cost. . In addition, since a digitized feedback signal is obtained, it is easy to process data such as reading the maximum and minimum values and calculating the average value during each operation. It is easy to construct a learning system that stores the information, and by this, it is possible to easily read out a storage pattern corresponding to each article and reproduce appropriate and accurate feedback control.

According to the second aspect of the present invention, the transient response at the initial stage of the vibration of the transport unit is reduced, so that the fine adjustment of the supply amount of the article to the downstream due to the overshoot becomes possible, and the steady vibration is quickly performed. Can be approached.

According to the third aspect of the present invention, since the amplitude and the like can be prevented from exceeding the allowable maximum value, there is no possibility that the amplitude and the like become larger than the allowable maximum value during a transient response. Large load is less likely to occur on the spring system and the like. Therefore, the durability of the spring system and the like is improved.

Further, according to the weighing device of the present invention, since the amplitude of the electromagnetic feeder can be feedback controlled, the fluctuation of the amplitude in one supply operation is reduced.
Therefore, a predetermined supply amount is obtained.

Further, according to the combination weighing system of the present invention, the acceleration and the like of each electromagnetic feeder are detected and the feedback control is performed so that the amplitude of the electromagnetic feeder becomes a predetermined value. Even if the thickness changes and the amplitude of the electromagnetic feeder fluctuates, the amplitude can be controlled immediately. Therefore, since a delay in response is less likely to occur, it is possible to supply the hopper with an amount of articles close to the target to be supplied to the hopper.

[Brief description of the drawings]

FIG. 1A is a conceptual diagram of a combination weighing system, and FIG.
1 is a schematic configuration diagram of a combination weighing system.

FIG. 2 is a side view of the electromagnetic feeder.

3A is a schematic configuration diagram illustrating an amplitude feedback control system, and FIG. 3B is a characteristic diagram illustrating a relationship between acceleration and displacement.

FIG. 4 Supply energy (supply power) to the electromagnetic feeder
FIG.

FIG. 5 is an explanatory diagram of a transient response characteristic of the electromagnetic feeder at an initial stage of vibration.

[Explanation of symbols]

3: electromagnetic feeder 4: pool hopper 6: weighing hopper 7: weight detector 10: acceleration sensor 12: (second) A / D converter 15: constant multiplication circuit (amplitude calculation means) 16: comparison circuit 17: FB controller (Feedback control circuit) 18: Excitation power supply 37: Feeder main body (conveyance unit) 39: Electromagnetic coil 60: FF controller (feed forward control means) 80: Maximum value storage unit 17A, 81: Control unit

Claims (6)

[Claims] 1. An electromagnetic coil connected to an excitation power supply, and a transport unit that is vibrably supported and transports an article, wherein the electromagnetic coil excites the transport unit to supply the article downstream, An electromagnetic feeder configured to control an amplitude of the transport unit to control a supply amount to a downstream. A sensor that detects acceleration or displacement of the transport unit, and converts the acceleration or displacement detected by the sensor into a digital amount. An A / D converter, an amplitude calculating means for obtaining the amplitude of the transport unit based on the converted digital amount, and an input to the electromagnetic coil based on a deviation obtained by comparing the amplitude calculated by the amplitude calculating means with a target amplitude. And a feedback control circuit for controlling the driving energy of the next vibration to make the next amplitude approach the target amplitude. Magnetic feeder. 2. The feedforward control unit according to claim 1, wherein the target amplitude is input, and when the target amplitude fluctuates, the drive energy input to the electromagnetic coil is controlled in accordance with an amount of change in the target amplitude. Equipped with an electromagnetic feeder. 3. The maximum value storage unit according to claim 1, wherein the maximum value storage unit stores an allowable maximum value of the amplitude, the acceleration, or the displacement, and controls to suppress the amplitude, the acceleration, or the displacement from exceeding the allowable maximum value. An electromagnetic feeder provided with a control unit. 4. The electromagnetic feeder according to claim 1, wherein the electromagnetic feeder is provided downstream of the electromagnetic feeder.
A weighing device comprising: a hopper that receives an item supplied by being vibrated one or more times; and a weight detector that detects the weight of the item input to the hopper. 5. The electromagnetic feeder according to claim 1, wherein the electromagnetic feeder is provided downstream of the electromagnetic feeder.
A pool hopper for receiving an article supplied by being vibrated one or more times, a weighing hopper for receiving an article temporarily stored in the pool hopper, and a weight detector for detecting a weight of the article put into the weighing hopper Weighing device having a vessel. 6. A plurality of sets of the weighing device according to claim 4 or 5, wherein a combination calculated value obtained by combining weighed values from a weight detector of the weighing device is compared with a combination target value, and the combination calculated value is obtained. A combination weighing system for determining a combination equal to or close to the combination target value.