JPH0564241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a servo control device for a servo actuator, and particularly to one that incrementally controls an absolute quantity.

[Prior art] The term “incremental” is used for “absolute”, but the term “absolute” refers to temperature, flow rate,
It refers to a state quantity such as pressure, viscosity, or concentration, and the quantity that matters is how much it has changed from zero. Incremental quantities refer to displacements such as position, orientation, or posture, and are quantities that do not necessarily have a reference value such as zero, and are solely concerned with how much they have displaced from their current location. Therefore,
The term "incremental value detection sensor" refers to a length measurement sensor, etc., and the term "absolute value detection sensor" refers to a pressure sensor, etc.

Now, in the servo control method of a fluid pressure servo actuator, for example,
Generally, unified control of flow rate control or positioning control is often used. However, in the case of press machines, injection molding machines, etc., for example, if central control were used, the operation of the actuator would be stiff and the finished product would be poor.

Therefore, a method has been developed in which pressure control (pushing force control) is added to flow rate control or positioning control to dualize the control amount, and by switching between these, the control by the actuator can be made soft and precise.

For example, the one shown in Figure 4 is a P-Q valve (manufactured by MOOG, trade name) developed for injection molding machines.
It is called. This is dual control of the speed or flow rate Q of the hydraulic cylinder 1 and the pushing force of the hydraulic cylinder 1, where cylinder speed = spool position control of the servo valve 2, and cylinder pushing force = cylinder head side pressure control. Both control methods are absolute methods aimed at controlling absolute quantities.

Mode switching between speed control and pushing force control is performed when the oil pressure constantly detected by the pressure detector 3 matches the set pressure _R2 , the pressure limit circuit 4 is activated, and until then the speed control using the set flow rate _R1 is switched. It is designed to automatically switch over to push force control. The circuit is entirely composed of analog elements, and the command values, which are set values, are both analog quantities.

However, in the above-mentioned P-Q valve, since all the circuits are constructed in an analog system, it is more difficult to provide a setting value that specifies a temporal change in the controlled amount than in a digital system. Although it is possible to control the voltage, which is a set value, over time, digital pulse control, which allows arbitrary control over time by changing the pulse rate, is far more advantageous.

Furthermore, the pressure control method is in principle an absolute method, and although the absolute method has its merits, it has the disadvantage that it is difficult to determine the set value for pressure control if the magnitude of the load (force) is unknown.

Furthermore, in the example shown in Fig. 4, speed and pressure switching control is performed, but since the switching is performed based on the comparison result in the pressure limit circuit 4, when switching from constant speed to pressure, the pressure As long as there is no rise, switching to pressure control is not possible.

[Problems to be Solved by the Invention] As described above, conventional servo control devices are configured using an analog method, so control accuracy is not necessarily good, and dual control methods are all absolute. Since it is a method, it is difficult to set the set value, and it also has the disadvantage that it is not possible to switch between two-way control arbitrarily.

The purpose of the present invention is to change the absolute control, which originally handles absolute quantities, to a digital incremental type in order to integrate the dual control control method, thereby realizing high precision and reducing the size of the load. It is an object of the present invention to provide a servo control device that allows the set value of an absolute amount to be easily determined even when the absolute amount is unknown.

Another object of the present invention is to realize higher accuracy and higher functionality of control by integrating the control method of dual control into an incremental method, and to switch between internal and external control. It is an object of the present invention to provide a servo control device in which switching can be performed arbitrarily and at any time by making it possible to perform switching from both.

[Means for Solving the Problems] The servo control device of the present invention, as shown in FIG. An absolute value detection sensor 11 that detects the absolute amount as an analog amount is attached.

The servo actuator 1 is supplied with incremental command pulses and absolute value load commands from the controller 20 and the detected absolute value from the servo actuator 10.
The servo control circuit 30 that controls 0 includes an absolute amount control means 31, an arithmetic means 32, and an output means 33.

The absolute amount control means 31 converts the detected absolute value from the absolute value detection sensor 11 into a digital amount and reads it as a reference value by a load command, and also changes the reference value according to the incremental command pulse to create an absolute command value. This is converted into analog and output.

The calculation means 32 is the absolute amount control means 3
The deviation between the analog absolute command value from 1 and the detected absolute value from the absolute value detection sensor 11 is calculated.

The output means 33 controls the servo actuator 10 by operating the operating section 12 of the servo actuator 10 according to this deviation.

Further, as shown in FIG. 2 corresponding to the embodiment, another servo control device of the present invention provides pulses to the servo actuator 10, which is controlled by the operation of the operation unit 12, with an incremental amount associated with the control thereof. An incremental value detection sensor 13 that detects the servo actuator 10 and an absolute value detection sensor 11 that detects the absolute amount associated with the operation of the servo actuator 10 as an analog amount are attached.

Servo control that controls the servo actuator 10 by being supplied with incremental command pulses, external load commands, set differential pressure, and external switching signals from the controller 20, and with detected incremental pulses and detected absolute values from the servo actuator 10. The circuit 30 includes an incremental amount control means 34 and an absolute amount control means 31.
, a calculation means 32 , a switching operation means 35 , a switching means 36 , and an output means 33 .

The incremental amount control means 34 counts the deviation between the detected incremental pulses from the incremental value detection sensor 13 and the incremental command pulses to create an incremental command, converts it into analog, and outputs it.

The switching operation means 35 compares the deviation from the calculation means 32 with the set differential pressure, and outputs an internal load command and a switching signal in response to an internal trigger signal or an external switching signal that is output when the deviation matches the set differential pressure.

The switching means 36 switches the signal supplied to the output means 33 from the incremental command value to the deviation based on the switching signal from the switching operation means 35.

The output means 33 controls the servo actuator 10 in response to a supply signal supplied via the switching means 36.
servo actuator 1 by operating the operation unit 12 of
Controls 0.

Note that the absolute amount control means 31 and the calculation means 32 are the same as those described above.

[Operation] According to the servo control device of the present invention, when a load command is supplied from the controller 20 to the servo control circuit 30, the absolute amount control means 31 receives the information currently detected by the absolute value detection sensor 11 in the servo actuator 10. The detected absolute value is read as the reference value. Then,
Since the absolute command value that is the output of the absolute amount control means 31 retains the detected absolute value that has just been read, the absolute command value applied to the calculation means 32 and the detected absolute value are equal. Therefore, the deviation becomes zero,
The servo actuator 10 is not controlled and maintains its current state. As a result, the servo actuator 10 is not shocked when the load command is supplied. In this way, the absolute value detected by the servo actuator 10 at the present time is set in the absolute amount control means 31.

After the currently detected absolute value is set in the absolute amount control means 31, the controller 20 controls the absolute amount control means 31 so that the set value becomes the desired absolute value.
The required number of incremental command pulses are supplied. Then, the absolute amount control means 31
The set value is increased or decreased to a desired absolute value. That is, the desired absolute value to be set in the absolute amount control means 31 is set by the incremental amount. Therefore, the absolute amount control, which is originally an absolute type, will be changed to an incremental type.

Now, when the desired absolute command value created by the incremental amount is output from the absolute amount control means 31, the deviation between this output and the detected absolute value that is fed back is determined by the calculation means 32. Output means 3
3. Then, the operating section 12 is operated according to the deviation to control the servo actuator 10.

Therefore, the servo actuator 10 is controlled so that its absolute amount becomes a desired value.

On the other hand, according to another servo control device of the present invention,
First, the controller 2
A necessary number of incremental command pulses are supplied from 0 to the incremental amount control means 34 of the servo control circuit 30. Then, the deviation between this incremental command pulse and the detected incremental pulse currently detected by the incremental value detection sensor 13 in the servo actuator 10 is determined by the incremental amount control means 34 and supplied to the output means 33. . As a result, the operating section 12 of the servo actuator 10 is operated in accordance with the deviation to control the servo actuator 10. Therefore, the servo actuator 10 is controlled so that its incremental amount becomes the target value.

However, when the absolute value detected by the absolute value detection sensor 11 becomes excessively large during the process of such incremental control, the incremental control is automatically switched to absolute control as follows.

Prior to this switching control, an external load command is input from the controller 20 to the servo control circuit 30 at an appropriate stage of the incremental control, that is, at a stage when the absolute amount is stable, and the servo control at the above stage is performed as described above. The detected absolute value of the actuator 10 is set and held in the absolute amount control means 31. After the above stage, the detected absolute value of the servo actuator 10 that is controlled under incremental control increases and greatly exceeds the reference value (set value) held in the absolute amount control means 31 at the above stage. When the deviation between the set value and the detected absolute value matches the set differential pressure supplied from the controller 20 to the switching actuating means 35, the switching actuating means 35 outputs an internal load command. Then,
The detected absolute value at the time when it matches the set differential pressure is newly read into the absolute amount control means 31 as a reference value. Also during this reading, the absolute command value that is the output of the absolute amount control means 31 and the absolute value detected by the absolute value detection sensor 11 are equal, as in the case described above.

Furthermore, since the switching signal is outputted from the switching actuating means 35 to the switching means 36 at the same time as the output of the internal load command, the supply signal that had been supplied to the output means 33 until then is changed from the incremental command value to the output of the absolute quantity control means 31. The absolute amount deviation is changed to . When the switching means 36 switches, the deviation is zero as described above, so even if the servo actuator 10 is placed under absolute control, there is no instantaneous operation under that control, and therefore, the switching is performed smoothly. be exposed. Here, the necessary number of incremental command pulses are sent from the controller 20 to the absolute amount control means 3 so that the detected absolute value at the time of switching set in the absolute amount control means 31 becomes the desired setting value.
1. Then, the set value of the absolute amount control means 31 is increased or decreased and changed to the desired absolute command value. That is, this changed value becomes the target value of the absolute amount, and the servo actuator 10 is absolutely controlled so as to reach this target value.

Incidentally, switching from incremental control to absolute control can be performed externally in addition to the automatic switching described above.

When the external switching signal is supplied from the controller 20 to the servo control circuit 30, the above-mentioned internal load command and switching signal are output, so even if the deviation does not match the set differential pressure, the incremental control can be changed to the absolute control. A switch is made to

[Example] Examples of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 shows an example of a servo control device of the present invention. This device includes a controller 20 that outputs incremental command pulses for increase or decrease and an absolute value load command, and a servo control circuit 30 that is supplied with these commands and a feedback signal of the detected absolute value and outputs a deviation as a manipulated variable.
and a servo actuator 10 that is controlled by operating an operating section 12 according to the deviation. The servo actuator 10 is equipped with an absolute value detection sensor 11 that detects the physical absolute amount associated with the control of the servo actuator 10 as an analog value, and the detected absolute value detected by this sensor is constantly fed back to the servo control circuit 30. It's getting old.

Incidentally, the absolute quantity control circuit 31 constituting the servo control circuit 30 receives the incremental command pulse for increase or decrease as a counter input, and also presets the detected absolute value, which is digitized upon receiving the absolute value load command, as a reference value. an absolute value setting counter 40 consisting of a presettable counter;
An A/D converter 42 that converts the analog detection absolute value amplified by the amplifier 41 into a digital value, and an absolute value setting counter 40
and a D/A converter 43 that converts the absolute command value outputted from the D/A converter 43 into an analog value.
The servo control circuit 30 adds the analog absolute command value, which is the output of the absolute amount control circuit 31, and the detected absolute value after amplification to a subtracter, which is an arithmetic means 32, to find the deviation between the two values, and calculates the deviation between the two values. The signal is supplied to a servo amplifier 44 serving as an output means 33 for converting the amount into an operation amount corresponding to the amount, and the operation unit 12 is operated based on the operation amount of the servo amplifier 44.

FIG. 2 shows an example of application of the present invention using a hydraulic cylinder as an example of a servo actuator.

The hydraulic cylinder 14 is controlled by a hydraulic pressure control valve 15 operated by a solenoid, and pressure control is added to the positioning control as this control element. To this end, a length measurement sensor 16 detects the position of the piston rod in the hydraulic cylinder 14 and converts it into a forward or backward position pulse train, and the pressure of the liquid flowing between the piston and the piston is detected and converted into an analog electrical signal. A pressure sensor 17 is provided.

In order to use only one pressure sensor 17, a control system is adopted in which only the hydraulic pressure on the piston head side varies, and the hydraulic pressure on the piston rod side does not vary.

Here, fluid force is practically expressed as the product of flow rate and pressure. Of these, flow rate is an absolute quantity like pressure, but unlike pressure, it is an incremental quantity and can be replaced at a position where it can be converted into velocity or flow rate. In order to use an incremental method corresponding to the number of input pulses to be adopted in the present invention, position is used instead of flow rate in this embodiment.

The controller 20 selectively outputs forward or backward position command pulses for each direction and pressure command pulses for pressure reduction or pressure increase. These position/pressure command pulses are sent to the length measurement sensor 16 and the pressure sensor 1.
It is designed to be formed based on each detected value of 7. In addition to the position/pressure command pulse, a pressure value load command, set differential pressure, and position/pressure cut signal are output. The controller 20 includes
Further, an indicator 21 such as a lamp is provided for determining whether the control currently being performed is position control or pressure control based on a switching signal from the servo control circuit 30.

The set differential pressure, pressure value load command, and position/pressure switching signal are all set or inputted by the operator in advance or when necessary.

The servo control circuit 30 mainly includes an incremental amount control means 34, an absolute amount control means 31, an arithmetic means 32, a switching operation means 35, a switching means 36, and an output means 33.

The incremental amount control means 34 uses a deviation counter to measure the positional deviation between the forward position command pulse and the detected position pulse in the same direction that is fed back, or the position deviation between the reverse position command pulse and the detected position pulse in the same direction that is also fed back. 50, and outputs the value from the A/D converter 51 as a servo position command value.

This incremental amount control means 34 employs a well-known digital servo system for positioning servo control, but in order to provide a PID function, an integrator and a feedback pulse are differentiated after the D/D converter 51. Connect an F/V converter as necessary to generate a speed feedback signal,
Responsiveness and positioning accuracy may be improved.

The absolute value control means 31 has the following features: the absolute value setting counter 40 is named a pressure value setting counter 52, the counter input is the same common input as the incremental amount control means 34, and the absolute value load command is It is the same as the one in Fig. 1, except that an OR circuit 53 is added that applies a load command to the pressure value setting counter 52 when this command or an internal load command is input, instead of a pressure value load command alone. Further, the calculation means 32 is also unchanged.

The switching operation means 35 determines the deviation between the analog pressure command value of the absolute amount control means 31 and the detected pressure value amplified by the amplifier 41, and compares this with the set differential pressure to determine whether the pressure deviation matches the set differential pressure. A comparator 54 outputs a position signal, a flip-flop circuit 55 outputs an internal trigger signal when this signal is output, and a flip-flop circuit 55 outputs an internal trigger signal or position /
It is composed of an OR circuit 56 that outputs an internal load command and a switching signal when a pressure switching signal is input.

The switching means 36 outputs the output means 33 according to the switching signal.
The supply signal to the incremental amount control means 3
The deviation is changed from the servo position command value of No. 4 to the servo pressure command value of the calculating means 32.

The output means 33 gradually brings the command value supplied via the switching means 36 to the final value in order to avoid sudden fluctuations in the cylinder 14 due to the difference between the two command values when the switching means 36 switches. It consists of a first-order delay circuit 57 and a servo amplifier 44 that converts the voltage that is the output of this circuit into a current and amplifies it so that the hydraulic control valve 15 is operated with an operating amount according to a command value. Note that the first-order delay circuit 57 can be omitted if the configuration is such that the count value of the deviation counter 50 is reset to zero when switching from position control to pressure control.

Now, the switching operation of the above device will be explained.

The positioning control in this device is an incremental type, and in order to unify the control method, the pressure control, which was originally an absolute type, was changed to an incremental type. For this purpose, it is necessary to read the pressure value at the time of starting the pressure control mode from the pressure sensor 17 into the pressure value setting counter 52. Therefore, using a pressure value load command from the controller 20, the detected pressure value is loaded into the pressure value setting counter 52. After loading, a pressure command pulse is applied to increase or decrease the content of this counter 52, and the added counter content becomes the pressure command value and passes through the switching means 36, output means 33, etc. to the hydraulic pressure control valve 1.
Operate 5. As described above, since the number of digital pulses is applied to the input of the servo control circuit 30, if the position/pressure switching signal is set to L level and the switching means 36 is forcibly switched to the pressure control side from the outside, Incremental control is possible from the point of switching.

This results in switching from position control to pressure control using an external signal, but switching back from pressure control to position control is performed by switching the position/pressure switching signal from L level to H level.
In this way, position control and pressure control can be freely switched at any time while the cylinder 14 is being controlled, so switching to pressure control is possible even when there is no increase in pressure. Incidentally, it is of course possible to control the pressure independently.

It can also be switched by an internal signal, taking advantage of the fact that the cylinder internal pressure changes due to changes in load. The deviation between the detected pressure value set in the pressure value setting counter 52 at a certain point in time and the current pressure value fed back from the pressure sensor 17 is taken, and this pressure deviation and the preset fluctuating differential pressure value are switched. The operating means 35 compares the two, and when the two match, the mode is switched to the pressure control mode.

In this way, the increase in cylinder internal pressure that fluctuates due to load is detected and an internal trigger is applied to automatically switch from position control to pressure control, making it possible to switch smoothly.

Switching to such a pressure control mode is effective when controlling an operation in which the cylinder 14 presses an object. If you try to control using only positioning control, the pressing force may become excessive,
However, if the position/pressure switching control described above is used, it is possible to control the necessary and sufficient pressing force, and even after switching to pressure control, the pressing force remains unchanged. It becomes possible to change the force finely. Specifically, it is highly effective when applied to a segment assembly robot in a shield that butts cement segments, a press control machine that employs a press saving method, or an injection molding machine.

As described above, according to this embodiment, the pressure control is an incremental control in which the command value can be set by a relative amount proportional to the number of pulses, so position control, which is originally an incremental control, can also be controlled by command pulses. Therefore, it is possible to perform extremely precise relative quantity control with the minimum unit of resolution determined by the number of command pulses, and also to perform dual position control and pressure control using command pulses from the same port of the controller 20. Since it can be controlled, the control circuit can be easily configured.

In the above embodiment, the entire servo control circuit is constructed from hardware, but as shown in FIG. D/A converter 51 and servo amplifier 44
and all other microcomputers 62
In this case, the above operations can be executed by changing the program. According to this,
The circuit can be further simplified.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

The servo control device according to claim 1 is provided with an absolute amount control means for reading the current value of the absolute value and changing it to an absolute command value which is a target value by means of incremental command pulses, thereby performing absolute control that originally deals with absolute amounts. Since it has been changed to a digital incremental type, it is possible to achieve high precision, and even when the magnitude of the load is unknown, it is possible to easily determine the set value of the absolute amount. Furthermore, by changing the absolute control to the incremental type, it becomes easy to integrate the dual control, especially the incremental control and the absolute control.

In the servo control device of Claim 2, the incremental amount control means is combined with an absolute amount control means that changes the absolute control that originally handles absolute amounts to an incremental type, so that the same incremental command pulse can be used for input. , the dual control control method can be easily integrated into the incremental method, and a switching means and a switching operation means are provided.
By making it possible to switch between dual control from both the internal and external sources, it is possible to switch between incremental control and absolute control in a timely manner, allowing the actuator to perform absolute control with high precision. High precision and high functionality of control can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the servo control device according to the present invention, FIG. 2 is a block diagram showing an example of application, and FIG. FIG. 4 is a block diagram showing an example of a conventional servo control device. In the figure, 10 is a servo actuator, 11 is an absolute value detection sensor, 12 is an operating section, and 13
3 is an incremental value detection sensor, 30 is a servo control circuit, 31 is an absolute amount control means, 3
2 is a calculation means, 33 is an output means, 34 is an incremental amount control means, 35 is a switching actuation means, 36
is a switching means.

Claims (1)

[Claims] 1. A servo actuator controlled by operation of an operating section, an absolute value detection sensor that detects an absolute amount accompanying control of the servo actuator in analog form, and a digitalized absolute value. is read as a reference value by a load command, and the reference value is changed in accordance with the incremental command pulse to create an absolute command value, which is converted into an analog and output. What is claimed is: 1. A servo control device comprising: arithmetic means for determining a deviation from a value; and an output means for controlling the servo actuator by operating an operating section of the servo actuator according to the deviation. 2. A servo actuator that is controlled by the operation of the operating unit, an incremental value detection sensor that pulse-detects the incremental amount associated with the servo actuator control, and an absolute value that detects in analog form the absolute amount associated with the operation of the servo actuator. A detection sensor, an incremental amount control means that creates an incremental command value according to the deviation between the detected incremental pulse and the incremental command pulse, converts it into an analog value and outputs it, and digitizes the detected absolute value to issue an external load command or an internal load command. Absolute amount control means that reads the reference value as a reference value, changes the reference value according to the incremental command pulse to create an absolute command value, converts it into an analog and outputs it, and converts the analog absolute command value and the detected absolute value. a calculation means for calculating the deviation; a switching operation means for comparing the deviation with a set differential pressure and outputting the internal load command and switching signal based on an internal trigger signal or an external switching signal that is output when the deviation matches the set differential pressure; a switching means for switching a signal supplied to the output means from an incremental command value to a deviation by a switching signal;
1. A servo control device comprising: output means for controlling a servo actuator by operating an operating section of the servo actuator in accordance with a supply signal.