JP6004315B2 - Pressure control device and pressure control method - Google Patents

Description

  The present invention relates to a pressure control that controls a force acting on a pressure receiving body without using a force detector such as a load cell in a machine that operates a working body via a power transmission means by a servo motor to apply a force to the pressure receiving body. The present invention relates to an apparatus and a pressure control method.

  Conventionally, as a pressure control device for an electric injection molding machine, a closed loop control unit for injection pressure, a closed loop control unit for injection speed, a disturbance observer calculation unit, a load cell for detecting injection pressure, and an encoder for detecting injection speed The injection pressure closed loop control unit adjusts the operation signal obtained from the pressure set value and the pressure detection value detected by the load cell by the controller, and outputs the injection speed command value. The torque input to the electric motor for the injection shaft is calculated based on the operation signal obtained from the estimated invalid speed estimated by the observer calculation unit, and feedback control is performed so that the pressure of the injection shaft matches the pressure set value. Is known (for example, see Patent Document 1). However, the load cell has a complicated structure for incorporation into the machine in the injection shaft system from the electric motor to the injection screw, and the detector itself is expensive, and because of the structure for attaching the strain gauge to the detection unit There is a risk of detector failure.

  Therefore, in order to avoid problems related to the load cell, it is known that pressure control is performed without using a load cell (force sensor) by configuring an observer that does not require a load cell (for example, Patent Document 2).

  Further, the electric injection molding machine requires a step (pressure holding step) of maintaining a predetermined pressure and continuing pressurization after injection and filling the mold. That is, the pressure patterns used in the electric injection molding machine can be classified into four types of patterns corresponding to each process, for example, as shown in FIG. FIG. 19 shows an example of a pressure pattern used in the electric injection molding machine. The pressure pattern can be divided for each step of (1) pause, (2) injection (resin injection), (3) holding pressure, and (4) back pressure (resin metering). In the pause step (1), the electric motor is stopped, the product in the mold is ejected, the mold is clamped for the next injection, and the like is prepared for injection. In the injection step (2), the electric motor is operated to inject resin into the mold at a constant speed. At this time, the pressure in the mold rises according to the amount of resin injected at a constant speed. In the pressure-holding step (3), when the resin is cooled in the mold, a constant pressure is maintained, a decrease in filling pressure due to the back flow of the resin is prevented, and replenishment is performed when the resin is cooled and contracted. In the back pressure process of (4), the resin for the next injection is filled in the heating cylinder by the rotation of the screw and the retraction of the injection shaft. Then, the plastic resin is melted by the heat of the heating cylinder and the shear heat generated by the screw rotation. By repeating these steps as one cycle, an injection molded product is continuously produced.

  In the (3) pressure holding step shown in FIG. 19, when an electric motor is applied so as to maintain a constant pressure, the electric motor may be overloaded. In order to avoid such a problem, an effective load factor of an electric motor (servo motor) is reduced by performing pressure control by superimposing a vibration component on a required target pressure. (For example, refer to Patent Document 3).

  However, when the pressure control method described in Patent Document 3 is applied to the control device for the electric injection molding machine of Patent Document 2, a false signal that is not detected by the pressure detected by the load cell is detected by the pressure estimated by the observer. There is a case. In the electric injection molding machine, there is a problem that an estimated pressure value on which such a false signal is superimposed cannot be used as a feedback signal for feedback control. An example of a pressure control method for solving this problem is described in Patent Document 4.

  In the pressure control method described in Patent Document 4, the drag generated in response to the vibration superimposed as a current command is based on a control model in which the force acting on the driven part via the mechanical impedance element is identified as a disturbance. A configured disturbance observer unit is used. According to this configuration, it is possible to estimate the force acting on the driven part by reducing the influence of vibration superimposed on the current command according to the characteristics of the mechanical impedance element. Then, by controlling the operation of the servo motor based on the force estimated by the disturbance observer unit, the force that the operating body acts on the pressure receiver even when the pressure control is performed by superimposing the vibration component on the target pressure. Can be accurately controlled without using a force detector such as a load cell.

  However, when the applicant uses the pressure control method described in Patent Document 4, depending on the conditions, the force can be estimated correctly when the pressure is constant, but the transient in which the pressure changes stepwise. It has been confirmed that undershoot and overshoot may occur without correct force estimation in the state. An example of a control method for solving this problem is described in Non-Patent Document 1. Although the technique described in Non-Patent Document 1 can ensure the estimation accuracy for the superposition of the vibration component by the parameter related to the attenuation characteristic of the observer, the estimation accuracy in the transient state is reduced, Although it is possible to improve the estimation accuracy in the above, the reduction in accuracy due to the superimposition of vibration components may occur in a steady state. That is, in the technique described in Non-Patent Document 1, the estimation accuracy of the transient state and the estimation accuracy of the steady state are improved by switching the attenuation coefficient of the observer to two values according to the pressure change. Is. In the technique described in Non-Patent Document 1, two types of observers having different parameters are operated in parallel, and the estimated value is ensured by switching the estimated value stepwise in accordance with a pressure change.

JP-A-10-44206 Japanese Patent No. 40222646 JP 2004-114427 A JP 2011-186669 A

Ryo Furusawa, Kiyoshi Oishi, Junichi Kageyama, Masaru Takatsu, Shiro Urushibara, "Study on Force Sensorless Pressure Control of Electric Injection Molding Machine Using Parallel Higher Order Reaction Force Observer", Proc. II-799-802, September 6, 2011

  However, in the technique described in Non-Patent Document 1, two observers having different parameters are operated in parallel, and the estimated values of the force output from each observer are used while being switched. Observer execution requires relatively large computer resources. For this reason, the technique described in Non-Patent Document 1 has a problem that a large computer resource is required to execute two observers in parallel.

  The present invention has been made in view of the above circumstances, such as an electric injection molding machine, etc., in a machine that operates a working body via a power transmission means by a servo motor and applies a force to a pressure receiving body. A pressure control method apparatus and a pressure control method using a servo motor capable of accurately controlling the pressure acting on a pressure receiving body without using a force detector such as a load cell and without requiring a large computer resource. The purpose is to provide.

The present invention is characterized by the following points in order to solve the above problems.
That is, the pressure control device using a servo motor according to claim 1, to actuate the driven parts via the power transmission unit by a servomotor, in a machine that applies a force to the pressure receiving member by the driven part, the pressure receiving A pressure control device that controls the force applied to the body by controlling the output torque or rotational speed of the servo motor by a control means, the control means comprising a drive unit, a power transmission unit, and a driven unit. An observer that is constructed with respect to the constructed control model of the machine, and that estimates a force received by the driven part based on a current command to the driving part and rotation information from the driving part; and the driving part based on the force which the observer is estimated by the rotation information of the current command and the drive unit with respect to the feedback to the driven unit to feedback control the force applied to the pressure receiving A control unit, wherein the observer is constructed with respect to the control model using predetermined parameters and predetermined state variables, and according to a change in force received by the driven unit, A change in a predetermined state variable is predicted, the predetermined state variable is changed using the predicted value, and a force acting on the driven part is estimated by changing the predetermined parameter. And

  A pressure control device using a servo motor according to claim 2 is the pressure control device according to claim 1, wherein when the observer predicts a change in the predetermined state variable, the value of the state variable in a steady state It is characterized by predicting.

  A pressure control device using a servo motor according to claim 3 is the pressure control device according to claim 2, wherein when the observer predicts a change in the predetermined state variable, the value of the state variable in a steady state Is predicted using the final value theorem.

A pressure control method using a servo motor according to claim 4 activates the driven part via the power transmission unit by a servomotor, in a machine that applies a force to the pressure receiving member by the driven part, on the pressure receiving body A pressure control method for controlling the force to be applied by controlling the output torque or rotation speed of the servo motor by a control means, wherein the control means is constructed of a drive unit, a power transmission unit, and a driven unit. An observer constructed for a control model of the machine and estimating the force received by the driven unit based on a current command to the driving unit and rotation information from the driving unit; and a current for the driving unit based on the force which the observer is estimated by the rotation information of the command and the drive unit, and the feedback control unit for the driven unit is a feedback control of the force applied to the pressure receiving And the observer is constructed with respect to the control model using predetermined parameters and predetermined state variables, and the predetermined state variables according to a change in force received by the driven part. And a change in the predetermined state variable using the predicted value, and a change in the predetermined parameter to estimate a force acting on the driven part.

  In the pressure control device and the pressure control method using the servo motor, the machine rotates the ball screw shaft or the ball nut through the pulley and the belt by the servo motor, and the ball nut or An electric injection molding machine that performs molding by operating an injection screw of an injection mechanism via a ball screw shaft and injecting molten resin into a mold clamped by the mold clamping mechanism while controlling the pressure.

The present invention has the following excellent effects.
That is, according to the pressure control device using the servo motor according to claim 1 and the pressure control method according to claim 4, the observer transmits the predetermined parameter and the predetermined state variable for constructing the observer to the driven unit. When changing according to the change in the force received by the object, it is changed using the predicted value of the change in the state variable. Therefore, when changing the parameter using one observer, the change in the parameter is adjusted. The state variable can be changed appropriately. Therefore, for example, even if two observers are not operated in parallel, the force can be accurately estimated by switching two types of parameters.
This eliminates the need for a special means for incorporating the load cell into the machine, thereby simplifying the construction of the machine and improving the reliability of the pressure control device using the servo motor.

It is a block diagram which shows the control apparatus of the electric injection molding machine to which the pressure control apparatus using the servomotor which concerns on one embodiment of this invention is applied. It is a block diagram which shows the structure of an injection pressure setting part. It is a figure shown about the command value of pressure control. It is a figure which shows the control model of this embodiment. It is a block diagram in case a control object is comprised as a two-inertia system control model. It is a figure shown about the control model in this embodiment. It is a figure similarly shown about a control model. Similarly, it is a state variable diagram of the control model. It is the state variable diagram which similarly showed the control model in the other form. It is the state variable diagram of the control model which similarly added the disturbance observer part. FIG. 11 is a block diagram illustrating a configuration example of a parameter and state variable setting unit 100 illustrated in FIG. 10. 11 is a flowchart showing an example of operation of the parameter and state variable setting unit 100 shown in FIG. 10. It is a block diagram which shows the other form which applied the pressure control apparatus using the servomotor which concerns on one embodiment of this invention to the control apparatus which controls the injection pressure of an electric injection molding machine. It is a figure which shows the relationship between a linear friction compensation part and an observer. It is a figure which shows an example of a Coulomb friction compensation characteristic. It is a figure for demonstrating the time change of the repulsion torque (pressure estimated value) of the injection shaft estimated using the observer in the injection control apparatus of this embodiment. It is a figure for demonstrating the estimation result by a general observer system. FIG. 17 is a list of parameters of the experimental system shown in FIG. 16. It is the figure which showed an example of the pressure pattern in an injection molding machine.

(First embodiment)
Hereinafter, a pressure control device using a servo motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows an example in which a pressure control device using a servo motor according to an embodiment of the present invention is applied to a control device for controlling the injection pressure of an electric injection molding machine. In FIG. 1, reference numeral 1 denotes an electric injection molding machine (machine), a heating cylinder 4 having a nozzle 3 at a tip attached to a support plate 2, and a rotation around the axis in the heating cylinder 4 in an axial direction. An injection screw (pressure receiving body) 5 that is movably inserted and a support base 6 that rotatably supports the outer end of the injection screw 5 are provided. The support base 6 is screwed to the ball screw shaft 8 with a pair of ball screw shafts 8 rotatably supported with respect to the support plate 2 and another support plate 7 disposed opposite thereto. It is supported at two locations via a ball nut 9.

A pulley 10 is attached to one end of each ball screw shaft 8, and a timing belt (belt) 13 is stretched between the pulley 10 and a pulley 12 attached to the output shaft of the servo motor 11. The rotation of the servo motor 11 causes the ball screw shafts 8 to rotate through the timing belt 13 and the pulleys 10 and 12, and the support base 6 reciprocates through the ball nuts 9 screwed into these. As a result, the injection screw 5 moves in the axial direction thereof, and a mold (FIG. 3) is obtained by clamping the molten resin measured at the tip of the heating cylinder 4 by the rotation of the injection screw 5 by a mold clamping mechanism. (Not shown). Reference numeral 14 denotes a pulse encoder (position detector) that generates a pulse corresponding to the rotational position of the servo motor 11.

  On the other hand, a control device (control means) 15 for controlling the injection pressure for injecting the molten resin into the mold includes an injection speed setting unit 16 for setting the injection speed set value VSV by the operator, and an injection for setting the injection pressure set value. The servo motor 11 detected by the pressure detector 17 and the rotational angular velocity (rotation information) ωm (see FIG. 4) derived based on the current rotational position θ of the servomotor 11 detected by the pulse encoder 14 and the current detector 18. Is provided with an observer 19 for estimating an injection pressure feedback value from a current value (current command) I for the above and an injection pressure feedback control unit 20. The injection pressure feedback control unit 20 includes an adder 21 for obtaining a deviation value between the injection pressure feedback value estimated by the observer 19 and the injection pressure setting value by the injection pressure setting unit 17, and performs PID calculation on the deviation value. The first PID calculator 22 to be executed, the comparator 23 for comparing the output value MV of the PID calculator 22 with the injection speed setting value VSV by the injection speed setting unit 16, and MV> VSV in the comparator 23 In this case, the PID calculator 22 is composed of a switch 25 for disconnecting the integration element 22a from the circuit.

  Further, the control device 15 clamps (limits) the injection speed command unit 26 that obtains the speed command value SV from the output value MV, and the speed command value SV input from the injection speed command unit 26 by the injection speed set value VSV. ) To output an output value VLIN (VLIN = SV when VSV> SV, VLIN = VSV when VSV ≦ SV), and rotation based on the rotational position θ from the pulse encoder 14. An injection speed feedback input circuit 28 for converting into an angular speed (rotation information) ωm, and a deviation value between the output value VLIN of the injection speed limiter 27 and the rotational angular speed ωm output from the injection speed feedback input circuit 28 by an adder 29 The injection speed feedback control unit 31 that performs the PID calculation by the second PID calculator 30 on the deviation value, and the flow from the current detector 18. An adder 32 that calculates a deviation value between the feedback current and the calculation output of the second PID calculator 30 and a PID calculator 33 for current control that performs PID calculation of the deviation value obtained by the adder 32 are provided. ing. The output current of the current control PID calculator 33 finally becomes a current command value (current command) I to the servo motor 11. The PID calculators 22 and 30 are variable control constants.

Next, the observer 19 constructs the electric injection molding machine 1 based on a control model composed of a drive unit, a power transmission unit, and a driven unit, an operation command for the drive unit of the control model, and an injection speed It is constructed as an estimator that estimates the force acting on the driven part from the rotational angular velocity (rotation information) of the driving part converted by the feedback input circuit 28. Further, the observer 19 receives the pressure set value P output from the injection pressure setting unit 17 and changes predetermined parameters and control variables constituting the observer 19 in accordance with the change in the pressure set value P.
In this embodiment, the observer 19 is applied to a two-inertia control model as shown in FIG.
That is, as shown in FIG. 4, the control model (control model) 38 of the electric injection molding machine 1 includes the servo motor 11 via the torque constant element 35a having the torque constant Kt and the addition point 35b. The driving unit 35 is constituted by a transmission element including a torque / rotation element 35c coupled to the torque constant element 35a. The torque / rotation element 35c includes a pulse encoder (position detector) 14 and an injection speed feedback input circuit 28, and obtains the rotation angular speed ωm of the servo motor 11 as an output of the drive unit 35. explain.

  Further, the control model 38 includes a pair of rotational angular velocity conversion elements having gear ratios (rotational ratios) Rg in which the pulleys 10 and 12 and the timing belt 13 are respectively coupled to the addition point 35b and the drawing point 35d of the drive unit 35. 36a, 36b, a spring constant element 36c having the spring constant Ks of the timing belt 13 coupled to one rotational angular velocity conversion element 36a, and the other coupled to the spring constant element 36c and via an addition point 36d The rotational angular velocity converting element 36b and the converting element 36e coupled to the rotating angular velocity converting element 36b are configured as a power transmitting unit 36.

  In the control model 38, the ball screw shaft 8, the ball nut 9, the support base 6 and the like are coupled to the spring constant element 36c via the addition point 37a and from the lead point 37b to the addition point 36d. It is constructed and constructed as a driven portion 37 composed of a transmission element including a driven element 37c coupled to the conversion element 36e.

The torque / rotation element 35c includes a primary-side equivalent inertia moment Jm and a viscosity coefficient Dm, and the driven-side element 37c includes a secondary-side equivalent inertia moment JL and a viscosity coefficient DL. Yes.
The observer 19 is supplied with a current command value (current command) ICMD (hereinafter, the current command value may be expressed as Iq) for the drive unit 35 from a lead point 35f and from the drive unit 35. The rotation angular velocity (rotation information) ωm of the servo motor 11 that is the output of the servo motor 11 is supplied from the injection speed feedback input circuit 28, and the estimated value τext_dc (hat) of the DC component of the external force that is the estimated torque (force or pressure) is obtained. Output.
The observer 19 includes a disturbance observer unit 19a for deriving a state variable based on a current command value ICMD and a rotational angular velocity ωm supplied to the observer 19, and a state variable derived by the disturbance observer unit 19a, that is, a disturbance A vibration removing unit 19b that reduces the influence of disturbance estimated by the observer unit 19a is provided. A detailed description of the observer 19 will be given later.

A command value for pressure control in the injection control device will be described with reference to FIGS. 2 and 3.
FIG. 2 is a block diagram showing a configuration of the injection pressure setting unit 17.
FIG. 3 is a diagram showing command values for pressure control.
The injection pressure setting unit 17 sets the holding pressure setting values Pi (P1 to P3) in the injection pressure setting value P as constant values that do not change with respect to time t, as shown in FIG. The setting portion 17a and the constant pressure holding pressure Pi set in the constant value setting portion 17a are processed, and the pressure having a predetermined frequency f (period ω0) and amplitude A as shown in FIG. A set value processing unit 17b that outputs a holding pressure command value with fluctuation (vibration), a frequency setting unit 17c that sets a frequency f (cycle ω0) of the holding pressure command value, and an amplitude A of the holding pressure command value And a changeover switch (switching means) 17e for switching and connecting one of the constant value setting unit 17a and the set value processing unit 17b to the injection pressure feedback control unit 20. I have.
The changeover switch 17e is used to change the setting of whether the servomotor 11 is rotated by a constant pressure holding value Pi from the constant value setting portion 17a or a pressure holding command value Pc from the setting value processing portion 17b. Is to do. The constant value setting unit 17a, the frequency setting unit 17c, and the amplitude setting unit 17d are configured to appropriately input numerical values using a setting key or the like.

  The set value processing unit 17b receives a constant holding pressure set value Pi input from the constant value setting unit 17a as shown in FIG. 3A from the frequency setting unit 17c and the amplitude setting unit 17d. The required calculation is performed based on the frequency f and the amplitude A, and as shown in FIG. 3B, the pressure change is repeated as time elapses above and below the constant holding pressure setting value Pi. A holding pressure command value Pc with vibrations consisting of a sin curve, a cosine curve, a triangular wave, a trapezoidal wave, a rectangle and the like having a constant amplitude A and a constant frequency f is processed, and control data corresponding to the holding pressure command value Pc is described above. This is stored in the storage area of the injection pressure feedback control unit 20 via the changeover switch 17e.

Thus, the set pressure processing unit 17b displays the holding pressure setting value Pi input from the constant value setting unit 17a based on the frequency f and the amplitude A input from the frequency setting unit 17c and the amplitude setting unit 17d, respectively. The pressure holding command value Pc accompanied by vibration as shown in 3 (b) is processed. This holding pressure command value Pc is stored in the storage area of the injection pressure feedback control unit 20 through the changeover switch 17e together with the filling pressure set value P0 set by the constant value setting unit 17a.
For a detailed control method of the pressure control command value in the injection control device, refer to Patent Document 3 and the like.

FIG. 4 is a diagram illustrating a control model of the present embodiment.
In the control model 38 shown in FIG. 4, when the current command value ICMD is input to the torque constant element 35 a of the drive unit 35 (servo motor 11), the driven unit 37 is operated via the power transmission unit 36. . As a result, the rotational position θm of the drive unit 35 changes and the rotational angular velocity ωm as an output changes. Then, the observer 19 takes in the current command value ICMD and the rotational angular velocity ωm. A deviation between the rotational angular velocity ωL to be originally generated by the current command value ICMD and the captured actual rotational angular velocity ωm occurs.
The observer 19 estimates the repulsive torque applied to the drive unit 35 based on the deviation of the derived rotational angular velocity. A resistance force (estimated torque (estimated value τext_dc (hat)) of the direct current component of the external force) to the force that the driven unit 37 receives from the resistor model is estimated from the resistance torque. This estimated torque (estimated value τext_dc (hat) of the DC component of the external force) is used as an input signal for feedback control of the injection pressure of the electric injection molding machine 1.

FIG. 5 is a configuration diagram when the control target is configured as a two-inertia control model.
First, differential equations relating to the respective state variables when the observer is configured as a two-inertia reaction force estimation observer will be sequentially shown. The variables shown in each equation are: ICMD is a motor current command value, Kt is a torque constant, Rg is a gear ratio, Ks is a spring constant, Jm is a motor inertia moment, Dm is a motor viscosity coefficient, JL is a load side inertia moment, DL Is the load-side viscosity coefficient.

  Further, since it can be developed as a state variable diagram 38a as shown in FIG. 8, the rotational angular velocity (rotation information) ωL on the load side (driven unit 37), the servo motor side (driving unit 35) and the load side Is the first derivative of the load side torque τL and the load side torque τL that the injection screw 5 receives from the rotation position difference (rotation angle difference) θs, the servo motor side rotation angular velocity ωm, and the resin pressure (force estimated by the observer 19). (Dot), the second derivative of the load side torque τL is shown as τL (two dots). In the equation, τL (dot) has one point (dot) on τL. Further, τL (two dots) has two points (dots) on τL.

  A differential equation of the torsion angle θs, which is the difference in rotational position (rotational angle difference) between the servo motor side (drive unit 35) and the load side (driven unit 37), is shown as equation (1).

  A differential equation of the rotational angular velocity (rotation information) ωL on the load side (driven portion 37) is shown as equation (2).

  A differential equation of the rotational angular velocity ωm on the servo motor side (drive unit 35) is shown as equation (3).

FIG. 6 is a diagram showing the definition of disturbance in the present embodiment.
The drive object of the moment of inertia Jm is driven according to the torque τm supplied from the servo motor side shown in FIG. 6 to obtain the rotational angular velocity ωm. However, the rotational angular velocity ωm changes with the influence of the load side torque τL from the load side with respect to the supplied torque τm.
In the present embodiment, the harmonic component τext_ac of the external force is superimposed on the DC component τext_dc of the external force corresponding to the force command value for driving the injection screw (pressure receiving body) 5 (hereinafter referred to as “injection shaft”) of the electric injection molding machine 1. Thus, control is performed so that the static frictional force does not affect the injection shaft of the electric injection molding machine 1. The fundamental frequency of the harmonic component τext_ac of the external force is shown as ω0.
The injection shaft of the electric injection molding machine 1 is driven by the command value on which the harmonic component τext_ac of the external force is superimposed. When the injection shaft is driven to pressurize the molten resin (injection target), a harmonic component of the reaction force is generated.
Since the harmonic component of the reaction force is generated by the harmonic component τext_ac of the external force driven based on the command value, it is generated at the same frequency component, that is, the fundamental frequency ω0.

With a normal observer, if only the harmonic input component superimposed on the input signal is used, the disturbance input can be estimated without being affected by the harmonic. However, in the case of the electric injection molding machine 1, since this disturbance input is a reaction force when the injection shaft pushes the molten resin, the reaction force having the same frequency as the superimposed harmonic force is also a reaction force caused by the injection of the injection shaft. Simultaneously with the force, the electric injection molding machine 1 is applied as a disturbance input.
The harmonic reaction force has the same frequency as the superimposed harmonic, but the molten resin has mechanical impedance, so even with the same frequency reaction force, the phase of the superimposed harmonic force and the phase of the reaction force are different. The phase value is unknown. Therefore, it cannot be modeled because it is impossible to predict what waveform reaction force is applied.
Therefore, the influence of this harmonic component cannot be completely eliminated by an estimation method using a normal observer. Normal observers are both state observers and disturbance observers.

FIG. 7 is a diagram illustrating a control model in the present embodiment.
Therefore, as shown in FIG. 7, the direct current component τext_dc of the external force received by the injection shaft passes through the mechanical impedance element 39 having the natural frequency of the same frequency as the harmonic component τext_ac of the external force superimposed by the reaction force due to the injection pressure. Therefore, a high-order disturbance observer that is not affected by the natural frequency ω0 is considered as load side torque τL applied to the injection shaft.
In other words, this higher-order disturbance observer is constructed by constructing a disturbance observer unit 19a that uses the load-side torque τL applied to the injection shaft as a disturbance input, and includes the estimated value of the load-side torque τL in the state quantity that is the estimated output. .
Note that the load side torque τL acting on the injection shaft varies with the external force τext. The external force τext is an addition value of the DC component τext_dc of the external force and the harmonic component τext_ac of the superimposed external force, and is expressed as Expression (4).

This higher-order disturbance observer estimates the disturbance input (DC component τext_dc of the external force) before passing through the mechanical impedance element 39 having the natural frequency without being influenced by the phase of the reaction force of the harmonic component τext_ac of the external force. can do.
As a result, the disturbance input (reaction force) can be estimated without being influenced by the harmonics of the force pressed by the electric injection molding machine 1 and the harmonics received by the molten resin from the environment.

The disturbance observer unit 19a regards an unknown disturbance input as a state variable, adds a state equation, and estimates the disturbance input.
In the injection molding machine modeled by the two-inertia system according to the present embodiment, the load side torque τL is affected by the mechanical impedance element 39 and affects the torque τm.
Moreover, the differential equation regarding the state variable of the disturbance observer unit 19a is shown as Expression (5).

FIG. 9 is a state variable diagram showing the control model 38 of the electric injection molding machine 1 in another form.
The control model 38b of the electric injection molding machine 1 shown in FIG. 9 can be represented by a state equation expressed as Equation (6) and an output equation expressed as Equation (7).

In Expressions (6) and (7), A represents a system matrix, B and D represent control matrices, x represents a state variable, u represents an input variable, y represents an output variable, and C represents Indicates the output matrix.
In order to apply the higher-order disturbance observer to the reaction force estimation observer, model parameters are applied and a differential expression of each state variable is derived and expressed as Expression (8).

  In the differential equation shown in Equation (8), the rotational speed (rotation information) ωL on the load side (driven unit 37), the difference in rotational position between the servo motor side (drive unit 35) and the load side (rotational angle difference) ) Θs, rotation speed ωm on the servo motor side, load side torque τL received by the injection screw 5 from the resin pressure (force estimated by the observer 19), τL (dot) which is a first derivative of the load side torque τL, and load side When τL (two dots), which is the second derivative of the torque τL, is given as the state variable x, a state equation is obtained as equation (9) and an output equation is obtained as equation (10).

FIG. 10 is a state variable diagram of a control model in which the control model 38 of the electric injection molding machine 1 is shown in another form and a disturbance observer unit is added.
Based on the configuration shown in FIG. 10, the disturbance observer unit 19 a in the observer 19 can be identified. The disturbance observer unit 19 a illustrated in FIG. 10 includes elements 41 to 52 that are basic elements of the observer for the control model 38, and a parameter and state variable setting unit 100. The parameter and state variable setting unit 100 receives the pressure set value P and changes predetermined parameters in the elements 41, 49 and 51 and the state variable x (hat) in accordance with the pressure set value P. The predetermined parameter in the elements 41, 49 and 51 is the attenuation coefficient ζ in the present embodiment. The state variable x (hat) is changed by setting a value in the steady state of the state variable x (hat) predicted after a predetermined time in the integration element 43 after changing the parameter. Element 41 is a transfer function matrix Bh, element 42 is an adder, element 43 is an integral element (ie, 1 / s function), element 44 is a branch point, and element 45 is a transfer function matrix Ch. Element 46 is a branch point, element 47 is an adder, element 48 is a multiplier of coefficient K, element 49 is a transfer function matrix Ah, element 52 is an adder, and element 51 is a transfer function matrix Dh.
For the transfer function matrices Ah, Bh, Ch, and Dh in the disturbance observer unit 19a shown in FIG. 10, for example, based on the state equation shown as the equation (9), for example, “Gopinus design method” is used to reduce higher-order disturbances. Designed as a reaction force estimation observer with consideration.

  In this embodiment, the disturbance observer unit 19a is configured as a two-inertia-type reaction force estimation observer that removes an arbitrary frequency component. The observer 19 performs force estimation by removing only the frequency component superimposed by the injection pressure setting unit 17. Equations (11) and (12) show state equations representing the observer portion 19a.

  In equations (11) and (12), ζ represents an attenuation coefficient. Further, a, b, c, d, and e are parameters determined as follows by the pole α of the disturbance observer unit 19a. However, in order to simplify the equation, L = 1 / JL.

Here, Ah, Bh, and Dh represent transfer function matrices, matrix x1 represents state variables, matrix u1 represents input variables, matrix y1 represents output variables, and Ch represents an output matrix.
The direct current component τext_dc (hat) of the reaction force estimation value obtained by removing the input vibration component from τL (hat), τL (dot hat), and τL (two dot hat) obtained from the equations (11) and (12) is It is calculated by.

τL (hat), τL (dot hat), and τL (two dot hat) are the estimated value of the estimated load-side torque τL, the estimated value of the first derivative of τL, and the estimated value of the second derivative of τL, respectively.
By the procedure shown above, the observer 19 having the disturbance observer unit 19a as an element can be configured.
Further, it is assumed that the vibration removing unit 19b to which the state variable is supplied from the disturbance observer unit 19a has a characteristic opposite to that of the mechanical impedance element 39 described above. An estimated value of the DC component τext_dc of the external force is derived by the observer 19.

  On the other hand, the parameter and state variable setting unit 100 shown in FIG. 10 can be configured as shown in FIG. 11, for example. The parameter and state variable setting unit 100 illustrated in FIG. 11 includes a setting change necessity determination unit 101 and a parameter and state variable change unit 102. The setting change necessity determination unit 101 receives the pressure setting value P input from the injection pressure setting unit 17, and when the pressure setting value P changes to satisfy a predetermined determination condition, the parameter and state variable changing unit 102 is instructed to change parameters and state variables. The parameter and state variable changing unit 102 receives an instruction from the setting change necessity determining unit 101, and changes a predetermined parameter, that is, the value of the attenuation coefficient ζ in the present embodiment. Also, the parameter and state variable changing unit 102 receives an instruction from the setting change necessity determining unit 101, predicts a predetermined change in the state variable, and changes the state variable in the element 43 using the prediction result. That is, the state variables x1, x2, x3, x4, and x5 in the expressions (11) and (12) are changed. At that time, the parameter and state variable changing unit 102 predicts the value of the state variable in the steady state using the final value theorem, for example, when predicting the change of the state variable.

  The process in which the parameter and state variable changing unit 102 predicts the value of the state variable in the steady state using the final value theorem is performed as follows. That is, the parameter and state variable changing unit 102 applies the pulse transfer function from the system input Iq (= ICMD) to the state variables x1, x2, x3, x4, and x5 in order to improve the estimation error at the time of parameter switching. Define as follows.

  Then, using the final value theorem in a discrete system, the final value of each state variable when the input is a step function of Iq is as follows.

  When switching parameters, the final value of each state variable after switching is calculated from Equation (15) and replaced with the state variable before switching. The parameters are switched only in the steady state of the pressure holding process shown in FIG. In the pressure holding step (3), since the motor speed is substantially zero in the steady state, the calculation is performed assuming that the term of the motor speed is zero.

  In addition, when the state equations shown in the equations (11) and (12) are expressed in a discrete system, the equations (16) and (17) are obtained.

  When the state equations are (16) and (17), the pulse transfer function Gi (z) (i = 1,..., 5) is expressed by the equations (18) to (22).

  Moreover, each variable in Formula (18)-(22) is represented as follows.

  In addition, when the example of operation | movement of the parameter and state variable setting part 100 is made into a flowchart, it can represent as shown, for example in FIG. That is, the parameter and state variable setting unit 100 determines whether or not the pressure change value P indicates a change that satisfies a predetermined condition by the setting change necessity determination unit 101 (step S1). The change in which the pressure set value P satisfies a predetermined condition is, for example, that the pressure set value P has a value corresponding to the pressure holding step (3), or a certain level or more in the pressure holding step (3). For example, having a variation in size. When it is determined that the condition is satisfied in step S1, after waiting for a predetermined time (step S2), the parameter and state variable changing unit 102 sets the value of the steady state state variable to the final value in accordance with an instruction from the setting change necessity determining unit 101. The prediction is performed using the theorem, the state variable is changed using the predicted value, and the parameter (that is, the attenuation coefficient ζ) is changed (step S3).

Next, a modification of the above embodiment will be described.
(Second Embodiment)
Hereinafter, a pressure control device using a servo motor according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 13 shows another embodiment in which a pressure control device using a servo motor according to an embodiment of the present invention is applied to a control device for controlling the injection pressure of an electric injection molding machine. The same components as those in FIGS. 1 and 4 are denoted by the same reference numerals.
The electric injection molding machine (machine) 1 shown in FIG. 13 includes a linear friction compensator 40 in addition to the control model 38 and the observer 19 shown in FIG.
The linear friction compensation unit 40 includes a Coulomb friction interpolation unit 41 that performs a Coulomb friction interpolation operation, and a coefficient operator 42 that multiplies the compensation value converted by the Coulomb friction interpolation unit 41 by a predetermined proportional coefficient.
The linear friction compensator 40 reduces the influence of the Coulomb friction when the servo motor 11 is reversed. The linear friction compensator 40 can reduce the influence of the frictional force by interpolating the characteristics in the vicinity of the change point in order to reduce the steep change that occurs at the change point where the rotation direction changes.

FIG. 14 is a diagram illustrating a relationship between the linear friction compensation unit and the observer.
The linear friction compensation unit 40 generates a motor torque compensation amount due to a change in frictional force based on the rotational angular velocity ωm of the servo motor 11 branched from the branch point 35d. The generated motor torque compensation amount is added to the motor torque by the adder 43. Thereby, the compensated motor torque is supplied to the observer 19.
That is, the control model configured as the observer 19 is not configured to compensate for the Coulomb friction force. However, since the input control command value ICMD corresponds to the motor torque to be generated, the influence of the static friction force can be reduced by the above compensation method.

FIG. 15 is a diagram illustrating an example of Coulomb friction compensation characteristics.
The graph shown in FIG. 15 shows the conversion characteristics of the Coulomb friction interpolation unit 41.
The vertical axis represents the friction force compensated according to the rotational angular velocity, and the horizontal axis represents the rotational angular velocity.
The range of the motor speed value from −v0 to + v0 is interpolated with the sin characteristic.
A specific interpolation characteristic is shown as Expression (23).

  In equation (23), the setting range of the coulomb friction interpolation speed v0 can be set in increments of 1 (rotation / minute), for example, from 1 (rotation / minute) to 15 (rotation / minute). In this case, the standard value is 10 (rotations / minute).

  Next, the result of verifying the effect of the present invention will be described with reference to FIGS. 16 and 17. FIG. 16 shows the simulation result of the estimated force value when the parameters and the state variables are changed. FIG. 16A shows a pressure response waveform and an observer mode signal, and FIG. 16B shows state variables. Here, the observer mode represents an operation mode in which the attenuation coefficient ζ is 0.0 when 0 and the attenuation coefficient ζ is 0.7 when 1. When the simulation result shown in FIG. 16 is seen, it can be confirmed that the large estimation error at the time of parameter switching, which is seen in the change of the estimated value when the state variable of FIG. 17 is not changed, is improved. According to this result, it was confirmed that the state variable was appropriately corrected at the time of switching by the configuration of the present embodiment. A list of parameters used in the simulation is shown in FIG.

In addition, the structure shown as embodiment of this invention shows one embodiment, A structure, a capacity | capacitance, a quantity, etc. can be changed in the range which does not change the summary of this invention.
For example, in the present embodiment, the characteristic of the mechanical impedance element 39 that generates a disturbance is shown as a secondary system, but a required order can be selected. The order of the load side torque τL estimated by the disturbance observer unit 19a is determined in accordance with the selected order of the mechanical impedance element, and the characteristic of the vibration removing unit 19b at the subsequent stage is also determined by the mechanical impedance element 39 (resonance system). Change to the reverse characteristic (attenuation system) characteristic corresponding to.

In the Coulomb friction compensation shown as means for friction compensation, the interpolation function is shown as a sin function, but other functions that change monotonously (such as polygonal line approximation and trapezoidal interpolation) can be used.
Further, the amount of friction compensation is appropriately determined according to the control system to be applied because it depends on the configuration of the control system to be configured.
Further, the rotation information of the servo motor referred to by the observer can be position information detected as a rotation angle or rotation angular velocity information.

In the above description, the example in which the pressure control device using the servo motor according to the present invention is applied to the case where the injection pressure is controlled by the injection screw in the injection mechanism of the electric injection molding machine 1 has been shown. Not limited to this, it can be applied to control of the back pressure applied to the injection screw during weighing, or the movable plate can be moved directly or indirectly via a linear movement mechanism in which a ball nut is screwed onto the ball screw shaft by a servo motor. The present invention can also be applied to the case of controlling the mold clamping pressure in the mold clamping mechanism for clamping the mold between the movable platen and the fixed platen, or the case of controlling the ejecting pressure of the ejector.
Furthermore, the linear movement mechanism formed by screwing the nut onto the screw shaft via the transmission mechanism by the electric motor is operated, and the pressure plate connected to the linear movement mechanism is moved, and the pressure plate and the fixed plate are moved. In a press machine that press-molds a workpiece in between, the pressure (force) applied to the pressure platen can be controlled, and the pressure (force) can be controlled in other industrial machines.

In addition, in the machine which operates an operating body via the power transmission means by the servo motor 11 of the present embodiment and applies force to the injection screw 5 (pressure receiving body) by the operating body, control of the force applied to the injection screw 5 is controlled. Is a pressure control device that controls the output torque or the rotational speed of the servo motor 11 by the control means, and the control means 15 controls the machine constructed by the drive unit, the power transmission unit, and the driven unit. An observer 19 that is constructed for the model and estimates the force received by the driven unit based on the current command to the driving unit and the rotation information from the driving unit, and the current command to the driving unit and the rotation of the driving unit A feedback control unit that feedback-controls the force that the operating body acts on the pressure-receiving body based on the force estimated by the observer 19 based on the information. The observer 19 is constructed with respect to the control model using a predetermined parameter (attenuation coefficient ζ) and a predetermined state variable, and according to a change in the force received by the driven part (37), By predicting a change in a predetermined state variable (matrix x1 or variables x1 to x5), changing the predetermined state variable using the predicted value and changing a predetermined parameter, the driven unit (37) is changed. Estimate the acting force.
Thereby, for example, even if two observers are not operated in parallel, the two types of parameters can be switched to accurately estimate the force. Further, since no special means for incorporating the load cell into the machine is required, the structure of the machine can be simplified and the reliability of the pressure control device using the servo motor can be increased.

In addition, the disturbance observer unit 19a of the present embodiment predicts the value of a steady state state variable when predicting a change of a predetermined state variable, or more specifically, the value of a steady state state variable is set to a final value. Or predict using the theorem.
These calculations can be performed relatively easily as compared with the case of obtaining the transient value. Therefore, for example, when the change of the state variable is predicted when the force is estimated by switching two types of parameters, the amount of calculation required for the prediction is not greatly increased.

1 Electric injection molding machine (machine)
4 Heating cylinder 5 Injection screw (pressure receiving body)
6 Support base 8 Ball screw shaft 9 Ball nuts 10 and 12 Pulley 13 Timing belt (belt)
14 Pulse encoder (position detector)
DESCRIPTION OF SYMBOLS 15 Control apparatus 16 Injection speed setting part 17 Injection pressure setting part 18 Current detector 19 Observer 20 Injection pressure feedback control part 19a Disturbance observer part 100 Parameter and state variable setting part

Claims (4)

Via a power transmission unit to operate the driven part by a servomotor, in a machine that applies a force to the pressure receiving member by the driven unit, a control of the force applied to said pressure receiving member, the servo motor output by the control means A pressure control device for controlling torque or rotational speed,
The control means is constructed with respect to a control model of the machine constructed from a drive unit, a power transmission unit, and a driven unit, and is based on a current command to the drive unit and rotation information from the drive unit. An observer for estimating the force received by the driven part;
A feedback control unit that feedback-controls the force applied to the pressure receiving body by the driven unit based on the force estimated by the observer based on the current command to the driving unit and the rotation information of the driving unit ;
With
The observer is constructed for the control model using a predetermined parameter and a predetermined state variable, and changes the predetermined state variable according to a change in the force received by the driven unit. A servo motor is used that predicts, changes the predetermined state variable using the predicted value, and estimates the force acting on the driven part by changing the predetermined parameter. Pressure control device. The pressure control apparatus using a servo motor according to claim 1, wherein the observer predicts a value of a state variable in a steady state when predicting a change in the predetermined state variable. The servo motor according to claim 2, wherein the observer predicts a value of a steady state state variable using a final value theorem when predicting a change in the predetermined state variable. Pressure control device using. Via a power transmission unit to operate the driven part by a servomotor, in a machine that applies a force to the pressure receiving member by the driven unit, a control of the force applied to said pressure receiving member, the servo motor output by the control means A pressure control method for controlling torque or rotational speed,
The control means is constructed with respect to a control model of the machine constructed from a drive unit, a power transmission unit, and a driven unit, and is based on a current command to the drive unit and rotation information from the drive unit. An observer for estimating the force received by the driven part;
A feedback control unit that feedback-controls the force applied to the pressure receiving body by the driven unit based on the force estimated by the observer based on the current command to the driving unit and the rotation information of the driving unit ;
Use
The observer is constructed for the control model using a predetermined parameter and a predetermined state variable, and changes the predetermined state variable according to a change in the force received by the driven unit. A servo motor is used that predicts, changes the predetermined state variable using the predicted value, and estimates the force acting on the driven part by changing the predetermined parameter. Pressure control method.

Images