Servo motor control device

Abstract

To provide a servomotor controller capable of restricting pressure during velocity control and position control without requiring adjustment of parameters relating to pressure restriction.SOLUTION: A speed controller includes a pressure acquisition unit 9, a pressure deviation value calculator 2, a pressure command value calculator 3, a specified pressure acquisition unit 12, a pressure limiter 4, a pressure controller 5, and a motor speed control unit 15. The pressure limiter 4 maintains a pressure command value Prc1 when the pressure command value Prc1 is lower than a specified pressure Prs, and sets the specified pressure Prs to the pressure command value when the pressure command value Prc1 exceeds the specified pressure Prs.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for a servo motor.

Background Art

[0002] In the prior art, an injection molding machine is known that controls the injection screw speed in the injection process and controls the injection screw pressure in the holding pressure process. Further, an injection molding machine is known that limits the injection pressure in the injection process in order to prevent resin formation defects due to the injection pressure being too high.

[0003] For example, Patent Document 1 discloses a control device that performs pressure limitation so that the execution value of the injection pressure does not exceed a preset injection pressure upper limit value in the injection process. The control device includes a speed control circuit that detects the execution value of the injection speed and performs feedback control based on the deviation between the execution value and the set value, a pressure limitation circuit that detects the execution value of the injection pressure and outputs a calculation only when the execution value exceeds the injection pressure upper limit value, and an addition circuit that adds the output of the pressure limitation circuit and the output of the speed control circuit. Thereby, during the injection speed control in the injection process, the execution value of the injection pressure is detected and the injection pressure is limited so as not to exceed the injection pressure upper limit value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in a configuration where the output of such a speed control circuit is corrected by the output of a pressure limit circuit, the output of the pressure limit circuit for limiting the output of the speed control circuit during pressure limit is required. Further, in order to limit the pressure as commanded, the pressure control gain must be adjusted in consideration of the output of the speed control circuit. However, since the output of the speed control circuit varies depending on the load state, it is difficult to adjust the pressure control gain. Therefore, there is room for further improvement in the drive control of the servo motor.

[0006] Therefore, the present invention provides a control device for a servo motor that does not require adjustment of parameters related to pressure limit and can perform pressure limit during speed control or position control.

Means for Solving the Problems

[0007] A control device for a servo motor according to one aspect of the present invention is a control device for a servo motor that controls a servo motor that drives a linear motion mechanism for moving an object based on a speed command value, a pressure acquisition unit that acquires a detected pressure from a pressure sensor that detects the pressure with which the linear motion mechanism presses the object, a pressure deviation value calculator that calculates a pressure deviation value indicating how much the detected pressure is to be changed based on the speed command value, a pressure command value calculator that calculates a pressure command value by adding the pressure deviation value and the detected pressure, a designated pressure acquisition unit that acquires a designated pressure, a pressure limiter that limits the pressure command value based on the designated pressure, a pressure controller that calculates a motor speed command value by controlling the pressure so that the detected pressure matches the pressure command value limited by the pressure limiter, a motor speed control unit that performs speed control on the servo motor according to the motor speed command value, and has the pressure limiter is when the pressure command value is less than the designated pressure, the pressure command value is maintained as it is, When the pressure command value exceeds the specified pressure, set the specified pressure to the pressure command value.

[0008] A control device for a servo motor according to one aspect of the present invention is a control device for a servo motor that controls a servo motor driving a linear motion mechanism for moving an object based on a position command value, an encoder that detects the position of the servo motor, a position controller that calculates a position deviation value from the detected position and the position command value, and calculates a speed command value from the position deviation value, a pressure acquisition unit that acquires a detected pressure from a pressure sensor that detects the pressure with which the linear motion mechanism presses the object, a pressure deviation value calculator that calculates a pressure deviation value indicating how much the detected pressure is to be changed based on the speed command value, a pressure command value calculator that adds the pressure deviation value and the detected pressure to calculate a pressure command value, a specified pressure acquisition unit that acquires a specified pressure, a pressure limiter that limits the pressure command value based on the specified pressure acquired from the specified pressure acquisition unit, a pressure controller that controls the pressure so that the detected pressure matches the pressure command value limited by the pressure limiter and calculates a motor speed command value, a motor speed control unit that speed-controls the servo motor according to the motor speed command value, and has The pressure limiter When the pressure command value is less than the specified pressure, maintains the pressure command value as it is, When the pressure command value exceeds the specified pressure, sets the specified pressure to the pressure command value.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a control device for a servo motor that can limit pressure during speed control or position control without requiring adjustment of parameters related to pressure limitation.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments, members having the same reference numerals as those already described will be omitted for the sake of convenience of explanation. Also, the dimensions of each member shown in the drawings may be different from the actual dimensions of each member for the sake of convenience of explanation.

[0012] (First Embodiment) FIG. 1 is a block diagram showing the configuration of a servo motor control device according to a first embodiment of the present invention. The servo motor control device according to the first embodiment is a control device that can control the speed of a motor within a set limit pressure range by setting from the outside the pressure range (hereinafter also referred to as "limit pressure range") when injecting (hereinafter also referred to as "injection process") or holding pressure (hereinafter also referred to as "holding pressure process") a material such as molten resin into a mold in an injection molding machine equipped with a servo motor. The servo motor drives and controls a linear motion mechanism that moves an object.

[0013] As shown in FIG. 1, a control device for a servo motor M (hereinafter also referred to as a motor control device 100) includes a pressure deviation value calculator 2, a pressure command value calculator 3, a pressure limiter 4, a pressure deviation value calculator 14, a pressure controller 5, a motor speed control unit 15, a pressure acquisition unit 9, an encoder 10, a speed calculator 11, and a designated pressure acquisition unit 12. The motor speed control unit 15 is composed of a speed deviation value calculator 6, a speed controller 7, and a torque controller 8.

[0014] For the motor control device 100 configured as described above, a speed command value Vc for controlling the motor speed Vm of the servo motor M is input from the outside, and a designated pressure value Prs for limiting the pressure Pr of the injection molding machine IM is acquired by the designated pressure acquisition unit 12. The designated pressure acquisition unit 12 may acquire the designated pressure value Prs recorded in advance from a non-volatile memory (not shown), or may acquire the designated pressure value Prs from a device such as an external input device. Based on the speed command value Vc and the designated pressure value Prs, the motor control device 100 performs speed control of the motor speed Vm of the servo motor M under a desired speed and a certain pressure limit.

[0015] The desired speed command value Vc given from the outside is input to the pressure deviation value calculator 2. The pressure deviation value calculator 2 calculates a pressure deviation value Prd indicating how much the current pressure Pr of the injection molding machine IM needs to be changed based on the input speed command value Vc.

[0016] The pressure deviation value calculator 2 inputs the calculated pressure deviation value Prd to the pressure command value calculator 3. Further, a pressure sensor 13 provided in the injection molding machine IM detects the pressure Pr of the injection molding machine IM, and the pressure acquisition unit 9 acquires the detected pressure Pr and inputs it to the pressure command value calculator 3. The pressure command value calculator 3 adds the pressure deviation value Prd and the pressure Pr to calculate a pressure command value Prc1 based on the speed command value Vc.

[0017] The pressure command value calculator 3 inputs the calculated pressure command value Prc1 to the pressure limiter 4. A specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM is input to the pressure limiter 4. Based on the pressure command value Prc1 and the specified pressure value Prs, the pressure limiter 4 calculates a pressure command value Prc2 so as to limit the pressure Pr of the injection molding machine IM according to the specified pressure value Prs.

[0018] The calculated pressure command value Prc2 is input to the pressure deviation value calculator 14. Also, the pressure Pr acquired by the pressure acquisition unit 9 is input to the pressure deviation value calculator 14. The pressure deviation value calculator 14 subtracts the current pressure Pr of the injection molding machine IM from the pressure command value Prc2, performs a pressure control calculation in the pressure controller 5, and calculates a motor speed command value Vmc1.

[0019] The motor speed command value Vmc1 calculated by the pressure controller 5 is input to the speed deviation value calculator 6 of the motor speed control unit 15. Also, the encoder 10 detects the motor position P of the servo motor M and inputs the detected motor position P to the speed calculator 11. The speed calculator 11 differentiates the motor position P to calculate the motor speed Vm. The calculated motor speed Vm is input to the speed deviation value calculator 6. The speed deviation value calculator 6 calculates a speed deviation value Vd by subtracting the current motor speed Vm from the motor speed command value Vmc1.

[0020] The calculated speed deviation value Vd is input to the speed controller 7. The speed controller 7 is composed of a proportional-integral controller or the like and calculates a motor torque command value Tmc based on the speed deviation value Vd.

[0021] The calculated motor torque command value Tmc is input to the torque controller 8. The torque controller 8 controls the servo motor M so that a desired (as per the command value) motor torque T is output based on the motor torque command value Tmc.

[0022] Then, the encoder 10 detects the motor position P moved by the motor torque T output from the servo motor M, differentiates the detected motor position P with the speed calculator 11 to calculate the motor speed Vm, and performs speed control so that the motor speed command value Vmc1 matches the current motor speed Vm of the servo motor M. In this way, the control loop by the motor control device 100 is executed.

[0023] Next, the operation of the pressure control loop in the pressure controller 5 will be described. In the motor control device 100, for example, if the pressure controller 5 is configured as a proportional controller and its gain is G, the operation of the pressure control loop in the pressure controller 5 is as follows.

[0024] Pressure command value Prc2 - Pressure Pr = Pressure deviation value Prd2 ··· (1) Pressure deviation value Prd2 × Gain G of the proportional controller = Motor speed command value Vmc1 ··· (2)

[0025] From equations (1) and (2), the pressure command value Prc2 can be obtained by inverse calculation from the motor speed command value Vmc1 as follows. Pressure deviation value Prd2 = Motor speed command value Vmc1 / Gain G of the proportional controller ··· (3) Pressure command value Prc2 = Pressure deviation value Prd2 + Pressure Pr ··· (4)

[0026] In this embodiment, for the speed command value Vc given from the outside, the pressure command value Prc1 based on the speed command value Vc is calculated using the relationships of equations (3) and (4) above. Pressure deviation value Prd based on the speed command value Vc = Speed command value Vc / G ··· (5) Pressure command value Prc1 based on the speed command value Vc = Pressure deviation value Prd based on the speed command value Vc + Pressure Pr ··· (6)

[0027] Then, for the pressure command value Prc1 based on the obtained speed command value Vc, pressure limitation is performed with the specified pressure value Prs to obtain the pressure command value Prc2. When the injection molding machine IM is pressure-controlled based on this pressure command value Prc2, Motor speed command value Vmc1 = Pressure deviation value Prd2 × Proportional controller gain G = (Pressure command value Prc2 - Pressure Pr) × Proportional controller gain G

[0028] Here, when the pressure command value Prc1 is within the limit pressure range, that is, when the pressure command value Prc1 calculated based on the speed command value Vc is not subject to the pressure limit by the specified pressure value Prs, the pressure command value Prc2 = the pressure command value Prc1 based on the speed command value Vc. In this case, the pressure command value Prc1 calculated based on the speed command value Vc is set as the pressure command value Prc2 as it is.

[0029] Therefore, Motor speed command value Vmc = (Pressure command value Prc1 based on the speed command value Vc - Pressure Pr) × Proportional controller gain G = {(Pressure deviation value Prd based on the speed command value Vc + Pressure Pr) - Pressure Pr} × Proportional controller gain G = (Pressure deviation value Prd based on the speed command value Vc) × Proportional controller gain G = (Speed command value Vc / Proportional controller gain G) × Proportional controller gain G = Speed command value Vc That is, the motor speed command value Vmc1 coincides with the speed command value Vc, and based on this motor speed command value Vmc, the servo motor M is speed-controlled so that the motor speed Vm of the servo motor M is speed-controlled to the speed as per the motor speed command value Vmc, that is, the speed as per the speed command value Vc.

[0030] On the other hand, when the pressure command value Prc1 is not within the limit pressure range, that is, when the pressure command value Prc1 calculated based on the speed command value Vc exceeds the pressure limit range defined by the specified pressure Prs, the pressure limiter 5 sets the pressure command value Prc2 to the pressure limit value (specified pressure Prs). For example, when the pressure command value Prc1 is greater than the maximum value of the limit pressure range, the maximum value is set as the pressure command value Prc2. Then, the pressure control of the servo motor M based on the specified pressure Prs is performed, and the pressure Pr is controlled to the specified pressure value Prs. In addition, when it is desired to suppress the steady deviation during pressure control, the pressure controller is composed of a proportional-integral controller, with proportional control during speed control and proportional-integral control during pressure limitation.

[0031] Thus, if the specified pressure value Prs is set to the upper limit value within the allowable range of the machine, the servo motor M can be speed-controlled while keeping the pressure within the allowable range.

[0032] Note that the specified pressure Prs can also be determined based on a predetermined threshold value, a predetermined table value, a predetermined function value, etc. In this case, "predetermined" of course includes the fact that it can be arbitrarily determined, and further includes the fact that it can be arbitrarily set at any time such as during the manufacturing, testing, shipping, and use of the motor speed control device.

[0033] As described above, the motor control device 100 according to the present embodiment can realize speed control with a pressure Pr limiting function with a simple configuration in which a pressure command value Prc1 is calculated based on a speed command value Vc, pressure limiting is performed to obtain a motor speed command value Vmc1, and the servo motor M is speed-controlled based on the motor speed command value Vmc1. When the pressure Pr does not exceed the set pressure limit range, the motor speed Vm of the servo motor M can be speed-controlled as set by the speed command value Vc. On the other hand, when the pressure command value Prc1 exceeds the pressure limit range, the pressure limiter sets the pressure command value Prc1 to the pressure limit value Prs, so that the pressure Pr can be limited to the specified pressure value Prs. Thereby, no new parameters for pressure control are required. Also, when the motor speed command value Vmc1 does not exceed the set pressure limit range, the gain G of the pressure controller 5 does not affect the pressure control, so that the adjustment of the gain G becomes easy.

[0034] (Second Embodiment) FIG. 2 is a block diagram showing the configuration of a motor control device according to a second embodiment of the present invention. The motor control device according to the second embodiment externally sets a pressure limit range and a speed range of an injection molding machine (hereinafter also referred to as a "limit speed range") in which a servo motor is mounted in an injection process and a holding pressure process, and controls the servo motor within the set pressure limit range and the limit speed range. The motor control device according to the present embodiment can drive the servo motor by speed control while limiting the pressure in the injection process and drive the servo motor by pressure control while limiting the speed in the holding pressure process.

[0035] As shown in FIG. 2, a control device for a servo motor M (hereinafter also referred to as a motor control device 200) includes a pressure deviation value calculator 2, a pressure command value calculator 3, a pressure limiter 4, a switching unit 16, a pressure deviation value calculator 14, a pressure controller 5, a speed limiter 17, a motor speed control unit 15, a pressure acquisition unit 9, an encoder 10, a speed calculator 11, a specified pressure acquisition unit 12, and a specified speed acquisition unit 18. The motor speed control unit 15 is composed of a speed deviation value calculator 6, a speed controller 7, and a torque controller 8. The motor control device 200 according to the second embodiment of the present invention shown in FIG. 2 has a configuration in which a switching unit 16 and a specified speed acquisition unit 18 are added to the motor control device 100 of the first embodiment shown in FIG. 1.

[0036] For the motor control device 200 having such a configuration, a speed command value Vc for controlling the motor speed Vm of the servo motor M and a pressure command value Prc for controlling the pressure Pr of the injection molding machine IM are input from the outside. The specified pressure acquisition unit 12 acquires a specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM, and the specified speed acquisition unit 18 acquires a specified speed value Vs for limiting the motor speed Vm of the servo motor M. The specified pressure acquisition unit 12 and the specified speed acquisition unit 18 may acquire the specified pressure value Prs and the specified speed value Vs recorded in advance from a non-volatile memory (not shown), or may acquire the specified pressure value Prs and the specified speed value Vs by being input from the outside. Thereby, the motor control device 200 performs speed control of the motor speed Vm of the servo motor M and pressure control of the pressure Pr of the injection molding machine IM under a desired speed command value Vc and a constant pressure limit, and a desired pressure command value Prc and a speed limit.

[0037] A desired speed command value Vc given from the outside is input to the pressure deviation value calculator 2. The pressure deviation value calculator 2 calculates a pressure deviation value Prd indicating how much the current pressure Pr of the injection molding machine IM needs to be changed based on the input speed command value Vc.

[0038] The calculated pressure deviation value Prd is input to the pressure command value calculator 3. Also, a pressure sensor 13 provided in the injection molding machine IM detects the pressure Pr of the injection molding machine IM, and the detected pressure Pr is acquired by the pressure acquisition unit 9 and input to the pressure command value calculator 3. The pressure command value calculator 3 adds the pressure deviation value Prd and the pressure Pr, and calculates a pressure command value Prc1 based on the speed command value Vc.

[0039] The calculated pressure command value Prc1 is input to the pressure limiter 4. A specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM is input to the pressure limiter 4. The pressure limiter 4 calculates a pressure command value Prc2 so as to limit the pressure Pr of the injection molding machine IM according to the pressure command value Prc1 and the specified pressure value Prs.

[0040] The calculated pressure command value Prc2 and a desired pressure command value Prc given from the outside are input to the switching unit 16. The switching unit 16 outputs the pressure command value Prc2 as the pressure command value Prc3 to drive the servo motor M by speed control in the injection process, and outputs the pressure command value Prc as the pressure command value Prc3 to drive the servo motor M by pressure control in the holding pressure process.

[0041] The output pressure command value Prc3 is input to the pressure deviation calculator 14. Also, the pressure Pr acquired by the pressure acquisition unit 9 is input to the pressure deviation calculator 14. The pressure deviation calculator 14 subtracts the current pressure Pr of the injection molding machine IM from the pressure command value Prc3, and performs a pressure control calculation by the pressure controller 5 to calculate a motor speed command value Vmc1.

[0042] The calculated motor speed command value Vmc1 is input to the speed limiter 17. A specified speed value Vs for limiting the motor speed Vm of the servo motor M is input to the speed limiter 17. When the pressure command value Prc2 is output in the switching unit 16, the speed limiter 17 calculates a motor speed command value Vmc2 so as to limit the motor speed Vm of the servo motor M according to the motor speed command value Vmc1 and the specified speed value Vs based on the motor speed command value Vmc1 and the specified speed value Vs. When the pressure command value Prc is output in the switching unit 16, the speed limiter 17 sets the specified speed value Vs to a high value so as not to perform speed limiting, and calculates so that the motor speed command value Vmc1 becomes the motor speed command value Vmc2.

[0043] The calculated motor speed command value Vmc2 is input to the speed deviation value calculator 6 of the motor speed control unit 15. The configurations after the motor speed control unit 15 (the speed deviation value calculator 6, the speed controller 7, and the torque controller 8) are the same as those of each configuration in the first embodiment shown in FIG. 1. Therefore, the description thereof will be omitted.

[0044] Also, the operation of the pressure control loop in the pressure controller 5 in the pressure holding process is the same as the operation of the pressure control loop in the pressure controller 5 described in the first embodiment. Therefore, the description thereof will also be omitted.

[0045] As described above, in the injection process and the pressure holding process, by performing pressure limiting during speed control and performing speed limiting during pressure control after switching from speed control to pressure control, it becomes possible to control the speed of the servo motor M and the pressure Pr of the injection molding machine IM.

[0046] (Third Embodiment) FIG. 3 is a block diagram showing the configuration of a control device for a servo motor according to a third embodiment of the present invention. The control device for a servo motor according to the third embodiment is a control device that can control the position of a servo motor within a set limit pressure range by setting the limit pressure range in an injection molding machine equipped with the servo motor from the outside during the injection process and the holding pressure process.

[0047] As shown in FIG. 3, the control device for the servo motor M (hereinafter also referred to as the motor control device 300) includes a position deviation value calculator 19, a position controller 20, a pressure deviation value calculator 2, a pressure command value calculator 3, a pressure limiter 4, a pressure deviation value calculator 14, a pressure controller 5, a motor speed control unit 15, a pressure acquisition unit 9, an encoder 10, a speed calculator 11, and a specified pressure acquisition unit 12. The motor speed control unit 15 is composed of a speed deviation value calculator 6, a speed controller 7, and a torque controller 8. The motor control device 300 according to the third embodiment of the present invention shown in FIG. 3 has a configuration in which a position controller 20 is added to the motor control device 100 of the first embodiment shown in FIG. 1.

[0048] A position command value Pc for controlling the motor position P of the servo motor M is input to the motor control device 300 having such a configuration from the outside. The specified pressure acquisition unit 12 acquires a specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM. The specified pressure acquisition unit 12 may acquire the specified pressure value Prs recorded in advance from a non-volatile memory (not shown), or may acquire the specified pressure value Prs by being input from the outside. Based on the position command value Pc and the specified pressure value Prs, the motor control device 300 performs position control of the motor position P of the servo motor M under a desired position command value Pc and a certain pressure limit.

[0049] The desired position command value Pc given from the outside is input to the position deviation calculator 19. Also, the encoder 10 detects the motor position P of the servo motor M, and the detected motor position P is input to the position deviation calculator 19. The position deviation value calculator 19 calculates a position deviation value PD by subtracting the current motor position P of the servo motor M from the position command value Pc, and calculates a speed command value Vc from the position deviation value PD by the position controller 20.

[0050] The calculated speed command value Vc is input to the pressure deviation value calculator 2. The pressure deviation value calculator 2 calculates a pressure deviation value Prd indicating how much the current pressure Pr of the injection molding machine IM needs to be changed based on the input speed command value Vc.

[0051] The calculated pressure deviation value Prd is input to the pressure command value calculator 3. Also, the pressure sensor 13 provided in the injection molding machine IM detects the pressure Pr of the injection molding machine IM, and the detected pressure Pr is acquired by the pressure acquisition unit 9 and input to the pressure command value calculator 3. The pressure command value calculator 3 adds the pressure deviation value Prd and the pressure Pr and calculates a pressure command value Prc1 based on the speed command value Vc.

[0052] The calculated pressure command value Prc1 is input to the pressure limiter 4. A specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM is input to the pressure limiter 4. The pressure limiter 4 calculates a pressure command value Prc2 so as to limit the pressure Pr of the injection molding machine IM according to the pressure command value Prc1 and the specified pressure value Prs.

[0053] The calculated pressure command value Prc2 is input to the pressure controller 5. Also, the pressure Pr acquired by the pressure acquisition unit 9 is input to the pressure deviation calculator 14. The pressure deviation calculator 14 subtracts the current pressure Pr of the injection molding machine IM from the pressure command value Prc2, and the pressure controller 5 performs a pressure control calculation to calculate a motor speed command value Vmc1.

[0054] The motor speed command value Vmc1 calculated by the pressure controller 5 is input to the speed deviation value calculator 6 of the motor speed control unit 15. The configurations after the motor speed control unit 15 (the speed deviation value calculator 6, the speed controller 7, and the torque controller 8) are the same as those of each configuration of the first embodiment shown in FIG. 1. Therefore, descriptions thereof are omitted.

[0055] Also, the operation of the pressure control loop in the pressure controller 5 during the pressure holding process is the same as the operation of the pressure control loop in the pressure controller 5 described in the first embodiment. Therefore, descriptions thereof are also omitted.

[0056] As described above, in the injection process, by performing pressure limitation during position control, it becomes possible to control the motor position P of the servo motor M and the pressure Pr of the injection molding machine IM.

[0057] (Fourth Embodiment) FIG. 4 is a block diagram showing the configuration of a motor control device according to a fourth embodiment of the present invention. The motor control device according to the fourth embodiment is configured to set a limit pressure range and a limit speed range from the outside in an injection process and a pressure holding process in an injection molding machine equipped with a servo motor, drive the servo motor by position control in the injection process, drive the servo motor by pressure control in the pressure holding process, and switch between pressure limitation during position control and speed limitation during pressure control.

[0058] As shown in Fig. 4, the control device of the servo motor M (hereinafter also referred to as the motor control device 400) includes a position deviation value calculator 19, a position controller 20, a pressure deviation value calculator 2, a pressure command value calculator 3, a pressure limiter 4, a switching unit 16, a pressure deviation value calculator 14, a pressure controller 5, a speed limiter 17, a motor speed control unit 15, a pressure acquisition unit 9, an encoder 10, a speed calculator 11, a specified pressure acquisition unit 12, and a specified speed acquisition unit 18. The motor speed control unit 15 is composed of a speed deviation value calculator 6, a speed controller 7, and a torque controller 8. The motor control device 400 according to the fourth embodiment of the present invention shown in Fig. 4 has a configuration in which a switching unit 16, a specified speed acquisition unit 18, and a position controller 20 are added to the motor control device 100 of the first embodiment shown in Fig. 1.

[0059] For the motor control device 400 with such a configuration, a speed command value Vc for controlling the motor speed Vm of the servo motor M and a pressure command value Prc for controlling the pressure Pr of the injection molding machine IM are input from the outside. A specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM is acquired by the specified pressure acquisition unit 12, and a specified speed value Vs for limiting the motor speed Vm of the servo motor M is acquired by the specified speed acquisition unit 18. The specified pressure acquisition unit 12 and the specified speed acquisition unit 18 may acquire the specified pressure value Prs and the specified speed value Vs recorded in advance from a non-volatile memory (not shown), or may acquire the specified pressure value Prs and the specified speed value Vs input from the outside. Thereby, the motor control device 200 performs position control of the motor position P of the servo motor M and pressure control of the pressure Pr of the injection molding machine IM under a desired position command value Pc, a constant pressure limit, a desired pressure command value Prc, and a speed limit.

[0060] A desired position command value Pc given from the outside is input to a position deviation value calculator 19. Further, an encoder 10 detects a motor position P of a servo motor M, and the detected motor position P is input to the position deviation value calculator 19. The position deviation value calculator 19 calculates a position deviation value PD by subtracting the current motor position P of the servo motor M from the position command value Pc, and calculates a speed command value Vc from the position deviation value PD by a position controller 20. The calculated speed command value Vc is input to a pressure deviation value calculator 2. The pressure deviation value calculator 2 calculates a pressure deviation value Prd indicating how much the current pressure Pr of the injection molding machine IM needs to be changed based on the input speed command value Vc.

[0061] The calculated pressure deviation value Prd is input to a pressure command value calculator 3. Further, a pressure sensor 13 provided in the injection molding machine IM detects the pressure Pr of the injection molding machine IM, and the detected pressure Pr is acquired by a pressure acquisition unit 9 and input to the pressure command value calculator 3. The pressure command value calculator 3 adds the pressure deviation value Prd and the injection pressure Pr to calculate a pressure command value Prc1 based on the speed command value Vc.

[0062] The calculated pressure command value Prc1 is input to a pressure limiter 4. A specified pressure value Prs for limiting the pressure Pr of the injection molding machine IM is input to the pressure limiter 4. The pressure limiter 4 calculates a pressure command value Prc2 so as to limit the pressure Pr of the injection molding machine IM according to the pressure command value Prc1 and the specified pressure value Prs.

[0063] The calculated pressure command value Prc2 and a desired pressure command value Prc given from the outside are input to a switching unit 16. The switching unit 16 outputs the pressure command value Prc2 as a pressure command value Prc3 to drive the servo motor M by position control in the injection process, and outputs the pressure command value Prc as a pressure command value Prc3 to drive the servo motor M by pressure control in the holding pressure process.

[0064] The output pressure command value Prc3 is input to the pressure controller 5. Also, the pressure Pr acquired by the pressure acquisition unit 9 is input to the pressure deviation calculator 14. The pressure deviation calculator 14 subtracts the current pressure Pr of the injection molding machine IM from the pressure command value Prc3, and the pressure controller 5 performs a pressure control operation to calculate the motor speed command value Vmc1.

[0065] The calculated motor speed command value Vmc1 is input to the speed limiter 17. A specified speed value Vs for limiting the motor speed Vm of the servo motor M is input to the speed limiter 17. When the pressure command value Prc2 is output in the switching unit 16, the speed limiter 17 calculates the motor speed command value Vmc2 based on the motor speed command value Vmc1 and the specified speed value Vs so as to limit the motor speed Vm of the servo motor M according to the motor speed command value Vmc1 and the specified speed value Vs. When the pressure command value Prc is output in the switching unit 16, the speed limiter 17 sets the specified speed value Vs to a high value so as not to perform speed limiting, and calculates so that the motor speed command value Vmc1 becomes the motor speed command value Vmc2.

[0066] The calculated motor speed command value Vmc2 is input to the speed deviation value calculator 6 of the motor speed control unit 15. The configurations after the motor speed control unit 15 (the speed deviation value calculator 6, the speed controller 7, and the torque controller 8) are the same as those of each configuration of the first embodiment shown in FIG. 1. Therefore, the descriptions thereof are omitted.

[0067] Also, the operation of the pressure control loop in the pressure controller 5 during the holding pressure process is the same as the operation of the pressure control loop in the pressure controller 5 described in the first embodiment. Therefore, the descriptions thereof are also omitted.

[0068] As described above, in the injection process and the holding pressure process, by performing pressure limiting during position control and speed limiting during pressure control after switching from position control to pressure control, it is possible to control the motor position P of the servo motor M and the pressure Pr of the injection molding machine IM.

[0069] As described above, the embodiments of the present invention have been explained. Needless to say, the technical scope of the present invention should not be construed in a limited manner by the description of these embodiments. These embodiments are merely examples, and it is understood by those skilled in the art that various modifications of the embodiments are possible within the scope of the invention described in the claims. The technical scope of the present invention should be determined based on the scope of the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0070] 100, 200, 300, 400 Motor control device 2 Pressure deviation value calculator 3 Pressure command value calculator 4 Pressure limiter 5 Pressure controller 6 Speed deviation value calculator 6 7 Speed controller 8 Torque controller 9 Pressure acquisition unit 10 Encoder 11 Speed calculator 12 Specified pressure acquisition unit 13 Pressure sensor 14 Pressure deviation value calculator 15 Motor speed control unit 16 Switching unit 17 Speed limiter 18 Specified speed acquisition unit 19 Position deviation value calculator 20 Position controller M Servo motor IM Injection molding machine Pr Pressure P Motor position Vm Motor speed Vc Speed command value Vmc, Vmc1, Vmc2 Motor speed command value Prc, Prc1, Prc2, Prc3 Pressure command value Pc Position command value Tmc Motor torque command value Vd Speed deviation value Prd Pressure deviation value Prs Specified pressure value Vs Specified speed value

Claims

1. A control device for a servo motor that controls a servo motor driving a linear motion mechanism for moving an object based on a speed command value, a pressure acquisition unit that acquires a detected pressure from a pressure sensor that detects the pressure with which the linear motion mechanism presses the object; a pressure deviation value calculator that calculates a pressure deviation value indicating how much the detected pressure is to be changed based on the speed command value; a pressure command value calculator that calculates a pressure command value by adding the pressure deviation value and the detected pressure; a specified pressure acquisition unit that acquires a specified pressure; a pressure limiter that limits the pressure command value based on the specified pressure; a pressure controller that controls the pressure so that the detected pressure matches the pressure command value limited by the pressure limiter and calculates a motor speed command value; and a motor speed control unit that performs speed control on the servo motor according to the motor speed command value, wherein the pressure limiter maintains the pressure command value as it is when the pressure command value is less than the specified pressure, and sets the specified pressure to the pressure command value when the pressure command value exceeds the specified pressure, a control device for a servo motor.

2. The control device for the servo motor further includes a switching unit that switches between the output of the pressure limiter and a pressure command input from the outside, the control device for a servo motor according to claim 1.

3. The control device for the servo motor further includes a specified speed acquisition unit that acquires a specified speed, and a speed limiter that limits the motor speed command value based on the specified speed, wherein the speed limiter maintains the motor speed command value as it is when the pressure command is selected by the switching unit and the motor speed command value is less than the specified speed, The control device for a servo motor according to claim 2, wherein when the pressure command is selected in the switching unit and the motor speed command value exceeds the specified speed, the specified speed is set to the motor speed command value.

4. A control device for a servo motor that controls a servo motor driving a linear motion mechanism for moving an object based on a position command value, an encoder for detecting the position of the servo motor, a position controller that calculates a position deviation value from the detected position and the position command value, and calculates a speed command value from the position deviation value, a pressure acquisition unit that acquires a detected pressure from a pressure sensor that detects the pressure with which the linear motion mechanism presses the object, a pressure deviation value calculator that calculates a pressure deviation value indicating how much the detected pressure is to be changed based on the speed command value, a pressure command value calculator that adds the pressure deviation value and the detected pressure to calculate a pressure command value, a specified pressure acquisition unit that acquires a specified pressure, a pressure limiter that limits the pressure command value based on the specified pressure acquired from the specified pressure acquisition unit, a pressure controller that controls the pressure so that the detected pressure matches the pressure command value limited by the pressure limiter and calculates a motor speed command value, and a motor speed control unit that speed-controls the servo motor according to the motor speed command value. The pressure limiter, when the pressure command value is less than the specified pressure, maintains the pressure command value as it is, when the pressure command value exceeds the specified pressure, sets the specified pressure to the pressure command value.

5. The control device for the servo motor, has a switching unit that switches between the output of the pressure limiter and a pressure command input from the outside.

6. The control device of the servo motor is, a specified speed acquisition unit that acquires a specified speed, and further includes a speed limiter that limits the motor speed command value based on the specified speed. The speed limiter is, when the pressure command is selected in the switching unit and the motor speed command value is lower than the specified speed, the motor speed command value is maintained as it is, The control device of the servo motor according to claim 5, wherein when the pressure command is selected in the switching unit and the motor speed command value is higher than the specified speed, the specified speed is set as the motor speed command value.

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