JP2007192785A - Motor-driven servo cylinder with absolute position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor-driven servo cylinder with an absolute position detector, capable of restarting an absolute position detecting operation continuously from the state at a stopped time, without any disturbance, when a main electric power supply is restored. <P>SOLUTION: A self-locking function of a mechanical function provided intrinsically in a brake mechanism or a trapezoidal thread mechanism is utilized in the best use, by using the brake mechanism for stop-holding a servo motor shaft when the main electric power supply is turned off, or the trapezoidal thread mechanism in a rotation-direct operation mechanism of the cylinder, electric power is supplied to be electrified for a micro time (time until a brake is actuated) from a backup electric power supply, after the main electric power supply is turned off, the backup electric power supply is stopped thereafter to reduce remarkably an electric power consumption of a battery, an electric double layer capacitor having infinite recharge performance is used therein in stead of the battery, and replacement work is eliminated by this manner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric servo cylinder that replaces a pneumatic cylinder and greatly reduces the drive energy consumption and significantly improves controllability such as multipoint stop and variable speed during movement.

  There is a strong demand for an electric servo cylinder with an absolute position detection device that does not require an origin return operation when starting work or restarting after a power failure because of its convenience.

  In a conventional absolute position detection device that obtains absolute position data of a moving body based on the output of an incremental encoder and the moving direction of the moving body whose amount of movement is detected by the incremental encoder, the power supply from the main power supply is disconnected due to a power failure or accident. A backup power supply is provided so that the absolute position data can be maintained even when the power supply is stopped. Since the backup power source is composed of a battery, if the recovery from a power failure or accident is delayed, the output voltage of the backup power source is lowered and the power source cannot be backed up. Therefore, it has been conventionally practiced to reduce power consumption during backup by choppering an electronic circuit inside the absolute position detection device when the power source is changed from the main power source to the backup power source.

  The conventional means as described above requires a chopper circuit having a complicated structure and increases the number of circuit components. Although the combination of the battery and the chopper circuit can be expected to increase the backup time, it has the disadvantage that replacement work based on the time limit of the battery having a finite capacity and its life is inevitable.

  In order to solve the above problems, the present invention provides an incremental encoder that detects the amount of movement of a moving body, a counter circuit that obtains absolute position data from the moving direction of the moving body and a pulse signal output from the incremental encoder, and a main power source. Absolute position detection comprising a backup power source used for backup during a period when the power supply of the power supply is stopped and a power supply control circuit that switches the power supply to the backup power supply when the power supply from the main power supply is stopped An electric servo cylinder with an absolute position detection device provided with a device is an object of improvement.

In the first aspect of the invention, after the supply of power from the main power supply is stopped, the servo motor output shaft forced stop electromagnetic brake is operated to completely stop the rotation of the servo motor. Based on the command from the determination means after confirming the complete stop, the storage means stores the final count value from the counter circuit,
Hold.

  Next, when power is supplied from the main power supply, the final count value stored in the storage means is set in the counter circuit by the setting means. Thereafter, the electromagnetic brake is released. The power supply control circuit is configured to stop the supply of power from the backup power supply after the storage means stores the final count value.

  In claim 2, instead of using the forced stop brake after the main power OFE, the frictional force inherent in the screw mechanism is used as a brake function by using a trapezoidal screw for the rotation-linear motion conversion mechanism of the servo cylinder part, After the servo shaft is completely stopped, the operation is exactly the same as the operation of the first aspect.

In claim 3, since the power consumption of the backup power supply when the main power supply is OFF, which is a feature of the present invention, is extremely small, it is not necessary to use a normal battery, and an electric double layer capacitor having particularly excellent recharge characteristics is provided. It becomes possible to use it, and it becomes possible to remove the work of battery replacement.

  According to the absolute position detection apparatus of the present invention, after the power supply from the main power supply is stopped, the servo motor output shaft is automatically forced to stop the rotation shaft, the counter circuit counts the final count value, and the final count value is stored in the storage means. Stores the stored value even when there is no power supply, and when the supply from the main power supply is resumed, the stored final count value is set in the counter circuit by the setting means, so that the main power supply is restored The absolute position detection operation can be resumed without any trouble from the stop state. In the present invention, since the power supply control circuit stops the power supply from the backup power supply when the storage means stores the final count value, the power supply from the backup power supply can be shortened and the power consumption can be significantly reduced. This low power consumption characteristic makes it possible to use an electric double layer capacitor with excellent recharging characteristics instead of using a normal battery that has been used as a backup power supply, thus eliminating the need for battery replacement work. .

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 1 is an incremental encoder, 2 is a counter circuit, 3 is a power supply control circuit, and 4a is after the supply of power from the main power supply is stopped. , A shift amount detection circuit or a speed zero detection circuit used as a determination means for determining whether or not the counter circuit 2 has counted the final count value, 5 is a storage circuit, 6 is a setting means, 7 is a brake circuit, and 8 is a servo. An electromagnetic brake for forcibly stopping the motor output shaft, 9 is a servo amplifier, 10 is a motor winding excitation phase determination circuit in the servo amplifier 9, and 11 is a cylinder having a function of converting the rotation operation of the servo motor into a linear motion operation. Is a servo motor.

The incremental encoder 1 may be either a rotary type or a linear type, detects the amount of movement of the moving body, and outputs an A channel signal and a B channel signal that are 90 degrees out of phase. The counter circuit 2 is composed of an up / down counter, and calculates absolute position data from the A channel and B channel pulse signals output from the incremental encoder 1 and different in phase by 90 degrees. The power supply control circuit 3 receives the main power supply and the output of the backup power supply composed of a battery. When the supply of power from the main power supply is stopped, the power supply is switched to the backup power supply.
When the main power is turned off, a brake holding signal is output from the brake circuit 7, and the brake 8 operates so as to forcibly stop the rotation of the servo motor 12. When the servo motor 12 stops rotating, the output of the pulse signal from the encoder 1 stops, so the change in the count value of the counter circuit 2 remains unchanged. The change amount detection circuit, that is, the zero speed detection circuit 4a determines whether or not the counter circuit 2 has counted the final count value after the supply of power from the main power supply is stopped. If the detected change amount is zero, it is determined that the value at that time is the final count value.

  The storage circuit 5 stores the final count value in response to a command from the zero speed detection circuit 4, and holds the stored value even when no power is supplied. An EEPROM can be used as the storage means of the storage circuit 5 that can hold the stored value even when such power is not supplied.

  The power supply control circuit 3 operates so as to stop the supply of power from the backup power supply after the storage circuit 5 stores the final count value. Specifically, after the zero speed detection circuit 4 detects that the change speed or change amount of the count value within a predetermined time is zero and the storage circuit 5 completes the storage of the final count value, the backup power supply The power supply control circuit 3 is configured to stop the supply of power from the power supply. FIG. 2 shows an example of the configuration of the power supply control circuit 3. 3a is a switching regulator (SW regulator), 3b is a relay, 3c and 3d are diodes, and 3e is a regulator. In the figure, when the main power source 13 is in an ON state, that is, when power is supplied from the main power source 13, the judging means 4 (the zero speed detection circuit 4a in the embodiment of FIG. 1) that receives the output from the switching regulator 3a. ), The relay 3b is in an OFF state (open state). At this time, the switching regulator 3a converts AC power from the main power supply 13 into DC power, and the DC power is input to the regulator 3e through the diode 3c, and is supplied from the regulator 3e to the encoder 1 and the control circuit. When the main power supply 13 is in an OFF state (a state in which power supply from the main power supply is stopped), the output of the switching regulator 3a is lost, and the determination unit 4 starts the determination operation and at the same time the relay 3b is in the ON state (closed state). Thus, the output of the backup power source 14 is instantaneously supplied to the regulator 3e through the diode 3d, and power supply from the regulator 3e to the encoder 1 and its control circuit is continued. Thereafter, when the determination unit 4 completes the determination operation and the storage circuit 5 stores the final count value, the relay 3b is turned off by the output from the determination unit 4, and the power supply from the backup power source 14 is stopped. In order for the relay 3b to be in the OFF state after the determination means 4 stores the final count value in the storage circuit 5, the relay 3b may be provided with a delay circuit or a timer circuit. In the example of FIG. 2, the determination unit 4 starts the determination operation with the output from the switching regulator 3 a and the relay 3 b operates at the same time, but the structure of the relay 3 b is configured to supply power from the main power supply 13. A configuration may be adopted in which the presence or absence is directly detected and the power is directly turned on when the power supply of the main power supply 13 is lost.

  Returning to FIG. 1, when the power supply from the main power supply 13 is resumed, the setting means 6 operates to set the final count value stored in the storage circuit 5 in the counter circuit 2. The setting means 6 is configured to perform a setting operation when power is supplied from the main power supply 13. Thereby, after the main power supply is restored, the counter circuit 2 continues the absolute position data of the moving body detected when the main power supply is stopped, and resumes the output of the absolute position detection data without any trouble. As described above, the power supply control circuit 3 operates to stop the supply of power from the backup power supply when the storage circuit 5 stores the final count value, so that the power consumption of the backup power supply can be greatly reduced. it can. In particular, in this embodiment, since the servo motor output shaft forced stop electromagnetic brake 8 and the speed zero detection circuit 4a are used as the determination means, the final count value can be stored in the storage circuit 5 in the shortest time. This makes it possible to minimize the power consumption of the backup power supply. In addition, because the servo motor output shaft forced stop electromagnetic brake 8 is used, the servo shaft moves even when externally moving the cylinder shaft when the main power supply is stopped. Absolute position data is saved correctly. Furthermore, as described above, since the battery backup time is extremely short (about 1 second at the maximum), the means for configuring the backup power source does not need a general battery, and uses an electric double layer capacitor or the like. This makes it possible to save the trouble of replacing the battery life.

In an electric servo cylinder with an absolute position detection device configured and operated in this way, a general brushless servomotor has the performance that there is no restriction that the torque generated at the initial operation before the motor winding excitation phase determination is reduced. Will be. The reason will be described below. In FIG. 1 of the embodiment, the counter circuit 2 always stores the absolute position data of the servo motor rotating shaft regardless of whether or not the main power is present. By guiding this absolute position data to the motor winding excitation phase determination circuit 10 in the servo amplifier 9, it becomes possible to determine the optimum excitation phase in any case.
Of course, it is self-evident that in the system manufacturing stage where the brushless servomotor, the absolute position detection device, and the servo amplifier are first combined, the combination adjustment of the three is necessary. The above-mentioned effect comes out after this combination is executed once.

  FIG. 3 is a flowchart showing an example of an algorithm for realizing the embodiment of FIG. 1 using a microcomputer. The steps of this flowchart will be described. First, in this embodiment, the main power supply OFF is detected in step ST1, and when the main power supply is OFF, the backup power supply is turned on in step ST2, and the shaft brake is operated in step ST3. . In step ST4, the zero speed detection circuit 4a detects whether the change speed of the count value is zero. When zero speed is detected, the count value of the counter circuit 2 is stored in the storage circuit 5 in step ST5. Thereafter, in step ST6, the backup power supply is turned off. When the main power is turned on in step ST7, the count value stored in the counter circuit 2 is preset by the action of the setting means 6 in step ST8.

  FIG. 4 is a cross-sectional view of a trapezoidal screw mechanism used in a rotation-linear motion conversion mechanism, which is one of the basic configurations of the present invention, and FIG. 5 is generally used when configuring a rotation-linear motion conversion mechanism. Sectional drawing of the ball screw mechanism used is shown. FIG. 5 is a cross-sectional view of the trapezoidal screw mechanism of FIG. 4, wherein 15 is a nut cross-section and 16 is a screw cross-section. When the trapezoidal screw mechanism is used as the rotation-linear motion conversion mechanism, the nut 15 is assembled so as not to rotate by the rotation prevention mechanism when the screw 16 is driven to rotate by the servo motor 12. As a result, the nut 15 moves linearly parallel to the rotation axis of the screw 16. Similarly to the case of the trapezoidal screw mechanism, the ball screw mechanism shown in FIG. 5 performs the straight movement of the nut 17 by the mechanism that stops the rotation of the nut 17. The difference between the trapezoidal screw mechanism and the ball screw mechanism, which are the same rotation-linear motion conversion mechanism, is in both types of power transmission systems. The trapezoidal screw mechanism is a mechanism that is converted into a linear force parallel to the rotation axis through the frictional force of the surface between the screw 16 that rotates and the nut 15 provided with the rotation prevention mechanism from the sectional view of FIG. In the case of the ball screw mechanism of FIG. 5, the rotational force is converted into a straight force through the rolling friction of the ball 18 inserted between the screw 19 and the nut 17. Therefore, when the frictional forces of both types are compared, naturally the frictional force is larger in the trapezoidal screw mechanism method. In general, the fact that the frictional force is large tends to be avoided due to inefficiency, but when used in cylinder applications, it is possible to change this minus side of the trapezoidal screw mechanisms 15 and 16 to a plus side. is there. This is because a large frictional force inherently has a self-locking function (a function of preventing the screw 16 from rotating backward due to a disturbing linear advance force applied to the nut 15 from the outside of the cylinder), and Since it is a power transmission system through the contact surface, the impact resistance performance is significantly superior to the ball screw mechanism system in which power transmission is performed by point contact through the ball 18. In the present invention, by utilizing this self-locking function very effectively, it is possible to stop the servo motor shaft without using an external brake and maintain the state. On the contrary, when the ball screw mechanism is used, it is necessary to use an external brake for stopping the shaft because it does not have a self-locking function as shown in FIG.

  FIG. 6 is a block diagram when an electric double layer capacitor is used as a backup power source. As described above, the present invention immediately switches to the backup power source (electric double layer capacitor) 20 when the main power source 13 is turned off. The power supply from the backup power source 20 is very short time due to the self-locking function of the servo motor output shaft forced stop electromagnetic brake 8 or the trapezoidal screw mechanism. Therefore, the power consumed during this period is also extremely small. Since the power consumption is extremely small, it is possible to use not an ordinary battery but an electric double layer capacitor whose performance has been remarkably improved in recent years as the backup power source. In addition, the electric double layer capacitor has an infinite number of recharge characteristics in principle, so unlike the case of using a general battery with a limited number of times of charge, it is not necessary to replace the battery due to its life. Maintenance performance is significantly improved. The wiring connected from the switching regulator 3a to the electric double layer capacitor 20 is a circuit for recharging the electric double layer capacitor when the main power supply is ON.

  The electric servo cylinder with absolute position detection device demonstrates its features in a multi-axis system. That is, when an instantaneous power failure occurs in an application such as a multi-axis robot, an example in which the robot stops instantaneously during work is a phenomenon often seen in production factories. In such a case, in the robot system using the incremental encoder, when the power is restored, it is necessary to interrupt the work performed before the momentary power failure, return all the robot axes to the origin once, and then return to the work. In a production factory with a large number of robots to be used, the time loss required for the return to origin operation cannot be tolerated. However, if a robot system using an electric servo cylinder with an absolute position detection device was used, when the power was restored, the work that was interrupted without performing the return to origin operation from the place where it was stopped due to an instantaneous power failure. It is possible to continue to resume. The present invention eliminates the need to replace the battery after operating the electric servo cylinder with a highly convenient absolute position detecting device for a certain period of time, and further simplifies the mechanical structure and the electric circuit and allows it to be supplied at low cost. The effects in the industry are immeasurable.

These are block diagrams which show the Example of the electric servo cylinder with an absolute position detection apparatus of this invention. 2 is an internal block diagram of a power supply control circuit 3 in the block diagram of the embodiment of FIG. FIG. 3 is a flowchart showing an example of an algorithm in a case where the embodiment of FIG. 1 is realized using a microcomputer. FIG. 2 is a sectional view of a trapezoidal screw mechanism that is a basic component of the present invention. These are sectional structure diagrams of a ball screw mechanism generally used as a rotation-linear motion conversion mechanism. FIG. 3 is a block diagram of the periphery of a power supply control circuit when a backup power supply is changed from a battery to an electric double layer capacitor that is a component of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Incremental encoder 2 Counter circuit 3 Power supply control circuit 3a Switching (SW) regulator 3b Relay 3c Diode 3d Diode 3e Regulator 4a is speed zero detection circuit 4 Judgment means 5 Memory circuit 6 Set means 7 Brake circuit 8 For servo motor output shaft forced stop Electromagnetic brake 9 Servo amplifier 10 Motor winding excitation phase determination circuit 11 in servo amplifier 9 Cylinder (rotation-linear motion conversion mechanism)
12 Servo Motor 13 Main Power Supply 14 Backup Power Supply 15 Trapezoidal Screw Mechanism Nut 16 Trapezoidal Screw Mechanism Screw 17 Ball Screw Mechanism Nut 18 Ball Screw Mechanism Ball 19 Ball Screw Mechanism Screw 20 Electric Double Layer Capacitor

Claims (3)

An electric servo cylinder with an absolute position detection device composed of an absolute position detection device and an electric servo cylinder. The absolute position detection device includes an incremental encoder, an absolute position measurement counter circuit, a backup power supply, a power supply control circuit, and a servo motor shaft brake circuit. A device that activates the servo motor shaft brake after the main power supply is turned off, and a circuit that stores the final count value after the servo motor shaft complete stop, and retains that value even when the main power supply is not supplied, and a brushless servo amplifier A circuit for maintaining the winding excitation phase in the circuit, a circuit for setting the count value in the counter, a circuit means for determining the winding excitation phase in the brushless servo amplifier from the count value, and a servo motor shaft brake after the counter setting is completed. Absolute position detection characterized by having an opening device Device with electric cylinder. Instead of using the servo motor shaft brake according to claim 1, the rotation-linear motion conversion mechanism of the cylinder portion is constituted by a trapezoidal screw mechanism, so that the intrinsic self-locking function of the trapezoidal screw rotation-linear motion conversion mechanism is servoed. An electric servo cylinder with an absolute position detection device, characterized by being used as a motor shaft brake. 3. An electric servo cylinder with an absolute position detection device according to claim 1, wherein an electric double layer capacitor is used as a backup power source.

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