JP2003009563A - Servo motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently utilize the capability of a servo motor. SOLUTION: A servo motor controller comprises a temperature detecting means 10 for detecting the temperature of the servo motor 2 for driving a movable member 3. The controller further comprises a control means 13 for controlling the servo motor 2 based on the temperature so that an accelerating/ decelerating time constant τof the member 3 is changed in response to the detected temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device used for controlling a movable body in various devices.

[0002]

2. Description of the Related Art The performance of a servomotor decreases due to temperature rise due to operation and temperature rise due to surrounding heat. Therefore, the worst condition is assumed in selection. For this reason, in the steady state, the capability of the servo motor is often not fully utilized. As a solution to such a problem, there has been proposed one in which the maximum operating speed is increased or decreased according to the temperature increase (for example, Japanese Patent Laid-Open No. 64-20990).

[0003]

However, the load acting on the servomotor is greater during acceleration / deceleration than during maximum speed. Therefore, if the maximum speed is increased or decreased according to the temperature, the capacity of the servo motor cannot be fully utilized.

An object of the present invention is to provide a servo motor control device which can fully utilize the capabilities of the servo motor. Another object of the present invention is to simplify the configuration for temperature detection. Yet another object of the present invention is to enable safe use of servomotors while fully utilizing motor capacity.

[0005]

The structure of the present invention will be described with reference to FIG. 1 corresponding to the embodiment. This servo motor control device (8) comprises a temperature detecting means (10) for detecting the temperature of a servo motor (2) for driving a movable body (3), and the movable body (3) of the movable body (3) according to the detected temperature. A temperature-corresponding control means (13) for controlling the servomotor (2) so as to change the acceleration / deceleration time constant (τ) is provided. According to this configuration, the temperature-corresponding control means (13) controls the acceleration / deceleration time constant (τ) of the movable body (2) to change according to the temperature detected by the temperature detection means (10). For example, the temperature-corresponding control means (13) changes so that the acceleration / deceleration time constant (τ) increases steplessly or stepwise in two or more steps as the temperature rises. By increasing the acceleration / deceleration time constant (τ), even if the capacity of the servo motor (2) is lowered due to the temperature rise, the load of the servo motor (2) is reduced and the driving of the movable body (3) is hindered. Can be done without. Therefore, unlike the conventional case, it is not always necessary to assume the worst condition for operation, and the acceleration / deceleration time constant (τ) can be controlled with a small value while the temperature of the servo motor (2) is not rising. That is, control can be performed so as to perform rapid acceleration and rapid deceleration, and the ability of the servo motor (2) can be fully utilized. Further, the load acting on the servo motor (2) becomes the largest at the time of acceleration / deceleration. Therefore, by changing the acceleration / deceleration time constant (τ) according to the temperature, the servo motor (2) is different from the case where the maximum speed is changed. The ability of (2) can be utilized more effectively.

The temperature detecting means (10) does not necessarily have to detect the temperature of the servo motor (2) directly, but may be any one that can detect the temperature of the servo motor (2) as a result. For example, the temperature detecting means (1
0A (FIG. 4) is a detection unit (11A) for detecting the current value of the servo motor (2), and the detection current value of the detection unit is converted into temperature from the current value of the servo motor (2) and the motor characteristics. The conversion unit (12A) may be included. The current value and the temperature of the servo motor (2) have a fixed relationship as a motor characteristic, and if the temperature change due to an external cause can be ignored, the current value can be converted into the temperature. Detection unit (11A) that detects the current value of the servo motor (2)
Is always provided when current control of the servomotor (2) is performed by feedback control. In addition, a current detector may be provided for safety monitoring. Therefore, by using the current detection unit (11A) used for other control and monitoring in this way, temperature detection can be performed only by conversion without providing sensors for temperature detection. Therefore, the structure is simple and inexpensive.

The temperature-corresponding control means (13) may change the acceleration / deceleration time constant (τ) of the movable body (3) according to the rate of change of the temperature detected by the temperature detection means (10). For example, when the rate of change is large, the acceleration / deceleration time constant (τ) is increased. That is, the acceleration / deceleration is made gentle. By performing control by looking at the temperature change rate of the servo motor (2) in this way, it is possible to change the acceleration / deceleration time constant (τ) before the temperature rises and respond with good responsiveness.
Therefore, the servo motor (2) can be safely used while fully utilizing the motor capacity, and the motor capacity can be further utilized.

[0008]

1 is a block diagram of a first embodiment of the present invention.
3 to FIG. FIG. 1 shows a conceptual configuration of a machine control device to which this servo motor control device is applied. The controlled machine 1 has a drive mechanism 4 that drives a movable body 3 by a servomotor 2. The drive mechanism 4 drives the movable body 3 forward and backward through the ball screw 5 by the servo motor 2. The controlled machine 1 is, for example, a transfer device, and is a device or the like for loading and unloading a workpiece with respect to a processing device such as a machine tool or a sheet metal processing machine. The machine control device 6 is a device that controls the controlled machine 1, and is configured by a numerical control device and a programmable controller. The machine control device 6 decodes a machining program (not shown) by the machine control means 7 and executes it to give various operation commands to the controlled machine 1. The servo motor 2 in the controlled machine 1 is controlled via the servo motor control device 8 by a drive command given from the machine control means 7. The drive command is given by, for example, a position command.

The servo motor control device 8 has a servo driver 9 for controlling the current supplied to the servo motor 2 in accordance with a given drive command. Servo driver 9
Is capable of variably setting the acceleration / deceleration time constant τ, and is constituted by, for example, a software servo. It is assumed that the servo driver 9 accelerates with a set acceleration / deceleration time constant τ, continues to drive at a constant speed when the maximum speed is reached, and performs deceleration with the above acceleration / deceleration time constant τ before stopping, so-called trapezoidal control. is there.

The servo motor control device 8 controls the servo motor 2 so that the temperature detecting means 10 for detecting the temperature of the servo motor 2 and the acceleration / deceleration time constant τ of the movable body 3 are changed according to the detected temperature. And a temperature-corresponding control means 13 for controlling the temperature. The temperature detecting means 10 is composed of a detecting unit 11 and a temperature calculating unit 12. The detection unit 11 is a temperature sensor including a thermocouple, a semiconductor element, and the like, and the temperature calculation unit 12 is a unit that adds calibration processing and other appropriate processing to the detection value detected by the detection unit 11.

The temperature-corresponding control means 13 changes the acceleration / deceleration time constant τ of the movable body 3 so as to change the acceleration / deceleration time constant τ set in the servo driver 9. It is preferable that the temperature-corresponding control means 13 changes the acceleration / deceleration time constant τ in at least three steps in accordance with the temperature detected by the temperature detection means 10. The acceleration / deceleration time constant τ may be changed steplessly. In this embodiment, the temperature range is divided into three stages, and the acceleration / deceleration time constants τ1 to τ3 are set for each of the first to third stages determined in order from the lower range. The acceleration / deceleration time constants τ1 to τ3 are set to a larger value, that is, a value for gradual acceleration / deceleration, in a higher temperature range. τ1 to τ3 have a relationship of τ1 <τ2 <τ3. An example of the processing contents of the temperature corresponding control means 13
A flow chart is shown in FIG.

The temperature-corresponding control by the servo motor control device 8 having the above configuration will be described with reference to FIGS. When the servo motor 2 starts, the acceleration / deceleration time constant τ of the first stage
The initial setting is 1 (step S1). Temperature detecting means 10
Is always performed, and if the detected temperature is within the temperature range of the first stage (S2), the acceleration / deceleration time constant τ1 is maintained (S1). When it exceeds the temperature range of the first stage, it is determined whether or not it is the temperature range of the second stage (S3), and when it is the temperature range of the second stage, the acceleration / deceleration time constant τ2 is set (S3).
4). When the temperature range is not in the second stage temperature range, that is, in the third stage temperature range, the acceleration / deceleration time constant τ3 is set. The temperature is constantly detected as described above, and when the temperature decreases, the temperature is changed to the acceleration / deceleration time constants τ1 and τ2 at the stage corresponding to the decreased temperature. In FIG. 2, step S
Although the temperature range is determined separately for S2 and S3, it is also possible to determine at which stage the temperature is in a single determination. The set temperature for changing the acceleration / deceleration time constants τ1 to τ3 may be changed depending on whether the temperature rises or falls. That is, hysteresis may be provided.

FIG. 3 shows an example of the operation of the servomotor 2 from start to stop. The same figure (A) shows the case where it operates with the smallest acceleration / deceleration time constant τ1, and the same figure (B) shows the case where it operates with the intermediate acceleration / deceleration time constant τ2. In this way, by increasing the acceleration / deceleration time constant τ when the temperature of the servo motor 2 rises, even if the capacity of the servo motor 2 is lowered due to the temperature rise, the load on the servo motor 2 is reduced and the movable body 3 can be driven without any trouble. Therefore, unlike the conventional case, it is not always necessary to operate under the assumption of the worst condition, and the acceleration / deceleration time constant τ can be controlled with a small value while the temperature of the servo motor 2 is not rising, that is, sudden acceleration, Control can be performed so as to perform rapid deceleration, and the capability of the servo motor 2 can be fully utilized. Further, since the load acting on the servo motor 2 becomes the largest during acceleration / deceleration, by changing the acceleration / deceleration time constant τ according to the temperature, the servo motor 2 can be compared with the case where the maximum speed is changed.
Can utilize their abilities more effectively. Note that, as shown by the dashed speed curve in FIG. 2B, when the temperature rises, the maximum speed may be decreased in addition to the change of the acceleration / deceleration time constant τ.

In the above embodiment, an example in which a temperature sensor for directly detecting the temperature of the servomotor 2 is used as the detecting portion 11 of the temperature detecting means 10 has been described.
Is only required to detect the temperature of the servo motor 2 as a result. For example, as in the second embodiment shown in FIG. 4, the temperature detecting means 10A detects the current value of the servomotor 2 from the detection section 11A and the current value of the servomotor 2 and the motor characteristics from the detection section 11A. The conversion unit 12A for converting the detected current value of 1 to the temperature may be included. The detection unit 11A is an ammeter. The current value of the servo motor 2 and the temperature have a fixed relationship as a motor characteristic, and if the temperature change due to external factors can be ignored, the current value can be converted into the temperature. The detection unit 11A that detects the current value of the servo motor 2 is always provided when the current control of the servo motor 2 is performed by feedback control. Therefore, by using the current detection unit 11A used for other control as described above, temperature detection can be performed only by conversion without providing any temperature detection sensor.
Therefore, the structure is simple and inexpensive. Other matters in this embodiment are the same as those in the first embodiment.

In the first and second embodiments, the temperature-corresponding control means 13 includes the temperature detecting means 10, 10.
The acceleration / deceleration time constant τ of the movable body 3 may be changed according to the rate of change of the detected temperature by A. The rate of change in the detected temperature is the change in temperature per unit time.

FIG. 5 shows an example of the controlled machine 1.
The controlled machine 1 in this example is a loader for sheet metal, and conveys a plate-shaped work W as a material to the sheet metal processing machine 20. In this sheet metal loader, a work support member 24 is installed on a traveling body 22 that can travel along a rail 21 via a lifting mechanism 23 so as to be lifted and lowered. The work supporting member 24 has a plurality of suction pads 25 for vacuum-sucking the work W. The traveling body 22 is provided with a servomotor 26 for traveling and a servomotor 27 for vertically moving the elevating mechanism 23, and the elevating mechanism 23 is provided with a brake mechanism (not shown). The servo motor control device 8 according to the first or second embodiment is used to control at least one of the traveling and lifting servo motors 26 and 27.

FIG. 6 shows another example of the controlled machine 1. The controlled machine 1 of this example is a machine tool 30 such as a lathe.
Is a loader that conveys the work WA. The machine tool 30 has a spindle 30a and a tool rest 30b. This loader includes a traveling body 32 that can travel along a rail 31.
Further, an elevating body 34 is installed to be movable up and down via a front and rear moving table 33, and a loader head 35 capable of gripping a work WA is provided at a lower end of the elevating body 34. Running body 3
2, the front-rear moving table 33, and the elevating body 34 are driven by servomotors 36, 37, 38, respectively. The servo motor control device 8 according to the first or second embodiment is used to control at least one of the servo motors 36, 37, and 38.

When the loader shown in FIGS. 5 and 6 is the controlled machine 1, the servo motor control device 8 and the machine control device 6 of each of the above-described embodiments are added with the following functions. Is preferred. That is, the temperature-corresponding control means 13 in the servo motor control device 8 causes the servo driver 9 to turn off the servo motor when the temperature detected by the temperature detection means 10 becomes equal to or higher than the set temperature for pause. For a servomotor such as an elevator shaft that receives a load in the servo-off state, a braking means (not shown) is caused to perform a braking operation when the servomotor is off. The set temperature for pause is set to a temperature higher than the set temperature for changing the acceleration / deceleration time constant τ. Further, when the temperature detected by the temperature detecting means 10 becomes equal to or higher than the preset temperature for rest, the machine control device 6 places the works W and WA gripped by the work supporting member 24 or the loader head 35 at a predetermined place. After operating the controlled machine 1 as described above, the machine 1 may be controlled to stop.

The servo motor control device 8 and the machine control device 6 restore the operation when the temperature detected by the temperature detection means 10 becomes equal to or lower than the set temperature for restoration. This restoration is, for example, one of restoration of the acceleration / deceleration time constant τ, processing of returning servo-off to servo-on, and processing of restoration from the pause.

[0020]

According to the servo motor control device of the present invention, the temperature detecting means for detecting the temperature of the servo motor for driving the movable body and the acceleration / deceleration time constant of the movable body are changed according to the detected temperature. Since the temperature-responsive control means for controlling the servo motor is also provided, the capacity of the servo motor can be fully utilized. In the case where the temperature detecting means has a detection unit for detecting the current value of the servo motor and a conversion unit for converting the detection current value of the detection unit into temperature from the current value of the servo motor and the motor characteristics, Since the dedicated sensors for temperature detection are unnecessary, the structure is simple and the cost can be reduced. When the temperature-corresponding control means is configured to change the acceleration / deceleration time constant of the movable body in accordance with the rate of change of the temperature detected by the temperature detecting means, the safe servo motor Can be used.

[Brief description of drawings]

FIG. 1 is a block diagram of a conceptual configuration of a machine control device to which a servo motor control device according to a first embodiment of the present invention is applied.

FIG. 2 is a flowchart showing a processing example of a temperature corresponding control means in the servo motor control device.

FIG. 3 is an explanatory diagram of an example of a velocity curve before and after changing the acceleration / deceleration time constant by the temperature corresponding control means.

FIG. 4 is a block diagram of a conceptual configuration of a machine control device to which a servo motor control device according to a second embodiment of the present invention is applied.

FIG. 5 is a front view showing an example of a controlled machine.

FIG. 6 is a front view showing another example of the controlled machine.

[Explanation of symbols]

1 ... Machine control device 2 ... Servo motor 3 ... Movable body 6 ... Machine control device 7 ... Machine control means 8 ... Servo motor control device 9 ... Servo driver 10, 10A ... Temperature detecting means 11, 11A ... Detection unit 12A ... Conversion unit 13 ... Control means for temperature 20 ... Sheet metal processing machine 26, 27 ... Servo motor 30 ... Machine tools 36-38 ... Servo motor τ, τ1 to τ3 ... Acceleration / deceleration time constant W, WA ... work

Claims (3)

[Claims] 1. A temperature detecting means for detecting a temperature of a servo motor for driving a movable body, and a temperature-corresponding control for controlling a servo motor so that an acceleration / deceleration time constant of the movable body is changed according to the detected temperature. And a servo motor control device. 2. The temperature detecting means has a detecting section for detecting a current value of the servo motor, and a converting section for converting the detected current value of the detecting section into a temperature based on the current value of the servo motor and motor characteristics. The servo motor control device according to claim 1. 3. The servo motor control device according to claim 1, wherein the temperature-corresponding control means changes the acceleration / deceleration time constant of the movable body according to the rate of change of the temperature detected by the temperature detecting means.