KR20140088633A - Method for controlling feed axix brake of machine tool - Google Patents

Abstract

The present invention relates to a brake control method capable of preventing a feed shaft from free falling and minimizing the interference between a brake and a motor by optimizing the deviation between the start up point of the motor and the operation point of the brake when turning on and off the feed shaft, which is controlled in the gravity direction in a machine tool. The feed shaft brake control method according to an embodiment of the present invention includes a step of determining whether a servo motor-on signal to have the motor work on the static feed shaft and a brake-off order signal have been received; a step of generating the servo motor starting signal when the servo motor-on signal and brake-off signal have been received; a step of renewing a previously-set brake-off delay time; a step of determining whether the renewed brake-off delay time has passed since the generation point of the servo motor starting signal; and a step of generating the brake-off signal once the brake-off delay time has elapsed.

Description

Technical Field [0001] The present invention relates to a method of controlling a feed shaft of a machine tool,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of controlling a feed shaft brake of a machine tool, and more particularly, to a method of controlling a feed shaft brake of a machine tool by optimizing a deviation between a starting point of a motor and an operating point of a brake, To a brake control method for preventing gravity drop and minimizing interference between the brake and the motor.

The machine tool can repeatedly perform the process of shutting off the power of the servo motor, which is the driving force of the feed shaft, and re-supplying the power according to internal / external factors. In this case, a brake is used to prevent gravity from dropping due to the weight of the spindle or the load of the transporting shaft itself when the power is interrupted. That is, it serves to transfer the movement of the transport shaft through the brake.

In this way, the braking operation of the conveying axis in the machine tool is performed not only when turning on / off the first mechanical device, but also during the process of shutting off the power of the servo motor and re- do.

In particular, according to the safety regulations such as CE, etc. applied in Europe, it is regulated that the power of the servo motor is cut off and re-supplied to protect the user even in the case of opening the door of the machine. The braking operation frequently occurs.

Referring to FIG. 1, the power of the servomotor is generally supplied through a power supply module 20, and power interruption by the power supply part 20 is performed by the CNC which is the numerical control part 10. Also, the power can be unintentionally shut off by an external device (for example, an emergency switch).

When the power is interrupted, the transfer shaft in the gravity direction starts the brake operation of the servo motor 40 before the power is shut off. Normally, the transfer axis in the gravity direction is delayed by operation time of the brake, loosening of the ball screw And a certain amount of falling occurs due to twisting or the like at the time of braking operation. This is transmitted to the numerical control unit 10 through a position measuring means such as a position pulse coder, and is integrated into a position deviation within the controller.

Accordingly, the numerical control unit 10 carries the movement of the feed axis to the corresponding position in accordance with a command such as position / speed, or an operation of maintaining the corresponding position when there is no position command. At this time, an operation of continuously reducing the accumulated positional deviation is performed.

That is, when the power of the servo motor 40 is re-supplied after the power of the servo motor 40 is cut off, a position error (Position Error) corresponding to a previously dropped amount accumulated in the numerical control unit 10, The numerical control unit 10 and the servomotor 40 immediately start the operation for reducing this, and the brake must be released substantially at the start of this operation.

If the actual release of the brake is delayed, the brake is damaged due to the position control and the feed operation of the feed shaft to reduce the position deviation before the brake earthed is released.

On the contrary, if the release of the brake is performed quickly, the brake is released before the operation of the motor for supporting the transfer shaft is released, causing a free fall of the transfer shaft due to gravity, which also causes mechanical damage.

Therefore, at a time point when the power of the motor is interrupted and then supplied again, the controller of the gravity axis motor resumes its operation to optimize the timing at which gravity can be supported and the timing at which the brake is released I need to give.

However, since there is a time delay between the time when the brake start command is generated and the time when the brake is actually completed (validated) depending on the driving speed of the brake, the timing of re- There is a problem that it is difficult to meet the point where it is solved.

In particular, since there is no method for detecting the time delay between the starting time of the brake operation and the time when the brake operation is actually enabled, the power off and on of the servomotor 40 can be detected, (For example, after 200 ms) at a time point at which the subsequent brake operation start time is set to be constant, the brake is released after the operation of the motor occurs to support the transport shaft.

Referring to FIG. 2, a method of controlling a feed shaft brake of a conventional machine tool includes the steps of determining whether a servomotor start command and a brake release command signal of a feed axis are received (S10) A step S30 of judging whether or not a break release delay time set from the time of generation of the start signal of the servo motor has elapsed, and a step S30 of judging whether or not the break release signal (Step S40).

Therefore, if the set break release delay time does not coincide with the actual motor start time and the time gap between the start of the brake operation and the start time of the brake operation, Likewise, machine damage can occur.

Further, since the control module and mechanical structure of the servo motor, the state of the brake, and the like are increased in use time and aged, a change occurs. Therefore, in the conventional method using the set time difference, It can not cope with the changed situation. Therefore, it is possible to cause the gravity drop phenomenon of the transport shaft or to accelerate the damage of the brake and the machine with the lapse of time.

As a result, when the power is re-supplied to the transfer shaft in the gravity direction, the timing at which the position control of the servomotor is resumed and the timing at which the brake is actually released can not be optimized. As a result, the brake is continuously damaged and the brake life is shortened have.

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing points, and it is an object of the present invention to provide a machine tool which can optimize the operation timing of a brake with respect to a transfer shaft acting in the direction of gravity to prevent gravity free fall or abnormal load on the transfer shaft, Which is capable of stabilizing the transfer axis and extending the service life of the brake.

According to an aspect of the present invention, there is provided a method of controlling a feed shaft brake of a machine tool, the method comprising: determining whether a servo motor start command and a brake release command signal are received from a stopped feed shaft; Generating a start signal of the servo motor when the release signal is received, updating the set break release delay time, determining whether the updated break release delay time has elapsed from the generation start signal of the servo motor And generating a brake release signal when the brake release delay time has elapsed, wherein the step of updating the brake release delay time determines whether or not a gravity drop has occurred in the transport shaft, And calculates the break release delay time Characterized in that the update.

In the control method according to the present invention, the step of updating the brake release delay time may include: determining whether a gravity drop of the transfer shaft of the machine tool has occurred; And a step of extending the break release delay time previously set by the drop time and updating the new break release delay time with a new break release delay time.

In the control method according to the present invention, the step of updating the brake release delay time may include a step of determining whether a gravity drop of the transfer shaft of the machine tool has occurred, and a step of determining whether the gravity drop of the transfer shaft has occurred, And a step of shortening the previously set brake release delay time by the generation time of the abnormal load and updating the new brake release delay time with a new brake release delay time.

As described above, according to the present invention, since the predetermined break release delay time is applied, the operation timing of the brake is optimized to prevent an abnormal load or gravity free fall of the transfer axis. It minimizes the damage of the brake and stabilizes the transmission shaft drive and extends the service life of the brake.

Further, the update of the brake release delay time is fed back in the direction of eliminating it based on the drop time of the gravity of the transfer shaft where the damage of the machine tool occurs and the abnormal load generation time of the servo motor. So that the optimum brake operation timing can be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a configuration for driving and controlling a machine tool transfer shaft; Fig.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]
FIG. 3 and FIG. 4 are diagrams illustrating a method of controlling a feed shaft brake of a machine tool according to an embodiment of the present invention.
5 is a view showing a case where the timing of release of the feed shaft brake of the machine tool is proper.
Fig. 6 is a view showing a case where a gravity drop of the transfer shaft occurs due to a quick release timing of the transfer shaft brake of the machine tool. Fig.
Fig. 7 is a view showing a case where an abnormal load is generated in the feed shaft and the servo motor due to a delay in releasing the feed shaft brake of the machine tool; Fig.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. Hereinafter, a method of controlling a feed shaft brake of a machine tool according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Generally, the feed shaft of the machine tool is repeatedly operated and stopped frequently during machining, and the brake device is interlocked to prevent sagging of the feed shaft in the gravity direction.

The power of the servomotor for driving the feed axis can be cut off by the numerical control unit or an external device (Emergency Switch, etc.), but the power supply is finally generated by the numerical control unit (CNC).

That is, the numerical control unit determines the point of time to re-supply the power of the servomotor, generates a command of the command, and determines the start point of the release of the brake to which the command is applied.

In this process, the numerical control unit (CNC) must determine and control the mutual timing for the two commands. In other words, it is necessary to generate the respective commands in consideration of the time point at which the torque is actually generated in the servomotor and the gravitational support and control of the transfer shaft is performed and the time at which the ownership of the brake is substantially canceled do.

The method of controlling the axis of the feed shaft of the machine tool according to the embodiment of the present invention differs from the conventional method in which the fixed point of time of two instructions is fixed by using a fixed delay time factor, And an optimum brake operation timing can be maintained in real time in accordance with a change in the state of the machine.

In other words, the numerical control section can grasp the factors that can detect the deflection of the feed axis or the abnormal load condition of the motor such as the position encoder, the motor load (Motor load, or the motor disturbance) And indirectly estimates a time point at which the brake is controlled by feeding back the calculation result.

More specifically, referring to FIG. 3, a method of controlling a feed shaft brake of a machine tool according to an embodiment of the present invention includes determining whether a servo motor start command and a brake release command signal are received with respect to a feed shaft in a stop state (ST1 A step (ST2) of generating a start signal of the servo motor when a start and a brake release signal of the servo motor is received, a step (ST3) of updating a set break release delay time, (ST4) of confirming whether or not the brake release delay time has elapsed, and a step (ST5) of generating a brake release signal when the updated brake release delay time has elapsed.

Generally, an operator generates a start and a brake release command signal for the servo motor. The generated signal is used to determine whether the servo motor start command and the brake release command signal for the feed axis are received during the above process (ST1) As shown in FIG.

Then, when the servo motor start and brake release signals are received, the start signal of the servo motor is generated and the drive of the feed shaft is resumed by generating the start signal of the servo motor (ST2).

At this time, if the brake is released immediately, it takes a certain period of time until the power of the transport shaft is supplied, so that the transport shaft falls down gravitationally. Therefore, it is preferable that the generation of the brake release signal is delayed until a predetermined time when the power of the transfer shaft is supplied.

For example, referring to the timing chart of FIG. 5, when the set break release delay time T is ideal, the displacement error of the feed shaft exists due to the release of the ball screw, Since the brakes are released correctly when the servomotor is driven, there is no abnormal load due to the conflict between the position controller of the motor and the external brake.

Therefore, in the step ST3 of updating the set break release delay time, the new break release delay time is not updated but the break release delay time T that was previously set and stored will continue to be applied. However, If a drop or servo motor abnormal load occurs, the set break release delay time needs to be updated to remove it.

Referring to FIG. 6, when the driving timing of the transport shaft brake is fast, a free fall of the transport shaft occurs, so that a gravity drop amount (position encoder: h) deviating from the displacement due to the ball screw is generated, Since the drop time at which the gravitational drop amount h occurs should be removed, the fall time t1 is calculated by inversely calculating the gravitational acceleration based on the drop amount h, and then fed back to the break release delay time to obtain an accurate break release delay time Can be updated.

That is, since the release of the traction axis brake is generated as quickly as the fall time, the drop time t1 is added to the first brake release delay time T to calculate the new brake release delay time T ' Direction.

Therefore, the step ST3 of updating the brake release delay time includes a step (ST31) for judging whether or not a gravity drop of the transfer shaft of the machine tool has occurred, specifically, as shown in step 4, (ST32) of decreasing the dropping time, and updating (ST33) a new break release delay time by extending from the previously set break release delay time by the inverse fall time.

4, the process of determining whether gravity drop of the conveying shaft has occurred (ST31) and the process of calculating the falling time of the gravity drop amount (ST32) are performed through a Servo Amplifier Module (SVM) It is possible. That is, the search control section (10 in FIG. 1) can detect the gravitational drop and the gravitational drop amount of the transfer axis directly by receiving the positional information of the transfer axis from the servo amplifier (30 in Fig. 1) and calculating it through internal calculation.

A gravity drop detection recording unit for performing this process may be additionally provided in the numerical control unit (10 in FIG. 1) or the servo amplifier (30 in FIG. 1). The gravity drop detection record unit may be integrated with a numerical control unit or a servo amplifier And can be implemented in various forms.

Therefore, if the numerical controller CNC includes an equation for inversely calculating the fall time from the drop amount, it is possible to invert the drop time t1 in real time, and to drop the fall time t2, which is set in the numerical control unit CNC, It is possible to perform the step of extending and updating the new break release delay time T 'by the time t1 and updating it.

This process is a process for eliminating the free fall phenomenon of the conveying shaft due to early release of the brake because the brake driving timing is earlier than the proper timing, and the updated new brake release delay time T 'is set until the next updating step It is applied as the brake release delay time.

Referring to FIG. 7, when brake release timing is delayed, when brake release is delayed, the control of the servo motor is interrupted by the brake, resulting in an abnormal load of the servo motor. Therefore, The abnormal load occurrence time t2 at which the abnormal load occurs can be calculated.

That is, since the release of the brake is delayed by the abnormal load generation time t2, the new brake release delay time T 'is calculated by subtracting the abnormal load generation time t2 in the first brake release delay time T The brake release timing is updated in a direction to advance.

Therefore, when the gravity drop of the conveying shaft does not occur in the step ST3 of updating the brake release delay time shown in Fig. 4, the step (ST34) of calculating the abnormal load generation time in the servo motor and the step (ST35) of shortening the brake release delay time to a new brake release delay time.

Likewise, since the servo motor is controlled by the numerical control unit (CNC), it is possible to detect the abnormal load and to detect the abnormal load by detecting the change in the torque of the motor. It will be able to directly detect the duration (? 2).

Therefore, in the numerical control unit CNC, the abnormal load generation time t2 in real time is shortened by the abnormal load generation time t2 in the break release delay time T set in the numerical control unit CNC, It is possible to perform the step of calculating and updating the time T '.

In addition, the numerical control unit CNC may include a transport shaft load detection recording unit for performing such a process. The transport shaft load detection recording unit itself may be formed as a separate module or the like.

If a free fall of the feed axis occurs at the first break release delay time T, the new break release delay time T 'to be updated is added at the same time to add the drop time t1, It can be summarized by subtracting the abnormal load occurrence time (t2) and calculating it.

As a result, according to the feed shaft brake control method of the present invention, the feed shaft brake reaction timing is detected by the numerical control unit (CNC), and the feedback start timing of the brake is optimized in accordance with the detected reaction speed Effect can be obtained.

Therefore, it is possible to implement a feedback system that calculates and updates the updated break start time automatically in the numerical control unit (CNC) and reflects it in the next action, and automatically detects the start point of the feed shaft brake every time the machine tool is used Adaptive brake control method can be implemented.

As a result, at the point of time when the motor power is interrupted and then supplied again, the gravity direction transfer axis motor resumes its operation so that the state where gravity can be supported and the time point when the brake release is completed and the shaft is released is optimized. Machine damage can be minimized.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, will be.

Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, And all changes or modifications derived from equivalents thereof should be construed as being included within the scope of the present invention.

Claims (3)

A step (ST1) of judging whether or not the servomotor start and the brake release command signal are received with respect to the transfer shaft in the stopped state;
A step (ST2) of generating a start signal of the servo motor upon receipt of a start and a brake release signal of the servo motor;
A step (ST3) of updating the set break release delay time;
A step (ST4) of judging whether or not the updated break release delay time has elapsed from a generation time of the start signal of the servo motor; And
And generating a brake release signal (ST5) when the brake release delay time has elapsed,
The step (ST3) of updating the break release delay time includes:
Determining whether or not a gravity drop of the transfer shaft has occurred, calculating a drop time or an abnormal load generation time according to a determination result, and updating the brake release delay time to the brake release delay time. The method according to claim 1,
The step (ST3) of updating the break release delay time includes:
A step (ST31) of judging whether or not gravity drop of the conveyance shaft has occurred;
A step (ST32) of inversely calculating a dropping time in a dropping amount when gravity dropping occurs in the transfer axis as a result of the judgment; And
A step (ST33) of extending the brake release delay time previously set by the fall time and updating with a new brake release delay time,
And controlling the braking force of the braking mechanism. The method according to claim 1,
The step (ST3) of updating the break release delay time includes:
A step (ST31) of judging whether or not gravity drop of the conveyance shaft has occurred;
A step (ST34) of calculating a generation time of an abnormal load in the servo motor when the gravity drop of the transfer axis does not occur as a result of the determination; And
A step (ST35) of shortening the brake release delay time previously set by the occurrence time of the abnormal load to a new brake release delay time,
Further comprising the steps of: detecting a braking force of the braking mechanism;

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