JPH0360940A - Load weight corresponding type speed control method - Google Patents

Abstract

PURPOSE:To realize a speed-up at the weight tool changing time by limiting the output at acceleration time to the value equivalent to a light tool and operating at the optimum speed corresponding to the transfer weight, in the case of controlling the tool changing speed of a machining center. CONSTITUTION:A servomotor is actuated by limiting the output at an acceleration time to the acceleration torque limited value equiv. to the load of a light weight, achievable speeds V1, V2 which become slower as the load weight at a set acceleration completed position (a) is larger are detected and a speed command value is switched to this achieving speed. Now, when a heavy tool is held on a changing arm and the revolving at 180 deg. is performed by the servomotor, the delay against the acceleration command becomes larger. The achieving speed V2 of the commanded acceleration distance completion position (a) is detected now, the speed command value is re-written to V2 from V1, the arm is revolved at the designated speed V2 and deceleration is performed. Since the heavy tool reaches at the speed V2 to this deceleration start position and the light tool at the speed V1, they are smoothly decelerated and stopped at a target position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a speed control method for a device that handles tools or workpieces of different weights, such as an automatic tool changer for a machine tool or an automatic pallet changer. be.

2. Description of the Related Art Conventionally, for example, the tool changing speed in an automatic tool changing device of a machining center is often set to a constant speed that allows smooth acceleration and deceleration of the heaviest tool.

Problems to be Solved by the Invention When the tool change speed described in the conventional technology is constant, the maximum weight tool with a large deceleration load due to the moment of inertia during deceleration at the end of the operation is set to the target slow speed. Although speed amplification is possible for lightweight tools, it is inefficient at slow constant speeds.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to provide a load weight-adaptive speed control method that can operate at an optimal speed corresponding to the conveyed weight. This is what we are trying to provide.

Means for Solving the Problems In order to achieve the above-mentioned object distantly, the present invention provides a load weight responsive speed control method which limits the output during acceleration to an acceleration torque limit value commensurate with a light weight load, and controls the servo motor. , detects the respective attained speeds that become slower as the load weight increases at a predetermined acceleration end position, and switches the speed command value to the attained speeds.

When starting multiple moving objects with different load weights using a servo motor whose output during acceleration is limited to the acceleration torque limit value, the one with the smaller weight will have a shorter acceleration distance to reach the speed command value. The heavier one has a longer acceleration distance.The end point of this shorter acceleration distance is set as the acceleration end position, the speed reached at this position is detected, and the command value is switched to this speed to terminate the acceleration. The larger the load weight, the slower the moving body is driven.

Embodiment An embodiment will be explained with reference to FIGS. 1 and 2. In a known machining center, an exchange arm shaft 2 is supported by a frame 1 of an automatic tool changer so as to be able to move in the axial direction and rotate between 90'' and 180@, and an exchange arm 3 is fixed to the tip of the exchange arm shaft 2. A servo motor 4 is fixed to the frame 1 concentrically with the exchange arm shaft 2, and a position detector 5 is fixed concentrically to the servo motor 4.The NC-driven servo motor 4 moves the exchange arm 3. Rotation indexing is now performed.

Next, the feed shaft servo system for rotating the exchange arm 3 will be explained using block wArgJ in FIG. The program memory 6 is a part that stores the Canadian program, and the program interpreter 7 is a part that sorts and outputs the information called from the program memory 6.The 0 position command calculation part 8 receives the position command value from the program interpreter 7. The speed command calculation unit 9, which calculates the difference between the current position and the current position from the position detector 5 and outputs a signal, calculates the command (target) speed at each moment of acceleration/deceleration based on the speed command value, and calculates each speed. The portion that converts into a current value, current (torque)≧The ivy 10 is a portion that limits the current, and the power amplification portion 11 is a portion that drives the servo motor 4. The above is a general servo system. The acceleration torque limit-current conversion section 12 converts the acceleration torque limit 7) value sent from the program interpretation section into a current value, and the speed detection section 13 at the acceleration end position detects the end of the specified acceleration distance from the program interpretation section. This is the part that detects the speed at position a.

Next, the operation of this embodiment will be explained. A heavy tool is now gripped by the exchange arm 3, and the servo motor 4
A rotation of ° is about to take place.

The position command value and the speed command value are sent from the program interpretation section 7 to the position command calculation section 8 and the speed command calculation section 9 at the same time as the start command.
The acceleration torque limit value and acceleration distance command value are also output. The position command calculation unit 8 that receives the command calculates the difference between the current position (angle) from the position detector 5 and the command position (angle), and sends a signal to the speed command calculation unit 9.
Here, the ever-changing command (target) speed at the time of startup (acceleration) is determined, which is further converted into a current value and output to the current (torque) ξ ivy 10. On the other hand, the acceleration torque limit ξ limit value is converted into an IIJ control current value by the acceleration torque limit-current converter 12 and inputted to the current (torque) limiter lO, and the power amplifier 11 converts the value to a small value suitable for a lightweight tool. The servo motor 4 is started with the limited acceleration torque value. As shown in the graph showing the relationship between speed and movement position in Figure 2, the startup state at this time is that the acceleration command is accelerated with a slight delay in following the acceleration command and reaches the command speed V. This is normal, and in the case of a lightweight tool, the acceleration torque limit value is set so that the tool accelerates approximately along this line. However, in this case where an IT tool is being gripped, the delay with respect to the acceleration command becomes even greater. On the other hand, the acceleration distance specified value and the position signal from the position detector 5 are input to the speed detection section 13 at the acceleration end position. amount) has been calculated. Then, the reached speed ■2 at the commanded acceleration distance end position a is detected and a speed conversion command is sent to the program interpreter 7, and the speed command value changes from ■1 to ■
2, the exchange arm 3 is rotated at a specified speed ■ that is slower than when using a lightweight tool, and the target 1806
When a predetermined deceleration start position, which is set slightly before reaching the turning position, is reached, the speed command calculation unit 9 issues a deceleration command that changes every moment, and deceleration is performed. At this deceleration start position, the heavy tool is at a slow speed vt, and the light tool is at a fast speed v1.
Since the difference in deceleration load due to the moment of inertia is very small, deceleration is performed smoothly and the target position is stopped.

Although this embodiment has been described with respect to speed control of an automatic tool changer of a machining center, it is of course applicable to speed control of an automatic pallet changer, a table rotation device, a transport robot, etc.

Effects of the Invention Since the present invention is configured as described above, it produces the following effects. The servo motor is started with the output during acceleration limited to a small value, the speed reached at the end position of the command acceleration distance is detected, and the speed command value is switched, so that the speed is slower for heavy tools and faster for lightweight tools. Since the tool can be moved with ease, there is no unreasonable load placed on the machine structure, and as the lightweight tool becomes faster, operating time is shortened and non-cutting time is reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a servo motor system including a perspective view of a part of the tool changer, and FIG. 2 is a graph diagram showing the relationship between movement position and speed during acceleration. 4. Servo motor

Claims (1)

[Claims] (1) Start the servo motor (4) by limiting the output during acceleration to an acceleration torque limit value commensurate with the light load, and the larger the load weight at the set constant acceleration end position (a), the slower the speed will be. Each attained speed (V_1 or V_2
) and switching the speed command value to the reached speed.