JP2001317612A - Vibration damping control cam mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration dumping technique including a design technique for a cam curve capable of realizing increase in speed of a mechanism for positioning a final movable part by using a cam mechanism with low rigidity of a machine and hard to increase speed. SOLUTION: An acceleration/deceleration time of the cam mechanism is set to a period of vibration of a primary vibration characteristic value of a system or a period thereof multiplied by an integer, and a point of inflection of command velocity is made to coincide with a primary node of the vibration of the system. A bad influence of the primary characteristic value is thereby removed and rigidity of the whole mechanism of a driven mechanism driven by a cam is increased, and the increase in speed is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a combination mechanism of a motor, a cam and its driven mechanism widely used in industrial machines and the like, which does not require any function other than the intended function of the driven mechanism (rotational motion, linear motion). The present invention relates to a vibration suppression technique for realizing a high-speed operation of a mechanism while suppressing vibration.

[0002]

2. Description of the Related Art Attempts to increase the speed of a mechanism of a type in which a driven mechanism is controlled by a cam driven by a motor use a linear acceleration / deceleration curve or an S-shaped acceleration / deceleration curve based on a cam curve, and the driven mechanism generates harmful vibration. In general, a method of adjusting the displacement speed so as not to induce (in order not to excite the first-order eigenvalue which could not be controlled) so as not to give an impact as much as possible.

[0003]

However, since these prior arts leave the processing of the primary eigenvalues unacceptable, the acceleration / deceleration time determined by the cam curve and the rotation speed of the cam is reduced by the primary vibration of the system. Since the setting can be performed only in a range where the influence of the eigenvalue does not occur, only a remarkably limited low operation speed performance can be realized.

An object of the present invention is to provide a control technique capable of realizing a high-speed mechanism of a type in which a driven mechanism is controlled by a cam driven by a motor.

The basic technology of the present invention is disclosed in Japanese Patent Application No. 2000-2000.
No. 118052 and Japanese Patent Application No. 2000-120691, which are based on the vibration suppression method of “specifying the acceleration / deceleration control time when changing the speed to the commanded speed to an integral multiple of the vibration natural value (period)”.

[0006]

The biggest factor that hinders the speeding up of the mechanism is that in a typical trapezoidal command speed control, the acceleration / deceleration time is not affected by the primary vibration eigenvalue of the system. In the present invention, the cam curve and the number of rotations of the cam are set so that the acceleration / deceleration time is equal to the vibration period of the primary vibration eigenvalue of the system or an integral multiple thereof. By matching the acceleration inflection point of the mechanism (the bending point of the commanded velocity) with the node of the primary vibration of the system, the adverse effect of the primary eigenvalue of the system is eliminated, thereby realizing a high-speed mechanism. Things.

When the present invention is applied, at the acceleration inflection point of the mechanism, the speed difference and the equivalent spring potential energy of the system do not occur between the commanded speed and the actual speed of the driven mechanism. The impact force accompanying the change becomes zero, and it is possible to prevent the occurrence of harmful vibrations due to uncontrollable primary eigenvalues, and as a result, it is possible to operate the servo system at high speed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, which is a typical mechanism generally existing in the world in which a cam rotated by a motor is driven and a driven mechanism of the cam is controlled.

The motor 2 is rotated by the controller 1, and the cam 3 having the cam groove 3-1 connected to the motor via the coupling 20 is rotated. A cam follower 4 fits into the cam groove 3-1. The driven lever 5 holds the cam follower 4 at one end, and has an elongated hole 5-1 provided at the other end.
Hold the pin 8 provided on the movable portion 7 and swing around the shaft 6. The final movable part 7 is guided by the guide wall 9 on the side and makes a reciprocating linear movement.

The object to be controlled in this mechanism is the positioning of the final movable part 7.

However, this mechanism has various play and the spring property of the structural material after the driven lever 5.

The main points of play are between the cam groove 3-1 and the cam follower 4, between the driven lever 5 and the shaft 6, the slot 5
1 and between the pin 8 and between the guide wall 9 and the final movable part 7. These act equivalently as springs for the vibration of the whole system of the mechanism.

[0013] Acting directly as a spring is the torsion and flexure of the driven lever and other engaging parts.

These parts having spring properties can be expressed as an equivalent spring (spring constant k) 10 as a whole.

Assuming that the equivalent mass (W) 11 in the radial direction of the cam 3 of the driven mechanism after the driven lever 5, FIG.
2 can be expressed by a vibration system (equivalent model) composed of a spring and a mass, which support the equivalent mass 11 by the equivalent spring 10 as shown in FIG. 9 'is a virtual guide wall of a virtual engagement point of the equivalent spring 10 with the groove 3-1 of the cam 3.

FIG. 3 illustrates such a mechanism.
Move the final movable part 7 to the target position (command position) along the cam curve
Target speed when positioning at
Commonly used acceleration / deceleration curves (trapezoidal wavy OAEF)
And that the cam curve becomes oaefg. When the motor rotates at a constant speed, the cam groove 3
This command speed is created by the shape of -1. In the acceleration / deceleration curve, the acceleration during OA is accelerated at a constant acceleration, the acceleration during AE is zero, and the acceleration during EF is decelerated at a constant acceleration. Naturally, the cam curve is a quadratic curve between 0a and ef.

The behavior of the load system represented by the primary vibration model as shown in FIG. 3 will be described with reference to FIG. When the cam follower 4 is linearly displaced at such a command speed due to the rotation of the cam 3, the speed of the linear motion of the equivalent mass 11 (final movable portion 7) is initially reduced by the spring contraction, becomes lower than the command speed, and the potential energy in the spring is reduced. Then, the spring begins to expand while releasing this stored potential energy, the speed becomes faster than the commanded speed, and approaches the commanded speed with the release of energy. That is, as indicated by a virtual speed curve from the point 0 to the point A to the point B, an oscillating speed change centered on the command speed is repeated. It is well known that the oscillation period T and amplitude P of the system represented by such an equivalent model are given by the following equations.

T = (k / m) 0.5 P = C1 sin ωt + C2cos ωt (where k is a spring constant, m is mass, ω is angular velocity, C1
C2 is a constant)

Next, if the speed command is bent at a point A in FIG. 4 so as to have a constant speed, that is, if the acceleration linearly accelerated at a constant acceleration up to the point A is set to zero, the actual speed of the system is A to C. It is easily assumed that a vibration waveform represented by

However, when the node A where the potential energy of the spring becomes zero (the actual speed is at the command speed) and the node A coincide with the node of the vibration of the actual speed of the system, the actual speed after the point A is as shown in FIG. As shown by the straight lines A to C to D, there is no vibration.

This will be described with reference to FIG. A,
Points G and H are switching points for switching to the constant speed Vc. According to FIG. 6, when switching is performed at points G and H (the actual position is near the command position), the speed difference = Vh-Vc is not zero, and the potential energy of the spring is not zero. Point A
The speed difference and the potential energy of the spring become zero only in the case of the switching at. This speed difference and the potential energy of the spring become the impact force that excites the equivalent spring of the equivalent model. Therefore, the only condition is that the switching at the point A does not generate an impact force. There will be no switching points other than nodes of oscillation of the primary eigenvalue of the system. FIG. 6 shows the time from the start to the point A, that is, the acceleration time Tu.
The presence or absence of an impact force acting on the spring is schematically represented by the magnitude of p and the natural value T1 of the vibration of the system.

FIG. 7 shows how the actual speed of the subsequent system changes due to the impact force at the three acceleration switching points shown in FIG.

From the above description, the selection of the switching point may be made by selecting a node of the vibration so that it can be easily estimated from FIGS. 4, 5, and 6, and may be set to an integral multiple of the primary eigenvalue of the vibration. Understand

Further, it is easy to understand that the operation principle at the time of deceleration is exactly the same as that at the time of acceleration, and a description thereof will be omitted.

As a switching point, a node of vibration (1 of vibration)
In order to select the next eigenvalue (an integral multiple of the eigenvalue), the eigenvalue of the vibration system of the mechanism is measured, and the cam curve is determined according to the rotation speed of the motor to be used.

The controller 1 controls the motor 3 power drive and the rotation speed.

In the above embodiment, the example in which the groove cam is provided on the surface perpendicular to the rotation axis of the cam has been described.
It is obvious that the above concept is applied to a cam that moves linearly or a cylindrical groove cam as long as the driven mechanism vibrates.

[0028]

As described above, according to the present invention, it is possible to completely remove the adverse effect of the primary eigenvalue of the system from all vibration systems, and to drive a low-rigidity machine with less vibration. The mechanism can be speeded up by the effect of shortening the acceleration / deceleration time. In addition, the higher the rigidity of the mechanism, the higher the eigenvalue, so that the acceleration / deceleration time can be shortened and the speed of the mechanism can be further increased. ,

[Brief description of the drawings]

FIG. 1 is a typical mechanism in which a cam rotated by a motor is driven and a driven mechanism of the cam is controlled in one embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an equivalent circuit after the driven lever in FIG. 1;

FIG. 3 shows a target cam curve in the mechanism of the embodiment and a command speed (a commonly used acceleration / deceleration curve) for positioning the final movable portion 7 at a target position along the cam curve.
(Trapezoidal wavy))

FIG. 4 is a conceptual diagram of a relationship between an actual speed, a commanded speed, and an acceleration switching point of a system when the acceleration is switched without applying the present invention.

FIG. 5 is a diagram showing a relationship between an actual speed, a command speed, and an acceleration switching point of a system when the present invention is applied;

FIG. 6 is a diagram schematically showing the presence or absence of an impact force acting on a spring depending on the time from the start to the point A, that is, the acceleration time Tup and the magnitude of the eigenvalue T1 of the vibration of the system.

FIG. 7 is a diagram showing an acceleration switching point and a state of vibration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Controller 2 Motor 3 Cam 3-1 Cam groove 4 Cam follower 5 Follower lever 5-1 Slot 6 Axis 7 Last movable part 8 Pin 9 Guide wall 9 'Virtual guide wall 10 Equivalent spring 11 Equivalent mass 20 Coupling

Claims (1)

[Claims] 1. A motor driven by a motor, a cam driven by the motor, and a driven mechanism subsequent to a cam follower that performs a predetermined displacement operation by the cam. The acceleration / deceleration control time is specified by a cam curve so as to be a period t1 of the primary eigenvalue of the vibration of the driven mechanism or an integral multiple thereof, thereby suppressing the vibration of the driven mechanism and enabling the driven mechanism to operate at high speed. A mechanism characterized by: