JPH02158802A - Stabilizing method for mechanism system - Google Patents

Abstract

PURPOSE:To stabilize mechanism system, and to make it of high rigidity by making the vibration characteristic of the mechanism system change freely in appearance by connecting control system in parallel with the mechanism system so that a force command value or a current command value to the mechanism system is made to be its input, and its output is added together with the output of the mechanism system. CONSTITUTION:The control system (control part A) is connected in parallel with the mechanism system whose elastic modes up to the secondary one are taken into consideration. Then, if constants a1*, a2* are selected so as to satisfy a1*+a1>0, a2*+a2>0, an apparent vibration characteristic 20 log¦y/Fs¦ becomes as shown in a figure. However, Fs is force command, a1, a2 are inherent modes, and (y) is a position in appearance. This shows the characteristic similar to the time of the establishment of collocation, and if it is speed-fed back, since all vibration roots proceed to a stable area, the vibration root is stabilized. Thus, by adding forwarding control system in parallel with the objective mechanism system to be controlled, the vibration characteristic of the mechanism system can be made to change freely in appearance, and the system can be stabilized and can be made to be of high rigidity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method for stabilizing a machine #I system having vibration characteristics with multiple degrees of freedom when controlling the system.

[Prior Art] Conventionally, when performing positioning control and speed control of a mechanical system that has vibration characteristics with multiple degrees of freedom, the vibration characteristics of the mechanical system are measured and the vibration characteristics are measured in order to stabilize and increase the rigidity of the system. Based on the data, notch filters, phase lead compensators, etc. were configured. Furthermore, since the vibration characteristics of a mechanical system vary depending on the structure and configuration, notch filters, phase lead compensators, etc. have been designed to suit each characteristic.

FIG. 5 is a block diagram of a conventional example showing a stabilization method using a notch filter, and FIGS. 6(a) and 6(b) are diagrams showing the vibration characteristics of the mechanical system and the characteristics of the notch filter, respectively.

In FIG. 5, χref is a position command, F is a control force, and χ is a position. In the case of FIG. 6(a), since the vibration characteristics of the mechanical system are taken into consideration up to the third-order elastic mode, three notch filters are required, resulting in a very complicated circuit configuration.

[Problem to be solved by the invention] The conventional methods described above have the following drawbacks.

(1) When using a notch filter, the center frequency of the filter is almost always made to match the resonant frequency of the mechanical system, and if the resonant frequency of the mechanical system changes for some reason, the notch filter loses its effectiveness.

(2) All phase lead compensators use differentiators, and it is impossible to construct a complete differentiator with an electronic circuit, considering noise and the like. Therefore, a differentiator is usually composed of a low-pass filter and a bare circuit, and the range of differentiation is up to the cut frequency of this low-pass filter. In other words, phase lead compensation is limited to a specific frequency range in order to avoid high gain in the high frequency range, so the resonance point of the mechanical system exists in the high frequency range, which has a negative effect on the stability of the system. If this occurs, it is necessary to use a notch filter (1
) causes the same problem.

(3) When dealing with servos, the question is, "To what extent can the loop gain be increased?"

Therefore, if the mechanical system to be controlled has vibration characteristics (generally, most of them do), this vibration characteristic (resonance) tends to make the entire servo system unstable, increasing the loop gain. The limit is lower. When it is desired to increase the loop gain to within this limit, it becomes difficult to obtain the required system characteristics.

(4) In order to stabilize the vibrator of the mechanical system using the phase compensators of the position loop and velocity loop, each phase compensator has a complicated configuration, and moreover, it must be configured to match the vibration characteristics of the mechanical system. Necessary and not universal.

[Means for Solving the Problems] The method for stabilizing a mechanical system of the present invention includes inputting a force command value or a current command value to the mechanical system,
A control system is connected in parallel with the mechanical system so that the output is added to the output of the mechanical system, and the coefficients of the second-order term and zero-order term of the denominator of the transfer function of the control system are Using the values of the modal mass and modal stiffness, the coefficient of the numerator of the transfer function of the control system is determined by considering the eigenmode component of each vibration mode of the mechanical system,
It is characterized by freely manipulating the arrangement of zero points of the system composed of the mechanical system and the control system.

[Operation Notes] In the configuration, by manipulating the characteristics of the control system (value of the numerator of the transfer function), the vibration characteristics of the mechanical system can be apparently freely changed, resulting in a controlled object that is easy to control. This makes it possible to stabilize the system and increase its rigidity. Furthermore, since a complicated circuit configuration such as a notch filter is not required, the control device becomes extremely simple.

[Embodiments] Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a control device to which the stabilization method of the present invention is applied, and FIG. 2 is a block diagram of a control device to which the stabilization method of the present invention is applied.

A diagram showing the vibration characteristics of only the mechanical system when a2 is 0.

In FIGS. 3 and 4, a♂=-2a in FIG. 1.

FIG. 7 is a diagram showing vibration characteristics and root locus vibrations when a2°=-2a2 is selected.

In this embodiment, as shown in FIG. 1, a control system (control unit A in the figure) is connected in parallel to a mechanical system that takes even the secondary elastic mode into consideration. A velocity loop and a position loop (control unit B in the figure) are arranged outside these systems. In Figure 1, S is the Laplace operator, p is the position loop gain, Kv is the velocity loop gain, χref is the position command, Fs is the force command, aI * a 2 is the eigenmode,
mQ''m2 is the modal mass, k, 2 is the modal stiffness, a
l t 82' is a constant, χ is a position, and y is an apparent position.

In Fig. 1, the vibration characteristic 201ogl x/F l of only the mechanical system when a, , a, < O is the anti-resonance point between the primary and secondary resonance points, as shown in Fig. 2. However, there is no anti-resonance point before the first-order resonance point, and it is clear that if this is fed back with velocity as it is, the first- and second-order vibrators will move into an unstable region. It is. Therefore, as shown in FIG. 1, the control system A is added in parallel to the mechanical system, and at this time, the constant a I * a29 is
+" + a + > O, a2" + 82>0 is selected to satisfy the apparent vibration characteristics of 201og
Iy/Fs I is as shown in Figure 3 (Figure 3 is a,
”=-2a, , a2”=-2a2).

Figure 3 shows the same characteristics as when colocation is established (the sensor position and the actuator position match), and when this is speed fed back, all the vibrators move into the stable region and become stable. become The root locus at this time is as shown in FIG. The eigenmodes when collocation is established are all positive numbers. al”
= "-2al +a2" = -2a2, so the eigenmode in the characteristic from F to y, including the mechanical system and control unit A, is a, +a, "=a, + (-2a,) = -a.

a2+a2”=-82 Therefore, it becomes a positive number.

In the above example, al+82" is changed to al"=-2 in order to make it similar to when the collocation with apparent vibration characteristics is established.
I chose 8+ * 82”=-2az, but a l +
Since 821 can be freely selected by the control unit A,
In the apparent vibration characteristics, it is possible to create or eliminate anti-resonance, or change the frequency of the anti-resonance point.

[Effects of the Invention] As explained above, the present invention has the advantage that by adding a forward-facing control system in parallel to the mechanical system to be controlled, the vibration characteristics of the mechanical system can be apparently freely changed. , it is possible to obtain a controlled object that is easy to control, stabilize the system and increase rigidity, and because it does not require complicated circuit configurations such as a notch filter, the control device becomes extremely simple. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a control device to which the stabilization method of the present invention is applied, and FIG. 2 is a block diagram of a control device to which the stabilization method of the present invention is applied. Diagram showing the vibration characteristics of only the mechanical system when a2 is 0, Part 3
Figure 4 is a, "= -2aa2" in Figure 1.
Fig. 5 is a block diagram of a conventional stabilization method using a notch filter, and Fig. 6 shows the vibration characteristics of the mechanical system and the characteristics of the notch filter. FIG. Patent applicant: Yaskawa Electric Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. In a control device for controlling a mechanical system having vibration characteristics with multiple degrees of freedom, a force command value or a current command value to the mechanical system is input,
A control system is connected in parallel with the mechanical system so that the output is added to the output of the mechanical system, and the coefficients of the second-order term and zero-order term of the denominator of the transfer function of the control system are Using the values of the modal mass and modal stiffness, the coefficient of the numerator of the transfer function of the control system is determined by considering the eigenmode component of each vibration mode of the mechanical system,
A method for stabilizing a mechanical system, characterized by freely manipulating the arrangement of zero points of a system constituted by the mechanical system and the control system.