Electricity: motive power systems – Positional servo systems – 'reset' systems
Reexamination Certificate
2000-04-24
2001-06-26
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Positional servo systems
'reset' systems
C318S621000, C318S610000, C388S906000
Reexamination Certificate
active
06252369
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a motor speed controller that enables a quick response, and a gain setting method of the controller.
BACKGROUND OF THE ART
A speed controller of an electric motor may be used for not only making a following action to a speed command but also making a high-speed positioning action by adding a position controlling loop outside a speed loop. It is essential that the speed controlling system is able to follow a speed command at a high speed and high accuracy. Hereinafter, prior arts pertaining to the abovementioned field of art are listed, and a description is given of features in each case.
(1) Motor speed controller which feeds back only speed signals resulting from a position differential
In this art, if a proportional gain of the speed loop is increased to achieve a high speed response, high harmonic ripple components in the detecting speed is accordingly amplified to cause the torque wave form to be distorted, whereby such a problem occurs, where motor noise and vibrations are increased. Where an electric motor driven by the motor speed controller actuates a mechanism, distortion of the abovementioned torque waveform will become a source of vibration with respect to resonance elements of the mechanism and power transmitting system, or the existence of resonance characteristics may damage margin in stability of the control loop, whereby resonance noise occurs when driving the mechanism and the control system may be made unstable. Therefore, since the size of the proportional gain of the motor speed controller is limited due to distortion of the torque waveform and decrease in the allowance in stability of the controlling loop, such a problem occurs, by which the response characteristics of the speed-controlling system cannot be improved.
(2) Method for passing a speed-detected output through a low-pass filter
A method for passing a speed-detected output through a low-pass filter to decrease noise is considered in order to smoothen the torque waveform, wherein since the allowance in stability of the control loop is damaged by an increase in phase delay, the proportional gain of the speed-controlling system cannot be increased, and the response characteristics cannot be improved.
(3) Method for applying a same-dimensions (status) observer
It is considered that a same-dimensions (status) observer is concurrently applied in the speed-controlling system in order to smoothen the torque waveform and secure allowance in stability of the controlling system. Since the same-dimensions (status) observer is a prediction type, it can be easily imagined that speed signals having less phase delay can be outputted, and the speed signals can be achieved.
(4) Method for controlling vibrations by using an equivalent rigid body observer
Japanese Patent Application No. 12785 of 1994 (Laid-Open Patent Publication No. 337057 of 1995) and Japanese Patent Application No. 233528 of 1995 (Laid-Open Patent Publication No. 56183 of 1997) exist as a means for increasing the proportional gain of the speed-controlling system, which drives a mechanism system influenced by mechanical resonance elements, with allowance in stability of the control loop secured. These are such that a control structure consisting of an equivalent rigid body observer, low-pass filter, high-pass filter and vibration controlling gain is added to the speed-controlling system.
Shortcomings and problems pertaining to the present invention are summarized as follows;
(a) Generally, even though a speed-controlling system is of a proportional plus integral type since a constant deviation occurs in detected signals due to disturbance such as Coulomb friction in the status observer, there is a problem in that the output of the speed controlling system is not coincident with the command speed. Therefore, usual status observers cannot be applied to the speed-controlling system as it is.
(b) In a motor speed controller using an equivalent rigid body observer, there are a number of parameters to be adjusted. It is necessary to add and adjust at least three parameters in total, such as a observer gain, time constants of low-pass filter and high-pass filter, and vibration controlling gain in addition to normal control parameters of the speed controlling system.
(c) There is no adjustment procedure for high-speed responses in the speed controlling system, or if any, the adjustment procedure is complicated. Thus, in the prior art, there are a number of parameters to be adjusted, whereby the adjustment procedure is complicated, and a problem occurs, in which no adjustment procedure is provided.
As a means for solving the above, by taking a larger observer gain than the gain of the speed controlling system, setting is determined so that the dynamic characteristics of the observer do not influence the dynamic characteristics of the speed controlling system, wherein there are many cases where adjustment of the controlling system is simplified.
(d) The speed controlling system, in which an observer is incorporated, is not constructed so that the response characteristics thereof can be easily improved. That is, in this case, since the cut-off frequency of the observer (as a filter) is high, the mechanical resonance components cannot be sufficiently reduced by the observer, whereby the proportional gain of the speed controlling system could not be increased (A detailed description is given later).
Based on the above consideration, it is therefore an object of the invention to provide a motor speed controller having a control structure by which the number of parameters to be adjusted may be reduced, and the proportional gain of the speed controlling system is increased, in a speed controlling system in which an equivalent rigid body observer (observer) is incorporated, and steps for adjusting so as to easily accelerate the speed response in the controlling system.
DISCLOSURE OF THE INVENTION
In the following description, the following reference symbols are defined as follows;
s: Laplacian operator
&zgr;
s
: Attenuation coefficient of an observer
&ohgr;
s
: Frequency band of an observer
Kv: Proportional gain
Cf(s): Transmission function of stabilizing compensator described later.
In order to solve the abovementioned shortcomings and problems, according to a first aspect of the invention, a motor speed controller comprising:
a speed-controlling means having a proportional operating means, which controls the angular velocity of a motor;
a modeled equivalent rigid body model in a first order lag system in which viscos friction is made into a time constant;
a first compensating means for carrying out a proportional operation;
a second compensating means for carrying out an integration operation;
a means for adding motor torque signals, outputted from the speed-controlling means, output of the first compensating means, and output of the second compensating means, inputting the sum thereof into the equivalent rigid body model, and inputting a differential signal obtained by subtracting the output of the equivalent rigid body model from the speed signals of the speed-controlling means into the first and second compensating means; and
a means which defines a proportional gain of the first compensating means in terms of the product of the first gain (&zgr;
s
) and the second gain (&ohgr;
s
), defines an integration of the second compensating means in terms of a square of the second gain, multiplies the proportional gain (Kv) of the proportional operating means of the speed-controlling means by a band setting coefficient (&agr;) established in advance, and makes it into a feedback input to the second gain (&ohgr;
s
),
wherein output of the equivalent rigid body model is made into a feedback input to the speed-controlling means as a detected speed.
Also, according to a second aspect of the invention, in addition to a motor speed controller as set forth in the first aspect, a gain setting method for the controller is featured in repeating the steps of taking the band setting coefficient as a value esta
Kaku Yasuhiko
Kitazawa Takashi
Okubo Tadashi
Armstrong Westerman Hattori McLeland & Naughton LLP
Kabushiki Kaisha Yaskawa Denki
Leykin Rita
Nappi Robert E.
LandOfFree
Motor speed controller and gain setting method of the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor speed controller and gain setting method of the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor speed controller and gain setting method of the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2466860