Electricity: motive power systems – Positional servo systems – Pulse-width modulated power input to motor
Patent
1987-10-05
1989-05-16
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Pulse-width modulated power input to motor
388811, 388900, 388906, G05B 1128
Patent
active
048313173
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a method for controlling a servomotor, and more particularly, to a drive control method for a servomotor, in which a high output can be fetched from the servomotor by means of a motor-current control unit of a simple construction.
2. Description of the Related Art
The recent mainstream of servomotor drive control is PWM control using semiconductor switching elements, such as power transistors, thyristors, etc. Also, there is a demand that a high output should be obtained from servomotors. In order to obtain a high output from a servomotor, a large current must be supplied to the semiconductor elements. It is difficult, however, to obtain semiconductor elements which permit a large current to be applied thereto. Even if a large current is allowed to flow through a semiconductor element, moreover, the semiconductor element has the property of generating heat in its active region, and hardly in its cut-off region and saturated region. Therefore, the calorific value of the semiconductor element increases in proportion to the chopping frequency, so that the chopping frequency must be lowered. If the chopping frequency is lowered, however, motor control inevitably becomes difficult. Thereupon, a tentative arrangement is provided such that each of the switching elements of a PWM control section is composed of a plurality of semiconductor elements, and the driving current of the servomotor is increased by reducing the currents flowing through the individual semiconductor elements. In such a case, however, current concentration in the semiconductor elements (or large current flow only in some of the semiconductor elements) is caused, so that the driving current cannot be increased in proportion to the number of parallel-connected semiconductor elements.
Conventionally, therefore, a high output is obtained by operating a plurality of motors in a parallel manner. In this case, however, it is necessary to mechanically connect the individual motors with one another and with an output shaft. This results in an increase in cost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a drive control method for a servomotor, in which a high output can be fetched from the servomotor while preventing switching elements of a motor-current control unit from being damaged by excess current.
Another object of the present invention is to provide a drive control method for a servomotor which can be effected by using a motor-current control unit of a simple construction.
A method for controlling a servomotor according to the present invention comprises steps of integrating the deviation between a command current for each of two or more independent winding portions and a current flowing through each of the winding portions, with use of an integrating element corresponding to each of the winding portions, the two or more winding portions constituting an armature winding of each phase of the servomotor; amplifying the currents flowing through the individual winding portions by means of proportional elements corresponding to the individual winding portions; obtaining the deviations between the outputs of the individual integrating elements and the outputs of the proportional elements corresponding thereto; obtaining a control signal by adding the individual deviations; and controlling the currents supplied to the indivudal winding portions for substantially independent and equal values by the use of one PWM control means responsive to the control signal.
Thus, according to the present invention, the control signal is obtained with use of the integrating element and the proportional element corresponding to each of the plurality of winding portions, which constitute the armature winding of each phase of the servomotor. Therefore, the current flowing through the individual winding portions can be controlled independently for equal values by the use of one PWM control means. Thus, a high output can be obtained from the servomotor, and be
REFERENCES:
patent: 4623827 (1986-11-01), Ito
Kobayashi Toshio
Sakamoto Keiji
Bergmann Saul M.
Fanuc Ltd
Shoop Jr. William M.
LandOfFree
Method for controlling a servomotor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling a servomotor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling a servomotor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2325496