Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
2001-04-13
2003-04-22
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S276000, C318S611000
Reexamination Certificate
active
06552507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to control of acceleration/deceleration of a motor and particularly relates to generation of an acceleration/deceleration curve to make it possible to suppress vibration given to a subject of control such as a robot manipulator when a command to move by a short distance is given to the subject of control.
2. Description of the Related Art
Heretofore, a manipulator works by repeating a movement operation wherein an end effector is moved from a taught point to the next taught point as designated by a user. In the movement operation from a taught point to another taught point, acceleration/deceleration control is applied over a servomotor actuating a joint of the manipulator. Hence, the end effector is accelerated on the basis of a predetermined acceleration/deceleration curve until the effector reaches a predetermined maximum velocity. After a predetermined constant velocity period, the end effector is decelerated on the basis of the predetermined acceleration/deceleration curve in the same manner as in the case of acceleration. Hence, the operation of stopping the end effector at the next taught point is achieved. In such servomotor acceleration/deceleration control, a trapezoidal acceleration/deceleration curve may be used. In such an acceleration/deceleration curve, however, acceleration becomes discontinuous at a velocity switching point when acceleration starts, ends, etc. Both impact and vibration of the manipulator become large at such a velocity switching point. To avoid such impact and vibration, therefore, there has been proposed acceleration/deceleration control in which such an acceleration/deceleration curve is changed smoothly over the whole region from the start point through the maximum velocity to the end point to thereby ensure continuity of acceleration.
Such acceleration/deceleration control, however, has a problem that vibration of the manipulator is intensified when a commanded quantity of motor movement is smaller than a minimum quantity of movement which is required to allow the movement of the motor to reach predetermined operating velocity and operating acceleration (hereinafter defined as “a small movement”) . To solve the problem of vibration in such small movement, Japanese Patent Application No. 2-22559 has proposed a method in which: simulation is made in advance to generate a correction data table; optimum maximum velocity, acceleration time and deceleration time are determined on the basis of the correction table; and a velocity curve is corrected on the basis of these values to thereby suppress vibration.
Data in the correction table are, however, obtained as results of simulation and are not determined on the basis of predetermined algorithm. Hence, trial and error must be repeated for generating such a correction table.
SUMMARY OF THE INVENTION
The present invention is designed upon such circumstances as described above, and a first object thereof is to provide a method for determining a maximum velocity and a maximum acceleration so as to generate an acceleration/deceleration curve by which vibration given to a mechanical system can be suppressed when a quantity of movement corresponding to the small movement, as described above, is commanded in acceleration/deceleration control with acceleration kept continuous. A second object is to provide an acceleration/deceleration generating method for generating an acceleration/deceleration curve on the basis of the maximum velocity and maximum acceleration determined by the aforementioned maximum velocity and maximum acceleration determining method. A third object is to provide an acceleration/deceleration control method using the aforementioned maximum velocity and maximum acceleration determining method. A fourth object is to provide an acceleration/deceleration control apparatus using the aforementioned acceleration/deceleration control method. A fifth object is to provide a motor control apparatus using the aforementioned acceleration/deceleration control method. The above objects are achieved as described in the following enumerated paragraphs.
(1) According to an aspect of the present invention, a motor velocity/acceleration determining method is configured as follows. In acceleration/deceleration control of changing acceleration continuously to thereby make acceleration or deceleration, there is provided a method of determining velocity and acceleration of a motor for generating an acceleration/deceleration curve of the motor when a commanded quantity of motor movement is smaller than a minimum quantity of motor movement required to reach a predetermined maximum velocity and a predetermined maximum acceleration. The method includes a step of determining a maximum operating velocity and a maximum operating acceleration for performing a designated jerk control in accordance with the commanded quantity of motor movement so as to make the maximum absolute value of a jerk parameter value (the jerk parameter, or jerk value, is here defined as the differential value of acceleration) not larger than a predetermined value or equal to the predetermined value.
(2) According to another aspect of the present invention, a motor velocity/acceleration determining method is configured as follows. In acceleration/deceleration control for changing acceleration continuously, there is provided a method of determining velocity and acceleration of a motor for generating an acceleration/deceleration curve of the motor when a commanded quantity of motor movement is smaller than a minimum quantity required to reach a predetermined maximum velocity and a predetermined maximum acceleration. The method includes a step of determining a maximum operating velocity and a maximum operating acceleration by selecting and performing one of two processes in accordance with the commanded quantity of motor movement. The two processes consist of a first process of determining a maximum operating velocity for performing a designated acceleration control in accordance with the commanded quantity of motor movement while adopting the predetermined maximum acceleration as a maximum operating acceleration for the control, and consist of a second process of determining a maximum operating velocity and a maximum operating acceleration for performing a designated jerk control in accordance with the commanded quantity of motor movement so as to make the maximum absolute value of the jerk value, which is the differential value of acceleration, not larger than a predetermined value or equal to the predetermined value.
(3) According to a further aspect of the present invention, a motor velocity/acceleration determining method is such that, in the above paragraph (2), the predetermined value in the designated jerk control is the maximum absolute value of jerk value in the designated acceleration control at a switching point where the first and second processes are switched.
(4) According to a still further aspect of the present invention, a motor velocity/acceleration determining method is such that, in the above paragraph (3), the maximum absolute value of jerk value at the switching point is specified on the basis of the maximum operating velocity which is required to obtain the commanded quantity of motor movement with the predetermined maximum acceleration.
(5) According to another aspect of the present invention, a motor velocity/acceleration determining method is such that, in any one of the above paragraphs (3) and (4), setting of the switching point can be changed at user's option.
(6) According to a further aspect of the present invention, a motor velocity/acceleration determining method is such that, in any one of the above paragraphs (3) to (5), the switching point is designated by a nondimensional parameter.
(7) According to a still further aspect of the present invention, a motor velocity/acceleration determining method is such that, in the above paragraph (6), the parameter is set to be a ratio with respect to the minimum quantity of motor movement.
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