Method of determining permissible speed of an object and controlling the object

• US 20030216822A1
• Filed: 10/28/2002
• Published: 11/20/2003
• Est. Priority Date: 05/15/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sato, Tomonori
• Granted Patent: US 6,748,300 B2
• Time in Patent Office: Days
• US Class Current: 700/63
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 2219/37435 Vibration of machine
• CPC Class Codes: G05B 2219/42077 Position, speed or current, combined with vibration feedback
• CPC Class Codes: G05B 2219/43203 Limitation of speed, permissible, allowable, maximum speed
• CPC Class Codes: Y10T 83/474 With work feed speed regulator
• CPC Class Codes: Y10T 83/4743 With means to vary cyclically speed of work

Abstract

Command path and command speed within a predetermined range are read. The predetermined range is time required for the object to move between two points on the command path. Speed command for each time is temporarily generated based on the read command path and the command speed. Frequency component that corresponds to mechanical vibration due to movement of the object and that is included in a speed command for the each time is calculated. Speed at which the frequency component becomes equal to or smaller than a preset reference value is determined as the permissible speed. Moving speed of the object is controlled so as not to exceed the calculated permissible speed.

Claims

1. A method for determining a permissible speed of an object moving along a command path at a specific point or a specific region on the command path, the method comprising:

reading command path and command speed within a predetermined range, the predetermined range being a time required for the object to move along the command path from the specific point or the specific region or a distance for which the object moves along the command path from the specific point or the specific region;

temporarily generating a speed command for each time based on.the read command path and the command speed;

calculating a frequency component that corresponds to mechanical vibration due to the movement of the object and which is included in a speed command for the each time; and

calculating the permissible speed at which the frequency component becomes equal to or smaller than a preset reference value.

2. The method according to claim 1, wherein

if the frequency component that corresponds to the mechanical vibration is calculated, a specific frequency component is extracted by extracting a specific frequency component by Fourier-transforming the speed command for the each time, extracting a specific frequency component by wavelet-transforming the speed command for the each time, extracting a specific frequency component by Laplace-transforming the speed command for the each time, extracting a specific frequency component by performing a filtering processing or performing an arithmetic operation which obtains correlation between the speed command for the each time and a predetermined time waveform.

3. The method according to claim 1, wherein

the specific region is a region between the specific points or a small region which is obtained by further segmenting the region between the specific points.

4. The method according to claim 1, wherein

the reference value is such that it is different for each axis or same for all the axes.

5. The method according to claim 1, wherein

the reading of the command path and the command speed, generation of speed command, calculation of the frequency component, and calculation of the permissible speed is repeatedly executed until the frequency component that corresponds to the mechanical vibration becomes sufficiently close to a permissible value, a change in the calculated permissible speed becomes sufficiently small or the number of times of repetition becomes sufficiently large.

6. The method according to claim 1, wherein

the permissible speed is determined by adding at least one constraint among a trajectory error constraint, a speed constraint, an acceleration constraint, a jerk constraint, and a speed difference constraint.

7. The method according to claim 1, wherein

the moving time is set to be equal to or longer than a quarter of a cycle of the mechanical vibration, and the moving distance is set to be equal to or larger than a quarter of a product between the cycle of the mechanical vibration and a command speed.

8. A speed control apparatus, which controls moving speed of an object based on a permissible speed at a specific point or a specific region on a command path, comprises a permissible speed decision unit, the permissible speed decision unit

reads the command path and a command speed within a predetermined range, the predetermined range being a time required for the object to move from the specific point or the specific region or a distance for which the object moves from the specific point or the specific region,

temporarily generates a speed command for each time based on the command path and the command speed,

calculates a frequency component that corresponds to mechanical vibration and which is included in a speed command for the each time, and

calculates the permissible speed at which the frequency component becomes equal to or smaller than a preset reference value.

9. The apparatus according to claim 8, wherein

if the frequency component that corresponds to the mechanical vibration is calculated, the permissible speed decision unit extracts a specific frequency component by extracting a specific frequency component by Fourier-transforming the speed command for the each time, extracting a specific frequency component by wavelet-transforming the speed command for the each time, extracting a specific frequency component by Laplace-transforming the speed command for the each time, extracting a specific frequency component by performing a filtering processing or performing an arithmetic operation which obtains correlation between the speed command for the each time and a predetermined time waveform.

10. The apparatus according to claim 8, wherein

the specific region is a region between the specific points or a small region which is obtained by further segmenting the region between the specific points.

11. The apparatus according to claim 8, wherein

the reference value is such that it is different for each axis or same for all the axes.

12. The apparatus according to claim 8, wherein

the permissible speed decision unit repeatedly executes the reading of the command path and the command speed, generation of speed command, calculation of the frequency component, and calculation of the permissible speed until the frequency component that corresponds to the mechanical vibration becomes sufficiently close to a permissible value, a change in the calculated permissible speed becomes sufficiently small or the number of times of repetition becomes sufficiently large.

13. The apparatus according to claim 8, wherein

the permissible speed decision unit determines the permissible speed by adding at least one constraint among a trajectory error constraint, a speed constraint, an acceleration constraint, jerk constraint, and a speed difference constraint.

14. The apparatus according to claim 8, wherein

the moving time is set to be equal to or longer than a quarter of a cycle of the mechanical vibration, and the moving distance is set to be equal to or larger than a quarter of a product between the cycle of the mechanical vibration and a command speed.

15. A speed control apparatus that controls moving speed of an object based on a permissible speed, the apparatus comprising:

a reading unit that reads command path and command speed within a predetermined range, the predetermined range being a time required for the object to move along the command path from the specific point or the specific region or a distance for which the object moves along the command path from the specific point or the specific region;

a speed command generation unit that temporarily generates a speed command for each time based on the read command path and the command speed;

a frequency component calculation unit that calculates a frequency component that corresponds to mechanical vibration due to the movement of the object and that is included in a speed command for the each time; and

a permissible speed calculation unit that calculates the permissible speed at which the calculated frequency component becomes equal to or smaller than a preset reference value;

an object control unit that controls the moving speed of the object so as not to exceed the calculated permissible speed.