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

• US 6,748,300 B2
• Filed: 10/28/2002
• Issued: 06/08/2004
• Est. Priority Date: 05/15/2002
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sato, Tomonori
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): KOSOWSKI, ALEXANDER J
• Application Number:
  US10/281,124
• Publication Number:
  US 20030216822A1
• Time in Patent Office: 589 Days
• Field of Search: 700/181, 700/304, 700/174, 833/12--13, 832/63
• US Class Current: 700/304
• 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 feed speed of an object moving along a command path, at a specific part of the command path, the method comprising:

reading command path and command feed speed within a range, the range being one of (i) time required for the object to move along the command path at the command feed speed from the specific part and (ii) distance which the object moves along the command path from the specific part;

generating a tentative speed command waveform based on the command path read and the command feed speed read;

calculating a frequency component that corresponds to mechanical vibration of the object that is included in the tentative speed command waveform; and

calculating a permissible feed speed of the object at which the frequency component does not exceed a reference value.

2. The method according to claim 1, wherein, when the frequency component that corresponds to the mechanical vibration of the object is calculated, extracting a specific frequency component by Fourier-transforming the speed command waveform, extracting a specific frequency component by wavelet-transforming the speed command waveform, extracting a specific frequency component by Laplace-transforming the speed command waveform and extracting a specific frequency component by filtering or obtaining, by an arithmetic operation, correlation between the speed command waveform and a reference time waveform.

3. The method according to claim 1, wherein the specific part is a region between specific points, the method including segmenting the region between the specific points.

4. The method according to claim 1, wherein the command path is resolved into components along respective axes, and the reference value is either different or identical for each of the axes.

5. The method according to claim 1, including repeatedly reading the command path and the command speed, generating the speed command, calculating the frequency component, and calculating the permissible feed speed until the frequency component that corresponds to the mechanical vibration becomes sufficiently close to a permissible value, change in the permissible feed speed calculated becomes sufficiently small, or number of repetitions becomes sufficiently large.

6. The method according to claim 1, including determining the permissible feed speed 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, including setting the range, when a time, to be at least equal to one-quarter of a cycle of the mechanical vibration of the object, and setting the range, when a distance, to be at least equal to one-quarter of a product of the cycle of the mechanical vibration of the object and the command speed of the object.

8. A speed control apparatus which controls moving speed of an object, based on a permissible feed speed at a specific part of a command path, the apparatus comprising:

a permissible speed decision unit, the permissible speed decision unit reading

the command path and a command feed speed within a range, the range being one of(i) time required for the object to move relative to the specific part and (ii) or distance which the object moves along the command path at the command feed speed from the specific part,

generating a tentative speed command waveform based on the command path and the command feed speed,

calculating a frequency component that corresponds to mechanical vibration of the object that is included in the tentative speed command waveform, and

calculating the permissible feed speed of the object at which the frequency component does not exceed a reference value.

9. The apparatus according to claim 8, wherein, when the frequency component that corresponds to the mechanical vibration of the object is calculated, the permissible speed decision unit extracts a specific frequency component by Fourier-transforming the speed tentative command waveform, extracts a specific frequency component by wavelet-transforming the tentative speed command waveform, extracts a specific frequency component by Laplace-transforming the tentative speed command waveform, and extracts a specific frequency component by filtering or obtains, by an arithmetic operation, correlation between the tentative speed command waveform and a reference time waveform.

10. The apparatus according to claim 8, wherein the specific part is a region between specific points, the method including segmenting the region between the specific points.

11. The apparatus according to claim 8, wherein the command path is resolved into components along respective axis, and the reference value is either different or identical for each of the axes.

12. The apparatus according to claim 8, wherein the permissible speed decision unit repeatedly reads the command path and the command speed, generates the speed command, calculates the frequency component, and calculates the permissible feed speed until the frequency component that corresponds to the mechanical vibration becomes sufficiently close to a permissible value, change in the calculated permissible feed speed becomes sufficiently small, or number of times of repetition becomes sufficiently large.

13. The apparatus according to claim 8, wherein the permissible feed 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, including setting the range, when a time, to be at least equal to one-quarter of a cycle of the mechanical vibration of the object, and setting the range, when a distance, to be at least equal to one-quarter of a product of the cycle of the mechanical vibration of the object and the command speed of the object.

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

a reading unit that reads command path and command feed speed within a range, the range being one of (i) time required for the object to move along a command path relative to a specific part and (ii) distance which the object moves along the command path at the command feed speed from the specific part;

a speed command generation unit that generates tentative speed command waveform based on the command path read and the command feed speed read;

a frequency component calculation unit that calculates a frequency component that corresponds to mechanical vibration of the object that is included in the tentative speed command waveform;

a permissible speed calculation unit that calculates the permissible feed speed of the object at which the frequency component calculated does not exceed a reference value; and

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

16. An apparatus for determining a permissible feed speed of an object moving along a command path, at a specific part of the command path, the method comprising:

a reading unit that reads command path and command feed speed within a range, the range being one of (i) time required for the object to move along the command path from the specific part and (ii) distance which the object moves along the command path from the specific part;

a speed command generation unit that generates a tentative speed command waveform based on the command path read and the command feed speed read;

a frequency component calculating unit that calculates a frequency component that corresponds to mechanical vibration of the object that is included in the tentative speed command waveform; and

a permissible speed calculation unit that calculates a permissible feed speed of the object at which the frequency component does not exceed a reference value.