Feedback controller for NC controlled machine tools

• US 5,105,135 A
• Filed: 10/31/1990
• Issued: 04/14/1992
• Est. Priority Date: 11/08/1989
• Status: Expired due to Fees

• Current Assignee: Okuma Machinery Works Ltd.
• Original Assignee: Okuma Machinery Works Ltd.
• Inventors: Kitaori, Shigeya, Nashiki, Masayuki
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US07/608,977
• Time in Patent Office: 531 Days
• Field of Search: 318/560-632, 318/254, 318/271, 318/135, 318/430-434
• US Class Current: 318/568.11
• CPC Class Codes: B23Q 5/10 driven essentially by electrical means
• 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 2219/41112 Control parameter such as motor controlled by a torque signal
• CPC Class Codes: G05B 2219/41375 Observe speed and select torque as function of position reference, to compensate torque
• CPC Class Codes: G05B 2219/42074 Position feedback and speed feedback, speed measured with tacho

Abstract

In a feedback controller for NC controlled machine tools, the position and the velocity of a work is detected and compared with the desired position. By this comparison, the work velocity is calculated and compared with the current velocity, which determines torque of a driving motor. A torque compensation signal generator, receiving the current velocity, generates a compensation signal according to a predetermined velocity/torque function. The signal is composed with a torque signal passed to a driving motor, and torque compensation is performed. A periodic reaction detector detects periodic fluctuation of the work caused by periodic load fluctuation, and a torque compensation direction causes a signal generator to suppress the fluctuation at desired occasions.

Claims

1. A feedback controller for NC controlled machine tools comprising:

(a) a driving motor driven by a torque signal to drive a work to be controlled for causing the work to have a current position and a current velocity at each instant;

(b) a position detector that detects the current position of the work;

(c) a velocity detector that detects the current velocity of the work;

(d) a position director that indicates a predetermined desired current position of the work;

(e) a feedback position adjustor for comparing the predetermined desired current position of the work and the current position of the work that is detected by the position detector for producing a desired current velocity of the work proportional to the difference between the compared positions;

(f) a feedback velocity adjustor that produces a first torque signal component by comparing the desired current velocity and the current work velocity detected by the velocity detector, the first torque signal component being proportional to the difference between the compared velocities;

(g) a torque compensation signal generator connected to the velocity detector for generating a second torque signal component which is a selected function of the current work velocity detected by the velocity detector; and

(h) means for combining the first and second torque signal components to produce the torque signal in such that the presence of the second torque signal component in the torque signal reduces the difference between the current work position detected by the position detector and the desired current position of the work indicated by the position director.

2. A feedback controller according to claim 1 wherein said torque compensation signal generator is switchable between an active state for generating the second torque signal component and an inactive state in which the second torque signal component is not generated, and further comprising a torque compensation director connected to said torque compensation signal generator for switching said torque compensation signal generator between its active and inactive states.

3. A feedback controller according to claim 2 wherein said torque compensation signal generator is constructed for generating the second torque signal component according to any one of a plurality of respectively different functions, and said torque compensation director is operative for changing the function according to which the second torque signal component is generated.

4. A feedback controller according to claim 3 further comprising a periodic fluctuation detector that detects periodic velocity fluctuations of the work, and wherein said torque compensation director is connected to said periodic fluctuation detector for changing the function according to which the second torque signal component is generated in response to the periodic velocity fluctuation detected by said periodic fluctuation detector.