Servo press controller

• US 6,237,479 B1
• Filed: 09/27/1999
• Issued: 05/29/2001
• Est. Priority Date: 03/31/1997
• Status: Expired due to Term

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: Douba, Eiji
• Primary Examiner(s): GERRITY, STEPHEN FRANCIS
• Application Number:
  US09/402,015
• Time in Patent Office: 610 Days
• Field of Search: 100/43, 100/48, 100/99, 100/342, 100/343
• US Class Current: 100/43
• CPC Class Codes: B30B 1/186 Control arrangements
• CPC Class Codes: B30B 15/14 Control arrangements for mechanically-driven presses
• CPC Class Codes: B30B 15/28 Arrangements for preventing distortion of, or damage to, presses or parts thereof

Abstract

The present invention relates to a servo press controller which can prevent the servo runaway caused by the malfunction of CPUs, the faults of a position sensor, or other troubles to thereby increase the safety of the servo press. For this purpose, first to third CPUs (21, 22, 23) each of which conducts a different control among the input of set data, the calculation of a servo position command, and the calculation of a servo speed command send and receive watch dog signals between itself and another CPU for monitoring each other'"'"'s condition by checking whether the watch dog signals sent from the partner computer are normal or not, and, when there is an abnormality in any computer, stopping the servo press (1) for emergency.

Claims

1. A servo press controller which drives a slide supported on a frame to be rectilinearly movable by a servo motor to thereby conduct press working, said servo press controller comprising:

an operation input element which inputs press operation signals including an operation mode and an operation starting signal for a press by means of manipulation of an operation switch by an operator or communication from the outside, and outputs said inputted press operation signals;

a first CPU which previously stores set data including motion data of said slide and starting conditions of the press, outputs said stored set data at the time of press starting, and decides whether press starting is possible or not based on said stored set data and the press operation signals inputted from said operation input element to thereby output a press starting signal;

a second CPU which decides that press starting is possible based on the set data inputted from said first CPU and the press operation signals inputted from said operation input element, and calculates and outputs a position command of said servo motor based on the motion data in said set data at least when said press starting signal shows that press starting is possible;

a first position sensor for detecting the position of said slide;

a second position sensor for detecting the rotational position of said servo motor;

a third CPU which inputs position signals from at least either of said first position sensor or said second position sensor, and calculates and outputs a speed command with at least one of said inputted position signals as a position feedback signal, based on a position deviation between the position command from said second CPU and said position feedback signal; and

a servo amplifier for controlling a driving current of said servo motor in such a manner that a speed deviation between the speed command inputted from said third CPU and a speed feedback value of said servo motor calculated based on the position signal inputted from said second position sensor decreases,

wherein said first to third CPUs have the function of sending and receiving watch dog signals at least either of between said first CPU and said second CPU, or between said second CPU and said third CPU to thereby check whether the partner CPU is in normal operation, and have the function that when one CPU is judged to be abnormal by said check, the partner CPU stops the press for an emergency.

2. The servo press controller in accordance with claim 1,

wherein respective software languages for said first CPU and said second CPU are different.

3. The servo press controller in accordance with claim 1,

wherein respective computers of said first CPU and said second CPU are different in at least either of CPU chip model number or CPU chip manufacturer.

4. The servo press controller in accordance with claim 1,

wherein said third CPU inputs respective position signals from said first position sensor and said second position sensor, calculates respective position data of said slide based on said inputted respective position signals, and checks abnormalities in said first position sensor and said second position sensor based on a difference between said calculated respective position data.

5. The servo press controller in accordance with any one of claim 1, claim 2, or claim 3,

wherein respective input power supply lines or power supply voltages of said first CPU and said second CPU are different.