Numerical control apparatus

• US 6,404,160 B2
• Filed: 06/06/2001
• Issued: 06/11/2002
• Est. Priority Date: 12/24/1998
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yamada, Yoshinori, Sagasaki, Masakazu
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): Leykin, Rita
• Application Number:
  US09/879,240
• Publication Number:
  US 20020003416A1
• Time in Patent Office: 370 Days
• Field of Search: 318/30-89, 318/560-696, 364/474-1-4, 82/11.1
• US Class Current: 318/600
• CPC Class Codes: G05B 19/18 Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form G05B19/418 takes precedence
• CPC Class Codes: G05B 19/414 Structure of the control system, e.g. common controller or multiprocessor systems, interface to servo, programmable interface controller
• CPC Class Codes: G05B 19/4141 characterised by a controller or microprocessor per axis
• CPC Class Codes: G05B 2219/50216 Synchronize speed and position of several axis, spindles
• CPC Class Codes: G05B 2219/50218 Synchronize groups of axis, spindles

Abstract

In a numerical control apparatus 1, a synchronous control management unit 11 manages the dominant relation of plural axes to be controlled synchronously. In case of the position control system, in the axis control unit which controls the reference axis, a synchronous position calculation processing unit 74 calculates the command position to the reference axis. On the other hand, in the axis control unit which control the synchronous axis, the synchronous position calculation processing unit 74 calculates the moving stroke per unit time of the synchronous axis, thereby calculating the command position to the synchronous axis. One axis control unit which controls the reference axis and plural axis control units for controlling the synchronous axes issue the calculated command positions, and control the individual corresponding motors, and therefore control plural axes synchronously to one reference axis, and further control other axis synchronously by reference to the corresponding synchronous axis.

Claims

1. A numerical control apparatus for synchronously controlling a plurality of spindle motors or servo motors, driven by a machine tool according to a processing program, the numerical control apparatus comprising:

a memory unit which stores the processing program;

a synchronous control management unit which manages a dominant relation of a plurality of axes to be controlled synchronously; and

a plurality of axis control units, having information about a reference axis as a reference of synchronous control or having information about a synchronous axis for operating synchronously with the reference axis stored according to the dominant relation of the axes managed by the synchronous control management unit, for controlling the corresponding spindle motors or servo motors on the basis of a calculated command position,

wherein one of said axis control units having set the information about the reference axis, and the other axis control units having set the information about the synchronous axis, control the corresponding plurality of spindle motors or servo motors, and the plurality of axes can be controlled synchronously in relation to the reference axis.

2. The numerical control apparatus according to claim 1, wherein each of the plural axis control units includes:

an axis control system changeover unit for changing over to either a speed control system for driving the corresponding motor depending on a speed command value described in the processing program or a position control system for driving depending on a moving stroke per unit time converted from the speed command value;

an axis control command converting unit for calculating the moving stroke per unit time from the speed command value with respect to the reference axis;

a reference position output for issuing the moving stroke per unit time of the reference axis, calculated in the axis control command value converting unit, to another axis control unit,

a reference position input unit for receiving the moving stroke per unit time of the reference axis calculated in another axis control unit; and

a synchronous position calculation processing unit for calculating the command position corresponding to the pertinent axis, on the basis of the moving stroke per unit time calculated by the axis control command value converting unit or the moving stroke received in the reference position input unit,

wherein, in the position control system, when controlling the reference axis, the synchronous position calculation processing unit adds the moving stroke of the reference axis calculated in the axis control command converting unit to a reference position of the reference axis, and calculates the command position of the reference axis, and

when controlling the synchronous axis, the synchronous position calculation processing unit calculates the moving stroke per unit time of the synchronous axis, based on the moving stroke per unit time received in the reference position input unit, a gear ratio of the synchronous axis to the reference axis, command rotation ratio, and command unit time ratio, and adds the moving stroke per unit time to a reference position of the synchronous axis, thereby calculating the command position of the synchronous axis.

3. The numerical control apparatus according to claim 2, wherein the axis control system changeover unit of the axis control unit which controls the synchronous axis calculates a theoretical command position by subtracting the speed command value described in the processing program, a theoretical value of position deviation amount calculated from a position control gain of the motor, and a delay amount corresponding to a sampling delay time of feedback position, from the feedback position of the axis, and changes over from an ordinary speed control system to the position control system in a contracted state of fluctuation of the position deviation amount.

4. The numerical control apparatus according to claim 1, wherein each of the axis control units further comprises a synchronous position correction unit for correcting a fluctuation of the axis by calculating a position correction amount from a position deviation amount of the reference axis and a position deviation amount of the synchronous axis, and adding the position correction amount to the command position of the synchronous axis.

5. The numerical control apparatus according to claim 4, wherein the synchronous position correction unit in the axis control unit for controlling the synchronous axis multiplies the position deviation amount of the reference axis by a command rotation ratio of the reference axis and the synchronous axis, and a command unit time ratio, and calculates a difference between a calculation result and the position deviation amount of the reference axis, then determines a value of passing the obtained difference through the primary delay filter according to a specific time constant determined by a parameter as the position correction amount.

6. The numerical control apparatus according to claim 4, wherein each of axis control units includes a theoretical position deviation amount calculation processing unit for calculating a theoretical position deviation amount from a speed control value described in the processing program and the position control gain of the corresponding motor,

wherein, the synchronization position correction unit in the axis control unit for controlling the synchronous axis calculates a difference between the theoretical position deviation amount of the reference axis calculated in the theoretical position deviation amount calculation processing unit and an actual position deviation amount obtained from the reference axis, and determines a value calculated from the difference, a command rotation ratio of the synchronous axis to the reference axis, and a command unit time ratio, as the position correction amount.

7. The numerical control apparatus according to claim 4, wherein each one of the axis control units includes a synchronous correction amount fixing unit for calculating an average of the position deviation amount in steady rotation on the reference axis and the synchronous axis for synchronous control, and further calculates their difference,

wherein, the synchronous position correction unit in the axis control unit for controlling the synchronous axis determines a difference calculated in the synchronous correction amount fixing unit as the position correction amount.

8. The numerical control apparatus according to claim 4, wherein the memory unit incorporates a synchronous correction coefficient holding unit for calculating an average of the position deviation amount in steady rotation on the reference axis and the synchronous axis for synchronous control, at a time of initial adjustment of the machine tool, and holds a value obtained by dividing this average by the speed control value as a coefficient for obtaining the position deviation amount,

wherein, the synchronous position correction unit in the axis control unit for controlling the synchronous axis calculates the average of the position deviation amount in steady rotation on the reference axis and the synchronous axis for synchronous control, by applying the speed command value by the coefficient held in the synchronous correction coefficient holding unit and obtains this difference as the position correction amount.

9. The numerical control apparatus according to claim 1, further comprising a synchronous correction amount error canceling unit for canceling a variation component of the position deviation amount caused by a variation due to disturbance, by subtracting a difference between the average of the position deviation amount in steady rotation on the synchronous axis for synchronous control and an actual position deviation amount, temporarily from the position correction amount.

10. The numerical control apparatus according to claim 1, further comprising:

a multi-level acceleration and deceleration parameter memory unit for storing a multi-level acceleration and deceleration speed generated by the acceleration and deceleration pattern of an ordinary speed control system, a multi-level reference acceleration and deceleration time constant, and a multi-level acceleration and deceleration time constant multiplying factor by manipulating a parameter setting screen;

a reference inclination amount calculation unit for calculating a reference inclination amount, as an acceleration and deceleration speed per unit time, from a maximum rotating speed and the multi-level reference acceleration and deceleration time constant of the reference axis and synchronous axis;

a multi-level acceleration and deceleration pattern calculation unit for calculating an appropriate multi-level acceleration and deceleration pattern from the set multi-level acceleration and deceleration pattern; and

a multi-level acceleration and deceleration decision unit for determining the multi-level acceleration and deceleration pattern to be noticed to the synchronous control management unit.