Computer control system for generating geometric designs

• US 5,926,389 A
• Filed: 02/08/1994
• Issued: 07/20/1999
• Est. Priority Date: 02/15/1991
• Status: Expired due to Term

• Current Assignee: Trounson Automation LLC (General Patent Corporation)
• Original Assignee: James E. Trounson
• Inventors: Trounson, James E.
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Garland, Steven R.
• Application Number:
  US08/193,634
• Time in Patent Office: 1,988 Days
• Field of Search: 364/474.28, 364/474.29, 364/474.3, 364/474.31, 364/167.02, 364/167.07, 364/167.09, 364/188, 364/130, 364/474.12, 318/599-603, 395/84
• US Class Current: 700/187
• CPC Class Codes: G05B 19/251 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: G05B 19/4142 characterised by the use of a microprocessor G05B19/4141 takes precedence
• CPC Class Codes: G05B 19/4144 characterised by using multiplexing for control system
• CPC Class Codes: G05B 2219/34086 At fixed periods pulses from table drive plural axis in unison
• CPC Class Codes: G05B 2219/34089 Parametric, polynomial representation of path per axis as function of time
• CPC Class Codes: G05B 2219/34213 Same microprocessor for data input and for servocontrol
• CPC Class Codes: G05B 2219/34236 Multiplex for servos, actuators
• CPC Class Codes: G05B 2219/34279 Pc, personal computer as controller
• CPC Class Codes: G05B 2219/34359 Real time based interrupt to control axis, other function
• CPC Class Codes: G05B 2219/35321 Display only tool locus, dynamic
• CPC Class Codes: G05B 2219/37525 Mean, average values, statistical derived values
• CPC Class Codes: G05B 2219/41408 Control of jerk, change of acceleration
• CPC Class Codes: G05B 2219/42064 Position, speed and acceleration
• CPC Class Codes: G05B 2219/42237 Pwm pulse width modulation, pulse to position modulation ppm
• CPC Class Codes: G05B 2219/42244 Enter acceleration, jerk, generator outputs acceleration, speed, position by integration
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A servo control system for a machine tool or the like requires only a single computational resource, such as a microprocessor, to provide coordinated control along multiple axes. No active control mechanism is required for any axis outside of the single resource. A real time multitasking approach enables the single resource to control multiple axes of motion, with the control of each individual axis being carried out by means of simple, yet effective, routines that conserve computing power. The routines also facilitate the generation of geometric designs in other media, such as the display of such shapes on a video screen or via a printer.

Claims

1. A system for controlling the formation of geometric shapes in materials by moving a tool relative to a workpiece along multiple axes of movement, comprising:

means defining data representative of geometric shapes to be cut or otherwise formed in materials;

means for converting said data into a description of a path to be followed by the tool and storing said description;

a plurality of motors respectively associated with said multiple axes, each of said motors providing relative movement between the tool and the workpiece along an associated one of said axes;

a plurality of feedback devices respectively associated with said plurality of motors for providing feedback information indicative of at least one of the actual position and velocity of the tool along an associated axis; and

a single active processor for controlling said data defining means and said data converting means, for receiving feedback information from each of said feedback devices, and for controlling the operation of each of said motors to provide coordinated relative movement between the tool and the workpiece along each of said multiple axes in accordance with said stored path description.

2. The servo system of claim 1 wherein said single active processor comprises a single microprocessor.

3. The servo system of claim 1 wherein said active processor produces said coordinated relative movement of the tool by controlling said motors in a cyclic manner, wherein each cycle comprises a sequential reading of feedback information and generation of a motor control signal for each of the axes being controlled.

4. The system of claim 3 wherein said data comprises a sequence of operations which define said geometric shape, and said data converting means processes said sequence of operations to produce a table that describes the movement of the tool along each axis, relative to the workpiece, for each cycle of operation.

5. The system of claim 1 wherein said data defining means includes a user interface by means of which a user communicates with said single active processor to define and/or modify geometric shapes, and wherein said single active processor stores said data in response to communications received from a user through said user interface.

6. A method for providing coordinated movement of a device along multiple axes of motion by means of a single active processor, comprising the steps of:

a) determining desired movement of the device along each of said axes of motion for successive increments of time;

b) carrying out one cycle of control in said active processor for one of said increments of time, said cycle including the steps of;

i) determining, on the basis of said desired movement, at least one of a desired position and desired velocity of the device along one of said axes;

ii) detecting at least one of the actual position and actual velocity of the device along said one axis;

iii) calculating at least one of a position error and a velocity error along said one axis for said increment of time;

iv) generating a pulse-width modulated control signal to produce movement along said one axis that is effective to reduce said error by;

determining a center value indicative of the average width of the pulse-width modulated signal over plural previous cycles of operation;

computing a response based on said error and detecting whether said response is less than or greater than a reference value;

increasing said center value when said response is greater than said reference value and decreasing said center value when said response is less than said reference value; and

summing said center value and said response to determine the width of said pulse-width modulated signal; and

v) sequentially repeating steps i, ii and iii for each of the other axes; and

c) repeating step b for each of the successive increments of time.

7. The method of claim 6 wherein said step of determining desired movement includes the steps of:

parametrically representing the path of movement of the device along one axis for successive periods of time;

determining the coefficients of a polynomial which describes at least a portion of said parametric representation;

computing recursive values for at least position and velocity at the beginning of a period of time from said coefficients; and

storing said recursive values in a table.

8. The method of claim 7 further including the steps of computing a recursive value for acceleration from said coefficients, and storing said value in said table.

9. The method of claim 8 further including the steps of computing a recursive value for change of acceleration from said coefficients, and storing said value in said table.

10. The method of claim 8 further including the step of computing desired position for successive increments of time by cyclically summing said stored velocity value with said stored position value, to compute a new position value, summing said stored acceleration value with said stored velocity value to compute a new velocity value, and updating said table with said new values.