Method and apparatus for adaptively positioning a machine element

• US 3,917,930 A
• Filed: 11/25/1974
• Issued: 11/04/1975
• Est. Priority Date: 11/25/1974
• Status: Expired due to Term

• Current Assignee: Charles B. Perry, Harvey William Rohmiller, James Andrew Davey
• Original Assignee: Charles B. Perry, Harvey William Rohmiller, James Andrew Davey
• Inventors: Perry, Charles B., Davey, James Andrew, Rohmiller, Harvey William
• Primary Examiner(s): Botz, Eugene G.
• Application Number:
  US05/526,584
• Time in Patent Office: 344 Days
• Field of Search: 235/151.11
• US Class Current: 318/561
• CPC Class Codes: G05B 19/4163 Adaptive control of feed or cutting velocity without NC B23Q15/12
• CPC Class Codes: G05B 2219/33324 What to diagnose, whole system, test, simulate
• CPC Class Codes: G05B 2219/41177 Repetitive control, adaptive, previous error during actual positioning
• CPC Class Codes: G05B 2219/49169 Compensation for temperature, bending of tool

Abstract

A method and apparatus is disclosed for use with a drive system iteratively moving a machine element through a positioning cycle in response to input signals defining each of the positions in the cycle. During an initial application of each of the input signals, compensation values corresponding to the input signals are produced and stored. Each compensation value represents the difference between the desired position as defined by the input signal and the actual final position as determined by a measuring circuit. During a subsequent application of each of the input signals, they are modified by a corresponding compensation value thereby causing the actual final position of the machine element to more closely coincide with the desired position.

Claims

1. An apparatus for iteratively modifying input signals representing desired changes of positions of a controlled element as a function of position errors generated during previous occurrences of said input signals, said apparatus being operative with an actuator control circuit for commanding an actuator to move the controlled element through cycles of positioning motions in response to the cyclic occurrence of the input signals, said controlled element being connected to a measuring circuit for producing an output signal representing the actual position of the controlled element, the apparatus comprising:

a. storage means for storing compensation signals, said storage means including means for producing initial compensation signals;

b. means having one input responsive to the input signals and a second input connected to the storage means for producing command signals, each command signal representing the algebraic sum of an Input signal and a corresponding previously determined compensation signal;

c. means having inputs responsive to the command signals and the measuring circuit and having an output connected to the actuator control circuit for producing 1. a motion signal in response to a non-zero difference between a command signal and a corresponding output signal, and 2. a stop signal in response to a zero difference between the command signal and the corresponding output signal;

d. means repsonsive to the input signals and the output signals for producing measured compensation signals, each measured compensation signal representing the difference between the desired position of the element and the actual final position of said element; and

e. means responsive to the measured compensation signals and the previously determined compensation signals and connected to the storage means for producing new compensation signals and loading said new compensation signals in the storage means in place of the corresponding previously determined compensation signals whereby said new compensation signals operate as the previously determined compensation signals during a subsequent occurrence of the input signals.

2. An apparatus for iteratively compensating input signals representing desired changes of position of a controlled element as a function of position errors generated during previous occurrences of said input signals, said apparatus being operative with an actuator control circuit for commanding an actuator to move the controlled element through cycles of positioning motions in response to the cyclic occurrence of the input signals, said controlled element being connected to a measuring circuit for producing an output signal representing the actual position of the controlled element, the apparatus comprising:

a. storage means for storing compensation signals, said storage means including means for producing initial compensation signals;

b. means having one input responsive to an input signal and a second input connected to the storage means for producing a command signal representing the algebraic sum of the input signal and a previously determined compensation signal;

c. means having inputs responsive to the command signal and an output signal and having an output connected to the actuator control circuit for producing a motion signal in response to a non-zero difference between the inputs and terminating the motion signal in response to a zero difference between the inputs;

d. means responsive to the input signal and the measuring circuit for producing a measured compensation signal representing the difference between the desired position of the element and the actual final position of said controlled element; and

e. means responsive to the measured compensation signal and the previously determined compensation signal and connected to the storage means for producing a new compensation signal and transferring said new compensation signal to the storage means in place of the previously determined compensation signal whereby said new compensation signal becomes the previously determined compensation signal during a subsequent execution of said first input signal.

3. The apparatus of claim 2, wherein the means for producing a measured compensation signal comprises:

a. means responsive to the input signal and a final output signal representing the final position of the controlled element for producing a first signal representing the magnitude of the difference between the input signal and the final output signal and a second signal representing the sign of said difference magnitude;

b. means for storing the first and second signals; and

c. means responsive to the first signal for detecting a zero magnitude.

4. The apparatus of claim 3, wherein the means for producing a new compensation signal comprises means responsive to the first signal, the second signal, and the previously determined compensation signal for algebraically adding the first signal and the previously determined compensation signal to produce a first new compensation signal.

5. The apparatus of claim 4, wherein the means for producing a new compensation signal further comprises:

a. means responsive to the second signal and the previously determined compensation signal for algebraically summing an incremental magnitude with the previously determined compensation signal to produce a second new compensation signal; and

b. means responsive to the detecting means and connected to the algebraic summing means for inhibiting the algebraic summing means in response to the first signal having a zero magnitude.

6. The apparatus of claim 5, wherein said apparatus further comprises means for producing an automatic mode signal and a non-automatic mode signal.

7. The apparatus of claim 6, wherein the means for producing a new compensation signal further comprises:

a. first gating means responsive to the nonautomatic mode signal and the first new compensation signal for transfering the first new compensation signal to the storage means in place of the previously determined compensation signal; and

b. second gating means responsive to the automatic mode signal and the second new compensation signal for transfering the second new compensation signal to the storage means in place of the previously determined compensation signal.

8. An apparatus for iteratively modifying an input signal representing a change in position of a controlled element as a function of a positioning error generated during a previous occurrence of said input signal, said apparatus being operative with an actuator control circuit for commanding an actuator to move the controlled element through displacements in response to the input signal, said controlled element being connected to a measuring circuit for producing an output signal representing the actual distance traversed by the element, the apparatus comprising:

a. storage means for storing a previously determined compensation signal;

b. means responsive to the input signal and the previously determined compensation signal for producing a command signal representing the algebraic sum of the input signal and the previously determined compensation signal;

c. means having inputs responsive to the command signal and the output signal and having an output in communication with the actuator control circuit for producing a motion signal in response to a non-zero difference between the inputs and producing a stop signal in response to a zero difference between the inputs;

d. means responsive to the measuring circuit and the storage means for producing a sign signal as a function of the relative magnitude between a final value of the output signal and the input signal;

e. means responsive to the previously determined compensation signal and the sign signal for modifying the previously determined compensation signal by a predetermined incremental magnitude as a function of the sign signal to produce a new compensation signal; and

f. gating means responsive to the modifying means and connected to the storage means for transferring the new compensation signal to the storage means in place of the previously determined compensation signal.

9. An apparatus for iteratively compensating input signals representing changes of position of a controlled element as a function of positioning errors generated during previous occurrences of said input signals, said apparatus being operative with an actuator control circuit for commanding an actuator to move the controlled element through cycles of positioning motions in response to the cyclic occurrence of the inputs signals, said controlled element being connected to a measuring circuit for producing an output signal representing the actual position of the controlled elemnt, the apparatus comprising:

a. an input signal store for storing the input signals;

b. a compensation signal store for storing active Compensation signals corresponding to the input signals, said compensation signal store including means for establishing an initial value for the active compensation signals;

c. a first adder circuit connected to the input signal store and the compensation signal store for producing a command signal representing the algebraic sum of an input signal and a corresponding active compensation signal;

d. a comparator connected to the first adder circuit and the measuring circuit for producing a motion signal in response to a nonzero difference between the command signal and an output signal and a stop signal in response to a zero difference between the command signal and the output signal;

e. a subtraction circuit connected to the input signal store and the measuring circuit for calculating the difference between the input signal and the final value of the output signal to produce a measured compensation signal;

f. a measured compensation signal store connected to the subtractor circuit for storing the magnitude of the measured compensation signal;

g. a sign storage circuit connected to the subtractor circuit for storing a sign signal representing the sign of the measured compensation signal;

h. a zero detection circuit connected to the subtraction circuit for determining a zereo magnitude of the measured compensation signal;

i. a second adder circuit connected to the measured compensation signal store, the sign store, and the compensation signal store for producing a first new compensation signal as a function of the algebraic sum of the active compensation signal and the measured compensation signal;

j. a one bit adder-subtracter circuit connected to the sign store, the zero detection circuit and the active compensation store for producing a second new compensation signal by modifying the active compensation signal by a predetermined increment as a function of the sign store, said adder-subtracter circuit being inhibited in its operation in response to a zero magnitude of the measured compensation signal;

k. a switching circuit for selectively producing an automatic mode signal and a non-automatic mode signal; and

l. a gating network responsive to the first and second new compensation signals and the switching circuit for selectively loading

10. A method for iteratively modifying an input signal representing a change of position of a controlled element as a function of a positioning error generated during a previous occurrence of said input signal, said method causing an actuator control circuit to command an actuator to move the controlled element through positioning motions in response to the cyclic occurrence of the input signal, said controlled element being connected to a measuring circuit for producing an output signal representing the actual position of the controlled element, the method comprising the steps of:

a. storing an initial compensation signal corresponding to the input signal;

b. adding the input signal to the stored compensation signal to produce a command signal;

c. comparing the command signal to the output signal to generate a motion signal in response to a non-zero difference magnitude between the command signal and the output signal;

d. producing a measured compensation signal representing the difference between the desired position and the actual final position of the controlled element;

e. changing the stored compensation signal as a function of the measured compensation signal to produce a new compensation signal;

f. storing the new compensation signal in place of the stored compensation signal; and

g. iteratIng steps (b) through (f) for each subsequent occurrence of the input signal.

11. The method according to claim 10, wherein the step of producing a measured compensation signal further comprises the step of:

a. calculating the difference between the input signal and a final value of the output signal representing the final position achieved by the controlled element and producing a measured compensation signal and a sign signal as a function of the magnitude and sign of the difference, respectively; and

b. storing the measured compensation signal and the sign signal.

12. The method of claim 11, wherein the step of changing the stored compensation signal further comprises the step of algebraically adding the measured compensation signal to the stored compensation signal to produce the new compensation signal.

13. The method of claim 10, wherein the step of producing a measured compensation signal further comprises:

a. determining the relative magnitude between the input signal and a final value of the output signal to produce a sign signal;

b. storing the sign signal; and

c. detecting a zero difference magnitude between the input signal and the final value of the output signal.

14. The method of claim 13, wherein the step of changing the stored compensation signal further comprises the step of:

a. adding a predetermined incremental magnitude to the stored compensation signal as a function of the sign signal to produce the new compensation signal; and

b. inhibiting the addition of the predetermined incremental magnitude in response to a zero difference magnitude between the input signal and the final value of the output signal.