Method and system for adaptive control of turning operations

• US 6,476,575 B1
• Filed: 06/11/2001
• Issued: 11/05/2002
• Est. Priority Date: 09/02/1998
• Status: Expired due to Term

• Current Assignee: Omat, Ltd.
• Original Assignee: Omat, Ltd.
• Inventors: Fainstein, Boris, Takachnik, Eduard, Rubashkin, Igor, Zuckekrman, Mark
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): Duda, Rina I.
• Application Number:
  US09/786,322
• Time in Patent Office: 512 Days
• Field of Search: 318/568.22, 318/569, 318/571, 318/632, 409/80, 409/186, 409/188, 408/8, 408/9, 408/10, 408/11, 408/12, 408/13
• US Class Current: 318/569
• CPC Class Codes: G05B 19/4163 Adaptive control of feed or cutting velocity without NC B23Q15/12
• CPC Class Codes: Y10T 408/16 with control means energized in response to activator stimulated by condition sensor
• CPC Class Codes: Y10T 408/165 to control Tool rotation
• CPC Class Codes: Y10T 408/17 to control infeed
• CPC Class Codes: Y10T 408/175 to control relative positioning of Tool and work
• CPC Class Codes: Y10T 409/300896 with sensing of numerical information and regulation without mechanical connection between sensing means and regulated means [i.e., numerical control]
• CPC Class Codes: Y10T 409/306832 with infeed control means energized in response to activator stimulated by condition sensor
• CPC Class Codes: Y10T 409/306944 In response to work condition

Abstract

An adaptive control system for adaptively controlling a turning operation performed at a work piece by a turning tool adjusts a controlled input operation parameter F to maintain an output operation parameter ΔM substantially at a predetermined value ΔM_o to compensate variation of the output operation paramemeter ΔM caused by the variation of at least one operation condition B=B (t). The system comprises a sensor (8) of the output operation parameter ΔM for providing a signal U_c proportional to a current value ΔM_c and an adaptive controller (10) for determining a value F_c to which the input operation parameter F should be adjusted, as a function of kU_c, where k is a signal transmission coefficient which comprises an invariant signal transmission coefficient component k_o inversely proportional to ΔM_o. The adaptive controller includes an amplifier transforming the signal U_c into k_oU_c, and an input parameter override unit controlled to adjust the controlled operation input parameter to F_c. The adaptive controller further comprises a correction processing means calculating k_cU_c, where k_c is a varying signal transmission coefficient component whose current values depend on the variation of the operation condition B=B (t). The adaptive controller is capable of calculating k=f (k_o, k_c).

Claims

1. A method of adaptively controlling a turning operation performed on a workpiece by a turning tool, by controlling an adjustable input operation parameter F of the movement of the turning tool relative to the workpiece, to maintain an output operation parameter Δ

M substantially at a predetermined value Δ

M_o and thereby to substantially compensate the variation of said output operation parameter Δ

M caused by the variation of at least one operation condition B=B(t) varying in time, the method comprising the steps of;

(a) measuring a current value Δ

M_c of the output parameter Δ

M,

(b) estimating the relation between Δ

M_c and Δ

M_o by multiplying Δ

M_c by a correction coefficient K which comprises an invariant correction coefficient component K_o inversely proportional to Δ

M_o, and

(c) determining a value F_c to which the input operation parameter F should be adjusted, as a function of KΔ

M_c;

characterized in that

(d) said correction coefficient K comprises a varying correction coefficient component whose current value K_c changes in accordance with the variation of said operation condition B=B(t), the step (b) further comprising calculating the current value K_c and calculating K=ƒ

(K_o,K_c).

2. A method according to claim 1, wherein K=K_o−

K_c.

3. A method according to claim 1, wherein the operation input parameter F is a feed rate of the turning tool.

4. A method according to claim 1, wherein the operation output parameter Δ

M is a cutting torque developed by a drive rotating the workpiece.

5. A method according to claim 1, wherein the predetermined value Δ

M_o of the output parameter is a maximal value Δ

M_max which this parameter may have when the varying operation condition B differs to a maximal extent from its original or nominal value.

6. A method according to claim 5, wherein the invariant correction coefficient component K_o is defined as $K_o=\frac{A}{\Delta }$



 



Mmax,

where $A=\frac{F_{\mathrm{id}}}{F_o},$

with F_id being an idle feed and F_o being a pre-programmed basic feed rate.

7. A method according to claim 1, wherein the varying operation condition B is a real physical parameter.

8. A method according to claim 7, wherein said parameter is the depth of cut h_c=h_c(t).

9. A method according to claim 7, wherein current values of the varying coefficient component K_c are obtained based on sensing current values of said parameter.

10. A method according to claim 1, wherein the varying operation condition B is a mathematical equivalent of one or more physical parameters of the cutting process.

11. An adaptive control system for adaptively controlling a turning operation performed at a workpiece by a turning tool, by adjusting a controlled input operation parameter F to maintain an output operation parameter Δ

M substantially at a predetermined value Δ

M_o and thereby to substantially compensate variation of said output operation parameter Δ

M caused by the variation of at least one operation condition B=B(t), the system comprising;

a sensor of the output operation parameter Δ

M for providing a signal U_c proportional to a current value Δ

M_c;

an adaptive controller for determining a value F_c to which the input operation parameter F should be adjusted, as a function of kU_c, where k is a signal transmission coefficient which comprises an invariant signal transmission coefficient component k_o inversely proportional to Δ

M_o, said controller including an amplifier capable of transforming the signal U_c into k_oU_c; and

an input parameter override unit capable of being controlled by said adaptive controller to adjust the controlled operation input parameter to F_c;

characterized in that

said controller further comprises a correction processing means for calculating k_cU_c, where k_c is a varying signal transmission coefficient component whose current values depend on the variation of said operation condition B=B(t), the controller being capable of calculating k=ƒ

(k_o,k_c).

12. An adaptive controller according to claim 11, further capable of calculating k=k_o−

k_c, and calculating k_o as $k_o=\frac{A}{U_o},$

where U_o is a signal from the sensor of the operation output parameter corresponding to the value Δ

M_o.

13. An adaptive controller according to claim 12, wherein Δ

M_o=Δ

M_max and U_o=U_max.

14. An adaptive controller according to claim 11, wherein said sensor of the output operation parameter Δ

M is a sensor of a cutting torque developed by a drive rotating the workpiece.

15. An adaptive controller according to claim 11, wherein said input parameter override unit is a feed rate override unit.

16. An adaptive controller according to claim 11, wherein said correction processing means comprises a sensor or for sensing current values of the operation condition B, to be subsequently used in the calculation of k_c.

17. An adaptive controller according to claim 11, wherein said correction processing means comprises a calculator for calculating current values of the operation condition B, to be subsequently used in the calculation of k_c.