Adaptive control for machine tools
First Claim
1. The method of adaptively controlling a plant process to maintain the value of a process parameter [M] substantially in agreement with the value of a desired set point [m], the plant having an automatic adjustment device [33b] responsive to a command signal [Qc ] to change at least one physical variable [Q], changes in said variable [Q] in turn causing the parameter [M] to change, the response of the parameter [M] to the variable [Q] being time variant in a fashion that is not predeterminable, said method comprising:
- (a) supplying a command signal [Qc ] to said adjustment device [33b] so that the latter produces the physical variable [Q],(b) sensing the actual value of the physical parameter [M], andsaid method being characterized by and including(c) obtaining an estimate [Qp ] of the present value of the physical variable [Q], and thereafter(d) correctively changing said command signal [Qc ] to take on a new value [Qcn ] equal to the estimate [Qp ] of the present value of the physical variable [Q] multiplied by the ratio of the set point value [m] to the actual value of the physical parameter [M].
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Accused Products
Abstract
An adaptive control for a turning machine which adjusts the machining rate to maintain the actual horsepower dissipated at the cutter tip at a constant set point despite changing workpiece and cutter parameters. The machining rate is adjusted by control of the machine drive and tool feed to achieve required SFM and IPR values, respectively, within maximum and minimum SFM and IPR limits. "Speed" and "Axis" override controls are also provided. The rate of adjustment of SFM and IPR to a deviation of the cutter tip horsepower from the set point is inversely proportional to the measured system gain so that the response factor of the control loop is maximized. The commanded machining rate of (SFM) (IPR) product is periodically determined by estimating the actual machining rate and multiplying the estimate by the ratio of the set point to the cutter tip horsepower. The cutter tip horsepower is determined by subtracting the electrical loss, mechanical friction loss, and the net power required for net acceleration of the drive, from the measured electrical power supplied to the drive motor. The cutting efficiency is monitored to perform tool wear, tool breakage, and tool protection functions. The adaptive control also has soft engagement and soft disengagement functions for initiating and terminating the adaptive machining process.
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Citations
73 Claims
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1. The method of adaptively controlling a plant process to maintain the value of a process parameter [M] substantially in agreement with the value of a desired set point [m], the plant having an automatic adjustment device [33b] responsive to a command signal [Qc ] to change at least one physical variable [Q], changes in said variable [Q] in turn causing the parameter [M] to change, the response of the parameter [M] to the variable [Q] being time variant in a fashion that is not predeterminable, said method comprising:
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(a) supplying a command signal [Qc ] to said adjustment device [33b] so that the latter produces the physical variable [Q], (b) sensing the actual value of the physical parameter [M], and said method being characterized by and including (c) obtaining an estimate [Qp ] of the present value of the physical variable [Q], and thereafter (d) correctively changing said command signal [Qc ] to take on a new value [Qcn ] equal to the estimate [Qp ] of the present value of the physical variable [Q] multiplied by the ratio of the set point value [m] to the actual value of the physical parameter [M]. - View Dependent Claims (2, 3, 4)
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5. An adaptive feedback control system for regulation of a plant having an automatic adjustment device [33b] establishing the value of at least one physical variable [Q] affecting a process [33d] in the plant, the control system accepting a set point value [m] corresponding to a particular physical parameter of the process [33d] that is responsive to the value of the physical variable [Q], the control system having a process sensor [33e] monitoring the value [M] of the physical parameter, wherein the improvement comprises:
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means [33c, 59] for obtaining an estimate [Qp ] of the present value of the physical variable [Q], and ratio calculator means [33a] for commanding the adjustment device to urge the physical variable [Q] to take on a value substantially equal to the product of the estimate [Qp ] of the present value of the physical variable and the ratio of the set point value [m] to the value [M] of the physical parameter indicated by the process sensor. - View Dependent Claims (6, 7, 8)
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9. The method of adaptively controlling a plant process to maintain a process parameter [M] substantially in agreement with the value of a desired set point signal [m], the plant having an adjustment device [33b] responsive to a command signal [Qc ] to change at least one physical variable [Qm ], changes in said variable [Qm ] in turn causing the plant to change said parameter [M] with a time-variant gain transfer function [Gp(s) =M/Qm ] which is not predeterminable, said method comprising
(a) supplying a command signal [Qc ] to said adjustment device so that the latter produces the physical variable [Qm ], (b) producing a first signal [Mo ] representing the actual value of the parameter [M] created by the plant, and said method being characterized by and including (c) producing a second signal representing the actual value of the variable [Qm ], and (d) correctively changing said command signal [Qc ] to take on a new value [Qcn ] equal to said second signal multiplied by the ratio of said set point value to the value of said first signal, such that Qcn =Qm · - (m/Mo).
- View Dependent Claims (10, 11)
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12. The method of adaptively controlling a plant process to maintain a process parameter M substantially in agreement with the value of a desired set point signal m, the plant acting to change the parameter M according to changes in at least one input signal Ip with a time-variant gain (Gp(s) =M/Ip) which is not predeterminable, said method comprising
(a) supplying to the plant an input signal Ip, (b) producing a signal Mo representing the actual value of the parameter M created by the plant, and said method being characterized by and including (c) correctively changing said input signal Ip to take on a new value Ipn equal to its original value Ipold multiplied by the ratio of the set point signal to the actual value signal Mo, such that Ipn =Ipold ·
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19. In an adaptive control for a physical system, such system acting in response to an input signal Ip to change a controlled parameter HP which is affected by variables in addition to said input signal, the combination comprising:
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(a) means for producing a set point signal HPd representing a desired value for the parameter HP, (b) repetitive means for producing a signal HPm representing the actual value of the parameter HP while the system is operating with a known value Ipo of the input signal Ip, (c) repetitive means for determining a new value Ipn for the input signal Ip based upon the ratio HPd /HPm of the set point to the actual value multiplied by the known Ipo, such that Ipn =(HPd /HPm)·
Ipo and(d) repetitive means for changing the input signal Ip to agree with the determined value Ipn, so that the actual value HPm of the controlled parameter HP converges toward the value of the set point signal HPd despite variations in the variables other than the input signal Ip which affect the controlled parameter HP.
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20. The method of adaptively controlling a plant process to maintain a process parameter M substantially in agreement with the value of a desired set point signal m, the plant having an adjustment device responsive to at least one command signal Ipc to vary a physical variable Ip which affects the parameter M with a gain Gp(s) =M/Ip which is time variant and non-predeterminable, said method comprising
(a) creating at least one command signal Ipc, (b) multiplying said command signal by an operator-adjustable override factor K to produce a final command signal Ipco such that Ipco =K· - Ipc,
(c) creating a set point signal m representing a desired value of the parameter M, (d) multiplying said set point m by the same operator-adjustable factor K to produce a final set point signal Mo, (e) sensing, and representing by a signal Mo, the actual value of said parameter M, (f) sensing, and representing by a signal Ipm, the actual value of said physical variable Ip, and (g) correctively changing said command signal Ipc to take on a new value Ipcn equal to the value of the actual variable Ip multiplied by the ratio of the final set point signal mo to the actual value signal Mo, such that Ipcn =Ipm ·
(mo /Mo) whereby said parameter M converges in value toward agreement with the value of said set point signal m when the factor K is 1.0, but upon operator-performed adjustment of said override factor K to values other than 1.0 to modify the range of variation of said variable Ip, the negating of the override action is avoided by a corresponding change in the effective set point mo at which said parameter is maintained. - View Dependent Claims (21)
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22. An iterative control system for regulating a physical plant [70'"'"'], the plant receiving a control signal [Ip ] and emitting an output value [M], the control system receiving a set point value [m], and the control system having a calculator [73"] for repetitively generating the control signal [Ip ] as a predetermined control function [f(M, m)] of the output value [M] and the set point value [m], the function being predetermined so that the output value [M] tends to track the set point value [m], wherein the improvement comprises:
the control system having a user adjustable override control [64, 65] supplying an override factor [K], means for scaling the control function [f] of the calculator [73"] by the scale factor [K] to generate the control signal [Ip ] so that the value of the control signal [Ip ] is substantially equal to the product [Kf] of the control function [f] and the scale factor [K], and wherein the set point value [m] is scaled by the scale factor [K] before being applied to the control function [f], so that the tendency of the control function [f] to negate the override action is avoided by a correspondingly scaled set point value [Km] being applied to the control function [f]. - View Dependent Claims (23)
- 24. In a control system for a machine tool having means to rotate and feed a workpiece relative to a cutter, and wherein the relative surface speed, designatable SFM, of such rotation with respect to the cutter edge is kept in agreement with a first set point signal SFMo, and the relative feed, designatable IPR of the cutter edge into the workpiece, is kept in agreement with a second set point signal IPRo, the system further having means for producing actual value signals SFMm and IPRm which change in response to changes in SFMo and IPRo, respectively,
(a) means for producing command signals SFMc and IPRc representing commanded values of relative speed and feed, (b) operator adjustable means for overriding said commanded values to produce said set point signals SFMo and IPRo from the command signals SFMc and IPRc such that - space="preserve" listing-type="equation">SFM.sub.o =KS.sub.o ·
SFM.sub.c
space="preserve" listing-type="equation">IPR.sub.o =KI.sub.o ·
IPR.sub.cwhere KSo and KIo are multipliers adjustable in value by the machine operator from a normal value of 1.0, (c) means for producing a set point signal HPd representing the machining power desired to be applied in creating said relative rotation, (d) means for periodically updating at least one of the command signals SFMc, IPRc in response to changes in at least a respective one of the actual value signals SFMm, IPRm, during operation of the machine according to the relationship
space="preserve" listing-type="equation">CS=(HP.sub.d /HP.sub.a)·
KS.sub.o ·
KI.sub.o ·
MCSwhere CS is the said one of said two command signal, MCS is the corresponding actual value signal, and HPa is the actual power applied in maintaining said relative rotation, thereby effectively to change the power set point HPd to HPd ·
KSo ·
KIo by the same percentage as the changes in percentage of both the speed and feed when the operator makes adjustments of said means (b). - space="preserve" listing-type="equation">SFM.sub.o =KS.sub.o ·
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25. In a control system for a machine tool having means to rotate and feed a workpiece relative to a cutter, and wherein the relative surface speed, designatable SFM, of such rotation with respect to the cutter edge is kept in agreement with a first set point signal SFMo ;
- and the relative feed, designatable IPR of the cutter edge into the workpiece, is kept in agreement with a second set point signal IPRo,
(a) means for producing command signals SFMc and IPRc representing commanded values of relative speed and feed, (b) operator adjustable means for overriding said commanded values to produce said set point signals SFMo and IPRo from the command signals SFMc and IPRc such that
space="preserve" listing-type="equation">SFM.sub.o =KS.sub.o ·
SFM.sub.c
space="preserve" listing-type="equation">IPR.sub.o =KI.sub.o ·
IPR.sub.cwhere KSo and KIo are multipliers adjustable in value by the machine operator from a normal value of 1.0, (c) means for producing a set point signal HPd representing the machining power desired to be applied in creating said relative rotation, (d) means for periodically updating at least one of said two command signals SFMc, IPRc during operation of the machine according to the relationship
space="preserve" listing-type="equation">CS.sub.i =HP.sub.d /HP.sub.a ·
KS.sub.o ·
KI.sub.o ·
CS.sub.(i-1)where CS is the said one command signal and HPa is the actual power applied in maintaining said relative rotation, thereby effectively to change the power set point HPd to HPd ·
KSo ·
KIo by the same percentage as the changes in percentage of both the speed and feed when the operator makes adjustments of said means (b).
- and the relative feed, designatable IPR of the cutter edge into the workpiece, is kept in agreement with a second set point signal IPRo,
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26. An automatic control system for a machine tool accepting a desired power signal comprising, in combination,
means for measuring the power consumed by the machine drive in moving the cutting tool relatively at a controllable surface speed transversely across a workpiece surface, generating a measured power signal indicating actual machining power, automatic means for generating a relative machining rate command signal which changes according to the ratio of the desired power signal to the measured power signal, drive control means responsive to said command signal for adjusting said relative surface speed to thereby bring and hold the actual machining power in substantial agreement with said desired power signal.
- 39. A control system for a machine tool, such machine tool having
(i) drive means to relatively rotate a workpiece and a cutter at a surface speed designatable as SFM, (ii) feed means to relatively feed the workpiece and cutter at a feed rate designatable as IPR, (iii) means responsive to input signals SFMo and IPRo for controlling said means (i) and (ii) to keep the actual speed and feed SFMa and IPRa in agreement with such signals, and said machine tool having physical characteristics such that a cutting efficiency factor CEF, proportional to horsepower per cubic inch per minute of workpiece material removal, varies according to the relation - space="preserve" listing-type="equation">CEF∝
HP/[(SFM)(IPR)]
where HP is the power applied to cause said relative rotation and such power varies with both SFM and IPR as well as other variables, said control system comprising, in combination; (a) means for signaling a desired power HPd, (b) means for initially setting said signals SFMo and IPRo to desired starting values of SFM and IPR, (c) means for signaling the actual power HPa applied to cause said relative rotation and means for signaling the actual surface speed SFMa, at spaced intervals in time while said machine and system are operating with known input signals SFMo and IPRo, (d) means for determining a new value signal SFMn during each spaced time interval according to the relation
space="preserve" listing-type="equation">SFM.sub.n =HP.sub.d /HP.sub.a ·
SFM.sub.a,and (e) means for substituting the new value signal SFMn for the previous SFMo signal value, during each time interval. - View Dependent Claims (41, 42)
- space="preserve" listing-type="equation">CEF∝
- 40. A control system for a machine tool, such machine tool having
(i) drive means to relatively rotate a workpiece and a cutter at a surface speed designatable as SFM, (ii) feed means to relatively feed the workpiece and cutter at a feed rate designatable as IPR, (iii) means responsive to input signals SFMo and IPRo for controlling said means (i) and (ii) to keep the actual speed and feed SFMa and IPRa in agreement with such signals, and said machine tool having physical characteristics such that a cutting efficiency factor CEF, proportional to horsepower per cubic inch per minute of workpiece material removal, varies according to the relation - space="preserve" listing-type="equation">CEF∝
HP/[(SFM)(IPR)]
where HP is the power applied to cause said relative rotation and such power varies with both SFM and IPR as well as other variables, said control system comprising, in combination; (a) means for signaling a desired power HPd, (b) means for initially setting said signals SFMo and IPRo to desired starting values of SFM and IPR, (c) means for signaling the actual power HPa applied to cause said relative rotation and means for signaling the actual surface speed SFMa, at spaced intervals in time while said machine and system are operating with known input signals SFMo and IPRo, (d) means for determining a new value signal SFMn during each spaced time interval according to the relation
space="preserve" listing-type="equation">SFM.sub.n =HP.sub.d /HP.sub.a ·
SFM.sub.o,and (e) means for substituting the new value signal SFMn for the previous SFMo signal value, during each time interval. - space="preserve" listing-type="equation">CEF∝
- 43. A control system for a machine tool, such machine tool having
(i) drive means to relatively rotate a workpiece and a cutter at a surface speed designatable as SFM, (ii) feed means to relatively feed the workpiece and cutter at a feed rate designatable as IPR, (iii) means responsive to input signals SFMo and IPRo for controlling said means (i) and (ii) to keep the actual speed and feed SFMa and IPRa in agreement with such signals, and said machine tool having physical characteristics such that a cutting efficiency factor CEF, proportional to horsepower per cubic inch per minute of workpiece material removal, varies according to the relation - space="preserve" listing-type="equation">CEF∝
HP/[(SFM)(IPR)]
where HP is the power applied to cause said relative rotation and such power varies with both SFM and IPR as well as other variables, said control system comprising, in combination; (a) means for signaling a desired power HPd, (b) means for initially setting said signals SFMo and IPRo to desired starting values of SFM and IPR, (c) means for signaling the actual feed IPRa and the actual power HPa, applied to cause said relative rotation, at spaced intervals in time while said machine and system are operating with known input signals SFMo and IPRo, (d) means for determining a new value signal IPRn during each spaced time interval according to the relation,
space="preserve" listing-type="equation">IPR.sub.n =(HP.sub.d /HP.sub.a)·
IPR.sub.a,and (e) means for substituting the new value signal IPRn for the previous IPRo signal value, during each time interval. - View Dependent Claims (44, 47)
- space="preserve" listing-type="equation">CEF∝
- 45. A control system for a machine tool, such machine tool having
(i) drive means to relatively rotate a workpiece and a cutter at a surface speed designatable as SFM, (ii) feed means to relatively feed the workpiece and cutter at a feed rate designatable as IPR, (iii) means responsive to input signals SFMo and IPRo for controlling said means (i) and (ii) to keep the actual speed and feed SFMa and IPRa in agreement with such signals, and said machine tool having physical characteristics such that a cutting efficiency factor CEF, proportional to horsepower per cubic inch per minute of workpiece material removal, varies according to the relation - space="preserve" listing-type="equation">CEF∝
HP/[(SFM)(IPR)]
where HP is the power applied to cause said relative rotation and such power varies with both SFM and IPR as well as other variables, said control system comprising, in combination; (a) means for signaling a desired power HPd, (b) means for initially setting said signals SFMo and IPRo to desired starting values of SFM and IPR, (c) means for signaling the actual power HPa, applied to cause said relative rotation, at spaced intervals in time while said machine and system are operating with known input signals SFMo and IPRo, (d) means for determining a new value signal IPRn during each spaced time interval according to the relation,
space="preserve" listing-type="equation">IPR.sub.n =HP.sub.d /HP.sub.a ·
IPR.sub.o,and (e) means for substituting the new value signal IPRn for the previous IPRo signal value, during each time interval. - View Dependent Claims (46)
- space="preserve" listing-type="equation">CEF∝
- 48. A control system for a machine tool, such machine tool having
(i) drive means to relatively rotate a workpiece and a cutter at a surface speed designatable as SFM, (ii) feed means to relatively feed the workpiece and cutter at a feed rate designatable as IPR, (iii) means responsive to input signals SFMo and IPRo for controlling said means (i) and (ii) to keep the actual speed and feed SFMa and IPRa in agreement with such signals, and said machine tool having physical characteristics such that a cutting efficiency factor CEF, proportional to horsepower per cubic inch per minute of workpiece material removal, varies according to the relation - space="preserve" listing-type="equation">CEF∝
HP/[(SFM) (IPR)]
where HP is the power applied to cause said relative rotation and such power varies with both SFM and IPR as well as other variables, said control system comprising, in combination; (a) means for signaling a desired power HPd, (b) means for initially setting said signals SFMo and IPRo to desired starting values of SFM and IPR, (c) means for signaling the actual power HPa, applied to cause said relative rotation, at spaced intervals in time while said machine and system are operating with known input signals SFMo and IPRo, (d) means for determining the relative machining rate Q generally as the product of the machining parameters SFM, IPR according to the relation Q=(IPRa) (SFMa), (e) means for determining a new commanded relative machining rate value signal Qn during each spaced time interval according to the relation
space="preserve" listing-type="equation">Q.sub.n =HP.sub.d /HP.sub.a ·
Q,and (f) means for determining new value signals SFMn and IPRn such that Qn =(SFMn)(IPRn), and (g) means for setting the input signals SFMo, IPRo equal to the new SFMn, IPRn signal values, respectively, during each time interval. - View Dependent Claims (49, 50, 51)
- 50. The combination as claimed in claim 48, wherein means (f) for determining new value signals SFMn and IPRn further comprises means for comparing the new relative machining rate Qn to a maximum threshold Q3 defined as the product of a maximum IPR limit IPRmax and a maximum SFM limit SFMmax, and means for setting SFMn to SFMmax and setting IPRn to IPRmax if Qn exceeds Q3.
- 51. The combination as claimed in claim 48, further comprising means for comparing the new relative machining rate Qn to a minimum threshold Q1 defined as the product of a minimum IPR limit IPRmin and a minimum SFM limit SFMmin, and means for taking corrective action if Qn is less than Q1.
- space="preserve" listing-type="equation">CEF∝
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52. In a numerically-controlled machine tool system having a holder for a workpiece, a cutting tool, a cutting tool holder, a feed motor means accepting a feed velocity control signal for feeding the cutting tool into the workpiece, a drive motor means accepting a drive velocity control signal for establishing a relative transverse velocity of the cutting tool across the surface of the workpiece, a drive power measuring means for generating a measured drive power signal indicating power required to maintain the drive velocity, a drive velocity measuring means for generating a measured drive velocity signal indicating the drive velocity, numerical converter means for converting measured signals to numerical values and numerical control values to control signals, and a digital computing means for entering machining parameters and performing numerical and logical functions and interfaced to said numerical converter means, the improved control method which comprises the steps of:
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(a) inputting a set point signal representing desired machining power into the digital computing means, and (b) inputting the numerical values of the measured drive power signal and the measured drive velocity signal into the digital computing means, and (c) computing a drive velocity numerical control value approximately proportional to the product of the numerical value of the measured drive velocity signal and the set point signal, divided by the numerical value of the measured drive power signal, (d) outputting the drive velocity numerical control value to the numerical converter means for conversion to the drive velocity control signal, and (e) repeating steps (b) through (d) generally continuously while feeding the cutting tool into the workpiece throughout a substantial part of the machining process, so that the machine tool system is adaptively controlled to maintain machining at a generally constant power level corresponding to the desired machining power despite changing functional relations between machining parameters. - View Dependent Claims (53)
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54. In a numerically-controlled machine tool system having a holder for a workpiece, a cutting tool, a cutting tool holder, a feed motor means accepting a feed velocity control signal for feeding the cutting tool into the workpiece, a drive motor means accepting a drive velocity control signal for establishing a relative transverse velocity of the cutting tool across the surface of the workpiece, a drive power measuring means for generating a measured drive power signal indicating power required to maintain the drive velocity, a drive velocity measuring means for generating a measured drive velocity signal indicating the drive velocity, a feed velocity measuring means for generating a measured feed velocity signal indicating feed velocity, numerical converter means for converting measured signals to numerical values and numerical control values to control signals, and a digital computing means for entering machining parameters and performing numerical and logical functions and interfaced to said numerical converter means, the improved control method which comprises the steps of:
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(a) inputting a desired machining power set point into the digital computing means, (b) inputting the numerical values of the measured drive power signal and the measured feed velocity signal into the digital computing means, (c) computing a feed velocity numerical control value proportional to the product of the numerical value of the measured feed velocity signal and the power set point, divided by the numerical value of the measured drive power signal, and (d) outputting the feed velocity numerical control value to the numerical converter means for conversion to the feed velocity control signal. - View Dependent Claims (55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73)
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Specification