US3679955A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control system for compensating for dimensional errors due to cutting tool wear in an automatic machine tool
Assignee: General Electric Co
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Filing: 1971-06-07
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Granted: 1972-07-25
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Expires: 1991-06-07
Abstract
Abstract A control system including apparatus which compensates for wear of the cutting tool. In a contouring control wherein the programmed instantaneous velocity along the contour is represented by a vector V, first and second compensating arrangements measure the motion of the first and second axes drive motors and multiply output signals indicative thereof by a geometrical function of the angle between the programmed tangential path of the cutting tool and one of the axis and by a factor related to the magnitude of tool wear to produce compensation signals. The compensation signals are applied to motor control loops to cause the actual tangential path of the cutting tool to be offset by a distance vector C which is normal to the vector V and has a magnitude equal to that of cutting tool wear.
Inventors
- 👤 John M Rhoades
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:17
CPC Classifications
G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/19; G05B19/33; G05B19/37; G05B19/371; G05B2219/00; G05B2219/30; G05B2219/37; G05B2219/37251; G05B2219/50; G05B2219/50295; G05B2219/50334
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
290 words
In a control system for commanding the motion of first and second drive means for producing relative motion between a cutting tool and a workpiece in an automatic machine tool and including first and second means providing command signals to first and second closed position control loops for driving said first and second drive means, a data input unit providing output data indicative of the desired resultant commanded motion, and a function generator having an input connected to said data input means and first and second outputs connected to said first and second command means respectively for producing first and second outputs respectively indicative of the desired motion in said first and second degrees of freedom, means for compensating the relative motion for dimensional errors introduced by wear on a cutting tool comprising in combination: a. velocity indicating means for producing an output indicative of the motion of said first drive means; b. a multiplier circuit having first and second inputs and an output, said first input being connected to said velocity indicating means and said second input being coupled to the output of said data input means, said multiplier circuit providing an output proportional to the first input and having a gain varying in response to the magnitude of the output of said data input means; c. an offset circuit having an input coupled to the output of said multiplier circuit, said offset circuit being settable to modify the magnitude of the output of said multiplier circuit in accordance with the magnitude of the dimensional error to be compensated; and d. means coupling the output of said offset circuit to the second means providing command signals to modify the command signal supplied to the second closed position control loop.
Claim 2
Dependent Claim
290 words
In a control system for commanding the motion of first and second drive means for producing relative motion between a cutting tool and a workpiece in an automatic machine tool and including first and second means providing command signals to first and second closed position control loops for driving said first and second drive means, a data input unit providing output data indicative of the desired resultant commanded motion, and a function generator having an input connected to said data input means and first and second outputs connected to said first and second command means respectively for producing first and second outputs respectively indicative of the desired motion in said first and second degrees of freedom, means for compensating the relative motion for dimensional errors introduced by wear on a cutting tool comprising in combination: a. velocity indicating means for producing an output indicative of the motion of said first drive means; b. a multiplier circuit having first and second inputs and an output, said first input being connected to said velocity indicating means and said second input being coupled to the output of said data input means, said multiplier circuit providing an output proportional to the first input and having a gain varying in response to the magnitude of the output of said data input means; c. an offset circuit having an input coupled to the output of said multiplier circuit, said offset circuit being settable to modify the magnitude of the output of said multiplier circuit in accordance with the magnitude of the dimensional error to be compensated; and d. means coupling the output of said offset circuit to the second means providing command signals to modify the command signal supplied to the second closed position control loop.
Claim 3
Dependent Claim
21 words
A control system according to claim 1 wherein said velocity indicating means comprises a tachometer coupled to said first drive means.
Claim 4
Dependent Claim
173 words
A control system according to claim 2 wherein said multiplier circuit comprises: a. a first resistor having a first terminal connected to the first input of said multiplier circuit; b. an operational amplifier having a first input terminal connected to the second terminal of said first resistor and an output terminal connected to the output terminal of said multiplier circuit; c. an adjustable resistance connected across said operational amplifier; and d. means connected to the second input of said multiplier circuit for varying said adjustable resistance across said operational amplifier in proportion to the output of said data input means so that the ratio of said adjustable resistance to the value of said first resistor is inversely proportional to the ratio of the output of said data input means and a predetermined maximum velocity to provide an output of said multiplier circuit which is representative of a geometrical function of the angle of relative motion with respect to the axis defining the degree of freedom in which said first drive means produces motion.
Claim 5
Dependent Claim
97 words
A control system according to claim 3 wherein said adjustable resistance comprises a plurality of resistors and a switch connected in series with each resistor, and means connecting each combination of a resistor and a switch in parallel across said operational amplifier, and in which said connecting means being responsive to the output of said data input means comprises a switching circuit having an input connected to the second input of said multiplier circuit, said switching circuit being arranged to vary the resistance connected across said operational amplifier as the output of said data input means varies.
Claim 6
Dependent Claim
36 words
A control system according to claim 3 further comprising polarity reversing means connected between the output of said multiplier circuit and the input of said offset circuit for determining the direction of compensation to be provided.
Claim 7
Dependent Claim
93 words
A control system according to claim 5 wherein said polarity reversing means comprises: a. a first switch connected in series between the output of said multiplier circuit and the input of said offset circuit; b. a second switch, an operational amplifier, and a first resistor all connected in series across said first switch; and c. a second resistor connected across said operational amplifier, said first and second switches being ganged so that when one of said switches is closed, the other is open, and said operational amplifier having a gain of minus one.
Claim 8
Dependent Claim
83 words
A control system according to claim 6 further comprising a second compensating means and a tachometer coupled to said second drive means, the output of said tachometer being coupled to the input of said compensating means and the output of said second compensating means being coupled to modify the command signals applied to said first closed control loop, the offset circuits included in said first and second compensating means being set to modify the output of each multiplier circuit in the same proportion.
Claim 9
Dependent Claim
67 words
A control system according to claim 7 wherein each of said offset circuits comprises a variable resistance being settable so that its value inversely corresponds to the magnitude of compensation to be provided, and further comprising a timer motor mechanically coupled to adjust said resistances, the rate of adjustment produced by said motor being chosen to correspond to the rate of tool wear during a cutting operation.
Claim 10
Dependent Claim
20 words
A control system according to claim 1 wherein said velocity indicating means comprises the first output of said function generator.
Claim 11
Dependent Claim
154 words
A control system according to claim 9 wherein the output of said data input means and said function generator are digital and said multiplier circuit comprises: a. a first digital-to-analog converter having an input connected to the first input of said multiplier circuit; b. a second digital-to-analog converter having an input connected to the second input of said multiplier circuit; and c. an operational amplifier having first and second inputs respectively connected to the outputs of said first and second digital-to-analog converters and an output connected to the output teRminal of said multiplier circuit, said second digital-to-analog converter being connected between the output terminal of said operational amplifier and its second input terminal to vary the gain thereof in response to the output of the data input unit, whereby said multiplier circuit produces an output proportional to the pulse rate input ratio of said second input to said first input of said multiplier circuit.
Claim 12
Dependent Claim
41 words
A control system according to claim 10 further comprising a second compensating means having an input coupled to the second output of said function generator and an output coupled to modify the command signals supplied to said first closed control loop.
Claim 13
Dependent Claim
147 words
A control system according to claim 11 wherein; a. said offset circuit in each compensating arrangement comprises an operational amplifier having a first input terminal, a second input terminal, and an output terminal; and b. means connected across each of said operational amplifiers for varying its gain in proportion to the degree of compensation to be provided, said means for varying the gain of each of said operational amplifiers comprising a digital-to-analog converter connected between the output terminal of each of said operational amplifiers and its second input terminal, a digital multiplier for connection to a source of clock pulses, said digital multiplier producing a pulse rate indicative of the rate of tool wear, and a counter connected to said digital multiplier and providing an input to each of said digital-to-analog converters, whereby the gain of said operational amplifiers is proportional to the number in the counter.
Claim 14
Dependent Claim
33 words
A control system according to claim 12 further comprising a preset register connected to said counter for setting a number in said counter indicative of an initial degree of compensation to be provided.
Claim 15
Dependent Claim
30 words
A control system according to claim 1 wherein said offset circuit comprises a variable resistance, said resistance being settable to inversely correspond to the magnitude of compensation to be provided.
Claim 16
Dependent Claim
38 words
A control system according to claim 14 further comprising a timer motor mechanically coupled to adjust said variable resistance, the rate of adjustment produced by said motor corresponding to the rate of tool wear during a cutting operation.
Claim 17
Dependent Claim
44 words
A control system according to claim 1 wherein said offset circuit comprises an operational amplifier having a first input terminal, an output terminal, and means connected across said operational amplifier for varying its gain in proportion to the degree of compensation to be provided.
Claim 18
Dependent Claim
77 words
A control system according to claim 16 wherein said means for varying the gain outside operational amplifier comprises a digital-to-analog converter connected between the output terminal of said operational amplifier and its second input terminal for varying the gain of said operational amplifier, a digital multiplier for connection to a source of clock pulses, a counter coupled to said digital multiplier and providing an output to said analog-to-digital converter indicative of the expected rate of tool wear.
Claim 19
Dependent Claim
33 words
A control system according to claim 17 further comprising a preset register connected to said counter for setting a number in said counter indicative of an initial degree of compensation to be provided.
Claim 20
Dependent Claim
209 words
In a control system in which a first source of input data is provided indicative of the desired relative motion between a workpiece and a tool and first and second inputs are provided respectively indicative of the desired motion of first and second drive means and first and second degrees of freedom to produce the desired first and second components of relative motion, a method for compensating the relative motion for dimensional errors due to wear on the cutting tool comprising the steps of: a. measuring the velocity of said first drive means to produce a first velocity indicating signal; b. multiplying said first velocity indicating signal by the ratio of the instantaneous velocity of saiD relative motion to a maximum velocity to produce a first multiplier output; c. multiplying first said output by plus or minus one to correspond to motion in first or second directions within said first degree of freedom to produce a first signal indicative of the direction of compensation to be provided in said second degree of freedom; d. multiplying said last-named signal to produce an offset signal corresponding to the magnitude of compensation to be provided; and e. utilizing said offset signal to modify the command signals applied to said second drive means.
Claim 21
Dependent Claim
209 words
In a control system in which a first source of input data is provided indicative of the desired relative motion between a workpiece and a tool and first and second inputs are provided respectively indicative of the desired motion of first and second drive means and first and second degrees of freedom to produce the desired first and second components of relative motion, a method for compensating the relative motion for dimensional errors due to wear on the cutting tool comprising the steps of: a. measuring the velocity of said first drive means to produce a first velocity indicating signal; b. multiplying said first velocity indicating signal by the ratio of the instantaneous velocity of saiD relative motion to a maximum velocity to produce a first multiplier output; c. multiplying first said output by plus or minus one to correspond to motion in first or second directions within said first degree of freedom to produce a first signal indicative of the direction of compensation to be provided in said second degree of freedom; d. multiplying said last-named signal to produce an offset signal corresponding to the magnitude of compensation to be provided; and e. utilizing said offset signal to modify the command signals applied to said second drive means.
Claim 22
Dependent Claim
121 words
A method according to claim 17 further comprising the steps of: a. measuring the velocity of said second drive means to produce a second velocity indicating signal; b. multiplying said second velocity indicating signal by the ratio of the instantaneous velocity of said relative motion to said maximum velocity to produce a second multiplier output; c. multiplying said second multiplier output by plus or minus one to produce a second signal indicative of the direction of compensation to be provided in said first degree of freedom; d. multiplying said last-named signal to produce an offset output corresponding to the magnitude of compensation to be provided; and e. utilizing said offset signal to modify command signals applied to said first drive means.
Claim 23
Dependent Claim
21 words
A method according to claim 18 wherein the input data indicative of the desired velocity of each drive means is measured.
Claim 24
Dependent Claim
21 words
A method according to claim 19 wherein the input data indicative of the desired velocity of each drive means is measured.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-25 | 1976-01-24 | 1976-07-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-25 | 1980-01-24 | 1980-07-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-25 | 1984-01-24 | 1984-07-25 | $7700.00 | Window Closed / Lapsed |