US3798430A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reduction of servo following errors in position and velocity control systems of the iteratively computing type
Assignee: Giddings and Lewis LLC
•
Filing: 1973-02-27
•
Granted: 1974-03-19
•
Expires: 1993-02-27
Abstract
Abstract Methods and apparatus for reducing following errors in the servo drives of positioning and velocity control systems wherein the commanded position is signaled and updated by increments Delta X during each successive equal time periods Delta T, -so as to cause the controlled member movable along any axis X to travel at a velocity Vx Delta X/ Delta T. The commanded position is updated by iterative computations at least once during each period Delta T, and the Delta X increments to be used for such updating are numerically signaled and can be changed as frequently as once during each period Delta T. In order to create a feed forward signal for application to the servo in a sense additive to the position command signal, the digitally signaled number Delta X is converted into a corresponding analog signal. In the preferred arrangement, this conversion is accomplished by a counter which is preset to the number Delta X at regularly recurring instants and arranged to count down whenever the number held in the counter is other than zero. A decoder responsive to a predetermined count, for example zero, not only terminates the counting action until the next presetting but also produces a constant frequency, variable duty cycle squarewave having an average or dc. value proportional to the number Delta X and which serves as an accurate feed forward input to the servo.
Inventors
- 👤 J Simon
- 👤 T Bullock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:49
CPC Classifications
G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/19; G05B19/33; G05B19/37; G05B19/371; G05B2219/00; G05B2219/30; G05B2219/41; G05B2219/41187; G05B2219/41461; G05B2219/42; G05B2219/42072; G05B2219/42207
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
185 words
In a positioning system for moving an element to successive positions along an axis in accordance with numerical commands, the combination comprising a. means for measuring off successive equal time periods Delta T, b. means for producing first signals digitally rePresenting a changeable number Delta X, where Delta X is proportional to the velocity Vx at which said element is to be moved, c. means for producing second signals digitally representing a changeable command number XSC and for changing it by the amount Delta X during each period Delta T, d. means for converting said second signals into a correspondingly changing analog command signal, e. means for producing an analog feedback signal representing the actual position of the element along the axis, f. means responsive to said first signals for producing an analog feed forward signal proportional to the changeable number Delta X, g. means for combining said feedback signal subtractively and said feed forward signal additively with said command signal to produce a modified error signal, and h. amplifier and motor means responsive to said error signal for driving said element along the path.
Claim 2
Dependent Claim
185 words
In a positioning system for moving an element to successive positions along an axis in accordance with numerical commands, the combination comprising a. means for measuring off successive equal time periods Delta T, b. means for producing first signals digitally rePresenting a changeable number Delta X, where Delta X is proportional to the velocity Vx at which said element is to be moved, c. means for producing second signals digitally representing a changeable command number XSC and for changing it by the amount Delta X during each period Delta T, d. means for converting said second signals into a correspondingly changing analog command signal, e. means for producing an analog feedback signal representing the actual position of the element along the axis, f. means responsive to said first signals for producing an analog feed forward signal proportional to the changeable number Delta X, g. means for combining said feedback signal subtractively and said feed forward signal additively with said command signal to produce a modified error signal, and h. amplifier and motor means responsive to said error signal for driving said element along the path.
Claim 3
Dependent Claim
31 words
The combination set forth in claim 1 further including means for adjusting the constant of proportionality relating said feed forward signal to the number Delta X represented by said first signals.
Claim 4
Dependent Claim
43 words
The combination set forth in claim 1 further characterized in that said adjusting means is adjusted to make said constant of proportionality substantially equal to 1/A, where A is the gain in the generalized transfer function A/s of said amplifier and motor means.
Claim 5
Dependent Claim
193 words
The combination set forth in claim 1 further characterized in that said means (f) comprises a digital counter; means responsive to said first signals for presetting said counter, once during each of successive equal time periods Delta T'', to hold a count state or number N, where N differs from a predetermined count state or number P by the magnitude of the number Delta X; means for supplying recurring pulses to said counter to cause it to count toward said predetermined count state P at all times that it does not hold the number P; means for producing a squarewave voltage which has one level when said counter is in its P state and a second level when said counter is not in its P state, whereby the duty cycle and the average value of said squarewave voltage varies in proportion to changes in the number Delta X; and means for converting said squarewave voltage into a dc. voltage which varies according to changes in said average value; the periods Delta T'' being shorter than said periods Delta T and the period of said recurring pulses being shorter than said periods Delta T''.
Claim 6
Dependent Claim
183 words
In combination with means for producing a first set of signals XSC digitally representing the commanded position of a member movable along an axis, means for producing a second set of signals digitally representing a changeable number Delta X, means responsive to said second set of signals for changing said first signals to increment the number XSC by the amount Delta X during each of successive equal time periods Delta T, a D-to-A converter for converting said first signals into a correspondingly changing analog command signal, and servo drive means responsive to said command signal and including position feedback means for driving said member along the axis to keep its actual position substantially in agreement with that represented by the XSC number, the improvement which comprises: a. means responsive to said second set of signals for producing a feed forward analog signal which dynamically varies to be proportional to said number Delta X as the latter changes, and b. means for additively combining said feed forward signal with said command signal and making said servo drive means responsive to the effective sum thereof.
Claim 7
Dependent Claim
183 words
In combination with means for producing a first set of signals XSC digitally representing the commanded position of a member movable along an axis, means for producing a second set of signals digitally representing a changeable number Delta X, means responsive to said second set of signals for changing said first signals to increment the number XSC by the amount Delta X during each of successive equal time periods Delta T, a D-to-A converter for converting said first signals into a correspondingly changing analog command signal, and servo drive means responsive to said command signal and including position feedback means for driving said member along the axis to keep its actual position substantially in agreement with that represented by the XSC number, the improvement which comprises: a. means responsive to said second set of signals for producing a feed forward analog signal which dynamically varies to be proportional to said number Delta X as the latter changes, and b. means for additively combining said feed forward signal with said command signal and making said servo drive means responsive to the effective sum thereof.
Claim 8
Dependent Claim
75 words
The combination set forth in claim 5 further characterized in that said servo drive means has a transfer function generally representable by A/s where A represents gain and s is a derivative operator, and said means (a) includes means for making the factor of proportionality relating said feed forward signal To the number Delta X substantially equal to 1/A, such that the feed forward signal in magnitude and polarity is approximately equal to Delta X/A.
Claim 9
Dependent Claim
104 words
In a system having a servo drive with feedback to move a member along an axis, and means for supplying a primary input signal to said servo drive which changes during each of successive equal periods Delta T an amount corresponding to a changeable number Delta X represented by a set of digital signals, the combination comprising a. means responsive to said digital signals for producing an analog signal substantially instantaneously proportional to the number Delta X, and b. means for supplying said analog signal as a secondary input to said servo drive and in a sense to additively supplement said primary input signal.
Claim 10
Dependent Claim
104 words
In a system having a servo drive with feedback to move a member along an axis, and means for supplying a primary input signal to said servo drive which changes during each of successive equal periods Delta T an amount corresponding to a changeable number Delta X represented by a set of digital signals, the combination comprising a. means responsive to said digital signals for producing an analog signal substantially instantaneously proportional to the number Delta X, and b. means for supplying said analog signal as a secondary input to said servo drive and in a sense to additively supplement said primary input signal.
Claim 11
Dependent Claim
222 words
In a positioning system having a servo drive with feedback to move a member along an axis, in response to a primary input signal; together with means for changing said primary input signal, during each of successive equal time periods Delta T, an amount corresponding to a changeable number Delta X represented by a set of digital signals; the combination comprising a. a digital counter, b. means responsive to said digital signals to preset said counter to a count state N which differs from a predetermined count state P by the amount Delta X, c. a source of regularly recurring pulses, d. means responsive to output signals from said counter and representing its count state for supplying said pulses to said counter to make the latter count toward said count state P at all times when it is not in state P, e. means for producing a squarewave signal having first and second levels when said counter respectively is and is not in said count state P, f. means for converting said squarewave signal into an analog signal which varies according to the duty cycle of said squarewave, and g. means for supplying said analog signal as a supplementary input signal to said servo drive and causing the latter to respond to the additive combination of the primary and supplementary input signals.
Claim 12
Dependent Claim
222 words
In a positioning system having a servo drive with feedback to move a member along an axis, in response to a primary input signal; together with means for changing said primary input signal, during each of successive equal time periods Delta T, an amount corresponding to a changeable number Delta X represented by a set of digital signals; the combination comprising a. a digital counter, b. means responsive to said digital signals to preset said counter to a count state N which differs from a predetermined count state P by the amount Delta X, c. a source of regularly recurring pulses, d. means responsive to output signals from said counter and representing its count state for supplying said pulses to said counter to make the latter count toward said count state P at all times when it is not in state P, e. means for producing a squarewave signal having first and second levels when said counter respectively is and is not in said count state P, f. means for converting said squarewave signal into an analog signal which varies according to the duty cycle of said squarewave, and g. means for supplying said analog signal as a supplementary input signal to said servo drive and causing the latter to respond to the additive combination of the primary and supplementary input signals.
Claim 13
Dependent Claim
97 words
The combination set forth in claim 8 further characterized in that said means (d) and (e) are constituted by a decoder connected to receive output signals from the counter which represent its count state and including means for producing a response signal having first or second levels when the counter respectively is or is not in said count state P, said response signal being said squarewave, and a gate having its output connected to the counting input of said counter and having two inputs respectively connected to receive (i) said recurring pulses and (ii) said response signal.
Claim 14
Dependent Claim
129 words
The combination set forth in claim 8 further characterized in that said number Delta X may be positive or negative and its sign represented by 0 or 1 level of one bit signal in said set of digital signals, and said means (e) includes e1. means for making said squarewave signal have a first positive level when bit signal is a 1 and said counter is not in its count state P, e2. means for making said squarewave signal have a second negative level, equal in magnitude to the first, when said bit signal is a 0 and said counter is not in its count state P, and e3. means for making said squarewave signal have a third, zero level when said counter is in its count state P.
Claim 15
Dependent Claim
18 words
The combination set forth in claim 8 further characterized in that said predetermined count state P is zero.
Claim 16
Dependent Claim
46 words
The combination set forth in claim 11 further characterized in that said presetting means sets said counter to a count state N which is equal to the number Delta X, and said counter is a down counter which counts downwardly in response to said recurring pulses.
Claim 17
Dependent Claim
47 words
The combination set forth in claim 11 further characterized in that said presetting means sets said counter to a count state N which is the complement of the number Delta X, and said counter Is an upward counter which counts upwardly in response to said recurring pulses.
Claim 18
Independent Claim
212 words
The method of moving a member along an axis to keep its position dynamically in agreement with a changing position command, said method comprising the steps of a. measuring off successive equal time periods Delta T, b. producing a first set of digital signals representing a commanded position number XSC, c. producing a second set of digital signals representing a changeable increment number Delta X, where Delta X Vx/ Delta T and Vx is the desired velocity of said member, d. utilizing said second set of signals to change the first set of signals during each period Delta T so as to change the number XSCi + Delta X XSCi 1, e. converting said first set of signals into an analog command signal which varies according to the changes in the number XSC, f. converting said second set of signals into an analog feed forward signal which varies according to the changes in the number Delta X, and g. utilizing said command and feed forward signals as additive inputs to a servo positioning drive means coupled to move the member along the axis, said drive means having a position feedback loop, whereby the following error between the actual position and the commanded position represented by said first set of signals is reduced.
Claim 19
Independent Claim
212 words
The method of moving a member along an axis to keep its position dynamically in agreement with a changing position command, said method comprising the steps of a. measuring off successive equal time periods Delta T, b. producing a first set of digital signals representing a commanded position number XSC, c. producing a second set of digital signals representing a changeable increment number Delta X, where Delta X Vx/ Delta T and Vx is the desired velocity of said member, d. utilizing said second set of signals to change the first set of signals during each period Delta T so as to change the number XSCi + Delta X XSCi 1, e. converting said first set of signals into an analog command signal which varies according to the changes in the number XSC, f. converting said second set of signals into an analog feed forward signal which varies according to the changes in the number Delta X, and g. utilizing said command and feed forward signals as additive inputs to a servo positioning drive means coupled to move the member along the axis, said drive means having a position feedback loop, whereby the following error between the actual position and the commanded position represented by said first set of signals is reduced.
References Cited (Backward Citations)
US2829329A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-18 | 1977-09-17 | 1978-03-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-18 | 1981-09-17 | 1982-03-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-18 | 1985-09-17 | 1986-03-19 | $7700.00 | Window Closed / Lapsed |