GB2081475A - Position control process and apparatus for a positioning cylinder drive - Google Patents
Position control process and apparatus for a positioning cylinder drive Download PDFInfo
- Publication number
- GB2081475A GB2081475A GB8122808A GB8122808A GB2081475A GB 2081475 A GB2081475 A GB 2081475A GB 8122808 A GB8122808 A GB 8122808A GB 8122808 A GB8122808 A GB 8122808A GB 2081475 A GB2081475 A GB 2081475A
- Authority
- GB
- United Kingdom
- Prior art keywords
- subtraction unit
- output
- actual
- signal
- positioning
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
- G05B19/21—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device
- G05B19/23—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for point-to-point control
- G05B19/231—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using an incremental digital measuring device for point-to-point control the positional error is used to control continuously the servomotor according to its magnitude
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/41—Servomotor, servo controller till figures
- G05B2219/41176—Compensation control, position error with data from lookup memory
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/41—Servomotor, servo controller till figures
- G05B2219/41309—Hydraulic or pneumatic drive
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/43—Speed, acceleration, deceleration control ADC
- G05B2219/43115—Adaptive stopping
Description
SPECIFICATION
Position control process and apparatus for a positioning cylinder drive The invention relates to a process and an apparatus for position-control process systems of the kind in which a control deviation or error is arranged to be compensated for by producing a correcting value from comparison of the values of the actual or measured position with a reference or discrete position value.
Such systems are known in which a fluidoperated positioning cylinder, supplied with fluid by means of a servo valve, is mechanically connected to a carriage (e.g. a workpiece support) which is to be displaced and positioned. The position of the carriage with respect to the stationary part of the machine in which it is incorporated is recorded by a highresolution position-measuring system. The servo-valve itself is so controlled by an electrical signal that the carriage moves into the required position and is held in such position. Provided for this purpose is an electronic position-control system, of which the controller receives from a subtraction unit the control deviation which is formed from a reference value and an actual value and produces an appropriate adjustment output to actuate the servo-valve.
With control systems of the type under consideration here, the controller should, for stability reasons, show basically only a Pcharacteristic, but not an )-characteristic. Consequently, in such a position-control system, a remaining control deviation will always be present, which originates from zero point displacements of the electronic amplifiers and the positioning members (here represented as a whole as servo-valve), from unequal piston surfaces in the positioning cylinder, from leakage in that cylinder, etc. The remaining control deviation is expressed in such a way that, after the reference/actual value comparison and corresponding displacement of the carriage, the latter does in fact stop, i.e. the actual value no longer changes, but nevertheless a small positional error is present, which is caused by the said inaccuracies in the system.This prositional error corresponds to a residual voltage which occurs at the outputs of the subtraction unit with the stopping of the drive means. This positional error, i.e. the remaining control deviation, results from the fact that the perfect reference value position is either not reached or is exceeded, in dependence upon the sign of the algebraic sum of the aforementioned zero point displacements. If a very accurate position control is to be produced, the residual voltage at the output of the subtraction unit, which forms the difference between reference value and actual value, must be equal to zero with the stoppage of the drive means, or must at least be below a value which corresponds to the smallest resolution step of the position-measuring system. However, this is particularly difficult to obtain with a positioning cylinder drive with a servo-valve.
To deal with this problem, in accordance with a computer-controlled profiling machine tool which is known from German Offeniegungsschrift 2602 187, a correction is produced for a relatively slow servo-valve zero point travel and displacements of the amplifier biassing. According to Fig. 4A of this publication, the residual voltage is tapped off at the output of the subtraction unit and integrated in an integrating inverter, which is connected parallel to the controller, and is then switched as a corrective voltage to a current amplifier which is arranged before the servo-valve.
What is a disadvantage with this known solution is that the correction cannot become effective immediately, because the integration time constant has to be chosen to be relatively large, in order to avoid instability. Furthermore, the integrator and the two amplifiers which are connected following the latter and which together form the combined integrator and inverter, themselves have zero point displacements which cannot be corrected. In addition, there is constant correction, because the voltage following the subtraction unit is constantly tapped and integrated. This constant correction can produce uneveness in the drive means, which makes necessary a corresponding sensitivity adjustment, which can only lead to a loss of sensitivity in the control system.
It is the object of the invention to provide an alternative position-control process and system with which the sustained control deviation can be compensated for.
According to one aspect of the invention, there is provided position-control process for a positioning cylinder drive, in which, for compensating for a remaining control deviation or error between reference and actual position values arising in a positioning process, a correcting signal is produced from a signal received at the output of a subtraction unit provided in a control circuit for comparison of the positional reference and actual values, the compensation for the deviation or error being performed after said positioning process and with the adjusting drive stationary, whereupon said output signal is stored and transmitted as a correcting signal to the subtraction unit and adjustment of the positioning cylinder being made in accordance with said correcting signal.
According to another aspect of the invention, there is provided position-control process for a positioning cylinder drive, in which, for compensating for a remaining control deviation or error between reference or actual position values arising in a positioning process, a correcting signal is produced from a signal received at the output of a subtraction unit provided in a control circuit for the comparison of the reference and actual values, the compensation for the deviation or error being performed when the output signal of the subtraction unit passes through zero during the positioning process, the reference value/actual value difference existing at this instant being stored and the corrected reference value/actual value difference being transmitted as a correcting signal to the subtraction unit.
The invention thus provides a new procedure for correcting the remaining control deviation, with which either a residual voltage at the output of the subtraction unit is detected and stored in the stopped position of the control cylinder drive, or the difference between reference actual values is detected and stored at the instant when the output signal of the subtraction unit is zero. These stored values can then be added with the suitable sign as correction signal.Whereas, with the first-mentioned variant of the process according to the invention, the stoppage is either achieved by a sufficiently long wait or is ascertained by actual value observation and then the measurement is carried out for one operating point, what happens in the secondmentioned variant of the process according to the invention is that during the movement of the carriage and at the instant at which the output signal of the subtraction unit becomes zero, the difference between reference value and actual value, which is constantly formed, is stored and then fed in as a correcting signal.
In this second-mentioned variant, preferably an auxiliary signal is transmitted to the subtraction unit, in order to ensure that the positioning drive passes through the position at which the output signal of the subtraction unit passes through zero. This ensures that the carriage reaches the position at which the output signal of the subtraction unit passes through zero. As regards the auxiliary signal, this may be an auxiliary voltage or a digital auxiliary value, depending on how the control system is designed.
By the use of the process of the present invention it is possible for the correcting signal to be accurately determined and stored, and this can also take place as often as desired. The correcting signal may be measured not only at one specific point, but anywhere along the path of movement of the carriage. Whereas the loop in which the correcting signal is formed with the known system described above constantly operates and never supplies a fixed value, it is now possible to take off a discrete value only once in the control circuit, to store and transmit this as a correcting signal to the input of the subtraction unit. By this means, there are avoided problems as regards stability or unsteadiness, such as those which occur with the known system.In addition, the process can be easily applied with the digital establishment of the reference value and of the actual value, although it may also in principle be used with analogue systems having a storage capability* The value of the correcting signal generated can also be regarded as a guide or standard for the good functioning of the drive means of the adjusting or positioning cylinder, so that a warning can be given when a certain tolerance in its value is exceeded.
For performing the process according to the first mentioned variant above, there may be provided apparatus comprising a reference position value generator and an actual position value generator, the outputs of which are connected to two outputs of a subtraction unit which forms the difference between reference and actual values, a controller connected following the subtraction unit for controlling an actuating device acting on the positioning cylinder drive for movement of the displacement member with respect to a fixed member, the relative positions of which members can be monitored by a high-resolution measuring system connected to the actual position value generator, compensation means for producing said correcting signal comprising a stop indicator having respective connections to the reference position value generator and to a switch closable by said indicator,said switch being in a connecting line between the output of the subtraction unit and one input of a measurement store, said store being connected by way of another input to the stop indicator and by way of its output to a further input of the substraction unit.
For performing the process according to the second-mentioned variant above, there may be provided apparatus comprising a reference position value generator and an actual position value generator, the outputs of which are connected to two inputs of a subtraction unit the output from which is employed to actuate a controller connected following the subtraction unit for controlling an actuating device for the positioning cylinder drive for movement of a displaceable member with respect to a fixed member, the relative positions of which members can be monitored by a high-resolution measuring system connected to the actual .position value generator, compensation means for producing said correcting signal comprising a zero comparator connected to the output of the subtraction unit, a difference generator' connected to the reference and actual value generators, and a measurement store having inputs connected to the outputs of the difference generator and of the zero comparator respectively, and having an output connected to another input of the subtraction unit.
Two embodiments of the invention will now be described in more detail, by way of exam- pie, with reference to the accompanying drawings, wherein: Figure 1 is a basic example for a positioncontrol system, in which the invention can be used, Figure 2 and 3 are block circuit diagrams for the two embodiments of the invention, in which the control system and the positionmeasuring system have been omitted for the sake of clarity, and Figure 4 is an explanatory diagram illustrating the adjusting displacements to a desired value S against a time base.
In Fig. 1, an adjustment or positioning drive cylinder 1 is connected mechanically to a slide or carriage 2, which is mounted to be displaceable on a fixed bed 3. The carriage 2 is moved and positioned in relation to a position-measuring system 4 by the drive cylinder 1. For this purpose a servo-valve 5 supplies hydraulic fluid under pressure to one or the other side of the piston in the drive cylinder 1, corresponding to a positioning value. The position-measuring system delivers the measurement information, i.e. the control value, to an actual value generator 6, which is connected to one input of a subtraction unit 7. Another input of the said unit 7 is connected to a reference value generator 8, which supplies the reference value for the carriage position.The subtraction unit 7 forms, from the reference value and the actual value, the control deviation, which is supplied to a controller 9, which produces the positioning value from said deviation and transmits it to the servo-valve 5.
If no zero point deviations were to be present in the control system, the carriage, when it stops again after the control process, would have the positional value which is indicated by S in Fig. 4 and the control deviation, i.e. the position voltage at the output of the subtraction unit, would be zero when the carriage stops. Because of the zero point deviations or errors of the members contained in the system, concerning which the servo-valve 5 and the positioning drive cylinder 1 have the major share, the carriage 2 comes to a stop however, at a position which corresponds to a positional value situated above or below the reference value S in Fig. 4 reached by the broken-line curve or chain-dotted curve respectively.
Fig. 2 shows again a control system according to the invention, but the members 1, 2 and the position-measuring system 4 illustrated in Fig. 1 have here been omitted for the sake of simplicity. Fig. 2 additionally shows a digital-analogue converter 10, which is optionally present and which is only used when that part of the system preceding the controller 9 operates digitally while the controller itself is an analogue controller. Connected to the actual value generator 6 is a stoppage indicator 11, which acts through one output on an electronic switch 12, connected between the output of the subtraction unit 7 and one input of a measurement store 13, another input of which is connected to the stoppage indicator 11. The output of the said store 13 is connected to a third input of the subtraction unit 7.When the adjusting or positioning drive has come to a stop, after executing the control operation, the stop indicator 11 1 briefly closes the switch 12, so that the residual voltage which is present at the output of the subtraction unit 7 at the instant of stopping and which corresponds to the remaining control deviation is registered and stored by the measurement store 13. The store 13 then delivers a correcting signal to the subtraction unit, which has the consequence that, after stoppage has occurred, the drive is once again adjusted, i.e. the carriage 2 is moved to the reference position value S.
This position of the carriage is then used as a reference point and, from then on, the same correction is made with each carriage adjustment. With this embodiment of the invention, there is a sufficiently long waiting time until the stoppage is reached, whereupon the stoppage indicator initiates the function as previously described.
Fig. 3 shows a second embodiment of the invention, in which a zero comparator 14 is used instead of the stop indicator 11 of Fig.
2. In addition, the actual value generator 6 and the reference value generator 8 are, on the one hand, each again connected to one input of the subtraction unit 7, but are, on the other hand, each connected to one input of a difference generator 15. The output of the latter is connected to the measurement store 1 3, the correcting signal output of which is once again connected to the third input of the subtraction unit 7. The zero comparator 14 is connected between the output of the subtraction unit and another input of the measurement store 13. Finally, an auxiliary signal circuit 16 is connected to a fourth input of the subtraction unit 7.
As regards the functioning of this circuit, whereas it was necessary in the system of Fig. 2 to wait for the drive means to stop and then the voltage present at the output of the subtraction unit was measured and stored, the procedure in this embodiment is that, at the moment at which the output signal of the subtraction unit 7 is zero, which is detected by the zero comparator 14, the measurement store 13 is triggered by the latter, which store then registers and stores the difference between reference value and actual value as formed in the difference generator 15. After storage of the value had taken place, the auxiliary voltage signal is interrupted by means of a switch 17.The stored value is then delivered with the suitable sign in the form of a correcting signal for compensation of the remaining control deviation or error to the subtraction unit 7, with the result that the carriage is adjusted to the exact positional value S (Fig. 4). In the constructional form of the control system of Fig. 3, it is therefore not necessary to wait until the adjusting drive has come to a halt, in order then to measure the remaining control error. For this purpose, however, it has to be ensured that the carriage actually reaches the point T (Fig. 4), in which the output signal of the subtraction unit is equal to zero. Provided for this purpose is the auxiliary signal circuit 16.This latter feeds a digital (or analogue) auxiliary signal having the correct sign into the subtraction unit 7, so that the point T, which is situated on the straight line parallel to the time axis and passing through the point S and in which the difference between reference value and actual value passes through zero, is also actually passed through by the drive and can be detected by the zero comparator 14.
In the two constructional forms, which are shown in Figs. 2 and 3, the correcting signal can be exactly established and stored, not only for one reference point, but it can also be measured as often as desired, and not only at one specific point, but anywhere along the control system. In both cases, the controller is essentially a P-controller, the remaining control deviation or error of which is very exactly eliminated by the subsequent correction with assistance of the correcting signal delivered from the measurement store. Problems as regards stability or unsteadiness, which would occur with the use of an integrator, are thereby avoided. In the systems as described, the reference value and the actual value are produced in digital form, for which reason, as stated, the D/A converter 10 is to be additionally used when the controller 9 operates analogically.
The value of the correcting signal also represents a standard indicative of the good functioning of the adjusting drive. It can be employed when a certain tolerance is exceeded (e.g. with servo-valves which are not functioning properly) in order to give an alarm or to switch off the machine which is equipped with the positioning cylinder drive.
Claims (11)
1. Position-control process for a positioning cylinder drive, in which, for compensating for a remaining control deviation or error between reference and actual position values arising in a positioning process, a correcting signal is produced from a signal received at the output of a subtraction unit provided in a control circuit for comparison of the positional reference and actual values, the compensation for the deviation or error being performed after said positioning process and with the adjusting drive stationary, whereupon said output signal is stored and transmitted as a correcting signal to the subtraction unit and adjustment of the positioning cylinder being made in accordance with said correcting signal.
2. A process according to claim 1 wherein said correcting signal is stored for use in compensating the control deviation or error in a subsequent operation of the control process^
3. Position-control process for a positioning cylinder drive, in which, for compensating for a remaining control deviation or error between reference or actual position values arising in a positioning process, a correcting signal is produced from a signal received at the output of a subtraction unit provided in a control circuit for the comparison of the reference and actual values, the compensation for the deviation or error being performed when the output signal of the subtraction unit passes through zero during the positioning process, the reference value/actual value difference existing at this instant being stored and the corrected reference value/actual value difference being transmitted as a correcting signal to the subtraction unit.
4. A process according to claim 3 wherein an auxiliary signal is transmitted to the subtraction unit, in order to ensure that the positioning drive passes through the position at which the output signal of the subtraction unit passes through zero.
5. Position-control apparatus for carrying out the process and according to claim 1, comprising a reference position value generator and an actual position value generator, the outputs of which are connected to two outputs of a subtraction unit which forms the difference between reference and actual values, a controller connected following the subtraction unit for controlling an actuating device acting on the positioning cylinder drive for movement of the displaceable member with respect to a fixed member, the relative positions of which members can be monitored by a high-resolution measuring system connected to the actual position value generator, compensation means for producing said correcting signal comprising a stop indicator having respective connections to the reference position value generator and to a switch closable by said indicator, said switch being in a connecting line between the output of the subtraction unit and one input of a measurement store, said store being connected by way of another input to the stop indicator and by way of its output to a further input of the subtraction unit.
6. Position-control apparatus for carryingout the process according to claim 3 comprising a reference position value generator and an actual position value generator, the outputs of which are connected to two. inputs of a subtraction unit the output from which is employed to actuate a controller connected following the subtraction unit for controlling an actuating device for the positioning cylin- der drive for movement of a displaceable member with respect to a fixed member, the relative positions of which members can be monitored by a high-resolution measuring system connected to the actual position value generator, compensation means for producing said correcting signal comprising a zero comparator connected to the output of the subtraction unit, a difference generator connected to the reference and actual value generators, and a measurement store having inputs connected to the outputs of the difference generator and of the zero comparator respectively, and having an output connected to another input of the subtraction unit.
7. Apparatus according to claim 6 comprising an auxiliary signal circuit connected to a further input of the subtraction unit.
8. Apparatus according to any one of claims 4 to 6 wherein a D/A converter is connected before the controller.
9. Position-control process substantially as described herein with reference to Fig. 2 or Fig. 3 of the accompanying drawings.
10. Position-control apparatus constructed and arranged for use and operation substantially as described herein with reference to the Fig. 2 or Fig. 3 of the accompanying drawings.
11. A machine tool comprising positioncontrol apparatus according to any one of claims 5 to 8 or 10.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH565780 | 1980-07-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2081475A true GB2081475A (en) | 1982-02-17 |
| GB2081475B GB2081475B (en) | 1984-05-31 |
Family
ID=4297244
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8122808A Expired GB2081475B (en) | 1980-07-24 | 1981-07-23 | Position control process and apparatus for a positioning cylinder drive |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0044967A3 (en) |
| JP (1) | JPS5752915A (en) |
| DE (1) | DE3039129C2 (en) |
| GB (1) | GB2081475B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2322458A (en) * | 1997-02-21 | 1998-08-26 | Bosch Gmbh Robert | Regulation of a setting element |
| GB2334792A (en) * | 1998-02-06 | 1999-09-01 | Langston Corp | Adaptive control of overshoot in the position of a member |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58189706A (en) * | 1982-04-28 | 1983-11-05 | Fanuc Ltd | Speed compensation system of speed command system |
| SE456458B (en) * | 1983-07-12 | 1988-10-03 | Nobel Elektronik Ab | control loop |
| JPS62171015A (en) * | 1986-01-23 | 1987-07-28 | Canon Inc | Positioning controller |
| JP2918271B2 (en) * | 1990-02-26 | 1999-07-12 | 三菱製紙株式会社 | Thermal recording medium |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE140391C (en) * | ||||
| US3555254A (en) * | 1967-04-17 | 1971-01-12 | Gerber Scientific Instr Co | Error correcting system and method for use with plotters, machine tools and the like |
| US3596266A (en) * | 1968-07-12 | 1971-07-27 | Houdaille Industries Inc | Numerical control system and method |
| JPS5119111B2 (en) * | 1971-09-07 | 1976-06-15 | ||
| DE2157897B1 (en) * | 1971-11-23 | 1973-02-15 | W H Joens & Co GmbH, 4000 Dussel dorf | ELECTRIC CONTROLLER WITH P OR PD BEHAVIOR |
| US3911347A (en) * | 1972-02-20 | 1975-10-07 | Xenex Corp | Adaptive control system |
| DE2327387C3 (en) * | 1973-05-29 | 1978-10-12 | Pfaff Pietzsch Industrieroboter Gmbh, 7505 Ettlingen | Drive for handling equipment |
| US4101817A (en) * | 1976-07-06 | 1978-07-18 | Okuma Machinery Works Ltd. | Position-correctable numerical control system |
| JPS5338877A (en) * | 1976-09-21 | 1978-04-10 | Oki Electric Ind Co Ltd | Drift compensation system for servo-system |
-
1980
- 1980-10-16 DE DE19803039129 patent/DE3039129C2/en not_active Expired
-
1981
- 1981-07-04 EP EP81105192A patent/EP0044967A3/en not_active Withdrawn
- 1981-07-23 GB GB8122808A patent/GB2081475B/en not_active Expired
- 1981-07-24 JP JP11544081A patent/JPS5752915A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2322458A (en) * | 1997-02-21 | 1998-08-26 | Bosch Gmbh Robert | Regulation of a setting element |
| GB2322458B (en) * | 1997-02-21 | 1999-03-10 | Bosch Gmbh Robert | Regulation of a setting element |
| US5909722A (en) * | 1997-02-21 | 1999-06-08 | Robert Bosch Gmbh | Method and device for controlling a final controlling element in closed-loop |
| GB2334792A (en) * | 1998-02-06 | 1999-09-01 | Langston Corp | Adaptive control of overshoot in the position of a member |
| ES2152875A1 (en) * | 1998-02-06 | 2001-02-01 | Lansgton Corp | Adaptive control of overshoot in the position of a member |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3039129C2 (en) | 1983-06-23 |
| GB2081475B (en) | 1984-05-31 |
| JPS5752915A (en) | 1982-03-29 |
| EP0044967A2 (en) | 1982-02-03 |
| DE3039129A1 (en) | 1982-02-11 |
| EP0044967A3 (en) | 1982-02-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |