DD140391A1 - PROCESS FOR CONTROLLING PHYSICAL SIZES - Google Patents

Abstract

A method for the controlled adjustment of physical quantities, in particular for constantly repeating individual processes, is applicable, for example, to positioning processes of mechanical objects with regard to the path or angle in the precision apparatus technique. By applying the invention, a substantially shortening with the highest accuracy of positioning and thus an increase in the Arbeitproduktivitaet is to be made possible in almost overswinging setting the position by the control accuracy of the system is sufficiently large, so that the Stoergroessenabhaengigkeit is lowered and still the Ueberschwingneigung is low. The object is achieved by the fact that the control deviation in a position controller, the structure of which is shown in FIG. 3, is increased non-linearly as a function of the amplitude of the control deviation, and at the same time the phase deviation of the system deviation is corrected non-linearly in the position controller. For small control deviations greater amplification than for large shelves and for small deviations, a frequency-dependent phase advance of 90 degrees and more is generated while maintaining the amplitude.-Fig.1-

Description

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Field of application of the invention;

The invention relates to a method for fast, highly accurate, regulated adjustment of physical variables, especially in constantly repetitive adjustment operations, called in further positioning.

The invention is applicable, for example, in positioning operations of mechanical objects with respect to path or angle in the precision device technology.

Characteristic of the known technical solutions: A large number of controlled positioning systems are known in which a predetermined position is approached by the use of incremental position dividers (stepper motors) or other motor drives with defined control functions. Furthermore, there are a variety of controlled positioning, in which the measured value of the position is fed back to the actuator via a regulator. Furthermore, solutions for high-precision positioning are known in which in the vicinity of the position value to be reached a switch from coarse to Peintrieb (change gear, special actuator control, 2 actuators or the like) takes place. This changeover serves to expand the control range of the control system, to achieve a greater resolution and to allow the position of the position to be adjusted as far as possible without the need for supervision. Controlled positioning is unsuitable for highest accuracy requirements because

- there would be extreme demands on the manufacturing tolerances of the components;

the accuracy of the changeover affects the accuracy of the positioning; ·

- Disturbance variables occur with statistical properties, (temperature changes, fluctuations of the frictional forces, mechanical shocks such as shocks, building vibrations »unevenly running gears and others), which are no longer determinable detected and therefore can not be taken into account in a controller.

The analysis of controlled positioning shows that the application of switching arrangements is inappropriate because

- In the immediate vicinity of the position, the gain is reduced by the switching to Peintrieb, which degrades the stabilizing effect of the controller and increases the Störsabhängigkeit of the system; - The positioning time of the system is increased, although 'of course, the reduction of the gain leads to a reduction of the overshoot tendency of the system.

Object of the invention:

The aim of the invention is, with almost overshoot-free setting of the position a significant reduction of the positioning time with the highest accuracy of positioning and. thereby enabling an increase in labor productivity.

The object of the invention is to develop a method in which the control accuracy of the system is sufficiently large so that the Störgrößenabhängigkeit is lowered and still the overshoot tendency is low.

The object is achieved by a method for fast, highly accurate, regulated positioning, in which the physical quantity to be set is changed via a positioning system with a large modulation range and the signals required for positioning are obtained via a measuring system.

According to the invention, the control deviation in a position controller is dependent on its amplitude.

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linearly amplified and corrected simultaneously in the position controller, the phase angle of the control deviation nonlinear. Furthermore, with small control deviations, the position controller additionally receives feedback signals which are obtained directly from the object or from the measuring system. For small deviations, a greater gain than for large shelves and a frequency-dependent phase advance of 90 ° and more are to be generated while maintaining the amplitude.

10. As a control system with a large Auesteuerbereich actuators are used with internal feedback, so that a coarse fine switching is not required. Furthermore, it is stated that the dynamic properties of the object to be adjusted are known or measurable and time-invariant within certain limits and that a measuring system with the required resolution and accuracy (depending on the specific task also relative accuracy) and the necessary long-term stability is present with which can be measured dynamically.

Embodiment:

In the following the invention will be explained with reference to an embodiment. In the accompanying drawing show

1 shows the basic structure of a high-precision positioning

systems ·

Fig. 2a u. 2b den.Frequenzgang of the object to be controlled • Fig. 3 shows the structure of the position controller • Fig. 4a and. 4b the frequency response of the open. Control circuit with non-linear position controller.

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FIG. 1 shows in a block diagram the structure of a fast high-precision positron system, which relates to an example of the highly accurate controlled positioning of mechanical objects. A mechanical object 5 is moved by way of a drive system which consists of an amplifier 1 and a drive motor 2 as well as of a tachometer 3 located in the feedback branch with a downstream drive controller 4. The position in which the object 5 is located in each case is determined by means of a measuring system 6, and from the actual position x (t) and the position command value χ · the control deviation £ formed.

In a Beschleunigungsmeßsysteni 7 are temporal derivatives of. Movement size of the mechanical object 5 is determined, which is necessary for the optimization of the control s ind.

The temporal derivative of Bewegungsgrb'ße is next to the control deviation £ a position controller 8 fed «For moving the object 5, a ball-bearing measuring slide is provided, which rolls on a vibration-isolated base bed. The range of movement is 250 mm, the required positioning accuracy + 0.1 / μm and the required positioning time for the transition from any position to a new position 1a 'located at a distance of 10 mm.

The measuring slide is driven by a ball discharge spindle whose nut is connected to the measuring slide via a gimbal coupling. The drive (motor tachometer group) is attached to the spindle via a single-stage, loose gearbox. The mechanical design, which was realized in compliance with the dynamic requirements, shows a pronounced resonance point at 30 Hz with very low damping, which results from the slide dimensions in correspondence with the spring properties of the gimbal bearings. Other resonance points are above 100 Hz.

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-s 209 419

The motor circuit with tacho feedback is designed so that for input voltages at the amplifier of 1.5 mV ... 7 ₅ 5 V the speed depends linearly on the input voltage. Maximum speed about 5000 rpm, minima! Speed about 1 rpm. With a gear reduction ratio of 1: 25 and a spindle increase of 5 mm / rev, carriage speeds of 3 »3 / um / s ... 17 mm / s can be linearly controlled and paths of less than 50 nm can be resolved

 The cut-off frequency of the drive is above 80 Hz. The mechanical object 5 with drive can be described by neglecting nonlinear effects caused by friction and residual effects by the following transfer function:

ν / ( _Ό ) '- x (p) ^χ ϊ change of direction in mm ° U (p) Uj input voltage in V

_oR (p) (Eq: 1) ·

pT (1 + pT _A ) (1 + 2D ₀ T ₀ .p + T ^)

T integration time constant 270 ms

T. Time constant drive with load 4.6 ms T Time constant of the resonant element 5.3 ms D Damping of the resonant element .0.1 K Dimension factor 1 mm / V

W _o pCp) contains further resonance points and time constants

in the range above 100 Hz, for basic considerations, the approximation V / u (p) = 1 is permissible.

The vibration-isolated basic bed shows resonance behavior at 0.5 Hz in the x-direction: this resonance point is excited by the carriage movement and, in the uncontrolled state, causes interference amplitudes of 20 / Um at 0.5 Hz on the slide. For such Störamplituden can be compensated, the loop gain at 0.5 Hz must be greater than 200

 As measuring system 6 is a Laserwegmeßsystem with a

'35 resolution of 40 nm used. The time constants of the

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Measuring system 6 and its dead time are far outside the frequency range of interest.

FIGS. 2a and 2b show the frequency response for the complete object 5 to be controlled taking into account equation 1. It can be seen from the amplitude response in Fig. 2a and the phase response in Fig. 2b that with a P-controller and dynamic correction, the system does not meet the desired parameters.

FIG. 3 shows the structure of the position controller 8.

In addition to the displacement signal x (t), the acceleration α ~ ^ 1 ± Σ ^{on the} measuring slide is measured directly and. parallel ver

'dt ² '.

is working. The current actual value of the position x (t), which is present as a dynamic counter reading of the measuring system 6, is subtracted from the setpoint value x ', the error signal 5, applied in digital form. (t) is processed separately according to amount and sign. By way of a logical coupling of a DA converter 9, the gain change is realized in the example in such a way that for small desired actual value differences

and for large setpoint-actual value differences

The switching point £ is about 10yum.

The signal £ is fed via an analog amplifier 10 with adjustable gain V _R1 f » 2 (amplitude channel) to a switch 11, in which it receives the sign that in a zero discriminator 12 from the sum formed in the transfer member 13 of the" signed in the switch 14 _Error signal £ _Qn and 'his.durcbi .. Mff generate derivative. 2B ()

T "- 2B ~ * - is determined (phase channel).

illJi

-T-

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A switched-off linear filter 15 with low-pass characteristics T _Ko = 190 ms, T ^ _{= 1β mB ### 50 ma (a} .

adjustable) leads to an additional reduction of the amplitude response in the range of 0.8 ... 10Hz. The acceleration feedback via the amplifier 16 acts as a damping of the resonance parts.

4a and 4b show the frequency response of the open loop with non-linear position controller, curves 1 for small nominal Istvvertdifferenzen, curves 2 for large shelves.

By changing the switching point and the gain V ^ ₁ can si-ch the 'transient response in the large, by changing the time constant Tj, the transient response to optimize immediately by the target position.

Claims (4)

- 6 - & \ jr ν -ν ι τ? Claim for invention 1. A method for fast, highly accurate, controlled adjustment of physical quantities, in which the physical size is changed via a control system with a large modulation range and the measurement required for adjusting actual value.e won, especially for fast, highly accurate, controlled positioning mechanical Objects, characterized in that the. Control deviation in a position controller depending on its amplitude nonlinear amplified , and at the same time in the position controller, the phase angle of the control deviation is non-linearly corrected. 2. The method according to item 1, d.ä characterized in that at small control deviations in addition to the position controller · feedback signals are fed, which are obtained directly from the object or from the measuring system. 3. The method according to item 1, characterized in that with small control deviations a greater gain than in large shelves. 4 · Method according Pkt «1, characterized in that at small deviations a frequency-dependent phase advance of 90 ° and r.
Amplitude is generated. Advance of 90 ° and more while maintaining the Dazu._fjLi_Seiten Zeidinunqen