DD140391B1 - PROCESS FOR CONTROLLING PHYSICAL SIZES - Google Patents

Description

Field of application of the invention:

The invention relates to a position controller for fast, highly accurate, controlled adjustment of physical variables, especially in constantly repetitive one-Stellvorgängen, 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 controllers (stepper motors) or other motorized 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 achieved, a switch from coarse to fine drive (change gear, special actuator control, 2 actuators, etc.) takes place. This changeover serves to extend the control range of the positioning system, to achieve a greater resolution and to allow the position to be adjusted as free of overshoot as possible. A controlled positioning is unsuitable for the highest precision

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

3378

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

- Disturbance variables with statistical properties occur (temperature changes, fluctuations of the frictional forces, mechanical shocks such as shocks, building vibrations, irregular running gear u.a.), Which are no longer determinable detected and therefore at a. Control can not be taken into account ·

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 switch to fine drive, which degrades the stabilizing effect of the regulator and increases the Störgrößenabhäng ¹ } e;

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 to allow a substantially shortening of the Positionierzweit with the highest accuracy of positioning and thus an increase in labor productivity with virtually overshoot-free setting of the position ·

Explanation of the essence of the invention;

The object of the invention is to develop a position controller, in which the control accuracy of the system is sufficiently large, so that the Störgrößenabhängigkeit is lowered and yet the tendency to overshoot is low · The task is solved by a position controller for fast, highly accurate, controlled positioning, at the physical quantity to be set is changed by means of a control system with a large control range, and the signals required for positioning are obtained via a measuring system.

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

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

As Stellellsystera with a large modulation range actuators are used with internal feedback, so that a coarse fine switching is not required. Furthermore, it is enforced 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 and relative accuracy) and the necessary long-term stability is present with which can be measured dynamically.

Ausführungsbeiapiel:

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

Fig. 1 shows the basic structure of a Hochgenauigkeitspositioniersystems

Fig. 2a u. 2b shows the frequency response of the object to be controlled FIG. 3 shows the construction of the position regulator FIG. 4a and FIG. 4b the frequency response of the open loop with non-linear position controller.

Figure 1 shows in block diagram the structure of a high speed, high accuracy positioning system, which looks at an example of highly accurate controlled positioning of mechanical objects. A mechanical object 5 is moved by way of a drive system which comprises an amplifier 1 and a drive motor 2 and also a speedometer 3 located in the feedback path 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. formed from the actual position value x (t) and the position setpoint χ the control deviation £ .

In an acceleration measuring system 7 time derivatives of the amount of movement of the mechanical object 5 are determined, which are required for the optimization of the control.

The time 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 movement range is 250 mm, the required positioning accuracy + 0.1 / um and the required positioning time for the transition from any position to a new position 1 s 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 cardan joint. 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 mass in combination with the spring properties of the gimbal bearings. Other resonance points are above 100 Hz.

The motor scale with tacho-click coupling is designed so that for input voltages at the amplifier of 1.5 mV ... 7.5 V, the speed depends linearly on the input voltage. Maximum speed approx. 5000 rpm, minimum speed approx. 1 rpm. With a gear reduction ratio of 1: 25 and a spindle increase of 5 mm / rev, carriage speeds of 3 »3 / ura / 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:

W (p) = ^χ ( ^ρ ) ^Χί Change in direction in mm ° U (p) U: Input voltage in V

W ₀ Cp) = - -. W _oR (p) (Eq: 1)

pT (1 + pT _A ) (i + 2D _o T _o p + Tjp ^)

T Integration time constant 270 тэ Тд Time constant drive with load 4 »6 ms T Time constant of the resonance element 5.3 ms D Resonance element damping 0.1 K Dimension factor 1 mm / V

W p (p) contains further resonance points and time constants in the range above 100 Hz, for fundamental considerations

the approximation ^w _oR (p) = 1 is permissible. The vibration-isolated basic bed shows resonance behavior at O ₁ S Hz in the x-direction

 This resonance point is excited by the carriage movement and causes in the unregulated state noise 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, a Laserwegmeßaystem is used with a resolution of 40 nm. The time constants of the

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

FIGS. 2a and 2b show the frequency response for the complete, regulating object 5, taking equation 1 into account. It is apparent 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.

Figure 3 shows the structure of the position controller 8. In addition to the path signal x (t), the acceleration dx (t) is measured directly on the measuring slide and parallel ver dt. ²

is working. The current actual value of the position x (t), which is present as a dynamic counter reading, the measuring system 6, is subtracted from the setpoint x _Q , the applied in digital form error signal f ,. (t) is separated by amount

S and signed signs. By way of a logical coupling of an .OA converter 9, the amplification change is realized in the example in such a way that, for low nominal actual value diffusers

16HlS ₀ I «/ as .5SZ, _d . _h . ₁₂₅

£ ⁰

1bit and for large © Setpoint-actual value differences

The switching point S is approx. 10 / um.

The signal £ "" is supplied via an analog amplifier 10 with

adjustable gain V _R1 2 »2 (amplitude channel) supplied to a Umechalter 11 in which ea daa sign receives, in a zero discriminator 12 from the sum formed in the transfer element 13 of the sign correct error signal formed in the switch 14 _gn and. his, dure ^ differentiate generated derivative

£ ". 2 pounds is determined (phase channel).

^Ж dt

A naktageschaltetes linearst filter 15 with Tiefpaßeigenschaften T _Ro = 190 ms, T _{R1 = 16 mg ### 50 ma (ein} .

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

Pig. 4a and 4b show the frequency response of the open loop with non-linear position controller, curves 1 for small setpoint-actual value differences, curves 2 for size trays.

By changing the switching point and the gain V _R1 can be the transient response in the large, by changing the time constant Ty. to optimize the transient response immediately around the nominal position.

Claims (1)

-δ- invention claim Position controller for fast, highly accurate adjustment of physical quantities, in particular for positioning mechanical objects, in which the error signals generated by a measuring system via a setpoint-actual value comparison, via an amplifier stage and in parallel via a non-linear phase correction stage of a switching stage for generating a manipulated variable for a control system with a large drive range are supplied, the amount of which depends exclusively on the degree of amplification of the error signal and whose sign is determined by the phase correction stage, characterized by a correction element with non-linear transfer characteristic in the amplifier stage. For this .. Jf .. pages drawings