CN104898413A - Large-stroke high-resolution driver system - Google Patents

Abstract

The invention discloses a large-stroke high-resolution driver system, which is composed of a mechanical driving part, a data acquisition part and a computer control part, wherein the mechanical driving part comprises components such as a servo motor, the servo motor is fixed with a motor support, the output shaft of the servo motor is connected with a ball screw via a coupling, the ball screw passes through a bearing set, a screw nut is fixed with one end of a nut sleeve, the other end of the nut sleeve is fixed with an angle bar, the angle bar is fixed on a sliding table assembly, one side of the angle bar is provided with a top rod, and rotation movement of the servo motor can be converted into linear movement of the top rod finally; the data acquisition part comprises a dual-frequency laser interferometer and a data acquisition card AD interface mutually connected; and the computer control part comprises an industrial computer and a data acquisition card DA interface mutually connected. The movement range is large, and 100nm resolution can be realized through an initially-built experimental platform.

Description

Long Distances high resolving power drive system

Technical field

The present invention relates to a kind of drive system, especially relate to a kind of base Long Distances high resolving power drive system.

Background technology

In the research field such as astrophysics and High Power Laser Pulses, the demand of heavy-caliber optical grating is more and more higher.But, utilize optical grating graduating machine or holography method to be all difficult to obtain bigbore diffraction grating.Two pieces or above little grating are formed large grating by current employing connecting method, and by mechanical method of adjustment minimizing phasic difference to each other, have become the important method obtaining heavy-caliber optical grating both at home and abroad.And in the process, how to improve the positioning precision driving adjustment, make the resolution of driving when finely tuning can reach 20nm-100nm, setting range can reach grade simultaneously, has become the important research content of wherein.

Both at home and abroad be designed with a lot for high resolving power driver on a large scale, wherein applying maximum is the form that piezoelectric ceramics adds ball screw, but because piezoelectric ceramics stroke is little and there is non-linear, sluggish and creep, and grand micro-two-stage drive mode need be adopted, make cost and control difficulty greatly to increase; High-precision linear electric motors cost is high, and control system is complicated; The factor that the telescopic driving of novel magnetic hysteresis exists the impact such as electromagnetic exposure and heating location exists.And in the design of control system, due to the existence of friction, making driver there is obvious difference grand moving with fine motion field, new control theory, as neural network and fuzzy control, does not show especially significantly advantage when solving practical problems.

Summary of the invention

In view of the above-mentioned problem mentioned, the present invention proposes a kind of Long Distances high resolving power drive system, it adds servomotor based on ball screw and carries out accurate positioning control based on two-frequency laser interferometer, for realizing the high-precision drived control on a large scale.

The present invention is that to solve the problems of the technologies described above the technical scheme of employing as follows: a kind of Long Distances high resolving power drive system, it is characterized in that, it is by Mechanical Driven part, part of data acquisition and computing machine control section three part composition, Mechanical Driven part comprises servomotor, motor support base, shaft coupling, bearing seat, ball screw, feed screw nut, nut sleeve, gusset, slide unit assembly, servomotor and motor support base are fixed, the output shaft of servomotor is connected with ball screw by shaft coupling, ball screw is through bearing seat, one end of feed screw nut and nut sleeve is fixed together, the other end and the gusset of nut sleeve are fixed together, gusset is fixed on above slide unit assembly, the side of gusset is provided with push rod, the rotary motion of servomotor finally can be converted to the rectilinear motion of push rod, part of data acquisition comprises interconnective two-frequency laser interferometer and data collecting card AD mouth, and computing machine control section comprises interconnective industrial computer and data collecting card DA mouth.

Further, the analog signals that described part of data acquisition collects, being converted to digital quantity by data collecting card AD mouth is input in industrial computer, at industrial computer according to the displacement detected, calculate the controlled quentity controlled variable size of servomotor again, and complete the output control of servomotor by data collecting card DA mouth.

Further, the mathematical model of described Long Distances high resolving power drive system tested by System Discrimination the transport function that obtains identification for as shown in the formula:

$G\left(s\right)=\frac{X\left(s\right)}{U\left(s\right)}=\frac{247.6}{s(s+120.5)}.$

Compared with prior art, the present invention has following beneficial effect: one, and the moving range of the driver that the present invention proposes can arrive 10mm, and combined high precision sensor can realize the accurate location in Long Distances.Two, cost performance is high, and motion rigidity is better.Three, by the optimization of control algolithm, the resolution of driving conveniently can be improved, and without the need to changing the hardware configuration of driver.

Accompanying drawing explanation

Fig. 1 is the structural representation of the Mechanical Driven part of Long Distances high resolving power drive system of the present invention.

Fig. 2 is the schematic diagram of the pure mathematics model of driver.

Fig. 3 is that the entirety of system controls schematic diagram.

Fig. 4 is the schematic diagram of the basic structure of the controller of design.

Fig. 5 is the schematic diagram of the 1mm step response experimental result of driver.

Fig. 6 is the schematic diagram of 20 μm of step response results of driver.

Fig. 7 is the schematic diagram of the 100nm step response result of driver.

Embodiment

It is as follows that the present invention specifically implements accompanying drawings:

The structure of the Long Distances high resolving power drive system in this embodiment is see Fig. 1.The Mechanical Driven part of Long Distances high resolving power drive system of the present invention comprises servomotor 1, motor support base 2, shaft coupling 3, bearing seat 4, ball screw 5, feed screw nut 6, nut sleeve 7, gusset 8, slide unit assembly 10, servomotor 1 is fixed with motor support base 2, the output shaft of servomotor 1 is connected with ball screw 5 by shaft coupling 3, ball screw 5 is through bearing seat 4, feed screw nut 6 is fixed together with one end of nut sleeve 7, the other end and the gusset 8 of nut sleeve 7 are fixed together, and gusset 8 is fixed on above slide unit assembly 10, the side of gusset 8 is provided with push rod 9, the rotary motion of servomotor finally can be converted to the rectilinear motion of push rod.The screw pair assembly of ball screw is installed on slide unit assembly by gusset, for ensureing the straight-line guidance effect exported, realizes final actuation movement by push rod.

The pure mathematics model of the driver in this embodiment as shown in Figure 2, wherein exports control voltage V, is converted into servomotor output torque T _app, and driving servomotor to rotate, feed screw nut pair can be equivalent to a spring-damp system, and the feed screw nut pair that rotates through of final servomotor transforms the straight-line displacement X driven as push rod.Wherein the implication of each parameter representative is as shown in table 1:

Table 1

Symbol	Implication
		M	Slide unit quality
J	The moment of inertia of rotating part
		R m	Electric motor resistance
K i	Torque constant
		K v	Back electromotive force constant
C sd	Rotary damping
		K n	Elasticity coefficient between feed screw nut
C n	Ratio of damping between feed screw nut
		h	Transmit ratio
G m	Servo enlargement factor

Entirety in this example controls schematic diagram as shown in Figure 3, Long Distances high resolving power drive system of the present invention is by Mechanical Driven part, part of data acquisition and computing machine control section three part composition, part of data acquisition comprises interconnective two-frequency laser interferometer and data collecting card AD mouth, computing machine control section comprises interconnective industrial computer and data collecting card DA mouth, two-frequency laser interferometer is fixed on the linear drives direction of Mechanical Driven part, its laser beam of launching is returned by the reflecting prism 11 be arranged on gusset, and on spectroscope, produce interference fringe with incident beam, and exported by the analog output mouth of two-frequency laser interferometer.Position wherein in order to realize driver tip is detected, use the two-frequency laser interferometer with nanometer resolution as position feedback element, the laser that two-frequency laser interferometer sends is reflected by the reflecting prism be installed in driver physical construction and forms interference fringe, and then is converted to analog output under the effect of internal processor.The analog signals that part of data acquisition collects, being converted to digital quantity by the AD passage (i.e. data collecting card AD mouth) of data collecting card is input in industrial computer, at industrial computer according to the displacement detected, calculate the controlled quentity controlled variable size of servomotor again, and complete the output control of servomotor by the DA passage (i.e. data collecting card DA mouth) of data collecting card.

In order to obtain the mathematical model of Long Distances high resolving power drive system of the present invention, obtain control voltage U to driver displacement X between transport function, namely the present invention can by System Discrimination test obtain identification transport function be such as formula (1):

$G\left(s\right)=\frac{X\left(s\right)}{U\left(s\right)}=\frac{247.6}{s(s+120.5)}...\left(1\right)$

Wherein G (s) is the expression-form of transport function Laplace transformation, and X (s) represents the Laplace transformation of drive system displacement, and U (s) represents the Laplace transformation of control voltage.

In order to test the performance of this driver, the present invention devises the controller of a PID, and realize the Control release of step output signal, as shown in Figure 4, it comprises proportional component K to controller architecture _p, integral element and differentiation element three parts, simultaneously in order to suppress the interference of high-frequency signal, with the addition of a first order inertial loop composition low-pass filter in differentiation element.

Wherein the selection of three parameters of PID controller is tried to achieve by zero-pole assignment method, and concrete computation process is as follows:

If the transport function of servo-driver is such as formula (2):

$G_p\left(s\right)=\frac{d}{s(s+c)}...\left(2\right)$

Reference formula (1) is known, d=247.6, c=120.5.

Closed loop transfer function, T (s) of ball screw positioning system is write as such as formula (3):

$T\left(s\right)=\frac{G_c\left(s\right)G_p\left(s\right)}{1+G_c\left(s\right)G_p\left(s\right)}=\frac{K_{p}d[(\frac{T_d}{T_f}+1)s^2+(\frac{1}{T_i}+\frac{1}{T_f})s+\frac{1}{T_i{T}_f}]}{s^4+(c+\frac{1}{T_i{T}_f})s^3+[K_{p}d(\frac{T_d}{T_f}+1)+\frac{1}{T_i{T}_f}c]s^2+K_{p}d[\frac{1}{T_i}+\frac{1}{T_f}]s+K_{p}d\frac{1}{T_i{T}_f}}...\left(3\right)$

Wherein Kp is scale-up factor, and Ti is integration time constant, and Td is derivative time constant, and Tf is the coefficient of wave filter.

If be configured to multiplicity of pole (-p, 0), then the expression formula (3) of closed-loop system transport function can be rewritten into such as formula (4):

$T\left(s\right)=\frac{G_k\left(s\right)}{{(s+p)}^4}...\left(4\right)$

Wherein p represents the value of multiplicity of pole, and after Gk (s) then represents the Laplace transformation after simplifying, expression formula divides subitem.

By the denominator in formula (4) and formula (3) denominator one_to_one corresponding, by four parameters in the known formula of solving equation (3), such as formula (5):

$\left\{\begin{array}{c}{K}_p=\frac{15p^4-4{\mathrm{cp}}^3}{d{(4p-c)}^2}\\ T_i=\frac{15p-4c}{4p^2-\mathrm{cp}}\\ T_d=\frac{81p^4-108{\mathrm{cp}}^3+54c^2{p}^2-12c^{3}p+c^4}{(15p^4-4{\mathrm{cp}}^3)(4p-c)}\\ T_f=\frac{1}{4p-c}\end{array}\right....\left(5\right)$

Thus by calculating four parameters can determining controller, and determine after finally contrasting by analysis in conjunction with actual experiment.

Further, the present invention chooses the position of different limit P, obtains the parameter of a series of different PID controller, as shown in table 2 below:

Table 2

p	K p	T i	T d	T f
					20π	26.94	0.0560	0.0014	0.0077
40π	76.92	0.0292	0.0041	0.0026

60π	157.94	0.0197	0.0039	0.0016
					80π	269.02	0.0148	0.0035	0.0011
100π	410.01	0.0119	0.0031	0.0008

The present invention carries out preliminary experimental verification by the Experimental Hardware platform built, and wherein the sample frequency of data collecting card is 1000Hz, and the saturation voltage of servomotor is 2V, and top speed is 130r/min.Revise according to during actual experiment, the value of closed-loop experiment PID controller is K _p=26.94, T _i=0.056, T _d=0.0014, T _f=0.0077.

In order to test the control performance of the PID controller of design, by needing the data after sampling to each sensor, calculate through the closed-loop control system shown in Fig. 4, the real-time calculating basis of driving voltage is such as formula (6):

$\left\{\begin{array}{c}{u}_p\left(k\right)=K_p*\mathrm{error}\left(k\right)\\ u_i\left(k\right)=\frac{K_p{T}_s}{T_i}\underset{i=0}{\overset{k}{\mathrm{\Σ}}}\frac{\mathrm{error}\left(k\right)+\mathrm{error}(k-1)}{2}\\ u_d\left(k\right)=\frac{T_f}{T_s+T_f}{u}_d(k-1)+K_p\frac{T_d}{T_s+T_f}(\mathrm{error}\left(k\right)-\mathrm{error}(k-1))\end{array}\right....\left(6\right)$

The output control voltage of controller is such as formula (7):

u(k)＝u _p(k)+u _i(k)+u _d(k).........(7)

Fig. 5, Fig. 6, Fig. 7 are respectively and carry out 1mm, 20um, the step response experimental result of 100nm, ± 50nm is all less than through calculating the corresponding steady-state error value of 100nm ~ 1mm step, the wherein step response of 1mm and 20 μm, it is fine that experiment and emulation coincide, and response is slightly slow because the impact that rubbed is comparatively large for the step response of 100nm.After system responses enters stable state, steady-state error is almost identical with the noise profile of measuring system, and does not have obvious overshoot, and regulating time is within 1s, the requirement of most of high-accuracy positioning control system can be met, be thus applicable among high-resolution Position servo control system.

Moving range of the present invention is comparatively large, can have been realized the resolution of 100nm, and the rigidity of structure is higher by the experiment porch tentatively built, and response speed is very fast, is applicable to require the high-resolution working environment of Long Distances.The present invention carries out Nano grade and tests to other step response of grade, the actuator response situation of the different moving range of comparative analysis, calculated by the steady-state error of driver tip position, find that the PID controller of employing incomplete differential can realize the accurate location in Long Distances moving range, and response speed is very fast, overshoot is very little.

Claims (3)

1. a Long Distances high resolving power drive system, it is characterized in that, it is by Mechanical Driven part, part of data acquisition and computing machine control section three part composition, Mechanical Driven part comprises servomotor, motor support base, shaft coupling, bearing seat, ball screw, feed screw nut, nut sleeve, gusset, slide unit assembly, servomotor and motor support base are fixed, the output shaft of servomotor is connected with ball screw by shaft coupling, ball screw is through bearing seat, one end of feed screw nut and nut sleeve is fixed together, the other end and the gusset of nut sleeve are fixed together, gusset is fixed on above slide unit assembly, the side of gusset is provided with push rod, the rotary motion of servomotor finally can be converted to the rectilinear motion of push rod, part of data acquisition comprises interconnective two-frequency laser interferometer and data collecting card AD mouth, and computing machine control section comprises interconnective industrial computer and data collecting card DA mouth.

2. Long Distances high resolving power drive system according to claim 1, it is characterized in that, the analog signals that described part of data acquisition collects, being converted to digital quantity by data collecting card AD mouth is input in industrial computer, at industrial computer according to the displacement detected, calculate the controlled quentity controlled variable size of servomotor again, and complete the output control of servomotor by data collecting card DA mouth.

3. Long Distances high resolving power drive system according to claim 1, is characterized in that, the mathematical model of described Long Distances high resolving power drive system tested by System Discrimination the transport function that obtains identification for as shown in the formula:

。