Ultraprecise in-situ measurement device and ultraprecise processing method based on flexible probe
Technical field
The invention belongs to optical measurement and processing technique field, relate to a kind of original position ultra precise measurement device that is applicable to super-precision machine tools.
Background technology
The complex-curved ultraprecise processing of nanoscale is the field, forward position of advanced manufacturing technology, it is one of core support technology of modern high technology product key components and parts manufacturing, in Application for Field such as Aero-Space, national defence, new forms of energy, communication, microelectronics, photoelectron, medical treatment more and more widely, greatly improve the working (machining) efficiency of Primary Component, become the embodiment of national national economy, national defence and a scientific and technical comprehensive strength.At present, the types of applications field also proposes requirements at the higher level gradually to the complex-curved machining accuracy of nanoscale, and therefore, the complex-curved manufacturing of high accuracy nanoscale is the main task of present ultraprecise manufacture field.Except considering from processing method the raising of surface figure accuracy, rely on Error Compensation Technology progressively to improve the surface figure accuracy step that is absolutely necessary, wherein it is highly important that the means that data are obtained, i.e. ultra precise measurement technology.Existing measuring technique all exist the scanning range little, measure that face shape is simple relatively, the shortcoming of off-line measurement, work in-process can be introduced secondary clamping and position error, also hindered simultaneously the integrated automation of processing, measurement and compensation process, therefore, become the focus of research based on the nano-precision in-situ measurement system of ultra-precision machine tool.Measuring method has fast, the non-invasive advantage of speed, but because of the optical texture complexity, system architecture is difficult for miniaturization, be difficult in the ultra-precision machine tool confined space, realize the original position placement, and also be the major reason that influences its original positionization.Be subjected to the restriction of the numerical aperture and the field range of optical system simultaneously, this optical non-contact method is not suitable for the measurement of deep camber face shape.Therefore, design can be carried out optics in-situ measurement system that deep camber measures and has very that important use is worth.
Summary of the invention
The objective of the invention is to overcome the above-mentioned deficiency of prior art, propose a kind of gauge head structure of can the auxiliary optical measuring system carrying out in site measurement.The present invention can prolong and reduce optical measuring system by the proposition and the design of flexible probe, and realizes the measurement of deep camber face shape by the Flexible Control of gauge head, thereby solves an optical measuring system original positionization and a deep camber surface shape measurement difficult problem.The present invention adopts following technical scheme:
A kind of ultraprecise in-situ measurement device based on flexible probe, it is characterized in that, described measurement mechanism comprises flexible probe, image transmission optical fibre, couples mirror, high-accuracy turntable and optical three-dimensional measurement system, described flexible probe is placed on the high-accuracy turntable, it is centered close on the axis of rotating shaft of turntable, the tested surface image that flexible probe is gathered, successively by image transmission optical fibre, couple mirror and be transferred into the optical three-dimensional measurement system.
The present invention also provides a kind of ultraprecise processing method that adopts described measurement mechanism to realize simultaneously, comprises the following steps:
(1) set up the XYZ machining coordinate system of system of processing, making the turntable rotating shaft be parallel to machining coordinate is X-axis, and the assembling flexible probe, make its by by image transmission optical fibre, couple mirror and link to each other with the optical three-dimensional measurement system;
(2) demarcate flexible probe, determine gauge head end face and rotating shaft axis apart from d;
(3) required processing work is carried out roughing and ultraprecise processing;
(4) anglec of rotation of establishing by flexible probe is θ, moves the directions X deviation delta X that determines cutter and gauge head with the location of lathe, carries out in site measurement, and the measurement data points of the finished surface that is directly obtained by flexible probe is (x
1, y, z
1), then this absolute machining coordinate in the XYZ coordinate system of system of processing is (dcos θ+x1+ Δ X, y, dsin θ+z
1);
(5) the absolute machining coordinate point of finished surface face shape model data direct and institute's processing work is compared, obtain its machined surface shape error information;
(6) carry out machining path correction and compensation processing according to the face shape error data, in site measurement and compensation processing by repeatedly realize the ultraprecise processing of controlled shape of workpiece.
As preferred implementation, the installation step of the flexible probe of mentioning in (1) step is:
(1) design couples mirror, connects image transmission optical fibre and measuring system, at the fixing object lens of the optical fiber other end, with as flexible probe;
(2) high-accuracy turntable is fixed on the rigid platfor, rigid platfor is fixed on the machining tool, and with high-accuracy turntable and processing knife rest and the parallel placement of cutter;
(3) flexible probe is fixed in high-accuracy turntable by anchor clamps, adjustment makes on its axis that is centered close to the turntable rotating shaft;
(4) with the processing plane of machining tool as datum plane, the position of adjusting cutter and flexible probe is aligning on Y direction and the Z direction at machining coordinate.
In addition, the flexible probe demarcating steps in (2) step is: adopt the flexible probe that assembles that the cross central line of standard concave spherical crown is measured, then all measurement point (x that directly obtained by flexible probe
1, z
1) all with axis direction, anglec of rotation θ and lathe respective coordinates (x
0, z
0) relevant, and satisfy spherical equation, the spherical equation group of utilizing measurement point to set up, by the optimization computation method determine gauge head end face and rotating shaft axis apart from d.
The present invention has following characteristics: (1) flexible probe can prolong original measuring system, and miniaturization, is easy to realize in site measurement, guarantees the off-line measurement ability of original measuring system simultaneously; (2) flexible probe can be realized the measurement of deep camber face shape by rotation control, breaks through optical measuring system face shape curvature measurement restriction; (3) flexible probe is not limited on the super precision lathe and uses, and can also be applied in other ultraprecise processing methods; (4) flexible probe also is not limited to a certain measuring method, every application that all can realize flexible probe based on the method for optical measurement by this idea; (5) flexible probe can be applied in the system of processing in site measurement of other precision, and also can be applied to other needs the miniaturization measuring system, but measuring system own is difficult in other application of miniaturization.
Description of drawings
Fig. 1 is based on the structural representation of flexible probe measurement mechanism;
Fig. 2 flexible measuring schematic diagram;
Fig. 3 rotates the control schematic diagram;
Fig. 4 system calibrating schematic diagram.
Description of reference numerals is as follows: 1 flexible probe; 2 high-accuracy turntables; 3 image transmission optical fibres; 4 couple mirror; 5 optical three-dimensional measurement systems; 6 super precision lathes; 7 diamond cutters.
The specific embodiment
The present invention will be further described below in conjunction with drawings and Examples.
The present invention proposes a kind of can directly being placed on the super-precision machine tools, realize the flexible probe of the in site measurement on deep camber surface.The measurement mechanism that has assembled this flexible probe comprises: flexible probe, image transmission optical fibre, couple mirror, optical three-dimensional measurement system, high-accuracy turntable.The structure that its in site measurement is used as shown in Figure 1.
The optical measurement of gauge head connects image transmission optical fibre by coupling mirror, realizes tested IMAQ by the object lens of the other end.Light can conduct to required light illumination the measured object surface, transmits simultaneously by the measurement image of tested object plane shape modulation, and gauge head obtains image, realizes and directly gather the measurement of image.This structural equivalents prolongs original optical measuring system, and the small-sized object lens that turn to optical fiber, is called gauge head.This gauge head has the little characteristics of volume, is positioned on the super-precision machine tools than original measuring system is easier, realizes in site measurement.
Owing to many-sided influences such as the numerical aperture that is subjected to optical measuring system, measuring distances, the scope of its measurement also is subjected to certain restriction, especially is difficult to the measurement of competent deep camber face shape.Here select a kind of flexible optical fibre, increase the free degree of gauge head, realize face shape tracking measurement, and then realize the deep camber surface shape measurement.Gauge head can carry out the angle rotation according to the curvature of tested surface shape, realizes the adjustment of gauge head direction of measurement, keeps gauge head to be approximately perpendicular to tested zone, realizes the measurement of deep camber face shape, as shown in Figure 2.Because optical fiber carries out Flexible Control in this process, therefore, the present invention claims that this gauge head is a flexible probe.As shown in Figure 3, XYZ coordinate is a machining coordinate system.The angle adjustment of flexible probe relies on high-accuracy turntable to realize, according to the possible curvature direction of tested surface, need carry out the rotation control of two aspects, that is: the vertical reclining (it is X-axis that rotating shaft is parallel to machining coordinate) of horizontal nutation of flexible probe (it is Y-axis that rotating shaft is parallel to machining coordinate) and flexible probe.In order to control conveniently, in compliance control, only horizontal nutation is wherein carried out turntable control, finish by high-accuracy turntable.And,, can avoid the debugging and the control difficulty of two turntables like this because the nearer numerical aperture of flexible probe that relies on of measuring distance contains for the normal vector of vertical reclining.It is the sciagraphy mistake on XZ plane at machining coordinate that the method mistake direction of the control turntable of this method is modified to the mistake of tested surface method by the mistake of tested surface method.
During measurement, flexible probe of the present invention is applied on the super precision lathe, the optical measuring system of application is based on the laser auto focusing measuring method, by the design of spiral measuring route with is connected the realization flexible measuring with numerical control of machine tools.Prove this method practical by experiment, can realize the in site measurement of optical measuring system.Concrete measuring process is as follows:
(1) flexible probe assembling.Couple the design of mirror at the optical characteristics of selected optical three-dimensional measurement system, make it to connect the object lens of image transmission optical fibre and measuring system, the image transmission optical fibre other end connects measures object lens.The design that couples mirror and optical fiber object lens need guarantee to measure conditional requests such as required numerical aperture and measuring distance.Precise rotating platform is fixed on the rigid platfor, and with the turret systems overall fixed on machining tool, and with processing knife rest and the parallel placement of cutter, as shown in Figure 1, according to the workpiece to be machined caliber size, the distance of turntable and knife rest is adjusted accordingly, to guarantee that processing causes interference to turntable to reality in process.The object lens of flexible probe are fixed on the precise rotating platform by particular jig, it are centered close on the turret axis by laser interferometer test adjustment.Machining is carried out on the plane, with the plane as datum plane, the position of adjusting cutter and flexible probe is aligning on Y direction and the Z direction at machining coordinate, move the directions X deviation delta X that determines cutter and gauge head with the location of lathe, with the unification that guarantees that machining coordinate system and flexible probe are measured coordinate system.
(2) the Flexible Control turntable is demarcated.In the process of flexible measuring, be unusual important step to the demarcation of the position of gauge head and turntable rotating shaft relation, be exactly specifically definite gauge head end face and turret axis apart from d.After carrying out the flexible probe assembling and adjusting, Fig. 3 intermediate station rotating shaft n
1(Δ X, 0, d) variable in can be determined, wherein d is a unknown quantity, need be that scaling method is demarcated by Fig. 4, promptly two mutually perpendicular center lines to the bigger known recessed spherical crown of curvature carry out in site measurement, and the radius of spherical crown is R, the spherical crown surface figure accuracy is higher, general PV value (this required precision can be adjusted accordingly according to required certainty of measurement) below 100nm.Only the cross central line of recessed spherical crown is measured and to be realized the rotor shaft direction demarcation.To the measurement of horizontal axial line, only can finish to displacement, according to all measurement point (x of measuring principle by the rotation of turntable 1 and the x and the z of lathe itself
1, z
1) all with axis direction, anglec of rotation θ and lathe respective coordinates (x
0, z
0) relevant, can be expressed as,
All measurement points satisfy spherical equation, can carry out wherein finding the solution of unknown parameter d by the optimization computation method.
(3) after carrying out above setting and demarcating, all system's unknown quantitys are all definite, can utilize in site measurement institute's finished surface to be carried out the ultraprecise processing of controlled shape.The steps include: earlier required processing work to be carried out ultraprecise roughing and fine finishining, carry out in site measurement according to machining path then.Measurement data points (the x that directly obtains by flexible probe
1, y, z1), needing earlier, the calculating of process turntable rotation amount transfers interim measurement data point (dcos θ+x1, y, dsin θ+z to
1), ask for absolute machining coordinate (dcos θ+x1+ Δ X, y, the dsin θ+z of finished surface then to side-play amount according to the X of rotating shaft
1), these data are transformed into machining coordinate system fully, can be directly and the face shape model data of institute's processing work compare, obtain its machined surface shape error information, thereby correctly estimate face shape error.Carry out machining path correction and compensation processing according to face shape evaluation result, in site measurement and compensation processing by repeatedly realize the ultraprecise processing of controlled shape of workpiece.