TWI759970B - Optical scale ball bar and measurement data processing method thereof - Google Patents

Abstract

The present disclosure provides an optical scale ball bar with an extra second readhead, including a first optical scale, a second optical scale, a first readhead and a second readhead. The first readhead reads the first optical scale and delivers a first measurement value including a first Abbe error, and the second readhead reads the second optical scale and delivers a second measurement value including a second Abbe error. The first Abbe error and the second Abbe error are related. The present disclosure also provides a method to process the first measurement value and the second measurement value according to the relation between the first Abbe error and the second Abbe error to eliminate the first Abbe error and to obtain a correct measurement value.

Description

Optical ruler club and its measurement value processing method

The present invention relates to an optical scale club and its measurement value processing method, and in particular, to an optical ruler club with double reading heads and its measurement value processing method.

The two ends of the ball shaft are provided with a ball bearing formed by a measuring ball and a ball socket, and a displacement sensor is provided to measure the distance between the ball centers of the two ends of the ball bearing (may be referred to as the center distance). Because the ball bearing has no rotational restraint, the ball shaft can rotate freely about the axis formed by the ball center of the two-end ball bearing, and there is an uncertain spin angle. The ball shaft in this manual can also be a ball bearing with a measuring ball at one end and a ball socket at one end, and other types of joints such as universal joints at the other end. When the club is used to measure the distance between two points in space, there is an included angle with the horizontal plane, which can be called the inclination angle. The measurement attitude of the club is determined by three factors: center distance, lean angle and spin angle.

Because the displacement sensor of the club is not completely ideal, there is a backlash between the linear guiding elements, the self-weight will cause the structure to deflect, and the environmental temperature change will cause the thermal deformation of the components, etc., resulting in the difference between the measured value of the club and the center distance. Without a simple linear relationship, measurement errors will occur.

Some practitioners use the optical ruler as a displacement sensor. This kind of club can be called an optical ruler club. The optical ruler club includes a ruler assembly and a read head assembly. The read head is fixed on the read head assembly, and the grating ruler is fixed on the ruler. On the assembly, the ruler assembly and the read head assembly are equipped with guiding elements, such as guide rods and bushings, so that the ruler assembly and the read head assembly can guide each other for linear movement, and the displacement sensing signal of the read head can be a wire or Send wirelessly. In this kind of optical scale club, there will be a measurement error when there is a backlash between the bushing and the guide rod. After investigating the cause of this error, it is found that the backlash between the bushing and the guide rod makes the read head relative to the grating ruler. They are no longer parallel, there is a deflection angle between the two, and the measuring point on the grating scale will be offset by the deflection angle, so that the read head senses additional displacement, resulting in a measurement error, which is the same as the read head to the grating The distance between feet is related to the deflection angle, so it can be classified as Abbe error.

In order to describe the movement of the optical scale club reading head relative to the grating scale, a grating scale coordinate system can be defined, which takes the center line of the grating scale surface as the X and _S axes, and the direction in which the center distance increases due to the movement of the grating scale relative to the reading head is the positive direction, the normal direction of the ruler surface is the positive Z _S axis direction, and then the Y _S axis is defined by the right-hand rule. Under this definition, the rotation of the read head relative to the X and _S axes of the grating ruler coordinate system is called roll, the rotation of the Y and _S axes is pitch (Pitch), and the rotation of the Z and _S axes is yaw (Yaw).

When there is a backlash between the guiding elements of the optical scale ball, such as the bushing and the guiding rod, under the action of gravity, the scale assembly and the read head assembly will rotate with the measuring ball at the end as the rotation center. When the scale surface of the ball bar grating scale is facing upwards, the reading head will have a pitch rotation relative to the grating scale with respect to the Y and _S axes of the grating scale coordinate system. This pitch rotation will change the measurement point, resulting in the above Abbe error. The bending rigidity of the optical scale club is limited, and the optical scale club will deflect under the action of gravity, and this deflection will also cause the reading head to rotate relative to the grating scale, which also causes the Abbe error mentioned above.

Please refer to FIG. 1 , wherein FIG. 1 shows a schematic diagram of a conventional optical scale club 100 placed on a calibration plate 10 , and the calibration plate 10 is placed horizontally. The optical scale club 100 can be composed of a read head assembly 101 and a ruler assembly 103. The read head assembly 101 includes a read head 102, the ruler assembly 103 includes a grating ruler 104, and the measuring balls at the two ends are respectively represented by P _B and P _P It means that the rotation angle of the read head 102 relative to the grating ruler 104, the rotation angle of the Xs axis is the roll angle A, the rotation angle of the Ys axis is the pitch angle B, the rotation angle of the Zs axis is the yaw angle C, and the grating ruler 104 is relatively When the head 102 moves in the positive direction of the Xs axis, the center distance becomes larger.

Please refer to FIG. 2A, wherein FIG. 2A shows another schematic diagram of a conventional optical scale club 100 placed on a calibration plate 10, FIG. 2A is a front view, the spin angle is 0 degrees, and two quantities are assumed The center-to-center distance between probe balls _PB and _PP is d (not shown in Figure 2A). When the scale surface of the grating ruler 104 is horizontal, and the Zs axis (shown in Figure 1) points upward, the spin angle at this time is defined as 0 degrees, and the measurement value is d1. Under this measurement attitude, when the optical ruler When there is a backlash between the bushing of the club 100 and the guide rod, under the action of gravity, the ruler assembly 103 and the reading head assembly 101 will respectively rotate the measuring balls P _P and P _B at their ends, that is, the reading head 102 is opposite to each other. The grating ruler 104 has a pitch rotation about the Y and _S axes of the grating ruler coordinate system (shown in Fig. 1), which causes the read head 102 to be no longer parallel to the grating ruler 104, and a pitch angle B ₁ appears between the two, as shown in Fig. 2A. as shown in the figure.

The optical path design of the read head 102 is such that when the read head 102 and the scale surface of the grating ruler 104 are parallel, the plane formed by the light emitted from the read head 102 and the light reflected from the surface of the grating ruler 104 is perpendicular to the surface of the grating ruler 104, Therefore, when the reading head 102 is not parallel to the scale surface of the grating ruler 104, and there is _a pitch angle B1 between the two, the plane formed by the emitted light and the reflected light is no longer perpendicular to the surface of the grating ruler, but has a pitch angle B1. _The measuring point It will be offset on the X and _S axes of the grating scale coordinate system (shown in Figure 1), and the read head 102 senses this additional offset, resulting in a measurement error e. The size of the measurement error e is determined by the reading head 102. The distance between the head 102 and the surface of the grating scale 104 and the pitch angle B1 are determined, so it is _a kind of Abbe error.

Please refer to FIG. 2B , wherein FIG. 2B shows another schematic diagram of a conventional optical scale club 100 placed on a calibration plate 10 . FIG. 2B and FIG. 2A are the same optical scale club 100 . The optical ruler club 100 rotates -90 degrees, that is, the spin angle of the optical ruler club 100 is -90 degrees, and the scale surface of the grating ruler 104 changes from horizontal to vertical. At this time, the center distance between the centers of the two ball seats is d ( (not shown in FIG. 2B ) has not changed, but the measuring attitude of the optical scale club 100 has changed, and the spin angle is -90 degrees. Due to the backlash and gravity, the read head assembly 101 has a deflection angle _C1 relative to the scale assembly 103. This deflection angle _C1 causes the measurement point to shift laterally from the scale surface of the grating scale 104. It can be found that the optical scale The club 100 has a new measurement value d2, and d1>d2.

When the spin angle of the optical scale club 100 is -90 degrees, under the action of gravity, the back gap between the guide rod and the bushing causes the read head 102 to rotate relative to the grating scale 104 (Yaw), that is, to Z The _S -axis (shown in Fig. 1) rotates, and there is a yaw angle C ₁ . At this time, the measurement point on the grating ruler 104 is mainly in the Y _S -axis (shown in Fig. 1) direction of the grating ruler, not Moving in the X- _S axis direction of the grating ruler or the measurement direction will hardly cause the measurement value to change. Therefore, in this measurement attitude, that is, when the spin angle is -90 degrees, the reading head 102 will not read Additional measurement error, there is no Abbe error in the measurement value d2.

At this time, let d*=d1–d2, the Abbe error is d*, which is also the largest Abbe error caused by the backlash, and when the spin angle changes from 0 degrees to -90 degrees, the Abbe error gradually increases from the maximum to the maximum. reduced to zero. When the spin angle is known, the Abbe error can be calculated from the maximum Abbe error and the spin angle. Note that when the spin angle is 0 degrees, the same back gap will cause different pitch angles at different center distances, and the corresponding maximum Abbe errors are also different.

Please refer to FIG. 3 , wherein, FIG. 3 is a schematic diagram illustrating a measurement posture of a conventional optical ruler club 100 used for measuring the distance between two points in a three-dimensional space. In a reference coordinate system (with X _R axis, Y _R axis and Z _R axis), there are two measuring balls P _B and P _P , the center distance between the measuring balls P _B and P _P is d, and the optical ruler club The inclination angle between 100 and the horizontal plane is α, the spin angle is γ, the normal vector of the grating scale is n _S , and the measurement attitude is determined by the center distance d, the inclination angle α and the spin angle γ. Since the measuring balls P _B and P _P are adsorbed in the magnetic ball socket not shown in the figure, there is no additional restraint design, the optical scale club 100 can spin, and the spin angle γ is unknown, so the optical scale ball The measured attitude of the rod 100 is unknown, and the Abbe error caused by the backlash cannot be determined.

To eliminate the Abbe error caused by the backlash in the optical scale club, a pre-force can be applied between the guiding elements, but it is extremely difficult to precisely control the magnitude of the pre-force, which will cause additional friction between the guiding elements and affect the precise measurement , In addition, even if there is zero backlash at the beginning, after long-term use, wear will still cause backlash between the guide elements.

In view of this, how to eliminate the Abbe error and other errors caused by backlash in the measurement value has become the goal of the relevant industry.

An embodiment of the present invention provides an optical scale club, which is used to measure the distance between the two ends of the ball and the center of the measuring ball, and includes a first grating scale and a first reading head. The first reading head starts from the first reading head. The grating scale reads out a first measurement value, wherein, under the influence of gravity, there is a first Abbe error in the first measurement value. a second grating scale, there is an angle between a normal line of the scale surface of the first grating scale and a normal line of the scale surface of the second grating scale, the second reading head reads out an additional second measurement value from the second grating scale , there is also a second Abbe error in the second measurement value, there is a relationship between the first Abbe error and the second Abbe error, and the first measurement value and the additional second measurement value are processed based on the relationship, eliminating The first Abbe error.

According to an embodiment of the aforementioned optical scale club, wherein the second grating scale and the first reading head are disposed on a first component, the first grating scale and the second reading head are disposed on a second component, The first component and the second component are linearly guided to each other.

According to an embodiment of the aforementioned optical scale club, the first grating scale and the second grating scale are arranged on a scale assembly, the first reading head and the second reading head are arranged on a reading head assembly, and the reading The head assembly and the ruler assembly are linearly guided to each other.

According to an embodiment of the aforementioned optical scale club, wherein the first light The scale and the second scale can be arranged parallel to or perpendicular to each other.

According to an embodiment of the aforementioned optical scale club, the signs of the first Abbe error and the second Abbe error are opposite.

According to an embodiment of the aforementioned optical scale club, the relationship may be a proportional relationship, a higher-order function relationship, or a sine and cosine function relationship.

According to an embodiment of the aforementioned optical scale club, the optical scale club is connected with a restrainer, and the restraint restrains the spin of the optical scale club.

According to an embodiment of the aforementioned optical scale club, the optical scale club is applied to a parallel mechanism six-dimensional measuring device.

According to an embodiment of the aforementioned optical scale club, the first grating scale and the second grating scale are relative or absolute.

Another embodiment of the present invention provides a method for processing measurement values of an optical ruler and club, which includes a first measurement value obtaining step, a second measurement value obtaining step, and a measurement value processing step. In the first measurement value obtaining step, a first reading head is used to read out a first measurement value, and the first measurement value includes a first Abbe error; in the second measurement value obtaining step, a second measurement value is obtained. The read head reads out a second measurement value, the second measurement value includes a second Abbe error, and there is a known relationship between the first Abbe error and the second Abbe error; in the measurement value processing step, according to The known relationship processes the first measurement value and the second measurement value to obtain a correct measurement value.

According to an embodiment of the method for processing the measurement value of an optical scale and club, in the measurement value processing step, the known relationship is a proportional relationship, a higher-order function relationship, or a sine and cosine function relationship.

According to an embodiment of the method for processing the measurement value of the optical scale club, in the measurement value processing step, a proportional value is obtained from the actual center distance of the optical scale club and an inclination angle, and is processed according to the proportional value The first measurement value and the second measurement value are used to obtain the correct measurement value.

According to an embodiment of the method for processing the measurement value of the optical scale club, in the measurement value processing step, a maximum Abbe error is obtained from the actual center distance and an inclination angle of the optical scale club. Abbe error processing the first measurement value and the second measurement value to obtain the correct measurement value.

According to an embodiment of the method for processing the measurement value of the optical scale club, in the measurement value processing step, the first measurement value and the second measurement value are processed based on the actual spin angle of the optical ruler club , to get the correct measurement value.

According to an embodiment of the method for processing the measurement value of the optical scale club, in the measurement value processing step, the spin angle of the optical ruler club is obtained from a restraint condition of a restrainer.

10: Correction plate

100: Optical ruler club

200, 300, 400: Optical ruler club

102: Read head

104: grating ruler

101, 210, 401: Read head assembly

103, 220, 403: Ruler assembly

350: First Component

360: Second component

402: First Reader

404: Second grating ruler

405: Second Reader

406: The first grating ruler

407, 408: Signal wires

500: Processing method of measurement value of optical ruler and club

A: rollover angle

B,B ₁ : pitch angle

C,C ₁ : yaw angle

d: center distance

e: measurement error

g ₁ , g ₂ : distance

h: offset distance

n _S : grating normal vector

P,Q,P*,Q*: measuring point

P',Q': arc point

P _B ,P _P : measuring ball

R ₁ : first read head

R ₂ : Second read head

S01: the first measurement value acquisition step

S02: the second measurement value acquisition step

S03: Measured value processing steps

S ₁ : The first grating scale

S ₂ : Second grating scale

Xs, Ys, Zs: axes of grating ruler coordinate system

X _R , Y _R , Z _R : the axes of the reference coordinate system

α: Inclination angle

θ: rotation angle

γ: spin angle

Figure 1 shows a schematic diagram of a conventional optical scale club placed on a calibration plate; Figure 2A shows another schematic diagram of a conventional optical scale club placed on a calibration plate; Figure 2B Another schematic diagram showing a conventional optical ruler club placed on a calibration plate; Figure 3 shows a conventional optical ruler club used for two-point spacing in three-dimensional space Figure 4 shows a schematic diagram of an optical scale club according to the first embodiment of the present invention; Figure 5 shows a schematic diagram of an optical scale club according to the second embodiment of the present invention 6 shows a schematic diagram of an optical scale club according to a third embodiment of the present invention; and FIG. 7 shows a schematic diagram of a method for processing measurement values of an optical scale club according to a fourth embodiment of the present invention.

The present invention provides an optical scale club with double read heads, which can eliminate Abbe error caused by the influence of gravity in the measurement value. In order to eliminate the Abbe error caused by the backlash of the optical scale club, in the optical scale club of one embodiment, in addition to the original first grating scale and the corresponding first read head, an additional second read head and Corresponding to the second grating scale, the first reading head measures the first measurement value of the first grating scale, the additional second reading head measures the additional second measuring value of the second grating scale, and the first grating scale surface There is an angle between a normal line and a normal line of the second grating scale surface, the first measurement value and the second measurement value respectively include the first Abbe error and the second Abbe error, the first Abbe error There is a relationship between the error and the second Abbe error, and the first measurement value and the additional second measurement value are processed based on the relationship to eliminate the first Abbe error. In one embodiment, the optical scale ball is composed of two first components and second components that are linearly guided with each other, the first component is provided with a first reading head and a second grating scale, and the second component is provided with There is a first grating ruler and a second read head. The first component and the second component are provided with guide rods, and are additionally equipped with bushings.

In another embodiment, the optical scale ball is composed of two linearly guided ruler assemblies and a read head assembly, the ruler assembly is provided with a first grating ruler and a second grating ruler, and the read head assembly is provided with a first readout head and second read head. There are guide rods on the ruler assembly and the reading head assembly, and a bushing is also installed.

In one embodiment, the first grating scale and the second grating scale have a known angle. In one embodiment, the first grating scale and the second grating scale are arranged parallel or perpendicular to each other.

In one embodiment, the optical scale club of the present invention is applied to a parallel mechanism six-dimensional measuring device. The parallel mechanism six-dimensional measuring device may include an upper plate and a lower plate, and the six optical scale clubs are respectively Connecting the upper plate and the lower plate, because the Abbe error of each optical scale ball is eliminated or almost eliminated, each optical scale ball has accurate measurement value, which makes the parallel mechanism six-dimensional measurement device extremely effective. High measurement accuracy.

The present invention also provides a method for processing the measurement value of an optical ruler and a club. The first measurement value is processed according to the known relationship between the first Abbe error and the second Abbe error in the first measurement value and the second measurement value. With the second measurement value, the correct measurement value is obtained.

In one embodiment, the scale surface of the first grating scale and the scale plane of the second grating scale are parallel to each other, the signs of the first Abbe error and the second Abbe error are opposite, and the first Abbe error and the second Abbe error are opposite to each other. There is a proportional relationship between the shell errors, and the first measurement value and the second measurement value are processed according to the proportional relationship to obtain the correct measurement value. This proportional relationship changes with the center distance of the optical scale club. In the embodiment, the ratio between the first Abbe error and the second Abbe error under different center distances and inclination angles of the optical scale club is stored, and the measurement is obtained from the actual center distance and inclination angle of the optical scale club. A ratio value between the first Abbe error and the second Abbe error, and the first measurement value and the second measurement value are processed according to the ratio value.

In another embodiment, the scale plane of the first grating scale and the scale plane of the second grating scale are perpendicular to each other, the first Abbe error and the second Abbe error have a sine and cosine function relationship, and the first The measurement value and the second measurement value are used to obtain the correct measurement value. In another embodiment, the correct measurement value is obtained from the first measurement value, the second measurement value and the maximum Abbe error when the center distance is known. In one embodiment, the maximum Abbe error value of the optical scale club at different center distances and inclination angles is pre-established and stored, and the maximum Abbe error value is obtained from the actual center distance and inclination angle of the optical scale club during measurement. The error value is used to process the first measurement value and the second measurement value to obtain the correct measurement value. In one embodiment, the correct measurement value is obtained from the first measurement value, the second measurement value and the spin angle of the optical scale club.

The details of the optical scale club with double read heads and the measurement value processing method of the optical scale club with double read heads of the present invention will be described later.

Please refer to FIG. 4 , which shows a schematic diagram of an optical scale club 200 with dual read heads according to the first embodiment of the present invention. The optical scale club 200 is designed in such a way that a grating ruler and a grating ruler constitute a component. It includes a read head assembly 210 and a ruler assembly 220. The read head assembly 210 includes a first read head R ₁ and a second read head R ₂ , and the ruler assembly 220 includes a first grating scale S ₁ and a second grating scale S ₂ , the first grating scale S ₁ , the second grating scale S ₂ , the first reading head R ₁ and the second reading head R ₂ have the arrangement shown in FIG. 4 . The _first grating scale S1 and the _second grating scale S2 are arranged parallel to each other in opposite directions of the scale planes, and the setting angle is 180 degrees. The measuring balls at the two ends of the optical scale club 200 are represented by P _B and P _P. The design parameters Including the distances g ₁ , g ₂ between the first grating scale S ₁ and the second grating scale S ₂ and the centerlines of the two measuring balls _PB and _PP , and the first reading head R ₁ and the second reading head R ₂ in The offset distance h of the measurement direction. When the read head assembly 210 and the scale assembly 220 have no relative rotation, the measurement points on the _first grating scale S1 and the _second grating scale S2 are P and Q respectively, and the read head assembly 210 and the scale assembly 220 have a relative rotation angle θ , the measuring points on the first grating ruler S ₁ and the second grating ruler S ₂ are P*, Q*, respectively, and the measuring points of P and Q are turned to the arc points P', Q' respectively, P _P P=P _P P', P _P Q=P _P Q', so the first Abbe error of the first grating S1 and the _{second Abbe error of the second grating S 2 are} P'P* and Q'Q* respectively , it should be noted that by arranging the _first grating scale S1 and the _second grating scale S2 on the upper and lower sides of the center line of the two measuring spheres _PB and _PP , the first Abbe error of the _first grating scale S1 P'P* is a negative value, while the second Abbe error Q'Q* of the _second grating scale S2 is a positive value.

Please refer to FIG. 5 , which shows a schematic diagram of an optical scale club 300 with dual read heads according to the second embodiment of the present invention. The optical scale club 300 is designed in such a way that the read head and the grating ruler form a component, A first assembly 350 and a second assembly 360 are included. The first read head R ₁ and the second grating scale S ₂ are fixed on the first assembly 350 , and the corresponding first grating scale S ₁ and the second grating scale S 2 are fixed on the second assembly 360 . The second reading head R ₂ , the first grating scale S ₁ and the second grating scale _{S 2} are arranged in parallel with each other in opposite directions, and the setting angle is 180 degrees. _PP said. The design parameters include the distances g ₁ , g ₂ between the first grating scale S ₁ and the second grating scale S ₂ and the centerlines of the two measuring balls P _B and P _P , and the first reading head R ₁ and the second reading head R ₂ The offset distance h in the measurement direction. When the first element 350 and the second element 360 have no relative pitch rotation, the measurement points on the _first grating scale S1 and the _second grating scale S2 are P and Q, respectively, and the first element 350 and the second element 360 When there is a relative rotation angle θ, the measuring points on the first grating scale S ₁ and the second grating scale S ₂ are P*, Q* respectively, the measuring point of P is turned to the arc point P', P _P P=P _P Therefore, the first Abbe error of the _first scale S1 and the _second Abbe error of the second scale S2 are P'P* and QQ*, respectively. The first Abbe error P'P* of the first read head R ₁ in Fig. 5 is a negative value, and the second Abbe error QQ* of the second read head R ₂ is a positive value.

，第一量測值

中之第一阿貝誤差為e ₁，第二讀頭的第二量測值為

，第二量測值

中之第二阿貝誤差為e ₂，e ₁與e ₂間的比例值為k：

e ₁=k＊e ₂ (4)；解式(2)-(4)，可以得出：

Therefore, for such an optical scale club with two parallel grating scales (ie, the first grating scale and the second grating scale), the distances g ₁ , g ₂ and the offset distance h are design parameters, which are actually practical after production and assembly. Design parameters will deviate. The rotation angle θ itself will increase with the increase of the clearance due to the wear of the guide element. Although the relationship between P'P*, QQ* or Q'Q* and the rotation angle θ is a nonlinear relationship or a high-order function relationship, because P'P*, QQ* or Q'Q* are very small, and the relationship between P'P*, QQ* or Q'Q* and the rotation angle θ can be approximated by a linear relationship, for example, the proportional value k is used to establish P'P* and The relationship between QQ*: P'P*=k×QQ* (1); in this way, when the correct measurement value is m, the first measurement value of the first reading head is

, the first measured value

The first Abbe error is e ₁ , and the second measurement of the second reading head is

, the second measurement value

The second Abbe error is e ₂ , and the ratio between e ₁ and e ₂ is k:

e ₁ =k* e ₂ (4); Solving equations (2)-(4), we can get:

，及第二讀頭的第二量測值

計算得出，比例值k可以由實驗得出，當二光柵尺因製造組裝或其他設計因素不是絕對平行而是有一角度，可以得出一實際之比例值k。特定設計參數下，k=1，

，此正負號相反之第一阿貝誤差e ₁與第二阿貝誤差e ₂，可透過第一量測值

與第二量測值

之相加而消除。另外，在式(5)中無球桿之自旋角因素，e ₁與e ₂因自旋角而變化時，式(4)之比例關係依然成立，這是此類具有二平行光柵尺之光學尺球桿的好處。比例值k隨中心距離及傾斜角變化時，也可進行量測實驗建立比例值k與中心距離及傾斜角之函數關係，量測時依光學尺球桿實際之中心距離及傾斜角得出比例值k。 It can be seen in formula (5) that when the scale value k is known, the correct measurement value m can be determined by the scale value k, and the first reading head's No. a measure

, and the second measurement value of the second read head

It is calculated that the proportional value k can be obtained by experiments. When the two grating scales are not absolutely parallel but have an angle due to manufacturing assembly or other design factors, an actual proportional value k can be obtained. Under specific design parameters, k=1,

, the first Abbe error e ₁ and the second Abbe error e ₂ with opposite signs can be obtained through the first measurement value

with the second measurement

are added and eliminated. In addition, without the spin angle factor of the club in equation (5), when e ₁ and e ₂ change due to the spin angle, the proportional relationship of equation (4) still holds. The benefits of optical ruler clubs. When the proportional value k changes with the center distance and the inclination angle, measurement experiments can also be performed to establish the functional relationship between the proportional value k and the center distance and inclination angle. When measuring, the ratio is obtained according to the actual center distance and inclination angle of the optical scale club. value k.

Please refer to FIG. 6 , which shows a schematic diagram of an optical scale club 400 with dual read heads according to a third embodiment of the present invention. The two grating scale surfaces of the optical scale club 400 are arranged perpendicular to each other. And includes a read head assembly 401 and a ruler assembly 403, the read head assembly 401 is fixed with a first read head 402 and a second read head 405, a first grating ruler 406 and a second grating ruler 404 is fixed on the scale assembly 403, the first grating scale 406 and the second grating scale 404 are perpendicular to each other, and the setting angle can be 90 or -90 degrees, considering the manufacturing and assembly errors of the first grating scale 406 and the second grating The 404-foot plane will not be absolutely vertical, there will be some slight deviation. The signal wire 407 of the first reading head 402 and the signal wire 408 of the second reading head 405 are led out from the same side of the optical scale ball 400 . The advantage of arranging the first grating scale 406 and the second grating scale 404 perpendicular to each other is that the first Abbe error in the first measurement value has an orthogonal relationship with the second Abbe error in the second measurement value, for example, When the optical scale club 400 is placed horizontally on two ball sockets not shown, the scale surface of the first grating scale 406 is vertical, and the scale plane of the second grating scale 404 is horizontal, the first Abbe error is zero , and the second Abbe error has a maximum value; when the optical scale club 400 spins 90 degrees (that is, the spin angle is 90 degrees), the first grating ruler 406 scale surface becomes horizontal, and after the scale face is upward, the second grating scale The scale plane of 404 becomes vertical. At this time, the first Abbe error has a maximum value, and the second Abbe error is zero. By arranging two grating scales perpendicular to each other, the optical scale club 400 can process the first measurement value by processing the first measurement value. and the second measurement value to obtain the correct measurement value.

In such an optical scale ball 400 with two grating scales arranged perpendicular to each other, the first Abbe error and the second Abbe error can be expressed by a trigonometric function relationship, as shown in the following two equations, wherein the first measurement of the first reading head 402 The value is m ₁ , the second measurement value of the second reading head 405 is m ₂ , then: m ₁ =m+a. sin(γ ₁ ) (6); and m ₂ =m+a. cos(γ ₁ ) (7).

Among them, γ ₁ is the spin angle, m is the correct measurement value without Abbe error, and a is the maximum Abbe error. When γ ₁ =0, the scale surface of the first grating scale 406 is vertically forward, and there is no Abbe error in the first measurement value m ₁ (ie, the first Abbe error is zero); the scale plane of the second grating scale 404 is Horizontally, there is a maximum Abbe error a in the second measurement m ₂ .

由式(6)、(7)二式可以得出γ₁解為：

則m之二解中有效解為：

From the above formulas (6) and (7), it can be concluded that (m ₁ -m) ² +(m ₂ -m) ² =a ² (8); from formula (8), it can be concluded that m has two solutions :

From formulas (6) and (7), the solution of γ ₁ can be obtained as:

Then the effective solution in the second solution of m is:

During measurement, the first measurement value m ₁ measured by the first reading head 402 and the second measurement value m ₂ measured by the second reading head 405 can be obtained, and the maximum Abbe error obtained by formula (8) a, the measurement value m without Abbe error is obtained from equation (11). Note that the error relationship in equation (11) does not include the spin angle γ ₁ , that is, equation (11) is valid for any spin angle, which is the advantage of setting two mutually perpendicular grating scales.

The spin angle γ1 of the optical scale club in the above formulas (6) and ( ₇ ) can be obtained by designing a restrainer, which is the subject of another patent application of the inventor of this patent, the following Just a brief introduction.

The two ends of the optical scale club are ball bearings formed by balls and ball sockets. The optical scale club can spin freely, and the spin angle is unknown. For this reason, a restrainer can provide a restraint condition to restrain the self of the optical scale club. Spin, the spin angle of the optical ruler club can be calculated from the constraint conditions. In one embodiment, the restraint may include a secondary restraint fixed on one end of the optical scale club, and a main restraint fixed outside the optical scale club, the secondary restraint moves together with the optical scale club, and the main restraint moves together with the optical scale club. The restraining member has a shape, which constitutes a restraining condition for the matching slave restraining member. The secondary restraining member can be a ball, a rod, fixed on the optical ruler and club, and has specified geometric characteristics, such as being set in the grating ruler coordinate system X _S - At a specific position and a specific direction on the Z _S plane, the main restraint is fixed outside the optical scale club, and has a shape that cooperates with the secondary restraint. Restricted to move in this gap, the spin angle of the optical ruler club can be calculated from the position and direction of the shape. In an embodiment of the invention, the secondary restraint member is a ball connected to one end of the optical scale club, and is restricted to move on the center of an arc track by the primary restraint member.

In another embodiment, the restraint may include a return spring and a spring seat, the spring seat is fixed outside the optical scale ball, one end of the return spring is fixed on the optical scale ball and has a starting point, and the other end is fixed on the optical scale ball. There is an end point on the spring seat, and the return spring between the start point and the end point has a force balance state, this force balance state constitutes a constraint condition, which determines the spin angle of the optical scale club. The spring deviates from the force balance state to generate a restoring force, so that the optical scale club has a new spin angle in the new force balance state.

式(13)顯示可以由第一量測值m₁、第二量測值m₂及已知之自旋角γ₁算出無阿貝誤差之量測值m，此式(13)更凸顯垂直設置二光柵尺的好處：計算無阿貝誤差之量測值m時，可以不考慮導引元件磨損時阿貝誤差之變化，也可以不考慮中心距離變化時阿貝誤差之變化。式(13)顯示，當此類二光柵尺垂直設置的光學尺球桿400，額外以拘束器拘束其自旋，由拘束條件計算得出自旋角γ₁後，即不需預先進行量測實驗建立其在不同量測姿態下之最大阿貝誤差a，僅需由第一量測值m₁、第二量測值m₂，及由拘束條件算出之自旋角γ₁，即可以準確計算得出無阿貝誤差之量測值m。此式(13)方法也可以與式(11)方法交互比對使用。 Therefore, in Fig. 6, the optical scale club 400 with double read heads with two grating scales vertically arranged, under the condition that the spin angle _γ1 is known, can be obtained from the formulas (6) and (7):

Equation (13) shows that the measurement value m without Abbe error can be calculated from the first measurement value m ₁ , the second measurement value m ₂ and the known spin angle γ ₁ . This formula (13) highlights the vertical setting Advantages of two grating scales: When calculating the measurement value m without Abbe error, it is not necessary to consider the change of Abbe error when the guiding element is worn, or the change of Abbe error when the center distance changes. Equation (13) shows that when the optical scale club 400 with such two grating scales is vertically arranged, its spin is restrained by an additional restrainer, and after the spin angle γ ₁ is calculated from the restraint conditions, there is no need to measure in advance. The experiment establishes its maximum Abbe error a under different measurement attitudes. It only needs to use the first measurement value m ₁ , the second measurement value m ₂ , and the spin angle γ ₁ calculated from the constraint conditions, which can be accurate The measurement value m without Abbe error is calculated. The method of formula (13) can also be used for interactive comparison with the method of formula (11).

When the spin angle γ ₁ =45 degrees, the numerator and denominator of formula (13) are both zero, and the first measurement value m ₁ and the second measurement value m ₂ are the same at this time. Therefore, when γ ₁ =45 degrees, we can return to equation (6) or (7), and obtain m from the known maximum Abbe error a:

It can be seen from this that the restraint used by the optical scale club with two grating scales vertically arranged is best to avoid the spin angle γ ₁ =45 degrees during measurement, and can be monitored by formula (8) under different measurement attitudes The maximum Abbe error a, in this way, when the spin angle γ ₁ =45 degrees or near, the measurement value m without Abbe error can still be calculated.

Please refer to FIG. 7 , and also refer to FIGS. 4 to 6 , wherein FIG. 7 is a schematic diagram of a method 500 for processing measurement values of an optical ruler and club according to the embodiment of FIG. 6 of the present invention. The method 500 for processing a measurement value of an optical ruler and club may include a first measurement value obtaining step S01 , a second measurement value obtaining step S02 , and a measurement value processing step S03 . In the first measurement value acquisition step S01, the first measurement value is read out by the _first reading head R1, and the first measurement value includes the first Abbe error; in the second measurement value acquisition step S02, the second measurement value is obtained by the second measurement value. The read head R2 reads out the _second measurement value, the second measurement value includes the second Abbe error, and there is a known relationship between the first Abbe error and the second Abbe error; and the measurement value processing step S03 , and process the first measurement value and the second measurement value according to the known relationship to obtain a correct measurement value. The details of the method 500 for processing the measurement value of the optical ruler and club are as described above, and will not be repeated here.

The above describes an optical scale club with dual read heads, which can be obtained by the arrangement of the first read head, the second read head, the first grating scale and the second grating scale and the corresponding measurement value processing method. For correct measurement values, professionals can make other designs to eliminate Abbe errors according to the configuration and method proposed in the present invention, but they are all included in the inventive method or principle disclosed above. They are perpendicular to each other, and there can be other angles between them. The first Abbe error and the second Abbe error have a corresponding relationship, which can be processed to obtain the correct measurement value. The club can also use other types of displacement. Sensor, in addition, the two ends of the optical scale ball rod with dual read heads of the present invention are not limited to ball joints, but can also be other types of joints, such as pivot joints or universal joints Joint (U-joint).

Although the present invention has been disclosed above in embodiments, it is not intended to To limit the present invention, any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be regarded as defined by the appended patent application scope.

400: Optical ruler club

401: Read head assembly

402: First Reader

403: Ruler assembly

404: Second grating ruler

405: Second Reader

406: The first grating ruler

407, 408: Signal wires

Claims (15)

An optical scale club, used for measuring the distance between the two ends of the ball and the center of the measuring ball, comprises a first grating ruler and a first reading head, the first reading head reads out an optical scale from the first grating ruler The first measurement value, wherein, under the influence of gravity, there is a first Abbe error in the first measurement value. In order to eliminate the first Abbe error, the optical scale club is additionally provided with a second reading head and a first Two grating scales, there is an angle between a normal line of the scale surface of the first grating scale and a normal line of the scale plane of the second grating scale, the second reading head reads an additional second quantity from the second grating scale measurement value, there is also a second Abbe error in the second measurement value, there is a relationship between the first Abbe error and the second Abbe error, and the first measurement value and additional The second measurement value cancels the first Abbe error. The optical scale club of claim 1, wherein the second grating scale and the first read head are disposed on a first component, and the first grating scale and the second read head are disposed on a first On the two components, the first component and the second component are linearly guided to each other. The optical scale club of claim 1, wherein the first grating scale and the second grating scale are arranged on a scale component, and the first reading head and the second reading head are arranged on a reading head On the assembly, the read head assembly and the ruler assembly are linearly guided to each other. The optical scale club as claimed in claim 1, wherein the No. 1 A grating scale and the second grating scale are arranged parallel to or perpendicular to each other. The optical scale club of claim 1, wherein the first Abbe error and the second Abbe error have opposite signs. The optical scale club of claim 1, wherein the relationship is a proportional relationship, a higher-order function relationship, or a sine and cosine function relationship. The optical scale club as claimed in claim 1, wherein the optical scale club is connected with a restrainer, and the restrainer restrains the spin of the optical scale club. The optical scale club according to claim 1, wherein the optical scale club is applied to a parallel mechanism six-dimensional measuring device. The optical scale club according to claim 1, wherein the first grating scale and the second grating scale are relative or absolute. A method for processing measurement values of optical rulers and clubs, comprising: a first measurement value acquisition step, using a first reading head to read out a first measurement value, and the first measurement value includes a first Abbe error; a second measurement value obtaining step, using a second reading head to read out a second measurement value, the second measurement value includes a second Abbe error, and the first Abbe There is a known relationship between the error and the second Abbe error; and a measurement value processing step, processing the first measurement value and the second measurement value according to the known relationship to obtain a correct measurement value . The method for processing the measurement value of an optical ruler and club according to claim 10, wherein, in the measurement value processing step, the known relationship is a proportional relationship, a higher-order function relationship, or a sine and cosine function relationship. The method for processing the measurement value of an optical scale club according to claim 10, wherein, in the measurement value processing step, a proportional value is obtained from the actual center distance and the inclination angle of the optical scale club, and according to the ratio The first measurement value and the second measurement value are processed to obtain the correct measurement value. The method for processing the measurement value of an optical scale club according to claim 10, wherein, in the measurement value processing step, a maximum Abbe error is obtained from the actual center distance and inclination angle of the optical scale club, according to The maximum Abbe error processes the first measurement value and the second measurement value to obtain the correct measurement value. The method for processing the measured value of an optical scale club according to claim 10, wherein, in the measurement value processing step, the first measured value and the first measured value are processed based on the actual spin angle of the optical scale club. Two measurement values, get the correct measurement value. The method for processing the measurement value of an optical scale club according to claim 14, wherein, in the measurement value processing step, the spin angle of the optical scale club is obtained from a restraint condition of a restrainer.

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