JP5111844B2 - Articulated coordinate measuring device - Google Patents

Description

In the present invention, a user moves a multi-joint type measurement arm to bring a contact or non-contact type probe attached to the tip of the measurement arm close to an arbitrary point on the object to be measured. The present invention relates to an apparatus capable of measuring a spatial coordinate of an arbitrary point on an object having a shape.

In an articulated coordinate measuring device in which a flexible measuring arm moves in space and measures the position, dimensions, etc. of the object to be measured, an angle sensor such as a rotary encoder is built in corresponding to each joint of the measuring arm. Based on the rotation angle of each joint detected by these angle sensors and the length of the joint between the joints and between the joint and the probe, the spatial coordinates of the tip of the probe are calculated.

In such a measuring apparatus, various devices have been devised in order to reduce the measurement error. For example, in Patent Document 1, each joint is provided with an end stop that becomes a limit of rotation of the joint, and an angle sensor of each joint turns on a light when the angle of the joint is too close to the end stop. It is disclosed that the user is prompted to readjust the direction of the arm by generating a warning sound.

Further, in this publication, after assembling the measurement arm, a deviation from a design value caused by machining or assembling of each member of the arm is obtained based on a measurement result using a calibration jig, and the obtained positional deviation is calculated. It is also disclosed that a more accurate coordinate measurement can be realized by incorporating the value into a motion equation for obtaining the spatial coordinates of the tip of the arm.

JP-A-8-261745

When performing measurement with an articulated coordinate measuring apparatus as described above,
If the measuring device is stressed by pulling the measuring arm strongly or by forcibly shrinking the measuring arm, the arm will bend and the position change will not appear in the output of the angle sensor. Even if it does not change, there is a disadvantage that the angle sensor detects rotation and the measurement error becomes large.

The specific posture of the measurement arm that increases the measurement error in this way cannot be detected by whether or not the angle of each joint has approached its end stop, so the user notices that the measurement error has increased. The measurement continued.

In addition, in order to improve the operability and safety of the arm, a configuration in which a balancer is provided near the base of the measurement arm is known. However, since the load force of the balancer varies depending on the posture of the measurement arm, the measurement device is applied A difference occurs in stress, which also causes a large measurement error.

Such a balancer is configured using, for example, a spring, and elastic energy is accumulated in the spring according to the amount of turning from the neutral position of the arm.
Reduces the force that the measuring arm tries to fall from its root under its own weight. Due to the action of this spring, the user can lightly move the measurement arm during measurement, and the risk of the arm falling when the measurement is stopped and the hand is released can be reduced.

The force with which the spring attempts to lift the measurement arm changes according to the neutral position of the arm, that is, the amount of rotation from the state where the measurement arm stands vertically from the root.
Then, the above-described calibration of the positional deviation is performed, for example, so that the measurement error is minimized in the vicinity of a point where the gravity applied to the measurement arm balances with the force with which the spring lifts the measurement arm. In this case, as the measurement arm is lifted above the balance point, the balancer force actually applied to the measurement arm becomes weaker. Conversely, as the measurement arm is pushed below the balance point, the measurement arm actually Since the force of the balancer applied to is increased, this difference in balancer force widens the measurement error.

The error due to the difference in balancer force is reduced if a balancer with a small force is used, but in this case, the weight of the measurement arm exceeds the balancer's force. The arm falls from the root, and safety is impaired.

In view of the circumstances as described above, the present invention provides an articulated coordinate measuring apparatus capable of notifying a user whether or not a measurement arm is in a measurement posture in which measurement accuracy is kept good. One purpose.

Another object of the present invention is to provide an articulated coordinate measuring apparatus capable of obtaining spatial coordinates with high measurement accuracy even when there is a difference in the force generated by the balancer depending on the posture of the measurement arm. is there.

The articulated coordinate measuring apparatus according to the present invention can attach a probe to one end, the probe attaching member, the first link, and the second link are sequentially connected, and the other end is attached to the support member. A measurement arm and a processor that calculates spatial coordinates corresponding to the position of the probe based on the angle of each joint of the measurement arm. The measurement arm includes a wrist joint that provides a bending action of the probe attachment member relative to the first link, an elbow joint that provides a bending action of the first link relative to the second link, and a bending action of the second link relative to the support member. And a shoulder joint to be provided. In addition to the above, the measurement arm further includes a joint that provides a torsional motion of the probe attachment member with respect to the first link, a joint that provides the torsional motion of the first link with respect to the second link, and the joint with respect to the support member It is good also as a thing further provided with at least 1 among the joints which provide the twist operation | movement of a 2nd link.

When the user tries to measure the far side by pulling this measuring arm, the measurement error may increase beyond the allowable range, but according to the first invention of the present invention,
Before the measurement is performed in such a state, a warning is given to the user based on the parameters related to the posture of the measurement arm, so that the user who is warned can maintain the measurement arm with good measurement accuracy. The measurement can be continued by returning to the posture, and the accuracy of the spatial coordinates output as a result can be improved.

Although a single parameter (for example, only one of the first and second parameters described later) may be used as the above parameter, the first parameter related to the angle formed by the link of the measurement arm and the arrival of the measurement arm When the second parameter relating to the distance is used in combination, a warning can be surely given before the measurement error exceeds the allowable range.

Regarding the first parameter, for example, the fact that the angle formed by the first link and the second link is close to 180 ° means that the measurement arm is almost fully extended, and the measurement error becomes closer to 180 °. Therefore, if the angle limit (eg, 170 °) at which the desired measurement accuracy is obtained is exceeded or approached, an alarm is issued.

For the second parameter, for example, as the distance between the wrist joint and the base fulcrum of the measurement arm increases, the state where the measurement arm is fully extended is closer.
If the distance limit (for example, 1300 mm when the length from the wrist joint in the fully extended state to the fulcrum of the measurement arm is 1350 mm) is exceeded, or if the limit is approached, Make a warning.

Here, the distance from the wrist joint to the fulcrum of the measurement arm is typically used here, but this is often done by the user holding and moving near the wrist joint of the measurement arm. This is due to the fact that a force that causes a measurement error is hardly applied to the member. However, if the user often moves the measurement arm around the probe or probe mounting member, the distance from the tip of the probe to the fulcrum of the measurement arm or the predetermined position of the probe mounting member The distance to the fulcrum may be used, and such an implementation is within the scope of the present invention. Further, as the fulcrum of the measurement arm, any of a position of the shoulder joint, a position where the other end is attached to the support member, and an arbitrary position between them may be adopted depending on the configuration of the measurement apparatus.

The above-mentioned distance is obtained by, for example, obtaining the position of the wrist joint or the like using a processor provided in the measurement apparatus, and calculating the distance between the obtained position and the position of the fulcrum of the measurement arm known in advance. Can be sought.

The measuring apparatus according to the first aspect of the present invention described above is a first device that detects from the angle of the elbow joint that the angle formed by the first link and the second link exceeds a predetermined value and approaches 180 °. And a second means for detecting that the distance of the position of the wrist joint with respect to the fulcrum of the measurement arm exceeds a predetermined value, and at least one of the first and second means detected. In this case, a warning means for warning the user is provided.

In the measurement control method according to the first aspect of the present invention described above, there is a possibility that the measurement error caused by the pulling force on the measurement arm of the user trying to measure the position away from the support member by the probe exceeds the allowable range. This is characterized in that a processor is detected based on whether or not a predetermined parameter relating to the posture of the measurement arm exceeds a predetermined value, and a warning is given to the user when the detection is detected.

Next, the measuring device according to the second invention of the present invention is provided at or near the shoulder joint and generates a force that lifts the elbow joint side of the second link against the gravity applied to the measuring arm. The balancer is further provided.

In the case of a measuring device equipped with such a balancer, the force of the balancer is generally the smallest when the measuring arm is standing vertically and increases as the measuring arm rotates downward around the shoulder joint. On the other hand, the calibration after the measurement arm is assembled is performed at a point where the force of the balancer takes a certain value, for example, at a point where the force generated by the balancer balances with the gravity applied to the measurement arm. If the user tries to measure by bending the measurement arm out of the range, the measurement error may increase beyond the allowable range.

According to the second invention of the present invention, the parameter related to the posture of the measurement arm before the measurement error is measured in a state deviating from a predetermined range that is an allowable range due to the strength of the balancer. Therefore, the user who has been warned can return the measurement arm to a posture in which the measurement accuracy is kept good, and can continue the measurement. Accuracy can be increased.

Regarding the parameters in the second invention, for example, if the state in which the second link is horizontal is the point at which the force of the balancer becomes a predetermined value,
When the link rotates up around the shoulder joint and approaches vertical, the balancer's force becomes too weak, and when the second link rotates down around the shoulder joint and approaches vertical, the balancer's force is Since the shoulder joint angle is too strong, a warning is issued if the shoulder joint angle exceeds the limit of the angle at which the desired measurement accuracy can be obtained (for example, ± 80 ° when the horizontal state is 0 °) or approaches that limit. To.

Here, the point at which the force of the balancer takes a predetermined value is not limited to a point that balances with gravity, and any other state may be adopted. In addition, if the deterioration of measurement accuracy with the stronger balancer force is acceptable, only the warning for the weaker balancer force (in the above example, rotate more than 80 ° from horizontal to upward) Only when the balancer's force is strong (in the above example, the warning only occurs when the wheel is rotated 80 ° or more downward from the horizontal). Alternatively, different angles (eg, + 80 ° and −70 ° from the horizontal) may be set as the upper limit and the lower limit.

The measuring apparatus according to the second aspect of the present invention described above is a detecting means for detecting that the second link is bent from a shoulder joint angle exceeding a predetermined range determined based on a force generated by the balancer. And warning means for giving a warning to the user when the detection means detects.

In the measurement control method according to the second aspect of the present invention described above, the posture that the user's measurement arm that wants to measure the desired position with the probe takes into account the influence of the force on the measurement arm of the balancer. May cause a measurement error that exceeds the specified value based on whether a predetermined parameter related to the posture of the measurement arm exceeds a predetermined value, and if a detection is detected, a warning to the user is issued. It is characterized by performing.

The first and second inventions described above are effective even when combined.
For example, the first means for detecting that the angle formed by the first link and the second link exceeds a predetermined value and approaches 180 °, and the distance from the wrist joint to the fulcrum exceeds the predetermined value. And second means for detecting that the second link is bent with respect to the support member beyond a predetermined range determined based on the force generated by the balancer. It is also possible to provide a warning to the user when at least one of these first to third means detects.

In both the first and second inventions described above, in addition to warning the user, if the output of the spatial coordinates from the processor is stopped, the user can obtain a spatial coordinate value with poor measurement accuracy. It can be surely prevented from being used.
As a method of canceling the output of the spatial coordinates, it is possible to stop taking the angles of the joints into the processor so that the calculation of the spatial coordinate values is not performed, or the spatial coordinate values calculated by the processor are sent to the outside. It is also possible not to output.

As described above, when the warning to the user and the output stop of the spatial coordinate value are used together, when each observed parameter reaches a predetermined value slightly before the limit value at which the desired measurement accuracy can be obtained, It is also effective to start the warning, and to discontinue the output of the spatial coordinate value when the user continues to move the measurement arm and the parameter exceeds the limit value by ignoring this warning.

Finally, the measuring device according to the third aspect of the present invention is provided at or near the shoulder joint and generates a force that lifts the elbow joint side of the second link against the gravity applied to the measuring arm. The balancer is further provided, and an equation including a term for correcting an error caused by a change in the force generated by the balancer depending on the angle of the shoulder joint is used as an equation for the processor to calculate the spatial coordinates. And For example, a parameter representing the deflection generated in the second link by the balancer force is included in the above equation, and a value determined based on the angle of the shoulder joint is used as the value of the parameter representing the deflection.

According to the third aspect of the present invention, even when the force of the balancer decreases or increases depending on the posture of the measurement arm, the processor calculates the spatial coordinates so as to absorb the error caused by this, and therefore is output. The accuracy of spatial coordinates can be increased.

The second invention of the present invention is intended to avoid measurement errors caused by the influence of the balancer's force by warning the user, whereas the third invention of the present invention is based on the strength of the balancer. By correcting the influence by software used by the processor, the measurement error is approximately removed. Therefore, the third invention can be implemented as an alternative to the second invention, or in combination with the second invention (until the measurement error cannot be completely eliminated even if corrected by software). If the second link is bent, the user may be warned).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating an appearance of an example of an articulated coordinate measuring apparatus according to the present embodiment. The measurement arm is composed of a probe attachment portion 2, a first link 5, a second link 8, and six joints, and the probe 1 is attached to the probe attachment portion 2. A sixth joint is attached to the strut that supports the measurement arm and provides rotation between the measurement arm and the strut.

The No. 1 joint (wrist joint) 3 provides the bending operation (rotation around the A axis in FIG. 2) of the probe mounting portion 2 with respect to the first link 5, and the No. 2 joint 4 is the probe with respect to the first link 5. Provides torsional motion of the mounting part 2 (rotation around the B axis in Fig. 2), No.3
The joint (elbow joint) 4 is bent by the first link 5 with respect to the second link 8 (C in FIG. 2).
No. 4 joint 7 provides torsional motion of the first link 5 relative to the second link 8 (rotation around the D axis in FIG. 2), and No. 5 joint (shoulder joint). 9 provides the bending action (rotation around the E axis in FIG. 2) of the second link 8 with respect to the column 11;
The joint 10 provides torsional motion (rotation about the F axis in FIG. 2) of the second link 8 with respect to the column 11. Each of the joints No. 1 to No. 6 incorporates an angle sensor such as a rotary encoder, and the rotation angle around each axis is detected. No.2,
The twisting operation of the No. 4 and No. 6 joints may have a limit in the rotation angle or may rotate endlessly.

The column 11 is installed on a movable table 12, and the table 12 is provided with a dedicated processor 13 and a computer 14. Dedicated processor 13
The rotary encoder of each joint is connected by wire or wirelessly, and the output of each rotary encoder is input to the dedicated processor 13. The dedicated processor 13 determines the position of the tip of the probe 1 based on the input angle of each joint and the fixed positional relationship of each member (including the length of the link and the probe).
X, Y, Z) coordinates can be calculated. The computer 14 can start and execute various application programs, and the spatial coordinate value calculated by the dedicated processor 13 is input to the application program.

The measurement arm can attach various probes to the probe attachment portion 2. The probe 1 in FIG. 1 has its tip brought into contact with the surface of the object to be measured,
The coordinates of the contact point are obtained, but this can be replaced with a non-contact type probe as shown in FIG. 3, for example. In the example of FIG. 3, the non-contact type laser probe 3
1 is mounted on the probe mounting portion 2 in which the probe 1 is incorporated into a probe joint 32 that provides rotation around the G axis. In order to specify the position of the sensor portion of the non-contact type probe 31, a rotary encoder is also built in the probe joint 32,
In this case, the dedicated processor 13 obtains the spatial coordinates of the tip of the probe based on No. 1 to No. 6 and the angle of each joint of the probe. Non-contact probe 3
The result of sensing by laser 1 is input to the non-contact type probe controller 33 separately from the angle of each joint, and the sensing result processed here and the coordinates of the probe tip obtained by the dedicated processor 13 are synthesized. Thus, data on the surface of the object to be measured is obtained.

The measurement arm is illustrated in FIGS. 4 and 5 so that the measurement accuracy does not deteriorate beyond the allowable range when the user moves the measurement arm configured in this way to measure the position coordinates of the object to be measured. When the posture is such that the user is warned, a warning is given to the user. 4 and 5 show an example in which the probe 31 of FIG. 3 is used, the same control is performed when the probe 1 of FIG. 1 is used.

FIG. 4 shows an example of parameters for specifying a posture in which the measurement error increases beyond the allowable range when the user is going to measure the far side by pulling the measurement arm.

One parameter is the angle of No. 3 joint (elbow joint) 6. In this example, the angle sensor of the No. 3 joint 6 is 0 ° when the first link 5 and the second link 8 are at right angles.
Is set to show. When the angle sensor of the No. 3 joint 6 exceeds + 80 °, the first link 5 and the second link 8 become nearly parallel, and the measurement error exceeds the allowable range. Therefore, in this case, the specific posture limit is 80 ° (170 ° in terms of the relative angle between the first link 5 and the second link 8).

Another parameter is the distance between the center position of No. 1 joint (wrist joint) 3 and the fulcrum of the measurement arm. As the fulcrum of the measurement arm, for example, the center position of the No. 6 joint 10 attached to the column 11 can be used. The maximum length of the measurement arm in FIG. 4 up to the No. 1 joint 3 is 1350 mm. However, if the distance from the arm fulcrum of the No. 1 joint 3 exceeds 1300 mm, the measurement error increases beyond the allowable range. In this case, 1300 mm is the specific posture limit.

When either of the above two parameters approaches the specific posture limit, the measuring device warns the user by a method such as sounding an alarm sound or blinking a light. For example, if the angle of the No. 3 joint 6 exceeds 78 ° or the distance of the No. 1 joint 3 exceeds 1270 mm, the user is warned. After that, if the angle of the No. 3 joint 6 exceeds 80 ° or the distance of the No. 1 joint 3 exceeds 1300 mm, the dedicated processor 13 acquires the signal from the angle sensor of each joint or the spatial coordinates. Stop at least one of the output processes. At this time, while continuing the warning to the user, the sound quality and volume of the alarm sound, lighting of the light, etc. may be changed, or other methods that allow the user to recognize that the output of the spatial coordinates has been stopped. You may take it.

As shown in FIGS. 1 and 2, the measurement arm of this example has a probe mounting portion 2 with A.
Because it rotates 360 ° around the axis or endlessly, the user can
In many cases, the measurement arm is moved near the object to be measured. For this reason, in the measurement arm of this example, the distance from the No. 1 joint 3 is used as a parameter for specifying the posture, not the position of the probe mounting portion 2 or the distance from the tip of the probe 1 to the arm fulcrum.

FIG. 5 shows a state in which the magnitude of the force generated by the balancer of the measurement arm varies depending on the posture of the measurement arm, and parameter values for specifying the posture in which the measurement error increases beyond the allowable range due to the influence of the balancer. An example is shown.

As the balancer, various known configurations can be employed. For example, a structure in which a spring assembly as shown in JP-A-61-168491 is coupled to the No. 5 joint 9 or a torsion coil spring as shown in JP-A-58-34791 is used. There is a configuration to be incorporated into the No. 5 joint 9. USP5189
As shown in Japanese Patent No. 797, a link support member is provided in parallel with the second link.
There is also a configuration in which a spring is provided adjacent to the .5 joint 9 and the force of this spring is transmitted to the second link via the link support member.

In any form of balancer, in the measurement arm of this example, as shown in FIG. 5, if the second link 8 is lifted around the No. 5 joint 9, the balancer's force becomes weaker. If the two links 8 are pushed down, the balancer's power increases. In this example,
The neutral state in which the user has released his / her hand from the measurement arm is a state in which the second link 8 is substantially horizontal and the first link 5 is vertically suspended from the ground. In this state, the gravity and balancer applied to the measurement arm. Balances the force that tries to push up the measuring arm. In the vicinity of this balanced state, calibration and various adjustments after assembly of the measurement arm are performed so that the highest measurement accuracy can be obtained.

In the case of this example, a measurement error exceeding the allowable range occurs due to the influence of the balancer force. Therefore, as shown in FIG. 5, the specific posture limit where the balancer force becomes too weak and a measurement error exceeding the allowable range occurs. As a result, the angle sensor of the No. 5 joint 9 sets a value of + 80 °. In this example, the angle sensor of the No. 5 joint 9 is set to indicate 0 ° when the second link 8 is parallel to the ground. In terms of the relative angle with the two links 8, it is 170 °. When the specific posture limit approaches (for example, when the angle sensor of No. 5 joint 9 becomes 78 °)
As in the example of FIG. 4, the user is warned and the acquisition of data from the angle sensor and / or the output of the spatial coordinates is not performed when the specific posture limit is exceeded.

Even when the force of the balancer becomes too strong, the specific posture limit can be set similarly (in the example of FIG. 5, the angle sensor of the No. 5 joint 9 is −70 °), but in the measurement arm of this example, the measurement arm Since it is difficult to take such a posture that pushes down, it is possible to omit the lower user warning function in anticipation that the user will not exceed the lower specific posture limit.

FIG. 6 shows an internal configuration example of the dedicated processor 13 for performing measurement control based on the specific posture limit described in FIGS. 4 and 5. The outputs from the rotary encoders of the No. 1 to No. 6 joints are input to the counter circuit 61 and become signals representing the angles of the joints. The processor unit 60 of the dedicated processor 13 includes a condition determination unit 62 and a coordinate calculation unit 63 described below.

The coordinate calculation unit 63 reads, from the storage unit 65, design values that define a fixed positional relationship between the members of the measurement arm and positional deviations (calibration values) from the design values obtained after the measurement arm is assembled. And the angle of each joint input from the counter circuit 61 are substituted into the equation of motion to calculate the (X, Y, Z) coordinates of the probe tip. The calculated coordinates are sent to the application program of the computer 14 via the communication interface 68.

The condition determination unit 62 performs the following three processes according to the example of FIGS.
First, a process of comparing the angle of No. 3 joint input from the counter circuit 61 with values stored in the condition determination setting value storage unit 64 (78 ° and 80 ° in the example of FIG. 4). It is. Then, if the angle of the No. 3 joint exceeds 78 °, the condition judging unit 62 sends a signal to the speaker or lamp 67 via the warning interface 66 to warn the user and exceed 80 °. For example, the output of the spatial coordinate value from the coordinate calculation unit 63 is stopped.

Second, the angle of each joint input from the counter circuit 61 is input to the coordinate calculation unit 63 to calculate the position of the No. 1 joint. Based on the calculation result, the distance from the No. 1 joint to the arm fulcrum is calculated. This is a process of calculating the distance and comparing the calculation result with the values (1270 mm and 1300 mm in the example of FIG. 4) stored in the condition determination setting value storage unit 64. If the calculated distance exceeds 1270 mm, the condition determination unit 62 sends a signal to the speaker or the lamp 67 via the warning interface 66 to warn the user, and if the calculated distance exceeds 1300 mm, the coordinate calculation unit The output of the spatial coordinate value from 63 is stopped.

The third processing is to compare the angle of the No. 5 joint input from the counter circuit 61 with values stored in the condition determination setting value storage unit 64 (78 ° and 80 ° in the example of FIG. 5). It is. Then, if the angle of the No. 5 joint exceeds 78 °, the condition determination unit 62 sends a signal to the speaker or lamp 67 via the warning interface 66 to warn the user and exceed 80 °. For example, the output of the spatial coordinate value from the coordinate calculation unit 63 is stopped.

By stopping the output of the spatial coordinate value from the coordinate calculation unit 63 as described above,
The output of the spatial coordinate value from the processor unit 60 or the dedicated processor 13 is stopped. The condition judgment setting value 64, the measurement arm design value, and the calibration value 65 are R
It can be incorporated in the dedicated processor 13 in the form of a storage medium such as OM or RAM.
Further, the counter circuit 61, the alarm interface 66, and the storage units 64 and 65 can be configured as the control unit 69.

Although described here as the processor unit 60, the condition determination unit 62 and the coordinate calculation unit 63 may be configured as separate processors, or a program that describes the processing of the condition determination unit 62 when there is one processor. And may be configured to operate according to a program describing the processing of the coordinate calculation unit 63 at another time.

The bending motion of the No. 3 joint and No. 5 joint has a rotation angle limit on the structure of the measurement arm, but regardless of the physical rotation limit, the specific posture limit described above, Is warned and the output of the spatial coordinate value is stopped.

The specific posture limit value shown in FIG. 4 and FIG. 5 as an example may be set to the same value for measurement devices manufactured by the same design, but the verification data for each measurement device. It is also possible to decide according to. In the latter case, it is possible to specify an arm posture with reduced measurement accuracy including an error factor specific to each measuring apparatus, and thus the effect of maintaining an arm posture with which a stable measurement result can be obtained becomes higher.

An example of a method for obtaining verification data for each measuring apparatus is shown in FIG. In the example of FIG. 7, for example, 1 meter block gauges are placed at various locations around the front of the measuring device, and measurement is performed on each of them. Check the joint arrival position and the No.5 joint angle, and determine the limit value of each parameter. FIG. 7A shows the arrangement of the block gauge when the measuring apparatus is viewed from directly above, and FIG. 7B shows the arrangement of the block gauge when the measuring apparatus is viewed from the side. In addition to FIG. 7, the limit value of each parameter may be determined using the results of measurement with special gauges arranged at various positions.

Below, when the effect of balancer strength is roughly removed with correction software,
The operation contents of the coordinate calculation unit 63 and the accompanying storage unit 65 in FIG. 6 will be described.

First, the equation of motion used by the coordinate calculation unit 63 gives a spatial coordinate value of the probe tip P of the six-joint type three-dimensional coordinate measuring apparatus, and is a transformation matrix obtained by multiplying a matrix of 4 rows and 4 columns by 6 or more. Here, the second link part affected by the balancer force will be described in a simplified manner.

In the model shown in Fig. 8 (model where the influence of balancer force can be ignored), No
.4 In the coordinate system of the second link mechanism ignoring the joint, the spatial coordinate value of the probe tip P viewed from the No. 3 joint is the spatial coordinate value P of the probe tip P viewed from the No. 5 joint.
The equation of motion of the 4 × 4 conversion matrix to be converted into (x, y, z) is as shown in the following equation (1).

数式（１）において、Ａは、第２リンクの長さであり、Ｙは、No.5関節の角度
である。数式（１）には、バランサーの強弱による影響を補正する項が含まれて
いないため、数式（１）により計算されるＰ（ｘ，ｙ，ｚ）は、バランサーの力
の変化に伴う動的な測定誤差を有する。

In Equation (1), A is the length of the second link, and Y is the angle of No. 5 joint. Since the formula (1) does not include a term for correcting the influence of the balancer strength, P (x, y, z) calculated by the formula (1) is dynamic according to the balancer force change. Measurement error.

On the other hand, in this embodiment, as shown in FIG. 5, when the second link is rotated around the No. 5 joint, an equation of motion that takes into account that dynamic deflection occurs due to the strength of the balancer force F is obtained. Use. That is, the coordinate calculation unit 63 in the present embodiment is
Four lines for converting the spatial coordinate value of the probe tip P viewed from the No. 3 joint to the (corrected) spatial coordinate value P0 (x, y, z) of the probe tip P viewed from the No. 5 joint. For example, the following mathematical formula (2) is used as the equation of motion of the four-row transformation matrix. This mathematical formula (2) is derived by modeling the above-described deflection as shown in FIG.

数式（２）において、Ｂは、図９に示すように、No.3関節中心からたわみによ
る変曲点までの距離であり、Ｃは、No.5関節中心からたわみによる変曲点までの
距離であり、Ｂ＋ＣはほぼＡ（第２リンクの長さ）に等しいとする。Ｙは、No.5
関節の角度であり、Ｘは、たわみによるNo.3関節部の誤差角度ΔNo.3である。な
お、たわみによるNo.5関節部の角度誤差ΔNo.5は、No.5関節の検出角度Ｙに含ま
れて検知される。

In Equation (2), B is the distance from the No. 3 joint center to the inflection point due to deflection, as shown in FIG. 9, and C is the distance from the No. 5 joint center to the inflection point due to deflection. And B + C is approximately equal to A (the length of the second link). Y is No.5
This is the angle of the joint, and X is the error angle ΔNo. 3 of the No. 3 joint due to deflection. Note that the angle error ΔNo. 5 of the No. 5 joint due to the deflection is detected by being included in the detection angle Y of the No. 5 joint.

Formula (2) includes approximate correction in the case where there is one inflection point due to deflection as a term for correcting the influence of the balancer strength. That is, the mathematical formula (2
) Includes sinX, cosX, B, and C as terms that vary depending on the balancer strength. However, B and C may be treated as fixed values. X reflects changes due to balancer strength, and takes different values depending on the angle Y of the No.5 joint (
X increases as the balancer force increases, and X decreases as the balancer force decreases.)

Therefore, for example, a correction value X that is approximately internally interpolated from a correction constant set for each predetermined angle of the No. 5 joint is calculated, and this is substituted into the equation (2) to obtain the equation (2).
P0 (x, y, z) calculated by 2) is obtained by approximately removing the dynamic measurement error accompanying the change in the balancer force. The correction constant used here may be stored in the storage unit 65 as a calibration file, and the value can be changed according to the situation. Further, by detecting the balancer force with a sensor, a correction value may be calculated automatically (in real time), and the calculated value may be set.

In the above example, correction on the YZ plane of the second link is shown (the Y and Z coordinate values are affected by the correction). However, measurement errors can also be approximately eliminated for X coordinate values by similar correction. . The second link that receives the force of the balancer moves in conjunction with the rotation of the joints of No.4, No.5, and No.6, so if you correct not only the Y and Z coordinate values, but also the X coordinate value Thus, the spatial coordinate value P0 can be calculated with higher accuracy.

In the above example, the model having one inflection point has been described. However, even when a plurality of inflection points may exist due to the structure of the arm, the transformation matrix can be similarly developed. Furthermore, errors due to the influence of torsion can be corrected similarly by developing the transformation matrix.

In the above example, the spatial coordinate value (x, y, z) viewed from the No. 3 joint is converted to the spatial coordinate value viewed from the No. 5 joint, but the reverse conversion is of course also possible. Is possible.

In addition, when the influence by the balancer strength is generated in the link mechanism or joint part other than that shown in FIG. 9, it is analyzed how many axes the rotational movement or parallel movement is, and the above equation of motion is expressed. By incorporating it, it is possible to apply a wide range of corrections.

Although the embodiments of the present invention have been described above, it goes without saying that the above-described embodiments can be modified by those skilled in the art within the scope of the present invention. For example, the present invention can be applied to an articulated measuring apparatus having a configuration other than the configuration shown in FIG. The measurement arm in FIG. 1 is basically configured such that the second link is supported horizontally with respect to the vertical support and the first link hangs down from the vertical support. Of course, the present invention can also be applied to an apparatus in which the basic posture is when two links are perpendicular.

As described above, according to the present invention, the measurement device can detect whether or not the measurement posture in which the measurement arm is not subjected to the stress that causes the measurement error is maintained, and informs the user when the measurement posture is removed. Therefore, stable measurement results can be obtained.

In addition, when the stress that causes the measurement error is the balancer force of the measurement arm, it is possible to maintain a measurement posture in which a stable measurement result can be obtained by notifying the user as described above. It is also possible to obtain an accurate measurement result by correcting the influence of the balancer force and calculating the spatial coordinates.

The figure which shows the external appearance of an example of the articulated type coordinate measuring apparatus which concerns on this embodiment. The figure which shows the rotation direction of each joint of the measurement arm of FIG. The figure which shows the other example of the probe which can be attached to the measurement arm of FIG. The figure which shows an example of the parameter for pinpointing the attitude | position which a measurement error becomes large exceeding an allowable range, when a user is pulling a measurement arm and is measuring the far side. The figure which shows an example of the parameter for specifying the attitude | position in which a measurement error becomes large exceeding a tolerance | permissible_range by the influence of the balancer from which the generated force changes with attitude | positions of a measurement arm. The figure which shows the internal structural example of the exclusive processor of FIG. The figure which shows an example of the verification method for calculating | requiring the parameter of FIG.4 and FIG.5 peculiar to each measuring apparatus. The model figure for demonstrating the equation of motion of the 2nd link part of the measurement arm of FIG. The figure which illustrates the basic form of the bending which generate | occur | produces in the 2nd link part of FIG.

Explanation of symbols

1 Probe 2 Probe mounting part 3 No.1 joint (wrist joint)
4 No.2 joint 5 First link 6 No.3 joint (elbow joint)
7 No.4 joint 8 Second link 9 No.5 joint (shoulder joint)
10 No. 6 joint 11 support 12 stand 13 dedicated processor 14 computer 31 non-contact type probe 32 probe joint 33 non-contact type probe controller 60 processor unit 61 counter circuit 62 condition determination unit 63 coordinate calculation unit 64 condition determination setting value storage unit 65 Design value and calibration value storage unit 66 of measurement arm 66 Alarm interface 67 Speaker and / or lamp 68 Communication interface 69 Control unit

Claims (6)

A probe can be attached to one end, a probe attachment member, a first link and a second link are connected in order, and an articulated measurement arm with the other end attached to a support member;
A processor for calculating a spatial coordinate corresponding to the position of the probe based on an angle of each joint of the measurement arm;
Based on whether or not a predetermined parameter related to the posture of the measurement arm exceeds a predetermined value, it is possible that a measurement error caused by the user's applied force deflecting the measurement arm may exceed an allowable range. for a storage means for storing said predetermined value,
Warning means for giving a warning to a user when it is detected that there is the possibility based on whether a predetermined parameter relating to the posture of the measurement arm exceeds a predetermined value stored in the storage means; equipped with,
As the predetermined parameter relating to orientation of the measuring arm, characterized by Rukoto with either or both of the second parameter related reach of the first parameter and the measuring arm with respect to the angle the link makes the measuring arm Articulated coordinate measuring device. The articulated coordinate measuring apparatus according to claim 1, wherein the force applied by the user is a force pulling the measurement arm away from the support member. The articulated coordinate measuring apparatus according to claim 1, wherein the force applied by the user is a force for contracting the measuring arm toward the support member. A probe can be attached to one end, a probe attachment member, a first link and a second link are connected in order, and an articulated measurement arm with the other end attached to a support member;
A processor for calculating a spatial coordinate corresponding to the position of the probe based on an angle of each joint of the measurement arm;
Provided shoulder joint or near the measuring arm, the balancer for the upper has the elbow joint end of the second link against the force of gravity exerted on the measuring arm to generate a so that force,
Based on whether or not a predetermined parameter related to the posture of the measurement arm exceeds a predetermined value, a measurement error caused by the force applied by the balancer being deflected by the measurement arm may exceed an allowable range. to detect a storage means for storing said predetermined value,
Warning means for giving a warning to a user when it is detected that there is the possibility based on whether a predetermined parameter relating to the posture of the measurement arm exceeds a predetermined value stored in the storage means; equipped with,
As the predetermined parameter relating to orientation of the measuring arm, characterized by Rukoto with either or both of the second parameter related reach of the first parameter and the measuring arm with respect to the angle the link makes the measuring arm Articulated coordinate measuring device. The apparatus further comprises means for stopping the output of the spatial coordinates from the processor in response to detection that a predetermined parameter relating to the posture of the measurement arm exceeds a value stored by the storage means. The articulated coordinate measuring apparatus according to any one of claims 1 to 4 . A probe can be attached to one end, a probe attachment member, a first link and a second link are connected in order, and an articulated measurement arm with the other end attached to a support member;
Wherein provided in the shoulder joint or near the measuring arm, the upper having the elbow joint end of the second link against the force of gravity exerted on the measuring arm is a so that force, so as to deflect the measuring arm A balancer to generate
Corresponding to the position of the probe by inputting the angle of each joint of the measurement arm into an equation including a term that corrects an error caused by the force that deflects the measurement arm varies depending on the angle of the shoulder joint An articulated coordinate measuring apparatus comprising a processor for calculating spatial coordinates.

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