JPH05181515A - Method for calculating axial angle in articulated robot - Google Patents

Abstract

PURPOSE:To improve operability for a coordinate transformation processing and to execute a work in an robot orbit reducing excess operations without narrowing the operational range of a robot by automatically selecting a posture parameter for shortening a moving distance. CONSTITUTION:A posture parameter SP is composed of data (a1, a2 and a3) of three bits. Prior to the calculation, the posture parameters SP of these three bits are successively decided and for this execution example, however, the posture parameters are successively decided in the order of the posture parameter a1 for the first axis - the a2 for the fifth axis - the a3 for the sixth axis. Respective axial angles at a position P are decided by using the decided posture parameter, the position of a control point and the direction of a tool. When the above-mentioned processing is completed, the respective axial angles at the next position on the robot orbit are calculated, afterwards, such a processing is repeatedly executed. This method can be applied to any articulated robot excepting for a 6-axis robot as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an articulated robot, and more particularly, to the position of a control point and the attitude of a tool, as well as the angle of each axis of an articulated robot using attitude parameters that define the operating angle range of the axis. The present invention relates to a method for calculating an axis angle in a multi-joint robot specified as one.

[0002]

2. Description of the Related Art At present, a teaching playback system is the mainstream as a teaching method for industrial robots. However, according to this teaching playback method, it is necessary to interrupt the work in order to create the robot program. In particular, recently, the teaching time tends to increase due to the increase in the number of robots installed in the production line and the diversification of target work, and the reduction in production efficiency due to the line stop is becoming a problem.

For this reason, an off-line program system which can create a robot program without stopping the work or the production line is drawing attention.

This off-line program system teaches, confirms operation, and deletes data without using the robot body or actual work.
It is possible to transmit data, and a computer creates a work model and a robot model corresponding to the actual work and robot, displays these models in three-dimensional graphic form, and displays the robot model on the display screen. A robot program is created by moving the robot model. The created program is transferred to the actual robot via the data transmission line.

In the off-line programmer,
Teaches the position of the control point and the attitude of the tool in a rectangular coordinate system,
In many cases, this rectangular coordinate system is transmitted to the robot main body, the robot main body converts the coordinates into an articulated coordinate system, and the robot is driven by a command from the coordinate-converted articulated coordinate system.

By the way, there are cases where the value of each axis in the articulated coordinate system cannot be uniquely determined even if the position of the control point and the attitude of the tool are specified in the Cartesian coordinate system.

For example, in a 6-axis robot, the position of the control point (X, Y, Z) and the direction of the tool (a, b, c)
Even if is specified, the angle of each axis of the robot is not fixed to one, and there are several combinations. Therefore, conventionally, an angle of each axis is determined as one by using a so-called posture parameter SP in addition to the position of the control point and the direction of the tool.

As one example, the attitude parameter SP is 3
Bit data (a1, a2, a3) has the following structure.

A1 ... 1st bit, the control point is the front / back surface of the robot (0: front surface 1: rear surface) a2 ... 2nd bit, 5 axis angle positive / negative (0: positive 1: negative) a3 ... 3rd bit, Positive / negative of 6-axis angle (0: positive 1: negative) As shown in FIG. 3, when the control point is in front of the rotation axis of the first axis, it is called the front, and when it is behind, it is called the back.

When coordinate conversion is performed by the off-line programming method using such posture parameters, the operator conventionally teaches not only the position and posture of the robot but also the posture parameters.

In an off-line program system for a specific application in the fields of gas cutting and panel welding, the position of the control point (X, Y, Z) and the direction of the tool (a, b,
Only c) was calculated, and the posture parameters were fixed and used.

[0012]

However, in the method of selecting the posture parameter by the operator,
In addition to deteriorating operability, if an incorrect posture parameter is selected, a large posture change may occur, and even the robot and peripheral devices may be destroyed in order to perform an operation that cannot be predicted by the operator. Further, the method of fixing the posture parameter may be difficult to deal with depending on the application, and may be an inefficient robot system in which the movement range cannot be fully utilized.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for calculating an axis angle in an articulated robot which enables efficient robot work and good operability. ..

[0014]

According to the present invention, the angle of each axis of the articulated robot is specified as one by using the position of the control point and the attitude of the tool as well as the attitude parameter that defines the range of the operating angle of the axis. In the method of calculating an axis angle in a multi-joint robot that performs coordinate conversion, the angle of each axis is obtained in correspondence with each value of the posture parameter in the coordinate conversion, and the value of each obtained posture parameter is obtained. The angle change amount between the angle of each axis corresponding to and the axis angle of the control point before the control point calculated previously is calculated for each axis, and the attitude parameter with the smaller angle change is the attitude at the control point. The axis angle selected as a parameter and determined by the selected posture parameter is selected as the axis angle at the current control point.

[0015]

According to the structure of the present invention, the angles of the respective axes when the posture parameters are changed are respectively obtained, and the obtained angles of the respective axes and the axes of the control point before the control point calculated previously are obtained. The angle change amount with respect to the angle is obtained, and the posture parameter corresponding to the smaller value of the angle change amount is selected as the posture parameter at the control point.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

FIG. 1 is a flow chart showing an embodiment of the present invention. In this case, the present invention is as shown in FIG.
It is applied to the axis robot. In FIG.
θ1 is the first axis angle, θ2 is the second axis angle, θ3 is the third axis angle, θ4 is the fourth axis angle, θ5 is the fifth axis angle, and θ6 is the sixth axis angle.

Hereinafter, referring to the flow chart of FIG. 1, the position of the control point (X, Y, Z) and the direction of the tool (a, b,
A method of determining each axis angle θ1 to θ6 of the 6-axis robot based on c) and the posture parameter SP will be described.

The posture parameter SP is 3-bit data (a1, a2, a3) and has the following structure as described above.

A1 ... 1st bit, the control point is the front / back surface of the robot (0: front surface 1: rear surface) a2 ... 2nd bit, 5 axis angle positive / negative (0: positive 1: negative) a3 ... 3rd bit, Positive / negative of 6-axis angles (0: positive 1: negative) In this case, each axial angle θ1 to θ6 at a certain position P on the movement trajectory of the robot is calculated.

First, prior to the above calculation, each axis angle θ1 at the position P'one before the position P on the movement locus.
′ To θ6 ′ are obtained (step 100). That is, when the previous position P ′ is the first position on the movement trajectory of the robot, the posture parameter SP is fixed, and therefore the Cartesian coordinates (X ′, Y ′, Z ′) of the position P ′. , Tool direction (a ', b', c ') and attitude parameter SP
From this, each axis angle θ1 ′ to θ6 ′ can be uniquely determined, and when the position P ′ is the second position or later of the robot movement locus, the following steps 110 to 240 are executed. When calculating the position P, the axial angles θ1 ′ to θ6 ′ have already been obtained.

That is, when the previous position P'is the first position on the locus of movement of the robot, P '= {X', Y ', Z', a ', b', c ', S
From P}, Θ = {θ1 ′, θ2 ′, θ3 ′, θ4 ′, θ5 ′,
Inverse conversion to θ6 ′} will be performed.

Next, the position of the position P and (X, Y,
Z) and the attitude (a, b, c) of the tool, the work size,
It is determined based on the position and direction of the peripheral device of the robot (step 110). At this time, the posture parameter SP is still undecided.

Hereinafter, the above 3-bit attitude parameter SP
In this embodiment, the posture parameters are sequentially determined in the order of the posture parameter a1 for the first axis, the posture parameter a2 for the fifth axis, and the posture parameter a3 for the sixth axis. I will do it.

Determination of posture parameter a1 for the first axis First, P = {X, Y, Z, a, b, c, SP with SP = 000 (a1 = 0, a2 = 0, a3 = 0). } To Θ =
Inverse conversion to {θ1, θ2, θ3, θ4, θ5, θ6}
The first axis angle θ1 (000) is extracted from the obtained axis angles (step 120).

P (000) → Θ (000) = {θ1 (000), θ2 (00
0), θ3 (000), θ4 (000), θ5 (000), θ6 (000)} Next, SP = 100 (a1 = 1, a2 = 0, a3 = 0), and P = {X, Y , Z, a, b, c, SP}, Θ =
Inverse conversion to {θ1, θ2, θ3, θ4, θ5, θ6}
The first axis angle θ1 (100) is extracted from the obtained axis angles (step 130).

P (100) → Θ (100) = {θ1 (100), θ2 (10
0), θ3 (100), θ4 (100), θ5 (100), θ6 (100)} Next, in the case of SP = 000, the first axis angle θ1 (000) and the position at the previous position P ′ The absolute value | θ1 (000) -θ1 '| of the difference from the 1-axis angle θ1' is calculated, and the first axis angle θ1 (100) and the first position P'at the position 1'before SP = 100.
The absolute value | θ1 (100) −θ1 ′ | of the difference from the shaft angle θ1 ′ is obtained, and both are compared (step 140). Then, as a result of this comparison, the first bit a1 (0 or 1) of the orientation parameter SP having the smaller value among these angular differences is determined as the orientation parameter for the first axis (step 150).

Determination of attitude parameter a2 for the fifth axis When determining the attitude parameter a2 for the fifth axis,
The posture parameter a1 for the first axis is fixed to the value determined in the previous step 150. That is, when "0" is selected as a1, SPs "000" and "010" are used to determine the posture parameter a2 for the fifth axis. In this case, it is assumed that "0" is selected as a1.

First, SP = 000 (a1 = 0, a2 = 0,
a3 = 0), P = {X, Y, Z, a, b, c, S
From P}, Θ (000) = {θ1 (000), θ2 (000), θ3 (000),
Inverse conversion to θ4 (000), θ5 (000), θ6 (000)} is performed, and the fifth axis angle θ5 (000) is extracted from the obtained axis angles (step 160). The fifth axis angle θ when SP = 000 or SP = 100 calculated in step 160
Since 5 (a100) has already been obtained in the previous step 120 or 130, it is not necessary to perform the actual calculation in this step.

Next, SP = 010 (a1 = 0, a2 = 1,
a3 = 0), P = {X, Y, Z, a, b, c, S
The inverse transformation from P} to Θ = {θ1, θ2, θ3, θ4, θ5, θ6} is performed, and the fifth axis angle θ1 (010) is obtained from each axis angle obtained.
Is extracted (step 170).

P (010) → Θ (010) = {θ1 (010), θ2 (01
0), θ3 (010), θ4 (010), θ5 (010), θ6 (010)} Next, in the case of SP = 000, the fifth axis angle θ5 (000) and the first position P ′ The absolute value of the difference from the 5-axis angle θ5 ′ | θ5 (000) −θ5 ′ | is obtained, and the fifth axis angle θ1 (010) when SP = 010 and the fifth value at the previous position P ′ are obtained.
The absolute value | θ1 (100) −θ5 ′ | of the difference from the shaft angle θ5 ′ is obtained, and both are compared (step 180). Then, as a result of this comparison, the second bit a2 (0 or 1) of the orientation parameter SP having the smaller value among these angular differences is determined as the orientation parameter for the fifth axis (step 190).

Determining the attitude parameter a3 for the sixth axis When determining the attitude parameter a2 for the sixth axis,
The posture parameter a1 for the first axis is fixed to the value determined in step 150, and the posture parameter a2 for the fifth axis is fixed to the value determined in step 190. In this case, it is assumed that "0" is selected as a1 and "1" is selected as a2. Therefore, in this case, as the SP, "010" and "011" are the posture parameters a for the sixth axis.
Used to determine 3.

First, SP = 010 (a1 = 0, a2 = 1,
a3 = 0), P = {X, Y, Z, a, b, c, S
From P}, Θ (010) = {θ1 (010), θ2 (010), θ3 (010),
Inverse conversion to θ4 (010), θ5 (010), θ6 (010)} is performed, and the sixth axis angle θ6 (010) is extracted from the obtained axis angles (step 200). Note that the sixth axis angle θ6 (010) calculated in this step 200 is the same as in the previous step 160 or 170.
You do not need to do any actual calculation in this step, as it has already been calculated in.

Next, SP = 011 (a1 = 0, a2 = 1,
a3 = 1), P = {X, Y, Z, a, b, c, S
P} is converted to Θ = {θ1, θ2, θ3, θ4, θ5, θ6}, and the sixth axis angle θ6 (011) is obtained from the obtained axis angles.
Is extracted (step 210).

P (011) → Θ (011) = {θ1 (011), θ2 (01
1), θ3 (011), θ4 (011), θ5 (011), θ6 (011)} Next, the sixth axis angle θ6 (010) in the case of SP = 010 and The absolute value | θ6 (010) -θ6 ′ | of the difference from the 6-axis angle θ6 ′ is calculated, and the sixth axis angle θ6 (011) when SP = 011 and the sixth position at the immediately preceding position P ′.
An absolute value | θ6 (011) −θ6 ′ | of the difference from the shaft angle θ6 ′ is obtained and both are compared (step 220). Then, as a result of this comparison, the third bit a3 (0 or 1) of the orientation parameter SP having the smaller value among these angular differences is determined as the orientation parameter for the sixth axis (step 230).

When each posture parameter is determined as described above, each axis angle at the position P is determined using the determined posture parameter, the position of the control point, and the tool direction (step 240). ). It should be noted that the finally obtained axis angles should have already been obtained by the inverse transformation of step 210 or step 220.

When the above processing is completed, each axis angle at the next position on the robot trajectory is obtained, and thereafter such processing is repeatedly executed.

The present invention can be applied to articulated robots other than the 6-axis robot. Also, the posture parameters are not limited to those described in the embodiment, and a posture parameter that defines the movement range of another axis may be used, and the movement range may be defined by other contents (in positive and negative Instead, for example, a posture parameter that defines the movement range by the axis angle) may be used.

Although the posture parameters are determined in order in the embodiment, all combinations of possible values of the posture parameters may be examined.

[0040]

As described above, according to the present invention,
Since the posture parameter with a small movement distance is automatically selected, the operability of the coordinate conversion process is improved, and the work of an efficient robot trajectory with less extra movement is performed without narrowing the movement range of the robot. obtain.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.

FIG. 2 is a diagram showing a 6-axis robot to which the present invention is applied.

FIG. 3 is a diagram illustrating a front / back surface of one axis.

[Explanation of symbols]

 θ1 ... 1st axis angle θ2 ... 2nd axis angle θ3 ... 3rd axis angle θ4 ... 4th axis angle θ5 ... 5th axis angle θ6 ... 6th axis angle

Claims (2)

[Claims] 1. A multi-joint robot that performs coordinate conversion that specifies the angle of each axis of the multi-joint robot as one by using a posture parameter that defines a motion angle range of the axis in addition to the position of the control point and the posture of the tool. In the method of calculating the axis angle in, in the coordinate conversion, the angle of each of the axes corresponding to each value of the posture parameter is respectively obtained, and the angle of each axis corresponding to the value of each obtained posture parameter and The angle change amount with each axis angle of the control point before the control point calculated previously is obtained for each axis, and the posture parameter with the smaller angle change amount is selected as the posture parameter at the control point, and the selected A method for calculating an axis angle in an articulated robot, characterized in that an axis angle determined by a posture parameter is selected as an axis angle at a control point this time. 2. The multi-joint robot is a 6-axis robot, and the posture parameter is a parameter for determining whether the control point is the front surface or the back surface of the robot, a parameter for determining positive / negative of a 5-axis angle, and a 6-axis. The method for calculating an axis angle in an articulated robot according to claim 1, including a parameter for determining whether the angle is positive or negative.