JPH06226663A - Robot positioning control device - Google Patents

Abstract

PURPOSE:To confirm positioning correctly by obtaining the deviation between the target position of each shaft corresponding to the target position of the tool tip and the driving position of each shaft at the time of being driven in such a way as to coincide with the target position at both teaching time and playback time, and comparing both deviations with each other. CONSTITUTION:A six-axis robot with tools (hands) provided at the tips of arms has plural arms 7 driven by the respective shafts, and a motor 16 for driving each shaft is controlled by a controller 10. In the case of positioning this robot, the pulse signals of a pulse encoder 17 additionally provided at the motor 16 are taken into a CPU 11 through a counter 15, and the deviation between the target position of each shaft and the driving position of each shaft at the time of being driven in such a way as to coincide with the target position is stored at the teaching time. The deviation is compared with the deviation obtained in the same way at the playback time. In the case of the difference between both deviations being the threshold value or less on every shaft, positioning is judged to be completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning control device for various robots such as industrial robots, and more particularly, accurately confirms the positioning even if the position deviation of each axis becomes large due to the influence of the posture of the robot or the carrying load. The device that can be used for

[0002]

2. Description of the Related Art In a so-called teaching / playback type robot, during teaching, each axis of the robot is sequentially driven so that the tool tip of the robot coincides with each target position, and the tool tip position is sequentially taught. During playback, each axis of the robot is sequentially driven so that the tip of the tool of the robot coincides with the position of each tip of the taught tools, and the robot is sequentially positioned. Here, during playback, the robot is positioned sequentially by sequentially executing the program according to the teaching result.When executing this program, make sure that the robot is correctly positioned at the taught position. After that, the processing is shifted to the movement command regarding the next teaching position.

Here, as a general method of confirming the completion of positioning, there is a method of determining that the positioning is completed when the positional deviation between the target position of each axis of the robot and the current position falls within an allowable range.

However, such positioning confirmation has not been performed at the time of teaching work. Therefore,
When a workpiece with a heavier weight than usual is attached or a large hand is attached and it has a larger load than the standard, or when the so-called transport load or the robot's posture affects it, a certain amount of each robot axis The position deviation of the axis is outside the permissible range, and teaching may be performed in that state. When the move command of the above program is executed in such a state,
With respect to the above-mentioned predetermined axis, the position deviation is out of the allowable range and the positioning cannot be confirmed, and an error occurs and the program cannot be executed.

Therefore, in order to solve such a problem, when the power is turned on to perform the teaching work, the position deviation of each axis of the robot at that time is taken in and is obtained at the time of the playback and the taken-in position deviation. When the difference from the position deviation falls within a predetermined allowable range, it is considered that the positioning is completed. That is, the fact that the position deviation differs depending on each axis is taken into consideration.

[0006]

However, even with such a positioning confirmation system, if the power is turned on and the position deviation is taken in under a light load condition, when a heavy load condition occurs during playback. However, the deviation may be out of the allowable range, and an error occurs that the positioning cannot be confirmed. On the contrary, if the power is turned on in the heavy load state and the position deviation is taken in, an error occurs that the positioning cannot be confirmed in the light load state during playback.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a positioning control device which can always perform accurate positioning confirmation in consideration of the fact that the position deviation varies for each teaching position. .

[0008]

Therefore, in the present invention, at the time of teaching, each axis of the robot is sequentially driven so that the tool tip of the robot coincides with each target position, the tool tip position is sequentially taught, and at the time of playback. In a robot positioning controller that sequentially drives each robot axis so that the tool tip of the robot matches the taught tool tip position, the robot positioning control device corresponds to the tool tip target position during teaching. The deviation between the target position of each robot axis and the drive position of each axis when each robot axis is driven so as to match the tool tip target position is stored for each taught tool tip position, and during playback, , The target position and front of each axis of the robot corresponding to the stored tool tip position The deviation from the driving position of each axis when each axis of the robot is driven so as to match the stored tool tip position is obtained, and the difference between the obtained deviation and the stored deviation is for all axes. When it is less than or equal to a predetermined threshold value, it is determined that the positioning at the tool tip position is completed, and only when the determination is made, the next tool tip position is positioned.

[0009]

According to this structure, at the time of teaching, the target position of each robot axis corresponding to the tool tip target position and the drive position of each axis when the robot axis is driven so as to match the tool tip target position The deviation is stored for each taught tool tip position. At the time of playback, the deviation between the target position of each robot axis corresponding to the stored tool tip position and the drive position of each axis when the robot axis is driven so as to match the stored tool tip position is obtained. When the difference between the calculated deviation and the stored deviation is less than or equal to the predetermined threshold value for all the axes, it is determined that the positioning at the tool tip position has been completed. Then, after the completion of the positioning is confirmed in this way, the positioning of the next tool tip position is similarly performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a robot positioning control apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the controller of the embodiment. In the embodiment, it is assumed that the controller controls the 6-axis robot 8 shown in FIG. That is, the robot 8 applied to the embodiment has first to sixth axes 6 whose rotation positions are represented by θ1 to θ6 as shown in FIG. Assume a vertical articulated robot equipped with 9. The controller 10 of FIG. 1 drives and controls each axis of the robot 8 and an arm or the like driven by each axis (for example, the arm 7 in the case of the second axis 2 (see FIG. 3)). It is configured. In FIG. 1, only the arm 7 is shown as a representative for convenience of explanation, but in reality, all the other elements of the robot 8 such as the other arm and the lower swing body are drive-controlled by the controller 10.

The memory 12 stores a program created according to a teaching result, which will be described later.
The PU 11 calls the above-mentioned program step by step, interprets the instruction, and sequentially executes the processing.

That is, assuming that the operation of the arm 7 of the robot 8 is controlled, the pulse signal output from the pulse encoder 17 as a position detector attached to the motor 16 for rotating the arm 7 will be described. Counter 15
The control amount is input to the CPU 11 via the, the control amount is calculated in the CPU 11, and the control amount is output to the servo amplifier 14 corresponding to the second axis 2 via the D / A converter 13. As a result, a driving signal is applied from the servo amplifier 14 to the motor 16, and the driving force of the motor 16 drives the arm 7, that is, the second shaft 2 by a predetermined amount. The other axes, namely the 1st axis and the 3rd to 6th axes, are similarly driven and controlled.

FIG. 2 is a block diagram showing the control system of the controller 10, and constitutes a feedback control system as shown in FIG.

A target trajectory calculating section 18 shown in the figure calculates the target trajectory of the tool tip position of the robot 8 based on the teaching result. That is, during the teaching work of the robot 8, each axis of the robot 8 is sequentially driven by the remote controller so that the tool tip of the robot 8 coincides with each preset target position, and the tool tip position is sequentially taught. Work is done. As a result, 6 degrees of freedom (X, Y, Z, A, B, C)
The tool tip positions having (three-dimensional positions for X, Y, and Z, and angles for A, B, and C) are sequentially stored in the memory 12 (see FIG. 5).

As a result, the target trajectory of the tool tip is calculated by the target trajectory calculating section 18 based on each of the tool tip positions which are taught and stored in the memory 12, and the successive target positions on the target trajectory are calculated. A calculation for converting to the target position θd (θ1d to θ6d) of each axis 1 to 6 is performed, and this is sequentially output at the time of playback.

On the other hand, the encoder 17 sequentially outputs the present rotational positions θ (θ1 to θ6) of the shafts 1 to 6. As a result, the deviation ei (i = i = i) between the target position θd and the current position θ
1 to 6; e1 = .theta.1d-.theta.1, e2 = .theta.2d-.theta.2, ..., And these are added to the servo calculation unit 19.

In the servo calculation unit 19, the added deviation e
Is calculated to be zero and is applied to the motor 16 via the servo amplifier 14. As a result, the motor 16 drives each element of the robot 8 including the arm 7 so that the tool tip position is on the target trajectory.

In this way, the axes 1 to 6 of the robot are sequentially driven and the positioning of the robot 8 is sequentially performed. In this embodiment, it is sequentially confirmed that the positioning of the tool tip position is completed during playback. The determination is made and the subsequent processing is advanced. Therefore, the above determination process will be described.

By the way, in the vertical articulated robot 8 shown in FIG. 3, the position deviation of each axis often takes different values for each teaching position due to the influence of so-called transport load and posture. That is, FIG. 3 (a)
When attempting to maintain the posture described above, the positional deviations of the axes 1 to 6 are small as shown in FIG. The numbers shown in FIG. 4 represent the position deviations of the axes 1 to 6 by the number of pulses output from the encoder 17. In addition, FIG.
In order to maintain the posture of FIG. 2, the positional deviation of the second axis 2 increases from “4” to “11” in the posture (a), and in the posture of FIG. Therefore, the load becomes large, the position deviation of the second shaft 2 becomes large as "15", and the position deviation of the third shaft 3 also becomes large as "11".

In this example, it is assumed that the above-mentioned conventional technique is applied. Now, assuming that the allowable value of the position deviation is 10 pulses, the point is taught without any problem because the positioning is not confirmed during the teaching work. However, when executing the movement command of the taught program during playback, it is confirmed whether or not the robot 8 is positioned at the teaching position. However, FIG.
In the postures of (b) and (c), the position deviation of the second axis 2 or the third axis 3 exceeds the permissible value of 10 pulses, so an error that the positioning cannot be confirmed occurs and It becomes infeasible.

Therefore, in this embodiment, in order to eliminate such inconvenience, each tip position of the tool of the robot 8 is taught at the time of teaching as described above, and these are stored in the memory 12 as well as previously set. 1 to 6 when the axes 1 to 6 of the robot 8 are driven so as to match the target positions of the axes 1 to 6 of the robot 8 corresponding to the respective target positions of the tool tip
The deviation from the driving position of the tool is calculated for each taught tool tip position, and these are stored in the memory 12.

More specifically, the position deviations of the axes 1 to 6 for the respective postures as shown in FIGS. 3 (a), 3 (b) and 3 (c) where the tool tip positions are different are shown in FIG. Is obtained at. The position deviation acquired at this time is set to the offset value eioff.
set (i indicates each axis 1 to 6). On the other hand, memory 1
The inside of 2 has a table as shown in FIG. 5, and this table stores an instruction and various data relating to the instruction for each step. Therefore, an area for newly storing the offset value eioffset of each axis is provided in the data relating to the movement command, and when a point (X, Y, Z, A, B, C) is taught, each axis 1 at that time is taught in this area. The position deviation eioffset of ˜6 is stored.

At the time of playback, the memory 12
The tool tip position stored in the table, that is, the target position θd of each axis 1 to 6 of the robot 8 corresponding to the target trajectory calculated by the target trajectory calculation unit 18 and each axis of the robot 8 so as to match the target trajectory. A deviation ei from the drive position θ of each shaft 1 to 6 when driving 1 to 6 is obtained.

Then, the difference between this deviation ei and the stored offset value ei offset is calculated, and it is determined whether this difference is equal to or less than a predetermined allowable value elimit as shown in the following equation (1).

| Ei-ei offset | ≦ elimit (1) where i: number of axes ei: position deviation of each axis ei offset: each axis offset value stored at each step elimit: allowable value of position deviation When the expression 1) is satisfied for all the axes 1 to 6, it is determined that the positioning at the tool tip position at that time is completed. Specifically, the axial position deviations ei during playback are as shown in FIG. On the other hand, each axis offset value acquired at the time of teaching also shows a value close to the value shown in FIG. This is because if the tip positions of the tools are the same and the postures are the same, the influences due to the different postures and the influence due to the conveyance load are eliminated, and the deviations of the respective axes show substantially the same values. For example, the offset value e2offset of the second axis 2 becomes "12" in the posture of FIG. 3C, and the position deviation e2 in the same posture
It is almost equal to "15". Therefore, if elimit is set to “10” as the threshold value and the above equation (1) is applied,
The above formula (1) is satisfied. If the formula (1) is similarly satisfied for the other axes, it is determined that the positioning of the tool tip position at that time is completed. Then, when it is determined that the process is completed, the process moves to the next movement command on the program, and thereafter, the positioning of the next tool tip position is similarly performed.

On the other hand, if the above equation (1) is not satisfied for any one of the axes 1 to 6, it is judged that the positioning at the tool tip position has not been completed, and that an error has occurred. Take appropriate measures.

According to such an embodiment, even if the position deviation itself fluctuates due to the influence of the posture and the carrying load on the robot 8, it is possible to always perform accurate positioning confirmation and perform the work accurately. Will be able to. Moreover, it is only necessary to add an area for newly storing the offset value of each axis to the memory for storing the teaching program at each step, and the memory map of the software can be changed without remodeling the hardware. It is only necessary to do so, and there is an additional effect that it can be implemented easily and at low cost.

[0029]

As described above, according to the present invention, even if the position deviation of the robot changes due to the influence of the posture and the carrying load, it is possible to always perform accurate positioning confirmation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus of an embodiment of a robot positioning control apparatus according to the present invention.

FIG. 2 is a control block diagram of the controller shown in FIG.

FIG. 3 is a diagram exemplifying a posture that a robot applied to the embodiment can take.

FIG. 4 is a table showing the positional deviation of each axis for each posture shown in FIG.

FIG. 5 is a diagram showing an example of contents of a table stored in the memory shown in FIG.

[Explanation of Codes] 1 to 6 1st axis to 6th axis 7 Arm 8 Robot 9 Hand 10 Controller 11 CPU 12 Memory

Claims (1)

[Claims] 1. During teaching, each axis of the robot is sequentially driven so that the tool tip of the robot coincides with each target position to sequentially teach the tool tip position, and at the time of playback, the tool tip of the robot is taught. In a robot positioning control device that sequentially drives each robot axis to match each tool tip position and sequentially positions the robot, the target position of each robot axis corresponding to the tool tip target position and the tool tip when teaching The deviation from the driving position of each axis when the robot axes are driven so as to match the target position is stored for each taught tool tip position, and corresponds to the stored tool tip position during playback. Match the target position of each axis of the robot and the stored tool tip position When each axis of the robot is driven, the deviation from the driving position of each axis is calculated, and the difference between the calculated deviation and the stored deviation is below a predetermined threshold value for all axes. If it is, it is determined that the positioning at the tool tip position is completed, and only when the determination is made, the next tool tip position is positioned.