JPS63174893A - Manipulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a manipulator, which requires absolute positional accuracy suitable for use in a narrow space, especially where there are some structures around it. This relates to a manipulator.

(Prior Art) Although conventional industrial manipulators claim to have high positional accuracy, this accuracy is a positional accuracy related to repeatability, and when arbitrary tip coordinates are given from the base of the manipulator, It does not mean absolute positional accuracy indicating how close to the coordinates.

Since a normal manipulator has an incremental encoder directly connected to the actuator, it does not detect the position of the tip output from the actuator via the gear head (including errors due to gear play, etc.).

(Problem to be solved by the invention) Therefore, from the point of view of the above-mentioned absolute positional accuracy.

It is inevitable that errors will occur. To put it in an extreme way, even if the actuator and gearhead are empty,
The robot controller cannot detect abnormalities. Furthermore, since an incremental encoder is used, if there is an accident, the encoder is cleared due to an erroneous operation, or a miscount due to noise, the current posture of the manipulator becomes unclear.

When the manipulator is inserted and used in a narrow place, it becomes difficult to return the manipulator to its original state, which may cause damage to surrounding structures and the like.

The present invention has been made based on the above-mentioned circumstances, and provides a manipulator that can obtain absolute position accuracy and can return to its original state even if the encoder count is messed up due to an accident or erroneous operation.

(Means for Solving Problems) The manipulator of the present invention includes an incremental encoder directly connected to an actuator that drives the tip of the manipulator, and an absolute encoder directly connected to a joint shaft driven by the actuator via a gear head and a bevel gear mechanism. It is characterized by having the following.

(Function) In the manipulator of the present invention having the above configuration, if the outputs of the incremental encoder and absolute encoder are used and the actuator is controlled using an appropriate control circuit, it is possible to control only the output axis of the joint part. It is possible to eliminate positional errors at the tip caused by backlash in the gear system, and further to eliminate instability of movement.

(Embodiment) FIG. 1 is a schematic diagram showing the configuration of one joint of a manipulator according to an embodiment of the present invention. In this figure, the joint part 2 of the manipulator 1 is housed in a cylindrical body 3 and serves as an actuator for the joint part, including a DC motor 4, a gear head 5 driven by the DC motor 4, and a gear head 5 connected to an output shaft 5a of the gear head 5. It has a large bevel gear 6a and a pair of small bevel gears 6b that mesh with the large bevel gear 6a, and the pair of small bevel gears 6b are mounted on a central piece 7a, one of which is rotatable and the other. has a mouth-shaped joint shaft 7 that is fixedly supported. The large bevel gears 6a and 6b and the joint shaft 7 constitute a bevel gear mechanism 6.

A manipulator tip 1a is fixed to the tips of both leg pieces 7b of the joint shaft 7, and an absolute encoder 8 is attached to an extension of the center piece 7a of the joint shaft 7 that protrudes from the cylinder body 3.
is installed.

The DC motor 4 also has a brake 9. A tacho generator 10 is attached. In the figure, 11 is an incremental encoder directly connected to the DC motor 4, and 12 is a limit switch for detecting the position of the tip 1a.

When the DC motor 4 is rotated, the large bevel gear 6a is rotated at low speed via the gear head 5, and the small bevel gear 6b is also rotated. Thus, the small bevel gear 6b that is fixedly supported by the center piece 7a rotates the joint shaft 7, causing the distal end portion 1a to swing about the center piece 7a of the joint shaft 7. Although only one joint is shown in this figure, even if the manipulator has a plurality of joints, those joints are constructed in the same manner as described above.

In the manipulator of the present invention having the above configuration, since the gear head 5 and the bevel gear mechanism 6 are interposed between the incremental encoder 11 and the absolute encoder 8, play in the gear head 5 and the bevel gear mechanism 6 may be the cause. This causes a deviation between the two encoders.

The manipulator of the present invention is controlled by a control circuit shown in FIG. When the operator or the host computer inputs data on the coordinates of the tip 1a, its posture, and moving speed to the interpolation calculation circuit 20, the interpolation calculation circuit 20 combines the data with the data regarding the current posture input from the absolute encoder 8. The angle error (converted to the count value of the incremental encoder) of the joint at each minute time is determined by comparing the At the same time, data from absolute encoder 8 is transferred to incremental encoder 1 via converter 21 and counter value converter 22.
1 counter circuit 23. The timing circuit 24 generates timing pulses, and the speed calculation circuit 25
receives the data, calculates joint velocity data, and outputs it to the servo driver 26.

Further, the timing circuit 24 sends a timing pulse to the counter value conversion circuit 22, and converts the counter value of the absolute encoder 8 to the incremental encoder 11.
preset to the counter value.

In addition, in FIG. 2, 27 indicates an operator or an emergency stop switch, and 28-1, 28-2 indicates a relay contact.

The actuator is controlled by the above control routine.

With the above method, the joint (the tip 1a) is driven while correcting the error moment by moment based on the data regarding the actual state of the tip 1a given by the absolute encoder 8 and the data from the incremental encoder 11. The instability of the speed of the tip 1a is eliminated, and at the same time, the absolute position accuracy of the tip 1a is obtained.

Figure 3 shows the position of the tip at the interpolation point between points A and B using the output shaft position sensor, and between points A and B while checking the sensor directly connected to the actuator. , indicates that the drive is performed. In this figure, a twisting joint is shown, and 0 indicates a bending joint.

Note that the present invention is not limited to the above embodiments. For example, instead of absolute and incremental encoders,
Potentiometers or resolvers may also be used.

[Effects of the Invention] As is clear from the above, in the manipulator of the present invention, it is possible to eliminate the positional error of the tip caused by the backlash of the gear system that occurs when controlling only the output shaft of the joint, and furthermore, the manipulator of the present invention can The instability of can be eliminated.

Further, even if the counter value of the incremental encoder becomes abnormal for some reason, the control circuit corrects it, thereby improving the reliability of the manipulator.

[Brief explanation of the drawing]

Claims (1)

[Claims] A manipulator comprising: an incremental encoder directly connected to an actuator that drives the tip of the manipulator; and an absolute encoder directly connected to a joint shaft driven by the actuator via a gear head and a bevel gear mechanism.