JPH0446784A - Work tool positioning device - 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] [Industrial Application Field] The present invention is applicable to parts insertion, removal, and
The present invention relates to a work tool positioning device that positions a work tool in the vertical direction or in the horizontal movement direction, which is attached to the tip of a versatile industrial robot used for assembly, etc.

[Prior Art] Conventionally, with the effort to save labor in assembling parts, robots with orthogonal coordinates have two tables that move in two directions on a plane, or horizontally articulated robots with multiple arms that can freely rotate in the horizontal direction. Many types of robots are in use. Since this type of robot only moves its tip on a flat surface, it is equipped with a work tool lifting device that lowers the work tool to a predetermined position. As shown in FIG. 6, this working tool elevating device l has a housing 21 that is attached to a support part of a robot (not shown), and a screw shaft 22 is attached to the housing 21, and a working tool 7 is attached to the lower end of the housing 21.
The spline shaft 23 to which the spline shaft 23 is attached is arranged in parallel in an upright direction. The screw shaft 2
A ball screw bearing 3 is screwed into the shaft 2, and the ball screw bearing 3 is configured to move up and down together with a spline shaft 23 via a bearing stand 24. Further, the screw shaft 22 is configured to rotate in response to the rotation of a drive motor 25, and the rotation of the screw shaft 22 causes the ball screw bearing 3 and the spline shaft 23 to move up and down, causing the lower end of the spline shaft 23 to be attached to the working tool. 7 is configured to move up and down.

The spline shaft 23 also includes spline bearings 5 rotatably held at the upper and lower parts of the support part of the robot.
A pulley 26 is attached to one side of the spline bearing 5, and rotates integrally with the spline bearing 5. The pulley 26 is configured to transmit the rotation of another motor (not shown) via a belt transmission mechanism (not shown), and rotates the spline shaft 23 at that position to rotate the power tool 7. It is configured to hold in any position.

[Problems to be Solved by the Invention] In this work tool positioning device, when the positioning of the robot is completed, the drive motor 25 is rotated to rotate the screw shaft 22, and the ball screw bearing 3 is lowered by a predetermined amount to lower the spline along with the screw shaft 22. The shaft 23 is lowered, but the moving speed of the spline shaft 23 is determined by the rotational speed of the screw shaft 22, and in order to lower it at high speed, the drive motor 25 must be rotated at high speed, and when the drive motor is stopped, There are drawbacks such as inability to position at an accurate height due to inertia. Further, when lowering the power tool 7 at a constant speed, the drive motor 25 must be accelerated to a predetermined high speed in a short time, and since the drive motor 25 itself has a fairly large inertia, the drive motor 25 screw shaft 22
In addition to the torque required to accelerate the robot, it is necessary to generate torque to accelerate the drive motor 25 itself, which requires a large drive motor 25, which increases its weight and reduces the torque required to drive the robot. This increases the size of the robot drive motor (not shown), resulting in insufficient torque.

The present invention aims to eliminate the above-mentioned drawbacks, and can be used at the tip of a robot to move the work tool up and down using not only a motor for linear movement of the work tool, but also a motor for rotation of the work tool. An object of the present invention is to provide a work tool positioning device configured to move the work tool at high speed without increasing the speed of the motor used for lifting and lowering, and to accelerate the work tool to high speed in a short time without increasing the size of the motor used for lifting and lowering. It is something to do.

[Means for Solving the Problems] In order to solve the above problems, a ball spline shaft having a spiral groove and a spline groove is provided, and a power tool that moves together with the ball spline shaft is connected to one end thereof. A ball screw bearing and a spline bearing are fitted and disposed on the ball spline shaft, and when the ball screw bearing rotates, the ball spline shaft moves linearly, and when the spline bearing rotates, the ball spline shaft rotates as a unit. It is configured as follows.

On the other hand, a ball screw bearing motor and a spline bearing motor are provided corresponding to the ball screw bearing and the spline bearing, respectively, and the ball screw bearing and the spline bearing are configured to rotate as these motors rotate, respectively. has been done. The control unit for the ball screw bearing motor and the spline bearing motor is configured to drive the spline bearing motor in a direction opposite to the rotational direction of the ball screw bearing motor when the spline bearing motor is driven. .

[Operation] In the above-mentioned work tool positioning device, the ball screw bearing motor is driven, and when the ball screw bearing rotates in response to the rotation, the ball spline shaft moves linearly. At the same time, the spline bearing motor is driven in the opposite direction to the ball screw bearing motor, the spline bearing rotates in response to the rotation, and the ball spline shaft rotates together with the spline bearing. The rotation direction of this ball spline shaft is opposite to the rotation direction of the ball screw bearing, so the ball screw bearing and the ball spline shaft rotate relative to each other, and the ball screw bearing rotates at a speed that is the sum of the speed of the ball spline shaft. Therefore, the ball spline shaft and the power tool can be moved to a predetermined position at high speed without increasing the rotation of the ball screw bearing motor.

In addition, when the ball spline shaft is moved by the ball screw bearing motor, the ball spline shaft can also be moved in the same direction by the spline bearing motor at the same time, so the ball spline shaft can be moved in a short time without using a large motor. It can be accelerated to a predetermined high speed and the work tool can be immediately moved at a constant speed.

[Example] Hereinafter, an example will be described about a work tool lifting device as an example of a work tool positioning device attached to an articulated robot. In FIG. 1, ``■'' is a power tool lifting device fixed to the tip of an arm 2 of an articulated robot (not shown) that rotates on a horizontal plane in response to rotation of a motor (not shown). The tip of the arm 2 serves as a support for the power tool elevating device 1, and two motor storage portions 2a and 2b are provided concentrically in a direction intersecting this.

The motor housings 2a and 2b each include a ball screw bearing direct drive motor 4 (hereinafter referred to as a ball screw bearing motor) that transmits rotation to a ball screw bearing 3 (described later), and a spline bearing 5 (described later). A spline bearing direct drive motor 6 (hereinafter referred to as spline bearing motor) is fixed. The ball screw bearing motor 4 and the spline bearing motor 6 have the same structure, and the motor storage portion 2a,
An annular stator 4a attached to fit into stator 2b
, 6a and a rotor 4b having a hollow hole in the center, 6b
It consists of These two rotors 4 b , '6
A ball spline shaft 8 having a working tool 7 attached to its lower end is arranged so as to pass through the hollow part b. Further, this ball spline shaft 8 is cut with a spiral groove 8a having a predetermined lead angle and a spline groove 8b extending along its axis at positions dividing the outer circumference into three equal intervals. , the balls 3a and 5a in the ball screw bearing 3 and the spline bearing 5 are fitted into the spline grooves 8b, respectively.

A ball screw bearing 3 is connected to the upper part of the rotor 4b of the ball screw bearing motor 4 so as to rotate together with the ball screw bearing 3, and this ball screw bearing 3 is screwed into the helical groove 8a of the ball spline shaft 8. It is configured as follows. Further, the ball screw bearing 3 is guided by a casing 9a fixed to the support portion of the arm 2, and is configured to be rotatable at that position. Further, a first pulley 10 is connected to the lower part of the rotor 4b of the ball screw bearing motor 4 so as to rotate together with the rotor 4b, and the rotation of the first pulley 10 causes a first belt mechanism (not shown) to rotate. The rotation of the ball screw bearing motor 4 is controlled by a first encoder (not shown) installed in the arm 2 via the first encoder (not shown).

On the other hand, a spline bearing 5 is connected to the rotor 6b of the spline bearing motor 6 located in the other motor storage portion 2b of the arm 2 so as to rotate together with the spline bearing 5 located below the rotor 6b. is configured to fit into the spline groove 8b of the ball spline shaft 8. The spline bearing 5 is rotatably held within a casing 9b attached to the support portion of the arm 2, and is configured to rotate together with the rotation of the spline bearing motor 6.

Further, a second pulley 12 is connected to the upper part of the rotor 6b of the spline bearing motor 6 so as to rotate together with the rotor 6b, and the rotation is transmitted into the arm 2 via a second belt mechanism (not shown). The rotation of the spline bearing motor 6 is controlled by an attached second encoder (not shown).

A first pulley 10 and a second pulley are provided on the partition wall 2c of the arm 2.
A brake means 14 is fixed between the pulley 12 and the pulley 12 to brake the rotation thereof, and the power to the robot is cut off to prevent the ball spline shaft 8 from falling due to the weight of the rear work tool 7. It is configured.

On the other hand, the ball screw bearing motor 4 and the spline bearing motor 6 are connected to a control device 15 as shown in FIG. This control device 15 sequentially calls pre-stored working positions to position the arm 2, and after completing the positioning of the arm 2, the control device 15 determines the target height position of the power tool 7, the initial non-rotation descending distance, and the non-rotation descending distance before stopping. , the rotation angle and the maximum speed will be described later.
a main control unit 17 that sends information to the user; a storage unit 18 that stores the height position of the work tool 7 and other necessary information corresponding to each work position;
Motor drive units 19a and 19b, which will be described later, are provided corresponding to the ball screw bearing motor 4 and the spline bearing motor 6, respectively, in response to command values from the main control unit 17.
A position command generation unit 16 that commands a target position and a target rotation angle for each predetermined control cycle, and a current command value corresponding to the target position and target rotation angle for each control cycle are supplied to power supply units 20a and 20b, which will be described later. Motor drive unit 19a
, 19b and a current according to the current command value to each motor 4,
A power supply unit 20a supplies power to the power supply unit 6.

20b, and a first rotation detection section 11 consisting of a pulse encoder.
and a second rotation detection section 13.

The position command generating section 16 has a first rotation detecting section 11 and a second rotation detecting section 11.
While detecting the completion of positioning of the height position of the work tool from the rotation detection unit 13, as shown in FIG. and rotation angle, a position command value is calculated for each control cycle according to the target movement speed pattern of each motor 4, 6, and is stored for each control cycle. At this time, only the ball screw bearing motor 4 is operated until the work tool 7 moves the initial no-rotation descending distance, and then the ball screw bearing motor 4 and the spline bearing motor are operated until the work tool 7 reaches the position where the non-rotation descending distance remains before stopping. The position command value is selected so that the spline bearings 6 and 6 face each other and the spline bearing 5 undergoes (n rotations + target rotation angle), and thereafter only the ball screw bearing motor 4 is driven. Also, work tool 7
The position command value is selected so that the moving speed of does not exceed the maximum speed.

2) Set O in the control count register.

3) Retrieve the target position of each motor 4, 6 according to the number of times of control and store it in each target position register.

4) Add +1 to the control count register.

5) Determine whether the value of the control count register has reached the total control count, and if it has not reached this, return to 2).

6) Store the final target position in each target position register, and
).

It is configured as follows.

Further, as shown in FIG. 4, the motor drive sections 19a and 19b perform the following steps: 1) Read the target position in the target position register and determine the positional deviation between the dirt and the current position.

2) Calculate the target speed according to the positional deviation from a predetermined relational expression between the positional deviation and the speed.

3) Calculate the speed deviation from the difference between the target speed and the current speed.

4) A current command value corresponding to the speed deviation is sent to the power supply unit 20a.
, send to 20b and return to ■).

It is configured as follows.

Note that it is desirable that the control cycle of the position command generating section 16 be an integral multiple of the control cycle of the motor drive sections 19a and 19b.

In the work tool lifting device described above, when the arm 2 of the robot is positioned at a predetermined work position, the main control unit 17 outputs the target height position of the work tool 7 corresponding to the work position, the initial non-rotation descending distance, and the no-rotation movement before stopping. The 0-position command generation unit 16, which receives the rotational descent distance and maximum speed, calculates the target position for each control number from these values and stores it. moreover,
The position command generation unit 16 sequentially retrieves the target position for each control count and stores it in the target position register corresponding to each motor 4, 6, respectively. On the other hand, the target position stored in the target position register is read into the motor drive units 19a and 19b, a position deviation obtained from the difference between the target position and the current position is calculated, and a target speed corresponding to this position deviation is calculated. Calculated. A speed deviation is calculated from this target speed and the current speed, and a current command value corresponding to this speed deviation is sent to the power supply sections 20a and 20b.
, 20b supply power to each motor 4, 6.

At this time, a position command value is given so that only the ball screw bearing 3 rotates and the spline bearing 5 does not rotate until the work tool 7 descends by the initial no-rotation descending distance, and after that, the work tool does not rotate before stopping. A position command value is given so that the ball screw bearing 3 and the spline bearing 5 are in opposite directions until reaching the position where the rotational descent distance remains, and the spline bearing 5 is at (n rotor target rotation angle), and then the ball screw bearing A position command value is given only to 3.

(See Figures 5A and 5B) When the power supply units 20a and 20b simultaneously output power to the ball screw bearing motor 4 and the spline bearing motor 6 according to their respective current command values, the ball screw When the bearing motor 4 rotates a predetermined amount of movement, the ball screw bearing 3 rotates as a unit in response to the rotation, and the ball spline shaft 8 descends by a predetermined amount. Power is supplied to rotate the ball spline shaft 8 in a direction opposite to the rotation direction of the ball spline shaft 8, and as the spline bearing 5 rotates, the ball spline shaft 8 rotates together. At this time, since the rotation of the ball spline shaft 8 is opposite to the rotation direction of the ball screw bearing 3, the ball screw bearing 3 and the ball spline shaft 8 rotate relatively, and the ball screw bearing 3 The rotational speed of the shaft 8 is accelerated, and the ball spline shaft 8 can be lowered by the rotation of the ball screw bearing motor 4 and the spline bearing motor 6.

Further, when the motor control is repeated and the current position of the power tool reaches a position with a non-rotation descending distance remaining before stopping,
The current position of the spline bearing motor 6 is retrieved and a position command value is given so that this matches the target rotation angle given by the main control unit 17. Motor control is repeated.

When the current position of the working tool 7 becomes the target height position and the posture of the working tool 7 becomes the desired posture, the positioning of the working tool 7 is completed, a positioning completion signal is output, and preparations are made for the next work.

[Effects of the Invention] As explained above, the present invention is configured to transmit the rotation of a motor to a ball spline shaft to which a working tool is attached via a ball screw bearing and a spline bearing, respectively, and to raise and lower the working tool. Since the rotation directions of the motors are configured to face each other when the ball spline shaft is rotated, the ball spline shaft can move up and down in response to the rotation of not only the ball screw bearing motor but also the spline bearing motor. Not only can the work tool be moved at high speed without increasing the rotational speed of the ball screw motor, but the rotation of each motor is simultaneously transmitted to the ball spline shaft and the ball spline shaft is lowered, so the work tool can be moved in a short time. It has advantages such as being able to accelerate up to a predetermined high speed and moving the work tool immediately at a constant speed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts of a working tool lifting device as an example of the present invention, FIG. 2 is a block diagram showing the configuration of a control device according to the present invention, and FIG. 3 is a main part of a position command generating section according to the present invention. FIG. 4 is a flowchart explaining the operation of the main parts of the motor drive unit according to the present invention, and FIGS. 5A and 5B show the relationship between the movement amount and rotation angle of the power tool. The characteristic diagram, FIG. 6, is a sectional view of a main part of a conventional power tool lifting device. 1 Working tool lifting device, 2 Arm, 2a, 2b Motor storage section, 2c Partition wall, 3
Ball screw bearing, 3a ball, 4 direct drive motor for ball screw bearing, 4a stator, 4b rotor, 5 spline bearing,
5a ball, 6 direct drive motor for spline bearing, 6a stator, 6b rotor, 7 work tool, 8 ball spline shaft, 8a spiral groove, 8b spline groove, 9a, 9b casing, IO first pulley,
11 first rotation detection section, 12 second pulley, 1
3 second rotation detection section, 14 brake means, 1
5 control device, 16 position command generation section,
17 main control section, 18 storage section.

Claims (1)

[Scope of Claims] A ball spline shaft having a spiral groove and a spline groove is arranged, a work tool that rotates together with the shaft is connected to one end thereof, and a ball screw bearing and a spline bearing are fitted to the ball spline shaft. On the other hand, a ball screw bearing motor and a spline bearing motor are provided to rotate the ball screw bearing and the spline bearing, respectively, and when driving the ball screw bearing motor, the spline bearing motor is connected to the ball screw bearing motor. A work tool positioning device characterized by being connected to a control device that drives a screw bearing motor in a direction opposite to the rotational direction.