CN114683257A

CN114683257A - Robot and robot control method

Info

Publication number: CN114683257A
Application number: CN202111571140.0A
Authority: CN
Inventors: 矢泽隆之; 荒川洋
Original assignee: Nidec Sankyo Corp
Current assignee: Nidec Sankyo Corp
Priority date: 2020-12-28
Filing date: 2021-12-21
Publication date: 2022-07-01
Also published as: TW202224887A; JP2022104003A; TWI819444B; KR20220094145A

Abstract

The invention provides a robot and a control method of the robot, which can detect the rotation abnormality of a screw shaft of a ball screw more appropriately. The robot includes: a ball screw having a screw shaft and a nut member; a motor for rotating the screw shaft; a power transmission mechanism for transmitting power of the motor to the screw shaft; an encoder that detects rotation of the motor; and a detection mechanism having a detected member fixed to the screw shaft and a sensor for detecting the detected member, and detecting rotation of the screw shaft. The control unit, which receives the output signal of the encoder and the output signal of the sensor of the detection mechanism, detects whether or not a rotation abnormality has occurred in the screw shaft based on the output signal of the encoder and the output signal of the sensor of the detection mechanism.

Description

Robot and robot control method

Technical Field

The present invention relates to a robot such as an industrial robot. Further, the present invention relates to a method of controlling a robot such as an industrial robot.

Background

Conventionally, a horizontal articulated industrial robot that conveys a substrate such as a glass substrate is known (for example, see patent document 1). The industrial robot described in patent document 1 includes: a hand for carrying the substrate; an arm rotatably connected to the hand at a distal end side; a body portion supporting the arm; and a base movably supporting the body portion in a horizontal direction. The body part includes: an arm support which supports the base end side of the arm and can be lifted; a support frame for supporting the arm support in a liftable manner; a base constituting a lower end portion of the body portion and horizontally movable with respect to the base; and a revolving frame fixing a lower end of the support frame and rotatable with respect to the base.

The industrial robot described in patent document 1 includes a lifting mechanism that lifts and lowers the arm rest together with the hand and the arm. The elevating mechanism includes, for example, a ball screw, a motor for rotating a screw shaft of the ball screw, and a power transmission mechanism for transmitting power of the motor to the ball screw. The motor is a servo motor. The elevator mechanism includes an encoder that detects rotation of a motor, and the motor is controlled based on an output signal of the encoder. The power transmission mechanism includes, for example, a speed reducer. An arm bracket is attached to the nut member of the ball screw.

In order to improve the safety of the industrial robot, the industrial robot described in patent document 1 includes a stopper for stopping a screw shaft of the ball screw. The brake is, for example, an electromagnetic brake of a non-excited operation type, and directly stops the screw shaft. In the industrial robot described in patent document 1, since it is estimated that a rotation abnormality occurs in the screw shaft of the ball screw when a rotation abnormality of the motor is detected based on an output signal of the encoder, the brake is operated to bring the screw shaft of the ball screw to an emergency stop when the rotation abnormality of the motor is detected based on the output signal of the encoder.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open publication No. 2017-24096

Disclosure of Invention

[ problems to be solved by the invention ]

In the case of the industrial robot described in patent document 1, for example, the following situation may occur: when an abnormality occurs in the power transmission mechanism, the screw shaft of the ball screw does not normally rotate although the motor normally rotates. In the case of industrial robots, for example, the following situations may also arise: when the power transmission mechanism is abnormal and no longer transmits power between the motor and the ball screw, the screw shaft of the ball screw rotates although the motor is stopped.

However, in the industrial robot described in patent document 1, when such a situation occurs, it is not possible to detect a rotation abnormality of the screw shaft of the ball screw based on an output signal of an encoder that detects rotation of the motor. Therefore, in the industrial robot, the following situation may occur: although the screw shaft of the ball screw is not normally rotated, the screw shaft of the ball screw cannot be urgently stopped.

Accordingly, an object of the present invention is to provide a robot including a ball screw and a motor for rotating a screw shaft of the ball screw, in which a rotation abnormality of the screw shaft of the ball screw can be detected more appropriately. Further, an object of the present invention is to provide a robot control method capable of more appropriately detecting a rotation abnormality of a screw shaft of a ball screw in a robot including the ball screw and a motor for rotating the screw shaft of the ball screw.

[ means for solving the problems ]

In order to solve the problem, a robot according to the present invention includes: a ball screw having a screw shaft and a nut member moving along the screw shaft; a motor for rotating the screw shaft; a power transmission mechanism for transmitting power of the motor to the screw shaft; an encoder that detects rotation of the motor; a detection mechanism having a detected member fixed to the screw shaft and a sensor for detecting the detected member, and detecting rotation of the screw shaft; and a control unit that inputs an output signal of the encoder and an output signal of the sensor, and detects whether or not a rotation abnormality occurs in the screw shaft based on the output signal of the encoder and the output signal of the sensor.

In order to solve the above problem, a method for controlling a robot according to the present invention includes: a ball screw having a screw shaft and a nut member moving along the screw shaft; a motor for rotating the screw shaft; a power transmission mechanism for transmitting power of the motor to the screw shaft; an encoder that detects rotation of the motor; and a detection mechanism having a detected member fixed to the screw shaft and a sensor for detecting the detected member, and detecting rotation of the screw shaft, wherein the robot control method is characterized in that whether or not a rotation abnormality occurs in the screw shaft is detected based on an output signal of the encoder and an output signal of the sensor.

In the present invention, the robot includes a detection mechanism having a detected member fixed to a screw shaft of the ball screw and a sensor for detecting the detected member, and detects rotation of the screw shaft. In the present invention, whether or not a rotation abnormality has occurred in the screw shaft is detected based on the output signal of the encoder and the output signal of the sensor, which detect the rotation of the motor. Therefore, in the present invention, even when an abnormality occurs in the power transmission mechanism and the screw shaft does not normally rotate although the motor normally rotates or the screw shaft rotates even though the motor is stopped, for example, the rotation abnormality of the screw shaft can be detected based on the output signal of the encoder and the output signal of the sensor. Therefore, in the present invention, the rotational abnormality of the screw shaft can be more appropriately detected.

In the present invention, it is preferable that the robot includes a brake for stopping the screw shaft, and the control unit operates the brake when the control unit detects that the screw shaft has a rotation abnormality. With such a configuration, the screw shaft of the ball screw can be stopped suddenly when the screw shaft is not rotating normally. Therefore, the safety of the robot can be improved.

In the present invention, the robot includes, for example: a hand for carrying a conveying object; an arm rotatably coupled to a hand at a distal end side; and a lifting mechanism for lifting the hand and the arm, wherein the lifting mechanism comprises a ball screw, a motor, a power transmission mechanism, an encoder, a detection mechanism and a brake, the axial direction of the screw shaft is consistent with the vertical direction, and the hand and the arm are arranged on the nut component. In this case, when the screw shaft of the ball screw is not rotated normally, the screw shaft can be stopped suddenly to prevent the conveyance object, the hand, and the arm mounted on the hand from falling.

In the present invention, it is preferable that the robot includes two brakes, and the control unit operates the two brakes and shifts the operation start timing of the two brakes when the occurrence of the rotation abnormality of the screw shaft is detected. With such a configuration, even if one of the two brakes fails, the screw shaft can be stopped urgently by the other brake. In addition, with this configuration, the operation start timings of the two brakes are shifted from each other, so that it is possible to prevent a sudden braking force from the two brakes from acting on the screw shaft.

In the present invention, the robot includes, for example, two stoppers that coincide in the axial direction of the screw shaft. At this time, although the robot includes two brakes, the two brakes can be compactly arranged.

[ Effect of the invention ]

As described above, in the present invention, in the robot including the ball screw and the motor for rotating the screw shaft of the ball screw, it is possible to more appropriately detect the rotation abnormality of the screw shaft of the ball screw.

Drawings

Fig. 1 is a plan view of a robot according to an embodiment of the present invention.

Fig. 2 is a side view of the robot shown in fig. 1.

Fig. 3 is a diagram for explaining the structure of the lifting mechanism for lifting and lowering the hand and the arm shown in fig. 2.

Fig. 4 (a) is an enlarged view of a portion E of fig. 3, and fig. 4 (B) is a bottom view showing the probe mechanism from the direction F-F of fig. 4 (a).

Fig. 5 is a block diagram showing a configuration of an elevating mechanism electrically connected to a control unit of the robot shown in fig. 1.

[ description of symbols ]

1: robot

2: substrate (glass substrate, object to be conveyed)

3: hand (W.E.)

4: arm(s)

5: body part

6: base component

7: arm support

8: support frame

9: base station

10: revolving frame

12: a first arm part

13: second arm part

15: first supporting frame

16: second supporting frame

17: lifting mechanism

20: screw shaft

21: nut component

22: ball screw

23: motor with a stator having a stator core

24: power transmission mechanism

25. 26: brake

27: encoder for encoding a video signal

28: detection mechanism

31. 32: belt pulley

33: leather belt

35: detected component

35 a: fixed part of quilt

35 b: light shielding part

36: sensor with a sensor element

40: control unit

Detailed Description

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

(Overall Structure of robot)

Fig. 1 is a plan view of a robot 1 according to an embodiment of the present invention. Fig. 2 is a side view of the robot 1 shown in fig. 1.

The robot 1 of the present embodiment is a horizontal articulated industrial robot that transports a glass substrate 2 (hereinafter referred to as "substrate 2") of a liquid crystal display as a transport object. The robot 1 includes: two hands 3 for carrying the substrate 2; two arms 4 rotatably connected to the respective hands 3 at the tip ends thereof; a body portion 5 supporting the two arms 4; and a base member 6 that supports the main body 5 movably in the horizontal direction. The body portion 5 includes: an arm holder 7 which supports the base end side of the arm 4 and is liftable; a support frame 8 for supporting the arm holder 7 in a liftable manner; a base 9 constituting a lower end portion of the body portion 5 and horizontally movable with respect to the base member 6; and a revolving frame 10 which fixes the lower end of the support frame 8 and is rotatable with respect to the base 9.

The arm 4 includes two arm portions, i.e., a first arm portion 12 and a second arm portion 13. The base end side of the first arm portion 12 is rotatably coupled to the arm bracket 7. The base end side of the second arm portion 13 is rotatably connected to the tip end side of the first arm portion 12. The hand 3 is rotatably connected to the tip end side of the second arm portion 13. The arm 4 is extendable and retractable in the horizontal direction so that the hand 3 moves substantially linearly in a fixed direction. The robot 1 includes an arm drive mechanism that drives the arm 4.

The support frame 8 elevatably holds the hand 3 and the arm 4 via the arm bracket 7. The support frame 8 includes: a columnar first support frame 15 for holding the arm holder 7 in a liftable and lowerable manner; and a columnar second support frame 16 that elevatably holds the first support frame 15. The robot 1 includes a guide mechanism that guides the first support frame 15 in the up-down direction, and a guide mechanism that guides the arm bracket 7 in the up-down direction. The robot 1 further includes a lifting mechanism 17 (see fig. 3), and the lifting mechanism 17 lifts and lowers the arm support 7 with respect to the first support frame 15 and also lifts and lowers the first support frame 15 with respect to the second support frame 16. That is, the robot 1 includes a lifting mechanism 17 that lifts and lowers the hand 3 and the arm 4. The specific structure of the lifting mechanism 17 will be described later.

Revolving frame 10 is formed in a flat substantially rectangular parallelepiped shape with a small thickness in the vertical direction. Furthermore, revolving frame 10 is formed in a long and thin substantially rectangular parallelepiped shape. The lower end portion of the second support frame 16 is fixed to the upper surface of the revolving frame 10 on the front end side. The base end side of revolving frame 10 is supported on base 9 so as to be rotatable with the vertical direction as the rotation axis direction.

Revolving frame 10 is disposed above base 9. The robot 1 includes a turning mechanism that turns the revolving frame 10 with respect to the base 9. The robot 1 includes a horizontal movement mechanism for horizontally moving the base 9 with respect to the base member 6, and a guide mechanism for horizontally guiding the base 9.

(Structure of lifting mechanism)

Fig. 3 is a diagram for explaining the structure of the lifting mechanism 17 for lifting the hand 3 and the arm 4 shown in fig. 2. Fig. 4 (a) is an enlarged view of a portion E of fig. 3, and fig. 4 (B) is a bottom view showing the probe mechanism 28 from the direction F-F of fig. 4 (a).

The lifting mechanism 17 includes: a ball screw 22 having a screw shaft 20 and a nut member 21 moving along the screw shaft 20; a motor 23 for rotating the screw shaft 20; and a power transmission mechanism 24 for transmitting the power of the motor 23 to the screw shaft 20. The elevator mechanism 17 includes a stopper 25 and a stopper 26 for stopping the screw shaft 20. The lifting mechanism 17 of this embodiment includes two

brakes

25 and 26. Further, the lifting mechanism 17 includes: an encoder 27 that detects rotation of the motor 23; and a detection mechanism 28 that detects rotation of the screw shaft 20.

The screw shaft 20 is disposed such that the axial direction of the screw shaft 20 coincides with the vertical direction. That is, the axial direction of the screw shaft 20 coincides with the vertical direction. The screw shaft 20 is rotatable with the vertical direction as the rotation axis direction. The nut member 21 is engaged with the screw shaft 20.

The nut member 21 moves in the up-down direction along the screw shaft 20. The arm bracket 7 or the first support frame 15 is fixed to the nut member 21. That is, the hand 3 and the arm 4 are attached to the nut member 21 via the arm bracket 7 or via the first support frame 15 and the arm bracket 7.

The motor 23 is a servomotor. The motor 23 is controlled based on an output signal of the encoder 27. The power transmission mechanism 24 includes: a pulley 31 fixed to an output shaft of the motor 23; a pulley 32 fixed to a lower end side portion of the screw shaft 20; and a belt 33 mounted on the pulley 31 and the pulley 32. The encoder 27 includes a member to be detected fixed to the rotation shaft of the motor 23, and a sensor that detects the member to be detected.

The brake 25 and the brake 26 are electromagnetic brakes having the same structure and the same shape. Specifically, the

brakes

25 and 26 are electromagnetic brakes of an excitation-less operation type. The

brakes

25 and 26 include a rotating plate fixed to the screw shaft 20, a brake plate and an armature (armature) disposed across the rotating plate, a spring member that biases the armature toward the rotating plate, and a coil for driving the armature, and directly stop the screw shaft 20. The two

stoppers

25, 26 overlap in the axial direction of the screw shaft 20. In this embodiment, the stopper 25 and the stopper 26 are disposed vertically symmetrically. The two

brakes

25 and 26 are disposed below the pulley 32.

The detection mechanism 28 includes a detected member 35 fixed to the screw shaft 20, and a sensor 36 that detects the detected member 35, and directly detects the rotation of the screw shaft 20. The sensor 36 is, for example, a transmission-type optical sensor including a light emitting element and a light receiving element arranged to face the light emitting element. The detected member 35 is formed by bending a thin steel plate into a predetermined shape. The detected member 35 is fixed to the lower end surface of the screw shaft 20.

The detected member 35 includes a fixed portion 35a fixed to the lower end surface of the screw shaft 20, and a light shielding portion 35b shielding between the light emitting element and the light receiving element of the sensor 36. The detection target member 35 of this embodiment includes two light blocking portions 35b arranged at a 180 ° pitch with respect to the axial center of the screw shaft 20. The number of the light blocking portions 35b of the detection target member 35 may be three or more. For example, the detected member 35 may include four light blocking portions 35b arranged at 90 ° intervals with respect to the axial center of the screw shaft 20. The light shielding portion 35b may be formed in a disc shape. At this time, a plurality of slit holes penetrating the light shielding portion 35b in the vertical direction are formed at a constant pitch in the circumferential direction of the light shielding portion 35 b.

(Emergency stop operation of screw shaft)

Fig. 5 is a block diagram showing the configuration of the lifting mechanism 17 electrically connected to the control unit 40 of the robot 1 shown in fig. 1.

The motor 23, the brake 25, and the brake 26 are electrically connected to the control unit 40 of the robot 1. Specifically, the driving coil of the motor 23 and the coils of the brake 25 and the brake 26 are electrically connected to the control unit 40. The encoder 27 (specifically, a sensor of the encoder 27) and the sensor 36 are electrically connected to the control unit 40. The control unit 40 receives an output signal of the encoder 27 (specifically, an output signal of a sensor of the encoder 27) and an output signal of the sensor 36.

The control section 40 detects whether or not a rotation abnormality has occurred in the screw shaft 20 based on the output signal of the encoder 27 and the output signal of the sensor 36. Specifically, for example, when the output signal of the sensor 36 is input although the output signal of the encoder 27 is not input, or when the output signal of the sensor 36 is not input although the output signal of the encoder 27 is input, the control unit 40 determines that the rotation abnormality has occurred in the screw shaft 20.

Then, for example, when the rotational speed of the screw shaft 20 calculated based on the output signal of the encoder 27 and the rotational speed of the screw shaft 20 calculated based on the output signal of the sensor 36 differ by a predetermined value or more (that is, when the relationship between the rotational speed of the motor 23 and the rotational speed of the screw shaft 20 is not fixed and the rotational speed of the motor 23 and the rotational speed of the screw shaft 20 are not synchronized), the control unit 40 determines that a rotational abnormality has occurred in the screw shaft 20.

When the control unit 40 detects that the screw shaft 20 has a rotation abnormality, it operates the two

brakes

25 and 26 to bring the screw shaft 20 to an emergency stop. At this time, the control unit 40 shifts the operation start timing of the two

brakes

25 and 26. That is, the control unit 40 shifts the timing of starting application of voltage to the coil of the brake 25 and the timing of starting application of voltage to the coil of the brake 26.

(main effects of this form)

As described above, the robot 1 of the present embodiment includes the detection mechanism 28 for detecting the rotation of the screw shaft 20, and the detection mechanism 28 includes the detected member 35 fixed to the screw shaft 20 and the sensor 36 for detecting the detected member 35. In the present embodiment, the control unit 40 detects whether or not a rotation abnormality has occurred in the screw shaft 20 based on the output signal of the encoder 27 and the output signal of the sensor 36.

Therefore, in the present embodiment, even when an abnormality occurs in the power transmission mechanism 24 and the screw shaft 20 does not normally rotate although the motor 23 normally rotates, or even when the screw shaft 20 rotates even though the motor 23 is stopped, for example, the rotation abnormality of the screw shaft 20 can be detected based on the output signal of the encoder 27 and the output signal of the sensor 36. Therefore, in this embodiment, the rotation abnormality of the screw shaft 20 can be detected more appropriately.

In this embodiment, when the control unit 40 detects that a rotation abnormality has occurred in the screw shaft 20, the control unit operates the

brakes

25 and 26 to bring the screw shaft 20 to an emergency stop. Therefore, in this embodiment, the base plate 2, the hand 3, and the arm 4 can be prevented from falling off when the screw shaft 20 is abnormally rotated, and as a result, the safety of the robot 1 can be improved. In addition, in the present embodiment, since the lifting mechanism 17 includes the two

brakes

25 and 26, even if the brake 25 fails, for example, the screw shaft 20 can be stopped urgently by the brake 26.

In this embodiment, the control unit 40 shifts the operation start timing of the two

brakes

25 and 26 when the two

brakes

25 and 26 are operated. Therefore, in the present embodiment, it is possible to prevent the abrupt braking force of the two

brakes

25 and 26 from acting on the screw shaft 20. In addition, in the present embodiment, since the two

brakes

25 and 26 overlap in the axial direction of the screw shaft 20, even if the lifting mechanism 17 includes the two

brakes

25 and 26, the two

brakes

25 and 26 can be disposed compactly.

(other embodiments)

The above-described embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

In the illustrated form, the support frame 8 may also comprise a cylindrical frame. At this time, the lifting mechanism 17 lifts and lowers the arm rest 7 relative to the support frame 8. In the above-described embodiment, the robot 1 may include a lifting mechanism for lifting and lowering the arm support 7 with respect to the first support frame 15, and a lifting mechanism for lifting and lowering the first support frame 15 with respect to the second support frame 16, respectively. In this case, the two elevating mechanisms are configured similarly to the elevating mechanism 17.

In the above-described embodiment, the operation start timings of the two

brakes

25 and 26 may be the same when the control unit 40 detects that the screw shaft 20 has abnormal rotation. In the above-described embodiment, the number of the stoppers included in the lifting mechanism 17 may be one. In the above-described aspect, the power transmission mechanism 24 may include a speed reducer and may further include a gear train. The power transmission mechanism 24 may be an output shaft of the motor 23 and a coupling attached to the screw shaft 20 to connect the output shaft of the motor 23 and the screw shaft 20. In the above-described embodiment, the sensor 36 may be a reflective optical sensor, or may be a sensor other than an optical sensor such as a proximity sensor.

In the above-described aspect, the robot 1 may include a hand holding portion that holds the hand 3 so as to be capable of linear movement of the hand 3 in the horizontal direction. At this time, the robot 1 includes a horizontal drive mechanism that linearly moves the hand 3 in the horizontal direction with respect to the hand holding portion. The horizontal driving mechanism includes, similarly to the lifting mechanism 17: a ball screw 22 having a screw shaft 20 and a nut member 21; a motor 23 for rotating the screw shaft 20; a power transmission mechanism 24 for transmitting power of the motor 23 to the screw shaft 20; an encoder 27 that detects rotation of the motor 23; and a detection mechanism 28 that detects rotation of the screw shaft 20. The screw shaft 20 is disposed so that the axial direction of the screw shaft 20 coincides with the horizontal direction, and the hand 3 is attached to the nut member 21. The horizontal drive mechanism may include the brake 25 and the brake 26, or may not include the brake 25 and the brake 26.

In the above-described embodiment, the main body 5 is movable in the horizontal direction, but the main body 5 may be fixed. In the above-described embodiment, the arm 4 may include three or more arm portions. In the above-described embodiment, the robot 1 may be a robot that transports objects to be transported other than the substrate 2. Further, a robot to which the present invention is applied may be a robot other than an industrial robot.

Claims

1. A robot, comprising:

a ball screw having a screw shaft and a nut member moving along the screw shaft; a motor for rotating the screw shaft; a power transmission mechanism that transmits power of the motor to the screw shaft; an encoder that detects rotation of the motor; a detection mechanism having a detected member fixed to the screw shaft and a sensor for detecting the detected member, and detecting rotation of the screw shaft; and a control unit for inputting the output signal of the encoder and the output signal of the sensor,

the control section detects whether or not a rotation abnormality is generated in the screw shaft based on an output signal of the encoder and an output signal of the sensor.

2. The robot of claim 1, comprising:

a stopper stopping the screw shaft,

the control unit operates the brake when detecting that the screw shaft has a rotational abnormality.

3. A robot as claimed in claim 2, comprising:

a hand for carrying a conveying object; an arm rotatably coupled to the hand at a distal end side; and a lifting mechanism for lifting the hand and the arm,

the lifting mechanism comprises the ball screw, the motor, the power transmission mechanism, the encoder, the detection mechanism and the brake,

the axial direction of the screw shaft is consistent with the up-down direction,

the hand and the arm are attached to the nut member.

4. A robot as claimed in claim 2 or 3, characterized by comprising two of said brakes,

the control unit operates the two brakes and shifts the operation start timing of the two brakes when detecting that the screw shaft has a rotational abnormality.

5. A robot as claimed in claim 2 or 3, characterized by comprising two of said brakes,

the two stoppers coincide in the axial direction of the screw shaft.

6. A control method of a robot, the robot comprising: a ball screw having a screw shaft and a nut member moving along the screw shaft; a motor for rotating the screw shaft; a power transmission mechanism that transmits power of the motor to the screw shaft; an encoder that detects rotation of the motor; and a detection mechanism having a detected member fixed to the screw shaft and a sensor for detecting the detected member, and detecting rotation of the screw shaft,

detecting whether a rotation abnormality is generated in the screw shaft based on an output signal of the encoder and an output signal of the sensor.