JP2009050951A - Industrial robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrial robot of a jointed-arm type, which has a balancing mechanism for excellently generating balancing force even if the robot is configured such that the position of each joint is changed every moment or the mass of load is changeable on an as-needed basis. <P>SOLUTION: The industrial robot has an arm 3 having one end thereof axially supported on a base stand 1 in a rotatable manner, and the balancing mechanism 4 having one end thereof connected to the base stand 1 and the other end thereof connected to the arm 3. The balancing mechanism 4 has a driving mechanism consisting of a reduction gear mechanism 41 and a servo motor 42. Thus the industrial robot always applies adequate balancing force by applying force for maintaining a balance to gravity moment acting on the arm 3, to the servo motor 42 of the balancing mechanism 4 on an as-needed basis. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an articulated industrial robot having a plurality of arms, and more particularly to an industrial robot having a balance mechanism that holds a swingably provided arm at its stop position.

  A vertical articulated industrial robot having a plurality of arms includes a base portion that is turnable about a vertical axis of an installation surface, and a first arm that stands up rotatably on the base portion, In many cases, the first arm has a second arm extending in the horizontal direction and rotatably supported at the upper end of the first arm. In the vertical articulated robot of this form, the first arm tends to incline due to its own weight and the weight of the second arm, so that the first arm can be stopped at its rotational position. A so-called balance mechanism is provided that imparts to the first arm a force that balances the moment of gravity acting on the arm.

  Conventionally, as the balance mechanism, Patent Document 1 of the applicants discloses a technique of a spring balance mechanism, and FIG. 1 of the embodiment shows another spring balance mechanism and a balance mechanism using a counterweight. ing. As disclosed in these cases, conventionally, a balance mechanism is generally configured by a pneumatic cylinder or a hydraulic cylinder having a spring or a pressure storage tank that does not require an external drive source.

  On the other hand, Patent Document 2 discloses a method of using a balancing motor provided separately from a lifting motor as a drive source and balancing the gravity by the principle of virtual relative power. However, such a configuration is a balance mechanism that can be realized for the first time by a specific mechanism as disclosed in this document, and provides a balance mechanism in a general-purpose vertical articulated structure such as a vertical articulated industrial robot. It was not a thing.

  As a technique aiming at the realization of gravity balance in a general-purpose vertical articulated structure, Patent Document 3 discloses a balance mechanism using a pneumatic cylinder that stores air pressure necessary for gravity balance according to the posture of the arm. Is disclosed. However, such a configuration stores the air pressure necessary to balance the gravity for each posture of the arm, and the posture of each joint of the multi-joint structure changes from moment to moment, or the mass of the load changes every time However, it did not give or suggest a solution.

  Further, Patent Document 4 discloses a method of obtaining a gravity balance by moving a balance weight of a wall surface cleaning robot with a balancer motor. Such a configuration balances the change in balance force when the posture of the arm is changed by changing the position of the weight for the balancer. The configuration is similar in principle to that of the above-mentioned Patent Document 2, but when the robot operates, the weight for the balancer also becomes an inertial load, so the gravitational load is canceled. The acceleration / deceleration torque adds the torque necessary for the acceleration / deceleration of the balancer, and does not necessarily reduce the load on the arm drive shaft during operation.

  Further, Patent Document 5 discloses a method of reducing a load by a cylinder using a pressure fluid in a balancer using a ball screw and an electric motor. However, what is disclosed in such a document did not give or suggest a solution when the posture of each joint of a multi-joint structure changes from moment to moment or the mass of a load changes each time. .

Japanese Patent No. 3813542 JP 2006-282300 A JP-A-6-262561 JP-A-11-192196 Japanese Patent No. 3347844

  The present invention was made in order to solve the above-described problems of the prior art, and is an articulated industrial robot having a drive mechanism in which the balance mechanism itself generates a drive force, Preferably, there is provided an industrial robot having a balance mechanism that can generate a balance force even when the posture of each joint changes from moment to moment or the mass of a load changes each time. For the purpose.

  In order to solve the above-described problem, in the invention described in claim 1, one end of the arm 3 is rotatably supported by the base portion 1, one end is connected to the base portion 1, and the other An industrial robot characterized in that the balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42. With such a configuration, the balance mechanism 4 itself has a drive mechanism that independently generates a drive force.

  Further, in the invention described in claim 2, one end is rotatably supported by the base portion 1 and one end is connected to the base portion 1, and the other end is connected to the arm 3. The balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42, and the servo motor 42 has a gravity balance around the center of rotation of the base portion 1 of the arm 3. An industrial robot characterized by generating a driving torque in a direction to cancel the force Fg was provided.

  In general, a moment of gravity acts on the arm 3 whose one end is pivotally supported by the base 1 depending on the posture of each joint axis including the arm 3 and the load held on the joint shaft at the tip. Therefore, in the balance mechanism 4 in which one end is connected to the base part 1 and the other end is connected to the arm 3, it is desirable to apply a force that balances the aforementioned gravitational moment acting on the arm 3. However, if the posture of each joint axis including the arm 3 changes from moment to moment or the mass of the load changes every time, the gravitational moment also changes. Therefore, a spring that does not require a conventional external drive source, With a balance mechanism constituted by a pneumatic cylinder or a hydraulic cylinder having a pressure storage tank, an appropriate balance force cannot always be applied. On the other hand, in the invention according to claim 2 of the present application, the balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42, and the servo motor 42 is arranged around the rotation center of the base portion 1 of the arm 3. Since the driving torque is generated in the direction to cancel the gravity balance force Fg, even if the posture of each joint axis including the arm 3 changes every moment or the mass of the load changes every time, the arm 3 By applying a force that balances the moment of gravity acting on the servo motor 42 of the balance mechanism 4 each time, an appropriate balance force can always be applied.

  In the invention according to claim 3, one end of the arm 3 is rotatably supported by the base portion 1, and the other end of the arm 3 opposite to the base portion 1 is rotatably supported. Arm 8, wrist portion 10 connected to the other end of arm 8 opposite to arm 3, drive mechanism of wrist portion 10 mounted on the connecting portion between arm 3 and arm 8, one end Is connected to the base unit 1 and has a balance mechanism 4 connected to the arm 3 at the other end. The balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42. Arm length (L1, L2), center of gravity (L12, L22), and mass (M1, M2) in the longitudinal direction of each of arm 3 and arm 8, mass (M11) of drive mechanism of wrist 10, Wrist 10 mass (ML) and arm 3 and arm 8 has a gravity load calculation circuit 5 for calculating the gravity balance force Fg around the rotation center of the base portion 1 of the arm 3 based on the angles (θ1, θ2) formed by the respective longitudinal directions of 8 with the horizontal direction, An industrial robot is provided in which the servo motor 42 of the balance mechanism 4 generates a drive torque in a direction to cancel the gravity balance force Fg calculated by the gravity load calculation circuit 5. In addition to the mass of the wrist 10 main body, the mass (ML) of the wrist 10 includes the mass of the end effector when the wrist 10 is equipped with an end effector. In the case of a hand device, the mass of the article gripped by the hand device is included.

  In the invention according to claim 3, the arm length (L 1, L 2), the center of gravity (L 12, L 22), the mass (M 1, M 2) in the longitudinal direction of each of the arm 3 and the arm 8, Based on the mass (M11) of the drive mechanism, the mass (ML) of the wrist 10 and the angles (θ1, θ2) between the longitudinal directions of the arms 3 and 8 and the horizontal direction, the base of the arm 3 The gravity balance force Fg around the rotation center of the part 1 is calculated. Since the servo motor 42 of the balance mechanism 4 generates drive torque in a direction to cancel the calculated gravity balance force Fg, the postures of the arm 3 and the arm 8 change from moment to moment or are attached to the wrist portion 10. Even when the mass of the load of the article etc. gripped by the end effector changes each time, the servo motor 42 of the balance mechanism 4 applies the force that balances the gravity moment (gravity balance force Fg) acting on the arm 3 each time. By applying, the balance mechanism 4 can always apply an appropriate balance force to the arm 3.

  In the invention according to claim 3, the gravity balance force Fg is preferably calculated by the equation (1) (claim 4). However, in Formula (1), L1 is the arm length in the longitudinal direction of the arm 3, L2 is the arm length in the longitudinal direction of the arm 8, L12 is the center of gravity of the arm 3, L22 is the center of gravity of the arm 8, and M1 is The mass of the arm 3, M2 is the mass of the arm 8, M11 is the mass of the driving mechanism of the wrist unit 10, ML is the mass of the wrist unit 10, θ1 is the angle between the longitudinal direction of the arm 3 and the horizontal direction, and θ2 is the arm 8 Is the angle formed by the longitudinal direction of the horizontal direction.

  As the configuration of the speed reduction mechanism 41 described above, various known configurations can be applied. For example, the speed reduction mechanism 41 includes a rack and a pinion (Claim 6). (Claim 5) or a rotational speed reduction mechanism may be adopted (Claim 7).

  According to the present invention, in the balance mechanism of an articulated industrial robot having a multi-axis configuration, it is possible to provide a balance mechanism having a drive mechanism that uniquely generates a drive force, and unbalance due to gravity by the operation of the robot body. Even when the force changes from moment to moment, or when the mass of the load changes each time, the balance mechanism can generate a more accurate gravity balance force. Therefore, it is possible to use it for arm operation without reducing the size of the drive unit, and further, without using the force generated by the drive unit for the unbalanced force generated by gravity. It became possible to improve performance. Further, the use of the present invention is not limited to a vertical articulated structure, and even a linear motion robot can be effectively applied as long as it is subjected to a gravity load.

  The best mode for carrying out the present invention will be described with reference to the drawings. First, it demonstrates, referring FIG. 1 which is a conceptual diagram of the industrial robot which has the balance mechanism which concerns on this embodiment. In the industrial robot having the vertical articulated structure shown in FIG. 1, the arm 3 is connected to the base unit 1 via the drive unit 2 so as to be rotatable (rotatable in the left-right direction on the paper surface of FIG. 1). ing. The drive unit 2 is preferably composed of a rotary speed reducer and a servo motor (not shown). In order to reduce the gravitational load acting on the drive unit 2, a balance mechanism 4 is provided. One end of the balance mechanism 4 is connected to the base portion 1, and the other end is connected to the arm 3. The balance mechanism 4 includes a drive mechanism that includes a speed reduction mechanism 41 and a servo motor 42. The speed reduction mechanism 41 includes a linear motion speed reduction mechanism including a screw and a nut or a rack and a pinion.

  Further, an arm 8 is rotatably connected to the arm 3 at the end of the arm 3 opposite to the base portion 1. A wrist portion 10 is rotatably connected to the arm 8 at the other end of the arm 8 opposite to the arm 3. The wrist portion 10 has a degree of freedom of 1 to 3 axes including a rotation axis with respect to the arm 8. An arbitrary end effector (not shown) such as a welding gun or a robot hand can be attached to the wrist 10.

Next, control of the balance mechanism will be described with reference to FIG. 2 which is a block diagram showing a control unit of the balance mechanism according to the present embodiment. As shown in FIG. 2, the control unit of the balance mechanism according to the present embodiment includes a gravity load calculation circuit 5 that calculates a gravity balance force, a servo motor drive circuit 6 that generates a torque that balances the calculated gravity balance force, and The gravity load calculation circuit 5 is composed of a storage table 7 in which parameters necessary for calculation are stored.
The aforementioned parameters stored in the storage table 7 include at least the arm length L1 in the longitudinal direction of the arm 3, the arm length L2 in the longitudinal direction of the arm 8, the gravity center position L12 of the arm 3, and the gravity center of the arm 8. The position L22, the mass M1 of the arm 3, the mass M2 of the arm 8, the mass M11 of the driving mechanism of the wrist 10 and the mass ML of the wrist 10 are included. The aforementioned gravity load calculation circuit 5, servo motor drive circuit 6, and storage table 7 constituting the control unit of these balance mechanisms are incorporated in a robot control device (not shown) that controls the industrial robot. In the above-described gravity load calculation circuit 5, the angle (θ 1, θ 2,..., Θn) formed by the longitudinal direction of each joint axis of the arm 3 changing with the operation of the robot and the horizontal direction is stored in the storage table 7. Based on the above-described parameters, the gravity balance force Fg around the rotation center of the base portion 1 of the arm 3 is calculated.

  Here, the calculation processing according to the present embodiment executed in the gravity load calculation circuit 5 will be described with reference to FIG. 3 which is a conceptual diagram for explaining the calculation in the gravity load calculation circuit 5 according to the present embodiment. . In FIG. 3, the meaning of each symbol is as follows. First, regarding the J1 axis arm corresponding to the arm 3 described above, θ1 is an angle between the longitudinal direction of the J1 axis arm and the horizontal direction, L1 is the arm length in the longitudinal direction of the J1 axis arm, and M1 is the mass of the J1 axis arm. , L12 is the distance from the J1 axis rotation center of the center of gravity of the J1 axis arm, that is, the position of the center of gravity of the J1 axis arm. Next, with respect to the J2 axis arm corresponding to the aforementioned arm 8, θ2 is an angle formed by the longitudinal direction of the J2 axis arm and the horizontal direction, L2 is the arm length in the longitudinal direction of the J2 axis arm, and M2 is the length of the J2 axis arm. The mass L22 is the distance from the J2 axis rotation center of the center of gravity of the J2 axis arm, that is, the position of the center of gravity of the J2 axis arm. As a method of detecting the angle θ1 formed by the longitudinal direction of the J1 axis arm with the horizontal direction and the angle θ2 formed by the longitudinal direction of the J2 axis arm and the horizontal direction, a position attached to the servo motor that drives each axis arm is used. What is necessary is just to calculate based on the detection data obtained from the detector.

  Next, regarding the load on the wrist portion 10, ML is the mass of the load on the wrist portion 10 at the arm tip (tip of the J2 axis arm). In addition to the mass of the wrist 10 main body, the load mass of the wrist 10 includes the mass of the end effector when the wrist 10 is equipped with an end effector. In this case, the mass of the article gripped by the hand device is included. Further, regarding the load of the drive unit, M11 is the mass of the drive unit, for example, the mass of a servo motor (not shown) for driving the drive shaft of the wrist 10 described above.

  In this case, the gravity balance force Fg around the rotation center of the base 1 of the J1 axis arm, that is, around the J1 axis rotation center is given by the following equation (1).

  Therefore, in the gravity load calculation circuit 5, the angle θ1 formed by the longitudinal direction of the J1 axis arm and the horizontal direction and the angle θ2 formed by the longitudinal direction of the J2 axis arm and the horizontal direction are periodically calculated based on the equation (1). The gravity balance force Fg around the J1 axis rotation center is calculated every time (for example, every calculation cycle of the control unit of the balance mechanism shown in FIG. 2), and this is input to the servo motor drive circuit 6 to drive the balance mechanism 4. The servo motor 42 that generates the drive torque generates a driving torque in a direction that cancels the gravity balance force Fg. Thereby, even when the postures of the joints of the J1 axis arm and the J2 axis arm change from moment to moment, the balance mechanism 4 can generate an accurate gravity balance force.

  FIG. 4 is an explanatory view of the mechanism portion of the balance mechanism, which describes the above-described FIG. 1 in more detail. The drive unit 2 of the arm 3 includes a speed reduction mechanism 21 illustrated with gears, and a servo motor 22 that rotates the gears of the speed reduction mechanism 21. The servo motor 22 of the drive unit 2 is attached to the base unit 1, a gear is attached to the tip of the servo motor 22 of the drive unit 2, and the gear attached to the arm 3 (J1 axis arm) is engaged by tooth engagement. By rotating, the arm 3 (J1 axis arm) is rotated with respect to the base unit 1. The balance mechanism 4 includes a speed reduction mechanism 41 composed of a rack and a pinion, and a servo motor 42 that rotates a pinion gear. The balance mechanism 4 has one end attached to the base 1 and the other end attached to the arm 3 (J1 axis arm). Also, an arm 8 (J2) connected to the opposite side of the base 3 of the arm 3 (J1 axis arm) by a drive unit 9 of an arm 8 (J2 axis arm) attached to the arm 3 (J1 axis arm). The axis arm) is rotationally driven with respect to the arm 3 (J1 axis arm).

  Incidentally, the configuration of the speed reduction mechanism 41 of the balance mechanism 4 is not limited to the speed reduction mechanism configured by the rack and pinion shown in FIG. 4 described above, but a speed reduction mechanism configured by screws and nuts as a similar linear motion speed reduction mechanism. It is good. Further, instead of these linear motion reduction mechanisms, a drive mechanism comprising a rotation speed reduction mechanism and a servo motor is used on the opposite side of the drive unit 2 (back side of the paper surface of FIG. 1) via the arm 3 shown in FIG. Thus, a similar function may be achieved.

  Specifically, FIG. 5 is a mechanism diagram showing an embodiment in which a speed reduction mechanism 41 is a rotational speed reduction mechanism, compared to FIG. 4 which is an embodiment of a linear motion speed reduction mechanism composed of the rack and pinion described above. is there. FIG. 6 is an enlarged cross-sectional view for explaining the balance mechanism of FIG. Note that a description of the same components as those in FIG. 4 is omitted. A servo motor 42 of the balance mechanism 4 is attached to the base 1, a gear is attached to the tip of the servo motor 42, and a gear of the speed reduction mechanism 41 of the balance mechanism 4 attached to the arm 3 (J1 axis arm). The arm 3 (J1 axis arm) is rotated with respect to the base part 1 by rotating the teeth by meshing teeth.

  In both of the embodiments shown in FIGS. 4 and 5, the gear of the speed reduction mechanism 41 of the balance mechanism 4 attached to the arm 3 (J1 axis arm) is rotated in the direction of meshing teeth. By generating force, the balance force is generated. That is, the servo motor 42 of the balance mechanism 4 generates a drive torque as a balance force in a direction to cancel the gravity balance force Fg around the rotation center of the J1 axis that is the rotation axis of the J1 axis arm calculated by the above-described equation (1). I will let you.

  The embodiment of the present invention has been described above. In FIG. 3 described above, the description has been given with the joint shaft structure of the two-axis configuration of the J1 axis arm and the J2 axis arm. However, even if it is expanded to the six-axis structure that is the axis configuration of a general vertical articulated robot, The gravity balance force can be easily obtained geometrically as in the case of the two-axis configuration described above. Further, the use of the present invention is not limited to a vertical articulated structure, and even a linear motion robot can be effectively applied as long as it is subjected to a gravity load. Further, regarding the load attached to the wrist portion 10, the method according to the present embodiment can be applied even when the mass of the load changes each time including the presence or absence of the load. Needless to say, this is possible because the load mass ML is handled as a variable. For example, in the case of a transport robot that transports an article gripped by a robot hand as an end effector by an industrial robot, as described above, the load ML of the wrist 10 includes the mass of the article that is the object to be transported. Therefore, the balance mechanism 4 can generate an accurate gravity balance force even in a usage pattern in which the mass of an article that is a transported object changes each time. In this way, the method according to the present embodiment can provide a solution for gravity balance when the posture of each joint axis of the multi-joint structure changes from moment to moment or the load mass changes each time. It becomes.

It is a conceptual diagram of the industrial robot which has the balance mechanism 4 which concerns on this embodiment. It is a block diagram which shows the control part of the balance mechanism 4 which concerns on this embodiment. It is a conceptual diagram for demonstrating the calculation of the gravity load calculating circuit 5 which concerns on this embodiment. It is explanatory drawing of the mechanism part of the balance mechanism 4 which described FIG. 1 in detail. FIG. 5 is a mechanism diagram showing an embodiment in which the speed reduction mechanism 41 is a rotation speed reduction mechanism with respect to FIG. 4. It is an expanded sectional view for demonstrating the balance mechanism 4 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base part 2 Drive part of arm 3 Deceleration mechanism of drive part 2 Servo motor of drive part 2 3 Arm (J1 axis arm)
DESCRIPTION OF SYMBOLS 4 Balance mechanism 41 Deceleration mechanism of balance mechanism 4 42 Servo motor of balance mechanism 4 5 Gravity load calculation circuit 6 Servo motor drive circuit 7 Storage table 8 Arm (J2 axis arm)
DESCRIPTION OF SYMBOLS 9 Drive part of arm 8 91 Deceleration mechanism of drive part 92 Servo motor of drive part 10 Wrist part L1 Arm length of arm 3 in the longitudinal direction L2 Arm length of arm 8 in the longitudinal direction L12 Position of center of gravity of arm 3 L22 The center of gravity of the arm 8 M1 The mass of the arm 3 M2 The mass of the arm 8 M11 The mass of the driving mechanism of the wrist 10 ML The mass of the wrist 10 θ1 The angle between the longitudinal direction of the arm 3 and the horizontal direction θ2 The longitudinal direction of the arm 8 is Angle made with the horizontal direction

Claims (7)

An arm 3 whose one end is rotatably supported by the base 1;
A balance mechanism 4 having one end connected to the base portion 1 and the other end connected to the arm 3;
The balance mechanism 4 has a drive mechanism composed of a speed reduction mechanism 41 and a servo motor 42, and is an industrial robot. An arm 3 whose one end is rotatably supported by the base 1;
A balance mechanism 4 having one end connected to the base portion 1 and the other end connected to the arm 3;
The balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42,
The industrial robot according to claim 1, wherein the servo motor 42 generates a drive torque in a direction to cancel the gravity balance force Fg around the rotation center of the base portion 1 of the arm 3. An arm 3 whose one end is rotatably supported by the base 1;
An arm 8 rotatably supported on the other end of the arm 3 opposite to the base 1;
A wrist portion 10 connected to the other end of the arm 8 opposite to the arm 3;
A drive mechanism for the wrist portion 10 mounted on a connecting portion between the arm 3 and the arm 8;
A balance mechanism 4 having one end connected to the base portion 1 and the other end connected to the arm 3;
The balance mechanism 4 has a drive mechanism including a speed reduction mechanism 41 and a servo motor 42,
The arm length (L1, L2), the center of gravity (L12, L22), and the mass (M1, M2) in the longitudinal direction of each of the arm 3 and the arm 8, and the mass (M11) of the drive mechanism of the wrist 10 Based on the mass (ML) of the wrist portion 10 and the angles (θ1, θ2) formed by the longitudinal directions of the arms 3 and 8 with respect to the horizontal direction, the base portion 1 of the arm 3 A gravity load calculation circuit 5 for calculating a gravity balance force Fg around the center of rotation;
The industrial robot characterized in that the servo motor 42 of the balance mechanism 4 generates a drive torque in a direction to cancel the gravity balance force Fg calculated by the gravity load calculation circuit 5. The industrial robot according to claim 3, wherein the gravity balance force Fg according to claim 3 is calculated by the equation (1).

  The industrial robot according to claim 1, wherein the speed reduction mechanism 41 is a linear motion speed reduction mechanism.   The industrial robot according to claim 5, wherein the linear motion reduction mechanism includes a rack and a pinion.   The industrial robot according to claim 1, wherein the speed reduction mechanism 41 is a rotation speed reduction mechanism.

Images