JPH0471672B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an arm of an articulated robot.
The present invention relates to a method of reducing the load torque of an arm driving actuator by offsetting the rotational force due to the arm's own weight.

[Background of the invention]

Automation of production processes is progressing year by year, and many attempts are being made to achieve flexible automation, especially by introducing robots into assembly processes. The robots used for this purpose are often articulated robots that have a large working range compared to the installation space.

FIG. 1 is a schematic explanatory diagram of the mechanism of the articulated robot. This articulated robot 1 normally has an upper arm 3 rotatably supported on a rotating base 2, a forearm 4 at the tip of the upper arm 3, and a wrist 5 at the tip thereof. The structure is pivoted on the For this reason, the actuator 6 for driving the upper arm 3
The required output of the drive actuator 7 for the forearm 4 to maintain the posture changes depending on the posture of the upper arm 3 and forearm 4 even when the wrist portion 5 is not gripping a workpiece.

FIG. 2A is a schematic diagram showing the torque due to the arm's own weight, and FIG. 2B is a chart showing the relationship between the required torque for posture maintenance and the arm posture.

Assuming that the torque for maintaining the posture of arm 10 is T, the weight of arm 10 is W, the distance from rotation axis 11 to center of gravity 12 of arm 10 is L, and the rotation angle of arm 10 from the vertical posture is θ. , T=WLsinθ holds true.

When θ=0°, that is, when the arm is vertical, the position holding torque is zero, but when θ=90°, that is, when the arm is horizontal, it becomes WL. As described above, in order to maintain the position of the arm in an articulated robot, when selecting a drive actuator, it is necessary to take into account the above-mentioned arm position holding torque in addition to the load holding/transfer (acceleration) torque. For this reason, it is necessary to select an actuator with a large capacity compared to the robot's component gripping ability, which also poses the problem of increasing the robot's own weight. Furthermore, as is clear from Figure 2B, when accelerating and moving an arm held at a certain angle clockwise or counterclockwise, the output required by the actuator at that time depends on whether it is along the direction of gravity or against it. There was a problem that the torque changed greatly and the acceleration characteristics were different. For this reason, countermeasures have been taken, such as changing the gain constant of the actuator for clockwise acceleration and counterclockwise acceleration, but this is not a sufficient countermeasure when load fluctuations are large, and the problem remains.

[Purpose of the invention]

The present invention was created in view of the above-mentioned circumstances to eliminate the drawbacks of the prior art, and its purpose is to provide a method that can reduce the output torque of an actuator for supporting the weight of a robot arm. , which aims to contribute to the miniaturization and energy saving of actuators.

[Summary of the invention]

In order to achieve the above object, the present invention provides an arm of an articulating robot, a rotation shaft that horizontally supports the base end of the arm and rotates integrally with the arm, and an actuator that rotates the arm by driving an actuator, the method for reducing a load torque due to the arm's own weight that occurs when the arm rotates from a vertical reference position, wherein the rotation axis and the rotation A spring is mounted between a fixed member provided on the outer circumference of the shaft to generate reaction torque in the clockwise and counterclockwise directions to form a spring mechanism coaxial with the rotating shaft. The formed spring mechanism generates a reaction torque that rotates the arm in a direction opposite to the direction of rotation from the reference posture in approximately proportion to the rotation angle of the arm from the reference posture, and counterbalancing the reaction torque applied to the arm and the torque generated on the rotation shaft due to the arm's own weight, so that the arm can be held at any rotational position;
The present invention is characterized in that the load torque of the actuator is reduced.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 3 to 5.

FIG. 3 is a partially sectional side view of an example of a robot configured to carry out the method of the present invention, and FIG. 4 is a partially sectional front view of the robot.

As shown in FIG. 3, the robot of this example comprises a robot arm 10, a rotating shaft 11, a base portion 15 for supporting the rotating shaft, an actuator 16 for driving the arm, and a spring mechanism portion 17.

As shown in FIGS. 3 and 4, the spring mechanism 17 is attached to the base portion 15 coaxially with the rotating shaft 11, and includes compression coil springs 18, 19 that generate a reaction force against the rotation of the rotating shaft 11. It is composed of an intermediate rotary plate 20 and a fixed plate (fixed member) 21. Note that the intermediate rotating plate 20 is slidable with respect to the rotating shaft 11 and the fixed plate 21. spring 18
As shown in the figure, the spring 19 is disposed between a spring receiver 22 protruding from the circumference of the rotating shaft 11 that rotates together with the arm 10 and a spring receiver 23 inside the intermediate rotating plate 20. Spring receiver 24 and fixed plate 2
It is arranged between the spring receivers 25 of 1.

The effects of this configuration will be explained below.
When the arm 10 of the robot rotates in the direction of arrow A (clockwise as seen from the spring mechanism), the rotating shaft 11 also rotates by the same angle. Then, the spring 18 is bent by the spring receiver 22 on the rotating shaft 11, and a reaction force is generated that returns the rotating shaft 11 to its original state. At this time, since the intermediate rotating plate 20 does not move, the spring 19 does not generate a reaction force against the rotating shaft 11. If the counterclockwise moment due to the reaction force of the spring 18 and the clockwise moment due to the weight of the arm 10 including the hand etc. are made equal, the arm 10 becomes equivalent to a zero gravity state, and can be moved clockwise with a small force. Or you can move it counterclockwise.

FIG. 5A is a chart in which the reaction torque due to the above spring is added to the chart of FIG. 2B mentioned above. arm 1
The clockwise rotational moment due to the weight of 0 is sinθ
Therefore, it is difficult to make the moment of the reaction force by the spring 18 equivalent over the entire rotation angle of the arm 10. FIG. 5B is a chart showing the difference between the two moments mentioned above. Even if the reaction force by the spring 18 is proportional to θ, the difference ΔT between this and the moment due to the weight of the arm 10 is small, so the arm 1
The output torque of the actuator required to maintain the zero position is small. Similarly, when the arm 10 rotates from the vertical position in the counterclockwise direction B, the rotation axis 11
Since the spring 1 rotates together with the intermediate rotary plate 20,
Deflect 9. If the magnitude of the moment due to the reaction force of the spring 19 is selected in the same manner as in the case of the spring 18 described above, the arm 10 can be brought into a state close to weightlessness even if it is rotated clockwise or counterclockwise from the vertical position. , the position holding torque can be small. As is clear from the figure, when the spring 19 acts, the rotating shaft 11 and the intermediate rotary plate 20 rotate together, so the spring 18 does not exert a reaction force on the rotating shaft 11.

FIG. 6A is a front view of a different example of a robot configured to carry out the method of the present invention, and FIG. 6B is a side view of the same. The illustrated components are provided on the base, and reference numeral 11 is a rotating shaft fixed to the arm 10. The torsion coil spring 30 is the rotating shaft 1
1, and its one end 32 is hooked onto a pin (fixing member) 36 attached to a fixed plate 35, bypassing a pin 34 disposed on the flange surface of the rotating shaft 11. The other coil end 33 is connected to pins 34 and 36.
The coil end 32 is arranged symmetrically with respect to the coil end 32, and is hooked on a pin 36.

When the rotating shaft 11 rotates clockwise (direction A in the figure), the pin 34 also rotates. A torsion coil spring 30 has one end 32 fixed to a pin 36 and the other end 33
Since the spring rotates together with the pin 34, a reaction force due to the torsion of the spring acts on the pin 34. The resulting moment can produce the same effect as in the previous embodiment.

When the method of the present invention is carried out using a robot constructed as in the above two examples, the effect is limited to a range of plus or minus 90 degrees from the standard posture with the arms upright; Since the range of motion of the upper arm and forearm is within the above angle,
There is no problem in practical use.

Further, when installing the spring, it may be better to apply an appropriate preload, but it goes without saying that this can be set arbitrarily by devising the spring or the mounting location.

In addition, when carrying out the method of the present invention, if it is desired to have a damper effect on the rotational movement of the arm, the seventh
As shown in the figure, a sealed oil chamber 40 may be provided around the rotating shaft 11, a sweeper 41 may be fixed to the rotating shaft 11, and a throttle plate 42 may be appropriately disposed.

〔Effect of the invention〕

As detailed above, by applying the load torque reduction method based on the arm's own weight according to the present invention, it is possible to reduce the output torque of the actuator for supporting the robot arm's own weight, resulting in miniaturization and energy saving of the actuator. It makes a huge contribution to the

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory view of the mechanism of the articulated robot, FIG. 2A is a model diagram, and FIG. 2B is a chart showing the holding torque. FIG. 3 is a partially sectional side view of an example of a robot configured to carry out the method of the present invention, and FIG. 4 is a partially sectional front view of the robot. FIGS. 5A and 5B are charts for explaining the effects of the present invention. FIG. 6 shows a portion of an example of a robot different from the one described above, configured to carry out the present invention, in which FIG. 6A is a front view and FIG. 6B is a side view. FIG. 7 is a sectional view showing an example of a damper used in conjunction with the implementation of the present invention. 10... Robot arm, 11... Arm rotation axis,
18, 19... Compression coil spring, 20... Intermediate rotating plate, 21... Fixed plate (fixing member), 30... Torsion coil spring.

Claims (1)

[Claims] 1 An arm of an articulated robot, a rotation shaft that horizontally supports the base end of the arm and rotates integrally with the arm, and an actuator that drives the rotation shaft to rotate the arm. In the method for reducing the load torque due to the arm's own weight that occurs when the arm rotates from a vertical reference position, the rotation shaft and a fixing member provided on an outer peripheral portion of the rotation shaft In between, a spring is installed to generate a reaction torque in the clockwise and counterclockwise directions to form a spring mechanism coaxial with the rotation axis, and the formed spring mechanism causes the arm to move from the reference posture. A reaction torque that rotates the arm in the opposite direction to the rotation direction of the arm is generated approximately in proportion to the rotation angle from the reference posture of the arm, and the reaction torque applied to the rotation axis and the dead weight of the arm A method for reducing load torque due to the arm's own weight, characterized in that the load torque on the actuator is reduced by counteracting the torque generated on the rotation shaft so that the arm can maintain any rotational position.