JP2006159406A - Robot having horizontal arm - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robot having horizontal arms which can have high stiffness and excellent controllability by suppressing the vibration and the shift of their trajectories, caused by stopping the arms and changing their speed, through eliminating their backlash and improving their spring constants. <P>SOLUTION: The robot has a plurality of the horizontal arms 12, 13, 14, in which a spring force serving as a force for turning the arms toward their one side directions is applied to driving shafts for turning the respective horizontal arms in the horizontal plane. The robot further comprises a cylinder 31, a rack 30, a pinion 33, and chains 34, 35 provided across the neighboring arms. The straight motion caused by the cylinder 31 is converted into a turning driving torque by means of the rack 30 and the pinion 33. The driving torque is transmitted to the driving shafts of the respective arms via the chains 34, 35 serving as power transmitting means arranged across the neighboring arms. As a result, the spring forces are applied to the respective driving shafts as turning torques in their one side directions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a robot having a horizontal arm, and is particularly useful when applied to an industrial robot having a horizontal articulated arm.

  FIG. 10A is a plan view showing an industrial robot having a horizontal articulated arm according to the prior art, and FIG. 10B is a side view thereof. The robot is a four-axis robot. The first axis is a vertical movement axis that moves up and down along a vertically arranged support column 1, and the second, third, and fourth axes are indicated by arrows in FIG. 10 (a). It is a horizontal rotation axis that revolves in a horizontal plane. In both figures, 2 is a 2-axis arm, 3 is a 3-axis arm, 4 is a wrist flange with 4 axes, O1 is a 1-axis lift center, O2 is a 2-axis rotation center, and O3 is a 3-axis rotation center. , O4 is the rotation center of four axes. These first axis to fourth axis are driven by a 1 axis to 4 axis servo motor (not shown) via a reduction gear, respectively.

  In the robot, the rotation center axes O2 to O4 around the 2, 3, and 4 axes are not subjected to a vertical force due to the gravity of the arm, and thus are not subjected to a static rotational load. The reduction gear connected to the 2nd to 4th axis servo motors for rotating the second, third and fourth axes may be a reduction gear for a robot such as a harmonic drive (differential reduction gear) or an RV reduction gear. Accompanied by gear backlash and lost motion (detailed later). For this reason, if a horizontal external force is applied, it swings in the rotational direction. In addition to the external force in the horizontal direction, torque is generated by the moment of inertia of the arm itself during acceleration / deceleration of the arm, causing the arm to swing in the rotational direction. Backlash and lost motion are inevitably present in the reducer, and it is difficult to control the reducer backlash with semi-closed loop control, but it can be reduced by control methods such as feedforward and disturbance observers. Proposed.

  Here, the characteristics of the speed reducer used in the industrial robot will be described together with its rigidity (spring constant / lost motion) and concepts such as backlash. FIG. 11 is a characteristic diagram showing a twist angle with respect to a rotational (torsion) torque applied to the output side of the speed reducer when the input shaft (input gear) of the speed reducer is fixed and torque is applied to the output shaft (shaft). In this case, a twist corresponding to this torque is generated on the output side, and a hysteresis curve as shown in the figure is drawn. As shown in FIG. 11, the lost motion is the twist angle at the midpoint of the hysteresis curve width at ± 3% of the rated torque, the backlash is the twist angle at the torque “zero” of the hysteresis curve, and the spring constant is b / a Means the constants defined in. The rigidity of the reduction gear is expressed by the spring constant and lost motion indicated by the hysteresis curve. The RV reducer is particularly excellent in this rigidity.

  In the prior art, the method of mechanically removing the backlash and lost motion of the horizontal articulated arm is not adopted, and the vibration of the arm and the deviation of the trajectory due to the backlash and lost motion that occur during acceleration / deceleration are controlled horizontally. It is dealt with by changing to multi-joint orientation. For example, measures are taken such as: a speed pattern at the time of acceleration / deceleration is made into a smooth S-curve curve, feed forward is used, disturbance observer control is performed, etc.

JP-A-8-47878 JP-A-6-270080 Japanese Patent Application Laid-Open No. 60-72004

  The following problems occur in the measures as described above. In the case of feedforward and disturbance observer control, the speed is reduced in the semi-closed loop control in which the position is detected by the encoder at the rear of the servomotor which is a drive source for driving the 2, 3 axis arms 2, 3 and the wrist flange 4, respectively. The vibration state of the arm at the time of stop cannot be detected by an encoder, or it cannot be completely detected by the motor current.

  On the other hand, in the closed loop control system in which the arm position detection means is provided on the arm side, the vibration state at the time of deceleration and stop can be fed back, and the feedforward and disturbance observer control is effective, but depending on the presence or absence of the arm load and the bending posture Since the moment of inertia applied to the rotation axis of the arm changes greatly, it is difficult to determine the optimal control parameter under all conditions, and thus it has not reached a practical level. -Even when the acceleration / deceleration speed pattern is a smooth S-curve curve, there are difficulties in application for applications that require external force or require quick operation (short tact time). is there. This is because the spring in the torsional rigidity direction of the reduction gear remains weak and there is backlash.

  Furthermore, the structure in which the position detector is provided on the output side is not generally adopted in the joint axis of the robot due to the complexity of the structure, the complicated maintenance, the cost increase, the restriction of the wiring path, etc. .

  In view of the above-described conventional technology, the present invention eliminates horizontal arm play and improves the spring constant, thereby eliminating vibrations during stopping and acceleration / deceleration and vibration of the trajectory, and has high rigidity and good controllability. An object of the present invention is to provide a robot having a horizontal arm that can be an arm.

  The configuration of the present invention that achieves the above object is characterized by the following points.

1) A spring force that is a rotational force in one direction is applied to a drive shaft that rotates a horizontal arm in a horizontal plane.

2) In the robot having the horizontal arm described in 1), the robot has a plurality of horizontal arms, and is a tension link provided between the adjacent arms, and one side of a drive shaft that rotates each horizontal arm in a horizontal plane. A spring force that is a rotational force in the direction is applied.

3) In the robot having the horizontal arm described in 1), this robot has a plurality of horizontal arms, and each horizontal arm is rotated in a horizontal plane by a tension link provided between the odd-numbered or even-numbered axes. A spring force, which is a rotational force in one direction, is applied to the drive shaft.

4) In the robot having the horizontal arm described in 1), this robot has a plurality of horizontal arms, and each horizontal arm is placed in a horizontal plane via one tension link and a link branched from the tip of the tension link. A spring force that is a rotational force in one direction is applied to each drive shaft that rotates inside.

5) In the robot having the horizontal arm described in 1), this robot has a plurality of horizontal arms, and both ends are connected to the odd-numbered or even-numbered axis arms and the two links are rotatably connected. A drive shaft having a link formed so as to be movable in a vertical plane and a spring force applying means for applying a spring force that opens between both ends of the link and rotating each horizontal arm in a horizontal plane A spring force, which is a turning force in one direction, was applied to

6) In the robot having the horizontal arm described in 1), the robot has a plurality of horizontal arms, converts linear movement by the cylinder into a rotational driving force using a rack and a pinion, and converts the driving force between adjacent arms. A spring force, which is a rotational force in one direction, is applied to each drive shaft by transmitting to the drive shaft of each arm via an endless track-shaped power transmission means such as a chain and a belt provided in.

7) In the robot having the horizontal arm described in 6), the driving force of the power transmission means in the endless track shape is obtained by gravity acting on the counterweight.

  According to the present invention, since it is configured such that a spring force that is a rotational force in one direction can be applied to each horizontal axis, good controllability can be ensured. The robot according to the present invention can be applied not only to a general industrial robot but also to a robot having a horizontal multi-joint type arm of a manual manipulator to ensure particularly remarkable controllability. This is because the present invention is particularly effective because the control system cannot follow the rapid acceleration / deceleration instructed by the operator during manual operation. In addition, when an external force is applied during an operation such as handling, the amount of deflection due to an increase in the spring constant can also be controlled, so that the operation is facilitated in this respect as well. On the other hand, since an industrial robot also suppresses the amount of bending and has high rigidity, it can be applied to applications requiring external force such as deburring and processing and requiring rigidity.

  The robot according to the embodiment of the present invention is provided with a tension link such as a spring between the arms of the horizontal articulated arm, and a drive system that drives each arm by applying a tension force or a compression force with the tension link. Applying a load in one direction to the reducer, removing backlash, removing acceleration / deceleration and stopping by removing the lost motion area, and increasing the torsion spring constant of the reducer (see Fig. 11) The natural frequency of the mechanical system is increased, and as a result, the controllability of the robot is improved.

  Next, a more detailed embodiment of the present invention will be described in detail with reference to the drawings. In general, in the case of a robot having four axes, the arm posture during the operation of the horizontal articulated arm is, as shown in FIG. 1, whether the three-axis joint 3 a is located on the right or left, Although the joint configuration of the system will be described, in the following embodiments, there will be exemplified ones that exhibit the effect by limiting the target work to any system and those that exhibit the effect in any system.

  In normal work, a robot is often taught and operated by any system. Even when the right-handed system and the left-handed system exist in the same job, the dead link (tension (tension) where the spring link of the tension link is at an angle of zero, that is, the axis of the tension link overlaps the straight line connecting the two joints of the arm. It is effective except for the position where the spring's tensile force does not act. Further, each embodiment includes a tension link for applying an external force to the arm, and a force is applied in the rotation direction of the arm by a member that generates a force such as a tension, a compression spring, air, or a hydraulic cylinder in the tension link. The following six examples can be given as a method for applying the force in this case. Incidentally, in Examples 1 to 4, tension is always applied in one direction in either the right-handed system or the left-handed system. In Examples 5 and 6, tension is always applied to one side in the entire operation range of the robot regardless of the right-hand system or the left-hand system. In addition, the robot main body of the Example shown below is common to each Example, and only the provision structure of the spring force with respect to each axis | shaft differs. Therefore, in the drawings showing the embodiments, the same parts are denoted by the same reference numerals, and redundant description is omitted.

<Example 1>
FIG. 2A is a plan view of the robot according to this embodiment, and FIG. 2B is a side view thereof. As shown in both figures, the robot according to the present embodiment is a four-axis robot, and the first axis moves up and down along the vertically arranged support columns 11, and the second, third, fourth, and fourth axes. This is a horizontal rotation axis whose axis rotates in a horizontal plane. In both figures, 12 is a two-axis arm, 13 is a three-axis arm, 14 is a four-axis arm, O11 is a one-axis lift center, O12 is a two-axis rotation center, O13 is a three-axis rotation center, and O14 is It is a 4-axis rotation center. The tension links 15, 16, and 17 are members that house a tension spring or a compression spring inside the cylinder and apply a tension force or a compression force between members connected to both ends of the tension links 15, 16, or 17, or a pneumatic cylinder or a hydraulic cylinder. It is a member which similarly gives a tensile force or a compression spring force by giving. The tension link 15 is pivotally attached to a position deviated from the rotation center O12 on the biaxial side on the tension link 15, and the distal end is rotated on the triaxial side so as to be coaxial with the rotation center O13. The tension link 15 is configured so that the spring force of the tension link 15 acts on the reduction gear of the motor that constitutes the drive system of the biaxial arm 12. The tension link 16 is pivotally attached to a position deviated from the rotation center O13 on the three-axis side on the tension link 16, and the tip end portion is rotated on the four-axis side so as to be coaxial with the rotation center O14. The tension link 16 is configured so that the spring force of the tension link 16 acts on the reduction gear of the motor that constitutes the drive system of the triaxial arm 13. The tension link 17 is pivotally attached so that its base end portion is coaxial with the rotation center O13 on the three axis side, and the tip end portion is rotated to a position deviated from the rotation center O14 on the four axis side. The tension link 17 is configured so that the spring force of the tension link 17 acts on the reduction gear of the motor constituting the drive system of the four-axis arm 14.

  In addition, you may attach a tension link in the aspect as shown to Fig.3 (a), (b). As shown in both drawings, in this modification, the positions of the tension link 16 ′ corresponding to the tension link 16 shown in FIG. 2 and the tension link 17 ′ corresponding to the tension link 17 shown in FIG. .

  In this embodiment, the spring characteristics can be set finely and precisely for each axis.

<Example 2>
FIG. 4A is a plan view of the robot according to this embodiment, and FIG. 4B is a side view thereof. As shown in both drawings, in this embodiment, a predetermined spring force is applied by a single tension link 18. That is, while the biaxial arm 12 and the triaxial arm 13 are bent, the proximal end portion of the tension link 18 is rotatably attached to a position displaced from the rotational center O12 on the biaxial side, and the distal end portion Is pivotably attached to a position deviated from the rotation center O14 on the four-axis side, and is configured so that a rotation load can be applied to the two, three, and four axes simultaneously.

  In this embodiment, only one tension link 18 is required, and the structure is simplified. On the other hand, since the operating range of the arm is limited due to the limitation of the spring stroke, it is necessary to select and install a stroke that matches the operating range.

<Example 3>
FIG. 5A is a plan view of the robot according to this embodiment, and FIG. 5B is a side view thereof. As shown in both figures, the present embodiment applies a predetermined spring force with a single tension link 19, but differs in that the other links 20, 21 are branched from the tip of the tension link 19. . That is, in a state where the biaxial arm 12 and the triaxial arm 13 are bent, the base end portion of the tension link 19 is rotatably attached to a position displaced from the rotational center O12 on the biaxial side. The proximal ends of the links 20 and 21 are rotatably connected to the distal end portion of the tension link 19, and the distal end portion of the link 20 can be rotated so as to be coaxial with the rotation center O13 on three axes. And the tip of the link 21 is rotatably attached to a position displaced from the rotation center O14 on the four-axis side. Thus, the rotation load can be simultaneously applied to the 2, 3, and 4 axes. The lengths of the links 20 and 21 are configured to be adjustable.

  In this embodiment, only one tension link 19 is required as in the second embodiment, and not only the structure is simplified, but also the links 20 and 21 are branched. It can be adjusted by changing the link length.

<Example 4>
FIG. 6A is a plan view of the robot according to the present embodiment, and FIG. 6B is a side view thereof. As shown in both figures, in this embodiment, two links 22 and 23 for connecting the two-axis side and the four-axis side in a vertical plane are provided, and the spring force of the tension link 24 is provided between these links 22 and 23. It is comprised so that it may act. That is, the distal end portion of the link 22 and the proximal end portion of the link 23 are rotatably connected to each other, and the proximal end portion of the link 22 is rotated to a position deviated from the rotation center O42 on the biaxial side. The front end of the link 23 is attached to a rotation center O44 on the four-axis side so as to be movable. Here, the attachment parts of the links 22 and 23 on the two-axis side and the four-axis side ensure rotation in the vertical plane of the links 22 and 23 and are in a horizontal plane with respect to the two-axis side and the four-axis side. However, the links 22 and 23 are attached to the two-axis side and the four-axis side via the bearings 25 and 26 so that they can rotate. The cylinder portion of the tension link 24 is attached in the middle of the link 22 and the rod portion of the tension link 24 is attached in the middle of the link 23. The tension link is attached to each of the two to four axes via the links 22 and 23. 24 spring force is applied. In this case, the spring force may be obtained by providing a rotary spring at the connecting portion of the links 22 and 23.

  In this embodiment, only one tension link 24 is required, and not only the structure is simplified, but also a spring force is applied via the links 22 and 23 that rotate in the vertical plane. Can be secured.

<Example 5>
FIG. 7A is a plan view of the robot according to the present embodiment, and FIG. 7B is a side view thereof. As shown in both figures, this embodiment is configured so that tension is always applied to one side in the entire operating range of the biaxial and triaxial arms 12 and 13 regardless of the right hand system and the left hand system. In this embodiment, the rotation range of the closed chain (or belt) connected to the biaxial and triaxial arms 12 and 13 and the spring load portion is set to a linear stroke so that it can be obtained by a rack and pinion system. It is.

  More specifically, the tension link 27 is pivotally attached to the position where the base end portion is deviated from the rotation center O13 on the three-axis side, and the tip end portion is deviated from the rotation center O14 on the four-axis side. On the other hand, sprockets 28 and 29 are fixedly attached to the shaft serving as the pivot center of the biaxial arm 12 and the shaft serving as the pivot center of the triaxial arm 13 respectively. The rack 30 is connected to the tip of the piston rod 31a of the cylinder 31, and is arranged in the robot body so as to move linearly along the cam followers 32 that are linearly arranged by the expansion and contraction of the piston rod 31a. The pinion gear 33 that meshes with the rack 30 is configured to rotate along with the linear movement. Chains 34 and 35 are suspended between the pinion gear 33 and the sprocket 28, and between the sprocket 28 and the sprocket 29, respectively. As a result, the rotational force of the pinion gear 33 is transmitted to the sprocket 28 via the chain 34, and the accompanying rotational force of the sprocket 28 is transmitted to the sprocket 29 via the chain 35. Due to the rotation of the sprockets 28 and 29, the biaxial and triaxial arms 12 and 13 are given a spring force which is a rotational force in one direction. Here, the rack 30, the cylinder 31, the cam follower 32, and the pinion gear 33 are configured to move up and down integrally with the biaxial arm 12 as the biaxial arm 12 moves up and down.

  In the present embodiment, the load on the four-axis arm 14 is applied by the tension link 27. However, the rotation axis of the four-axis arm 14 is directly set in the same manner as the two-axis and three-axis arms 12 and 13. It is good also as a structure which rotates.

<Example 6>
FIG. 8A is a plan view of the robot according to this embodiment, and FIG. 8B is a side view thereof. As shown in both figures, in this embodiment, as with the robot of the fifth embodiment, tension is always applied to one side regardless of the right-handed system and the left-handed system in the entire operating range of the biaxial and triaxial arms 12 and 13. It is configured. That is, the rotational force of the sprockets 28 and 29 in the fifth embodiment is obtained by the gravity acting on the counterweight 36, and the configuration relating to the tension link 27, the sprockets 28 and 29, the chains 34 and 35, etc. is exactly the same as in the fifth embodiment. It is.

  In this embodiment, the sprocket 38 that suspends the chain 34 between the sprocket 37 is fixed coaxially with the bevel gear 39, and the axis of the bevel gear 39 that is orthogonal to the rotation axis thereof is defined as the rotation axis. And is connected to the counterweight 36 via a chain 41, a sprocket 42, a chain 43, a sheave 44 and a wire rope 45 in sequence. The counterweight 36 moves up and down along a guide rail 46 disposed vertically to the biaxial arm 12 via a connecting member so as to move up and down integrally with the biaxial arm 12. That is, the counterweight 36, the chain 41, the sprocket 42, the chain 43, the sheave 44, the wire rope 45, and the guide rail 46 are configured to move up and down integrally with the biaxial arm 12.

  According to the present embodiment, a spring force corresponding to the weight of the counterweight 36 can be applied to the biaxial and triaxial arms 12 and 13. According to this embodiment, the load amount cannot be controlled by simultaneous control, but the load amount can be adjusted by adjusting the weight of the counterweight 36. In the present embodiment, similarly to the fifth embodiment, the four-axis arm 14 may be configured to directly rotate the rotation shaft in the same manner as the two-axis and three-axis arms 12 and 13. In addition, since air, oil, a motor, and the like are not used, there is no failure and a predetermined function can be ensured even if the drive source is cut off as in the case of air, oil, a motor, or the like.

  FIG. 9 shows characteristics corresponding to FIG. 11 when the preload amount due to the action of the spring force is set to 50% torque of the speed reducer of each axis on the plus side in each embodiment as described above. As is apparent with reference to the figure, according to each embodiment, when the robot is stopped or decelerated and stopped, the gear is pushed to one side by the preload, not the lost motion region having a low spring constant. . Thus, in normal robot operation, about ± 70% of the rated torque of the reducer is used at a constant speed, and about ± 200% is used during acceleration / deceleration.

  In the embodiment as described above, when an air cylinder and a hydraulic cylinder are used as the spring force applying means and these pressures are detected, the load amount can be adjusted by adjusting the pressure in this case. Conversely, it is possible to calculate the optimum load amount from the viewpoint of the arm and change the load amount by simultaneous control. In addition, when a predetermined spring force is obtained by the motor driving method, the load amount can be adjusted by current detection.

It is explanatory drawing for demonstrating the concept of the right hand type | system | group and the left hand type | system | group in the robot which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the robot which concerns on Example 1 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the modification of the robot which concerns on Example 1 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the robot which concerns on Example 2 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the robot which concerns on Example 3 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the robot which concerns on Example 4 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the robot which concerns on Example 5 of this invention, (a) is the top view, (b) is the side view. It is a figure which shows the robot which concerns on Example 6 of this invention, (a) is the top view, (b) is the side view. It is a characteristic view which shows the characteristic of the reduction gear which transmits a driving force to each axis | shaft of the robot which concerns on the Example of this invention. It is a figure which shows the robot which concerns on a prior art, (a) is the top view, (b) is the side view. It is a characteristic view which shows the characteristic of the reduction gear which transmits a driving force to each axis | shaft of the robot which concerns on a prior art.

Explanation of symbols

11 1 axis arm 12 2 axis arm 13 3 axis arm 14 4 axis arms 15, 16, 17, 18, 19, 24, 27 Tension links 20, 21, 22, 23 Links 28, 29 Sprocket 30 Rack 31 Cylinder 33 Pinion gear 34 , 35 Chain 36 Counterweight

Claims (2)

In a robot having a horizontal arm obtained by applying a spring force that is a rotational force in one direction to a drive shaft that rotates the horizontal arm in a horizontal plane,
This robot has a plurality of horizontal arms, converts linear movement by cylinders into rotational driving force with racks and pinions, and transmits this driving force to an endless track like a chain and belt provided between adjacent arms. A robot having a horizontal arm, wherein a spring force that is a rotational force in one direction is applied to each drive shaft by transmitting to the drive shaft of each arm through means. The robot having a horizontal arm according to claim 1,
A robot having a horizontal arm, characterized in that the driving force of an endless track-shaped power transmission means is obtained by gravity acting on a counterweight.

Images