JP4702744B2 - Coordinated transport system and method using a plurality of robots having a gripping mechanism with backlash and sliding - Google Patents

Description

  The present invention provides a coordinated transport by a plurality of robots that transports a single hard (not stretched or contracted) transported by a plurality of robots (for example, an automated guided vehicle, a robot arm, a moving carriage with a robot arm, etc.). The present invention relates to a system and method.

  Conventionally, research and development has been carried out in which a single transported object is transported by a plurality of robots / moving bodies. For example, the following Non-Patent Document 1 is used.

  There are a variety of cooperative transport methods, but according to the cooperative transport method described in Non-Patent Document 1 below, (1) communication between robots is unnecessary, and (2) one robot (hereinafter referred to as a leader). If only one knows prior information about the transported object / transport route, the remaining one or more robots (hereinafter referred to as followers) have a feature of operating according to the reader without prior information. Due to this feature, only one robot has intelligence, and the other robots only need to be able to follow this coordinatedly, thereby simplifying the overall system configuration. For this reason, it is easier to apply to actual products than other cooperative transport methods.

  The method of the following nonpatent literature 1 is demonstrated in detail with reference to FIG.7 and FIG.8.

FIG. 7 is a diagram showing the relationship between the position error and the trajectory of the prior art. When the transported object 55 is transported in the traveling direction R, the operation of the reader 51 is transmitted to the follower 52 through the transported object 55, and the follower 52 estimates the operation (target trajectory x _d ) of the reader 51 from this motion, and the estimated target trajectory x get _e . Specifically, a situation is considered in which both the reader 51 and the follower 52 are gripping the conveyed product 55 “without slipping” by the spring dampers 53 and 54 having the same strength. The same strength spring dampers 53 and 54 have the same value of the compliance coefficient K. When the reader 51 operates, the spring damper 53 extends, but the follower 52 also has the spring damper 54 of the same strength, so the extension amount (position error Δx _l ) of the spring damper 53 on the leader side and the follower side The extension amount (position error Δx _f ) of the spring damper 54 is equal. Therefore, if the follower 52 knows the extension amount (position error Δx _f ) of its own spring damper 54, the value 2Δx _f , which is twice this value, becomes the target trajectory (leader target trajectory x _d ) of the reader 51 and the target of the follower 52. It can be seen that the difference (estimation error) between the trajectories (follower target trajectory x _e ). By passing this through a certain filter, the follower 52 can estimate the target trajectory of the reader 51 that it should follow. If the follower 52 operates so as to follow this, the follower 52 follows the reader 51 and operates.

FIG. 8A is a diagram showing a filter 60 for the above estimation. When the G ₁ and the transfer function of filter 60, transfer function G ₁ is the value 2Derutax _f obtained by doubling the position error [Delta] x _f is input, estimates the follower target trajectory x _e. That is, as shown in FIG. 8 (b) was equivalent transformation of the filter 60 of FIG. 8 (a), the difference between the estimated target trajectory _{x e} and the reader target trajectory _{x d (x d -x e)} , the estimated error 2Δx Estimated target trajectory _xe is estimated so that _f is equal. In this way, if the closed loop system is stable, the target trajectory can be estimated from the estimation error. For example, the transfer function G ₁ (s) = (as + b) / s ² can be selected. Actually, it is not necessary to use a spring / damper for the gripping portion, and the gripping portion may be virtually gripped with a spring / damper characteristic by a force control method such as impedance control.
Hirata, Kominato, et al. "Distributed cooperative control of multiple mobile robots that realize object transfer without the need for geometric relations between robots", Transactions of the Japan Society of Mechanical Engineers (C), Vol. 69, No. 677, pp.204-211, 2003

  By the way, in the cooperative transport system shown in FIG. 7, in order for the movement of the reader 51 to be transmitted to the follower 52 through the transported object 55, it is necessary to transmit the force accurately and immediately. For this purpose, it is not desirable that the gripping part is slippery. If there is a slip, the force of pushing and pulling will not be transmitted while it is slipping. As a method for the robot to hold and fix the transported object 55, (1) there is a method of lifting an eyebolt of the transported object with a hook of a manipulator. Also, (2) there is a method of making holes in the robot stage, loading platform and transported object, and fastening them through pins. In this case, the hole is made larger than the pin thickness in order to facilitate insertion. Further, (3) there is a method of placing a conveyed product on a stage / load bed attached to the robot via a vibration proof rubber or vibration proof damper. All of these fixing methods have backlash and slip. If these play and slip methods are used, the force may not be accurately transmitted due to the elasticity of the slipping or gripping part, and as a result, the follower cannot accurately estimate the movement of the leader and therefore does not follow the leader. Or, there is a possibility that the purpose of cooperative conveyance cannot be achieved by colliding.

  The present invention has been made in view of the above circumstances, and is an object of cooperative transport even if there is a backlash in the reader and follower gripping part, which is a connection part between the leader and the transported object, or the transported object and the follower. It is an object of the present invention to provide a cooperative transfer system using a plurality of robots, a cooperative transfer method using a plurality of robots, and a follower type robot.

  In order to solve the above-described problem, a coordinated transport system using a plurality of robots according to the present invention is based on a reader that grips a transported object, and also grips the transported object, and based on a difference between the target trajectory of the reader and its own target trajectory. In a collaborative transport system using a plurality of robots that transport a transported object in cooperation with a follower that estimates a target trajectory, a backlash / slip determination unit that determines whether or not the gripper of the follower has a backlash on the transported object. Orbit estimation that causes the follower target orbit to be estimated differently when it is determined by the rattling / slip judging unit that the gripping part of the follower has rattle / slip and when there is no rattling / slip. A part.

  In the cooperative transport system using a plurality of robots, the backlash / slip determination unit may determine whether the gripper has backlash / slip based on the movement direction of the gripper and the direction of position deviation. preferable.

  The backlash / slip determination unit determines that there is no backlash / slip in the gripping part when the direction of movement and the position deviation of the gripping part are the same, and the movement direction and position deviation of the gripping part are determined. When the directions are different, it is preferable to determine that there is a possibility that there is a backlash / slip in the grip portion.

  In addition, when the backlash / slip determination unit determines that there is no backlash / slip in the follower gripping portion, the trajectory estimation unit determines the difference between the target trajectory of the leader and its own target trajectory as an estimation error. Is preferably passed through a predetermined filter to estimate the target trajectory.

  The trajectory estimation unit outputs a trajectory that causes the leader to decelerate and stop when the backlash / slip determination unit determines that there is a possibility that backlash / slip exists in the follower gripping portion. It is preferable.

  In order to solve the above-described problem, the follower-type robot according to the present invention is a cooperative transport system that transports the same transport object in a coordinated manner, and grips the transport object with respect to a reader that grips the transport object. And a follower-side robot that estimates a target trajectory based on a difference between the target trajectory of the leader and its own target trajectory, and determines whether or not the grip portion of the follower with respect to the transported object has play or slippage. When the backlash / slip determining unit and the backlash / slip determining unit determine that there is a possibility that there is a backlash / slip in the gripping portion of the follower, and when there is no backlash / slip, A trajectory estimator for differently estimating the target trajectory.

  Further, in order to solve the above-described problem, the coordinated transport method using a plurality of robots according to the present invention is based on a reader that grips a transported object, the grip of the transported object, and a difference between its own target trajectory and an actual trajectory. A backlash / slip determination step for determining whether or not there is any backlash / slip in a gripping portion of the follower with respect to the transported object in a collaborative transport method using a plurality of robots that transport the transported object in cooperation with a follower that estimates a target trajectory. When the backlash / slip determination step determines that there is a possibility that there is backlash / slip in the follower gripping part, and when it is determined that there is no backlash / slip, the follower target trajectory is estimated. A trajectory estimation step for differentiating.

  There is a slip in the robot's gripping part.

  In the latter case, the force is transmitted firmly without slipping, so that the application condition of the filter 60 for estimation that has been conventionally used is satisfied.

On the other hand, in the former case, the force and motion are not transmitted accurately, so the filter A cannot be applied as it is. This is because the position error (Δx _f ) of the self acquired by the follower does not represent the accurate movement of the reader, so that even if this value is passed through a filter, an accurate value cannot be estimated. Therefore, in this case, the estimation result is output from the estimator on the safe side, that is, a trajectory that gently stops after a while. As a result, when there is no backlash or slip, the estimator estimates and outputs the trajectory of the leader by the conventional method, and when there is a possibility that backlash or slip exists, the follower decelerates and stops. Such as outputting a simple trajectory. Microscopically, a trajectory that follows and follows the movement of the leader is repeated, and a trajectory that follows the leader is obtained macroscopically.

  The method for determining the presence or absence of backlash / slip can be determined from the direction of movement and the position deviation of the gripper. In order to estimate a trajectory that stops gently, the output and state of the estimator may be fed back to the input of the estimator so that the pole of the estimator becomes a stable pole excluding one origin pole.

  If the follower performs a follow-up operation on the trajectory estimated in this way, the follower follows the leader as a result.

  According to the present invention, the purpose of cooperative transport can be achieved even if there is a backlash or slip in the reader and follower gripping part, which is the connecting part between the leader and the transported object, or the transported object and the follower.

  That is, since the filter 60 according to Non-Patent Document 1 can be expanded to a mechanism with slipping and backlash by simply adding a trajectory generation mechanism that gives a stop operation, for example, the switch 42 and the gain multiplier 41, the reliability with respect to the conventional method is improved. It is possible to expand the system while taking over.

  The conventional method does not matter whether it is fixed to the floor or mobile. Even if it is a moving body, an arbitrary moving method (2-wheel, 4-wheel, omnidirectional movement, crawler, etc.) can be selected. A patent limited to two wheels has been filed in the prior art (Japanese Patent Laid-Open No. 2000-42958), but the present invention is more versatile because it does not matter the movement method.

  Moreover, even if it is not a hard conveyance thing, it can be conveyed even if it is a thing to some extent flexible (thing which expands and contracts). This is because a trajectory that advances when the follower is pulled by the leader is estimated, and a trajectory that stops when the conveyed object is bent and the force is not transmitted is estimated.

  Hereinafter, the best mode for carrying out the present invention will be described. The following embodiment relates to a cooperative transfer system using a plurality of robots. Each robot has a gripping mechanism such as a hook, which has a backlash, which is called backlash. The conveyed object is grasped by lifting an eyebolt attached to the conveyed object by a grasping mechanism such as a hook.

  FIG. 1 is an external view of a cooperative transfer system 1 using two robots. Specifically, it is a cooperative transport system 1 including mobile carts 10 and 20 having robot arms 13 and 23 whose hand portions are hooks 14 and 24 and a transported object 30 to which eyebolts 31 and 32 are attached. In this cooperative transport system 1, the mobile carriages 10 and 20 have the robot arms 13 and 23, and a grip portion is provided at the tip of the robot arms 13 and 23. This is an example, and the robot arms 13 and 23. Needless to say, the present invention also includes a configuration in which a gripping portion is provided at a predetermined location of the mobile carriage without having the above. In other words, the present invention is also applicable to a robot other than the configuration in which the conveyed object is gripped by the robot arm.

  The mobile carriages 10 and 20 may be remotely operated by an operator or may behave autonomously. It can be applied to industrial robots, disaster rescue robots, welfare robots, or entertainment robots.

  The movable carriage 10 can be moved in two or more directions on a horizontal plane by turning two wheels 12 or four wheels to be steered, which are attached to the lower part of the body portion 11, such as front and rear and turn, front and rear, left and right, and turn. The robot arm 13 is formed by connecting a metal, ceramic, resin, or other material having rigidity so as to be able to rotate or rotate at a plurality of joint portions. The L-shape is L-shaped with one end locked by the upright portion, and the L-shaped corner rotates at an arbitrary angle. Move. The upright part and the L-shaped part of the robot arm 13 receive the rotational force from the motor arranged in the body part 11 or the robot arm 13 as a driving force through a mechanism part such as a gear or a shaft, and rotate or rotate. Move. For this reason, the robot arm 13 can lift one end of the conveyed product 30 in a state where the hook 14 is hung on the eyebolt 31. The configuration of the mobile carriage 20 is the same.

  These two mobile trolleys 10 and 20 incorporate a computer having a CPU, a ROM, and a RAM, and control for cooperative transport is performed. For example, based on Non-Patent Document 1 above, (1) communication between robots is not required, and (2) only one robot (hereinafter referred to as a leader) knows advance information about a transported object / transport route. Thus, the remaining one or more robots (hereinafter referred to as followers) have a feature of operating according to a reader without prior information. Due to this feature, only one robot has intelligence, and the other robots only need to be able to follow this coordinatedly, thereby simplifying the overall system configuration. For this reason, it is easier to apply to actual products than other cooperative transport methods.

  Now, let the mobile carriage 10 be a leader. The reader 10 moves in the direction of arrow R in FIG. The mobile carriage 20 is a follower. The follower 20 operates according to the reader 10.

  However, both the reader 10 and the follower 20 are lifted by the robot arms 13 and 23 by using a fixing method in which the conveyed object 30 is hooked on the eyebolts 31 and 32 by hooks 14 and 24. In the fixing method using the hooks 14 and 24, there is a case where there is a backlash or a slip in the gripping portion depending on the relationship between the position and speed of the eyebolts 31 and 32 and the hooks 14 and 24, and there is a case where they do not exist.

  When there is no backlash / slip in the gripping part, the force from the reader 10 and the follower 20 is transmitted to the transported object 30 firmly without slipping of the hook and the eyebolt. Since this satisfies the application condition of the filter 60 for the described estimator, it can be estimated using this.

However, if there is a possibility that there is a backlash / slip in the gripping part, the force may not be accurately transmitted due to slippage or elasticity of the gripping part. As a result, the follower 20 accurately detects the movement of the reader 10. It may not be possible to estimate. This is because the position error (Δx _f shown in FIG. 5) acquired by the follower 20 does not represent the accurate movement of the reader 10, so even if this value is input to the filter 60, an accurate value cannot be estimated. Because.

  Therefore, in the cooperative transport system 1 according to this embodiment, when there is a possibility that the grip portion has a backlash / slip, the estimation result is on the safe side, that is, a trajectory that gently stops after a while is estimated. Output from.

  As a result, when the estimator slips and there is no backlash, the follower 20 estimates and outputs the trajectory of the reader 10 according to the conventional method (Non-Patent Document 1 above). An operation such as outputting a trajectory that stops is performed. Microscopically, a trajectory that follows the movement of the reader 10 and a trajectory that stops are repeated, but a macroscopic trajectory that follows the reader 10 is obtained.

  FIG. 2 is a diagram illustrating a state in which the eye bolts are lifted by using the hooks 14 and 24 for the grip portion and hung on the eye bolts 31 and 32. The method for determining whether or not the grip portion has slipping or backlash can be determined from the movement direction and the position deviation direction of the grip portion.

  In FIG. 2, Case [1] is a case where the direction of the position deviation and the motion speed are the same. In this case, as shown in (a), the direction of movement of the hook and the force from the eyebolt to the hook are the same direction, and the hook 14 is considered to be pulled by the eyebolt 31, so slipping and backlash are very small. It can be estimated by a conventional method (Non-Patent Document 1).

  Case [2] is a case where the direction of the position deviation and the motion speed are opposite (different). In this case, either the hook 14 is pulled by the eyebolt 31 as shown in (b) or is slipping in the play as shown in (c). If (b), the conventional method (Non-Patent Document 1) can be applied, but if (c), it is slippery and loose, and it is necessary to estimate the trajectory to stop. Since (b) or (c) cannot be distinguished only from the position deviation / velocity of the gripping part, in case [2], a trajectory that stops regardless of (b) or (c) is taken.

  In the case [1] of FIG. 2, that is, when position error × gripping part speed> 0 (the direction of the position deviation and the gripping part speed is the same), it is the same as the filter 60 of FIG. is there. In case [2], that is, when position deviation × gripping part speed <0 (the direction of the position deviation and the gripping part speed is reversed), the position error of the follower 20 is not input to the estimator, and the state of the estimator 40 is changed. Originally, state feedback is performed to the input of the estimator so that the output of the estimator 40 converges to a certain constant value.

FIG. 3 is a diagram showing one embodiment of a configuration of a filter (trajectory estimator) for trajectory estimation used in the cooperative transport system 1. A filter often used in the conventional method is (as + b) / s ² .

A method of selecting the feedback gain K in the gain multiplier 41 in one embodiment will be described. The filter 60 ((as + b) / s ² ) shown in FIG. 8 has two origin poles, and the gain K is selected by the pole placement method so that one of these poles becomes a stable pole. That is, in order to estimate a trajectory that stops gently, for example, the output and state of the estimator may be fed back so that the pole of the estimator becomes a stable pole excluding one origin pole.

As a result, the filter ((as + b) / s ² ) gradually converges to a constant value. The input switching to the filter 60A is performed by the switch 42.

  If the follower 20 follows the estimated trajectory obtained by the trajectory estimator 40, the follower 20 can follow the reader 10 as a result.

  FIG. 4 is a characteristic diagram showing changes in the travel distance with respect to the time of the leader 10 and the follower 20 when the transported object 30 is actually transported in the cooperative transport system 1 by the two robots of the present embodiment. . The characteristics of the reader 10 indicated by C-10 and the characteristics of the follower 20 indicated by C-20 extend almost in the same manner. This indicates that the travel distance of the follower 20 increases following the travel distance of the reader 10. That is, it can be seen that the follower 20 operates following the reader 10.

  FIG. 5 shows the trajectories of the tip of the reader 10 (hook 14) and the tip of the follower 20 (hook 24) when the transported object 30 is transported by the cooperative transport system 1 using the two robots. FIG. The horizontal axis indicates the position in the x direction, and the vertical axis indicates the position in the y direction. A leader actual trajectory start point SP-10 and a leader actual trajectory end point EP-10 are shown in the actual trajectory T-10 at the tip of the reader 10. In addition, a follower actual trajectory start point SP-20 and a follower actual trajectory end point EP-20 are shown in the actual trajectory T-20 at the hand of the follower 20. Further, the center point between the leader and the follower is used as the trajectory of the conveyed product 30. This transported object trajectory T-30 shows a transported object actual trajectory start point SP-30 and a transported object actual trajectory end point EP-30. In this way, the two robots cooperatively transport the transported object while drawing the locus of the leader hand position and the follower hand position shown in FIG.

  As described above, according to the cooperative transport system 1 described above, for example, the switch 42 and the gain K can be simply added to the filter 60 according to the conventional method by adding a mechanism for stopping when there is a possibility that rattling / slip exists. By adding a gain multiplier 41 that multiplies, the mechanism can be extended to a mechanism with slipping and backlash. Therefore, it is possible to expand the system while maintaining the reliability of the conventional method. In particular, in the case of FIG. 3, since the input of the estimator is switched by the switch 42 instead of switching the estimator itself, a device for generating a trajectory that stops is prepared separately, and the continuity of the trajectory when the estimator is switched There is no need to devise a technique to maintain sex. Even if the input is discontinuous, the output is continuous because the filter 60 includes an integrator. The shape of the trajectory when stopping is determined by the stability pole set by the gain K, and the trajectory immediately stops as the absolute value increases.

  The conventional method does not matter whether it is fixed to the floor or mobile. Even if it is a moving body, an arbitrary moving method (2-wheel, 4-wheel, omnidirectional movement, crawler, etc.) can be selected. A patent limited to two wheels has been filed in the prior art, but the present invention is more versatile because it does not matter the movement method.

  Moreover, even if it is not a hard conveyance thing, it can be conveyed even if it is a thing to some extent flexible (thing which expands and contracts). This is because a trajectory that advances when the follower is pulled by the leader is estimated, and a trajectory that stops when the conveyed object is bent and the force is not transmitted is estimated.

  In addition, although the said cooperative conveyance system 1 was set as the structure which uses one follower 20 with respect to the reader | leader 10, this invention is applicable to the cooperative conveyance system 45 by three robots as shown in FIG. Of course. In this system, the two followers 20a and 20b each have the trajectory estimator 40 for the leader 10 that is about to transport the transported object 46 in the direction of the arrow L, and perform coordinated transport.

It is an external view of the cooperative conveyance system by two robots. It is a figure explaining a state when using a hook for a grasping part, hanging on an eyebolt, and lifting an eyebolt. It is a figure which shows an example of a structure of the filter (trajectory estimator) for the trajectory estimation used with the said cooperative conveyance system. It is a figure which shows the distance of a leader and a follower. It is a figure which shows the locus | trajectory of the hand of a robot, and a conveyance center position. It is an external view of the cooperative conveyance system by three robots. It is a figure which shows the relationship between a position error and a track | orbit of a prior art. It is a figure which shows the filter for the estimation by a prior art.

Explanation of symbols

1 Cooperative transport system with two robots 10 Mobile cart (leader)
13 Robot arm 14 Hook 20 Moving cart (follower)
23 Robot arm 24 Hook 30 Carrying object 31 and 32 Eye bolt

Claims (5)

A reader that grips the conveyed object via an actual or virtual spring damper;
The conveyed object is gripped by the gripper via the actual or virtual spring damper of the same strength as the leader's spring / damper, and the gripper follows the estimated target trajectory of the reader. A follower for transporting an object to be conveyed, the follower having a function of detecting a positional deviation of a gripping part based on an extension amount of a spring / damper of the follower;
In a coordinated transport system with multiple robots,
A backlash / slip determination unit that determines whether or not there is a backlash / slip in the follower gripping portion based on the detected positional deviation of the gripping portion of the follower and the movement direction of the gripping portion;
When it is determined that there is a backlash or slip, the leader decelerates and stops, and the target trajectory of the leader is estimated. When it is determined that there is no backlash or slip, the target trajectory of the reader is estimated based on the detected position deviation. A multi-robot cooperative transport system comprising: a trajectory estimator for estimating a trajectory so that the follower can follow the leader regardless of the presence or absence of backlash or slip . The backlash / slip determination unit determines that the gripper does not have backlash / slip when the direction of movement of the gripper and the direction of position deviation are the same, and the motion direction of the gripper and the direction of position deviation are cooperative transport system with multiple robot according to claim 1, wherein the different time is characterized by determining a backlash-slip is on the grip portion. The trajectory estimation unit, when the backlash / slip determination unit determines that there is no backlash / slip in the follower gripping portion, the estimation error is a value twice the difference between the target trajectory of the follower and its own actual trajectory, The multi-robot according to claim 1, wherein the target trajectory is estimated by passing the estimation error through a filter G ₁ (s) in which the transfer function G ₁ (s) (1 + G ₁ (s)) ^-1 is stable. Collaborative transport system. In a coordinated transport system with multiple robots ,
For a reader that grips the conveyed object via an actual or virtual spring damper,
The conveyed object is gripped by the gripper via the actual or virtual spring damper of the same strength as the leader's spring / damper, and the gripper follows the estimated target trajectory of the reader. A follower-type robot that conveys a conveyed object and has a function of detecting a positional deviation of a gripping part based on an extension amount of a spring / damper,
A backlash / slip determination unit that determines whether or not the gripper has a backlash / slip based on the detected positional deviation of the gripper and the movement direction of the gripper,
When it is determined that there is a backlash or slip, the leader decelerates and stops, and the target trajectory of the leader is estimated. A follower type robot comprising: a trajectory estimation unit that estimates a trajectory so that tracking of a leader is realized regardless of whether or not there is a backlash or a slip . A reader that grips the conveyed object via an actual or virtual spring damper;
The conveyed object is gripped by the gripper via the actual or virtual spring damper of the same strength as the leader's spring / damper, and the gripper follows the estimated target trajectory of the reader. A follower for transporting an object to be conveyed, the follower having a function of detecting a positional deviation of a gripping part based on an extension amount of a spring / damper of the follower;
In a cooperative transport method by a plurality of robots having
A backlash / slip determination step of determining whether or not there is a backlash / slip in the gripping portion of the follower based on the detected positional deviation of the gripping portion of the follower and the movement direction of the gripping portion;
When it is determined that there is a backlash or slip, the leader decelerates and stops, and the target trajectory of the leader is estimated. And a trajectory estimation step for estimating the trajectory so that the follower can follow the leader regardless of the presence or absence of backlash or slippage .

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