Robot simulation device

A robot simulation device includes, a model generation unit which generates a three-dimensional wire-shaped member model from a plurality of mass points and a plurality of spring elements, a focus point setting unit which sets a plurality of focus points on the wire-shaped member model, a simulation unit which performs a simulation of the behavior of the wire-shaped member associated with the operation of the robot using the wire-shaped member model, and a display unit which displays focus point images, together with wire-shaped member images, using position data of the plurality of mass points and position data of the plurality of focus points which are obtained via the simulation.

RELATED APPLICATION

The present application claims priority of Japanese Application No. 2014-226164, filed Nov. 6, 2014, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a robot simulation device which simulates the operation of a robot on which a wire-shaped member is arranged.

2. Description of the Related Art

In a robot on which a wire-shaped member is arranged, it sometimes happens that the wire-shaped member is subjected to torsion in association with the operation of the robot. In this regard, a device is conventionally known that is configured to calculate the torsion amount of a wire-shaped member based on the torsion due to rotation of the wire-shaped member at a first fixing point and a second fixing point where the wire-shaped member is fixed and the positional relationship between the first fixing point and the second fixing point (refer to Japanese Laid-open Patent Publication No. 2005-293331, for example). Further, such a device is known in the art that is configured to generate a simulation model of wire-shaped member from a plurality of mass points and springs connecting the mass points together and perform a simulation of the behavior of the wire-shaped member (refer to Japanese Laid-open Patent Publication No. 2013-35083, for example).

However, with the device disclosed in Japanese Laid-open Patent Publication No. 2005-293331 referred to above, it is difficult to grasp the torsioned state at each part in the longitudinal direction of the wire-shaped member (e.g., the torsioned state at an intermediate point between the first fixing point and the second fixing point) since the torsion amount of the wire-shaped member is calculated in view of the first fixing point and the second fixing point. Further, the torsioned state of the wire-shaped member cannot be easily grasped merely by performing a simulation of the behavior of the wire-shaped member as in the device disclosed in Japanese Laid-open Patent Publication No. 2013-35083 referred to above.

SUMMARY OF INVENTION

An aspect of the present invention is a robot simulation device which simulates a behavior of a wire-shaped member arranged on a robot, the robot simulation device including a model generation unit which generates a three-dimensional model of the wire-shaped member from a plurality of mass points set along the longitudinal direction of the wire-shaped member so as to define the outer circumferential surface of the wire-shaped member and a plurality of spring elements connecting the plurality of mass points together. The robot simulation device includes a focus point setting unit which sets, on the three-dimensional model of the wire-shaped member, a plurality of focus points for grasping the torsioned state of the wire-shaped member. The robot simulation device includes a simulation unit which simulates the behavior of the wire-shaped member associated with the operation of the robot using the three-dimensional model of the wire-shaped member. The robot simulation device includes a display unit which displays focus point images representing the focus points, together with wire-shaped member images representing the profile of the wire-shaped member, using time-series position data of the plurality of mass points and time-series position data of the plurality of focus points, which are obtained via the simulation performed by the simulation unit.

DETAILED DESCRIPTION

Referring now toFIGS. 1 to 5, description will be made of a robot simulation device according to an embodiment of the present invention. The robot simulation device is a device which simulates the operation of a robot offline, for example, and displays the result of the simulation. The robot simulation device according to the present embodiment may be applied to a vertical articulated robot, for example. The vertical articulated robot includes a plurality of arms which are rotationally driven by a servomotor, and a hand attached to an arm distal end.

In this type of robot, a wire-shaped member is wired along the plurality of arms. More specifically, a wire-shaped member arrangement unit is provided on the outer circumferential surface of the arm. The wire-shaped member is fixed to the arrangement unit partly in the longitudinal direction. The wire-shaped member is a general term of wiring, piping or the like including wiring such as a power line for a servomotor, a variety of signal lines or the like, plumbing for feeding a liquid or gas, etc. The wire-shaped member may use not only a material having a high elasticity such rubber or the like but also a material having a low elasticity such as optical fiber cable or the like, for example.

The wire-shaped member is moved in unison with the robot at an arrangement unit since the wire-shaped member is arranged on the robot via the arrangement unit. Therefore, the wire-shaped member may be deformed in association with the operation of the robot so as to be subjected to torsion. When the wire-shaped member is formed of an optical fiber cable and subjected to torsion, the wire-shaped member may be broken or damaged. In order to avoid this, it is preferred to grasp beforehand the torsioned state of the wire-shaped member associated with the operation of the robot. Thus, in the present embodiment, the robot simulation device is configured as described below.

FIG. 1is a block diagram illustrating the configuration of a robot simulation device1according to an embodiment of the present invention. The robot simulation device1is configured to include an arithmetic processing unit including CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and other peripheral circuitry. The robot simulation device1includes, as a functional structure, a model generation unit11, a focus point setting unit12, a simulation unit13, and a display unit14.

The model generation unit11generates a three-dimensional model of the robot (robot model), and a three-dimensional model of the wire-shaped member which is attached to the robot model at a wire-shaped member arrangement unit formed on the robot model. The robot model and the wire-shaped member model represent a three-dimensional shaped robot and a wire-shaped member, respectively, and may be generated using CAD data or the like of the robot and the wire-shaped member inputted via an unillustrated input unit, for example.

FIG. 2is a perspective view illustrating an example of the wire-shaped member model2having a circular cross section. As illustrated inFIG. 2, the wire-shaped member model2is formed of a plurality of mass points3, and a plurality of spring elements4connecting the mass points3together. The mass point3includes a first mass point31and second mass points32, which are located on a plane20perpendicular to the longitudinal direction of the wire-shaped member. The first mass point31is located at the diametrical center of the plane20. The second mass points32are located around the first mass point31at circumferentially uniform intervals so as to define an outer circumferential surface of the wire-shaped member. The first mass points31and the second mass points32are located at uniform intervals along the longitudinal direction the wire-shaped member. Each mass point3has mass information, three-dimensional position information (position data), and three-dimensional speed information. The mass of each mass point3may be of a value equal to the mass of the wire-shaped member divided by the number of the mass points.

The spring elements4include first springs41connecting together the second mass points32located on the circumferences of the respective planes20. The spring elements4include second springs42extending radially from the first mass points31and connecting the first mass points31to the second mass points32on the planes20. The spring elements4include third springs43arranged in line along the longitudinal direction of the wire-shaped member and connecting sequentially the first mass points31together and the second mass points32together. The spring elements4include fourth springs44connecting together diagonally the second mass points32arranged in the longitudinal direction. The first springs41and the second spring42represent the diametric elasticity of the wire-shaped member. The third springs43and the fourth springs44represent the longitudinal elasticity of the wire-shaped member.

The focus point setting unit12sets, on the wire-shaped member model2, a plurality of focus points33to grasp the torsioned state of the wire-shaped member. InFIG. 2, the focus points33are set on parts in the circumferential direction of the wire-shaped member model. More specifically, the focus points33are set on the second mass points32connected sequentially together via the third springs43in line along the longitudinal direction of the wire-shaped member. The focus points33may be arbitrarily set by the user on the wire-shaped member model2via an input unit.

The simulation unit13causes the robot model to operate in accordance with a predetermined operation program and simulates the behavior of the wire-shaped member associated with the operation of the robot. In other words, in association with the operation of the robot, the simulation unit13calculates, for each predetermined unit time, the elastic force, gravity, and damping force from the spring elements4acting on the respective mass points3of the wire-shaped member model2. The simulation unit13executes simulation (physical simulation) so that the position of each mass point3is changed for each unit time.

In this instance, when a mass point3A and a mass point3B are connected with each other via the spring element4, an elastic force F1of the spring element4acting on the mass point3A can be calculated in accordance with the following equation (1):
F1=(unit vector directed from 3A to 3B)×(spring constant)×(spring expansion amount)  (I)
In the above equation (I), let it be assumed that the expansion amount of the spring element4(spring expansion amount) is a value equal to the length of the spring element4under a certain condition from which the natural length of the spring element4is subtracted. The natural length of the spring element4corresponds to the distance between the mass points3A and3B under a natural condition in which there are no expansion and bending of the wire-shaped member model2.

The damping force of the spring element includes a damping force F2suppressing the vibration of the spring and a damping force F3suppressing the translational motion of each mass point3, which can be calculated in accordance with the following equations (II) and (III), respectively:
F2=v×(inner product ofv)×(damping coefficient of the vibration)  (II)
F3=(speed of each mass point)×(damping coefficient of the translational motion)  (III)
In the above equation (II), v is a unit vector of (the speed of the mass point3B minus the speed of the mass point3A). The damping forces F2and F3act to slow the motion of the spring.

A gravity F4acting on each mass point3can be calculated in accordance with the following equation (IV):
F4=(unit vector in the direction of the gravity)×(gravity acceleration)×(mass of the mass point)  (IV)

When the mass point3of the wire-shaped member model2collides with a certain interference plane, a repulsion force acts on the mass point. In view of this, the repulsion force acting on the mass point may be calculated in addition to the elastic force, gravity, and damping force. In this instance, the value of the component, in the vertical direction of the collided plane, of the speed of the mass point at the time of the collision becomes a value that the speed prior to the collision is multiplied by a repulsion factor and the sign is reversed. Then, the repulsion force can be calculated by multiplying the mass of the mass point to the acceleration obtained by dividing by unit time the amount of change in speed between before and after the collision.

The simulation unit13calculates the resultant force of the forces F1to F4acting on each mass point3, and calculates the acceleration of the mass point3by dividing the resultant force by the mass of the mass point. Further, the simulation unit13calculates an amount of change in speed of the mass point3in accordance with (the acceleration)×(unit time), and calculate the speed of the mass point3by adding the amount of change to the speed of the mass point3. Moreover, the simulation unit13calculates an amount of displacement of the mass point3in accordance with the speed×unit time, and calculates the position of the mass point3by adding the amount of displacement to the three-dimensional position data of the mass point3.

In other words, the simulation unit13changes, for each unit time, the position of the mass point3at the wire-shaped member arrangement unit in conformity to the motion of the robot. The simulation unit13calculates the forces F1to F4acting on each mass point3as described above, and calculates the resultant force of these forces. The simulation unit13simulates the behavior of the wire-shaped member by updating the speed and position of each mass point13. In this manner, the time-series position data of each mass point3can be obtained. Further, since the focus points33are part of the mass points3, the position data of the focus points33can also be obtained.

The display unit14includes a display monitor, and a display control unit for displaying an image on the display monitor. The display unit14displays the three-dimensional wire-shaped member image representing the profile of the wire-shaped member using the time-serial position data of each mass point3obtained via the simulation executed by the simulation unit13. Further, the display unit14displays three-dimensional focus point images representing the focus points33using the time-serial position data of the plurality of focus points33. In other words, the display unit14displays, on the display monitor moving images of the wire-shaped member image and the focus point image which change for each predetermined time.

FIG. 3is a view illustrating examples of wire-shaped member images51and focus point images52. InFIG. 3, the wire-shaped member images51are represented by solid lines, and the focus point images52are represented by black circles. The focus points33are set in line in the longitudinal direction of the wire-shaped member with the same phase in the circumferential direction of the wire-shaped member. Hence, when the wire-shaped member is torsioned, the focus point images52are represented in a torsioned state on the wire-shaped member images51. In this manner, the user can easily grasp the torsioned state of the wire-shaped member.

The robot simulation device according to the present embodiment is further equipped with the function of calculating a torsion amount of the wire-shaped member in order to quantitatively display the torsioned state of the wire-shaped member. The torsion amount is calculated by the simulation unit13, for example.FIG. 4is a view for explaining the procedure of calculating the torsion amount. InFIG. 4, the planes20nand20n+1 are planes of the wire-shaped member model which are adjacent to each other and in which the mass points3are set, the mass points31nand31n+1 are mass points which are located at the centers of the planes20nand20n+1, respectively, and the mass points32nand32n+1 are mass points which are located in the same position (same phase) with each other in the circumferential direction on the circumferences of the planes20nand20n+1, respectively. The mass points32nand32n+1 are the focus points33, for example.

The torsion amount of the wire-shaped member between the planes20aand20n+1 can be defined by the angle between a plane defined by the mass points31n,32n,and31n+1 and a plane defined by the mass points31n+1,32n+1, and31n.Then, as directed toward the distal end (hand side) in the longitudinal direction of the wire-shaped member, it is defined such that the right-handed torsion is plus and the left-handed torsion is minus. Under such definition, by integrating the torsion amount from a first wire-shaped member arrangement unit formed in the robot model to a second wire-shaped member arrangement unit adjacent to the first wire-shaped member arrangement unit, it is possible to calculate the total torsion amount of the wire-shaped member between from the first wire-shaped member arrangement unit to the second wire-shaped member arrangement unit.

The simulation unit13, during the execution of simulation, calculates the torsion amount of the wire-shaped member for each unit time and stores it in a storage unit. In this manner, it is possible to seek a maximum value and a minimum value of the torsion amount. Further, the simulation unit13calculates an average value of the maximum value and the minimum value and seeks such a wire-shaped member arrangement orientation (target arrangement orientation) as to decrease the average value. The display unit14displays the target arrangement orientation on the display unit.

When the maximum value of the torsion amount is +50° and the minimum value is −10°, for example, the average value is +20°. Then, a value of torsion amount such as to cancel the average value, i.e., −20° is displayed. The torsion amount as displayed represents the target arrangement orientation (degree) of the wire-shaped member. The user rotates the wire-shaped member at one wire-shaped member arrangement unit through this angle (−20°) from the initial state (the state in which the simulation is executed) and then arranges the wire-shaped member. In other words, the user imparts a predetermined amount of initial torsion to the wire-shaped member and then arranges the wire-shaped member. In this manner, it is possible to decrease the maximum torsion amount of the wire-shaped member at the time of actual operation of the robot. When an optical fiber, etc., having a low elasticity are used as the wire-shaped member, it is possible to prevent the wire-shaped member from being broken or damaged.

FIG. 5is a flow chart illustrating an example of the process performed by the robot simulation device1. The process illustrated in this flow chart is started when a simulation starting command is inputted via an input unit, for example, after part of the mass points3are set as the focus points33by the processing at the focus point setting unit12as illustrated inFIG. 2.

At step S1, the model generation unit11generates a robot model. At step S2, the model generation unit11generates a wire-shaped member model2as being associated with the robot model. At step S3, the simulation unit13causes the robot model to operate in accordance with a predetermined operation program and performs a simulation of the wire-shaped member associated with the operation of the robot.

At step S4, the display unit14displays the wire-shaped member images51and the focus point images52on the display monitor based the result of the simulation. At step S5, the simulation unit13calculates a maximum value and a minimum value for the torsion amount of the wire-shaped member. At step S6, the simulation unit13calculates an average value for the torsion amount, and calculates a target arrangement orientation of the wire-shaped member, i.e., a rotation amount of the wire-shaped member at the wire-shaped member arrangement unit such as to decrease the average value. The display unit14displays the result of the above.

According to the present embodiment, it is possible to achieve the following advantages:(1) The robot simulation device1includes the model generation unit11which generates the three-dimensional wire-shaped member model2from the plurality of mass points3set along the longitudinal direction of the wire-shaped member so as to define the outer circumferential surface of the wire-shaped member and the plurality of spring elements4connecting the plurality of mass points3together. The robot simulation device1includes the focus point setting unit12which sets, on the wire-shaped member model2, the plurality of focus points33to grasp the torsioned state of the wire-shaped member. The robot simulation device1includes the simulation unit13which simulates the behavior of the wire-shaped member associated with the operation of the robot using the wire-shaped member model2. The robot simulation device1includes the display unit14which displays the focus point images52, together with the wire-shaped member images51, using the time-series position data of the plurality of mass points3and the time-series position data of the plurality of focus points33which are obtained via the simulation. Thus, by displaying the focus point images52, together with the wire-shaped member images51, via the display unit14, it is possible for the user to easily grasp the torsioned state in the longitudinal direction of the wire-shaped member.(2) Further, the simulation unit13calculates the maximum torsion amount of the wire-shaped member based on the time-series position data of the plurality of focus points33, and calculates a wire-shaped member arrangement orientation (target arrangement orientation) such as to decrease the maximum torsion amount. The user may arrange the wire-shaped member in conformity to the target arrangement orientation. For example, it is possible to decrease the maximum torsion amount of the wire-shaped member at the time of actual operation of the robot by the user arranging the wire-shaped member with the wire-shaped member being rotated through a predetermined angle at wire-shaped member arrangement unit so as to impart initial torsion to the wire-shaped member.(3) The setting of the focus points33is easy since the plurality of mass points3(second mass points32), which are set on parts in the circumferential direction of the wire-shaped member model2in line along the longitudinal direction of the wire-shaped member model2, are set as the focus points33. Further, since part of the mass points3are made to be the focus points33, it is not necessary to calculate the position date of the focus points33independently of the position data of the mass points3, thus, it is easy to calculate the position data of the focus points33.

In the above-described embodiment, part of the mass points3are set as the focus points33, points other than the mass points3may be set as the focus points. In the above-described embodiment, the mass points located at the same phase in the circumferential direction of the wire-shaped member in line along the longitudinal direction of the wire-shaped member are made to be the focus points33, the focus points33are not limited thereto. In other words, whatever the control of the focus point setting unit12may be, when points which are located in a predetermined positional relationship with each other so as to make it possible to grasp the torsioned state of the wire-shaped member are made to be the focus points33.

In the above-described embodiment (FIG. 2), the model generation unit11generates the wire-shaped member model2from the first mass points31and second mass points32, the first springs41, the second springs42, the third springs43, and the fourth springs44. However, whatever the wire-shaped member model2may be, when it is generated from a plurality of mass points and a plurality of spring elements connecting the mass points together, and the control of the model generation unit11is not limited to what is described above.

In the above-described embodiment, it is configured so that the display unit14displays the wire-shaped member images and the focus point images using the position data of the plurality of mass points and the position data of the plurality of focus points33for each predetermined unit time which are obtained via the simulation performed by the simulation unit13. However, the display unit14may be configured to display a still image at a predetermined point of time, and the control of the display unit14is not limited to what is described above. In the above-described embodiment (FIG. 3), the focus point images52are represented by black circles, whatever the configuration of the focus point image52may be, when it is a mark representing the focus point33. For example, it may be configured so that the focus point image52is represented in a display color different from that of other image so as to be identifiably represented.

In the above-described embodiment, the simulation unit13seeks the target arrangement orientation of the wire-shaped member as an angle (initial torsion amount) at the wire-shaped member arrangement unit, it may be configured so that as the target arrangement orientation, other information is provided via the display unit14, and the configuration of the simulation unit13is not limited to what is described above.

In the above-described embodiment, the robot simulation device is applied to an articulated robot, the present invention is not limited to such a form but is applicable to a variety of robots on which the wire-shaped member is arranged.

According to the present invention, it is easy for the user to grasp the torsioned state of each part in the longitudinal direction of the wire-shaped member since the time-series position data of the plurality of focus points set on the three-dimensional model of the wire-shaped member is acquired via simulation and the focus point images are displayed using the position data of the focus points.

The above description is merely by way of example, and the present invention is not restricted by the above-described embodiment and modifications thereto as long as they do not impair the features of the present inventions. The components of the above-described embodiment and modifications thereto include substitutable and obviously substitutable components while maintaining the identity of the invention. In other words, the present invention encompasses any other form conceivable within the scope of the technical idea of the present invention as well. Further, it is also possible to arbitrarily combine the above-described embodiment and one or more of the modifications.