JP2016020011A - Robot device and control method of robot device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that in a conventional robot device, when picking up a workpiece stored in a storage part with variation, if determination of whether interference between the storage part and gripping means occurs is performed by interference calculation between polygons, it takes calculation time and tact time is increased.SOLUTION: A robot device determines whether interference between a storage part and gripping means occurs by determining whether a position attitude of a workpiece is within a gripping prohibition position attitude range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a robot apparatus, and more particularly to a robot apparatus that determines whether or not a workpiece storage unit and a gripping means interfere when picking up a workpiece.

  Attempts have been made to perform automatic production by introducing robotic devices to the production line. When laying a production line with such a robotic device, workpieces are supplied to the production line mainly using a parts feeder so that the accuracy of the position and posture of the workpiece is continuously maintained in good condition. It was done. On the other hand, the parts feeder is generally expensive, and there are many inconveniences that the parts feeder is not designed to be used because it is often designed for each workpiece shape.

Therefore, it is desired to use a parts tray 303 provided with a plurality of storage units 302 as a common work supply means that is reused in various production lines, for example, as shown in FIG. (For the sake of explanation, the problems will be described below with reference to FIG. 3 illustrating the present invention.)
Each storage unit 302 stores one work 301 of the same type. When such a parts tray is used, the shape of the storage part is not designed exclusively for the shape of the work, so the position and orientation of the work are not uniquely determined inside the storage part, and there is a certain range of variation. It will be supplied to the process in a certain state.

  The operation of picking up a workpiece having a variation with a robot apparatus having gripping means such as a gripper hand is hereinafter referred to as a random pick. In order to execute the random pick, since the work is not arranged at a predetermined position and orientation, it is necessary to check whether a specific storage unit in the parts tray 303 interferes with the gripping means when picking up the work. .

  As described above, a technique disclosed in Patent Document 1 is known regarding a robot apparatus that verifies whether or not a storage unit and a gripping unit interfere in a process of picking up a workpiece from a supply system having a variation in the position and orientation of the workpiece. In Patent Document 1, the position and orientation of the gripping means is determined from the position and orientation of the workpiece to be gripped, and thereafter, determination is performed by performing interference calculation between the gripping means model (polygon) and the storage unit model (polygon) online. It was.

JP 2002-331480 A

  In order to execute the random pick process as shown in FIG. 3 using the robot apparatus described in Patent Document 1 described above, online determination is performed to determine whether the storage unit and the gripping means do not interfere with each other. Interference between polygons is calculated. Since the calculation of interference between polygons generally takes a long time, there is a problem that the tact time increases.

  An object of the present invention is to provide a robot apparatus that performs high-speed interference determination between a storage unit and a gripping means in such a process.

A robot apparatus comprising a vision sensor, a robot having a gripping means, and a control unit for controlling the vision sensor and the robot,
The control unit is set based on the position and orientation data at the time of the gripping operation by the robot and the geometric data of the workpiece and the storage unit of the workpiece. Position and orientation data is stored in advance,
The control unit obtains position and orientation data of a workpiece imaged by the vision sensor and a storage unit of the imaged workpiece,
Compare the acquired position and orientation data of the imaged workpiece and the storage unit with the position and orientation data for which the gripping operation is prohibited to determine the presence or absence of interference between the robot and the storage unit,
The said control part performs control which hold | grips the said workpiece | work provided in the accommodating part with the said robot based on the said determination regarding the presence or absence of interference.

  Since it is determined whether or not the storage unit and the gripping means do not interfere with each other with reference to the grip prohibition position / posture range obtained in advance without using the interference calculation between polygons, the determination can be performed at high speed.

It is a block diagram of the robot apparatus concerning this invention. It is a block diagram of the software module concerning this invention. It is the figure which simulated the process which can be suitably performed by this invention. It is the figure which looked down at parts tray from the upper surface. It is a flowchart which shows operation | movement of the robot apparatus concerning this invention. It is a flowchart which calculates | requires a holding | grip prohibition position and posture range. It is a figure explaining duplication of a work model. It is a figure explaining the setting of a grip prohibition position and posture range. (A) The figure explaining the case where a holding means and an accommodating part interfere, (b) The figure explaining the case where a grasping means and an accommodating part do not interfere. It is a flowchart explaining another Example concerning this invention.

Example 1
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a robot apparatus to which the present invention can be applied. The robot apparatus of this embodiment includes a robot 305 having a gripper hand or a three-claw chuck as a gripping means 304, a vision sensor 306, and a computer 101 as a control unit. The computer 101 is installed with software modules for controlling the robot and the vision sensor, transmitting / receiving data, performing simulation, and the like. The computer 101 includes a CPU 102, a ROM 103, a RAM 104, and an input / output circuit (hereinafter referred to as I / O) 105. The CPU 102 executes each software module based on the program. The ROM 103 stores the software module, the geometric data of the storage unit, and the like. The RAM 104 reads and writes data for calculation. The I / O 105 exchanges data with the outside such as a user or a robot.

  FIG. 2 is a diagram showing a configuration of software modules executed in the robot apparatus.

  The overall control module 201 includes a UI module 202, a prohibited posture setting module 203, an operation simulation module 208, and a robot control module 209, which will be described later, and plays a role of operating them in a coordinated manner.

  The UI module 202 is used by the operator to input a work position / posture range and a work position / posture step size, which will be described later.

  The prohibited posture setting module 203 includes a work position setting module 204, a work position / posture step size setting module 205, a work model duplication module 206, and an interference check module 207.

  In the work position setting module 204, the operator inputs the variation width of the work position / posture assumed in the storage unit from the UI module 202, and sets it as a work position / posture range.

  In the work position / posture step size setting module 205, the operator inputs a step width for dividing the work position / posture range from the UI module and sets it as the work position / posture step size. If the step size is small, there are many types of workpiece positions and postures that can be set, but the number of data increases.

  The workpiece model duplication module 206 duplicates a workpiece model in which the position and orientation are shifted according to the workpiece position and orientation range and the workpiece position and orientation increment from the workpiece model in which the position and orientation of the workpiece with respect to the storage unit are in an ideal state. Here, the case of duplicating is given as an example, but the same effect can be obtained by setting a new work model instead of duplicating.

  The interference check module 207 stores the geometric shapes of the gripping means and the storage unit, and determines whether the gripping means and the storage part do not interfere with each of the replicated work models when attempting to grip. To check.

  The motion simulation module 208 performs robot motion verification including inverse kinematics calculation and movable range check.

  As will be described below, an operation simulation step is performed to verify whether or not the robot can operate with respect to the position and orientation of the workpiece outside the range of the position and orientation data for which gripping is prohibited.

  The robot control module 209 controls the robot 305 based on the result of the inverse kinematic calculation and controls the gripping means 304.

  The vision sensor control module 210 controls the vision sensor 306 and calculates the position and orientation of the workpiece from the imaged result. That is, the control unit acquires data of the position and orientation of the work imaged by the vision sensor and the work storage unit.

  FIG. 3 is a diagram simulating a random pick process suitably performed by a robot apparatus to which the present invention can be applied. A parts tray 303 composed of a plurality of storage units 302 divided by partitions is arranged at a predetermined position from the robot 305. In addition, one work 301 is stored in each storage section 302. As the operation of the robot, first, the position and orientation of the workpiece 301 are measured using the vision sensor 306. Based on the measurement result, the robot 305 is controlled to grip the workpiece 301 by the gripper-shaped gripping means 304 and pick it up from the storage unit 302. FIG. 4 is a top view of the parts tray 303 in which workpieces are stored.

  The operation of the robot apparatus to which the present invention can be applied will be described below. FIG. 5 is a flowchart illustrating the robot control in this embodiment performed by executing the software module shown in FIG.

  First, a method for obtaining a position and orientation range in which gripping is prohibited in advance offline will be described with reference to the flowchart of FIG. Setting this range is an effective constraint for the position and orientation that the robot can take, and is one of the features of this embodiment.

  The method for obtaining the position and orientation range in which gripping is prohibited includes the following steps S111 to S115.

S111: Preliminary Experiment Step Here, the workpiece position / posture range uses a numerical value statistically obtained from a preliminary experiment result using an actual part tray and workpiece, but is not limited to this method. As a virtual preliminary experiment, a method may be considered in which the workpiece position and orientation are virtually varied using random numbers using a simulator, and the range of variation is estimated by performing an interference check between the storage unit and the virtual workpiece.

S112: Work Position / Posture Range Setting Step The operator inputs the work position / posture range obtained in S111 to the computer 101. When the degrees of freedom of translation and rotation are summed up, variations in a maximum of six degrees of freedom (X, Y, Z, θ _X , θ _Y , θ _Z ) will be taken into account. 8 shows one model case.

Here, as shown in FIG. 8A, only a total of two degrees of freedom of the translation direction (X) and the in-plane rotation direction (θ) are considered, but the present invention is not limited to this. If the right hand of FIG. 8 is the X direction, the upper hand of the paper is the Y direction, and the front of the paper is the Z direction, the in-plane rotation direction (θ) corresponds to θ _Z of the six degrees of freedom described above. In the model case given here, it is assumed that the workpiece is stably placed in the storage portion of the parts tray 303 and that there is no instability of the workpiece (that is, degrees of freedom of θ _X and θ _Y ).

  Here, the workpiece position / posture range is set such that the variation width ΔX in the translation direction (X): −1 [mm] to +1.5 [mm], the variation width Δθ in the in-plane rotation direction (θ): −10 [degree] to +10 It is assumed that it is set as [degree].

S113: Step for setting step size of workpiece position and posture The operator inputs the step size for dividing the previously determined workpiece position and posture range to the computer 101 as the workpiece position and posture step width. If the step size is made finer, a more precise simulation becomes possible, but there is a trade-off that the amount of calculation increases. Here, it is assumed that the workpiece position / posture step size is set as a step size of 0.5 [mm] in the translational direction (X) and a step size of 5 [degree] in the in-plane rotation direction (θ). As a result, six variations in the translation direction (X) and five variations in the in-plane rotation direction (θ) were defined.

S114: Work model duplication step As shown in FIG. 7, based on the work position / posture range obtained previously and the step size of the work position / posture range based on the ideal position of the work with respect to the storage unit, Duplicate the model. Specifically, the work model 601 (Σ_c1) is changed to Σ_c1 (1, 1) (+5 [degree] with respect to the ideal position and orientation), Σ_c1 (1, 2) (+10 [degree] with respect to the ideal position and orientation),.・ Reproduce as follows. In this embodiment, since there are 6 variations in the translation direction (X) and 5 variations in the in-plane rotation direction (θ), 30 different work models including the original are duplicated. Is done.

  Even if a plurality of work models are directly generated without using the work model duplication method, the same applies.

S115: Interference Check Step The calculation described below is performed by the computer 101.
For each of the 30 prepared work models, the position and orientation of the robot provided with gripping means having a predetermined relative position and orientation relationship are calculated. In the following description, the relative position and orientation between the gripping means in the robot and each input work model, which are particularly susceptible to interference, are calculated.

  If the position and orientation of the gripping means with respect to the respective work models are calculated, the position and orientation of the gripping means in the storage unit coordinate system 602 is determined, so that an interference check can be executed. That is, it is possible to determine whether or not the storage unit and the gripping unit interfere using the geometric model of the storage unit, the geometric model of the gripping unit, and the respective work models stored in the interference check module. FIG. 9A shows a schematic diagram when interference occurs, and FIG. 9B shows a schematic diagram when interference does not occur. In FIG. 9A, it can be seen that the cross section 901 of the gripping means 304 partially overlaps with the storage portion, that is, interferes. The position and orientation range of the work model determined by the computer 101 when the gripping means and the storage unit interfere as a result of the check are set as the position and orientation range where gripping is prohibited. Here, the position and orientation of the gripping means are calculated. However, depending on the shape of the robot and the arrangement of the workpiece, it may be assumed that a link constituting the robot interferes with the storage unit. In that case, it is preferable to identify a part of the robot that is expected to interfere, or to generate and use position and orientation data for the gripping operation by the robot for the entire robot.

  The calculation process and setting process of position and orientation data will be described more specifically with reference to FIG. The content of the matrix in FIG. 8B is the state of the grip prohibition position / posture range before the execution of the interference check step. Each box of the matrix is in a state where it is unclear whether or not interference between the storage unit and the gripping means will occur with respect to the variation (30) in the translation direction (X) variation and the in-plane rotation direction (θ) variation. Is marked with “?”. Here, when one set of variation in the translation direction (X) and variation in the in-plane rotation direction (θ) is determined, the position and orientation of the gripping means in the storage unit coordinate system is uniquely determined, so that interference with the storage unit can be checked. . FIG. 8C shows the result of the computer checking all sets. A group in which a cross is described like a group in which the deviation from the ideal position and orientation is (X = −1 [mm], θ = −10 [degree]) is the result of interference check, This means that it is determined that interference occurs. As a result of the interference check, it is determined that interference does not occur in the group in which the mark from the ideal position and orientation is indicated by a circle such as a group of deviation (X = 0 [mm], θ = 0 [degree]). Means that. As a result of performing the interference check for all the pairs, a pair indicated by a cross is set as a position and orientation range in which gripping is prohibited.

  On the table of FIG. 8C, it can be seen that the group with a circle is a continuous single connection region. That is, it can be expected that the workpiece can be gripped while avoiding the interference between the storage unit and the robot by avoiding the region marked with x and selecting a posture selected from the region marked with circle.

The method for obtaining the position and orientation range in which gripping is prohibited has been described above. Although the above calculation process has been described as being performed by the computer 101, it may be stored in a computer that is a control unit of the robot apparatus after being calculated by another computing machine.
Hereinafter, it is assumed that this data is stored in a computer that is a control unit of the robot apparatus, and how to use this data online will be described with reference to the flowchart of FIG.

S210: Vision detection The position and orientation of the workpiece are detected by the vision sensor 306. At this time, the position and orientation of the workpiece is expressed by a value in a vision coordinate system (a coordinate system based on the vision sensor).

S220: Coordinate conversion The vision detection result is converted into a value in the storage unit coordinate system (a coordinate system based on the storage unit). By detecting the characteristic points of each storage unit 302 in advance by the vision sensor 306, the positional relationship between the vision sensor 306 and each storage unit 302 can calculate a calibration value, and thus coordinate conversion is possible.

S230: Grasping Prohibition Position / Posture Range Check The control unit checks whether the position / posture of the workpiece is within the range of the position / posture for which gripping is determined in advance. For example, when X = −1 [mm] and θ = 10 [degree], since it is in the gripping prohibition position / posture range, it is NG. When X = 0 [mm] and θ = 0 [degree], it is OK because it is not in the gripping prohibition position / posture range.

  That is, through a series of steps, the acquired position and orientation data of the workpiece and the storage unit are compared with the position and orientation data for which the gripping operation is prohibited to determine the presence or absence of interference between the robot and the storage unit. Yes.

S240: Judgment 1
If the check result is NG, the process proceeds to S290, the work is skipped, the process returns to S210, and the position / posture of the next work is detected. If OK, go to the next step.

S250: Inverse kinematic check Since it is known that the workpiece that has cleared the above-described check in S230 does not interfere with the storage unit and the gripping means when attempting to grip, the reverse kinematics of the robot is checked.
Finding the position and orientation of the movable end from the position and angle of the joint of the robot is called kinematics,
Conversely, obtaining the position and angle of each joint from the position and orientation of the movable end is called inverse kinematics.
That is, in this step, the position and angle of the robot joint are obtained from the position and orientation of the gripping means.

S260: Judgment 2
If the check result is NG, the process proceeds to S290, the work is skipped, the process returns to S210, and the position / posture of the next work is detected. If OK, go to the next step.

S270: Grasping Operation Since the workpiece that has cleared the checks in S230 and S240 can be gripped, the robot control module causes the robot and the gripping means to pick up.

S280: Judgment 3
If all the works have not been tried, the process proceeds to S290, and the process returns to S210 for the next work. Otherwise it ends.

S290: Work skip (target next work)
Switch the workpiece to be gripped to the next workpiece.

  By passing through the processes after determination 1, the control unit performs control for gripping the workpiece provided in the storage unit by the robot based on the determination regarding the presence or absence of interference.

  As described above, according to the present embodiment, it is possible to determine the interference between the storage unit and the gripping means with reference to the recorded position and orientation range in which gripping is prohibited. The amount is small and can be judged at high speed. As is apparent from the flowchart shown in FIG. 5, the feature of this embodiment is that a posture that is not within the range of the position and posture in which gripping is prohibited is first selected, and then whether or not the robot can take that posture is checked. There is.

  The conventional technology first selects a specific position and posture that the robot can take (using inverse kinematics check, etc.) and checks whether interference occurs in that posture, so excessive computation time is required. It was.

  In the present embodiment, when the inverse kinematics check is performed, since the position and orientation in which gripping has already been prohibited is excluded, it has an excellent effect that the calculation load is small.

(Example 2)
Hereinafter, another embodiment of the present invention will be described with reference to the flowchart of FIG. Since the rough flow is the same as that of the previous embodiment, the steps with differences are shown below. For example, S310 to S330 are the same as S210 to S230, and each process except the determination process that is characteristic of the present embodiment to be described below is the same, and the description thereof is omitted.

S340: Judgment 1
If the gripping prohibition position / posture range check executed in the check result in S330 is NG, the process proceeds to S390: swing operation. If OK, go to the next step.

  Note that the step of skipping the workpiece may be set similarly as described in the first embodiment. In that case, the system may be configured so as to shift to S390: swinging operation when part or all of the workpieces are in the gripping prohibition position / posture range as a result of the workpiece skipping.

S360: Judgment 2
If the check result in S350 is NG, the process proceeds to S390: swing operation. If OK, go to the next step.

S380: Judgment 3
When the trial is completed for all the workpieces, the process is terminated. Otherwise, the symmetry is updated to the remaining workpieces placed on the parts tray, and the same is repeated from the vision detection step of S310.

S390: Swinging operation The parts tray is gripped and swung by the gripping means to change the work arrangement condition, and then the process returns to S310: Vision detection.

  As described above, in the present embodiment, even for the work that could not be picked up in the initial state, the arrangement condition in the storage unit is changed and the retry is performed, so that the possibility that all the supplied work can be picked up is increased. Also play.

101 computer 102 CPU
201 Overall Control Module 301 Work 302 Storage Unit 303 Parts Tray 304 Gripping Unit 305 Robot 306 Vision Sensor 601 Work Model 602 Storage Unit Coordinate System 901 Cross Section of Gripping Unit

Claims (7)

A robot apparatus comprising a vision sensor, a robot having a gripping means, and a control unit for controlling the vision sensor and the robot,
The control unit is set based on the position and orientation data at the time of the gripping operation by the robot and the geometric data of the workpiece and the storage unit of the workpiece. Position and orientation data is stored in advance,
The control unit obtains position and orientation data of a workpiece imaged by the vision sensor and a storage unit of the imaged workpiece,
Comparing the acquired position and orientation data of the workpiece and the storage unit with the position and orientation data for which the gripping operation is prohibited, and determining the presence or absence of interference between the robot and the storage unit;
The said control part performs control which hold | grips the said imaged workpiece | work provided in the accommodating part with the said robot based on the said determination regarding the presence or absence of interference.   The control unit is configured to perform control to change the arrangement of a workpiece with respect to the storage unit by swinging the storage unit by the robot when it is determined that the storage unit and the robot interfere with each other. Item 2. The robot device according to Item 1. A robot apparatus control method comprising: a vision sensor; a robot including a gripping means; and a control unit that controls the vision sensor and the robot,
The control unit stores position and orientation data at the time of a gripping operation by the robot, and position and orientation data that is set based on geometric data of the workpiece and the workpiece storage unit and is prohibited from the gripping operation. ,
Capturing with the vision sensor, obtaining the position and orientation data of the workpiece and the storage unit of the workpiece;
A determination step of comparing the acquired position and orientation data of the workpiece and the storage unit with the position and orientation data in which the gripping operation is prohibited to determine the presence or absence of interference between the robot and the storage unit;
The control unit gripping the workpiece provided in the storage unit by the robot based on the determination on the presence or absence of interference;
A method for controlling a robot apparatus comprising the steps of:   4. The control of the robot apparatus according to claim 3, wherein in the determination step, a determination is made based on a position and a posture of the geometric model of the storage unit with respect to a work model arranged for the geometric model of the storage unit. Method.   5. The control of the robot apparatus according to claim 4, wherein the position / posture determined to interfere with the geometric model of the gripper and the geometric model of the storage unit is recorded as a position / posture in which the gripping operation is prohibited. Method. The control unit includes a step of swinging the storage unit by the robot and changing the arrangement of the workpiece with respect to the storage unit when it is determined that the storage unit and the robot interfere with each other. The control method of the robot apparatus according to any one of 3 to 5.   The operation simulation step of verifying whether or not the robot can be operated with respect to the position and orientation of the workpiece outside the range of the position and orientation data for which gripping is prohibited is further provided. A control method for a robot apparatus according to one item.

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