JP6322948B2 - Robot control apparatus, robot system, robot, robot control method, and program - Google Patents

Description

  The present invention relates to a robot control device, a robot system, a robot, a robot control method, and a program.

  In Patent Document 1, in the impedance control of the robot, when the pressing reaction force acting on the robot tip exceeds a predetermined magnitude, a temporary target position is obtained so that the pressing reaction force becomes a set limit value, A robot control device is described in which a target position is obtained by adding a position correction amount corresponding to a pressing reaction force to the temporary target position.

JP 2000-301479 A

  However, with the technique of Patent Document 1, when the current position of an object such as a workpiece has deviated more than expected from the target position, it is difficult to move the object to the target position. For example, in the fitting work for fitting the work into the hole, the work can be completed by pressing the work against the edge of the hole by impedance control. However, if the workpiece position is far from the hole, the current position is corrected because the impedance control cannot detect how the workpiece is displaced (direction, distance, etc.) from the hole. It is difficult to complete the work. In order to complete the robot work, the user's work occurs, for example, the user corrects the robot trajectory and teaches again.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to efficiently move an object to a target position even when the position of the object is shifted in the operation by the robot.

  A first aspect of the present invention that solves the above problem is that a target image that is an image including the end point when the end point of the movable part of the robot is at the target position, and the end point is at the current position An image acquisition unit that acquires a current image that is an image including the end point, and a command value that moves the end point from the current position to the target position based on the current image and the target image Generated by a first control unit, a second control unit that generates a command value for moving the end point based on an output from a force detection unit that detects a force acting on the movable unit, and the first control unit And a third control unit that moves the movable unit using the command value generated and the command value generated by the second control unit. That. Thereby, even if the position shift of the target object occurs, the position of the movable part can be corrected with high accuracy by the command value of the first control part. Further, even when the trajectory of the movable part based on the command value of the first control unit becomes inefficient, it can be corrected to an efficient trajectory by the command value of the second control unit.

  The second aspect of the present invention that solves the above-described problem is a control unit that controls the movable unit so as to bring the end point of the movable unit of the robot closer to the target position, and the end point when the end point is at the target position. An image acquisition unit that acquires a target image that is an image including an end point, and a current image that is an image including the end point when the end point is at a current position, and the control unit includes the The robot control apparatus is characterized in that the movement of the movable part is controlled based on a current image and the target image and an output from a force detection part that detects a force acting on the movable part. As a result, even when a positional deviation of the object occurs, the position of the movable part can be corrected with high accuracy by the control based on the image. Further, even when the trajectory of the movable part by the control based on the image becomes inefficient, it can be corrected to an efficient trajectory by the control based on the force.

  In the above robot control device, the third control unit adds the command value generated by the first control unit and the command value generated by the second control unit with predetermined weights, respectively. The movable portion may be moved using the command value. Thereby, the trajectory of the movable part and the accuracy of the work can be adjusted so as to become the desired trajectory and the work accuracy.

  The robot control apparatus may include an input unit that receives a setting of the predetermined weight from a user. Thereby, the weight can be set so as to be the trajectory desired by the user and the accuracy of the work.

  In the robot control apparatus, the third control unit may determine the predetermined weight based on a distance between the current position and the target position. Thereby, since a weight changes according to distance, it can control accurately. Further, since the weight changes continuously according to the distance, the control can be switched smoothly.

  In the robot control apparatus, the third control unit may determine the distance based on an image acquired by the image acquisition unit. Thereby, since a distance can be determined based on the same image as the image used by the first control unit, an increase in image processing load can be prevented.

  In the robot control apparatus, the third control unit may increase a predetermined weight corresponding to the command value generated by the second control unit as the distance decreases. At a position where the effect of force control is effectively obtained, such as a position close to the target position, the inefficient trajectory by the first control unit can be corrected, and the movable unit can be moved more efficiently.

  In the robot control apparatus, the third control unit sets a predetermined weight corresponding to the command value generated by the second control unit to 0 when the distance is larger than a predetermined value. May be a feature. In a position where the effect of force control cannot be effectively obtained, such as a position far from the target position, the movable part can be efficiently moved by the first control part.

  A third aspect of the present invention that solves the above-described problems is a movable portion, a force detection portion that detects a force acting on the movable portion, and the end point when the end point of the movable portion is at a target position. An image acquisition unit that acquires a target image that is an image including the current image and a current image that is the image including the end point when the end point is at the current position, and based on the current image and the target image, A first control unit that generates a command value for moving the end point from the current position to the target position, and a second control unit that generates a command value for moving the end point based on an output from the force detection unit And a third control unit that moves the movable unit using the command value generated by the first control unit and the command value generated by the second control unit. It is a robot. Thereby, even if the position shift of the target object occurs, the position of the movable part can be corrected with high accuracy by the command value of the first control part. Further, even when the trajectory of the movable part based on the command value of the first control unit becomes inefficient, it can be corrected to an efficient trajectory by the command value of the second control unit.

  According to a fourth aspect of the present invention for solving the above-mentioned problems, a movable part, a force detection part for detecting a force acting on the movable part, and the movable part so as to bring an end point of the movable part closer to a target position. A control unit that controls, a target image that is an image including the end point when the end point is at a target position, and a current image that is an image including the end point when the end point is at a current position; An image acquisition unit that acquires the image, and the control unit controls the movement of the movable unit based on the current image, the target image, and an output from the force detection unit. It is a robot. As a result, even when a positional deviation of the object occurs, the position of the movable part can be corrected with high accuracy by the control based on the image. Further, even when the trajectory of the movable part by the control based on the image becomes inefficient, it can be corrected to an efficient trajectory by the control based on the force.

  A fifth aspect of the present invention that solves the above problem is a robot having a movable part, a target image that is an image including the end point when the end point of the movable part is at a target position, and the end point. An image acquisition unit that acquires a current image that is an image including the end point when the is at the current position, and the end point is moved from the current position to the target position based on the current image and the target image A first control unit for generating a command value to be generated, a second control unit for generating a command value for moving the end point based on an output from a force detection unit for detecting a force acting on the movable unit, And a third control unit that moves the movable unit using the command value generated by the first control unit and the command value generated by the second control unit. A robot system. Thereby, even if the position shift of the target object occurs, the position of the movable part can be corrected with high accuracy by the command value of the first control part. Further, even when the trajectory of the movable part based on the command value of the first control unit becomes inefficient, it can be corrected to an efficient trajectory by the command value of the second control unit.

  A sixth aspect of the present invention that solves the above-described problems is a robot having a movable part, a control unit that controls the movable part so that the end point of the movable part approaches a target position, and the end point is a target. An image acquisition unit that acquires a target image that is an image including the end point when in a position and a current image that is an image including the end point when the end point is in a current position; The control unit controls the movement of the movable unit based on the current image and the target image, and an output from a force detection unit that detects a force acting on the movable unit. System. As a result, even when a positional deviation of the object occurs, the position of the movable part can be corrected with high accuracy by the control based on the image. Further, even when the trajectory of the movable part by the control based on the image becomes inefficient, it can be corrected to an efficient trajectory by the control based on the force.

  The seventh aspect of the present invention that solves the above problem is that a target image that is an image including the end point when the end point of the movable part of the robot is at the target position, and the end point is at the current position An image acquisition step of acquiring a current image that is an image including the end point, and generating a command value for moving the end point from the current position to the target position based on the current image and the target image Generated by the first control step, the second control step for generating a command value for moving the end point based on the output from the force detection unit for detecting the force acting on the movable unit, and the first control unit And a third control step of moving the movable part using the command value generated and the command value generated by the second control unit, That is a robot control method. As a result, even when a position shift of the object occurs, the position of the movable part can be corrected with high accuracy by the command value of the first control step. Further, even when the trajectory of the movable part based on the command value of the first control step becomes inefficient, it can be corrected to an efficient trajectory by the command value of the second control step.

  An eighth aspect of the present invention that solves the above-described problem is a control step of controlling the movable unit so that the end point of the movable unit of the robot is brought close to the target position; and the control unit when the end point is at the target position. An image acquisition step of acquiring a target image that is an image including an end point and a current image that is an image including the end point when the end point is at a current position, and the control step includes the current step The robot control method is characterized in that the movement of the movable part is controlled based on an image, the target image, and an output from a force detection part that detects a force acting on the movable part. As a result, even when a positional deviation of the object occurs, the position of the movable part can be corrected with high accuracy by the control based on the image. Further, even when the trajectory of the movable part by the control based on the image becomes inefficient, it can be corrected to an efficient trajectory by the control based on the force.

  The ninth aspect of the present invention that solves the above-described problem is the control of the movable part based on the image including the end point of the movable part of the robot, and the output from the force detection part that detects the force acting on the movable part. And a control method of the movable part based on the robot control method. As a result, even when a positional deviation of the object occurs, the position of the movable part can be corrected with high accuracy by the control based on the image. Further, even when the trajectory of the movable part by the control based on the image becomes inefficient, it can be corrected to an efficient trajectory by the control based on the force.

  A tenth aspect of the present invention that solves the above problem is a program for a robot control device, and a target image that is an image including the end point when the end point of the movable part of the robot is at the target position; An image acquisition unit that acquires a current image that is an image including the end point when the end point is at the current position; and based on the current image and the target image, the end point is moved from the current position to the target. A first control unit that generates a command value to move to a position, and a second control unit that generates a command value to move the end point based on an output from a force detection unit that detects a force acting on the movable unit And a third control unit that moves the movable unit using the command value generated by the first control unit and the command value generated by the second control unit, Serial to function robot controller, a program, characterized in that. Thereby, even if the position shift of the target object occurs, the position of the movable part can be corrected with high accuracy by the command value of the first control part. Further, even when the trajectory of the movable part based on the command value of the first control unit becomes inefficient, it can be corrected to an efficient trajectory by the command value of the second control unit.

1 is a diagram illustrating an example of a schematic configuration of a robot system 1 according to an embodiment of the present invention. 2 is a diagram illustrating an example of a functional configuration of a robot system 1. FIG. It is a figure which shows an example of the flow of data and control in the robot system. It is a figure explaining an example of the setting method of the weight which shows the ratio which synthesize | combines command value. It is a figure explaining an example of the fitting operation | work by force control. It is a figure explaining an example of the fitting operation | work by force control. It is a figure explaining an example of the fitting operation | work by a visual servo. It is a figure explaining an example of the fitting operation | work by parallel control of force control and visual servo. FIG. 6 is a flowchart showing an example of the operation of the robot control apparatus 10. 2 is a diagram illustrating an example of a hardware configuration that realizes functions of a robot control device 10. FIG.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of a schematic configuration of a robot system 1 according to an embodiment of the present invention. As shown in FIG. 1, the robot system 1 includes a robot control device 10, a robot 20, and an imaging device 30. The robot control apparatus 10 is communicably connected to the robot 20 and the imaging apparatus 30.

  The robot control device 10 controls the entire robot 20. In addition, the robot control device 10 controls imaging by the imaging device 30.

  The robot 20 operates according to a control signal from the robot control apparatus 10 and performs work. The work content of the robot is not particularly limited. For example, a work of fitting the work W1 on the work table T in the hole H of the work W2 can be considered. The workpiece can be called a work object.

  The robot 20 includes an arm 22 including one or more joints 23 and one or more links 24, a hand 26 provided at the tip of the arm 22, and between the tip of the arm 22 and the hand 26 (referred to as a wrist portion). And a force sensor 25 provided in (1).

  The force sensor 25 detects a force and a moment acting on the hand 26, for example. The output of the force sensor 25 is sent to the robot controller 10 and used for impedance control of the robot 20 by the robot controller 10. As the force sensor 25, for example, a 6-axis force sensor capable of simultaneously detecting six components of a force component in the translational three-axis direction and a moment component around the three rotation axes can be used. Of course, the number of axes of the force sensor 25 is not particularly limited, and may be three axes, for example. The force sensor 25 can also be referred to as a force detection unit.

  The hand 26 includes, for example, a plurality of fingers, and can hold the object W (W1, W2) with at least two fingers. The hand 26 may be detachable from the distal end portion of the arm 22. The hand 26 can be said to be a kind of end effector. The end effector is a member for gripping, lifting, lifting, adsorbing, or processing a workpiece. The end effector can take various forms such as a hand, a hook, and a suction cup. Further, a plurality of end effectors may be provided for one arm.

  A unit including the arm 22, the force sensor 25, and the hand 26 can also be referred to as a movable part or a manipulator (hereinafter referred to as a movable part). In the example of FIG. 1, the robot 20 has two movable parts 21. In order to operate each part, such as the joint 23 and the hand 26, the movable part 21 is provided with an actuator (not shown), for example. The actuator includes, for example, a servo motor and an encoder. The encoder value output by the encoder is used for, for example, feedback control of the robot 20 by the robot control device 10 or a drive control unit 200 (see FIG. 2) of the robot 20 described later.

  The robot 20 drives each joint 23 in conjunction with each other according to a control command given from the robot controller 10, thereby setting a target position (hereinafter referred to as an end point) set at the tip of the arm 22 or the like. It can be moved freely within the movable range or directed in any direction. Further, an object or the like can be grasped or released with the hand 26.

  Note that the position of the end point is not limited to the tip of the arm, and may be set to the tip of the end effector, for example.

  The imaging device 30 captures a work area of the robot 20 (for example, a three-dimensional space that is a workable range by the movable unit 21 on the work table T), and generates image data. In the example of FIG. 1, two imaging devices 30 are installed on the work table T at different angles. The imaging device 30 can employ, for example, a visible light camera or an infrared camera. An image captured by the imaging device 30 is input to the robot control device 10.

  The configuration of the robot system 1 described above is the main configuration in describing the features of the present embodiment, and is not limited to the configuration example described above. Further, the configuration of a general robot system is not excluded.

  For example, FIG. 1 shows an example in which the number of joints is six (six axes), but the number of joints (also referred to as “number of axes”) and the number of links may be increased or decreased. In addition, the shape, size, arrangement, structure, and the like of various members such as joints, links, and hands may be changed as appropriate.

  For example, the installation position of the imaging device 30 is not particularly limited, and may be installed on a ceiling or a wall. Further, instead of or in addition to the imaging device 30, the imaging device may be provided at the tip portion, the body portion, or the head portion of the arm 22 of the robot 20. For example, the imaging device 30 may be connected to the robot 20. In this case, an image captured by the imaging device 30 is input to the robot control device 10 via the robot 20. Further, the robot control device 10 may be built in the robot 20.

  FIG. 2 is a diagram illustrating an example of a functional configuration of the robot system 1.

  The robot 20 has a drive control unit 200.

  Based on the control command output from the robot control device 10, the encoder value of the actuator, the sensor value of the sensor, and the like, the drive control unit 200 makes the end point position the target position indicated by the control command. Drive the actuator. The current position of the end point can be obtained from, for example, an encoder value in the actuator.

  The robot control apparatus 10 includes a visual servo unit (first control unit) 100, a force control unit (second control unit) 110, an image acquisition unit 120, and a third control unit 130. The visual servo unit 100 includes an image processing unit 102 and a first trajectory generation unit 104. The force control unit 110 includes a sensor information acquisition unit 112 and a second trajectory generation unit 114.

  The visual servo unit 100 acquires an image captured by the imaging device 30 via the image acquisition unit 120. The visual servo unit 100 is a visual control method for tracking a target by measuring a change in position relative to the target as visual information based on the acquired image and using it as feedback information. Servo is executed to move the arm 22. In this embodiment, the robot based on the three-dimensional position information of the target calculated using a method such as a stereogram for recognizing an image as a three-dimensional image using two images causing parallax as visual servo. Adopt a position-based method to control As the visual servo, an image-based method for controlling the robot based on the feature amount extracted from the target image and the feature amount extracted from the current image may be employed.

  The image processing unit 102 recognizes an end point from the image acquired from the image acquisition unit 120 and extracts an image including the recognized end point. Note that image recognition processing performed by the image processing unit 102 can use various general techniques, and thus description thereof is omitted.

  Based on the image extracted by the image processing unit 102 (hereinafter referred to as the current image) and the image when the end point is at the target position (hereinafter referred to as the target image), the first trajectory generation unit 104 The trajectory of the point, that is, the amount and direction of movement of the end point are set. The target image may be acquired in advance in a storage unit such as a memory.

  Further, the first trajectory generation unit 104 determines a target angle of each actuator provided in each joint 23 based on the set movement amount and movement direction of the end point. Further, the first trajectory generation unit 104 generates a command value that moves the arm 22 by the target angle and outputs the command value to the third control unit 130. The trajectory generation process, the target angle determination process, the command value generation process, and the like performed by the first trajectory generation unit 104 can use various general techniques, and thus will not be described in detail.

  The force control unit 110 performs force control (also referred to as force sense control) based on sensor information (sensor values indicating force information and moment information) from the force sensor 25 of the robot 20. In this embodiment, impedance control is performed as force control. Impedance control is used to set the mechanical impedance (inertia, damping coefficient, stiffness) generated when external force is applied to the robot hand (hand 26, etc.) to a value convenient for the intended work. It is a position and force control technique. Specifically, for example, in a model in which a mass, a viscosity coefficient, and an elastic element are connected to an end effector unit of a robot, control is performed so as to contact an object with a set mass, viscosity coefficient, and elastic coefficient.

  In order to perform force control, it is necessary to detect the force and moment applied to the end effector such as the hand 26, but the method of detecting the force and moment applied to the end effector is limited to that using a force sensor. Absent. For example, it is possible to estimate the external force exerted on the end effector from each axis torque value of the arm 22. Therefore, in order to perform force control, the arm 22 only needs to have means for acquiring a force applied directly or indirectly to the end effector.

  The sensor information acquisition unit 112 acquires sensor information (such as detected sensor values) output from the force sensor 25 of the robot 20. The sensor information acquisition unit 112 can also be called a force detection unit.

  The second trajectory generation unit 114 determines the moving direction and moving amount of the end point by impedance control. Further, the second trajectory generation unit 114 determines a target angle of each actuator provided in each joint 23 based on the moving direction and moving amount of the end point. Further, the second trajectory generation unit 114 generates a command value that moves the arm 22 by the target angle, and outputs the command value to the third control unit 130. The trajectory generation process, the target angle determination process, the command value generation process, and the like performed by the second trajectory generation unit 114 can use various general techniques, and thus detailed description thereof is omitted.

  In the robot 20 having joints, when the angle of each joint is determined, the position of the end point is uniquely determined by forward kinematics processing. In other words, an N-joint robot can express one target position by N joint angles. Therefore, if the set of N joint angles is set as one target joint angle, the trajectory of the end point becomes the target joint angle. Think of it as a set. Therefore, the command values output from the first trajectory generation unit 104 and the second trajectory generation unit 114 may be values related to positions (target positions) or values related to joint angles (target angles). May be.

  The image acquisition unit 120 acquires an image captured by the imaging device 30 and outputs the acquired image to the visual servo unit 100 and the third control unit 130.

  The third control unit 130 has weights set for the command value output from the visual servo unit (first control unit) 100 and the command value output from the force control unit (second control unit) 110, respectively. To synthesize. Further, the third control unit 130 outputs an instruction to the robot 20 to move the position of the end point, that is, the movable unit 21 based on the combined command value.

  The third control unit 130 also recognizes two positions (for example, the current position of the end point and the target position of the end point) from the image acquired from the image acquisition unit 120, and determines the distance from the current position to the target position. calculate. And the ratio of the weight which synthesize | combines command value is set according to the length of the said calculated distance. The third control unit 130 has a function of acquiring sensor information output from the force sensor 25 of the robot 20 (may be referred to as a “force detection unit”). Details of the processing of the third control unit 130 will be described later.

  FIG. 3 is a diagram illustrating an example of the flow of data and control in the robot system 1.

  In the visual servo unit 100, a visual feedback loop for making the current position close to the target position using information from the imaging device 30 is rotating. The first trajectory generation unit 104 acquires a target image as information regarding the target position. Further, the first trajectory generation unit 104 converts the current image and the target position on the current image into a coordinate system on the robot because the target position is represented on the coordinate system on the image. Further, the first trajectory generation unit 104 generates a trajectory and a command value (here, a target angle) based on the current current image and the target image after conversion.

  In the force control unit 110, a feedback loop for bringing the hand of the robot into contact with an object with an impedance set as a target (target impedance) based on sensor information from the force sensor 25 is rotating. The second trajectory generation unit 114 generates a trajectory and a command value (here, a target angle) so that the value of the acquired sensor information becomes the target impedance.

  The third control unit 130 outputs a command value based on the command value output from the first trajectory generation unit 104 and the command value output from the second trajectory generation unit 114 to the robot 20. Specifically, the third control unit 130 multiplies the command value output from the first trajectory generation unit 104 by the weight α (0 ≦ α ≦ 1), and outputs the command output from the second trajectory generation unit 114. The value is multiplied by the weight β (β = 1−α), and a command value obtained by combining these is output to the robot 20. It can be said that the weight α and the weight β are values indicating a ratio for combining the visual servo command value and the force control command value. A method for setting the ratio of α and β will be described later.

  Since the load of image processing is generally high, the interval at which the visual servo 100 outputs the command value (for example, every 30 milliseconds (msec)) is the interval at which the force control unit 110 outputs the command value (for example, 1 It is assumed that it is longer than every millisecond (msec). In this case, when the command value is not output from the visual servo 100, the third control unit 130 multiplies the command value output from the force control unit 110 by the weight α, and finally the command value output from the visual servo 100. Is multiplied by the weight β, and a combination of these is output to the robot 20. The third control unit 130 may temporarily store the command value finally output from the visual servo 100 in a storage unit such as a memory, and read and use the command value.

  The drive control unit 200 acquires a command value (target angle) from the robot control device 10. The drive control unit 200 acquires the current angle based on the encoder value of each actuator provided in each joint 23 and calculates the difference (deviation angle) between the target angle and the current angle. Further, the drive control unit 200 calculates the moving speed of the arm 22 based on the deviation angle (for example, the higher the deviation angle, the faster the moving speed), and the movable unit 21 is moved by the deviation angle calculated by the calculated moving speed. Move.

  FIG. 4 is a diagram illustrating an example of a method for setting a weight indicating a ratio for combining command values. FIG. 4 shows a graph in which the vertical axis represents the ratio of weight α and weight β, and the horizontal axis represents the distance from the current position to the target position. Note that α + β = 1 as described above.

  The current position can be, for example, the current position of the endpoint. Further, the target position can be, for example, the position of the end point in the target image. Of course, the current position and the target position are not limited to the position of the end point. For example, the current position is the position of a specific point of the workpiece W gripped by the hand 26, and the target position is also the position of the workpiece W in the target image. Good.

  In the example of FIG. 4, the relationship between the distance d from the current position to the target position and the weight ratio is such that the ratio of the coefficient α decreases monotonically (the ratio of β decreases as the distance d from the current position to the target position decreases). Monotonous increase). The method of changing the ratio may be curvilinear or linear. For example, the robot control apparatus 10 can receive a setting of how to change the ratio from the user via an input unit such as a keyboard.

  Further, in the example of FIG. 4, when the distance d is smaller than the predetermined distance c, the ratio of the coefficient α starts to decrease from the maximum value 1. The predetermined distance c can be set to a distance that is expected to effectively obtain the force control effect. A method for setting the predetermined distance will be described with reference to FIGS. 5 to 8 by taking as an example the operation of fitting the workpiece W1 into the hole H of the workpiece W2.

  For example, as shown in FIG. 5 (a diagram illustrating an example of a fitting operation by force control), the position of the contact surface between the workpiece W1 and the workpiece W2 is far from reaching the edge of the hole H as a result of the movement of the workpiece W1. Consider a case where the position has shifted. In this case, even if the impedance control is started when the workpiece W1 contacts the workpiece W2 and the workpiece W1 is pressed against the workpiece W2, the workpiece W1 does not enter the hole H. That is, the effect of impedance control cannot be obtained. On the other hand, as shown in FIG. 6 (a diagram for explaining an example of the fitting operation by force control), the position of the contact surface between the workpiece W1 and the workpiece W2 reaches the edge of the hole H as a result of the movement of the workpiece W1. Consider a case. In this case, when impedance control is started when the workpiece W1 contacts the workpiece W2 and the workpiece W1 is pressed against the workpiece W2, the workpiece W1 is easily fitted into the hole H. That is, the effect of impedance control can be obtained. Thus, the smaller the distance d, the higher the possibility of obtaining the effect of impedance control.

  Therefore, for example, if the distance at which the impedance control effect cannot be obtained is c1 (for example, 2 mm) and the accuracy error of the operation of the robot 20 is c2 (for example, 3 mm), the distance can be defined as c = c1 + c2. The setting of the distance c is preferably adjusted by the user according to the work content and the robot specifications. The robot control apparatus 10 can accept the setting of the distance c from the user via an input unit such as a keyboard, for example.

  Note that, for example, as shown in FIG. 7 (a diagram illustrating an example of a fitting operation by visual servo), the position of the contact surface between the workpiece W1 and the workpiece W2 reaches the edge of the hole H as a result of the movement of the workpiece W1. Consider the case. In this case, when the workpiece W1 is moved by visual servoing without starting impedance control when the workpiece W1 contacts the workpiece W2, depending on the situation, the end point may not be the shortest, that is, an inefficient trajectory. There is a possibility to move. On the other hand, as shown in FIG. 8 (a diagram for explaining an example of the fitting operation by the parallel control of force control and visual servo), the position of the contact surface between the workpiece W1 and the workpiece W2 is changed to the hole H as a result of the movement of the workpiece W1. Consider the case where it reaches the edge of In this case, when the impedance control is started when the workpiece W1 comes into contact with the workpiece W2, the trajectory of the end point by the visual servo is corrected by the trajectory by the impedance control. Therefore, the workpiece W1 is moved to the hole H with a more efficient trajectory. The possibility of being fitted increases.

  The third control unit 130 acquires an image from the image acquisition unit 120 at an arbitrary interval such as an interval at which the force control unit 110 outputs a command value, and acquires two positions (for example, the current position of the end point and the end point) Are recognized by image processing, and the distance from the current position to the target position is calculated. Further, the third control unit 130 acquires the values of the weight α and the weight β corresponding to the calculated distance based on the calculated distance and the relationship between the distance and the weight ratio, and uses them for the synthesis of the command value. Set as the weight to be used. A table defining the relationship between the distance and the weight ratio may be stored in advance in the storage unit, and the third control unit 130 may determine the weight ratio by referring to this table. The unit 130 may determine the weight ratio using a predetermined function formula.

  In this way, by using the visual servo and force control command values at the same time (performing parallel control), the position can be accurately corrected by the visual servo even if the position of the object is displaced. . Even when the visual servo trajectory becomes inefficient, it can be corrected to an efficient trajectory by force control.

  Further, as the distance between the current position and the target position increases, the ratio of the command value for force control becomes smaller than the ratio of the command value for visual servo. Therefore, at a position where the effect of force control cannot be effectively obtained, such as a position far from the target position, the movable part can be efficiently moved by the visual servo.

  Further, as the distance between the current position and the target position becomes smaller, the ratio of the visual servo command value becomes smaller than the ratio of the force control command value. Therefore, at a position where the effect of force control is more effectively obtained, such as a position close to the target position, the inefficient trajectory by the visual servo can be corrected, and the movable part can be moved more efficiently.

  Further, the weight is continuously changed (monotonically increased or monotonously decreased) according to the distance to the target position. Therefore, switching from visual servo to force control can be made smooth.

  FIG. 9 is a flowchart showing an example of the operation of the robot control apparatus 10. This process is started, for example, when an operation start instruction is input via a button or the like (not shown). In FIG. 9, the operation | work which fits the workpiece | work W1 in the hole H of the workpiece | work W2 is considered. In this work, for example, the work W1 is moved from the initial position by visual servo, and the work W1 once contacts the vicinity of the hole H of the work W2, and then the work W1 is fitted into the hole H by visual servo and impedance control. Go through the flow.

  When the flow of FIG. 9 is started, the third control unit 130 moves the end point using the visual servo unit 100 (step S1). The third control unit 130 acquires sensor information from the force sensor 25 of the robot 20 and determines whether or not an external force is applied to the hand of the robot based on the acquired sensor information (step S2). If no external force is applied to the hand of the robot (N in step S2), the third control unit 130 continues the process of step S1.

  When an external force is applied to the hand of the robot (Y in step S2), the third control unit 130 measures a distance d from the current position of the end point to the target position (step S3). The third control unit 130 sets a weight ratio corresponding to the measured distance d based on the distance d measured in step S3 and a table defining the relationship between the distance and the weight α and weight β (step S4).

  Then, the third control unit 130 moves the end point using the visual servo unit 100 and the force control unit 110 (step S5). Specifically, as described above, the visual servo unit 100 and the force control unit 110 each calculate a command value. The third control unit 130 multiplies the command value output from the visual servo unit 100 by the coefficient α set in step S4 and multiplies the command value output from the force control unit 110 by the coefficient β set in step S4. Is output to the robot 20.

  Further, the visual servo unit 100 determines whether or not a condition for terminating the visual servo is satisfied (step S6). For example, the visual servo unit 100 obtains a difference between the target image and the current image, and determines that the visual servo is to be ended when the difference is equal to or less than a predetermined threshold. If the condition for ending the visual servo is not satisfied (N in step S6), the visual servo unit 100 returns the process to step S2.

  When the condition for ending the visual servo is satisfied (Y in step S6), the force control unit 110 determines whether the condition for ending the force control is satisfied (step S7). For example, based on the sensor information from the force sensor 25, the force control unit 110 determines to end the force control when the external force at the hand of the robot is equal to or greater than a predetermined threshold. When the condition for ending the force control is not satisfied (N in Step S7), the force control unit 110 returns the process to Step S2. When the condition for ending the force control is satisfied (Y in step S7), the force control unit 110 ends the process of the flowchart of FIG.

  FIG. 10 is a diagram illustrating an example of a hardware configuration that implements the functions of the robot control apparatus 10.

  The robot controller 10 includes, for example, an arithmetic device 91 such as a CPU (Central Processing Unit), a main storage device 92 such as a RAM (Random Access Memory), an HDD (Hard Disk Drive), and the like as shown in FIG. An auxiliary storage device 93, a communication interface (I / F) 94 for connecting to a communication network by wire or wireless, an input device 95 such as a mouse, keyboard, touch sensor, and touch panel, and a display device 96 such as a liquid crystal display It can be realized by a computer 90 including a read / write device 97 that reads and writes information from and on a portable storage medium such as a DVD (Digital Versatile Disk).

  For example, the functions of the visual servo unit 100, the force control unit 110, the image acquisition unit 120, the third control unit 130, etc. are executed by the arithmetic unit 91 by executing a predetermined program loaded from the auxiliary storage device 93 or the like into the main storage device 92. It is realized by doing. The input unit is realized, for example, when the arithmetic device 91 uses the input device 95. The storage unit is realized by the arithmetic device 91 using the main storage device 92 or the auxiliary storage device 93, for example. The communication function with the robot 20 and the imaging device 30 is realized by the arithmetic device 91 using the communication I / F 94, for example. The predetermined program may be installed from, for example, a storage medium read by the read / write device 97 or may be installed from the network via the communication I / F 94.

  The drive control unit 200 of the robot 20 can be realized by, for example, a controller board including an application specific integrated circuit (ASIC) including an arithmetic device, a storage device, a circuit, and the like.

  The functional configuration of the robot system 1 described above is classified according to main processing contents in order to facilitate understanding of the configuration of the robot system 1. The present invention is not limited by the way of classification and names of the constituent elements. The configuration of the robot system 1 can be classified into more components depending on the processing content. Moreover, it can also classify | categorize so that one component may perform more processes. Further, the processing of each component may be executed by one hardware or may be executed by a plurality of hardware.

  Further, the functions and processing sharing of the robot control device 10 and the robot 20 are not limited to the illustrated example. For example, at least a part of the functions of the robot control device 10 may be included in the robot 20 and realized by the robot 20. Further, for example, at least a part of the functions of the robot 20 may be included in the robot control device 10 and realized by the robot control device 10.

  In addition, each processing unit in the above-described flowchart is divided according to main processing contents in order to facilitate understanding of the processing of the robot control apparatus 10. The present invention is not limited by the way of dividing the processing unit or the name. The processing of the robot control device 10 can be divided into more processing units according to the processing content. Moreover, it can also divide | segment so that one process unit may contain many processes.

  The embodiment of the present invention has been described above. According to the present embodiment, even when a position shift of the object occurs in the operation by the robot, the object can be efficiently moved to the target position.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiment. In addition, it is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention. The present invention may be provided as a robot system having a robot and a control device separately, or may be provided as a robot including the control device in the robot, or may be provided as a control device. . The present invention can also be provided as a method for controlling a robot or the like, a program for controlling a robot or the like, and a storage medium storing the program.

1: Robot system, 10: Robot control device, 20: Robot, 21: Movable part, 22: Arm, 23: Joint, 24: Link, 25: Force sensor, 26: Hand, 30: Imaging device, 90: Computer 91: arithmetic device, 92: main storage device, 93: auxiliary storage device, 94: communication I / F, 95: input device, 96: display device, 97: read / write device, 100: visual servo unit, 102: image processing 104: first trajectory generation unit 110: force control unit 112: sensor information acquisition unit 114: second trajectory generation unit 120: image acquisition unit 130: third control unit 200: drive control Part

Claims (9)

A target image that is an image including the end point when the end point of the movable part of the robot is at the target position, and a current image that is an image including the end point when the end point is at the current position are acquired. An image acquisition unit;
A first control unit that generates a first command value for moving the end point from the current position to the target position based on the current image and the target image;
A second control unit that generates a second command value for moving the end point based on an output from a force detection unit that detects a force acting on the movable unit;
The first command value and the second command value are respectively moved by using a third command value obtained by adding a predetermined weight that is changed corresponding to the distance to the target position . Three control units;
A robot control apparatus comprising: The robot control device according to claim 1 ,
An input unit for receiving a setting of the predetermined weight from a user;
A robot control apparatus comprising: The robot control device according to claim 1 ,
The third control unit determines the distance based on the image acquired by the image acquisition unit;
A robot controller characterized by that. The robot control device according to claim 1 ,
The third control unit increases the weight corresponding to the second command value as the distance decreases.
A robot controller characterized by that. The robot control device according to claim 1 ,
The third control unit, when said distance is larger than the predetermined value, the weighting corresponding to the second command value to 0,
A robot controller characterized by that. Moving parts;
A force detection unit for detecting a force acting on the movable unit;
An image for acquiring a target image that is an image including the end point when the end point of the movable unit is at a target position, and a current image that is an image including the end point when the end point is at the current position. An acquisition unit;
A first control unit that generates a first command value for moving the end point from the current position to the target position based on the current image and the target image;
A second control unit that generates a second command value for moving the end point based on an output from the force detection unit;
The first command value and the second command value are respectively moved by using a third command value obtained by adding a predetermined weight that is changed corresponding to the distance to the target position . Three control units;
A robot characterized by comprising: A robot having moving parts;
An image for acquiring a target image that is an image including the end point when the end point of the movable unit is at a target position, and a current image that is an image including the end point when the end point is at the current position. An acquisition unit;
A first control unit that generates a first command value for moving the end point from the current position to the target position based on the current image and the target image;
A second control unit that generates a second command value for moving the end point based on an output from a force detection unit that detects a force acting on the movable unit;
The first command value and the second command value are respectively moved by using a third command value obtained by adding a predetermined weight that is changed corresponding to the distance to the target position . Three control units;
A robot system characterized by comprising: A target image that is an image including the end point when the end point of the movable part of the robot is at the target position, and a current image that is an image including the end point when the end point is at the current position are acquired. An image acquisition step;
A first control step for generating a first command value for moving the end point from the current position to the target position based on the current image and the target image;
A second control step of generating a second command value for moving the end point based on an output from a force detection unit that detects a force acting on the movable unit;
The first command value and the second command value are respectively moved by using a third command value obtained by adding a predetermined weight that is changed corresponding to the distance to the target position . Three control steps;
A robot control method comprising: A program for a robot controller,
A target image that is an image including the end point when the end point of the movable part of the robot is at the target position, and a current image that is an image including the end point when the end point is at the current position are acquired. An image acquisition unit;
A first control unit that generates a first command value for moving the end point from the current position to the target position based on the current image and the target image;
A second control unit that generates a second command value for moving the end point based on an output from a force detection unit that detects a force acting on the movable unit;
The first command value and the second command value are respectively moved by using a third command value obtained by adding a predetermined weight that is changed corresponding to the distance to the target position . As three control units
Causing the robot control device to function;
A program characterized by that.

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