JP2019141966A - Robot control device, robot and robot system - Google Patents

Abstract

To provide a robot control apparatus capable of causing a robot to accurately perform work based on an output value output from a force detection unit. A control unit for controlling a robot having an arm and a force detection unit provided on the arm is provided, and the force detection unit includes a detection unit for detecting a value indicating an acceleration / deceleration state of the force detection unit. And the said control part is a robot control apparatus provided with the initialization part which initializes the said force detection part based on the detection result by the said detection part. [Selection] Figure 4

Description

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

  Research and development of technologies that allow robots to perform work by force control are being conducted. Here, force control is control based on the output value output from the force detection unit. The force detection unit is a sensor that detects an external force that has acted on a force detection part that is a predetermined part among parts of the robot. The force detection unit is, for example, a force sensor or a torque sensor. The external force includes a translational force acting on the force detection site and a rotational moment acting on the force detection site. The translational force includes three translational forces that act in the directions of the X axis, the Y axis, and the Z axis in the three-dimensional coordinate system associated with the force detection portion. The rotational moment includes three rotational moments acting around the X axis, the Y axis, and the Z axis. That is, the force detection unit detects each of the three translational forces and the three rotational moments as the external force, a signal corresponding to each of the detected three translational forces, and the detected three rotational moments. Information indicating each of the signals corresponding to each of these is output as external force information. That is, these six signals are output values output by the force detection unit.

  In force control, a robot having a force detection unit (or a robot control device that controls the robot) calculates a difference between an output value output from the force detection unit and a reference output value that is a reference output value. To do. The reference output value is an output value output by the force detection unit when no external force is applied to the robot. The robot determines that an external force having a magnitude corresponding to the calculated difference has acted on the force detection portion. That is, the robot is a translation that is the difference between the output value for the translational force and the reference output value for the translational force for each of the three translational forces that have acted on the force detection site among the output values output from the force detection unit. Calculate the difference. In addition, the robot has a rotation that is a difference between the output value of the rotation moment and the reference output value of the rotation moment for each of the three rotation moments that have acted on the force detection portion among the output values output from the force detection unit. Calculate the difference. Then, the robot determines that the resultant force of the translational force corresponding to the magnitude of each of the three translational differences has acted on the force detection portion, and has a magnitude corresponding to the magnitude of each of the three rotational differences. It is determined that the combined rotational moment is applied to the force detection site.

  Here, each of the above six reference output values changes due to the temperature around the force detection unit, accumulation of leakage current in the capacitor in the force detection unit, etc. (ie, temperature drift, time drift, etc.) Is known to occur). When at least one of the six reference output values changes, the robot equipped with the force detection unit may reduce the accuracy of work by force control. From such circumstances, the robot often initializes the force detection unit at a timing before performing work by force control. The initialization of the force detection unit is the magnitude of the output values (that is, the output values for each of the three translational forces and the output values for each of the three rotational moments) output from the force detection unit during initialization. Is set as a reference output value (that is, a reference output value for each of the three translational forces and a reference output value for each of the three rotational moments) (that is, zero adjustment of the force detection unit is performed). It is.

  In this regard, a robot arm, a force sensor, and a control unit that controls the operation of the robot arm are provided. The control unit starts initialization of the force sensor after the robot arm starts decelerating, and the robot arm There is known a robot that cancels the initialization state of the force sensor when the speed of the sensor is equal (see Patent Document 1).

JP2015-182165A

  This robot includes a sensor (for example, an inertia sensor, an acceleration sensor, a gyro sensor, or the like) that detects an angular velocity or an acceleration of an inertia detection part that is a predetermined part among the parts of the robot. Therefore, the robot can determine whether or not the robot arm has started decelerating based on the output value output from the sensor. Here, the sensor outputs, for example, a signal corresponding to the magnitude of the angular velocity or a signal corresponding to the magnitude of the acceleration as the output value. However, in the robot, the force sensor and the sensor are provided at different positions, and it may not be possible to accurately determine whether the force sensor has started deceleration.

  In order to solve the above problem, one aspect of the present invention includes a control unit that controls a robot having an arm and a force detection unit provided in the arm, and the force detection unit is in an acceleration / deceleration state of the force detection unit And a control unit that includes an initialization unit that initializes the force detection unit based on a detection result of the detection unit.

  One embodiment of the present invention is a robot controlled as the robot by the robot control device described above.

  One embodiment of the present invention is a robot system including the robot and the robot control device described above.

It is a figure showing an example of composition of robot system 1 concerning an embodiment. It is a figure which shows an example of the relationship between the speed of the control point T when a certain work is performed by the robot 20, and the time elapsed in the work. 2 is a diagram illustrating an example of a hardware configuration of a robot control device 30. FIG. 2 is a diagram illustrating an example of a functional configuration of a robot control device 30. FIG. 6 is a flowchart showing a specific example 1 of a process flow in which the robot control device 30 initializes the force detection unit FS. 10 is a flowchart showing a specific example 2 of a flow of processing in which the robot control device 30 initializes the force detection unit FS.

<Embodiment>
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Robot system configuration>
First, the configuration of the robot system 1 will be described.
FIG. 1 is a diagram illustrating an example of a configuration of a robot system 1 according to the embodiment. The robot system 1 includes a robot 20 and a robot control device 30. The robot system 1 includes an imaging unit, an image processing device that controls the imaging unit, an information processing device that controls the robot control device 30, a teaching device that teaches the robot control device 30 about the operation of the robot 20, and the like. May be.

  The robot 20 is a single-arm robot including an arm A and a base B that supports the arm A. The single arm robot is a robot having one arm (arm) like the arm A in this example.

  The arm A includes an end effector E, a manipulator M, and a force detection unit FS. The arm A may be configured without the end effector E.

  The end effector E is an end effector that holds an object. In this example, the end effector E includes a finger portion, and holds the object by holding the object by the finger portion.

  The manipulator M includes six joints. Each of the six joints includes an actuator (not shown). That is, the arm A including the manipulator M is a 6-axis vertical articulated arm. The arm A performs an operation with six degrees of freedom by a coordinated operation by the base B, the end effector E, the manipulator M, and the actuators of each of the six joints included in the manipulator M. The arm A may be configured to operate with a degree of freedom of 5 axes or less, or may be configured to operate with a degree of freedom of 7 axes or more.

  Here, the end effector E and each of the six actuators (provided in the joints) included in the manipulator M are connected to the robot controller 30 via a cable so as to be communicable. Thereby, the end effector E and each of the six actuators provided in the manipulator M perform an operation based on the control signal acquired from the robot control device 30. Note that wired communication via a cable is performed according to standards such as Ethernet (registered trademark) and USB (Universal Serial Bus), for example. The end effector E may be configured to be connected to the robot control device 30 by wireless communication performed according to a communication standard such as Wi-Fi (registered trademark). In addition, a part or all of the six actuators included in the manipulator M may be connected to the robot control device 30 by wireless communication performed according to a communication standard such as Wi-Fi (registered trademark).

  The force detection unit FS is provided between the end effector E and the manipulator M. The force detection unit FS is, for example, a force sensor (force sensor). The force detection unit FS detects an external force acting on a hand (not shown) of the robot 20. The hand is an end effector E or an object held by the end effector E. The external force includes a translational force that translates the hand. The translation force includes three translation forces acting in the directions of the X axis, the Y axis, and the Z axis in the three-dimensional coordinate system associated with the force detection unit FS. The external force includes a rotational moment (torque) that rotates the hand. The rotational moment includes three rotational moments acting around each of the X axis, the Y axis, and the Z axis. That is, the force detection unit FS detects each of the three translational forces and the three rotational moments as the external force. Then, information indicating each of the detected signal corresponding to each of the three translational forces and the detected signal corresponding to each of the three rotational moments is output as external force information to the robot controller 30 through communication. . That is, these six signals are output values output by the force detection unit FS.

  The external force information is used for force control of the robot 20 by the robot control device 30. The force control is control based on the output value output from the force detection unit FS, that is, control based on external force information output from the force detection unit FS to the robot control device 30, for example, compliant motion such as impedance control. It is control.

  The force detection unit FS detects external force at a predetermined sampling period. The sampling period of the force detection unit FS is, for example, about 100 milliseconds, but may be shorter than 100 milliseconds or longer than 100 milliseconds. The force detection unit FS outputs external force information indicating the magnitude of the detected external force to the robot control device 30 every time an external force is detected. The force detection unit FS may be configured to detect an external force in response to a request from the robot control device 30 and output external force information indicating the magnitude of the detected external force to the robot control device 30.

  The force detection unit FS includes a detection unit IS. Thereby, the robot 20 can be reduced in size.

  The detection unit IS is a sensor that detects an acceleration / deceleration state value that is a value indicating the acceleration / deceleration state of the force detection unit FS. Here, the acceleration / deceleration state of the force detection unit FS is either a state where the force detection unit FS is not accelerating or decelerating or a state where the force detection unit FS is accelerating or decelerating. The acceleration / deceleration state value is the angular velocity of the force detection unit FS or the acceleration of the force detection unit FS. Below, the case where an acceleration / deceleration state value is the acceleration of the force detection part FS is demonstrated as an example. That is, the detection unit IS is an acceleration sensor in this example. In the present embodiment, when referred to as acceleration, it means acceleration or deceleration.

  Further, the detection unit IS detects the acceleration of the part of the arm A where the force detection unit FS is provided as the acceleration of the force detection unit FS. That is, in this example, since the detection unit IS is built in the force detection unit FS, the acceleration of the part between the end effector E and the manipulator M among the parts of the arm A is detected as the acceleration of the force detection unit FS. To do.

  After detecting the acceleration / deceleration state value, the detection unit IS outputs acceleration / deceleration state information, which is information indicating the detected acceleration / deceleration state value, to the robot controller 30 through communication. Here, the detection unit IS is connected to a cable from which the force detection unit FS outputs external force information to the robot control device 30, and outputs acceleration / deceleration state information to the robot control device 30 through the cable. That is, the force detection unit FS and the detection unit IS are communicably connected to the robot control device 30 through a common cable. Thereby, the robot 20 can reduce wiring. Note that at least one of the force detection unit FS and the detection unit IS may be configured to be connected to the robot control device 30 so as to be communicable wirelessly.

  The detection unit IS detects the acceleration / deceleration state value at a predetermined sampling period. In this example, the sampling period of the detection unit IS is synchronized with the sampling period of the force detection unit FS. In other words, the timing at which the force detection unit FS detects an external force and the timing at which the detection unit IS detects the acceleration / deceleration state value are the same except for errors. Thereby, the robot control device 30 acquires the external force information indicating the external force detected at a certain timing and the acceleration / deceleration state information indicating the acceleration / deceleration state value of the force detection unit FS detected at the timing in association with each other. be able to. As a result, the robot control device 30 can specify the external force detected by the force detection unit FS at a certain timing as an external force according to the acceleration / deceleration state of the force detection unit FS at the timing. Note that the sampling period of the detection unit IS may not be the same as the sampling period of the force detection unit FS.

  The robot control device 30 is a robot controller that controls the robot 20. The robot control device 30 causes the robot 20 to perform a predetermined operation based on an operation program stored in advance in a memory included in the robot control device 30. The memory is not shown in FIG.

  More specifically, the robot control device 30 sets a control point T, which is a virtual point that moves with the arm A of the robot 20, at a predetermined position of the arm A. The control point T is, for example, a TCP (Tool Center Point) for the arm A. The control point T may be another virtual point that moves with the control point T instead of the TCP. The predetermined position is, for example, the position of the center of gravity of the end effector E. Note that the predetermined position may be another position corresponding to the arm A instead of the position of the center of gravity.

  A control point coordinate system, which is a three-dimensional orthogonal coordinate system that moves with the control point T, is associated with the control point T. The position of the control point T is represented by the position of the origin of the control point coordinate system in the robot coordinate system. The posture of the control point T is represented by the direction of each coordinate axis in the control point coordinate system in the robot coordinate system. Here, the robot coordinate system is a three-dimensional coordinate system associated with the base B of the robot 20.

  For example, the robot control device 30 operates the arm A by position control based on the teaching point specified by the above-described operation program. In this example, the position control of the arm A is control for making the control point T coincide with the teaching point specified by the operation program. Further, the robot control device 30 acquires external force information from the force detection unit FS and operates the arm A by force control based on the acquired external force information. Further, the robot control device 30 operates the arm A by both the position control and the force control.

  Here, the teaching point is a virtual point that is a target for the robot 20 to match the control point T. The teaching point is associated with teaching point position information, which is information indicating the position of the teaching point in the robot coordinate system, and teaching point posture information, which is information indicating the attitude of the teaching point in the robot coordinate system. When the robot 20 matches the control point T to a certain teaching point, the position of the control point T matches the position of the teaching point. In this case, the posture of the control point T matches the posture of the teaching point.

  The robot control device 30 operates the arm A and causes the robot 20 to perform a predetermined operation. The predetermined work may be any work as long as the work includes work by force control. The work by force control is work including an operation to be performed by the robot 20 by force control. In other words, the operation is an operation that the robot 20 performs based on the output value output from the force detection unit FS. That is, the predetermined work includes, for example, a work of gripping an object by the end effector E by force control, a work of placing an object held by the end effector E in a predetermined area by force control, and the like. Included as work by force control.

  In the force control, the robot control apparatus 30 acquires external force information from the force detection unit FS at a predetermined cycle. Each time the robot control device 30 acquires external force information, the robot control device 30 calculates a difference between the output value indicated by the acquired external force information and a reference output value that is a reference output value. The reference output value is an output value output by the force detection unit FS when no external force is acting on the hand of the robot 20. The robot control device 30 determines that an external force having a magnitude corresponding to the calculated difference has acted on the hand. That is, the robot control device 30 calculates the difference between the output value for the translational force and the reference output value for the translational force for each of the three translational forces that act on the hand among the output values output from the force detection unit FS. A certain translational difference is calculated. Further, the robot control device 30 calculates the difference between the output value of the rotation moment and the reference output value of the rotation moment for each of the three rotation moments that have acted on the hand among the output values output from the force detection unit FS. A certain rotation difference is calculated. Then, the robot control device 30 determines that the resultant force of the translational force having a magnitude corresponding to the magnitude of each of the three translational differences has acted on the hand, and a magnitude corresponding to the magnitude of each of the three rotational differences. It is determined that a combined rotational moment of the rotational moments has acted on the hand.

  In the force control, the robot control device 30 moves the control point T so that the external force determined to have acted on the hand satisfies a predetermined end condition. The external force refers to the three translational forces described above and the three rotational moments described above. Then, the robot control device 30 ends the operation of the robot 20 by force control when the end condition is satisfied. The termination condition may be any condition as long as it is a condition for the external force. For example, the end condition is that a translational force having a predetermined magnitude acts on the hand of the robot 20 in the positive direction of the Z axis in the three-dimensional coordinate system associated with the force detection unit FS. The translational force does not act in the direction along each of the X axis and the Y axis in the three-dimensional coordinate system, and the rotational moment does not act around each of the X axis, the Y axis, and the Z axis.

  Further, the robot control device 30 initializes the force detection unit FS based on the detection result by the detection unit IS when causing the robot 20 to perform work by force control. Thereby, the robot control apparatus 30 can make the robot 20 perform the work by force control with high accuracy. Here, the detection result by the detection unit IS is an acceleration / deceleration state value detected by the detection unit IS.

<Outline of processing for robot controller to initialize force detector>
Hereinafter, an overview of a process in which the robot control device 30 initializes the force detection unit FS will be described with reference to FIG.

  FIG. 2 is a diagram illustrating an example of the relationship between the speed of the control point T and the time elapsed in the work when the robot 20 performs a certain work. The horizontal axis of the graph shown in FIG. 2 indicates time. The vertical axis of the graph indicates the speed. Further, a curve F shown in the graph shows a change in the speed with the passage of time. Each of the period R1 and the period R2 shown in the graph indicates a period in which the control point T is accelerated or decelerated in the work. More specifically, in the period R1, the acceleration is stopped when the speed of the control point T reaches the speed V shown in FIG. Indicates the period until vibration stops. In other words, the vibration is a repeated acceleration / deceleration movement of the control point T. The period R2 indicates a period from when the control point T that has been moving at the speed V starts to be decelerated until the movement of the control point T is stopped and the vibration of the control point T stops.

  When the control point T is accelerating or decelerating, an inertial force corresponding to the acceleration or deceleration of the control point T acts on the force detection unit FS. Due to the action of the inertial force on the control point T, during the period when the control point T is accelerating or decelerating, the aforementioned reference output value varies according to the acceleration of the control point T. This period is the period R1 and the period R2 in the example shown in FIG. For this reason, in the robot control device X different from the robot control device 30, the force detection unit FS is initialized during the period until the predetermined standby period elapses after the movement of the control point T is stopped. Often not. The robot control device X is, for example, a conventional robot control device. In addition, this period is, in other words, a period until acceleration / deceleration of the control point T stops. However, the period during which the control point T is accelerating or decelerating varies for each operation of the robot 20. For this reason, the waiting period is estimated to be the longest period of time during which the control point T is accelerating or decelerating in the operation of the robot 20 so as not to reduce the accuracy of the operation performed by the robot 20. The period must be longer than the required period. As a result, it may be difficult for the robot control device X to improve the efficiency of the work performed by the robot 20.

  Therefore, the robot control device 30 initializes the force detection unit FS based on the detection result by the detection unit IS as described above. More specifically, the robot control device 30 initializes the force detection unit FS when the acceleration / deceleration state value output from the detection unit IS indicates that the force detection unit FS is not accelerating or decelerating. . As a result, the robot control device 30 can initialize the force detection unit FS without excessive passage of time after the force detection unit FS no longer accelerates or decelerates. As a result, the robot control apparatus 30 can cause the robot 20 to perform the work by force control with high accuracy and can improve the efficiency of the work.

  The initialization of the force detection unit FS is performed by resetting the magnitude of the output value output from the force detection unit FS at the time of initialization as a reference output value (that is, the zero point of the force detection unit FS). To match). Here, the output value is an output value for each of the three translational forces and an output value for each of the three rotational moments. The reference output value is a reference output value for each of the three translational forces and a reference output value for each of the three rotational moments.

  In this example, the detection unit IS is built in the force detection unit FS as described above. For this reason, the acceleration / deceleration state value output from the detection unit IS indicates the acceleration / deceleration state of the force detection unit FS. Thereby, the robot controller 30 accurately determines whether the acceleration / deceleration state of the force detection unit FS is a state where the force detection unit FS is not accelerating or decelerating based on the acceleration / deceleration state value. can do. In the example illustrated in FIG. 2, the period in which the force detection unit FS is not accelerated or decelerated is a period sandwiched between the period R1 and the period R2.

  Hereinafter, the configuration of the robot control device 30 and the process in which the robot control device 30 initializes the force detection unit FS will be described in detail.

<Hardware configuration of robot controller>
Hereinafter, the hardware configuration of the robot control device 30 will be described. FIG. 3 is a diagram illustrating an example of a hardware configuration of the robot control device 30.

  The robot control device 30 includes, for example, a processor 31, a memory 32, and a communication unit 34. Further, the robot control device 30 communicates with the robot 20 via the communication unit 34. These components are communicably connected to each other via a bus.

The processor 31 is, for example, a CPU (Central Processing Unit). The processor 31 may be another processor such as an FPGA (Field Programmable Gate Array) instead of the CPU. The processor 31 executes various programs stored in the memory 32.
The memory 32 includes, for example, a hard disk drive (HDD), a solid state drive (SSD), an electrically erasable programmable read-only memory (EEPROM), a read-only memory (ROM), and a random access memory (RAM). The memory 32 may be an external storage device connected via a digital input / output port such as a USB instead of the one built in the robot control device 30. The memory 32 stores various information processed by the robot control device 30, various images, operation programs, and the like.
The communication unit 34 includes, for example, a digital input / output port such as USB, an Ethernet (registered trademark) port, and the like.

  The robot control device 30 may be configured to include one or both of an input device such as a keyboard, a mouse, and a touch pad, and a display device having a display.

<Functional configuration of robot controller>
Hereinafter, the functional configuration of the robot control device 30 will be described with reference to FIG. 4. FIG. 4 is a diagram illustrating an example of a functional configuration of the robot control device 30.

  The robot control device 30 includes a memory 32, a communication unit 34, and a control unit 36.

  The control unit 36 controls the entire robot control device 30. The control unit 36 includes an acquisition unit 361, an initialization unit 363, and a robot control unit 365. These functional units included in the control unit 36 are realized by the processor 31 executing various commands stored in the memory 32, for example. Also, some or all of the functional units may be hardware functional units such as LSI (Large Scale Integration) and ASIC (Application Specific Integrated Circuit).

The acquisition unit 361 acquires external force information from the force detection unit FS. The acquisition unit 361 acquires acceleration / deceleration state information from the detection unit IS.
The initialization unit 363 initializes the force detection unit FS based on the external force information and the acceleration / deceleration state information acquired by the acquisition unit 361.
The robot control unit 365 operates the robot 20 based on an operation program stored in advance in the memory 32. At this time, the robot control unit 365 operates the robot 20 by at least one of position control and force control.

<Specific example 1 of the flow of processing in which the robot controller initializes the force detection unit>
Hereinafter, with reference to FIG. 5, a specific example 1 of a flow of processing in which the robot control device 30 initializes the force detection unit FS will be described. FIG. 5 is a flowchart showing a specific example 1 of a process flow in which the robot control device 30 initializes the force detection unit FS. In the specific example 1, the robot control device 30 initializes the force detection unit FS in a state where the control point T is stationary among the states where the control point T is not accelerating or decelerating. Note that the processing of the flowchart shown in FIG. 5 shows processing performed by the robot control device 30 in accordance with an operation program stored in advance in the memory 32.

  The initialization unit 363 generates a variable n that can store an integer in the storage area of the memory 32. Then, the initialization unit 363 initializes the generated variable n (Step S110). More specifically, the initialization unit 363 generates a variable n and then stores 0 in the variable n stored in the memory 32.

  Next, the robot control unit 365 specifies a teaching point indicating a standby position among teaching points designated by an operation program read in advance from the memory 32. The standby position is a position indicated by a teaching point that first matches the control point T when the robot 20 starts a predetermined operation. The robot control unit 365 operates the robot 20 based on the specified teaching point, and moves the position of the control point T to the standby position (step S120). That is, the robot control unit 365 operates the robot 20 to make the control point T coincide with the teaching point. Then, when the teaching point and the control point T coincide with each other, the robot control unit 365 stops the operation of the robot 20.

  Next, the acquisition unit 361 acquires external force information from the force detection unit FS and acquires acceleration / deceleration state information from the detection unit IS. Then, the initialization unit 363 determines whether or not the acceleration / deceleration state value indicated by the acceleration / deceleration state information acquired by the acquisition unit 361 is less than a predetermined first threshold (step S130). When it is determined that the acceleration / deceleration state value is equal to or greater than the first threshold (step S130—NO), the initialization unit 363 initializes the variable n (step S190). Then, the acquisition unit 361 transitions to step S130, acquires external force information from the force detection unit FS again, and acquires acceleration / deceleration state information from the detection unit IS again. On the other hand, when it is determined that the acceleration / deceleration state value is less than the first threshold (step S130—YES), the initialization unit 363 adds 1 to the variable n (step S140). That is, in this case, the initialization unit 363 adds 1 to the integer stored in the variable n stored in the memory 32, and stores the integer after adding 1 in the variable n.

  After the process of step S140 is performed, the initialization unit 363 determines whether or not the integer stored in the variable n is greater than or equal to a predetermined number of times (step S150). The determination in step S150 corresponds to determination that the robot 20 is in a stopped state for a predetermined period. Here, the predetermined number of times is, for example, three times. The number of times may be one time, two times, or four or more times. When the initialization unit 363 determines that the integer stored in the variable n is less than the predetermined number of times (step S150-NO), the acquisition unit 361 transitions to step S130, and the external force is detected from the force detection unit FS. Information is acquired again, and acceleration / deceleration state information is acquired again from the detection unit IS. On the other hand, when it is determined that the integer stored in the variable n is equal to or greater than the predetermined number of times (YES in step S150), the initialization unit 363 indicates that the force detection unit FS is not accelerating or decelerating. Then, it is determined that the acceleration / deceleration state value indicates, and the force detection unit FS is initialized (step S160). That is, when the acceleration / deceleration state value is continuously below the first threshold for a predetermined number of times or more, the initialization unit 363 determines that the force detection unit FS is not accelerating or decelerating, and The detection unit FS is initialized.

  Next, the robot control unit 365 operates the robot 20 and starts work by force control (step S170). The work that the robot control unit 365 starts in step S170 for the robot 20 may be any work as long as the work is based on force control.

  Next, the robot control unit 365 ends the work that the robot control unit 365 has started for the robot 20 in step S170, based on the external force information acquired from the force detection unit FS in a predetermined cycle in the force control. It is determined whether or not the condition is satisfied (step S180). When it is determined that the end condition is not satisfied (step S180—NO), the robot control unit 365 causes the robot 20 to continue the operation started in step S170. Then, the robot control unit 365 transitions to step S180 and determines again whether or not the end condition is satisfied. On the other hand, when it is determined that the end condition is satisfied (step S180—YES), the robot control unit 365 stops the operation of the robot 20 and ends the process.

<Specific example 2 of the flow of processing in which the robot controller initializes the force detection unit>
Hereinafter, with reference to FIG. 6, a specific example 6 of a processing flow in which the robot control device 30 initializes the force detection unit FS will be described. FIG. 6 is a flowchart illustrating a specific example 2 of a process flow in which the robot control device 30 initializes the force detection unit FS. In the second specific example, the robot control device 30 initializes the force detection unit FS in a state where the control point T is moving at a constant speed among the states where the control point T is not accelerating or decelerating. Note that the processing in the flowchart shown in FIG. 6 shows processing performed by the robot control device 30 in accordance with an operation program stored in advance in the memory 32. Further, in the flowchart shown in FIG. 6, steps that perform the same processes as those in the flowchart shown in FIG.

  After the process of step S110 shown in FIG. 6 is performed, the robot control unit 365 specifies a teaching point indicating a standby position among teaching points designated by an operation program read from the memory 32 in advance. The robot control unit 365 operates the robot 20 based on the specified teaching point, and starts to move the position of the control point T to the standby position (step S210). That is, the robot control unit 365 starts to move the arm A so that the control point T coincides with the teaching point. Then, the robot control device 30 performs the processing from step S130 to step S160 while the position of the control point T is moving to the standby position.

  After the process of step S160 is performed, the robot control unit 365 stands by until the position of the control point T matches the standby position (step S220). When the position of the control point T coincides with the standby position (step S220—YES), the robot control unit 365 stops the movement of the control point T (step S230). Then, the robot control unit 365 transitions to step S170, operates the robot 20, and starts work by force control.

  In the flowchart shown in FIG. 6, the process of step S230 may be omitted. That is, the robot control device 30 is configured to cause the robot 20 to start work by force control during the period in addition to initializing the force detection unit FS while the control point T is moving at a constant velocity. There may be. Thereby, the robot control apparatus 30 can further improve the efficiency of the work performed by the robot 20 by force control.

  As described with reference to FIGS. 5 and 6, the robot control device 30 initializes the force detection unit FS based on the detection result by the detection unit IS. That is, when the acceleration / deceleration state value indicates that the force detection unit FS is not accelerating or decelerating, the robot control device 30 initializes the force detection unit FS and the force detection unit FS is accelerating or decelerating. When the acceleration / deceleration state value indicates the state, the force detection unit FS is not initialized. As a result, the robot control device 30 can initialize the force detection unit FS without excessive passage of time after the force detection unit FS no longer accelerates or decelerates. As a result, the robot control apparatus 30 can cause the robot 20 to perform the work by force control with high accuracy and can improve the efficiency of the work.

  Note that the robot control device 30 may be configured to perform both the processing of the flowchart shown in FIG. 5 and the processing of the flowchart shown in FIG. 6 when causing the robot 20 to perform a predetermined operation. It may be configured to perform either one of them.

  Further, the robot 20 described above may be a multi-arm robot instead of the single-arm robot. A multi-arm robot is a robot having two or more arms. The two or more arms are, for example, two or more arms A. Here, the robot having two arms among the multi-arm robot is also referred to as a double-arm robot. That is, the robot 20 may be a double-arm robot having two arms or a multi-arm robot having three or more arms. The two arms are, for example, two arms A. The three or more arms are, for example, three or more arms A. The robot 20 may be another robot such as a SCARA robot (horizontal articulated robot), a Cartesian coordinate robot, or a cylindrical robot. The orthogonal coordinate robot is, for example, a gantry robot.

  Further, the end effector E described above may be configured to hold the object by lifting the object by air suction, magnetic force, other jigs, or the like. In this example, holding means that the object can be lifted.

  Further, the force detection unit FS described above may be a torque sensor that detects an external force applied to the end effector E or an external force applied to an object held by the end effector E. In addition, the force detection unit FS may be another sensor that detects an external force acting on the end effector E or an external force acting on the object. Further, the force detection unit FS may be configured to be provided in another part of the robot 20 instead of the configuration provided between the end effector E and the manipulator M. In this case, the force detection unit FS detects an external force acting on the part.

  Further, the initialization unit 363 described above may have a configuration provided in the force detection unit FS instead of the configuration provided in the control unit 36. In this case, the force detection unit FS includes a CPU, an FPGA, and the like. When the force detection unit FS includes the initialization unit 363, the robot system 1 is conscious that the accuracy of the work to be performed by the robot 20 by force control is reduced unless the user initializes the force detection unit FS. Without causing the robot 20 to perform the work by force control with high accuracy.

  Moreover, the initialization part 363 demonstrated above may be the structure with which the force detection part FS is provided in addition to the structure with which the control part 36 is provided.

  Further, the robot control device 30 described above may be configured to perform the process of initializing the force detection unit FS once in the work period in which the robot 20 performs a predetermined work. It is also possible to employ a configuration that is repeated every time a predetermined time elapses within the work period. This is because the temperature change in the space where the robot 20 is working is usually small. This is also because the accumulation of leakage current in the capacitor in the force detector FS is usually small.

  As described above, the robot control device includes the control unit that controls the robot having the arm and the force detection unit provided on the arm, and the force detection unit detects a value indicating the acceleration / deceleration state of the force detection unit. The control unit includes an initialization unit that initializes the force detection unit based on the detection result of the detection unit. In this example, the arm is the arm A. In this example, the force detector is a force detector FS. The control unit is the control unit 36 in this example. The value indicating the acceleration / deceleration state is an acceleration / deceleration state value. In this example, the detection unit is the detection unit IS. The initialization unit is an initialization unit 363 in this example. As a result, the robot control apparatus can reduce the size and wiring of the robot, and can cause the robot to accurately perform work based on the output value output from the force detection unit.

  In the robot control device, the value indicating the acceleration / deceleration state is an angular velocity or an acceleration. Accordingly, the robot control apparatus can cause the robot to accurately perform work based on the output value output from the force detection unit based on the angular velocity of the force detection unit or the acceleration of the force detection unit.

  In the robot control device, the initialization unit initializes the force detection unit when the value indicating the acceleration / deceleration state indicates that the force detection unit is not accelerating or decelerating. As a result, the robot control device can initialize the force detection unit in a state where the force detection unit is stationary or performing a constant velocity motion.

  In the robot controller, the initialization unit determines that the value indicates a state in which the force detection unit is not accelerating or decelerating when the value indicating the acceleration / deceleration state is equal to or less than a predetermined threshold. To do. The threshold value is the first threshold value in this example. Thereby, the robot control apparatus can suppress erroneously determining that the force detection unit is accelerating or decelerating that the force detection unit is not accelerating or decelerating.

  Further, in the robot control device, the initialization unit is in a state where the force detection unit is not accelerating or decelerating when the value indicating the acceleration / deceleration state is continuously equal to or greater than a predetermined number of times and is equal to or less than a predetermined threshold Is determined to be indicated by the value. Thereby, the robot controller more reliably suppresses erroneous determination that the force detection unit is accelerating or decelerating that the force detection unit is not accelerating or decelerating. be able to.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and changes, substitutions, deletions, and the like are possible without departing from the gist of the present invention. May be.

  Further, a program for realizing the function of any component in the above-described apparatus may be recorded on a computer-readable recording medium, and the program may be read into a computer system and executed. The device is, for example, a robot control device 30. Here, the “computer system” includes hardware such as an OS (Operating System) and peripheral devices. The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD (Compact Disk) -ROM, or a storage device such as a hard disk built in the computer system. . Furthermore, “computer-readable recording medium” means a volatile memory (RAM) inside a computer system that becomes a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

In addition, the above program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
Further, the above program may be for realizing a part of the functions described above. Further, the program may be a program that can realize the above-described functions in combination with a program already recorded in a computer system, a so-called difference file, a difference program, or the like.

DESCRIPTION OF SYMBOLS 1 ... Robot system, 20 ... Robot, 30 ... Robot control apparatus, 31 ... Processor, 32 ... Memory, 34 ... Communication part, 36 ... Control part, 361 ... Acquisition part, 363 ... Initialization part, 365 ... Robot control part, A ... Arm, FS ... Force detector, IS ... Detector

Claims (7)

A control unit for controlling a robot having an arm and a force detection unit provided on the arm;
The force detection unit includes a detection unit that detects a value indicating an acceleration / deceleration state of the force detection unit,
The control unit includes an initialization unit that initializes the force detection unit based on a detection result of the detection unit.
Robot control device. The value indicating the acceleration / deceleration state is angular velocity or acceleration.
The robot control apparatus according to claim 1. The initialization unit initializes the force detection unit when the value indicates a state where the force detection unit is not accelerating or decelerating,
The robot control apparatus according to claim 1 or 2. The initialization unit determines that the value indicates a state in which the force detection unit is not accelerating or decelerating when the value is equal to or less than a predetermined threshold.
The robot control device according to claim 3. The initialization unit determines that the value indicates a state in which the force detection unit is not accelerating or decelerating when the value is not more than the threshold continuously for a predetermined number of times,
The robot control device according to claim 4. Controlled as the robot by the robot control device according to any one of claims 1 to 5,
robot. The robot;
A robot controller according to any one of claims 1 to 5;
A robot system comprising:

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