Robot system, control method, article manufacturing method, control program, and recording medium

Abstract

To solve the problem that when a teacher directly moves a robot by using hands and teaches work operation to the robot, conventional impedance control is difficult to enable the teacher to sensuously feel contact between the robot and a work object, and accordingly teaching work cannot be efficiently performed.SOLUTION: A working robot includes an arm, a hand, a control part, a handling part for receiving operation force applied by a teacher when it teaches operation, an operation force detection part for detecting the operation force, and a reaction force detection part for detecting reaction force received by the hand from a work object. When the teacher teaches the operation, in a case in which the reaction force is not detected by the reaction force detection part, the control part adjusts a parameter of impedance control so that resistance in movement of the hand is decreased, and in a case in which the reaction force is detected by the reaction force detection part, the control part adjusts the parameter of the impedance control so that the resistance in movement of the hand is increased, when the hand is moved in a direction of the operation force detected by the operation force detection part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a working robot and a method for teaching the robot a working movement, and more particularly to a working robot that allows an instructor to directly apply force to the robot to teach it a working trajectory. [Background technology]

[0002] Previously, when teaching a robot to perform an action, a remote control terminal such as a teaching pendant was used to move the tip of the end effector to a specified position, and the taught position was memorized while visually confirming the position. In this case, it was necessary to individually adjust the movement speed and acceleration between taught positions. With teaching methods using a teaching pendant, coordinates were input numerically or the robot was moved by repeated jog movements, which was cumbersome and not very user-friendly, making teaching inefficient. As one method for improving operability in teaching, for example, Patent Document 1 describes a technique in which an instructor teaches a robot while operating it by directly applying force to the robot with his or her hands. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-250728 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, when an instructor applies force to the end effector of the robot main body in order to teach a trajectory, the force is detected by a sensor and the end effector is controlled to move in the direction of this force. In this case, the end effector is controlled to move only in a direction determined by the direction of the operating force applied to the sensor and the operating direction selected by the operating direction setting switch. Such a device allows the instructor to operate the robot with his or her own hands, which is convenient as it allows the instructor to perform teaching tasks more intuitively than when using a remote control such as a teaching pendant.

[0005] However, with the control method described in Patent Document 1, the robot automatically moves in the direction of the applied operating force, so even if the robot comes into contact with a workpiece, it is difficult for the instructor to intuitively sense the contact. As a result, even if the instructor attempts to perform delicate position control while bringing the robot into contact with the workpiece, the robot may apply excessive force to the workpiece, preventing the instructor from teaching as intended. For example, when teaching a robot to hold a flexible cable and insert it into a connector, the instructor may not be able to sense with his or her fingers whether the tip of the flexible cable is in contact with the connector, whether it is sliding against the connector, etc. This may result in the instructor being unable to apply an appropriate operating force, causing the flexible cable to deform into a shape different from the intended shape, making it impossible to insert the cable properly, and making it impossible to teach the robot precise operations. [Means for solving the problem]

[0006] One aspect of the present invention includes a robot, a control unit, an operation force detection unit that detects information regarding an operation force when a user operates a predetermined part of the robot, and a reaction force detection unit that detects information regarding a reaction force received by the predetermined part from an object, wherein the control unit controls a parameter for impedance control of the robot to control the resistance force when the user operates the predetermined part, and when the operation force is not detected, the parameter has a reference value set for generating a resistance force to maintain the posture of the robot, and by changing the parameter from the reference value in accordance with the reaction force and the operation force, the control unit executes control to make it easier for the user to move the predetermined part and control to make it more difficult for the user to move the predetermined part. death , If the reaction force is not detected when the user operates the predetermined part, the device makes it easier for the user to move the predetermined part, and if the reaction force is detected when the user operates the predetermined part, the device makes it difficult for the user to move the predetermined part. The robot system is characterized by the above.

[0007] Another aspect of the present invention is a control method for a robot system including a robot, a control unit, an operating force detection unit that detects information related to an operating force when a user operates a predetermined part of the robot, and a reaction force detection unit that detects information related to a reaction force received by the predetermined part from an object, wherein the control unit controls a parameter for impedance control of the robot to control the resistance force when the user operates the predetermined part, and in a state where the operating force is not detected, a reference value for generating a resistance force to maintain the posture of the robot is set for the parameter, and the parameter is changed from the reference value in accordance with the reaction force and the operating force, thereby executing control to make it easier for the user to move the predetermined part and control to make it more difficult for the user to move the predetermined part. death , If the reaction force is not detected when the user operates the predetermined part, the device makes it easier for the user to move the predetermined part, and if the reaction force is detected when the user operates the predetermined part, the device makes it difficult for the user to move the predetermined part. The control method is characterized by the above. [Effects of the Invention]

[0008] During teaching, the control unit controls the impedance control system parameters so that the instructor can easily sense the reaction force acting on the hand, allowing the instructor to easily sense contact or sliding between the hand and the workpiece during the teaching task. This makes it possible to efficiently perform teaching tasks that require delicate control of force, and to efficiently generate task programs that specify the magnitude and direction of the force the robot should exert during the task. In addition, it is possible to generate control programs with task algorithms that enable the impedance control system parameters to be switched during the task.

[0009] During work, the robot can accurately perform tasks even if the work object is misaligned, thanks to a work algorithm that switches impedance control system parameters while measuring the reaction force acting on the hand or the force applied by the hand to the work object. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a simplified configuration of a working robot according to a first embodiment. [Figure 2] FIG. 1 is a simplified functional block diagram of a first embodiment. [Figure 3] FIG. 4 is a flowchart illustrating a teaching process according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a parameter table of an impedance control system. [Figure 5] FIG. 1 is a diagram showing a series of teaching operations in stages. [Figure 6] 10A and 10B are diagrams showing the reaction force received by the hand in stages. [Figure 7] FIG. 10 is a diagram showing the contents of a control program for a task generated by teaching. [Figure 8] 10A to 10C are diagrams for explaining the effects of the embodiment during work. [Figure 9] FIG. 10 is a diagram showing a simplified configuration of a working robot according to a second embodiment. [Figure 10] FIG. 10 is a diagram showing a simplified configuration of a working robot according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] The configuration, teaching method, and working operations of a working robot according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a diagram showing the configuration of a working robot of this embodiment. The working robot shown in Fig. 1 includes a robot arm 11, a hand 12 mounted on the tip of the robot arm, a handling unit 13 attached between the robot arm 11 and the hand 12, and a robot controller 14 as a control unit for the entire working robot.

[0012] The robot arm 11 is an articulated robot arm with multiple axes, and each joint axis has a built-in torque sensor, and is equipped with a motor and an encoder (not shown). In this embodiment, a six-axis arm is used, but an arm with a different configuration may also be used.

[0013] The encoders mounted on each joint axis of the robot arm 11 can detect angle information of each joint and can transmit the measurement results to the robot controller 14 at a predetermined interval. The robot controller 14 can calculate the posture of the robot arm 11 based on the results detected by the encoders.

[0014] The torque sensors mounted on each axis of the robot arm 11 can detect the force acting on the robot arm 11. That is, each torque sensor can measure the torque acting on each joint axis, and can communicate the measurement results to the robot controller 14 at a predetermined interval.

[0015] The hand 12 also has a built-in six-axis force sensor that can detect the reaction force applied when the hand 12 comes into contact with a workpiece. The force sensor can measure the forces on each of the X, Y, and Z axes, as well as the moments around each axis, and can transmit the measured forces to the robot controller 14 at a predetermined interval. The robot controller 14 can calculate the direction and magnitude of the reaction force applied to the hand from the workpiece based on the calculated posture of the robot arm and the measurement results of the force sensor. Therefore, it can be said that the robot controller and six-axis force sensor constitute a reaction force detection means or reaction force detection unit. The force applied by the hand to the workpiece and the reaction force from the workpiece have an action-reaction relationship, with the magnitudes being equal but the directions being opposite. Therefore, the robot controller 14 can also calculate the force applied by the hand to the workpiece based on the calculated robot arm posture and the measurement results of the force sensor.

[0016] Based on the calculated posture of the robot arm, the torque detected by the torque sensor, and the reaction force detected by the six-axis force sensor, the robot controller 14 can calculate the direction and magnitude of the operating force applied to the handling unit 13 by the instructor. Specifically, the direction and magnitude of the operating force applied to the handling unit 13 can be calculated by subtracting the reaction force detected by the six-axis force sensor from the torque detection result detected by the torque sensor. Therefore, it can be said that the robot controller, torque sensor, and six-axis force sensor constitute an operation force detection means or an operation force detection unit. In this embodiment, the torque sensors mounted on each axis of the robot arm 11 and the six-axis force sensor of the hand 12 are arranged so as to sandwich the handling unit 13. By adopting such an arrangement, it is possible to improve the detection accuracy of the external force (operation force) applied to the handling unit and the reaction force from the work object.

[0017] The robot controller 14 is a computer with a built-in CPU, RAM, ROM, I / O ports, etc., and sends and receives signals to and from motors, sensors, encoders, etc. within the robot arm, and can also be connected to external networks and computers. The robot controller 14 generates drive commands to the motors of each joint axis of the robot arm 11 and can control the position of each joint axis through feedback control. In this case, the robot controller 14 can perform force feedback control, which changes the drive commands to the motors based on the operating force and reaction force obtained from the measurement results of the torque sensor and force sensor. In other words, unlike simple position control, this is control that adds force feedback and sets the physical response of the hand 12 to a state desirable for performing teaching work.

[0018] In this embodiment, the robot controller 14 can adjust the parameters of the impedance control system used to drive the motors of each joint axis, depending on the posture of the robot arm 11 and the operational force applied to the handling unit 13 by the instructor. For example, as shown by P0 on the left side of FIG. 5 , when the gripped workpiece 51 held by the hand 12 is separated from the assembly target workpiece 52 without contacting it, the reaction force detected by the six-axis force sensor is zero. In this case, the robot controller 14 makes it easier for the robot arm to move in the direction of the operational force applied by the instructor to the handling unit 13. Specifically, the robot controller 14 adjusts the parameters of the impedance control system so that the robot arm can be easily moved in the direction of the operational force applied by the instructor to the handling unit 13. Specifically, the robot controller 14 adjusts either or both of the virtual viscosity coefficient and virtual elastic coefficient of the control parameters of the joint axis to be driven for movement. In this case, the adjustment amount of the impedance control system parameters may be changed for each joint depending on the ratio and magnitude of the movement amount of each joint axis. Here, the virtual viscosity coefficient and virtual elasticity coefficient are control parameters that, when performing force control, produce the same effect as if a viscosity element and an elastic element were connected to the tip of the robot. The virtual viscosity coefficients [N / (mm / s)] and [Nm / (deg / s)] are parameters that indicate the force required to achieve a constant speed, so to make it easier to move the hand 12, the virtual viscosity coefficients are set to be small.

[0019] Furthermore, in this embodiment, when teaching a work trajectory, the parameters of the impedance control system for each joint axis can be adjusted based on the reaction force from the workpiece measured by the force sensor. For example, as shown in P1 of FIG. 5 , when the gripped workpiece 51 held by the hand 12 is in contact with the assembly target workpiece 52, the six-axis force sensor detects the reaction force received from the assembly target workpiece 52 via the gripped workpiece 51. When a reaction force is detected, the robot controller 14 controls the hand 12 so as to make it difficult to move in the direction of the operating force applied by the instructor. Specifically, the virtual viscosity coefficient and virtual elasticity coefficient of the control parameters of the joint axis of the robot arm that is driven to move the hand 12 in the direction of the operating force applied by the instructor to the handling unit 13 are changed to make it difficult to move. In this case, the adjustment amount of the impedance control system parameters may be changed for each joint depending on the rate and magnitude of the movement of each joint axis. The virtual viscosity coefficients [N / (mm / s)] and [Nm / (deg / s)] are parameters that indicate the force required to achieve a certain speed, so to make it difficult to move, i.e., to make the instructor feel a resistance force when applying an operating force, the virtual viscosity coefficient is set to a large value. As described above, the state in which the parameters are adjusted so that the resistance to the movement of the hand 12 is small relative to the movement direction of the hand 12, i.e., the direction of the operating force applied by the instructor, is the state in which it is easy to move the hand 12. Conversely, the state in which the parameters are adjusted so that the resistance to the movement of the hand 12 is large relative to the movement direction of the hand 12, i.e., the direction of the operating force applied by the instructor, is the state in which it is difficult to move the hand 12.

[0020] The method for adjusting the parameters of the impedance control system of this embodiment can also be described as follows. When the robot hand or the workpiece held by the robot hand is not in contact with the work object, the force sensor of the robot hand does not detect a reaction force. When no reaction force is detected, the robot controller 14 adjusts the parameters of the impedance control system based on the detected operational force so that the robot hand can be easily moved in the direction of the operational force applied by the instructor. When the robot hand or the workpiece held by the robot hand is in contact with the workpiece, the force sensor of the robot hand detects the reaction to the force applied by the robot hand to the workpiece, i.e., the reaction force from the workpiece. When the reaction force is detected, the robot controller 14 adjusts the parameters of the impedance control system so that the instructor feels it is difficult to move the robot in the direction of the operating force. Note that when the force sensor detects a reaction force, the parameters of the impedance control system may be adjusted with reference to not only the reaction force but also the operating force.

[0021] Furthermore, simply increasing or decreasing the virtual viscosity coefficient and virtual elastic coefficient of the impedance control system does not necessarily make it easier for the instructor to feel contact or sliding with the work object. For example, if the virtual elastic coefficients [mm / N] and [deg / Nm] are set too large, the reaction force from the assembly object may be absorbed by the spring component, and the force may not be transmitted to the operating unit. Since the parameters may need to be changed depending on the magnitude of the calculated reaction force, it is desirable to prepare a parameter table for the impedance control system according to the magnitude of the reaction force in advance.

[0022] FIG. 2 is a functional block diagram showing in simplified form the functional blocks included in the robot controller 14. As shown in FIG. Reference numeral 21 denotes a torque sensor serving as a first sensor for detecting an operating force, 22 denotes a force sensor serving as a second sensor for detecting a reaction force, and 23 denotes an encoder provided on each axis of the robot.

[0023] Reference numeral 24 denotes a data acquisition / storage unit consisting of an I / O port, memory, etc. It takes in and stores the force measured by the torque sensor 21, the force measured by the force sensor 22, and the information measured by the encoder 23 of each axis of the robot. Reference numeral 25 denotes a robot mechanical model registration section, which stores various information including the shape and dimensions of the robot arm.

[0024] Reference numeral 26 denotes a robot posture calculation unit, which calculates the position and posture of the robot arm based on the measurement results of the encoder stored in the data acquisition / storage unit 24 and information from the robot mechanical model registration unit 25 . Reference numeral 27 denotes an end effector information registration unit, which stores various information including the shape and dimensions of the hand.

[0025] Reference numeral 28 denotes a hand coordinate calculation unit, which calculates the position and posture of the hand based on the posture information calculated by the robot posture calculation unit 26 and information from the end effector information registration unit 27 . Reference numeral 29 denotes an operating force calculation unit, which calculates the operating force (external force) applied to the handling unit 13 based on the measurement value of the torque sensor 21, the posture information calculated by the robot posture calculation unit 26, and the hand position and posture information calculated by the hand coordinate calculation unit 28.

[0026] Reference numeral 30 denotes a reaction force calculation unit, which calculates the reaction force (external force) received by the hand from the work object based on the measurement value of the force sensor 22 and the position and orientation information of the hand. Note that by reversing the direction of the calculated reaction force, it is also possible to calculate the force applied by the robot hand to the work object. Reference numeral 31 denotes an impedance control system parameter setting unit which, during teaching, sets the virtual viscosity coefficient and / or virtual elastic coefficient of the impedance control system to a state suitable for teaching using the handling unit 13 based on the calculation results of the operating force and the reaction force. During work, the virtual viscosity coefficient and / or virtual elastic coefficient of the impedance control system are switched appropriately based on a switching signal from an impedance control system parameter setting switching unit 34.

[0027] Reference numeral 32 denotes a robot motion plan generation unit, which generates and stores a work program for executing the taught work motion by referring to the measurement values of the torque sensor 21 and the force sensor 22 at the time of teaching and the parameter setting values of the impedance control system parameter setting unit 31. The generation of the work program will be described later.

[0028] Reference numeral 33 denotes a robot operation command unit, which generates commands to be transmitted to the drive system (motor) of each joint axis of the robot arm in accordance with the control parameters set by the impedance control system parameter setting unit 31. Reference numeral 34 denotes an impedance control system parameter setting switching unit, which switches parameter settings based on the measured values of the torque sensor 21 and the force sensor 22 during work, and switches between force control and position control.

[0029] The functions of each block of the robot controller 14 described above are achieved by utilizing hardware resources such as an internal CPU, memory storing programs for each function, RAM for temporarily storing data, and I / O ports for sending and receiving data. Also, 35 is a robot drive system that drives the motors of each joint axis of the robot arm in accordance with instructions issued from the robot operation command unit 33.

[0030] Next, Fig. 3 is a flowchart showing the control flow during teaching in this embodiment. When the teaching operation is started, first in step S1, reference values of the parameters of the impedance control system are set. Specifically, initial values of the parameters of the impedance control system stored in advance in the memory of the robot controller 14 are read. The reference values of the parameters of the impedance control system are set taking into account the robot's own weight so that the robot does not start moving under its own weight.

[0031] Next, in step S2, it is confirmed whether the torque sensor 21, which is the first sensor, detects an operating force by the instructor. If an operating force is not detected, the parameters are maintained at the reference values. When the torque sensor 21 detects the operating force, in step S3, the parameters of the impedance control system are automatically set so as to make it easier to move the hand 12 in the direction in which the operating force is applied.

[0032] Next, in step S4, it is confirmed whether the second sensor, the force sensor 22, has detected a reaction force from the work object. If the force sensor 22 detects a reaction force from the work object, in step S5, parameters are automatically set so that the instructor feels a resistance force in the direction of the reaction force from the work object and it becomes difficult to move the hand 12 in the direction of the operating force.

[0033] In step S6, it is determined whether a program stop command has been acquired. Until the stop command is acquired, the parameters of the impedance control system are updated based on the forces detected by the torque sensor 21 and the force sensor 22, and the teaching operation continues.

[0034] An example of a parameter table for the impedance control system is shown in Figure 4. The virtual viscosity coefficient and virtual elasticity coefficient are set according to the magnitude of the reaction force from the work object. The parameter table may be set and selected appropriately for each work object, such as a workpiece to be held by the hand or a workpiece to be assembled, or the same table may be used uniformly.

[0035] Next, an example of an instructor teaching a work operation will be described with reference to Fig. 5. Fig. 5 shows a series of teaching operations divided into stages P0 to P4, with time flowing from left to right in the figure. The instructor teaches an operation in which the instructor manually operates the handling unit to move the hand 12 and fit the gripped workpiece 51 held by the hand 12 into a recess in the workpiece 52 to be assembled. The gripped workpiece 51 is one part of the work object, and the workpiece 52 to be assembled is another part of the work object.

[0036] First, in state P0, the hand 12 gripping the gripped workpiece 51 is positioned above the assembly target workpiece 52, and the instructor is holding the handling unit. The instructor applies an operating force in the -Z direction to the handling unit 13 to move the hand vertically downward, approaching the assembly target workpiece 52. State P1 is a state in which the gripped workpiece 51 and the assembly target workpiece 52 are in contact. When the gripped workpiece 51 comes into contact with the top surface of the assembly target workpiece 52, the instructor moves the gripped workpiece 51 in the +X direction while maintaining contact, and approaches the recessed portion of the assembly target workpiece 52. That is, the instructor applies a light operating force in the -Z direction while also applying an operating force to move the gripped workpiece 51 in the +X direction.

[0037] Next, in state P2, as a preliminary step before moving to the fitting operation, the instructor is checking whether the gripped workpiece 51 has reached a corner of the recessed portion of the assembly target workpiece 52. As will be described later with reference to FIG. 6 , according to the impedance control of this embodiment, the ease of movement for the instructor changes when the reaction force changes, so the instructor can easily recognize that the gripped workpiece 51 has reached a corner of the recessed portion. Therefore, when the gripped workpiece 51 reaches the corner of the recessed portion, the instructor changes the operating force applied to the handling unit to correct the posture of the hand 12. In state P3, the posture of the hand 12 is corrected so that the gripped workpiece 51 can be fitted into the groove (recess) of the workpiece 52 to be assembled. In state P4, an operating force is applied to the handling unit in the -Z direction to move the hand 12 in the -Z direction, and the gripped workpiece 51 is fitted onto the workpiece 52 to be assembled.

[0038] The reaction force received by the hand during the above teaching operation and the operation of the impedance control system will be described with reference to FIG.

[0039] 6, on the way from P0 to P1, the gripped workpiece 51 gripped by the hand 12 has not yet come into contact with the assembly target workpiece 52, and therefore the six-axis force sensor of the hand 12 does not detect any reaction force. In this state, the impedance control system parameter setting unit 31 of the robot controller 14 adjusts the parameters of the impedance control system so that the hand 12 can easily move in the direction of the operating force applied to the handling unit 13.

[0040] When the hand reaches P1, the gripped workpiece 51 comes into contact with the assembly target workpiece 52, generating a reaction force in the +Z direction. This reaction force is transmitted to the hand 12 via the gripped workpiece 51. When the six-axis force sensor in the hand 12 detects this reaction force, the impedance control system parameter setting unit 31 adjusts the parameters of the impedance control system so that the hand 12 is less likely to move in the direction of the operating force applied to the handling unit 13. Even if the instructor attempts to move the hand by applying an operating force, he or she will feel a resistance force in the same direction as the reaction force. This allows the instructor to sense with his or her fingertips that the gripped workpiece 51 has come into contact with the assembly target workpiece 52 and to move on to the next teaching operation. If the instructor cannot sense the contact of the gripped workpiece 51, in this example, he or she will continue to apply an operating force in the downward direction (-Z direction). This will apply excessive force between the gripped workpiece 51 and the assembly target workpiece 52, potentially damaging one or both of them. Furthermore, if the gripped workpiece 51 is a flexible member, even if it is not damaged, it may be deformed, making subsequent operations (for example, insertion operations) difficult. However, according to this embodiment, the instructor can easily sense the reaction force in the Z direction from the assembly target object, which allows the instructor to carry out the teaching task with more precise control of the force after the gripped workpiece comes into contact with the assembly target workpiece.

[0041] Next, while moving the gripped workpiece 51 from P1 toward P2 to search for the position of the mating portion, the instructor operates the handling unit 13 to move the gripped workpiece 51 in the +X direction while pressing it against the assembly target workpiece 52 in the -Z direction. Reaction forces are generated in the -X and +Z directions. These reaction forces are transmitted to the hand 12 via the gripped workpiece 51 and detected by the six-axis force sensor of the hand 12. When the reaction forces are detected, the impedance control system parameter setting unit 31 adjusts the parameters of the impedance control system so that the hand 12 is less likely to move in the direction of the operating force applied to the handling unit 13. Even if the instructor attempts to move the hand by applying an operating force, he or she will feel a resistance force in the same direction as the reaction force. This allows the instructor to sense the frictional force generated when sliding the gripped workpiece 51 against the assembly target workpiece 52 as a resistance force with his or her fingertips, allowing him or her to perform the operation of searching for the position of the mating portion as desired.

[0042] Then, as shown on the right side of Figure 6, when the gripped workpiece 51 reaches P2 at the corner of the recess of the workpiece 52 to be assembled, the reaction force changes so that it suddenly decreases. With the impedance control of this embodiment, the teacher can sense the change in reaction force as a change in resistance with high sensitivity with their hands, and can easily sense that the corner of the recess has been reached. Since the teacher can sense that the workpiece to be assembled has reached the corner, they can change the posture of their hand without overrunning it and begin the insertion operation into the recess.

[0043] FIG. 7 is a diagram for explaining the contents of the task control program created by the robot motion plan generating unit 32 in order to perform the taught fitting and assembly task motion. In the figure, graph Z shows the change in the Z coordinate of the tip of the hand. For example, from state P0 to state P1, it descends vertically, and from state P1 to state P2, there is no change in the coordinate in the Z direction.

[0044] Graph X indicates the change in the X coordinate of the tip of the hand. For example, there is no change in the X coordinate from state P0 to state P1, but there is movement in the X direction from state P1 to state P2.

[0045] Furthermore, Fz in the graph indicates the reaction force in the Z direction detected by the second sensor, the force sensor 22. For example, it can be seen that when the gripped workpiece 51 comes into contact with the assembly target workpiece 52 in state P1, a large reaction force is detected instantaneously. It can also be seen that from state P1 to state P2, the reaction force in the Z direction remains almost constant due to impedance control. Furthermore, Fx in the graph indicates the reaction force in the X direction detected by the second sensor, the force sensor 22. For example, from state P1 to state P2, it can be seen that an almost constant reaction force is received in the -X direction from the workpiece 52 to be assembled.

[0046] First, in the teaching stage, the instructor moves the hand only in the -Z direction from P0 to P1. Until it comes into contact with the workpiece to be assembled, no reaction forces Fx or Fz are generated, and only the position in the Z direction changes. Upon contact with the workpiece to be assembled, a +Fz force is generated, and the +Fz force increases until the operator detects the contact and stops the robot. From P1 to P2, the operator applies a constant force in the -Z direction while moving the robot in the +X direction. Until it reaches the corner of the recessed portion of the workpiece to be assembled, a reaction force (+Fz) against the force pressing in the -Z direction and a reaction force (-Fx) due to friction in the -X direction are generated. The position in the +X direction changes until the operator senses that it has reached the corner of the recessed portion of the workpiece to be assembled and stops the movement in the X direction. From P2 to P3, the instructor changes the robot's posture. At P3, the gripped workpiece comes into contact with the wall of the groove to be assembled. In the section from P3 to P4, the instructor moves the gripped workpiece in the -Z direction while following the wall surface of the recess in the workpiece to be assembled, and fits the gripped workpiece into the workpiece to be assembled.

[0047] In this embodiment, the robot controller stores the robot positions and postures from P0 to P4 in the teaching stage and the force profile information of the torque sensors and force sensors, and the robot motion plan generation unit 32 generates a task motion program. In other words, rather than teaching only the robot's posture and position (trajectory), the robot is also taught the reaction force that it receives from the work object at each stage of the work, in other words, the magnitude and direction of the force to be applied to the work object.

[0048] In the task operation program generated by the robot operation plan generation unit 32, the impedance control system parameter setting switch unit 34 switches the impedance control parameters based on the detection information of the force sensor 22, which is the second sensor. The work steps for executing a work operation program will be specifically described below with reference to Figure 7. The work operation program may be stored in memory within the robot controller 14 when it is taught, or may be temporarily stored in an external storage device and then loaded into the robot controller 14 via a network or a computer-readable storage medium.

[0049] In the section from P0 to P1, the reaction force detected by the force sensor 22 is 0. In this section, the robot operation command unit 33 sends a drive signal in the position control mode to the robot drive system 35 so that the X coordinate of the hand is a constant value and the Z coordinate is an operation expressed by a linear function (proportional).

[0050] Thereafter, when the force sensor 22 detects a sudden change in the reaction force Fz, the robot controller determines that state P1 has been reached, and the impedance control system parameter setting switching unit 34 switches the impedance control parameters. The switching may be performed on the condition that the rate of change (differential value) of the reaction force Fz exceeds a predetermined threshold, or on the condition that the numerical value of the reaction force Fz itself exceeds a predetermined threshold.

[0051] In the section from P1 to P2, the X coordinate is expressed by a linear function (proportional), and the Z coordinate is controlled to be a constant value. Because the reaction force is almost constant throughout this entire section, the robot operation command unit 33 sends a force control mode drive signal to the robot drive system 35 so that the force applied to the tip of the robot remains constant. In other words, the operation mode is switched from position control mode to force control mode.

[0052] Thereafter, when the force sensor 22 detects a sudden change in the reaction force Fx, the robot controller determines that state P2 has been reached, and the impedance control system parameter setting switching unit 34 switches the impedance control parameters. The switching may be performed on the condition that the rate of change (differential value) of the reaction force Fz exceeds a predetermined threshold, or on the condition that the numerical value of the reaction force Fz itself exceeds a predetermined threshold. In the section from P2 to P3, the posture of the hand is changed, but neither the X nor Z coordinates change linearly, and the reaction forces Fx and Fz are not constant. Because the force is not a constant value throughout the entire section, the robot operation command unit 33 sends a drive signal in the position control mode to the robot drive system 35 so as to reproduce the movement trajectory of the posture change at the time of teaching.

[0053] In the section from P3 to P4 where the posture change is complete, the X coordinate is constant and the Z coordinate is proportional, both of which are expressed by linear functions. Because the reaction force is almost constant throughout the entire section, the robot operation command unit 33 sends a force control mode drive signal to the robot drive system 35 so that the force applied to the tip of the robot is constant.

[0054] Thereafter, when the force sensor 22 detects a sudden change in the reaction force Fz, the robot controller determines that state P4 has been reached and sends a signal to the robot drive system 35 to terminate drive. The termination may be conditional on the rate of change (differential value) of the reaction force Fz exceeding a predetermined threshold, or on the numerical value of the reaction force Fz itself exceeding a predetermined threshold.

[0055] According to this embodiment, by switching the impedance control system parameters while measuring the reaction force acting on the hand, it is possible to accurately execute the taught operation even if the position of the work object is shifted.

[0056] Figures 8(a) to 8(d) are simplified diagrams to explain this, with Figure 8(a) showing the positional relationship between the gripped workpiece and the workpiece to be assembled during teaching, and Figures 8(b) to 8(d) showing the case where the workpiece to be assembled is set at a position deviated from the teaching position shown by the dotted line to the position shown by the solid line during operation.

[0057] If the hand is controlled only by position coordinates during operation, and the workpiece to be assembled is placed differently from when it was taught, state P2, i.e., reaching the corner of the recess, cannot be detected correctly, and subsequent changes in the hand's posture or fitting operation in the -Z direction cannot be performed correctly. Not only will the fitting operation not be possible, but in some cases, the workpiece or the robot itself may be damaged.

[0058] However, in this embodiment, the parameters of the impedance control system are taught so that the force sensor 22 can sensitively detect that the workpiece has reached the corner of the recessed portion of the workpiece to be assembled. In FIG. 8(b), by controlling the force to continue to be applied in a fixed direction until the corner of the recessed portion is detected based on the reaction force measured by the force sensor 22, the workpiece can be properly operated even if the workpiece to be assembled is misaligned. In FIG. 8(c), the relative positions of the gripped workpiece and the workpiece to be assembled are the same as when they were taught, so it is only necessary to reproduce the trajectory of the posture change. In FIG. 8(d), when a sudden change in the reaction force Fz is detected, it can be determined that state P4 has been reached. This determination can be made based on the condition that the rate of change (differential value) of the reaction force Fz exceeds a predetermined threshold, or the value of the reaction force Fz itself exceeds a predetermined threshold.

[0059] As described above, according to this embodiment, a task program is generated by performing impedance control that allows the instructor to easily sense the contact state between the hand and the workpiece, thereby enabling efficient teaching of the position, posture, and force to be applied. Furthermore, a task algorithm can be generated that switches the impedance control system parameters during the task based on the reaction force measured during teaching.

[0060] Although the above explanation has been simplified to make it easier to understand, when an instructor actually teaches by hand, it is difficult to move in a straight line without error, and it is also difficult to continue to apply a constant force. Therefore, when actually generating a control program for work movements, it is preferable to filter data that has become oscillatory during teaching, and to separate and eliminate movements and forces that are not originally intended by the instructor.

[0061] Furthermore, since the force sensor's detection value may change due to the influence of its own weight depending on the posture, it is desirable to always perform zero-point calibration in a specific posture or to perform zero-point calibration for each movement so that the detected reaction force is not affected by the posture.

[0062] [Second embodiment] Fig. 9 is a diagram showing a simplified configuration of a second embodiment of the present invention. In Fig. 9, the robot device includes a robot arm 91, a hand 92 mounted on the tip of the arm, a handling unit 93 with a built-in force sensor attached between the hand 92 and the robot arm 91, and a robot controller 94. Explanation of parts common to the first embodiment will be omitted.

[0063] In the first embodiment, the operating force applied to the handling unit by the instructor was detected based on the measurement values of the torque sensors of each joint and the reaction force detected by the six-axis force sensor. However, in this embodiment, the force is measured using a force sensor built into the handling unit 93. In this embodiment, the robot controller and the force sensor built into the handling unit 93 can be said to constitute an operation force detection means or an operation force detection unit.

[0064] In the first embodiment, the process for calculating the direction and magnitude of the operating force is somewhat complicated, but according to the present embodiment, the operating force can be detected more easily. A force sensor built into the handling unit 93 measures the operating force applied to the robot arm 91 and can transmit the measurement results to the robot controller 94 at a predetermined interval.

[0065] In this embodiment, the same effects as in the first embodiment can be achieved by detecting the operating force of a person with a force sensor built into the handling unit 93 and detecting the reaction force from the assembly object with a force sensor built into the hand 92. In order to minimize the influence of the reaction force from the assembly object when detecting the operating force of a person, it is desirable to position the force sensor built into the handling unit 93 as far away from the hand 92 as possible within the handling unit.

[0066] As in the first embodiment, in the teaching stage, a work program is generated by performing impedance control that makes it easy for the instructor to sense the reaction force acting on the hand, so that a trajectory with high positional accuracy can be efficiently taught. Then, a work algorithm can be generated that switches the impedance control system parameters during work based on the reaction force measured during teaching.

[0067] During work, by switching the impedance control system parameters while measuring the reaction force acting on the hand, the taught operation can be accurately executed even if the position of the work object shifts.

[0068] [Third embodiment] FIG. 10 is a diagram showing a simplified configuration of the third embodiment of the present invention. In FIG. 10, the robot device comprises a robot arm 101, a hand 102 mounted on the tip of the robot, and a handling unit 103 attached between the robot arm 101 and the hand 102. It also comprises a robot controller 104 that generates drive commands for the robot, and an assembly base 107. The robot arm 101 is an articulated robot, and each joint axis has a built-in torque sensor, and each joint axis is equipped with a motor and an encoder (not shown). The example shows an operation in which a gripped workpiece 105 gripped by the hand 102 is fitted into a workpiece 106 to be assembled. Explanations of parts common to the first embodiment will be omitted.

[0069] In the first embodiment, the reaction force from the workpiece was measured using a force sensor provided in the hand as a second sensor. In the present embodiment, the force applied by the hand to the workpiece is measured using a force sensor built into the assembly base 107 on which the workpiece 106 to be assembled is placed as the second sensor. That is, the workpiece 106 to be assembled is set on the assembly base 107, which has a built-in force sensor as a second sensor, and the built-in force sensor measures the force applied by the robot hand to the workpiece. The force applied by the hand to the workpiece and the reaction force received by the hand from the workpiece have an action-reaction relationship, with the magnitudes being equal but the directions being opposite. Therefore, based on the measurement results of the force sensor built into the assembly base 107, the robot controller can calculate the reaction force acting on the hand. In this embodiment, the robot controller and the force sensors built into the assembly base can be said to constitute a reaction force detection means or a reaction force detection unit.

[0070] In this embodiment, a force sensor built into the assembly base 107 detects the force applied by the hand to the workpiece to be assembled, and the robot controller calculates the reaction force acting on the hand. In addition, the operating force applied by the instructor to the handling unit 103 is detected based on the difference between the measurement result of the torque sensor built into the robot arm 101 and the reaction force calculated by the robot controller. This embodiment can also achieve the same effects as the first embodiment.

[0071] That is, in the teaching stage, a work program is generated by performing impedance control that allows the instructor to easily sense the contact state between the hand and the workpiece, allowing for efficient teaching of the position, posture, and force to be applied. Then, a work algorithm can be generated that switches the impedance control system parameters during work based on the reaction force calculated during teaching.

[0072] During work, the force applied by the hand to the work object is measured, the reaction force acting on the hand is calculated, and the impedance control system parameters are switched, allowing the instructed operation to be performed accurately even if the work object is misaligned.

[0073] [Other embodiments] The embodiments of the present invention are not limited to the first to third embodiments described above, but can be modified or combined as appropriate, and many variations are possible within the technical concept of the present invention. For example, the working robot is not limited to a robot with a six-axis controlled arm, and the work performed by the robot is not limited to fitting parts together. The present invention can be widely applied to the manufacturing work of goods using various types of working robots. The hand attached to the tip of the arm is not limited to the above-described embodiment, and may be any of various manipulators. The shape and installation position of the handling unit are not limited to those of the above-described embodiment, as long as the handling unit has a mechanism that allows the instructor to easily apply operating force to the hand or robot arm using their hands, and it is preferable to provide a grip or the like that is easy to hold in a position with good visibility. Furthermore, not all work steps need to be taught by direct manual operation by the instructor, and some steps may be taught using a remote control device such as a teaching pendant or a simulator. The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0074] 11···Robot arm / 12···Hand / 13··Handling unit / 14···Robot controller / 21···Torque sensor / 22···Force sensor / 23··Encoder / 24···Data acquisition / storage unit / 25···Robot mechanical model registration unit / 26···Robot posture calculation unit / 27···End effector information registration unit / 28···Hand coordinate calculation unit / 29···Operation force calculation unit / 30···Reaction force calculation unit / 31···Impedance control system parameter setting unit / 32···Robot motion plan generation unit / 33···Robot motion command unit / 34···Impedance control system parameter setting switching unit / 35···Robot drive system / 51···Gripped workpiece / 52···Workpiece to be assembled / 93···Handling unit with built-in force sensor / 107···Assembly base with built-in force sensor

Claims

1. Robots and A control unit; an operation force detection unit that detects information about an operation force when a user operates a predetermined portion of the robot; a reaction force detection unit that detects information about a reaction force received by the predetermined portion from an object, The control unit a parameter for controlling impedance of the robot is controlled to control a resistance force when the user operates the predetermined part; When the operational force is not detected, a reference value for generating a resistance force for maintaining the posture of the robot is set in the parameter, by changing the parameter from the reference value in accordance with the reaction force and the operating force, executing control to make it easier for the user to move the predetermined portion and control to make it difficult for the user to move the predetermined portion; If the reaction force is not detected when the user operates the predetermined part, the device makes it easier for the user to move the predetermined part, and if the reaction force is detected when the user operates the predetermined part, the device makes it difficult for the user to move the predetermined part. A robot system characterized by:

2. 2. The robot system according to claim 1, The control unit automatically setting the parameter for control that makes it easier for the user to move the predetermined part and the parameter for control that makes it difficult for the user to move the predetermined part when impedance control of the robot is performed according to the reaction force and the operating force; A robot system characterized by:

3. 3. The robot system according to claim 1, the control unit includes a parameter table having information regarding the parameters in control for making it easier for the user to move the predetermined part and the parameters in control for making it harder for the user to move the predetermined part, A robot system characterized by:

4. 4. The robot system according to claim 1, The control unit In the control for making it easier for the user to move the predetermined part and the control for making it harder for the user to move the predetermined part, a direction of a resistance force is controlled when the user operates the predetermined part, according to a direction of the reaction force and a direction of the operating force. A robot system characterized by:

5. 5. The robot system according to claim 1, The control unit acquiring the operation force based on posture information of the robot, position and posture information of the predetermined part, and a detection result of the operation force detection unit; acquiring the reaction force based on the position and orientation information of the predetermined part and the detection result of the reaction force detection unit; A robot system characterized by:

6. 6. The robot system according to claim 1, The control unit When a workpiece is held at the predetermined portion and the user operates the predetermined portion while the workpiece is in contact with the object, the resistance force when the user operates the predetermined portion is controlled in the same direction as the reaction force generated by the workpiece and the object, thereby allowing the user to feel the frictional force between the workpiece and the object. A robot system characterized by:

7. 7. The robot system according to claim 1, The reference value is a value that prevents the robot from moving under its own weight. A robot system characterized by:

8. The robot system according to any one of claims 1 to 7, the robot is a robot arm having multiple axes; the robot is provided with an operation unit that receives the operation force, The robot arm is provided with an end effector as the predetermined portion. A robot system characterized by:

9. The robot system according to claim 8, the operation force detection unit has a torque sensor provided on the shaft or a torque sensor provided on the operation unit, the reaction force detection unit has a force sensor provided in the end effector or a force sensor provided in a table on which the object is placed, A robot system characterized by:

10. 10. The robot system according to claim 8, The operation unit is provided between the robot arm and a force sensor provided in the end effector. A robot system characterized by:

11. The robot system according to any one of claims 1 to 10, The control unit In a control that makes it easier for the user to move the predetermined part, the resistance force when the user operates the predetermined part is made smaller than the resistance force at the reference value, and in a control that makes it harder for the user to move the predetermined part, the resistance force when the user operates the predetermined part is made larger than the resistance force at the reference value. A robot system characterized by:

12. The robot system according to any one of claims 1 to 11, The control unit When the user operates the predetermined part of the robot and teaches the robot an action, a control is executed to make it easier for the user to move the predetermined part and a control is executed to make it harder for the user to move the predetermined part. A robot system characterized by:

13. The robot system according to claim 12, The control unit During the teaching, an operation program for operating the robot is acquired, the operation program including the magnitude and direction of the force to be applied to the object based on the reaction force when the user operates the predetermined part, and the position and posture of the robot changed by the user operating the predetermined part. A robot system characterized by:

14. 13. The robot system according to claim 12, wherein the user teaches the robot an action for manufacturing an article by bringing the workpiece held by the robot into contact with the target object, the control unit acquires an operation program for controlling the robot to manufacture an article based on instructions from the user, and controls the robot based on the operation program to manufacture the article. A method for manufacturing an article.

15. Robots and A control unit; an operation force detection unit that detects information about an operation force when a user operates a predetermined portion of the robot; a reaction force detection unit that detects information about a reaction force received by the predetermined portion from an object, The control unit a parameter for controlling impedance of the robot is controlled to control a resistance force when the user operates the predetermined part; When the operational force is not detected, a reference value for generating a resistance force for maintaining the posture of the robot is set in the parameter, by changing the parameter from the reference value in accordance with the reaction force and the operating force, executing control to make it easier for the user to move the predetermined portion and control to make it difficult for the user to move the predetermined portion; If the reaction force is not detected when the user operates the predetermined part, the device makes it easier for the user to move the predetermined part, and if the reaction force is detected when the user operates the predetermined part, the device makes it difficult for the user to move the predetermined part. A control method comprising:

16. A control program for causing a computer functioning as the control unit to execute the control method according to claim 15.

17. A computer-readable recording medium storing the control program according to claim 16.

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