JP6794194B2 - Manufacturing methods for robotic devices, control methods, programs, recording media and articles - Google Patents

Description

The present invention is a robot device for stopping the operation of the robot upon receiving a stop directive in the middle of the force control, control method, a program, a method of manufacturing a recording medium and the object article.

The robot is mainly controlled by either position control or force control. In position control, when a work that involves contact with a work is performed, if there is a position error of the work, a load is applied to the work or the robot, which makes the work difficult.

Therefore, position-based force control (admittance control) is performed as force control. In the position-based force control, a position command value that imitates the work is calculated based on the value of the force sensor provided at the tip of the robot. When a stop command was received during position-based force control, the robot was decelerated and stopped by switching to position control (see Patent Document 1).

However, since the position-based force control uses the position control as a minor loop, its responsiveness is lower than the responsiveness of the position control. Generally, the response frequency of position control is constrained by the natural frequency of the robot. In particular, at the time of contact, it is difficult to improve the responsiveness due to the problem of stability.

Therefore, a robot that performs force control with high responsiveness is being developed. Specifically, torque-based force control has been developed that can improve responsiveness without being restricted by the natural frequency of the robot by controlling the force with the torque command value.

Japanese Patent No. 5371882

However, the robot has a machine difference due to a component manufacturing error, and a positioning error occurs. It is difficult to accurately grasp the machine difference, and when the robot is operated by position control, it moves to a position slightly deviated from the target position.

Therefore, in the highly responsive torque-based force control, when the state of imitating the force control as in Patent Document 1 is switched to the position control and stopped, the target in the position control is affected by the difference of the robot. The robot stops at a position deviated from the position. Therefore, when the robot and the work or the work held by the robot and another work are in contact with each other, there is a problem that both the robot and the work are overloaded.

Further, the torque base force control is highly responsive. If the speed is high, it takes time for the robot to decelerate and stop when a stop command is received. Therefore, there is a possibility that the robot cannot stop at the stop target position and goes too far. If the robot goes too far toward the stop target position, there is a problem that the robot and the work are similarly overloaded.

For example, when a fitting operation such as a peg-in hole is performed by using torque-based force control, if the vehicle is decelerated and stopped by position control, there is an excess due to misalignment caused by a machine difference and high responsiveness. For this reason, an unreasonable force is applied to the work, and the work may be caught in the fitting hole. Since it is difficult to remove the work caught in the fitting hole, there is a problem that it takes time to recover. In addition to the fitting operation, if the work is decelerated and stopped by position control during the pressing operation such as pressing the work with a certain force, the work will be pressed with an excessive force, and as described above, the robot or the work will be overloaded. There was a problem that it took.

Therefore, an object of the present invention is to reduce the load applied to the robot or the work and stop the operation of the robot when a stop command is received in the middle of force control.

The robot device of the present invention outputs a command value to the motor so that the motor, the sensor that detects the force acting on the predetermined portion, and the force acting on the predetermined portion become the force target value. and, based on the command value, and controls the driving of the motor, when receiving a stop command, the predetermined site, remain in position when receiving the stop command, and causes decline the force target value It is characterized by including a control unit that executes stop processing.

According to the present invention, when a stop command is received during torque base force control, it is possible to stop the operation of the robot while reducing the load applied to the robot or the work.

It is a perspective view which shows the schematic structure of the robot apparatus which concerns on 1st Embodiment. It is a block diagram which shows the robot control device of the robot device which concerns on 1st Embodiment. It is a control block diagram which shows the control system of the robot apparatus which concerns on 1st Embodiment. It is a flowchart at the time of force control of a robot in 1st Embodiment. It is a flowchart at the time of position control of a robot in 1st Embodiment. It is a schematic diagram which shows the state which the assembly work is performed by the robot in 1st Embodiment. It is a block diagram which shows the detail of the force control part of FIG. It is a flowchart which shows the manufacturing method of the assembly part which concerns on 1st Embodiment. (A) to (c) are graphs showing the force target value with respect to time. It is a graph of the position of the hand and the position target value with respect to time. (A) is a graph showing the displacement of the robot hand when the stop processing is performed while maintaining the torque base force control. (B) is a graph showing the displacement of the robot hand when the position control is switched to and the stop processing is performed. (A) to (d) are graphs showing the speed target value _Pref (・) with respect to time. (A) to (b) are graphs showing the rigidity coefficient _Kref with respect to time. (A) to (b) are graphs showing the viscosity coefficient D _ref with respect to time. It is a control block diagram which shows the control system of the robot apparatus which concerns on 5th Embodiment. It is a graph which shows the change of the hand force F with respect to the time at the time of working contact.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a perspective view showing a schematic configuration of a robot device according to the first embodiment. As shown in FIG. 1, the robot device 100 includes an articulated robot 200 and a robot control device 300 as a control unit that controls the operation of the robot 200. Further, the robot device 100 includes a teaching pendant 400 as a teaching device for transmitting teaching data to the robot control device 300. The teaching pendant 400 is operated by an operator and is used to specify the operation of the robot 200 and the robot control device 300.

The robot 200 is a vertical articulated robot. Specifically, the robot 200 includes a vertically articulated robot arm 251 and a robot hand 252 as an end effector attached to the tip of the robot arm 251. Hereinafter, the case where the end effector is the robot hand 252 will be described, but the present invention is not limited to this, and a tool or the like may be used. The base end of the robot arm 251 is fixed to the pedestal B. The robot hand 252 grips (supports) an object (part, tool, etc.).

The robot 200, that is, the robot arm 251 has a plurality of joints, for example, six joints (six axes) J _{1 to} J ₆ . The robot arm 251 has a plurality of (six) servomotors 201 to 206 that rotationally drive the joints J _{1 to} J ₆ around the joint axes A _{1 to} A ₆ , respectively.

In the robot arm 251, a plurality of links (frames) 210 _{0 to} 210 ₆ are rotatably connected by joints J _{1 to} J ₆ . Here, from the proximal side to the distal side, the link ₂₁₀ 0-210 ₆ are sequentially connected in series. The robot arm 251 can point the hand of the robot 200 (the tip of the robot arm 251) in any three-dimensional posture at any three-dimensional position as long as it is within the movable range.

The position and orientation of the robot arm 251 can be expressed in a coordinate system. The coordinate system To represents the base end of the robot arm 251, that is, the coordinate system fixed to the pedestal B, and the coordinate system Te represents the coordinate system fixed to the hand of the robot 200 (the tip of the robot arm 251).

Here, the hand of the robot 200 is the robot hand 252 in the first embodiment when the robot hand 252 does not grip (support) an object. When the robot hand 252 grips (supports) an object, it is referred to as a hand of the robot 200 including the robot hand 252 and the gripping (supporting) object (for example, a part or a tool). That is, regardless of whether the robot hand 252 is holding the object or not holding the object, the tip of the robot arm 251 is called the hand.

Each servomotor 201 to 206, has an electric motor (motor) 211 to 216 for driving each joint _J 1 through J ₆ respectively, and a sensor unit 221 to 226 respectively connected to the motors 211 to 216 There is. Each sensor unit 221 to 226 has a position sensor (angle sensor) that detects the position (angle) of each joint J _{1 to} J ₆ , that is, generates a signal according to the position (angle). Further, each sensor unit 221 to 226 has a torque sensor that detects the torque of each joint J _{1 to} J ₆ , that is, generates a signal corresponding to the torque. Further, each servomotor 201 to 206 has a speed reducer (not shown) and is connected to a frame driven by each joint J _{1 to} J ₆ directly or via a transmission member such as a belt or bearing (not shown). ing.

Inside the robot arm 251 is a servo control unit 230 as a drive control unit that controls the drive of the electric motors 211 to 216 of the servo motors 201 to 206.

The servo control unit 230, based on the torque command value corresponding to each joint _J 1 through J ₆ input, so that the torque of each joint J1~J6 to follow the torque command value, the current to the motors 211 to 216 It outputs and controls the drive of each electric motor 211-216. Although the servo control unit 230 is described as being composed of one control device in the first embodiment, it is composed of an aggregate of a plurality of control devices corresponding to each of the electric motors 211 to 216. You may be. Further, in the first embodiment, the servo control unit 230 is arranged inside the robot arm 251 but may be arranged inside the housing of the robot control device 300.

Further, the robot arm 251 of the robot 200 has a plurality of brakes (for example, disc brakes) 231 to 236 that brake each of the joints J _{1 to} J ₆ . By activating the brakes 231 to 236, the joints J _{1 to} J ₆ can be fixed so that the joints J _{1 to} J ₆ do not move.

Further, in the first embodiment, the teaching pendant 400 has a stop button 401 as a stop operation unit that transmits a stop command to the robot control device 300 by the operation of the operator.

Next, the robot control device 300 will be described. FIG. 2 is a block diagram showing a robot control device of the robot device according to the first embodiment. The robot control device 300 is composed of a computer and includes a CPU (Central Processing Unit) 301 as a processing unit. Further, the robot control device 300 includes a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and an HDD (Hard Disk Drive) 304 as storage units. Further, the robot control device 300 includes a recording disk drive 305 and various interfaces 306 to 309.

A ROM 302, a RAM 303, an HDD 304, a recording disk drive 305, and various interfaces 306 to 309 are connected to the CPU 301 via a bus 310. A basic program such as a BIOS is stored in the ROM 302. The RAM 303 is a storage device that temporarily stores various data such as the calculation processing result of the CPU 301.

The HDD 304 is a storage device that stores the arithmetic processing results of the CPU 301, various data acquired from the outside, and the like, and also records the program 330 for causing the CPU 301 to execute the arithmetic processing described later. The CPU 301 executes each step of the robot control method based on the program 330 recorded (stored) in the HDD 304.

The recording disk drive 305 can read various data, programs, and the like recorded on the recording disk 331.

The teaching pendant 400 is connected to the interface 306. The CPU 301 receives input of teaching data from the teaching pendant 400 via the interface 306 and the bus 310.

The servo control unit 230 is connected to the interface 309. The CPU 301 acquires signals from the sensor units 221 to 226 via the servo control unit 230, the interface 309, and the bus 310. Further, the CPU 301 outputs the torque command value data of each joint to the servo control unit 230 via the bus 310 and the interface 309 at predetermined time intervals.

A monitor 321 is connected to the interface 307, and various images are displayed on the monitor 321 under the control of the CPU 301. The interface 308 is configured to be connectable to an external storage device 322, which is a storage unit such as a rewritable non-volatile memory or an external HDD.

In the first embodiment, the case where the computer-readable recording medium is the HDD 304 and the program 330 is stored in the HDD 304 will be described, but the present invention is not limited to this. The program 330 may be recorded on any recording medium that can be read by a computer. For example, as the recording medium for supplying the program 330, the ROM 302 shown in FIG. 2, the recording disk 331, the external storage device 322, and the like may be used. To explain with specific examples, flexible disks, hard disks, optical disks, magneto-optical disks, DVD-ROMs, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memories, HDDs, ROMs, and the like can be used as recording media. it can.

FIG. 3 is a control block diagram showing a control system of the robot device according to the first embodiment. The CPU 301 of the robot control device 300 functions as a force detection unit 504, a force control unit 505, and a position target value generation unit 506 by executing the program 330. The servo control unit 230 includes a plurality of switching control units 511 to 516 (six because it has six joints), a plurality of position control units 521 to 526 (six because it has six joints), and a plurality of (six joints). Therefore, it functions as the motor control units 531 to 536 of 6).

Each sensor unit 221 to 226 has each angle sensor (position sensor) 551 to 556 and each torque sensor 541 to 546. Each angle sensor 551 to 556 is a rotary encoder that detects the angle (position) of each electric motor 211-216 or each joint J _{1 to} J ₆ , that is, generates a signal according to the angle (position). is there.

In the first embodiment, the angle sensors 551 to 556 directly detect the angles θ _{1 to} θ ₆ of the electric motors 211 to 216. The angle _q 1 to q ₆ of each joint _J 1 through J ₆ on the basis of the reduction ratio or the like of the reduction gear, not shown, can be determined from the angle theta ₁ through? _6. Thus, each angle sensor 551 to 556 would indirectly detect the angle _q 1 to q ₆ of each joint _J 1 through J _6.

Each torque sensor 541 to 546, the torque τ ₁ ~τ ₆ of each joint _J 1 through J ₆ detects respectively, i.e. a sensor which generates a signal corresponding to the torque. The position detection unit 550, which is a sensor that detects the position (including the posture) P of the hand of the robot 200 by a plurality of angle sensors 551 to 556, that is, generates a signal corresponding to the position P, is configured. Further, a force detection unit 540, which is a sensor that detects a force (hand force) F acting on the hand of the robot 200 by a plurality of torque sensors 541 to 546, that is, generates a signal corresponding to the force F is configured.

The teaching pendant 400 outputs the force target value F _ref included in the force teaching data 501 and the position target value _Pre included in the position teaching data 502 to the CPU 301 by the operation of the operator. The force target value _Ref is a target value of the hand force of the robot 200, and is set by the operator using the teaching pendant 400. The position target value _Pre is a target value of the hand position of the robot 200, and is set by the operator using the teaching pendant 400. The robot model 503 is stored in the external storage device 322.

Further, the teaching pendant 400 outputs a stop command to the force control unit 505 of the CPU 301 when the stop button 401 is operated by the operator.

The force detection unit 504 uses signals corresponding to the torques τ _{1 to} τ ₆ acquired from the torque sensors 541 to 546 and the angles q _{1 to} q ₆ acquired from the angle sensors 551 to 556, and uses the signals of the hand of the robot 200. The current position P (t) and the hand force F of the robot 200 at that time are obtained. At this time, the force detection unit 504 obtains the current position P (t) of the hand of the robot 200 by using signals corresponding to the angles q _{1 to} q ₆ acquired from the angle sensors 551 to 556. The force detection unit 504 may calculate the hand force F of the robot 200 by using a force sensor (not shown) attached to the hand.

The force control unit 505 sets the values of the robot model 503 (virtual mass M _ref ), the force target value F _ref , the position target value _Pref , the rigidity coefficient K _ref , the viscosity coefficient D _ref , the current position P (t), and the force F. Receives the input of the indicated signal. Then, the force control unit 505 uses these values to determine the torque command value τ _MFref1 ~τ _MFref6 for each joint _J 1 through J _6. At this time, the force deviation between the hand force F and the force target value F _ref , the position deviation between the hand position P (t) and the position target value _Pref , and the speed P (t) (・) and the speed target value of the hand. speed deviation between P _ref (·) is determined torque command value τ _MFref1 ~τ _MFref6 to be smaller. The force control unit 505 outputs the obtained torque command values τ _{MFref1 to} τ _MFref6 to the switching control units 511 to 516. Here, the velocity P (t) (・) is obtained by differentiating the position P (t) with respect to time, and the velocity target value _Pref (・) is obtained by differentiating the position target value _Pref with respect to time. .. Therefore, in the first embodiment, the force control unit 505 obtains the speed P (t) (.) Of the hand from the position P (t) of the hand, which is the detection result of the position detection unit 550. The position detection unit 550 may perform a calculation and output the data itself of the speed P (t) (・) of the hand. In this case, the position detection unit 550 detects the speed of the hand. It also serves as a unit, that is, a sensor that generates a signal corresponding to the speed of the hand. In addition, (・) means the first derivative with time.

Position target value generating unit 506, angle command value for each joint _J 1 through J ₆ by inverse kinematic calculation from the position target value _{P ref} of the hand (position command _value) q _{ref1 to q} seek _Ref6, the angle command value q the _ref1 to q _Ref6 outputs to the position control unit 521 to 526.

Each position control unit 521 to 526, the torque command so that the angular deviation between the angle _q 1 to q ₆ of each joint _J 1 through J ₆ and angle command value _q ref1 _{to q Ref6} of the joints _J 1 through J ₆ is reduced determine the value τ _MPref1 ~τ _MPref6. In addition, to reduce this angle deviation is to reduce the angle deviation between the angle of each electric motor _211-216 and the angle command value _obtained by _{converting the} angle command values q _{ref1 to} q _ref6 by the reduction ratio of the reduction gear or the like. Equivalent. Each position control unit 521 to 526 outputs the torque command value τ _MPref1 ~τ _MPref6 each switching control unit 511 to 516.

Each switching control unit 511 to 516 switches and controls a force control mode for performing torque-based force control and a position control mode for performing position control. Each switch control unit 511 to 516, the force control mode is output to each motor control unit 531 to 536 each torque command value τ _MFref1 ~τ _MFref6 as the torque command value τ _Mref1 ~τ _Mref6. Each switch control unit 511 to 516, the position control mode is output to each motor control unit 531 to 536 each torque command value τ _MPref1 ~τ _MPref6 as the torque command value τ _Mref1 ~τ _Mref6.

Each motor control unit 531 to 536 _sets each current Cur _{1 to} Cur ₆ so as to realize each torque command value τ Mref ₁ to τ _{Mref 6} based on the angles (positions) θ _{1 to} θ ₆ of the electric motors ₂₁₁ to 216. Energize each electric motor 211-216.

Next, the force control of the robot 200 will be described. FIG. 4 is a flowchart when the robot 200 is force-controlled in the first embodiment.

First, the operator inputs the force target value F _ref and the position target value _Pref into the teaching pendant 400 (S1). The force target value F _ref is stored in the force teaching data 501, and the position target value _Pre is stored in the position teaching data 502. The position target value _Pre is a position at which the force control operation is started.

Force control unit 505, so that the hand force F is to follow the force target value _{F ref,} i.e. using a robot model 503 so that the deviation becomes smaller with hand force F and the force target value _{F ref} torque command for each motor 211 to 216 value (force) is calculated τ _MFref1 ~τ _MFref6 (S2).

Each switch control unit 511 to 516, the output torque command value (force) τ _MFref1 ~τ _MFref6 as the torque command value τ _Mref1 ~τ _Mref6 to each motor control unit 531 to 536 (S3).

Each motor control unit 513 to ₅₃₆ performs energization control so as to realize each torque command value τ Mref ₁ to τ _{Mref 6} based on the angles θ _{1 to} θ ₆ of the electric motors 211 to ₂₁₆ (S4).

When the electric motors 211 to 216 are energized, the joint torques τ _{1 to} τ ₆ are generated (S5).

The angle sensors 551 to 556 detect angles q _{1 to} q ₆ of the joints J _{1 to} J ₆ (angles θ _{1 to} θ ₆ of the electric motors 211 to 216). Each torque sensor 541 to 546 detects the torque τ ₁ ~τ ₆ of each joint _J 1 ~J ₆ (S6). Angle _q 1 to q ₆ and the torque τ ₁ ~τ ₆ of each joint _J 1 through J ₆ of each joint _J 1 through J ₆ is fed back to the CPU301 of the robot controller 300.

Force detection unit 504 (CPU 301) is, the torque τ ₁ ~τ ₆ of each joint _J 1 through J ₆ based robot model 503 to angle _q 1 to q ₆ of each joint _J 1 through J _6, the current position P It is converted into the hand force F applied to the hand of the robot 200 in (t) (S7). It is also possible to use the angle theta ₁ through? ₆ of the electric motor 211 to 216 instead of the angle _q 1 to q ₆ joints _J 1 through J _6.

The CPU 301 determines whether or not the drive is completed (S8), and if not (S8: No), repeats steps S2 to S7. By driving the electric motors 211 to 216 according to the above flow, it is possible to control the force F applied to the hand of the robot 200 to a desired force target value _Ref . The order of the flowcharts shown in FIG. 4 is not limited, and force control can be performed in any other order.

Next, the position control of the robot 200 will be described. FIG. 5 is a flowchart when the position of the robot 200 is controlled in the first embodiment.

First, the operator inputs the position target value _Pre into the teaching pendant 400 (S11). The position target value _Pre is stored in the position teaching data 502.

Position target value generating unit 506, based on the robot model 503 converts the position target value _{P ref} of the angle command value _q ref1 _{to q Ref6} of the joints _J 1 ~J ₆ (S12).

Each position control unit 521 to 526 is, for each joint _J 1 through J ₆ angle _q 1 to q ₆ angle command value _q ref1 _{to q Ref6} the motors 211-216 to follow the of the joints _J 1 through J ₆ torque command value (angle) is calculated τ _MPref1 ~τ _MPref6 (S13). The signal indicating the angles of the joints _J 1 through J _6, may be used angle theta ₁ through? ₆ of the electric motor 211 to 216 instead of the angle _q 1 to q _6.

Each switch control unit 511 to 516, the output torque command value (angle) τ _MPref1 ~τ _MPref6 as the torque command value τ _Mref1 ~τ _Mref6 to each motor control unit 531 to 536 (S14).

Note that steps S15, S16, S17, and S18 are the same as steps S4, S5, S6, and S8, and description thereof will be omitted. By driving each of the electric motors 211 to 216 according to the above flow, it is possible to control the hand position P of the robot 200 so as to follow a desired position target value _Pre .

The force control in steps S1 to S8 and the position control in steps S11 to S18 are switched by the switching control units 511 to 516, and one of the controls is selected according to the work.

FIG. 6 is a schematic view showing a state in which the robot in the first embodiment is performing the assembling work. In the first embodiment, the robot hand 252 is moved downward by the torque base force control, and the columnar work W1 which is the first component supported (grasped) by the robot hand 252 is changed to the annular work W2 which is the second component. Assemble (fit) Perform the assembly work (fitting work).

FIG. 7 is a block diagram showing details of the force control unit 505 of FIG. FIG. 8 is a flowchart showing a method of manufacturing the assembled parts according to the first embodiment. The force control unit 505 includes a stop command confirmation unit 601, a deceleration parameter setting unit 602, and a force control calculation unit 603.

First, the force control unit 505 starts the assembly work (S21). During this assembly operation, the stop command confirmation unit 601 determines whether or not a stop command for stopping the operation of the robot 200 has been received, that is, whether or not the stop button 401 has been pressed (S22: determination process, determination step). .. The stop command may be a stop command issued via the teaching pendant 400 of FIG. 1 when the CPU 301 determines that the device needs to be stopped due to some abnormality. Further, the stop command may be written in advance in a robot program that defines the operation of the robot 200, or may be a case where the operation of the robot 200 is stopped based on the robot program.

The force control calculation unit 603 performs calculations by equations (1) and (2) based on the following variables.
_-Given position target value: _Pref
・ Given force target value: _Ref
-Given rigidity coefficient: _Kref
-Given viscosity coefficient: D _ref
-Inertia matrix included in the robot model: Λ _ref
・ Current position: P (t)
・ Force: F
-Jacobian calculated from the robot model and joint velocity q (・): J (q)
-Inertia matrix calculated by inverse dynamics calculation: M (q)
-Coriolis centrifugal matrix calculated by inverse dynamics calculation: c (q, q (・))
-Gravity vector calculated by inverse dynamics calculation: g (q)
-Matrix calculated from J (q), M (q) and current position P (t): Λ (P (t))

The equation (1) is an example of force control, and is not limited to this. When the stop command confirmation unit 601 determines that the stop command has not been received (S22: No), the force control calculation unit 603 outputs the torque command value to the switching control units 511 to 516 of FIG. 3 from the equation (1). to calculate the τ _MFref1 ~τ _MFref6. Then, the force control calculation unit 603 determines whether or not the assembly work has been completed (S23). If the assembling work is completed (S23: Yes), the process is terminated as it is, and if the assembling work is not completed (S23: No), the process returns to the process of step S22.

When it is determined that the stop command confirmation unit 601 has received the stop command to stop the operation of the robot 200 (S22: Yes), the deceleration parameter setting unit 602 attenuates the force target value _Ref when stopping the operation of the robot 200. (S24: Stop processing, stop step). Specifically, the deceleration parameter setting unit 602 _attenuates the force target value _Ref to 0 within a preset stop target time from the time _ttriger that receives the stop command. That is, the force target value F _ref becomes a time-dependent term such as F _ref = F (t) after the time t _trigger when the stop command is received. The force control calculating unit 603, from the formula (1), calculates the torque command value τ _MFref1 ~τ _MFref6 for outputting the switching control unit 511 to 516 of FIG.

There are several possible attenuation methods depending on the purpose. 9 (a) to 9 (c) are graphs showing force target values with respect to time. Specifically, FIG. 9A is a graph showing a force target value _Ref , which is linearly attenuated with respect to time from the time t _trigger when the stop command is received. FIG. 9B is a graph showing the force target value _Ref , which is attenuated stepwise with respect to the time from the time t _trigger when the stop command is received. FIG. 9 (c) is a graph showing the force target value _Ref , which is non-linearly attenuated with respect to time from the time t _trigger when the stop command is received. The force target value F _ref is a vector consisting of translational XYZ and rotation XYZ, but in FIGS. 9A to 9C, only one direction is shown for simplification.

The force target value _Ref shown in FIGS. 9 (a) to 9 (c) decreases monotonically with time. The force target value _Ref shown in FIG. 9A is linearly decreased. The force target value _Ref shown in FIG. 9B is the time t _trigger at which the stop command is received and is instantly switched to “0”, and is used when deceleration is desired to be performed faster than in FIG. 9A. For example, it can be used when the speed at the time of the stop command is slow or when the work W1 wants to stop as soon as possible without contacting the work W2. The force target value _Ref shown in FIG. 9 (c) is non-linear and attenuated, and can be used when the movement at the start of deceleration and at the completion of stop is smoother than in FIG. 9 (a). For example, it can be used when it is desired to stop the work W1 without imposing a load on it. The method of damping the force target value shown in the figure is an example, and is not limited to this. Further, the case where the force target value _Ref is attenuated to 0 has been described, but the present invention is not limited to this, and for example, the force target value _Ref may be attenuated to a value near 0.

According to the first embodiment, when the CPU 301 receives a stop command during torque base force control, the operation of the robot 200 can be stopped while reducing the load applied to the robot 200 and the works W1 and W2.

Further, in step S24, in the first embodiment, the deceleration parameter setting unit 602, the time _{t TRIGGER} after having received the stop instruction, the value _{P (t} current position the position target value _{P ref} is a control target of the force control _TRIGGER ). In other words, the deceleration parameter setting unit 602, a target position value _{P ref} for obtaining the respective torque command values τ _MFref1 ~τ _MFref6 a fixed value _{P (t triger) (P ref} = P (t triger)).

FIG. 10 is a graph of the position of the hand and the position target value with respect to time. The position target value _Pre is a vector consisting of translational XYZ and rotation XYZ, but in FIG. 10, only one direction is shown for simplification. As shown in FIG. 10, there is a position deviation between the position target value _Pre and the actual position P at the moment when the stop command is received, but the position target value _Pre is fixed immediately after receiving the stop command. By _{setting the} value P (t _trigger ), the position deviation becomes extremely small. Force control calculating unit 603 uses the changed parameter, it calculates a torque command value τ _MFref1 ~τ _MFref6.

According to the first embodiment, the force target value F _ref is attenuated, and the position target value _Pre is set to a fixed value, so that the position of the hand of the robot 200 is fixed while reducing the load applied to the robot 200 and the work. The operation of the robot 200 can be stopped in this state.

Next, in FIG. 8, the CPU 301 determines whether or not the robot 200 has stopped in step S24 (S25: stop determination process, stop determination step). Whether or not the operation of the robot 200 has stopped is determined by whether or not the current speed P (t) (.) Calculated from the current position P (t) is within a preset threshold value. That is, when the velocity P (.) Of the hand converges within the threshold value, the robot 200 has stopped.

When the CPU 301 determines that the operation of the robot 200 has stopped in step S25 (S25: Yes), the CPU 301 operates the brakes 231 to 236 and fixes the joints J _{1 to} J ₆ of the robot 200 by the brakes (S25: Yes). S26: Fixing process, fixing step). In this case, the motor control units 531 to 536 stop the power supply to the motors 211 to 216. As a result, even if an external force acts on the robot 200 or the work W1 after stopping the operation of the robot 200, the robot 200 does not move.

FIG. 11A is a graph showing the displacement of the robot hand 252 in the X direction (horizontal direction with respect to the base of the robot hand) when the stop processing is performed while maintaining the torque base force control. FIG. 11A corresponds to the experimental result of the first embodiment. Since the robot 200 is decelerated and stopped while maintaining the force control, the position deviation of the hand is small. In particular, since the position target value _Pre is fixed to the value of the current position when the stop command is received (see FIG. 10), fluctuations from the time when the hand receives the stop command are effectively suppressed.

FIG. 11B is a graph showing the displacement of the robot hand 252 in the X direction when the position control is switched to and the stop processing is performed. FIG. 11B corresponds to the experimental result of the comparative example. Since the position shift of the robot hand 252 caused by the difference of the robot 200 is large and the speed of the hand of the robot 200 is high, if the position target value _Pre is fixed at the value when the stop command is received (see FIG. 10). , It goes too far from the time when the minion receives the stop order. As a result, the position deviation becomes large after the stop command.

According to the first embodiment, when a stop command is received during force control, the robot 200 attenuates the force target value and fixes the position target value to the current position when the stop command is received. It will stop following the work W2 in contact. Therefore, the operation of the robot 200 can be stably stopped while maintaining the force control.

Further, the position deviation of the hand of the robot 200 is small, and in the case of a soft work, the work can be prevented from being destroyed, and in the case of a hard work, the robot 200 can be prevented from being overloaded and the robot 200 can be prevented from being damaged. In addition, since the workpieces do not get caught (bite), it is easy to return after stopping.

[Second Embodiment]
Next, the robot device according to the second embodiment will be described. In the second embodiment, a case where the speed target value _Pref (.) Is attenuated instead of fixing the position target value _Pref described in the first embodiment in the robot stop processing will be described. The configuration of the robot device in the second embodiment is the same as that in the first embodiment. Further, in the robot control method (manufacturing method of assembled parts) in the second embodiment, a part of the processing of the CPU 301, specifically, the processing of the deceleration parameter setting unit 602 in FIG. 7 is different from that of the first embodiment. Only the processing of the deceleration parameter setting unit 602 will be referred to.

Deceleration parameter setting unit 602 in the second embodiment, the time _{t TRIGGER} after having received the stop instruction, attenuate the force target value _{F ref} and the speed target value _{P ref} (·). In other words, the speed target value _{P ref} (·) is a time _{t TRIGGER} after having received the stop _instruction, depending on the P ref (·) = time as in P (t) (·) term.

The second embodiment is effective when the speed of the actual hand when the CPU 301 receives the stop command is faster than that of the first embodiment. The method of attenuating the force target value _Ref is the same as that of the first embodiment.

There are several possible attenuation methods depending on the purpose. 12 (a) to 12 (d) are graphs showing the speed target value _Pref (.) With respect to time. Specifically, FIG. 12 (a) is a graph showing the stop command receiving time _t speed target value attenuated in linear with respect to time from _{triger P ref} (·). 12 (b) is a graph showing the speed target value attenuated _{P ref} (·) stepwise with respect to time from the time _{t TRIGGER} which has received the stop instruction. Figure 12 (c) is a graph showing the speed target value attenuated by a non-linear _{P ref} (·) with respect to time from the time _{t TRIGGER} which has received the stop instruction. Figure 12 (d) is a graph showing the velocity target value _{P ref} obtained by attenuating (·) with respect to time while the overshoot from the time _{t TRIGGER} which has received the stop instruction. The velocity target value _Pref (.) Is a vector consisting of translational XYZ and rotation XYZ, but in FIGS. 12 (a) to 12 (d), only one direction is shown for simplification.

The speed target value _Pref (・) shown in FIGS. 12 (a) to 12 (c) decreases monotonically with time. The velocity target value _Pref (・) shown in FIG. 12A is linearly decreased. Speed target value _{P ref} (·) shown in FIG. 12 (b), which has switched instantaneously to "0" at time _{t TRIGGER} which has received the stop instruction, reduces the faster rate than FIG 12 (a) Use when you want. For example, it can be used when the speed at the time of the stop command is slow or when the work W1 wants to stop as soon as possible without contacting the work W2.

The speed target value _Pref (・) shown in FIG. 12 (c) is non-linearly attenuated, and can be used when it is desired to make the movement of the deceleration start and deceleration completion time smoother than in FIG. 12 (a). it can. For example, it can be used when it is desired to stop without applying a load. The velocity target value _Pref (・) shown in FIG. 12 (d) is faster because it is swung to the opposite side of “0” and then converged to “0” in consideration of the overshoot of the position. It is possible to decelerate and stop. The method of attenuating the speed target value shown in the figure is an example, and is not limited to this. Further, the case where the speed target value _Pref (.) Is attenuated to 0 has been described, but the present invention is not limited to this, and for example, the velocity target value may be attenuated to a value near 0.

As described above, according to the second embodiment, when the CPU 301 receives a stop command during the force control, the force target value is attenuated and the speed target value is attenuated, so that the robot 200 maintains the force control. The operation stops. Therefore, the work W1 in contact with the work W2 can stop the operation of the robot 200 following the work W2. Therefore, the operation of the robot 200 can be stopped without overloading the robot 200 and the works W1 and W2. In addition, since the workpieces do not bite each other, it is easy to return after stopping.

[Modification 1]
In the second embodiment, the case where the speed target value _Pref (・) is attenuated instead of fixing the position target value _Pref described in the first embodiment in the robot stop processing has been described, but these are combined. You may. That is, the deceleration parameter setting unit 602, the time _{t TRIGGER} after having received the stop instruction, while attenuating the force target value _{F ref,} to fix the position target value _{P ref} to a fixed value _{P (t TRIGGER),} the speed target value P Attenuate _ref (・). The method of fixing the position target value and the method of attenuating the force target value are the same as those of the first embodiment, and the method of attenuating the speed target value is the same as that of the second embodiment.

Since the three parameters of the force target value, the position target value, and the speed target value are changed at the same time, the robot 200 can be decelerated and stopped in a shorter time as compared with the first embodiment and the second embodiment.

[Third Embodiment]
Next, the robot device according to the third embodiment will be described. In the third embodiment, the deceleration parameter setting unit 602 of FIG. 7 described in the first embodiment, the damping force target value F _ref, in addition to a fixed position target value P _ref, from the force teaching data 501 of FIG. 3 Attenuates the given stiffness coefficient _Kref . That is, the rigidity coefficient K _ref of the robot 200 becomes a time-dependent term such as K _ref = K _ref (t) after the time t _trigger when the stop command is received.

The rigidity coefficient K _ref may be set higher depending on the workpiece to be assembled and the method of assembly.

In the third embodiment, the deceleration parameter setting unit 602 attenuates the rigidity coefficient K _ref of the robot 200 when the position target value _Pre is set to a fixed value in the stop processing (stop step). By attenuating the rigidity coefficient K _ref , the work W1 is softer than the first embodiment and follows the work W2, so that the operation of the robot 200 can be stopped stably.

There are several possible attenuation methods depending on the purpose. 13 (a) to 13 (b) are graphs showing the rigidity coefficient _Kref with respect to time. Specifically, FIG. 13A is a graph showing the rigidity coefficient K _ref linearly attenuated with respect to time from the time t _trigger that received the stop command. FIG. 13B is a graph showing the rigidity coefficient K _ref which is non-linearly attenuated with respect to time from the time t _trigger when the stop command is received. Although the rigidity coefficient K _ref is a matrix, only one element of the matrix is shown for simplification of explanation.

The rigidity coefficient _Kref shown in FIGS. 13 (a) and 13 (b) decreases monotonically with time. The rigidity coefficient K _ref shown in FIG. 13 (a) is linearly attenuated. The rigidity coefficient K _ref shown in FIG. 13B is used when it is non-linearly attenuated and it is desired to make the movements of the deceleration start time and the deceleration completion time smoother than when the damping is linearly attenuated. For example, it is used when it is desired to stop the operation of the robot 200 without applying a load.

The illustrated attenuation method is an example and is not limited to this. Further, the entire matrix of rigidity coefficients may be attenuated, or only the elements of the matrix related to a desired direction may be attenuated depending on the movement of the robot.

As described above, according to the third embodiment, when the CPU 301 receives a stop command during the force control, the robot 200 operates while maintaining the force control by changing the force target value, the position target value, and the rigidity coefficient. Stops. Therefore, it is possible to stop the operation of the robot 200 following the work W2 in contact with the work W1. In addition, it is possible to imitate the work more flexibly than when the rigidity coefficient is not attenuated. Therefore, the load on the robot and the work is small, and the operation of the robot can be stopped. In addition, since the workpieces do not bite each other, it is easy to return after stopping.

[Fourth Embodiment]
Next, the robot device according to the fourth embodiment will be described. In the fourth embodiment, the deceleration parameter setting unit 602 of FIG. 7 described in the second embodiment attenuates the force target value _Ref and the speed target value _Pref (・), and the force teaching data 501 of FIG. Attenuates the viscosity coefficient D _ref given by. That is, the viscosity coefficient D _ref of the robot 200 becomes a time-dependent term such as D _ref = D _ref (t) after the time t _trigger when the stop command is received.

Depending on the work to be assembled and the method of assembly, the viscosity coefficient D _ref may be set higher.

In the fourth embodiment, the deceleration parameter setting unit 602 attenuates the viscosity coefficient D _ref of the robot 200 when the speed target value _ref (.) Is attenuated in the stop processing (stop step). By attenuating the viscosity coefficient D _ref , the robot 200 can be stably stopped because it follows the work softly as compared with the second embodiment.

There are several possible attenuation methods depending on the purpose. 14 (a) to 14 (b) are graphs showing the viscosity coefficient D _ref with respect to time. Specifically, FIG. 14 (a) is a graph showing the viscosity coefficient D _ref linearly attenuated with respect to time from the time t _trigger when the stop command was received. FIG. 14B is a graph showing the viscosity coefficient D _ref , which is non-linearly attenuated with respect to time from the time t _trigger when the stop command is received. Although the viscosity coefficient D _ref is a matrix, only one element of the matrix is shown for simplicity of explanation.

The viscosity coefficient D _ref shown in FIGS. 14 (a) and 14 (b) decreases monotonically with time. The viscosity coefficient D _ref shown in FIG. 14A is linearly attenuated. The viscosity coefficient D _ref shown in FIG. 14B is non-linearly attenuated, and is used when it is desired to make the movements of the deceleration start time and deceleration completion time smoother than when the deceleration start time and deceleration completion time are attenuated linearly. For example, it is used when it is desired to stop the operation of the robot 200 without applying a load.

The illustrated attenuation method is an example and is not limited to this. Further, the entire matrix of viscosity coefficients may be attenuated, or only the elements of the matrix related to the desired direction may be attenuated depending on the movement of the robot.

As described above, according to the fourth embodiment, when the CPU 301 receives a stop command during the force control, the robot 200 operates while maintaining the force control by changing the force target value, the speed target value, and the viscosity coefficient. Stops. Therefore, it is possible to stop the operation of the robot 200 following the work W2 in contact with the work W1. In addition, it is possible to imitate the work more flexibly than when the viscosity coefficient is not attenuated. Therefore, the load on the robot and the work is small, and the operation of the robot can be stopped. In addition, since the workpieces do not bite each other, it is easy to return after stopping.

[Modification 2]
In the modified example 2, the deceleration parameter setting unit 602 of FIG. 7 gives the force teaching data 501 of FIG. 3 in addition to the damping of the force target value, the fixation of the position target value, and the attenuation of the speed target value. The rigidity coefficient and the viscosity coefficient are attenuated. The method of attenuating the rigidity coefficient is the same as that of the third embodiment, and the method of attenuating the viscosity coefficient is the same as that of the fourth embodiment.

When the initial values of the rigidity coefficient and the viscosity coefficient are given higher, by attenuating the rigidity coefficient and the viscosity coefficient, the robot 200 is softer than the first modification and follows the work, so that it is stable. The operation of the robot can be stopped.

[Fifth Embodiment]
Next, the robot device according to the fifth embodiment will be described. FIG. 15 is a control block diagram showing a control system of the robot device according to the fifth embodiment. In the fifth embodiment, the work contact detection unit 604 is provided between the stop command confirmation unit 601 and the deceleration parameter setting unit 602 shown in FIG. 7 of the first embodiment.

The work contact detection unit 604 obtains a force acting on the hand by using a sensor that generates a signal corresponding to the force acting on the hand. As described in the first embodiment, the sensors that generate signals according to the force acting on the hand are a plurality of torque sensors 541 to 546 (FIG. 3) that generate signals corresponding to the torques of each joint. .. That is, the force detection unit 504 uses the torques τ _{1 to} τ ₆ acquired from the torque sensors 541 to 546 and the angles q _{1 to} q ₆ acquired from the angle sensors 551 to 556 to the current position of the hand of the robot 200. P (t) and the hand force F of the robot 200 at that time are calculated. The force detection unit 504 may calculate the hand force F of the robot 200 by using a force sensor (not shown) attached to the hand.

The work contact detection unit 604 compares the calculated hand force F with a predetermined threshold value stored in the storage unit in advance. When the hand force F exceeds a predetermined threshold value, the process proceeds to the deceleration parameter setting unit 602, and as shown in the first to fourth embodiments, the operation of the robot 200 is stopped while the force is controlled. That is, determine the respective values and respective torque command values τ _Mref1 ~τ _Mref6 for each motor 211 to 216 such that a force deviation between the target force value is reduced of a plurality of the torque sensor 541 to 546. Here, torque command value τ _Mref1 ~τ _Mref6 is a torque command value τ _MFref1 ~τ _MFref6 described in the first embodiment. As described above, in the fifth embodiment, the stop processing described in the first to fourth embodiments is executed when the force F acting on the hand exceeds a predetermined threshold value set in advance. In the fifth embodiment, even when the hand force F is at a predetermined threshold value, the robot proceeds to the deceleration parameter setting unit 602, and as shown in the first to fourth embodiments, the robot 200 remains in force control. Stop the operation of.

When the calculated hand force F is less than a predetermined threshold value, that is, when contact is not detected, the work contact detection unit 604 switches from force control to position control in the switching control units 511 to 516 to operate the robot 200. Make a stop. That is, the torque command values τ _{Mref1 to} τ _Mref6 for each of the motors 211 to ₂₁₆ are obtained so that the respective values of the plurality of angle sensors 551 to 556 become predetermined values. Here, torque command value τ _Mref1 ~τ _Mref6 is a torque command value τ _MPref1 ~τ _MPref6 described in the first embodiment. As described above, when the force F acting on the hand is less than a predetermined threshold value, the operation of the robot 200 is stopped by the position control that brings the respective values of the plurality of angle sensors 551 to 556 closer to the preset predetermined values. When the force F is a predetermined threshold value, the operation of the robot 200 is stopped by the force control, but the operation of the robot 200 may be stopped by the position control.

As described above, if an attempt is made to stop while controlling the force before contacting the work, it may not be possible to stop until the work or the like is contacted because there is no work to be imitated. When the work is not in contact with the work, the robot 200 can be stopped quickly by switching to the position control and stopping the robot 200.

FIG. 16 is a graph showing the change in the hand force F with respect to the time when the work is in contact. The hand force F is a vector consisting of translational XYZ and rotation XYZ, but for the sake of simplicity, only one direction is shown.

Work contact detection is performed by determining the hand force F according to a threshold value set in advance for the work. Note that the contact detection based on the threshold value shown in FIG. 16 is an example, and the present invention is not limited to this. For example, the threshold value may be determined based on the rate of change in hand force.

As described above, according to the fifth embodiment, when the CPU 301 receives a stop command during the force control and it is determined that the CPU 301 is not in contact with the work, the force control is used to switch to the position control and stop. The robot can be stopped faster than when it is stopped.

The present invention is not limited to the embodiments described above, and many modifications can be made within the technical idea of the present invention. In addition, the effects described in the embodiments of the present invention merely list the most preferable effects arising from the present invention, and the effects according to the present invention are not limited to those described in the embodiments of the present invention.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Further, in the above-described embodiment, the case where the robot 200 (robot arm 251) is vertically articulated has been described, but the present invention is not limited to this. The robot may be various robots such as a horizontal articulated robot, a parallel link robot, and a Cartesian robot. That is, the drive direction of the joint is not limited to the drive in the rotational direction, but also includes the drive in the linear motion direction (expansion and contraction drive). Further, although the case where the joint is driven by the electric motor has been described, the present invention is not limited to this, and for example, an artificial muscle or the like may be used. Further, in the above-described embodiment, the case where the robot has six joints has been described, but the number of joints is not limited to this.

Further, in the above-described embodiment, the case where the force detection unit is composed of a plurality of torque sensors has been described, but the present invention is not limited to this, and even if the force sensor is provided at the tip of the robot arm. Good.

100 ... Robot device, 200 ... Robot, 211-216 ... Electric motor (motor), 251 ... Robot arm, 252 ... Robot hand, 300 ... Robot control device (control unit)

Claims (17)

A motor, a sensor that detects the force acting on a predetermined part,
A command value is output to the motor so that the force acting on the predetermined portion becomes the force target value.
Control the drive of the motor based on the command value,
When receiving a stop command, the predetermined site is a feature in that the stay in position when receiving the stop command, and and a control unit that performs a stop process to decrease little of the force target value Robot device to do. The control unit
Wherein when receiving a stop command, the force was set so that the target value is decline, and sets the position of said predetermined site when receiving the stop command to the position command value,
Claims, characterized in that for outputting the command value force detected by the sensor becomes the force target value set to decline, and the the position target value position is set in the predetermined site The robot device according to 1. In the stop process, the control unit outputs the command value so that the deviation between the position of the predetermined portion and the position target value becomes small based on the sensor that detects the position of the predetermined portion. The robot device according to claim 2. The robot device according to claim 3, wherein the sensor for detecting the position of the predetermined portion is an encoder. The robot device according to any one of claims 1 to 4, wherein the control unit reduces the rigidity coefficient used for obtaining the command value in the stop processing. Wherein the control unit obtains the speed of the predetermined portion to obtain a signal from a sensor for detecting the position of said predetermined part, said at stop process, the predetermined said command value so that the speed of the site to decline The robot device according to any one of claims 1 to 5, wherein the robot device is characterized by outputting. Further having a sensor for detecting the speed of the predetermined part,
Wherein the control unit, wherein the acquired signals from the sensor for detecting the speed of the predetermined part, in the stop process, the rate of said predetermined site and outputs the command value as to decline Item 2. The robot device according to any one of Items 1 to 5. Wherein, in the stop process, the robot apparatus according to claim 6 or 7, characterized in that to decrease little of the velocity target value. Wherein the control unit is configured in the stop processing, the robot apparatus according to claim 8, characterized in that to decrease less of the viscosity coefficient used for calculating the command value. It has a brake that brakes the motor
The robot device according to any one of claims 1 to 9, wherein the control unit fixes a joint of the robot device by the brake after stopping by the stop process. The robot device according to any one of claims 1 to 9, wherein the sensor that detects the force acting on the predetermined portion is a sensor that detects the torque of the joint. The robot device according to any one of claims 1 to 11, further comprising an input device for transmitting the stop command in the control unit. When the control unit receives the stop command, the control unit executes the stop process when the force acting on the predetermined portion exceeds a preset predetermined threshold value, and the force acting on the predetermined portion is said. The robot device according to claim 1, wherein when the value is less than a predetermined threshold value, the robot device is stopped by bringing the position of the predetermined portion closer to a predetermined value set in advance. A control method for a robot device having a motor, a sensor for detecting a force acting on a predetermined part, and a control unit.
The control unit
A command value is output to the motor so that the force acting on the predetermined portion becomes the force target value.
Control the drive of the motor based on the command value,
When receiving the stop command, control wherein said predetermined site is the remains position when receiving the stop command, and executes the stopping process to decrease little of the force target value, it is characterized. A program for causing a computer to execute the control method according to claim 14. A computer-readable recording medium on which the program according to claim 15 is recorded. A method for manufacturing an article, which comprises manufacturing the article using the robot device according to any one of claims 1 to 13.

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