JP7327991B2 - Control method, control program, recording medium, robot system, article manufacturing method, and input device - Google Patents

Description

The present invention relates to a robotic device.

Single-axis robots and multi-joint robots have different axis configurations, but they share the common problem that, for example, the transmission mechanism has a control error. In this specification, single-axis robots and multi-joint robots are simply collectively referred to as "robot apparatus" and "robot" without distinguishing between them.

Also, the robot apparatus has joints that movably connect the links, and there are different types of these joints: rotary joints and linear joints. The configurations and effects dealt with in this specification are also common to these. Therefore, the angle of the revolute joint and the expansion/contraction position of the prismatic joint are not distinguished from each other, and both mean the positional relationship of the link that connects them. .

In addition, notations such as "joint velocity", "joint acceleration", and "joint jerk" are also used for time differentiation of the joint positions. Similarly, the torque of a rotary joint and the thrust (driving force) of a linear motion joint may be referred to as the "thrust of a joint" without distinguishing between them. Link parameters as joint control conditions include information such as the length, weight, center of gravity position, second moment of inertia, etc. of links as loads supported by joints.

In recent years, partly because of the declining birthrate, aging population, and labor shortage, the number of cases where articles are manufactured on a production line using a robot device is increasing. Such production lines are required to be able to perform precise and high-speed machining and assembly like human hands, and to carry out work at high speed.

On the other hand, in robot devices used in this type of production system, a reduction gear, ball screw, or the like is installed between the load and the power source for the purpose of increasing the thrust of the power source and converting rotary motion into linear motion. A transmission mechanism is often arranged. However, this type of transmission mechanism has factors that impede the precision of robot motion. For example, the factors include torsion, angular error due to meshing of reduction gear teeth, backlash, friction, minute vibration of small parts, angular error due to ball screw deformation, screw resonance, and lost motion.

In response to the reduction in precision caused by such factors, the robot device improves the assembly precision by directly measuring the acting force applied to the hand of the robot. In order to measure the force acting on the hand of the robot, a force sensor may be mounted on the hand of the robot. However, when not only measuring the acting force but also dynamically controlling it, other joints, frames, cables, etc. are interposed between the joints that drive the robot and the sensors on the hands, which slows down the reaction and shortens the work time. I have a growing problem.

Also known is a configuration in which a sensor that directly detects thrust applied to joints connecting links of a robot is arranged (for example, Patent Document 1 below). The tip of the robot arm, that is, the force acting on the workpiece can be detected from the thrust acting on each joint of the robot arm, and high-response work can be achieved by direct control of the joint torque. In robots, there is also known a control switching method in which a position control mode is used when moving in a work space and a force control mode is used to control the acting force in the vicinity of a workpiece.

On the other hand, in a production line using this type of robot device, a stop signal for urgently stopping the robot device may be transmitted from a plant host control device or a work terminal such as a teaching pendant. When performing such an emergency stop, it is difficult to stop the robot apparatus immediately after the stop signal, and a special stop control mode may be executed. For example, there is known a control method of decelerating and stopping along a teaching trajectory when making an emergency stop during position control (Patent Document 2 below).

JP-A-10-286789 Japanese Patent Application Laid-Open No. 01-119809

For example, in the technique described in Patent Literature 2, when an emergency stop is made during position control, the position control mode is used to decelerate and stop along the teaching trajectory. However, when the stop control mode is forcibly switched to the position control in this manner, a problem may occur. For example, if an emergency stop occurs at a position on the teaching trajectory programmed to work while contacting the workpiece in the force control mode, the original control in the force control mode will not work. If the work is touched while only the position control mode is activated, there is a possibility that the robot's full force will be applied to the work due to the actions of the motor control integral/disturbance observer, etc., resulting in damage to the work and the robot itself. There is

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to stop a robot device without damaging a workpiece or the robot device in stop control for stopping the robot device in response to a stop signal.

A first aspect of the present invention is a robot having a predetermined part, a first sensor that acquires information about the position of the predetermined part, a second sensor that acquires information about the force applied to the predetermined part, and a control device. and a first mode using position control based on the first sensor to stop the robot when the controller stops the robot ; A second mode is a control method characterized in that force control based on the second sensor is used to stop the robot and allow the user to select either the first mode or the second mode. .
A second aspect of the present invention includes a robot having a predetermined part, a first sensor that acquires information about the position of the predetermined part, a second sensor that acquires information about the force applied to the predetermined part, and a control device. and wherein, when the controller stops the robot , a first mode stops the robot using position control based on the first sensor , and a second mode uses force control based on the second sensor to stop the robot and allow the user to select either the first mode or the second mode .
A third aspect of the present invention includes a robot having a predetermined part, a first sensor that acquires information about the position of the predetermined part, and a second sensor that obtains information about the force applied to the predetermined part. an input device for commanding a robot system, wherein when the input device stops the robot , a first mode stops the robot using position control based on the first sensor ; A second mode is characterized in that the robot is stopped using force control based on the second sensor, and the first mode or the second mode is displayed on a display so as to be selectable by the user. It is a device.
A fourth aspect of the present invention includes a robot having a predetermined part, a first sensor that acquires information about the position of the predetermined part, and a second sensor that obtains information about the force applied to the predetermined part. A method for controlling an input device for issuing a command to a robot system, wherein when the robot is to be stopped, a first mode uses position control based on the first sensor to stop the robot, and a second mode is to stop the robot using the position control based on the first sensor. A control method characterized by stopping the robot using force control based on a second sensor, and displaying the first mode or the second mode on a display so as to be selectable by the user.

According to the above configuration, when the stop signal is input (received) during the position control mode, the force control mode is enabled and the stop control mode is executed. This makes it possible, for example, to take advantage of impedance control in force control mode. Therefore, in stop control for stopping the robot device in response to a stop signal, the robot device can be stopped without damaging the workpiece or the robot.

It is an explanatory view showing a schematic structure of a robot device. It is an explanatory view showing a schematic structure of a robot control device. FIG. 4 is an explanatory diagram of a control block of a robot arm; FIG. 4 is a flow chart diagram showing a control procedure for force-controlling the robot in the embodiment of the present invention; FIG. 4 is a flow chart diagram showing a control procedure for controlling the position of the robot in the embodiment of the present invention; FIG. 4 is a flow chart diagram showing robot control according to the embodiment of the present invention; (A) and (B) are explanatory diagrams showing robot motions according to the embodiment of the present invention. FIG. 4 is an explanatory diagram showing robot motion according to the embodiment of the present invention; FIG. 4 is an explanatory diagram showing robot motion according to the embodiment of the present invention; (A) and (B) are explanatory diagrams showing robot motions according to the embodiment of the present invention. (A) and (B) are explanatory diagrams showing an example of a screen of the external input device. FIG. 4 is a flow chart diagram showing control during automatic operation of the robot apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The configuration shown below is merely an example, and, for example, details of the configuration can be changed as appropriate by those skilled in the art without departing from the spirit of the present invention. Further, the numerical values taken up in this embodiment are reference numerical values and do not limit the present invention.

As shown in FIG. 1, the robot apparatus 100 of this embodiment includes a robot arm 200 (robot apparatus) as an articulated robot, a robot controller 300 that controls the robot arm 200, and an external input device 400. .

The external input device 400 is a teaching device that transmits data on a plurality of teaching points to the robot control device 300, and is used by the operator to specify the motion of the robot arm 200. FIG. The external input device 400 is sometimes called a "teaching pendant". Further, the robot arm 200, the robot controller 300, and the external input device 400 constitute a robot system together with a host controller 420 connected via a network or the like in a plant such as a production line in which these are arranged. This robot system is used to manufacture articles such as industrial products and parts thereof by having the robot arm 200 perform assembly and processing operations on the work W, for example.

The robot arm 200 is a six-joint robot in this embodiment. The robot arm 200 has a plurality (six) of servomotors 201 to 206 that rotationally drive the joints J1 to J6 about the joint axes A1 to A6, respectively.

In this embodiment, the robot arm 200 of FIG. 1 is a multi-joint robot arm having six joints, and includes joints J1 to J6 and links connected by these joints. Joints J1-J6 are driven by servo motors 201-206, respectively. A plurality (six) of servomotors 201 to 206 rotationally drive the joints J1 to J6 about the joint axes A1 to A6, respectively.

The robot arm 200 can orient its hand (the tip of the robot arm 200) in any three-dimensional position and any posture in any three directions within its movable range. In general, the position and orientation of the robot arm 200 can be represented by a properly set three-dimensional coordinate system. In FIG. 1, T _o indicates a coordinate system fixed to the base of the robot arm 200 , and T _e indicates a coordinate system fixed to the hand of the robot arm 200 . In this embodiment, it is assumed that the joints J1 to J6 are rotary joints, but the following description also applies to a configuration using prismatic joints.

A robot hand 252 is attached to the tip of the robot arm 200 as a gripping device. The robot arm 200 can be used, for example, to grip a work W with a robot hand 252 as a gripping device, fit it to an object, or press it. By causing the robot arm 200 to perform such work, it is possible to assemble the workpiece gripped by the robot hand 252 as a gripping device and the object, and manufacture an article such as an industrial product or its parts.

In a revolute joint configuration such as the present embodiment, "joint position" means the angle of the joint. Also, the joints J1 to J6 may be prismatic joints, in which case the "position of the joint" is the position of the prismatic joint, and the "torque of the joint" is the force applied to the prismatic joint. Further, the temporal differentiation of joint position information can be handled by the concepts of "joint velocity", "joint acceleration", and "joint jerk".

In this embodiment, each of the servo motors 201-206 includes electric motors 211-216 and sensor units 221-226 connected to the electric motors 211-216 (see FIG. 3). Each of the sensor units 221 to 226 includes a position sensor (angle sensor) for detecting joint angles and a torque sensor (force sensor) for detecting joint torque. Each of the servomotors 201-206 includes a speed reducer (not shown) and is coupled to a drive system that drives the joints J1-J6 via belts, bearings, and the like. The drive source for each joint is not limited to the servomotors 201 to 206, and may be, for example, an artificial muscle.

Further, the robot arm 200 has a servo control section 230 as a drive control section for driving and controlling the electric motors 211-216 of the servo motors 201-206. Based on the input torque command value, the servo control unit 230 outputs a current command to each electric motor 211 to 216 so that the torque of each joint J1 to J6 follows the command torque, and operates each electric motor 211 to 216. to control. In this embodiment, the servo control unit 230 is configured by one control device, but servo control units corresponding to the electric motors 211 to 216 may be provided.

FIG. 2 shows the functional block configuration of the robot control device 300. As shown in FIG. The robot control device 300 includes a CPU 301 as a control unit, a ROM 302, a RAM 303, a HDD (hard disk drive) 304, a recording disk drive (recording medium) 305 as storage units, 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 . For example, the ROM 302 stores a program 330 that is read by the CPU 301 (computer) to perform control described later. The RAM 303 constitutes a storage unit that can temporarily store results of arithmetic processing by the CPU 301 and the like. The HDD 304 is used to store arithmetic processing results, various data (including best command trajectory and best evaluation value), and the like.

An external input device 400 (teaching pendant) is connected to the interface 306 , and the CPU 301 receives teaching point data input from the external input device 400 via the interface 306 and the bus 310 .

The servo control unit 230 is connected to the interface 309, and the CPU 301 outputs target torque data for 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 can be displayed on the monitor 321. FIG. An external storage device 322 such as a rewritable nonvolatile memory or an external HDD can be connected to the interface 308 . The recording disk drive 305 can read various data and programs recorded on a recording disk (recording medium) 331 . A recording disk 331, for example, can be used as a computer-readable recording medium on which the program according to the present invention is recorded. However, the computer-readable recording medium in which the program according to the present invention is recorded may be, for example, a non-volatile memory such as the external storage device 322 or an external HDD.

FIG. 3 shows in detail a control system for controlling each joint of the robot arm 200. As shown in FIG. A control block indicated by 100 in FIG. 3 corresponds to the control system of the robot apparatus 100 described above. The electric motors 211 to 216 of the joints of the robot arm 200 are connected to the sensor units 221 to 226 composed of position sensors 551 to 556 and torque sensors 541 to 546, respectively. The information detected by the position sensors 551 to 556 and the torque sensors 541 to 546, that is, the angle information (q _{1 .} . . q ₆ ) and torque information (τ _{1 .} . . τ ₆ ) of each joint axis are fed back to the corresponding control blocks. be.

The robot device 100 also includes a servo control unit 230 (FIG. 1). The servo control unit 230 includes motor control units 531 to 536 that issue operation commands to the electric motors 211 to 216, position control units 521 to 526 that perform position control, and switching control units 511 to 516 that perform switching control with force control. Prepare.

In addition, the robot control device 300 inputs the detected force (F) value to the position target value generation unit 506 that issues a drive command to the servo control unit 230, the force control unit 505, and the force control unit. A force detection unit 504 is provided.

A robot model 503 described by various parameters of the robot arm 200 is stored in, for example, the external storage device 322 in FIG. The robot control device 300 acquires the robot arm information of this robot model 503 and controls the robot arm 200 based on the necessary control rules. The external input device 400 (teaching pendant) constitutes an input unit for commanding force teaching data 501 (F _ref ) and position teaching data 502 (P _ref ) for inputting a target motion to the robot control device 300 . .

FIG. 4 shows the force control mode flow for controlling the motion of the robot arm 200 . The illustrated control procedure is stored in the ROM 302 or the external storage device 322 as a control program for the CPU 301 .

In step S1 of FIG. 4, the operator (operator, manager, user) inputs a position target value and a force target value, for example, prior to actual robot operation. The position target value and force target value input here are stored as force teaching data 501 and position teaching data 502 as position command values and force command values. This position target value includes position data for switching from the moving position control mode to the force control mode, for example, when the robot arm 200 starts to come into contact with the workpiece during normal operation. In this force control mode, the external input device 400 outputs force teaching data 501 to the force control section 505 (FIG. 3).

In step S2, the force control unit 505 controls the motor torque command value (force) based on the robot model 503 so that the force applied to the hand of the robot arm 200 follows the force teaching data 501 (F _ref ) as the force target value. is calculated (Fig. 3). The robot model 503 used at this time is stored in, for example, the external storage device 322 as described above.

In step S3, the switching control units 511 to 516 output motor torque command values τ _{MFref1 . . . 6} to each joint as force command values. In step S4, the motor control units 531 to 536 use the position information θ _{1 .} (Fig. 3).

In step S5, the electric motors 211 to 216 generate joint torques τ _{1 . . . 6} by being energized. Then, in step S6, in the sensor units 221 to 226 mounted on each joint, the position sensors 551 to 556 detect the position information θ _{1 . . . 6} , and the torque sensors 541 to 546 detect the joint torque τ _{1 .} (Fig. 3). The detected position information θ _{1 . . . 6} (joint angles) and joint torque τ ₁ .

In step S7, the force detection unit 504 can convert the joint torques τ _{1 . .} . A motor angle may be used instead of the joint angle to obtain the force F applied to the end of the robot arm 200 . In that case, for example, position sensors are used to detect the angles of the drive shafts of the electric motors 211 to 216 on the input side of the reduction gears of the joints (not shown). The force _{control unit 505 outputs motor torque command values τ MFref1 .} These command values are output as motor torque command values τ _{Mref1 . . . 6} via switching control units 511-516.

In step S8, it is determined whether or not the drive in the force control mode has ended using a predetermined determination condition, and if not, the drive control of steps S2 to S7 is repeated. ₆ (joint angles) obtained by the force detection unit 504 from the position sensors 551 to 556, for example. Alternatively, it is further determined whether or not the actual value of the force F applied to the hand of the robot arm 200 (the reaction force from the workpiece) has reached a predetermined dynamic state corresponding to the assembly completion state.

As described above, in the force control mode, it is possible to control the force applied to the hand of the robot arm so as to conform to the desired force target value. Although details are not shown, the force control process performed by the force control unit 505 may include so-called impedance control.

This impedance control is elastic control that imparts elasticity to the response motion of the joint, for example, control that drives the hand position as if it were restrained by springs and dampers. This impedance control uses a spring constant K and a damping constant C as control parameters, and the physical characteristics (elasticity and damping characteristics) of the joint in question are set to these constants (K, C). ) is executed so that For example, in FIG. 3, the order of connecting the electric motors 211 to 216 and the sensor units 221 to 226 is merely an example, and force control can be performed not only in this connection order but also in other connection orders.

FIG. 5 shows the flow of the position control mode that controls the motion of the robot arm 200. As shown in FIG. The illustrated control procedure is stored in the ROM 302 or the external storage device 322 as a control program for the CPU 301 .

At step S11 in FIG. 5, the operator inputs a position target value, for example, prior to the actual robot operation. The input target position value is stored in the position teaching data 502 as the position command value P _ref . This position target value is represented by global coordinates in the work space of a reference position placed at the tip of the robot arm 200, for example. Therefore, in step S12, the position target value generator 506 converts the position target values into joint position command values q _{ref1 . . . 6} based on the robot model 503 . At this time, the joint position (joint angle) of each joint that realizes the reference position arranged at the tip of the arm or the like is obtained by inverse kinematics calculation.

In step S13, the position control units 521 to 526 generate motor torque command values τ _{MPref1 . . . 6} so that the joint angles q ₁ . At this time, as described above, the motor angle detected on the input side of the speed reducer (not shown) may be used instead of the joint angle as the signal indicating the joint angle. In step S14, the switching control units 511 to 516 output the command values generated by the position control by the position control units 521 to 526 to the motor control units 531 to 536 of the respective joints as the motor torque command values τ _MFref1 .

Thereafter, the processes of steps S15, S16, S17 and S18 in FIG. 5 are equivalent to the processes of steps S4, S5, S6 and S8 in FIG. 4, respectively. The determination of the end of driving in the position control mode in S18 is performed, for example, by detecting whether the workpiece gripped by the robot hand 252 has reached a predetermined assembly position. As described above, it is possible to control the hand position of the robot arm to a desired target value in the position control mode.

The force control mode in steps S1 to S8 in FIG. 4 and the position control mode in steps S11 to S18 in FIG. one is selected. Alternatively, the switching control units 511 to 516 may be configured to combine the force control mode and the position control mode with appropriate weighting. That is, the switching control units 511 to 516 combine motor torque command values τ _{MFref1 . . . 6} by force control and motor torque command values τ _{MPref1 . 6} .

Next, with reference to FIGS. 11A, 11B and 12, an example of a user interface that can be implemented by the external input device 400 will be described. The external input device 400 that implements a user interface (GUI) described below constitutes a user interface device (means) that receives user operations related to robot control in the robot system of this embodiment. The external input device 400 may be configured as a so-called teaching pendant, or may be a control terminal using a PC or the like.

11A and 11B show an example of the display screen 700 of the display device provided in the external input device 400. FIG. This display screen 700 is, for example, a GUI configuration, and metaphors such as illustrated buttons and menus can be configured to be enabled or selected by clicking or tapping with a pointing device such as a mouse or a finger, for example. The robot arm control mode is selected by button 701 . Here, two buttons, a manual button and an automatic button, are arranged as the button 701, but a single button may be used as long as the button toggles between automatic and manual settings. If the button 701 has a two-button structure as shown in the drawing, a so-called radio button operation method is adopted, and automatic/manual setting is exclusively selected. For example, pressing the auto button switches the mode from manual to auto, disabling the manual mode. Of the automatic/manual modes, the manual mode is selected when teaching the robot arm 200 or performing work in close proximity to the robot arm 200 . This manual mode is essential when the external input device 400 is a teaching pendant or the like, but may not be provided if the external input device 400 is a control terminal used for robot programming. Further, the automatic mode is a mode for executing a preset motion, and is used when the robot arm 200 reproduces a robot motion that has already been taught.

In the example of FIG. 11, a stop button 702 is provided on the display screen 700 . This stop button 702 is used, for example, to forcibly stop the robot program being executed.

In the GUI of FIG. 11, a stop control mode (stop mode) for stopping the robot arm 200 in accordance with the operation of the stop button 702 or the like can be selected using a menu 706 . Menu 706 can be configured as a drop-down menu, for example, as shown in FIG. 11B. In this example, the stop control mode selectable by the menu 706 is, for example, one of three types of stop control modes (stop modes): shortest, trajectory following, and shock mitigation. Also, the default stop control mode can be a shortest stop mode that stops the robot arm 200 in the shortest distance or the shortest time, for example.

In addition to setting from the menu 706, it is conceivable to describe the stop mode in the operation program and individually set the stop mode in an arbitrary operation section. For example, in this method, when the stop mode is described in the operation program, the stop mode setting of the operation program has priority over the setting of the external input device 400 .

The operating program may be edited directly from the external input device 400. FIG. A button 707 is for shifting the display screen 700 to an edit mode (not shown). A button 708 is used to execute a loaded or selected motion program to move the robot arm 200 .

Furthermore, indicators 703 and 704 and a status screen 705 are arranged on the GUI screen of FIG. Indicators 703 and 704 are used to display the servo status and operating speed (in %), respectively. Various statuses represented by character strings such as log information, error messages, and warning messages can be displayed using the status screen 705 having a configuration such as a text box.

FIG. 12 shows an example of stop control performed according to the stop control mode (stop mode) selected on the display screen 700 of FIG. 11 when the robot arm 200 is operated based on the operation program.

To automatically operate the robot arm 200, for example, the automatic mode is designated by the button 701 of the user interface shown in FIG. 11, and the control mode of the robot arm is set to the automatic mode. Also, when an appropriate start button (not shown) provided on the user interface is pressed (S41: FIG. 12), the CPU 301 reads various programs such as an operation program (S42) and shifts the robot to the start state. After that, in the activation state, by operating the button 708, for example, the button 708 (execution button) of the user interface shown in FIG. 11 (S43), the robot arm 200 starts automatic operation according to the set robot program.

In this automatic operation, the CPU 301 generates a trajectory from one teaching point to the next teaching point (S44) and causes the robot arm 200 to execute it. In the automatic operation of one trajectory from this teaching point to the next teaching point, the trajectory is calculated from the current value information and target value information of the electric motors 211-216. If no stop signal is input, command values are output to the electric motors 211 to 216 (S46), and the operation point is interpolated based on the teaching trajectory until the target command value is reached (S47). In addition, in the automatic operation loop of one track, it is determined at any time whether a stop signal has been input from the stop button 702 of the user interface of FIG. 11 (or the host controller 420 of the plant: FIG. stop signal detection step).

When the stop signal is input (S45), the CPU 301 determines the current stop mode (stop control mode) previously set using the external input device 400 in steps S48, S52, and S57, and determines the current stop mode (stop control mode) according to the stop mode. Perform stop processing. When the stop mode is the "shortest" mode (S48), a command value is output to decelerate and stop each of the electric motors 211 to 216 at a predetermined maximum deceleration determined for each joint (S49). This maximum deceleration is, for example, a value mechanically determined according to the structure, specifications, etc. of the mechanism employed for the joint. In a robot apparatus, such mechanical limit values are usually set not only for deceleration (velocity) but also for acceleration, jerk, and the like. Therefore, in the shortest stop of this "shortest" mode, control is performed so that not only deceleration (speed) but also other predetermined constraint conditions determined on the mechanism are not exceeded. After that, when the robot arm 200 stops (S50), the brake (not shown) arranged at the joint is brought into the brake lock state (S51), the arm is made to hold the position and posture at the time of stopping, and the process ends.

In this "shortest" stop mode (S48-S51), it is possible to stop in the shortest time or the shortest distance. However, since overshoot occurs due to the inertia of the robot arm 200 and the trajectory of the arm is not considered, the robot arm 200 may come out of the taught trajectory and interfere with surrounding workpieces and devices. There is

In addition, when the stop mode is the "trajectory following" mode (S52), when the stopping process is performed from the current value, the change in acceleration/deceleration is restricted to a certain value or less, and the previously taught teaching trajectory can be followed. is reset to the target value (S53), and the robot arm 200 is stopped. Even in this stop mode, the output of command values to the electric motors 211 to 216 (S54) and the brake lock (S56) after stopping the arm (S55) are the same as described above. In the "trajectory following" mode, control is performed to maintain the trajectory during teaching, so interference with the workpiece or other objects will not occur if the surrounding conditions are the same as during teaching. However, stopping times and distances may be longer compared to "shortest" mode.

Further, the stop control when the stop control mode is the "impact mitigation" mode is executed as shown in FIG. 6, for example. FIG. 6 shows the control procedure for stopping the robot arm in the "shock mitigation" mode. The illustrated control procedure is stored in the ROM 302 or the external storage device 322 as a control program for the CPU 301 .

In FIG. 6, each step (process) of force control in steps S2 to S8 and position control in steps S11 to S18 are the same as those described in FIGS. 4 and 5, respectively, so detailed description is omitted below. do. In the "impact relaxation" mode of this embodiment, when a stop signal is input during position control, for example, during one trajectory from a teaching point to a teaching point while moving toward a workpiece, force control is performed during stop control. to enable impact mitigation.

In step S19 of FIG. 6, it is determined whether or not a stop signal has been input by the stop button 702 of the user interface 700 of FIG. 11 (or the host controller 420 of the plant) (stop signal detection step). A stop button 702 is operated for an emergency stop by a sudden event. In addition, when the host controller 420 (FIG. 1) generates the stop signal, the host controller generates it based on the error status signal of another device arranged in the plant, or from the error status of the other device. A stop signal may be generated directly. Also, the stop signal may be generated due to a status abnormality inside the robot control device 300 or the robot arm 200, exceeding a set limit, or the like. If no stop signal is generated in step S19, the robot control loop in the position control mode of steps S13 to S18 proceeds.

If the stop signal is input in step S19, the process advances to step S20 to determine whether the robot arm 200 or robot hand 252 is in contact with another device/work. For this determination, for example, a force sensor (not shown) that detects the force F applied to the tip of the robot arm 200 can be used. Contact may also be detected by determining whether the threshold is exceeded based on the current of the motor, the hand of the robot, or the value of a force sensor installed on the side of the workpiece or other device.

If no contact is detected in step S20, the robot arm 200 is controlled with the force control (S2-S8) enabled. As a result, the robot arm 200 is controlled to approach the target position (set in S11) of the end point of the current trajectory by force control. On the other hand, when contact is detected in step S20, the contact position P of contact is stored (S21). Here, the suffix n of the contact position Pn is the number of contact times, and is incremented each time contact is made using a register of the CPU 301 or a counter arranged on the RAM 303 .

In step S22, it is determined whether or not the contact of the robot arm 200 is the first time. When the number of times of contact is 1 (n=1), the spring constant K of the force control section 505 is increased in step S23. As a result, even if the hand position deviates from the position target value, the hand can be stopped without generating unnecessary force.

Furthermore, when the number of times of contact is 2 or more (n≧2), control is performed to stop at the center of the contact point (contact position) in step S24. The position target value set at the center (middle) of the contact point (contact position) is, for example, the center of gravity of the contact position Pn (n=1, 2, . . . k). Thus, the center of gravity of the contact position Pn (n=1, 2, . Therefore, it can be considered that the probability of interference with other objects at that position is extremely low. The coordinates of the center of gravity of the contact position Pn (n=1, 2, . . . k) can be obtained by the following equation, for example.

In step S25, the spring constant raised at the first contact is returned to the original value so that the robot arm 200 is stopped at the target position set at the center (middle) of the contact point as described above. By restoring the spring constant, the function of approaching the position target value of the impedance control in the force control mode works.

The operation of the robot arm 200 in the impact relaxation mode of this embodiment as described above will be described in detail below with reference to FIGS. 7 to 10. FIG.

FIG. 7A shows how the robot device 100 inserts the workpiece W1 gripped by the hand into the concave portion of the workpiece W2. In this figure, the trajectory of the workpiece for inserting the workpiece W1 into the recess of the workpiece W2 is indicated by a broken line. In order for the robot device 100, which is an articulated robot, to move the workpiece W1 substantially linearly as shown, it is necessary to control each joint axis simultaneously. In addition, in a posture near the maximum reach length of the robot arm, the control of the linear motion becomes even more difficult due to restrictions on the movable range of each joint. Therefore, the actual trajectory of the workpiece may deviate from the target trajectory. Also, it is conceivable that the actual trajectory of the workpiece deviates from the target trajectory due to the influence of the previous operation (residual vibration, etc.). For example, in the example of FIG. 7B, the workpiece W1 is displaced from the original insertion position and posture in the concave portion of the workpiece W2 due to the restrictions on the movable range of each joint and the effects of vibration as described above.

Due to the circumstances described above, in the conventional deceleration stop along the teaching trajectory, even if the operation should not be in contact due to residual vibration or control response, as shown in FIG. may contact (collide). That is, even if the position target value D1 is reset to a position on the teaching trajectory O2 indicated by the one-dot chain line indicated by the star in FIG. , the workpiece W1 may take a trajectory similar to that of O1 and contact may occur. When the robot stops during position control as shown in FIG. 8, the contact force generated by the contact between the workpieces W1 and W3 is not eliminated even after the workpieces W1 and W3 are stopped, and the gripped workpiece and the robot device are overloaded via the contact point TP. continues to hang.

On the other hand, in this embodiment, when a stop signal is input and the robot shifts to the stop control mode, the force control mode in which the force applied to the robot is detected and operated is activated. As described above, when contact is detected by force detection or the like, the contact position Pn is stored, and at the same time, if the number of contacts n is 1, the spring constant (virtual elastic coefficient) of impedance control, which is a parameter of force control, is stored. Raise As a result, the virtual elasticity of each joint of the robot arm 200 can be increased, the force to move toward (return to) the position target value can be reduced, and the force generated by contact can be alleviated.

Furthermore, in the control of the impact relaxation mode of the present embodiment, for example, a position between a plurality of contact points generated by the elastic response of the joint and having an extremely low possibility of contact with another object is reset as the position target value. . For example, as shown in FIG. 9, it is assumed that work W1 comes into contact with works W4 and W5 in the stop control mode. In this case, the first contact (P4) with the workpiece W4 increases the spring constant (virtual elastic modulus) of the joint, and the elastic motion of the robot joint causes the second contact (P5) with the workpiece W5. occur. In this case, the position target value is reset to the center of gravity G of the first and second contact points. As a result, the workpiece W1 passes through the trajectory O7 and is operated with a position target at a position in the space between the two contact points where the possibility of contact with another object on the route to the center of gravity G is extremely low. Become. 7 to 10, the position (black circle) of the work W1 corresponds to the center of gravity or the geometric center of the work W1, but for calculation, other reference positions such as the hand center of the robot arm 200 are used. may be used to calculate the coordinates of the contact point or target position. Further, in the operation of the trajectory O7 reset as described above, the spring constant (virtual elastic modulus) in the impedance control of the joint, which was increased by the first contact, is returned to the original value. As a result, the workpiece can be reliably moved to the reset stop position target.

In the example of FIG. 6, only the second contact is taken into account, but different control may be performed in the case of a larger number of contacts. When the first contact, the second contact, .

In addition, cases such as those shown in FIGS. 10A and 10B are conceivable for multiple contacts with other objects that occur when the elasticity of the joints of the robot arm 200 is increased. In FIG. 10(A), the workpiece W1 contacts the outer periphery of the recess for the first time and contacts the bottom of the recess for the second time in the middle of the trajectory O6 toward the interior of the recess of the workpiece W6. In FIG. 10B, the work W1 is in first and second contact with the flat upper surface of the work W7. In both cases of FIGS. 10A and 10B, contact forces are generated in the same direction. In such a contact mode, even if the stop position target is reset to the center of gravity G, there is a possibility that avoidance of recontact with the works W6 and W7 cannot be guaranteed. That is, when the contact force is generated in the same direction as shown in FIGS. 10A and 10B, the contact force cannot be reduced even if the center of gravity of the contact point is simply set as the position target value. do not have.

Therefore, the direction of the reaction force generated at a plurality of contact points is determined, and if the direction of the reaction force generated by contact at a plurality of contact points is almost the same direction, contact is made from the position of the center of gravity of the plurality of contact points. Control may be performed to move in the direction of the reaction force. For example, as shown in FIGS. 10A and 10B, the target stop positions D2 and D3 are positions moved by a predetermined distance in the direction of the force generated with reference to the positions of the centers of gravity of the plurality of contact points. take control. By performing such re-setting control of the stop position targets D2 and D3, stop control can be performed with a position target in the space between the contact points where the possibility of contact with another object is extremely low.

Moreover, there is a possibility that the workpiece W1 gripped by the robot arm 200 will be stopped by biting into the object to be assembled. For example, if an attempt is made to operate with a set spring constant (virtual elastic modulus) at the calculated target position value, but the robot arm does not move, it is conceivable that the force applied to the tip of the robot arm does not reach the target force value. Considering such a case, if the force information obtained from the torque sensors 541 to 546 does not reach the force target value even after a certain period of time has passed, the position target value is set before the contact point is counted ( (past) operation trajectory. In that case, until the target force value is obtained, the position target value may be repeatedly set backward (in the past) and reset.

As described above, according to the present embodiment, when the stop signal is input (received) during the position control mode, the force control mode (impedance control) is enabled in that stop control mode. Thereby, even if contact with another object occurs, the elastic response of the robot device can stop the robot device without damaging the workpiece, the robot device, or other objects in the working environment. In addition, even when the robot device contacts another object multiple times, by resetting the position target so as to stop at the center point, the robot device can be reliably stopped without contacting the other object. be able to. Also, the recovery operation of the robot device can be easily performed.

Although the case where the robot arm 200 is a 6-joint robot having 6 joints has been described, the number of joints is not limited to this. The driving direction of the joints is not limited to rotational driving, but includes linear driving (extension/contraction driving). Further, although the servo motors 201 to 206 are shown as the driving sources of the robot joints in the above description, the driving sources of the joints are not limited to the servo motors 201 to 206, and may be, for example, artificial muscles. Further, the various embodiments described above are applied to a machine that can automatically perform stretching, bending, stretching, vertical movement, horizontal movement, turning, or a combination of these operations based on the information in the storage device provided in the control device. Applicable.

The present invention provides a program that implements one or more functions of the above embodiments 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. But it can be done. It can also be implemented by a circuit (for example, ASIC) that implements one or more functions.

DESCRIPTION OF SYMBOLS 100... Robot apparatus 200... Robot arm 221-226... Sensor part (position and torque) 300... Robot control apparatus (computer) 302... Storage part J1-J6... Joint 501... Force teaching data 502... Position teaching data 503 Robot model 504 Force detector 505 Force controller 506 Position target value generator 511 to 516 Switch controller 521 to 526 Position controller 531 to 536 Motor Control unit 541 to 546...Torque sensors 551 to 556...Position sensors.

Claims (29)

Control of a robot system including a robot having a predetermined part, a first sensor that acquires information about the position of the predetermined part, a second sensor that acquires information about the force applied to the predetermined part, and a control device a method,
The control device
When stopping the robot, a first mode uses position control based on the first sensor to stop the robot , and a second mode uses force control based on the second sensor to stop the robot. allowing the first mode or the second mode to be selectable by a user;
A control method characterized by: In the control method according to claim 1,
The control device is
displaying the first mode and the second mode on the display unit so that the user can select the mode;
A control method characterized by: In the control method according to claim 1 or 2,
The first mode includes control to stop the robot so that the stop time or the stop distance is shortened based on mechanical constraints of the robot, and control to stop the robot while maintaining the trajectory set when the position control is executed. has at least one of
A control method characterized by: In the control method according to any one of claims 1 to 3,
The second mode reduces and stops the force applied to the predetermined portion.
A control method characterized by: In the control method according to any one of claims 1 to 4,
The control device is
When the robot is stopped in the second mode and the second sensor determines that the number of times of contact between the predetermined portion and the object is two or more, the Stop so that the predetermined part is located,
A control method characterized by: In the control method according to any one of claims 1 to 4,
The control device is
When the robot is stopped in the second mode, if it is determined based on the second sensor that the number of times of contact between the predetermined portion and the object is two or more, the moving the predetermined portion by a predetermined amount in the direction of the reaction force from the object acquired based on the second sensor at the time of contact, and then stopping;
A control method characterized by: In the control method according to claim 6,
The control device is
When the direction of the reaction force at the contact positions is substantially the same, the predetermined portion is moved from a position between the contact positions in the direction of the reaction force from the object acquired based on the second sensor at the contact. Move a predetermined amount and stop
A control method characterized by: In the control method according to any one of claims 5 to 7,
the position between the contact positions is the center of gravity between the contact positions;
A control method characterized by: In the control method according to any one of claims 1 to 8,
The control device is
executing the second mode by controlling a virtual elastic modulus set for the robot, which is a parameter used when executing the force control;
A control method characterized by: In the control method according to any one of claims 1 to 9,
The control device
enabling the first mode or the second mode to be individually set in a predetermined section in the operation section in the position control;
A control method characterized by: In the control method according to claim 2,
The control device is
displaying the state of the robot on the display unit;
A control method characterized by: In the control method according to claim 11,
At least one of a servo state and an operating speed is displayed as the state of the robot.
A control method characterized by: In the control method according to claim 2,
The control device is
displaying the first mode and the second mode on the display unit using a drop-down menu;
A control method characterized by: In the control method according to claim 2,
The control device is
displaying an operation program of the robot on the display unit so that the user can edit it;
A control method characterized by: The control method according to claim 14,
By editing the operation program, the first mode or the second mode can be individually set in a predetermined section in the operation section in the position control.
A control method characterized by: In the control method according to claim 2,
The control device is
displaying a text screen that displays information about the robot in text on the display unit;
A control method characterized by: 17. The control method of claim 16,
The control device is
displaying at least one of log information about the robot, error information about the robot, and warning information about the robot on the text screen;
A control method characterized by: In the control method according to claim 2,
The control device is
displaying which mode is selected from the first mode and the second mode on the display unit;
A control method characterized by: In the control method according to claim 2,
The control device is
displaying a stop button for stopping the robot on the display unit;
A control method characterized by: The control method according to claim 2,
The control device is
displaying, on the display unit, an automatic mode in which the robot executes a set action and a manual mode in which the robot is taught the action so that the user can select;
A control method characterized by: In the control method according to claim 2,
The display unit is provided in an external input device connected to the control device,
A control method characterized by: In the control method according to any one of claims 1 to 21,
The robot has joints for operating the predetermined parts,
The first sensor is an encoder that acquires information regarding the angle of the joint, and the second sensor is a torque sensor that acquires information regarding the torque applied to the joint.
A control method characterized by: In the control method according to any one of claims 1 to 22,
The control device
executing the first mode or the second mode when the robot is stopped while the position control is being executed;
A control method characterized by: A robot system comprising: a robot having a predetermined portion; a first sensor that acquires information about the position of the predetermined portion; a second sensor that obtains information about the force applied to the predetermined portion; and a controller. hand,
The control device
When stopping the robot, a first mode uses position control based on the first sensor to stop the robot , and a second mode uses force control based on the second sensor to stop the robot. allowing the first mode or the second mode to be selectable by a user;
A robot system characterized by: 25. A method of manufacturing an article, wherein the article is manufactured using the robot system according to claim 24 . An input device for issuing a command to a robot system comprising a robot having a predetermined part, a first sensor for acquiring information about the position of the predetermined part, and a second sensor for obtaining information about the force applied to the predetermined part. and
The input device is
When stopping the robot, a first mode uses position control based on the first sensor to stop the robot , and a second mode uses force control based on the second sensor to stop the robot. and displaying the first mode or the second mode on the display unit so that the user can select the mode.
An input device characterized by: An input device for issuing a command to a robot system comprising a robot having a predetermined part, a first sensor for acquiring information about the position of the predetermined part, and a second sensor for obtaining information about the force applied to the predetermined part. A control method of
when stopping the robot, a first mode stops the robot using position control based on the first sensor, and a second mode stops the robot using force control based on the second sensor; displaying the first mode or the second mode on a display so that the user can select the mode;
A control method characterized by: A control program for causing a computer to execute the control method according to any one of claims 1 to 23 or 27 . A computer-readable recording medium storing the control program according to claim 28 .

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