JP2021088042A - Robot control device, gripping system and robot hand control method - Google Patents

Abstract

To provide a robot hand control device that can switch control from a gripping state into a carrying state by a simple and high-speed method.SOLUTION: A robot control device 102 controls a robot 101 equipped with a robot hand 107 having gripping parts for gripping a work-piece, and comprises: a virtual impedance part 500 that calculates a position corrected value of a target position at which the gripping parts 203 and 204 move, using gripping force response values at the time when the gripping parts 203 and 204 grip the work-piece; a memorizing part 501 that memorizes the position corrected value calculated by the virtual impedance part 500; and a position control part 502 that controls positions of the gripping parts 203 and 204 with respect to the work-piece, while reflecting the position corrected value at arbitrary timing memorized by the memorizing part 501 on position response values at the time when the gripping parts 203 and 204 grip the work-piece.SELECTED DRAWING: Figure 5

Description

The present invention relates to a robot control device, a gripping system, and a robot hand control method. More specifically, the present invention includes a robot control device for controlling the operation of a robot hand that grips a work by switching between force control and position control. The present invention relates to a gripping system and a robot hand control method.

When gripping a work that is an object to be gripped using a robot in a factory or the like, the work is gripped by a robot hand attached to the tip of the robot arm, and the robot arm is operated in that state to receive acceleration. Inertial force is generated in the work.

Then, when the work is conveyed at high speed while the force is controlled by the robot hand, the reaction force generated by the inertial force is detected and the grip portion of the robot hand moves, which may impair the grip stability. There is sex. Further, if the force is controlled while the contact state is not maintained, there is a risk that the robot hand will run away because it moves freely. Therefore, conventionally, a method of switching between position control and force control has been proposed in order to stabilize gripping.

For example, Patent Document 1 describes a position control means for controlling the position of a link driven by a combination of position control and force control, and the magnitude of an external force does not exceed a set value even when the position of the link is controlled. The position control means with external force restraint that prioritizes force control over the position control, the force control means that performs force control of the link, the position control means, the position control means with external force restraint, and the force control means are switched. A robot device is described that includes a position and force control integration means that controls the drive of the joint and integrates position control and force control.

Japanese Unexamined Patent Publication No. 2009-066685

However, in the technique described in Patent Document 1, a position control mode with external force restraint is used in order to continuously switch between position control and force control. This prevents the motor command values from becoming discontinuous before and after switching and giving a shock to the work, but there is a problem that switching takes time and the procedure becomes complicated by using another mode.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a robot control device capable of switching control from gripping to a transporting state by a simple and high-speed method.

The robot control device according to the present invention in order to solve the above problems
Controls a robot with a robot hand that has a grip that grips the workpiece,
A virtual impedance unit that calculates a position correction value of a target position where the grip portion moves by using a grip force response value when the work is gripped by the grip portion.
A storage unit that stores the position correction value calculated by the virtual impedance unit, and a storage unit.
A position control unit that controls the position of the grip portion with respect to the work by reflecting the position correction value stored by the storage unit at an arbitrary time point in the position response value when the work is gripped by the grip portion. , Equipped with.

Further, the gripping system according to the present invention includes the robot control device, the robot hand, and a robot arm for moving the robot hand to a predetermined position.

Further, the robot hand control method according to the present invention is a robot hand control method having a grip portion for gripping a work.
A calculation step of calculating the position correction value of the target position where the grip portion moves by using the grip force response value when the work is gripped by the grip portion, and
A storage step for storing the position correction value calculated in the calculation step is included.
The position of the grip portion with respect to the work is controlled by reflecting the position correction value stored by the storage unit at an arbitrary time point in the position response value when the work is gripped by the grip portion.

According to the robot control device according to the present invention, the control can be switched from the gripping state to the transporting state by a simple and high-speed method. The effects described here are not necessarily limited, and may be any of the effects described in the present specification.

It is a schematic diagram which shows the structural example of the gripping system which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the example of the internal structure of the robot hand which concerns on 1st Embodiment of this invention. It is a block diagram which shows the schematic structure example of the gripping system which concerns on 1st Embodiment of this invention. It is a block diagram which shows the functional structure of the robot control apparatus which concerns on 1st Embodiment of this invention. It is a functional block diagram which shows the hand control part of the robot control apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the operation of the robot which concerns on 1st Embodiment of this invention. It is a functional block diagram which shows the hand control part of the robot control apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the operation of the robot which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the operation of the robot which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each of the embodiments described below shows an example of a typical embodiment of the present invention, and the scope of the present invention is not narrowly interpreted by this. In addition, any of the following configurations of each embodiment can be combined with the configurations of other embodiments.

<First Embodiment>
First, a configuration example of the gripping system according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a configuration example of the gripping system 100 according to the present embodiment.

As shown in FIG. 1, as an example, the gripping system 100 includes a robot main body 101, a robot control device 102 connected to the robot main body 101, an input device 103 for inputting a command or the like to the robot control device 102, and robot control. It includes an upper control system 104 connected to the device 102.

The robot main body 101 includes a base portion 105, a robot arm 106 connected to the base portion 105, and a robot hand 107 attached to the tip of the robot arm 106.

The robot arm 106 is a 6-axis vertical articulated robot and includes actuators (electric motor, hydraulic / pneumatic actuator, etc.) and position detecting means (encoder, camera, etc.). The robot arm 106 can move the robot hand 107 to a predetermined position. However, the robot arm to which the present invention is applied is not limited to this. For example, a vertical articulated robot other than the 6-axis robot, a horizontal articulated robot, or the like may be used.

The robot hand 107 is driven by a vane motor, which is a pneumatic actuator, and includes an encoder as a position detecting means. Further, the robot hand 107 can be provided with a force sensor as a gripping force detecting unit. The gripping force may be estimated from the state quantity of the robot hand 107 such as the value of the pressure sensor. It is desirable that the robot hand 107 can control a small gripping force with high accuracy.

Next, the internal structure of the robot hand 107 according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic view showing an example of the internal structure of the robot hand 107 according to the present embodiment.

As shown in FIG. 1, the robot hand 107 is attached to the robot arm 106. The robot hand 107 is a first that connects the hand body 202, the first grip 203 and the second grip 204 attached to the tip of the hand body 202, and the grips 203 and 204 and the hand body 202. It includes a parallel link 205 and a second parallel link 206.

The robot hand 107 further includes a first gear 207 and a second gear 208, which are gear mechanisms for transmitting power between the first parallel link 205 and the second parallel link 206, and the first parallel link 205 and the hand body. It includes an input shaft 209 that connects the 202 and transmits the driving force of an actuator (not shown) to the first parallel link 205.

The first grip portion 203 is rotatably connected to one end of the first parallel link 205, and the second grip portion 204 is rotatably connected to one end of the second parallel link 206. The surfaces of the first grip portion 203 and the second grip portion 204 are arranged so as to face each other, and the work can be gripped from both side surfaces of the work, for example.

The other ends of the first parallel link 205 and the second parallel link 206 are rotatably connected to the hand body 202 via the first gear 207 and the second gear 208, respectively. In the robot hand 107, the first grip portion 203 and the first parallel link 205 are the main transmission mechanisms, and the driving force of the actuator is transmitted from the input shaft 209 connected to the actuator.

The driving force transmitted from the actuator is transmitted from the first gear 207 connected to the first parallel link 205 to the driven system paired with the driving system via the second gear 208 connected to the first gear 207. It is transmitted to the second parallel link 206 and the second grip portion 204, which are transmission mechanisms. As a result, the two parallel links 205 and 206 are driven synchronously by one actuator, and the left and right grip portions 203 and 204 can operate in conjunction with each other.

Next, the system configuration of the gripping system 100 according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram showing a schematic configuration example of the gripping system 100 according to the present embodiment.

As shown in FIG. 3, in addition to the robot arm 106 and the robot hand 107, the robot main body 101 includes a camera device 301 which is an imaging device for imaging a work or the like.

The robot control device 102 includes a CPU, an input / output unit 302 for inputting / outputting signals, and a memory unit 303 having a RAM or ROM. Each configuration of the CPU, the input / output unit 302, and the memory unit 303 is connected so as to be able to transmit signals to each other via a bus. The RAM or ROM is a computer-readable recording medium on which a program for executing the control method of the robot hand 107 is recorded. The robot control device 102 can control the robot main body 101 and the robot hand 107 by executing various programs, and cause the robot main body 101 and the robot hand 107 to execute various functions.

The CPU functions as an arithmetic processing unit, and reads and executes various programs stored in a ROM, RAM, an external storage device, and the like. The ROM stores programs used by the CPU, device constants, and the like. The RAM primarily stores a program used by the CPU, variables that change sequentially during program execution, and the like.

The input / output unit 302 includes a communication device, an A / D converter, a D / A converter, a motor drive circuit, and the like in order to connect an external device or a peripheral device to the robot control device 102 via an interface. Specific communication methods for communication devices include, for example, serial communication standards such as RS232C / 485, data communication compatible with the USB standard, general network protocol Ethernet (registered trademark), and industrial use. It may be EtherCAT (registered trademark), EtherNet / IP (registered trademark), or the like used as a network protocol.

Further, the robot control device 102 may be connected to a storage device which is a data storage device or a drive device which is a reader / writer for a recording medium via an input / output unit 302.

The robot arm 106 includes an arm encoder 304 that is a position detecting means of the robot arm 106, and an electric motor 305 that is an actuator.

The robot hand 107 includes a hand encoder 306 that is a position detecting means of the robot hand 107, and a vane motor 307 that is an actuator. Further, although not shown, the robot hand 107 also includes a gripping force estimator as a gripping force detecting unit.

The arm encoder 304 detects the rotation position of the robot arm 106, converts the rotation position into an electric signal, and outputs the rotation position to the input / output unit 302. Further, the hand encoder 306 detects the rotation positions of the first parallel link 205 and the second parallel link 206, converts the rotation positions into electrical signals, and outputs the rotation positions to the input / output unit 302.

The vane motor 307 is powered by air pumped from a compressed air source 308 such as a compressor.

The robot body 101 further includes a servo valve 309 that supplies compressed air to the vane motor 307, and a pressure sensor 310 that detects the pressure of the servo valve 309.

The servo valve 309 is configured to receive the compressed air used for driving the vane motor 307 from the compressed air source 308, and adjusts the pressure of each port of the vane motor 307 by receiving the input value from the input / output unit 302. It is driven by that.

The pressure of each port is detected by the pressure sensor 310. It is configured to convert the pressure into an electrical signal and output it to the input / output unit 302.

The input device 103 provides a keyboard, a mouse, a touch panel, a button, a switch, a lever, a pedal, a remote control means using infrared rays or other radio waves, or an operation means operated by a user such as a personal computer equipped with these or a teaching pendant. I have. Inputs and settings by the user are performed using the input device 103. The input device 103 may create a program for causing the robot to execute various functions. The program may be written in a low-level language such as machine language or a high-level language such as robot language.

The status notification device 311 receives and displays information on the operating state of the robot body 101 and the gripping state of the work from the robot control device 102, so that the user can visually and intuitively recognize the information. The status notification device 311 may be a display device such as a liquid crystal panel, a teaching pendant, or a lighting lamp, or may be a notification device that notifies information by a warning sound, voice, or the like. Further, the screen of the personal computer or the teaching pendant may also serve as the status notification device 311 and may include an application for inputting and status notification.

The host control system 104 is composed of, for example, a sequencer (PLC), a monitoring control system (SCADA), a process computer (procon), a personal computer, various servers, or a combination thereof, and is connected to the robot control device 102 by wire or wirelessly. .. An instruction is output based on the operating status of each device constituting the production line including the robot control device 102, and the production line is managed in an integrated manner.

For example, the work is specified by image recognition by the camera device 301 or a detection means such as an ID tag, and a gripping pattern instruction is transmitted to the robot control device 102 before the gripping operation, so that the robot arm 106 has an appropriate gripping pattern according to the item. And the robot hand 107 can be operated.

Further, by receiving and collecting information such as the size of the work, the time until the gripping is completed, and the gripping state from the robot control device 102, it can be used for monitoring the defect rate and the cycle time. Further, the robot arm 106 may be returned to the home position or each device may be stopped depending on the information on the gripping state.

In FIG. 1, the robot control device 102 is integrated, but for example, control devices may be separately configured for each functional configuration described later or for the robot arm 106 and the robot hand 107, and may be connected to each other by wire or wirelessly. Good. Further, in the present embodiment, the robot control device 102 is provided outside the robot arm 106 and the robot hand 107, but this may be provided inside the robot arm 106 and the robot hand 107.

The above is an example of the schematic configuration according to the present embodiment. Each component may be configured by using general-purpose members, or may be configured by hardware specialized for the function of each component. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at each time when the present embodiment is implemented.

Next, the functional configuration of the robot control device 102 according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing a functional configuration example of the robot control device 102 according to the present embodiment.

As shown in FIG. 4, as an example, the robot control device 102 includes a work recognition unit 401, an input / output processing unit 402, a target value generation unit 403, a display control unit 404, an arm control unit 405, and hand control. A unit 406 is provided.

The work recognition unit 401 is connected to each function unit of the input / output processing unit 402, the trajectory generation unit 403, the display control unit 404, the arm control unit 405, and the hand control unit 406, and receives input from each function unit or the outside. Output instructions to each functional unit and control each functional unit.

The input / output processing unit 402 acquires signals output from the camera device 301, a sensor, or the like, performs filtering, or the like, and calculates information on the robot body 101 and its surrounding environment (for example, the state quantity of the robot hand 107). It is output to the arm control unit 405 and the hand control unit 406 as necessary pressure sensors 310, values of the arm encoder 304 and the hand encoder 306). Further, the input / output processing unit 402 outputs an output (for example, an input value to the servo valve 309) from the arm control unit 405, the hand control unit 406, or the like to another system component such as an actuator.

The target value generation unit 403 generates a target trajectory so that the robot arm 106 and the robot hand 107 pass through a point taught in advance, and the position and gripping force for each hour in order to realize the target gripping motion. Generate a target value. The position of the work may be recognized from the image acquired by the camera device 301 or the like, and the target trajectory may be autonomously generated.

The display control unit 404 causes the status notification device 311 to display a screen for displaying the operation flow and the operation state of the robot main body 101.

The arm control unit 405 controls the robot arm 106 based on the target trajectory and sensor information generated by the target value generation unit 403.

The hand control unit 406 controls the robot hand 107 based on the target trajectory and sensor information generated by the target value generation unit 403. Further, the hand control unit 406 includes a control unit described later.

Further, in the gripping system 100 according to the present embodiment, the determination algorithm and the result of the gripping operation, which will be described later, are stored in the memory 303 or transmitted to the upper control system 104.

In addition, a part or all of these functions may be realized by a dedicated integrated circuit constructed for a specific application such as a hardware circuit, an ASIC or an FPGA. Further, the number of computers for executing the program in the present embodiment is not particularly limited. For example, a plurality of computers including a host control system and the like may execute the program in cooperation with each other.

In the present embodiment, the storage device in which various programs for executing a series of processes are stored is described as the memory 303 incorporated in the robot control device 102, but the present invention is not limited to this. The program for executing the gripping system 100 according to the present embodiment may be recorded in a storage device distributed to provide the program to the user separately from the robot control device 102 if the computer can read it. .. The storage device is composed of, for example, a magnetic storage device, a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like. It may also be downloaded from the network and installed or updated.

Further, the robot control device 102 is not limited to a control device incorporating dedicated hardware, and may be, for example, a general-purpose personal computer capable of executing various functions by installing various programs. ..

Next, with reference to FIG. 5, the functional configuration before and after the power switching of the hand control unit 406 according to the present embodiment will be described. FIG. 5 is a functional block diagram showing a hand control unit 406 of the robot control device 102 according to the present embodiment. FIG. 5A is a diagram showing a functional configuration of the hand control unit 406 before switching, and FIG. 5B is a diagram showing a functional configuration of the hand control unit 406 after switching.

As shown in FIG. 5A, in the case of the functional configuration before switching, the hand control unit 406 includes a virtual impedance unit 500, a storage unit 501, and a position control unit 502 that controls the positions of the grip units 203 and 204 with respect to the work. It includes a driving force control unit 503. In this case, the target value generation unit 403 receives the input value from the external input and outputs the gripping force target value to the virtual impedance unit 500. Further, the target value generation unit 403 outputs the position target value to the position control unit 502. The driving force control unit 503 is connected to the robot hand 107 via the input / output unit 402.

As shown in FIG. 5B, in the case of the functional configuration after switching, the hand control unit 406 includes a storage unit 501, a position control unit 502, and a driving force control unit 503.

In the gripping operation, it is necessary to shorten the time required to start the transfer while positioning at a constant speed. However, in position control, an excessive force may be generated at the time of contact due to fluctuations in the size and arrangement of the workpiece. For that purpose, it is necessary to control the gripping force while positioning and controlling the robot hand 107.

Admittance control is known as a method of controlling the gripping force while performing position control. By operating the gripping portion while performing admittance control, the gripping force applied to the work can be controlled, so even if the size and arrangement of the work fluctuate, gripping can be performed without applying an excessive contact force to the work. .. Further, in a state where the gripping force before contacting the work is not generated, the admittance control is equivalent to the position control, and it is not necessary to switch the control method before and after the contact. On the other hand, during transportation, the parameter setting may be strongly affected by the inertial force during high-speed transportation as well as force control. Therefore, by switching to position control during transportation, the grip is stabilized during high-speed transportation.

The admittance control is based on the position control, and gives a position correction value to the position control in order to realize the target gripping force. This position correction value is calculated so that the force and the position are related by the virtual impedance unit 500 that inputs the gripping force target value and the gripping force response value. The hand control unit 406 of the present embodiment has a storage unit 501 that stores the position correction value calculated by the virtual impedance unit 500.

The rotation angle of the link detected by the encoder is input to the hand control unit 406 via the input / output unit 302. The input rotation angle is coordinate-transformed to be the distance between the gripping members and calculated as a position response value.

The virtual impedance unit 500 calculates the position correction value of the target position where the gripping units 203 and 204 move by using the gripping force target value and the gripping force response value when the gripping units 203 and 204 grip the work. Admittance control is performed by reflecting the position correction value at an arbitrary time point stored in the storage unit in the position control in the position response value when the work is gripped by the gripping units 203 and 204. In the present embodiment, as an example, the sum of the position correction value of the target position and the position target value generated by the target value generation unit 403 is set as the new position target value. The amount of correction may include not only the position but also the velocity and acceleration which are the time derivatives thereof. Further, in the present embodiment, the gripping force response value is estimated by the gripping force estimator (not shown).

The difference between the position target value and the position response value from the control target when the work is gripped by the gripping units 203 and 204 is input to the position control unit 502. The position control unit 502 executes an operation such that the difference between the position target value and the position response value from the controlled object is set to 0, and generates a driving force reference value as the calculation result. Further, when the position control unit 502 determines that the work to be gripped is a work that has been gripped in the past and has stored the position correction value in the storage unit 501, the position control unit 502 corresponds to the work stored in the storage unit 501 in the past. The position can be controlled by reflecting the position correction value on the position target value of the position control unit 502.

The difference between the driving force reference value and the force response value from the controlled object is input to the driving force control unit 503. The driving force control unit 503 controls the driving force by giving a driving force signal such that the difference between the driving force reference value and the driving force response value from the control target is 0 to the robot hand 107 to be controlled as an input. Running. The input in this embodiment is the voltage applied to the servo valve 309 or the like mounted as the driving force control device.

The pneumatic actuator can obtain a speed and a gripping force suitable for the operation of the robot hand 107 even if the speed is not reduced or the reduction ratio is small. Therefore, it is relatively easy to estimate the gripping force from the state quantity of the robot hand 107. By adopting a configuration that does not use a force sensor, the system can be inexpensive and the risk of failure can be reduced. Further, since it has back drivability, it is suitable for applications of the robot hand 107 that requires impact suppression at the time of contact and gripping force control.

Next, the operation of the robot main body 101 according to the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing an example of the operation of the robot main body 101 according to the present embodiment.

First, in step S1, the work recognition unit 401 recognizes the type of work by a signal from the camera device 301 or the outside. The target value generation unit 403 generates a position target value and a gripping force target value based on the recognized result, and moves the robot body 101 to the gripping operation start position. After the movement is completed, the process proceeds to step S2.

In step S2, the robot hand 107 starts moving the grip portions 203 and 204 according to the target value generated in step S1. At the stage before contact with the work, the impact force at the time of contact with the work is relaxed by setting the admittance control gripping force target value to a small value.

In step S3, the hand control unit 406 determines the contact between the work and the grip unit 203 or 204. When the gripping force reaches the contact detection threshold, the contact is completed.

If no contact is detected, the process returns to the start state of step S3, and the grip portions 203 and 204 continue to move. When the contact is detected, the process proceeds to step S4. If the contact cannot be detected after a certain period of time has elapsed, the user may be notified of the occurrence of an abnormality through the status notification device 311.

In step S4, the target value generation unit 403 continuously changes the gripping force target value from the contact detection threshold value to the target gripping force. Step S4 includes a calculation step of calculating the position correction value of the target position where the grip portions 203 and 204 move by using the grip force response value when the virtual impedance unit 500 grips the work by the grip portions 203 and 204. I'm out. The robot control device 102 can change the gripping force of the gripping units 203 and 204 according to the position correction value calculated by the virtual impedance unit 500.

In step S5, the hand control unit 406 determines that the gripping is completed if the gripping force detected by the gripping force estimator, which is the gripping force detecting unit, is within the target range. After determining that the gripping is completed, the process proceeds to step S6. If it is not determined that the grip is completed, the process returns to the start state of step S5, and the grip portions 203 and 204 continue to grip the work. Step S5 includes a detection step in which the gripping force estimator detects the gripping force at the gripping portions 203 and 204. If the work is not in its original position or is gripped in an unintended posture, the normal transfer process is interrupted and measures such as notifying the user that the work is not properly gripped are taken. Is preferable. For example, if the gripping complete state is not reached after a certain period of time has elapsed, the user may be notified of the occurrence of an abnormality through the state notification device 311.

In step S6, the hand control unit 406 sets the position correction value, which is the output of the virtual impedance unit 500, in the storage unit 501 when it is determined that the grip is completed, that is, when the grip of the admittance control in step S5 is completed, and sets the control system. Switch and end the process. Step S6 includes a storage step of storing the position correction value calculated by the virtual impedance unit 500 in the calculation step. After the setting is completed, the admittance control is switched to the position control by stopping the update of the position correction value stored in the storage unit 501. As a result, it is possible to switch to position control only without causing fluctuations in the gripping force. Furthermore, by performing only position control, the inertial force generated by the transfer does not impair the gripping stability. In the robot control device 102 according to the present embodiment, when the gripping force detected by the gripping force estimator reaches the target gripping force, the storage unit 501 can store the position correction value calculated by the virtual impedance unit 500. ..

It is preferable to take measures such as notifying the user even if the gripped work falls during transportation. The position and gripping force of the gripping portion and their changes are determined during transportation, and when the threshold value deviates from the preset value, the user is notified of the abnormality through the status notification device 311. As a result, the robot control device 102 according to the present embodiment can switch from admittance control to position control in order to improve stability during transportation.

According to the gripping system 100 according to the present embodiment, during the transport operation, the position correction value when the work is gripped by the target gripping force by admittance control is stored, and the target position is corrected (feedforward). Therefore, it is possible to switch to position control easily and at high speed without going through another mode. By switching to position control, the workpiece can be gripped in a stable state, and a gripping system capable of high-speed transfer can be provided.

<Second Embodiment>
Next, the gripping system according to the second embodiment of the present invention will be described with reference to FIGS. 7 and 8. The difference between this embodiment and the first embodiment is that the correction amount by the virtual impedance unit 500 is not determined for each gripping operation, but the data obtained when gripping previously is used. The main configuration of the gripping system according to the present embodiment is the same as that of the first embodiment.

The control unit before and after the control switching of the control unit included in the hand control unit 406 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a functional block diagram showing a control unit of the robot hand 107 according to the present embodiment.

As shown in FIG. 7, the hand control unit 406 includes a target position generation unit 403, a position control unit 502, a storage unit 501, and a driving force control unit 503, similarly to the control unit after switching in the first embodiment. And have. The driving force control unit 503 is connected to the robot hand 107.

Next, the operation of the robot main body 101 according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing an example of the operation of the robot main body 101 according to the present embodiment.

First, in step S11, the work recognition unit 401 recognizes the type of work by a signal from the camera device or the outside. The target value generation unit 403 generates a position target value and a gripping force target value based on the recognized result, and moves the robot body 101 to the gripping operation start position. After the movement is completed, the process proceeds to step S12.

In step S12, the work recognition unit 401 confirms whether or not the actual data exists because it was previously gripped in step S12. In the case of the work to be gripped for the first time, the process proceeds to step S13, and the process proceeds in the same flow as in the first embodiment of FIG. If there is actual data in the second and subsequent processes, the process proceeds to step S20.

In step S13, the robot hand 107 starts moving the grip portions 203 and 204 according to the target value generated in step S11. At the stage before contact with the work, the impact force at the time of contact with the work is relaxed by setting the admittance control gripping force target value to a small value.

In step S14, the hand control unit 406 determines the contact between the work and the grip unit 203 or 204. When the gripping force reaches the contact detection threshold, the contact is completed.

If no contact is detected, the process returns to the start state of step S14, and the grip portions 203 and 204 continue to move. When the contact is detected, the process proceeds to step S15. If the contact cannot be detected after a certain period of time has elapsed, the user may be notified of the occurrence of an abnormality through the status notification device 311.

In step S15, the hand control unit 406 starts storing the time-series data of the position correction value in the storage unit.

In step S16, the target value generation unit 403 continuously changes the gripping force target value from the contact detection threshold value to the target gripping force.

In step S17, the hand control unit 406 determines that the gripping is completed if the gripping force is within the target range. After determining that the gripping is completed, the process proceeds to step S18. If it is not determined that the grip is completed, the process returns to the start state of step S17, and the grip portions 203 and 204 continue to grip the work. If the work is not in its original position or is gripped in an unintended posture, the normal transfer process is interrupted and measures such as notifying the user that the work is not properly gripped are taken. Is preferable.

In step S18, the hand control unit 406 ends the recording of the time series data of the position correction value.

In step S19, the hand control unit 406 sets the position correction value, which is the output of the virtual impedance unit when the admittance control gripping is completed, in the storage unit, and ends the process. After the setting is completed, the admittance control is switched to the position control by stopping the update of the position correction value stored in the storage unit. As a result, it is possible to switch to position control only without causing fluctuations in the gripping force. Furthermore, by performing only position control, the inertial force generated by the transfer does not impair the gripping stability.

From the next time onward, in step S20, the hand control unit reads out the actual data of the position correction value from the storage unit 501 according to the external input.

In step S21, the hand control unit 406 controls the robot hand 107 by reflecting the position correction value on the position target value of the position control unit.

In step S22, the hand control unit 406 determines that the gripping is completed if the gripping force is within the target range. After determining that the gripping is completed, the process proceeds to step S22. If it is not determined that the grip is completed, the process returns to the start state of step S22, and the grip portions 203 and 204 continue to grip the work. If the work is not in its original position or is gripped in an unintended posture, the normal transfer process is interrupted and measures such as notifying the user that the work is not properly gripped are taken. Is preferable. For example, if the gripping complete state is not reached after a certain period of time has elapsed, the user may be notified of the occurrence of an abnormality through the state notification device 311. After that, the process is completed by gripping the work with the gripping portions 203 and 204.

According to the gripping system according to the present embodiment, in addition to the same effect as the gripping system according to the first embodiment, gripping is performed only by position control in the subsequent gripping, so that gripping due to aged deterioration due to friction of the mechanism is caused. Factors affecting force detection accuracy and actual grip stability can be reduced.

When gripping multiple types of workpieces, the total size of time series data may be large. In this case, the data may be temporarily stored in the host control system or storage device, and the data may be read out as appropriate. In this case, the time series data is transmitted to the host control system or the storage device after the storage is completed in step S18.

<Third Embodiment>
Next, the gripping system according to the third embodiment of the present invention will be described. The difference between this embodiment and the first embodiment is that in the first embodiment and the second embodiment, one actuator is used to drive the robot hand 107, but the grip portions 203 and 204 are independently operated by separate actuators. It is a point that may work. In the third embodiment, the robot hand 107 having two opposing grip portions is separately driven by two actuators. The main configuration of the gripping system according to the present embodiment is the same as that of the first embodiment and the second embodiment.

The operation of the robot main body 101 according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing an example of the operation of the robot main body 101 according to the present embodiment.

First, in step S1, the work recognition unit 401 generates a target value of the gripping unit from each of the gripping pattern instruction signals input from the outside, and starts the gripping operation.

In step S2, the robot hand 107 starts the gripping operation with the force target value set to a small value before the contact with the work.

In step S3, the hand control unit 406 determines the contact between the work and the grip unit 203 or 204. If no contact is detected, the process returns to the start state of step S3, and the grip portions 203 and 204 continue to move. Unlike the first embodiment, when any of the grip portions 203 or 204 comes into contact with the work, the process cannot proceed to step S31. The grip portion 203 or 204 that has come into contact first maintains contact with the work until the other grip portion 204 or 203 comes into contact with the work. When both grip portions 203 and 204 come into contact with the work, the process proceeds to step S31.

In step S31, the hand control unit 406 determines whether or not the other grip portion 203 or 204 that is not in contact with the work is in contact with the work. If they are in contact, the process proceeds to step S4, and if they are not in contact, the process of step S31 is repeated until they are in contact. Subsequent processing is the same as in steps S4 to S6 of FIG.

The force target value shall be the same value for both grip portions 203 and 204 at each time. If the gripping force of each of the gripping portions 203 and 204 is within the target range, it is determined that the gripping is completed. When completed, each position correction value is set in the storage unit, and the admittance control is switched to the position control.

For gripping from the next time onward, the stored value may be reflected in the position target value of the position control unit in the same manner as in steps S20 to S22 of the second embodiment.

According to the gripping system according to the present embodiment, the same effects as those of the first embodiment and the second embodiment can be obtained. Further, since each gripping portion operates independently, it is possible to properly grip even if the center of the robot hand and the center of the work are deviated from each other.

The gripping system according to the present embodiment has the same basic operation even if the degree of freedom of the robot hand 107 is increased, and is not particularly limited. Further, even if a plurality of joints are interlocked with one degree of freedom, it can be applied without any problem.

Although the gripping system according to the present embodiment has been described in detail above, the present invention is not limited to these embodiments and can be appropriately modified without departing from the spirit of the present invention.

For example, in the present embodiment, the position detection means using an encoder has been described, but a potentiometer may be used.

Further, although the actuator using a vane motor has been described and described, the present invention is not particularly limited to this, and for example, actuators such as electric motors (AC motors, DC motors, stepping motors, etc.), hydraulic motors, and pneumatic cylinders. Also, the shape, quantity and type of the actuator are not particularly limited.

Further, in the embodiment, a compressed air source such as a compressor is used as the power source, but the present invention is not limited to this, and a power source may be used as the power source. Or a motor driver may be used.

Further, although the gripping force estimator has been described as the gripping force detecting unit, the present invention is not particularly limited to this, and for example, a force sensor, a current detecting circuit, or the like may be used, and can be appropriately changed according to a signal that can be detected.

The present invention relates to a technique applied to a robot equipped with a robot hand that grips an object to be gripped, for example, in a production factory, and has industrial applicability.

100 Gripping system 101 Robot body 102 Robot control device 103 Input device 104 Upper control system 105 Base part 106 Robot arm 107 Robot hand 202 Hand body part 203 First grip part 204 Second grip part 205 First parallel link 206 Second parallel link 207 1st gear 208 2nd gear 209 Input shaft 301 Camera device 302 Input / output unit 303 Memory 304, 306 Encoder 305 Electric motor 307 Bane motor 308 Compressed air source 309 Servo valve 310 Pressure sensor 311 Status notification device 401 Work recognition unit 402 Input / output Processing unit 403 Target value generation unit 404 Display control unit 405 Arm control unit 406 Hand control unit 500 Virtual impedance unit 501 Storage unit 502 Position control unit 503 Driving force control unit

Claims (8)

A robot control device that controls a robot having a robot hand having a grip portion for gripping a work.
A virtual impedance unit that calculates a position correction value of a target position where the grip portion moves by using a grip force response value when the work is gripped by the grip portion.
A storage unit that stores the position correction value calculated by the virtual impedance unit, and a storage unit.
A position control unit that controls the position of the grip portion with respect to the work by reflecting the position correction value stored by the storage unit at an arbitrary time point in the position response value when the work is gripped by the grip portion. ,
A robot control device equipped with. The first aspect of the present invention further comprises a gripping force detecting unit, which stores a position correction value calculated by the virtual impedance unit in the storage unit when the gripping force detected by the gripping force detecting unit reaches a target gripping force. The robot control device described. When the position control unit determines that the work is a work that has been gripped in the past and has stored the position correction value in the storage unit, the position correction unit corresponds to the work stored in the storage unit in the past. The robot control device according to claim 1 or 2, wherein the position is controlled by reflecting the value in the position target value of the position control unit. The robot control device according to any one of claims 1 to 3,
With the robot hand
A robot arm that moves the robot hand to a predetermined position,
Gripping system with. It is a control method of a robot hand having a grip portion for gripping a work.
A calculation step of calculating the position correction value of the target position where the grip portion moves by using the grip force response value when the work is gripped by the grip portion, and
A storage step for storing the position correction value calculated in the calculation step is included.
Control of the robot hand that controls the position of the grip portion with respect to the work by reflecting the position correction value at an arbitrary time point stored in the storage unit in the position response value when the work is gripped by the grip portion. Method. Further including a detection step for detecting the gripping force at the gripping portion.
The robot hand control method according to claim 5, wherein the position correction value is stored in the storage step when the gripping force detected in the detection step reaches the target gripping force. When it is determined that the work is a work that has been gripped in the past and has stored the position correction value, the position correction value corresponding to the work stored in the past is reflected in the position target value to control the position. , The robot hand control method according to claim 5 or 6. A computer-readable recording medium on which a program for executing the robot hand control method according to any one of claims 5 to 7 is recorded.

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