JP2020157459A - Control method and robot system - Google Patents

Abstract

To provide a control method and a robot system that are able to prevent excessive load on a contact object and able to achieve a high speed of a work.SOLUTION: A control method comprises: a force acquisition step of acquiring a detection value from a force detection unit; a first command value calculation step of obtaining a first command value by adding a first amount of correction, obtained from the detection value, a first force control parameter and a target force, to a command value of a position; and a second command value calculation unit that obtains a second command value by adding a second amount of correction, obtained from the detection value and a second force control parameter, to the first command value. If a mass coefficient of the first force control parameter is m1, a coefficient of viscosity of the first force control parameter is d1, a mass coefficient of a second force control parameter is m2, a coefficient of viscosity of the second force control parameter is d2, and a coefficient of elasticity of the second force control parameter is k2, m2<m1 or d2<d1 is satisfied, and k2>0 is satisfied.SELECTED DRAWING: Figure 4

Description

The present invention relates to control methods and robot systems.

For example, Patent Document 1 discloses a force control device that controls a robot including an arm and a force detection unit. In the force control device described in Patent Document 1, when the arm performs work, when the arm is located at a position far from the object, the first force control is performed using a parameter having a high moving speed, and the arm moves. When moving to a position closer to the object, the second force control is performed with a parameter whose moving speed is slow. Further, the above control is realized by setting a switching point for switching from the first force control to the second force control.

Japanese Unexamined Patent Publication No. 2011-104740

However, if the switching point for switching from the first force control to the second force control is too close to the object, the arm may come into contact with the object in the state of the first force control in which the moving speed is relatively fast. , The object may be overloaded. On the other hand, if the switching point is too far from the object, the distance for operating the arm in the state of the second force control in which the moving speed is relatively slow becomes long, and the work takes time. In this way, it is difficult to speed up the work while preventing an excessive load from being applied to the object.

The present invention has been made to solve the above-mentioned problems, and can be realized as follows.

The control method of the present invention is a control method for controlling a robot having an arm and a force detection unit for detecting a force applied to the arm.
A force acquisition process for acquiring a detected value from the force detection unit, and
The first command value calculation process for obtaining the first command value by adding the first correction amount obtained from the detected value, the first force control parameter, and the target force to the command value of the position.
The second command value calculation step of adding the second correction amount obtained from the detected value and the second force control parameter to the first command value to obtain the second command value, and
It has an execution process for operating the robot based on the second command value.
The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient and an elastic modulus.
The mass coefficient of the first force control parameter is m1, the viscosity coefficient of the first force control parameter is d1, the mass coefficient of the second force control parameter is m2, and the viscosity coefficient of the second force control parameter is d2. When the elastic modulus of the second force control parameter is k2,
Satisfy m2 <m1 or d2 <d1 and satisfy k2> 0.

The robot system of the present invention includes an arm and
A force detection unit that detects the force applied to the arm,
A control unit that controls the operation of the arm is provided.
The control unit acquires the detection value from the force detection unit and obtains the detection value.
The first correction amount obtained from the detected value, the first force control parameter, and the target force is added to the command value of the position to obtain the first command value.
The second correction amount obtained from the detected value and the second force control parameter is added to the first command value to obtain the second command value.
The robot is operated based on the second command value.
The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient and an elastic modulus.
The mass coefficient of the first force control parameter is m1, the viscosity coefficient of the first force control parameter is d1, the mass coefficient of the second force control parameter is m2, and the viscosity coefficient of the second force control parameter is d2. When the elastic modulus of the second force control parameter is k2,
Satisfy m2 <m1 or d2 <d1 and satisfy k2> 0.

FIG. 1 is a diagram showing an overall configuration of the robot system of the first embodiment. FIG. 2 is a block diagram of the robot system shown in FIG. FIG. 3 is a flowchart for explaining a control operation performed by the control device shown in FIG. FIG. 4 is a graph showing the relationship between acting force and time. FIG. 5 is a graph showing the relationship between acting force and time. FIG. 6 is a graph showing the relationship between acting force and time. FIG. 7 is a diagram showing an overall configuration of the robot system of the second embodiment. FIG. 8 is a block diagram for explaining the robot system with a focus on hardware. FIG. 9 is a block diagram showing a modification 1 centering on the hardware of the robot system. FIG. 10 is a block diagram showing a modification 2 centering on the hardware of the robot system.

<First Embodiment>
Hereinafter, the control method and the robot system of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings. In the following, for convenience of explanation, the + Z-axis direction in FIG. 1, that is, the upper side is referred to as “upper”, and the −Z-axis direction, that is, the lower side is also referred to as “lower”. Further, regarding the robot arm, the base 11 side in FIG. 1 is also referred to as a “base end”, and the opposite side, that is, the end effector 20 side is also referred to as a “tip”. Further, the Z-axis direction in FIG. 1, that is, the vertical direction is defined as the "vertical direction", and the X-axis direction and the Y-axis direction, that is, the left-right direction is defined as the "horizontal direction".

As shown in FIG. 1, the robot system 100 includes a robot 1 and a robot control device for controlling the robot 1 (hereinafter, simply referred to as “control device 3”), and executes the control method of the present invention.

The robot 1 is a single-armed 6-axis vertical articulated robot in the present embodiment, and an end effector 20 can be attached to the tip of the robot 1. The robot 1 is a single-arm type articulated robot, but the robot 1 is not limited to this, and may be, for example, a double-arm type articulated robot.

The control device 3 is arranged apart from the robot 1, and can be configured by a computer or the like having a built-in CPU (Central Processing Unit), which is an example of a processor. The robot 1 has a base 11 and a movable portion 10.

The base 11 is a support that supports the movable portion 10 so as to be driveable from below, and is fixed to a floor in a factory, for example. In the robot 1, the base 11 is electrically connected to the control device 3 via the relay cable 18. The connection between the robot 1 and the control device 3 is not limited to the wired connection as shown in FIG. 1, and may be, for example, a wireless connection, and further, via a network such as the Internet. May be connected.

In the present embodiment, the movable portion 10 has a first arm 12, a second arm 13, a third arm 14, a fourth arm 15, a fifth arm 16, and a sixth arm 17. Arms are connected in this order from the base 11 side. The number of arms included in the movable portion 10 is not limited to six, and may be, for example, one, two, three, four, five, or seven or more. Further, the size such as the total length of each arm is not particularly limited and can be set as appropriate.

The base 11 and the first arm 12 are connected to each other via a joint 171. The first arm 12 is rotatable around the first rotation axis with the first rotation axis parallel to the vertical direction as the rotation center with respect to the base 11. The first rotation axis coincides with the normal of the floor on which the base 11 is fixed.

The first arm 12 and the second arm 13 are connected via a joint 172. The second arm 13 is rotatable with respect to the first arm 12 about a second rotation axis parallel to the horizontal direction. The second rotation axis is parallel to the axis orthogonal to the first rotation axis.

The second arm 13 and the third arm 14 are connected via a joint 173. The third arm 14 is rotatable about a third rotation axis parallel to the second arm 13 in the horizontal direction. The third rotation shaft is parallel to the second rotation shaft.

The third arm 14 and the fourth arm 15 are connected to each other via a joint 174. The fourth arm 15 is rotatable with respect to the third arm 14 with the fourth rotation axis parallel to the central axis direction of the third arm 14 as the rotation center. The fourth rotation axis is orthogonal to the third rotation axis.

The fourth arm 15 and the fifth arm 16 are connected via a joint 175. The fifth arm 16 is rotatable with respect to the fourth arm 15 with the fifth rotation axis as the rotation center. The fifth rotation axis is orthogonal to the fourth rotation axis.

The fifth arm 16 and the sixth arm 17 are connected via a joint 176. The sixth arm 17 is rotatable with respect to the fifth arm 16 with the sixth rotation axis as the rotation center. The sixth rotation axis is orthogonal to the fifth rotation axis.

Further, the sixth arm 17 is a robot tip portion located on the tip end side of the movable portion 10. The sixth arm 17 can be rotated together with the end effector 20 by driving the movable portion 10.

The robot 1 includes a motor M1, a motor M2, a motor M3, a motor M4, a motor M5 and a motor M6 as drive units, and an encoder E1, an encoder E2, an encoder E3, an encoder E4, an encoder E5 and an encoder E6. The motor M1 is built in the joint 171 and relatively rotates the base 11 and the first arm 12. The motor M2 is built in the joint 172 and relatively rotates the first arm 12 and the second arm 13. The motor M3 is built in the joint 173 and relatively rotates the second arm 13 and the third arm 14. The motor M4 is built in the joint 174 and relatively rotates the third arm 14 and the fourth arm 15. The motor M5 is built in the joint 175 and relatively rotates the fourth arm 15 and the fifth arm 16. The motor M6 is built in the joint 176 and relatively rotates the fifth arm 16 and the sixth arm 17.

Further, the encoder E1 is built in the joint 171 and detects the position of the motor M1. The encoder E2 is built in the joint 172 and detects the position of the motor M2. The encoder E3 is built in the joint 173 and detects the position of the motor M3. The encoder E4 is built in the joint 174 and detects the position of the motor M4. The encoder E5 is built in the joint 175 and detects the position of the motor M5. The encoder E6 is built in the joint 176 and detects the position of the motor M6.

The encoders E1 to E6 are electrically connected to the control device 3, and the positions of the motors M1 to M6 are transmitted to the control device 3 as an electric signal. Then, based on this position information, the control device 3 drives the motors M1 to M6 via a motor driver (not shown). That is, controlling the movable portion 10 means controlling the motors M1 to M6.

Further, in the robot 1, a force detecting unit 19 for detecting a force is detachably installed on the movable unit 10. Then, the movable unit 10 can be driven in a state where the force detecting unit 19 is installed. The force detection unit 19 is a 6-axis force sensor in this embodiment. The force detection unit 19 detects the magnitude of the force on the three detection shafts orthogonal to each other and the magnitude of the torque around the three detection shafts. That is, the force components in each of the X-axis, Y-axis, and Z-axis orthogonal to each other, the force component in the W direction around the X-axis, the force component in the V direction around the Y-axis, and the Z-axis circumference. The force component in the U direction is detected. In this embodiment, the Z-axis direction is the vertical direction. Further, the force component in each axial direction can be referred to as a "translational force component", and the force component around each axis can also be referred to as a "torque component". Further, the force detection unit 19 is not limited to the 6-axis force sensor, and may have other configurations.

In this embodiment, the force detection unit 19 is installed on the sixth arm 17. The location where the force detection unit 19 is installed is not limited to the sixth arm 17, that is, the arm located closest to the tip side, and may be, for example, between other arms or adjacent arms.

The end effector 20 can be detachably attached to the force detection unit 19. The end effector 20 has a function of holding, sucking, screwing, and the like. Further, in the robot system 100, a tool center point TCP is set at the tip of the end effector 20 in the robot coordinate system.
The operation of such a robot 1 is controlled by the control device 3.

Next, the control device 3 will be described.
It includes a control device 3 and a teaching device 4 (teaching pendant). The control device 3 is a configuration example of the robot control device of the present invention. The control device 3 is communicably connected to the robot 1 by a relay cable 18. The component of the control device 3 may be provided in the robot 1. The control device 3 and the teaching device 4 are connected by a cable or wirelessly. The teaching device 4 may be a dedicated computer or a general-purpose computer in which a program for teaching the robot 1 is installed. For example, a teaching pendant, which is a dedicated device for teaching the robot 1, may be used instead of the teaching device 4. Further, the control device 3 and the teaching device 4 may be provided with separate housings as shown in FIG. 1, or may be integrally configured.

The teaching device 4, the teaching program for loading the control unit 3 generates an execution program for the target position S _t and the target force f _St to be described later to the control unit 3 and the argument has been installed. The teaching device 4 includes a display 41, a processor, RAM, and a ROM, and these hardware resources cooperate with the teaching program to generate an execution program.

As shown in FIG. 2, the control device 3 is a computer in which a control program for controlling the robot 1 is installed. The control device 3 includes a processor and a RAM or ROM (not shown), and these hardware resources cooperate with the program to control the robot 1.

Further, the control device 3 includes a coordinate conversion unit 31, a coordinate conversion unit 32, a correction unit 33, a first force control unit 34, a second force control unit 35, a command integration unit 36, and a position control unit 37. And have. The control device 3 can control the operation of the robot 1 by force control or the like. “Force control” means changing the position of the end effector 20, that is, the position of the tool center point TCP and the postures of the first arm 12 to the sixth arm 17 based on the detection result of the force detection unit 19. It is the control of the operation of the robot 1. Force control includes, for example, impedance control and force trigger control.

In the force trigger control, the force detection unit 19 detects the force, and the movable unit 10 is made to move or change the posture until a predetermined force is detected by the force detection unit 19.

Impedance control includes copying control. First, to briefly explain, in impedance control, the force applied to the tip of the movable portion 10 is maintained at a predetermined force as much as possible, that is, the force detected by the force detection unit 19 in the predetermined direction is the target force as much as possible. The operation of the movable portion 10 is controlled so as to maintain the f _St. As a result, for example, when impedance control is performed on the movable portion 10, the movable portion 10 performs an operation of imitating the object in the predetermined direction. In addition, 0 is also included in the target force _fSt . For example, in the case of copying operation, the target value can be set to "0". The target force _fSt can be a numerical value other than 0. The target force _fSt can be appropriately set by the operator.

The control device 3 stores the correspondence between the combination of the rotation angles of the motors M1 to M6 and the position of the tool center point TCP in the robot coordinate system. Further, the control unit 3 stores on the basis of at least one of the target position S _t and the target force f _St for each step of the work robot 1 performs the command. Command to the target position S _t and the target force f _St argument (parameter) is set for each step of the work robot 1 performs.

Control device 3, and the target position S _t and the target force f _St which is set so as to coincide with the tool center point TCP, which controls the first arm 12 to the sixth arm 17 based on the command. Target force f _St is the force to be detected force detection unit 19 in accordance with the operation of the first arm 12 to the sixth arm 17. Here, the letter "S" represents any one of the directions of the axes (X, Y, Z, U, V, W) that define the robot coordinate system. In addition, S also represents a position in the S direction. For example, in the case of S = X, X-direction component of the position specified in the robot coordinate system becomes _{S t} = _X t, _X-direction component of the desired force is _f St _{= f Xt.}

Further, in the control device 3, when the rotation angles of the motors M1 to M6 are acquired, the coordinate conversion unit 31 shown in FIG. 2 sets the rotation angle at the position S of the tool center point TCP in the robot coordinate system based on the correspondence relationship. Convert to (X, Y, Z, V, W, U). Then, the specific coordinate transformation unit 32, the position S of the tool center point TCP, on the basis of the detection value of the force detection unit 19, the action force f _S acting actually on the force detector 19 in the robot coordinate system To do.

The point of action of action force f _S is, the tool center point TCP is separately defined as the origin O. The origin O corresponds to the point where the force detecting unit 19 detects the force. The control device 3 stores a correspondence relationship that defines the direction of the detection axis in the sensor coordinate system of the force detection unit 19 for each position S of the tool center point TCP in the robot coordinate system. Accordingly, the control apparatus 3, based on the position S of the tool center point TCP in the robot coordinate system and the corresponding relationship can identify the action force f _S in the robot coordinate system. Moreover, the torque acting on the robot, and the action force f _S, can be calculated from the distance from the tool contact point (contact point of the end effector 20 and the workpiece) until the force detection unit 19 is identified as a torque component ..

Correction unit 33 performs gravity compensation against the action force _{f S.} The gravity compensation, is to remove the component of the force or torque due to the gravity from the action force f _S. Action force f _S subjected to gravity compensation can be regarded as a force other than gravity acting on the end effector 20.

The correction unit 33 performs inertia compensation against the action force _{f S.} The inertia compensation, is to remove the component of the force or torque due to the inertial force from the action force f _S. The acting force f _S for which inertial compensation has been applied can be regarded as a force other than the inertial force acting on the end effector 20.

Next, impedance control will be described.
Impedance control is an active impedance control that realizes virtual mechanical impedance by motors M1 to M6. The control device 3 executes such impedance control in a process in a contact state in which the end effector 20 receives a force from the work, which is an object, such as a work fitting work, a screwing work, and a polishing work. In addition to such a step, for example, the safety can be improved by controlling the impedance when a person comes into contact with the robot 1.

In the impedance control, by substituting the equations of motion described later target force f _St derives the rotation angle of the motor M1~ motor M6. The signals for which the control device 3 controls the motors M1 to M6 are PWM (Pulse Width Modulation) modulated signals. The mode for controlling the motor M1~ motor M6 to derive the rotation angle from the target force f _St based on the equation of motion of the force control mode. The control device 3, the end effector 20 is in the process of non-contact state to which no external force is applied, to control the motor M1~ motor M6 rotation angle to derive a linear operation from the target position S _t. The mode for controlling the motor M1~ motor M6 from the target position S _t at a rotation angle of deriving the linear operation of the position control mode. The control unit 3, by integrating the rotation angle that derives the rotation angle and the target force f _St deriving a linear operation from the target position S _t is substituted into the equation of motion, for example by linear combination, the motor M1 at a rotation angle by integrating -The robot 1 is also controlled in the hybrid mode in which the motor M6 is controlled. The control device 3 can autonomously switch between the position control mode, the force control mode, and the hybrid mode based on the detection values of the force detection unit 19 or the encoders E1 to E6, and the position according to the input command. It is also possible to switch between control mode, force control mode and hybrid mode. From the above configuration, the control device 3 can drive the movable portion 10 so that the end effector 20 is in the target posture at the target position and the target force and moment act on the end effector 20.

Control device 3, by substituting the targeted force f _St and action force f _S in the equation of motion of the impedance control, specifying the force from the correction amount [Delta] S. The force-derived correction amount ΔS is the position where the tool center point TCP should move in order to eliminate the force deviation Δf _S (t) from the target force f _St when the tool center point TCP receives mechanical impedance. It means the size of S. The following equation (1) is an equation of motion for impedance control.

The left side of the equation (1) is the first term obtained by multiplying the second-order differential value of the position S of the tool center point TCP by the virtual inertia coefficient m (hereinafter referred to as “mass coefficient m”) and the position S of the tool center point TCP. The second term is obtained by multiplying the differential value of the above by the virtual viscosity coefficient d (hereinafter referred to as “viscosity coefficient d”), and the position S of the tool center point TCP is multiplied by the virtual elastic modulus k (hereinafter referred to as “elastic modulus k”). It is composed of the third term. The right side of the equation (1) is composed of a force deviation Δf _S (t) obtained by subtracting the actual force f from the target force f _St. The differentiation in the equation (1) means the differentiation with time. In the step of the robot 1 performs, to some cases a constant value is set as the target force f _St, there is a case where a function of time as the target force f _St is set.

The mass coefficient m means the mass virtually possessed by the tool center point TCP, the viscosity coefficient d means the viscosity resistance virtually received by the tool center point TCP, and the elastic modulus k means the virtual mass of the tool center point TCP. It means the spring constant of the elastic force received.

As the value of the mass coefficient m increases, the acceleration of operation decreases, and as the value of the mass coefficient m decreases, the acceleration of operation increases. As the value of the viscosity coefficient d increases, the speed of operation slows down, and as the value of the viscosity coefficient d decreases, the speed of operation increases. As the value of the elastic modulus k increases, the springiness increases, and as the value of the elastic modulus k increases, the springiness decreases.

In the present specification, the mass coefficient m, the viscosity coefficient d, and the elastic modulus k are referred to as control parameters. The mass coefficient m, the viscosity coefficient d, and the elastic modulus k may be set to different values for each direction, or may be set to common values regardless of the direction. Further, the mass coefficient m, the viscosity coefficient d, and the elastic modulus k can be appropriately set by the operator before the work.

In this way, the robot system 100 obtains the detection value of the force detection unit 19, the preset control parameters, and the correction amount obtained from the preset target force. This correction amount is the force-derived correction amount ΔS described above, and is the difference from the position where the tool center point TCP should be moved from the position where the external force is received. Then, this force-derived correction amount ΔS is added to the position control command value (hereinafter, simply referred to as “command value”) used for moving to the position where the external force is received to obtain a new command value. Then, by controlling the robot with this new command value, the tool center point TCP is moved to the position where the force-derived correction amount ΔS is added, the impact applied by the external force is mitigated, and the object in contact with the robot is subjected to. , It is possible to alleviate the load. As a result, the work can be performed safely and stably.

Further, as will be described later, the first force control unit 34 calculates the first correction amount ΔS1, and the second force control unit 35 calculates the second correction amount ΔS2. The position control unit 37 has a position control instruction obtaining unit 371, generates a position command in accordance with the target position S _t set by the operator. Further, the first correction amount ΔS1, the second correction amount ΔS2, and the position command are integrated by the command integration unit 36 and executed by the execution unit 361 to execute the control method of the present invention.

Here, the operation is performed relatively quickly by setting the mass coefficient m, the viscosity coefficient d, and the elastic coefficient k, but when an external force is received, the tool center point TCP is moved to a position in which the force-derived correction amount ΔS is added. A mode that takes a relatively long time, and a mode that operates relatively slowly, but it does not take a relatively long time to move the tool center point TCP to a position that takes into account the force-derived correction amount ΔS when an external force is applied. And can be realized. In the force control device described in Patent Document 1, when the arm performs work, when the arm is located at a position far from the object, the first force is controlled by using a parameter having a high moving speed, and the arm is operated. When is moved to a position closer to the object, the second force is controlled by the parameter whose moving speed is slow. Further, the above control is realized by setting a switching point for switching from the first force control to the second force control.

However, if the switching point for switching from the first force control to the second force control is too close to the object, the arm may come into contact with the object in the state of the first force control in which the moving speed is relatively fast. , The object may be overloaded. On the other hand, if the switching point is too far from the object, the distance for operating the arm in the state of the second force control in which the moving speed is relatively slow becomes long, and the work takes time. In this way, it is difficult to speed up the work while preventing an excessive load from being applied to the object.

Therefore, in the robot system 100, by performing the following control by the control device 3, it is possible to realize high-speed work while preventing an excessive load from being applied to the object. Hereinafter, the control operation of the robot system 100 will be described. As an example, force control performed when the tip of the end effector 20 comes into contact with an object will be described. In the following, the operator to set the target position S _t, the target force f _St, mass coefficients m, viscosity coefficient d and the elastic coefficient k, describing the state of starting the operation of the robot 1.

First, as shown in FIG. 3, acquisition of the encoder value is started in step S101. Specifically, the acquisition of the encoder values of the encoders E1 to E6 is started.

Next, in step S102, the force applied to the robot 1 is detected and acquired. This process is the force acquisition process. When the force detection unit 19 detects an external force and acquires it, the force applied to the force detection unit 19 is coordinate-converted in step S103. That is, the force in the force detection unit 19 acts on the reality identified in the robot coordinate system, and converts the applied force f _S which joined the tool center point TCP. Then, in step S104, performs gravity compensation against the action force _{f S.} In other words, to remove the component of the force or torque due to the gravity from the action force f _S. Then, in step S105, it performs the inertia force compensation for acting force _{f S.} In other words, to remove the component of the force or torque due to the inertial force from the action force f _S.

In step S106, the position control command value is calculated. Specifically, it calculates the next position to move from the moment when an external force is applied. In this step, the position control command value to be issued next is predicted from the direction and speed when an external force is received. Let this predicted position control command value be P _next .

Then, in step S107, the first correction amount ΔS1 is obtained from the acting force f _S , the first force control parameter, and the target force f _St. That is, these are substituted into the above equation (1). The first correction amount ΔS1 is the difference between the position where the external force is received and the position where the tool center point TCP should be moved by receiving the external force. Then, the first correction amount ΔS1 is added to the command value used for moving to the position where the external force is received to obtain the first command value. The first force control parameter is a mass coefficient m = m1, a viscosity coefficient d = d1, and an elastic coefficient k = k1.

Then, in step S108, the second correction amount ΔS2 obtained from the action force f _S and the second power control parameter, by summing the first command value, obtaining a second command value. That is, these are substituted into the above equation (1). The second force control parameter is a mass coefficient m = m2, a viscosity coefficient d = d2, and an elastic modulus k = k2. Further, the target force _fSt is set to 0. That is, it can be ignored.

Here, in the present invention, m2 <m1 or d2 <d1 is satisfied, and k2> 0. As a result, it is possible to speed up the work while preventing an excessive load from being applied to the object in contact. Hereinafter, a specific description will be given.

If force control is executed with a command value calculated using only the first force control parameter, since m2 <m1 and d2 <d1, the force control is in a mode in which acceleration and speed are relatively slow. When this relatively slow mode is represented by a graph with time on the horizontal axis and action force on the vertical axis, the graph is as shown in FIG. This mode, it takes a relatively long time until the action force f _S is the target force f _St, stable action force f _S approaches the target force f _St.

If force control is executed with the command value calculated using only the second force control parameter, m2 <m1 and d2 <d1 are satisfied and k2> 0, so that the acceleration and speed are relatively fast. In addition, the force is controlled in a mode having springiness. A graph in which the acceleration and velocity are relatively fast and the mode has springiness is represented by a graph with time on the horizontal axis and action force on the vertical axis, as shown in FIG. However, the target force _{f St} not zero, a case in which the same value as S107. In this mode, the time required for the acting force f _S to reach the target force f _St is relatively short, but the fluctuation range of the acting force is relatively large, and the acting force f _S becomes the same value as the target force f _St. It takes a relatively long time to stabilize.

Therefore, as described above, in the present invention, the second correction amount ΔS2 obtained from the acting force f _S and the second force control parameter is obtained from the acting force f _S , the target force f _St, and the first force control parameter. Add up to 1 command value to obtain the 2nd command value. Then, by executing the force control with the second command value, the force control can be performed in the mode in which the mode as shown in FIG. 4 and the mode as shown in FIG. 5 are combined. Thus, as shown in FIG. 6, is relatively short time to the action force f _S reaches the target force f _St, and suppresses the amplitude of the applied force f _S, further action force f _S is it is possible to shorten the time to stabilize to the same value as the target force f _St. From the above, it is possible to solve the above-mentioned conventional problems, that is, it is not necessary to set the switching point as in the conventional case, and the work is performed while preventing an excessive load from being applied to the object in contact. Can be speeded up.

If only one of m2 <m1 and d2 <d1 is satisfied and k2> 0 is satisfied, the effect of the present invention can be sufficiently obtained.

Further, when the elastic modulus of the first force control parameter is k1, it is preferable that k2> k1 is satisfied. This contributes to speeding up the work.

Then, in step S109, the position control command value P _next calculated in step S106 and the first correction amount ΔS1 calculated in step S107 are added to calculate the first corrected command value. This step is the first command value calculation step.

Then, in step S110, the first corrected command value calculated in step S109 and the second corrected amount ΔS2 are added to calculate the second corrected command value. This step is the second command value calculation step.

Next, in step S111, the second corrected command value is converted into the command value of the joints 171 to 176, and in step S112, the command value is converted into the final command value corresponding to the motors M1 to M6 and executed. This step is an execution step of operating the robot 1 based on the second command value.

As described above, the robot system 100 includes a first arm 12 to a sixth arm 17, a force detecting unit 19 for detecting a force applied to the first arm 12 to the sixth arm 17, and a first arm 12. A control device 3 which is a control unit for controlling the operation of the sixth arm 17 is provided. Further, the control device 3 acquires the detected value from the force detection unit 19, adds the first correction amount obtained from the detected value, the first force control parameter, and the target force to the command value of the position, and adds the first command value. Is calculated, the second correction amount obtained from the detected value and the second force control parameter is added to the first command value, the second command value is obtained, and the robot 1 is operated based on the second command value. is there. The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient, and an elastic modulus, the mass coefficient of the first force control parameter is m1, and the viscosity coefficient of the first force control parameter is d1. When the mass coefficient of the second force control parameter is m2, the viscosity coefficient of the second force control parameter is d2, and the elastic modulus of the second force control parameter is k2, m2 <m1 or d2 <d1 is satisfied, and , K2> 0 is satisfied. As a result, it is possible to speed up the work while preventing an excessive load from being applied to the object in contact.

Further, the control method of the present invention executed by the robot system 100 includes a first arm 12 to a sixth arm 17 which is an arm, and a force detecting unit 19 for detecting a force applied to the first arm 12 to the sixth arm 17. This is a control method for controlling the robot 1 having the above. Further, in this control method, the force acquisition process for acquiring the detected value from the force detecting unit 19 and the first correction amount obtained from the detected value, the first force control parameter, and the target force are added to the command value of the position. The first command value calculation process for obtaining the first command value and the second correction amount obtained from the detected value and the second force control parameter are added to the first command value to obtain the second command value. It has a calculation step and an execution step of operating the robot 1 based on the second command value. The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient, and an elastic modulus, the mass coefficient of the first force control parameter is m1, and the viscosity coefficient of the first force control parameter is d1. When the mass coefficient of the second force control parameter is m2, the viscosity coefficient of the second force control parameter is d2, and the elastic modulus of the second force control parameter is k2, m2 <m1 or d2 <d1 is satisfied, and , K2> 0 is satisfied. As a result, it is possible to speed up the work while preventing an excessive load from being applied to the object in contact.

Further, in the second command value calculation step, the mass coefficient m or the viscosity coefficient d of the second force control parameter may be increased according to the second correction amount ΔS2. As a result, the step of setting the second force control parameter in advance can be omitted, and the effect of the present invention can be obtained by a simpler method.

<Second Embodiment>
Hereinafter, the control method of the present invention and the second embodiment of the robot system will be described with reference to FIG. 7, but the differences from the above-described embodiments will be mainly described, and the same matters will be omitted.

As shown in FIG. 7, the robot 1 of the present embodiment further includes an additional member 21. The additional member 21 is connected to the sixth arm 17 and has a natural frequency higher than the natural frequency of the first arm 12 to the sixth arm 17. As a result, the end effector 20 can be easily vibrated, and the synergistic effect with k2> 0 described above can enhance the responsiveness in force control.

Further, the additional member 21 is connected to the tip end portion of the sixth arm 17 and is connected to the base end side of the end effector 20. That is, it is located on the most tip side among the first arm 12 to the sixth arm 17. As a result, the tool center point TCP and the additional member 21 can be brought as close as possible to each other, and the responsiveness in force control can be further enhanced.

<Other configuration examples of robot system>
FIG. 8 is a block diagram for explaining the robot system with a focus on hardware.

FIG. 8 shows the overall configuration of the robot system 100A in which the robot 1, the controller 61, and the computer 62 are connected. The control of the robot 1 may be executed by reading the command in the memory by the processor in the controller 61, or by reading the command in the memory by the processor existing in the computer 62 and executing the command through the controller 61. ..

Therefore, either one or both of the controller 61 and the computer 62 can be regarded as a "control device".

<Modification example 1>
FIG. 9 is a block diagram showing a modification 1 centering on the hardware of the robot system.

FIG. 9 shows the overall configuration of the robot system 100B in which the computer 63 is directly connected to the robot 1. The control of the robot 1 is directly executed by reading the command in the memory by the processor existing in the computer 63.
Therefore, the computer 63 can be regarded as a "control device".

<Modification 2>
FIG. 10 is a block diagram showing a modification 2 centering on the hardware of the robot system.

FIG. 10 shows the overall configuration of a robot system 100C in which a robot 1 having a built-in controller 61 and a computer 66 are connected, and the computer 66 is connected to a cloud 64 via a network 65 such as a LAN. The control of the robot 1 may be executed by reading the command in the memory by the processor existing in the computer 66, or by reading the command in the memory through the computer 66 by the processor existing in the cloud 64 and executing the control. May be good.

Therefore, any one, two, or three of the controller 61, the computer 66, and the cloud 64 can be regarded as a "control device".

Although the control method and the robot system of the present invention have been described above with reference to the illustrated embodiment, the present invention is not limited thereto. Further, each part constituting the robot system can be replaced with an arbitrary configuration capable of exhibiting the same function. Moreover, an arbitrary composition may be added.

1 ... Robot, 3 ... Control device, 4 ... Teaching device, 10 ... Movable part, 11 ... Base, 12 ... 1st arm, 13 ... 2nd arm, 14 ... 3rd arm, 15 ... 4th arm, 16 ... 5th arm, 17 ... 6th arm, 18 ... relay cable, 19 ... force detection unit, 20 ... end effector, 21 ... additional member, 31 ... coordinate conversion unit, 32 ... coordinate conversion unit, 33 ... correction unit, 34 ... 1st force control unit, 35 ... 2nd force control unit, 36 ... command integration unit, 37 ... position control unit, 41 ... display, 61 ... controller, 62 ... computer, 63 ... computer, 64 ... cloud, 65 ... network, 66 ... Computer, 100 ... Robot System, 100A ... Robot System, 100B ... Robot System, 100C ... Robot System, 171 ... Joint, 172 ... Joint, 173 ... Joint, 174 ... Joint, 175 ... Joint, 176 ... Joint, 361 ... Execution unit, 371 ... Position control command acquisition unit, E1 ... Encoder, E2 ... Encoder, E3 ... Encoder, E4 ... Encoder, E5 ... Encoder, E6 ... Encoder, M1 ... Motor, M2 ... Motor, M3 ... Motor, M4 ... Motor , M5 ... motor, M6 ... motor, O ... origin

Claims (6)

A control method for controlling a robot having an arm and a force detecting unit for detecting a force applied to the arm.
A force acquisition process for acquiring a detected value from the force detection unit, and
The first command value calculation process for obtaining the first command value by adding the first correction amount obtained from the detected value, the first force control parameter, and the target force to the command value of the position.
The second command value calculation step of adding the second correction amount obtained from the detected value and the second force control parameter to the first command value to obtain the second command value, and
It has an execution process for operating the robot based on the second command value.
The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient and an elastic modulus.
The mass coefficient of the first force control parameter is m1, the viscosity coefficient of the first force control parameter is d1, the mass coefficient of the second force control parameter is m2, and the viscosity coefficient of the second force control parameter is d2. When the elastic modulus of the second force control parameter is k2,
A control method characterized in that m2 <m1 or d2 <d1 is satisfied and k2> 0 is satisfied. When the elastic modulus of the first force control parameter is k1,
The control method according to claim 1, which satisfies k2> k1. The control method according to claim 1 or 2, wherein in the second command value calculation step, the mass coefficient or the viscosity coefficient of the second force control parameter is increased according to the second correction amount. With the arm
A force detection unit that detects the force applied to the arm,
A control unit that controls the operation of the arm is provided.
The control unit acquires the detection value from the force detection unit and obtains the detection value.
The first correction amount obtained from the detected value, the first force control parameter, and the target force is added to the command value of the position to obtain the first command value.
The second correction amount obtained from the detected value and the second force control parameter is added to the first command value to obtain the second command value.
The robot is operated based on the second command value.
The first force control parameter and the second force control parameter include a mass coefficient, a viscosity coefficient and an elastic modulus.
The mass coefficient of the first force control parameter is m1, the viscosity coefficient of the first force control parameter is d1, the mass coefficient of the second force control parameter is m2, and the viscosity coefficient of the second force control parameter is d2. When the elastic modulus of the second force control parameter is k2,
A robot system characterized in that m2 <m1 or d2 <d1 is satisfied and k2> 0 is satisfied. The robot system according to claim 4, further comprising an additional member connected to the arm and having a natural frequency higher than the natural frequency of the arm. The robot system according to claim 4 or 5, wherein the additional member is connected to a tip end portion of the arm.

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