Robotic Device

Abstract

To prevent trouble in adjusting a pressurizing force applied on a workpiece even when mass of a processing part 2 increases in a robot device 1 which three-dimensionally moves the processing part 2 for polishing or friction-stir welding the workpiece.SOLUTION: A processing part 2 of a robot device 1 includes a gravity reducing part 12 which gives force in an opposite direction to gravity on a tool 10. An air cylinder as the gravity reducing part 12 includes a following piston 19, and a case 21. The piston 19 is integrated with the tool 10. The case 21 is integrated with a body 17 which does not displace relatively to the robot 3. The piston 19 is controlled to displace relatively to the case 21. The force in the opposite direction to the gravity acts on the tool 10 when the piston 19 makes to displace relatively to the case 21.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a robot device that includes a processing unit having a tool for grinding or friction stir welding a workpiece (hereinafter sometimes referred to as a workpiece), and that moves this processing unit three-dimensionally by a robot. [Background technology]

[0002] Conventionally, the following configuration has been known for such robot devices. That is, in the robot device, the robot has an articulated arm, and holds a processing unit including a polishing tool or a joining tool at the tip of the arm. The robot device performs polishing or friction stir welding on the workpiece by controlling the operation of the robot to displace the tool three-dimensionally along a predetermined trajectory (see, for example, Patent Documents 1 and 2).

[0003] Moreover, in recent years, there has been an increasing demand for the quality of the finished workpiece after machining, and in addition to controlling the position of the tool by controlling the operation of the robot, there is also a growing demand for varying the pressure that the tool applies to the workpiece according to the situation. However, in order to satisfy such requirements, it is necessary to add an actuator that changes the pressure force and a mechanism that transmits the pressure force from the actuator to the tool to the processing unit, which increases the mass of the processing unit, and this can make it difficult to adjust the pressure force using the actuator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6239172 [Patent Document 2] JP 2015-85485 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to prevent any hindrance to the adjustment of the pressing force applied to a workpiece even when the mass of a processing unit increases, in a robot apparatus that three-dimensionally moves a processing unit for polishing or friction stir welding the workpiece.

Means for Solving the Problems

[0006] The robot apparatus according to the first aspect of the present disclosure includes the following processing unit and robot. First, the processing unit polishes a predetermined workpiece while applying a pressing force thereto. Further, the robot holds the processing unit as an end effector and is controlled so that the processing unit is displaced three-dimensionally. Further, the processing unit has the following acting unit, pressing force adjusting unit, and gravity relaxation unit. First, the acting unit polishes the workpiece. Further, the pressing force adjusting unit includes an actuator that generates an output for changing the pressing force, , and ball screw and adjusts the pressing force by relatively displacing the acting unit with respect to the robot by the output of the actuator.

[0007] Furthermore, the gravity relaxation unit exerts a force in a direction opposite to gravity on the acting unit. The gravity relaxation unit includes a movable part integrated with the acting unit and a fixed part integrated with a part in the processing unit that does not relatively displace with respect to the robot. The movable part is controlled to relatively displace with respect to the fixed part, and by relatively displacing the movable part with respect to the fixed part, a force in a direction opposite to gravity is exerted on the acting unit. The ball screw has a screw and a slide member as follows. The screw is rotated by the output of the actuator, and the slide member has a screw hole that screws into the screw, so that its rotation is restricted and it is driven linearly by the rotation of the screw. The slide member holds a unit consisting of an action part and a motor that drives the action part. Furthermore, the robot is fastened to a body. That is, the body houses the screw and the portion of the slide member near the screw hole, and the slide member moves linearly when the screw rotates inside the body. The movable part is fastened to the slide member and is integrated with the operating part via the slide member and the motor, and the fixed part is fixed to the body. In the gravity mitigation portion, the movable portion exerts a force on the sliding member in the opposite direction to gravity due to relative displacement of the movable portion with respect to the fixed portion, thereby exerting a force on the acting portion in the opposite direction to gravity.

[0008] According to the robot apparatus according to the second aspect of the present disclosure, the processing unit performs friction stir welding while applying a pressing force to a predetermined workpiece, and the acting unit performs friction stir welding on the workpiece. This solves the problem of preventing any problems in adjusting the pressure applied to the workpiece in a robot device that moves a processing part in three dimensions for polishing or friction stir welding the workpiece, even when the mass of the processing part increases. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an overall configuration diagram of a robot device (embodiment); DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The robot device according to the embodiment will be described based on the following examples. EXAMPLES

[0011] [Configuration of the embodiment] The configuration of a robot device 1 according to the embodiment will be described with reference to FIG. The robot device 1 includes a processing unit 2, a robot 3, a control unit 4, and a detection unit 5, as described below. First, the processing unit 2 polishes a specified workpiece while applying a pressure, and the robot 3 holds the processing unit 2 as an end effector and is controlled by the control unit 4 so that the processing unit 2 is displaced three-dimensionally.

[0012] Here, the robot 3 has a multi-joint arm 6, and holds the processing unit 2 at the tip of the arm 6 as an end effector. Servo motors 7a, 7b, and 7c are incorporated in each joint of the arm 6, and the control unit 4 controls the operation of the robot 3 by controlling the servo motors 7a, 7b, and 7c. The robot 3 displaces the processing unit 2 three-dimensionally along a predetermined trajectory through the operation control by the control unit 4.

[0013] The servo motors 7a, 7b, and 7c are energized and controlled by the control unit 4, and have a well-known brushless structure in which, for example, a stator and a rotor are each equipped with a three-phase coil and a permanent magnet. The servo motors 7a, 7b, and 7c are each equipped with an encoder 8a, 8b, and 8c that detects the rotation angle of the rotor.

[0014] The control unit 4 is a control unit including a microcomputer of a known structure and performs calculations and the like for controlling the energization of the servo motors 7a, 7b, 7c, etc. Here, the control unit 4 is provided with an inverter circuit for changing the amount of energization to the servo motors 7a, 7b, 7c, as well as the microcomputer, and a current sensor for detecting the current energized to the servo motors 7a, 7b, 7c, etc. The current sensor is formed of a known current detection resistor.

[0015] The control unit 4 detects the position and posture of the processing unit 2 based on the signals output from the encoders 8a, 8b, and 8c. Furthermore, the control unit 4 controls the energization of the servo motors 7a, 7b, and 7c so that the detected values ​​of the position and posture of the processing unit 2 approximately match command values ​​set based on a predetermined trajectory. As a result, the processing unit 2 moves three-dimensionally along the predetermined trajectory to polish the workpiece. As described later, the control unit 4 also controls the pressure adjustment unit 11 and the gravity relaxation unit 12 of the processing unit 2. The processing unit 2 will be described in further detail below.

[0016] The processing unit 2 has the following action unit 10, pressure adjustment unit 11 and gravity relaxation unit 12. First, the action part 10 is for polishing a workpiece (hereinafter, the action part 10 may be referred to as a tool 10). The tool 10 constitutes a unit together with a motor 7d that drives the tool 10 itself.

[0017] The tool 10 is, for example, a grindstone or the like, which is pressed against a portion of the surface of the workpiece to be polished and is driven to rotate by a motor 7d. The motor 7d has a known brushless structure. The motor 7d also has a known inverter circuit, a current sensor, a controller, and the like, and controls the rotation speed based on the current flowing through the motor 7d. The current sensor is, for example, a known current detection resistor.

[0018] Next, the pressure adjusting unit 11 includes an actuator that generates an output for changing the pressure, and displaces the tool 10 relative to the robot 3 by the output of the actuator to adjust the pressure.

[0019] The actuator is, for example, a servo motor 7e as follows. That is, similar to the servo motors 7a, 7b, and 7c, the servo motor 7e has a well-known brushless structure in which a stator and a rotor are equipped with three-phase coils and permanent magnets, respectively, and is controlled by the control unit 4. The servo motor 7e is also equipped with an encoder 8e that detects the rotation angle of the rotor.

[0020] The control unit 4 controls the power supply to the servo motor 7e based on the signal output from the encoder 8e. The control unit 4 is provided with an inverter circuit for changing the amount of power supplied to the servo motor 7e, and a current sensor for detecting the current supplied to the servo motor 7e. The current sensor is formed of a well-known current detection resistor.

[0021] Further, the pressure adjusting unit 11 includes the following ball screw 14 and the like in addition to the servo motor 7e serving as an actuator. First, the ball screw 14 is a well-known mechanical element that converts rotational motion into linear motion, and includes a screw 15 and a slide member 16 as described below. That is, the screw 15 is rotationally driven by the output of the servo motor 7d, and the slide member 16 has a screw hole that screws into the screw 15, so that its rotation is restricted, and the slide member 16 is linearly driven by the rotation of the screw 15.

[0022] Furthermore, the slide member 16 holds a unit consisting of the tool 10 and the servo motor 7d. Furthermore, the screw 15 and a portion of the slide member 16 near the screw hole are housed in a predetermined body 17, and the body 17 is fastened to the tip of the robot 3. When the screw 15 rotates inside the body 17, the slide member 16 moves linearly.

[0023] As described above, in the processing unit 2, the torque generated by the servo motor 7e is converted into thrust by the ball screw 14 and transmitted to the tool 10 via the slide member 16. In addition, the thrust transmitted to the tool 10 acts on the workpiece as a pressing force. The pressure adjusting unit 11 is controlled by the control unit 4 as follows.

[0024] For example, the control unit 4 calculates a target value of the pressure force based on the trajectory of the processing unit 2, and further calculates a command value of the current flowing through the servo motor 7e. The control unit 4 then controls the power supply to the servo motor 7e so that the detection value obtained from the signal of the current sensor approximately matches the command value. This allows the pressure force to be freely changed based on the trajectory of the processing unit 2, thereby improving the finish quality of the processed workpiece.

[0025] Furthermore, the gravity mitigation unit 12 applies a force to the tool 10 in the direction opposite to gravity. Here, the gravity mitigation unit 12 is, for example, an air cylinder, and includes a movable part and a fixed part as described below. First, the movable part is integrated with the tool 10 and displaces together with the tool 10, and the fixed part is integrated with a part that does not displace relatively to the robot 3.

[0026] The air cylinder includes a piston 19 driven by air pressure, a case 21 that houses the piston 19 and forms an air pressure chamber 20, and a spring 22 that biases the piston 19 in the opposite direction to the air pressure. Also, a drive unit 23 is provided to allow compressed air to flow in and out of the pressure chamber 20.

[0027] The drive unit 23 has a well-known configuration including solenoid valves and the like which open and close the inlet and outlet flow paths of the compressed air to the pressure chamber 20, and controls the inflow and outflow of the compressed air to the pressure chamber 20 in response to commands from the control unit 4 (hereinafter, the force that the gravity relaxation unit 12 exerts on the tool 10 and which is in the opposite direction to gravity may be referred to as the relaxation force).

[0028] Here, the piston 19 has a tip end protruding outside the case 21 fastened to the slide member 16, is integrated with the tool 10 via the slide member 16 and the motor 7d, and corresponds to the above-mentioned movable part. The case 21 is a part fixed to the body 17 and does not move relative to the robot 3, and corresponds to the above-mentioned fixed part. In addition, the control unit 4 commands the drive unit 23 to control the piston 19 to be displaced relative to the case 21, and as a result of this control, the piston 19 attempts to be displaced relative to the case 21, and a relaxation force acts on the tool 10.

[0029] Next, the detection unit 5 detects the angular difference between the direction of the pressure force and the direction of gravity, and is, for example, a digital angle meter with a built-in gyro sensor, and is, for example, integrated into the body 17. The control unit 4 controls the relaxation force based on the angular difference detected by the detection unit 5. Specifically, for example, the smaller the angular difference, the greater the component of gravity that acts in the direction of the pressure force, so the control unit 4 controls the gravity relaxation unit 12 to strengthen the relaxation force as the angular difference becomes smaller. In other words, the air pressure in the pressure chamber 20 is increased.

[0030] [Effects of the embodiment] The robot device 1 of the embodiment includes the following processing unit 2 and robot 3. First, the processing unit 2 polishes the workpiece while applying pressure to it. The robot 3 holds the processing unit 2 as an end effector and is controlled so that the processing unit 2 is displaced three-dimensionally. The processing unit 2 has a tool 10, a pressure adjustment unit 11, and a gravity reduction unit 12 as described below. First, the tool 10 polishes the workpiece. The pressure adjustment unit 11 includes a servo motor 7e that generates an output for changing the pressure, and displaces the tool 10 relative to the robot 3 by the output of the servo motor 7e to adjust the pressure.

[0031] Furthermore, the gravity mitigation unit 12 exerts a force on the tool 10 in the direction opposite to gravity. The air cylinder serving as the gravity mitigation unit 12 includes the following piston 19 and case 21. That is, the piston 19 is integrated with the tool 10, and the case 21 is integrated with the body 17 which does not displace relatively to the robot 3. The piston 19 is controlled to displace relative to the case 21, and as the piston 19 attempts to displace relative to the case 21, a force in the direction opposite to gravity acts on the tool 10.

[0032] As a result, the force (relaxation force) that the gravity absorbing part 12 exerts on the tool 10 can mitigate the effect of the mass of the processing part 2 on the operation of the tool 10. Therefore, even if the pressing force adjustment part 11 is applied to the processing part 2 and the mass of the processing part 2 increases, it is possible to prevent any hindrance to the adjustment of the pressing force.

[0033] The robot device 1 also includes a control unit 4 that controls the force that the gravity mitigation unit 12 applies to the tool 10, and a detection unit 5 that detects the angular difference between the direction of the pressure force and the direction of gravity. The control unit 4 controls the force that the gravity mitigation unit 12 applies to the tool 10 based on the angular difference detected by the detection unit 5. This allows the relaxation force to be adjusted according to the direction of the pressure force. That is, the relaxation force can be controlled by taking into account the mass of the processing unit 2, that is, the effect of gravity acting on the processing unit 2 on the pressure force. This allows the pressure force to be controlled with higher accuracy.

[0034] [Modifications] The embodiment discloses a specific example, and it goes without saying that the present invention is not limited to the embodiment. For example, according to the robot device 1 of the embodiment, the tool 10 is for grinding the workpiece, but the tool 10 may be, for example, a welding tool for friction stir welding two workpieces to be welded.

[0035] According to the robot device 1 of the embodiment, the motor 7d, which constitutes a unit with the tool 10, has an inverter circuit, a current sensor, a controller, and the like, and controls the rotation speed based on the current passed through the motor 7d, but the form of the motor 7d is not limited to that of the embodiment. For example, an air-driven motor may be used as the motor 7d. Furthermore, the control unit 4 may be equipped with an inverter circuit and a current sensor for controlling the motor 7d, and the motor 7d may be equipped with an encoder for detecting the rotation angle of the rotor, so that the control unit 4 controls the motor 7d.

[0036] Furthermore, according to the robot device 1 of the embodiment, an air cylinder is adopted as the gravity mitigation unit 12, and air pressure is used as the mitigation force, but for example, a solenoid may be adopted as the gravity mitigation unit 12, and magnetic attractive force may be used as the mitigation force, a hydraulic cylinder may be adopted, and hydraulic force may be used as the mitigation force, or a motor may be adopted, and the torque of the motor may be converted into thrust and used as the mitigation force. [Explanation of symbols]

[0037] 1 Robot device 2 Processing unit 3 Robot 4 Control unit 7d Servo motor (motor) 7e servo motor (actuator) 10 tool (action part) 11 pressure adjustment part 12 gravity relaxation part 14 Ball screw 15 screw 16 Slide member 17 body 19 Piston (moving part) 21 Case (fixed part)

Claims

1. a processing unit that applies pressure to a predetermined workpiece while polishing it; a robot that holds the processing unit as an end effector and is controlled so that the processing unit is displaced three-dimensionally; The processing unit includes: An operating portion for polishing the workpiece; a pressure adjusting unit that includes an actuator that generates an output for changing the pressure force and a ball screw, and that adjusts the pressure force by displacing the action unit relative to the robot using the output of the actuator; A gravity mitigation portion that exerts a force on the action portion in a direction opposite to the direction of gravity, This gravity relief section is the robot includes a movable part integrated with the action part, and a fixed part integrated with a portion of the processing part that does not move relative to the robot, the movable part is controlled to move relative to the fixed part, and the movable part exerts a force on the action part in a direction opposite to gravity by attempting to move relative to the fixed part, the ball screw includes a screw that is rotationally driven by the output of the actuator, and a slide member that has a screw hole that screws into the screw, is restricted in rotation, and is linearly driven by the rotation of the screw; The slide member holds a unit including the action portion and a motor that drives the action portion, Furthermore, a body is fastened to the robot, the body accommodating the screw and a portion of the slide member adjacent to the screw hole, and the slide member moves linearly within the body as the screw rotates; the movable portion is fastened to the slide member and is integrated with the action portion via the slide member and the motor, and the fixed portion is fixed to the body, The robot device is characterized in that, in the gravity mitigation portion, a force in the opposite direction to gravity is exerted on the action portion by the movable portion exerting a force on the sliding member in a direction opposite to gravity due to a relative displacement of the movable portion with respect to the fixed portion.

2. A processing unit that performs friction stir welding while applying pressure to a predetermined workpiece; a robot that holds the processing unit as an end effector and is controlled so that the processing unit is displaced three-dimensionally; The processing unit includes: An operating portion for friction stir welding the workpieces; a pressure adjusting unit that includes an actuator that generates an output for changing the pressure force and a ball screw, and that adjusts the pressure force by displacing the action unit relative to the robot using the output of the actuator; A gravity mitigation portion that exerts a force on the action portion in a direction opposite to the direction of gravity, This gravity relief section is the robot includes a movable part integrated with the action part, and a fixed part integrated with a portion of the processing part that does not move relative to the robot, the movable part is controlled to move relative to the fixed part, and the movable part exerts a force on the action part in a direction opposite to gravity by attempting to move relative to the fixed part, the ball screw includes a screw that is rotationally driven by the output of the actuator, and a slide member that has a screw hole that screws into the screw, is restricted in rotation, and is linearly driven by the rotation of the screw; The slide member holds a unit including the action portion and a motor that drives the action portion, Furthermore, a body is fastened to the robot, the body accommodating the screw and a portion of the slide member adjacent to the screw hole, and the slide member moves linearly within the body as the screw rotates; the movable portion is fastened to the slide member and is integrated with the action portion via the slide member and the motor, and the fixed portion is fixed to the body, The robot device is characterized in that, in the gravity mitigation portion, a force in the opposite direction to gravity is exerted on the action portion by the movable portion exerting a force on the sliding member in a direction opposite to gravity due to a relative displacement of the movable portion with respect to the fixed portion.

3. The robot device according to claim 1 or 2, A control unit that controls a force exerted by the gravity mitigation unit on the action unit; a detection unit for detecting an angular difference between a direction of the pressure force and a direction of gravity, The robot device is characterized in that the control unit controls the force that the gravity mitigation unit applies to the action unit based on the angle difference detected by the detection unit.

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