JP2018015821A - Direct teaching device of parallel link robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct teaching device of a parallel link robot which is easily handleable and stable, and can perform direct teaching with a simple and inexpensive constitution.SOLUTION: A parallel link robot has at least three link mechanisms which connect a base body part and a movable part and arrange a joint between the base body and the movable part, and a stepping motor which moves the movable part relatively with respect to the base body while bending the movable part with each joint of the link mechanisms as a driving source. Therein, a holding part capable of directly touching the movable part and actuating the movable part is provided and a switch for turning on/off excitation of the stepping motor is provided near the holding part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a teaching device for a parallel link robot, and more particularly to a direct teaching device in which a teaching operator performs teaching by directly operating a movable part of a parallel link robot.

  Similar to other industrial robots, the parallel link robot can be taught by jogging each axis and setting the end effector provided on the movable part to the desired position / posture as a teaching point. Direct teaching in which a teaching worker directly operates a movable part of a robot is known.

  In Patent Document 1, in a parallel link robot having a servo motor and an electromagnetic brake in each axis drive unit, a suspension unit that connects the base unit and the movable unit of the robot and applies a force against gravity by expansion and contraction to the movable body. The parallel link robot that enables the teaching worker to easily operate the movable body part that is the output part with a light force by turning off the servo motor and the electromagnetic brake of the driving part during teaching. Is described.

Japanese Patent No. 5054842

  In the robot described in Patent Document 1 described above, it is possible for the teaching worker to directly touch the movable portion and operate the movable portion with a light force. A program is created. This means that the position of each axis of the robot is read and recorded at regular sampling times over the entire path while the teaching worker performs an operation along the trajectory to be taught. Therefore, if the worker performs a useless operation in the middle of teaching or makes a mistake in the route, the recorded work program must be edited and corrected. Such a work program editing work needs to be frequently performed using an operation panel or a personal computer connected to the robot, which is a troublesome work. In addition, a structural mechanism for allowing the operator to move the movable part with a light force during teaching is required, which causes an increase in cost.

  On the other hand, a method of creating a work program by jogging each axis of a conventional robot, setting the end effector of the output unit to a desired position / posture, and recording the coordinates as a teaching point is certain, The operation of jogging each axis of the robot and aligning the position coordinates is very laborious.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a direct teaching device for a parallel link robot capable of performing simple direct teaching with a simple and inexpensive configuration. To do.

  In order to solve the above-mentioned problems, a direct teaching apparatus for a parallel link robot according to the present invention connects at least a base part and a movable part, and has at least three links in which joints are arranged between the base part and the movable part. In a parallel link robot provided with a mechanism and a stepping motor provided as a drive source, which is provided in the base part and is bent at each joint of the link mechanism to move the movable part relative to the base part. A gripping member that can be operated by an operator directly touching the movable portion is provided, and a switch for turning ON / OFF the excitation of the stepping motor is provided in the vicinity of the gripping member.

  According to the present invention, it is possible to directly teach a simple parallel link robot with a simple and inexpensive configuration, and the operability during teaching operation is improved by providing a clear gripping part on the movable part. The movable part can be moved stably. In addition, by arranging switches and buttons necessary for the teaching operation in the vicinity of the gripping part of the movable part, the teaching operator can perform the teaching operation without releasing his hands from the movable part. It is possible to realize a direct teaching device for a parallel link robot with excellent efficiency.

1 is a schematic configuration diagram of a parallel link robot according to an embodiment of the present invention. Block diagram showing part of the stepping motor control system Diagram showing two-phase excitation pulse signal 1 is a schematic configuration diagram of a balancer mechanism of a parallel link robot according to an embodiment of the present invention. Operational diagram of balancer mechanism Diagram of load torque due to gravity and counter torque generated by balancer Partial enlarged view of movable part of parallel link robot The block block diagram which concerns on embodiment of this invention Diagram showing an example of teaching data

(Example)
FIG. 1 is a schematic configuration diagram of a parallel link robot 100 according to an embodiment of the present invention.

  In FIG. 1, a parallel link robot 100 includes a base portion 101 as a fixed member, three sets of link structure portions, and a movable portion 102 including an output shaft. A stand 103 that supports the base body 101 is disposed below the base body 101.

  The base portion 101 has a box shape, and the first motor 104 and the second motor 105 are fixed to the left and right symmetrical positions of the side surface portion of the base portion 101, and the third motor 106 is fixed to the upper surface portion via attachment members. Has been. The first motor 104, the second motor 105, and the third motor 106 are stepping motors with built-in reduction gears, and the first arm 107, the second arm 108, and the third arm 109 are connected to the respective rotation output shafts. ing. A first link 110, a second link 111, and a third link 112, which are a pair of parallel links, are connected to the arms 107, 108, and 109 through joint members 110b, 111b, and 112b, respectively. The other end is connected to an output shaft 113, which is a movable part, via joint members 110a, 111a, and 112a.

  The three motors arranged so as to surround the box-shaped base portion 101 are such that the first motor 104 and the second motor 105 have a rotation axis in the vertical direction, and the third motor 106 has a rotation axis. It is supported in the horizontal direction.

  The output shaft 113 is provided with a protruding shaft that protrudes in a horizontal direction obliquely forward from the central axis, and the first link 110 and the second link 111 are respectively connected to the left and right sides via the joint members 110a and 111a. It is connected. Further, a support shaft 113a orthogonal to the output shaft 113 is attached and fixed to the upper end portion of the output shaft 113, and the third link 112 is connected to both ends of the support shaft 113a from above via a joint member 112a. It is connected.

  Due to the parallel links of the first link 110 and the second link 111, the posture (tilt) of the output shaft 113 is held constant (substantially in the vertical direction) regardless of the position where the first arm 107 and the second arm 108 rotate. The Further, the parallel link of the third link 112 restrains the rotation of the output shaft 113 around the axis regardless of the position where the third arm 109 rotates, and the direction is held constant.

  In the parallel link robot 100 according to the embodiment of the present invention, the joint members 110a and 110b and the joint members 111a and 111b are ball joints having three degrees of freedom for rotation, and the joint members 112a and 112b are two degrees of freedom for rotation. A universal joint with a degree is used. Any of these joint members has no functional problem as long as they have two degrees of freedom, but the joint member itself can be made compact by using a ball joint. However, in this case, in order to prevent the parallel link mechanism from being twisted, the bridge members 114 and 115 are required as restricting members that restrict the rotation of the first link 110 and the second link 111 around the axis. The bridge members 114 and 115 are arranged near both ends of the two link shafts so as to span the two link shafts. Each of the bridge members 114 and 115 has an axis orthogonal to the first link 110 and the second link 111, and is rotatably supported by the axis. As a result, the two link shafts can be moved relative to each other while maintaining the parallel state, and the degree of freedom about the axis of each link can be constrained.

  By driving the first arm 107 by the first motor 104 and driving the second arm 108 by the second motor 105, the output shaft 113 moves in a substantially horizontal direction. When the output shaft 113 is moved in the vertical direction by driving the third arm 109 by the third motor 106, the first link 110 and the second link 111 are tilted with a deviation from the horizontal. Therefore, the position of the output shaft 113 in the three-dimensional space (predetermined space) is determined based on the amount of drive of the first, second, and third arms in consideration of the amount of inclination of the first link 110 and the second link 111. Can be calculated geometrically from Further, it is possible to calculate the driving amounts of the first, second, and third motors from the spatial position coordinates of the output shaft 113 by calculation of inverse kinematics.

  Next, a stepping motor provided in an embodiment of the present invention will be described. FIG. 2 is a block diagram showing a part of a control system of a stepping motor which is a drive source of the parallel link robot of the present invention. FIG. 3 is a diagram showing a pulse signal of a two-phase excitation method. In FIG. 2, 11 is a stepping motor for driving an arm of a parallel link parallel link robot, and 12 is a CPU (control device) for outputting an operation command, which is connected via a motor driver D. The motor driver D includes a power transistor for driving the stepping motor 11 and a signal output port 14 that receives a command from the CPU 12 and outputs a pulse signal at a predetermined timing. When the pulse signals p1 to p4 shown in FIG. 3 are output from the signal output port 14 in response to a command from the CPU 12, the stepping motor 11 uses the power transistor 15 that has received the pulse signals p1 to p4 as a unit of step angle. Driven by rotation. Since the detent torque due to the attractive force of the rotor magnet acts even when the stepping motor 11 is stopped (in a non-excited state), the rotational position can be maintained with a high holding torque.

  By cooperatively controlling the rotation amounts of the first motor 104, the second motor 105, and the third motor 106, the movable portion 102 including the output shaft 113 is translated in three axes with respect to the base portion 101 that is a fixed member. Can do exercise.

  Next, the balancer mechanism 200 provided on the third arm 109 will be described. An end effector such as a chuck 117 is attached to the tip of the movable portion 102, and when a work weight is included, a large moment due to gravity acts. The balancer mechanism 200 offsets the moment due to gravity by applying a counter torque that acts in a direction opposite to the moment due to gravity to the third arm 109 that mainly moves the output shaft 113 in the vertical direction. The load on the third arm 109 is reduced, and when the third motor 106 is stopped, the third arm 109 is prevented from descending and the end effector position is maintained without using expensive parts such as an electromagnetic brake. It becomes possible to do.

  In FIG. 4, an auxiliary arm 201 that swings around a support shaft J <b> 2 as a fulcrum is connected and fixed to the third arm 109 via a connection link 202. Both ends of the tension spring 203 are fixed to the joint support shaft 112c of the third link 112 disposed at the tip of the third arm 109 and the fixing hole 201a of the tip of the auxiliary arm 201. The third arm 109 is always biased toward the auxiliary arm 201 by 203.

  In the above configuration, when the third arm 109 rotates around the output shaft J1 of the third motor 106, the auxiliary arm 201 interlocks and swings around the support shaft J2 as a fulcrum. At this time, regarding the positions of the joint portions J3 and J4 of the connecting link 202, the distance from the joint portion J1 to J3 of the third arm 109 is L1, the distance from the joint portion J2 to J4 of the auxiliary arm 201 is L2, and L1 < By setting to be L2, the rotation angle of the auxiliary arm 201 can be made smaller than the rotation angle of the third arm 109.

  In this case, the rotation angle (output angle) of the auxiliary arm 201 with respect to the rotation angle (input angle) of the third arm 109 is geometric from the four-joint link mechanism model having the joint portion J1 and the joint portion J2 as fixed joints. Can be calculated automatically.

  The gravitational torque acting on the third arm 109 is a torque due to the total gravity including the arm and the link, chuck, and workpiece connected to the arm, but differs depending on the posture (rotation angle) of the arm. Assuming that the angle formed by the third arm 109 with the horizontal plane is θ, the gravitational torque acting on the arm is a function of cos θ. For example, in the range of 0 ° ≦ θ ≦ 90 °, θ = 0 °, that is, the third It becomes maximum when the arm 109 becomes horizontal, and decreases as θ increases as shown in FIG.

  The tension spring 203 that connects the third arm 109 and the auxiliary arm 201 compensates for the gravitational torque acting on the third arm 109 according to the rotation angle of the arm. The extension amount of the tension spring 203 can be varied according to the rotation angle of the third arm 109 due to the difference in the rotation angle due to the interlocking of the third arm 109 and the auxiliary arm 201 described above. θ = 0 °, that is, when the third arm 109 is horizontal, the extension amount of the tension spring 203 is large, a large tensile force acts on the third arm 109, and a large compensation torque is generated. As shown in FIG. 5, as the rotation angle θ of the third arm 109 increases, the extension amount of the tension spring 203 decreases, and the tensile force by the tension spring 203 decreases, and the compensation torque generated in the third arm 109. Becomes smaller.

  FIG. 6 is an example of a graph showing the relationship between the gravitational torque acting on the arm and the compensation torque generated on the arm by the tension spring 203 according to the posture (rotation angle) of the arm. In FIG. 6, the horizontal axis represents the angle (rotation angle) θ (deg) formed by the third arm 109 with the horizontal plane, and the vertical axis represents the torque T (Nm). A is a gravitational torque acting on the third arm 109, which is a function of cos θ, and has a curve as shown in the figure. B shows the compensation torque generated in the third arm 109 by the tension spring 203, and the extension amount and tension direction of the tension spring 203 (the third arm 109 and the tension spring) according to the rotation angle of the arm. Since the angle formed with (203) changes, a curve as shown in the figure is obtained.

  The compensation torque generated in the third arm 109 can also be calculated by calculation as a function of the rotation angle θ of the third arm 109, so that the auxiliary arm 201 and the curve such that the curves of A and B coincide with each other. By setting the position of the connecting link 202, the spring constant of the tension spring 203, the mounting position, and the like, it is possible to maintain the torque balance around the joint portion J1 of the third arm 109.

  When the stepping motor is not excited, the detent torque of the third motor 106 acts on the third arm 109. Therefore, in consideration of the detent torque value of the third motor 106, if the difference between the two is within a predetermined range, that is, the compensation torque generated in the arm and the detent torque of the motor at any rotation angle θ. Is set to be equal to or greater than the gravitational torque acting on the arm to prevent the third arm 109 from dropping when the power to the stepping motor is cut off when the power is stopped. The position of the end effector can be maintained.

  In the balancer mechanism 200 of the present embodiment, a simple and inexpensive configuration does not depend on the rotation angle of the arm, enables self-weight compensation in a wide arm rotation range, and spring force for generating torque necessary for compensation. Since the spring member can be made compact, the robot main body can be miniaturized.

  Next, a direct teaching method for the parallel link robot 100 according to an embodiment of the present invention will be described. FIG. 7 is a partially enlarged view of the movable portion 102 of the parallel link robot 100. In FIG. 7, an end effector support member 118 is coaxially provided below the output shaft 113 with the operation portion 119 interposed therebetween. . A chuck 117 that is an end effector is fitted and attached to a mounting portion of the end effector support member 118 and is detachably fixed by a bolt 120.

  The operation unit 119 is provided with a grip member 121 that allows an operator to safely grip and move the movable unit 102 directly during teaching. In addition, the stepping motors of the first motor 104, the second motor 105, and the third motor 106 can be simultaneously switched on and off, and the excitation ON / OFF state is linked to the switching button 122. An LED (display means) 123 for displaying and a registration button 124 for registering the position information of the movable unit 102 in the teaching data are provided.

It is desirable that the excitation ON / OFF switch button 122 and the registration button 124 be in the vicinity of the gripping member 121 so that the teaching operator can operate the gripping member 121 while gripping it.
Further, an LED (display means) 123 that displays the excitation ON / OFF state in conjunction with the switch button 122 allows the teaching operator to check the excitation state of the stepping motor at a glance while operating the movable unit 102. Increases efficiency. For example, in this embodiment, the LED (display means) 123 is turned on when excitation is turned on, and the LED (display means) 123 is turned off when excitation is turned off.

  FIG. 8 is a diagram showing an electrical block configuration. Signals of buttons and the like provided in the operation unit 119 of the movable unit 102 of the parallel link robot 100 are input to the controller 125. The controller 125 that controls the operation of the parallel link robot 100 is configured mainly with a microcomputer, and includes a CPU 12 and ROM 16 and RAM 17 as storage means. The ROM 16 includes a memory such as an electrically rewritable flash memory in addition to a general read-only memory. The ROM 16 stores various control programs for driving and controlling the parallel link robot 100, including a control program related to direct teaching described later.

  Further, the CPU 12 is connected to the stepping motors of the first to third motors 104 to 106 via the motor drivers D1 to D3, and further, encoders S1 to S3 are provided on the output shafts of the motors. By outputting the rotation detection signal to the controller 125, the position of the movable unit 102 is detected. Position information (X, Y, Z coordinates) of the movable unit 102 is sequentially monitored by a display unit 125 such as a PC or an operation panel connected to the controller 125.

  If the stepping motors of the first motor 104, the second motor 105, and the third motor 106 are brought into a non-excited state by the excitation ON / OFF switch button 122 at the time of teaching, the holding force of each motor is released, so the parallel link robot The 100 movable parts 102 can be easily moved. Further, the position of the movable portion 102 is stably maintained even in the non-excited state by the detent torque of the stepping motor and the balancer mechanism 200 described above. Furthermore, since the position detection means (encoders) S1 to S3 of each motor are counting even in the non-excited state, the position information of the movable part 102 is always output.

  After the movable unit 102 equipped with the end effector is moved in accordance with a predetermined teaching point, the registration point position information (X, Y, Z coordinates) is registered in the teaching data shown in FIG. 9 by pressing a registration button. It is possible. Simple teaching data can be created by moving the movable unit 102 along a series of teaching points and sequentially registering the position information of each teaching point.

  The teaching data is created and edited by a PC or an operation panel and stored in the ROM or RAM in the control unit 12.

  The teaching data in FIG. 9 includes teaching point position information (X, Y, Z coordinates), target moving speed, stop time, and I / O condition settings for connection to the outside including the end effector (IO input / output). In addition, a command (COM) or the like in serial communication connected to the outside can be set. These items other than the position information are input and created separately from the direct teaching work. Further, it is also possible to use the method of creating teaching data by finely adjusting the position of each teaching point by a conventional jog operation after setting and registering roughly teaching points by direct teaching work. In this case, only the jog operation is performed from the beginning, which is far more efficient than positioning the movable part.

  In this embodiment, the parallel link robot provided with the three-axis stepping motor has been described. Similarly, for the parallel link robot provided with the fourth to sixth axes using the stepping motor as the drive source of each axis. Even can be applied. In this case as well, the position and orientation (rotation angle) of the end effector mounted on the movable part by performing the teaching operation when the excitation of each stepping motor is turned off by the excitation ON / OFF switch button and teaching point registration button provided on the movable part. Can be sequentially registered in the teaching data.

  In addition, the size, shape, position, and the like of the gripping member in the present embodiment are not limited to those illustrated in the drawings, and may be provided directly on the end effector as long as the workability of the teaching work is taken into consideration. The LED (display means) 123 may change the lighting color in conjunction with the excitation ON / OFF switching button 122. Further, not only LEDs but also display means such as an LCD may be used.

100 Parallel Link Robot 101 Base Unit 102 Movable Unit 104 First Motor (Stepping Motor)
105 Second motor (stepping motor)
106 Third motor (stepping motor)
109 Third arm 117 Chuck 119 Operation unit 121 Holding member 122 Excitation ON / OFF switch button 123 LED (display means)
124 Teaching point registration button 200 Balancer mechanism S1 to S3 Encoder

Claims (3)

  At least three link mechanisms in which a base part and a movable part are connected, and a joint is disposed between the base part and the movable part, and provided at the base part and bent at each joint of the link mechanism In a parallel link robot using a stepping motor that moves the movable part relative to the base part as a drive source, the parallel link robot includes a gripping member that can be operated by directly touching the movable part. A direct teaching device for a parallel link robot, characterized in that a switch for turning on / off the excitation of the stepping motor is provided in the vicinity of the member.   Position detecting means capable of detecting the position of the movable part by an encoder provided on the output shaft of the stepping motor, teaching operation is performed when excitation of the stepping motor is OFF, and predetermined position information of the movable part is taught 2. The direct teaching apparatus for a parallel link robot according to claim 1, wherein a teaching point registration button capable of sequentially registering teaching data as point position information is provided in the vicinity of the gripping member. The direct teaching apparatus for a parallel link robot according to claim 1 or 2, further comprising a balancer mechanism that cancels a moment due to gravity of the movable portion and maintains a position when excitation of the stepping motor is OFF.

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