JP2004276181A - Parallel link stage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain uneven speed of a parallel link stage and the generation of vibration while using a general personal computer. <P>SOLUTION: This parallel link stage device 1 includes: a parallel link stage 2 and a control part 3 for controlling the operation thereof. The control part 3 includes: a trajectory command generating part 17 generating a command value representing the position and angle of an end effector part 5 at prescribed intervals of control; a reverse kinematic operating part 18 for calculating the travel of an actuator 9 according to a generated command value; and a servo part 16 for calculating a control signal given to the actuator 9 according to the calculated travel. A buffer part 15 for storing the travel for two or more times calculated in the reverse kinematic operating part 18 to be sequentially output to a servo part 16 at every period of control is provided between the reverse kinematic operating part 18 and the servo part 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a precision stage using a parallel link mechanism.
[0002]
[Prior art]
2. Description of the Related Art A precision stage using a parallel link mechanism capable of performing a relative movement of a total of six degrees of freedom, including three degrees of freedom of translation and three degrees of rotation, has been known. As shown in FIG. 3, the precision stage 100 includes a base 100a serving as a whole base, an end effector 100b on which a work object such as a sample is mounted, an ultrasonic motor 100c serving as a driving source, A slider portion 100d moved by an ultrasonic motor 100c, an optical scale 100g for detecting a movement amount of the slider portion 100d, and a movable link portion 100e for mechanically connecting the slider portion 100d and the end effector portion 100b. And a bearing portion 100f that connects between the end effector portion 100b and the movable link portion 100e and between the movable link portion 100e and the slider portion 100d while maintaining a degree of freedom in the rotational direction. (For example, see Patent Document 1).
[0003]
In the precision stage 100, a plurality of members other than the base portion 100a and the end effector portion 100b are formed according to a desired degree of freedom. For example, Patent Literature 1 discloses a precision stage having six degrees of freedom, and these members are provided six by six.
[0004]
Also, the precision stage 100 includes a trajectory command generation unit 101 that generates a movement path, a movement speed, and a target position of the end effector unit 100b, and a movement position of each of the slider units 100d based on the position of the end effector unit 100b. An inverse kinematics operation unit 102 for calculating a moving speed and a servo unit 103 for controlling the driving of each ultrasonic motor 100c using the operation result of the inverse kinematics operation unit 102 as a command value are connected.
With the recent high performance and low price of personal computers, it is conceivable that the trajectory command generation unit 101 and the inverse kinematics calculation unit 102 are performed by a personal computer.
[0005]
[Patent Document 1]
JP-A-2000-98257 (FIG. 3, paragraph 0022, etc.)
[0006]
[Problems to be solved by the invention]
However, in this case, although the arithmetic processing itself can be performed at a high performance in the personal computer, the processing result of the operation system of the personal computer is diversified, so that the arithmetic result is calculated at an accurate time period on the order of milliseconds. It is difficult to output to the servo unit 103. As a result, it is conceivable that the operation of the stage unit 100 may have uneven speed or unnecessary vibration.
[0007]
It is possible to adopt a special operation system that guarantees real-time performance, or to implement a part of the arithmetic function by hardware having an NC function. However, this increases the cost of the entire precision stage system. There is.
[0008]
The present invention has been made in view of the above circumstances, and has as its object to provide a parallel link stage that suppresses the occurrence of speed unevenness and vibration while using a general personal computer.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 provides a base, an end effector disposed at a distance from the base, and at least three sets of link units disposed between the base and the end effector. And a control unit for controlling the operation of the parallel link stage, wherein each of the link units is swingably connected to the end effector unit, and A trajectory command that is movably connected and includes a drive link including an actuator fixed to the base unit, wherein the control unit generates a command value indicating a position and an angle of the end effector unit at predetermined control intervals. A generation unit; an inverse kinematics calculation unit that calculates the amount of movement of the actuator of each drive link based on the command value generated by the trajectory command generation unit; A servo unit that calculates a control signal to be applied to the actuator based on the moved amount, and a plurality of movements calculated in the inverse kinematics calculation unit between the inverse kinematics calculation unit and the servo unit. Provided is a parallel link stage device provided with a buffer unit for storing an amount and sequentially outputting the amount to a servo unit at a predetermined control cycle.
[0010]
According to the present invention, the actuator of each drive link is operated by the operation of the inverse kinematics calculation unit based on the command value indicating the position and angle of the end effector unit for each predetermined control interval generated by the operation of the trajectory command generation unit. Is calculated. The calculated movement amount is temporarily stored in the buffer unit and then output to the servo unit. When the servo unit receives the movement amount, the servo unit calculates a control signal to be applied to each actuator based on the movement amount and inputs the control signal to the actuator to displace the drive link. A movable link is swingably connected to the drive link, and the movable link is swingably connected to the end effector unit. Therefore, the link portion including the drive link and the movable link is moved in accordance with the amount of movement of the actuator. The effector unit is displaced so as to match the position and angle indicated by the command value.
[0011]
In this case, since the movement amount for a plurality of times is stored in the buffer unit and is sequentially output at each predetermined control cycle, the trajectory command generation unit and the inverse kinematics calculation unit of the control unit perform the control cycle when the actuator operates. There is no need to perform calculations every time. As a result, even if a personal computer is used as the control unit, it is possible to control the servo unit with an accurate control cycle on the order of milliseconds, preventing the end effector unit from generating speed irregularities and unnecessary vibration. It is possible to do.
[0012]
The invention according to claim 2 provides the parallel link stage device according to claim 1, wherein the trajectory command generation unit and the inverse kinematics calculation unit are configured by a personal computer.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
A parallel link stage device according to an embodiment of the present invention will be described below with reference to FIG.
As shown in FIG. 1, a parallel link stage device 1 according to the present embodiment includes a parallel link stage 2 and a control unit 3 that controls the parallel link stage.
[0014]
The parallel link stage 2 includes a base section 4 fixed to an external structure, an end effector section 5 disposed at an interval from the base section 4, and a section between the base section 4 and the end effector section 5. And six sets of link portions 6 arranged at the same position.
The base unit 4 and the end effector unit 5 are formed, for example, in a disk shape. The base portion 4 is maintained in a horizontal state, for example, by being fixed to an external structure. Further, the end effector unit 5 is provided with a jig (not shown) for holding the work object mounted.
[0015]
Each link section 6 is configured by connecting a drive link 7 attached to the base section 4 and a movable link 8 attached to the end effector section 5.
The drive link 7 includes, for example, an actuator 9 composed of an ultrasonic linear motor, a slider 10 linearly moved by the actuator 9, and an optical scale 11 capable of detecting a displacement of the slider 10. The actuator 9 is fixed to the base portion 4 in a horizontal state at a predetermined inclination angle, for example, an angle of 0 ° to 45 °.
[0016]
The movable link 8 is a rod-shaped member having a fixed length. An upper joint 12 and a lower joint 13 formed of ball joints are attached to both ends of the movable link 8, and the upper joint 12 at one end is a lower surface of the end effector unit 5. And the lower joint 13 at the other end is attached to the slider 10 of the drive link 7.
The optical scale 11 is fixed to the main body of the actuator 9, and detects a change in the stroke of the slider 10 and sends it to the control unit 3.
[0017]
The control unit 3 includes a personal computer 14, a buffer box 15 connected to the personal computer 14, and a motor controller / driver 16 (servo unit) connected to the buffer box 15.
The personal computer 14 includes a trajectory command generator 17 and an inverse kinematics calculator 18. The trajectory command generator 17 generates command values indicating the position and angle of the end effector unit 5 at predetermined control intervals. Further, the inverse kinematics calculation unit 18 calculates the amount of movement of the slider 10 in the actuator 9 of each drive link 7 based on the command value generated by the trajectory command generation unit 17.
[0018]
The buffer box 15 includes a memory (not shown) for storing the amount of movement of the slider 10 calculated by the inverse kinematics calculation unit 18, and stores the positions and angles of the plurality of end effector units 5 at predetermined control intervals. The amount of movement of the slider 10 to achieve this is stored for a plurality of times. Then, the oldest data among the stored movement amounts of the slider 10 is output to the motor controller / driver 16.
[0019]
The motor controller / driver 16 operates the actuator 9 based on the movement amount of the slider 10 input from the buffer box 15 and the stroke change input from the optical scale 11. These personal computer 14, buffer box 15 and motor controller / driver 16 are connected by high-speed communication means 19. The high-speed communication unit 19 is a communication unit that can perform data communication in a sufficiently short time with respect to the control cycle of the parallel link stage 2.
[0020]
The operation of the thus configured parallel link stage device 1 according to the present embodiment will be described below.
When the position and orientation of the work target are changed to desired positions and postures using the parallel link stage device 1 according to the present embodiment, the end on which the work target is mounted is operated by the operation of the personal computer 14. A command value for the position and angle of the effector unit 5 is generated. In the personal computer 14, the internal trajectory command generation unit 17 is operated, and a plurality of command values are generated at predetermined control intervals, for example, every several milliseconds.
[0021]
Next, based on the generated command value, the inverse kinematics operation unit 18 in the personal computer 14 is operated, and the movement amount of the slider 10 of each drive link 7 corresponding to each command value is calculated. The calculated movement amount of each slider 10 is stored in the buffer box 15 in association with each of a plurality of command values. Then, in a state where a predetermined number of movement amounts are stored in the buffer box 15, the data is output from the buffer box 15 to the motor controller / driver 16 in order from the oldest data at the control intervals.
[0022]
In the motor controller / driver 16, a control signal of the actuator 9 according to the movement amount of each slider 10 is generated and supplied to the actuator 9, and the detection signal from the optical scale 11 matches the movement amount of the slider 10. Is adjusted as follows. The actuator 9 moves the slider 10 according to the supplied control signal. Since the lower joint 13 provided at one end of the movable link 8 is attached to the slider 10, the movable link 8 is displaced. Further, since the end effector unit 5 is attached to the other end of the movable link 8 via the upper link 12, the end effector unit 5 is moved by the displacement of the movable link 8, and the work object on the end effector unit 5 is moved. Is changed.
[0023]
As described above, according to the parallel link stage device 1 according to the present embodiment, the calculation result in the personal computer 14 is not directly input to the motor controller / driver 16, but is stored in the buffer box 15 once. It is output to the motor controller / driver 16 at predetermined control intervals. Therefore, in the personal computer 14, there is no need to end the calculation strictly at each control interval and output the result. In other words, the personal computer 14 does not need to operate at a relatively short, accurate period of the order of milliseconds, and can be a commercially available general personal computer without a special operating system or hardware. According to the parallel link stage device 1 according to the present embodiment, even when such a general personal computer 14 is used, the speed unevenness and the vibration when the work object mounted on the end effector unit 5 is displaced. There is an effect that can be prevented.
[0024]
Next, an assembly adjustment device 20 including the parallel link stage device 1 according to the above-described first embodiment will be described with reference to FIG.
The assembling adjustment device 20 includes an overall control computer 21 for performing overall control, the parallel link stage device 1, a robot controller 22 controlled by the overall control computer 21, and a robot 23 controlled by the robot controller 22. Have.
[0025]
The general control computer 21 is a personal computer, and is connected to a personal computer 14 constituting the control unit 3 of the parallel link stage device 1 by a high-speed communication unit 24.
The robot 23 is a device that spatially moves a hand 25 that grips a work target mounted on the end effector unit 5 of the parallel link stage 2, a camera 26 that detects the position and posture of the work target, and the like. The operation is performed by the operation of the robot controller 22 which receives a command from the overall control computer 21. In the drawing, reference numeral 27 denotes a component pallet on which a plurality of components as work objects are arranged.
[0026]
The operation of the assembling adjustment device 20 configured as described above will be described below.
First, the robot controller 22 that has received an instruction from the overall control computer 21 operates the robot 23 and places the hand 25 and the camera 26 at a position where a target component is taken out from the component pallet 27. When the hand 25 and the camera 26 are arranged at predetermined positions, the camera 26 is operated, and the work target on the component pallet 27 is imaged. The captured image data is sent to the overall control computer 21, where the position and orientation of the work target are recognized by image processing. The overall control computer 21 sends an instruction to the robot controller 22 to arrange the hand 25 at a position and a posture at which the work object can be gripped based on the recognized position and posture of the work object. The robot controller 22 activates the robot 23 based on the instruction sent from the overall control computer 21 and then activates the hand 25 to grip the work target.
[0027]
The gripped work target is conveyed onto the end effector unit 5 of the parallel link stage 2 by the operation of the robot 23 by the robot controller 22 and mounted on the end effector unit 5. Then, the operation target is fixed on the end effector unit 5 by the operation of a jig (not shown).
Thereafter, the operation of the parallel link stage device 1 causes the parallel link stage 2 to displace the work object so as to be in an appropriate position and posture suitable for assembly.
[0028]
In this case, since the plurality of calculation results stored in the buffer box 15 are output to the parallel link stage 2 at appropriate control intervals, the parallel link stage 2 achieves a smooth movement operation without unnecessary vibration. Can be. Therefore, it is possible to prevent an unexpected displacement from occurring due to the vibration of the work object held by the jig. As a result, the component gripped by the hand 25 can be assembled without causing interference with the work target on the end effector unit 5.
[0029]
In the above embodiment, the general control computer 21 is provided separately from the control unit 3 of the parallel link stage device 1. However, instead of this, the general control computer 21 is provided with the control unit of the parallel link stage device 1. 3 may be included. This makes it possible to provide a less expensive assembly adjustment device 20.
[0030]
【The invention's effect】
As described above, according to the parallel link stage device of the present invention, it is possible to suppress uneven speed and unnecessary vibration of the parallel link stage, and to operate the parallel link stage smoothly. In particular, when the parallel link stage is used for assembling parts, it is possible to assemble properly without causing interference with a partner part to be assembled. In addition, there is an effect that a general personal computer can be used without using a special control device, and the product cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a parallel link stage device according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an example of an assembling adjustment device using the parallel link stage device of FIG. 1;
FIG. 3 is a block diagram showing a conventional parallel link stage device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Parallel link stage apparatus 2 Parallel link stage 3 Control part 4 Base part 5 End effector part 6 Link part 7 Drive link 8 Movable link 9 Actuator 15 Buffer box (buffer part)
16 Motor controller / driver (servo unit)
17 Orbit command generation unit 18 Inverse kinematics calculation unit

Claims (2)

A parallel link stage including a base, an end effector disposed at an interval with respect to the base, and at least three sets of links disposed between the base and the end effector; A control unit for controlling the operation of the parallel link stage,
The link section includes a movable link swingably connected to the end effector section, and a drive link that is swingably connected to the movable link and includes an actuator fixed to the base section,
A trajectory command generation unit configured to generate a command value indicating a position and an angle of the end effector unit for each predetermined control interval; and a drive link based on the command value generated by the trajectory command generation unit. An inverse kinematics calculation unit that calculates the amount of movement of the actuator, and a servo unit that calculates a control signal to be applied to the actuator based on the calculated amount of movement,
A buffer unit is provided between the inverse kinematics calculation unit and the servo unit, which stores a plurality of movement amounts calculated in the inverse kinematics calculation unit and sequentially outputs the movement amounts to the servo unit at a predetermined control cycle. Parallel link stage equipment. The parallel link stage device according to claim 1, wherein the trajectory command generation unit and the inverse kinematics calculation unit are configured by a personal computer.

Images