Method for path planning for an array-based pick-and-place operation performed with a robot arm and compensator for use in the method

Abstract

Method for path planning for an array-based pick-and-place operation performed with a robot arm, which includes: Step a: Operating a robot arm to perform an initial calibration; Step b: Generating a coordinate position of the next pick-and-place point using a controller; Step c: Instruct the robot arm with the controller to perform a pick-and-place procedure according to the coordinate position of the next pick-and-place point; Step d: Detecting an X-axis displacement and a Y-axis displacement of the robot arm during the pick-and-place procedure using an X-axis position sensor and a Y-axis position sensor, and feeding a detection result back to the controller; Step e: Calculate a coordinate error of the pick-and-place point from step b according to the X-axis displacement and the Y-axis displacement of the robot arm with the controller; and Step f: Calculating a position compensation value of the robot arm according to the coordinate error from step e using the controller, where step b follows step f. wherein the X-axis position sensor (12) and the Y-axis sensor (14) are arranged together in a compensator (10) of the robot arm, which includes: a first element (16); a second element (18) connected to a lower surface of the first element (16); a linear X-axis guide (20) which is arranged on the second element (18) so that the second element (18) can move in an X-axis direction relative to the first element (16) through the linear X-axis guide (20); a linear Y-axis guide (22) which is arranged on the second element (18) so that the second element (18) can move in a Y-axis direction relative to the first element (16) through the linear Y-axis guide (22); two X-axis return spring elements (24) facing away from each other, arranged between the first element (18) and the second element (18) and aligned in the X-axis direction to exert a return force on the second element (18); two Y-axis return spring elements (26) facing away from each other, arranged between the first element (16) and the second element (18) and aligned in the Y-axis direction to exert a return force on the second element (18); an X-axis position sensor (12) arranged and adapted at one end of the linear X-axis guide (24) to detect a distance traveled by the linear X-axis guide (20); and a Y-axis position sensor (14) which is arranged and adapted at one end of the linear Y-axis guide (26) to detect a distance traveled by the linear Y-axis guide (22).

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The present invention relates to robot arms and in particular to a method for planning the path for an array-based pick-and-place operation performed with a robot arm, and to a compensator for use in the method. 2. Description of the state of the art

[0002] An array-based pick-and-place operation performed with a robot arm is prone to an accumulation of errors. As a result, the robot arm can only operate within a limited working time. Prior art EP 2190634 discloses compensation in the XY plane using a linear guide and a parallel four-rod connection, employing a spring sensor to generate an alarm signal when the distance traveled is too great, causing the robot arm to cease operation. However, the spring sensor in EP 2190634 cannot accurately determine the distance traveled by the robot arm in the XY direction. Furthermore, the alarm signal emitted by the spring sensor causes the robot arm to stop operating, thus preventing it from completing the remainder of the array-based pick-and-place operation.

[0003] US 4,745,681 discloses a detection method using force sensors arranged near a gripper, wherein pressurized gas is introduced into or released through a pin hole, the gripper is repeatedly moved so that a pin can be aligned with the hole as closely as possible when an unbalanced gas pressure is detected, and wherein the pin is inserted into the pin hole by the gripper as soon as the force sensors detect that the gas pressure is uniformly distributed. However, the invention claimed in US 4,745,681 has the following disadvantages: it takes too long to wait for the gas pressure levels to equalize; the cost is too high because the gripper requires four sensors; and it cannot be applied to precision products. SUMMARY OF THE INVENTION

[0004] One object of the present invention is to provide a method for planning the path for array-based pick-and-place operations performed with a robot arm, in order not only to perform array-based pick-and-place tasks entirely through signal feedback and position compensation, but also to eliminate the accumulation of errors.

[0005] To solve these and other problems, the present invention provides a route / path / track planning method which comprises the following steps: (Step a) Operate a robot arm to perform an origin calibration; (Step b) Establishing a coordinate position of the next pick-and-place point using a controller; (Step c) Instructing the robot arm using the controller to perform a pick-and-place operation according to the coordinate position of the next pick-and-place point; (Step d) Detecting an X-axis displacement and a Y-axis displacement of the robot arm during the pick-and-place operation and feeding the detection result back to the controller using an X-axis position sensor and a Y-axis position sensor; (Step e) Calculating a coordinate error of the pick-and-place point according to the X-axis displacement and the Y-axis displacement of the robot arm using the controller; (Step f) and calculating a position compensation value of the robot arm according to the coordinate error using the controller, with Step f followed by Step b.

[0006] Preferably, at the end of a pick-and-place cycle, the controller determines whether the final pick-and-place point has been identified. If the determination is positive, the controller instructs the robot arm to stop operation, and if it is negative, it executes step d. Through repeated feedback and compensation, it is not only possible to eliminate the amplification of errors but also to fully execute array-based pick-and-place operations. BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS Fig. Figure 1 is a flowchart of the present invention; Fig. Figure 2 is a perspective view of a compensator provided by the present invention; Fig. Figure 3 is an exploded view of the compensator provided by the present invention; and Fig.Figure 4 is a schematic view of the path planning of the present invention. DETAILED DESCRIPTION OF THE FORM OF EXECUTION OF THE INVENTION

[0007] In Fig. 1. A path planning method of the present invention comprises the following steps:

[0008] Step a (S1): Operating a robot arm to perform an origin calibration.

[0009] Step b (S2): Generating a coordinate position of the next pick-and-place point using a controller.

[0010] Step c (S3): Instruct the robot arm, using the controller, to perform a pick-and-place procedure according to the coordinate position of the next pick-and-place point.

[0011] Step d (S4): Detecting an X-axis displacement and a Y-axis displacement of the robot arm during the pick-and-place procedure and feeding a detection result back to the controller, using an X-axis position sensor 12 and a Y-axis position sensor 14, as described in Fig. 3 shown.

[0012] In this embodiment, the X-axis position sensor 12 and the Y-axis position sensor 14 are arranged together in a compensator 10 of the robot arm. Fig. 3 The compensator 10 provided by the present invention comprises not only the X-axis position sensor 12 and the Y-axis position sensor 14, but also a first element 16, a second element 18, a linear X-axis guide 20, a linear Y-axis guide 22, two opposing X-axis return spring elements 24, and two opposing Y-axis return spring elements 26.

[0013] The upper surface of the first element 16 is connected to the robot arm.

[0014] The upper surface of the second element 18 is connected to the lower surface of the first element 16. The lower surface of the second element 18 is connected to an end tool (not shown).

[0015] The linear X-axis guide 20 is arranged on the upper surface of the second element 18, so that the second element 18 can move in an X-axis direction with respect to the first element 16 through the linear X-axis guide 20.

[0016] The linear Y-axis guide 22 is arranged on the upper surface of the second element 18, so that the second element 18 can move in a Y-axis direction relative to the first element 16 through the linear Y-axis guide 22.

[0017] The X-axis return spring elements 24 are arranged horizontally between the first element 16 and the second element 18 and are aligned in the X-axis direction to exert a restoring force on the second element 18, allowing the second element 18 to return to its original position when it is not subjected to a force from the side.

[0018] The Y-axis restoring spring elements 26 are arranged horizontally between the first element 16 and the second element 18 and are aligned in the Y-axis direction to exert a restoring force on the second element 18, allowing the second element 18 to return to its original position when no lateral force is applied to it.

[0019] The X-axis position sensor 12 is arranged at one end of the linear X-axis guide 20 to detect the distance traveled by the linear X-axis guide 20.

[0020] The Y-axis position sensor 14 is arranged at one end of the linear Y-axis guide 22 to detect the distance traveled by the linear X-axis guide 22.

[0021] Step e (S5): Calculate the coordinate error of the pick-and-place point from step b according to the X-axis displacement and the Y-axis displacement of the robot arm with the controller.

[0022] Step f (S6): Calculate a position compensation value for the robot arm according to the coordinate error from step e using the controller. Step f is followed by step b.

[0023] The steps listed above are described below in Fig. Section 4, Table 1 explains and illustrates this using six array-based pick-and-place points. The origin coordinates are designated P0. The coordinates assigned to the first pick-and-place point and generated by the controller are designated P1. The controller receives coordinate error ε from P1.1xy After the pick-and-place operation has been performed at P1, the controller then generates the second pick-and-place point. The coordinates of the second pick-and-place point are designated P2. The controller receives a coordinate error ε. 2xy After the pick-and-place operation at point P2, the controller generates a third pick-and-place point. The coordinates of this third pick-and-place point are designated P3. During the pick-and-place operation at P3, the controller calculates a position compensation value based on the two previously obtained coordinate errors ε. 1xy , ε 2xy , so that the controller corrects and changes the pick-and-place position of the robot arm to P3' according to the calculated position compensation value and coordinate error ε 3xyThe coordinates of the fourth pick-and-place point are designated P4. During the pick-and-place operation performed at P4 by the controller, the controller calculates a position compensation value according to the previously obtained coordinate error ε. 1xy , so that the controller corrects and changes the pick-and-place position of the robot arm to P4' according to the calculated position compensation value and coordinate error ε 4xy The coordinates of the fifth pick-and-place point are designated P5. During the pick-and-place operation performed at P5 by the controller, the controller calculates a position compensation value based on the two previously obtained coordinate errors ε. 3xy , ε 4xy , so that the controller corrects and changes the pick-and-place position of the robot arm to P5' according to the calculated position compensation value and coordinate error ε 5xyreceived from P5. Details of the rest of the procedure can be derived analogously. Table 1 Original position Coordinate error Corrected position P1 e 1xy P1 P2 e 2xy P2 P3 e 3xy P3'=P3+e 1xy +e 2xy P4 e 4xy P4'=P4+e 1xy P5 e 5xy P5'=P5+e 3xy +e 4xy

[0024] After completion of a pick-and-place operation, the controller determines whether the final pick-and-place point has been identified. If so, the controller instructs the robot arm to stop operation. If not, step d is triggered.

[0025] The present invention is therefore characterized in that: during each operation of the pick-and-place process performed with the robot arm, the X-axis and Y-axis position sensors 12, 14 detect coordinate errors of a pick-and-place point, so that the controller calculates a position compensation value based on the sum of the coordinate error vectors and corrects the pick-and-place position of the robot arm according to this position compensation value. By repeating the aforementioned process sequence, it is possible not only to eliminate the amplification of errors but also to fully execute array-based pick-and-place tasks, thereby solving the problem of the present invention.

Claims

[1] Method for path planning for an array-based pick-and-place performed with a robot arm, which comprises: Step a: Operating a robot arm to perform an origin calibration; Step b: Generating a coordinate position of a next pick-and-place point with a controller; Step c: Instruct the robot arm with the controller to perform a pick-and-place procedure according to the coordinate position of the next pick-and-place point; Step d: Detecting an X-axis displacement and a Y-axis displacement of the robot arm during the pick-and-place process with an X-axis position sensor and a Y-axis position sensor and feeding back a detection result to the controller; Step e: Calculating a coordinate error of the pick-and-place point of step b according to the X-axis displacement and the Y-axis displacement of the robot arm with the controller; and Step f: Calculating a position compensation value of the robot arm according to the coordinate error of step e with the controller, where step b follows step f, wherein the X-axis position sensor (12) and the Y-axis sensor (14) are arranged together in a compensator (10) of the robot arm, which includes: a first element (16); a second element (18) connected to a lower surface of the first element (16); a linear X-axis guide (20) arranged on the second element (18) such that the second element (18) can move in an X-axis direction relative to the first element (16) through the linear X-axis guide (20); a linear Y-axis guide (22) arranged on the second element (18) such that the second element (18) can move in a Y-axis direction relative to the first element (16) through the linear Y-axis guide (22); two opposite X-axis return spring elements (24) arranged between the first element (18) and the second element (18) and aligned in the X-axis direction to exert a return force on the second element (18); two opposite Y-axis return spring elements (26) arranged between the first element (16) and the second element (18) and aligned in the Y-axis direction to exert a return force on the second element (18); an X-axis position sensor (12) arranged at one end of the linear X-axis guide (24) and adapted to detect a distance traveled by the linear X-axis guide (20); and a Y-axis position sensor (14) arranged at one end of the linear Y-axis guide (26) and adapted to detect a distance traveled by the linear Y-axis guide (22). [2] The method of claim 1, wherein after completion of an operation of the pick and place method in step c, the controller determines whether a final pick and place point has been identified, wherein upon a positive determination the controller instructs the robot arm to cease operation, and upon a negative determination step d is initiated.

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