Industrial robots, which are used in automatic production in the automotive industry, for example, operate in such a manner, when fitted with various tools (grippers, spot/laser welding tongs, deburring tools, etc.), that they perform different tasks such as parts transport and handling, welding, joining etc. If a plurality of processes are intended to be performed by a single robot, this robot needs to be able to change its tool during the machining process. To this end, the robot is typically provided with a tool changer which allows tools to be picked up and deposited without manual intervention by an operator.
An application which requires the use of a tool changer can have the following appearance: A gripper fitted on the robot tip or on the robot head is used by the robot to grasp a workpiece in a workpiece holder and to move with the grasped workpiece to the machining station, where the workpiece is fixed. This involves the workpiece being placed onto the workpiece holder, generally by an operator, or involves the workpiece being directly placed onto the workpiece holder, generally by an operator, or being placed directly into the gripper of the robot. The gripper is then deposited in a gripper rack and the robot takes back a suitable tool for machining the workpiece from a tool holder, takes the gripper again and moves to the workpiece holder in order to put a new workpiece into the machining station. The finished workpiece can be removed from the workpiece holder by the robot or an operator and deposited in a workpiece store.
This means that the robot is provided with a tool changer and in so doing is used and operates in proximity to an operator. When a tool changer of this kind or various different tools is/are being used by an industrial robot, there is the risk that the operator operating in proximity to the robot will be injured, for example if the robot is carrying a welding gun instead of a gripper and takes it into the area which contains the loading station or workpiece holder.
The motions of a robot are prescribed by a program. Errors can occur if the program itself contains an error; it is also possible for the operator who starts the robot to make an error, for example by setting a program pointer to the wrong location and starting the robot, and there may also be an external PLC error, or the PLC program and the robot program do not operate in sync, particularly after a restart.
It is therefore desirable to provide additional safety which prevents the robot from entering particular areas of the machining booth when an incorrect tool is detected, or from exiting a particular area of the booth when a dangerous tool is mounted on the robot.
An aspect of the invention is to provide a method for increasing safety when operating a robot, particularly an industrial robot, which achieves or at least increases the protection of an operator in a simple manner.
The invention thus involves the tool changer producing at least one safe, particularly two-channel, signal for identifying the fitted tool, each tool having an explicit signature associated with it and therefore different kinds of tools being able to be explicitly identified by means of the safe signal.
This signal may be electrical, magnetic, electrostatic; it may be a light signal or use radio waves or comprise other known means. Each signal signature has at least one associated virtual wall which is activated or deactivated when the signal is applied.
To further improve the protection of an operator, the virtual wall may be complemented or replaced by a virtual protective space or an axial region of the robot into which the robot is prevented from entering, particularly with an inadmissible or dangerous tool. In this case, the speed of motion particularly of the robot head is intended to be stopped or significantly reduced to a harmless speed of motion when the virtual wall or the virtual protective space is approached.
The invention prevents particularly the head of a robot which is carrying a dangerous tool, for example a welding gun, from being moved, particularly quickly and at high speed, into the area which may contain an operator, who could be injured by the robot. It is naturally possible for the robot head to enter the relevant area at very slow speed, so that the risk of injury no longer exists or is minimized. On the other hand, particularly when welding guns are being used, which can be at high temperature, entry into a protected zone must be prevented at all costs.
The invention and further advantageous refinements and improvements of the invention will be explained and described in more detail with reference to the drawings, which show a few exemplary embodiments of the invention and in which:
When the workpiece has been deposited in the machining station 15, the robot head or the robot arm with the gripper moves along the dotted line 16 to a gripper depositing station 17, deposits the gripper, moves along the likewise dotted line 18 to a tool holder 19 and picks up a new tool, the gripper holder 17 and the tool holder being in a common holding device 20. This holding device 20 is used for changing the tools. From the tool holder 19, the robot 12 with the relevant tool moves along the solid line 21 to the machining station 15 and, when machining of the workpiece has ended, moves via the line 22 back to the tool holder, deposits the tool there and moves along the line 23 to the gripper holder 17, takes a gripper and moves with it along the dotted line 24 to the loading station 11, where the robot 13 picks up a new workpiece and the machining operation is repeated anew as just described.
In the area of the loading station 11, which may contain an operator, the operator is at particular risk from the robot if the robot performs an incorrect motion and/or draws alongside the loading station 11 with a dangerous tool, such as a hot welding gun.
Accordingly, the robot 13 and the robot arm 12 have associated motion sensors or speed-of-motion sensors which measure the buckling motions of the robot arm 12 or the rotary motion of the robot 13 and convert them into signals which are supplied to a signal-processing and control device. The signals processed in this device are compared with suitable limit-value parameters. What is known as a virtual wall 25 can be penetrated by the robot only if the correct tool is fitted on the robot. The tool can move only on the trajectory marked by solid arrows. Moving along the dotted path 14, 24 through the virtual wall 25 results in the robot being switched off if it is carrying an inadmissible tool. In the illustration shown in
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The robot head 60 of the arm 12, which is not shown in the figure, has a holding element 61 on it which is mounted on the robot head flange and on which a tool can be automatically connected or mounted. The mounting element 61 has a tool carrier 62 cooperating with it which has two elements 63 and 64 fitted on it which store a code associated with the tool. These elements 63, 64 have connecting contact pins 65 and 66 which, when the tool carrier 62 is connected, are inserted into suitable mating contacts on two code pickup elements 67 and 68 when the tool is brought against the operator control element 61. Furthermore, the tool carrier 62 also has two signaling elements 69 and 70 fitted on it which interact with corresponding holding elements 71 and 72 and supply a “tool connected” signal to a piece of decision logic 74 via a respective data line 73. The code pickup elements 67 and 68 are connected to the decision logic by means of further data lines 75 and 76, said decision logic supplying a control unit 77 with a “tool code confirmed” signal via data lines 78 on the control unit 77. Furthermore, the decision logic uses a line 79 to transmit an “OK” signal and uses a data line 80 to transmit an “error” signal to the control unit 77. This control unit actuates a robot protection device 81 which, if the tool code is incorrect and an “error” signal is supplied to the control unit 77, switches off the robot or significantly reduces the speed of motion to safe values.
To identify whether the robot has a correct tool, a flowchart is shown in
If a correct tool is now in position, the two codes from the code carrier elements 63 and 64 are supplied to a code reader 105. The processing device 106 checks whether code 1 and code 2 are the same; if not, an “error signal” code 107 is produced which possibly leads back to the initial step 100 again. If the two codes are the same, a check is performed to determine whether the codes correspond to the expected codes, which is done in a processing device 108; if the code is the same as the expected code, the machining is continued with the tool in 109; otherwise, an “incorrect tool” signal is output, so that the process then starts again from the beginning.
200 denotes the starting block, with which a robot is put into operation. In this case, it is first of all detected whether the tool A is provided, which is shown by the block 201. If so, 202 checks whether the robot is in the permitted zone, and if not then a stop signal 203 is produced; when a reset operation 204 has been performed, the stop signal is removed at 205 if the reset operation has been completed successfully. If the reset operation 204 has not been successful, it is repeated again.
If the codes are the same and if the codes are expected, that is to say if the codes are correct, work continues with the tool in 220.
Number | Date | Country | Kind |
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10 2006 046 759.0 | Sep 2006 | DE | national |
This is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2007/007685, filed on Sep. 4, 2007, which claims priority to German Application No. DE 10 2006 046 759.0, filed on Sep. 29, 2006. The International Application was published in German on Apr. 10, 2008 as WO 2008/040426.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP07/07685 | 9/4/2007 | WO | 00 | 3/30/2009 |