Robot-laser system

Abstract

A robot-laser system having a minimum number of mirrors for reflecting a laser beam from a fixed laser beam source to a desired location wherein the mirrors are mounted within the hollow, servo-controlled parts of the robot to move therewith. Only a single mirror is mounted within is associated controlled part to reflect the laser beam as it travels between adjacent controlled parts. The robot has a number of degrees of freedom constituted by two orthogonally related linear movements along intersecting longitudinal axes and two orthogonally related rotary joints having intersecting pivotal axes. Preferably, two of the mirrors are mounted so that the laser beam strikes and is reflected from both points of axes intersection within two of the controlled parts. In one of disclosed embodiments a mirror mounted in the base of the robot reflects the laser beam from the source to the other mirrors.

Description

six-axes six-axis manipulator with freedom to rotate about axes 11, 12, and 13 and freedom to move linearly along axes 11, 12 and 13. The robot 14 can be used for such heavy duty applications as welding of industrial components such as automobile bodies. The robot 14 need only carry and support relatively lightweight mirrors instead of heavy welding equipment or clumsy and heavy laser beam-guiding articulations. This lightweight payload allows the robot 14 to be built with simplicity of design, ease of use, high accuracy and low cost.

The robot 14 comprises an arm assembly movably mounted on a hollow base, generally indicated at 24. The arm assembly includes an outer arm, generally indicated at 16 and an inner arm, generally indicated at 17. The arms 16 and 17 are hollow and are fluidly interconnected to allow a laser beam 18 generated by a laser beam source 18a to pass therethough after passing through the base 24. A first third mirror 19 is fixedly mounted on a top surface of the inner arm 17 by a support 20. A second fourth mirror 22 is fixedly supported on a mounting member 23 which, in turn, is fixedly mounted to a lower base section 25 of the hollow base 24. The support 20 is located within a cavity 21 formed in the outer arm 16 so that the laser beam 18 relfected from the second fourth mirror 22 at a junction point 47 is, in turn, reflected at a 90° angle from the first third mirror 19 at a junction point 41.

The base 24 includes an upper base section 26 which rotates about the axis 11 relative to the lower base section 25 upon actuation of a servo motor 27. The servo motor 27 is mounted on the outer surface of the lower base portion 25. Bearings 30 rotatably support the upper section 26 on the lower section 25. The servo motor 27 is mechanically coupled to the upper base section 26 by gearing 28 mounted on the output shaft 29 of the servo motor 27 to rotate therewith.

The inner arm 17 and, consequently, the entire arm assembly is mounted on the upper base section 26 to rotate therewith. More particularly, a lower portion of the inner arm 17 is connected to a drive nut 31 which is threadedly engaged on a drive screw 32, one end of which in turn, is rotatably supported at the top of the upper base section 26 by bearings 37. The opposite end of the screw 32 is coupled to the drive shaft 33 of a servo motor 34 by a coupling 35. The servo motor 34, in turn, is fixedly mounted on a U-shaped suport 39 of the upper base section 26. The inner arm 17 is slidably supported within the support 39. Because the drive screw 32 is fixedly connected to the lower portion of the inner arm 17, rotation of the drive screw 32 alternately raises or lowers the inner arm 17 along the axis 11 relative to the support 39.

The outer arm 16 moves linearly along the axis 12 by mens of a rack and pinion gear connection to a servo motor 40 mounted on the inner arm 17. More particularly, a pinion gear 36 is mounted on a drive shaft 38 of the servo motor 40 to rotate therewith. A rack 42 is fixedly mounted on the outer arm 16 in driving engagement with the pinion gear 36. A slide portion 44 of the inner arm 16 17 is slidably supported within the arm 17 by linear bearings 46.

The robot 14 also includes a two-axes two-axis wrist mechanism, generally indicated at 48, which is supported for rotation about the a first wrist axis 12 on the outer arm 16 by bearings 49. The wrist mechanism 48 includes a hollow inner knuckle 50 and a hollow outer knuckle 52 supported on the inner knuckle 90 for rotation about the axis 13 by bearings 54. The axes 12 and 13 intersect at a first junction point 43. The inner knuckle 50 is rotatably driven about the axis 12 by a servo motor 56 which is mounted on the top surface of the outer arm 16. Gearing 58 interconnects the inner knuckle 50 to the drive shaft 60 of the servo motor 56 to transfer the rotary motion of the drive shaft 60 to the inner knuckle 90.

In the same fashion, the outer knuckle 52 is rotatably driven about the a second wrist axis 13 by a servo motor 62 which is mounted on the inner knuckle 50. Gearing 64 interconnects the outer knuckle 52 to the drive shaft 66 67 of the servo motor 62 to transfer the rotary motion of the drive shaft 66 to the outer knuckle 52.

A third first mirror 66 is fixedly mounted on the inner surface of the inner knuckle 50 to reflect the laser beam 18 between the second third mirror 19 and a fourth second mirror 68 which is fixedly mounted on the inner surface of the outer knuckle 52. A focusing lens 70 is fixedly mounted 46 within the outer knuckle 52 between the mirror 68 and the free end of the wrist mechanism 40 to focus the laser beam 18 on along a third wrist axis 69 and onto a workpiece for worpiece or material processing. The axes 13 and 69 intersect at a second junction point 45.

The lower section 25 of the base 24 is mounted for sliding movement along the axis 15 on a track, generally indicated at 72. The track 72 includes a drive screw 74 which extends between a pair of spaced apart flange portions 76 of an elongated support, generally indicated at 78. One end of the drive screw is rotatably supported on the support 78 by bearings 80. The other end of the drive screw 74 is in driving engagement with the drive shaft 82 of a servo motor 84 through a coupling 86. The servo motor 84 is mounted on the support 78.

The base 24 of the robot 14 is mounted on a slide member 88 which in turn, is mounted for movement on the drive screw 74 by a drive nut 90. Extensible light shields or bellows 92 91 extend between the laser source 18a and the lower section 25 of the base 24 to protect the laser beam from the environment during movement of the robot 14 on the track 72.

The laser beam source 18a is preferably located in a fixed position. However, it is to be understood that alternatively. the laser beam source may be mounted on the wrist, the base or the inner or outer arms of the robot 14 depending on the weight of the laser beam source and the load-carrying capacity of the particular robot part.

The laser beam 18 is aimed in a direction parallel to the axis 15 so that it is reflected by the mirror 22 to travel along the axis 11 until it strikes the mirror 19. The laser beam 18 reflects off the mirror 19 and travels along the axis 12 until it strikes the mirror 66. The laser beam 18 then reflects off the mirror 66 and travels along the axis 13 until it strikes the mirror 68. The laser beam 18 reflects off the mirror 68 and travels along an axis 69 spaced apart and parallel to the axis 12. The lens 70 focuses the laser beam 18 before the laser beam 18 exits the wrist mechanism 48. alternately, the mirror 68 can be shaped as a focusing mirror to eliminate the lens 70.

While not shown, the robot 14 may include other equipment such as grippers, fixtures or other equipment. Also, the robot-laser system 10 may include additional mirrors in order to help in directing the laser beam 18 favorably to a workpiece.

Referring now to FIGS. 3 and 4 there is illustrated a second embodiment of a wrist mechanism 48' including servo motors 56' and 62' and mounted at the free end of a modified outer arm 16' for rotation of its inner and outer knuckles 50' and 52', respectively.

The servo motor 56' rotatably drives the inner knuckle 50' through a shaft 92 which is coupled at one end thereof to the rotary drive shaft 60' of the servo motor 56' by a coupling 93. The shaft 92 extends in a direction parallel to the axis 12 and is rotatably supported therein by a bearing block 94. Gearing 96 couples the inner knuckle 50' to the opposite end of the shaft 92. Bearings 49' rotatably support the inner knuckle 50' on the outer arm 16'.

In a similar fashio, the servo motor 62' rotatably drives the outer knuckle 52' through a shaft 98 which is coupled at one end thereof to the rotary drive shaft 66' 67' of the servo motor 62' by coupling 100. The shaft 98 extends along a direction parallel to the axis 12 and is rotatably supported therein by a bearing block 102. Gearing, including a central gear 104 couples the outer knuckle 52' to the opposite end of the shaft 98. Bearings 54' rotatably support the outer knuckle 52' and the central gear 104 on the inner knuckle 50'.

Externally mounted mirror assemblies, generally indicated at 106 and 108, are adjustably mounted on the inner and outer knuckles 50' and 52', respectively, to allow adjustment of the position of their corresponding mirrors 66' and 68'.

Referring now to FIG. 5 there is illustrated a third embodiment of a wrist mechanism, generally indicated at 48". The mechanism 48" is substantially the same as the wrist mechanism 48 except that an outer knuckle 52" is directly coupled to the rotary drive axis 66" shaft 67" of a servo motor 62" to rotate about the axis 13. The servo motor 62" is mounted on a flange member 109 fixedly mounted on the inner knuckle 50". Bearings 54" rotatably support the outer knuckle 52" on the inner knuckle 50".

Referring now to FIG. 6 there is illustrated a second embodiment of a robot-laser system collectively indicated by reference numeral 10'. The system 10' includes a robot, generally indicated at 14', which is mounted on a floor, such as a factory floor 110 which has space there-under for mounting a laser source 18a' therein. For the sake of simplicity, only the bottom portion of the robot 14' is shown since the top portion is substantially identical to that of the robot 14. The robot 14' comprises a five-axes manipulator with freedom to rotate about three axes (only one of which is shown at 11' in FIG. 6) and freedom to move linearly along two axes (only one of which is shown at 11' in FIG. 6). The construction of FIG. 6 allows the mirror 22 to be eliminated.

TEACHING THE ROBOT OF THE ROBOT-LASER SYSTEM

In programming or teaching any one of the robots 14 or 14', the positions of the mirrors are ignored since they are fixed relative to the robot part in which they are mounted. Teaching can be done by beaming a low power laser beam or ordinary light via a source (not shown) which is temporarily attached to the robot. Such a light beam will simulate the path of the high power beam under normal operation. After such a source is attached to the robot, the robot can be led through a desired path by any of several commonly utilized methods. One method, such as used with light-weight manipulators, is simply to lead the unpowered manipulator by hand. Another is to command individual axes to move as desired from a push button terminal or by means of a joy stick (neither of which are shown). A third method utilizes a force sensing device (not shown) which is attached to the robot and senses the force applied when the robot is led through its path. The programmable controller is utilized to read the sensor transducer outputs to command the drive circuits of the actuators or servos of the robot and provide the desired motion.

The operator decides on the desired path by aiming the light beam to the desired location on the workpiece At specific points along the desired path, axes axis positions can be recorded as well as the desired status of the laser beam i.e. whether it is triggered "on" or "off" at what power level when "on". The recording command is usually input by pushing a button that commands the controller to read the output of the several feedback devices. These devices may indicate the position of the robot actuators and/or the status of the support equipment at any recording point.

Once path points are recorded they are usually stored in computer memory or peripheral discs for recall in a playback mode whereby the robot can retrace the path described by the recorded points. In the playback mode the force sensor, if used, can be removed as well as any auxiliary light beam source.

The advantages of the above-described robot-laser systems are numerous. For example, the number of mirrors required to be used in manipulating the laser beam has been greatly reduced from the number required by the prior art. There is less power loss and there is full control of laser beam orientation through robot programmability. Teaching such robot-laser systems through the lead-through method is made relatively easy. Furthermore, slight mirror misalignment in assembly is not fatal since all the mirrors are under active feedback control through their associated robot part in which they are mounted. Finally, the reduced cost and the higher precision attainable by use of light-weight manipulators enhances the commerical prospects of such robot-laser systems.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims

1. A robot-laser system for providing a laser beam at a desired location, the system comprising:

a laser beam source for generating a laser beam;

a robot having at least three degrees of freedom and including a base and a single motorized robot arm having a motor mounted on said arm supported on said base, the robot arm having first and second elongated arm parts, the second arm part projecting from the first arm part, the robot arm having a wrist mechanism located at the distal end of the second arm part, said arm parts and said wrist mechanism being hollow and fluidly interconnected to define a laser beam path therewithin extending through said first arm part, along the entire projecting length of said second arm part and through said wrist mechanism, said arm parts and said wrist mechanism being adpated to direct the laser beam therewithin; and

at least one mirror for reflecting the laser beam, a single mirror being mounted to and supported by said arm therewithin at a position of fluid interconnection between the arm parts to move therewith and reflect the laser beam wherein a first one of said degrees of freedom comprises a linear movement of said first arm part along an axis coincident with said laser beam path, a second one of said degrees of freedom comprises a linear movement of said second arm part along a second axis coincident with said laser beam path through the second arm part and a third one of said degrees of freedom comprises a rotary movement of one of said arm parts about said laser beam path; and

first and second drive means for linearly driving the first and second arm parts, respectively, and third drive means for rotatably driving the one of said arm parts about said laser beam path.

2. A robot-laser system for providing a laser beam at a desired location, the system comprising:

a laser beam source for generating a laser beam;

a robot having at least three degrees of freedom and including a hollow base and a single motorized robot arm having a motor mounted on said arm supported on said base, the base being fluidly interconnected to said source, the robot arm having a hollow first arm part and an elonaged, hollow second arm part projecting from the first arm part, the robot arm having a hollow wrist mechanism located at a distal end of the second arm part, said wrist mechanism having at least one rotational axis and at least one knuckle rotatably supported on said axis; said first arm part being fluidly interconnected with said base, said first arm part being fluidly interconnected to said second arm part and said second arm part and said wrist mechanism being fluidly interconnected to define a laser beam path therewithn extending through the base, through the first arm part, along the projecting length of said second arm part and through said wrist mechanism; said base, said first and second arm parts and said wrist mechanism being adpated to direct the laser beam therewithin; and

at least two mirrors for reflecting the laser beam, a first one of said mirrors being mounted to and supported by said knuckle therewithin to move therewith and reflect the laser beam, and a single mirror being supported by said arm therewithin at a position of fluid interconnection between the arm parts to reflect the laser beam to the first one mirror wherein a first one said degrees of freedom comprises a linear movement of said first arm part along an axis coincident with said laser beam path, a second one of said degrees of freedom comprises a linear movement of said second part along a second axis coincident with said laser beam path through the second arm part and a third one of said degrees of freedom comprises a rotary movement of one of said arm parts about said laser beam path; and

first and second drive emans for linearly driving the first and second arm parts, respectively, and third drive means for rotatably driving said one of said arm parts about said laser beam path.

3. The invention as claimed in claim 1 or claim 2 wherein said robot has at least five degrees of freedom.

4. The invention as claimed in claim 1 or claim 2 wherein said first and second degrees of freedom are constituted by two orthogonally related linear movements along intersecting longitudinal axes, and wherein the single mirror is mounted so that the laser beam strikes the single mirror at the point of intersection of the longitudinal axis axes.

5. The invention as claimed in claim 1 or claim 2 wherein the number of mirrors is less than the number of degrees of freedom of the robot.

6. The invention as claimed in claim 1 or claim 2 including focusing means mounted on said robot for focusing the reflected laser beam at the desired location.

7. The invention as claimed in claim 6 wherein said focusing means comprises a focusing lens.

8. The invention as claimed in claim 1 or claim 2 including a track wherein said robot is mounted on said track to move thereon.

9. The system as claimed in claim 1 or claim 2 wherein said base is fluidly interconnected to said source by an aperture extending completely through a wall of said base.

10. The system of claim 1 or claim 2 wherein each of said first, second and third drive means includes a servo motor.