Abstract:
A robot installation includes a first robot and a second robot. The first robot is attached to a fixed position in relation to the second robot such that the second robot lies within a reach of at least one drive arm of the first robot.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to mounting of parallel kinematics robots in relation to each other. 
       BACKGROUND 
       [0002]    Parallel kinematics robots comprise a plurality of drive arms each connected, directly or via a gearbox, to a respective shaft of a servo motor at one end. At the opposite end each drive arm is connected to one or more rods transmitting the rotating movement of the drive arms to a respective movement of an end effector. The servo motors and the respective drive arms work in parallel in the sense that manipulation of one drive arm does not affect the position of the remaining drive arms. 
         [0003]    A delta robot is one well known type of parallel kinematics robot that can comprise three drive arms. Each drive arm is connected to an end effector with two rods having a ball joint at each end. The drive arms rotate about respective servo motor axes, the servo motors being arranged symmetrically such that their axes intersect at 60 degrees angles. U.S. Pat. No. 7,188,544 discloses one type of a delta robot comprising three drive arms. Delta robots can also comprise four or more drive arms. 
         [0004]    WO200366289 discloses other and less well known types of parallel kinematics robots comprising three or more drive arms. The robots according to WO200366289 differ from delta robots in that the rotational axes of the drive arms are parallel, and in many embodiments the drive arms even have one common rotational axis. 
         [0005]    Conventionally, when two or more parallel kinematics robots are installed at a robot installation, the robots are attached to fixed positions in relation to each other such that the drive arms of one robot can never reach and thereby collide with the remaining robots. This is because it is not considered desirable to limit the work area of a robot with external obstacles. Instead, all the drive arms are enabled to rotate within the constraints defined only by the robot itself. Even though a great advantage in terms of space occupied is achieved if two robots are installed close to each other, doing so has not been considered feasible because of the caused limitations to the work areas of the robots. 
       SUMMARY 
       [0006]    One object of the invention is to provide a robot installation which allows to install two robots close to each other and still keep the sizes of the respective work areas acceptable. 
         [0007]    These objects are achieved by the device according to appended claim  1 . 
         [0008]    The invention is based on the realization that certain types of parallel kinematics robots are better adapted to be installed close to each other than others. Especially, robots in which the drive arms are arranged in an asymmetrical manner, and in which the drive arms rotate about parallel axes, the work area remains relatively large even when the rotation of one of the drive arms is strongly limited. 
         [0009]    According to a first aspect of the invention, there is provided a robot installation comprising a first robot and a second robot. Each of the robots comprises a first shaft and a second shaft extending in a first direction from respective actuators, a third shaft extending in a second direction form a respective actuator, the second direction being opposite to the first direction, a frame defining fixed positions of the first, second and third shafts in relation to each other, a first drive arm attached to the first shaft, a second drive arm attached to the second shaft, and a third drive arm attached to the third shaft, wherein the first robot is attached to a fixed position in relation to the second robot such that the second robot lies within a reach of at least one drive arm of the first robot. 
         [0010]    According to one embodiment of the invention, the first and the second robots are identical. 
         [0011]    According to one embodiment of the invention, the robot installation comprises at least three robots, such as at least four, five, six or eight robots, each robot being attached to a fixed position in relation to the remaining robots such that each robot lies within a reach of at least one drive arm of the remaining robots. 
         [0012]    According to one embodiment of the invention, the third drive arm is not perpendicular to the third shaft. 
         [0013]    According to one embodiment of the invention, the third drive arm is inclined by 45 degrees in relation to the third shaft. 
         [0014]    According to one embodiment of the invention, the first robot is attached to a fixed position in relation to the second robot such that the second robot lies within a reach of the third drive arm of the first robot. 
         [0015]    According to one embodiment of the invention, the first robot is attached to a fixed position in relation to the second robot such that the frame or at least one drive arm of the second robot lies within a reach of at least one drive arm of the first robot. 
         [0016]    According to one embodiment of the invention, the first robot is attached to a fixed position in relation to the second robot such that the frame or at least one drive arm of the second robot lies within a reach of the third drive arm of the first robot. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The invention will be explained in greater detail with reference to the accompanying drawings, wherein 
           [0018]      FIGS. 1 a -1 b    show one embodiment of a robot that can be used with advantage in the context of the present invention, 
           [0019]      FIG. 2  shows one embodiment of the invention, 
           [0020]      FIG. 3  shows one embodiment of the invention, and 
           [0021]      FIGS. 4 a -4 b    show two robots corresponding to the embodiment of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Referring to  FIGS. 1 a  and 1 b   , a parallel kinematics robot  10  which is especially suitable to be applied in the context of the present invention comprises a frame  20  to which a first, second and third actuators  30 ,  40 ,  50  in the form of servo motors are fixedly attached. First and second shafts  60 ,  70  extend in a first direction  90  from the first and second actuators  30 ,  40 , respectively, and a third shaft  80  extends in a second direction  100  form the third actuator  50 . The second direction  100  is opposite to the first direction  90 . A first drive arm  110  is attached to the first shaft  60 , a second drive arm  120  is attached to the second shaft  70 , and a third drive arm  130  attached to the third shaft  80 , each drive arm  110 ,  120 ,  130  rotating along with the respective shaft  60 ,  70 ,  80  about a respective rotation axis. 
         [0023]    The robot  10  according to  FIG. 1  reaches a relatively large work area even when the rotation of the third drive arm  130  is strongly limited. For example, the rotation of the third drive arm  130  can be limited to 180 degrees such that it never crosses its rotational axis in the direction show in  FIG. 1   b.  This in its turn means that a first frame surface  160  opposite to the third drive arm  130  becomes an ideal surface for attaching the robot  10  to an external obstacle. For example, a beam  140  extending from the frame  20  in the second direction  100  can be attached directly to the first frame surface  160  without any practical limitation to the work area of the robot  10 . 
         [0024]    Obviously, instead of the beam  140  of  FIG. 1 , any external obstacle may extend from the first frame surface  160  in the second direction  100  without severely limiting the work area of the robot  10 . According to the present invention the external obstacle is another robot  10 . Referring to  FIG. 2 , according to one embodiment of the invention eight identical robots  10  are installed close to each other. The eight robots  10  form four pairs, and within each pair the robots  10  are mutually within the reach of the other robot  10 . To be more precise, the third drive arm  130  of each robot  10  collides with the frame  20  of the neighbouring robot  10  when the respective third shaft  80  is rotated far enough. It goes without saying that such collision shall be prohibited in a real application by controlling the movements of the robots  10  appropriately, but for the purpose of defining the present invention it is essential that one robot  10  is physically within the reach of another robot  10 . In the present case “being within the reach of another robot” implies that the third drive arm  130  of a first robot  10  collides with a second robot  10  when the third shaft  80  of the first robot  10  is attempted to rotate about a full circle. Furthermore, when considering whether one robot  10  is within the reach of another robot  10 , in the context of the present invention any physical obstacles preventing a collision between the two robots  10  shall be omitted. 
         [0025]    The dotted lines in  FIG. 2  represent possible positions of fixtures to which the robots  10  are attached. The work areas of the robots may overlap each other. However, collisions between the robots are prohibited by controlling the movements of the robots appropriately. 
         [0026]    Referring to  FIG. 3 , according to one embodiment of the invention the third drive arm  130  is inclined by 45 degrees in relation to the third shaft  80  i.e. there is an inclination angle  150  with a value of 45 degrees between these two elements. By doing this the frame  20  can be made much shorter compared with embodiments where the third drive arm  130  is perpendicular to the third shaft  80  i.e. where the inclination angle  150  has a value of 90 degrees. Because of the inclination the distal end of the third drive arm  130 , i.e. the end not attached to the third shaft  80 , follows the same trajectory as the corresponding distal end of the embodiment according to  FIGS. 1 and 2 . Consequently, the embodiment of  FIG. 3  is identical with that of  FIGS. 1 and 2  from the kinematics point of view. However, as illustrated in  FIG. 3 , robots  10  with non-perpendicular third drive arms  130  can be installed more compactly in relation to each other. 
         [0027]    As before, it is to be understood that the collision of two neighbouring third drive arms  130  can be easily avoided by appropriate control of the robots  10 , but for the purpose of defining the present invention they shall be considered to be within the reach of each other as the physical dimensions of the installation enable a collision. It is furthermore possible to incline the first and second drive arms  110 ,  120  such as to make them non-perpendicular with the respective first and second shafts  60 ,  70  whenever feasible. The inclination angles  150  are by no means limited to 90 or 45 degrees but can be anything between 90 and about 30 degrees. 
         [0028]    The invention is not limited to the embodiments shown above, but the person skilled in the art may modify them in a plurality of ways within the scope of the invention as defined by the claims.