provide two separate pivot points having different radii from the axis of rotation x of the concentric hubs 12 and 12 39 when moved the drive arms 20 and 20 39 generally follow a circular path about the axis of rotation the drive arms 20 and 20 39 are therefore adapted to accommodate the radial and lateral offset of the pivot points 24 24 39 34 and 34 39 a cantilevered first upper strut 22 is pivotally attached at one end to the first drive arm 20 at pivot point 24 similarly a cantilevered second upper strut 22 39 is pivotally attached to the second drive arm 20 39 at pivot point 24 39 the opposite apogee ends 26 and 26 39 shown in fig2 b and 2c of the first and second upper struts 22 and 22 39 are attached to a first blade 30 so that the structure of the drive arms 20 and 20 39 and upper struts 22 and 22 39 form a frog leg type connection between the first blade 30 and the concentric hubs 12 and 12 39 the drive arms 20 and 20 39 the upper struts 22 and 22 39 and the blade 30 make up the upper linkage the robot 10 also includes a second blade 30 39 mounted in spaced parallel relationship to the first blade 30 a first lower strut 32 is attached at one end to the lower drive arm 20 at pivot point 34 and a second.