(which are depicted as grey rectangles in the figure). Three components make up the center of the hinge,  two identical linkage arms and a central spreader support component. Three hinge lines, labeled A, B and C, enable the range of motion as depicted in the bottom of the figure: where starting on the left, the hinge  is at 0 degrees and progresses through to 360 degrees on the right. From 0 to 180 degrees, the top hinge line (B) is active, while from 180 to 360 the bottom hinge lines (A and C) are active. During joint rotation, the spreader support bisects the angle formed by the links, which keeps the transverse force resultants at the tip of the spreader balanced and the spreader in pure compression. Tendon Routing Options: Ev aluation and Selection A large number of options are available for implementing the TALISMAN architecture including: the  number of motor/drive systems used per joint, the location of the motor/drive systems along the links or  on the spreaders, cable routes, and full versus partial antagonistic control. A simple test bed was  designed and constructed to allow a variety of tendon-drive options to be easily implemented, operated  and evaluated so that a configuration could be chosen to implement into a full-scale two-link articulating  joint prototype. The test bed consists of two arm links connected at a central hub, with the left arm fixed,as shown in Figure 5. The spreader is attached to the hub and under ideal operations, would remain  centered between the two arms. A counter-balance is attached to the rotating arm to off-load the arm  weight so that the actuation system essentially experiences zero load as it rotates the joint. Four major architecture options were evaluated by varying the number and location of motor/gear-box  systems on the arms or spreader, as summarized in Figure 6. In the figure, the locations of motors,  springs, pulleys, capstans and stops (tendon tie-down points) are indicated with icons. The figure also uses sequences of numbers and/or letters to indicate tendon routing and circulation. None of the options  tested in the lab were the full antagonistic actuation version (the required control system is still being developed); all included springs so that the stiffness in one rotation direction reached that of the cables  while the stiffness in the other direction was limited to that of the passive springs. The major attributes of  each of the tendon routing and motor/spring position options, all of which are shown in Figure 6, are: /g120Option 1: one motor/gearbox system, two capstans with one having half the diameter of the other, the  motor/gear-box is mounted at a distance along the arm equal to ½ the length of the spreader.  /g120Option 2: two motor/gearbox systems, each motor/gearbox system has a single capstan, both  capstans are the same diameter, the motor/gear-boxes are each mounted at a distance along the  arm equal to ½ the length of the spreader, one on either side of the center of rotation, two  independent cable loops used.   /g120Option 3a: two motor/gear-box systems; each motor/gearbox system has a single capstan, both  capstans are the same diameter; the motor/gear-boxes are each mounted at a distance along the  arm that is approximately equal to the length of the spreader, one on either side of the center of rotation; cable routing is top of spreader, around drive capstan system, around pulley on bottom of  spreader, up spreader arm to hub (with the spring between the pulley and hub).  /g120Option 3b: this option is the same as Option 3a except; the cable routing was modified to; top of  spreader, around drive capstan system, around pulley on bottom of spreader, through pulley (only) on  opposite drive system along arm to hub (with the spring between the pulley and hub); modified 3a such that two springs are attached to each other with their connection point to the right of the hub.  /g120Option 4: one motor/gear-box system; motor/gearbox system has two capstans, one capstan is half  the diameter of the other; the motor/gear-box is mounted at the top of the spreader; two independent  cable loops, identical to Option 2; used the new constant-spring-force mechanisms for each loop.  /g120Option N: not evaluated in test-bed, but his option would be a fully antagonistic arrangement with no  passive spring elements. All of the options were rated against the set of criteria listed in Table 2. The fully antagonistic option (N)  would be preferred in an implemented system, due to its high stiffness over the full 360-degree rotationrange and its high degree of controllability and performance. However, the control system for this option is the most complex, and although it is currently being developed, was not available immediately. In order  409