Joint single-axis

FIGURE 68.11 The problem caused by misplacement of a single-axis orthotic joint (a) is overcome by an orthosis (b) with a self-aligning axis. (The Laser system, courtesy of Hugh Steeper, Ltd., U.K.)... 

For single-axis joints, the matrix functions used to transform vector quantities between coordinate frames are functions of these four parameters. These transformations will be defined in the following pages. The modelling conventions used for more complex joint structures will be discussed in the next section. 

When using this general joint model, the location of link coordinate frames is the same as described in Section 2.2. In fact, fn single-axis joints, the joint variables, axis alignment, and spatial coordinate transformations all remain unchanged by this new model. The choice of joint variables, axis alignment, and the spatial transformations between coordinate systems become more complex for multi-axis joints, however. These issues will not be discussed in detail here. Details concerning these transformations may be found in [9] and [36]. 

Single-axis arm designed with an ultrasonic motor basic active/passive joint torque control... 

The legend displays the meaning of the object shapes found in the figure. For example, link L, is a quaternary. There are three different types of links quaternary, ternary, and binary. A quaternary link has four joints, the ternary has three, and the binary has two. A circle represents a revolute single-axis joint. The two shaded circles are the joints that connect the foot to fibula and tibula. These points are insignificant in this study. 

Fig. 8. Coordinate system of the co-cured single and double lap joints for calculating stress distributions in the ply-axis.

FIGURE 49.25 Very small locus of instant center of rotation for the elbow joint demonstrates that the axis may be replicated by a single line drawn from the inferior aspect of the medial epicondyle through the center of the lateral epicondyle, which is in the center of the lateral projected curvature of the trochlea and capitellum. (From Morrey B.F. and Chao E.Y.S. 1976. /. Bone Joint Surg. 58A 501. With permission.)... 

The axes of rotation of the CMC joint have been described as being fixed [Hollister et al., 1992], but others beUeve that a polycentric center of rotation exists [Imaeda et al., 1994]. Holhster et al. [1992] found that axes of the CMC joint are fixed and are not perpendicular to each other, or to the bones, and do not intersect. The flexion/extension axis is located in the trapezium, and the abduc-tion/adduction axis is on the first metacarpal. In contrast, Imaeda et al. [1994] found that there was no single center of rotation, but rather the instantaneous motion occurred reciprocally between centers of rotations within the trapezium and the metacarpal base of the normal thumb. In flexion/extension. 

Thickness of the upper part in a single-lap joint Thickness of the lower part in a single-lap joint Thickness of the centre plate in a double-lap joint Thickness of the side plate in a double-lap joint Distance from e.g. to fastener i in x-direction Distance from e.g. to fastener i in y-direction Angle between Fj and the x-axis Relative displacement between the joined members... 

Fig. 16.5 (a) Simulation of aperture for 9-irun diameter tunnel blue oval) placed on the ACL footprint red area) to cover the footprint area as much as possible, (b) Arthroscopic view of single-bundle reconstruction covering the ACL footprint with the oval-shaped tunnel aperture. The diameter of the socket is 8 mm. (c) Schema of lateral view of the femoral condyle. Lines of 45 and 60° anterior from the proximal-distal axis are drawn from the lateral epicondyle red dot). An area around 2 cm from the lateral epicondyle on the lines is indicated green area). Pink area Attachment of the lateral head of gastrocnemius. Blue line Attachment of the joint capsule... 

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