THE EFFECT OF SPEED ON GAIT ASYMMETRY IN SUBJECT WITH CONGENITAL TIBIAL DEFICIENCY: A CASE STUDY

In the case study, gait asymmetry changes in different speed of walking with ankle-foot prosthesis were identified for developmental tibial deficiency. Joint kinematic, spatial-temporal, and kinetic gait parameters were collected using 3D motion capture system and 3D treadmill simultaneously. Mean values, SD, and symmetry index were calculated for selected gait parameters and descriptively analysed. Results show gait asymmetry of all of the measured parameters. Kinematic joint angular ranges increase with increasing walking speed. Inverse dynamic results present changes in step length and duration which enhance changes in ground reaction force characteristics. The symmetry index shows gait asymmetry, which increases with faster gait speed. Further research is needed to verify this suspect gait asymmetry increasing tendency and to generalise results to ankle-foot prosthesis population with congenital tibial deficiency or transtibial amputation.

Designing a Translational Parallel Manipulator Based on the 3SS Kinematic Joint

Nowadays, translational parallel manipulators are widely used in industrial applications related to pick and place tasks. In this paper, a new architecture of a translational parallel manipulator without floating prismatic joints and without redundant constraints is presented, which leads to a robust design from the manufacturing and maintenance point of view. The frame configuration has been chosen with the aim of achieving the widest and most regular operational workspace completely free of singularities. Besides, the position equations of the proposed design are obtained in a closed form, as well as the singularity locus. It will be shown that the proposed design owns a very simple kinematics so that the related equations can be efficiently implemented in the control of the robot. In addition, the Jacobian condition number assessment shows that a wide part of the operational workspace is well-conditioned, and also the existence of an isotropic configuration will be proved. Finally, a prototype has been built by following a modular design approach.

Recognition of Kinematic Joints of 3D Assembly Models Based on Reciprocal Screw Theory

Reciprocal screw theory is used to recognize the kinematic joints of assemblies restricted by arbitrary combinations of geometry constraints. Kinematic analysis is common for reaching a satisfactory design. If a machine is large and the incidence of redesign frequent is high, then it becomes imperative to have fast analysis-redesign-reanalysis cycles. This work addresses this problem by providing recognition technology for converting a 3D assembly model into a kinematic joint model, which is represented by a graph of parts with kinematic joints among them. The three basic components of the geometric constraints are described in terms of wrench, and it is thus easy to model each common assembly constraint. At the same time, several different types of kinematic joints in practice are presented in terms of twist. For the reciprocal product of a twist and wrench, which is equal to zero, the geometry constraints can be converted into the corresponding kinematic joints as a result. To eliminate completely the redundant components of different geometry constraints that act upon the same part, the specific operation of a matrix space is applied. This ability is useful in supporting the kinematic design of properly constrained assemblies in CAD systems.