Abstract

Stroke is a major cause of lower-limb paresis, and clinical practice has long shown that early, repetitive gait training can accelerate motor recovery. End-effector gait trainers mounted on a wheeled walker provide a portable and low-cost alternative to bulky treadmill-based exoskeletons. This paper presents a geared five-bar linkage as the trajectory-generating mechanism of a Walker Gait Trainer (WGT), a single-actuator rehabilitation device for over-ground use. The two cranks of the five-bar linkage are linked by a gear train made up of two identical spur gears and an intermediate idler. This arrangement reduces the dimensional synthesis problem from four defect constraints, Grashof, order, and two circuit constraints, to a single order constraint, because branch and circuit defects are removed by design when both cranks are compelled to rotate continuously. Dimensional synthesis is formulated as a path-generation problem based on seven precision points obtained from normative gait data, and the mechanism dimensions are found through a systematic design-by-analysis search carried out interactively in the GIM kinematic simulation environment, using the closed-form kinematic model developed in this study. The final mechanism is then reconstructed in GIM as a kinematic cross-check of the closed-form model. The geared five-bar linkage reproduces the typical teardrop ankle path of healthy gait with one fewer link than conventional six-bar designs, while also adding the gear ratio as an extra parameter for shaping the trajectory, which is not available in six-bar topologies. The paper also presents the full device integration, in which the input crank is powered by a single speed-controlled actuator mounted on the walker frame, together with a three-dimensional CAD assembly model.

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