The main technical challenge of the SMILING project was the development of a wearable non-invasive computer-controlled system that applies chaotic perturbations to the lower extremities during walking through small alterations of the height and slope of weight-bearing surfaces.
The SMILING system in its present format is a complete system for walking assessment and training and it consists of four main modules: i) a motorized pair of shoes, ii) a user friendly portable control unit, iii) a set of PC based algorithms for ad hoc perturbation generation, iv) a complete facility for walking assessment.
The motorised shoes provide perturbation of walking in successive strides, to change the user's perception of the ground's surface at each foot contact. Each motorised shoe has four actuators, two in the forefoot and two in the heel, which are able to change their height independently up to 25 mm in order to provide different inclinations of the support surface at each step.
Movement of the four actuators is done in a very short time, about 280 msec, which is the time the foot is off the ground during the swing phase of walking.
This requires fast-moving actuators which are moved under synchronized control to their desired final configuration, taking into account different shoe sizes.
From the perspective of motion control of the shoes, it was necessary to equip each shoe with sensors able to detect the swing and stance phases of gait, to identify the timing of the motors' actuation.