Control of force impulse in human-machine impact

The clinical study of postural control requires a disturbance to be imposed to the subject under evaluation. Among various kinds of disturbance, a mechanical stimulation, consisting in an impulsive force impressed to a certain point of the body, can be used. This paper describes the study of a device conceived to generate such a disturbance. The device is based on a commercial pneumatic actuator, equipped with appropriate force and motion feedback sensors, and properly controlled. The major item is to take into account the interaction between the device and the human, in order to individuate the optimal control technique to generate the desired force pattern. A mathematical model of the device and the human-machine interaction is presented and a sliding mode control technique is proposed. Finally, the results of simulations are reported and discussed.