With the growth of the elderly population and the consequent increase on the number of people with motor impairments, a variety of mobility and supporting devices have appeared focussing on the different types and degrees of disability. Among these devices, there are wheelchairs, canes, walkers, and many others. This work is centred on the walkers, presenting a proposal to reduce problems of these devices, increasing the stability during the gait, providing locomotion energy and minimizing brake problems. The content of this paper is a part of the four-wheeled robotic walker, SIMBIOSIS, controlled by a multimodal interface based on user's navigational intentions. This interface is composed by a set of sensor subsystems. This paper presents one of them - an upper limb force interaction measuring platform.