• upper-limb prosthesis
• stiffness modulation
• myoelectric control

The hand is a very complex organ that possesses an incredible versatility. Besides its grasping and manipulation functions, the hand can be considered a sensory organ and it also plays a role in social interactions. The loss of a hand is therefore a major traumatic event that can have great impact in the life of an individual. Prostheses have been developed to help persons with amputation to restore the lost functionality. In particular, body powered and cosmetic prostheses have been used for centuries and are still commonly prescribed today. More recently, a new generation of prostheses has seen the incorporation of electrically-powered actuators controlled via electromyographic (EMG) signals from the muscles in the residual limb. Despite the advances made in the design of these dexterous anthropomorphic hand prostheses, roughly one third of these prescribed prostheses are completely rejected by their users. The factors that lead to the abandonment of these technologically advanced myoelectric prostheses are mainly two: the difficulty in control and the lack of adequate sensory feedback. This thesis aims to provide a contribution in this context, both for the control of powered prostheses and for the restitution of haptic feedback. Taking a holistic approach to deal with the design possibilities concerning the next generation of prosthetic interfaces, three main topics are investigated. First, an analysis on hand stiffness modulation strategies is presented; the relationship of finger stiffness with the EMG activity of the forearm’s muscles is investigated and the possible implications for prosthetic design are explored. Second, a device for proprioceptive feedback in upper-limb prosthetics is presented. The haptic feedback device, which uses a rolling contact to convey information on the opening of an artificial hand, was developed and experimentally evaluated as part of this thesis. Finally, two different paradigms for the control of upper-limb prostheses are explored: (i) the use of a cable-driven interface, in which the interface was used for the control of a robotic hand prosthesis and was tested on person with amputation; (ii) the use of algorithms for the simultaneous and proportional EMG control of multiple joints, presenting experimental results from tests with able-bodied subjects and people with amputation.