  Technological advances in multi-articulated prosthetic hands have outpaced
the methods available to amputees to intuitively control these devices.
Amputees often cite difficulty of use as a key contributing factor for
abandoning their prosthesis, creating a pressing need for improved control
technology. A major challenge of traditional myoelectric control strategies
using surface electromyography electrodes has been the difficulty in achieving
intuitive and robust proportional control of multiple degrees of freedom. In
this paper, we describe a new control method, proprioceptive sonomyographic
control that overcomes several limitations of myoelectric control. In
sonomyography, muscle mechanical deformation is sensed using ultrasound, as
compared to electrical activation, and therefore the resulting control signals
can directly control the position of the end effector. Compared to myoelectric
control which controls the velocity of the end-effector device, sonomyographic
control is more congruent with residual proprioception in the residual limb. We
tested our approach with 5 upper-extremity amputees and able-bodied subjects
using a virtual target achievement and holding task. Amputees and able-bodied
participants demonstrated the ability to achieve positional control for 5
degrees of freedom with an hour of training. Our results demonstrate the
potential of proprioceptive sonomyographic control for intuitive dexterous
control of multiarticulated prostheses.
