Self-sensing feedback control of multiple interacting shape memory alloy actuators in a 3D steerable active needle

Percutaneous needle-based intervention is a technique used in minimally invasive surgical procedures such as brachytherapy, thermal ablation, and biopsy. Targeting accuracy in these procedures is a defining factor for success. Active needle steering introduces the potential to increase the targeting accuracy in such procedures to improve the clinical outcome. In this work, a novel 3D steerable active flexible needle with shape memory alloy actuators was developed. Active needle actuation response to a variety of actuation scenarios was analyzed to develop a kinematic model. Shape memory alloy actuators were characterized in terms of their actuation strain, electrical resistance, and required electrical power to design a self-sensing electrical resistance feedback control system for position tracking control of the active needle. The control system performance was initially tested in position tracking control of a single shape memory alloy actuator and then was implemented on multiple interacting shape memory alloy actuators to manipulate the 3D steerable active needle along a reference path. The electrical resistance feedback control of the multiple interacting shape memory alloy actuators enabled the active needle to reach target points in a planar workspace of about 20 mm. Results demonstrated shape memory alloys as promising alternatives for traditional actuators used in surgical instruments with enhanced design, characterization, and control capabilities.