In this paper, an impedance control is proposed for a robotic needle with a fiber optic force sensor. The fiber optic force sensor is placed at the tip of the needle to directly measure the interaction force between needle and soft tissue, overcoming the noise like friction force. The sensor is sensitive to the temperature condition, and their relationship is first established, and then used to compensate for the temperature influence to enhance the force measurement. An impedance control is presented based on insertion model whose impedance parameters are identified in terms of acquired test data, and experimental results show that the control strategy is effective to avoid excessive insertion force, reducing the risk of robotic needle.

In this study, a feedback control law is proposed to steer a robotic needle using force information from a fiber optic sensor. This sensor is integrated into the lumen at the distal end of the needle to measure the needle insertion force. The force signals are analyzed via wavelet transform to identify the boundaries of layered soft tissues in real time. The boundaries information is then used in the robotic needle steering scheme to reduce as much as possible the insertion force, and mitigate the risk of tissue injury. Porcine belly tissue phantoms are herein used in the ex vivo tests of robotic needle insertion, and comparative study has been done with and without insertion force feedback. Experimental results show that the force feedback control approach proposed reduces effectively the insertion force.