Cyclic Motion Control for Programmable Bevel-Tip Needle 3D Steering: A Simulation Study

Abstract

Flexible, steerable, soft needles are desirable in Minimally Invasive Surgery to achieve complex trajectories while maintaining the benefits of percutaneous intervention compared to open surgery. One such needle is the multi-segment Programmable Bevel-tip Needle (PBN), which is inspired by the mechanical design of the ovipositor of certain wasps. PBNs can steer in 3D whilst minimizing the force applied to the surrounding substrate, due to the cyclic motion of the segments. Taking inspiration also from the control strategy of the wasp to perform insertions and lay their eggs, this paper presents the design of a cyclic controller that can steer a PBN to produce a desired trajectory in 3D. The performance of the controller is demonstrated in simulation in comparison to that of a direct controller without cyclic motion. It is shown that, while the same steering curvatures can be attained by both controllers, the time taken to achieve the configuration is longer for the cyclic controller, leading to issues of potential under-steering and longer insertion times.

Biologically Inspired Surgical Needle Steering: Technology and Application of the Programmable Bevel-Tip Needle

“…Results from [ 43 ] show that the CAC exhibited under steering, particularly over 3D trajectories. This effect is replicated here, as can be seen from the trajectory tracks in Figure 8 and Figure 9 .…”

“…The cyclic controller was extended in [ 43 ] to handle 3D trajectories with a cyclic period of 2 s, increasing the control frequency four-fold, and presented the design for position and velocity profiles of simulated motors to drive the four needle segments in SIMULINK and MATLAB 2017b© (MathWorks Inc., Massachusetts, USA). The results from this work showed that the cyclic controller under-steered when following curvilinear paths, the effects of which were more pronounced on 3D trajectories.…”

“…In a cyclic period, each segment moves forward and backward for part of the time—the forward and retraction speeds are bounded and constant, but the period for which each is active in a cycle is variable depending on the desired offset to be achieved. This implementation is limited in that a new command is only able to be processed once a cyclic period has finished, placing an upper bound on the control frequency, and that it takes longer to achieve the desired offset compared to the DPC [ 43 ]. However, as the net speed is constant, the insertion takes the same overall time as for the DPC on the same path.…”

“…This percentage value ranging allows the maximum time a segment is moving forward to be increased by up to the value of the factor: Consequently, the retraction period of this segment will be reduced. The full mathematical model of the CAC is presented in detail in [ 41 , 43 ]. The control parameters used for this work are summarised in Table 1 .…”

“…Consequently, the retraction period of this segment will be reduced. The full mathematical model of the CAC is presented in detail in [41,43]. The control parameters used for this work are summarised in Table 1.…”