A Variable Stiffness Robotic Probe for Soft Tissue Palpation

Abstract

Abstract-During abdominal palpation diagnosis, a medical practitioner would change the stiffness of their fingers in order to improve the detection of hard nodules or abnormalities in soft tissue to maximise haptic information gain via tendons. Our recent experiments using a controllable stiffness robotic probe representing a human finger also confirmed that such stiffness control in the finger can enhance the accuracy of detecting hard nodules in soft tissue. However, the limited range of stiffness achieved by the antagonistic springs variable stiffness joint subject to size constraints made it unsuitable for a wide range of physical examination scenarios spanning from breast to abdominal examination. In this paper, we present a new robotic probe based on a variable lever mechanism (VLM) able to achieve stiffness ranging from 0.64 N.m/rad to 1.06 N.m/rad, that extends the maximum stiffness by around 16 times and the stiffness range by 33 times. This paper presents the mechanical model of the novel probe, the Finite Element (FE) simulation as well as experimental characterization of the stiffness response for lever actuation.

Stiffness Imaging With a Continuum Appendage: Real-Time Shape and Tip Force Estimation From Base Load Readings

“…Finally, the fact that the presented shape and force estimation methods do not rely on any shape sensors [10], means they can be employed effectively as good basis models for Nonlinear Kalman Filter design if position measurements are not easily possible [2]. However, the large difference between the estimated values by the continuum and rigid probe suggest the importance of employing a stiffness controllable structure as in [29] to improve the estimation accuracy. Furthermore, we plan to investigate the effective palpation velocity and induced force, and comparing the results with the employed techniques by physicians, as in [28].…”

Conditioned haptic perception for 3D localization of nodules in soft tissue palpation with a variable stiffness probe

“…As described in [22], the VLM probe (see Fig 1) is composed of a variable stiffness joint based on a variable lever mechanism and two sensors: a Cyskin tactile sensor [2] placed on the VLM probe fingertip and an ATI NANO 25 placed at the equivalent wrist level. The stiffness variation of the VLM probe is based on position control of a flexible carbon rod.…”

“…Our approach presented in this paper is inspired by recent studies that provide a better insight into the interaction between perception and action [14,21]. In particular, we propose a novel control algorithm tested with the Variable Lever Mechanism (VLM) probe [22] to detect and localize an embedded nodule in soft tissues. Thanks to its controllable stiffness and its two sensing modalities (kinesthetic and haptic) we used the VLM probe to demonstrate that the compliance of the joints plays a significant role in the haptic detection, the localization, and the depth estimation of a nodule.…”

Non-Destructive Robotic Assessment of Mango Ripeness via Multi-Point Soft Haptics

“…Recent years have seen a rapid development of robotics technology in the context of agriculture, mainly related to transport and harvesting [14]- [17]. Moreover, technological advances in tactile sensing and perception [18], [19] have changed the landscape for tactile based inference procedures [20], [21]. In this context, however, robotics solutions for post-harvest quality assessment remain a largely unexplored area.…”