Fusing Dexterity and Perception for Soft Robot-Assisted Minimally Invasive Surgery: What We Learnt from STIFF-FLOP

In recent years we have seen tremendous progress in the development of robotic solutions for minimally invasive surgery (MIS). Indeed, a number of robot-assisted MIS systems have been developed to product level and are now well-established clinical tools; Intuitive Surgical’s very successful da Vinci Surgical System a prime example. The majority of these surgical systems are based on the traditional rigid-component robot design that was instrumental in the third industrial revolution—especially within the manufacturing sector. However, the use of this approach for surgical procedures on or around soft tissue has come under increasing criticism. The dangers of operating with a robot made from rigid components both near and within a patient are considerable. The EU project STIFF-FLOP, arguably the first large-scale research programme on soft robots for MIS, signalled the start of a concerted effort among researchers to investigate this area more comprehensively. While soft robots have many advantages over their rigid-component counterparts, among them high compliance and increased dexterity, they also bring their own specific challenges when interacting with the environment, such as the need to integrate sensors (which also need to be soft) that can determine the robot’s position and orientation (pose). In this study, the challenges of sensor integration are explored, while keeping the surgeon’s perspective at the forefront of ourdiscussion. The paper critically explores a range of methods, predominantly those developed during the EU project STIFF-FLOP, that facilitate the embedding of soft sensors into articulate soft robot structures using flexible, optics-based lightguides. We examine different optics-based approaches to pose perception in a minimally invasive surgery settings, and methods of integration are also discussed.

Crashworthiness Analysis of a Thin-Walled Structure in the Frontal Part of Automotive Chassis

With increasing road accidents, researchers found a need to reduce the impact which gets transferred to the driver and passengers during a collision. Chassis is the main rigid component which transmits the impact or jerk to the entire vehicle. So, the changes can be done in the frontal head tube shape in order to achieve maximum energy absorption. The objective of this article is to produce a thin-walled impact absorption structure. The unique strength absorption, the maximum crushing force, all through the frontal impact are the primary dimensional parameters of the performance. Explicit dynamics feature of Ansys can be used and the results of Peak Force (PF) and Specific Energy Absorption (SEA) can be acquired virtually. Based on the results, the shape with the highest amount of SEA can be concluded as the best shape so that it can be used to absorb the maximum energy while collision of the vehicle takes place. The results show an increment of 30% in SEA.

Homogenization in BV of a model for layered composites in finite crystal plasticity

In this work, we study the effective behavior of a two-dimensional variational model within finite crystal plasticity for high-contrast bilayered composites. Precisely, we consider materials arranged into periodically alternating thin horizontal strips of an elastically rigid component and a softer one with one active slip system. The energies arising from these modeling assumptions are of integral form, featuring linear growth and non-convex differential constraints. We approach this non-standard homogenization problem via Gamma-convergence. A crucial first step in the asymptotic analysis is the characterization of rigidity properties of limits of admissible deformations in the space BV of functions of bounded variation. In particular, we prove that, under suitable assumptions, the two-dimensional body may split horizontally into finitely many pieces, each of which undergoes shear deformation and global rotation. This allows us to identify a potential candidate for the homogenized limit energy, which we show to be a lower bound on the Gamma-limit. In the framework of non-simple materials, we present a complete Gamma-convergence result, including an explicit homogenization formula, for a regularized model with an anisotropic penalization in the layer direction.

Fabric Circuit Board Connecting to Flexible Sensors or Rigid Components for Wearable Applications

Electronic textiles demand a new family of flexible circuit boards in the construction of fiber or fiber assemblies. This paper presents a stretchable woven fabric circuit board (FCB) with permanent as well as detachable electrical connections to sensors or other wearable electronics components. The woven FCB was created by integrating conductive yarns into an elastic woven fabric. Permanent connection was designed between the conductive tracks and flexible sensors; detachable connection was achieved by the helical structure of conductive yarns wrapping around the rigid component electrode encapsulated within elastomeric layer. The developed FCB, with its connections to flexible sensors or rigid components, is porous, flexible, and capable of stretching to 30% strain. The woven FCB with permanent connection to temperature sensors has a large fatigue life of more than 10,000 cycles while maintaining constant electrical resistance due to crimped configurations of the conductive track in the elastic fabric substrate and stable contact resistance. A prototype of the FCB assembly, with independent light-emitting diodes electrically linked and mechanically supported by the woven FCB, is also demonstrated for wearable applications.

Vibration Assessment of Thermowells

ASME PTC 19.3 2016 code does not provide clear guideline on how to deal with the vibration problems of existing thermowells that are currently in operation and may be operating near inline or transverse vibration zone. While the code allows passing through the in-line vibration zone, it prohibits operation completely in transverse vibration due to lock-in phenomenon. Once lock-in occurs, the thermowell gets into resonance and in the absence of adequate damping in the system, the thermowell vibration amplitude would keep on building with every cycle till eventual failure. It was identified that several operating assets had thermowells operating in the prohibited zone as per ASME PTC 19.3 and were facing a greater process safety risk. Damping though difficult to predict, plays very crucial role in amplitude when thermowell is operated in critical zone i.e. within 20% of natural frequency. Hence it is very important to estimate the damping factor. ASME PTC 19.3 2016 have suggested conservative damping factor (ζ) of 0.0005 based on the lab studies. The test set-up assumes the piping system as rigid component, whereas, in the field piping systems are flexible. Using a conservative damping in the stress calculations leads to a high fictitious stress indicating failure of the thermowell. In the present paper, a method is suggested to quantify the damping in the system by utilizing actual site vibration measurement of thermowell in the finite element analysis and thus a more realistic assessment of the stresses in the thermowell can be made. This assessment presented a much larger damping present in the system than ASME suggested and led asset to continue operate the plant with no risk of unplanned downtime as well as technical integrity of equipment. The results are presented for one sample thermowells.

Optimization Methodology for an Automotive Cross-Member in Composite Material

Optimization methods are useful and effective techniques for the design and development of components from the weight reduction point of view. This paper presents an optimization methodology applied to the front cross-member of a Maserati chassis for metal replacement application with the objective of the minimization of the mass of the structure using composite materials. Firstly, a topological optimization of the front side of the vehicle is performed, and the available design space is considered to determine the optimal load path of the design volume and, consequently, to assess a preliminary geometry of the component under scrutiny. Secondly, free-size optimization of the preliminary cross-member design is developed, initially neglecting and subsequently considering the manufacturing constraints. In addition, a linear analysis of the cross-member, modeled as a rigid component, is carried out to evaluate the maximum contribution of this component on the structural performance of the front side of the vehicle. Finally, size and shuffle optimizations are carried out on the new design concept to determine the number and the thickness of the composite plies, and the optimal stacking sequence, respectively, in order to fulfill the structural requirements. A comparison between the new composite structure and the aluminium Maserati cross-member is presented.

Kineto-Elastic Analysis of a Compound Bow

This paper presents the kineto-elastic analysis of a compound bow which in each side of the limbs has two stacked eccentric cams connected by two inextensible cables and one inextensible string. A large deformation cantilever beam model was created to determine the center trajectories of the cams. The principle of finite element method was applied to calculate the deformation of the limbs by combining small deflections of segmented cantilever beam elements. Another part of this work is the construction of a quasi-static model to simulate the draw process. The displacements of cams, cables and string were analyzed by gradually drawing the bow string. The required draw force as a function of draw length was obtained, and verified by experiments. The kineto-elastic analysis procedure described in this paper can be used later for the optimal design of the shapes of the cams and limbs. The modeling and simulation procedure used for combining elastic components, flexible but inextensible string-cable components, and rigid component in a precision dynamic model of a mechanical system can also be applied to archery bows with more complex configuration, and to other similar mechanical systems.

The Influence of Slab on Yield Mechanism of RC Frame Structure

"Strong column weak beam" form of frame structure is widely considered to be a reasonable framework structure yield mechanism in the seismic damage. The current structure design is mostly on the basis of that yield mechanism for structural seismic design. Generally the structural engineers ignore the bearing capacity contribution of frame beams that comes from the slab in the seismic design. The structure engineers considered the slab as a rigid component and simply calculate the slab stiffness by magnification factor method, which ignores the core of the problem. This paper analyzes mainly the influence of the destruction of slab form frame structure , studying further how slab affect the yield mechanism of frame structure, and explores the destruction form of difference between two models after analyzing two structure models by the method of Push – over. It shows that the existence of slab make the yield mechanism of RC frame structures different from the design.