In Vitro Mitral Valve Model with Unrestricted Ventricular Access: Using Vacuum to Close the Valve and Enable Static Trans-Mitral Pressure

Current in vitro models of the left heart establish the pressure difference required to close the mitral valve by sealing and pressurizing the ventricular side of the valve, limiting important access to the subvalvular apparatus. This paper describes and evaluates a system that establishes physiological pressure differences across the valve using vacuum on the atrial side. The subvalvular apparatus is open to atmospheric pressure and accessible by tools and sensors, establishing a novel technique for experimentation on atrioventricular valves. Porcine mitral valves were excised and closed by vacuum within the atrial chamber. Images were used to document and analyze closure of the leaflets. Papillary muscle force and regurgitant flow rate were measured to be 4.07 N at 120 mmHg and approximately 12.1 ml/s respectively, both of which are within clinically relevant ranges. The relative ease of these measurements demonstrates the usefulness of improved ventricular access at peak pressure/force closure. Graphical abstract

Algorithmic Fingertip Repositioning for Enhanced In-Hand Manipulation of the Objects

This paper focuses on a method to relocate the robotic fingertips on the surface of the object when the fingertips instantaneously hold the object under precision grasp. Precision grasp involves holding the object using fingertips. Finger gaiting involves repositioning the fingertips on the surface of the object and then manipulation of the object. During repositioning, one contact point leaves the object surface and recontacts at the other point. A metric is defined on the set of feasible grasp configurations to limit deviation from force closure during repositioning of the fingertips. Then, a manipulability based metric is described to search for the optimal goal grasp states on the object's surface. The manipulability based metric is used to search the grasp state to relocate the contacts, such that the range of object motion is increased.

Design and Evaluation of a Novel Instrument Gripper for Handling of Surgical Instruments

Introduction: Contaminated surgical instruments are manually prepared for cleaning and disinfection in the reprocessing unit for medical devices (RUMED). Manual labour exposes staff to the risk of infection and is particularly stressful at peak times due to the large volume of instruments. Partial automation of processes by a robot could provide a solution but requires a gripper that can handle the variety of surgical instruments. This paper describes the development and first evaluation of an instrument gripper. Methods: First, an analysis of gripping geometries on basic surgical instruments is carried out. Based on the identified common features and a review of the state of the art of gripper technology, the SteriRob gripper concept is developed. The concept is compared with a force closure gripper in a series of tests using seven criteria. Results: Both gripping approaches investigated can be used for handling surgical instruments in a pick-and-place process. However, the SteriRob gripper can transmit significantly higher acting forces and torques. In addition, the gripping process is more robust against deviations from the expected instrument position. Conclusion: Overall, it has been shown that the developed instrument gripper is suitable for about 60% of reusable surgical instruments due to the focus on horizontal cylindrical geometries. Because of the large possible force transmission, this gripping approach is particularly suitable for tasks in which the robot assists with cleaning processes.

Beyond Soft Hands: Efficient Grasping With Non-Anthropomorphic Soft Grippers

Grasping and manipulation are challenging tasks that are nonetheless critical for many robotic systems and applications. A century ago, robots were conceived as humanoid automata. While conceptual at the time, this viewpoint remains influential today. Many robotic grippers have been inspired by the dexterity and functionality of the prehensile human hand. However, multi-fingered grippers that emulate the hand often integrate many kinematic degrees-of-freedom, and thus complex mechanisms, which must be controlled in order to grasp and manipulate objects. Soft fingers can facilitate grasping through intrinsic compliance, enabling them to conform to diverse objects. However, as with conventional fingered grippers, grasping via soft fingers involves challenges in perception, computation, and control, because fingers must be placed so as to achieve force closure, which depends on the shape and pose of the object. Emerging soft robotics research on non-anthropomorphic grippers has yielded new techniques that can circumvent fundamental challenges associated with grasping via fingered grippers. Common to many non-anthropomorphic soft grippers are mechanisms for morphological deformation or adhesion that simplify the grasping of diverse objects in different poses, without detailed knowledge of the object geometry. These advantages may allow robots to be used in challenging applications, such as logistics or rapid manufacturing, with lower cost and complexity. In this perspective, we examine challenges associated with grasping via anthropomorphic grippers. We describe emerging soft, non-anthropomorphic grasping methods, and how they may reduce grasping complexities. We conclude by proposing several research directions that could expand the capabilities of robotic systems utilizing non-anthropomorphic grippers.

Experimental tests of industrial-scale ripping of soil

Ripper attachments should ensure destruction of firm, frozen or rocky soil. Industrial rippers have the ability to forcibly penetrate the working body into soil in contrast to agricultural tillage machines. The ripper attachments have two-sided force closure. The resultant forces acting on the working tool from the side of soil depend on such ripping parameters as ripping depth and angle. Currently, these dependences are mainly studied experimentally. The article presents the experimental results on the ripping resistance force as a case-study of a tractor-mounted dozer–ripper manufactured at the Chelyabinsk Tractor Plant. The scope of the experiment covers three ripping depths and eight angles. It has been experimentally found that the dependence of the ripping resistance force on each of these parameters is quadratic. The authors propose to study the ripping process using a complex parameter which is a product of the ripping depth and the ripping angle. The use of the complex parameter in the two-factor analysis allowed reducing the degree of the studied dependence while preserving the required accuracy. The complex parameter reflects the relationship between the design parameters of the ripper tooth, ripping depth and angle. The article shows that the vertical penetration resistance linearly depends on the horizontal traction resistance. The authors obtained this dependence for loam of medium density. The authors’ approach makes it possible undertake optimization of ripping process subject to soil type.

Analysis of a Wearable Robotic System for Ankle Rehabilitation

As one of the most commonly injured joints of the human body, the ankle is often subject to sprains or fractures that require motion assistance to recover mobility. Whereas physiotherapists usually perform rehabilitation in one-on-one sessions with patients, several successful robotic rehabilitation solutions have been proposed in the last years. However, their design is usually bulky and requires the patient to sit or stand in a static position. A lightweight wearable device for ankle motion assistance, the CABLEankle, is here proposed for motion ankle exercising in rehabilitation and training. The CABLEankle is based on a cable-driven S-4SPS parallel architecture, which enables motion assistance over the large motion range of the human ankle in a walking gait. The proposed mechanism design is analyzed with kinematic and static models, and the force closure workspace of the mechanism is discussed with analytical results. Finally, the feasibility of the proposed design is investigated through numerical simulations over the ankle motion range as a characterization of the peculiar motion.

Use of Bézier curves in the design of the displacement law of the cam-follower mechanism: Von Mises effective Stress

Designing cams by BézierCurves has become increasingly common, since the mathematical development of this method is less complex. Bezier curves are Bernstein-based polynomials under a unitary domain, and in that sense, this article presents the design of a cam using Bezier curves of degrees 5, 7 and 9. And beyond, this article seeks to show the variation of the effective effort of Von Mises in a cam-follower mechanism composed of a disc cam and a roller follower with translation movement and force closure. The expressions that allow determining the variation of Von Mises' effort for each of the curves used are presented. This variation is presented by means of graphs in which it is observed that as the degree of the curve increases, the magnitude of the efforts is greater, and this increases the probability of failure in the mechanisms. In addition, it was found that there is an inverse relationship between the stress and the radius of the primary circle of the cam