DragonFlex – Smart Steerable Laparoscopic Instrument

Introduction: The steerable laparoscopic instrument prototype DragonFlex was recently developed with the vision of a minimalistic fully functional design, readily produced by additive manufacturing and requiring little assembly. Steering functionality is provided by rolling joints that, besides simplifying the assembly, help minimise cable fatigue and equalise force requirements on steering cables. However, the perfectly circular rolling joint design introduced some mechanism play, undermining the joint’s bending stiffness. Hence, the aim of this paper is to present an innovative solution for play reduction in rolling joints. Material and methods: The original play-compensating mechanism, a shaft-embedded compression spring, proved unsatisfactory for play reduction. Therefore, a new non-circular rolling joint curvature was designed with the objective to compensate for any cable slack and thus minimise the joint play. The new rolling joint design was evaluated in several tip deflection experiments and compared to the original one. Results and conclusions: The experimental results proved that the optimised rolling joint curvature significantly minimises play, thus being a major improvement compared to the original design. The optimised rolling joint was implemented in a new real-scale DragonFlex prototype. The presented optimisation method enables elimination of a conventionally used cable tensioning device and it is generally applicable to steerable minimally invasive instruments that use a rolling joint.

In this study, an intelligent tool system for flexible L-bending of sheet metals is developed. The punch and die are adaptively actuated by hydraulic cylinders incorporated in the punch and die, respectively. An adaptive structure with high stiffness and motion accuracy is designed and compared with a formerly developed one. The tool system can basically change the profile of the tools and pressure distribution along the workpiece during the L-bending process. The system is characterized by its capability to bend the workpiece to various bending radii and bend angles for different materials without tool change. Process control paths for obtaining desired bend radii and angles are determined off-line by a numerical simulation using the elasto-plastic model. The paths are stacked into a simulation database and used for real-time control of the L-bending process. The measured data from the sensors are input into a computer for controlling the actuators and learning the control model by comparing it with the simulated data. Several experiments have been carried out for obtaining various bend radii using two kinds of materials, SPC and aluminum alloy. The experimental results corresponded not only to various bending radii but also different materials. In addition, higher accuracy of the process control has been achieved by improving the structure of the tool system and learning the process control model. These results prove the validity and reliability of the proposed intelligent tool system.

The cantilever structure of serial manipulator leads to bending under high load and vibration at high speed which affects precision and creates other problems. Parallel manipulator offers alternative to serial manipulator with higher precision and high payload capacity. Parallel manipulator with less degrees of freedom are used for drilling, contour milling, welding and tapping application with better accuracy and faster repeatability. In this paper a 3DOF parallel kinematic machine is proposed for drilling applications. The configuration of proposed PKM (Parallel Kinematic Machine) is 2PUS+PRR. The moving platform is connected with fixed platform using two links with Prismatic-Universal-Spherical (PUS) joints and one link with Prismatic-Rotational -Rotational joints (PRR). Rotational, Universal and Spherical joints are passive joints whereas prismatic joints are actuated by screw pairs with stepper motor. This paper derives Kinematic analysis, velocity equations mathematically.

Our goal is to present a general approach for the planar chains with rotational links with clearances.This approach is realized in a multibody style, the main problem being the determination of the matrix of constraints.IntroductionThe application of the multibody type methods [1-13], made possible the elaboration of certain general algorithms for the numerical, dynamical and elasto-dynamical calculation of the kinematical and dynamical parameters for the mechanical systems' motions.These algorithms can be applied both to the determined kinematical mechanical systems with and without friction [4,9,14], respectively with one degree of mobility, and to the systems with one degree of mobility and a single motor element as, for instance, [2,7,12], the mechanical convertor of torque created by G. Constantinescu.The applications of the multibody type methods for the studying of the planar mechanical systems having articulations with clearances (rotational kinematical joints) [3,4,6,10,14], assumes the inserting of certain virtual without mass elements, which leads to singular matrix of inertia and, consequently, it does not permit the separation of the general system of equations in two systems from which result, in order, the time history of the reactions and then the time history of the kinematical parameters.In this paper we elaborate a multibody type method based on a new form of the matrix of constraints, method that permits the numerical dynamical study of the planar systems with rotational joints with or without clearance, with one or several degrees of freedom.

Human standing requires control of multisegmental configuration. Does the postural system normally allow flexible adjustment of configuration, or does it minimize degrees of freedom at the ankle, knee, and hip joints? Gentle, external, unpredictable, sagittal, mechanical perturbations (randomized force, 1-10 N; duration, 0.2-2 s; and leg) were applied to either knee of 24 healthy participants who stood symmetrically for 200 s. The translation of knee perturbation force to ankle, knee, and hip joint rotations in the perturbed and unperturbed legs was studied. We assessed whether consequent joint rotations indicated a stiff configuration-conserving or viscous energy-absorbing relationship to the knee perturbation. Two distinctive response patterns were observed. Twenty-two participants showed limited knee flexion and high ankle stiffness, whereas two participants showed substantial knee flexion, low ankle stiffness, measurable internal rotation of the unperturbed hip (0.4 ± 0.3 vs. 3.0 ± 1°, 5.7 ± 17 vs. 0.5 ± 0.3 N/°, 1.1 ± 0.4°, respectively; mean ± SD), and a viscous relationship between perturbation force and subsequent ankle flexion, knee flexion, and perturbed and unperturbed hip internal rotation. The size of knee-flexion response to knee perturbations was uncorrelated with the extent of unperturbed standing sway. Normal standing conceals a large interindividual range in leg control strategies, indicating adaptive potential to progress with development and skill acquisition and decline with age, disease, injury, and fear. Commonly, leg configuration was maintained stiffly. Less commonly, a bilateral, low-stiffness, energy-absorbing strategy utilizing the available degrees of freedom was shown. We propose that identification of individual coordination strategy has diagnostic and prognostic potential in relation to perceptual-posture-movement-fall interactions.

In this paper, Haptic End-effector for Medicine and Manufacturing (HEM2) with five degree of freedom (DoF) motion is developed for safer and more intuitive robotic surgery. In resent years, multi DoF forceps robots have been studied and developed to support surgeons. However, conventional multi DoF forceps robots cannot transmit force sensation to surgeons adequately. Force sensation is important for safe and accurate teleoperation. In this paper, a master-slave five DoF HEM2 is developed as a haptic forceps robot. Five DoF motion corresponds with the motion of human hand which can realize complex tasks. By implementing acceleration based bilateral control, force sensation can be transmitted. Spherical joint driven by parallel link mechanism realizes the bending motion of the end-effector. The coaxial driving power transmission mechanism is used to decrease the weight of movable part and improve backdrivability. Besides, the mechanism is composed of rigid parts. The performance of the five DoF HEM2 is validated by experiments.

Using the SIMONA Research Simulator for Human-machine Interaction Research

In inertial confinement fusion (ICF) experiment, target positioner is needed to position the target within a very small micro scale scope around the center of target chamber whose diameter is several meters. A kind of ICF target positioning robot system with 12 Degree of Freedom (DOF) is designed to realize the adjustment and alignment of target. The robot system includes 6 DOF precision parallel robot subsystem, target transport subsystem, target storage subsystem and target exchange subsystem, the mechanism structure and principle of every subsystem is dissertated. The system realizes micro scale position by parallel structure which is in the front of system, which make the system has the advantages of low mass, high stiffness, small cone angle, small volume and high precision. Control strategy based on the process and character of target position is studied. The iterative auto positioning method is brought forward, 6 DOF precision target position is realized by the loop adjustment of each DOF of the parallel robot. Experiments prove that the target positioning robot fulfilled accuracy requirement and has enough stability, and iterative auto positioning method is effective for target positioning.

With a light-slender and superior dexterous body, the cable-driven segmented redundant manipulators (CSRMs) are excellent candidates for operations in narrow confined space. However, their application is still largely limited due to their weak stiffness, low load capacity, and complex modeling and planning. In this article, we design a new type of CSRM with high stiffness and load capacity using hybrid active and passive cables, and propose a simplified kinematics modeling and configuration planning method. The manipulator is composed of three active-linkage segments and one active tool end-effector. Each active segment, driven by three active driving cables, has two degrees of freedom (DOFs). By utilizing the passive linkage cables, the segment can be fully constrained with high stiffness, and move with equal joint angles in nearly continuous shape. Based on such structural features, the kinematics equations about the active segment-joint variables (i.e., the equalpitch and yaw angles of the whole segment) are derived. The direct, inverse kinematics and differential kinematics are greatly simplified. To find suitable solutions under environment constraints, extended virtual joint (EVJ) is introduced for quick regional solutions searching and equivalent kinematic constraint analysis. Furthermore, a configuration planning method based on the simplified kinematics and equivalent EVJs is proposed for single obstacle avoidance and continuous narrow space crossing tasks. Finally, a prototype system is developed and typical experiments are performed. The results show the high linkage accuracy, improved stiffness, and load capacity of the developed CSRM and verify the adaptability of the proposed configuration planning method.

Autonomous underwater vehicles (AUVs) are poised to become an indispensable tool for ocean exploration, underwater research and development, and military activities. One of the key elements of these vehicles is dependability; there must be some form of fault recovery/fault tolerance in the control system. In this work, we use an approach involving synthesis of motions in degrees of freedom (DOF) that are unactuated, by combining motions in DOF that are actuated. The objective is to determine the usefulness of the method for a typical streamlined vehicle which is controlled by control surfaces rather than thrusters. We find that the method has difficulties in its present form because of the righting moment designed into the vehicle, but it is functional on a modified model of the vehicle.

In this thesis, we present a dynamical systems approach to adaptive controllers for locomotion control. The approach is based on a rigorous mathematical framework using nonlinear dynamical systems and is inspired by theories of self-organization. Nonlinear dynamical systems such as coupled oscillators are an interesting approach for the on-line generation of trajectories for robots with many degrees of freedom (e.g. legged locomotion). However, designing a nonlinear dynamical system to satisfy a given specification and goal is not an easy task, and, hitherto no methodology exists to approach this problem in a unified way. Nature presents us with satisfactory solutions for the coordination of many degrees of freedom. One central feature observed in biological subjects is the ability of the neural systems to exploit natural dynamics of the body to achieve efficient locomotion. In order to be able to exploit the body properties, adaptive mechanisms must be at work. Recent work has pointed out the importance of the mechanical system for efficient locomotion. Even more interestingly, such well suited mechanical systems do not need complicated control. Yet, in robotics, in most approaches, adaptive mechanisms are either missing or they are not based on a rigorous framework, i.e. they are based on heuristics and ad-hoc approaches. Over the last three decades there has been enormous progress in describing movement coordination with the help of Synergetic approaches. This has led to the formulation of a theoretical framework: the theory of dynamic patterns. This framework is mathematically rigorous and at the same time fully operational. However, it does not provide any guidelines for synthetic approaches as needed for the engineering of robots with many degrees of freedom, nor does it directly help to explain adaptive systems. We will show how we can extend the theoretical framework to build adaptive systems. For this purpose, we propose the use of multi-scale dynamical systems. The basic idea behind multi-scale dynamical systems is that a given dynamical system gets extended by additional slow dynamics of its parameters, i.e. some of the parameters become state variables. The advantages of the framework of multi-scale dynamical systems for adaptive controllers are 1) fully dynamic description, 2) no separation of learning algorithm and learning substrate, 3) no separation of learning trials or time windows, 4) mathematically rigorous, 5) low dimensional systems. However, in order to fully exploit the framework important questions have to be solved. Most importantly, methodologies for designing the feedback loops have to be found and important theoretical questions about stability and convergence properties of the devised systems have to be answered. In order to tackle this challenge, we first introduce an engineering view on designing nonlinear dynamical systems and especially oscillators. We will highlight the important differences and freedom that this engineering view introduces as opposed to a modeling one. We then apply this approach by first proposing a very simple adaptive toy-system, consisting of a dynamical system coupled to a spring-mass system. Due to its spring-mass dynamics, this system contains clear natural dynamics in the form of resonant frequencies. We propose a prototype adaptive multi-scale system, the adaptive frequency oscillator, which is able to adapt its intrinsic frequency to the resonant frequency of the body dynamics. After a small sidetrack to show that we can use adaptive frequency oscillators also for other applications than for adaptive controllers, namely for frequency analysis, we then come back to further investigation of the adaptive controller. We apply the same controller concept to a simple spring-mass hopper system. The spring-mass system consists of a body with two legs attached by rotational joints. The legs contain spring-damper elements. Finally, we present results of the implementation of the controller on a real robot, the experimental robot PUPPY II. This robot is a under-actuated robot with spring dynamics in the knee joints. It will be shown, that due to the appropriate simplification and concentration on relevant features in the toy-system the controller concepts works without a fundamental change on all systems from the toy system up to the real robot.

This paper presents the design, fabricate and evaluation of a Magnetic Resonance compatible finger rehabilitation device, which could not only be used as a finger rehabilitation training tool after stroke, but also to study the brain's recovery process during the rehabilitation therapy (ReT). The mechanics of this device are designed to be adjustable to different persons' finger phalanges, and also the gap between one finger to another can be easily changed. By using an ultrasonic motor as its actuator, the device has been designed to be portable, with a high torque output. In addition, the mechanical has been developed into two working models (passive and active) in order to overcome the intrinsic shortage of non-back drivability in ultrasonic motor. The result system enables the client to do extension and flexion rehabilitation exercises in two degrees of freedom (DOF) for each finger as well as one DOF motion on the thumb. Finally, experiment has been carried out to evaluate the performance of the device.

This paper is the first in a two-part series analyzing human arm and hand motion during a wide range of unstructured tasks. The wide variety of motions performed by the human arm during daily tasks makes it desirable to find representative subsets to reduce the dimensionality of these movements for a variety of applications, including the design and control of robotic and prosthetic devices. This paper presents a novel method and the results of an extensive human subjects study to obtain representative arm joint angle trajectories that span naturalistic motions during Activities of Daily Living (ADLs). In particular, we seek to identify sets of useful motion trajectories of the upper limb that are functions of a single variable, allowing, for instance, an entire prosthetic or robotic arm to be controlled with a single input from a user, along with a means to select between motions for different tasks. Data driven approaches are used to discover clusters and representative motion averages for the wrist 3 degree of freedom (DOF), elbow-wrist 4 DOF, and full-arm 7 DOF motions. The proposed method makes use of well-known techniques such as dynamic time warping (DTW) to obtain a divergence measure between motion segments, Ward's distance criterion to build hierarchical trees, and functional principal component analysis (fPCA) to evaluate cluster variability. The emerging clusters associate various recorded motions into primarily hand start and end location for the full-arm system, motion direction for the wrist-only system, and an intermediate between the two qualities for the elbow-wrist system.

This paper treats the problems of kinematics, stiffness and singularity analysis of the 3T2R 5-DOF 4-SPRR-SPR parallel robot mechanism. The degree of freedom is analyzed by screw theory and the inverse kinematics equation is established by vector method. The Jacobian matrix of driving and constraint are established by screw method. The stiffness and singularity distribution in working space is obtained by Jacobian matrix.The results show that the inverse solution of the mechanism is fast and convergent and the Jacobian matrix is complete.The stiffness index distributes evenly, changes smoothly and has certain symmetry. The stiffness index decreases gradually with the increase of Z value or rotation angle, which accords with the characteristics of the mechanism. When the rank of Jacobian matrix is less than 6, the mechanism will be singular. By making the rank of the Jacobian matrix 0, we get the 10 kinds singular positions of the mechanism.Because of its characteristics of five degrees of freedom, high stiffness and high bearing capacity, this mechanism has great application prospects in friction stir welding of complex surface in space.

In this paper, a novel 3D printed Rotational Joint (RJ) embedding an integrated elastic element is presented. The RJ, produced as a single piece by means of an FDM printer, comprises a traditional pin hinge coupled with a pair of spiral torsion springs, providing the desired compliance for the application at hand. Benefits of the proposed design include monolithic manufacturing and possibility to be successfully employed in robotic articulated devices requiring joint elasticity for their functioning. On the other hand, the sub-optimal RJ behavior, mainly caused by the unavoidable friction between 3D printed mating surfaces, must be accurately taken into account for design purposes. In this context, preliminary reliability tests have been performed showing promising results in terms of lifetime and negligible fatigue effects. Then, a mathematical model of the system is derived, which comprises the spring elasticity along with any frictional effects that may be due to either the pin hinge itself or the tendon transmission (frequently employed in underactuated robotic devices). The model parameters have been empirically evaluated by comparing simulated and experimental data. In addition, the last part of the paper describes how the proposed RJ can be effectively employed for the design of modular, underactuated fingers, providing three degrees of freedom and a single tendon transmission. To this end the model of the joint module proposed in this work will be the starting point for the geometry dimensioning of a finger with a desired free closure motion.