Exploring human hand fundamental biomechanical features and exploiting them to robotic hands have been proven to be an effective approach to enhancing artificial hands' performance, especially when interacting with various objects in dynamic unstructured environments. In this article, a bioinspired anthropomorphic robotic finger is first proposed, which embeds human finger musculoskeletal features in the design. Based on this design, three human-finger-like biomechanical advantages are systematically investigated and embodied in the bioinspired robotic finger. This article for the first time derives, presents, and experimentally verifies the mathematical models for the variable stiffness of finger ligamentous joints and self-adaptive morphing mechanism of finger flexible tendon sheaths, and validates and compares the influence of the reticular and linear extensor morphologies on fingertip feasible forces in three-dimensional (3-D) space. In this Part I of the article, two of the biomechanical properties, i.e., joint stiffness generated by the ligamentous joint of the finger, and fingertip feasible force space influenced by the reticular extensor mechanism are systematically investigated through theoretical modeling and experimental verification. Correspondingly, two biomechanical advantages were found, i.e., the ligamentous joint of the finger could provide anisotropic variable joint stiffness, enhancing the adaptivity, dexterity, and stability of fingers; and a reticular extensor mechanism could enlarge the fingertip feasible force space in 3-D space by 30.9% theoretically and 146.4% experimentally on average compared with the linear extensor, contributing to enrich force conditions during interactions. The third biomechanical advantage, i.e., fingertip force–velocity workspace can be augmented through the flexible tendon sheath, and grasping tests for a robotic hand designed with the aforementioned advantages are presented in Part II of this article.

The human hand has a fantastic ability to interact with various objects in the dynamic unstructured environment of our daily activities. We believe that this outstanding performance benefits a lot from the unique biological features of the hand musculoskeletal system. In Part I of this article, a bio-inspired anthropomorphic robotic finger was developed, based on which two human-finger-like biomechanical advantages were elaborately investigated, including the anisotropic variable stiffness associated with the ligamentous joints and the enlarged feasible force space associated with the reticular extensor mechanisms. In Part II, the fingertip force-velocity characteristics resulting from the flexible tendon sheath are studied. It indicates that the fingertip force–velocity workspace can be greatly augmented owing to the self-adaptive morphing of the flexible tendon sheaths, showing the average improvement of 41.2% theoretically and 117.5% experimentally compared with the results of 2 mm, 4 mm, and 6 mm size rigid tendon sheaths. Grasping tests and comparisons are then conducted with four three-fingered robotic hands (one with the robotic finger proposed in Part I, one with hinge joints, one with linear extensors, and one with rigid tendon sheaths) and the human hands of six subjects to handle various objects on flat, rough, and soft surfaces. The results show that the novel bio-inspired design in this research could improve the grasping success rates of the robotic hand. Compared with the grasping test results from the robotic hand with the bio-inspired robotic finger proposed in Part I, the overall grasping performance of a robotic hand with hinge joints, linear extensors, and rigid tendon sheaths decreases by 10%, 6%, and 17%, respectively. The results have also shown that with the embedded biomechanical advantages, even without complex control and sensory systems, the robotic fingers can achieve very comparable performance to human fingers in the grasping demonstrations presented, indicating average 94% of the success rate achieved by the human fingers. Successfully demonstrating 14 of 16 grasp types in the Cutkoskey taxonomy further shows the human-finger-like grasping capability of the proposed robotic fingers.

The use of snake-like robots for surgery is a popular choice for intra-luminal procedures. In practice, the requirements for strength, flexibility and accuracy are difficult to be satisfied simultaneously. This paper presents a computational approach for optimizing the design of a snake-like robot using serial rolling-joints and tendons as the base architecture. The method optimizes the design in terms of joint angle range and tendon placement to prevent the tendons and joints from colliding during bending motion. The resulting optimized joints were manufactured using 3D printing. The robot was characterized in terms of workspace, dexterity, precision and manipulation forces. The results show a repeatability as low as 0.9mm and manipulation forces of up to 5.6N.

Traditional robotic surgical systems rely entirely on robotic arms to triangulate articulated instruments inside the human anatomy. This configuration can be ill-suited for working in tight spaces or during single access approaches, where little to no triangulation between the instrument shafts is possible. The control of these instruments is further obstructed by ergonomic issues: The presence of motion scaling imposes the use of clutching mechanics to avoid the workspace limitations of master devices, and forces the user to choose between slow, precise movements, or fast, less accurate ones. This paper presents a bi-manual system using novel self-triangulating 6-degrees-of-freedom (DoF) tools through a flexible elbow, which are mounted on robotic arms. The control scheme for the resulting 9-DoF system is detailed, with particular emphasis placed on retaining maximum dexterity close to joint limits. Furthermore, this paper introduces the concept of gaze-assisted adaptive motion scaling. By combining eye tracking with hand motion and instrument information, the system is capable of inferring the user's destination and modifying the motion scaling accordingly. This safe, novel approach allows the user to quickly reach distant locations while retaining full precision for delicate manoeuvres. The performance and usability of this adaptive motion scaling is evaluated in a user study, showing a clear improvement in task completion speed and in the reduction of the need for clutching.

Suturing is an essential requirement for surgical robots. Current designs of needle drivers require significant forces to be applied so that the needle will not flip or slip between the jaws when inserted into the tissue. The required force implies that most designs are based on rigid instruments with a straight shaft that induces less dexterity. Flexible robotics provides great dexterity to achieve the task, although often it lacks the capability to apply large forces and therefore hold the surgical needle firmly. Solutions can be found in how the needle driver's jaws are designed. This paper presents improved designs for needle grasping tools for flexible robotic instruments, to be produced directly with selective laser melting. Features on the gripping surface were embedded to increase the gripping effectiveness even in the presence of limited grasping force. A detailed characterisation has been performed for each design showing improvements with respect to the state of the art.

This paper introduces the design and characterization of a robotic surgical instrument produced mainly with rapid prototyping techniques. Surgical robots have generally complex structures and have therefore an elevated cost. The proposed instrument was designed to incorporate minimal number of components to simplify the assembly process by leveraging the unique strength of rapid prototyping for producing complex, assemble-free components. The modularity, cost-effectiveness and fast manufacturing and assembly features offer the possibility of producing patient or task specific instruments. The proposed robot incorporates an integrated force measurement system, thus allowing the determination of the force exchanged between the instrument and the environment. Detailed experiments were performed to validate the functionality and force sensing capability of the instrument.

This paper presents kinematics and two dynamic characteristics including stiffness and natural frequency of a four degrees-of-freedom (DOFs) masticatory robot. Based on the biological architecture of human masticatory system, this robot is modeled in the form of a redundantly actuated parallel mechanism constrained by two point-contact higher kinematic pairs (HKPs). The aim of this robot is to chew samples of newly developed foods in a human way while the food textures can be characterized. The kinematics including inverse kinematics, workspace and singularity are studied systematically. The inverse kinematics is given in closed-form solutions. The workspace is generated by a numerical search method. In virtue of the Jacobian matrix derived from differential kinematics, the singularity and the stiffness are investigated. Via the derived stiffness matrix and mass matrix, natural frequency is also computed. Finally, simulation is carried out, one real incisor trajectory of a healthy human subject is reproduced, illustrating the robot is able to reproduce kinematic behaviors of the human masticatory system, and it owns a satisfactory performance in terms of stiffness and natural frequency. Comparison between the redundantly actuated masticatory robot and its two non-redundantly actuated counterparts also exhibits that the former owns better performance, in terms of a similar incisor's workspace as the Posselt envelope, no singularity, larger stiffness and higher natural frequency.

Additive manufacturing is a technology in constant evolution. It is able to produce objects otherwise either impractical or unfavorable for traditional manufacturing technologies, especially in relatively limited quantities. The advancement of Selective Laser Melting (SLM) has made it possible to manufacture functional, production-quality components directly from rapid prototyping for long-term use. This work studies the SLM process and identifies the optimal process parameters for the rapid manufacturing of a miniaturized robotic surgical instrument. The proposed robotic instrument has been designed to exploit the advantages of rapid manufacturing and rapid assembly, following a shift from large scale manufacturing of generalized surgical instruments to the production of small batches of patient or procedure-specific.

Precise and repetitive positional control of surgical robots is important to reduce time and risks of surgical procedures. These factors become particularly important when deploying the surgical system through a flexible path to areas with a tight workspace such as the stomach or oesophagus where high dexterity, flexibility, accuracy and stability are required. This paper presents a flexible access robot combining articulated joints and continuum flexible section for both transluminal and endoluminal surgeries. Kinematic model and control strategy for the flexible robot are described in the paper. The experiment simulating a transoral gastric procedure demonstrates great flexibility and dexterity of the device. The results show that good accuracy and repetitive control of the device are achieved, which demonstrate the potential application of the device for transluminal or endoluminal surgery.

Competing failure is an important reliability topic. Thus, the study of the statistical inference of accelerated life testing (ALT) with competing failures is of great significance. In contrast to the previous related studies that assumed that all competing failure modes were cross statistically independent, we study the statistical inference method for ALT considering the statistical dependence of the competing failure modes based on copula theory. With the copula function, we construct the statistically dependent relationship between the margin distributions of the competing failure modes and their joint distribution, and find the maximum likelihood estimation (MLE) model for the parameter estimations. We also present a simple engineering-based multi-dimensional copula construction method applied in the statistical inference for ALT with statistically dependent competing failure modes. The results and analysis of the case studies indicate that the statistical inference models and the multi-dimensional copula construction method derived in this article are not only correct and feasible but have good accuracy and universality. We have provided an effective, universally applicable method for the statistical inference of ALT in situations involving competing failures, statistically independent or dependent, which is of great significance to evaluating a product's lifetime in ALT.

Real-time shape sensing and state acquisition is important for closed-loop control of hyper-redundant snake robots in minimally invasive surgery. Due to the miniaturized size of such minimally invasive surgery robots, it is not feasible to use existing angular sensors involving rotary encoders. With recent advances of the MEMS technology, micro inertial sensors have shown their potential for robot state estimation. Previous studies have demonstrated that accurate joint angles can be estimated for one degree-of-freedom (DoF) joints. However, higher DoF joints of the robot can impose a number of challenges to the current joint angle estimation methods. This paper presents a micro-sensing platform and shape reconstruction algorithm for minimally invasive surgery snake robot with two DoF joints. The method incorporates both gravitational and gyroscopic sensing for calculating the rotation difference between any consecutive robot segments. The gyroscope measurements are first used as the input to predict the rotation difference by direct orientation integration. The orientation difference is then derived from the consecutive acceleration vectors to update the prediction through a complementary filter. To demonstrate the performance of our proposed approach, a robot prototype with two universal joints was fabricated. Detailed experimental results have demonstrated that high accuracy can be achieved by using the proposed method for joint angle estimation.

This paper describes a multitasking robotic platform for Minimally Invasive Surgery (MIS). The device is designed to be introduced through a standard trocar port. Once the device is inserted to the desired surgical site, it can be reconfigured by lifting an articulated section, and protruding two tendon driven flexible arms. Each of the arms holds an interchangeable surgical instrument. The articulated section features a 2 Degrees-of-Freedom (DoF) universal joint followed by a single DoF yaw joint. It incorporates an on-board camera and LED light source at the distal end, leaving a Ø3mm channel for an additional instrument. The main shaft of the robot is largely hollow, leaving ample space for the insertion of two tendon driven flexible arms integrated with surgical instruments. The ex-vivo and in-vivo experiments demonstrate the potential clinical value of the device for performing surgical tasks through single incision or natural orifice transluminal procedures.

This paper introduces an articulated robotic device based on universal joints with embedded micro motors for minimally invasive surgery. The device features an articulated distal tip with seven independently controllable degrees-of-freedom (DoF), arranged as two universal joints (intersecting pitch and yaw) and three single DoF joints (yaw only); two Ø3mm internal channels, one for an on-board camera for visualization and the other for passing interventional instruments. The design allows the robot to explore the entire peritoneal cavity from a chosen single incision point. A trans-vaginal procedure using the device to locate the uterine horn, as a model of a human fallopian tube, and apply an endoscopic clip was carried out during a live porcine trial to demonstrate the potential for performing a Natural Orifice Translumenal Endoscopic Surgery (NOTES) tubal ligation procedure.

This paper introduces a modular, mechatronic joint design for a flexible access minimally invasive surgical platform. The design features a hybrid tendon-micromotor actuation scheme coupled via an internal “ring gear”. This configuration transmits the rotary motion of the embedded micromotor to joint rotation in an efficient manner while also providing a hollow lumen through the centre of the joint unit. Detailed analyses of the joint design including tendon path length, positional accuracy and force/torque transmission characteristics are presented. The design has been incorporated into a dexterous, seven degree-of-freedom flexible access platform and its clinical efficacy for performing a Natural Orifice Translumenal Endoscopic Surgery (NOTES) diagnostic peritoneoscopy in an in-vivo environment is presented.