Rolling Contact Joints Research Articles

3D printer-driven design of a non-assembly titanium surgical instrument using compliant lattice flexures

Metal additive manufacturing is a promising technology for the production of functional medical products, due to its high shape complexity and resolution, and ability to withstand sterilization temperatures. This study explores the possibility of designing a completely non-assembly steerable surgical instrument using Selective Laser Melting. Despite its advantages for medical devices, the rough surface quality of unfinished parts can be problematic for non-assembly designs, leading to increased friction and wear in rigid body mechanisms and tendon-actuated mechanisms. We investigated printing of rolling contact joints with crossed flexures as low-friction joints, adjusted for printing in titanium for the design of the instrument. Grid-based lattice structures were incorporated as miniature flexures, and we explored the influence of various grid sizes on the flexibility and bending stiffness of the lattices. Based on this exploration, we altered the rolling joint configuration from two crossed flexures to a single straight flexure for our design. The resulting steerable surgical instrument design is completely non-assembly, including its actuation, facilitates easy removal of support structures, and requires no surface finishing steps. It has a diameter of less than 20 mm, facilitates opening and closing of a grasper, and steering of the grasper by 20 degrees.

Asymmetric Rolling Contact Joint for Enhanced Payload Capabilities

Asymmetric Rolling Contact Joint for Enhanced Payload Capabilities

Biomechanical comparative finite element analysis between a conventional proximal interphalangeal joint flexible hinge implant and a novel implant design using a rolling contact joint mechanism

BackgroundThe rolling contact joint (RCJ) mechanism is a system of constraint that allows two circular bodies connected with flexible straps to roll relative to one another without slipping. This study aims to compare the biomechanical characteristics between the conventional proximal interphalangeal joint (PIPJ) flexible hinge (FH) implant and the novel PIPJ implant adopting a RCJ mechanism during PIPJ range of motion using finite element (FE) analysis.MethodsThe three-dimensional (3D) surface shape of a conventional PIPJ FH implant was obtained using a 3D laser surface scanning system. The configuration and parameters of the novel PIPJ implant were adapted from a previous study. The two implants were assumed to have the same material characteristics and each implant was composed of a hyperelastic material, silicone elastomers. The configuration data for both implants were imported to a computer-aided design program to generate 3D geometrical surface and hyperelastic models of both implants. The hyperelastic models of both implants were imported into a structural engineering software to produce the FE mesh and to perform FE analysis. The FE analysis modeled the changes of mechanics during flexion–extension motion between 0° and 90° of two PIPJ implants. The mean and maximum values of von-Mises stress and strain as well as the total moment reaction based on the range of motion of the PIPJs were calculated. The mean values within the PIPJ’s functional range of motion of the mean and maxinum von-Mises stress and strain and the total moment reaction were also determined.ResultsThe maximum values for the von-Mises stress, and strain, as well as the total moment reactions of the conventional PIPJ FH and novel PIPJ implants were all at 90° of PIPJ flexion. The maximum value of each biomechanical property for the novel PIPJ implant was considerably lower compared with that of the conventional PIPJ FH implant. The mean values within the PIPJ’s functional range of motion of the maximum von-Mises stress and strain for the novel PIPJ implant was approximately 6.43- and 6.46-fold lower compared with that of the conventional PIPJ FH implant, respectively. The mean value within a PIPJ’s functional range of motion of the total moment reaction of the novel PIPJ implant was approximately 49.6-fold lower compared with that of the conventional PIPJ FH implant.ConclusionsThe novel PIPJ implant with an RCJ mechanism may offer improved biomechanical performance compared with conventional PIPJ FH implant.

Control and evaluation of a humanoid robot with rolling contact joints on its lower body.

In this paper, we introduce a new teen-sized humanoid platform dubbed DRACO 3, custom-built by Apptronik and altered for practical use by the Human Centered Robotics Laboratory at The University of Texas at Austin. The form factor of DRACO 3 is such that it can operate safely in human environments while reaching objects at human heights. To approximate the range of motion of humans, this robot features proximal actuation and mechanical artifacts to provide a high range of hip, knee, and ankle motions. In particular, rolling contact mechanisms on the lower body are incorporated using a proximal actuation principle to provide an extensive vertical pose workspace. To enable DRACO 3 to perform dexterous tasks while dealing with these complex transmissions, we introduce a novel whole-body controller (WBC) incorporating internal constraints to model the rolling motion behavior. In addition, details of our WBC for DRACO 3 are presented with an emphasis on practical points for hardware implementation. We perform a design analysis of DRACO 3, as well as empirical evaluations under the lens of the Centroidal Inertia Isotropy (CII) design metric. Lastly, we experimentally validate our design and controller by testing center of mass (CoM) balancing, one-leg balancing, and stepping-in-place behaviors.

Investigating the Stiffness Characteristics of a Tendon-Driven Continuum Manipulator Using Sensitivity Analysis: A Case Study in Transoral Laser Microsurgery

Continuum manipulators, with their characteristics of flexibility and dexterity, have gained significant interest in various applications across industries such as inspection, manufacturing, space exploration, and medical surgery. However, because of their inherent compliance, handling payloads may prove challenging due to shape distortion and deflection. This demonstrates the need to optimize the manipulator’s stiffness. The primary objective of this work was to show the merits of sensitivity analysis in the design of flexible surgical manipulators. Such analysis can guide important design decisions and enable the more efficient use of available resources, contributing to designing more effective prototypes. A new sensitivity analysis framework based on a multi-model and a multi-method approach was proposed to achieve this. This framework was then demonstrated by studying a tendon-driven rolling contact joint hyper-redundant manipulator for transoral laser microsurgery. In this analysis, the effects of independent design parameters on the stiffness of the manipulator were examined. Then, scaled-up 3D-printed prototypes were used to validate the accuracy of the stiffness model experimentally, which enabled us to assess the outcome of the sensitivity analysis framework. The results demonstrated that only two out of five design parameters for the considered manipulator significantly impacted the device’s performance. This information could enable the designer to efficiently allocate resources toward correctly setting these two most important parameters to achieve the desired system. Overall, the proposed analysis framework is a general tool that can be applied to any design architecture, helping to develop optimal manipulators for various applications.

ARC Joint: Anthropomorphic Rolling Contact Joint With Kinematically Variable Torsional Stiffness

As compliant joints not only compensate for the lack of actuated degrees of freedom of an under-actuated system and improve grasp stability but also prevent system failure from unexpected contacts, various types of compliant joints have been applied to end-effectors. Although joint compliance increases the success rate of power grasping, when the finger wraps around large objects, it can reduce the grasping success rate in pinch gripping when dealing with small objects using the fingertips. To overcome this drawback, we propose a novel rolling contact joint, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">anthropomorphic rolling contact joint</i> , that mimicked the structures of the human finger joint, tongue-and-groove, and collateral ligaments. The anthropomorphic rolling contact joint can passively adjust the torsional stiffness according to the joint angle without additional weight and space. With the anthropomorphic rolling contact joint, flexing the fingers for pinch grasping increases torsional stiffness of the joints and improves grasping stability. In this study, the characteristics and performance of anthropomorphic rolling contact joints were experimentally analyzed by varying the tongue-and-groove shape. Furthermore, it was demonstrated that the three-finger gripper with high torsional stiffness stably grasps small objects in the pinch grasping posture. In addition, because it is easy to manufacture, an anthropomorphic rolling contact joint has advantages in terms of maintenance.

Kinematics Modeling and Control of Spherical Rolling Contact Joint and Manipulator

Rolling contact joints are attracting increasing interest in applications to robotic fingers and manipulators, due to the potential of the absence of abrasion wear, the simplification of the controller, and the enlargement of reachable configurations. This article first proposes a novel two-degree-of-freedom (DOF) spherical rolling contact (SRC) joint, with the joint model elements being formulated, including <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rotation matrix</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">position vector</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">free modes</i> , as with those of classic joints. As an application, a new kind of serial manipulator formed by the SRC joints is presented, and its forward and inverse kinematics are modeled. The motions of the two-DOF SRC joint and manipulator are implemented using the FreeBOT, and the control method is proposed for the FreeBOT, such that the SRC joint and manipulator realize the motion control. The kinematics and control of the two-DOF SRC joint and manipulator are validated using physics simulations and on a real manipulator formed by FreeBOTs.

On the Design of an Adaptable Underactuated Hand Using Rolling Contact Joints and an Articulated Palm

Abstract Based on an optimized underactuated finger using rolling contact joints, a novel prosthetic hand is proposed in this paper to increase the adaptability to objects of highly underactuated grippers. The hand has 17 degrees-of-freedom and only one degree of actuation, yielding a robust and simple control. A manually operated thumb, able to reach three stable positions corresponding to the main grasping postures is first presented. Its rolling contact joints, introduce geometric twist and tilt, are designed in an iterative process using 3D modeled contacts. In parallel, the parameters of the thumb are optimized to maximize the distribution of contacts and the ability to hold objects. A joint located inside the hand allows the palm to arch, increasing the opposition of the ring finger, and the little finger to the thumb. The floating mechanism used to distribute the single actuation to the different degrees-of-freedom reduces friction while avoiding the unnecessary blocking of components. Finally, a prototype is designed and built to demonstrate the adaptation capabilities of the hand to diverse objects, which is enhanced by a gravity-dependent closing sequence and the deformation of the palm that maximizes the contribution of each finger. Novel possibilities are also presented such as the grasping and flipping of small objects on a hard surface.

On the Optimal Design of Underactuated Fingers Using Rolling Contact Joints

The design of underactuated fingers using rolling contact joints is addressed in this article in order to increase performance in robotic and prosthetic hands applications. Rolling contact joints have proven to be a promising alternative to revolute joints by increasing the range of motion, introducing compliance and decreasing internal friction. The conditions of optimal design for fingers using such joints are however not well stated. In order to fully exploit the potential of rolling-contact-joint based fingers, their design space is extended and performance metrics adapted to underactuated fingers are used in this letter. An optimization based on these metrics is performed over the large design space using genetic algorithms to find an optimal design. The solution obtained is then used to build a prototype and its performance is compared to that predicted by the model and to a comparative design using a realistic test bench.

Fluid Lubricated Dexterous Finger Mechanism for Human-Like Impact Absorbing Capability

This letter presents a novel three degree-of-freedom finger mechanism that features excellent impact absorbing performance, high force, and precision comparable to human hands. Inspired by human fingers, it has a simple structure with a minimum number of rigid components: seven rigid frames, several polymer wires, and flexible sheets. For impact absorption, rolling contact joints with a center ligament, instead of conventional revolute joints with bearings or bushings, were used. While this mechanism can be dislocated in the event of off-axis bending or twisting force and impact, it can return afterward without degrading precision. To achieve precise manipulation performance, a unique tendon guiding structure, which enables accurate kinematic modeling even though it is composed of soft and flexible materials, is proposed. To prevent loss of precision and robustness against friction, the whole mechanism is covered by an artificial skin and filled with lubrication liquid, which is similar to human synovial fluid. The developed finger mechanism can exert 40 N fingertip force in a straight pose and has 0.2 mm repeatability of fingertip position under multiple impacts. Various experiments including button clicking and wheel rotation of a computer mouse demonstrated the performance and potential usefulness of the proposed mechanism.

Novel implant design of the proximal interphalangeal joint using an optimized rolling contact joint mechanism

BackgroundThe aims of this study were to propose a novel implant design for the proximal interphalangeal joint (PIPJ) of the hand using a rolling contact joint (RCJ) mechanism and to derive an optimal implant design based on human PIPJ kinematics.MethodsIn total, 10 participants with normal PIPJs were enrolled in this study. True lateral finger radiographs were obtained in 10° increments from 0º (full extension) to 120° flexion of PIPJ. Radiographs were used to determine the average center of rotation, which formed the basis of a mathematical expression of the PIPJ kinematics. The variations in extensor tendon excursions in relation to the range of motion of PIPJ were determined using results from previous cadaveric studies. As the next step, a PIPJ implant design using an RCJ mechanism that was most consistent with the mathematically expressed PIPJ kinematics and tendon excursions was determined using a constrained optimization algorithm.ResultsThe final proposed PIPJ implant had a relatively constant center of rotation over the entire PIPJ range of motion among the participants. In addition, the extensor tendon excursions of the proposed implant as applied to the phalangeal bones were similar to those of the human tendon. The proposed PIPJ implant achieved an acceptable position of the RCJ surface on the proximal and middle phalanges, which was derived from the constrained optimization algorithm.ConclusionsA novel PIPJ implant design using an RCJ mechanism demonstrated acceptable outcomes in terms of PIPJ human kinematics and tendon excursions.

Design of a Bioinspired Robotic Hand: Magnetic Synapse Sensor Integration for a Robust Remote Tactile Sensing

Integrating tactile sensors into robotic applications is still a challenge because of sensor interconnection and various form factors. Newly developed magnetic synapse sensors have high sensitivity and remote sensing capability, but integration with a robotic finger is an issue because of the air-transmitting tubes that need to be connected from the sensor to the remotely located base unit. This study proposes an integrated design of a multijoint robotic finger with magnetic synapse sensors inspired by the human's joint structure and synapse system. The joint unit inspired by human's finger joints for the usage of the magnetic synapse sensors can easily has hollow channels and insert air-transmitting tubes through a rotating joint compared to the traditional pin joint. The rolling contact joint also minimizes the length variation of the tube when the joint rotates because the center of rotation changes. Modularized sensor units capable of changing the sensor sensitivity and sensing range have been developed and applied to the remote tactile sensing system. A three-finger gripper with three joints per finger with an integrated three-tactile sensor array was prototyped to explore the feasibility of the units. The sensor sensitivity was 0.016 mV/kPa and the sensing range was 350 kPa. The robotic fingers integrated with a high-sensitivity sensor array can grasp objects with various shapes and compliance (i.e., artificial flowers, paper cups, and wine glasses) without damaging the objects using tactile feedback.

Analysis and design of rolling-contact joints for evaluating bone plate performance

An apparatus for testing maxillofacial bone plates has been designed using a rolling contact joint. First, a free-body representation of the fracture fixation techniques utilizing bone plates is used to illustrate how rolling contact joints accurately simulate in vivo biomechanics. Next, a deterministic description of machine functional requirements is given, and is then used to drive the subsequent selection and design of machine elements. Hertz contact stress and fatigue analysis for two elements are used to ensure that the machine will both withstand loads required to deform different plates, and maintain a high cycle lifetime for testing large numbers of plates. Additionally, clinically relevant deformations are presented to illustrate how stiffness is affected after a deformation is applied, and to highlight improvements made by the machine over current testing standards, which do not adequately re-create in vivo loading conditions. The machine performed as expected and allowed for analysis of bone plates in both deformed and un-deformed configurations to be conducted. Data for deformation experiments is presented to show that the rolling-contact testing machine leads to improved loading configurations, and thus a more accurate description of plate performance. A machine for evaluation of maxillofacial bone plates has been designed, manufactured, and used to accurately simulate in vivo loading conditions to more effectively evaluate the performance of both new and existing bone plates.

Analysis of Elliptical Rolling Contact Joints in Compression

AbstractThis paper presents elliptical rolling contact joints in compression as an alternative to circular rolling contact and conventional revolute joints where high quality force transmission—low friction and backlash—with variable output are desired. Parameters specific to the joint and its position are defined in terms of relative link angles and elliptical surface geometry. These relationships allow elliptical rolling contact joints to be incorporated in vector loop summations used in kinematic analysis. Notably, elliptical rolling contact is developed as the more general case of which circular rolling contact is a subset. Elliptical rolling contact joints are shown to offer several benefits over circular rolling contact, including reduced Hertz contact stresses, variable output velocity, maximum use of contact interface by distributing small rotations across surfaces of small curvature, reduced forces on constraining members, and no-slip pure rolling provided by either connecting links or flexures, without the need for gear teeth or friction.

Kinematics of Robot Fingers with Circular Rolling Contact Joints

AbstractThis paper examines the kinematics of robot fingers that use RR subassemblies coupled by rolling contact to provide versatile one degree‐of‐freedom mechanical joints. A three degree‐of‐freedom robot finger constructed with these joints is a 6R planar chain with the R‐joints coupled together in pairs. The focus is on coupling based on pure rolling of circular cylinders which can be realized by friction contact, gearing, or cable tendons. We derive the forward, inverse and rate kinematics for this 3(RR) open chain. We then focus on the two degree‐of‐freedom 2(RR) case to illustrate the geometry of the system. An example design of a robot finger that incorporates these joints in order to provide compact movement is provided. © 2003 Wiley Periodicals, Inc.

Quasi-linear position relationships in rolling joints.

The relationship between the angle of joint position and a linear actuation position, together with appropriate torque relationships, is developed for rolling contact joints with offset insertion by first considering more simple situations. The position relationship can be made quasi-linear by a suitable choice of dimensions, a factor which may be of consequence in design studies of orthotic and prosthetic upper extremity devices and in the field of manipulators.