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Motion platforms are used to study human behavior and brain function during passive motions. The software for controlling motion platforms is typically developed by the respective laboratories. Such customized, closed source solutions make replications of studies or multi-center collaborations difficult. Therefore, we developed PlatformCommander, an open-source software package for interfacing two often used motion platform models (6DOF2000E., MB-E-6DOF). The software includes a server implementing the interaction with the motion platform and additional devices, and a client application, connecting to the server and controlling experiments. PlatformCommander is ideal for the synchronization of data from different sources with high temporal precision.

Six degree of freedom manipulation provides full control over position and orientation, essential for many applications. However, six degree of freedom parallel kinematic manipulators (e.g. hexapods) either have a limited range of motion combined with a good repeatability when comprising flexure joints, or they have limited repeatability with a large workspace when using traditional rolling- or sliding-element bearings. In this paper, the design and optimization of a fully flexure-based large range of motion precision hexapod robot is presented. The flexure joints have been specifically developed for the purpose of large range of motion and high support stiffness for this manipulator. The obtained system allows for ±100 mm of translational and more than ±10° of rotational range of motion in each direction combined with a footprint of 0.6 m2 and a height of 0.4 m. Furthermore, a dedicated flexure-based design for the actuated joints combines high actuation forces with the absence of play and friction, allowing for accelerations exceeding 10 g. Experiments on a prototype validate the sub-micron repeatability, which is merely limited by the selected electronics. • A two-step optimization strategy for efficient optimization of complex flexure-based systems. • A new design for a large range of motion flexure-based precision hexapod which allows for high load capacity, high accelerations and high travel speed. • The realization of a prototype including experimental validation that provides validation of the repeatability and dynamic behavior. [ABSTRACT FROM AUTHOR]

Six-legged hexapod walking robots are well-known for their intrinsic stability during navigation and 6-DoF object manipulation. The robot must be operated under a stable workspace envelope to attain effective manipulation. The structural parameters of the robot dramatically influence the characteristics of the workspace. Most studies analyze the workspace only by varying the leg parameter of the robot, maintaining the base configuration constant. This study aims to investigate the effect of change in the base plate characteristics on the workspace for an axially symmetric hexapod robot with cyclic and elliptical configurations. Superimposing the lateral 2D workspace of each pair of legs evolved to obtain a 3D workspace. The quantitative data analysis of the workspace shows that the cyclic configuration has an average increase of 23.74 %, and the elliptical configuration has a reduction of 1.97 % reachable workspace volume compared with regular hexapods. Furthermore, regular, cyclic, and elliptical hexapods are fabricated and validated with the selective workspace analysis data to reinforce the results. This study shows that the change in the hexagonal base plate configuration has a significant influence on workspace characteristics. [ABSTRACT FROM AUTHOR]

• Integration of an ALIO hexapod (ALIO Industries, Colorado, USA) to a video oculography (VOG) system. • The system enables measuring vestibulo-ocular reflex of small animal under 6-degree of freedom motion real time. • The motion accuracy of the present system is 10 folds higher than the previous single axis VOG built on a servo motor. • Different approaches for eyeball tracking are compared for the implementation. We present a video oculography (VOG) system with 6-degree-of-freedom (6-DOF) mobility for real-time measurements of the binocular 3D eye position of a small animal. A hybrid hexapod that allowed for multi-axis complex motions with the resolution of the microscopic level was used to control the motion of the animal. The instantaneous eyeball movement of the animal was determined based on two approaches: (1) tracking of marker arrays affixed to the cornea; and (2) tracking the pupil outline. The tracking of the eyeball movement and the motion control of the hexapod were implemented with the LabVIEW virtual instruments. Compared with our previous measurements using a servo-motor-based single-axis VOG system, positional error reduced from more than 4% to less than 0.7%. Validation showed that the tracking errors in three rotational axes are less than 2% for the magnitude and less than 5° for the direction angle. The present VOG system is an effective tool for cross-axis 3D vestibulo-ocular reflex study on small animals. [ABSTRACT FROM AUTHOR]

The technological developments in the field of image based sensing have led to a vast growth in the use of drones in various domains. The drone is usually equipped with an image sensor (camera) which collect images over the target area. These images are then post-processed to extract the important information. Efficiency and accuracy of the image based sensing are largely dependent on the captured image quality. Therefore, it is important to prevent the transmission of the drone vibrations to the camera. Most of the current camera mounting systems use passive rubber mounts for isolation. However, these mounts are effective only in vertical direction and essentially adds damping to the system which degrades the performance of the isolation at high frequency. In this paper, a multi-degree of freedom isolation system, based on a Stewart platform configuration, is proposed for drone camera stabilization. The important features of the proposed isolation system are - (i) high frequency roll-off, (ii) no use of flexible joints, (iii) uses non-contact voice coil actuator thus avoiding spurious resonances of the legs, (iv) adjustable stiffness, (v) 3D printed lightweight parts and (vi) centralized control using a single sensor (inertial measurement unit). A prototype of the proposed system has been manufactured and validated experimentally. The proposed isolation system is found to reduce the response of the isolation system near resonance without compromising performance at high frequency. The application of the isolation system can be easily extended to other fields which require high quality image acquisition.

The development of a complex mechanical device with microcontroller control using of model-based design and Mathworks software products is described. The object was a robotic arm based on a parallel structure mechanism with six degrees of freedom. To create a microcontroller control system for this manipulator, a solution to the inverse kinematics problem was proposed. The operability of the model was proved using a moving computer model of geometric primitives in MATLAB. Analysis of the physical properties of developing object was carried out on the basis of its three-dimensional model, implemented by Simscape Multibody package and composed of solid-state models. The operability of the control system hardware was proved by Embedded Systems Toolbox, which also allowed to generate an executive code for selected Arduino Mega 2560 microcontroller board. The manipulator is a complete electromechanical device with cyclic microcontroller control, which allows to move the moving platform according to the predefined trajectories.

ABSTRAK Penelitian dengan topik robot hexapod telah banyak dikembangkan, namun sampai saat ini masih sedikit yang mengulas tentang kontrol keseimbangannya. Permasalahan yang kerap muncul adalah ketika robot berada dalam bidang miring, robot dapat terjatuh jika robot tidak dapat menyeimbangkan badan. Begitu pula dengan robot hexapod EILERO yang telah kami bangun. Untuk mengatasi permasalahan itu, selain pemodelan kinematik dan kinematika terbalik yang tepat, juga diperlukan suatu sistem keseimbangan yang baik. Dalam penelitian ini, kami menggunakan fuzzy logic untuk mengontrol keseimbangan robot EILERO dengan umpan balik data kemiringan dari sebuah sensor IMU. Setelah melalui beberapa pengujian yang komprehensif, didapatkan hasil bahwa robot dapat menyeimbangkan diri pada kondisi kemiringan papan pijakan antara -15° dan 15° pada orientasi kemiringan roll dan pitch. Robot mampu merespon dengan capaian steady state di bawah 3000 ms. Dengan demikian, robot EILERO semakin stabil dalam melintasi bidang yang tidak datar. Kata kunci: hexapod, EILERO, kinematika terbalik, fuzzy logic ABSTRACT Research on the topic of the hexapod robot has been developed a lot, but until now there is little that has been discussed about balance control. The problem that often arises is that when the robot is on an inclined plane, the robot can fall if the robot cannot balance its body. Likewise with the EILERO hexapod robot that we have built. To solve this problem, besides proper kinematic modeling and inverse kinematic modeling, a good balance system is also needed. In this study, we used fuzzy logic to control the balance of the EILERO robot, with tilt data feedback from an IMU sensor. After going through several comprehensive tests, the results show that the robot can balance itself on the slope of the stepboards between -15 ° and 15 ° in the orientation of roll and pitch tilt. The robot is able to respond with steady state achievements below 3000 ms. Thus, the EILERO robot is increasingly stable in traversing uneven planes. Keywords: hexapod, EILERO, inverse kinematic, fuzzy logic

In this paper, we present a solution of the inverse kinematic problem for a one-degree-of-freedom hexapod with a circular guide. The problem was solved applying analytical and numerical calculation methods using MATLAB package. The given algorithm for solving the inverse problem also allows studying the six-degree-of-freedom hexapod. The paper presents assembling computational models (virtual prototypes) of one- and six-degree-of-freedom hexapods with a circular guide. [ABSTRACT FROM AUTHOR]

Laser‐based surface modification methods have attracted considerable interest in the last 20 years due to their flexibility, efficiency, and multiple technical application that are possible. A particular challenge for these methods is the treatment of curved 3D surfaces. The presented study reports on the process optimization in laser texturing of 3D surfaces using Direct Laser Interference Patterning (DLIP). Periodic line‐like structures are fabricated using a picosecond‐pulsed laser on spherical stainless‐steel parts. The aim is to identify the possibility of processing curved geometries using an innovative hexapod positioning system. For this purpose, the effect of two different structuring strategies is investigated and compared by evaluating the obtained structure depths and the structure period of the fabricated structures as function of the position over the samples. All treated surfaces are examined using a confocal microscope. The results demonstrate an improvement in the structure homogeneity in terms of structure depth and period when using the fitted hexapod positioning approach. [ABSTRACT FROM AUTHOR]

In view of the demand for real-time acquisition of information and the superior performance of the robot in environmental detection，the system composition of the designed hexapod spider crawling robot and the analysis and calculation of the obstacle performance are introduced. The robot is composed of six mechanical legs and robot bodies，based on the Stm32f407 chip as the main controller，and uses the PID algorithm to control the whole robot to keep the balance，and completes the real-time response to the operation instruction through the image acquisition system. Based on the center of gravity transcendence，through theoretical study，centroid analysis and numerical calculation，the ability of the robot obstacle surmounting is analyzed，and the maximum height of the climbing staircase and the maximum width of crossing the transverse groove are obtained. This study provides a further basis for the design of a crawling robot.

Introduction: The use of hexapod circular external fixators in the treatment of various orthopedic conditions has become more common in recent years. One of the principle mounting requirements is that the fixator is orthogonally aligned to the mechanical axis of the limb. This creates the optimal mechanical environment for bone formation as any forces exerted on the fixator are transmitted as axial forces to the limb while eliminating unwanted motions such as rotation and shear. We describe a method to reliably obtain orthogonal mounting of periarticular rings during hexapod circular external fixator application. The technique is fast, accurate, and uses components readily available on all hexapod external fixator systems. Methods: The “hexapod orthogonal periarticular slack-wire stabilization (HOPSS) technique” uses a untensioned/slack wire as the second fixation element following the transverse reference wire. A wire fixation bolt is attached to the ring, and a second wire (slack wire) is placed through the wire fixation bolt to allow insertion in an antero–posterior direction. The wire is advanced through the near cortex and onto the far cortex after which the wire fixation bolt can be tightened and a final image intensifier check can be done. The technique can be used for the application rings to the metaphysis of long bones. Discussion: Orthogonal mounting for Ilizarov all-wire frames has been a crucial part of the surgical technique and has long been accepted as it promotes axial micromotion that supports callus formation and union and eliminated parasitic motion at the bone ends. The described technique uses readily available instruments and components to assist with perfect orthogonal mounting. Conclusions: The hexapod orthogonal periarticular slack-wire technique is a simple method for obtaining more accurate orthogonal mounting. It is quick and effective and does not require any additional equipment.

Aim: The correction accuracy of the Taylor Spatial Frame (TSF) fixator depends considerably on the precise determination of the mounting parameters (MP). Incorrect parameters result in secondary deformities that require subsequent corrections. Different techniques have been described to improve the precision of MP measurement, although exact calculation is reportedly impossible radiologically. The aim of this study was to investigate the accuracy of intraoperative and postoperative radiographic measurement methods compared to direct MP measurement from TSF bone mounting.Methods: A tibial Sawbone® model was established with different origins and reference ring positions. First, reference MPs for each origin were measured directly on the frame and bone using a calibrated, digital vernier calliper. In total 150 MPs measured with three different radiographic measurement techniques were compared to the reference MPs: digital radiographic measurements were performed using soft-copy PACS images without (method A) and with (method B) calibration and calibrated image intensifier images (method C).Results: MPs measured from a non-calibrated X-ray image (method A) showed the highest variance compared to the reference MPs. A greater distance between the origin and the reference ring corresponded to less accurate MP measurements with method A. However, the MPs measured from calibrated X-ray images (method B) and calibrated image intensifier images (method C) were intercomparable (p = 0.226) and showed only minor differences compared to the reference values but significant differences to method A (p < 0,001).Conclusion: The results demonstrate that MPs can be accurately measured with radiographic techniques when using calibration markers and a software calibration tool, thus minimizing the source of error and improving the quality of correction. [ABSTRACT FROM AUTHOR]

Introduction: Long-leg radiographs are used to plan and supervise the correction of bone deformity in patients treated with the Taylor Spatial Frame (TSF). Often radiographs are performed with malpositioning of the limb leading to wrong alignment measurements. The aim of this retrospective study was to show the usefulness of a simple device which might enhance the reproducibility of limb rotation on long-leg radiographs. Materials and methods: We included 20 consecutive patients with TSF treatment and at least three long-leg radiographs (4.9 ± 1.3). Eight out of 20 patients received radiographs with the help of a rotation rod (device with two clamps and a carbon tube). It is placed at the most frontal tab of the reference ring while conducting the radiograph. By this means, limb rotation can be controlled. To show the usefulness of this device, two observers measured the relation of the distances between the middle of the reference ring to the medial and lateral fourth hole on the reference ring (TSF-RR). The standard deviation and range of the TSF-RR of all radiographs for each patient was calculated and compared between patients without and with the rotation rod. Results: The standard deviations of TSF-RR in patients without the rotation rod was significantly higher compared to patients with rotation rod (observer 1: p = 0.0228, observer 2: p = 0.0038). Also, the range of the TSF-RR within one patient is significant higher (observer 1: p = 0.0279, observer 2: p = 0.0038) in patients without the rotation rod compared to patients with the rotation rod. Conclusions: The variability of rotation on radiographs was lower with the rotation rod. Therefore, more reproducible and better comparable radiographs can be conducted. Radiologic exposure might be reduced as repetition of wrongly positioned limbs on radiographs are less frequent. [ABSTRACT FROM AUTHOR]

The technology of computer-assisted six-axis frames is rapidly evolving. In this case report, we describe two cases of pediatric lower limb deformities treated by a novel hexapod device, the iFIXation system. For our knowledge, this is the first report in literature for its usage. The first case was a 14-years-old girl with posttraumatic shortening, varus and external rotation deformities of her lower limb around the ankle. All the deformities and shortening were corrected simultaneously with the iFIXation system. The second case was an 8-years-old girl with postinfection valgus and external rotation of the knee as well as shortening of the femur. Distal femoral deformities and shortening were simultaneously corrected by the iFIXation system and growth modulation to prevent recurrence of the deformity was done. The reported cases represent our earliest experience with the iFIXation system. [ABSTRACT FROM AUTHOR]

Background: The accuracy of hexapod circular external fixator deformity correction is contingent on the precision of radiographic analysis during the planning stage. The aim of this study was to compare the SMART Taylor spatial frame (TSF) in suite radiographic analysis methods with the traditional manual deformity analysis methods in terms of accuracy of correction. Methods: Sawbones models were used to simulate two commonly encountered clinical scenarios. Traditional manual radiographic analysis and digital SMART TSF analysis methods were used to correct the simulated deformities. Results: The final outcomes of all six analysis methods across both simulated scenarios were satisfactory. Any differences in residual deformity between the analysis methods are unlikely to be clinically relevant. All three SMART TSF digital analyses were faster to complete than manual radiographic analyses. Conclusion: With experience and a good understanding of the software, manual radiographic analysis can be extremely accurate and remains the gold standard for deformity analysis. In suite SMART TSF radiographic analysis is fast and precise to within clinically relevant parameters. Surgeons can with confidence trust the SMART TSF software to provide analysis and corrections that are clinically acceptable. [ABSTRACT FROM AUTHOR]

This paper presents a hexapod-type reconfigurable parallel mechanism that operates from a single actuator. The mechanism design allows reproducing diverse output link trajectories without using additional actuators. The paper provides the kinematic analysis where the analytical relationships between the output link coordinates and actuated movement are determined. These relations are used next to develop an original and computationally effective algorithm for the reconfiguration procedure. The algorithm enables selecting mechanism parameters to realize a specific output link trajectory. Several examples demonstrate the implementation of the proposed techniques. CAD simulations on a mechanism virtual prototype verify the correctness of the suggested algorithm.

In this research, we designed a stepwise synthetic method for Au@Pt hexapods where six elongated Au pods are arranged in a pairwise perpendicular fashion, sharing a common point (the central origin in a Cartesian-coordinate-like hexapod shape), featured with tip-selectively decorated Pt square nanoplates. Au@Pt hexapods were successfully synthesized by applying three distinctive chemical reactions in a stepwise manner. The Pt adatoms formed discontinuous thin nanoplates that selectively covered six concave facets of a Au truncated octahedron and served as etching masks in the succeeding etching process, which prevented underlying Au atoms from being oxidized. The subsequent isotropic etching proceeded radially, starting from the bare Au surface, carving the central nanocrystal in a concave manner. By controlling the etching conditions, Au@Pt hexapods were successfully fabricated, wherein the core Au domain is connected to six protruding arms, which hold Pt nanoplates at the ends. Due to their morphology, Au@Pt hexapods feature distinctive optical properties in the near-infrared region, as a proof of concept, allowing for surface-enhanced Raman spectroscopy (SERS)-based monitoring of in situ CO electrooxidation. We further extended our synthetic library by tailoring the size of the Pt nanoplates and neck widths of Au branches, demonstrating the validity of selective blocking and etching-based colloidal synthesis.

Morphology is a defining trait of any walking entity, animal or robot, and is crucial in obtaining movement versatility, dexterity and durability. Collaborations between biologist and engineers create opportunities for implementing bio-inspired morphologies in walking robots. However, there is little guidance for such interdisciplinary collaborations and what tools to use. We propose a development framework for transferring animal morphologies to robots and substantiate it with a replication of the ability of the dung beetle species Scarabaeus galenus to use the same morphology for both locomotion and object manipulation. As such, we demonstrate the advantages of a bio-inspired dung beetle-like robot, ALPHA, and how its morphology outperforms a conventional hexapod by increasing the (1) step length by 50.0%, (2) forward and upward reach by 95.5%, and by lowering the (3) overall motor acceleration by 7.9%, and (4) step frequency by 21.1% at the same walking speed. Thereby, the bio-inspired robot has longer and fewer steps that lower fatigue-inducing impulses, a greater variety of step patterns, and can potentially better utilise its workspace to overcome obstacles. Hence, we demonstrate how the framework can be used to develop legged robots with bio-inspired morphologies that embody greater movement versatility, dexterity and durability. [ABSTRACT FROM AUTHOR]

The headway of manipulator robots makes the development of a hexapod quite fast. Unfortunately, a hexapod is unstable to moving in a regular movement with some values added to programming algorithms. Various techniques implemented yet to the algorithms, like entering the degree values of each servo. However, to simplify the implementation of the algorithms, need some equations. This paper offered a hexapod control system based on Arduino that using Denavit-Hartenberg parameters to produce the equations. Various experiments have performed. Based on the experiments the offered system able to simplify the programming algorithms.

Aims: Severe infantile Blount's disease can result in a challenging multiplanar deformity of the proximal tibia with intra-articular and metaphyseal components. We describe our results using the Taylor's spatial frame (TSF) for acute tibial hemiplateau elevation combined with gradual metaphyseal correction in patients with severe infantile Blount's disease with an associated physeal bony bar. Patients and Methods: Eight patients (ten knees) underwent tibial hemiplateau elevation and metaphyseal correction from 2012 to 2016. We undertook a retrospective case note and radiographic review of clinical and radiographic outcomes. The mean age at the time of surgery of was 11.7 years and the mean length of follow-up was 18.2 months. Results: Improvement in radiographic parameters was seen in all patients. The mean tibiofemoral angle improved from −28.3° to −5.9° postoperatively. The angle between femoral condyles and the tibial shaft improved from the mean of 56.3° to 90.3°. The joint depression angle was also seen to improve from the mean 47.4° to 9.8°. No significant complications were seen. Conclusion: This technique is effective in correcting the complex deformity encountered in severe infantile Blount's disease. Use of the TSF may provide certain advantages in comparison to previously described approaches.

This review article aims to address common research questions in hexapod robotics. How can we build intelligent autonomous hexapod robots that can exploit their biomechanics, morphology, and computational systems, to achieve autonomy, adaptability, and energy efficiency comparable to small living creatures, such as insects? Are insects good models for building such intelligent hexapod robots because they are the only animals with six legs? This review article is divided into three main sections to address these questions, as well as to assist roboticists in identifying relevant and future directions in the field of hexapod robotics over the next decade. After an introduction in section (1), the sections will respectively cover the following three key areas: (2) biomechanics focused on the design of smart legs; (3) locomotion control; and (4) high-level cognition control. These interconnected and interdependent areas are all crucial to improving the level of performance of hexapod robotics in terms of energy efficiency, terrain adaptability, autonomy, and operational range. We will also discuss how the next generation of bioroboticists will be able to transfer knowledge from biology to robotics and vice versa.

We present a scalable two-level architecture for Hexapod locomotion through complex terrain without the use of exteroceptive sensors. Our approach assumes that the target complex terrain can be modeled by N discrete terrain distributions which capture individual difficulties of the target terrain. Expert policies (physical locomotion controllers) modeled by Artificial Neural Networks are trained independently in these individual scenarios using Deep Reinforcement Learning. These policies are then autonomously multiplexed during inference using a Recurrent Neural Network terrain classifier conditioned on the state history, giving an adaptive gait appropriate for the current terrain. We perform several tests to assess policy robustness by changing various parameters, such as contact, friction and actuator properties. We also show experiments of goal-based positional control of such a system and a way of selecting several gait criteria during deployment, giving us a complete solution for blind Hexapod locomotion in a practical setting. The Hexapod platform and all our experiments are modeled in the MuJoCo [1] physics simulator. Demonstrations are available in the supplementary video. [ABSTRACT FROM AUTHOR]

The surgical treatment of Charcot foot is a widely debated topic, with issues ranging from when to operate to how to properly correct a deformity. Historically, correction of a severe deformity was attempted in 1 acute surgical procedure that frequently required open reduction and internal fixation through large incisions. This 1-time procedure would often result in complications including under- or overcorrection of the deformity, neurovascular injury, or incision dehiscence leading to possible soft-tissue infection or osteomyelitis. This retrospective case series aims to evaluate stage 1 of a planned 2-stage approach to Charcot deformity correction, consisting of gradual modification with the use of computer-assisted external fixation. The purpose of using gradual correction was to safely and accurately correct the Meary and calcaneal inclination angles, which were measured using preoperative and postoperative digital radiographs. The procedure was performed on 18 Charcot foot deformities in 18 patients. Each of the feet had a notably significant rocker bottom deformity and most contained an ulceration. Complete ulcer healing was noted in 100% (13/13) of feet with an ulcer, and a statistically significant corrected Meary's (p <.05) and calcaneal inclination angle (p <.05) to within a normal range was achieved in all deformity corrections with few postoperative problems and complications noted. Average patient follow-up was 39.6 months with a minimum of at least 12 months necessary for inclusion in the study. Therefore, gradual Charcot deformity correction through the use of computer-assisted hexapod external fixation, demonstrates safe, accurate, and reproducible characteristics that adequately prepares the lower extremity for stage 2, the implantation of rigid internal fixation. [ABSTRACT FROM AUTHOR]

The paper introduces the ways to improve the control accuracy of the parallel kinematic mechanisms of space application. The sources of errors in positioning and orientation of the mechanism developed are given. The ways are suggested for compensating the kinematic and temperature errors of linear drives and mechanism members. [ABSTRACT FROM AUTHOR]

We report the development of a 3D positioner for the elemental mapping of non-flat surfaces of heritage targets and its implementation in the external beam of the AGLAE accelerator, a joint research activity of the IPERION-CH European program. The positioner operates in two steps: 1) object surface is digitized using a 3D scanner implemented in the beamline. Surface points are interpolated onto a rectangular grid suitable for beam scanning. 2) Object is scanned under the beam using X/Y/Z stages holding a hexapod robot for rotations. During scanning, target surface is positioned with the Z stage and oriented perpendicular to the beam using hexapod rotations. Areas up to 100 × 100 mm2 with a resolution of 50 µm and 30° curvature of can be mapped on objects of 200 mm and 5 kg max. System operation was tested by recording PIXE maps on the polychrome decoration of a curved porcelain pot. [ABSTRACT FROM AUTHOR]

The use of hexapod circular external fixation in acute tibia fracture care is increasing as more general orthopaedic surgeons are gaining expertise with the use of this treatment modality. Limited data is currently available on the complications that may be encountered with this treatment strategy.Aim: To review the complications and outcomes of acute diaphyseal tibia fractures definitively treated with hexapod circular external fixation at a high volume orthopaedic trauma centre.Methods: Retrospective review of clinical and radiological data of adult patients with acute diaphyseal tibia fractures treated with hexapod external fixation between 2012 and 2015 at a single centre.Results: A total of 102 diaphyseal fractures were definitively treated with hexapod circular external fixation. Union was achieved in 101 cases with an average time to union of 25.6 weeks. Complications included pin site infection (56%); wound complications (19.67%); osteitis (11.76%); malunion (15.69%) and knee and ankle joint contractures (31.32%).Conclusion: Hexapod circular external fixation as definitive treatment of for diaphyseal tibia fractures demonstrates an excellent union rate with acceptable time to union. Complications rates are comparable to that of all fine wire circular fixators. Malalignment in is however a concern, considering that this device enables the surgeon to achieve accurate alignment through gradual deformity correction aided by computer software. [ABSTRACT FROM AUTHOR]

Product miniaturisation is one of the key aspects of modern manufacturing technology. One of the ways to fabricate miniaturised product is micromachining using sophisticated computer numerically controlled (CNC) machine tools. However, conventional CNC machines are bulky, stationary, and unable to carry out parallel operations. This research aims to develop a modular robotic platform which would be able to carry out machining operation in mesoscale. Hexapod robots are legged mobile robots which are used for verities of applications. Here, we have implemented a hexapod robotic platform to support and move the cutting tool (in this case, a drilling tool). The robot was controlled from the host computer through serial communication. A graphical user interface (GUI) was designed and implemented to operate the robot and the drilling spindle. Several machining operations were carried out with the system to assess its performance. An innovative compensation algorithm has been proposed to improve the positional accuracy of the robot movement. The proposed algorithm takes into account spindle speed and linear velocity to mitigate the positional error. The positional accuracy was improved by more than 60% after implementing the error compensation scheme. In this research we managed to achieve sub-10 μm repeatability (≤ 10 μm) at the lowest spindle and point to point linear speed of 2500 RPM and 200 mm/min, respectively. The performance (in terms of positional accuracy) of the robot was also compared with that of an existing commercial micromachining system where the robot was found to be almost ~ 2× time poorer to that of the commercial machine. Finally, the machined holes' quality was measured in terms of circularity and taperness. It was observed that at the best machining parameters circularity deviation was as low as 29.4 μm while taperness was 0.54 degree. [ABSTRACT FROM AUTHOR]

The Evolutionary Robotics (ER) process has been applied extensively to developing control programs to achieve locomotion in legged robots, as an automated alternative to the arduous task of manually creating control programs for such robots. The evolution of such controllers is typically performed in simulation by making use of a physics engine-based robotic simulator. Making use of such physics-based simulators does, however, have certain challenges associated with it, such as these simulators' computational inefficiency, potential issues with lack of accuracy and the human effort required to construct such simulators. The current study therefore proposed and investigated an alternative method of simulation for a hexapod (six-legged) robot in the ER process, and directly compared this newly-proposed simulation method to traditional physics-based simulation. This alternative robotic simulator was built based solely on experimental data acquired directly from observing the behaviour of the robot. This data was used to construct a simulator for the robot based on Artificial Neural Networks (ANNs). To compare this novel simulation method to traditional physics simulation, the ANN-based simulators were used to evolve simple open-loop locomotion controllers for the robot in simulation. The real-world performance of these controllers was compared to that of controllers evolved in a more traditional physics-based simulator. The obtained results indicated that the use of ANN-based simulators produced controllers which could successfully perform the required locomotion task on the real-world robot. In addition, the controllers evolved using the ANN-based simulators allowed the real-world robot to move further than those evolved in the physics-based simulator and the ANN-based simulators were vastly more computationally efficient than the physics-based simulator. This study thus decisively indicated that ANN-based simulators offer a superior alternative to widely-used physics simulators in ER for the locomotion task considered. [ABSTRACT FROM AUTHOR]

• Spatial process forces are measured by six 1 DoF structure-integrated force sensors. • Forces are transformed by a control-integrated real-time dynamic measurement model. • The paper presents modeling, optimal system design, and experimental validation. • Similar characteristics to commercial 6 DoF F/T sensors can be reached. • Advantageous are costs, mounting capability, roughness, and available workspace. In machine tools, in-process force measurement is required by many manufacturing applications, where a particular demand for spatial measurements in up to 6 degrees of freedom (DoF) is growing. Beside expensive commercial 6 DoF force/torque sensors or vague drive current evaluation, sensor integration as part of machine components or joints has been discussed for a long time. The approach presented here, integrates 6 cost-efficient commercial 1 DoF force sensors in hexapod structures and kinematics, that are particularly suitable for sensor integration due to the absence of friction, the presence of mainly longitudinal forces and the availability of 6 DoF. These sensors can be placed at different positions, whereby this article focuses on a rigid hexapod-based end-effector. As the end-effector is not an independent measuring system, but part of a machine, that moves dynamically through the workspace and carries workpieces or tools, a suitable measurement model is necessary that addresses all those influences. After a brief literature overview and introduction to the approach, this work presents the dynamic measurement model including sensor and quasi-static error parameters, aspects about optimal framework design and several steps of validation and evaluation of the new measuring system. These include application of static loads, workspace analysis, dynamic transfer behaviour, rigid body dynamics compensation and, finally, process force measurement during a milling process. [ABSTRACT FROM AUTHOR]

• To our knowledge this is the first study to compare ORIF and HRF in AO/OTA 43.C3 pilon fractures. • The nonunion rate was 33% (10/30) in the ORIF group and 17,4% (4/23) in the HRF group. No significant difference was observed between nonunion rates. • ORIF had a significant higher rate of major complications, specifically deep infection compared to HRF. • HRF had a statistically significant rate of minor complication such as superficial infection of half-pins and k-wires. • There were no significant differences between both groups in terms of reoperations and incidence of ankle osteoarthritis at two-years follow up. Controversy exists regarding the optimal management of AO/OTA 43. C3 pilon fractures. Open reduction and internal fixation (ORIF) is the gold standard treatment, but serious soft tissue and infectious complications have been previously reported. Minimally invasive strategies using hexapod ring fixation (HRF) with supplemental limited internal fixation have been used to reduce the incidence of complications. Previous studies have included heterogeneous types of pilon fractures, with non-comminuted injuries being more likely to be treated with ORIF and complex fractures receiving HRF treatment. To our knowledge, no studies have compared the complications and reoperation rates between ORIF and HRF exclusively for C3 fractures. Retrospective study comparing 53 patients treated for AO/OTA 43.C3 pilon fracture with ORIF or HRF in a trauma level I center with at least a two-year follow-up. Patients treated between January 2015 and January 2019 received ORIF and those treated between January 2019 and January 2021 received HRF. Complications were divided into two groups: minor (superficial infection and malalignment) and major (non-union, deep infection, and amputation). Reoperations, prevalence of ankle osteoarthritis, and requirement for ankle arthrodesis/total ankle replacement were registered. We included 30 and 23 patients in the ORIF and HRF groups, respectively. The overall complication rate was similar in both groups, with 50% and 56,5% of the patients having complications in the ORIF and HRF groups, respectively (p:0,63). Minor complications were significantly more prevalent in the HRF group (p <0,001) whilst the ORIF group had a significantly higher rate of major complications (p <0,01). Superficial infections were highly prevalent in the HRF group (47,8%), as they were related to half-pin or K-wire infections. Deep infection was present only in the ORIF group, with 20% of the patients developing this major complication (p:0,03). Non-union rate, reoperations, ankle osteoarthritis, and the need for arthrodesis or ankle replacement showed no significant differences. In AO/OTA 43.C3 fractures, HRF is safe and effective, achieving high union rates with a significantly lower rate of major complications compared to ORIF. According to our results, ORIF should be used cautiously for these types of fractures, considering the increased risk of deep infection. [ABSTRACT FROM AUTHOR]

Structure-integrated force measurement in hexapod structures or kinematics offers great potential for spatial process force control in six degrees of freedom. Although force control has been studied for many years, research questions remain unanswered, especially when regarding parallel kinematic machine tools with numerical control and integrated sensors. This contribution summarizes the technology of structure-integrated force sensing in hexapod machine tools and develops two approaches to use the measured signals for direct hybrid/parallel force control. For different use-cases, such as teach-in or synchronous force/position control with variable task frame, different approaches of set-point specification and injection of manipulated values are studied from a practical point of view. As a result of the work, the feasibility of the force control with structure-integrated sensors on a commercial CNC can be confirmed through appropriate experiments. Furthermore, the realized G-Code integration represents a practical solution for programming force-controlled machine tools in an easy and concise way from the NC programme. [ABSTRACT FROM AUTHOR]

Well-defined PtNi nanocrystals represent one of the most efficient electrocatalysts to boost the oxygen reduction reaction (ORR), especially in the shape of octahedrons, nanoframes, and nanowires. However, the synthesis of complex PtNi nanostructure is still a great challenge. Herein, we report a new class of PtNi hexapods with high activity and stability toward ORR. The hexapods are prepared by selective capping and simultaneous corrosion. By controlling the oxidative etching, PtNi polyhedrons and nanoparticles are obtained, respectively. The intriguing hexapods are composed of six nanopods with an average length of 12.5 nm. Due to their sharp tips and three-dimensional (3D) accessible surfaces, the PtNi hexapods show a high mass activity of 0.85 A mgPt-1 at 0.9 V vs. RHE, which are 5.4-fold higher than commercial Pt/C, also outperforming PtNi polyhedrons and PtNi nanoparticles. In addition, the mass activity of PtNi hexapods maintains 92.3% even after 10,000 potential cycles.