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2022 ◽  
Author(s):  
Linh Nguyen

<pre>The paper proposes a new approach to efficiently control a three-dimensional overhead crane with six degrees of freedom (DoF). In addition to five usual output variables including three positions of the trolley, bridge and pulley and two swing angles of the hoisting cable, it is proposed to consider elasticity of the hoisting cable, which causes oscillation in the cable direction. That is, there exists $6^{th}$ under-actuated output in the crane system. To design an efficient controller for the six-DoF crane, it first employs the hierarchical sliding mode control approach, which not only guarantees stability but also minimizes sway and oscillation of the overhead crane when it transports a payload to desired location. Moreover, the unknown and uncertain parameters of the system caused by its actuator nonlinearity and external disturbances are adaptively estimated and inferred by utilizing the fuzzy inference rule mechanism, which results in efficient operations of the crane in real time. More importantly, stabilization of the crane controlled by the proposed algorithm is theoretically proved by the use of the Lyapunov function. The proposed control approach was implemented in the synthetic environment for the extensive evaluation, where the obtained results demonstrate its effectiveness.</pre>


2022 ◽  
Author(s):  
Linh Nguyen

<pre>The paper proposes a new approach to efficiently control a three-dimensional overhead crane with six degrees of freedom (DoF). In addition to five usual output variables including three positions of the trolley, bridge and pulley and two swing angles of the hoisting cable, it is proposed to consider elasticity of the hoisting cable, which causes oscillation in the cable direction. That is, there exists $6^{th}$ under-actuated output in the crane system. To design an efficient controller for the six-DoF crane, it first employs the hierarchical sliding mode control approach, which not only guarantees stability but also minimizes sway and oscillation of the overhead crane when it transports a payload to desired location. Moreover, the unknown and uncertain parameters of the system caused by its actuator nonlinearity and external disturbances are adaptively estimated and inferred by utilizing the fuzzy inference rule mechanism, which results in efficient operations of the crane in real time. More importantly, stabilization of the crane controlled by the proposed algorithm is theoretically proved by the use of the Lyapunov function. The proposed control approach was implemented in the synthetic environment for the extensive evaluation, where the obtained results demonstrate its effectiveness.</pre>


Robotics ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 7
Author(s):  
Yannick Roberts ◽  
Amirhossein Jabalameli ◽  
Aman Behal

Motivated by grasp planning applications within cluttered environments, this paper presents a novel approach to performing real-time surface segmentations of never-before-seen objects scattered across a given scene. This approach utilizes an input 2D depth map, where a first principles-based algorithm is utilized to exploit the fact that continuous surfaces are bounded by contours of high gradient. From these regions, the associated object surfaces can be isolated and further adapted for grasp planning. This paper also provides details for extracting the six-DOF pose for an isolated surface and presents the case of leveraging such a pose to execute planar grasping to achieve both force and torque closure. As a consequence of the highly parallel software implementation, the algorithm is shown to outperform prior approaches across all notable metrics and is also shown to be invariant to object rotation, scale, orientation relative to other objects, clutter, and varying degree of noise. This allows for a robust set of operations that could be applied to many areas of robotics research. The algorithm is faster than real time in the sense that it is nearly two times faster than the sensor rate of 30 fps.


Author(s):  
Changyu Xu ◽  
Zilin Yang ◽  
Shaun Wee Kiat Tan ◽  
Jianhuang Li ◽  
Guo Zhan Lum

Magnetic miniature robots (MMRs) are mobile actuators that can exploit their size to non-invasively access highly confined, enclosed spaces. By leveraging on such unique abilities, MMRs have great prospects to transform robotics, biomedicine and materials science. As having high dexterity is critical for MMRs to enable their targeted applications, existing MMRs have developed numerous soft-bodied gaits to locomote in various environments. However, there exist two critical limitations that have severely restricted their dexterity: (i) MMRs capable of multimodal soft-bodied locomotion have only demonstrated five-degrees-of-freedom (five-DOF) motions because the sixth-DOF rotation about their net magnetic moment axis is uncontrollable; (ii) six-DOF MMRs have only realized one mode of soft-bodied, swimming locomotion. Here we propose a six-DOF MMR that can execute seven modes of soft-bodied locomotion and perform 3-dimensional pick-and-place operations. By optimizing its harmonic magnetization profile, our MMR can produce 1.41-63.9 folds larger sixth-DOF torque than existing MMRs with similar profiles, without compromising their traditional five-DOF actuation capabilities. The proposed MMR demonstrated unprecedented dexterity; it could jump through narrow slots to reach higher grounds; use precise orientation control to roll, two-anchor crawl and swim across tight openings with strict shape constraints; perform undulating crawling across three different planes in convoluted channels. Keywords: Magnetic materials; soft actuators; miniature robots; locomotion. Corresponding author(s) Email:   [email protected]  


Author(s):  
Changyu Xu ◽  
Zilin Yang ◽  
Shaun Wee Kiat Tan ◽  
Jianhuang Li ◽  
Guo Zhan Lum

This Supplementary Information includes: Section S1- Fabrication method Section S2- Actuation method Section S3- Analysis of sixth-DOF torque Section S4- Experiments Figures S1-S31 Supporting Table References Other supplementary materials for this manuscript include the following: Supporting SI Videos S1-S10 Corresponding author(s) Email:   [email protected]  


2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Ningbo Jing ◽  
Ming Bu ◽  
Qi Ni ◽  
Hongguang Pan ◽  
Xuebin Qin ◽  
...  

The six-degree-of-freedom flexible joint manipulator is a complex system that suffers from the problem that the trajectory planning results are inconsistent with the control results. To keep the planned trajectory within the control range of the manipulator, a hierarchical structure control strategy is designed, which consists of a trajectory planning layer, a model predictive control layer, and a bottom control layer. Specifically, first, the target joint angles are obtained by a time-optimal trajectory planning algorithm based on a genetic algorithm in the trajectory planning layer. Second, in the model predictive control layer, considering the system physical constraints, the model predictive controller is adopted to provide the set points for the Proportion-Differentiation (PD) controllers. Finally, in the bottom control layer, the manipulator moves along the target trajectory under the PD controllers with the feedback control law. The simulation results show that, compared with the PD control strategy, the hierarchical structure control strategy can achieve better control performance and reduce the tracking error of the terminal trajectory by 33.70%.


2021 ◽  
Vol 12 (1) ◽  
pp. 182
Author(s):  
Maeruan Kebbach ◽  
Iman Soodmand ◽  
Sven Krueger ◽  
Thomas M. Grupp ◽  
Christoph Woernle ◽  
...  

The purpose of this computational study was to analyze the effects of different mobile-bearing (MB) total knee replacement (TKR) designs on knee joint biomechanics. A validated musculoskeletal model of the lower right extremity implanted with a cruciate-retaining fixed-bearing TKR undergoing a squat motion was adapted for three different MB TKR design variants: (I) a commercially available TKR design allowing for tibial insert rotation about the tibial tray with end stops to limit the range of rotation, (II) the same design without end stops, and (III) a multidirectional design with an additional translational degree-of-freedom (DoF) and end stops. When modeling the MB interface, two modeling strategies of different joint topologies were deployed: (1) a six DoF joint as a baseline and (2) a combined revolute-prismatic joint (two DoF joint) with end stops in both DoF. Altered knee joint kinematics for the three MB design variants were observed. The commercially available TKR design variant I yielded a deviation in internal-external rotation of the tibial insert relative to the tray up to 5° during knee flexion. Compared to the multidirectional design variant III, the other two variants revealed less femoral anterior-posterior translation by as much as 5 mm. Concerning the modeling strategies, the two DoF joint showed less computation time by 68%, 80%, and 82% for design variants I, II, and III, respectively. However, only slight differences in the knee joint kinematics of the two modeling strategies were recorded. In conclusion, knee joint biomechanics during a squat motion differed for each of the simulated MB design variants. Specific implant design elements, such as the presence of end stops, can impact the postoperative range of knee motion with regard to modeling strategy, and the two DoF joint option tested accurately replicated the results for the simulated designs with a considerably lower computation time than the six DoF joint. The proposed musculoskeletal multibody simulation framework is capable of virtually characterizing the knee joint dynamics for different TKR designs.


2021 ◽  
Vol 9 (12) ◽  
pp. 1451
Author(s):  
Kunyu Han ◽  
Xide Cheng ◽  
Zuyuan Liu ◽  
Chenran Huang ◽  
Haichao Chang ◽  
...  

Maneuverability, which is closely related to operational performance and safety, is one of the important hydrodynamic properties of an underwater vehicle (UV), and its accurate prediction is essential for preliminary design. The purpose of this study is to analyze the turning ability of a UV while rising or submerging; the computational fluid dynamics (CFD) method was used to numerically predict the six-DOF self-propelled maneuvers of submarine model BB2, including steady turning maneuvers and space spiral maneuvers. In this study, the overset mesh method was used to deal with multi-body motion, the body force method was used to describe the thrust distribution of the propeller at the model scale, and the numerical prediction also included the dynamic deflection of the control planes, where the command was issued by the autopilot. Then, this study used the published model test results of the tank to verify the effectiveness of the CFD prediction of steady turning maneuvers, and the prediction of space spiral maneuvers was carried out on this basis. The numerical results show that the turning motion has a great influence on the depth and pitch attitude of the submarine, and a “stern heavier” phenomenon occurs to a submarine after steering. The underwater turning of a submarine can not only reduce the speed to brake but also limit the dangerous depth. The conclusion is of certain reference significance for submarine emergency maneuvers.


Robotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 119
Author(s):  
Stephen David Monk ◽  
Craig West ◽  
Manuel Bandala ◽  
Nile Dixon ◽  
Allahyar Montazeri ◽  
...  

A novel, semi-autonomous radiological scanning system for inspecting irregularly shaped and radiologically uncharacterised objects in various orientations is presented. The system utilises relatively low cost, commercial-off-the-shelf (COTS) electronic components, and is intended for use within relatively low to medium radioactive dose environments. To illustrate the generic concepts, the combination of a low-cost COTS vision system, a six DoF manipulator and a gamma radiation spectrometer are investigated. Three modes of vision have been developed, allowing a remote operator to choose the most appropriate algorithm for the task. The robot arm subsequently scans autonomously across the selected object, determines the scan positions and enables the generation of radiological spectra using the gamma spectrometer. These data inform the operator of any likely radioisotopes present, where in the object they are located and thus whether the object should be treated as LLW, ILW or HLW.


2021 ◽  
Vol 2074 (1) ◽  
pp. 012066
Author(s):  
Ti Liu ◽  
Hongwei Mao ◽  
Dong Lei ◽  
Boming Li ◽  
Dahong Fu

Abstract Aiming at the connection of pipelines during the GIS installation process of power transmission and transformation projects, this subject designs and produces an intelligent GIS installation system based on 6-DOF parallel multi-axis motion control, which is applied to practical applications. The intelligent installation system can realize six independent motions and their combined motions in three-dimensional space. Relying on the multi-dimensional visual positioning system, through the six-degree-of-freedom parallel multi-axis motion control system, the precise docking during the installation of the precision GIS cavity can be realized.


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