Orientation Of Platform Research Articles

Direct and Inverse Kinematics of a 3RRR Symmetric Planar Robot: An Alternative of Active Joints

Existing direct and inverse kinematic models of planar parallel robots assume that the robot’s active joints are all at the bases. However, this approach becomes excessively complex when modeling a planar parallel robot in which the active joints are within one single kinematic chain. To address this problem, our article unveils an alternative for a 3RRR symmetric planar robot modeling technique for the derivation of the robot workspace and the analysis of its direct and inverse kinematics. The workspace was defined using a system of inequalities, and the direct and inverse kinematics models were generated using vectorial analysis and an optimized geometrical approach, respectively. The resulting models are systematically presented and validated. Two final model renditions are delivered supplying a thorough equation analysis and an applicability discussion based on the importance of the robot’s mobile platform orientation. The advantages of this model are discussed in comparison to the traditional modeling approach: whereas conventional techniques require the solution of complex eighth-degree polynomials for the analysis of the active joint configuration of these robots, these models provide an efficient back-of-the-envelope analysis approach that requires the solution of a simple second-degree polynomial.

Passive Visual Odometry of Mobile Transport Robots in Production Areas Using Anchor Points

The article considers the problem of determining the orientation of mobile transport robots, which are now actively used in almost all areas of industry. They make it possible to intensify production, free personnel from performing routine operations, and exclude the influence of the human factor from work. Based on the analysis of various variants of active orientation methods involving the use of binocular video systems installed on the vehicles themselves, it is proposed to use a passive orientation detection system. It includes a single stationary monocular video system, the replacement of onboard video systems on mobile robots with simple radiation sensors, as well as the use of anchor points in the area of their movement. The order of choice of anchor points in solving the problem of orientation of a mobile transport robot using a monocular video system, in particular for a rectangular interior space, is considered. Calculation formulas for determining the coordinates of the sensor from the pixel coordinates of its image obtained from a monocular video camera are determined. The general sequence of actions for determining the orientation of a mobile robotic platform is also considered. Unlike active systems, this method makes it possible to significantly simplify the hardware, significantly facilitate the analysis of the current position of the mobile robot and thereby reduce the computational complexity of calculations due to the fact that there is no need to use a complex mathematical apparatus. It is being replaced by simpler two-dimensional geometric calculations. This approach, due to the unified management, makes it possible to effectively coordinate the actions of a group of mobile transport robots when they are used together, greatly simplifies the solution of a number of tasks for optimizing the intra-shop movement of mobile vehicles.

A Neuromorphic Vision and Feedback Sensor Fusion Based on Spiking Neural Networks for Real‐Time Robot Adaption

For some years now, the locomotion mechanisms used by vertebrate animals have been a major inspiration for the improvement of robotic systems. These mechanisms range from adapting their movements to move through the environment to the ability to chase prey, all thanks to senses such as sight, hearing, and touch. Neuromorphic engineering is inspired by brain problem‐solving techniques with the goal of implementing models that take advantage of the characteristics of biological neural systems. While this is a well‐defined and explored area in this field, there is no previous work that fuses analog and neuromorphic sensors to control and modify robotic behavior in real time. Herein, a system is presented based on spiking neural networks implemented on the SpiNNaker hardware platform that receives information from both analog (force‐sensing resistor) and digital (neuromorphic retina) sensors and is able to adapt the speed and orientation of a hexapod robot depending on the stability of the terrain where it is located and the position of the target. These sensors are used to modify the behavior of different spiking central pattern generators, which in turn will adapt the speed and orientation of the robotic platform, all in real time. In particular, experiments show that the network is capable of correctly adapting to the stimuli received from the sensors, modifying the speed and heading of the robotic platform.

A robust control scheme for a 2PUS+RR parallel robot for ankle rehabilitation

AbstractThis paper presents a robust adaptive controller based on the backstepping technique using an extended state observer (ESO), implemented on a 2PUS+RR parallel robot, to minimize the trajectory tracking error. The proposed backstepping-ESO controller scheme is designed to compensate for the robot’s structured (parametric) and unstructured (nonlinear friction, external disturbances, and dynamics) uncertainties. The overall stability of the controller is guaranteed by the Lyapunov theory. Cosimulation in MATLAB-Simulink and ADAMS View is presented to validate the results of the ESO and backstepping controller implemented in the virtual and physical prototype. For the virtual prototype, it was determined that the system is stable in 2 s and presents a maximum absolute error of 3.5 × $10^{-6}$ m for the actuator position and 2.8 × $10^{-5}$ rad for mobile platform orientation. Regarding the physical robot, a maximum absolute error of 5 × $10^{-4}$ m for the actuator position and 0.0575 rad for the orientation of the robot mobile platform values do not represent a problem for ankle rehabilitation movements. Experimental results were also presented and compared with ankle motion to demonstrate that the applied control system meets the motion requirements of the ankle rehabilitator.

Dynamic Model of a Novel Planar Cable Driven Parallel Robot with a Single Cable Loop

Cable-Driven Parallel Robots (CDPRs) are a special kind of parallel manipulator that uses cables to control the position and orientation of the mobile platform or end effector. The use of cables instead of rigid links offers some advantages over their conventional rigid counterparts. As cables can only pull but not push, the number of cables (n) required to command the end-effector is always n+1. This configuration is known as fully-constrained, and it is the most extended configuration for CDPRs. Although CDPRs have many advantages, such as their ability to cover large working areas, one of their main problems is that their working area (workspace) is limited in comparison to its frame area (planar case) or frame volume (spatial case), due to the minimum and maximum allowed tensions. Depending on these tension values, the workspace can notoriously decrease. In order to tackle this problem, lots of works focus on solving kinematics or dynamics problems for cable sagging, i.e., they take into account sagging when modelling the robot kinematic and include these poses inside the usable robot workspace. Taking into account phenomena such as this increases the mathematical complexity of the problem, and much more complex techniques are required. On the other hand, the lack of workspace problem can be tackled by adding active or passive elements to the robot design. In this sense, this paper proposes two mechanical modifications: to add passive carriages to the robot frame and to use a single cable loop to command the end-effector position and orientation. This work presents the kinematic, static, and dynamic models of the novel design and shows the gain of workspace for a planar case while taking into account different parameters of the robot.

Early Maya E Groups, the Milky Way, and creation

AbstractI propose a “Milky Way / creation hypothesis” for the elongated eastern structures in early Maya E Groups: they were modeled on the Milky Way galaxy. These architectural arrangements, beginning in the Preclassic period (c. 900 B.C.–A.D. 200) in the southern Maya Lowlands, were adopted from predecessors in the Early Preclassic neighboring Gulf Coast region. The widespread overall similarity of E Groups suggests a shared belief system centered on myths about creation, and many of the characters (e.g., Maize God) and events of creation in Maya myths are set in the Milky Way. The general north–south axial orientation of the eastern platform, frequently pivoted northeast–southwest, is proposed to be related to the rainy season position of the Milky Way overhead. E Groups were probably multifunctional ritual theaters, the eastern platforms serving as stages for nighttime performances of creation stories. Late modifications into a tripart edifice, with structures or superstructures in the center and at both ends, replicated the major asterisms of the visible galaxy and/or the creator gods.

On Forward Kinematics of a 3SPR Parallel Manipulator

This letter presents a new numerical method to solve the forward kinematics (FK) of a parallel manipulator with a three-limb spherical-prismatic-revolute (3SPR) structure. Unlike the existing numerical approaches that require the manipulator’s Jacobian matrix and its inverse at each iteration, the proposed algorithm requires much less complex computations to estimate the FK parameters. A cost function is introduced that measures the difference between actual FK values and its estimates. At each iteration, the problem is handled in two steps. First, the estimates of the platform orientation from the heave estimates are obtained. Then, the heave estimates are updated along the gradient direction of the proposed cost function. To evaluate the performance of the proposed algorithm, we compare results with those of a Jacobian-based (JB) approach for a 3SPR parallel manipulator.

Orientation Determination in IMU Sensor with Complementary Filter

The use of unmanned aerial vehicles (UAV) systems has increased in recent years. Therefore,studies on UAVs have increased today. In this direction, the production of UAV systems with domestic resources has gained importance. In this study, it is desired to develop a domestic and national flight control card and software. In the flight control board designed for the UAV, it is aimed to keep the vehicle in balance in the air. Accurate measurement of platform orientation plays an important role in many applications such as aerospace, robotics, navigation, marine, machine interaction [1]. Inertial Measurement Unit (IMU) sensor was used to accurately measure the orientation of the UAV. IMU sensor is widely used in UAVs due to its light weight and low energy consumption. In this direction, the need for a filter has emerged in the IMU sensor, which is used to accurately measure the orientation of the unmanned aerial vehicle. In this study, a complementary filter was applied on the IMU sensor. Thanks to this filter, it has been observed that the accuracy of the data received from the IMU sensor has increased. Based on the data obtained, a Proportional Integral Derivative (PID) algorithm was developed, and the vehicle was kept in balance. In this study, ARMCortex-M4 based STM32F407VG microcontroller and MPU6050 as IMU sensor were used. Keil-uVision5 compiler is preferred for software. As a result, high accuracy in the orientation detection of unmanned aerial vehicles was obtained by applying a complementary filter on the IMU sensor.

Facilitator reflections on online delivery of simulation-based mental health education during COVID-19

PurposeDuring COVID-19, Maudsley Simulation successfully pivoted to fully online delivery of simulation-based education (SBE) in mental health. In migrating digitally, the simulation faculty experienced a range of new phenomena and challenges. The authors’ experiences may be transferable to other specialities and for other educator groups. By sharing the authors’ experiences, this study aims to support others adapt to online SBE.Design/methodology/approachThis piece represents the authors’ collective reflections on the challenges of adapting their facilitation skills to the online environment. It also offers various suggestions on how to improve the learner experience in view of these challenges.FindingsBeyond merely platform orientation and operating procedure familiarisation, the team gained insights into ensuring optimal learning, engagement and participant experience during online deliveries. Delivery of online SBE brings several potential barriers to psychological safety and these warrant careful consideration by experienced simulationists.Practical implicationsOptimising participant engagement and psychological safety remain key considerations despite this novel medium. Facilitators must be willing to adapt accordingly to begin delivering high-quality online SBE.Originality/valueFrom their experience, facilitators must reframe their debriefing expectations and adjust how they engage participants and manage group dynamics given the inherently different nature of this new learning environment.

“Transition to CAMHS SPR” – a Simulation Induction Course Provided for Newly Appointed Child and Adolescent Mental Health Service (CAMHS) Higher Trainees (HTs)

AimsThe transition between Core Psychiatry Training (CPT) and Psychiatry HTs is often anxiously anticipated by trainee psychiatrists, in view of the heightened responsibility and increased demand faced by trainees. The author wrote and delivered a one-day simulation induction course for newly appointed CAMHS HTs across London. The aim of this course was to improve participant's confidence, skills and knowledge in managing a range of conditions and challenging scenarios in children and young people (CYP) presenting to CAMHS. The course was also designed to improve HT's confidence in supporting junior colleagues and in managing conflict resolution. There was also an overarching aim of increasing human factor skills by focusing on these within the scenarios and debriefs.MethodsThe simulation training was delivered online and consisted of five scenarios commonly faced by CAMHS SPRs based in a variety of settings. Themes within the scenarios included eating disorders and deliberate self-harm, as well as managing risk, multiple demands, and the psychosocial factors contributing to mental illness. Professional actors, plants and virtual backgrounds were used to enhance fidelity of the scenarios. Platform orientation and an introduction to simulation were initially provided followed by “ice breaker” activities, which were used to promote psychological safety amongst participants. Each scenario lasted approximately 10 minutes. Following each scenario, participants were supported to engage in a debrief using the Maudsley Debrief model. Pre- and post-course evaluation questionnaires were given to participants to complete and comparative analysis was conducted.ResultsSeven participants completed both the pre- and post- course evaluation questionnaires. The mean sum score for course specific questions was 51.86 (SD = 9.56) pre course, and 68.00 (SD = 10.08) post course, showing a 31.12% increase in knowledge, skills, and confidence across the course specific domains.The mean sum score for the Human Factors Skills for Healthcare Instrument (HFSHI) was 76.67 (SD = 17.26) pre course, and 86.50 (SD = 16.54) post course, showing a 12.82% increase in human factors skills.ConclusionThis simulation course demonstrated it is an effective and innovative way to help with induction for HT, resulting in an increase in knowledge, skills and confidence in trainees transitioning from CPT to HT, both in terms of factors specific to managing CYP's care and in relation to broader human factor skills.

АНАЛИЗ ВЛИЯНИЯ СИНГУЛЯРНОСТЕЙ НА РЕШЕНИЕ ПРЯМОЙ ЗАДАЧИ КИНЕМАТИКИ И ГЕОМЕТРИЮ РАБОЧЕГО ПРОСТРАНСТВА ПЛАТФОРМЫ ГОФА-СТЮАРТА

One of the obligatory requirements for parallel mechanisms design is the exclusion from theworkspace of singularities in which the mechanism loses its controllability and malfunctions mayoccur. The analysis of the workspace of the mechanisms of a parallel structure is more complicatedthan that for the mechanisms of a serial structure, especially if the mechanism has more thanthree degrees of freedom. The article considers the problem of analyzing the influence of singularitieson the solution of the forward kinematics and the geometry of the workspace 3/6 of theGough-Stewart platform (commercial name - "Hexapod"). A numerical algorithm for solving theforward kinematics of platform has been developed. It is based on the direct use of the system ofequations of the platform's kinematic constraints. Approximation of the set of solutions to the systemof equations is based on deterministic methods of global optimization. An analysis of thechange in the number of forward kinematics near the zone of singularities is performed. The analysisconsists of two stages. The first stage consists in solving the forward kinematics for the positionand orientation of the platform, at which singularities arises. The second stage consists insolving the forward kinematics for the case of a singularity and the case near a singularity.As a result of solving the forward kinematics, a different number of forward kinematics solutionsfor different cases was revealed. An algorithm has been synthesized that makes it possible to determinea singularity-free workspace free for given ranges of change in the platform orientationangles specified by Euler angles. An analysis of the dependence of the change in the volume of theworkspace depending on the range of change in the angles of the platform orientation was carriedout. The algorithms are implemented programmatically in the C++ programming language.The modeling was performed using parallel computing and the implementation of the export ofthree-dimensional models of the positions of the platform and workspace to the universal format ofthree-dimensional models STL.

Local positioning system as a classic alternative to atomic navigation

A local positional system (LPS) is proposed, in which particles are launched at given velocities, and a sensor system measures the trajectory of the particles in the platform frame. These measurements allow us to restore the position and orientation of the platform in the frame of the rotating Earth, without solving navigation equations. When the platform velocity is known and if the platform orientation stays the same, the LPS technique allows a navigational accuracy of 100 $\mu$m per one hour to be achieved. In this case, the LPS technique is insensitive to the type of platform trajectory. If there are also velocimeters installed on the platform, then one can restore the platform velocity and angular rate of the platform rotation with respect to the Earth. Instead of navigational equations, it is necessary to obtain the classical trajectory of a particle in the field of a rotating gravity source. Taking into account the gravity-gradient, Coriolis, and centrifugal forces, the exact expression for this trajectory is derived, which can be widely used in atomic interferometry. A new iterative method for restoring the orientation of the platform without using gyroscopes is developed. The simulation allows us to determine the conditions under which the LPS navigation error per hour is approximately $10$ m.

Феномен мультимодального сервісного медіатексту комунікаційної платформи

<p><strong><em>The aim</em></strong><em> of the article is to investigate the issue of multimodal media text, which is now popular among authors and creators of content communication platforms.</em><em></em></p><p><strong><em>Research methodology</em></strong><em>. In the course of the research a descriptive method was used to outline modern current scientific approaches to the study of the issue, comparative method – to compare scientific views and derive the author’s definition.</em></p><p><strong><em>Results.</em></strong><em> The definition of modern researchers is given and the author’s own vision of the «multimodal media text» concept and its derivative – «multimodal service media text» is offered. Emphasis is placed on the need to identify and classify the term for the «Applied Social Communication Technologies» field, due to the spread of Internet communications and the growing popularity of communication platforms. The need to study multimodal service media text in view of its versatility, polythematic, diverse structure and other features inherent in the media texts of the network is noted. Attention is paid to different categories of mechanisms of perception of the visual component of the service media text. Multimodal service media text is presented as an applied unit of modern communication processes. Its informative and communicative properties are revealed. The ways of formation of communication modality of modern Internet platforms are outlined. The modern phenomenon of multimodality is described, which is formed taking into account two factors: communication processes and hypertext. The necessity of correct construction of the communication platforms’ content taking into account the multimedia nature of the text is substantiated. The mechanism of functioning of communication platforms capable of synthesizing different types of modal content (video, audio, photo, animation, textual) is studied.</em></p><p><strong><em>Scientific</em></strong><em> <strong>novelty.</strong> Communication multimodality is positioned in the article as a complex formation of symbols and code synthesis of different categories: linguistic and extralinguistic factors. All this gives grounds to study multimodal media text in social communications of the Internet sphere, where the text is now multimedia. It is offered to classify and structure the types of multimodal content according to the thematic orientation of the communication platform: culture, sports, politics, beauty industry, travel topics, etc.</em></p><p><strong><em>Practical meaning.</em></strong><em> The results of the study can be used in the educational process in the «Journalism» specialty.</em></p><p><strong><em>Key words:</em></strong><em> communication platform, multimodal media text, service media text, internet communications.</em></p><div><div><p> </p></div></div>

Application of evolutionary PSO algorithms to the problem of optimization of 6-6 UPU mobility platform geometric parameters

The article deals with the problem of optimization of parameters 6-6 UPU of the mobility platform using the Particle Swarm Optimization (PSO) algorithm. The optimization criterion is based on minimizing the dimensions of the structure, taking into account the required relationships between some parameters. The limitation of optimization is the condition of providing the required workspace, taking into account the platform orientation ranges. An algorithm for calculating the estimate of the occurrence of the required area in the workspace of the platform with given parameters is synthesized. Workspaces specified as an ordered set of integers. The results of mathematical modeling are presented.

Global analysis of floating offshore wind turbines with shared mooring system

Floating wind turbines (FWTs) with shared mooring systems can be one of the most cost- effective solutions in reducing mooring costs. First, the static configuration of a shared line is estimated using the elastic catenary equation. The present study investigates the global responses of two FWT with a shared mooring system. Two shared mooring configurations with different horizontal distances between the FWTs are considered. In the first configuration, the FWTs are placed 750m apart; and in the second configuration, they are placed 1000m apart. Two different environmental conditions (ECs) are used to simulate the global responses of the system in time domain. The shared mooring line results in higher extreme motions in surge and sway (degree of freedoms) DOFs due to the reduction of mooring restoring stiffness. The lower mooring restoring stiffness can be attributed to the reduction of one seabed anchoring point for each FWT as compared to a single FWT with three anchors installed. In the rotational DOFs, the shared mooring line configurations result in slight mean offset in each direction and significant increase in the motion standard deviations. This is caused by the reduced mooring stiffness associated with the change in platform orientation.

Compliance model of Exechon manipulators with an offset wrist

The stiffness of the Exechon hybrid manipulator is a crucial performance indicator as the manipulator is used as a 5-axis machine tool. Normally, the serial module of the Exechon is not included in the kinematic and stiffness analysis. In terms of kinematics, the parallel and serial modules are said to be decoupled, i.e. parallel module can be solved for position and the serial module can be used to compensate the parasitic orientation of the parallel platform. This is only possible when the serial module is a perfect spherical wrist. However, several models of Exechon technology have an offset wrist rather than a spherical one. Such an offset makes it impossible to obtain a kinematic decoupling.In all publications available in the literature, the Exechon is considered to have a perfect spherical wrist. Therefore, this paper presents the inverse kinematics and compliance model of Exechon manipulators with offset wrists. The unknown coefficients in the compliance model are determined by optimizing the model against experimental data. The resulting predictions are then compared against more experimental results to validate the model.

COMPUTED TOMOGRAPHY-GUIDED COMMISSURAL ALIGNMENT OF THE EVOLUT VALVE USING THE CUSP-OVERLAP TECHNIQUE, A RETROSPECTIVE PILOT STUDY

<h3>BACKGROUND</h3> Advancement of transcatheter aortic valve replacement (TAVR) and its long-term outcomes is warranted as it expands to a low-risk population. Procedural optimization using commissural alignment (CA) and the cusp-overlap technique have recently been suggested, especially for supra-annular self-expanding valves. The Evolut valve (EV) has two markers to guide valve position and orientation: the hat-marker and the flush port. Although the EV platform orientation with the flush port to the 3 o'clock position seems to improve the likelihood of CA, commissural malalignment (CMA) remains an issue in a significant number of patients. <h3>METHODS AND RESULTS</h3> To improve CA, starting October 2020, we implemented a systematic, simplified workflow for all patients receiving the EV. The workflow uses CT-guided fluoroscopic angles to determine the hat-marker position during cusp-overlap view. To determine if the CT-guided individualized positioning workflow of the EV improves CA, we retrospectively reviewed all patients with the EV implanted at our center. The study included only patients with native aortic valve stenosis, transfemoral access and the use of the cusp-overlap technique. From September 2019 to March 2021, a total of 52 patients were enrolled in the study. The Hat position during cusp overlap deployment angle was classified as Outer Curve (OC), Center Front (CF), Inner Curve (IC), and Center Back (CB). Overall, CF hat marker position was achieved in 25 (48%) patients. For this analysis, we combined CB and IC in one group (CBIC). CF position has optimal alignment in 23/25 (92%) patients, while CBIC position was associated with 6/13 (46%) of severe CMA. Severe commissural overlap with coronary orifices occurred more frequently in the CBIC position than the CF position (LAD 53.8% vs 4%, and RCA 53.8% vs 0%). The implementation of our workflow decreased the undesirable CBIC position from 41.4% to 4.3% (P=0.001). There was a significant decrease in Severe CMA (20.7% to 0% p=0.023), and proper alignment (< 30 degrees) was achieved in 95% of patients after the implementation of the workflow. <h3>CONCLUSION</h3> This study showed that the Hat-marker position during cusp-overlap fluoroscopic view predicts CA, with the CF position being the best for optimal CA. Besides, this study showed that a systematic and simplified CT-guided workflow could potentially improve CA and minimize severe coronary orifice overlap with the neo-commissures.

Hydrodynamic Behaviour of Floating Polygonal Platforms under Wave Action

The hydrodynamic behaviour of floating regular polygonal platforms under wave action was studied by conducting parametric studies. Considering triangular, square, hexagonal, and circular platforms of similar size and draft, the results show that their added mass, radiation damping, and RAOs are similar. However, the wave exciting forces are slightly different, particularly the horizontal forces. The polygonal platforms oriented with one of its corners in line with the prevailing wave direction can lead to a reduction in the horizontal force on the platform, a feature that helps in reducing the cost of a mooring system. Moreover, such oriented platforms are able to disperse the waves better in multiple directions and hence will not pose problems for ships or marine vessels passing by the platform on the weather side. Thus, the orientation of a polygonal platform is an important design consideration. From the comparison study among different polygonal platforms, their wave attenuation performances are slightly similar. The hydrodynamic analyses performed herein for the parametric studies were sped up considerably by using a significantly lesser number of Fourier coefficient sets for the series functions that define the velocity potentials when compared to those used by previous researchers in their analytical approaches. The adoption of the radius function defined by cosine-type radial perturbation does not only generate the geometric boundaries of polygonal platforms, but it also simplifies the formulation and quickens the computations.

IMAGE-BASED ORIENTATION DETERMINATION OF MOBILE SENSOR PLATFORMS

Abstract. Estimating the pose of a mobile robotic platform is a challenging task, especially when the pose needs to be estimated in a global or local reference frame and when the estimation has to be performed while the platform is moving. While the position of a platform can be measured directly via modern tachymetry or with the help of a global positioning service GNSS, the absolute platform orientation is harder to derive. Most often, only the relative orientation is estimated with the help of a sensor mounted on the robotic platform such as an IMU, with one or multiple cameras, with a laser scanner or with a combination of any of those. Then, a sensor fusion of the relative orientation and the absolute position is performed. In this work, an additional approach is presented: first, an image-based relative pose estimation with frames from a panoramic camera using a state-of-the-art visual odometry implementation is performed. Secondly, the position of the platform in a reference system is estimated using motorized tachymetry. Lastly, the absolute orientation is calculated using a visual marker, which is placed in the space, where the robotic platform is moving. The marker can be detected in the camera frame and since the position of this marker is known in the reference system, the absolute pose can be estimated. To improve the absolute pose estimation, a sensor fusion is conducted. Results with a Lego model train as a mobile platform show, that the trajectory of the absolute pose calculated independently with four different markers have a deviation &lt; 0.66 degrees 50% of the time and that the average difference is &lt; 1.17 degrees. The implementation is based on the popular Robotic Operating System ROS.

Workspace analysis and design of large-scale cable-driven printing robot considering cable mass and mobile platform orientation

This paper proposes a methodology to determine the printable workspace of a cable robot by taking cable mass and mobile platform orientation into account. This workspace has a characteristic feature of avoiding the collision of lower cables with the previous layers of the structure during 3D printing while maintaining cable tensions inside the prescribed positive tension bounds. Since redundant robot is taken into consideration, the printable workspace possesses multiple solutions and hence, a unique solution needs to be selected based upon a selection criterion. Therefore, to select a unique solution, this paper proposes a selection criterion to minimize cable sagging and compares it with the conventional selection criterion of minimizing cable tension. For comparative analysis, various factors such as printable workspace, cable tensions and platform deflection of the robot are considered. The proposed selection criterion is further utilized to study the impact of variation in the geometric parameters on the printable workspace and the capacity margin of the robot. Finally, an optimal design is proposed using genetic algorithm for the desired printable workspace as well as constraint minimum capacity margin with an objective to minimize the installation space of the cable robot.