Motion Platform Research Articles

Disain CAD Mekanisme Paralel Tiga Derajat Translasi Murni Dengan Rantai Kinematik Kombinasi Sambungan Revolut dan Prismatik


 
 
 
 In this study it was discussed kinematic design of a 3-RRRPP translational parallel mechanism. The design was carried out by using simulation performed using CAD software. Motion platform was analyzed based on screw and reciprocal screw theory. The evaluation mechanism performance was determined by introducing the stages of research in the form to determine mechanism parts such as base, links, and platform. The work was continued with the assembly process of each part. Furthermore, kinematic response represented by displacement of platform positions was figured out by a CAD simulation. Based on the results of the simulation, it was successfully designed the mechanism performing the translational motion of the Platform.
 
 
 
 
 

A computational framework for the co-optimization of platform hydrodynamic and passive structural control of floating offshore wind turbines

Floating offshore wind turbines extract rich and stable wind energy in the deep sea. However, they face severe sea conditions and high maintenance costs, and a promising method is needed to generate a high-performing, reliable, and robust design. Traditional sequential methods overlook the coupling between sub-systems and may miss the global optimum. The control co-design method, in contrast, focuses on the integrated optimization of the whole system. However, implementing co-simulation and co-optimization for co-design is challenging. In this study, a control co-design framework is developed and validated to couple the platform hydrodynamics with multi-physical wind turbines for integrated simulations and optimization. Based on this framework, the floating platform and tuned mass damper are co-optimized by establishing an efficient Kriging-enhanced Genetic algorithm. A case study is conducted using a 10 MW floating offshore wind turbine for demonstration. The platform shape and tuned mass dampers are parameterized by five and three design variables, respectively. To minimize platform mass, two formulations are proposed, that is, multi- and single-objective, for scenarios with and without consideration of structural loads. These formulas are solved under pre-defined turbulent wind and irregular wave conditions. Compared to the baseline model, the optimal design significantly reduces platform mass, enhancing both power generation and platform motion stability. After involving structural load in optimization, the optimal platform mass, energy production, and platform motion stability are degraded. These findings demonstrate the effectiveness of the co-design framework in optimizing platform geometry and passive structural control.

Analysis of Positioning Accuracy in Case of Design Errors in the Installation of Mecanum Wheels of the Mobile Platform

Introduction. Mobile robots capable of omnidirectional movement are widely used in various fields of human activity. To provide high accuracy of positioning of omnidirectional platforms with mecanum wheels, it is required to develop their detailed mathematical models used in the construction of a motion control system. Due to the complicated design of the mecanum wheels, various errors may occur during the construction of omnidirectional platforms, including the error of installing such wheels on the platform. Its effect on the accuracy of the platform movement has not been studied before. This work aims at assessing the positioning errors that arise due to the presence of design errors in the installation of mecanum wheels, and analyzing the effect of these errors on the accuracy of program motion testing when using control at the kinematic level.Materials and Methods. The analysis of positioning accuracy was based on mathematical modeling of the platform kinematics, taking into account structural errors in the installation of mecanum wheels. To describe the relationship between the angular speeds of rotation of the wheels and the speeds of the platform, the conditions of nonslip of the contact points on the support surface were used. Numerical calculations were carried out in the Wolfram Mathematica package.Results. A formula was obtained for estimating errors in platform pseudovelocities under program control formed at the kinematic level. The estimation of the errors of the platform speeds for simple movements was carried out. According to the calculation results, it has been shown that the speed errors are significant for robots with mecanum wheels operating autonomously.Discussion and Conclusion. The calculation results demonstrated the significant impact of wheel installation errors on the positioning accuracy of the mecanum-platform, and confirmed the need to take into account these design errors when creating autonomous mecanum-platforms. The constructed model of the robot's kinematics makes it possible to predict errors in platform speeds that arise under program control, as well as deviations of the coordinates of the geometric center of the platform from the program motion. The proposed kinematic model can be used to improve the positioning accuracy through forming a platform motion control that compensates for the influence of wheel installation errors.

Robotic Microsurgery in Extremity Reconstruction - Experience With a Novel Robotic System.

Background: Robotic systems have successfully been introduced into other surgical fields in the past. First attempts with different setups are made in the field of microsurgery. The Symani® Surgical System, a flexible platform consisting of two robotic arms, features motion scaling with tremor filtration to address the demands and complexity of microsurgery. Symani's NanoWrist Instruments are the world's smallest, wristed surgical instruments, intended to improve a surgeon's range of motion beyond the capability of the human hand. This combination allows surgeons to scale their hand movements while seamlessly articulating the robotic micro instruments. Purpose: We report on our experience in extremity reconstruction with this novel system.Research Design: The Symani Surgical System® was used for 6 cases of extremity reconstruction. The surgeon controlled the manipulators along with the footswitch while either sitting away from the operating table relying on 3D visualization with an exoscope or sitting at the operating table using a standard microscope.Data Collection: Microsurgical anastomoses were performed in 4 patients (3 end-to-end arterial anastomoses and one end-to-side arterial anastomosis) and nerve grafting was performed in 2 patients.Results: Microvascular anastomoses were slower vs conventional microsurgery, but all anastomoses were patent. Epineural coaptation showed proper fascicle alignment and tissue manipulation could be kept to a minimum. The platform's motion scaling allows the surgeon to perform precise micro-movements with only minimal tissue manipulation and hard-to-reach anatomy becomes accessible more easily.Conclusions: Robotic microsurgery might gain importance in the nearer future but more data will need to be collected.

Bidirectional vibration control for fully-coupled floating offshore wind turbines

The vast and stable wind resources present in deep waters have made deep-sea floating wind power the mainstream trend for future development. However, the operating environment of offshore floating wind turbines is complex and variable. The joint action of wind and waves causes significant platform motion and turbine vibration, reducing power generation efficiency, causing structural damage, and shortening the service life of turbines. Hence, this study focuses on the NREL 5 MW DeepCwind semi-submersible wind turbine and establishes a fully-coupled floating wind turbine model utilizing the SIMPACK multi-body dynamics software. The model includes aero-, hydro-, flexible body structure, mooring, control, and transmission chain components. 3D pendulum tuned mass dampers (3D-PTMD) and bilinear tuned mass dampers (2TMDs) are designed to control the bidirectional vibration causes due to wind-wave misalignment in the platform motion and nacelle displacement of the floating wind turbine. The research results show that: For the roll and pitch of the platform, there is only one platform roll or pitch main frequency, and the amplitude at the main frequency can be effectively reduced by setting the frequency of 2TMDs near the main frequency, thereby suppressing the vibration of the platform; For the displacement of the nacelle, in addition to the main frequency of platform roll or pitch, there is also a secondary frequency of first-order bending of the tower, 2TMDs corresponding to the main frequency can effectively reduce the amplitude at the main frequency, and 3D-PTMD corresponding to the secondary frequency can effectively reduce the amplitude at the secondary frequency, it is better to configure 2TMDs alone than 3D-PTMD alone, and it is best to configure both at the same time.

Identification of the human cerebral cortical hemodynamic response to passive whole-body movements using near-infrared spectroscopy.

This study aimed to investigate the cerebral cortical response to naturalistic vestibular stimulation induced by real physical motion and to validate the vestibular cerebral cortex previously identified using alternative vestibular stimulation. Functional NIRS data were collected from 12 right-handed subjects when they were sitting in a motion platform that generated three types of whole-body passive translational motion (circular, lateral, and fore-and-aft). The study found that different cortical regions were activated by the three types of motion. The cortical response was more widespread under circular motion in two dimensions compared to lateral and fore-and-aft motions in one dimensions. Overall, the identified regions were consistent with the cortical areas found to be activated in previous brain imaging studies. The results provide new evidence of brain selectivity to different types of motion and validate previous findings on the vestibular cerebral cortex.

Adaptive acquisition and recognition system of blade surface defects during machining process

This study proposes an adaptive acquisition and recognition system of blade surface defects during machining process. The study has developed a hardware system consisting of motion platforms with four degrees of freedom (DOF) and industrial camera systems, along with an optimized workflow for the acquisition of blade surface defects. Subsequently, the hill-climbing algorithm, the energy gradient function and an adaptive evaluate image definition method are utilized to acquire clear images of the blade surface which contains tiny machined surface defects. An improved you only look once v5 (YOLOv5) algorithm is finally proposed to recognize the type and location of blade surface defects. The improved YOLOv5 algorithm uses K-means++ algorithm to cluster marking boxes, introduces a convolutional block attention module (CBAM) attention mechanism in the cross stage partial network with 3 convolutions (C3 module), and adopts the efficient intersection over union (EIoU) loss function instead of the complete intersection over union (CIoU) loss function to improve the recognition accuracy. The result shows that the proposed adaptive acquisition and recognition system can clearly collect the blade surface defects. The improved YOLOv5 algorithm can identify the type and location of blade surface defects, and the mean average precision (mAP) improved by 1.4 % compared to the original YOLOv5.

A Composite Super-Twisting Sliding Mode Approach for Platform Motion Suppression and Power Regulation of Floating Offshore Wind Turbine

The floating platform motion of an offshore wind turbine system can exacerbate output power fluctuations and increase fatigue loads. This paper proposes a new scheme based on a fast second-order sliding mode (SOSM) control and an adaptive super-twisting extended state observer to suppress the platform motion and power fluctuation. Firstly, an affine nonlinear model of the floating wind turbine pitch system is constructed. Then, a fast SOSM pitch control law is adopted to adjust the blade pitch angle, and a new adaptive super-twisting extended state observer is constructed to achieve total disturbance observation. Finally, simulations are conducted under two cases of wind and wave conditions based on FAST (fatigue, aerodynamics, structures, and turbulence) and MATLAB/Simulink. Compared with the traditional proportional integral (PI) control scheme and standard super-twisting control scheme, the platform roll under the proposed scheme is reduced by 13% and 4%, and pitch is reduced by 16% and 3% in Case 1. Correspondingly, the roll is reduced by 9% and 15%, and pitch is reduced by 7% and 1% in Case 2. For the tower top pitch and yaw moment, load reductions of 7% and 3% or more are achievable compared with those under the PI control scheme. It is indicated that the proposed scheme is more effective in suppressing floating platform motion, stabilizing output power of the wind turbine system, and reducing tower loads.

Head-centric computing for vestibular stimulation under head-free conditions.

Background: The vestibular end organs (semicircular canals, saccule and utricle) monitor head orientation and motion. Vestibular stimulation by means of controlled translations, rotations or tilts of the head represents a routine manoeuvre to test the vestibular apparatus in a laboratory or clinical setting. In diagnostics, it is used to assess oculomotor postural or perceptual responses, whose abnormalities can reveal subclinical vestibular dysfunctions due to pathology, aging or drugs. Objective: The assessment of the vestibular function requires the alignment of the motion stimuli as close as possible with reference axes of the head, for instance the cardinal axes naso-occipital, interaural, cranio-caudal. This is often achieved by using a head restraint, such as a helmet or strap holding the head tightly in a predefined posture that guarantees the alignment described above. However, such restraints may be quite uncomfortable, especially for elderly or claustrophobic patients. Moreover, it might be desirable to test the vestibular function under the more natural conditions in which the head is free to move, as when subjects are tracking a visual target or they are standing erect on the moving platform. Here, we document algorithms that allow delivering motion stimuli aligned with head-fixed axes under head-free conditions. Methods: We implemented and validated these algorithms using a MOOG-6DOF motion platform in two different conditions. 1) The participant kept the head in a resting, fully unrestrained posture, while inter-aural, naso-occipital or cranio-caudal translations were applied. 2) The participant moved the head continuously while a naso-occipital translation was applied. Head and platform motion were monitored in real-time using Vicon. Results: The results for both conditions showed excellent agreement between the theoretical spatio-temporal profile of the motion stimuli and the corresponding profile of actual motion as measured in real-time. Conclusion: We propose our approach as a safe, non-intrusive method to test the vestibular system under the natural head-free conditions required by the experiential perspective of the patients.

Effects of the WEC shape on the performance of a novel hybrid WEC-FOWT system

A novel wind-wave energy hybrid concept is presented in this paper, consists of a floating semi-submersible wind turbine and multiple point absorption wave energy converters (WECs). Numerical simulations are conducted using the hydrodynamic analysis program AQWA, based on the three-dimensional (3D) potential theory. To ensure the reliability of the numerical model, the hydrodynamic responses of the semi-submersible platform and the WECs are validated using available experimental data. Finally, three WECs with different shapes are designed to investigate the shape on the performance of this hybrid system, including platform motion, mooring line tension and power captured by the WECs. The results demonstrate that the hybrid system with the circular truncated conical WECs has the best performance compared to the other two shaped WECs. In addition, the influence of the platform motion on the performance of the WEC array is negative. Overall, this study could provide some insights for the design of other wind-wave integrated systems.

Airborne Radar Doppler Spectrum Width as a Scale-Dependent Turbulence Metric

Abstract High-resolution airborne cloud Doppler radars such as the W-band Wyoming Cloud Radar (WCR) have, since the 1990s, investigated cloud microphysical, kinematic, and precipitation structures down to 30-m resolution. These measurements revolutionized our understanding of fine-scale cloud structure and the scales at which cloud processes occur. Airborne cloud Doppler radars may also resolve cloud turbulent eddy structure directly at 10-m scales. To date, cloud turbulence has been examined as variances and dissipation rates at coarser resolution than individual pulse volumes. The present work advances the potential of near-vertical pulse-pair Doppler spectrum width as a metric for turbulent air motion. Doppler spectrum width has long been used to investigate turbulent motions from ground-based remote sensors. However, complexities of airborne Doppler radar and spectral broadening resulting from platform and hydrometeor motions have limited airborne radar spectrum width measurements to qualitative interpretation only. Here we present the first quantitative validation of spectrum width from an airborne cloud radar. Echoes with signal-to-noise ratio greater than 10 dB yield spectrum width values that strongly correlate with retrieved mean Doppler variance for a range of nonconvective cloud conditions. Further, Doppler spectrum width within turbulent regions of cloud also shows good agreement with in situ eddy dissipation rate (EDR) and gust probe variance. However, the use of pulse-pair estimated spectrum width as a metric for turbulent air motion intensity is only suitable for turbulent air motions more energetic than the magnitude of spectral broadening, estimated to be <0.4 m s−1 for the WCR in these cases. Significance Statement Doppler spectrum width is a widely available airborne radar measurement previously considered too uncertain to attribute to atmospheric turbulence. We validate, for the first time, the response of spectrum width to turbulence at and away from research aircraft flight level and demonstrate that under certain conditions, spectrum width can be used to diagnose atmospheric turbulence down to scales of tens of meters. These high-resolution turbulent air motion intensity measurements may better connect to cloud hydrometeor process and growth response seen in coincident radar reflectivity structures proximate to turbulent eddies.

Modelling and analysis for the dynamic behavior of 6-DOF motion platform used for simulating aerospace mechanical environment

As high carrying capacity, high frequency response and high precision control performance are presented, the 6 degree of freedom (DOF) motion platform is chosen as the aerospace device to implement mechanical environment simulation experiment on the ground. In this paper, a dynamic model of the 6 DOF motion platform is firstly developed based on the Newton-Euler method. Then the attitude determination and the driving force are analyzed by solving the dynamic equations. Furthermore, a parametric modelling method for the 6 DOF motion platform is proposed and applied to obtain the expansion amounts and the driving forces of the 6 hydraulic rods in the motion platform by adopting the Adams software. Results show a good agreement with the computation results of the theory dynamic model, which demonstratesthe validity of the proposed modelling method for analysis of the dynamic behavior of the 6-DOF motion platform.

A Novel Composite Pitch Control Scheme for Floating Offshore Wind Turbines with Actuator Fault Consideration

It is of great importance to simultaneously stabilize output power and suppress platform motion and fatigue loads in floating offshore wind turbine control systems. In this paper, a novel composite blade pitch control scheme considering actuator fault is proposed based on an augmented linear quadratic regulator (LQR), a fuzzy proportional integral (PI) and an adaptive second-order sliding-mode observer. Collective pitch control was achieved via the fuzzy PI, while individual pitch control was based on the augmented LQR. In the case of actuator fault, an adaptive second-order sliding-mode observer was constructed to effectively eliminate the need for the upper bound of unknown fault derivatives and suppress the chattering effect. This paper conducted co-simulations based on FAST (Fatigue, Aerodynamics, Structures, and Turbulence) and MATLAB/Simulink to verify the effectiveness and superiority of the proposed scheme under different environmental conditions. It is shown that platform roll was reduced by approximately 54% compared to that under PI control. For the tower fore–aft moment, load reductions of 45% or more were achievable. The proposed scheme can greatly reduce the pitch and roll of the floating platform and loads in the windward direction of the wind turbine.

A Modified Iteration-Free SPGA Based on Removing the Linear Phase

In traditional Stripmap SAR imaging, the platform motion error will bring the phase error in the azimuthal direction to the image, which will have a series of effects on the imaging quality. The traditional autofocus algorithm—Stripmap Phase Gradient Algorithm (SPGA)—can estimate any order phase error above the second order in theory, but it is difficult to estimate the linear phase error, which leads to the discontinuity of the estimated phase error. It usually needs multiple iterations to focus an image, which is inefficient. Moreover, because the linear phase error cannot be estimated, the traditional SPGA cannot eliminate the target offset in the image, resulting in the distortion of the image in the azimuthal direction. According to the continuity of phase error, we propose a modified iteration-free SPGA based on removing the linear phase. Without iteration, the proposed autofocus algorithm can achieve comparable or even better results than traditional SPGA. In the simulation experiments, piecewise linear errors are added to the images of multiple targets. SPGA still fails to focus the image after six iterations. The average ILSR and ILSR are −7.11 dB and −3.99 dB, respectively, and the average number of point target drift is 8.42 pixels. The proposed algorithm optimizes the average ILSR and ILSR to −12.34 dB and −9.87 dB and reduces the average number of point target drift to 0.16 pixels. In the actual data processing, using image entropy as the evaluation criterion, the time consumption is only 19.25% of SPGA under the condition of achieving the same focusing quality.

Research on 2D Image Motion Compensation for a Wide-Field Scanning Imaging System with Moving Base

The wide-field imaging system carried on a high-altitude or near-space vehicle takes high-resolution images of the ground to measure and map targets. With the improvement of imaging resolution and measurement accuracy, the focal length of the wide-field imaging system is getting longer. The requirement for image motion compensation (IMC) accuracy is getting higher, and the influence of optical path coupling is increasing within the process of two-dimensional (2D) IMC. To further improve the IMC accuracy of the wide-field imaging system, an innovative IMC method is first proposed in this paper. The method is based on the 2D motion of the scanning platform and secondary mirror. Secondly, to solve the optical coupling problem in the process of 2D IMC, the coupling phenomenon is analyzed. The coupling relationships between 2D scanning motion, 2D secondary mirror motion and image motion is derived from the compensation process. A complete 2D IMC model is established, and a 2D IMC method, including an optical path decoupling correct regulator (ODCR), is designed. Finally, the method is verified in laboratory and field flight tests. The results show that the proposed method can effectively correct the coupling error of the optical path in the process of IMC and achieve high-resolution 2D IMC. When the scanning speed is 60°/s and the exposure time is 2 ms, the accuracy of the 2D IMC is up to 0.57pixels (RMS) in the pitch direction, and 0.46 pixels (RMS) in the roll direction.

Nonlinear Identification and Decoupling Sliding Mode Control of Macro-Micro Dual-Drive Motion Platform with Mechanical Backlash

Nonlinear Identification and Decoupling Sliding Mode Control of Macro-Micro Dual-Drive Motion Platform with Mechanical Backlash

Enhancing the sensitivity of atom-interferometric inertial sensors using robust control

Atom-interferometric quantum sensors could revolutionize navigation, civil engineering, and Earth observation. However, operation in real-world environments is challenging due to external interference, platform noise, and constraints on size, weight, and power. Here we experimentally demonstrate that tailored light pulses designed using robust control techniques mitigate significant error sources in an atom-interferometric accelerometer. To mimic the effect of unpredictable lateral platform motion, we apply laser-intensity noise that varies up to 20% from pulse-to-pulse. Our robust control solution maintains performant sensing, while the utility of conventional pulses collapses. By measuring local gravity, we show that our robust pulses preserve interferometer scale factor and improve measurement precision by 10× in the presence of this noise. We further validate these enhancements by measuring applied accelerations over a 200 μg range up to 21× more precisely at the highest applied noise level. Our demonstration provides a pathway to improved atom-interferometric inertial sensing in real-world settings.

On the selection of design waves for predicting extreme motions of a floating offshore wind turbine

Governments worldwide are setting ambitious targets for renewable energy sources as a response to the ongoing climate crisis, leading to increased investment in offshore wind. While fixed wind structures have restrictive water depth limitations, floating devices are being developed to harness the resource in deeper waters. As part of this development, accurate prediction of ultimate loads and platform motions is crucial for survivability and cost-competitiveness. Present design standards rely on time-consuming methodologies based on irregular sea state data to determine design loads. ‘Short design waves’ are a potential solution to speed up the process by simulating short wave profiles that target extreme responses, bypassing the need for modelling long-duration irregular sea states. This paper explores the application of short design waves to semi-submersible wind platforms, and aims to determine whether extreme motions produced by these methods are comparable with current design practices. Short design waves show promise for surge and heave extremes, but further refinement is needed to improve pitch predictions and align with industry standards. Based on the present comparison, short design waves have potential within early design stages, where a wide range of environmental conditions are explored, but their reliability and applicability in alternative scenarios requires further investigation.

Development of Boom Posture Adjustment and Control System for Wide Spray Boom

To obtain a more consistent droplet distribution and reduce spray drift, it is necessary to keep the entire spray boom parallel to the crop canopy or ground and maintain a certain distance from the spray nozzles to the crop canopy or ground. A high-performance boom active control system was developed for boom trapezoid suspension. The hydraulic system and hardware circuit of the boom control system were designed based on analyzing the configuration of active trapezoid suspension. The mathematical models of valve-controlled hydraulic cylinders and active boom suspensions were developed. Step response and frequency domain response analysis of passive suspension were conducted by Simulink simulations, and then key parameters of the boom suspension and hydraulic system were determined. A feedforward proportion integration differentiation (FPID) control algorithm was proposed to improve the tracking performance. The designed control system was assembled on a 24 m boom with trapezoid suspension. The response characteristic of the active boom control system was tested by the step signal and the sinusoidal signal from a six-degree-of-freedom hydraulic motion platform. Firstly, the tracking performance of the active balance control system for the PID (proportion integration differentiation) and FPID control algorithms was compared for a given 0.2 Hz sine signal. Then, for the ground-following control system, the response characteristics in challenging terrain and tracking performance in less challenging terrain were tested. Field experiment results indicate that the maximum rolling angle of the chassis was 3.896° while the maximum inclination angle of the boom was 0.453°. The results show that the designed boom adjustment and control system can effectively adjust the boom motion in real time and meet the requirements of field operation.

High-performance electroionic artificial muscles boosted by superior ion transport with Ti3C2Tx MXene/Cellulose nanocomposites for advanced 3D-motion actuation

Low-voltage driven electro-ionic soft actuators with large deformation strain are of promising candidate for high-performance artificial muscles, with practical applications in flexible electronics, biomedical assistive devices and soft robotics. However, enhancing the actuation response and long-term stability along with excellent bending properties simultaneously still remain significant challenges. Herein, an elaborate ionically crosslinked nanocomposite membrane, assembled with 1D bacterial cellulous (BC) nanofibers and 2D Ti3C2Tx MXene nanomaterials, is reported to improve constrained ion transport for high-performance electrically activated ionic actuator. The 3D interpenetrating frameworks, arising from the synergistic effects of such combination, not only serve to enhance ion selectivity through the presence of intrinsically negatively charged functional groups but also expand the initially confined pathways, thus diminishing the energy barrier to ion transport. As a result, the integrated superior functionalities of the soft actuator exhibit large bending strain of 0.88 % with the tip displacement of 10.8 mm, ultra-stable cycling performance (>99 % retention for 5 h), and ultrabroad material response range up to 18 Hz under an ultralow voltage exertion of 0.5 V. Furthermore, the demonstration of the prototype soft actuators as actuating tracking beams of 3D-adaptive motion platform for plate deformable mirror shows their potential applications of soft robotics, thereby offering a dependable solution for driving the next generation of sophisticated intelligent systems.