The numerical solution of multibody systems is not a straightforward problem. The formulation of the equations of motion is augmented with the constraint equations that lead to a set of differential ...algebraic equations (DAEs). These constraints govern the relative motion between the system’s components at the position level (geometric constraints) and may restrict the velocity of particular components (rolling constraints). There are several factors that determine the effectiveness of numerical integration methods and the extent of their applicability owing to the various motion circumstances. These factors include numerical stability throughout the integration and computation time, as well as allowable error percentage and the length of simulation time. In this regard, this research examines existing approaches for constraint stabilization during numerical integration and introduces a new methodology based on fuzzy control algorithm, whose coefficients are independent of the dynamic characteristics of different systems. Schematics of the new methodology are presented; two examples of spatial multibody systems with holonomic and nonholonomic constraints are solved to evaluate the effectiveness of the proposed method. It can be concluded that fuzzy control contributes an excellent solution for generic system configuration and is suitable for lengthy simulations with minimal computation time.
Modelling and simulation has become a general tool in product development of mechanical products. Building mathematical models of subsystems and components is one of the most important tasks in the ...analysis, design and optimization of any mechanical systems. Multibody system serves as a basis for many modern mathematical models of dynamic systems and has been applied in many areas of science. In the last decade, many algorithms and numerical manipulation tools have been developed to meet the increasing demands in the modeling and simulation of advanced mechanical systems in the industry. There are different methods used to define the body orientation in the spatial domain. Among these, Reference Point Coordinate Formulation with Euler Angles (RPCF-EA) and Reference Point Coordinate Formulation with Euler Parameters (RPCF-EP) are the most common ones. The main difference between them is that (RPCF-EA) defines the body orientation by using three successive angles, while (RPCF-EP) defines the same orientation using four parameters. In this paper, the formulation change of the equations of motion and the mapping of generalized forces into cartesian perspective are presented. In addition, three numerical examples are used to discuss the differences between using RPCF-EA and RPCF-EP in multibody systems with respect to the type of application. The first example demonstrates the suitability of each coordinates to model those systems subjected to a combination of holonomic and non-holonomic constraints. Second example, illustrates the differences between the two methods when modeling the types of joints that constraints the rotational motion, or make the relative rotation very small. Final example discusses the effectiveness of implementing RPCF-EA and RPCF-EP onto systems with gyroscopic motion, which has some numerical integration problems due to gimbal lock.
The purpose of this work is to investigate the construction of fuzzy embedded control systems combining fast execution and parallel processing capabilities provided by Field Programmable Gate Arrays ...(FPGAs) and Reconfigurable Inputs/Outputs (RIO) chips. A fixed-point fuzzy controller is developed and implemented on a fast mechatronic system with high-speed control and high channel count on an FPGA target. This paper provides a brief introduction to deploying Fuzzy Logic Control (FLC) methods using RIO-FPGA technology. It suggests a technique for implementing the three stages that constitute the FLC and the PD-like FLC and PID-like FLC structures into practice. Controllers with 1 and 2 degrees of freedom are developed and tested experimentally. Parallel loops, key challenging advantage of LabVIEW programming, are utilized for decoding feedback signals, generating pulse trains for actuator's drivers and for calculation of control gains. An NI-SbRIO board that combines deployable devices with a real-time processor, a re-configurable FPGA, and analogue and digital input–output ports is used. The experimental work demonstrates the significant enhancement of implementing reconfigurable embedded fuzzy control upon such mechatronic systems.
The Floating Frame of Reference (FFR) formulation is a well-established and reliable method for modeling flexible multi-body systems. The FFR formulation has been adopted for dynamic systems that are ...characterized by large rotations with relatively small deformations. Many scientific papers have pointed out these characteristics with the scrutiny of the simulation results and comparisons with other modeling techniques. However, the FFR is still enclosed in the theoretical aspects and simulation work and faces difficulties when being applied to practical systems. The crucial point in these difficulties centers on coordinate reduction and the associated mapping between nodal and modal coordinates. The process of selecting the necessary modes may be theoretically simple, but the situation is different when applied in a real operational environment. The strategy developed in this work combines the Operational Modal Analysis, specifically the Frequency Domain Decomposition (FDD) approach, and the FFR formulation to build a suitable model of practical multi-body systems. The output model has been validated experimentally. The results show that the proposed FFR-FDD method can be efficiently used to construct multi-body models for those systems that work in premise operational conditions.
The absolute nodal coordinate formulation (ANCF) has been used in the analysis of large deformation of flexible multibody systems that encompass belt drive, rotor blade, and cable applications. As ...demonstrated in the literature, the ANCF finite elements are ideal for isogeometric analysis. The purpose of this investigation is to establish a relationship between the B-splines, which are widely used in the geometric modeling, and the ANCF finite elements in order to construct continuum models of large-deformation geometries. This paper proposes a simplified approach to map the B-spline surfaces into ANCF thin plate elements. Matrix representation of the mapping process is established and examined through numerical examples successfully. The matrix representation of the mapping process is used because of its suitability of computer coding and to minimize the calculation time. The error estimation is carried out by analyzing the gap between the points of each ANCF element and the corresponding points of the portion of the B-spline surface. The
Hausdorff distance
is used to study the effect of the number of control points, the degree of interpolation, and the knot multiplicity on the mapped geometry. It is found that cubic interpolation is recommended for optimizing the accuracy of mapping the B-spline surface to ANCF thin plate elements. It is found that thin plate element in ANCF missing a number of basis functions which considered a source of error between the two surfaces, as well as it does not allow to converting the ANCF thin plate elements model to B-spline surface. In this investigation, an application example of modeling large-size wind turbine blade with uniform structure is illustrated. The use of the continuum plate elements in modeling flexible blades is more efficient because of the relative scale between the plate thickness and its length and width and the high flexibility of its structure. The numerical results are compared with the results of ANSYS code with a good agreement. The dynamic simulation for mapped surface model shows a numerical convergence, which ensures the ability of using the proposed approach for applications of dynamics for design and computer-aided design.
Soft continuum robots, inspired by the adaptability and agility of natural soft-bodied organisms like octopuses and elephant trunks, present a frontier in robotics research. However, exploiting their ...full potential necessitates precise modeling and control for specific motion and manipulation tasks. This study introduces an innovative approach using Deep Convolutional Neural Networks (CNN) for the inverse quasi-static modeling of these robots within the Absolute Nodal Coordinate Formulation (ANCF) framework. The ANCF effectively represents the complex non-linear behavior of soft continuum robots, while the CNN-based models are optimized for computational efficiency and precision. This combination is crucial for addressing the complex inverse statics problems associated with ANCF-modeled robots. Extensive numerical experiments were conducted to assess the performance of these Deep CNN-based models, demonstrating their suitability for real-time simulation and control in statics modeling. Additionally, this study includes a detailed cross-validation experiment to identify the most effective model architecture, taking into account factors such as the number of layers, activation functions, and unit configurations. The results highlight the significant benefits of integrating Deep CNN with ANCF models, paving the way for advanced statics modeling in soft continuum robotics.
The article proposes a dynamic for design (DFD) procedure for a novel aperture grating tiling device using the multibody system (MBS) approach. The grating device is considered as a rigid-flexible ...MBS that is built primarily based totally at the load assumptions because of grating movement. This movement is utilized in many industrial applications, such as the compression of laser pulse, precision measuring instruments, and optical communication. A new design procedure of tiling grating device frame is introduced in order to optimize its design parameters and enhance the system stability. The dynamic loads are estimated based on the Lagrange multipliers that are obtained from the solution of the MBS model. This model is fully non-linear and moves in the three-dimensional space, and the relative movement of its bodies is restricted by the description of the constraints function in the motion manifold. The mechanism of the grating device is structurally analyzed in keeping with the dynamic conduct and therefore the generated forces. The symbolic manipulation as well as the computational work of solving the obtained differential-algebraic equations (DAEs) is carried out using MATLAB Symbolic Toolbox. Once the preliminary design has been attained, the stress behavior of the grating device is examined using the MATLAB FEATool Multiphysics toolkit, regarding system stability and design aspects. Moreover, the design was constructed in real life, and the movement has been verified experimentally, which confirms the effectiveness of the proposed procedure. In conclusion, the DFD procedure with trade-off optimization is utilized successfully to design the grating unit for maximum ranges of grating movements.
Background
Owing to significant morbidity and mortality with the development of vascular complications in patients with acute invasive fungal rhinosinusitis (AIFRS), early identification, and rapid ...medical or surgical interventions that are essential for improving patients’ outcomes. For the purpose of presurgical mapping and management planning, magnetic resonance imaging (MRI) is essential for the early identification and improved delineation of disease extent.
Objective
To evaluate variable MRI manifestations in the detection of the vascular complications in patients with AIFRS and its impact on patients’ survival.
Methods
A retrospective study, included 24 patients with histopathological proven AIFRS to review the para nasal sinus MRI findings. MRI were evaluated for the sinus involvement and the extrasinus extension into the orbit and/or the brain. Vascular structures were assessed for the development of vascular complications, like ICA for thrombosis, attenuation or pseudoaneurysm, cavernous sinus and superior ophthalmic veins for thrombosis.
Results
Of the reviewed 24 patients, 16 had cavernous sinus thrombosis, 15 had ICA thrombosis, 10 had ophthalmic vein thrombosis, 4 had ICA attenuation and only two cases had pseudoaneurysm of the ICA. Vascular thrombosis was more common with mucormycosis with cavernous sinus and ophthalmic vein thrombosis which were significantly increased among non survivor patients (90%, 70%), as compared to the survivor patients (50%, 14.29%), with
P
= 0.04 and 0.005 respectively.
Conclusions
Vascular complications are common in patients with AIFRS. MRI is helpful in accurate detection of vascular complications in patients with AIFRS.
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