Visual Nastran 4D Research Articles

Simulation and control of multipurpose wheelchair for disabled/elderly mobility

© 2016 IOS Press and the author(s). This paper presents investigations into the development of modelling and control strategies for a multipurpose wheelchair as mobile transporter for elderly and disabled people. The research is aimed at helping people with physical weakness/disabilities in their upper and lower extremities to move independently without human intervention. A novel reconfiguration which allows multi-task operations in the same wheelchair system with improved design is modelled in Visual Nastran 4D (VN4D) software. A modular fuzzy logic control mechanism with integrated phases is introduced for the overall operations and two-wheeled stabilization of the wheelchair. It is shown that the proposed modular fuzzy control approach is able to ensure system stability while performing multipurpose tasks such as manoeuvrability on flat surfaces, stairs climbing (ascending and descending), standing in the upright position on two wheels and transformation back to standard four wheels with up to 50% less initial torque in comparison to previous designs.

Sit-to-Stand and Stand-to-Sit Control Mechanisms of Two-Wheeled Wheelchair.

This paper presents a mechanism for standing and sitting transformation of a wheelchair using a two-wheeled inverted pendulum concept with reduced torque requirement, in simulation studies. The motivation of this work is to design a compact standing mechanism to help an elderly/disabled person with functional limitation in lower extremities to maneuver in small and confined spaces and enable them to perform standard daily life routines independently. The wheelchair system at the upright standing position is tested with different travel distances, and the challenge is to control both sit-to-stand and stand-to-sit operations in a stable manner using flexible-joint humanoid. An additional spring/damping element is incorporated at each wheel to provide a comfortable ride for the user especially during stand-to-sit transformation task. A PD-fuzzy control with modular structure is implemented, and the performance of the system is observed through visual nastran 4d (vn4d) visualization software and simulation in matlab. The stand-to-sit performance tests have shown more than 38% reduction in tilt and back seat angles fluctuation in linear travel motion using a suspension system, while the initial tilt torque needed is 50% less than the amount required in previous designs.

The Study of Rolling Temperature Condition Influence on the Formation of Hot Strip Cross-Section Rolled on the Longitudinal-Wedge Mill

The mill of new construction is proposed in the article. To calculate the specialized metal forming processes the software of finite element analysis - MSC Super Forge MSC Visual Nastran 4D was used. Stress-strain state (SSS) of the rolled workpiece and heavy-loaded units of the proposed mill was calculated. The influence of the rolling temperature regimes on formation of hot-rolled strips cross-section was investigated. The hot-rolled strips were rolled on longitudinal wedge mill. It is proved that the workpiece is deformed in the conditions of soft SSS in a mill of new construction, in other words the amount of the elastic deformation and displacement of the rolls units are small. The investigation has also proved sufficiently high fixity of the joints of roller assembly work stand as well as that the equivalent voltage does not exceed the maximum permissible value for the material strength in heavy-loaded units of the mill.

Influence of Thermal Condition Prorollers to Formation of Cross-Section Profile of Hot-Rolled Strips, Rolled on the Longitudinal -Wedge Mill

This paper proposes a new design of mill. Using the software of finite element (FE) analysis, specialized for the calculation of metal forming processes MSC. SuperForge и MSC, visual Nastran 4D, calculated the stress-strain state (SSS) rolled billet and heavy-duty elements of the proposed mill. It is proved that when a new rolling mill thin strips deforming force reduced, the amount of elastic deformation and displacement rolls are small elements. The investigation has also shown that sufficiently high rigidity roller assembly work stand and resulting in heavy-duty elements of the equivalent voltage does not exceed the maximum allowable values, for the material strength.

PD-fuzzy Control of a Stair Climbing Wheelchair

This paper focuses on the development of a control strategy of a compact stair climbing wheelchair to maintain stable and balance while negotiating staircases in confined spaces for the elderly and disabled. The Visual Nastran 4D is used to develop a simulation models and linked with Matlab platform for control and visual assessment purposes. The challenges are to control front and rear motors as well as tilt angle to ensure system stability and maintain smoothness of the climbing process. PD-Fuzzy controls are developed, tested and associated performances are assessed through intensive visual approach.

Simulation of Chain Drive Based on MSC. Visual Nastran 4D

In the distance learning of the courses of Machine Parts and Design, the hypothesized experiment through internet is a kind of the significance teaching method. At present, multimedia, network technologies are extremely mature. Using the internet technology to realize the course learning can help the students to master the principle of chain drive easily. The key problem to realize the hypothesized experiment on the net is how to carry on the simulation of machine parts or components using the computer software. The realization method of the hypothesized simulation of chain drive is introduced in this paper based on MSC. Visual Nastran 4D software.

Development of a multi-body computational model of human head and neck

Experimental studies using human volunteers are limited to low acceleration impacts while whole cadavers, isolated cervical spine specimens, and impact dummies do not normally reflect the true human response. Computational modelling offers a cost effective and useful alternative to experimental methods to study the behaviour of the human head and neck and their response to impacts to gain insight into injury mechanisms. This article reports the approach used in the development of a detailed multi-body computational model that reproduces the head and cervical spine of an adult in the upright posture representing the natural lordosis of the neck with mid-sagittal symmetry. The model comprises simplified but accurate representations of the nine rigid bodies representing the head, seven cervical vertebrae of the neck, and the first thoracic vertebra, as well as the soft tissues, i.e. muscles, ligaments, and intervertebral discs. The rigid bodies are interconnected by non-linear viscoelastic intervertebral discs elements in flexion and extension, non-linear viscoelastic ligaments and supported through frictionless facet joints. Eighteen muscle groups and 69 individual muscle segments of the head and neck on each side of the body are also included in the model. Curving the muscle around the vertebrae and soft tissues of the neck during the motion of the neck is also modelled. Simulation is handled by the multi-body dynamic software MSC.visuaNastran4D. Muscle mechanics is handled by an external application, Virtual Muscle, in conjunction with MSC.visuaNastran4D that provides realistic muscle properties. Intervertebral discs are modelled as non-linear viscoelastic material in flexion and extension but represented by ‘bushing elements’ in Visual Nastran 4D, which allows stiffness and damping properties to be assigned to a joint with required number of degrees of freedom of the motion. Ligaments are modelled as non-linear viscoelastic spring-damper elements. As the model is constructed, the cervical spine motion segments are validated by comparing the segment response to published experimental data on the load-displacement behaviour for both small and large static loads. The response of the entire ligamentous cervical spine model to quasi-static flexion and extension loading is also compared to experimental data to validate the model before the effect of muscle stiffening is included. Moreover the moment-generating capacity of the neck muscle elements has been compared against in vivo experimental data. The main and coupled motions of the model segments are shown to be accurate and realistic, and the whole model is in good agreement with experimental findings from actual human cervical spine specimens. It has been shown that the model can predict the loads and deformations of the individual soft-tissue elements making the model suitable for injury analysis. The validation of the muscle elements shows the morphometric values, origins, and insertions selected to be reasonable. The muscles can be activated as required, providing a more realistic representation of the human head and neck. The curved musculature results in a more realistic representation of the change in muscle length during the head and neck motion.

Modeling a Viscoelastic Gymnastics Landing Mat during Impact

Landing mats that can undergo a large amount of area deformation are now essential for the safe completion of landings in gymnastics. The objective of this study was to develop an analytical model of a landing mat that reproduces the key characteristics of the mat-ground force during impact with minimal simulation run time. A force plate and two high-speed video cameras were used to record the mat deformation during vertical drop testing of a 24-kg impactor. Four increasingly complex point mass spring-damper models, from a single mass spring-damper system, Model 1, to a 3-layer mass spring-damper system, Model 4, were constructed using Matlab to model the mat's behavior during impact. A fifth model composed of a 3-layer mass spring-damper system was developed using visual Nastran 4D. The results showed that Models 4 and 5 were able to match the loading phase of the impact with simulation times of less than 1 second for Model 4 and 28 seconds for Model 5. Both Models 4 and 5 successfully reproduced the key force-time characteristics of the mat-ground interface, such as peak forces, time of peak forces, interpeak minima and initial rates of loading, and could be incorporated into a gymnast-mat model.