morphing rescue robot design and finite element

Background of Intelligent Robot

Requirements of Disaster Rescue Robots

Survival (Viability)

In the post-disaster environment, the hazards of toxic gas, poison, biochemicals, radioactivity, and secondary collapse make the ability of robots to adapt to the environment particularly important. In the post-disaster environment, the hazards of the environment must be considered in relation to the surface strength of the robot and line safety.

Mobility (Ability)

In terms of temperature, there may be high temperatures in the environment after the disaster, and therefore robots must be able to withstand these adverse conditions, which requires adequate materials in the robot structure. Due to environmental constraints, a robot's physical structure must be small enough to navigate the confined spaces of ruins and pipelines.

Perception Ability

Sometimes robots are damaged in disaster situations due to the inherent characteristics of disaster sites, low system reliability and failure, which means that system hardware and software fault tolerance as well as fault handling capacity are very important. For victim tracking, systems monitor for human bodies, clothing, footprints, voices, body temperatures and body position to determine if those trapped are alive as well as various personal details to help identify them.

Rescue Robot Development

Crawler Rescue Robots

Environmental testing also includes geological and topographic testing of the soil environment for two reasons: avoiding obvious threats and avoiding major environmental damage that could cause a second collapse. Foster-Miller (c) Minitrac robot from Inuktun Figure 1: Crawler rescue robot versions of three well-known robots.

Deformable (Polymorphic) Rescue Robots

The tracked robot was developed to meet the needs of military reconnaissance and the demolition of dangerous objects. This robot can flexibly adjust its shape and size according to the size and range of the search channel. a) Upright position (b) Semi-erect position (c) Normal position.

Bionic Rescue Robots

Figure 4(c) shows a mobile platform snake robot developed and installed by Carnegie Mellon University. a) A flying robot developed by University of.

Research Topic

The biggest advantage of the structure is that the size of the rescue robot can be changed according to the deployable structure, so that it has good mobility and adaptability to the environment. Finally, based on a simple strength calculation of the structure of the rescue robot, the structure of the rescue robot was designed and the structure was analyzed using finite elements.

Background of the Hoberman Sphere

The Hoberman Sphere is also considered a preferred conceptual design due to its compactness, which is shown in Figure 6. Like the AstroMesh, the Hoberman Sphere is a relatively lightweight design with small and thin subcomponents and boasts a large expansion ratio.

Hoberman Structure

In the Hoberman element, the connection point of the PRRP is point B which is shown in Figure 12(b). Therefore, the angle α was used to describe the degree of folding of the polygonal scissor structure. It was found that the design in this paper could change the size of the structure.

Second, ANSYS will be used to test numerical changes of the model strain and stress with different materials adopted.

Figure 9: Off center pantograph made of straight, identical rods. [4]

SolidWorks Model Design

D Printer Model

The easiest way to test how the designed model works in real life is to 3D print all the components and assemble the model. If there are problems in the assembled model or the assembly process, it will be necessary to return to the SolidWorks model to resolve these problems. Figures 31 and 32 are 3D prints of pairs of link one and link two, each connected by a long pin.

Considering the size of the 3-D printer, all the sizes of the 3-D printing components are reduced to a ratio of 3:1. In Figure 14, A, C, E, and G are shown connected by a single connector, while there were no problems in SolidWorks, during assembly, the connectors were not thick enough and the short pins were not long enough to connected both stably. To solve this, the connectors and short pins need to be redesigned to ensure that the structure is stable and mobile.

Figure 31: 3-D print of a pair of linkages-

Second Version of Design Model

The redesigned link-two has a left and right side, which are 20cm and 24cm long respectively, just like the previous link-two. For the redesigned link two, all variables are unchanged except angle θ, which has changed from 135o to 157.5o. To solve the connection problem of the previous model, the connector and a pin must be rethought.

The only difference from the previous design is the width and height, with the thickness and holes remaining unchanged. Because the bolt must connect the connector and still be movable, it cannot have all threads. The head is 1 cm, the shaft without thread is 4 cm, the shaft with thread is 2 cm and the diameter of the shaft with thread is 2.1 cm.

The nut is hexagonal in shape, 1.5 cm in height and 4 cm in width, with a threaded diameter of 2.4 cm for screwing the bolt. The long pin connecting the various links is unchanged from the previous design, as seen in Figures 25 and 26. Because the redesigned link-one and redesigned link-two have only changed in the angle θ, their length and width are the same which means the long pin did not need to be redesigned.

Figure 35: 3-D design of redesigned linkage-one in SolidWorks

FEA Analysis

Brief Introduction of Finite Element Analysis on ANSYS Workbench

It uses a variational method to minimize the error function and produce a stable solution.[11] Analogous to the idea of connecting many segments of a small straight approximation, the finite element method contains all possible methods, which connect many simple equations in small regions known as finite elements and use them to evaluate complex equations over larger regions. It considers the solution domain as consisting of many small interconnected subdomains called finite elements, and assumes a suitable (simplest) approximate solution for each element, and then derives the total satisfying conditions for this domain (such as the equilibrium condition of the structure) to obtain the solution of the problem. For most practical problems it is difficult to obtain exact solutions, the finite element not only has high accuracy, but also can adapt to various complicated shapes, thus becoming an effective tool of engineering analysis.[11]

Structure Analysis by FEA Method (ANSYS Workbench)

Finite Element Analysis Theory
Purpose of Finite Element Analysis (FEA)

Once the value of the node is obtained, the field function in the unit and even in the entire assembly can be determined by the established interpolation function. In the finite element discretization process, adjacent elements are continuous at the same node, but not necessarily at any point on the boundary. Assuming the function that represents the physical behavior of the unit, that is, the approximate continuous function that represents the solution of the unit;.

FEA can fully obtain its accurate internal mechanical information under the action of complex external forces, i.e. obtains three types of mechanical information (displacement, strain and stress) of the deformation body. Based on a detailed mechanical analysis, the structure of the design can be evaluated in terms of strength, stiffness and . other aspects, i.e. to change unreasonable design parameters in order to obtain a more optimal design. Therefore, the analytical structure can have a very complex shape, which can be not only a complex planar structure or an axisymmetric structure, but also can be a three-dimensional cage structure or a physical structure.

In the finite element method, the boundary condition does not need to introduce the characteristic equation for each element, but the relevant characteristic matrix is processed as necessary after the algebraic equation for the whole structure is obtained, so that the same field variable function is used for the interior and boundary elements. As the order size decreases or the order of the interpolation function increases, the finite element solution converges to the exact solution of the problem at hand. the interpolation function increases.[12] Therefore, the accuracy of the solution can be improved through grid encryption or the high-order interpolation function can be used to improve the accuracy of the solution, so that the analytical solution has a certain utility value. The finite element method can be used for the analysis of different types of materials such as isotropic materials, orthotropic materials, anisotropic materials and composite materials, as well as the analysis of composite structures composed of different materials.

ANSYS Software

Engineering Data
Geometry Setup
Meshing Procedure
Transient Setup

The second step of the transitional setup was to define the modeling geometry for SolidWorks. This imported model preserves the size of the model in SolidWorks, but the bolts and nuts were hidden for the geometric configuration. A major advantage of the design in this paper was that the structure could change its size to fit different sized spaces and environments.

A major defect of the design in this paper was that under the influence of an external driving force, the structure could gradually be fully expanded and maintain a stable status. Therefore, this paper conducted ANSYS to perform FEA of this design with the aim of better understanding the advantages and disadvantages of the design in this paper. Navy blue is especially prominent around the edges of the model, meaning there is minimal total distortion, while the inner portion is mostly red, meaning maximum total distortion.

The green line has been changed on the positive and negative sides of the graph, with irregular changes occurring over time, meaning that the force reaction on the Y-axis has fluctuated in positive and negative directions. The green line has changed on the positive and negative sides of the graph with uneven changes over time, which means that the force reaction on the Y axis has changed in the positive and negative directions. In addition, the size of the included angle between the arms and the number of links can be changed to change the size of the ball.

To test the feasibility of the design in real life, ANSYS was used for a finite element analysis of the transient structure from the perspective of total deformation and equivalent stress. The maximum equivalent stress was 107.85 MPa, which was mainly distributed within the structure, while the minimum was 3.5805e-05 MPa, which was mainly distributed in the peripheral part of the structure.