Designing and analysis of electro-mechanical telescopic mast

Transcription

1 Int. Journal of Applied Sciences and Engineering Research, Vol. 6, Issue 1, by the authors Licensee IJASER- Under Creative Commons License 3.0 Short Communication ISSN Designing and analysis of electro-mechanical telescopic mast Department of Mechanical Engineering, Yildiz Technical University, Istanbul, Turkey DOI: /ijaser.6001 Abstract: In this article, a sophisticated work is presented that includes determination of workspace volume of electromechanical telescopic antenna mast, while considering mechanical behavior of it. With the help of theoretical equations, optimization is done while taking into account of stiffness and dexterity analysis. Theoretical substructure is analysis and 3D data of Mast is developed in Siemens N.X CAD environment. In later stages of project, both 3D and theoretical data are linked together and thus, with changing design parameter of Mast itself, Siemens N.X CAD data adapts and regenerate itself with new set of parameters. To achieve optimum design with predefined parameters, different set of mast parameters are iterated through design optimization in mechanical structural analysis, and Antenna Mast Mechanism design is finalized and illustrated in 3D CAD environment, N.X. This study provides a technical solution to accomplish a generic Antenna Mast with optimized design. Key words: Electro-mechanical Telescopic Mast, Mast, Design, Structural Analysis, Siemens NX. 1. Introduction In many business sectors, it is needed a mechanism which is developed for the purpose of position control depending access distance. Usage areas and the working princible of this mechanism which is designed to utilize according to several features and functions are assigned the base of this research. It is intended to determine the optimal parameters of the telescopic electromechanical mast system for which the literature overview has been executed according to its aimed working capacity and the design of the system is intended to be carried out considering those parameters. Creating an optimal model which can satisfy the different working conditions will ensure the best design among the existing systems. 1.1 Mechanism of telescopic mast Telescopic mast is a product which is formed with lots of sections depending its access distance that states its length in fully opened position and its utilization purpose is to provide linear motion. All sections are designed as carrying each other on, and it is a product group which having purpose to carry the sections to the top by locking the outermost section with previous section. (Edward A. Marue (2002); Kenneth J. Pereira (2002)). They are divided into the groups according to the payload, fully opened length, utilization area and driving line. In defense industry, telescopic mast systems utilized as situating and carrying jammer systems, radar systems and camera systems on to provide frontier security. *Corresponding author ( gurgenmert@gmail.com) 1 Received on December, 2016; Published on January, 2017

2 Figure 1: Telescopic Mast (Geroh 2016) 1.2 Technical specifications of telescopic mast In frontier security, Telescopic Mast is one of the most important part of High Electronic Offensive System. This product is designed to raise an antenna which creates signals at high frequencies and to shape a specific geometry. Properties of the product in this scope as below; 1. Telescopic Mast must be set automatically and manually. 2. Telescopic Mast must have at least 8 meters of height and 5 meters of diameter. 3. Telescopic Mast s weight must not be over 600 kg. 4. Telescopic Mast s materials must be assigned as composite materials which prevent interference between the sections of antenna. 5. Telescopic Mast must be designed according to having 400 mm deflection in case of 120 km/h wind speed at fully opened position. 6. Telescopic Mast must be able to be operated at 10 inclination. 7. The vehicle which telescopic mast is placed on must have 25 lateral inclination angle and 31 climbing angle and Telescopic Mast must be able to be operated under the dynamic and static loads at those inclination angles. 8. Telescopic Mast must be able to be operated in case of 120 km/h wind speed. It must be able to carry 6 mm ice load at maximum load. 2. Design of drive line telescopic mast Design of the driving line of the system which fulfills the requirements in third chapter as shown in Figure 2. All segments are elevated with the help of that moving nut group on acme screw. No-back mechanism is used for preventing back movement and overloading of the motor, which may be caused from the forces on acme screw. By placing gear unit of acme screw and motor driving group into a separate axis, electromechanical clutch is utilized to prevent motor to draw current in manual operation. By manually 2

3 rotating the gear which is on side of clutch, power transmission between the motor and acme screw is broken and therefore rising of the system can only be operated manually. Figure 2: Elevation Drive Line 2.1 Acme Screw Design Acme screws named as power trasmition systems and they depend on type of thread. Especially they are suitable for transmission of high axial load. Acme Screw depend on thread type, classification three groups. Figure 3: Acme Thread Screws (Timothy H ; Wentzell, P.E 2004) Advantages of acme screw utilization 1. High payloads 2. Ease of production 3. Lower costs 3

4 4. Efficiency is higher than the other tooth types (Square thread type) 5. High torque capacity with small diameters 6. Resistant to impact forces 7. Ease of assembly. (Timothy H. (2004), Wentzell, P.E (2004)) Consequently, since the movement of the screw shaft which is used in Telescopic Mast rising axis is not precise, not working in multi-repetitive loops, working at high torque and a compact product is needed, an acme screw which has multiple aperture orifice is utilized in the design. 2.2 Determination of Tube Diameters and Length Considering technical requirements which states that fully opened length must be at least 8 meters and collecting three tubes inside one tube by moving all three tubes telescopically, closed length is determined as 4.2 meters. Since tubes are accepted as not carrying loads, it is determined to use glass fiber tubes with 3 mm thickness in pre-design which was realized in Siemens NX CAD software. Table 2: Draft Design Measurement Segment Inner Thickness Density Diameter Length (mm) (mm) (g/cm 3 ) (mm) 1.TUBE ,6 2.TUBE ,6 3.TUBE ,6 2.3 Lock Mechanism Lock mechanism is placed between second and third tubes. Third tube is the first moving segment and at last position when it is opened, it drives the lock mechanism and provides the locking of second and third tubes to each other. And movement during the opening of second tube proceeds as opening of second and third tubes together. Moreover, the system is fully closed by deactivating the lock by means of movement collet which exists in third tube s moving down while the system is closing. Figure 3: Lock Mechanism 4

5 3. Finite element analysis of system 3.1 Determination of Finite Element Meshing Structural analyzes were performed with finite elements approach by using Siemens NX Nastran software. Analyzes, sizing and optimization of composite tubes according to multiple slit diffraction were performed by using Hypersizer software. (N.Hamila 2008; P. Bossie 2008; S. Chatel 2008). Finite elements meshing were performed by using NX Nastran software. Element type and density were determined according to geometrical structure of the parts and their possible critical sections while the finite elements network were creating. Figure 4: Finite Element Meshing Type In the finite elements model of Telescopic Mast, delrin, aluminum and steel materials which were determined in CAD model were used as conformity to design. Tubes were determined as Glass Fiber-Epoxy Composite according to the data existing in literature. Some mechanical and physical features of those materials are given in Table 3. Table 3: Material Properties (Richard G.Budynas 2011) Material Elasticity Modul Poisson Density(kg/m 3 ) Yield Strengh GPa) Rate (MPa) AISI 4340 Steel AISI 4140 Steel Al Delrin AI 7075-T Density of glass giber epoxy resin materials are approximately 1920 kg/m 3. In this study, one-way fabric which was produced from 1200 TEX glass fiber cords material density is as 1920 kg/m Loading and Limit Condition of Mast System Distribution of 120 km/h wind speed load for Telescopic Mast unit is shown according to each tube in Table 4. 5

6 Table 4: Aerodinamic Forces Aero Dynamic Force Number Tube 3 Tube 2 Tube 1 Force (N) 225N 285N 470N Figure 5: Limit Condition Figure 6: Y axis Wind Force Direction 6

7 4. System optimization 4.1 Optimization Tubes Thickness Determination of the Composite tube s dimensions depends on fiber winding method and E-Glass Epoxy material fabric which is unidirectional sheet tape fabrics. Firstly, design of global FEM modeling for different scripts has performed. The scripts include making finite elements analysis to validate fully opened position of Mast for maximum wind forces. The results of these analysis, defining loads on all of segments and transfer to HYPERSIZER software. With the help of Hypersizer software, sizing for all of tubes which depends on displacement value of tubes end point was performed. Figure 7: Hypersizer (Craig Coiller 2002) Zero-degree layer are created by wrapping one way fabric, according to Fiber winding method, about 90 degree as 89.5 degree layers and 45/-45 degree layers are created by filament winding machines. According to Fiber winding method, lamination calculated by cross degree becoming as collateral. Depending on approved winding method, 1200 TEX E-Glass Fiber material and wrapping with 4 tows has been selected. This method used for lamination of all tubes, too. When performing analyzes, according to 120 km/h winding, allowing maximum displacement for each tube is 340 mm. For this displacement, making optimization of tube thicknesses values. Table 5: Optimized Tube Thickness Component Weight (kg) Thickness (mm) Tube Tube Tube

8 Figure 8: Maximum Displacement on X axis Against Wind Forces 4.2 Calculation of Final State Drive Line Stroke = = 4200 mm ; Overload = 120kg (Second and third segment sum. weight ) x 9.81 =1177,52 N ; System drive time is 60 second and system speed; Speed = Stroke / Time ; Speed= 70 mm/s; Specification of Drive line shown as Table 6. Table 6: Drive Line Requirements Drive Line Requirements Axial Force (N) 1177,2 Oto. Speed Of Elevation (mm/s) 70 Segment Number 3 Elevation Drive Line parameters has shown as Table 7. 8

9 Drive Line parameters M s M m n m I r I z n r n z n p m F Drive Line Torque (Nm) Nominal Motor Torque ( Nm) Motor Speed ( rpm) Transmission Rate Gear Transmission Rate Transmission Efficiency Gear Efficiency System Speed ( rpm) Acme Screw Pitch x Count ( mm) Acme Screw Efficiency System Required Load (N) Table 7: Drive Line Parameters n= Vx60 / p, M s= Fxp / 2x x m calculation for system torque and speed, criteria product selection are performed as ; M s = M m x I r x n r x I z x n z and n m= n x I r x I z. Criteria product selection values shown as Table 8. Table 8: Criteria Product Selection Dia/ Pitch Efficiency Acme Screw 32 mm / 8 mm 70% Trans. Rate Efficiency Gear Box 53 75% Torque Speed Motor 12,85 Nm 87,5 rpm 5. Results By carrying out optimization works for the tubes which are used in Telescopic Mast rising unit, optimal tube thicknesses, winding angles of glass fiber material, winding numbers were determined considering material s resistance. ( Larissa Cannon, 2012; Tom Nysetvold,2012; Glen Phelps,2012; Joshua Winn, 2012; C. Greg Jensen 2012). Structural components of Telescopic Mast like tube bearing components depending tube thicknesses in Telescopic Mast rising unit, lock and nut groups were optimized diameter about result of analysis. According to optimized system weights, selection and calculations of the products like screw shaft, motor, gear, clutch, no-back and chain gear that are used in driving line were realized in details by calculating driving line requirements. System design optimized and made design validation with the help of finite element analysis. In consequence, with the help of this study, design and optimization of similar Telescopic Mast products can easily be accomplished and Telescopic Mast products can be used in required conditions. 9

10 6. References 1. Craig Coiller,2002. Composite, Grid-Stiffened Panel Design for Post Buckling Using Hypersizer, pp Edward A. Marue, Kenneth J. Pereira, In an integrated telescoping mast-payload assembly, the payload forms the top telescoping section. Pat. No. 5, pp Geroh,2016. The 23rd Defense Industry Exhibition, pp Hamila N., P. Bossie, S. Chatel, Finite element simulation of composite reinforcement draping using a three node semi discrete triangle, pp Larissa Cannon, Tom Nysetvold, Glen Phelps, Joshua Winn and C. Greg Jensen How can N.X advanced Simulation Support Multi-User Design, pp Richard G.Budynas Shigley s Mechanical Engineering Desing, pp Timothy H. Wentzell, P.E Machine Design. Thomson Delmar Learning, pp