Structure Design of a Mobile Jack Robot *

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Proceeding of the I International Conference on Information and Automation Yinchuan, China, August 2013 Structure esign of a Mobile Jack Robot * Xizhe Zang, Yixiang Liu and Yanhe Zhu State Key

1 Proceeding of the I International Conference on Information and Automation Yinchuan, China, August 2013 Structure esign of a Mobile Jack Robot * Xizhe Zang, Yixiang Liu and Yanhe Zhu State Key Laboratory of Robotics and System Harbin Institute of Technology Harbin, Heilongjiang Province, China zangxizhe@hit.edu.cn Abstract - A novel type of mobile jack robot is proposed in view of the fact that the traditional method of debris jacking up is usually inefficient and unsafe. The jack robot has two motion modes: fast motion mode in which the robot can drive in straight line, veer and climb with the use of crawler and crawling mode in which the robot can open narrow gaps and cultivate spaces under debris by itself to enable it to pass through. The step-shaped structure on the robot s head is able to insert into a 40 mm gap and expand it to 410 mm gradually, to make enough spaces for rescue teams and other rescue tools to save out survivors under debris. The robot can jack up 1000 kg load driven by a singleacting hydraulic cylinder which generates 101 kn force at rated pressure 70 MPa. xperiments are carried out to verify the validity of the proposed design. Index Terms - rescue robot, jack robot, structure design, crawling. I. INTROUCTION As a kind of unexpected and devastating natural disaster, earthquakes have brought quite huge damage to humans since ancient times, and never stop. After an earthquake, many victims are buried under heavy debris, which is very hard for rescue parties to lift up by human power, especially when the space is too narrow to insert the jack. Furthermore, there are a variety of toxic and hazardous substances at the scene of the earthquake, and second collapse may occur at any time because of continual aftershocks and instability of ruins. The extremely dangerous rubble-filled environment is a great threaten to the safety of rescue parties. There are many great advantages to use rescue robots in rescue works. The first and most important is that rescue robots can carry on rescue operations in dangerous sites instead of rescue teams. What s more, multiple tools and sensors can be carried by rescue robots to accomplish different tasks. Thus research of rescue robots has been a hotspot in robotics. And rescue robots will play a more and more important role in disaster rescue operations. A variety of rescue robots which are used to search victims under debris and collect information in unknown environment have been developed. But so far, researches on the subject of jack robots are much few. As an earthquakeprone nation, Japan carried out research on jack robots in advance. Hideyuki Tsukagoshi, et al. in Tokyo Institute of Technology, proposed a new type of jack robot Bari-bari- I in 2004 [1]. The key of the robot is the step structure on its head which enables it to insert into narrow gaps and lift up heavy debris. The second, third, and fourth generation of prototype have already been developed so far [2], [3], [4]. J. Tanaka, et al. in Okayama University, designed a mobile jack robot in 2005 [5], whose driving method is based on a crawler drive. The robot s load capacity reaches 34 kn, however, its minimum inserting height is only 200 mm because of the limit of mechanical structure [6]. There are no related products yet at home. Therefore, a rescue robot which can go into narrow spaces and jack up debris in dangerous sites is desired urgently to assist rescue parties in more effective rescue operations promptly after disasters and ensure the safety of survivors and rescue parties. II. OUTLIN OF TH JACK ROBOT SYSTM A. Resume of the Jack Robot A novel type of mobile jack robot is developed on the basis of previous researches. The jack robot has three main functions: moving under rubbles, opening narrow gaps and jacking up debris. Controlled through an electric wire and a hydraulic tube, the robot can go into dangerous sites where rescue parties cannot approach and make enough spaces for rescue parties, other rescue robots and rescue tools to pass through and save out victims. The jack robot is designed based on modular design method, which consists of five modules including jack module, right support module, left support module, right transformable track module and left transformable track module, making it convenient to assemble and disassemble. The overview of the jack robot is shown in Fig. 1. Right transformable track module Right support module Jack module Fig.1 The jack robot Left transformable track module Left support module * This work is partially supported by National Hi-tech Research and evelopment Program of China rant #2012AA /13/$ I 1218

To satisfy the demands of different tasks, the jack robot has two motion modes: fast motion mode and crawling mode.

In crawling mode, it can insert into narrow gaps, cultivate spaces by itself to enable it to move into rubbles and pass through under the debris.

Specifications of the Jack Robot The size of the jack robot is 500 mm in length, 360 mm in width and 160 mm in height.

shown in Fig. 2 and Fig. 3. The robot is capable of jacking up 1000 kg load driven by a single-acting hydraulic cylinder which generates 101 kn force at 70 MPa.

2 To satisfy the demands of different tasks, the jack robot has two motion modes: fast motion mode and crawling mode. In fast motion mode, it possesses the ability of driving in straight line, veering and climbing on irregular ground, making it easier to arrive at destination point quickly. In crawling mode, it can insert into narrow gaps, cultivate spaces by itself to enable it to move into rubbles and pass through under the debris. After reaching the most appropriate operation place, the robot can jack up debris to support rescue works. B. Specifications of the Jack Robot The size of the jack robot is 500 mm in length, 360 mm in width and 160 mm in height. The robot has a step-shaped stand on its head which is able to insert into a 40 mm gap, and can jack up debris till 410 mm when the jack module spreads the step-shaped stand to the maximum height, as shown in Fig. 2 and Fig. 3. The robot is capable of jacking up 1000 kg load driven by a single-acting hydraulic cylinder which generates 101 kn force at 70 MPa. Major specifications of the jack robot are shown in Table I. III. TH SIN OF JACK ROBOT A. The Structure esign of Jack Module The jack module consists of step-shaped stand, base plate, hydraulic cylinder, connecting rods, upper rollers, nether rollers and hinge pins as shown in Fig. 4. One end of hydraulic cylinder is connected to base plate, and the other to connecting rods. When hydraulic cylinder extends, nether rollers are driven by connecting rods to move in the horizontal direction, while upper rollers do compound movement in the horizontal and vertical directions. Consequently, step-shaped stand is driven to rise. This kind of jack mechanism has several prominent advantages, such as a compact structure, a large bearing capacity and small installation space required by hydraulic cylinder. Upper rollers Step-shaped stand Connecting rods Hinge pins Fig. 2 The minimum height 40mm 410mm Base plate Fig. 4 Jack module B. The Structure esign of Support Module The structure of support module is shown in Fig. 5. Crawling driving motor, linear guide and ball screw are installed on support plate. One end of junction plate is connected to ball screw nut, and the other to connecting base, which is fixed on slider. And jack module is connected to connecting base by hinge pins. When the crawling driving motor drives ball screw to rotate by synchronous belt drive, ball screw nut moves along the screw axis, and slider is driven to slide on linear guide by junction plate and connecting base, thereby jack module also moves in the same direction. Linear guide Hydraulic cylinder Ball screw Nether rollers Ball screw nut Fig. 3 The maximum height TABL I MAJOR SPCIFICATIONS OF TH JACK ROBOT Item The jack robot Weight Size Minimum inserting height Maximum height Maximum payload 30kg 500mm 360mm 160mm 40mm 410mm 1000kg Support plate Crawling driving motor Junction plate Synchronous belt Fig. 5 Support module Slider Connecting base 1219

3 C. ynamics Analysis of Jack Module The external load is driven to rise by the hydraulic cylinder. ynamics analysis of the jack module aims to analyse the forces acting on the joints and find the relationship between driving force of hydraulic cylinder and the external load. On one hand, once the driving force of hydraulic cylinder is known, the maximum bearing capacity of the robot can be determined. On the other hand, if the bearing capacity is required to meet some demand, an appropriate hydraulic cylinder can be selected according to the driving force. Take the entire jack module in equilibrium as study object. The dynamics analysis image is shown in Fig. 6. In this figure, the parameter a refers to the distance from the hinge point K of hydraulic cylinder piston rod and links to point C, b to the horizontal distance from the acting point of the external load M to the hinge point, l to the length of links, to the angle between hydraulic cylinder and base plate, and to the angle between link A and base plate. P y C A a K b H M l x Fig. 6 ynamics analysis image of the jack module Suppose hinge constraints to be ideal, and forces of hydraulic cylinder impacted on the study object to be regarded as two forces of equal magnitude but in opposite directions, indicated by P and P. Thus, there are three active forces acting on the entire study object: external load M, forces P and P impacting on each end of hydraulic cylinder. According to the principle of virtual work, the total work done by all forces acting on a system in static equilibrium is zero on all possible virtual displacements which are consistent with the constraints of the system, i.e., F xi xi + F yi yi + F zi zi = 0 As shown in Fig. 6, create a rectangular coordinate and set the origin on point A, then we have, P x x PJ + P y y PJ M x M = 0 (1) From the analysis we know, P x = P cos P y = P sin x PJ = (l+a) sin (2) y PJ = a cos y M = 2l sin After variation, we can get, x PJ = (l+a) cos y PJ = a sin (3) y M = 2l cos After substitution in (1), we should get, F B J P P = 2M l cos (a sin( + )+l sin cos ) (4) Up to this point, the relationship between the driving force of hydraulic cylinder and the external load has been presented by (4). Then force analysis of all the joints is carried out using the principle of static equilibrium [7], [8]. Fig. 7 shows the force analysis images of each joint. A F F Ay F Ax F P/2 F C F Ay H A F Hy F y M/2 (a) Forces on the step-shaped stand F Hx F x K F Ax (b) Forces on all the links F y F x F y F x (c) Forces on link, link A and link BC Fig. 7 Force analysis images of each joint According to static force equilibrium equations, we can get separately, F = M (l cos b) (2l cos ) F F = M b (2l cos ) F Ax = M l cos cos (a sin( + )+l sin cos ) F Ay = (2M (l cos b)+p (a sin( + ) l sin( ))) (2l cos ) F B = (2M b P (a sin( + )+l cos sin )) (2l cos ) F Hx = (F Ax +(F F Ay ) cot ) 2 F Hy = (F Ay +3F F Ax tan ) 2 F x = ((F Ay F ) cot ) F Ax ) 2 F y = (F Ax tan F Ay F ) 2 F x = ((F Ay F ) cot 3F Ax ) 2 F y = (F Ax tan 3F Ay F ) 2 F Cx =(3F Ax (F Ay F ) cot ) 2 F Cy = (3F Ay +F 2F B F Ax tan ) 2 From the above equations, the magnitude of forces on each joint is relevant to the structural parameters of the jack module. Once the design of the jack module is completed, forces on each joint during the whole jacking up operations can be calculated according to these equations. F F H F C F Cy F Cx F F F F y F B B F x F B B 1220

. ynamics Simulation of Jack Module ynamics simulation of the jack module is carried out using the software AAMS.

A force of 10 kn is acted on the top of the step-shaped stand, and the relationship between required force and the stroke of hydraulic cylinder is obtained after simulation, as shown in Fig. 8.

8 The relationship between the force and the stroke of hydraulic cylinder Obviously the figure indicates that the required thrust of hydraulic cylinder decreases gradually when the hydraulic cylinder

Based on the simulation result, a single-acting hydraulic cylinder is selected, which generates 101 kn force at rated pressure 70 MPa, and the maximum stroke is 90 mm.

4 . ynamics Simulation of Jack Module ynamics simulation of the jack module is carried out using the software AAMS. Import the virtual prototype module of jack module into AAMS and set materials, joints and motions for the module. A force of 10 kn is acted on the top of the step-shaped stand, and the relationship between required force and the stroke of hydraulic cylinder is obtained after simulation, as shown in Fig. 8. (a) Analysis results when force is exerted on the first step (b) Analysis results when force is exerted on the second step Fig. 8 The relationship between the force and the stroke of hydraulic cylinder Obviously the figure indicates that the required thrust of hydraulic cylinder decreases gradually when the hydraulic cylinder extending. At the initial moment of jacking up operations, the required thrust of hydraulic cylinder reaches the maximum magnitude, kn. Based on the simulation result, a single-acting hydraulic cylinder is selected, which generates 101 kn force at rated pressure 70 MPa, and the maximum stroke is 90 mm.. Finite lement Analysis of Jack Module The jack module is applied to jacking up heavy debris. Obviously, sufficient strength and rigidity is essential to ensure the reliability, efficiency and safety when bearing a heavy load. ynamics simulation results of the jack module show that the initial moment when the force of hydraulic cylinder reaches maximum, is the most dangerous condition during the whole jacking up operations. So this working condition is the focus of finite element analysis. Meanwhile, when crawling under debris, the robot jacks up debris using each step of the step-shaped stand successively. Therefore, different stress states should be considered in the analysis. The static structure analysis tool in the software ANSYS Workbench is used to accomplish finite element analysis of the jack module. Three-dimensional model of the jack module built in SolidWorks is imported into ANSYS Workbench. Set material properties, contacts and element size for each part. After meshing the finite element model is obtained. Apply a load of 10 kn on each step of the step-shaped stand in proper order, and select equivalent stress and total deformation as the desired solving options. When the analysis completed, the equivalent stress and total deformation contours are obtained. Because of space restriction, only part of analysis results are shown in Fig. 9 when the force is exerted on the first, second, third, and fourth step. Fig. 10 shows the equivalent stress contours of the four links. (c) Analysis results when force is exerted on the third step (d) Analysis results when force is exerted on the fourth step Fig. 9 Finite element analysis results of the jack module (a) Analysis result of link (b) Analysis result of link CF (c) Analysis result of link BC (d) Analysis result of link A Fig. 10 Finite element analysis results of the links 1221

The analysis results above make clear that the stress and deformation of all parts are within legal limits and meet the design requirements.

Fast Motion Mode The transformable track modules on both sides of the jack robot are designed based on parallelogram four-bar linkage, of which the most striking feature is deformability.

11 and Fig. 12. In this case, track driving motors drive the robot to travel in straight line, veer or climb using tracks. Initial state (Fig.

14 (b)): Both support modules keep still relatively to the ground. The nut moves along the axis of the screw when the motor drives ball screw to rotate, driving the jack module to go forward.

At the same time, both support modules are driven to move upward, getting out of contact with the ground. Support modules go forward (Fig.

When the ball screw rotates, it also moves along its axis, and support modules on both sides are driven to move forward. Fall back (Fig.

The jack robot can keep on moving under the debris if executing the working cycle constantly, as shown in Fig. 14 (f), (g) and (h). Fig. 11 Before deformation Fig. 12 After deformation B.

More specifically, jack module is driven to move horizontally by electric motor when support modules support the load, while support modules go forward when jack module lifts up the load driven by

5 The analysis results above make clear that the stress and deformation of all parts are within legal limits and meet the design requirements. Additionally, the result that the stress and deformation of each stress state decrease is consistent with dynamics simulation results of the jack module. IV. LOCOMOTION MCHANISM OF TH JACK ROBOT A. Fast Motion Mode The transformable track modules on both sides of the jack robot are designed based on parallelogram four-bar linkage, of which the most striking feature is deformability. In fast motion mode, transformable track modules get deformed, making jack module and support modules rise and depart from the ground, while tracks make contact with the ground, as shown in Fig. 11 and Fig. 12. In this case, track driving motors drive the robot to travel in straight line, veer or climb using tracks. Initial state (Fig. 14 (a)): The hydraulic cylinder and the crawling driving motor do not work, and support modules on both sides are in contact with the ground. Jack module moves forward (Fig. 14 (b)): Both support modules keep still relatively to the ground. The nut moves along the axis of the screw when the motor drives ball screw to rotate, driving the jack module to go forward. Jack up (Fig. 14 (c)): When the piston rod of hydraulic cylinder extending, jack module spreads vertically and lifts up the load to a certain height gradually by the step-shaped stand. At the same time, both support modules are driven to move upward, getting out of contact with the ground. Support modules go forward (Fig. 14 (d)): Jack module keeps still relatively to the ground while supporting the load. When the ball screw rotates, it also moves along its axis, and support modules on both sides are driven to move forward. Fall back (Fig. 14 (e)): When the piston rod of hydraulic cylinder retracts, the step-shaped stand drops, and the load falls on support modules. By this point, a single working cycle has been completed. The jack robot can keep on moving under the debris if executing the working cycle constantly, as shown in Fig. 14 (f), (g) and (h). Fig. 11 Before deformation Fig. 12 After deformation B. Crawling Mode In crawling mode, jack module and support modules complete the operations of supporting the load and going forward alternately. More specifically, jack module is driven to move horizontally by electric motor when support modules support the load, while support modules go forward when jack module lifts up the load driven by hydraulic cylinder. In this way the robot s crawling is realized, which enables it to move under heavy debris. C. Simulation of Crawling Procedure Three-dimensional model of the jack robot is imported into AAMS to simulate the crawling procedure, as shown in Fig. 13. Fig. 14 shows the simulation results. Jack robot (a) (c) (e) (b) (d) (f) ebris round Fig. 13 Simulation image of the jack robot s crawling procedure (g) Fig. 14 Simulation results of the jack robot s crawling procedure The above simulation results indicates that the jack robot s crawling procedure can be accomplished by coordinated performance of the crawling driving motor and the hydraulic cylinder, making the expected locomotive functions realized. V. FIL TSTS In order to test the jack robot s performance of opening narrow gaps and jacking up debris, two field tests are carried out. (h) 1222

A. Open Narrow aps Put a board of about 2m in length and 1m in width on the ground and four steel plates on the board, of which the total weight is about 400 kg.

The robot can open narrow gaps and expand spaces by itself to enable it to pass through using crawling function. The proposed structure design is verified to be feasible. (a) (b) VI.

The step-shaped stand on the head of the jack robot can insert into a 40 mm gap and jack up to 410 mm under 1000 kg load, to make enough spaces for rescue teams, other rescue robots and tools.

6 A. Open Narrow aps Put a board of about 2m in length and 1m in width on the ground and four steel plates on the board, of which the total weight is about 400 kg. The gap between the board and the ground is only about 40 mm. Then the performance of the robot opening a gap is tested. The process of the robot opening a gap is shown in Fig. 15. The robot can open narrow gaps and expand spaces by itself to enable it to pass through using crawling function. The proposed structure design is verified to be feasible. (a) (b) VI. CONCLUTION A novel type of mobile jack robot which is aimed to go into dangerous sites, open narrow gaps and jack up debris is designed in view of the urgent demands for rescue robots in rescue works after earthquakes. The difference between the jack robot and conventional mobile robots is that the jack robot possesses the ability of cultivating spaces by itself to enable it to pass through under heavy debris. The step-shaped stand on the head of the jack robot can insert into a 40 mm gap and jack up to 410 mm under 1000 kg load, to make enough spaces for rescue teams, other rescue robots and tools. Tests of opening narrow gaps and jacking up a heavy box show that the design of the jack robot is feasible. In the future, our researches will focus on rescue robot system, which consists of a series of rescue robots, for example, the robot to cut barricades, to carry victims and the robot for power assist. Furthermore, how to improve rescue robots circumstance adaptability and abilities of autonomous planning and motion control is also an important issue. ACKNOWLMNT Thanks for the support of National Hi-tech Research and evelopment Program of China (863 Program, rant No. 2012AA041505). (c) (e) Fig. 15 Test of opening a narrow gap B. Jack Up a Heavy Box To test the jacking up capacity of the robot, one cubic meter of water is injected into a wooden box, of which the inner dimensions are 1m long, 1m wide and 1.2 m high. The total weight of the wooden box and water loaded on the jack robot is more than 1000 kg. In initial state, the robot is under the wooden box. As a result of the test, the robot is able to jack up the wooden box to 410 mm easily, as shown in Fig. 16. (d) (f) RFRNCS [1] H. Tsukagoshi, T. Tanaka, A. Kitagawa, and A. Yusuke, evelopment of a jack-up mobile robot for narrow space: Bari-bari-I, Nippon Kikai akkai Robotikusu, Mekatoronikusu Koenkai Koen Ronbunshu, vol. 2004, pp. 2P1-H-42, June [2] H. Tsukagoshi, A. Kitagawa, M. Ito, O. Kuniaki, K. Ichiro, and K. Takumi, Bari-bari-II: jack-up rescue robot with debris opening function, Proceedings of the 2008 I International Conference on Robotics and Automation(ICRA 2008), Pasadena, CA, pp , May [3] H. Tsukagoshi, M. Ito, I. Kiryu, and A. Yusuke, evelopment of jack-up mobile robot with debris opening function, Nippon Kikai akkai Robotikusu, Mekatoronikusu Koenkai Koen Ronbunshu, vol. 2006, pp. 2P2-12, [4] T. Satoshi, Rescue Robotics: T Project on Robots and Systems for Urban Search and Rescue, 1 st ed., London: Springer-Verlag London Ltd, 2009, pp [5] J. Tanaka, K. Suzumori, M. Takata, T. Kanda, and M. Mori, A mobile jack robot for rescue operation, Proceedings of the 2005 I International Workshop on Safety, Security and Rescue Robotics(SSRR 2005), Kobe, pp , June [6] M. Mori, J. Tanaka, K. Suzumori, and T. Kanda, Field test for verifying the capability of two high-powered hydraulic small robots for rescue operations, Proceedings of the 2006 I/RSJ International Conference on Intelligent Robots and Systems(IROS), Beijing, pp , Oct [7] X. Hu, J. Hu, and. He, The modeling of scissors elevation mechanism and research of key parameters, Mechanical Research & Application, vol. 19, no. 4, pp , August [8]. Sun, W. ong, and S. L, esign of heavy-loading hydraulic fork lifting deck propelled symmetrically, Mechinery esign & Manufacture, no. 6, pp , June (a) Initial state Fig. 16 Test of jacking up a heavy box (b) Jacking up the box 1223

Stress and Strain Analysis in Critical Joints of the Bearing Parts of the Mobile Platform Using Tensometry

Stress and Strain Analysis in Critical Joints of the Bearing Parts of the Mobile Platform Using Tensometry American Journal of Mechanical Engineering, 2016, Vol. 4, No. 7, 394-399 Available online at http://pubs.sciepub.com/ajme/4/7/30 Science and Education Publishing DOI:10.12691/ajme-4-7-30 Stress and Strain