Research on Modeling and Simulation of Tracked Robot

This work was sponsored by Science and Technology Plan Project of Shenyang(No. F13-181-9-00), Science and Technology Plan Project of Shenyang(No.F13-316-1-74), the Chinese Defense Advance Research Program of Science and Technology, China under Grant (No. 62501040412), LiaoningBaiQianWan Talents Program(No.2013921069),Talent Resources Development Special Funds of Shenyang(2010010403), The National High Technology Research and Development Program of China (No.2015AA042302).* Corresponding author ：haolina@Research on Modeling and Simulation of Tracked Roboton RecurDynJie Han and Zhen AnLina Hao *School of Mechanical Engineering and AutomationSchool of Mechanical Engineering and AutomationNortheastern UniversityNortheastern UniversityShenyang, Liaoning Province, ChinaShenyang, Liaoning Province, China983260686@haolina@Abstract - Research on robot suspension system is an effective way to improve the running stability of the tracked robot. This paper introduces the mechanical structure of the tracked robot and established the simulation model of tracked robot. The tracked robot was driving on a bumpy road simulation experiment by using RecurDyn simulation software. Through the simulation experiment of tracked robot model constructing different parameters of the suspension system, it provides an effective basis for the design and optimization of track robot model.Index Terms - tracked robot; suspension system; m odeling; RecurDyn; stationary .I. I NTRODUCTIONThe unstructured working environment that moving robots faced at work tend to have complex terrain features, often including unequal height’s road surface, stairs, ramps, etc., which demands highly running stationary. Currently, the dynamics simulation software mainly includes DADS, ADAMS, RecurDyn for moving robots in unstructured working environment. In the aspects of researching methods and content, Qingguo Luo and Dongya Si carried out simulation test on the acceleration and constant speed for tracked vehicles to verify the validity of the simulation model [1]. Yong Yan analyzed and evaluated the ride performance of tracked exploration vehicle by measuring their accelerations of different positions [2]. Yilong Wei and Zhihong Cheng performed the analysis of robot vehicles using the principle that the changes of robot vehicles angles affected by topography can reflect the stable performance of suspension [3]. Haitao Cheng and Jun Kong used the acceleration signal to make a survey of running stability of subway vehicles [4]. Baogang Duan modeled multi-tracked vehicles, and modeled their hydraulic systems with AMESim software, conduct modeling research and simulation analysis on the whole vehicle with Joint dynamic models [5].In this article, RecurDyn software is used to establish the model of cracked robot, and simulation tests are carried out to for cracked robots on the hard bumps and slopes of roads. In order to ensure the stability of the cracked robot driving, Suspension system parameters are differently selected and simulation compared. The ride performance of tracked robots does not yet have a standard evaluation program, so this test scenario refers to the measurement methods of wheeled robots, making an analysis and evaluation on ride performance bymeasuring the acceleration of its center of mass. The constructed model’s dynamic simulation tests of cracked robots under different suspension system parameters provide a direct reference for the design and optimization of the model of cracked robots.II. T HE INTRODUCTION OF TRACKED ROBOT STRUCTURE In Figure 1, 1 is a caterpillar preloaded wheel; 2 is a tracked belt; 3 is a tracked robotic suspension system; 4 is a supporting wheel; 5 is a driving wheel. Suspension system ensures that the machine is running smoothly, and the acceleration will not lead to great changes in the verticaldirection.Fig.1 Tracked robot structure diagramTracked driving device, which consists of two closed tracks, two idler wheels, two driving wheels and ten road wheels, uses the two rotated parallel closed track belts to complete the movement of the vehicle body, as shown in Figure 1. There are elastic and damping elements between the road wheel and the vehicle body to reduce vibration during movement of the vehicle, which is the suspension system in this case. In addition, the inducer is also equipped with tracked tensioning device to adjust the degree of tension, ensuring the stability of the tracked links in the process of driving [6,7]. III. T HE SIMULATION ANALYSIS OF TRACKED ROBOT MODEL A. The establish of tracked robot experimental modelSmall Track-robot platform must have a high degree of flexibility as well as excellent off-road capability [8]. The mechanical properties of its structure and the use of environment are both complex, and thus the design of suspension system and parameter selection work is very difficult. The study of tracked vehicles has been in the foundation of "Experience + test" a long time after the appearance of tracked vehicles. And the traditional research model is based on empirical formulas and extensive tests with much cost and long development cycle [6].Proceeding of the 2015 IEEEInternational Conference on Information and AutomationLijiang, China, August 2015During the study, we make a research using multi-body dynamics simulation software RecurDyn. Since the establishment of the model and the constraints is too complex in modeling with SolidWorks, the use of low-speed tracked module is more convenient[9].1) The establishment of driving wheel modelThe main function of the driving wheels: in driving conditions, the driving torque is changed into the tension that transferred from transmission to the driving wheels by driving tracked belts; in braking condition, braking torque coming from brakes turns to track brakes. In simulation, tooth surface shape of the driving wheels, which plays a major role in driving, has a great influence on the simulation results[6]. Creat the driving wheels in the subsystem o software Track / LM subsystem, select Track (LM) tab, click Create Sprocket, then enter its parameters defined interface to complete the definition, shown in Figure 2.Fig.2 Sprocket parameter adjustment interface2) Track ring systemBecause of the existence of the caterpillar, the tracked robot becomes a very complicated dynamic system for the multi contact collision. The track ring is composed of a lot of crawler plates connected with the pin, and it and other wheel joint constitute the crawler system[6]. The low speed caterpillar studied in this paper is equipped with the inducer wheel to ensure that the track is not divorced from the load wheel when the transmission is driven. The basic structure size of the crawler board is shown in Figure 3.Fig.3 The basic structure of the track shoe size3) Model construction of whole crawler robotIn the previous basis, first of all the body model of the tracked robot was made according to the requirements of design. Then according to the design size and location of the drive wheel and the guide wheel, we have designed them, as shown in Figure 4.Fig.4 The basic body parts model diagramThe crawler robot uses the crawler traveling device to support its own weight, and the torque transmitted through the transmission device is transformed to the traction force through the interaction between the track and the ground, and realizes its movement. Because the track can be used as the vehicle's own road, it is easy for the vehicle to pass through the bearing capacity of the ground. The track can travel in which the wheel vehicle cannot pass through the road and the sand etc[6]. Track is a more versatile driving tool, the overall modelas shown in Figure 5.Fig.5 Tracked Robots overall modelB. Simulation test of tracked robotThe key and difficult points of the virtual prototype technology for the robot system simulation analysis are the establishment of the correct mechanical model. The aim is to make it closer to the actual situation, and then predict and evaluate the overall performance of the tracked robot[6]. In this study, mainly through regulating suspension system parameters of tracked robot model to ensure the stability of tracked robot when driving on the road, so as to ensure the tracked robot model is established for the science and innovation. In this paper, the simulation steps of tracked robot model can be divided into six steps: to build a mechanical system,addconstraint structure and drives, setting pavement, simulation, simulation results analysis, the simulation results verify. 1) Adding structure constraints and driversAfter the establishment of the model of the robot system of the crawler robot, it is necessary to guarantee the freedom of movement by adding structure constraints, as shown in table I.TABLE IConstraint between the various components of robotMember name Number Restriction Remarks Wheel 10 Revolute Load bearing shaftDrive wheel 2 Revolute Drive shaft Guide wheel 2 Revolute Guide shaft Load bearing shaft 10 Fixed Long link 、Short linkShock absorber left 10 Revolute Short link Shock absorber right 10 Revolute Spring pin The left of the spring 2 Fixed Immobile block The right of the spring2 Fixed Guide wheel Rotating shaft 10 Fixed Robot body Drive shaft 2 Fixed Robot body Guide shaft 2 Fixed Robot body Immobile block 2 Fixed Robot body Tracked plate233BushingTracked plateAfter the structure constraint of the crawler robot is added, the driving force of the rotating part of the driving wheel is needed to ensure that the tracked robot can have the driving power, as shown in Figure 6.Fig.6 Adding body driving map2) Construct pavement modelRecurDyn provides two methods of setting up soil model: one is to define the soil model by the general contact force, and one is based on the theory of Beck to define the soil model [6,10]. In this paper, the general contact force theory is used toestablish the hard surface model, and two kinds of simulation pavement are provided, such as the bumpy road and the slope pavement, as shown in Figure 7.abFig.7 The vehicle and the road overall model: a) The robot bumps thepavement. b) Robot in the ramp pavement.3) Simulation experimentIn the dynamic simulation, the number of simulation steps of the unit time is more or the step size is shorter, the more real simulation results are reflected, but the disadvantage is that the simulation time will be long. In this simulation, the simulation time of the two pavements is six seconds and eight seconds. The crawler robot can finish the whole road, and the simulation can reach the experimental requirements. The driving speed of the engine is converted into the driving angle of the driving wheel by the chain drive, according to the design requirement. In the process of simulation, the suspension system vibration absorber used a number of different parameters in order to make a comparison reference [7]. Finally, only the most convincing parameters of the three groups of suspension system are listed. Through the stability judge index, it can provide the effective basis for the model design of crawler robot. 4) Simulation result analysisTo prevent confusion, the first description of the suspension system shock absorber parameters. Suspension system shock absorber parameters are mainly refers to the stiffness coefficient of the elastic element and the damping coefficient of the damper. Elastic element is used to cushion the vibration and the damping element is used to consume the energy of vibration. By changing the parameters of the suspension system to observe the mass center of the vehicle, the parameters of the suspension system are determined.In order to reflect the traveling smoothness of the tracked robot, we introduce the vibration acceleration. The actual vibration of the tracked robot will be more directly reactive, and it can provide reliable basis for the stability of the tracked robot.Simulation curve consists of three parameters respectively corresponding to the bumps and sloping surface vibration acceleration and acceleration of partial enlargement. two road vibration acceleration as shown in Figure 8[9].abFigure.8 under three kinds of conditions, vibration acceleration of robot centroid ：a) acceleration of the centroid of the robot under the bump. b)acceleration of centroid of robot under slope pavement.In the process of two kinds of pavement simulation, the initial state of the crawler robot is suspended. When the robot falls off the ground, the centroid of the tracked robot is larger and then tends to the normal value. Through the comparison of the data, it is not hard to find that the condition of the parameter two is the best. In the case of the parameter one, the observed curves of the bumps can be observed: the acceleration of the tracked robot is not symmetrical in the initial drop, which reflects the fact that the suspension system parameters are too small. In the case of two pavements, the parameters of the three case are similar to the parameters of the two case. However, the observed curves of the bumps can be observed: although its acceleration value is symmetric in the fall in the case of parameter three, its acceleration value is large. In order to explain the optimum of the parameters two more directly, we delete the time axis of the track robot falling down. In normal driving, the acceleration curve of the tracked robot is shown in Figure 9.abFigure.9 Three kinds of parameters under driving, acceleration of centroid when normal robot driving ：a) acceleration of the centroid of the robot underthe bump. b) acceleration of centroid of robot under slope pavement.Through the centroid curve of the tracked robot, the condition of the parameter two is the optimum parameters. Theacceleration of the parameter one is small, but the analysis of the acceleration curve of the bumpy road and the slope pavement shows that the parameters are too small and can't meet the design requirements. Parameter three can meet the design requirements, but it will be found after comparing with the parameter two that its numerical value is too large, which will lead to relatively strong vibration of tracked robot and does not meet the crawler robot driving stability index. 5) Simulation results verifyIn order to make the tracked robot model have better running smoothly, the suspension parameters of the crawler robot are adjusted by three groups, and the optimum parameters are obtained by simulation. The comparison between simulation parameters and theoretical values is shown in table II, and the simulation results are in good agreement with the results of theoretical calculation. The correctness of the model is verified.Table IISimulation results compared with theoretical value of suspension system oftracked robotAttributeSimulation valueTheoretical valueSpring 1 steel coefficient 8333 8234 Spring 2 steel coefficient 4583 4595 Spring 3 steel coefficient 4583 4595 Spring 4 steel coefficient 4583 4595 Spring 5 steel coefficient 11112 11045 Damper 1 damping coefficient 587 580 Damper 2 damping coefficient 4075 4083 Damper 3 damping coefficient 4075 4083 Damper 4 damping coefficient 4075 4083 Damper 5 damping coefficient98759816Among them, the coefficient of steel unit (N/m), damping coefficient unit (Ns/m)IV. C ONCLUSIONIn the RecurDyn environment, the simulation model of the tracked robot is established, and the vibration acceleration curve of the tracked robot centroid in the bumpy road and the slope pavement is obtained.A. The acceleration curve can be found: suspension system shock absorber parameter is different and tracked robot does have different driving state, so the simulation data can provide direct reference for the model design of the tracked robot.B. Through the simulation of the three groups of suspension system and the stability index, the better parameters of the suspension system are found. In the case of the parameters, the tracked robot can travel normally and the vibration is small, and it can meet the actual needs.C. Through the comparison of the better parameter by simulation and theoretical values, the model of the robot is reasonable in the initial design and can meet the design requirements.R EFERENCES[1]Q. Luo, D. Si, Z. Gong, X. Zhao. Dynamic simulation of TrackedVehicle Based on RecurDyn[J]. Vehicle and power technology, 2011,04:26-28+50.[2]Y. Yan. Research on the ride comfort of the mine trackedexploration vehicle [J]. Mechanical Engineer, 2014, 12: 176-178.[3]Y. Wei, Z. Cheng, H. Jiang, J. Zhang, Z. Li. The design andanalysis of the 6 wheel linkage suspension design for mobile robot[J]. Robot, 2013,06:665-671.[4]H. Cheng, J. Kong, X. Huang. Test of running stationary of metrovehicles[J]. Study on Urban Rail Transit, Study on Urban Rail Transit.[5] B. Duan. Research and simulation analysis of multi tracked vehiclemodeling[D]. Dalian University of Technology,2011. [6]Y. Chen. system dynamics simulation analysis of tracked vehicleAction[D]. Shenyang Ligong University,2012.[7]Ningbo Univ, Ningo, Shang, Weiyan; Qiu, Faju :Design andOptimization of the Suspension System on the Wheel-tracked Exploration Robot ,2011,pp. 294-298.[8]M. Hei. Design and kinematic analysis of tracked robotdeformation[D]. National University of Defense Technology,2010.[9] A. Chen, X. Mu, F. Du, H. Guo. Modeling and Simulation ofcrawler robot based on RecurDyn[J]. Mechanical design, 2013,10:36-39.[10]X. Chai. Study on the design of colloid buffer and suspensionsystem of a tracked vehicle[D]. North University of China,2010.。