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RecurDyn User Interview

• Hanwha R&E Center, Unmanned Technology Center
• Jin-Gyu Ock, Mechanism Part Chief

Q1. Thank you for agreeing to be interviewed. Please introduce yourself.

Hello, my name is Jin-Gyu Ock. I work at Hanwha R&E Center’s Unmanned Technology Center. I received my Ph.D. from Pusan National University’s Mechanical Design Engineering Department and CAELab under the supervision of Wan-Seok Ryu in 2009. I have been working for the Defense Industry Division of Hanwha Corporation since 2013. As Part Chief, I am in charge of the mechanism of unmanned robots. I specialize in multi-physical analysis that use multi-body dynamics, vehicle dynamics, optimum design, and fluid-structure interaction (FSI). Currently I work in the fields related to the manufacturing of mechanisms such as kinematic design, structural analysis, vibration analysis, and fatigue analysis..

Q2. Please tell us about Unmanned Technology Center.

The Unmanned Technology Center at the Hanwha R&E Center develops unmanned systems related to national security. The Unmanned Technology Center studies and develops unmanned systems, such as intelligent autonomous driving algorithms and networking, that are necessary for the unmanned technology business from small surveillance systems for the Army, Navy, and Air Force to the mid-to-large strategic systems by combining Korea’s world-class IT technologies with Hanwha’s system technologies. The systems that our center is currently developing can be largely classified into three types: Unmanned ground vehicles (UGVs), which are the ground weapon systems, unmanned underwater vehicles (UUVs), which are the unmanned underwater systems, and unmanned aerial vehicles (UAVs), which are the unmanned aerial systems.

Products Developed by the Unmanned Technology Center

Q3. Could you tell us the reason why you adopted RecurDyn?

When I came to the Unmanned Technology Center two and a half years ago, my first assignment was to perform the dynamic analysis of a ground robot using the multi-body dynamic analysis technology. Unmanned ground robots are composed of the main body that moves the robot, and the devices and sensors that are necessary for the role that the robot is expected to do. At the center, my colleagues had always used MSC and ADAMS as the dynamic analysis tool, so I did my task using ADAMS. At the time, the task was not difficult one, so, I could do my job without any problems.

Then I got the order to analyze a dynamic model of an unmanned ground robot by modeling the tracks of the robot accurately. This was a tough one to solve. The track belt of an unmanned ground robot is made of rubber. So, I needed to apply accurately the shape of the belt into the model and enter the property values of the belt accurately to derive the results that I wanted. Therefore, I thought about using RecurDyn, which could accurately apply the shapes of the contact objects and tracks. I decided to use the Track_LM toolkit that RecurDyn offered.

I was familiar with RecurDyn since I had used it in graduate school upon the recommendation of my advisor. So, I was not uncomfortable with the idea of using it again. But the problem was that the RecurDyn Track_LM toolkit was optimized for modeling and analyzing caterpillar tracks used for tanks and armored vehicles. Since RecurDyn only supported the caterpillar shapes provided by its library, it was not suitable for our system. As a matter of fact, the shape of the track belt that we were developing changed significantly depending on the weight of the platform. So, it was not an easy task to build a library containing the shapes that I wanted. After discussing it with the RecurDyn Technical Support team, I decided to find another way to solve the problem and gave up on the idea of using Track_LM.

Since I knew that RecurDyn was the best tool for solving contact problems, I studied the contact methods and analysis algorithms that Track_LM provides and developed an analysis method that is suitable for our system. I used the new modeling and analysis method to analyze the correlations between our system and the test and obtained an analysis accuracy of more than 90%. Analysis experts often say that an accuracy of 95% or higher is the realm of God, so you should be satisfied with an accuracy of 90% or higher. The results surprised me and made me to trust the RecurDyn’s contact algorithms even more. I’d like to the opportunity to thank the RecurDyn Development team, Jeong-Han Lee, Associate Manager at RecurDyn and an alumnus of CAELab, Pusan National University, as well as Woong-Sang Chung, Director of Optimal Design Corporation.

Q4. I am glad that you obtained good results using RecurDyn. What do you think are the merits of RecurDyn as a dynamic analysis software?

When I mentioned the reasons why I adopted RecurDyn, I mentioned its superior way of solving contact objects. And, above all, the best part is the technical support. I can call them anytime anywhere for technical support. When I was working on my doctorate, I tried to solve problems by myself instead of asking questions. Now that I am an employee of a company, I prefer calling the technical support team and asking questions. When I was in graduate school, people would scold me for asking questions without pondering on a problem deeply enough. But, it is a different story here. Why not call the technical support team and tell them your problems when you have them nearby? I think the fact that you can ask questions anytime anywhere is the best part of using RecurDyn, a local software program. Also, as I use RecurDyn, I often find myself comparing it with ADAMS. ADAMS’s Geometry Topology function is very convenient because it shows how the bodies are constrained to each other. This is something that I would like to see in RecurDyn, too.

[1] RecurDyn does not have this function, right?

Also, the coupled analysis of the dynamic analysis and structural analysis using RFlex and FFlex shows a very high accuracy. Even when I compare the results with Abaqus, which is frequently used for structural analyses, the accuracy is very high with an error of less than 1%. In addition, analyses performed together with control elements using Co-Link saves a lot of time.

Lastly, one of RecurDyn’s biggest advantages, I think, is the Import function and the shape management function in the Geometry tab. An engineer often uses Step files among the shape files when designing a mechanism, but ADAMS only recognizes Step files in 2D. To make it recognize them in 3D, you need to convert the files into Parasolid files and this is very cumbersome. But RecurDyn imports them in 3D, which is as convenient as a well-built CAD tool. Also, one of the main functions of RecurDyn is the Section View (Cutting Plane) function(2) in the Geometry tab. It allows you to analyze the mechanism design conveniently. There are thousands to ten thousands of bodies in an unmanned robot. So we need to know the correct constraint information between the bodies, and the Section View function is used for this purpose. Actually, this function is more convenient that CATIA, a CAD tool. The fact that I can use these features to manage my work hours efficiently is RecurDyn’s great merit.

Import and Section View Functions in the Geometry Tab

Q5. What would you like from FunctionBay?

Well, I was so excited to tell you all the good things about RecurDyn during the interview… When I stop to think about it, I tried to relay, as accurately as possible, how I feel when I use RecurDyn. In the next RecurDyn version, I would like to see an improvement in the analysis speed. I know that structural analysis programs have no physical restrictions in terms of supporting the parallel processing of a CPU. If I am correct, RecurDyn supports parallel processing but the number of CPU cores supported is restricted to 4. With the development of CPUs, there are some users who use computers with 8 or even 16 CPUs. If you were to get rid of the CPU restrictions for parallel processing and introduce an analysis using a GPU to improve the analysis speed, I would be very grateful when I use RecurDyn in the future. I hope you do well in Korea as well as in the world.

[1] RecurDyn V8R4 provides a function called RelationMap.

http://support.recurdyn.com/?p=3413 

[2] How to Use the Cutting Plane Function  

http://support.recurdyn.com/general-board/?mod=document&uid=51 

* This interview was provided by Optimal Design Corporation.