Don’t miss the first part of this post, “Creating a Monster with Simpack,” to learn about where Zollner Electronik AG engineers got their idea for designing the dragon and how they used SIMULIA‘s Simpack to bring fantasy to life.
Making a Dragon Move
Over 100 subassemblies (CAD geometries and mass properties) were imported into Simpack via ProSIM. Each component had different functions and subsequently different effects on the overall performance of the machine.
Because of the high number of moving parts and their combined overall weight, getting the robot to walk was an especially difficult task. Zollner engineers realized early on that evaluating contact and friction forces between the four feet and the ground was a priority. There were many variables that affected the stresses in the feet while walking, including the influence of wobbling masses such as the motor and hydraulic pumps or the weight of compressed oil within the cylinder.
To identify suitable stiffness and damping values, the team ran a variety of simulations to assess the range of flexibility of the leg subassemblies. They found that by optimizing the trajectory of each individual leg, the force from the impact of stepping on the ground could be reduced.
With the legs functioning as desired, walking and movement tests were then run on the robot as a whole—traversing a flat plane or a slope, moving in an arc, and turning on the spot. Simulating these stepping cycles provided information needed to strengthen the legs to prevent lateral buckling. The team then optimized the location of the components connected to the torso, and the motions of the neck and tail, by evaluating Tradinno’s total center of mass while walking.
Additional tests were done on the wings to find the best possible balance between weight and stability. The engineers also found ways to stabilize the dragon in the rare event of a complete front-leg failure. “It was clearly important to eliminate any potential risk to festival attendees,” says Pfeffer.
For smooth operation of the beast in action the Zollner team used MATLAB’s SIMAT interface in conjunction with Simpack to run closed-loop control tests to ensure that when the operator pressed a button on the controller, the robot would automatically perform the designated function. “Simpack was used to easily implement the geometry of the dragon to SIMAT and to connect it to MATLAB,” explains Pfeffer. “With SIMAT we simulated the control processes to be as realistic as possible—for example the motion of a walking leg. Our aim was to observe the behavior of the dragon’s hydraulics when it was walking and to determine whether or not the individual control circuits would interfere with one another.”
Simpack Simplifies Complexity
Zollner engineers value the simplicity of using Simpack for such complex design projects, where their team needs to work with maximum efficiency to produce high-quality, highperformance mechatronic systems.
“Simpack allows us to easily identify and solve design challenges,” says Pfeffer. “The software lets us know what works and what doesn’t, without the need for extensive field testing. If a design flaw is found, it also shows us exactly where and why the problem is occurring, making it easier for us to fix.”
With the world’s largest robot under their belt, there’s no telling what project the engineers at Zollner will tackle next, but it’s safe to say that Simpack will continue to play a key role in the design process of their next complex mechatronic assignment.
You can see their fire-breathing beast in action for yourself at the annual Further Drachenstich festival every August, or on the event’s website.
For More Information, visit Zollner Electronik AG’s website.
