For a number of reasons, the right-angle joints make the robot operate in a more natural state. "We found that, if we put the motor on the joint directly, we encountered some odd mass distribution problems, whereas, by using the right-angle motor/gearhead assemblies... we didn't see that happening. Plus, the assembly helped with the location of the proper center of gravity for the robot itself," Ames said.
With the proper joint assemblies, the components acted in a very predictable manner, which was essential when creating the control interface. "You want everything to move exactly as the mathematics and control software dictates," Ames said. The assembly allowed for the high-torque motor to operate smoothly at slow speeds. The team installed larger sprockets and a chain for each of the six joints. The idea was that the chain would become the weakest link -- like tendons -- and would be less expensive to replace.
The team is working toward surpassing the ability of wheeled robots, by focusing on collected data that shows that humans display a walking behavior that mirrors a mass-spring damper system, which is one of the simplest mechanical systems. The team is now on the path to replicating that system by using a combination of motors and gearheads, along with proprietary electronics, which means that the AMBER 2 robot is well on its way to being one of the first dynamically walking robots in the world.
You can watch videos of the AMBER 2 robot here.
Deb Setters is national marketing manager for Maxon Precision Motors.