Scientists Develop New Formula for Energy-Efficient Robots

Army scientists have developed a new formula that is bringing fresh insight into how an energy-efficient legged robot could be built.

The paper was published in PLOS One. 

Changing Army Vehicle Development

The U.S. Army Combat Capabilities Development Command, or DEVCOM, along with Army Research Laboratory’s Drs. Alexander Kott, Sean Gart and Jason Pusey are coming up with new ideas for building autonomous military robotic legged platforms. The team is focusing on making them operate as efficiently as any other ground mobile systems. 

The use of such systems could alter Army vehicle development, and according to the scientists, they don’t yet know why legged, wheeled and tracked systems fit the same curve, but the new findings are a step forward.

“If vehicle developers find a certain design would require more power than is currently possible given a variety of real-world constraints, the new formula could point to specific needs for improved power transmission and generation, or to rethink the mass and speed requirements of the vehicle,” Gart said.

Developing the New Formula

The scientists were inspired by a 1980s formula that shows relationships between the mass, speed and power expenditure of animals, and they developed a new formula that can be applied to a wide range of legged, wheeled and tracked systems, like ground robots.

The team believes they are the first to assemble and study the relationships that emerge from this data, despite it being around for 30 years. The findings demonstrate that legged systems are as efficient as wheeled and tracked platforms.

Kott serves as the laboratory’s chief scientist. 

“In the world of unmanned combat aerial vehicle and intelligent munitions, there is a growing role for dismounted infantry that can advance, often for multiple days, and attack in the most cluttered terrain such as mountains, dense forests and urban environments,” said Kott. “That's because such terrain provides the greatest cover and concealment against the unmanned aerial vehicles. That, in turn, demands that dismounted infantry should be assisted by vehicles capable of moving easily in such a broken terrain. Legged vehicles — possibly autonomous-would be very helpful.”

Energy Efficiency

According to Kott, one of the problems with legged robots is that they seem to have poor energy efficiency, and this can limit teaming with Soldiers. 

“For the past 30 years, U.S. military scientists have addressed a number of challenges in developing autonomous vehicles,” said Kott. “Ground vehicles that maneuver on wheels or tracks, and air vehicles that resemble small airplanes which we call fixed wing and small helicopters, which are rotary wing, are now quieter and easier to integrate in troop formations. But for legged platforms, many hurdles remain elusive, and a huge one is making them energy efficient.”

Soldiers cannot afford to carry fuel or batteries for “energy-thirsty legged robots,” he said.

With the new formula, the team found out that human-made legged platforms should be as efficient as wheeled and tracked platforms. 

The team collected diverse ground mobile system data and studied combined systems like the Ford Model T. 

According to Gart, the research will help designers determine trade offs among power, speed and mass for future terrestrial robots for defense purposes. 

The formula could also approximate the amount of power required by a vehicle.

“The Army must develop feasible yet ambitious targets for tradeoffs among the power, speed, and mass of future terrestrial robots,” Kott said. “It is undesirable to base such targets on current experience, because military hardware is often developed and used for multiple years and even decades; therefore, the specifiers and designers of such hardware must base their targets-competitive yet achievable-on future technological opportunities not necessarily fully understood at the time of design.”