Evolution of Quadruped Robots: Walking Truck vs. BigDog
Nearly 40 years after it was built, GE's Walking Truck quadruped robot was a major inspiration for Boston Dynamics' BigDog robot. Here's a comparison of Walking Truck and BigDog, what's changed and what still needs improvement.
The 1960s was certainly a time of change. Besides giving birth to hippies, an expanded distrust of government, and the Vietnam conflict, it also produced some interesting inventions, including GE’s Walking Truck. This four-legged vehicle was developed in 1968 for the United States Army to traverse rough terrain, with the idea that maybe something like the Walking Truck could be used in the jungles of Vietnam.
Each leg of the Walking Truck was controlled directly by a hydraulic system linked to the operator’s hands and feet. Despite its complexity, it was fairly easy to operate, requiring only about two hours of practice to train an operator. Because of the hydraulic control configuration, the operator could actually feel what he was stepping on or pushing. It could produce enough force to push a Jeep out of the way, and had the dexterity to balance on two legs.
Unfortunately, the Walking Truck also required 50 gallons of hydraulic oil per minute via an external hookup for operation. And despite its easy learning curve, using it exhausted the human operator after about 15 minutes. Funding for this project was cut, and we now have iconic images of helicopter fleets over Vietnam instead of, perhaps, Walking Trucks traipsing through the jungle.
The device now resides at the U.S. Army Transportation Museum in Fort Eustis, Virginia, now sporting stabilizing bars on its sides. These were meant to help in the case of a loss of balance.
BigDog Inspired by Walking Truck
Now 50 years later, man is still trying to replace our pack animals and all-terrain vehicles with something mechanical. One could see an era in the near future where pack-carrying soldiers and wheeled vehicles mingle with legged robots, similar to how animals and wheeled vehicles were used together in early 20th century military conflicts.
With four legs and near autonomy, Boston Dynamics’ BigDog, inspired by the Walking Truck nearly 40 years later, was designed to complement soldiers in the field, carrying their packs or other equipment into battle. At 2.5 feet tall and a weight of 240 pounds, this robot can carry a 340-pound load and climb up to a 35-degree slope. Perhaps “little mule” would be a more descriptive name for this pack bot, but that doesn’t really have the same ring to it.
Each leg is able to bend at the hip, knee, and ankle, for an interesting gait. The legs are powered by a hydraulic system pumped by a small 15 horsepower go-kart engine. The robot can be controlled via a soldier’s vest, or can be set up to follow its leader for hands-free use.
A newer version of BigDog, called “Spot,” weighs a slim 160 pounds. It is shown above traversing inside and outside, and seems to take abuse from humans in good form - or so the robots would have us believe before their uprising.
Mantis Hexapod Robot
Although it has six legs, the Mantis hexapod is quite reminiscent, in both scale and function, to the Walking Truck. Unlike the Big Dog series of robots, a person sits inside of Mantis. Although the operator doesn’t have to control each leg directly, it’s designed to work more like a vehicle than the mostly autonomous BigDog.
Power is provided by a 2.2 liter Turbo Diesel model, which pressurizes a hydraulic system, allowing the legs to move as needed. Impressively, the contraption was designed and built by a team of six people (including their financial backer). In addition to their dedication, this is certainly a testament to how far technology has come that this could be accomplished by such a small team.
The video above also shows it in action, pushing a trailer around with one of it’s legs around 0:45. Perhaps this is an intentional nod to the Walking Truck’s Jeep-moving ability. Also shown in the video, at around 1:00, Mantis can load itself onto a trailer, then fold its legs out of the way.
The Future of Walking Robots
Able to walk on four legs and push Jeeps out of the way as needed, the Walking Truck was an impressive feat of engineering. On the other hand, it required an operator to interact with each leg through a hydraulic system, and required an external tether.
Today, Boston Dynamics’ BigDog and Spot robots, and the Mantis Hexapod, each use a self-contained hydraulics system to actuate their appendages, now with advanced computer control.
Perhaps we could see the capabilities of the BigDog and Mantis in one robot in the future, able to carry a human operator and push heavy objects around, operating nearly autonomously. The human inside can then worry about more important tasks!