This robot runs, climbs, and opens doors -- without a gearbox

A patent-pending design makes this robot nimble enough to crawl through rough terrain. The Ghost Minitaur's creators say it can be used for search and rescue missions or as a platform for testing sensors for autonomous vehicles.
Written by Kelly McSweeney, Contributor

Ghost Robotics, a new R&D firm founded by University of Pennsylvania PhD candidates, has unveiled a dog-like robot that runs, climbs, leaps, and even uses its legs to open doors. While other research groups have already created similar adorable and functional robots (MIT's cheetah, for example), this one is different because it is completely gearless.

In technical terms, Ghost Minitaur is the first direct-drive legged robot using conventional rotary electric motors. What that translates to in real life is the patent-pending design eliminates the gearbox, which is a part that is expensive, complicated, and fragile. Direct drive also gives the motors the ability to act like springs, since the legs are adjusted and controlled via software instead of hardware.

Jiren Parikh, CEO of Ghost Robotics, tells ZDNet that getting rid of the gears helps minimize the equipment that stands between the robot and its environment, thus making the legs more sensitive and reactive. He says, "The legs have enough power to jump and do flips, but can also sense contact with an egg without breaking it. If it had gears, it would be much slower and tasks like this would be problematic."

Direct-drive legs

The robot's direct-drive legs don't require a gearbox. (Image: Ghost Robotics)

The Minitaur can be used as a platform to carry small payloads to hazardous environments where people can't or shouldn't travel. Traditional wheeled or tracked robots have trouble getting around rough terrain, but the direct-drive legs are agile.

Unlike traditional legged robots, this one "feels" the ground. Parikh explains:

We effectively use the motors, and the torque generated as sensors themselves. They are controlled to emulate springs, and then we estimate forces at the toe ('feeling the environment') by looking at how that virtual spring deforms. Again, direct-drive lets this 'feeling' work with high fidelity and very quickly. The robot is able to feel and react very quickly; in the door-opening task, it feels the knob then turns it around five times faster than the blink of an eye.

The unique sensing and traversing abilities mean it could be outfitted with sensors and then used to carry supplies for public safety, military missions, exploration of extreme environments, and search and rescue missions. For example, in a natural disaster, it could be deployed ahead of human aid workers to locate survivors, identify gas leaks, and check air quality. Minitaur could climb through debris and crawl into small areas to deliver essential supplies such as food, water, and medicine to people who are trapped under rubble.

It can also be used to develop and test the sensors that support autonomous vehicles -- an essential research task that will likely be in high demand now that NHTSA has rolled out a new policy for self-driving vehicles. Lastly, the "legs" of the robot can be integrated into other systems for applications in surgery, child and elderly care home robots, animal husbandry, lab applications, and food manufacturing.

Ghost Robotics is in its infancy, so the Minitaur has only been produced in small batches to date, with each robot selling for $10,000. However, the company's cofounder, Gavin Kenneally, told IEEE Spectrum that if production is scaled up, costs could drop to $1,500 per device.

Parikh said, "The devices are very fast, electric, and non-hydraulic, making them very low-cost to manufacture in volume."

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