(Reuters) - U.S. military ground robots have proven their wartime worth over the past decade, with thousands deployed for roles like bomb detection and 750 destroyed in action, saving at least that number of human lives, the military says.

Most of them have been small vehicles operated from a distance using video feeds from cameras on the robots. The military is now working on systems that can carry out more and more tasks autonomously with limited human oversight.

Here are some of the systems in development.

CARGO UNMANNED GROUND VEHICLE - Based on Oshkosh Corp truck manufacturer's TerraMax driving system, the Cargo UGV would enable a single driver to control several trucks at the same time, reducing the number of people in jeopardy on roads in a war zone.

The TerraMax system uses a broad range of high-tech sensors to give the vehicle's computer a picture of the world around it. The chief sensor is a three-dimensional LIDAR, or light detection and ranging system, a technology similar to radar that lets the system develop a picture of the world around it.

A global positioning system coupled with detailed maps of the route helps the system navigate and keep itself on the road.

A half a dozen video cameras, including one infrared for darkness, help it build an image of the world around it, enabling it to drive on its own in areas where GPS fails, or allowing a remote operator to take over and drive the vehicle from a nearby truck if the autonomous system runs into trouble.

The program has two more technical assessments, one in July and another at the end of August. Captain Warren Watts, the Marine Corps liaison with the project, said the program would then report to the Marine Corps Combat Development Command to decide whether to push ahead with work on the concept.

SQUAD MISSION SUPPORT SYSTEM - The Squad Mission Support System, currently being tested with troops in Afghanistan, looks like a golf cart's taller, tougher brother. Lockheed Martin bills the 5,000-pound (2,268 kg) system as the largest autonomous ground vehicle ever deployed with the infantry.

The mission of the SMSS is to carry the gear of foot soldiers who often find themselves toting packs weighing 100 pounds (45 kg) or more, which contributes to high levels of back injury.

It can carry some 1,200 pounds (544 kg) of gear. It can be driven, or allowed to drive by itself using points on an electronic map, or even programmed to follow behind a soldier at a fixed distance, regardless of whether the person is walking or running.

Four SMSS vehicles were deployed to Afghanistan at the end of 2011 and arrived at a forward operating base in January. Feedback has been positive, said project manager Myron Mills, and soldiers already are finding new and unexpected uses for the vehicles.

"When we originally envisioned the system, we envisioned that the soldiers would use it to carry their packs plus extra water and ammunition and MREs (meals ready to eat) and heavy weapons and things like that," he said.

"They have done all those things with the system, but in addition to that they've used the system to haul lots of field fortification and construction materials, like sandbags, concertina wire, fencing material and things like that," Mills said.

LEGGED SQUAD SUPPORT SYSTEM - A robot being developed by Boston Dynamics poses an extra challenge compared to the Oshkosh and Lockheed vehicles. In addition to navigating its environment, the Legged Squad Support System, or LS3, must be able to maintain its balance on four limbs while carrying a load.

Like the SMSS, the LS3 - dubbed the Alpha Dog - is designed to carry gear for a squad of ground troops.

Mark Raibert, head of Boston Dynamics, said the biggest challenge in developing the Alpha Dog was not perception but scaling up the robot from smaller versions of the technology while keeping the weight at the target 1,250 pounds (567 kg) including fuel and payload.

The vehicle, which is powered by a gasoline engine that drives a hydraulic system, underwent a limited prototype test in January. The company is working toward a first release of the robot in the early fall this year, with some initial ground tests toward the end of the year, Raibert said in an e-mail.

(This version of the story was corrected to fix the name of Lockheed's Squad Mission Support System in paragraph 9)

(Reporting By David Alexander; Editing by Will Dunham)