Robotic construction crew rolls up its sleeves

NASA researchers have successfully demonstrated the first use of multiple rovers that work together to perform tasks such as co-ordinated grasping, lifting and moving of an extended payload.

NASA researchers have successfully demonstrated the first use of multiple rovers that work together to perform tasks such as co-ordinated grasping, lifting and moving of an extended payload, while navigating through obstacles on natural terrain.

‘The Robotic Work Crew behaves a lot like its human counterpart might during a home construction project,’ said Paul Schenker, supervisor of the Mechanical and Robotics Technologies Group and principal investigator for the project at NASA’s Jet Propulsion Laboratory (JPL). ‘Consider the challenge two people face when transporting a long, heavy board through a busy work site,’

‘Each person alone, or in this case each rover, has a variety of behaviours for how to carry smaller things,’ Schenker explained. ‘The trick is to combine such individual behaviours to safely carry and manipulate bigger things. The rovers must share the workload and thinking, exchange important sensory cues and quickly comply with each other’s motions.’

During outdoor tests near JPL, in which the deployment of a solar power station was simulated, two such co-operating rovers autonomously approached, gripped and carried a 2.5-metre-long container over distances of more than 50 metre.

The Robotic Work Crew can reportedly traverse uneven, hazardous terrain. The crew visually detects and tracks its goal, identifies nearby objects in its path and works collectively to avoid obstacles. Throughout this process, the robots constantly update each other about payload forces and motions as felt at their respective grippers. If the beam is slipping, the rovers collectively sense the problem and compensate.

New software called Control Architecture for Multi-robot Planetary Outposts is the shared brain that commands the team of rovers. ‘The two robots tightly co-ordinate their individual sensory and control behaviours in an uncertain, fast-changing environment to accomplish a common goal,’ said Terry Huntsberger, project system engineer at JPL, who along with his colleague Paolo Pirjanian, led the development of the new control software.

‘The robot team robustly fuses this information into a bigger picture, coming up with a best co-operative control solution,’ Huntsberger continued. ‘We can easily add new behaviours and additional robots to the system. New behaviours can be simple, or more complex, with some behaviours building on top of numerous others already in place.’

The JPL researchers say the rovers function much like a construction crew without a foreman. They note that once the system has been programmed with basic behaviours and co-ordination models, it is a truly distributed and autonomous intelligence across the robot team that gets the job done, responding to situations of the minute.

‘Mars is hundreds of millions of miles from Earth; we can hardly predict every scenario the rovers may encounter or foresee every rock and hill,’ said Schenker. ‘But, it is possible to give two or more rovers a set of instinctively reactive behaviours, a shared network of sensing and control, and a democratic decision-making process that enables them to decide the best action strategies. Call it a case of robots networking for success,’ he said.