Cobalt Robotics, a San Mateo, California-based maker of autonomous security robots, closed a $35 million Series B round of financing led by global investment firm Coatue. Cobalt, which raised its $13 million Series A round in March 2018, has now raised a total of $50 million in funding.

Founded in 2016, Cobalt said it will use the new funding to expand throughout the United States. The company’s five-foot robots patrol workspaces along designated routes and use machine learning to spot anomalies, including open doors, environmental risks and intruders. If necessary, the robots can contact remote human support team to interpret and act on issues.

The autonomous security robots include 60-plus sensors, scans badges, act as a mobile PA system and communicate with access control readers to open doors and pass through closed areas. Once the robot is getting low on battery, it will autonomously return to its charging station.

“Our goal is to combine the best parts of machines (unwavering attention, perfect recall, and super-human sensing) with the best aspects of people (warmth, responsiveness, and adaptability) to create service robots that dramatically improve the quality of life for everyone and fundamentally redefine the modern workplace,” said Cobalt CEO Dr. Travis Deyle.

Cobalt uses a Robotics-as-a-Service (RaaS) model that combines the autonomous patrolling robots with remote human specialists. The RaaS model includes a monthly fee, which also covers software upgrades, and lowers the barrier to entry for potential customers.

“We believe Cobalt’s robotic security guards are revolutionizing the security services space and providing an unmatched experience for customers,” said Kris Fredrickson, Partner at Coatue. “In addition, we have been thoroughly impressed with the team’s philosophy that a great physical security service should positively impact not only the company’s operations but its culture as a whole.”

The physical security market is expected to reach nearly $119.4 billion in 2023. So Cobalt is not the only company developing autonomous security robots. Its competitors include Aptonomy, Knightscope, Otsaw Digital, Rapyuta Robotics and Robotic Security Systems.