Cobalt Robotics, a three-year-old startup building indoor security robots designed to work alongside human guards, today revealed that it’s secured $35 million in series B financing led by global investment firm Coatue. The capital infusion builds on a $13 million series A round in March 2018, bringing the San Mateo, California-based company’s total raised to nearly $50 million.

CEO Travis Deyle said the funding will support Cobalt’s nationwide expansion. “Security is fundamentally about trust and reputation, and it needs to be reinforced across all aspects of the company: founders, employees, technology, and financial backers,” he added. “Our financial backers — such as Bloomberg Beta, Sequoia Capital, and now Coatue — have been instrumental to our success so far, and they will be instrumental in our next phase of growth too.”

Cobalt’s five-foot cone-shaped, touchscreen- and LED-touting robots patrol workspaces along designated routes, leveraging AI and machine learning to spot anomalies like open doors, environmental risks, and intruders and call for human assistance when necessary. They’re capable of traversing both brightly and dimly lit environments thanks to over 60 sensors (including a 360-degree RGB sensor, infrared sensors, a thermal camera, depth and ultrasonic sensors, lidar, and environmental sensors), and they integrate with existing security platforms and a cloud-based performance monitoring dashboard.

The roving robots optionally scan badges and act as a mobile PA system and siren, and autonomously dock when they begin to run low on juice. And courtesy a recently introduced door integration capability, they’re able to pass through closed-off areas by communicating wirelessly with access control readers.

Cobalt customers pay a monthly subscription fee that includes access to the robots, software upgrades, and support from remotely based specialists. Deyle pitches it as a complement to — but not a replacement for — existing systems like manned security guards and access control systems (ACS).

“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 Deyle.

Cobalt isn’t the only one chasing after a physical security market expected to reach nearly $119.4 billion in 2023. There’s Knightscope security, which plans to raise over $50 million in what it hopes will be its pre-IPO financing, and Dutch startup Robotic Security Systems. Other rivals include Rapyuta Robotics, Aptonomy, and Otsaw Digital.

Cobalt says it’s established a veritable foothold, though, with deployments at facilities belonging to companies in technology, defense, finance, and manufacturing segments, including several in the Fortune 50. In anticipation of further growth, Cobalt this year expanded its engineering and operations teams and enhanced its security and facilities teams, according to Deyle.

“We believe Cobalt’s robotic security guards are revolutionizing the security services space and providing an unmatched experience for customers,” said Coatue partner Kris Fredrickson. “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.”