6 River Systems Inc., a developer of warehouse fulfillment robots cofounded by former executives of Kiva Systems LLC, announced Tuesday it has raised $6 million in financing from a group including iRobot Corp.

Boston-based 6 River Systems was founded in 2015 by executives from classroom technology provider Mimio and from Kiva Systems, the North Reading, Mass. firm that was acquired by Amazon.com Inc. in 2012 for $775 million after helping to pioneer the use of self-driving robots in warehouses.

Amazon has since rebranded Kiva as Amazon Robotics and ceased selling its products to any other companies, giving the e-commerce giant an advantage over its rivals in performing e-commerce fulfillment.

6 River Systems is now targeting that same application, with a mission to "redefine fulfillment automation for e-commerce and retail operations," the company website says. 6 River Systems plans to use the new funding to expand its engineering team and to support customer pilot programs now in progress.

"The acquisition of Kiva left a void in this space that has yet to be filled," Seth Winterroth of the early-stage venture fund Eclipse Ventures LLC, which joined iRobot in raising the investment, said in a statement. "This, coupled with rapid growth in e-commerce globally, has resulted in a need for next-gen automation tools."

By entering this market, 6 River Systems is joining a number of other robotics startups that are also aiming to follow Kiva's footsteps into the autonomous material handling systems business. Last week, the Canadian firm Clearpath Robotics Inc. rolled out a miniaturized model of its self-driving vehicle used in factories and warehouses. Other entries include Locus Robotics Corp. of Andover, Mass. and Harvest Automation Inc. of Billerica, Mass.

Despite only broad similarities to Kiva's approach of using robotic systems to automate fulfillment centers and cut labor costs, this new generation of companies may still face legal challenges in bringing their products to market.

Earlier this month, Harvest Automation pulled back on its plans to launch a robotic platform for shuttling merchandise around e-commerce warehouses, saying it lacked the marketing resources to break into the warehouse automation business. Instead, the company will continue to develop its sales in agricultural robotics applications such as plant nurseries, Harvest cofounder and CEO Charlie Grinnell told the Boston Globe.

In addition, some potential investors had concerns Amazon might sue for violating the patent portfolio it gained in the Kiva acquisition, but Grinnell called that scenario a red herring.

"We performed extensive IP freedom-to-operate research and always were able to convince investors that we were fine," Grinnell said in an email. "Our system is completely different from Kiva, so there really is no overlap once you look at the details."

Editor's note, March 31, 2016: This story has been modified from a previous version; the final two paragraphs were added.