It has been 16 years since iRobot introduced the Roomba robot vacuum cleaner.

Partly inspired by a novel robotics approach known as “fast, cheap and out-of-control,” the Roomba really was not much of a robot. It simply wandered around a room sucking up dust and debris. A second generation was able to autonomously make its way back to a recharging station.

It was a hit for iRobot, a spinoff from the Massachusetts Institute of Technology.

Since then, however, there have been waves of failed attempts to create more sophisticated home robotic products from companies in the United States, Japan, South Korea and Europe. There have been efforts to build humanoid robots, social companion robots, robots that cook, robots that do your dry cleaning, robots that fold your clothes and robots that change the kitty litter.

But there still is not a second successful home robot category beyond the humble vacuum cleaner.

Despite persistent optimism, roboticists and artificial intelligence (AI) researchers have learned that while computers can run mathematical circles around humans, things that humans do without thinking are the most difficult for machines.

Many researchers have come to believe that the recent breakthroughs in machine learning will not be enough to build robots adept at performing tasks in a home. That is likely to require several more technological breakthroughs.

The snail’s pace of development in home robots stands in striking contrast to the rapid advance of artificial intelligence in successful products such as Amazon’s Echo or even the Siri technology of iPhones.

“Not a single human has been replaced by a humanoid robot,” said Sebastian Thrun, the roboticist who started Google’s self-driving car program.

Japan and South Korea have been ahead of the United States in their enthusiasm for home robots, but companies there have had similarly disappointing results.

“At one point I remember the president of South Korea saying that there would be robots in most Korea homes by 2012,” said Tandy Trower, a software engineer who is focused on developing a mobile robot to permit older people to live independently at home. He said that while he remains optimistic that in the long run he will be able to develop a robot that acted as a partner or an assistant for aging people, he realizes that a commercial product is not on the near horizon.

Despite the repeated failures, many technologists remain optimistic that the home robot is just around the corner.

At Stanford University, roboticists are working on a next-generation robot that could potentially work in the home. Silvio Savarese, a computer scientist, is leading a team developing a robot called Jackrobbot. But getting it to move around a house is still difficult, even in a one-story home without stairs, he said.

Researchers at the University of California, Berkeley, are working on a robot that would wander the house picking up after its occupants. Ken Goldberg, a roboticist at the school, said the project faces two challenges: getting the price down to where such a device would be affordable, and getting people to be patient with the machine’s tedious pace.

“Doing anything time critical is difficult,” he said. “But if you are willing to leave the house and come back six hours later, the house is clean.”

His group also is experimenting with a robot that can make a bed — admittedly slowly, but he argues that it is not a task that has to be done at human speed.

Despite the new investments in research and development, veteran researchers are conscious that home robots have seemed imminent for decades.

“The problem,” said Kai-Fu Lee, a leading Chinese AI researcher, “is that low cost plus high expectations plus no patience makes it difficult to make a great product.”