Tag Archives: autonomous
#436180 Bipedal Robot Cassie Cal Learns to ...
There’s no particular reason why knowing how to juggle would be a useful skill for a robot. Despite this, robots are frequently taught how to juggle things. Blind robots can juggle, humanoid robots can juggle, and even drones can juggle. Why? Because juggling is hard, man! You have to think about a bunch of different things at once, and also do a bunch of different things at once, which this particular human at least finds to be overly stressful. While juggling may not stress robots out, it does require carefully coordinated sensing and computing and actuation, which means that it’s as good a task as any (and a more entertaining task than most) for testing the capabilities of your system.
UC Berkeley’s Cassie Cal robot, which consists of two legs and what could be called a torso if you were feeling charitable, has just learned to juggle by bouncing a ball on what would be her head if she had one of those. The idea is that if Cassie can juggle while balancing at the same time, she’ll be better able to do other things that require dynamic multitasking, too. And if that doesn’t work out, she’ll still be able to join the circus.
Cassie’s juggling is assisted by an external motion capture system that tracks the location of the ball, but otherwise everything is autonomous. Cassie is able to juggle the ball by leaning forwards and backwards, left and right, and moving up and down. She does this while maintaining her own balance, which is the whole point of this research—successfully executing two dynamic behaviors that may sometimes be at odds with one another. The end goal here is not to make a better juggling robot, but rather to explore dynamic multitasking, a skill that robots will need in order to be successful in human environments.
This work is from the Hybrid Robotics Lab at UC Berkeley, led by Koushil Sreenath, and is being done by Katherine Poggensee, Albert Li, Daniel Sotsaikich, Bike Zhang, and Prasanth Kotaru.
For a bit more detail, we spoke with Albert Li via email.
Image: UC Berkeley
UC Berkeley’s Cassie Cal getting ready to juggle.
IEEE Spectrum: What would be involved in getting Cassie to juggle without relying on motion capture?
Albert Li: Our motivation for starting off with motion capture was to first address the control challenge of juggling on a biped without worrying about implementing the perception. We actually do have a ball detector working on a camera, which would mean we wouldn’t have to rely on the motion capture system. However, we need to mount the camera in a way that it would provide the best upwards field of view, and we also have develop a reliable estimator. The estimator is particularly important because when the ball gets close enough to the camera, we actually can’t track the ball and have to assume our dynamic models describe its motion accurately enough until it bounces back up.
What keeps Cassie from juggling indefinitely?
There are a few factors that affect how long Cassie can sustain a juggle. While in simulation the paddle exhibits homogeneous properties like its stiffness and damping, in reality every surface has anisotropic contact properties. So, there are parts of the paddle which may be better for juggling than others (and importantly, react differently than modeled). These differences in contact are also exacerbated due to how the paddle is cantilevered when mounted on Cassie. When the ball hits these areas, it leads to a larger than expected error in a juggle. Due to the small size of the paddle, the ball may then just hit the paddle’s edge and end the juggling run. Over a very long run, this is a likely occurrence. Additionally, some large juggling errors could cause Cassie’s feet to slip slightly, which ends up changing the stable standing position over time. Since this version of the controller assumes Cassie is stationary, this change in position eventually leads to poor juggles and failure.
Would Cassie be able to juggle while walking (or hovershoe-ing)?
Walking (and hovershoe-ing) while juggling is a far more challenging problem and is certainly a goal for future research. Some of these challenges include getting the paddle to precise poses to juggle the ball while also moving to avoid any destabilizing effects of stepping incorrectly. The number of juggles per step of walking could also vary and make the mathematics of the problem more challenging. The controller goal is also more involved. While the current goal of the juggling controller is to juggle the ball to a static apex position, with a walking juggling controller, we may instead want to hit the ball forwards and also walk forwards to bounce it, juggle the ball along a particular path, etc. Solving such challenges would be the main thrusts of the follow-up research.
Can you give an example of a practical task that would be made possible by using a controller like this?
Studying juggling means studying contact behavior and leveraging our models of it to achieve a known objective. Juggling could also be used to study predictable post-contact flight behavior. Consider the scenario where a robot is attempting to make a catch, but fails, letting the ball to bounce off of its hand, and then recovering the catch. This behavior could also be intentional: It is often easier to first execute a bounce to direct the target and then perform a subsequent action. For example, volleyball players could in principle directly hit a spiked ball back, but almost always bump the ball back up and then return it.
Even beyond this motivating example, the kinds of models we employ to get juggling working are more generally applicable to any task that involves contact, which could include tasks besides bouncing like sliding and rolling. For example, clearing space on a desk by pushing objects to the side may be preferable than individually manipulating each and every object on it.
You mention collaborative juggling or juggling multiple balls—is that something you’ve tried yet? Can you talk a bit more about what you’re working on next?
We haven’t yet started working on collaborative or multi-ball juggling, but that’s also a goal for future work. Juggling multiple balls statically is probably the most reasonable next goal, but presents additional challenges. For instance, you have to encode a notion of juggling urgency (if the second ball isn’t hit hard enough, you have less time to get the first ball up before you get back to the second one).
On the other hand, collaborative human-robot juggling requires a more advanced decision-making framework. To get robust multi-agent juggling, the robot will need to employ some sort of probabilistic model of the expected human behavior (are they likely to move somewhere? Are they trying to catch the ball high or low? Is it safe to hit the ball back?). In general, developing such human models is difficult since humans are fairly unpredictable and often don’t exhibit rational behavior. This will be a focus of future work.
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Posted in Human Robots
#436174 How Selfish Are You? It Matters for ...
Our personalities impact almost everything we do, from the career path we choose to the way we interact with others to how we spend our free time.
But what about the way we drive—could personality be used to predict whether a driver will cut someone off, speed, or, say, zoom through a yellow light instead of braking?
There must be something to the idea that those of us who are more mild-mannered are likely to drive a little differently than the more assertive among us. At least, that’s what a team from MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) is betting on.
“Working with and around humans means figuring out their intentions to better understand their behavior,” said graduate student Wilko Schwarting, lead author on the paper published this week in Proceedings of the National Academy of Sciences. “People’s tendencies to be collaborative or competitive often spills over into how they behave as drivers. In this paper we sought to understand if this was something we could actually quantify.”
The team is building a model that classifies drivers according to how selfish or selfless they are, then uses that classification to help predict how drivers will behave on the road. Ideally, the system will help improve safety for self-driving cars by integrating a degree of ‘humanity’ into how their software perceives its surroundings; right now, human drivers and their cars are just another object, not much different than a tree or a sign.
But unlike trees and signs, humans have behavioral patterns and motivations. For greater success on roads that are still dominated by us mercurial humans, the CSAIL team believes, driverless cars should take our personalities into account.
How Selfish Are You?
About how important is your own well-being to you vs. the well-being of other people? It’s a hard question to answer without specifying who the other people are; your answer would likely differ if we’re talking about your friends, loved ones, strangers, or people you actively dislike.
In social psychology, social value orientation (SVO) refers to people’s preferences for allocating resources between themselves and others. The two broad categories people can fall into are pro-social (people who are more cooperative, and expect cooperation from others) and pro-self (pretty self-explanatory: “Me first!”).
Based on drivers’ behavior in two different road scenarios—merging and making a left turn—the CSAIL team’s model classified drivers as pro-social or egoistic. Slowing down to let someone merge into your lane in front of you would earn you a pro-social classification, while cutting someone off or not slowing down to allow a left turn would make you egoistic.
On the Road
The system then uses these classifications to model and predict drivers’ behavior. The team demonstrated that using their model, errors in predicting the behavior of other cars were reduced by 25 percent.
In a left-turn simulation, for example, their car would wait when an approaching car had an egoistic driver, but go ahead and make the turn when the other driver was prosocial. Similarly, if a self-driving car is trying to merge into the left lane and it’s identified the drivers in that lane as egoistic, it will assume they won’t slow down to let it in, and will wait to merge behind them. If, on the other hand, the self-driving car knows that the human drivers in the left lane are prosocial, it will attempt to merge between them since they’re likely to let it in.
So how does this all translate to better safety?
It’s essentially a starting point for imbuing driverless cars with some of the abilities and instincts that are innate to humans. If you’re driving down the highway and you see a car swerving outside its lane, you’ll probably distance yourself from that car because you know it’s more likely to cause an accident. Our senses take in information we can immediately interpret and act on, and this includes predictions about what might happen based on observations of what just happened. Our observations can clue us in to a driver’s personality (the swerver must be careless) or simply to the circumstances of a given moment (the swerver was texting).
But right now, self-driving cars assume all human drivers behave the same way, and they have no mechanism for incorporating observations about behavioral differences between drivers into their decisions.
“Creating more human-like behavior in autonomous vehicles (AVs) is fundamental for the safety of passengers and surrounding vehicles, since behaving in a predictable manner enables humans to understand and appropriately respond to the AV’s actions,” said Schwarting.
Though it may feel a bit unsettling to think of an algorithm lumping you into a category and driving accordingly around you, maybe it’s less unsettling than thinking of self-driving cars as pre-programmed, oblivious robots unable to adapt to different driving styles.
The team’s next step is to apply their model to pedestrians, bikes, and other agents frequently found in driving environments. They also plan to look into other robotic systems acting among people, like household robots, and integrating social value orientation into their algorithms.
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Posted in Human Robots