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End-to-End Training of Deep Visuomotor Policies

Sergey Levine, Chelsea Finn, Trevor Darrell, Pieter Abbeel

2015 · arXiv

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From the abstract

Policy search methods can allow robots to learn control policies for a wide range of tasks, but practical applications of policy search often require hand-engineered components for perception, state estimation, and low-level control. In this paper, we aim to answer the following question: does training the perception and control systems jointly end-to-end provide better performance than training each component separately? To this end, we develop a method that can be used to learn policies that map raw image observations directly to torques at the robot's motors. The policies are represented by deep convolutional neural networks (CNNs) with 92,000 parameters, and are trained using a partially observed guided policy search method, which transforms policy search into supervised learning, with supervision provided by a simple trajectory-centric reinforcement learning method. We evaluate our method on a range of real-world manipulation tasks that require close coordination between vision and control, such as screwing a cap onto a bottle, and present simulated comparisons to a range of prior policy search methods.

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8 selected excerpts · 8 total mentions

WilliamDhalgren
Neutral mention · rule
> AlphaGo essentially baked good movies into value and policy network by playing millions of times. I don't think that's a very good description of how AlphaGo was trained at all; you're essentially saying it merely overfits the training set, yet it clearly generalizes rather well to unseen board situations and still evaluates them sucessfully. No machine learning system would be found usefull if all it could do is merely memorize the training data. Re the use of deep reinforcement learning, well for one the role of reinforcement learning in the first version of AlphaGo, the one described in the Nature paper was rather limited, and a small part of its training; it just…
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made a ~3d KGS policy network into a ~5d KGS bot, and used to generate a training sample for the value net. If we had enough recorded human games to train the value net directly, that'd be an unnecessary step anyhow. And you could create such a training set w/o reinforcement learning since there are pure monte carlo bots stronger than 5d KGS - but that'd be far more computationally expensive. But its still not really true that there aren't obvious applications of deep reinforcement learning - indeed robotics is one promising application, and that seems rather relevant. this paper initially demonstrated an impressive improvement in manipulative tasks, and you can prob follow its numerous citations for newer stuff: http://arxiv.org/abs/1504.00702 I do agree that this exact architecture in AlphaGo prob doesn't have applications beyond just teaching us how to play go better; it seems too specialized. I believe they mean it in just the vaguest possible sense; that the kind of deep algorithms demonstrating incredible performance in AlphaGo have diverse applications; but this should not come as a surprise to anyone even loosely following what people have done with deep learning in the past couple of years anyhow.
deepnet
Neutral mention · rule
A Hinton inspired speculation about a Robot that plans & communicates. I posit that general A.I. must be embodied to develop, it must learn from the real world by interacting with it and learn by trial and error. Deep learning is a huge leap for AI. It learns best from raw data. Babies learn motor control & input interpretation first[1]. Moravec's paradox proposes learning these basics are the hard foundation that higher levels of reason build on. Abeel and Levine's work[2] where robots learn robust functions to map from pixels to motor torques for domestic tasks show solutions built on features learnt from raw data are more resilient than hand-engineered ones. These…
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trajectories through motor-torque space to produce a desired goal are intriguingly like planning. Mikolov's[3] Word2vec & Radford's Image Vectors[4] produce semantic spaces where vector math is akin to reasoning. Higher level control could be achieved through vector algebras deriving actions and things directly from the robots internal vector space of motor-torques and raw-pixels Thus internal vectors are like thoughts[5] which can interpret, reason, plan, and control. Karpathy shows internal vectors can bridge modalities from words to pictures[6]. If the higher level control vectors of actions and things could translate to the modality of language as verbs and nouns, perhaps the robot could discuss its plans, and receive orders. [1] - Thelen's Infant Development http://www.ncbi.nlm.nih.gov/pubmed/17107442 [2] - Levine, Finn, Darrel, Abeel http://arxiv.org/abs/1504.00702 & [2b] - Distributed Grasp Learning http://googleresearch.blogspot.co.uk/2016/03/deep-learning-f... [3] - Mikolov, Chen, Corrado, Dean http://arxiv.org/abs/1301.3781 [4] - Radford, Metz, Chintala https://github.com/Newmu/dcgan_code#arithmetic-on-faces [5] - Hinton https://youtu.be/IcOMKXAw5VA?t=32m55s [6] - Karpathy https://youtu.be/ZkY7fAoaNcg?t=38m31s
jpfr
Neutral mention · rule
Prototypical case of the 80/20 rule. He has implemented the happy case. But that system is nothing people realistically would want to drive their cars. What he did is impressive. But the results are not that outlandish for a talented person. 1) Hook up a computer to the CAN-Bus network of the car [1] and attach a bunch of sensor peripherals. 2) Drive around for some time and record everything to disk. 3) Implement some of the recent ideas from deep reinforcement learing [2,3]. For training, feed the system with the oberservations from test drives and reward actions that mimick the reactions of actual drivers. In 2k lines of code he probably does not have a car model that…
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can be used for path planning [4] (with tire slippage, etc.). So his system will make errors in emergency situations. Especially since the neural net has never experienced most emergencies and could not learn the appropriate reactions. And guess what, emergency situations are the hard part. Driving on a freeway with visible lane markings is easy. German research projects autonomously drove on the Autobahn since the 80s [5]. Neural networks were used for the task since about the same time [6]. [1] http://www.instructables.com/id/Hack-your-vehicle-CAN-BUS-wi... [2] http://arxiv.org/abs/1509.02971 [3] http://arxiv.org/abs/1504.00702 [4] http://www.rem2030.de/rem2030-wAssets/docs/downloads/07_Konf... [5] https://en.wikipedia.org/wiki/Eureka_Prometheus_Project [6] http://repository.cmu.edu/cgi/viewcontent.cgi?article=2874&c...
zhanwei
Neutral mention · rule
It seems to me to be all about having the right prior and planning for exploration. Policy search methods (http://arxiv.org/abs/1504.00702) assume that there aren't many trajectories that make sense (based on prior knowledge/testing in simulator) and search for the best ones among those that make sense using real-world data. Even within policy search you need some kind of exploration such injecting gaussian noise in trajectories. The hard part is to come up with a model for exploration.
davmre
Neutral mention · rule
The point is that supervised training on large networks requires millions or billions of examples. In RL, that means potentially billions of execution trajectories, which can be really expensive if you're executing on an actual, physical robot. And even then, supervised classification objectives are more informative than just a scalar reward: when a supervised system makes a wrong prediction you don't just tell it "sorry, that's wrong", you also tell it what the right prediction would have been. That extra information is really valuable for learning. In the black-box RL setting, you only see whether what you did was right or wrong, not what the right thing would have been…
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to do. And unlikely a classification system where the output space is relatively small (ImageNet has 1000 classes), an RL agent is searching over an exponentially large space of possible trajectories. Which means that without some additional source of supervision you can spend a long time wandering in the wilderness with no idea of whether what you're doing is reasonable or how to get any reward at all. And when you do get some reward, you have no idea which of the possibly hundreds or thousands of actions you took deserves the credit. A lot of recent RL research is about finding additional sources of supervision, such as training an agent to mimic the policy of an "expert" (e.g., a search algorithm that runs in a simulator to find an optimal solution, but which requires too much computation to actually apply directly at test time, as in http://arxiv.org/abs/1504.00702), or coming up with proxy objectives like "empowerment" or "curiosity" (which you can define in terms of information theoretic quantities, such as mutual information between the agents' action sequence and future state, e.g. http://arxiv.org/abs/1509.08731) to supplement the actual reward signal. This latter path, the notion of "intrinsic reward" that paulsutter alluded to, is in some sense the merger of RL with unsupervised learning, and a lot of the power is that you're getting new reward signals constantly, not just when you finally manage to achieve some arbitrarily difficult task.
nl
Neutral mention · rule
I don't know enough robotics to follow the paper[1] entirely, but this seems the relevant part for your question: We evaluated our method by training policies for hanging a coat hanger on a clothes rack, inserting a block into a shape sorting cube, fitting the claw of a toy hammer under a nail with various grasps, and screwing on a bottle cap. The cost function for these tasks encourages low distance between three points on the end-effector and corresponding target points, low torques, and, for the bottle task, spinning the wrist. The equations for these cost functions follow prior work.[23] The reference 23 points at S. Levine, N. Wagener, and P. Abbeel. Learning…
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contactrich manipulation skills with guided policy search. In International Conference on Robotics and Automation(ICRA), 2015. I haven't read that paper yet. Interestingly, they initialise the visual learning model using the ImageNet images. Was it 3 years ago that was considered a pretty much intractable problem, and now the fact a CNN can work on it well enough to be useful isn't even worth a complete sentence. [1] http://arxiv.org/pdf/1504.00702v1.pdf
deepnet
Neutral mention · rule
The 1st A.I. winter was 1973 when Donald Michie's work was eviscerated by the Lighthill report. Edinburgh University, under Michie, was leading the world in A.I. Michie, Ambler & Popplestone's 1969 Freddy Robot could assemble scattered bricks using A.I. vision & GOF symbolic AI. Michie (& Chambers) BOXES algorithm was succesfully learning to balance poles using reinforcement learning, from raw-sensor data outputting motor torques, real robotics trained end-to-end not simulated. Edinburgh had a rival LISP known as POPLOG (Popplestone & Burstal) used UK & Europe wide. BOXES was akin to todays Neural Nets. Geoff Hinton attended Edinburgh briefly in the aftermath. What might…
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have been ? Edinburgh had both symbolic A.I. planning, a working vision system & pragmatic bottom up machine learning until '73 & Lighthill. Edinburgh's was a unique approach - with bigger budgets the American labs favoured simulation (until 1985 when Rod Brooks showed it was a dead end) and without BOXES, Freddy became RAPT, symbolic, programmed GOFAI & no learning. RAPT failed because top-down reasoning was a computational quagmire in the real world & it was too fragile to the slightest decalibration. Edinburgh's hybrid GOFAI & behavior-based approaches got round calibration issues with SOMASS, Eddie & Push-Slide. But programmed solutions lacked the crucial element of learning - Michie's BOXES. Concurrently, Michie, exiled to Glasgow & private industry, found great success helping the Japanese revolutionise the assembly line & in the US with automated factory control & satellite piloting for NASA. All reinforcement learnt using BOXES but he & AI were pariah in the UK as he laments in 1987: [Michie from 18:24] http://www.bbc.co.uk/iplayer/episode/p0306rt1/micro-live-ser... Michie's nascent hybrid of raw sensor machine learning & GOFAI embodied in robots is just being rediscovered in Abeel & Levines work today. http://arxiv.org/abs/1504.00702 An AI winter is a terrible thing. Progress lost decades. Tragically the 2002 fire may have destroyed Michie's undigitised archive.
deepnet
Neutral mention · rule
Learning motor torques directly from vision is a very important result. https://youtu.be/EtMyH_--vnU This talk by Sergey Levine, Pieter Abbeel's PostDoc outlines Berkley's end-to-end deep-training visuomotor control in detail. Here is the paper : End-to-End Training of Deep Visuomotor Policies, Sergey Levine, Chelsea Finn, Trevor Darrell, Pieter Abbeel. http://arxiv.org/abs/1504.00702

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