Reinforcement Learning
Google's DeepMind AI grasps basic laws of physics
Google DeepMind's artificial intelligence team, alongside researchers at the University of California, Berkeley, has trained AI machines to interact with objects in order to evaluate their properties without any prior awareness of physical laws. The research project drew inspiration from child development and sought to train AI to mirror human capacity to interact with physical objects and infer properties such as mass, friction, and malleability. The study, entitled Learning to perform physics experiments via deep reinforcement learning, explained that while recent advances in AI have achieved'superhuman performance' in complex control problems and other processing tasks, the machines still lack a common sense understanding of our physical world โ 'it is not clear that these systems can rival the scientific intuition of even a young child.' Lead researcher Misha Denil and his team set about various trials in different virtual environments in which the AI was faced with a series of blocks and tasked with assessing their properties. In the first simulation, called Which is Heavier, the AI was given a set of four blocks which were the same size but varied in mass.
Jetson Developer Meetup
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Messing around with OpenAI Gym
First of all it might be useful to explain what OpenAI Gym actually does: OpenAI Gym aims to provide an easy environment to develop and test reinforcement learning algorithms. To be clear, OpenAI Gym doesn't power any algorithms itself, leaving it up to more specialised packages like TensorFlow or Theano. So what makes this the ultimate geek toy for AI-researchers? Well, this is because of the many environments OpenAI Gym provides, one of them being the'atari' environment. That's right, you can test the performance of your reinforcement learning algorithms on a variety of different atari games and what's more, you can automatically upload the performance of your algorithms and compare them to other people's approaches.
kidzik/osim-rl
OpenSim is a biomechanical physics environment for musculoskeletal simulations. Biomechanical community designed a range of musculoskeletal models compatible with this environment. These models can be, for example, fit to clinical data to understand underlying causes of injuries using inverse kinematics and inverse dynamics. For many of these models there are controllers designed for forward simulations of movement, however they are often finely tuned for the model and data. Advancements in reinforcement learning may allow building more robust controllers which can in turn provide another tool for validating the models.
Google's DeepMind AI --"Grasps Basic Laws of Physics"
When encountering novel object, humans and other animals are able to infer a wide range of physical properties such as mass, friction and deformability by interacting with themin a goal driven way. This process of active interaction is in the same spirit of a scientist performing an experiment to discover hidden facts. The study, entitled Learning to perform physics experiments via deep reinforcement learning, explained that while recent advances in AI have achieved'superhuman performance' in complex control problems and other processing tasks, the machines still lack a common sense understanding of our physical world โ 'it is not clear that these systems can rival the scientific intuition of even a young child.' "We found," the team concluded, "that state of art deep reinforcement learning methods can learn to perform the experiments necessary to discover these hidden properties of the physical world. By systematically manipulating the problem difficulty and the cost incurred by the AI agent for performing experiments, we found that agents learn different strategies that balance the cost of gathering information against the cost of making mistakes in different situations."
Memory Lens: How Much Memory Does an Agent Use?
Dann, Christoph, Hofmann, Katja, Nowozin, Sebastian
We propose a new method to study the internal memory used by reinforcement learning policies. We estimate the amount of relevant past information by estimating mutual information between behavior histories and the current action of an agent. We perform this estimation in the passive setting, that is, we do not intervene but merely observe the natural behavior of the agent. Moreover, we provide a theoretical justification for our approach by showing that it yields an implementation-independent lower bound on the minimal memory capacity of any agent that implement the observed policy. We demonstrate our approach by estimating the use of memory of DQN policies on concatenated Atari frames, demonstrating sharply different use of memory across 49 games. The study of memory as information that flows from the past to the current action opens avenues to understand and improve successful reinforcement learning algorithms.
Probabilistic Verification for Cognitive Models
Junges, Sebastian (RWTH Aachen University) | Jansen, Nils (University of Texas at Austin) | Katoen, Joost-Pieter (RWTH Aachen University) | Topcu, Ufuk (University of Texas at Austin)
Many robotics applications and scenarios that involve interaction with humans are safety or performance critical. A natural path to assessing such notions is to include a cognitive model describing typical human behaviors into a larger modeling context. In this work, we set out to investigate a combination of such a model with formal verification. We present a general and flexible framework utilizing methods from probabilistic model checking and discuss current pitfalls. We start from information about typical behavior, obtained from generalizing specific scenarios by the usage of inverse reinforcement learning. We translate this information in order to define a formal model exhibiting stochastic behavior (whenever significant data is present) or nondeterminism (if the model is underspecified or no significant data is present) that can be analyzed. This model for a human can be combined with a robot model by using standard parallel composition. The benefit is manyfold: First, safe or optimal strategies for involved robots regarding a human can be synthesized depending on the given model. In general, verification can determine if such benign strategies are even possible. Furthermore, the cognitive model itself can be analyzed with respect to possible unnatural behaviors; thereby feedback to developers of such models is provided. We evaluate and describe our approaches by means of a well-known model for visiomotor tasks and provide a framework that can readily incorporate other models.
Applying Adaptive Control in Modeling Human Motion Behaviors in Reinforcement Robotic Learning from Demonstrations
Tan, Huan (GE Global Research) | Zhao, Yang (GE Global Research) | Kannan, Balajee (GE Global Research)
In this paper, we propose to use an adaptive control method as the basis of a reinforcement learning algorithm for robotic imitation learning. In the learning stage, robots use adaptive control method-based reinforcement learning algorithm to learn the parameters of dynamical systems. In the generation stage, robots use the learned dynamic system parameters and the pre-defined controller to drive the configuration states of the robot to move along desired state trajectories. One simu-lation experiment and one practical experiment on a robot are carried out to validate the effectiveness of our algorithm. The experimental results validate that the learning of the system parameters converges very fast and the learning results can improve the system performance of generating similar motion trajectories.
Towards Behavior-Aware Model Learning from Human-Generated Trajectories
Loftin, Robert Tyler (North Carolina State University) | MacGlashan, James (Brown University) | Peng, Bei (Washington State University) | Taylor, Matthew E. (Washington State University) | Littman, Michael L. (Brown University) | Roberts, David L. (North Carolina State University)
Inverse reinforcement learning algorithms recover an unknown reward function for a Markov decision process, based on observations of user behaviors that optimize this reward function. Here we consider the complementary problem of learning the unknown transition dynamics of an MDP based on such observations. We describe the behavior-aware modeling (BAM) algorithm, which learns models of transition dynamics from user generated state-action trajectories. BAM makes assumptions about how users select their actions that are similar to those used in inverse reinforcement learning, and searches for a model that maximizes the probability of the observed actions. The BAM algorithm is based on policy gradient algorithms, essentially reversing the roles of the policy and transition distribution in those algorithms. As a result, BAM is highly flexible, and can be applied to continuous state spaces using a wide variety of model representations. In this preliminary work, we discuss why the model learning problem is interesting, describe algorithms to solve this problem, and discuss directions for future work.
Dimensionality Reduced Reinforcement Learning for Assistive Robots
Curran, William (Oregon State University) | Brys, Tim (Vrije Universiteit Brussel) | Aha, David (Navy Center for Applied Research in AI) | Taylor, Matthew (Washington State University) | Smart, William D. (Oregon State University)
State-of-the-art personal robots need to perform complex manipulation tasks to be viable in assistive scenarios. However, many of these robots, like the PR2, use manipulators with high degrees-of-freedom, and the problem is made worse in bimanual manipulation tasks. The complexity of these robots lead to large dimensional state spaces, which are difficult to learn in. We reduce the state space by using demonstrations to discover a representative low-dimensional hyperplane in which to learn. This allows the agent to converge quickly to a good policy. We call this Dimensionality Reduced Reinforcement Learning (DRRL). However, when performing dimensionality reduction, not all dimensions can be fully represented. We extend this work by first learning in a single dimension, and then transferring that knowledge to a higher-dimensional hyperplane. By using our Iterative DRRL (IDRRL) framework with an existing learning algorithm, the agent converges quickly to a better policy by iterating to increasingly higher dimensions. IDRRL is robust to demonstration quality and can learn efficiently using few demonstrations. We show that adding IDRRL to the Q-Learning algorithm leads to faster learning on a set of mountain car tasks and the robot swimmers problem.