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Yunfei Bai

Yunfei Bai

Yunfei Bai lead Machine Learning infrastructure, data and delivery efforts in Project Starline at Google. Before that, he founded the simulation team for Everyday Robots Project at X (formerly Google [x]). He built and managed cross geolocation teams with software engineers, researchers, and technical artists. He led the team to collaborate with Google Brain and DeepMind on a dozen research projects, including Sim2Real, and PaLM-SayCan. His research interests include deep learning, computer graphics, 3D computer vision, and robotics. He received a Ph.D. degree in Computer Science from Georgia Institute of Technology in 2015, under the advice of Dr. C. Karen Liu. His thesis focuses on designing algorithms for synthesizing human motion of object manipulation. He was a member of Computer Graphics Lab in Georgia Tech. He received a B.E. degree from Tsinghua University, China in 2010.
Authored Publications
Google Publications
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    Scalable Multi-Sensor Robot Imitation Learning via Task-Level Domain Consistency
    Armando Fuentes
    Eric Victor Jang
    Matt Bennice
    Mohi Khansari
    Nicolas Sievers
    Yuqing Du
    ICRA (2023) (to appear)
    Preview abstract Recent work in visual end-to-end learning for robotics has shown the promise of imitation learning across a variety of tasks. However, such approaches are often expensive and require vast amounts of real world training demonstrations. Additionally, they rely on a time-consuming evaluation process for identifying the best model to deploy in the real world. These challenges can be mitigated by simulation - by supplementing real world data with simulated demonstrations and using simulated evaluations to identify strong policies. However, this introduces the well-known ``reality gap'' problem, where simulator inaccuracies decorrelates performance in simulation from reality. In this paper, we build on top of prior work in GAN-based domain adaptation and introduce the notion of a Task Consistency Loss (TCL), a self-supervised contrastive loss that encourages sim and real alignment both at the feature and action-prediction level. We demonstrate the effectiveness of our approach on the challenging task of latched-door opening with a 9 Degree-of-Freedom (DoF) mobile manipulator from raw RGB and depth images. While most prior work in vision-based manipulation operate from a fixed, third person view, mobile manipulation couples the challenges of locomotion and manipulation with greater visual diversity and action space complexity. We find that we are able to achieve 77% success on seen and unseen scenes, a +30% increase from the baseline, using only ~16 hours of teleoperation demonstrations in sim and real. View details
    Preview abstract Reinforcement learning provides an effective tool for robots to acquire diverse skills in an automated fashion.For safety and data generation purposes, control policies are often trained in a simulator and later deployed to the target environment, such as a real robot. However, transferring policies across domains is often a manual and tedious process. In order to bridge the gap between domains, it is often necessary to carefully tune and identify the simulator parameters or select the aspects of the simulation environment to randomize. In this paper, we design a novel, adversarial learning algorithm to tackle the transfer problem. We combine a classic, analytical simulator with a differentiable, state-action dependent system identification module that outputs the desired simulator parameters. We then train this hybrid simulator such that the output trajectory distributions are indistinguishable from a target domain collection. The optimized hybrid simulator can refine a sub-optimal policy without any additional target domain data. We show that our approach outperforms the domain-randomization and target-domain refinement baselines on two robots and six difficult dynamic tasks. View details
    Learning Fast Adaptation with Meta Strategy Optimization
    Erwin Johan Coumans
    Sehoon Ha
    Learning Fast Adaptation with Meta Strategy Optimization (2020)
    Preview abstract The ability to walk in new situations is a key milestone on the path toward real-world applications of legged robots. In this work, we introduce a novel algorithm for training locomotion policies for legged robots that can quickly adapt to new scenarios with a handful of trials in the target environment. We extend the framework of strategy optimization that trains a control policy with additional latent parameters in the simulation and transfers to the real robot by optimizing the latent inputs. The key idea in our proposed algorithm, Meta Strategy Optimization (MSO), is to formulate the problem as a meta-learning process by exposing the same strategy optimization to both the training and testing phases. This change allows MSO to effectively learn locomotion skills as well as a latent space that is suitable for fast adaptation. We evaluate our method on a real quadruped robot and demonstrate successful adaptation in various scenarios, including sim-to-real transfer, walking with a weakened motor, or climbing up a slope. Furthermore, we analyze the generalization capability of the trained policy in simulated environments and show that our method outperforms previous methods in both simulated and real environments. View details
    Preview abstract We propose a self-supervised approach for learning representations of objects from monocular videos and demonstrate it is particularly useful in situated settings such as robotics. The main contributions of this paper are: 1) a self-supervising objective trained with contrastive learning that can discover and disentangle object attributes from video without using any labels; 2) we leverage object self-supervision for online adaptation: the longer our online model looks at objects in a video, the lower the object identification error, while the offline baseline remains with a large fixed error; 3) to explore the possibilities of a system entirely free of human supervision, we let a robot collect its own data, train on this data with our self-supervise scheme, and then show the robot can point to objects similar to the one presented in front of it, demonstrating generalization of object attributes. An interesting and perhaps surprising finding of this approach is that given a limited set of objects, object correspondences will naturally emerge when using contrastive learning without requiring explicit positive pairs. Videos illustrating online object adaptation and robotic pointing are available at this address: https://sites.google.com/view/object-contrastive-networks/home View details
    Preview abstract This paper focuses on the problem of learning 6-DOF grasping with a parallel jaw gripper in simulation. Compared to existing approaches that are specialized in three-dimensional grasping (i.e., top-down grasping or side-grasping), using a 6-DOF grasping model allows the robot to learn a richer set of grasping interactions given less physical constraints; hence, potentially enhancing the robustness of grasping and robot dexterity. However, learning 6-DOF grasping is challenging due to a high dimensional state space, difficulty in collecting large-scale data, and many variations of an object’s visual appearance (i.e., geometry, material, texture, and illumination). We propose the notion of a geometry-aware representation in grasping based on the assumption that knowledge of 3D geometry is at the heart of interaction. Our key idea is constraining and regularizing grasping interaction learning through 3D geometry prediction. View details
    Preview abstract Designing agile locomotion for quadruped robots often requires extensive expertise and tedious manual tuning. In this paper, we present a system to automate this process by leveraging deep reinforcement learning techniques. Our system can learn quadruped locomotion from scratch with simple reward signals. In addition, users can provide an open loop reference to guide the learning process if more control over the learned gait is needed. The control policies are learned in a physical simulator and then deployed to real robots. In robotics, policies trained in simulation often does not transfer to the real world. We narrow this reality gap by improving the physical simulator and learning robust policies. We improve the simulation using system identification, developing an accurate actuator model and simulating latency. We learn robust controllers by randomizing the physical environments, adding perturbations and designing a compact observation space. We evaluate our system on two agile locomotion gaits: trotting and galloping. After learning in simulation, a quadruped robot can successfully perform both gaits in real world. View details
    Using Simulation and Domain Adaptation to Improve Efficiency of Deep Robotic Grasping
    Paul Wohlhart
    Matthew Kelcey
    Mrinal Kalakrishnan
    Laura Downs
    Julian Ibarz
    Peter Pastor Sampedro
    Kurt Konolige
    ICRA (2018)
    Preview abstract Instrumenting and collecting annotated visual grasping datasets to train modern machine learning algorithms is prohibitively expensive. An appealing alternative is to use off-the-shelf simulators to render synthetic data for which ground-truth annotations are generated automatically. Unfortunately, models trained purely on simulated data often fail to generalize to the real world. To address this shortcoming, prior work introduced domain adaptation algorithms that attempt to make the resulting models domain-invariant. However, such works were evaluated primarily on offline image classification datasets. In this work, we adapt these techniques for learning, primarily in simulation, robotic hand-eye coordination for grasping. Our approaches generalize to diverse and previously unseen real-world objects. We show that, by using synthetic data and domain adaptation, we are able to reduce the amounts of real--world samples required for our goal and a certain level of performance by up to 50 times. We also show that by using our suggested methodology we are able to achieve good grasping results by using no real world labeled data. View details
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