在双皮德机器人上生成健壮步态的能力是他们在硬件上成功实现的关键。为此，这项工作扩展了混合零动力学（HZD）的方法 - 传统上，该方法仅在完美影响事件下通过周期性限制来说明机车稳定性 - 通过包含盐矩阵，以构成合成强大的步行步态的观点。通过共同将扩展盐矩阵的规范和步态生成过程中的机器人的扭矩最小化，我们表明合成的步态比单独使用任何一个术语产生的步态更强大。这些结果在模拟和硬件中显示了琥珀色3M平面和阿塔兰特较低体外外骨骼（无论有没有人类）。最终结果是实验验证，即将盐矩阵与HZD方法相结合，在实践中会产生更健壮的两足步行。

机器人系统的参数调整是一项耗时且具有挑战性的任务，通常依赖于人类操作员的领域专业知识。此外，由于许多原因，现有的学习方法不适合参数调整，包括：缺乏“良好机器人行为”的明确数值指标；由于依赖现实世界实验数据而导致的数据有限；以及参数组合的较大搜索空间。在这项工作中，我们提出了一种开源MATLAB偏好优化和用于系统探索高维参数空间的机器人工具箱（Polar）的学习算法，该算法使用基于人类的基于人类偏好的学习。该工具箱的这个目的是系统，有效地实现两个目标之一：1）优化人类操作员偏好的机器人行为； 2）学习操作员的基本偏好格局，以更好地了解可调参数和操作员偏好之间的关系。极性工具箱仅使用主观反馈机制（成对的偏好，共同反馈和序数标签）来实现这些目标，以推断出贝叶斯后验，而不是基本的奖励功能决定用户的偏好。我们证明了工具箱在模拟中的性能，并介绍了基于人类偏好的学习的各种应用。

将动态机器人带入野外，需要平衡性能和安全之间。然而，旨在提供强大安全保证的控制器通常会导致保守行为，并调整这些控制器，以找到性能和安全之间的理想权衡通常需要域专业知识或仔细构造的奖励功能。这项工作提出了一种设计范式，用于系统地实现平衡性能和强大安全性的行为，通过将基于安全感知的基于偏好（PBL）与控制屏障功能（CBF）集成来实现平衡性能和鲁棒安全性。融合这些概念 - 安全感知的学习和安全关键控制 - 提供了一种在实践中实现复杂机器人系统的安全行为的强大手段。我们展示了这种设计范式的能力，以实现在硬件上的模拟和实验上的四足机器人的安全和表演感知的自主操作。

在机器人辅助设备上执行时产生稳定的行走GAIT，即在机器人 - 辅助设备上执行时是一个具有挑战性的任务，通常需要域专家手工调整。本文提出了一种替代方法，在那里我们提出直接进入步态生成过程的肌肉骨骼模型，以直观地塑造所产生的行为。特别是，我们构建一个多域混合系统模型，将系统动态与肌肉模型相结合，以代表自然多连接步行。然后可以通过混合零动态（HZD）方法为该模型生成可提供稳定的行走Gaits。我们通过实验应用我们的综合框架，朝着两项受试者实现了对双致动的转发假体，AMPRO3的多端运动。结果表明，强制执行肌肉模型约束产生产生自然运动的Gaits（通过与运动捕获数据和肌电图进行比较分析）。此外，与使用标称HZD方法产生的Gaits相比，不禁用假肢使用者强烈优选使用我们的框架产生的Gaits，即使使用系统调整方法也是如此。我们得出结论，将机器人行走方法（特别是HZD）与肌肉模型结合的新方法成功地产生了拟人机器人辅助运动。

Imitation learning (IL) is a simple and powerful way to use high-quality human driving data, which can be collected at scale, to identify driving preferences and produce human-like behavior. However, policies based on imitation learning alone often fail to sufficiently account for safety and reliability concerns. In this paper, we show how imitation learning combined with reinforcement learning using simple rewards can substantially improve the safety and reliability of driving policies over those learned from imitation alone. In particular, we use a combination of imitation and reinforcement learning to train a policy on over 100k miles of urban driving data, and measure its effectiveness in test scenarios grouped by different levels of collision risk. To our knowledge, this is the first application of a combined imitation and reinforcement learning approach in autonomous driving that utilizes large amounts of real-world human driving data.

Reliably planning fingertip grasps for multi-fingered hands lies as a key challenge for many tasks including tool use, insertion, and dexterous in-hand manipulation. This task becomes even more difficult when the robot lacks an accurate model of the object to be grasped. Tactile sensing offers a promising approach to account for uncertainties in object shape. However, current robotic hands tend to lack full tactile coverage. As such, a problem arises of how to plan and execute grasps for multi-fingered hands such that contact is made with the area covered by the tactile sensors. To address this issue, we propose an approach to grasp planning that explicitly reasons about where the fingertips should contact the estimated object surface while maximizing the probability of grasp success. Key to our method's success is the use of visual surface estimation for initial planning to encode the contact constraint. The robot then executes this plan using a tactile-feedback controller that enables the robot to adapt to online estimates of the object's surface to correct for errors in the initial plan. Importantly, the robot never explicitly integrates object pose or surface estimates between visual and tactile sensing, instead it uses the two modalities in complementary ways. Vision guides the robots motion prior to contact; touch updates the plan when contact occurs differently than predicted from vision. We show that our method successfully synthesises and executes precision grasps for previously unseen objects using surface estimates from a single camera view. Further, our approach outperforms a state of the art multi-fingered grasp planner, while also beating several baselines we propose.

Hawkes processes have recently risen to the forefront of tools when it comes to modeling and generating sequential events data. Multidimensional Hawkes processes model both the self and cross-excitation between different types of events and have been applied successfully in various domain such as finance, epidemiology and personalized recommendations, among others. In this work we present an adaptation of the Frank-Wolfe algorithm for learning multidimensional Hawkes processes. Experimental results show that our approach has better or on par accuracy in terms of parameter estimation than other first order methods, while enjoying a significantly faster runtime.

Importance: Social determinants of health (SDOH) are known to be associated with increased risk of suicidal behaviors, but few studies utilized SDOH from unstructured electronic health record (EHR) notes. Objective: To investigate associations between suicide and recent SDOH, identified using structured and unstructured data. Design: Nested case-control study. Setting: EHR data from the US Veterans Health Administration (VHA). Participants: 6,122,785 Veterans who received care in the US VHA between October 1, 2010, and September 30, 2015. Exposures: Occurrence of SDOH over a maximum span of two years compared with no occurrence of SDOH. Main Outcomes and Measures: Cases of suicide deaths were matched with 4 controls on birth year, cohort entry date, sex, and duration of follow-up. We developed an NLP system to extract SDOH from unstructured notes. Structured data, NLP on unstructured data, and combining them yielded seven, eight and nine SDOH respectively. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression. Results: In our cohort, 8,821 Veterans committed suicide during 23,725,382 person-years of follow-up (incidence rate 37.18 /100,000 person-years). Our cohort was mostly male (92.23%) and white (76.99%). Across the six common SDOH as covariates, NLP-extracted SDOH, on average, covered 84.38% of all SDOH occurrences. All SDOH, measured by structured data and NLP, were significantly associated with increased risk of suicide. The SDOH with the largest effects was legal problems (aOR=2.67, 95% CI=2.46-2.89), followed by violence (aOR=2.26, 95% CI=2.11-2.43). NLP-extracted and structured SDOH were also associated with suicide. Conclusions and Relevance: NLP-extracted SDOH were always significantly associated with increased risk of suicide among Veterans, suggesting the potential of NLP in public health studies.

Multilevel Stein variational gradient descent is a method for particle-based variational inference that leverages hierarchies of approximations of target distributions with varying costs and fidelity to computationally speed up inference. This work provides a cost complexity analysis of multilevel Stein variational gradient descent that applies under milder conditions than previous results, especially in discrete-in-time regimes and beyond the limited settings where Stein variational gradient descent achieves exponentially fast convergence. The analysis shows that the convergence rate of Stein variational gradient descent enters only as a constant factor for the cost complexity of the multilevel version, which means that the costs of the multilevel version scale independently of the convergence rate of Stein variational gradient descent on a single level. Numerical experiments with Bayesian inverse problems of inferring discretized basal sliding coefficient fields of the Arolla glacier ice demonstrate that multilevel Stein variational gradient descent achieves orders of magnitude speedups compared to its single-level version.

Long short-term memory (LSTM) is a type of powerful deep neural network that has been widely used in many sequence analysis and modeling applications. However, the large model size problem of LSTM networks make their practical deployment still very challenging, especially for the video recognition tasks that require high-dimensional input data. Aiming to overcome this limitation and fully unlock the potentials of LSTM models, in this paper we propose to perform algorithm and hardware co-design towards high-performance energy-efficient LSTM networks. At algorithm level, we propose to develop fully decomposed hierarchical Tucker (FDHT) structure-based LSTM, namely FDHT-LSTM, which enjoys ultra-low model complexity while still achieving high accuracy. In order to fully reap such attractive algorithmic benefit, we further develop the corresponding customized hardware architecture to support the efficient execution of the proposed FDHT-LSTM model. With the delicate design of memory access scheme, the complicated matrix transformation can be efficiently supported by the underlying hardware without any access conflict in an on-the-fly way. Our evaluation results show that both the proposed ultra-compact FDHT-LSTM models and the corresponding hardware accelerator achieve very high performance. Compared with the state-of-the-art compressed LSTM models, FDHT-LSTM enjoys both order-of-magnitude reduction in model size and significant accuracy improvement across different video recognition datasets. Meanwhile, compared with the state-of-the-art tensor decomposed model-oriented hardware TIE, our proposed FDHT-LSTM architecture achieves better performance in throughput, area efficiency and energy efficiency, respectively on LSTM-Youtube workload. For LSTM-UCF workload, our proposed design also outperforms TIE with higher throughput, higher energy efficiency and comparable area efficiency.