publications

Articulation modeling enables robots to learn how an object’s joints move so they can manipulate it effectively. PokeNet is an end-to-end framework that learns articulation models from a single human demonstration without prior object knowledge. From point cloud sequences, it predicts joint parameters, infers manipulation order, and tracks joint states over time.

Diffusion models have been extensively leveraged for learning robot skills from demonstrations. These policies are conditioned on several observational modalities such as proprioception, vision, and tactile. However, observational modalities have varying levels of influence for different tasks that diffusion policies fail to capture. In this work, we propose Factorized Diffusion Policies (FDP), a novel policy formulation that enables observational modalities to have differing influence on the action diffusion process by design. This results in learning policies where certain observation modalities can be prioritized over others, such as vision > tactile or proprioception > vision. FDP achieves modality prioritization by factorizing the observational conditioning for the diffusion process, resulting in more performant and robust policies. Our factored approach shows strong performance improvements in low-data regimes, with a 15% absolute improvement in success rate on several simulated benchmarks when compared to a standard diffusion policy that jointly conditions on all input modalities. Moreover, our benchmark and real-world experiments show that factored policies are naturally more robust, with a 40% higher absolute success rate across several visuomotor tasks under distribution shifts such as visual distractors or camera occlusions, where existing diffusion policies fail catastrophically. FDP thus offers a safer and more robust alternative to standard diffusion policies for real-world deployment. Videos are available at https://fdp-policy.github.io/fdp-policy/.

Robots collaborating with humans must convert natural language goals into actionable, physically grounded decisions. For example, executing a command such as "go two meters to the right of the fridge" requires grounding semantic references, spatial relations, and metric constraints within a 3D scene. While recent vision language models (VLMs) demonstrate strong semantic grounding capabilities, they are not explicitly designed to reason about metric constraints in physically defined spaces. In this work, we empirically demonstrate that state-of-the-art VLM-based grounding approaches struggle with complex metric-semantic language queries. To address this limitation, we propose MAPG (Multi-Agent Probabilistic Grounding), an agentic framework that decomposes language queries into structured subcomponents and queries a VLM to ground each component. MAPG then probabilistically composes these grounded outputs to produce metrically consistent, actionable decisions in 3D space. We evaluate MAPG on the HM-EQA benchmark and show consistent performance improvements over strong baselines. Furthermore, we introduce a new benchmark, MAPG-Bench, specifically designed to evaluate metric-semantic goal grounding, addressing a gap in existing language grounding evaluations. We also present a real-world robot demonstration showing that MAPG transfers beyond simulation when a structured scene representation is available.

What happens when a pretrained generative robot policy is provided a constant initial noise as input, rather than repeatedly sampling it from a Gaussian? We demonstrate that the performance of a pretrained, frozen diffusion or flow matching policy can be improved with respect to a downstream reward by swapping the sampling of initial noise from the prior distribution (typically isotropic Gaussian) with a well-chosen, constant initial noise input – a golden ticket. We propose a search method to find golden tickets using Monte-Carlo policy evaluation that keeps the pretrained policy frozen, does not train any new networks, and is applicable to all diffusion/flow matching policies (and therefore many VLAs). Our approach to policy improvement makes no assumptions beyond being able to inject initial noise into the policy and calculate (sparse) task rewards of episode rollouts, making it deployable with no additional infrastructure or models. Our method improves the performance of policies in 38 out of 43 tasks across simulated and real-world robot manipulation benchmarks, with relative improvements in success rate by up to 58% for some simulated tasks, and 60% within 50 search episodes for real-world tasks. We also show unique benefits of golden tickets for multi-task settings: the diversity of behaviors from different tickets naturally defines a Pareto frontier for balancing different objectives (e.g., speed, success rates); in VLAs, we find that a golden ticket optimized for one task can also boost performance in other related tasks. We release a codebase with pretrained policies and golden tickets for simulation benchmarks using VLAs, diffusion policies, and flow matching policies.

Large scale pre-training on text and image data along with diverse robot demonstrations has helped Vision Language Action models (VLAs) to generalize to novel tasks, objects and scenes. However, these models are still susceptible to failure in the presence of execution-time impediments such as distractors and physical obstructions in the robot’s workspace. Existing policy improvement methods finetune base VLAs to improve generalization, yet they still struggle in unseen distractor settings. To address this problem, we investigate whether internet-scale pretraining of large vision-language models (VLMs) can be leveraged to reason about these impediments and mitigate policy failures. To this end, we propose StageCraft, a training-free approach to improve pretrained VLA policy performance by manipulating the environment’s initial state using VLM-based in-context reasoning. StageCraft takes policy rollout videos and success labels as input and leverages VLM’s reasoning ability to infer which objects in the initial state need to be manipulated to avoid anticipated execution failures. StageCraft is an extensible plug-and-play module that does not introduce additional constraints on the underlying policy, and only requires a few policy rollouts to work. We evaluate performance of state-of-the-art VLA models with StageCraft and show an absolute 40% performance improvement across three real world task domains involving diverse distractors and obstructions. Our simulation experiments in RLBench empirically show that StageCraft tailors its extent of intervention based on the strength of the underlying policy and improves its performance with more in-context samples. Videos of StageCraft in effect can be found at https://stagecraft-decorator.github.io/stagecraft/

In this work, we present an approach to identify sub-tasks within a demonstrated robot trajectory with the supervision provided by language instructions. Learning longer horizon tasks is challenging with techniques such as reinforcement learning and behavior cloning. Previous approaches have split these long tasks into shorter tasks that are easier to learn by using statistical change point detection methods. However, classical changepoint detection methods function only with low dimensional robot trajectory data and not with high dimensional inputs such as vision. Our goal in this work is to split longer horizon tasks, represented by trajectories into shorter horizon tasks that can be learned using conventional behavior cloning approaches using guidance from language. In our approach we use techniques from the video moment retrieval problem on robot trajectory data to demonstrate a high-dimensional generalizable change-point detection approach. Our proposed moment retrieval-based approach shows a more than 30% improvement in mean average precision (mAP) for identifying trajectory sub-tasks with language guidance compared to that without language. We perform ablations to understand the effects of domain randomization, sample complexity, views, and sim-to-real transfer of our method. In our data ablation we find that just with a 100 labelled trajectories we can achieve a 61.41 mAP, demonstrating the sample efficiency of using such an approach. Further, behavior cloning models trained on our segmented trajectories outperform a single model trained on the whole trajectory by up to 20%.

This work consists of two main components: designing a hardware-software co-design, MT+, for adapting the Mikami-Tabuchi algorithm for on-board path planning by drones in a 3D environment; and development of a specialized custom hardware accelerator CDU, as a part of MT+, for parallel collision detection. Collision detection is a performance bottleneck in path planning. MT+ reduces the delay in path planning without using any heuristic. A comparative analysis between the state-of-the-art path planning algorithm A* and Mikami-Tabuchi is performed to show that Mikami-Tabuchi is faster than A* in typical real-world environments. In custom-generated environments, path planning using Mikami-Tabuchi shows a latency improvement of 1.7× across varying average sizes of obstacles and 2.7× across varying obstacle density over state-of-the-art path planning algorithm, A*. Further, the experiments show that the co-design achieves speedups over a full software implementation on CPU, averaging between 10% to 60% across different densities and sizes of obstacles. CDU area and power overheads are negligible against a conventional single-core processor.

Humans can perform various combinations of physical skills without having to relearn skills from scratch every single time. For example, we can swing a bat when walking without having to re-learn such a policy from scratch by composing the individual skills of walking and bat swinging. Enabling robots to combine or compose skills is essential so they can learn novel skills and tasks faster with fewer real world samples. To this end, we propose a novel compositional approach called DSE- Diffusion Score Equilibrium that enables few-shot learning for novel skills by utilizing a combination of base policy priors. Our method is based on probabilistically composing diffusion policies to better model the few-shot demonstration data-distribution than any individual policy. Our goal here is to learn robot motions few-shot and not necessarily goal oriented trajectories. Unfortunately we lack a general purpose metric to evaluate the error between a skill or motion and the provided demonstrations. Hence, we propose a probabilistic measure - Maximum Mean Discrepancy on the Forward Kinematics Kernel (MMD-FK), that is task and action space agnostic. By using our few-shot learning approach DSE, we show that we are able to achieve a reduction of over 30% in MMD-FK across skills and number of demonstrations. Moreover, we show the utility of our approach through real world experiments by teaching novel trajectories to a robot in 5 demonstrations.

Paraphrase generation is a difficult problem. This is not only because of the limitations in text generation capabilities but also due that to the lack of a proper definition of what qualifies as a paraphrase and corresponding metrics to measure how good it is. Metrics for evaluation of paraphrasing quality is an on going research problem. Most of the existing metrics in use having been borrowed from other tasks do not capture the complete essence of a good paraphrase, and often fail at borderline-cases. In this work, we propose a novel metric ROUGEP to measure the quality of paraphrases along the dimensions of adequacy, novelty and fluency. We also provide empirical evidence to show that the current natural language generation metrics are insufficient to measure these desired properties of a good paraphrase. We look at paraphrase model fine-tuning and generation from the lens of metrics to gain a deeper understanding of what it takes to generate and evaluate a good paraphrase.

This paper surveys the current state of the art in document automation (DA). The objective of DA is to reduce the manual effort during the generation of documents by automatically integrating input from different sources and assembling documents conforming to defined templates. There have been reviews of commercial solutions of DA, particularly in the legal domain, but to date there has been no comprehensive review of the academic research on DA architectures and technologies. The current survey of DA reviews the academic literature and provides a clearer definition and characterization of DA and its features, identifies state-of-the-art DA architectures and technologies in academic research, and provides ideas that can lead to new research opportunities within the DA field in light of recent advances in artificial intelligence and deep neural networks.

Visual localization is the task of camera pose estimation, and is crucial for many technologies which involve localization such as mobile robots and augmented reality. Several convolutional neural network models have been proposed for the task against the more accurate geometry based computer vision techniques. However, they have several shortcomings and to our knowledge, this was the first effort that explored the use of an alternative architecture based on capsule-networks for the task. We achieved better results with capsules than with baseline-CNN PoseNet on small NORB dataset, modified for the task of camera pose estimation. Feature visualizations for both the networks produced more insights on their performance and behaviour. We found that there is a scope for improvement and hence propose few directions for future efforts.