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Liangliang Wang

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5 papers

2 author rows

EAAI Journal 2024 Journal Article

A descriptive behavior intention inference framework using spatio-temporal semantic features for human–robot real-time interaction

Liangliang Wang
Guanglei Huo
Ruifeng Li
Peidong Liang

Visual behavior intention inference is crucial for enabling escort robots to interact naturally with humans, which is very challenging due to the big inner-class similarity and the small intra-class distinguishability of successive actions in the assistive scenario. To attain a reliable behavior intention inference, not only the current state of behaviors is concerned, but also the semantic information in both spatial and temporal domains plays an important role. This paper presents a segmentation–detection–recognition hierarchical system to represent the spatio-temporal semantic features for formulating descriptions of body parts, trajectories and deep relationships of sub-behaviors. Specifically, a dense trajectory matching scheme based on temporal sampling and Binarized Normed Gradients (BING) algorithm is formulated to segment the 3-Dimensional (3D) behavior cubes, based on which, local trajectories are obtained by clustering dense trajectories according to the distance similarity, and the body parts are then detected by multi-kernel learning of the encoded local features. Moreover, a global three-stream context Convolutional Neural Networks (CNN) is proposed for behavior classification by designing a texture module using expansion, connection and 1D convolution implementations. Based on transfer learning, scene information is also recognized efficiently. Finally, the semantic descriptors are modeled by two cascaded And-Or Graphs (AoGs) constraining the spatial scenarios and temporal sequences. Our unified approach is demonstrated on two public benchmarks containing long-term activities and on an escort robot for real-world applications.

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ICRA Conference 2021 Conference Paper

Accurate and Robust Stereo Direct Visual Odometry for Agricultural Environment

Tao Yu
Junwei Zhou 0002
Liangliang Wang
Shengwu Xiong 0001

Vision-based localization and mapping in the agricultural environment is challenging due to the unstructured scene with unstable features, illumination variations, bumpy roads, and dynamic environmental objects. To address these challenges, we propose an accurate and robust stereo direct visual odometry system with modifications on Stereo-DSO. We firstly select some well-matched static stereo points in the latest keyframe to improve the accuracy of inverse depth calculation for tracking. The inverse depth can further distinguish close objects from background, which will avoid large and far-away scene objects in keyframe determination. To boost efficiency and accuracy at the tracking stage, we propose a point selection method to sample map points and remove outliers. Furthermore, altitude smoothness verification with a local flat ground assumption and recovery method for tracking failure on bumpy roads are proposed to improve the system’s robustness. Finally, a far-away keyframe is reserved in the sliding window to alleviate the orientation drift since the agricultural robots usually move straightly following the crop row. Our system achieved new state-of-the-art results on Flourish dataset and the recently released Rosario dataset.

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NeurIPS Conference 2019 Conference Paper

Random Tessellation Forests

Shufei Ge
Shijia Wang
Yee Whye Teh
Liangliang Wang
Lloyd Elliott

Space partitioning methods such as random forests and the Mondrian process are powerful machine learning methods for multi-dimensional and relational data, and are based on recursively cutting a domain. The flexibility of these methods is often limited by the requirement that the cuts be axis aligned. The Ostomachion process and the self-consistent binary space partitioning-tree process were recently introduced as generalizations of the Mondrian process for space partitioning with non-axis aligned cuts in the plane. Motivated by the need for a multi-dimensional partitioning tree with non-axis aligned cuts, we propose the Random Tessellation Process, a framework that includes the Mondrian process as a special case. We derive a sequential Monte Carlo algorithm for inference, and provide random forest methods. Our methods are self-consistent and can relax axis-aligned constraints, allowing complex inter-dimensional dependence to be captured. We present a simulation study and analyze gene expression data of brain tissue, showing improved accuracies over other methods.

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ICML Conference 2014 Conference Paper

Efficient Continuous-Time Markov Chain Estimation

Monir Hajiaghayi
Bonnie Kirkpatrick
Liangliang Wang
Alexandre Bouchard-Côté

Many problems of practical interest rely on Continuous-time Markov chains (CTMCs) defined over combinatorial state spaces, rendering the computation of transition probabilities, and hence probabilistic inference, difficult or impossible with existing methods. For problems with countably infinite states, where classical methods such as matrix exponentiation are not applicable, the main alternative has been particle Markov chain Monte Carlo methods imputing both the holding times and sequences of visited states. We propose a particle-based Monte Carlo approach where the holding times are marginalized analytically. We demonstrate that in a range of realistic inferential setups, our scheme dramatically reduces the variance of the Monte Carlo approximation and yields more accurate parameter posterior approximations given a fixed computational budget. These experiments are performed on both synthetic and real datasets, drawing from two important examples of CTMCs having combinatorial state spaces: string-valued mutation models in phylogenetics and nucleic acid folding pathways.

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NeurIPS Conference 2012 Conference Paper

Entangled Monte Carlo

Seong-Hwan Jun
Liangliang Wang
Alexandre Bouchard-Côté

We propose a novel method for scalable parallelization of SMC algorithms, Entangled Monte Carlo simulation (EMC). EMC avoids the transmission of particles between nodes, and instead reconstructs them from the particle genealogy. In particular, we show that we can reduce the communication to the particle weights for each machine while efficiently maintaining implicit global coherence of the parallel simulation. We explain methods to efficiently maintain a genealogy of particles from which any particle can be reconstructed. We demonstrate using examples from Bayesian phylogenetic that the computational gain from parallelization using EMC significantly outweighs the cost of particle reconstruction. The timing experiments show that reconstruction of particles is indeed much more efficient as compared to transmission of particles.

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