Chieh-Chih Wang

Simultaneous localization, mapping and moving object tracking

Simultaneous localization, mapping and moving object tracking (SLAMMOT) involves both simultaneous localization and mapping (SLAM) in dynamic environments and detecting and tracking these dynamic objects. In this paper, a mathematical framework is established to integrate SLAM and moving object tracking. Two solutions are described: SLAM with generalized objects, and SLAM with detection and tracking of moving objects (DATMO). SLAM with generalized objects calculates a joint posterior over all generalized objects and the robot. Such an approach is similar to existing SLAM algorithms, but with additional structure to allow for motion modeling of generalized objects. Unfortunately, it is computationally demanding and generally infeasible. SLAM with DATMO decomposes the estimation problem into two separate estimators. By maintaining separate posteriors for stationary objects and moving objects, the resulting estimation problems are much lower dimensional than SLAM with generalized objects. Both SLAM and moving object tracking from a moving vehicle in crowded urban areas are daunting tasks. Based on the SLAM with DATMO framework, practical algorithms are proposed which deal with issues of perception modeling, data association, and moving object detection. The implementation of SLAM with DATMO was demonstrated using data collected from the CMU Navlab11 vehicle at high speeds in crowded urban environments. Ample experimental results shows the feasibility of the proposed theory and algorithms.

Online simultaneous localization and mapping with detection and tracking of moving objects: theory and results from a ground vehicle in crowded urban areas

The simultaneous localization and mapping (SLAM) with detection and tracking of moving objects (DATMO) problem is not only to solve the SLAM problem in dynamic environments but also to detect and track these dynamic objects. In this paper, we derive the Bayesian formula of the SLAM with DATMO problem, which provides a solid basis for understanding and solving this problem. In addition, we provide a practical algorithm for performing DATMO from a moving platform equipped with range sensors. The probabilistic approach to solve the whole problem has been implemented with the Navlab11 vehicle. More than 100 miles of experiments in crowded urban areas indicated that SLAM with DATMO is indeed feasible.

LADAR-based detection and tracking of moving objects from a ground vehicle at high speeds

Detection and tracking of moving objects (DATMO) in crowded urban areas from a ground vehicle at high speeds is difficult because of a wide variety of targets and uncertain pose estimation from odometry and GPS/DGPS. In this paper we present a solution of the simultaneous localization and mapping (SLAM) with DATMO problem to accomplish this task using ladar sensors and odometry. With a precise pose estimate and a surrounding map from SLAM, moving objects are detected without a priori knowledge of the targets. The interacting multiple model (IMM) estimation algorithm is used for modeling the motion of a moving object and to predict its future location. The multiple hypothesis tracking (MHT) method is applied to refine detection and data association. Experimental results demonstrate that our algorithm is reliable and robust to detect and track pedestrians and different types of moving vehicles in urban areas.

Hand Posture Recognition Using Adaboost with SIFT for Human Robot Interaction

Hand posture understanding is essential to human robot interaction. The existing hand detection approaches using a Viola-Jones detector have two fundamental issues, the degraded performance due to background noise in training images and the in-plane rotation variant detection. In this paper, a hand posture recognition system using the discrete Adaboost learning algorithm with Lowe’s scale invariant feature transform (SIFT) features is proposed to tackle these issues simultaneously. In addition, we apply a sharing feature concept to increase the accuracy of multi-class hand posture recognition. The experimental results demonstrate that the proposed approach successfully recognizes three hand posture classes and can deal with the background noise issues. Our detector is in-plane rotation invariant, and achieves satisfactory multi-view hand detection.

PERCEPTION FOR COLLISION AVOIDANCE AND AUTONOMOUS DRIVING

The Navlab group at Carnegie Mellon University has a long history of development of automated vehicles and intelligent systems for driver assistance. The earlier work of the group concentrated on road following, cross-country driving, and obstacle detection. The new focus is on short-range sensing, to look all around the vehicle for safe driving. The current system uses video sensing, laser rangefinders, a novel light-stripe rangefinder, software to process each sensor individually, a map-based fusion system, and a probability based predictive model. The complete system has been demonstrated on the Navlab 11 vehicle for monitoring the environment of a vehicle driving through a cluttered urban environment, detecting and tracking fixed objects, moving objects, pedestrians, curbs, and roads.

Stereo-based simultaneous localization, mapping and moving object tracking

Vision based simultaneous localization and mapping (SLAM) has recently received much research interest. However, vision based SLAM could be corrupted with the inclusion of moving entities, which makes it hard to operate in dynamic environments. Simultaneous localization, mapping and moving object tracking (SLAMMOT) serves as a solution to deal with moving objects while performing SLAM. The existing work has shown the feasibility of monocular SLAMMOT in dynamic environments. However, monocular SLAMMOT inherits the observability issue of bearings-only tracking in which moving entities would be unobservable according to motions of the camera and moving objects. In this paper, stereo-based SLAMMOT is proposed to solve the observability issue as well as increase the accuracy of localization, mapping and tracking. Simulation and experimental results demonstrate that the proposed stereo SLAMMOT is superior than monocular SLAMMOT in dynamic environments.

Simultaneous localization of mobile robot and multiple sound sources using microphone array

Sound source localization is an important function in robot audition. The existing works perform sound source localization using static microphone arrays. This work proposes a framework that simultaneously localizes the mobile robot and multiple sound sources using a microphone array on the robot. First, an eigenstructure-based generalized cross correlation method for estimating time delays between microphones under multi-source environments is described. A method to compute the far field source directions as well as the speed of sound using the estimated time delays is proposed. In addition, the correctness of the sound speed estimate is utilized to eliminate spurious sources, which greatly enhances the robustness of sound source detection. The arrival angles of the detected sound sources are used as observations in a bearings-only SLAM procedure. As the source signals are not persistent and there is no identification of the signal content, data association is unknown which is solved using FastSLAM. The experimental results demonstrate the effectiveness of the proposed approaches.

RANSAC matching: Simultaneous registration and segmentation

The iterative closest points (ICP) algorithm is widely used for ego-motion estimation in robotics, but subject to bias in the presence of outliers. We propose a random sample consensus (RANSAC) based algorithm to simultaneously achieving robust and realtime ego-motion estimation, and multi-scale segmentation in environments with rapid changes. Instead of directly sampling on measurements, RANSAC matching investigates initial estimates at the object level of abstraction for systematic sampling and computational efficiency. A soft segmentation method using a multi-scale representation is exploited to eliminate segmentation errors. By explicitly taking into account the various noise sources degrading the effectiveness of geometric alignment: sensor noise, dynamic objects and data association uncertainty, the uncertainty of a relative pose estimate is calculated under a theoretical investigation of scoring in the RANSAC paradigm. The improved segmentation can also be used as the basis for higher level scene understanding. The effectiveness of our approach is demonstrated qualitatively and quantitatively through extensive experiments using real data.

Dealing with laser scanner failure: Mirrors and windows

This paper addresses the problem of laser scanner failure on mirrors and windows. Mirrors and glasses are quite common objects that appear in our daily lives. However, while laser scanners play an important role nowadays in the field of robotics, there are very few literatures that address the related issues such as mirror reflection and glass transparency. We introduce a sensor fusion technique to detect the potential obstacles not seen by laser scanners. A laser-based mirror tracker is also proposed to figure out the mirror locations in the environment. The mirror tracking method is seamlessly integrated with the occupancy grid map representation and the mobile robot localization framework. The proposed approaches have been demonstrated using data from sonar sensors and a laser scanner equipped on the NTU-PAL5 robot. Mirrors and windows, as potential obstacles, are successfully detected and tracked.

3D active appearance model for aligning faces in 2D images

Perceiving human faces is one of the most important functions for human robot interaction. The active appearance model (AAM) is a statistical approach that models the shape and texture of a target object. According to a number of the existing works, AAM has a great success in modeling human faces. Unfortunately, the traditional AAM framework could fail when the face pose changes as only 2D information is used to model a 3D object. To overcome this limitation, we propose a 3D AAM framework in which a 3D shape model and an appearance model are used to model human faces. Instead of choosing a proper weighting constant to balance the contributions from appearance similarity and the constraint on consistent 2D shape with 3D shape in the existing work, our approach directly matches 2D visual faces with the 3D shape model. No balancing weighting between 2D shape and 3D shape is needed. In addition, only frontal faces are needed for training and non-frontal faces can be aligned successfully. The experimental results with 20 subjects demonstrate the effectiveness of the proposed approach.