In order to relate information across cameras in a Dynamic Camera Cluster (DCC), an accurate time-varying set of extrinsic calibration transformations need to be determined. Previous calibration approaches rely solely on collecting measurements from a known fiducial target which limits calibration accuracy as insufficient excitation of the gimbal is achieved. In this paper, we improve DCC calibration accuracy by collecting measurements over the entire configuration space of the gimbal and achieve a 10X improvement in pixel re-projection error. We perform a joint optimization over the calibration parameters between any number of cameras and unknown joint angles using a pose-loop error optimization approach, thereby avoiding the need for overlapping fields-of-view. We test our method in simulation and provide a calibration sensitivity analysis for different levels of camera intrinsic and joint angle noise. In addition, we provide a novel analysis of the degenerate parameters in the calibration when joint angle values are unknown, which avoids situations in which the calibration cannot be uniquely recovered. The calibration code will be made available at https://github.com/TRAILab/AC-DCC.

Dynamic Camera Clusters (DCCs) are multi-camera systems where one or more cameras are mounted on actuated mechanisms such as a gimbal. Existing methods for DCC calibration rely on joint angle measurements to resolve the time-varying transformation between the dynamic and static camera. This information is usually provided by motor encoders, however, joint angle measurements are not always readily available on off-the-shelf mechanisms. In this paper, we present an encoderless approach for DCC calibration which simultaneously estimates the kinematic parameters of the transformation chain as well as the unknown joint angles. We also demonstrate the integration of an encoderless gimbal mechanism with a state-of-the art VIO algorithm, and show the extensions required in order to perform simultaneous online estimation of the joint angles and vehicle localization state. The proposed calibration approach is validated both in simulation and on a physical DCC composed of a 2-DOF gimbal mounted on a UAV. Finally, we show the experimental results of the calibrated mechanism integrated into the OKVIS VIO package, and demonstrate successful online joint angle estimation while maintaining localization accuracy that is comparable to a standard static multi-camera configuration.

Dynamic camera cluster (DCC) calibration determines a time-varying set of extrinsic calibration transformations between cameras in a multi-camera cluster, where one or more cameras are mounted on actuated mechanisms. In this paper, we present a novel active vision approach for DCC calibration, which directly reduces the parameter uncertainty by selecting calibration measurements using an information theoretic next-best-view policy. Our system automatically selects the next best measurement for the calibration by determining the optimal actuator inputs which minimize the predicted covariance of the extrinsic parameters. We show that our method is able to successfully estimate calibration parameters up to a user specified accuracy with no manual excitation. We test our method in simulation on a variety of actuated mechanisms and validate the results on a real 3 axis gimbal, and demonstrate our approach is able to achieve accurate calibrations using fewer measurement sets when compared to existing approaches.

Everyone, from a shopper buying shoes to a doctor palpating a growth, uses their sense of touch to learn about the world. 3D printing is a powerful technology because it gives us the ability to control the haptic impression an object creates. This is critical for both replicating existing, real-world constructs and designing novel ones. However, each 3D printer has different capabilities and supports different materials, leaving us to ask: How can we best replicate a given haptic result on a particular output device? In this work, we address the problem of mapping a real-world material to its nearest 3D printable counterpart by constructing a perceptual model for the compliance of nonlinearly elastic objects. We begin by building a perceptual space from experimentally obtained user comparisons of twelve 3D-printed metamaterials. By comparing this space to a number of hypothetical computational models, we identify those that can be used to accurately and efficiently evaluate human-perceived differences in nonlinear stiffness. Furthermore, we demonstrate how such models can be applied to complex geometries in an interaction-aware way where the compliance is influenced not only by the material properties from which the object is made but also its geometry. We demonstrate several applications of our method in the context of fabrication and evaluate them in a series of user experiments.