2,638 research outputs found

    Automatic Calibration of Multiple Coplanar Sensors

    Get PDF
    This paper describes an algorithm for recovering the rigid 3-DOF transformation (offset and rotation) between pairs of sensors mounted rigidly in a common plane on a mobile robot. The algorithm requires only a set of sensor observations made as the robot moves along a suitable path. Our method does not require synchronized sensors; nor does it require complete metrical reconstruction of the environment or the sensor path. We show that incremental pose measurements alone are sufficient to recover sensor calibration through nonlinear least squares estimation. We use the Fisher Information Matrix to compute a Cramer-Rao lower bound (CRLB) for the resulting calibration. Applying the algorithm in practice requires a non-degenerate motion path, a principled procedure for estimating per-sensopose displacements and their covariances, a way to temporally resample asynchronous sensor data, and a way to assess the quality of the recovered calibration. We give constructive methods for each step. We demonstrate and validate the end-to-end calibration procedure for both simulated and real LIDAR and inertial data, achieving CRLBs, and corresponding calibrations, accurate to millimeters and milliradians. Source code is available from http://rvsn.csail.mit.edu/calibration

    A microwave dielectric biosensor based on suspended distributed MEMS transmission lines

    Get PDF
    Design and characterization of a miniature microwave dielectric biosensor based on distributed microelectromechanical systems (MEMS) transmission lines (DMTL) is reported in this paper. The biosensor has been realized by bonding the DMTL device with an acrylic fluidic channel. In order to demonstrate the sensing mechanism, the sensor is used to detect the small variation of the concentration of aqueous glucose solutions by measuring the electromagnetic resonant frequency shift of the device. It is observed from the results that the second notch of the reflection coefficient (S-11) varies from 7.66 to 7.93 GHz and the third notch of the reflection coefficient varies from 15.81 to 15.24 GHz when the concentration of the glucose solution ranges from 0 to 347 mg/ml, which indicates that higher order notches have higher sensitivities if looking at the absolute change in frequency

    Flip-chip distributed MEMS transmission lines (DMTLs) for biosensing applications

    Get PDF
    Design and characterization of a flip-chip distributed MEMS transmission line (DMTL) are presented. The concept of using this DMTL as a biosensor is then introduced. Radio frequency experiments on the DMTL loaded with biosamples have been conducted using the most accessible materials, namely, deionized water and aqueous solutions of salts. Results show that the reflection coefficient (S11) of the solution-loaded DMTL is very sensitive to the salt concentration of the solution in the low-frequency ranges of 10 MHz-1 GHz and 3-4.5 GHz. At high frequencies, the relative dielectric constant of the biosample can also be quantitatively determined from the impedance of the DMTL

    An automatic critical care urine meter

    Get PDF
    Nowadays patients admitted to critical care units have most of their physiological parameters measured automatically by sophisticated commercial monitoring devices. More often than not, these devices supervise whether the values of the parameters they measure lie within a pre-established range, and issue warning of deviations from this range by triggering alarms. The automation of measuring and supervising tasks not only discharges the healthcare staff of a considerable workload but also avoids human errors in these repetitive and monotonous tasks. Arguably, the most relevant physiological parameter that is still measured and supervised manually by critical care unit staff is urine output (UO). In this paper we present a patent-pending device that provides continuous and accurate measurements of patient’s UO. The device uses capacitive sensors to take continuous measurements of the height of the column of liquid accumulated in two chambers that make up a plastic container. The first chamber, where the urine inputs, has a small volume. Once it has been filled it overflows into a second bigger chamber. The first chamber provides accurate UO measures of patients whose UO has to be closely supervised, while the second one avoids the need for frequent interventions by the nursing staff to empty the containe

    An automatic critical care urine meter

    Get PDF
    Nowadays patients admitted to critical care units have most of their physiological parameters measured automatically by sophisticated commercial monitoring devices. More often than not, these devices supervise whether the values of the parameters they measure lie within a pre-established range, and issue warning of deviations from this range by triggering alarms. The automation of measuring and supervising tasks not only discharges the healthcare staff of a considerable workload but also avoids human errors in these repetitive and monotonous tasks. Arguably, the most relevant physiological parameter that is still measured and supervised manually by critical care unit staff is urine output (UO). In this paper we present a patent-pending device that provides continuous and accurate measurements of patient’s UO. The device uses capacitive sensors to take continuous measurements of the height of the column of liquid accumulated in two chambers that make up a plastic container. The first chamber, where the urine inputs, has a small volume. Once it has been filled it overflows into a second bigger chamber. The first chamber provides accurate UO measures of patients whose UO has to be closely supervised, while the second one avoids the need for frequent interventions by the nursing staff to empty the containe

    Extrinisic Calibration of a Camera-Arm System Through Rotation Identification

    Get PDF
    Determining extrinsic calibration parameters is a necessity in any robotic system composed of actuators and cameras. Once a system is outside the lab environment, parameters must be determined without relying on outside artifacts such as calibration targets. We propose a method that relies on structured motion of an observed arm to recover extrinsic calibration parameters. Our method combines known arm kinematics with observations of conics in the image plane to calculate maximum-likelihood estimates for calibration extrinsics. This method is validated in simulation and tested against a real-world model, yielding results consistent with ruler-based estimates. Our method shows promise for estimating the pose of a camera relative to an articulated arm's end effector without requiring tedious measurements or external artifacts. Index Terms: robotics, hand-eye problem, self-calibration, structure from motio

    Cooperative monocular-based SLAM for multi-UAV systems in GPS-denied environments

    Get PDF
    This work presents a cooperative monocular-based SLAM approach for multi-UAV systems that can operate in GPS-denied environments. The main contribution of the work is to show that, using visual information obtained from monocular cameras mounted onboard aerial vehicles flying in formation, the observability properties of the whole system are improved. This fact is especially notorious when compared with other related visual SLAM configurations. In order to improve the observability properties, some measurements of the relative distance between the UAVs are included in the system. These relative distances are also obtained from visual information. The proposed approach is theoretically validated by means of a nonlinear observability analysis. Furthermore, an extensive set of computer simulations is presented in order to validate the proposed approach. The numerical simulation results show that the proposed system is able to provide a good position and orientation estimation of the aerial vehicles flying in formation.Peer ReviewedPostprint (published version
    corecore