Suseong Kim

Aerial manipulation using a quadrotor with a two DOF robotic arm

This paper presents aerial manipulation using a quadrotor with a two-DOF robot arm. By considering a quadrotor and robot arm as a combined system, the kinematic and dynamic models are developed, and an adaptive sliding mode controller is designed. With the controller, an autonomous flight experiment is conducted including picking up and delivering an object, which requires accurate control of a quadrotor and robot arm. Overall result shows that the proposed approach demonstrates satisfactory performance as a potential platform which can be utilized in various applications such as inspection, manipulation, or transportation in remote places.

Vision-Guided Aerial Manipulation Using a Multirotor With a Robotic Arm

This paper presents a vision guidance approach using an image-based visual servo (IBVS) for an aerial manipulator combining a multirotor with a multidegree of freedom robotic arm. To take into account the dynamic characteristics of the combined manipulation platform, the kinematic and dynamic models of the combined system are derived. Based on the combined model, a passivity-based adaptive controller which can be applied on both position and velocity control is designed. The position control is utilized for waypoint tracking such as taking off and landing, and the velocity control is engaged when the platform is guided by visual information. In addition, a guidance law utilizing IBVS is employed with modifications. To secure the view of an object with an eye-in-hand camera, IBVS is utilized with images taken from a fisheye camera. Also, to compensate underactuation of the multirotor, an image adjustment method is developed. With the proposed control and guidance laws, autonomous flight experiments involving grabbing and transporting an object are carried out. Successful experimental results demonstrate that the proposed approaches can be applied in various types of manipulation missions.

Operating an unknown drawer using an aerial manipulator

This paper is about opening and closing an unknown drawer using an aerial manipulator. To accommodate practical applications, it is assumed that the direction of motion and mechanical properties of the drawer are not given beforehand. A multirotor combined with a robotic arm is used for the manipulation task. Typical drawers are allowed to move in only one direction, which constrains the motion of the aerial manipulator while operating a drawer. To analyze this interaction, the dynamic characteristics of the aerial manipulator are modeled. Also, configuration of the aerial manipulator for exerting the desired force to a drawer is presented. To handle the uncertainties associated with the mechanism of a drawer, strategies exploiting velocity of the end effector are employed. The proposed approach is validated with experiments including opening and closing a common drawer, which is detected by a camera mounted in the palm of the end effector.

Monte Carlo simulations on performance of double-scattering Compton camera

A double-scattering Compton camera that can effectively obtain three-dimensional emission images in high-energy gamma-ray applications such as nuclear decommissioning and particle therapy monitoring has been developed. The double-scattering Compton camera utilizes two position-sensitive detectors as scatter detectors to determine the trajectory of a scattered gamma-ray, and a scintillation detector as absorber detector to measure the remaining energy of the double-scattered gamma-ray. The benefit of using two scatter detectors is the accurate determination of the gamma-ray trajectory after the scattering at the first scatter detector, which makes possible higher imaging resolution. In the present study, Geant4 Monte Carlo simulations were conducted to compare the performance of the double-scattering Compton camera with that of a similarly dimensioned single-scattering Compton camera for different source energies. Further, the optimal geometry of the multiple-detector-type double-scattering Compton camera was investigated for the purposes of increasing its imaging sensitivity. The results showed that the double-scattering Compton camera offers superior angular resolution over the entire energy range considered in the present study, whereas the single-scattering Compton camera provides greater sensitivity. The results also showed that, in general, the placement of additional detectors in the axial direction (i.e., stacking) is more effective for sensitivity improvement than doing so in the planar direction. This axial placement, however, lowers the imaging resolution. The double-scattering Compton camera exhibited the highest sensitivity when the additional scatter detectors were added to the first scatter detector in the axial direction, and exhibited the highest imaging resolution when the additional detectors were added to first scatter detector in the planar direction. Therefore, the results generally indicated that the first scatter detector is more important than the second not only for improving the sensitivity but also for maintaining a high imaging resolution. We believe that the present studys findings will provide valuable guidelines to researchers looking for the best Compton camera designs for certain objectives.

Surgical management of damaged inferior alveolar nerve caused by endodontic overfilling of calcium hydroxide paste

AIMnTo evaluate the neurosensory outcome of management of damaged inferior alveolar nerves caused by endodontic overfilling and to assess the efficacy of delayed surgical intervention.nnnMETHODOLOGYnNine patients who underwent surgical removal of extruded endodontic material were included. All patients were evaluated for neurosensory function using a set of standardized tests. The outcome of surgical intervention was evaluated through patient interview and quantitative statistical analysis.nnnRESULTSnSurgical procedures included foreign body removal, microsurgical external/internal decompression, excision of neuroma followed by nerve repair, and excision of damaged nerve segment with interpositional nerve graft. Seven of the nine patients had significant improvement according to the follow-up neurosensory assessment. Four patients reported significant improvement, three patients reported mild improvement and two patients reported no appreciable improvement in the Visual Analog Scale (VAS). Two patients who reported no appreciable improvement in VAS also did not achieve FSR. In these patients, calcium hydroxide was spread widely along the IAN and a surgical approach was obtained via sagittal spit osteotomy. The mean time to reach FSR was 222.7 (±41.8)xa0days with a range of 106-397xa0days. In the early repair group who received surgery within 60xa0days, three out of five patients achieved FSR in a mean time of 198.0 (±76.2)xa0days. The mean time to FSR in all four subjects who received surgical attention over 60xa0days after injury was 241.3 (±139.8)xa0days with a range of 106-397xa0days. As all four cases in the late repair group with limited amount of nerve injury achieved FSR, only 3 of 5 early repair cases with wide-spread injury achieved a similar outcome.nnnCONCLUSIONnThe results of this case series confirmed the notion that surgical management of the inferior alveolar nerve is effective in the treatment of nerve injuries caused by endodontic extrusion of calcium hydroxide paste. Delayed surgical repair of the inferior alveolar nerve can be indicated and helpful for the neurosensory recovery of damaged IAN, however, the surgical management was less effective in case of widespread nerve injuries.

Control of an aerial manipulator using on-line parameter estimator for an unknown payload

This paper presents an estimation and control algorithm for an aerial manipulator using a hexacopter with a 2-DOF robotic arm. The unknown parameters of a payload are estimated by an on-line estimator based on parametrization of the aerial manipulator dynamics. With the estimated mass information and the augmented passivity-based controller, the aerial manipulator can fly with the unknown object. Simulation for an aerial manipulator is performed to compare estimation performance between the proposed control algorithm and conventional adaptive sliding mode controller. Experimental results show a successful flight of a custom-made aerial manipulator while the unknown parameters related to an additional payload were estimated satisfactorily.

Robust acceleration control of a hexarotor UAV with a disturbance observer

This paper presents an acceleration control of a hexarotor unmanned aerial vehicle (UAV) in the earth-fixed frame with a disturbance observer (DOB). Unlike conventional cascade control structures where the outer-loop position controller generates the desired attitude command, the position controller in this paper generates the desired acceleration command in X, Y, Z axis of the earth-fixed frame. With acceleration control combined with DOB, the UAV could manage the lateral disturbance force that makes the trajectory tracking very challenging. This is a new concept compared with existing DOB-based UAV control approaches which aim to cancel the moment disturbance for precise attitude control. The small-gain theorem is used for stability analysis and Q-filter bandwidth design. Both simulation and actual experiment are shown to validate the performance of the proposed design.

Backstepping Control on SE(3) of a Micro Quadrotor for Stable Trajectory Tracking

This paper presents a back stepping controller based on SE(3) to track the desired trajectory for a quad rotor unmanned aerial vehicle. The controller consists of two parts: 1) a position control part and 2) an attitude control part. The position controller is used to track the desired Cartesian coordinates using position and velocity errors, while the attitude controller uses the rotation matrix error and body angular velocity error to stabilize attitude dynamics expressed on SO(3). Simulation results illustrate the more stable tracking performance of the proposed controller in noisy environments in comparison with geometric controller. Experimental results on a micro quad rotor show the satisfactory performance of the proposed controller.

Aerial grasping of cylindrical object using visual servoing based on stochastic model predictive control

This paper concentrates on design of a vision-based guidance command for aerial manipulation of a cylindrical object, using a stochastic model predictive approach. We first develop an image-based cylinder detection algorithm that utilizes a geometric characteristic of perspectively projected circles in 3D space. To enforce the object to be located inside sight of a camera, we formulate a visual servoing problem as a stochastic model predictive control (MPC) framework. By regarding x and y axes rotational velocities as stochastic variables, we guarantee the visibility of the camera considering underactuation of the system. We also provide experimental results that validate effectiveness of the proposed algorithm.

Vision-Based Collaborative Lifting Using Quadrotor UAVs

This paper presents vision-based lifting of a payload using two quadrotor UAVs. It is assumed that the exact position of a payload is not available. Specifically, for multiple UAVs to approach and connect the correct spots on the payload, image-based visual servo (IBVS) is adopted. A sliding mode controller is designed to track reference positions and velocities generated by IBVS. A scenario is designed from taking off to lifting the payload. The proposed methods and settings are validated with an experiment.