Chang-Sei Kim

Open-loop position control of a polymer cable–driven parallel robot via a viscoelastic cable model for high payload workspaces

A polymer cable–driven parallel robot has a wide range of potential industrial applications by virtue of its light actuator dynamics, high payload capability, and large workspace. However, due to a viscoelastic behavior of polymer cable and difficulty in actual cable length measurement, there have been inevitable position and tracking control accuracy problems such as pick and place a high payload application. In this article, to overcome control problem, we propose a model-based open-loop control with the cable elongation compensation via experimentally driven cable model and switching control logic without additional Cartesian space feedback signal. The approach suggests a five-element cable model that is made with series combination of a linear spring and two Voigt models as a function of payload and cable length that are available to be measured in real-time. Experimental results show that using the suggested method, the cable length error due to viscoelastic effect can be compensated, and thus the position control accuracy of the polymer cable–driven parallel robot improved remarkably especially in gravity direction.

A Polymer Cable Creep Modeling for a Cable-Driven Parallel Robot in a Heavy Payload Application

A polymer cable driven parallel robot can be an effective system in many fields due to its fast dynamics, high payload capability and large workspace. However, creep behavior of polymer cables may yield a posture control problem, especially in high payload pick and place application. The aim of this paper is to predict creep behavior of polymer cables by using different mathematical models for loading and unloading motion. In this paper, we propose a five-element model of the polymer cable that is made with series combination of a linear spring and two Voigt models, to portray experimental creep in simulation. Ultimately, the cable creep can be represented by payloads and cable length estimated according to the changes of actual payloads and cable lengths in static condition.

Dual tumor-targeted multifunctional magnetic hyaluronic acid micelles for enhanced MR imaging and combined photothermal-chemotherapy

Multifunctional polymeric micelles were developed as a promising dual tumor-targeted drug delivery platform for magnetic resonance (MR) imaging and combined photothermal-chemotherapy. HA-C16 copolymers were synthesized via peptide formation process with subsequent co-encapsulation of therapeutic agent docetaxel (DTX) and superparamagnetic iron oxide nanoparticles (SPIONs) to form the multifunctional micelles. The micelles exhibited uniform nanosize and remarkable colloidal stability in aqueous solution. The sustained drug release behavior from HA micelles was observed over the test period. Moreover, the specific targeting capability based on CD44 recptor-mediated endocytosis and the enhanced targeting efficacy by in presence of external magnetic field were investigated. The clustered SPIONs within micelles exerted excellent contrast effect with high r2 relaxivity in MR phantom test. Furthermore, the multifunctional micelles could readily convert light to heat to hyperthermia temperature upon near infrared light irradition and induce photothermal ablation to breast cancer cells. The combined photothermal therapy with DTX-mediated chemotherapy of the developed multifunctional polymeric micells could generate a synergistic therapeutic effect. Based on these findings, the resulting multifunctional micelles may provide high potential for multimodality theragnosis of cancer.

Folate receptor-targeted liposomal nanocomplex for effective synergistic photothermal-chemotherapy of breast cancer in vivo

An effective nanoparticle-based drug delivery platform holds great promise for non-invasive cancer therapy. This study explores the breast tumor regression in vivo by synergistic photothermal-chemotherapy based on liposomal nanocomplex (folic acid-gold nanorods-anticancer drug-liposome). The proposed liposomal nanocomplex can enhance the tumor targeting by functionalizing folic acid (FA) molecules on the surface of liposome that encapsulates both gold nanorods (AuNRs) and the doxorubicin (DOX) to combine the photothermal therapy and the chemotherapy, respectively. Herein, 7-nm gold nanorods were fabricated and co-encapsulated with DOX into nanoliposomes functionalized with FA, with an average diameter of 154u2009nm, for active targeting to the cancer cells. The experimental results showed that the FA targeting liposomes had better cellular uptake than the non-targeting liposomes (AuNRs-DOX-LPs). Especially, upon 5u2009min exposure to near infrared (NIR) irradiation (808u2009nm) triggered DOX release could be achieved to 46.38% in 60u2009min at pH 5.5. In addition, in vitro cell proliferation assays indicated that, with synergistic photothermal-chemotherapy, the targeting liposomes could significantly enhance the toxicity towards the cancer cells with the IC50 value of 1.90u2009±u20090.12u2009μg mL-1. Furthermore, in vivo experiments on the breast tumor-bearing mice showed that the targeting liposomes could effectively inhibit the growth of the tumors using the combined strategy.

Geometric Parameter Calibration for a Cable-Driven Parallel Robot Based on a Single One-Dimensional Laser Distance Sensor Measurement and Experimental Modeling

A cable-driven parallel robot has benefits of wide workspace, high payload, and high dynamic response owing to its light cable actuator utilization. For wide workspace applications, in particular, the body frame becomes large to cover the wide workspace that causes robot kinematic errors resulting from geometric uncertainty. However, appropriate sensors as well as inexpensive and easy calibration methods to measure the actual robot kinematic parameters are not currently available. Hence, we present a calibration sensor device and an auto-calibration methodology for the over-constrained cable-driven parallel robots using one-dimension laser distance sensors attached to the robot end-effector, to overcome the robot geometric uncertainty and to implement precise robot control. A novel calibration workflow with five phases—preparation, modeling, measuring, identification, and adjustment—is proposed. The proposed calibration algorithms cover the cable-driven parallel robot kinematics, as well as uncertainty modeling such as cable elongation and pulley kinematics. We performed extensive simulations and experiments to verify the performance of the suggested method using the MINI cable robot. The experimental results show that the kinematic parameters can be identified correctly with 0.92 mm accuracy, and the robot position control accuracy is increased by 58%. Finally, we verified that the developed calibration sensor devices and the calibration methodology are applicable to the massive-size cable-driven parallel robot system.

Real-time microrobot posture recognition via biplane X-ray imaging system for external electromagnetic actuation

PurposeAs a promising intravascular therapeutic approach for autonomous catheterization, especially for thrombosis treatment, a microrobot or robotic catheter driven by an external electromagnetic actuation system has been recently investigated. However, the three-dimensional (3D) real-time position and orientation tracking of the microrobot remains a challenge for precise feedback control in clinical applications owing to the micro-size of the microrobot geometry in vessels, along with bifurcation and vulnerability. Therefore, in this paper, we propose a 3D posture recognition method for the unmanned microrobotic surgery driven by an external electromagnetic actuator system.MethodsWe propose a real-time position and spatial orientation tracking method for a millimeter-sized intravascular object or microrobot using a principal component analysis algorithm and an X-ray reconstruction. The suggested algorithm was implemented to an actual controllable wireless microrobot system composed of a bullet-shaped object, a biplane X-ray imaging device, and an electromagnetic actuation system. Numerical computations and experiments were conducted for the performance verification.ResultsThe experimental results showed a good performance of the implemented system with tracking errors less than 0.4xa0mm in position and 2° in orientation. The proposed tracking technique accomplished a fast processing time, ~u20090.125xa0ms/frame, and high-precision recognition of the micro-sized object.ConclusionsSince the suggested method does not require pre-information of the object geometry in the human body for its 3D shape and position recognition, it could be applied to various elliptical shapes of the microrobot system with computation time efficacy and recognition accuracy. Hence, the method can be used for therapeutic millimeter- or micron-sized manipulator recognition in vascular, as well as implanted objects in the human body.