Youngshik Kim
Hanbat National University
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Publication
Featured researches published by Youngshik Kim.
The International Journal of Robotics Research | 2007
Youngshik Kim; Mark A. Minor
This paper presents a time invariant kinematic motion controller for wheeled mobile robots. Actuator capability, mechanical design, and traction forces governed by terrain features provide velocity and curvature limitations that are used in the design of the controller. A novel path manifold that considers curvature limitations is introduced to provide a desired path shape and convergence to the reference posture or trajectory. Lyapunov techniques are then used to derive a control law that asymptotically converges the robot to an arbitrarily small neighborhood of the path manifold. Posture regulation, path following, and trajectory tracking capability to a similarly scaled neighborhood of the target are provided. Controller parameters are optimized and initial conditions are identified that satisfy physical constraints of the robot and provide smooth commands. Curvature boundaries and asymptotic convergence naturally limit allowable initial conditions and are resolved by driving the robot to intermediate goal points within regions of allowable initial conditions. Posture regulation is evaluated in simulation and experiment on a Compliant Framed wheeled Modular Mobile Robot (CFMMR) for two different terrain surfaces. Trajectory tracking and path following of constant curvature references are evaluated in simulation and experiment, respectively.
international conference on control, automation and systems | 2010
Dong-Hwan Shin; Youngshik Kim; Jinung An
In this study we discuss two-segment legs parameters, torsional stiffness, knee angle, and link ratio, for a biologically inspired terrestrial robot with four legs. Each leg has two-segment links and a passive joint. Simulation results then verify soft legs effectiveness compared to a robot with stiff legs.
The International Journal of Robotics Research | 2010
Youngshik Kim; Mark A. Minor
This paper presents a kinematic motion control strategy for an n-axle Compliant Framed Modular wheeled Mobile Robot (CFMMR). This robot is essentially a passive-joint active-wheel snake robot where coordinated motion of the robot modules is critical for maximizing mobility and minimizing traction forces. A distributed master—slave kinematic motion control structure is proposed where the front axle module of the robot is the master and subsequent axle modules are slaves. An existing path manifold based controller is used to guide the motion of the master. Two steering algorithms with different specializations are then proposed for the slave modules. Performance of the steering algorithms is characterized based upon their capability to reduce traction forces, control final robot posture, and maneuver in a limited space. It is shown that these algorithms satisfy the physical constraints of the robot, which are characterized by path curvature and velocity limitations. Simulation and experimental results validate and characterize the performance of the algorithms.
IEEE Transactions on Robotics | 2007
Xiaorui Zhu; Youngshik Kim; Roy Merrell; Mark A. Minor
A novel motion control and sensing architecture for a two-axle compliant framed wheeled modular mobile robot (CFMMR) is proposed in this paper. The CFMMR is essentially a cooperative mobile robotic system with complex physical constraints and highly nonlinear interaction forces. The architecture combines a kinematic controller for coordinating motion and providing reference commands, robust dynamic controllers for following these commands and rejecting disturbances, and a sensor fusion system designed to provide accurate relative posture estimates. Requirements for each of these subsystems and their respective interconnections are defined in this paper in order to optimize system performance. Experimental results compare performance of the proposed architecture to sub-optimal configurations. Results derived from seven groups of experiments based upon 35 individual tests validate superiority of the architecture.
IEEE Transactions on Robotics | 2010
Youngshik Kim; Mark A. Minor
This paper presents coordinated kinematic control of compliantly coupled multirobot systems for payload transportation. In the robot, unicycle-type axles are connected to a moving platform in an array format using compliant frames. A coordinate system is attached to an ideal center point on the platform to establish robot kinematics. In order to drive the system along a reference trajectory, we coordinate axle velocity commands, while considering frame compliance, nonholonomic constraints, and rigid body kinematics, respectively. These commands are further coordinated to consider configuration stability and physical limitations. Simulation and experimental results evaluate the coordination algorithms for various trajectories.
Journal of Bionic Engineering | 2015
Kyung-min Lee; Youngshik Kim; Jamie Paik; Buhyun Shin
In this research we propose a novel inchworm robot, which is composed of an Electromagnetic Oscillatory Actuator (EOA) and claws. The EOA consists of a yoke, a magnet, and a coil. The overall robot size is 12.2 mm × 11 mm × 9 mm (length × height × width). The locomotion of the robot is achieved by different amounts of slips when the robot stretches and contracts its front leg. To realize locomotion, the working conditions were calculated theoretically and the calculated input signal was applied to the robot. The performance of the inchworm robot was evaluated experimentally with varying input voltages and frequencies. A simple op-amps based driving circuit was used to provide a square-wave input. Travel speed, average distance per step of the robot, and moving distance of the leg and body at each step were measured. The maximum travel speed was 36 mm·s−1 at 30 Hz, which validates our simple locomotion strategy experimentally.
international conference on robotics and automation | 2005
Youngshik Kim; Mark A. Minor
This paper presents a new curvature based smooth time invariant control law for posture regulation and path following control of unicycle type kinematic models. The control law is developed in polar coordinates for posture regulation using nonlinear Lyapunov techniques and extended for path following via waypoint navigation techniques. The algorithm is then applied to a two-axle compliant framed modular mobile robot. To this goal the complex robot kinematics are reduced to an equivalent unicycle kinematic model where we must consider physical constraints on wheel velocity and frame curvature. Bounded curvature and velocity expressions are thus derived as control inputs. The controller is then extended to compensate for non-ideal initial conditions and drift. Simulation and experimental results evaluate algorithm performance.
international conference on advanced intelligent mechatronics | 2005
Xiaorui Zhu; Youngshik Kim; Mark A. Minor
A novel motion control system for compliant framed wheeled modular mobile robots (CFMMR) is studied in this paper. This type of wheeled mobile robot uses rigid axles coupled by compliant frame modules to provide both full suspension and enhanced steering capability without additional hardware. The proposed control system is developed by combining a bounded curvature-based kinematic controller and a nonlinear damping dynamic controller. In particular, multiple forms of controller interaction are examined. A two-axle scout CFMMR configuration is used to evaluate the different control structures. Experimental results verify efficient motion control of posture regulation
Journal of Intelligent Material Systems and Structures | 2016
Bu Hyun Shin; Taesoo Jang; Bong-Jo Ryu; Youngshik Kim
In this study, novel modular shape memory alloy wire–based torsional actuators were designed and fabricated. These shape memory alloy–based actuators provide rotational displacements. The mechanical and thermal properties of a single module shape memory alloy torsional actuator were characterized. Next, a modular shape memory alloy torsional actuator was configured by connecting single actuator modules in series. This modular actuator can be used directly as a soft or biologically inspired robot. Finally, the rolling motion and shape transformation of the modular shape memory alloy torsional actuator (soft robot) were demonstrated with a simple open-loop-based control scheme experimentally validating the novel mobility and actuation of the proposed actuator. For a control input, sequentially coordinated square waves of electric current were supplied to the shape memory alloy actuating units.
Applied Mechanics and Materials | 2011
Youngshik Kim; Dong Hwan Shin; Oh Seok Kwon; Jin Ung An
This research presents a running model for a compliant wheel-leg hybrid mobile robot. A wheel-leg consists of three legs arranged by 120 degrees to each other and passive compliant joints. For simplicity, each leg is treated as a linear spring such that a traditional mass-spring model can be applied to model running of the wheel-leg hybrid robot. In order to achieve stable running, we propose a simple controller that can converge a robot leg to a desired angle of attack asymptotically during the swing phase. Hybrid wheel-leg running is then simulated and results are discussed.