• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.1-6
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• 2008

This paper presents muscle-inspired serial digital actuators, achieving the improvement of the range-to-precision and range-to-voltage performance. We propose a weight-balanced design for the serial actuators with serpentine springs using serial arrangement of digital actuators. We have measured the displacement range, precision, and drive voltage at unit and serial actuation of 1Hz. The serial digital actuators produce a full range displacement of $28.44{\pm}0.02{\mu}m$, accumulating the unit displacement of $2.8{\pm}0.5{\mu}m$ at the operating voltage of $4.47{\pm}0.07V$. In addition, the serial digital actuators having the displacement precision of $37.94{\pm}6.26nm$ do not accumulate the precision of the unit actuators, $36.0{\pm}17.7nm$. We experimentally verify that the serial digital actuators achieve the range-to-squared-voltage ratio of $1.423{\mu}m/V^2$ and the range-to-precision ratio of 749.6.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.746-755
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• 2009

Recently, NMEA2000 became the de facto standard of the communication protocol for the instrument level network in vessels, and it is anticipated that most of the vessels will be equipped with the sensors and actuators based on this protocol. The conventional serial communication specifications such as RS-232, RS-485, or even NMEA0183 are single-talker/multiple-listener and interconnection among multiple sensors and/or actuators usually results in a bundle of wires. On the other hand, NMEA2000 is a true bus type(multiple-talker/multiple-listener) protocol and theoretically up to 256 instruments can be hot-plugged. With the advent of the protocol, it is necessary to consider a new type of monitoring system for the instruments in vessels: In most traditional serial communication environments, a dedicated monitor or user interface was necessary for each sensor or actuator as it was simply not easy to collect data in a single place. With NMEA2000, the collection of various types of information is simple. An embedded system can be employed to combine, to arrange and to display informations from various types of devices. Assuming that the actuators and sensors on a vessel are interconnected by NMEA2000 standard, we devise a tentative interactive vessel monitoring system in which the following 4 kinds of informations are collected and delivered: the navigation, engine, weather and tanks informations.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.810-815
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• 2004

In this paper, we propose new parallel mechanism of a 3 dimensional biped robot whose each leg is composed of two 3-dof parallel platforms linked serially. This proposed parallel mechanism is able to move freely in the man-made environment and is applied to various fields, such as medical, welfare, and so on. And a total weight of each leg is expected to be lighter than serial linked leg. One side leg consists of a 3-dof orientation platform and 3-dof asymmetric parallel platform. The former consists of three active linear actuators and seven passive joints, and the latter of two active linear actuators, one active rotational actuator and eight passive joints. Thus, there are two kinds of parallel platforms each chain's elements and active joint's positions are different for the biped robot to move freely like a serial link without the kinematics constraints. The effectiveness and the performance of the proposed parallel mechanism and locomotion trajectory are shown in computer simulations with a 12-DOF parallel biped robot.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.202-208
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• 2008

A 6 DOF Multi axis simulation table (MAST) is used to perform vibration and fatigue tests for parts or assemblies of automobiles, aircraft, or other systems. It consists of a table and 6 linear actuators. For its attitude control, we have to adjust the lengths of 6 actuators properly. The system is essentially a parallel mechanism. Three actuators are connected to the table directly and other three actuators are connected indirectly. Because of these, the MAST shows also a serial mechanism#s property: the inverse kinematics is more complicated than a pure parallel mechanism and each actuator can operate independently. The authors have performed a kinematics analysis of the 6 DOF MAST. We have presented an analytical and a numerical solution for the inverse and forward kinematics, and we have verified the solutions by a 3D CAD software.

• Smart Structures and Systems
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• v.13 no.4
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• pp.711-730
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• 2014

In this paper the system dynamic influences in actuators with variable stiffness as contemporary used in robotics for safety and efficiency reasons are investigated. Therefore, different configurations of serial and parallel elasticities are modeled by dynamic equations and linearized transfer functions. The latter ones are used to identify the characteristic behavior of the different systems and to study the effect of the different elasticities. As such actuation concepts are often used to reach energy-efficient operation, a power consumption analysis of the configurations is performed. From the comparison of this with the system dynamics, strategies to select and control stiffness are derived. Those are based on matching the natural frequencies or antiresonance modes of the actuation system to the frequency of the trajectory. Results show that exclusive serial and parallel elasticity can minimize power consumption when tuning the system to the natural frequencies. Antiresonance modes are an additional possibility for stiffness control in the series elastic setup. Configurations combining both types of elasticities do not provide further advantages regarding power reduction but an input parallel elasticity might enable for more versatile stiffness selection. Yet, design and control effort increase in such solutions. Topologies incorporating output parallel elasticity showed not to be beneficial in the chosen example but might do so in specific applications.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.621-625
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• 2005

This paper presents a new hybrid serial-parallel robot(HSPR), which has six degrees of freedom driven by ball screw linear actuators and motored joints. This hybrid robot design presents a compromise between high rigidity of fully parallel manipulators and extended workspace of serial manipulators. The hybrid robot has a large, singularity-free workspace and high stiffness. Therefore, the presented kinematic structure of the hybrid robot is particularly suitable for multi-tasking machining processes such as milling, drilling, deburring and grinding. In addition to the machining processes, the hybrid robot can be used for welding, fixturing, material handling and so on. The study on design of the hybrid robot is performed. A kinematic analysis and mechanism description of the hybrid robot with six-controlled degree of freedom is presented. In the virtual design works by DADS, workspace and force analysis are discussed. A numerical model is treated to demonstrate our analysis and to determine the range of permissible extension of the struts. Also, we determine some important design parameters for the hybrid robot.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.60-68
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• 1998

Parallel link manipulators have an ability of more precise positioning than serial open-loop manipulators. However. general parallel link manipulators have been restricted to the real applications since they have limited workspace due to interference among actuators. In this study, we suggest a closed-loop manipulator with 6 degrees-of-freedom and with enlarged workspace. It consists of two parts for minimizing the interference among actuators. One part is lower structure with planar 3 degrees-of-freedom and the other is upper one with spatial 3 degrees-of-freedom. Forward kinematics and inverse kinematics are solved, research about singularity points are carried out and workspace is evaluated. The comparison of workspace between Stewart platform, which is the typical parallel link manipulator, and the suggested manipulator shows that the workspace of the latter is wider than that of the former. Especially, simulation results also show that the suggested manipulator is more suitable when there needs rotation in the end-effector.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.3
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• pp.360-371
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• 1998

In this paper, output precision characteristics of a planar 6 degree-of-freedom parallel mechanisms are investigated, where the 6 degree-of-freedom mechanism is formed by adding an additional link along with an actuated joint in each serial subchain of the planar 3 degree-of-freedom parallel mechanism. Kinematic analysis for the parallel mechanism is performed, and its first-order kinematic characteristics are examined via kinematic isotropic index, maximum and minimum input-output velocity transmission ratios of the mechanisms. Based on this analysis, two types of planar 6 degrees-of-freedom parallel manipulators are selected. Then, dynamic characteristics of the two selected planar 6 degree-of-freedom parallel mechanisms, via Frobenius norms of inertia matrix and power modeling array, are investigated to compare the magnitudes of required control efforts of both three large actuators and three small actuators when the link lengths of three additional links are changed. It can be concluded from the analysis results that each of these two planar 6 degrees-of-freedom parallel mechanisms has an excellent control-in-the-small characteristics and therefore, it can be very effectively employed as a high-precision macro-micro manipulator when both its link lengths and locations of small and large actuators are properly chosen.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2331-2336
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• 2005

This paper proposes a new haptic device using a parallel mechanism with gimbal type actuators. This device has three legs actuated by 2-DOF gimbal mechanisms, which make the device simple and light by fixing all the actuators to the base. Three extra sensors are placed at passive joints to obtain a unique solution of the forward kinematics problem. The proposed haptic device is developed for an operator to use it on a desktop in due consideration of the size of an average Korean. The proposed haptic device has a small workspace for on operator to use it on a desktop and more sensitivity than a serial type haptic device. Therefore, the motors of the proposed haptic device are fixed at the base plate so that the proposed haptic device has a better dynamic bandwidth due to a low moving inertia. With this conceptual design, optimization of the design parameters is carried out. The objective function is defined by the fuzzy minimum of the global design indices, global force/moment isotropy index, global force/moment payload index, and workspace. Each global index is calculated by a SVD (singular value decomposition) of the force and moment parts of the jacobian matrix. Division of the jacobian matrix assures a consistency of the units in the matrix. Due to the nonlinearity of this objective function, Genetic algorithms are adopted for a global optimization.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.171-177
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• 2010

This paper presents the development of a new 6-DOF parallel-kinematic motion simulator. The moving platform is connected to the fixed base by six P-S-U (Prismatic-Spherical-Universal) serial chains. Comparing with the well-known Gough-Stewart platform-type motion simulator, it uses commercialized linear actuators mounted at the fixed base whereas a 6-UPS manipulator uses telescopic linear ones. Therefore, the proposed motion simulator has the advantages of easier fabrication and lower inertia over a 6-UPS counterpart. Furthermore, since most forces acting along the legs are transmitted to the structure of linear actuators, smaller actuation forces are required. The inverse position and Jacobian matrix are analyzed. In order to further increase workspace, inclined arrangement of universal joints is introduced. The optimal design considering workspace and force transmission capability has been performed. The prototype motion simulator and PC-based real-time controller have been developed. Finally, position control experiment on the prototype has been performed.