Won Jee Chung

Optimal mechanism design of in-pipe cleaning robot

Recently, interests on cleaning robots workable in pipes (termed as in-pipe cleaning robot) are increasing because Garbage Automatic Collection Facilities (i.e, GACF) are widely being installed in Seoul metropolitan area of Korea. So far research on in-pipe robot has been focused on inspection rather than cleaning. In GACF, when garbage is moving, we have to remove the impurities which are stuck to the inner face of the pipe (diameter: 300mm or 400mm). Thus, in this paper, by using TRIZ (Inventive Theory of Problem Solving in Russian abbreviation), we will propose an in-pipe cleaning robot of GACF with the 6-link sliding mechanism which can be adjusted to fit into the inner face of pipe using pneumatic pressure(not spring). The proposed in-pipe cleaning robot for GACF can have forward/backward movement itself as well as rotation of brush in cleaning. The robot body should have the limited size suitable for the smaller pipe with diameter of 300mm. In addition, for the pipe with diameter of 400mm, the links of robot should stretch to fit into the diameter of the pipe by using the sliding mechanism. Based on the conceptual design using TRIZ, we will set up the initial design of the robot in collaboration with a field engineer of Robot Valley, Inc. in Korea. For the optimal design of in-pipe cleaning robot, the maximum impulsive force of collision between the robot and the inner face of pipe is simulated by using RecurDyn® when the link of sliding mechanism is stretched to fit into the 400mm diameter of the pipe. The stresses exerted on the 6 links of sliding mechanism by the maximum impulsive force will be simulated by using ANSYS® Workbench based on the Design Of Experiment(in short DOE). Finally the optimal dimensions including thicknesses of 4 links will be decided in order to have the best safety factor as 2 in this paper as well as having the minimum mass of 4 links. It will be verified that the optimal design of 4 links has the best safety factor close to 2 as well as having the minimum mass of 4 links, compared with the initial design performed by the expert of Robot Valley, Inc. In addition, the prototype of in-pipe cleaning robot will be stated with further research.

Thermal Model of High-Speed Spindle Units

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Implementation of LabVIEW®-based joint-linear motion blending on a lab-manufactured 6-axis articulated robot (RS2)

For fast and accurate motion of 6-axis articulated robot, more noble motion control strategy is needed. In general, the movement strategy of industrial robots can be divided into two kinds, PTP (Point to Point) and CP (Continuous Path). In recent, industrial robots which should be co-worked with machine tools are increasingly needed for performing various jobs, as well as simple handling or welding. Therefore, in order to cope with high-speed handling of the cooperation of industrial robots with machine tools or other devices, CP should be implemented so as to reduce vibration and noise, as well as decreasing operation time. This paper will realize CP motion (especially joint-linear) blending in 3-dimensional space for a 6-axis articulated (lab-manufactured) robot (called as “RS2”) by using LabVIEW® [6] programming, based on a parametric interpolation. Another small contribution of this paper is the proposal of motion blending simulation technique based on Recurdyn® V7, in order to figure out whether the joint-linear blending motion can generate the stable motion of robot in the sense of velocity magnitude at the end-effector of robot or not. In order to evaluate the performance of joint-linear motion blending, simple PTP (i.e., linear-linear) is also physically implemented on RS2. The implementation results of joint-linear motion blending and PTP are compared in terms of vibration magnitude and travel time by using the vibration testing equipment of Medallion of Zonic®. It can be confirmed verified that the vibration peak of joint-linear motion blending has been reduced to 1/10, compared to that of PTP.

A study on pressure and flow pulsation of swash plate type variable piston pump through analysis of pulsation variables and valve plate notch design for automation of hydraulic system

In order to improve efficiency/productivity and thus facilitate work at industry sites, hydraulic system uses hydraulic fluid and has higher power density than other power transfer systems. A swash plate type variable piston pump among hydraulic equipment is the most important and basic component composing the hydraulic system, which plays a role of converting mechanical energy into fluid energy. This paper focuses on the simulation technique that can estimate the reduction effect of the pressure/flow pulsation depending on analysis of pulsation variables and notch shape of valve plate of swash plate type variable piston pump. First, we will consider the theoretical kinematic analysis according to the variable swash plate angle and rotational velocity in order to design single piston pump using SimulationX®. Based on this kinematic analysis, we will analyze the pulsation variables such as piston diameter, maximum piston stroke including the swash plate angle and pitch circle diameter of swash plate type variable piston pump. Also, in designing the notch shape of valve plate of swash plate type variable piston pump as one of pulsation variables, we will investigate the effect of pulsation by comparing with two type notches (circular type vs. V type). Similarly we will analyze the pressure/flow pulsation notch types in nine piston pump model, which is mainly designed for the actual swash plate type variable piston pump. This paper not only can confirm that effect of the pressure/flow pulsation according to pulsation variables but also can be referred to as the development of SimulationX® based simulation technique to be applied to notch shape optimization for a swash plate type variable piston pump.

Optimization of cooperative motion for humanoid robots using a genetic algorithm

Humanoid robots usually consist of a number of joint actuators. Thus, it is essential to adequately control the torques of the joint actuators for achieving desirable motion. Also, torque profile needs to be properly generated especially when a robot is to be moved in cooperation with external environment. For the purpose, this paper proposed a method of optimizing humanoid-robot cooperative motion using a genetic algorithm to find an optimized posture in consideration of torque distribution. An eighteen degree-of-freedom humanoid robot was adopted in this study, and a motion pushing an object was considered. When the robot pushing an object moves from a position to one of the next candidate positions, the torques for all joints were calculated. Then, the torques obtained was reflected to an objective function, which was to be minimized by a genetic algorithm. Here, the objective function was designed in such a way that the surplus torques for all joints should be maximized. As a result of successive minimization processes, a posture optimized for the cooperative motion was found. To show the effectiveness of the proposed method, a series of simulations were carried out for a humanoid robot, and the results were analyzed. The simulation results show that the proposed method can be extended to the control of torques for humanoid robots cooperative with external environment.

A Study on simulationX® - based simulation technique to the design of valve plate and pressure pulsation characteristic according to precompression sections for swash plate type piston pump

Among the automation systems, hydraulic system which uses hydraulic fluid and conveys power, has a high density of power and facilitates a close control of load motion using a hydraulic actuator. Also, this hydraulic system has a quick response characteristic due to incompressibility. The swash plate type and bent axis type piston pumps which convert a rotary movement of a rotation axis into a reciprocating motion. In this paper, we deal with a variable swash plate type of piston pump and its basic structure is shown in Fig. 1. For safe operation of automated hydraulic equipment, hydraulic fluid should maintain smooth pressure increase and decrease in order to reduce this pulsation, but this pulsation highly varies depending on the shapes of the valve plate notch and an accurately designed valve plate can decrease pulsation and relieve a surge power in the pump. For such reasons, the shape of the valve plate notch or the design of valve plate itself is extremely important. So we analyze the effects of pressure and flow pulsation depending on the design factors, using a hydraulic analysis program, SimulationX® (Germany). Finally we will show the effectiveness of our proposed design of pre-compression sections on a valve plate in terms of low pulsation by using the hydraulic analysis program, SimulationX®.

Application of AMESim ® & CFX ® -based technique to the valve behavior characteristics of regulator for hydraulic winch

The hydraulic equipments using hydraulic fluid have higher power outputs than those of other systems, which is why they have long been used for automation in construction and machinery industry. Among the hydraulic equipments, the regulator used in the hydraulic winch, which is an item of the deck machinery, is one of the important parts that can improve the efficiency and the output in the hydraulic winch system. Our research defines a parameter design of the hydraulic regulator. Using AMESim®, we will conduct 1D Modeling. And by utilizing CFX® which then enables us to use 3D Modeling, our research will analyze a change in pressure of each port resulting from the regulators spring constant and a change in primary tension-compression field. Our research, then, will analyze an alteration in trait drawn from a change in the interval between spool and sleeve. As indicated by the results of our research, we believe it can be used for design of the regulator used for hydraulic winch in the deck machinery.

Implementation of a RecurDyn ® and LabVIEW ® -based 2-axis additional axes (tilting/rolling) strategy on a 6-axis articulate robot for improving process efficiency of welding

Present industrial sites need not only robots for simple repetitive works and welding but also industrial robots to perform diverse functions in combination with machine tools. Welding works require soft and accurate route movements of robots. It is not too much to say that it is indispensable to add additional axes to a process requiring these precise movements. Therefore, this paper aims to realize 2-axis additional axes, which increases processing efficiency of a robot by controlling in harmful environments or design fields beyond human reach. Ultimately, this is to create temporal and efficient profits in industrial processing sites including welding and assembling 6-axis articulated robot (RS2). Also, using RecurDyn®, a simulation-based technique is applied. And the motion paths of the welding rod will be compared for two cases in order to verify the necessity of the 2-axis additional axes: 1) when there are no 2-axis additional axes and 2) when there are 2-axis additional axes during welding using the RS2. For this purpose, the angle variations of RS2 axes required for a simulation are compared, on the assumption that each of the four points of the welding bed installed in the 2-axis additional axes of the welding rod in Solidworks® is point-welded. Then an actual 2-axis additional axes equipment will be grafted on to RS2 and the process times depending on the existence of 2-axis additional axes are compared using a PC-based robot control program, LabVIEW®. The comparison will imply that grafting a 2-axis additional axes equipment on to a 6-axis articulated robot make it possible to control a robot easily, to decrease the process route and the process time drastically, and to maximize robot efficiency.

Application of SimulationX®-based. Technique to the reduction of pressure pulsation according to tilting angles of a swash plate and notch shapes of a valve plate for swash plate type piston motor

Machinery industry has constantly driven research on automation systems that use mechanical energy to increase the efficiency, productivity and convenience of production systems. In particularly the hydraulic systems using hydraulic fluid have higher power outputs than those of other systems, which is why they have long been used in construction and machinery industry. Among hydraulic equipment, the swash-plate type piston motor is the most important and indispensable component in construction and machinery industry, converting fluid energy into mechanical energy. To design a less noisy and more stable swash-plate type piston motor, the tilting angles of swash plates and the notch shapes of valve plates need be investigated. This paper first will investigate a kinematic analysis of a swash-plate type piston motor model, using the hydraulic analysis program SimulationX® to 9 piston motor model and to simulate the tilting angle of swash-plate for the low-pressure pulsation and torque pulsation of the swash-plate type motor. Finally, we conducts modeling the notch shapes of the valve plate and analyse the effects of design parameters on torque stabilization and pressure pulsation as well as those of a non-notch, V-type notch and U-type notch on pulsation reduction and torque stabilization. The simulation result on pulsation reduction and torque stabilization will serve as reference data for determining some optimal figures in designing swash-plate type piston motors.

Design and optimization of a 2-link type overboarding mechanism for the drop/lift automation of an active/passive sonar system in a surface ship

Active/passive type sonar systems have the receiving array that measures sound waves, transmitter towed body that converts sound waves, transmitter towing cable that controls the depth of the transmitter towed body, and array cable that connects the receiving array and transmitter towed body. With the research on the active/passive sonar system, a variety of mechanisms of the overboarding unit suitable for the limited environments have been developed. The link mechanism for efficient drop/lift of sonar system was researched in the paper of Park et al. [2] However, single link and actuator were used here that structural stability is lacked. Also, efficiency of storage also falls because complete storage inside the hull is impossible. In this paper, a sub-actuator is added in the bottom part to strength the stability of drop/lift of sonar equipment in which a link mechanism is designed to enable complete storage in the hull through the optimization of GA (Genetic Algorithm) method using MATLAB®. The mechanism proposed in this paper is 2-link type with 2 actuators equipped and is classified into the main link part and sub-link part for kinematic analysis and optimization. Reduction of required space and stability is secured compared to the Park et al.s mechanism. This will have great advantage in the aspect of work efficiency and safety of workers, and maintenance.