Panyoung Kim

Path tracking for a hydraulic excavator utilizing proportional-derivative and linear quadratic control

This paper presents a three-dimensional path tracking strategy for a hydraulic excavator. It mainly aims to design the controller for allowing the excavator to follow typical working motions of a skillful operator such as leveling and truck loading. The performance of the designed controller is verified through real-time experiments using a 21-ton class excavator in which displacement sensors, electro-proportional pressure reducing valves, and communication devices are incorporated. Basically, proportional-derivative (PD) controller with dead zone compensation is used to control the cylinder displacements and swing angle. In order to enhance the performance, a linear quadratic outer-loop is introduced for boom, arm, and bucket joints, which compensates reference inputs of the nonlinear PD controller. Experiments of individual joints show that the designed outer-loop can provide faster rise time than the nonlinear PD controller itself. Furthermore, experimental results demonstrate the feasibility of the proposed algorithm for achieving autonomous compliant motions of both leveling and truck loading.

A Study on the Durability Design of a Hydraulic Cylinder for an Excavator

A hydraulic cylinder is a primary component of an excavator and is used for activating attachments such as boom, arm, and bucket. Generally, the cylinder is prone to structural problems such as buckling and fatigue failure caused by cyclic high pressure. Therefore, the safety margin for fatigue, yield, and buckling during the design lifetime should be evaluated at the durability-design stage. The durability design includes basic and detailed stages. In the basic design, the principal dimensions of the rod and tube are determined by considering the working force, speed, and range with respect to yield and buckling. In the detailed design, the dimensions of the rod notch, welds, tube end, gland, orifice, and cushion ring are determined by considering the fatigue safety. We present and discuss the overall procedure for durability design and the related analysis techniques.

Simulation-Aided Testing of Electro-Hydraulic Pump for Excavator

This paper presents a concept of pump HIL (Hardware-In the Loop) Simulation system for testing an electro-hydraulic pump of mid-class excavator. The pump HIL Simulation system integrates both the system analysis and the pump bench evaluation technique in order to enable the evaluation of the control performance of the pump during various operating condition with the entire excavator system. Hence, the analytical system model of the excavator is developed for calculating hydraulic load variation which applied to the pump during working cycle. To reflect the real dynamic characteristics of the pump, the pump in the system model is replaced with the real pump of the HIL test-bed. Moreover, linear controller is designed to test the discharge flow tracking performance of the pump and to validate the function of the HIL Simulation system. As a result, the proposed pump HIL Simulation system is verified and more effective for the advanced pump test-bed in the viewpoint of the performance evaluation.Copyright

Development of Wheel Loader V-Pattern Operator Model for Virtual Evaluation of Working Performance

* School of Mechanical and Aerospace Engineering, Seoul Nat’l Univ.** Hyundai Heavy Industries Co., LTD. (Received February 12, 2014 ; Revised July 18, 2014 ; Accepted August 1, 2014)Key Words: Event(이벤트), V-Pattern Working(V상차 작업), Operator Model(운전자 모델)초록: 본 논문에서는 가상의 V상차 작업을 위한 이벤트 기반의 휠로더 운전자 모델을 개발하였다. 운전자 모델 개발의 목적은 휠로더의 일반적인 작업인 V상차 작업 시 동역학적 해석과 작업성능을 가상의 시뮬레이션 모델과 운전자 입력을 이용해 예측 및 평가하는 것이다. V상차 작업은 4단계로 이루어져 있으며, 총 8 개의 이벤트로 인해 순차적으로 작업이 진행된다. 개발된 3D 휠로더 시뮬레이션 모델은 Matlab/Simulink 환경에서 구성 되었으며, 시뮬레이션 결과는 V상차 작업의 실차 데이터와 비교 되었다. 본 연구에서 개발된 운전자 모델로 향후 가상의 V상차 작업에 대한 작업성능 및 동역학적 해석이 가능할 것으로 본다.Abstract : This paper presents the development of an event-based operator model of a wheel loader for virtual V-pattern working. The objective of this study is to analyze the performance and dynamic behavior of the wheel loader for a typical V-pattern. The proposed typical V-pattern working is divided into four stages. The developed operator model is based on eight events, and the operators inputs are occurred sequentially by event. A 3D dynamic simulation model of the wheel loader is developed and used to analyze the dynamic behavior during working, and the simulation results are compared with the experimental data of V-pattern working. The proposed 3D dynamic simulation model and operator model are constructed using MATLAB/Simulink. The proposed operator model for V-pattern working is expected to enable evaluation of the working performance and dynamic behavior of the wheel loader.

A Study on the Dynamic Load Simulation for a Crawler Excavator Considering Ground Effect

A fatigue life is one of the key design factors for crawler excavators because they are usually operated in a very harsh working condition. In order to evaluate the fatigue life, the fatigue loads in various working conditions should be decided in advance. In case of the attachments such as boom and arm, the forces at the bucket tip due to digging and lifting are primary fatigue loads, which can be calculated relatively easily using design specifications. However, the forces at the track need to be considered additionally for the upper and lower frames. And it is almost impossible to measure the forces at track in a field test. In this study, a dynamic model of excavator including track system is implemented and dynamic load simulations are carried out to investigate the distribution of the reaction forces at each roller for the typical working scenarios. The model and the simulation technique are verified by comparison with the results of measurement in view of weight balance, cylinder forces, accelerations of counter weight and stresses at concerned points. The normalized distribution of the reaction forces at each roller in digging and lifting working mode are presented and the distribution is expected to be used as the baseline of fatigue load estimation for the upper and lower frames of various class crawler excavators. To get the multibody dynamic simulation results by the excavator motion, we used the commercial software such as Recurdyn for kinematic and dynamic modeling. Especially the track modeling of the excavator is composed using Track_LM module of the Recurdyn. And stress analysis of the frame is carried out using the NX-Nastran program.Copyright