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In order to enhance performance of robot systems in the manufacturing industry, it is essential to develop motion and task planning algorithms. Especially, it is important for the motion plan to be generated automatically in order to deal with various working environments. Although PRM (Probabilistic Roadmap) provides feasible paths when the starting and goal positions of a robot manipulator are given, the path might not be smooth enough, which can lead to inefficient performance of the robot system. This paper proposes a motion planning algorithm for robot manipulators using a twin delayed deep deterministic policy gradient (TD3) which is a reinforcement learning algorithm tailored to MDP with continuous action. Besides, hindsight experience replay (HER) is employed in the TD3 to enhance sample efficiency. Since path planning for a robot manipulator is an MDP (Markov Decision Process) with sparse reward and HER can deal with such a problem, this paper proposes a motion planning algorithm using TD3 with HER. The proposed algorithm is applied to 2-DOF and 3-DOF manipulators and it is shown that the designed paths are smoother and shorter than those designed by PRM.

Department of Electrical Engineering, Dong-A University, Busan 49315, Korea(Received 31 March 2016, Received in final form 19 April 2016, Accepted 20 April 2016)This study proposes the design algorithm of an electromagnetic linear actuator with a divided coil excitation system, such as thecolenoid (COL) system, using the equivalent magnetic circuit (EMC) method. Nowadays, the clamping device is used to holdworkpiece in the electrically driven chucking system and is needed to produce a huge clamping force of 40 kN like hydraulic system.The design algorithm for electromagnetic linear actuator can be obtained using the EMC method. At first, the parameter map is used todecide the slot width ratio in the initial design. Next, to make the magnetic flux density uniform at each pole, the pole width isadjusted by the pole width adjusting algorithm with EMC. When the dimensions of the electromagnetic linear actuator are decided, theclamping force is calculated to check the desired clamping force. The design results show that it can be used to hold a workpiecefirmly instead of using a hydraulic cylinder in a chucking system.Keywords: colenoid, electromagnetic linear actuator, equivalent magnetic circuit, electrically driven chucking system

We propose an enhanced controller to improve the robustness of Time Delay Control (TDC) for a robot manipulator in the presence of nonlinear friction, such as Coulomb friction. The problem of TDC is first analyzed with TDC as a trajectory control for a robot manipulator in the presence of nonlinear friction. Gradient estimation is used to solve this problem. The proposed controller is called TDC with Gradient Estimator (TDCGE). Comparing with a prior research to improve the robustness of TDC, named TDCSA, the TDCGE is much simpler to design. Through 1 DOF linear motor experiment, it is verified that the TDCGE is more robust against nonlinear friction than TDC and the TDCGE has a similar robustness to the TDCSA. In addition, it is confirmed that the TDCGE is easily implemented in the multi degree-of-freedom robot manipulator through a 3 DOF spatial robot manipulator experiment.

This paper presents a new state space representation of pneumatic vibration isolators (PVIs) and a design of a robust control, Time Delay Control (TDC), based on it. The new state space model, derived by using the input–output linearization method, is of the phase variable form with the air mass-flow as the control input. This model offers a framework that enables simultaneous suppression of both seismic vibration and direct disturbance (or payload disturbance) with an accelerometer only. Based on this model, TDC is designed and verified with experiments on a single chamber PVI with an accelerometer only. In the experiment, the PVI with TDC successfully suppresses seismic vibration and direct disturbance, both individually and simultaneously. Faced with seismic vibration, the transmissibility of the PVI with TDC has virtually no resonance peak at low frequency; under direct disturbance, the former achieves a 68 percent reduction in settling time of the latter. The final analysis of experimental result shows that TDC effectively estimates the modeling error along with other uncertainties and cancels them, while achieving desired closed-loop dynamics.

적응기술(adaptive skill)은 다운증후군을 포함한 지적장애 아동의 판별과 교육 배치에 기준이 될 뿐만 아니라, 일상생활 즉, 가정 및 학교, 지역사회에서 원만한 생활을 영위하기 위해 가장 기본이 되는 중요한 영역 중 하나이다. 따라서 본 연구에서는 다운증후군 아동의 적응기술에 대한 좀 더 폭넓은 이해를 위해 선행연구를 통해 발달기 다운증후군 아동의 적응기술 또는 일상생활기술에 영향을 미치는 것으로 규명된 요인들과 적응기술의 관계를 알아보고자 하였다. 이를 위해, 6~12세 사이의 다운증후군 아동 86명을 대상으로 운동기술 발달, 인지능력, 가족환경, 심리사회적 문제 등이 적응기술과 갖는 관련성을 탐색하였다. 대상자들의 적응기술은 Korea Institute for Special Education-Scales of Adaptive Behavior(KISE-SAB)를 적용하여 측정하였으며, 운동기술 발달은 Bruininks-Oseresky Test of Motor Proficiency(BOTMP), 인지능력은 Korea Institute for Special Education-Korea Intelligence Test for Children(KISE-KIT), 가족환경은 Family Adaptability and Cohesion Evaluation Scale(FACES), 사회심리적 문제는 Korea Child Behavior Checklist(K-CBCL)로 측정하였다. 또한 인구통계학적 변인으로 연령을 추가하였다. 위계적 중다회계분석 결과, 운동기술 발달이 다운증후군 아동의 적응기술을 40% 설명하는 것으로 나타나 가장 많은 영향력을 갖는 것으로 나타났으며, 부가적으로 가족환경이 5%의 영향력을 갖는 것으로 나타났다. 반면, 인지능력과 심리사회적 문제, 연령은 유의미한 영향력을 갖지 않는 것으로 나타났다. 이러한 결과는 운동기술 발달이 성숙되어 있고 긍정적인 가족 환경에서 성장하는 다운증후군 아동이 높은 수준의 적응기술을 보일 수 있다는 점을 시사하고 있다. 더불어, 다운증후군 아동의 적응기술 또는 일상생활기술의 발달을 목표로 하는 중재 프로그램에 다양한 형태의 신체활동 프로그램이 포함되어야 할 필요성에 근거가 될 수 있다고 할 수 있다.

An enhanced controller to improve the robustness of Time Delay Control (TDC) for a robot manipulator in the presence of hard nonlinearities is proposed. The problem of TDC is first analyzed with TDC as a trajectory control for a robot manipulator in the presence of hard nonlinearity. The method of steepest descent, which is a type of adaptive control scheme, is used to solve this problem in order to develop an enhanced controller. The proposed controller is called TDC with Adaptive Compensator (TDCAC). The adaptive compensator of TDCAC serves as a type of high pass filter for the effect of hard nonlinearities and is very intuitional for choosing the adaptive gain of the adaptive compensator. The robustness of TDCAC is verified by experiment.

Existing controls for the dual chamber pneumatic vibration isolator (DC-PVI) have the following problems: (1) unable to suppress both seismic vibration and direct disturbance (or payload disturbance) simultaneously; (2) complex and of high-order. In this paper, we have applied input-output linearization to the DC-PVI to derive a reduced-order model that enables the followings: (i) a reduced-order control design; (ii) simultaneous suppression with an accelerometer only. We have employed Time Delay Control (TDC), well-known for its simplicity and robustness to uncertainties and disturbance. Based on the reduced-order model and its corresponding TDC design, an active control scheme has been derived that requires only an accelerometer for its sensor. This scheme was experimented with a DC-PVI, which successfully suppresses seismic vibration and direct disturbance both separately and simultaneously. Faced with seismic vibration, the transmissibility of the DC-PVI with TDC has virtually no resonance peak at low frequency; under direct disturbance, the DC-PVI with TDC achieves a 65 percent reduction in settling time of that without TDC.

Based on previous feasibility study on one degree of freedom (1DOF) pneumatic active control of pneumatic springs, this paper presents procedures and results of a more realistic 3DOF active control of a pneumatic vibration isolation table. The 3DOF motion of the pneumatic table, consisting of heaving, rolling, and pitching, is controlled directly by adjusting air pressure in four pneumatic cylinders in a dynamic manner with pneumatic valves, without any external actuator such as an electromagnet or voice coil. The time delay control, which is a software chosen in this study, together with the hardware, i.e., the pneumatic actuator, is shown to be very powerful in enhancing the performance of vibration isolation for ground excitation as well as in settling time reduction for payload excitation through simulations and measurements on the 3DOF motion control system. New key results found in the experimental approach are that the pneumatic actuator shows a dynamic behavior of a second-order system, instead of a first-order system, which has been used in existing literatures so far, and that just feed-forward control of the pneumatic actuator by the second-order model can compensate for the inherently slow response characteristics of the pneumatic actuator very successfully. Effectiveness of the proposed active pneumatic control technique in the multi-input and multi-output system is shown via singular value decomposition analysis on the transmissibility matrix. Promising future of the proposed control and performance analysis technique is further discussed based on the results in the case of payload excitations as well.

Active pneumatic vibration isolators have been widely studied as the use of precision equipment increases. This paper focuses on the robust two-time-scale control design of an active pneumatic vibration isolator using the singular perturbation method and time delay control (TDC). The singular perturbation method, or more generally, the two-time-scale approach to feedback design is used to cope with the ill-conditioning of the pneumatic vibration isolator; TDC is used to overcome inevitable modeling errors in more accurate physical model of pneumatic vibration isolator and unknown disturbance such as base excitation. Because the proposed controller in this paper is based on more accurate physical model than rough model, accurate control is feasible. Numerical experiment demonstrates the effectiveness of the proposed robust two-time-scale control design.

Atopic dermatitis (AD) is a chronic, relapsing, inflammatory skin disease. Children with AD tend to have a higher prevalence of food allergies. This study investigated the clinical significance of food sensitization in AD patients. A total of 266 AD patients participated in this study. The prevalence of food sensitization and clinically relevant sensitization were compared in the subjects according to their age and AD severity. Sera from all patients were analyzed for food-specific IgE levels using the Pharmacia CAP System FEIA. The serum specific IgE levels for egg, milk, peanut and soybean were measured. Patients were regarded as sensitized to the food if their food-specific IgE levels were above 0.35 kUA/L. Also the food-specific IgE levels, the so-called diagnostic decision point, which is recommended as the clinically relevant level, for clinical food allergy, as suggested by Sampson et al, was used as an alternative method. From the measurement of food-specific IgE antibodies of the four foods, egg was the most highly sensitized and the main causative allergenic food in children with AD. The positive rates of specific IgE to the four major food allergens, and the prevalences of clinically relevant food sensitization, were higher for all foods tested in the group less than 1 year of age, and were significantly higher in moderate to severe AD compared to mild AD in infants and young children. In summary, presence of food specific IgE is prevalent in infants and young children with AD, and clinically relevant food sensitization is important in Korean infants and children with moderate to severe AD.