Recent research on humanoid robot actuators has shown that the use of series elastic actuators (SEAs) is necessary for accurate and robust torque control. Among the numerous implementations of an ...SEA, using a spring as an elastomer is considered to be the most suitable. However, a major disadvantage of this method in terms of torque control is the hysteresis of the elastomer. Although various hysteresis modeling methods have been studied to resolve the hysteresis problem of an elastomer, they are not sufficiently accurate to perform torque control. Therefore, we propose a hysteresis model and compensation method to estimate torque based on deformation for the hysteresis of an elastomer SEA to resolve the problems encountered in previous studies. Torque control is evaluated with the proposed hysteresis compensation method. Torque measurements obtained using the proposed hysteresis model improve the maximum error by up to 10% compared with that of Hooke's law, which has a maximum error of 25%. Torque control of an elastomer SEA can be performed with improved accuracy by using the proposed hysteresis model and compensation method.
Optogenetics refers to a technique that uses light to modulate neuronal activity with a high spatiotemporal resolution, which enables the manipulation of learning and memory functions in the human ...brain. This strategy of controlling neuronal activity using light can be applied for the development of intelligent systems, including neuromorphic and in‐memory computing systems. Herein, a flexible van der Waals (vdW) optoelectronic synapse is reported, which is a core component of optogenetics‐inspired intelligent systems. This synapse is fabricated on 2D vdW layered rhenium disulfide (ReS2) that features an inherent photosensitive memory nature derived from the persistent photoconductivity (PPC) effect, successfully mimicking the dynamics of biological synapses. Based on first‐principles calculations, the PPC effect is identified to originate from sulfur vacancies in ReS2 that have an inherent tendency to form shallow defect states near the conduction band edges and under optical excitation lead to large lattice relaxation. Finally, the feasibility of applying the synapses in optogenetics‐inspired intelligent systems is demonstrated via training and inference tasks for the CIFAR‐10 dataset using a convolutional neural network composed of vdW optoelectronic synapse devices.
A flexible van der Waals (vdW) optoelectronic synapse fabricated on 2D vdW layered rhenium disulfide, which features an inherent photosensitive memory nature derived from the persistent photoconductivity effect, is proposed. Following in‐depth analysis including density functional theory calculations on rhenium disulfide, its feasibility for hardware neural networks with learning ability is demonstrated using a convolutional neural network composed of vdW optoelectronic synapses.
Research on a terrain-blind walking control that can walk stably on unknown and uneven terrain is an important research field for humanoid robots to achieve human-level walking abilities, and it is ...still a field that needs much improvement. This paper describes the design, implementation, and experimental results of a robust balance-control framework for the stable walking of a humanoid robot on unknown and uneven terrain. For robust balance-control against disturbances caused by uneven terrain, we propose a framework that combines a capture-point controller that modifies the control reference, and a balance controller that follows its control references in a cascading structure. The capture-point controller adjusts a zero-moment point reference to stabilize the perturbed capture-point from the disturbance, and the adjusted zero-moment point reference is utilized as a control reference for the balance controller, comprised of zero-moment point, leg length, and foot orientation controllers. By adjusting the zero-moment point reference according to the disturbance, our zero-moment point controller guarantees robust zero-moment point control performance in uneven terrain, unlike previous zero-moment point controllers. In addition, for fast posture stabilization in uneven terrain, we applied a proportional-derivative admittance controller to the leg length and foot orientation controllers to rapidly adapt these parts of the robot to uneven terrain without vibration. Furthermore, to activate position or force control depending on the gait phase of a robot, we applied gain scheduling to the leg length and foot orientation controllers, which simplifies their implementation. The effectiveness of the proposed control framework was verified by stable walking performance on various uneven terrains, such as slopes, stone fields, and lawns.
In this paper, we propose a biped walking controller that optimized three push recovery strategies: the ankle, hip, and stepping strategies. We suggested formulations that related the effects of each ...strategy to the stability of walking based on the linear inverted pendulum with flywheel model. With these relations, we could set up an optimization problem that integrates all the strategies, including step time change. These strategies are not applied hierarchically, but applied according to each weighting factor. Various combinations of weighting factors can be used to determine how the robot should respond to an external push. The optimization problem derived here includes many nonlinear components, but it has been linearized though some assumptions and it can be applied to a robot in real time. Our method is designed to be robust to modeling errors or weak perturbations, by exploiting the advantages of the foot. Hence, it is very practical to apply this algorithm to a real robot. The effectiveness of the walking controller has been verified through abstracted model simulation, full dynamics simulation, and a practical robot experiments.
This paper describes a humanoid robotics platform (DRC-HUBO+) developed for the Defense Advanced Research Projects Agency Robotics Challenge (DRC) Finals. This paper also describes the design ...criteria, hardware, software framework, and experimental testing of the DRC-HUBO+ platform. The purpose of DRC-HUBO+ is to perform tasks by teleoperation in hazardous environments that are unsafe for humans, such as disaster zones. We identified specific design concepts for DRC-HUBO+ to achieve this goal. For a robot to be capable of performing human tasks, a human-like shape and size, autonomy, mobility, manipulability, and power are required, among other features. Furthermore, modularized joints and a user-friendly software framework were emphasized as design concepts to facilitate research on the robot tasks. The DRC-HUBO+ platform is based on DRC-HUBO-1 and HUBO-2. The torque of each joint is increased compared to that in DRC-HUBO-1 owing to its high reduction ratio and air-cooling system. DRC-HUBO+ is designed with an exoskeletal structure to provide it with sufficient stiffness relative to its mass. All wires are enclosed within the robot body using a hollow shaft and covers to protect the wires from external shock. Regarding the vision system, active cognition of the environment can be realized using a light-detection and ranging sensor and vision cameras on the head. To achieve stable mobility, the robot can transition from the bipedal walking mode to the wheel mode using wheels located on both knees. DRC-HUBO+ has 32 degrees of freedom (DOFs), including seven DOFs for each arm and six DOFs for each leg, and a solid and light body with a height of 170 cm and a mass of 80 kg. A software framework referred to as PODO, with a Linux kernel and the Xenomai patch, is used in DRC-HUBO+.
For the sustainable application of remote sensing and monitoring in the ocean environment, energy harvesting technology based on flow‐induced vibration is in the spotlight. Herein, based on the ...flow‐induced self‐excitation of an impacting‐sliding cylinder, a collectively exhaustive hybrid triboelectric nanogenerator (TENG) is reported, that utilizes both freestanding‐sliding (FS) and contact‐separation (CS) modes. Most importantly, the flow‐induced impacting cylinder (FIC) between two side walls is newly implemented to resolve the critical problem of the lock‐in phenomena occurring in conventional vortex‐induced vibration systems of circular cylinders. Owing to the presence of two side walls, the FIC based TENG (FIC‐TENG) shows a stable electrical power generation in a wide range of flow velocity (0.05–1.02 m s−1) without lock‐in phenomena. In addition, the collectively exhaustive FIC‐TENG can be used to continuously produce electric power utilizing both FS and CS hybrid modes. The energy harvesting performance is greatly enhanced by adopting nanopatterns on triboelectric surfaces in the CS mode TENG and a frequency upconversion effect of interdigitated electrodes in the FS mode TENG, resulting in proper remote operation of a wireless fidelity thermometer.
A flow‐induced impacting cylinder‐based hybrid mode triboelectric nanogenerator (FIC‐TENG) has great potential to effectively convert hydrokinetic energy in a wide range of flow velocity into electricity to address the lock‐in limitation. The energy harvesting performance of the FIC‐TENG improves due to line nanopatterns and interdigitated electrodes for large effective contact area and frequency upconversion, respectively.
The growing severity of environmental problems such as plastic waste and climate change has inspired active research into solutions based on recyclable and renewable energy devices. Triboelectric ...nanogenerators (TENGs) that convert wasted mechanical energy into electrical energy offer a solution that needs to be made recyclable to reduce or eliminate the generation of electronic waste (e‐waste) on their disposal. In this study, an all‐recyclable TENG (AR‐TENG) based on a thermoplastic polymer with a nanohole pattern is developed; it delivers an excellent output power density of 1.547 W m−2 (peak output voltage = 360 V, current = 22 µA) and shows superior mechanochemical stability by maintaining its performance after immersion into seawater or 1 000 000 cyclic tests. The practical utility of this AR‐TENG is demonstrated through its use to power a buoy‐type ocean monitoring system and an intelligent life jacket, whereas recyclability is demonstrated by the re‐fabrication of the AR‐TENG; reusability in other devices is validated by the successful fabrication of a plasmonic color filter. This work paves the way for the efficient harvesting of renewable energy without the concomitant production of e‐waste; therefore, it contributes to the mitigation of global environmental problems such as global warming and ozone depletion.
An all‐recyclable triboelectric nanogenerator (AR‐TENG) that exhibits high power density and excellent mechanochemical stability is developed. The recyclability is demonstrated through its disassembly and fabrication of the plasmonic color filter. An ocean energy harvesting system based on AR‐TENG is developed and used to power a buoy‐type ocean monitoring system and intelligent life jacket.
We report complete sequences of chloroplast (cp) genome and 45S nuclear ribosomal DNA (45S nrDNA) for 11 Panax ginseng cultivars. We have obtained complete sequences of cp and 45S nrDNA, the ...representative barcoding target sequences for cytoplasm and nuclear genome, respectively, based on low coverage NGS sequence of each cultivar. The cp genomes sizes ranged from 156,241 to 156,425 bp and the major size variation was derived from differences in copy number of tandem repeats in the ycf1 gene and in the intergenic regions of rps16-trnUUG and rpl32-trnUAG. The complete 45S nrDNA unit sequences were 11,091 bp, representing a consensus single transcriptional unit with an intergenic spacer region. Comparative analysis of these sequences as well as those previously reported for three Chinese accessions identified very rare but unique polymorphism in the cp genome within P. ginseng cultivars. There were 12 intra-species polymorphisms (six SNPs and six InDels) among 14 cultivars. We also identified five SNPs from 45S nrDNA of 11 Korean ginseng cultivars. From the 17 unique informative polymorphic sites, we developed six reliable markers for analysis of ginseng diversity and cultivar authentication.
•Studied CO2 absorption process using MDEA/PZ blended solvent for blue H2 production.•Suggested a novel solvent looping system of amine absorption process.•Performed techno-economic analysis and ...optimization of CO2 absorption process for SMR.•Achieved 0.622 and 0.751 GJ/ton CO2 of reboiler duty at 90% and 99% CO2 capture rate.•Achieved 99% CO2 capture rate at lower CO2 capture cost (42.44 USD/tonCO2) than 90%
Advanced CO2 capture processes for steam methane reforming that supplies large quantities of H2 to industries are critical for cost-effective blue H2 and CO2 production. In this study, a pre-combustion CO2 absorption process with a novel solvent looping system was developed to capture CO2 from SMR gas at a flow rate of 6946.5 kmol/h and 21 bar. A techno-economic analysis of the advanced absorption process using MDEA/PZ blended solvent was performed with respect to five key operating parameters. For 90 % and 99 % CO2 capture rates, the minimal reboiler duties were 0.622 and 0.751 GJ/CO2 ton, which were approximately 70 % lower than those of conventional post-combustion CO2 capture processes. Despite a significant increase in the CO2 capture rate (90 % to 99 %), the increase in energy consumption and OPEX was only 4 % while using the novel blended-solvent looping system through a low-pressure flash drum, resulting in a lower CO2 capture cost per ton at 99 % CO2 capture rate. The economic analysis suggested that the minimal CO2 capture cost decreased from 44.89 to 42.56 USD/CO2 ton as the capture rate increased. Furthermore, DNN models could predict the CAPEX and OPEX under higher than 98 % accuracy. DNN-based optimization with a multi-variable mutation of features revealed the optimum operating conditions for a minimum CO2 capture cost (42.44 USD/CO2 ton) over a short computational time (12 s). Thus, this study provides insights on the blended solvent and guidelines for a high-pressure CO2 absorption process with a solvent looping system for cost-effective blue H2 production.
This paper summarizes how Team KAIST prepared for the DARPA Robotics Challenge (DRC) Finals, especially in terms of the robot system and control strategy. To imitate the Fukushima nuclear disaster ...situation, the DRC performed eight tasks and degraded communication conditions. This competition demanded various robotic technologies, such as manipulation, mobility, telemetry, autonomy, and localization. Their systematic integration and the overall system robustness were also important issues in completing the challenge. In this sense, this paper presents a hardware and software system for the DRC‐HUBO+, a humanoid robot that was used for the DRC; it also presents control methods, such as inverse kinematics, compliance control, a walking algorithm, and a vision algorithm, all of which were implemented to accomplish the tasks. The strategies and operations for each task are briefly explained with vision algorithms. This paper summarizes what we learned from the DRC before the conclusion. In the competition, 25 international teams participated with their various robot platforms. We competed in this challenge using the DRC‐HUBO+ and won first place in the competition.
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