{"title":"Multi-objective path integral policy improvement for learning robotic motion","authors":"Hayato Sago, Ryo Ariizumi, Toru Asai, Shun-ichi Azuma","doi":"10.1007/s10015-025-01027-z","DOIUrl":"10.1007/s10015-025-01027-z","url":null,"abstract":"<div><p>This paper proposes a new multi-objective reinforcement learning (MORL) algorithm for robotics by extending policy improvement with path integral (<span>(text {PI}^2)</span>) algorithm. For a robot motion acquisition problem, most existing MORL algorithms are hard to apply, because of the high-dimensional and continuous state and action spaces. However, policy-based algorithms such as <span>(text {PI}^2)</span> can be applied to solve this problem in single-objective cases. Based on the similarity of <span>(text {PI}^2)</span> and evolution strategies (ESs) and the fact that ESs are well-suited for multi-objective optimization, we propose an extension of <span>(text {PI}^2)</span> and some techniques to speed up the learning. The effectiveness is shown via numerical simulations.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"534 - 545"},"PeriodicalIF":0.8,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10015-025-01027-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145161131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Performance improvement of Ear-EEG SSVEP-BCI using reliability score","authors":"Sodai Kondo, Hideyuki Harafuji, Ren Kiuchi, Asahi Saito, Kakeru Tanaka, Wataru Wakayama, Hisaya Tanaka","doi":"10.1007/s10015-025-01025-1","DOIUrl":"10.1007/s10015-025-01025-1","url":null,"abstract":"<div><p>Steady-state visual evoked potential (SSVEP) brain-computer interface (BCI) are known for high speed, accuracy, and multivalue input. Integrating ear-electroencephalogram (EEG) can make SSVEP-BCI more accessible for everyday use. This study introduces a reliability score to enhance the performance of ear-EEG SSVEP-BCI by dynamically adjusting measurement duration and enabling asynchronous detection. Two analysis methods, learning canonical correlation analysis (LCCA) and task-related component analysis, were evaluated. Using the reliability score, the accuracy for ear-EEG SSVEP-BCI reached <span>(100)</span>% with an information transfer rate (ITR) of <span>(22.36pm 3.54)</span> bits/min, compared to <span>(61.93pm 9.22)</span>% accuracy and <span>(15.32pm 4.59)</span> bits/min ITR without the reliability score. These findings demonstrate that the reliability score significantly improves ear-EEG SSVEP-BCI performance, suggesting its potential to enhance usability in practical applications. </p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"449 - 457"},"PeriodicalIF":0.8,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10015-025-01025-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Collision avoidance control of multiple UAVs using collision cones and control barrier functions","authors":"Thiviyathinesvaran Palani, Supuni Wijesundera, Hiroaki Fukushima","doi":"10.1007/s10015-025-01020-6","DOIUrl":"10.1007/s10015-025-01020-6","url":null,"abstract":"<div><p>This paper focuses on the collision avoidance of multiple UAVs using collision cones (CCs) and control barrier functions (CBFs). Each UAV is separately controlled toward a given goal while avoiding collision with other UAVs, which are considered moving obstacles. We first propose a new collision avoidance control method based on CCs and CBFs without numerical optimization. This method significantly lowers computational costs compared to existing optimization-based approaches. In addition, we propose a new optimization-based method using CCs and CBFs. A key feature of the proposed method is that the desired control input used in numerical optimization is modified based on CCs and CBFs, in contrast to existing methods that use a desired control input designed without considering obstacles. We evaluate and compare the effectiveness of the proposed methods through extensive simulations. Experimental results using real quadrotors are also shown.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"546 - 554"},"PeriodicalIF":0.8,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145169555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multi-objective optimization of flight schedules to maximize constraint tolerance by local search and archive mechanisms","authors":"Tomoki Ishizuka, Akinori Murata, Hiroyuki Sato, Keiki Takadama","doi":"10.1007/s10015-025-01021-5","DOIUrl":"10.1007/s10015-025-01021-5","url":null,"abstract":"<div><p>To introduce the concept of the “constraint tolerance” (i.e., a feasibility of solutions) in the flight scheduling problem, this paper proposes the optimization method that can find the feasible flight schedules by optimizing the original objective function while maximizing the constraint tolerance as much as possible. The proposed method further is improved by integrating it with the local search and archive mechanisms to obtain a wide range of Pareto-optimal solutions with a high constraint tolerance. A comparison between the proposed method and the conventional methods with or without adding a new objective function to maximize the constraint tolerance shows the statistical superiority of the proposed method.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 2","pages":"289 - 302"},"PeriodicalIF":0.8,"publicationDate":"2025-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143925685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stable dynamic patterns generated by retrograde model","authors":"Mari Nakamura","doi":"10.1007/s10015-025-01017-1","DOIUrl":"10.1007/s10015-025-01017-1","url":null,"abstract":"<div><p>A heterogeneous boid is a multi-agent system comprised of several types of agents that communicate locally. It forms diverse patterns of agent groups through various interactions. With appropriately tuned interactions, it forms stable patterns of a unified cluster with symmetrical structures that reflect local interactions. This ensures that these patterns remain stable, regardless of the number of agents (i.e., scalability). Prior research introduced the retrograde model, where two agent types exhibited reverse movement while a third type formed a unified cluster. By tuning the interaction, this model formed stable dynamic patterns. With a large number of agents, even under appropriate interactions, long-lasting metastable states emerge, making it difficult to distinguish them from stable patterns. In this study, by focusing on large-scale structures (cluster shape and agent flow), we reclassified three stable dynamic patterns formed by the retrograde model, removing the metastable states. We identify a new dynamic stable pattern, named as an irregular-oscillating pattern, by focusing on a cluster of specific shapes.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 2","pages":"236 - 244"},"PeriodicalIF":0.8,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143925572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Towards flexible swarms: comparison of flocking models with varying complexity","authors":"Lauritz Keysberg, Naoki Wakamiya","doi":"10.1007/s10015-025-01016-2","DOIUrl":"10.1007/s10015-025-01016-2","url":null,"abstract":"<div><p>One remarkable feat of biological swarms is their ability to work under very different environmental circumstances and disturbances. They exhibit a flexible kind of robustness, which accommodates external events without staying on rigid positions. Based on the observation that conventionally robust flocking models can be very complex and use information unavailable to biological swarm, we undertook a wide investigation into the properties of existing flocking models such as Boid, Couzin, Vicsek, and Cucker–Smale. That is, to see if a similar “natural” flexibility could be observed in flocking models with lower complexity. We established a toolset of three metrics which allows for a comprehensive evaluation of different flocking models. These metrics measure general model performance, robustness under noise, as well as a naive complexity of the model itself. Our results show a general trend for divergence between performance and robustness. The most robust models had a medium–high complexity. While our results show no clear relation between robustness and low complexity, we discuss examples for robust behavior with simple rules.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 2","pages":"219 - 226"},"PeriodicalIF":0.8,"publicationDate":"2025-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10015-025-01016-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143925571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"6DOF localization with AUKF based on triple RTK-GNSS","authors":"Takahiro Shimizu, Shoichi Maeyama","doi":"10.1007/s10015-025-01018-0","DOIUrl":"10.1007/s10015-025-01018-0","url":null,"abstract":"<div><p>SLAM (simultaneous localization and mapping) plays a crucial role in autonomous navigation. In a previous study, SLAM based on AUKF (augmented unscented Kalman filter), called AUKF-SLAM, was proposed. This study demonstrated that simultaneous estimation of kinematic parameters improves the accuracy on 2D SLAM in an indoor environment. We currently aim to develop the 3D AUKF-SLAM for outdoor use, and this paper presents the 6DOF localization based on AUKF as a preliminary step. To expand 2D (3DOF) localization to 6DOF localization, we adopted quaternion for attitude representation. However, it is not the best way to estimate each element of the four-dimensional vector of quaternion as state variables because they do not vary independently. As a solution to this problem, the idea of estimating the attitude error represented as the three-dimensional parameter called GRPs (generalized Rodrigues parameters) was proposed. In addition, it was reported that simultaneous estimation of the attitude error represented as GRPs and states not represented as errors is effective for the estimation of the motion of space crafts. Therefore, we applied this method to wheeled mobile robots to address the problem and realize the 6DOF localization based on AUKF. We implemented this system on ROS (robot operating system) and experimented in simulational and real environments. As a result, we demonstrated that it could perform 6DOF localization and estimation of the wheel radius simultaneously.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"493 - 501"},"PeriodicalIF":0.8,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145161656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Masahito Takano, Shiori Oyama, Kent Nagumo, Akio Nozawa
{"title":"Discrimination of stress coping responses on dimensionality-reduced facial thermal image space","authors":"Masahito Takano, Shiori Oyama, Kent Nagumo, Akio Nozawa","doi":"10.1007/s10015-025-01022-4","DOIUrl":"10.1007/s10015-025-01022-4","url":null,"abstract":"<div><p>This study investigates the use of facial skin temperature, measured through non-invasive facial thermal imaging, to classify stress-coping responses. While previous methods like Convolutional Neural Networks (CNN) and sparse coding have shown promise, capturing continuous changes in stress-coping states remains challenging. To address this limitation, we focus on t-SNE for dimensionality reduction, which compresses high-dimensional facial thermal data while preserving both local and global structure. Our findings show that facial thermal images from the same stress-coping response cluster together in the reduced space, allowing continuous monitoring of facial skin temperature changes. Additionally, the behavior of the data in the reduced space revealed a time lag between hemodynamic parameter variations and facial skin temperature distribution changes. These insights contribute to developing models that can continuously track stress-coping state changes.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"424 - 431"},"PeriodicalIF":0.8,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10015-025-01022-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145160968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Neuroevolution for vision-based seeking behavior in 3D soft voxel robots","authors":"Christian Hahm","doi":"10.1007/s10015-025-01019-z","DOIUrl":"10.1007/s10015-025-01019-z","url":null,"abstract":"<div><p>This paper details a simple experiment that tests two genetic encodings, NEAT and HyperNEAT, for the evolution of vision-based food-seeking behavior in neural-controlled 3D soft voxel robots. The evolution of food-seeking behavior is a preliminary step towards ecosystems of advanced artificial animals, in which the animals seek both food and mates. Two environments were tested: with and without deadly obstacles. Traditional evolutionary search was used, with an objective-based fitness function. Both NEAT and HyperNEAT encodings were tested for the evolution of robot neural controllers. The results of the experiment showed the NEAT encoding resulted in increasingly effective food-seeking behavior over time, whereas experiments with the HyperNEAT encoding did not achieve the desired behavior. This suggests that NEAT at least is a viable algorithm to evolve neural networks for the task of vision-based object-seeking in complex robots, and warrants further experimentation. On the other hand, HyperNEAT struggled with this task. This could be due to a number of reasons, including a common issue like EA being stuck in local optima, or because the encoding might struggle to evolve and represent irregular structures required for the task.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"502 - 511"},"PeriodicalIF":0.8,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10015-025-01019-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Estimation of floc condition in a dewatering process by image analysis using machine learning","authors":"Atsuki Fukasawa, Shinya Watanabe","doi":"10.1007/s10015-025-01014-4","DOIUrl":"10.1007/s10015-025-01014-4","url":null,"abstract":"<div><p>Dewatering is a crucial process in sludge treatment plants, and appropriate mixing of polymer and sludge is an important factor in achieving efficient dewatering. This study focused on the condition of flocs produced by mixing sludge and polymer, and estimated the floc condition through visual analysis of images. In this study, the estimation of floc condition was assumed to be a classification problem of mixer speed, and validation was conducted to classify the appropriate speed based on the images. The proposed methodology involved the development of a machine learning model characterized by high accuracy and transparency. This model was formulated using two features extracted from the images, i.e., the gaps between flocs and their texture, which are the parameters used by human operators to estimate floc condition. Explainable Boosting Machine was used as the machine learning model, which allows interpretation of the model’s contents and can be applied easily. The classification accuracy of this model was validated using both interpolated and extrapolated data, yielding accuracies exceeding 95% in both scenarios. Furthermore, comparative analysis was performed between the proposed transparent box model and a conventional Convolutional Neural Network (CNN) model. Despite its transparent box nature, the proposed approach demonstrated a comparable level of accuracy to the CNN model in this comparative study.</p></div>","PeriodicalId":46050,"journal":{"name":"Artificial Life and Robotics","volume":"30 3","pages":"439 - 448"},"PeriodicalIF":0.8,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145168380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}