bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflective pedagogical paradigm approach in mathematics learning
Authors: Saputro T V D , Mahmudi A
Published: September 2020

This study aimed to describe the trends of the reflective pedagogical paradigm approach in mathematics learning in Indonesia that could give a better recommendation of mathematics learning in the future. This study literature was taken through some of the open-access websites such as ERIC, Google Scholar, JSTOR, and Springer for 6 years latest. The researcher took the limitation in exploring the literature review by determining the sources’ keys such as Reflective Pedagogical Paradigm in Mathematics, Reflective Pedagogy, and Ignition Pedagogy. The study results of the trends of the reflective pedagogical paradigm approach in mathematics learning were research methodologies trends, the students’ learning impacts, and the relationship between Indonesian curriculum and the reflective pedagogical paradigm application in 21stcentury learning.
Mathematical probability: student’s misconception in higher education
Authors: Astuti D , Anggraeni L , Setyawan F
Published: September 2020

Probability is one of the mathematical concepts that are abstract for students. Probability concepts used in daily life. As a basis of statistics, students used the probability concept. This topic is one of the compulsory subjects learned in the Mathematics Education Study Program of Universitas Ahmad Dahlan. However, there are still many students who have difficulties in understanding the concept of probability. This study aims to describe students’ misconceptions in solving Probability problems. The research used descriptive method. The subjects in this study were the fourth-semester students of Mathematics Education Study Program Class C of Universitas Ahmad Dahlan. The results of this study found that there are four misconceptions made by students in solving Probability problems. First, students’ error in interpreting questions. Second, students’ errors in the procedure of proving the theorems of probabilities. Third, students’ misconceptions in the application of Bayes’ rules while they are solving problems. Fourth, students’ error in calculating the possibility of an event.
Solving Shortest Path Problems Using Mathematical Literacy Skill Figured Out By Pre-Service Teachers
Authors: Apriandi D , Murtafiah W , Ayuningtyas A D , Rudyanto H E
Published: September 2020

Mathematical literacy is an important ability to be taught to the mathematics pre-service teacher. The students who have good mathematical literacy skills will be sensitive to the mathematical concepts which are relevant to the phenomenon or problem. One of the problems that is given to mathematics pre-service teacher is the shortest path problem in Graph Theory courses. The purpose of this study is to explore the mathematical literacy abilities of the pre-service teacher in solving the shortest path problems. The research subjects were 56 mathematics pre-service teacher of Universitas PGRI Madiun, Indonesia. The data were collected through problem-solving tests which were then analyzed based on indicators of mathematical literacy ability namely formulate, employ, and interpret. The results shows that the mathematical literacy abilities of pre-service teacher in solving the shortest path problem consist of three categories, namely complete, incomplete, and incomplete mathematical literacy abilities. There are 9 students with complete mathematical literacy skills can formulate, employ, and interpret. There are 18 students with incomplete mathematical literacy skills can formulate and employ. There are 29 students with incomplete mathematical literacy can only formulate.
Contextual problem in mathematical problem solving: core ability in Realistic Mathematics Education
Authors: Pratiwi S A , Widjajanti D B
Published: September 2020

Problem solving is one of the ability existed in the component of Realistic Mathematics Education. This ability becomes more important for a student to understand, analyse and formulate the daily-life problem into formal mathematics, such as real-life problem, problem-based specific context, and the problem itself. Even though problem solving is an important component that must be mastered by the student in learning mathematics, not every student has a certain skill to understand and solve the problems occured in daily life. Many students do neither master the basic mathematics concepts nor know the specific criteria in problem solving ability. Regarding the fulfilment, this paper aims to investigate how to optimize problem solving ability using Realistic Mathematics Education as a part of student’s learning. The method used in this article is literature review in which the data collected through a study of several theories and the results of relevant scientific research such as mathematics learning, problem solving concept, Realistic Mathematics Education theory and the others. The result shows that the ability of problem solving and Realistic Mathematics Education interconnected each other, which is Realistic Mathematics Education has the important role in optimizing problem solving, especially in solving contextual problem. According to the result, this article contribute to improving teachers and students mathematics proficiency and deepening the learning theories especially the theories of mathematics problem solving to be more skilful and well-experienced in learning mathematics.
Collaborative classroom action research for mathematics and science teachers in Indonesia
Authors: Nurhasanah F , Sukandi U , Kuncoro A B , Rusilowati A , Hastuti W S , Prabowo A
Published: September 2020

Based on government regulation, as a part of career advancement for teachers in Indonesia, they need to do a Classroom Action Research (CAR) to reach the next level professional career. Unfortunately, this policy leads to problems that many teachers who find difficulties in doing classroom action research prefer using sort cut by asking agency to help them provide a well written classroom action research report. This situation triggered many people to take benefit by providing service for creating fake classroom action research for teacher as part of requirement in achieving next level in their career. There are some obstacles for teachers in doing classroom action research: (1) lack of knowledge theory in classroom action research; (2) lack of skill in designing instruments for data collection process; (3) lack of skill in analyzing the data; (4) lack of skill in writing the research report; (5) complicated regulation for teachers in conducting dissemination of their research. A model of TPD need to be formulated to overcome those obstacles and help mathematics and science teachers doing CAR for solving problems in their classroom or improving learning process and learning outcomes. A design research with engineering research approach is adopted as methodology of the study for designing a TPD model. The participants of the study are mathematics science teachers, lecturers, and supervisors from 5 provinces in Indonesia: North Sumatera, Riau, Jambi, Central Java, and East Borneo. This paper aims to describe the process and the result of the teachers’ professional development program for elementary and junior high school science and mathematics teachers in Indonesia through collaboration classroom action research with lecturer and school supervisors as the answer of those obstacles.
Mathematical resilience and mathematical problem-solving ability in Junior High School
Authors: Attami D , Budiyono  , Indriati D
Published: September 2020

In the process of mathematics learning, every student has different characteristics and attitudes to face adversity that called mathematical resilience. Mathematical resilience is one of the factors that have a role in supporting student achievement. This study investigated the relationship between mathematical resilience with mathematics problem-solving ability among junior high school students. Participants included 100 students at Sragen Region, Central Java Province, Indonesia. The method was used in this research is the survey method with the correlation and regression technique. Data sources included the questionnaire of mathematical resilience and written test. Findings revealed a significant, positive correlation between mathematical resilience and student’s mathematical problem-solving ability, with a contribution of 16.30% obtained by the regression model
Y
= 14.355 + 0.302
X
.The result indicated that positiveness response to learning mathematics, emotion regulation, curiosity and optimism in mathematical resilience beliefs were associated with mathematical problem-solving ability. Evidence presented to support and contribute to the value of students’ mathematical problem-solving abilities and provides a new approach for encouraging greater student participation and persistence in mathematics.
Flipped classroom research trends in mathematics learning in Indonesia
Authors: Apriska E , Sugiman
Published: September 2020

This study aims to analyse the trends and contents of flipped classroom research in mathematics learning in Indonesia based on articles that reported on national and international journals and proceedings since 2015-2019. The content analysis was used as a methodology. Twenty articles were analysed in term of methodologies, technology or instructional media, students attitude, and challenges encountered. The research was conducted by using the internet exploration by the keywords related to flipped classroom in mathematics learning. The result of the analysis were interpreted using descriptive analysis and percentages. This analysis found that various methodologies were practiced in flipped classroom research in Indonesia, but limited technology or instructional media were used for its practice. The use of flipped classroom in mathematics learning yielded a positive impact on students’ achievement when compared to the traditional classroom. Mixed results of student attitude toward flipped classroom in mathematics learning were discovered. Challenges of implementing flipped classroom were identified categorized into student-related challenges, teacher-related challenges, and operational challenges. Finally, some recommendations for future research are provided.
How do students promote mathematical argumentation through guide-redirecting warrant construction?
Authors: Muhtadi D , Sukirwan  , Hermanto R , Warsito  , Sunendar A
Published: September 2020

Argumentation is a mathematical discourse that is currently widely studied by researchers as a stepping stone in constructing mathematical evidence. A variety of argumentation studies display different formats and constructs ranging from Toulmin’s argumentation with a formal logic system to a general discourse that presents justifications and explanations for informal arguments with an inductive approach. It is based on the student’s difficulties in preparing a search warrant until later gave rise to the idea of reconstruction of the warrant and the importance of guide-redirecting warrant construction (GWC). The results showed that GWC could guide students in constructing statements and reasons or explanations towards the expected evidence. Students also realize that statements are related to reason and explanation in building whole arguments. Even so, the presentation of the statement is still aligned with the evidence submitted, so for reasons that display the axiomatic system, it still faces problems.
Reflective mathematical thinking process and student errors: an analysis in learning style
Authors: Ratnaningsih N , Hidayat E
Published: September 2020

Mathematical reflective thinking is one of the important thinking skills trained to students, but it has less attention. Student learning style is one of the factors that influence the mathematical reflective thinking process. The purpose of this study is to explore errors and reflective mathematical thinking processes seen from learning styles according to Honey and Mumford. This research was conducted at one of the junior high schools in Indonesia. This study uses a survey method, students with activist, reflector, theorist, and pragmatist learning styles. Data were collected through learning style questionnaires, mathematical reflective tests, and observations. All research instruments will first be tested for eligibility by validation by 2 experts. Data analysis techniques include data reduction, data presentation, and conclusion. The results of the analysis can be concluded that the mathematical reflective thinking processes of students with activist, pragmatist, and theorist learning styles had gone through the stages of reacting, elaboration, and contemplating appropriately. While students with reflector learning styles are only at the stages of reacting, and elaboration, they have not reached contemplating. This study provides teachers with an understanding of the importance of errors and thought processes of students in reflective thinking problems.
p-Summable Vector-Valued Sequence Spaces in Non-Archimedean 2-Normed Spaces
Authors: Nurnugroho B A , Prasetyo P W
Published: September 2020

Let (X, ‖., .‖) be a non-Archimedean 2-normed spaces. In this paper, we construct p-summable vector-valued sequence spaces in non-Archimedean 2-normed spaces ℓ

p
(X) for 1 ≤ p ≤ ∞. Futhermore, we show that ℓ

p
(X) is a non-Archimedean 2-semi-normed spaces and we also give some inclusion relations on ℓ

p
(X).
The Role of Progressive Mathematics in Geometry Learning
Authors: Warsito  , Muhtadi D , Sukirwan  , Saleh H
Published: September 2020

The purpose of this study is to analyze the learning trajectory that can help students understand the concept of volume cubes and beams with filling and arrangement boxes using dice context in grade VIII of junior high school (SMP). This research is a design research type of validation study that is implemented through Realistic Mathematics Education (RME). Design research is carried out in three stages, namely: preliminary design, teaching experiment consisting of cycle one and cycle 2, and retrospective analysis. The study was conducted in grade VIII of SMP at Tangerang City. The results of the study show that students can understand the volume of cubes and beams through progressive mathematical identified at the situational stage, recognizing the volume unit with the arrangement of unit cubes; referential stage, calculates the number of unit cubes that can be made on cubes and beams; general stage, found the capacity of objects in the form of cubes or beams based on known ribs and blocks; formally stage, calculate the volume of cubes and beams if the ribs are known.
Educational statistics textbooks to develop collaborative skills and critical thinking
Authors: Astuti D , Prabowo A , Hidayati N A , Khasanah U
Published: September 2020

Educational statistics textbook based cooperative learning is expected to facilitate teachers in delivering educational statistics lessons. This study aims to identify the characterization of the textbook based on the students characteristics. The research method used was research and development of the 4D (define, design, develop, and disseminate) model. This research was on define step. The first step of this study was analyzing the students and materials characterization. The next step was defining the characterization of the textbook based on students and materials characterization. The textbook was developing based on the characteristics. Data collected by the interviewing the students and observing the learning process. The characteristics of the textbook are (1) interactive, (2) show the contextual problem on education (3) facilitate to developing collaborative skill and critical thinking, and (4) task from the easy to hard task.
Mathematical statistics learning model based on the Indonesian national qualification framework
Authors: Syahputra E , Surya E , Utami D R
Published: September 2020

Learning model plays an important role in enhancing learning outcomes. This study aims to develop a learning model based on Indonesian National Qualification Framework. The learning model was applied in Mathematical Statistics class. The learning model trial was conducted along with Mathematical Statistics textbook trial. The trial was conducted in 8 meetings and was followed by 12 students of Mathematics Education Study Program. The trial’s result shows that the learning model and Mathematical Statistics textbook have high validity. Likewise, the learning outcomes show student high ability in understanding Mathematical Statistics. The test result shows that the average score of the students is 92.
Self regulated learning for social cognitive perspective in mathematics lessons
Authors: Zakiah N E , Fajriadi D
Published: September 2020

The research results describe of self-regulated learning for a social cognitive perspective in mathematics lessons. Students adapt to the social environment based on skills, knowledge, and skills previously owned. Every student in the social system adopts information and knowledge. Students learn through the social process of observing, imitating, and modeling the behavior of others. Students need to actively demonstrate independent learning orientation to find challenges and learning opportunities to acquire new skills and knowledge. About 116 new students from one of the state vocational high schools in West Java province of Indonesia participated in the self-regulated learning questionnaire from five aspects: organizations, elaboration, self-evaluation, learning strategies for examinations, and metacognition. We present responses to each self-regulated learning students about academic time management, summarized study materials in a personal way, evaluated their own learning and performance, were strategic in preparing for exams and reflected metacognitively during the study. From social cognitive theory, self-regulated learning is influenced by the students’ personal factors (cognitive, attitudes, and self-evaluation), behavior, and environment (social support). This research contributes to the understanding of students’ self-regulated learning and gives teachers insight into designing learning innovations.
Management of authentic assessment in mathematics lessons to develop 4C skills
Authors: Zakiah N E , Fajriadi D
Published: September 2020

Essential skills for 21st-century called 4c, namely critical thinking, creativity, collaboration, and communication. This ability is following the demands of the curriculum and can be developed in mathematics learning. Concerning assessment, all student views in a series of learning activities can be assessed objectively, as is, and not only based on the final results using an authentic assessment. Thus, this study aims to describe the management of authentic assessment in mathematics lessons to develop 4c skills. This study uses qualitative research with a case study method. The research subjects were mathematics teachers and grade X students at one of the state vocational high schools in West Java province. The data in this study came from observations, interviews, and documentation. Data analysis of aspects of the teacher’s role, support systems, social systems, instructional impacts, and assessment management. The results of this study indicate that: (1) The formulation of assessment instruments is carried out by formulating assessment objectives, making assessment grids, making instruments assessment following assessment guidelines, and analyzing the quality of the instruments; (2) Assessment of attitude aspects using observation and journals techniques. Knowledge assessment uses oral tests, written tests, and assignments according to the competencies being assessed. Skill assessments are conducted through practices or other techniques by competencies assessed using an assessment scale accompanied by a rubric; (3) Utilizing the results of the assessment to monitor and evaluate the process, learning progress, and improvement of students’ learning outcomes.
Students’ creativity level on solving mathematics problem
Authors: Thohari C A F , Budiyono  , Pratiwi H
Published: September 2020

There have been many attempts in order to build and train students’ creativity. However, there have been many obstacles faced regarding to how to encourage the students’ to be creative in the class. One of those obstacles faced is how to assess student’s creativity in solving mathematical problems; because there is a distinctive aspect for normal assessment and creativity assessment. Assessing creativity requires more specific limitations to creativity. By knowing the way to assess creativity, it will help teachers to understand to what extent students’ creativity can be used as a reflection in the effort to build creativity. This study aims to determine students’ creativity level on solving mathematics problem. The information of to what extend students’ creativity level. Moreover, this could be used as a consideration on planning learning strategy in order to increase student creativity on solving mathematics problem. This study employed qualitative research method. The subjects of this research are two 7th grade students of SMPN 1 Ngraho Bojonegoro. Data were collected through three steps namely writing test, interview, and observation. The conclusion of this study indicates that students’ creativity level on solving mathematics problem could be classified based on Siswono’s level of creativity. These levels are categorized into level 4 (very creative), level 3 (creative), level 2 (quite creative), level 1 (less creative), and level 0 (not creative). The first subject has the category of level 1 creativity (less creative). The second subject has the category of level 3 creativity (creative).
Geometry learning in vocational high school: Investigating the students’ difficulties and levels of thinking
Authors: Barut M E O , Retnawati H
Published: September 2020

Student’s difficulties and low-level thinking in geometry topic is not a new problem in mathematics education. It is portrayed on student’s low achievement both on national and international tests. Van Hiele’s model has been used as a useful framework to justify student’s difficulties as well as their level of thinking in geometry. Therefore, the aim of this study to investigate student’s difficulties and level of thinking using Van Hiele’s theory. Participants in this study were 12th grades vocational high school students. This study is descriptive qualitative research with a phenomenology approach. Data has been collected through a test and interviews. Further, the obtained data were analyzed by looking for a specific theme, then, the researcher found the inter-theme relationship in order to gain a proper understanding of student’s difficulties in geometry and level of student’s geometrical thinking. Based on data analysis, there are some difficulties faced by the student such as, unable to properly identify the geometry shapes based on their formal definition, lack of visualization ability, failed to understand specific terms or symbols of geometry, insufficiency in providing proper reasoning related relationship within geometric shapes. Moreover, it can be concluded that most of the students are on Level 1 of geometry thinking.
Comparison of image edge detection methods on potholes road images
Authors: Indriyani Tutuk , Utoyo Imam , Rulaningtyas Riries
Published: September 2020

Dinas pekerjaan Umum (DPU) in Surabaya in carrying out road repairs, especially in potholes, must know the position, area and depth. So it is important to do research to find out the surface area of potholes. To find out the surface area of the hole, the edge detection process is done first. Edge detection functions to get the edge of an object. Edge detection is obtained by utilizing a drastic change in the intensity value at the boundary of two areas. In this study, to determine the edge of an object (potholes road) by comparing three edge detection methods consisting of the Frei-Chen, Laplacian and Laplacian of Gaussian (LoG) methods. From the results of testing the Laplacian of Gaussian method has an average value of accuracy of 67%, sensitivity of 81.97% and specificity of 65.16%.The measurement results obtained by the Lapalacian of Gaussian method which is the best method for edge detection in potholes road images, because it produces the highest accuracy, sensitivity and specificity.
Open-ended mathematics module to improve students’ higher order thinking skill
Authors: Kurniawati S , Budiyono  , Saputro D R S
Published: September 2020

Higher order thinking skill (HOTS) is a more complex thinking skill using cognitive domains in C4 (analyzing), C5 (evaluating), and C6 (creating). This study aims to develop an initial mathematical module based on a valid prototype of open-ended mathematics module to help students to improve HOTS on the material of linear equation system in two variables. An open-ended approach is one of the learning approaches that can be used to increase HOTS students. This type of study was research and development (R&D). There are three stages of development research, namely (1) preliminary study consisting of 3 steps, namely initial research, analysis of the needs, and literature study, (2) product development consisting of three steps namely planning, initial product development, product testing and revision, (3) product efficacy testing, which is the stage of comparing modules developed with existing products. This research was conducted on the eighth-grade students of a public junior high school in Surakarta. The results obtained from this study was the average results of each initial module validation by media experts, material experts, and language experts are 3.27, 3.21, and 3.77. The product prototype is valid so it can be used to measure students’ HOTS.
FCM using squared euclidean distance for e-commerce classification in Indonesia
Authors: Khulaidah E Z , Irsalinda N
Published: September 2020

Clustering is a method of grouping data into several clusters so that the data in one cluster has a high level of similarity while the data between other clusters have a low level of similarity. One method used in clustering is Fuzzy C-Means (FCM) which is a data clustering technique in which the existence of each data point in a cluster is determined by the degree of membership in each cluster. The FCM algorithm has an objective function that requires distance. The distance used in this study is Squared Euclidean distance. The clustering conducted is the clustering of the popularity of e-commerce in Indonesia in 2019 using the variable average number of monthly visitors, number of website visitors, number of social media followers (Twitter, Instagram, and Facebook) as well as the number of workers. The result of this method is the level of popularity of e-commerce in Indonesia, which is divided into gold, silver, and bronze. Clustering results were tested with the Partition Entropy Index (PEI) and Classification Entropy (CE) if the results are getting closer to 0, the results are getting better. The result of PEI is 2.9697e-0, and CE is 2.5710e-04. So, based on the two indexes It can be concluded that FCM using Squared Euclidean distance is good to clustering.
Four-Tier Diagnostic Test Method to Identify Conceptual Understanding in Calculus
Authors: Fadhilatullathifi Z N , Ardiyanto B , Rahayu D D , Almukholani T , Rinayah I , Rahmawati F
Published: September 2020

The study aims to identify the ability to understand concepts with four-tier diagnostics test method. Every student has a different ability to understand mathematical concept. It is influenced by various factors such as intelligence, emotional conditions, environment, etc. This research uses the qualitative method with study case strategy. The data obtained from the four-tier diagnostic test on the calculus chapter. The subjects in this research are XIIth grade students. There are four stages of work in a four-tier diagnostic test, 1) question, 2) level of confidence in the answers, 3) reason, and 4) level of confidence in the reason. The result of this research show that most students have low ability to understand concepts. Most students are not sure of the answers to calculus problems given. Students also do not give the correct reason for the answer.
Relational Thinking Skills of Junior High School Students and Their Relationship with Creativity in Solving Mathematical Problems
Authors: Usodo Budi , Mardiyana  , Pramudya Ikrar , Sutopo  , Setiyawan Rubono
Published: September 2020

Relational thinking skills are the ability of children to see and use possible variations between numbers in one number sentence. This study aims to describe relational thinking skills and their relationship with the creativity of junior high school students in solving mathematical problems. This research uses quantitative and qualitative descriptive research methods. The subjects of this study were several 8th grade students in one of junior high schools in the city of Surakarta. Data collection methods used are test and interview methods. Analysis of the data used is quantitative and qualitative descriptive analysis. The results of the study showed that the relational thinking ability of junior high school students was less than 12,5 %. Most students only use computational thinking to solve math problems. From the interview results show that the low ability of students’ relational thinking, because the students have never been taught the use of relational thinking to solve mathematical problems. After giving several examples of the use of ways of thinking in solving problems, students can solve this problem in more than one way. The interview results show that students have creativity in solving mathematical problems.
Cooperative learning based on probabilistic thinking profile SMP Muhammadiyah 3 Mlati regency of Sleman
Authors: Taram Abdul , Sukestiyarno Y L , Rochmad  , Junaedi Iwan
Published: September 2020

The probabilistic thinking includes high order thinking skills (HOTS), which need to be trained to students through learning models. The probabilistic thinking Level of the students varies. So the purpose of the research is: (1) Want to know the high level of probabilistic thinking students SMP Muhammadiyah 3 Mlati Kabupaten Sleman, before and after following the model Prmbelajaran; (2) Want to know the effectiveness of cooperative learning model with peer tutor on heterogeneous group in raising the level of Probabilitik students of SMP Muhammadiyah 3 Mlati Kabupaten Sleman. The design of this research is research with the method of combination model or design concurrent trianggulation. The method of blending qualitative and quantitative analyses. The subject in this study was a grade IX students A and B of the odd semester of SMP Muhammadiyah 3 Mlati Kabupaten Sleman. Class IX A applies cooperative learning of NHT type and KLS IX B Implementing Cooperative learning of TGT type. With heterogeneous groups and peer tutors. The results of the study and its discussion gained interesting findings in this study, which is an effective learning Model to increase the level of probability thinking of SMP Muhammadyah 3 Mlati Sleman in solving probabilistic problems, is a learning model that blends three components (1) Cooperative Learning, (2) Heterorogative groups, and (3) peer tutors. This study was named the Learning model “Koophetebaya”.
Influence of cracks on the buckling of wind turbine towers
Authors: Capaldo M. , Orsatelli J. B. , Curt J. , Julan E.
Published: September 2020

The collapse of a wind turbine can be caused by the buckling of the tower when it is subjected to a critical load. This load is related, for instance, to a strong storm or a blade impact on the tower. Buckling occurs when the elastic limit is reached in part of the tower. Plasticity leads to bending with large rotations and large displacements. Structures are designed to avoid this phenomenon. However, a wind turbine is subjected during its entire service life to operation loads which cause fatigue of the structure. This results in the initiation of cracks and their propagation in the tower. These cracks can reduce the tower strength and it is, thus, interesting to study how the presence of such damage can affect the resistance of a wind turbine tower to the buckling. The influence of different parameters, such as position and length of the crack, is analyzed. Finally, the critical buckling load is related to wind site condition by considering an aero-elastic modeling of the wind turbine.
Validated extrapolation of measured damage within an offshore wind farm using instrumented fleet leaders
Authors: Noppe Nymfa , Hübler Clemens , Devriendt Christof , Weijtjens Wout
Published: September 2020

As the older wind farms are slowly reaching their design lifetime, topics like fatigue and lifetime assessment gain importance. To decide on a possible lifetime extension of the turbine and its foundation, an accurate fatigue assessment for every wind turbine in the farm is needed. As the installation of specific sensors needed for a fatigue assessment is too time consuming and costly, the “Fleet Leader Concept” is applied and validated in this paper. Here, a few turbines are instrumented and a fatigue assessment based on rainflow counting and Miner’s rule can be performed. For a farm-wide fatigue assessment, the obtained damage is extrapolated towards the other turbines. Sample based bootstrapping is performed to introduce an uncertainty on the results. A successful extrapolation was obtained for in-field measurements at an older offshore wind farm. In general, relative errors of less than 5% on damage were found.
An initial study into the potential of wind farm control to reduce fatigue loads and extend asset life
Authors: Harrison Matt , Bossanyi Ervin , Ruisi Renzo , Skeen Nick
Published: September 2020

A quasi-static open loop wind farm control approach is considered, where optimisation is carried out offline in a simulation environment to create a lookup table of yaw setpoints implemented by a central wind farm controller. The objective of the optimisation is to reduce blade root bending moment for all turbines on the site, thereby increasing the asset life, and this is achieved by querying a fatigue loads database in DNV GL’s LongSim software for wind farm control design, optimisation and verification. The Lillgrund 48-turbine layout is used for this example. The optimisation results in a small increase in annual energy production of 0.13% which is combined with a 0.4% increase in blade life, which is translated to an increase in asset life to yield a 0.5% increase in energy production over the farm lifetime. In this case we make the simplistic assumption that blades have the minimum life of all turbine components, and limit fatigue life. The results are a step towards wind farm control techniques which maintain and extend wind farm life, whilst simultaneously increasing energy production.
DTUWEC: an open-source DTU Wind Energy Controller with advanced industrial features
Authors: Meng Fanzhong , Lio Wai Hou , Barlas Thanasis
Published: September 2020

An open-source wind turbine controller, DTU Wind Energy Controller (DTUWEC), developed by Technical University of Denmark (DTU), is presented. The DTUWEC includes many advanced features and it is publicly available to the wind energy community. It is envisioned that this research work converts the old version of Basic DTU Wind Energy Controller into a generic, powerful and robust open-source wind turbine controller with a large number of developers and users in both research institutions and industries. DTUWEC is implemented in Fortran and offers the DNV-GL Bladed/OpenFAST style interface. Because of its open-source and modular characters, researchers are able to couple DTUWEC with different aero-elastic simulation codes to investigate the effect of different controllers on the wind turbine structural loads and power output, and to collaborate for future potential improvements.
Development and embedded deployment of a virtual load sensor for wind turbine gearboxes
Authors: Bosmans Jelle , Vanommeslaeghe Yon , Geens Luk , Fiszer Jakob , Croes Jan , Kirchner Matteo , Denil Joachim , Meulenaere Paul De , Desmet Wim
Published: September 2020

The loads to which a wind turbine gearbox is subjected during its lifetime can be a valuable source of information to decrease maintenance cost and downtime through enhanced monitoring, control and design. However, this load information is difficult to acquire since suitable direct load sensors are intrusive and expensive. Therefore, this paper focuses on indirect load measurement through a virtual sensing algorithm. The resulting virtual load sensor estimates the incoming load on the low speed planetary stage of the gearbox by combining strain measurements on the external surface of the ring gear with a physics-based model. The algorithm is deployed for real-time execution on low-cost embedded hardware to make a cost-effective load sensor. The effect of the configuration parameters of the virtual load sensor on the execution time and memory usage is examined in order to verify which configurations can be deployed. Since these configuration parameters also affect the estimation accuracy, the design of the virtual load sensor is tackled as a co-design problem. The resulting virtual load sensor, which is deployable for real-time execution, achieves an RMS estimation error of 0.6% in a numerical validation, using 4 strain gauges on the ring gear.
Wind Turbine Failure Prediction Using SCADA Data
Authors: Lima L A M , Blatt A , Fujise J
Published: September 2020

This paper proposes a failure prediction system for wind turbines using the Normal Behavior Model (NBM) approach. By using available SCADA data, the NBMs are trained to make predictions that reflect what would be a turbine’s normal operating condition. They are able to identify when a given operating condition is abnormal, which points towards probable component degradation. Alerts are raised based on the daily-averaged prediction error to help the O&M team in identifying turbines that need maintenance. The NBMs are comprised of numerous linear models with different inputs and training sets, according to an ensemble approach that aims to avoid overfitting and to reduce the amount of false-positive predictions.

Description and insights on various development steps are presented, such as data treatment, model selection, error calculation and alerts generations. Two test cases are shown using operational data from existing wind turbines, highlighting the system’s ability to generate alerts weeks before a severe fault occurs.
SCADA-based neural network thrust load model for fatigue assessment: cross validation with in-situ measurements
Authors: Santos Francisco d N , Noppe Nymfa , Weijtjens Wout , Devriendt Christof
Published: September 2020

In this contribution SCADA data and thrust attained through strain measurements are used to train a neural network model which predicts the thrust load of an offshore wind turbine. The model is subsequently cross-validated for different turbines with SCADA data outside of the training period as input and the thrust load from strain measurements as the expected output, and the impact of wind speed and different operating conditions studied. The results for the model, such as MAE, are kept generally under 2 %. The estimated thrust load signal is then converted into the damage equivalent stress caused by the quasi-static load, allowing to quantify the damage induced by the thrust load. The model performed, in general, well, but some over-/underpredictions are severely amplified when converting the loads into the damage equivalent stress.
Predicting the benefit of wake steering on the annual energy production of a wind farm using large eddy simulations and Gaussian process regression
Authors: Hoek Daan van der , Doekemeijer Bart , Andersson Leif Erik , Wingerden Jan-Willem van
Published: September 2020

In recent years, wake steering has been established as a promising method to increase the energy yield of a wind farm. Current practice in estimating the benefit of wake steering on the annual energy production (AEP) consists of evaluating the wind farm with simplified surrogate models, casting a large uncertainty on the estimated benefit. This paper presents a framework for determining the benefit of wake steering on the AEP, incorporating simulation results from a surrogate model and large eddy simulations in order to reduce the uncertainty. Furthermore, a time-varying wind direction is considered for a better representation of the ambient conditions at the real wind farm site. Gaussian process regression is used to combine the two data sets into a single improved model of the energy gain. This model estimates a 0.60% gain in AEP for the considered wind farm, which is a 76% increase compared to the estimate of the surrogate model.
Torque measurements from MW wind turbine Gearboxes: a system identification approach
Authors: Santiago U Gutierrez , van Wingerden J W , Polinder H , Sisón A Fernández
Published: September 2020

The gearbox is a critical component of modern MW wind turbines. An accurate model of the gearbox dynamics is needed to improve gearbox design, develop advanced control algorithms, and more effective fault diagnosis tools which could lead to lower the cost of energy from wind. The objective of this paper is to investigate how torque measurements can be used in a data-driven framework to build dynamic models of wind turbine gearboxes.

An initial torsional model has been derived from first principles considering the stiffness of the gears, shafts, and structural components in the gearbox together with the mechanical components of the test bench. This model has been used to create simulated data of the experiments performed on gearboxes and to apply system identification techniques to the simulated signals, with a focus on predictor based subspace identification methods. System identification has been applied to torque and speed data measured on physical tests of two 3.4MW gearboxes. Gearbox excitation frequencies and their harmonics dominate the measured signals and disturb the system identification algorithms. Several techniques have been investigated to remove the shaft rotation and gear mesh frequency harmonics of the torque and rotational speed signals based on time synchronous averaging.
Overview of FLORIS updates
Authors: Fleming Paul , King Jennifer , Bay Christopher J. , Simley Eric , Mudafort Rafael , Hamilton Nicholas , Farrell Alayna , Martinez-Tossas Luis
Published: September 2020

In this paper, we review updates made to the FLORIS (FLOw Redirection and Induction in Steady State) open-source framework for wind farm control modeling, design and analysis. The updates are focused on improvements for large arrays of turbines - including heterogenous inflows and incorporating second-order wake steering effects - design, and analysis tools for practical application of wind farm control, and improvements to the software architecture for best practices in modularization and cooperative development.
Real-time identification of clusters of turbines
Authors: Bernardoni Federico , Ciri Umberto , Rotea Mario , Leonardi Stefano
Published: September 2020

The implementation of wind farm control strategies requires knowledge of the turbines that are aerodynamically coupled through wake effects. As the wind changes direction, the clusters of coupled turbines may vary within the array. The present study proposes a simple method to identify clusters of turbines coupled by the wake interaction. The method uses the correlation of the power production fluctuations of the turbines in the wind farm. Large Eddy Simulations (LES) results of the flow in a 4×4 turbine array have been used to validate the proposed approach. This study introduces a tool which can be integrated into a control system to optimize wind plant power production.
Effects of dynamic induction control on power and loads, by LES-ALM simulations and wind tunnel experiments
Authors: Wang C , Campagnolo F , Sharma A , Bottasso C L
Published: September 2020

Dynamic Induction Control (DIC) has the potential of boosting wind farm power by enhancing wake recovery, whereby periodic pitch motions are used to exploit the natural instabilities of wind turbine wakes. This work studies DIC both experimentally and numerically. A thorough validation of an LES-ALM (Actuator Line Method) simulation tool is first conducted against experimental measurements. This shows that the CFD model is able to accurately simulate the power, loads and wake behavior of a wind turbine operating with DIC. The validated CFD model is then employed to study the effects of some DIC parameters. Results indicate an increase in the fatigue loads caused by the pitch activity that enhances wake recovery.
Launch of the FarmConners Wind Farm Control benchmark for code comparison
Authors: Göçmen Tuhfe , Kölle Konstanze , Andersen Søren Juhl , Eguinoa Irene , Duc Thomas , Campagnolo Filippo , Iribas-Latour Mikel , Astrain David , Bottasso Carlo , Meyers Johan , van Wingerden Jan Willem , Giebel Gregor
Published: September 2020

Careful validation of the modelling and control actions is of vital importance to build confidence in the value of coordinated wind farm control (WFC). The efficiency of flow models applied to WFC should be evaluated to provide reliable assessment of the performance of WFC. In order to achieve that, FarmConners launches a common benchmark for code comparison to demonstrate the potential benefits of WFC, such as increased power production and mitigation of loads. The benchmark builds on available data sets from previous and ongoing campaigns: synthetic data from high-fidelity simulations, measurements from wind tunnel experiments, and field data from a real wind farm. The participating WFC models are first to be calibrated or trained using normal operation periods. For the blind test, both the axial induction and wake steering control approaches are included in the dataset and to be evaluated through the designed test cases. Three main test cases are specified, addressing the impact of WFC on single full wake, single partial wake, and multiple wake. The WFC model outcomes will be compared during the blind test phase, through power gain and wake loss reduction as well as alleviation of wake-added turbulence intensity and structural loads. The probabilistic validation will be based on the median and quartiles of the observations and WFC model predictions. Every benchmark participant will be involved in the final publication, where the comparison of different tools will be performed using the defined test cases. Instructions on how to participate are also provided on farmconners.readthedocs.io.
Fault detection of wind turbine gearbox using thermal network modelling and SCADA data
Authors: Corley B. , Carroll J. , Mcdonald A.
Published: September 2020

This work uses a detailed understanding of the physics inside a wind turbine gearbox and SCADA temperature data as an alternative to data-driven techniques for fault detection. Thermal modelling based on the principles of heat transfer theory is used with the aim of understanding the thermal behaviour of a ‘healthy’ gearbox and use it to detect abnormal gearbox operating conditions. Data for turbines, ‘healthy’ and one month to fail, are analysed for two different failure modes to see if a fault can be detected in advance with the aim to improve physical understanding of wind turbine gearbox operation and condition monitoring techniques.