Parameter uncertainty dominates C-cycle forecast errors over most of Brazil for the 21st century

Identification of terrestrial carbon (C) sources and sinks is critical for understanding the Earth system as well as mitigating and adapting to climate change resulting from greenhouse gas emissions. Predicting whether a given location will act as a C source or sink using terrestrial ecosystem models (TEMs) is challenging due to net flux being the difference between far larger, spatially and temporally variable fluxes with large uncertainties. Uncertainty in projections of future dynamics, critical for policy evaluation, has been determined using multi-TEM intercomparisons, for various emissions scenarios. This approach quantifies structural and forcing errors. However, the role of parameter error within models has not been determined. TEMs typically have defined parameters for specific plant functional types generated from the literature. To ascertain the importance of parameter error in forecasts, we present a Bayesian analysis that uses data on historical and current C cycling for Brazil to parameterise five TEMs of varied complexity with a retrieval of model error covariance at 1∘ spatial resolution. After evaluation against data from 2001–2017, the parameterised models are simulated to 2100 under four climate change scenarios spanning the likely range of climate projections. Using multiple models, each with per pixel parameter ensembles, we partition forecast uncertainties. Parameter uncertainty dominates across most of Brazil when simulating future stock changes in biomass C and dead organic matter (DOM). Uncertainty of simulated biomass change is most strongly correlated with net primary productivity allocation to wood (NPPwood) and mean residence time of wood (MRTwood). Uncertainty of simulated DOM change is most strongly correlated with MRTsoil and NPPwood. Due to the coupling between these variables and C stock dynamics being bi-directional, we argue that using repeat estimates of woody biomass will provide a valuable constraint needed to refine predictions of the future carbon cycle. Finally, evaluation of our multi-model analysis shows that wood litter contributes substantially to fire emissions, necessitating a greater understanding of wood litter C cycling than is typically considered in large-scale TEMs.

Sensorless LC Filter Implementation for Permanent Magnet Machine Drive Using Observer-Based Voltage and Current Estimation

For pulse width modulation (PWM) inverter drives, an LC filter can cascade to a permanent magnet (PM) machine at inverter output to reduce PWM-reflected current harmonics. Because the LC filter causes resonance, the filter output current and voltage are required for the sensorless field-oriented control (FOC) drive. However, existing sensors and inverters are typically integrated inside commercial closed-form drives; it is not possible for these drives to obtain additional filter output signals. To resolve this integration issue, this paper proposes a sensorless LC filter state estimation using only the drive inside current sensors. The design principle of the LC filter is first introduced to remove PWM current harmonics. A dual-observer is then proposed to estimate the filter output current and voltage for the sensorless FOC drive. Compared to conventional model-based estimation, the proposed dual-observer demonstrates robust estimation performance under parameter error. The capacitor parameter error shows a negligible influence on the proposed observer estimation. The filter inductance error only affects the capacitor current estimation at high speed. The performance of the sensorless FOC drive using the proposed dual-observer is comparable to the same drive using external sensors for filter voltage and current measurement. All experiments are verified by a PM machine with only 130 μH phase inductance.

Parameter uncertainty dominates C cycle forecast errors over most of Brazil for the 21st Century

Identification of terrestrial carbon (C) sources and sinks is critical for understanding the earth system and to mitigate and adapt to climate change results from greenhouse gas emissions. Predicting whether a given location will act as a C source or sink using terrestrial ecosystem models (TEMs) is challenging due to net flux being the difference between far larger, spatially and temporally variable fluxes with large uncertainties. Uncertainty in projections of future dynamics, critical for policy evaluation, has been determined using multi-TEM intercomparisons, for various emissions scenarios. This approach quantifies structural and forcing errors. However, the role of parameter error within models has not been determined. TEMs typically have defined parameters for specific plant functional types generated from the literature. To ascertain the importance of parameter error in forecasts we present a Bayesian analysis that uses data on historical and current C cycling for Brazil to parameterise five TEMs of varied complexity with a retrieval of model error covariance at 1 degree spatial resolution. After evaluation against data from 2001–2017, the parameterised models are simulated to 2100 under four climate change scenarios spanning the likely range of climate projections. Using multiple models, each with per pixel parameter ensembles, we partition forecast uncertainties. Parameter uncertainty dominates across most of Brazil when simulating future stock changes in biomass C and dead organic matter (DOM). Uncertainty of simulated biomass change is most strongly correlated with net primary productivity allocation to wood (NPPwood) and wood mean residence times (MRTwood). Uncertainty of simulated DOM change is most strongly correlated with MRTsoil and NPPwood. Due to the coupling between these variables and C stock dynamics being bi-directional we argue that using repeat estimates of woody biomass will provide a valuable constraint needed to refine predictions of the future carbon cycle. Finally, evaluation of our multi-model analysis shows that wood litter contributes substantially to fire emissions necessitating a greater understanding of wood litter C-cycling than is typically considered in large-scale TEMs.

Research of Calibration Method for Industrial Robot Based on Error Model of Position

Based on the current situation of high precision and comparatively low APA (absolute positioning accuracy) in industrial robots, a calibration method to enhance the APA of industrial robots is proposed. In view of the "hidden" characteristics of the RBCS (robot base coordinate system) and the FCS (flange coordinate system) in the measurement process, a comparatively general measurement and calibration method of the RBCS and the FCS is proposed, and the source of the robot terminal position error is classified into three aspects: positioning error of industrial RBCS, kinematics parameter error of manipulator, and positioning error of industrial robot end FCS. The robot position error model is established, and the relation equation of the robot end position error and the industrial robot model parameter error is deduced. By solving the equation, the parameter error identification and the supplementary results are obtained, and the method of compensating the error by using the robot joint angle is realized. The Leica laser tracker is used to verify the calibration method on ABB IRB120 industrial robot. The experimental results show that the calibration method can effectively enhance the APA of the robot.

Using Repetitive Control with Force Feedback to Reduce Impedance of Exoskeletons for Gait Training

Transparent interaction, or the reduction of human-robot interaction forces, is an important quality of gait training exoskeletons. In this paper, we investigate the feasibility of using a repetitive controller for reducing impedance of gait training exoskeletons using force feedback. We used a two-mass spring damper model system, and simulated the application of repetitive force controllers with the objective of reducing the end-point impedance of the distal mass. We designed and applied three repetitive controllers: a 1st order, a 2nd order designed for random signal period error, and a 2nd order designed for constant signal period error. We compared these three repetitive controllers subject to plant model parameter error, random signal period error, and constant signal period error. Numerical simulations under nominal conditions show that via repetitive force control, it is possible to reduce the endpoint impedance to the targeted magnitude and RMSE force below the limit achievable with force controllers while guaranteeing passivity. Furthermore, we established that the application of a 2nd order repetitive controller designed for random period error is highly robust to random period error - exceeding the performance of the passive proportional controller up to 30% error of nominal frequency. Furthermore, this 2nd order repetitive controller designed for random period error maintains a 100% convergence rate through 60% plant parameter error.

ANALISIS PERAMALAN TINGKAT KEMISKINAN DI INDONESIA DENGAN MODEL ARIMA

Kemiskinan di Indonesia merupakan masalah yang kompleks dan multidimensi, karena tingkat kemiskinan di suatu negara akan mempengaruhi indikator keberhasilan baik dari segi pembangunan maupun perekonomian negara tersebut. Berdasarkan permasalahan tersebut diperlukan sebuah prediksi untuk mengetahui tingkat kemiskinan di Indonesia baik wilayah Perkotaan, Pedesaan maupun secara Nasional. Pada penelitian kali ini, peneliti menggunakan sebuah model dari Box Jenkins yaitu Auto Regresive Moving Average (ARIMA) untuk memprediksi tingkat kemiskinan di Indonesia pada masa yang akan datang. Dataset kemiskinan yang digunakan bersumber dari Badan Pusat Statistik (BPS) dengan data pengujian dari tahun 2011 hingga tahun 2020. Peneliti akan menggunakan 3 parameter error untuk mengevaluasi hasil tingkat kemiskinan di Perkotaan, Pedesaan maupun secara Nasional yaitu RMSE, MAE dan MAPE. Berdasarkan pengujian yang dilakukan bahwa dataset perkotaan menghasilkan model ARIMA(2,2,5) sebagai model ARIMA terbaik dengan RMSE=1.246582, MAE=0.923255 dan MAPE=12%, untuk dataset pedesaan menghasilkan model ARIMA(1,2,1) sebagai yang terbaik dengan RMSE=0.392650, MAE=0.311529 dan MAPE=2%. Sedangkan untuk dataset secara nasional menghasilkan model ARIMA(0,2,5) sebagai yang terbaik dengan RMSE=2.533166, MAE=2.090505 dan MAPE=20%. Dari 3 pengujian tersebut disimpulkan bahwa model ARIMA berhasil memprediksi tingkat kemiskinan di Indonesia baik wilayah Perkotaan, Pedesaan maupun secara Nasional dengan hasil baik.

EVALUASI PENGALAMAN PENGGUNA PADA E-COMMERCE SOCIOLLA.COM MENGGUNAKAN USABILITY TESTING DAN USER EXPERIENCE QUESTIONNAIRE (UEQ)

Sociolla merupakan e-commerce terlengkap dan terpercaya di Indonesia yang menjual produk kecantikan dan perawatan kulit dan tubuh. Demi mempermudah akses untuk mendapatkan kosmetik yang diinginkan, website Sociolla dibuat pada tahun 2015. Website sociolla bertujuan memudahkan konsumen untuk mendapatkan informasi mengenai kandungan dan harga kosmetik. Permasalahan yang terjadi pada website Sociolla adalah setiap pengguna yang melakukan interaksi pada website merasa bahwa website Sociolla memerlukan waktu yang cukup lama untuk setiap tugas. Dampak dari kesalahan sistem yang berulang tersebut, membuat banyaknya pengguna enggan melakukan aktivitas pada website. Dari permasalahan tersebut, maka dilakukanlah evaluasi usablity untuk mengetahui pengalaman pengguna menggunakan pengujian skenario Usability Testing, kuesioner SUS dan metode UEQ. Hasil pengujian skenario parameter Task Completed memiliki nilai keberhasilan sebesar 0.91, parameter Error Rate memiliki rata-rata jumlah kesalahan sebesar 0.05467, parameter Time per Completed Task memiliki rata-rata waktu sebesar 45.313 detik dan parameter Number of Clicks memiliki rata-rata sebesar 5 klik. Hasil kuesioner SUS mendapatkan skor 75.75 yang termasuk dalam kategori Acceptable. Hasil pengalaman pengguna menunjukkan yaitu pada metode UEQ, aspek pragmatic quality dengan nilai sebesar 3.05, dan aspek hedonic quality dengan nilai sebesar 2.23. Dalam penelitian ini dapat disimpulkan bahwa website Sociolla dapat diterima dengan baik oleh pengguna.