Paulius Kojis

Mr. Paulius Kojis

Vilnius Gediminas Technical University (Vilnius Tech) Transport and Logistics Competence Centre
orcid

Research Focus & Metrics

Academic Career Length

6Years (2021-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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17 January 2024 in Sensors
Verified
Journal Article
Open access
PDF file
Viktor SkrickijViktor Skrickij
Viktor Skrickij
Paulius KojisPaulius Kojis
Paulius Kojis
EŠEldar Šabanovič
Eldar Šabanovič
Barys ShyrokauBarys Shyrokau
Barys Shyrokau
Valentin IvanovValentin Ivanov
Valentin Ivanov
Integrated chassis control systems represent a significant advancement in the dynamics of ground vehicles, aimed at enhancing overall performance, comfort, handling, and stability. As vehicles transition from internal combustion to electric platforms, integrated chassis control systems have evolved to meet the demands of electrification and automation. This paper analyses the overall control structure of automated vehicles with integrated chassis control systems. Integration of longitudinal, lateral, and vertical systems presents complexities due to the overlapping control regions of various subsystems. The presented methodology includes a comprehensive examination of state-of-the-art technologies, focusing on algorithms to manage control actions and prevent interference between subsystems. The results underscore the importance of control allocation to exploit the additional degrees of freedom offered by over-actuated systems. This paper systematically overviews the various control methods applied in integrated chassis control and path tracking. This includes a detailed examination of perception and decision-making, parameter estimation techniques, reference generation strategies, and the hierarchy of controllers, encompassing high-level, middle-level, and low-level control components. By offering this systematic overview, this paper aims to facilitate a deeper understanding of the diverse control methods employed in automated driving with integrated chassis control, providing insights into their applications, strengths, and limitations.

27 October 2021 in Sensors
Verified
Journal Article
Open access
PDF file
EŠEldar Šabanovič
Eldar Šabanovič
Paulius KojisPaulius Kojis
Paulius Kojis
ŠŠŠarūnas Šukevičius
Šarūnas Šukevičius
Barys ShyrokauBarys Shyrokau
Barys Shyrokau
Valentin IvanovValentin Ivanov
Valentin Ivanov
Viktor SkrickijViktor Skrickij
Viktor Skrickij
With the automotive industry moving towards automated driving, sensing is increasingly important in enabling technology. The virtual sensors allow data fusion from various vehicle sensors and provide a prediction for measurement that is hard or too expensive to measure in another way or in the case of demand on continuous detection. In this paper, virtual sensing is discussed for the case of vehicle suspension control, where information about the relative velocity of the unsprung mass for each vehicle corner is required. The corresponding goal can be identified as a regression task with multi-input sequence input. The hypothesis is that the state-of-art method of Bidirectional Long–Short Term Memory (BiLSTM) can solve it. In this paper, a virtual sensor has been proposed and developed by training a neural network model. The simulations have been performed using an experimentally validated full vehicle model in IPG Carmaker. Simulations provided the reference data which were used for Neural Network (NN) training. The extensive dataset covering 26 scenarios has been used to obtain training, validation and testing data. The Bayesian Search was used to select the best neural network structure using root mean square error as a metric. The best network is made of 167 BiLSTM, 256 fully connected hidden units and 4 output units. Error histograms and spectral analysis of the predicted signal compared to the reference signal are presented. The results demonstrate the good applicability of neural network-based virtual sensors to estimate vehicle unsprung mass relative velocity.

16 March 2022 in Transport
Verified
Journal Article
Open access
PDF file
Paulius KojisPaulius Kojis
Paulius Kojis
EŠEldar Šabanovič
Eldar Šabanovič
Viktor SkrickijViktor Skrickij
Viktor Skrickij
This research presents a data-driven Neural Network (NN)-based Virtual Sensor (VS) that estimates vehicles’ Unsprung Mass (UM) vertical velocity in real-time. UM vertical velocity is an input parameter used to control a vehicle’s semi-active suspension. The extensive simulation-based dataset covering 95 scenarios was created and used to obtain training, validation and testing data for Deep Neural Network (DNN). The simulations have been performed with an experimentally validated full vehicle model using software for advanced vehicle dynamics simulation. VS was developed and tested, taking into account the Root Mean Square (RMS) of Sprung Mass (SM) acceleration as a comfort metric. The RMS was calculated for two cases: using actual UM velocity and estimations from the VS as input to the suspension controller. The comparison shows that RMS change is less than the difference threshold that vehicle occupants could perceive. The achieved result indicates the great potential of using the proposed VS in place of the physical sensor in vehicles.

22 January 2024 in IEEE Access
Verified
Journal Article
Open access
EŠEldar Šabanovič
Eldar Šabanovič
Paulius KojisPaulius Kojis
Paulius Kojis
VIValentin Ivanov
Valentin Ivanov
MDMiguel Dhaens
Miguel Dhaens
Viktor SkrickijViktor Skrickij
Viktor Skrickij
Vehicle comfort, handling, and stability can be improved by a semi-active suspension with advanced control algorithms using the vertical velocities of the sprung mass (SM) and the unsprung masses (UMs) as inputs. Displacement and acceleration sensors are often used to estimate vertical velocities of UMs. However, these sensors are expensive and are susceptible to degradation. Virtual sensors (VS) have been proposed as a solution, and previous research using simulation data has shown that artificial neural networks (ANNs) can provide usable UM vertical velocity estimates. This study aims at finding ANNs structure and input sample window size to achieve best performance on real-world data. Novel dataset was created and used to test VSs based on eight structures of ANNs combining multilayer perceptron, convolutional neural network, long-term short-term memory (LSTM), and bidirectional LSTM layers. This article presents the results of 104 combinations of ANN structure and sample window size, which required 6240 training sessions. A Bayesian search was used to tune the hyperparameters of ANNs’ layers minimizing the root-mean-square error (RMSE) of estimations on the validation data, while a grid search was used to select the sample window size that minimizes RMSE of estimation on test data, ensuring that selected combinations are well generalized. The VS based on ANN with convolutional layers, achieved the lowest RMSE of 0.0210 m/s, and processing time of 0.421 ms for a window size of 23 samples while estimating vertical velocities of vehicle UMs from real-world data.

29 July 2021 in Preprints.org
Verified
Preprint
Open access
PDF file
EŠEldar Šabanovič
Eldar Šabanovič
Paulius KojisPaulius Kojis
Paulius Kojis
ŠŠŠarūnas Šukevičius
Šarūnas Šukevičius
Barys ShyrokauBarys Shyrokau
Barys Shyrokau
Valentin IvanovValentin Ivanov
Valentin Ivanov
Viktor SkrickijViktor Skrickij
Viktor Skrickij
With the automotive industry moving towards automated driving, sensing is becoming an increasingly important part of enabling technology. The virtual sensors allow data fusion from various vehicle sensors and provide a prediction for measurement that is hard or too expensive to measure in another way or in the case of demand on continuous detection. In this paper, virtual sensing is discussed for the case of vehicle suspension control, where information about the relative velocity of the unsprung mass for each vehicle corner is required. The corresponding goal can be identified as a regression task with multi-input sequence input. The hypothesis is that the state-of-art method of Bidirectional Long-Short Term Memory (BiLSMT) can solve it. In this paper, a virtual sensor has been proposed and developed by training a neural network model. The simulations have been performed using an experimentally validated full vehicle model in IPG Carmaker. Simulations provided the reference data which was used for Neural Network (NN) training. The extensive dataset covering 26 scenarios has been used to obtain training, validation and testing data. The Bayesian Search was used to select the best neural network structure using root mean square error as a metric. The best network is made of 167 BiLSTM, 256 fully connected hidden units and 4 output units. Error histograms and spectral analysis of the predicted signal compared to the reference signal are presented. The results demonstrate the good applicability of neural network-based virtual sensors for the estimation of vehicle unsprung mass relative velocity.

1 January 2022
Verified
Book Chapter
Closed access
PDF file
Paulius KojisPaulius Kojis
Paulius Kojis
ADAlgimantas Danilevičius
Algimantas Danilevičius
EŠEldar Šabanovič
Eldar Šabanovič
Viktor SkrickijViktor Skrickij
Viktor Skrickij