| 1. |
- Asl, Reza Mohammadi, et al.
(författare)
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Fuzzy-Based Parameter Optimization of Adaptive Unscented Kalman Filter : Methodology and Experimental Validation
- 2020
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Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 8, s. 54887-54904
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Tidskriftsartikel (refereegranskat)abstract
- This study introduces a fuzzy based optimal state estimation approach. The new method is based on two principles: Adaptive Unscented Kalman filter, and Fuzzy Adaptive Grasshopper Optimization Algorithm. The approach is designed for the optimization of an adaptive Unscented Kalman Filter. To find the optimal parameters for the filter, a fuzzy based evolutionary algorithm, named Fuzzy Adaptive Grasshopper Optimization Algorithm, is developed where its efficiency is verified by application to different benchmark functions. The proposed optimal adaptive unscented Kalman filter is applied to two nonlinear systems: a robotic manipulator, and a servo-hydraulic system. Different simulation tests are conducted to verify the performance of the filter. The results of simulations are presented and compared with a previous version of the unscented Kalman filter. For a realistic test, the proposed filter is applied on the practical servo-hydraulic system. Practical results are discussed, and presented results approve the capability of the presented method for practical applications.
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| 2. |
- Asl, Reza Mohammadi, et al.
(författare)
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Integral Non-Singular Terminal Sliding Mode Controller for nth-Order Nonlinear Systems
- 2019
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 7, s. 102792-102802
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a new integral non-singular terminal sliding mode control method for nonlinear systems is introduced. The proposed controller is designed by defining a new sliding surface with an additional integral part. This new manifold is first introduced into the second-order system and then expanded to nth-order systems. The stability of the control system is demonstrated for both second-order and nth-order systems by using the Lyapunov stability theory. The proposed controller is applied to a robotic manipulator as a case study for second-order systems, and a servo-hydraulic system as a case study for third-order systems. The results are presented and discussed.
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| 3. |
- Eriksson, Björn, 1981-
(författare)
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Mobile Fluid Power Systems Design : with a Focus on Energy Efficiency
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work deals with innovative energy efficient fluid power systems for mobile applications. The subjects taken up concern to what extent and how energy losses can be reduced in mobile working hydraulics systems. Various measures are available for increasing energy efficiency in these kinds of systems. Examples include:Flow controlled systems The pump controller is switched from a load sensing toa displacement controlled one. The displacement is controlled in an open loopfashion directly from the operator’s demand signals. This reduces energy consumptionat the same time as dynamic issues that are attached to LS systemscan be avoided.Individual metering valve systems Flexibility is increased by removing the mechanicalcoupling between the meter-in and meter-out orifices in directionalvalves. An overview of this kind of system is given in the thesis. A designproposal that has been implemented is also presented. Initial test results areshown. Patents for this particular system have been applied for.Displacement control Metering losses are reduced by removing the directional valves.One pump is used for each load in such systems. This hardware layout involvesconsiderable changes compared to conventional systems. Displacementcontrolled systems are not studied in this work.In mobile applications, overall efficiency is often poor and losses are substantial. The measures listed above can help improve this significantly in such applications. A flow dividing system can decrease energy consumption by about 10% and an individual metering system by about 20%. Losses in pump controlled systems are difficult to give a figure for; the losses are rather attached to the pumps and motors and not to the system layout. However, the losses for these systems are presumably even lower than for individual metering systems. The main focus in this work is on individual metering systems but questions about which components and so on are also treated. For example, the Valvistor valve concept has been studied as part of this work.
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| 4. |
- Yung, I, 1986-
(författare)
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Automation of front-end loaders : electronic self leveling and payload estimation
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A growing population is driving automatization in agricultural industry to strive for more productive arable land. Being part of this process, this work is aimed to investigate the possibility to implement sensor-based automation in a particular system called Front End Loader, which is a lifting arms that is commonly mounted on the front of a tractor. Two main tasks are considered here, namely Electronic Self Leveling (ESL) and payload estimation. To propose commercially implementable solutions for these tasks, specific objectives are set, which are: 1) to propose a controller to perform ESL under typical disturbances 2) to propose a methodology for payload estimation considering realistic estimation conditions. Lastly, aligned with these goals, 3) to propose models for the Front End Loader under consideration for derivation of solutions of the specified tasks.The self-leveling task assists farmers in maintaining the angular position of the mounted implements, e.g. a bale handler or a bucket, with respect to the ground when the loader is manually lifted or lowered. Experimental results show that different controllers are required in lifting and lowering motions to maintain the implement's angular position with a required accuracy due to principle differences in gravity impact. The gravity helps the necessary correction in lifting motion, but works against the correction in lowering motions. This led us to propose a controller with a proportional term, a discontinuous term and an on-line disturbance estimation and compensation as well as the tuning procedure to achieve a 2 degrees tracking error for lowering motions in steady state. The proposed controller shows less sensitive performance to lowering velocity, as the main disturbance, in comparison to a linear controller.The second task, payload estimation, assists farmers to work within safety range as well as to work with a weight measurement tool. A mechanical model derived based on equations of motion is improved by a pressure based friction to sufficiently accurately represent the motion of the front end loader under consideration. The proposed model satisfies the desired estimation accuracy of 2\% full scale error in a certain estimation condition domain in constant velocity regions, with off-line calibration step and off-line payload estimation step. An on-line version of the estimation based on Recursive Least Squares also fulfills the desired accuracy, while keeping the calibration step off-line.
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