| 1. |
- Chugh, Tushar, 1989, et al.
(författare)
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Design and control of model based steering feel reference in an electric power assisted steering system
- 2018
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Ingår i: The Dynamics of Vehicles on Roads and Tracks. ; 1, s. 43-49
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Konferensbidrag (refereegranskat)abstract
- Electric Power Assisted Steering (EPAS) system is a current state of the art technology for providing the steering torque support. The interaction of the steering system with the driver is principally governed by the EPAS control method. This paper proposes a control concept for designing the steering feel with a model based approach. The reference steering feel is defined in virtual dynamics for tracking. The layout of the reference model and the control architecture is discussed at first and then the decoupling of EPAS motor dynamics using a feedback control is shown. An example of how a change in steering feel reference (as desired by the driver) creates a change in steering feedback is further exhibited. The ultimate goal is to provide the driver with a tunable steering feel. For this, the verification is performed in simulation environment.
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| 2. |
- Chen, Weitao, 1989, et al.
(författare)
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A Method to Improve Stability and Transparency for Mechanical Hardware-in-the-Loop Simulation
- 2021
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In mechanical hardware-in-the-loop (MHIL) simulation the test hardware and the simulated environment are coupled by an interface, which typically is a dynamometer rig. This interface determines the simulation accuracy and robustness. In this work, MHIL simulation is analysed in a linear robust control framework. The system consists of an inner loop formed by the load motor controller and the rig, and an outer loop formed by the test hardware and the simulated environment. While the inner loop tracking set the overall performance, instability and poor performance may be introduced by the outer loop. We demonstrate how delay tolerance of MHIL simulation varies with the outer loop dynamics. A new method is introduced to improve the robustness and accuracy. The method utilizes flexibility of the simulation model, and only software changes are needed. The proposed method is applied to an MHIL simulation for vehicle and electric power assisted steering (EPAS) system test. The effectiveness of the method is shown analytically and experimentally.
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| 3. |
- Chen, Weitao, 1989, et al.
(författare)
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An Architecture of Hardware and Driver in the Loop Simulation for Electric Power Assisted Steering System
- 2020
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Ingår i: Lecture Notes in Mechanical Engineering. - Cham : Springer International Publishing. - 2195-4356 .- 2195-4364. - 9783030380762
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Konferensbidrag (refereegranskat)abstract
- This paper introduces an architecture for virtual development of electric power assisted steering (EPAS) system, which is implemented at Volvo Cars. The architecture involves an EPAS power pack rig and driver in the loop, so engineers can test both the ECU software and electric motor on a virtual prototype vehicle. Eective results are shown for tests in low-mid frequency and at mid-high vehicle speed. Currently, the high frequency and low speed test is still challenging due to vibration and instability, which should be addressed by the control improvement.
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| 4. |
- Chen, Weitao, 1989
(författare)
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Co-Simulation in Virtual Verification of Vehicles with Mechatronic Systems
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In virtual verification of vehicle and mechatronic systems, a mixture of subsystems are integrated numerically in an offline simulation or integrated physically in a hardware-in-loop (HIL) simulation. This heterogeneous engineering approach is crucial for system-level development and widely spreads with the industrial standard, e.g. Functional Mock-Up Interface (FMI) standard. For the engineers, not only the local subsystem and solver should be known, but also the global coupled dynamic system and its coupling effect need to be understood. Both the local and global factors influence the stability, accuracy, numerical efficiency and further on the real-time simulation capability. In this thesis, the explicit parallel co-simulation, which is the most common and closest to the integration with a physical system, is investigated. In the vehicle development, the vehicle and the mechatronic system, e.g. an Electrcial Power Assisted Steering (EPAS) system can be simulated more efficiently by a tailored solver and communicative step. The accuracy and numerical stability problem, which highly depends on the interface dynamics, can be investigated similarly in the linear robust control framework. The vehicle-mechatronic system should be coupled to give a smaller loop gain for robustness and stability. Physically, it indicates that the splitting part should be less stiff and the force or torque variable should be applied towards the part with a higher impedance in the force-displacement coupling. Furthermore, to compensate the troublesome low-passed and delay effect from the coupling, a new coupling method based on H∞ synthesis is developed, which can improve the accuracy of co-simulation. The method shows robustness to the system dynamics, which makes it more applicable for a complex vehicle-mechatronic system.
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| 5. |
- Chen, Weitao, 1989, et al.
(författare)
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Design of Interface in Co-simulation for Electric Power Assisted Steering System Development
- 2018
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Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control.
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Konferensbidrag (refereegranskat)abstract
- Interface and causality have important effects on the co-simulation used in vehicle system development. In this paper we analyzed these effects by modeling a co-simulated dual mass-spring-damper system as a sampled-data system. By stability and frequency domain analysis we find that the co-simulation interface needs be designed where the coupling interface is less stiff and the force variable should be applied in the direction of larger mass, natural frequency and damping ratio. The analytical results have been verified through two test cases of co-simulation in electric power assisted steering (EPAS) system development: a multi-rate offline co-simulation and a hardware-in-loop (HIL) simulation. Both test cases showed more consistent and stable results using the suggested interface design.
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| 6. |
- Chen, Weitao, 1989, et al.
(författare)
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Explicit parallel co-simulation approach: analysis and improved coupling method based on H-infinity synthesis
- 2021
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Ingår i: Multibody System Dynamics. - : Springer Science and Business Media LLC. - 1573-272X .- 1384-5640. ; 52:3, s. 255-279
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Tidskriftsartikel (refereegranskat)abstract
- Co-simulation is widely used in the industry for the simulation of multidomain systems. Because the coupling variables cannot be communicated continuously, the co-simulation results can be unstable and inaccurate, especially when an explicit parallel approach is applied. To address this issue, new coupling methods to improve the stability and accuracy have been developed in recent years. However, the assessment of their performance is sometimes not straightforward or is even impossible owing to the case-dependent effect. The selection of the coupling method and its tuning cannot be performed before running the co-simulation, especially with a time-varying system. In this work, the co-simulation system is analyzed in the frequency domain as a sampled-data interconnection. Then a new coupling method based on the H-infinity synthesis is developed. The method intends to reconstruct the coupling variable by adding a compensator and smoother at the interface and to minimize the error from the sample-hold process. A convergence analysis in the frequency domain shows that the coupling error can be reduced in a wide frequency range, which implies good robustness. The new method is verified using two co-simulation cases. The first case is a dual mass–spring–damper system with random parameters and the second case is a co-simulation of a multibody dynamic (MBD) vehicle model and an electric power-assisted steering (EPAS) system model. Experimental results show that the method can improve the stability and accuracy, which enables a larger communication step to speed up the explicit parallel co-simulation.
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| 7. |
- Chen, Weitao, 1989, et al.
(författare)
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Integration and Analysis of EPAS and Chassis System in FMI-based co-simulation
- 2019
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Ingår i: Proceedings of the 13th International Modelica Conference. - : Linköing University Electronic Press. - 9789176851227 ; :157, s. 717-724
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Konferensbidrag (refereegranskat)abstract
- The vehicle steering characteristics and active functions can be virtually developed with a high-fidelity electric power assisted steering (EPAS) model and a multibody chassis model. The simulation of the EPAS model requires small integration step due to high stiffness and interfacing with the controller. The multibody chassis model is computationally heavy for each integration step due to calculation of large matrices. A mono-simulation based on a single solver is not efficient for this case. Instead a co-simulation (solver coupling) approach has been used to overcome the drawbacks.In this paper the EPAS system and chassis system are modeled in Dymola and further exported as separate functional mockup units (FMUs) and integrated with the control algorithms in Matlab. A co-simulation based on the explicit parallel calculation scheme (Jacobi scheme) has been used. A huge simulation speed-up has shown the potential and effectiveness of the approach. To understand its accuracy and tolerance, analysis on the numerical error and dynamics of the coupled-system are given.
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| 8. |
- Chen, Weitao, 1989, et al.
(författare)
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Real-time Co-simulation Method Study for Vehicle Steering and Chassis System
- 2018
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 51:9, s. 273-278
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Konferensbidrag (refereegranskat)abstract
- Real-time co-simulation is widely used in complex system development. This paper presented an application of our driver-in-the-loop simulator, the vehicle steering and chassis system are implemented on different real-time machines coupled with input-output signals. Results inconsistent with the mono simulation reference may be generated due to the real-time co-simulation drawbacks: the delay effect and coupling errors from modular integration. To overcome the drawbacks, a coupling element as an additional subsystem has been proposed by the author. The coupling element consists of a delay compensation part based on adaptive filters and a coupling error correction part based on the energy-preserving method. This coupling method has been tested with the vehicle steering and chassis model. More stable and consistent results are obtained. The frequency domain analysis and implementation method have been provided.
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| 9. |
- Chen, Weitao, 1989
(författare)
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Virtual prototyping of vehicular electric steering assistance system using co-simulations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Virtual prototyping is a practical necessity in vehicle system development. From desktop simulation to track testing, several simulation approaches, such as co-simulation and hardware-in-loop (HIL) simulation, are used. However, due to interfacing problems, the consistency of testing results may not be ensured. Correspondingly, inherent inaccuracies result from numerical coupling error and non-transparent HIL interface, which involves control tracking error, delay error, and attached hardware and noise effects. This work aims to resolve these problems and provide seamless virtual prototypes for vehicle and electric power-assisted steering (EPAS) system development. The accuracy and stability of explicit parallel co-simulation and HIL simulation are investigated. The imperfect factors propagate in the simulation tools like perturbations, yield inaccuracy, and even instability according to system dynamics. Hence, reducing perturbations (coupling problem) and improving system robustness (architecture problem) are considered. In the coupling problem, a delay compensation method relying on adaptive filters is developed for real-time simulation. A novel co-simulation coupling method on H-infinity synthesis is developed to improve accuracy for a wide frequency range and achieve low computational cost. In the architecture problem, a force(torque)-velocity coupling approach is employed. The application of a force (torque) variable to a component with considerable impedance, e.g., the steering rack (EPAS motor), yields a small loop gain as well as robust co-simulation and HIL simulation. On a given EPAS HIL system, an interface algorithm is developed for virtually shifting the impedance, thus enhancing system robustness. The theoretical findings and formulated methods are tested on generic benchmarks and implemented on a vehicle-EPAS engineering case. In addition to the acceleration of simulation speed, accuracy and robustness are also improved. Consequently, consistent testing results and extended validated ranges of virtual prototypes are obtained.
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