scholarly journals Hybrid Nonlinear Disturbance Observer Design for Underactuated Bipedal Robots

2018 ◽  
Author(s):  
Alireza Mohammadi ◽  
Seyed Fakoorian ◽  
Jonathan C. Horn ◽  
Dan Simon ◽  
Robert D. Gregg
Keyword(s):  
Disturbance Observer ◽  
Observer Design ◽  
Bipedal Robots ◽  
Nonlinear Disturbance Observer ◽  
Nonlinear Disturbance

scholarly journals Nonlinear disturbance observer design for robotic manipulators

2013 ◽  
Vol 21 (3) ◽  
pp. 253-267 ◽  
Author(s):  
A. Mohammadi ◽  
M. Tavakoli ◽  
H.J. Marquez ◽  
F. Hashemzadeh
Keyword(s):  
Disturbance Observer ◽  
Robotic Manipulators ◽  
Observer Design ◽  
Nonlinear Disturbance Observer ◽  
Nonlinear Disturbance

Robust Nonlinear Disturbance Observer Design for Estimation of Ammonia Storage Ratio in Selective Catalytic Reduction Systems

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
Jinbiao Ning ◽  
Fengjun Yan
Keyword(s):  
Selective Catalytic Reduction ◽  
Disturbance Observer ◽  
Catalytic Reduction ◽  
External Disturbance ◽  
Nox Reduction ◽  
Observer Design ◽  
Noise Attenuation ◽  
Nonlinear Disturbance Observer ◽  
Ammonia Storage ◽  
Nonlinear Disturbance

Urea-based selective catalytic reduction (SCR) system is a promising way to obtain high NOx reduction and commonly adopted in diesel engine aftertreatment systems. The ammonia storage ratio is critical for SCR feedback control but it is difficult to be directly measured by sensors. This paper aims to effectively estimate the ammonia storage ratio on line and reduce the cost of using ammonia sensors. In the proposed method, the ammonia storage ratio is treated as an external disturbance in the NOx dynamic model and estimated by the nonlinear disturbance observer (NDO) methods. Furthermore, to reduce estimation errors of ammonia storage ratio caused by the high-frequency measurement noises, a novel robust nonlinear disturbance observer (robust NDO) is proposed and compared with a typical design method (regular NDO). Both the NDOs are developed based on part of the three-state SCR model and cost-effective, since NOx sensors are only used. The stability and noise attenuation properties of both estimations were also analyzed in the paper. The simulation results based on the full-vehicle simulator of FTP-75 test demonstrate that the regular NDO and the robust NDO can effectively estimate the ammonia storage ratio even in cases where ammonia cross-sensitivity affects the response. Among the two observers, the robust NDO has better noise attenuation properties.

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