Improved Smith sliding mode control for air-fuel ratio of natural gas engine

doi:10.3785/j.issn.1008-973X.2026.03.022

Journal of ZheJiang University (Engineering Science)

2026, Vol. 60

Issue (3): 661-669 DOI: 10.3785/j.issn.1008-973X.2026.03.022

Improved Smith sliding mode control for air-fuel ratio of natural gas engine

Jiahui JIANG1(

),Yun LONG2,Chong YAO1,*(

),Rongjia LIN1,Enzhe SONG1,Yun KE1

1. Yantai Research Institute, Harbin Engineering University, Yantai 264000, China
2. College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China

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Abstract

A sliding mode control strategy based on predefined-time stability and improved Smith predictor was proposed in order to achieve precise air-fuel ratio tracking control for natural gas engines. The delay issue caused by hysteresis characteristics in air–fuel ratio control was effectively addressed. A delayed dynamic model of the air-fuel ratio was established based on the operating principle of natural gas engine. An improved Smith predictor was employed to estimate and compensate for the delay in order to overcome the large time delay in air-fuel ratio control. The improved Smith predictor effectively addressed parameter uncertainties and enhanced system adaptability and dynamic response by incorporating a compensation coefficient. The impact of the delay term on the closed-loop system was effectively eliminated. A predefined-time sliding mode controller was designed based on the compensated output in order to ensure the tracking performance of the control system. The system converged within a predefined time. Lyapunov functions were used to analyze the robustness and convergence performance of the system. An experimental platform was constructed, and various practical testing conditions were designed. Comparative tests with PID controllers and fast-converging sliding mode controllers were conducted. The proposed predefined-time sliding mode controller demonstrated improved stability, reduced overshoot and faster response, meeting the control requirements of natural gas engines.

Key words： natural gas engine air-fuel ratio sliding mode control nonlinear sliding mode Smith predictor predefined-time convergence

Received: 26 March 2025 Published: 04 February 2026

CLC:

TP 13

Fund: 山东省自然科学基金资助项目（ZR2023QE009）.

Corresponding Authors: Chong YAO E-mail: jjh18846037970@163.com;esmartcontrolheu@163.com

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	Jiahui JIANG
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	Enzhe SONG
	Yun KE

Cite this article:

Jiahui JIANG,Yun LONG,Chong YAO,Rongjia LIN,Enzhe SONG,Yun KE. Improved Smith sliding mode control for air-fuel ratio of natural gas engine. Journal of ZheJiang University (Engineering Science), 2026, 60(3): 661-669.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2026.03.022 OR https://www.zjujournals.com/eng/Y2026/V60/I3/661

天然气发动机空燃比的改进Smith滑模控制

为了实现天然气发动机空燃比的精确跟踪控制，提出基于预定义时间稳定性和改进的Smith预估器的滑模控制策略，有效解决了空燃比控制中由迟滞特性引发的滞后问题. 结合天然气发动机的工作原理，建立空燃比延迟动态模型. 为了克服空燃比控制中的大时延问题，采用改进的Smith预估器对空燃比的延迟进行估计和补偿. 改进的Smith预估器通过引入补偿系数，能够更好地解决参数不确定性，提高系统的适应性和动态响应性能，有效消除延迟项对闭环系统的影响. 基于补偿后的输出，设计预定义时间滑模控制器，确保控制系统的跟踪性能，使系统在预定义的时间内收敛，利用李雅普诺夫函数进行鲁棒稳定性分析和收敛性能分析. 搭建试验平台，设计多种实际测试条件，与PID控制器和快速收敛滑模控制器进行对比，验证了提出的预定义时间滑模控制器具有更好的稳定性、更小的超调及更快的响应速度，满足天然气发动机的控制要求.

关键词： 天然气发动机, 空燃比, 滑模控制, 非线性滑模, Smith预估器, 预定义时间收敛

Fig.1 Structure of natural gas engine

Fig.2 Structure of natural gas engine air-fuel ratio delay dynamic model

Fig.3 Schematic diagram of air-fuel ratio control strategy

Fig.4 Control structure diagram of Smith predictor

Fig.5 Improved Smith predictor control structure

Fig.6 Validation platform of natural gas engine

Fig.7 Flowchart of premixed natural gas engine model

Fig.8 Experimental effect diagram of excess air coefficient under constant speed and constant torque

Fig.9 Experimental effect diagram of excess air coefficient under sudden change in speed and torque

Tab.1 Comparison result of performance index in case 1 and case 2


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