Transactions of the Institute of Measurement and Control

Elkenawy, Ahmed; El-Nagar, Ahmad M; El-Bardini, Mohammad; El-Rabaie, Nabila M

doi: 10.1177/0142331220921259pmid: N/A

This paper proposes an observer-based adaptive control for unknown nonlinear systems using an adaptive dynamic programming (ADP) algorithm. First, a diagonal recurrent neural network (DRNN) observer is proposed to estimate the unknown dynamics of the nonlinear system states. The proposed neural network offers a simpler structure with deeper memory and guarantees the faster convergence. Second, a neural controller is constructed via ADP method using the observed states to get the optimal control. The optimal control law is determined based on the new structure of the critic network, which is performed using the DRNN. The learning algorithm for the proposed DRNN observer-based adaptive control is developed based on the Lyapunov stability theory. Simulation results and hardware-in-the-loop results indicate the robustness of the proposed ADP to respond the system uncertainties and external disturbances compared with other existing schemes.

Chao, Mi; Kai, Chen; Zhiwei, Zhang

doi: 10.1177/0142331220929816pmid: N/A

Foreign body detection is an important aspect that affects the quality of tobacco production. This paper describes a direct foreign body detection scheme using machine vision, which uses three cameras arranged around a tobacco bale to record its multiple surfaces and directly identify foreign bodies. In this study, color sorting table method (CSTM) was first used to identify and remove color-sensitive foreign bodies; thereafter, gray threshold method and double threshold method were used to further identify and remove foreign bodies with similar colors. The experimental results indicate that the multi-step hybrid identification method proposed herein can effectively identify and remove various foreign bodies in the production process of tobacco packs, with an accuracy rate of 97.8%, which meets the industrial requirements for foreign body detection. Compared with various existing devices and methods, it has the advantages of high detection efficiency and low cost.

Jiang, Jinlin; Wang, Yu; Cao, Heng; Zhu, Jun; Zhang, Xinbin

doi: 10.1177/0142331220930623pmid: N/A

In order to reduce the weight and improve the energy efficiency of the lower extremity exoskeleton, a novel pump-valve coordinated controlled (PVCC) hydraulic system is presented. This hydraulic system only uses one electro-hydrostatic unit (EHU) and two valves to drive two hydraulic cylinders at the hip and knee of the lower extremity exoskeleton. The PVCC hydraulic system has the advantage of high energy conversion efficiency of the electro-hydrostatic actuator (EHA), which consists of one EHU and one hydraulic cylinder. To meet the requirements of the moment and speed of each joint of the exoskeleton, the proportional valve and on-off valve are added to adjust the flow into two hydraulic cylinders. The performance of EHU is tested by some hydraulic experiments, and the performance of the PVCC hydraulic system is analyzed by AMESim. The results show that the novel hydraulic system can only use one EHU to drive two hydraulic cylinders simultaneously under the premise of meeting the functional requirements of the exoskeleton.

Sujatha, Vijay; Panda, Rames C

doi: 10.1177/0142331220931968pmid: N/A

This study analyzes with the technology of auto tuning using relay feedback test for non-square MIMO system through process modeling, identification, input-output pairing and control strategies. However, the control configuration selection based on conventional steady-state Relative Gain Array (RGA) matrix sometimes degrades the loop performance and it needs attention. This study also deals with the real challenges in time domain modeling and appropriate pairing of loops for non-linear chemical processes. The choice of input-output pairing for square system has been extended to non-linear chemical processes. This ensures the system’s stability by selecting an appropriate manipulated-controlled variable pairing in non-linear chemical processes and the same is also tested for benchmark of non-linear chemical processes. In this study, two types of non-square systems are considered: one is systems with excess input than output variables and the other is systems with excess output than input variables. Some benchmark non-linear chemical processes, such as processes with mild nonlinearity, moderate to high nonlinearity and highly nonlinearity, are also taken for this study. Three standard benchmark processes are used in analysis of nonlinear chemical processes, namely: (1) Continuous Stirred Tank Reactor (CSTR) process; (2) hydrogen-ion- concentration (pH) process and (3) distillation column and this procedure is illustrated via simulation of 3-by-2 and 2-by-3 non-linear chemical processes.

Song, Dalei; Li, Lin; Wang, Changbin; Hou, Renyu; Li, Chong

doi: 10.1177/0142331220932373pmid: N/A

Multi-vector arrangement is a novel propulsion architecture for remotely operated vehicles (ROV) because of its high manoeuvrability and efficiency, but the influence on the ROV dynamics and attitude servo control has not yet been clearly evaluated. This study fully investigated the kinematic behaviours of a hexagonal multi-vector propulsion ROV with communication delay constraint and reduced the complex model for precision control system design. An enhanced model-based PI robust controller (EMPRC) based on the nominal model is proposed to solve the nonlinear hydrodynamics and communication problems with high performance yaw control, whose stability is also analysed. The conventional proportional-integral-derivative (PID) and integral separation PID are used in the experiments for comparison. The results indicate that the proposed EMPRC can effectively track the desired attitude and reject the external disturbances, while the conventional ones are limited by the nonlinear dynamics and communication delays. The improvement is 3x on average in terms of overshoot, settling time and anti-disturbance recovery time compared to conventional algorithms and proves this proposed novel EMPRC is a practical solution for multi-vector propulsion ROVs.

Ren, He; Dai, Jing; Zhang, Huaguang; Zhang, Kun

doi: 10.1177/0142331220932634pmid: N/A

Benefitting from the technology of integral reinforcement learning, the nonzero sum (NZS) game for distributed parameter systems is effectively solved in this paper when the information of system dynamics are unavailable. The Karhunen-Loève decomposition (KLD) is employed to convert the partial differential equation (PDE) systems into high-order ordinary differential equation (ODE) systems. Moreover, the off-policy IRL technology is introduced to design the optimal strategies for the NZS game. To confirm that the presented algorithm will converge to the optimal value functions, the traditional adaptive dynamic programming (ADP) method is first discussed. Then, the equivalence between the traditional ADP method and the presented off-policy method is proved. For implementing the presented off-policy IRL method, actor and critic neural networks are utilized to approach the value functions and control strategies in the iteration process, individually. Finally, a numerical simulation is shown to illustrate the effectiveness of the proposal off-policy algorithm.

Hammami, Dine El Houda; Maraoui, Saber; Bouzrara, Kais

doi: 10.1177/0142331220933437pmid: N/A

This paper proposes a dual decomposition method for solving distributed model predictive control. This controller is designed for systems subject to communication constraints, in which nonlinear subsystems interconnected via dynamics and by constraints. The interconnections are relaxed by using gradient method, accelerated gradient and alternating direction methods of multipliers. Also, an event-based communication is proposed to handle the issue of communication constraints especially in embedded systems. In the proposed event-based communication strategy, each controller solves the optimization problem and communicate only if the prices are updated significantly, which can reduce the computation load and release the burden of the network while achieving global performance. Finally, the simulations study of the four-tank benchmark is presented to demonstrate the effectiveness of the proposed schemes.

Ren, Chang-E; Chen, CL Philip

doi: 10.1177/0142331220933773pmid: N/A

In this paper, the leader-following consensus control problem of discrete-time nonlinear multi-agent systems with unknown control directions is discussed. The preview future information of the leader is utilized when the distributed controllers are designed. Fuzzy logic system is directly introduced to approximate the uncertainty and unknown control directions and the adaptive distributed controller with preview information is put forward. The designed controller can drive all the states of followers to converge to a small neighbourhood of the leader’s state. In addition, all the states of followers remain bounded. Finally, the results of simulations can display the effectiveness of the presented algorithms.

Zhu, Yunru; Zheng, Yuanshi; Liu, Xingwen; Wang, Huaizhu

doi: 10.1177/0142331220934608pmid: N/A

This paper studies the fixed-time stability problem for positive nonlinear systems defined by cooperative vector fields. A criterion is derived to ensure fixed-time stabilization of the positive nonlinear systems using Lyapunov method. In addition, a sufficient condition is also presented for fixed-time stability of switched positive nonlinear systems under arbitrary switching. Simulation examples are provided to demonstrate the obtained results.

Li, Bo; Ban, Hanyu; Gong, Wenquan; Xiao, Bing

doi: 10.1177/0142331220935710pmid: N/A

This work presents a novel control strategy for the trajectory tracking control of the quadrotor unmanned aerial vehicle (UAV) with parameter uncertainties and external unknown disturbances. As a stepping stone, two fixed-time extended state observers (ESOs) are proposed to estimate the external disturbances and/or the parameter uncertainties for the position and attitude subsystems, respectively. Then, the fast terminal sliding mode-based improved dynamic surface control (DSC) approaches are developed. To eliminate the problem of “explosion of complexity” inherent in backstepping method-based controllers, the finite-time command filters and an error compensation signals are used in the design of the dynamic surface controllers. Subsequently, the practically finite-time stability of the closed-loop tracking system is guaranteed by utilizing the proposed control scheme. The simulation results are obtained to demonstrate the effectiveness and fine performance of the proposed trajectory tracking control approaches.