Predefined-Performance-Based Full-Process Control for Ultra-Close and High-Precision Formation Flying

Intelligent mixed H2/H∞ adaptive tracking control system design using self-organizing recurrent fuzzy-wavelet-neural-network for uncertain two-axis motion control system

This paper presents a fast and accurate robust path-following control approach for a fully actuated marine surface vessel in the presence of external disturbances. The path following is realized by simultaneously converging the yaw rate and sway velocity to their respective desired values, which are generated according to the path-following demand. An improved combined control strategy using an integral terminal sliding mode (ITSM) based composite nonlinear feedback (CNF) technique considering the external disturbances, time-varying tracking reference, input saturations and transient performance improvement is proposed in this study. The proposed ITSM-CNF combines the advantages of the CNF control in improving the transient performance and of the ITSM control in guaranteeing good robustness and finite-time convergence. A continuous and smooth sliding mode controller, based on an integral nonsingular terminal sliding surface, is added to the CNF controller to eliminate chattering. The overall stability of the closed-loop system is strictly proved based on the Lyapunov method. Simulations verify the effectiveness of the ITSM-CNF controller in improving the transient path-following performance, inhibiting overshoots, eliminating steady-state errors, rejecting external disturbances and removing chattering effects, considering input saturations, varying path curvature and finite-time convergence.

The interval type-2 fuzzy Proportional-Integral (PI) controller (IT2-FPI) might be able to handle high levels of uncertainties to produce a satisfactory control performance, which could be potentially due to the robust performance as a result of the smoother control surface around the steady state. However, the transient state and disturbance rejection performance of the IT2-FPI may degrade in comparison with the type-1 fuzzy PI (T1-FPI) counterpart. This drawback can be resolved via general type-2 fuzzy PI controllers which can provide a tradeoff between the robust control performance of the IT2-FPI and the acceptable transient and disturbance rejection performance of the type-1 PI controllers. In this paper, we will present a zSlices-based general type-2 fuzzy PI controller (zT2-FPI), where the secondary membership functions (SMFs) of the antecedent general type-2 fuzzy sets are adjusted in an online manner. We will examine the effect of the SMF on the closed-system control performance to investigate their induced performance improvements. This paper will focus on the case followed in conventional or self-tuning fuzzy controller design strategies, where the aim is to decrease the integral action sufficiently around the steady state to have robust system performance against noises and parameter variations. The zSlices approach will give the opportunity to construct the zT2-FPI controller as a collection of IT2-FPI and T1-FPI controllers. We will present a new way to design a zT2-FPI controller based on a single tuning parameter where the features of T1-FPI (speed) and IT2-FPI (robustness) are combined without increasing the computational complexity much when compared with the IT2-FPI structure. This will allow the proposed zT2-FPI controller to achieve the desired transient state response and provide an efficient disturbance rejection and robust control performance. We will present several simulation studies on benchmark systems, in addition to real-world experiments that were performed using the PIONEER 3-DX mobile robot that will act as a platform to evaluate the proposed systems. The results will show that the control performance of the self-tuning zT2-FPI control structure enhances both the transient state and disturbance rejection performances when compared with the type-1 and IT2-FPI counterparts. In addition, the self-tuning zT2-FPI is more robust to disturbances, noise, and uncertainties when compared with the type-1 and interval type-2 fuzzy counterparts.

In order to ensure the safety and stability of vehicle platoons, the spacing error between vehicles needs to be maintained within a given range and gradually converge to 0. Due to actuator saturations and time-varying uncertainties in vehicle dynamics, the vehicle platoon control remains a major challenge. This paper presents a robust control method for vehicle platoons, ensuring the spacing error performance within a compact prescribed band region. Firstly, an improved spacing modeling method is presented, embedded with an auxiliary variable to modify the spacing error. It effectively circumvents actuator saturations caused by excessively large initial errors. Then, bilateral constraints are imposed on the modified error to characterize collision avoidance and compact formation (CA&CF) performance, and subsequently the constrained error is transformed into an unconstrained state via potential function transformation. The uniform boundedness (UB) performance of the unconstrained state ensures the compact prescribed band region performance of the spacing error. Then, based on the constraint-following control theory, a robust controller is designed to ensure the system’s UB and uniform ultimate boundedness (UUB) performance. Finally, simulation results demonstrate the effectiveness of the proposed control.

This paper presents a design of robust PID controller structure for shunt FACTS controllers namely STATCOM and SVC. Robust STATCOM and SVC is designed using H-infinity loop-shaping technique. The performance of the controller is tested in single machine infinite bus power system to damp out the oscillations. The variation of transmission line reactances is considered as multiplicative uncertainty and the design is carried out by applying robustness criteria to improve both stability and performance. The performance of robust controller is compared with conventional PID controller in damping out the oscillations. It has been observed that the conventional PID controller is ineffective at operating points other than nominal. The robust design provides an extremely good damping characteristic over a range of operating conditions and it is evaluated based on the time domain specifications

Next-generation motion systems are expected to exhibit dominant flexible dynamical behavior. As a result, a dynamic relation between the measured variables and the performance variables is inevitable. The aim of the present paper is i) to develop a control framework to deal with unmeasured performance variables and ii) to implement the proposed methodology on a prototype experimental setup. A system identification for robust inferential control approach is pursued. Indeed, in the case that the performance variables cannot be measured directly, then these can be inferred from the measurements by means of a model. Experimental results i) confirm that prior approaches that aim at an improved response in terms of the measured variables can result in a deteriorated performance and ii) reveal that the proposed framework enables high performance robust inferential control.

Considering generator rotor and valve by external disturbances for turbine regulating system, the nonlinear large disturbance attenuation controller and parameter updating law of turbine speed governor system are designed using backstepping method. The controller not only considers transmission line parameter uncer-tainty, and has attenuated the influences of large external disturbances on system output. The nonlinear con-troller does not have the sensitivity to the influences of external disturbances, but also has strong robustness for system parameters variation, which is because of the transmission line uncertainty being considered in internal disturbances. The simulation results show that the control effect of the large disturbance attenuation controller more advantages by comparing with the control performance of conventional nonlinear robust controller.

Finite-time consensus of Markov jumping multi-agent systems with time-varying actuator faults and input saturation

Precise relative GPS navigation is essential technology for rendezvous and formation flying of spacecraft in Low Earth Orbit. Key design issues of precise relative GPS navigation software are studied and a novel formulation is proposed for the mission which requires high accuracy when the separation distance is up to several km. The navigation filter estimates float navigation solutions by extended Kalman filter with elaborate dynamics models, and resolves ambiguities of integer carrier phase biases to achieve high accuracy fix navigation solutions. A relative navigation software with the proposed formulation is implemented and evaluated in two different ways. One is a test using spacebourne GPS receivers and a GPS signal simulator to evaluate the performance and sensitivity of the software against variation of parameters. The other is a test using actual telemetry data from Gravity Recovery and Climate Experiment (GRACE) to demonstrate the software performance. The design, implementation, and results of the evaluation are presented and discussed on this paper.

In this paper, the conservativeness issue is addressed for networked control of discrete time systems through a quantized lossy channel. The quantized lossy channel is first characterized as an uncertainty disturbance in signal-to-noise-ratio forms with both the input and output signals of the channel. Then it is shown that appropriate uncertainty characterization should be applied to conduct robust stability control and robust performance control, in order to achieve less conservative design. Single-input-single-output quantized lossy channels with both relative-error and multiplicative-error quantization as well as a multiplicative random noise are presented to illustrate the main ideas.

This paper deals with robust speed servo control for DC motors based on a sliding mode control (SMC). SMC is well known for its robust control performance against external disturbances including motor parameter variations. An optimum switching plane, a key issue for SMC, is designed to minimize control error and input energy in a state space model. Voltage command which is an output of the sliding mode controller is induced to satisfy the Lyapunov’s second method for critical stability. The robust control performance of the suggested sliding mode control is evaluated by two experiments such as a load test and parameter variation test. The external load test was conducted by applying 100% and 80% of the rated torque using a powder brake. The parameter variation experiment was conducted by increasing nominal parameters of the motor used in the controller by 3 times. Moreover, the effectiveness of SMC is clarified by comparing with the PI control experimental results. The experimental results showed that SMC has stronger control performance against the disturbance and parameter changes than the PI controller.

In this article, robust attitude control schemes are proposed for the near-space vehicle with the backlash-like hysteresis and the time-varying unknown disturbance using backstepping technique. In the robust attitude control design, the backlash-like hysteresis is described by a dynamic equation which is decomposed as a linear term and a nonlinear term. To handle the nonlinear term in the dynamic equation of the backlash-like hysteresis and the time-varying unknown disturbance, they are treated as a compounded disturbance and the nonlinear disturbance observer is designed to estimate them. Based on the developed nonlinear disturbance observer, the robust backstepping attitude control is firstly developed for the near-space vehicle. Then, the robust sliding mode attitude control scheme is presented for the near-space vehicle to further enhance the robust attitude control performance. The convergence of all closed-loop signals is rigorously proved via Lyapunov analysis method under the developed robust attitude control schemes. Finally, simulation results are presented to illustrate the effectiveness of the proposed attitude control approaches.

We present several results of the leader-following paradigm in the formation flying of multiple spacecraft in free space. In this direction, ideas from elementary graph theory and linear matrix inequalities are combined with logic-based switching to shed light on the various control designs which are feasible using the leader-following mechanism for various formation flying scenarios.

This chapter studies the spacecraft rendezvous problem and the spacecraft formation flying problem by using the TPF approaches. For the spacecraft rendezvous problem, the target spacecraft can be in arbitrary eccentric orbits, and for the spacecraft formation flying problem, the reference spacecraft is assumed to be in a circular orbit. By clarifying that the T-H equation and C-W equation are both ANCBC and NCE, the TPF approach for stabilization and consensus of linear systems with input and output delays built in the previous chapters are extended to solve the considered problems. Some simulations are carried out to validate the effectiveness of the proposed approaches.

This paper presents a hardware-in-the-loop (HITL) simulation approach for multiple spacecraft formation flying. Considering a leader-follower formation flying configuration, a Fuzzy Logic controller is developed first to maintain the desired formation shape under external perturbations and the initial position offsets. Cold-gas on/off thrusters are developed to be introduced to the simulation loop, and the HITL simulations are conducted to validate the effectiveness of the proposed simulation configuration and Fuzzy Logic control.