90 research outputs found
State-Dependent Dynamic Tube MPC: A Novel Tube MPC Method with a Fuzzy Model of Disturbances
Most real-world systems are affected by external disturbances, which may be
impossible or costly to measure. For instance, when autonomous robots move in
dusty environments, the perception of their sensors is disturbed. Moreover,
uneven terrains can cause ground robots to deviate from their planned
trajectories. Thus, learning the external disturbances and incorporating this
knowledge into the future predictions in decision-making can significantly
contribute to improved performance. Our core idea is to learn the external
disturbances that vary with the states of the system, and to incorporate this
knowledge into a novel formulation for robust tube model predictive control
(TMPC). Robust TMPC provides robustness to bounded disturbances considering the
known (fixed) upper bound of the disturbances, but it does not consider the
dynamics of the disturbances. This can lead to highly conservative solutions.
We propose a new dynamic version of robust TMPC (with proven robust stability),
called state-dependent dynamic TMPC (SDD-TMPC), which incorporates the dynamics
of the disturbances into the decision-making of TMPC. In order to learn the
dynamics of the disturbances as a function of the system states, a fuzzy model
is proposed. We compare the performance of SDD-TMPC, MPC, and TMPC via
simulations, in designed search-and-rescue scenarios. The results show that,
while remaining robust to bounded external disturbances, SDD-TMPC generates
less conservative solutions and remains feasible in more cases, compared to
TMPC.Comment: 39 pages, 16 figures, 4 tables, 2 appendices, to be submitted to
"international journal of robust and nonlinear control", [40] from paper
cites our code to be submitted
Neural Network Observer-Based Prescribed-Time Fault-Tolerant Tracking Control for Heterogeneous Multiagent Systems With a Leader of Unknown Disturbances
This study investigates the prescribed-time leader-follower formation strategy for heterogeneous multiagent sys-tems including unmanned aerial vehicles and unmanned ground vehicles under time-varying actuator faults and unknown dis-turbances based on adaptive neural network observers and backstepping method. Compared with the relevant works, the matching and mismatched disturbances of the leader agent are further taken into account in this study. A distributed fixed-time observer is developed for follower agents in order to timely obtain the position and velocity states of the leader, in which neural networks are employed to approximate the unknown disturbances. Furthermore, the actual sensor limitations make each follower only affected by local information and measurable local states. As a result, another fixed-time neural network observer is proposed to obtain the unknown states and the complex uncertainties. Then, a backstepping prescribed-time fault-tolerant formation controller is constructed by utilizing the estimations, which not only guarantees that the multiagent systems realize the desired formation configuration in a user-assignable finite time, but also ensures that the control action can be smooth everywhere. Finally, simulation examples are designed to testify the validity of the developed theoretical method
An observer-based type-3 fuzzy control for non-holonomic wheeled robots
Non-holonomic wheeled robots (NWR) comprise a type of robotic system; they use wheels
for movement and offer several advantages over other types. They are efficient, highly, and maneuverable, making them ideal for factory automation, logistics, transportation, and healthcare. The control of this type of robot is complicated, due to the complexity of modeling, asymmetrical non-holonomic constraints, and unknown perturbations in various applications. Therefore, in this study, a novel type-3 (T3) fuzzy logic system (FLS)-based controller is developed for NWRs. T3-FLSs are employed for modeling, and the modeling errors are considered in stability analysis based on the symmetric Lyapunov function. An observer is designed to detect the error, and its effect is eliminated by a developed terminal sliding mode controller (SMC). The designed technique is used to control a case-study NWR, and the results demonstrate the good accuracy of the developed scheme under non-holonomic constraints, unknown dynamics, and nonlinear disturbances
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