Backstepping Control Based on Constrained Command Filter for Hypersonic Flight Vehicles with AOA and Actuator Constraints

An antisaturation backstepping control scheme based on constrained command filter for hypersonic flight vehicle (HFV) is proposed with the consideration of angle of attack (AOA) constraint and actuator constraints of amplitude and rate. Firstly, the HFV system model is divided into velocity subsystem and height subsystem. Secondly, to handle AOA constraint, a constrained command filter is constructed to limit the amplitude of the AOA command and retain its differentiability. And the constraint range is set in advance via a prescribed performance method to guarantee that the tracking error of the AOA meets the constraint conditions and transient and steady performance. Thirdly, the proposed constrained command filter is combined with the auxiliary system for actuator constraints, which ensures that the control input meets the limited requirements of amplitude and rate, and the system is stable. In addition, the tracking errors of the system are proved to be ultimately uniformly bounded based on the Lyapunov stability theory. Finally, the effectiveness of the proposed method is verified by simulation.

Research on the Potential of Front Wheel Steering Control for Vehicle Dynamics Control

The development of active steering control technology not only provides key actuators for intelligent vehicle motion control, but also expands vehicle stability and safety. This paper studies the potential control ability of the front-wheel steering control to the vehicle plane dynamics, and the controllable area boundary is designed on the phase plane of side slip angle and yaw rate. Previous studies have defined a dynamics stable area on the vehicle states phase plane, in which the vehicle state can autonomously return to a stable equilibrium point. The area outside the stable area are divided into the controllable area and the uncontrollable area in this paper. In the controllable area, the front-wheel steering control has the ability to pull the vehicle states back towards the stable area. Considering actuator constraints and model errors, based on the principle of safety design, a band-shaped critical area is designed to separate the controllable area from the uncontrollable area, and the linear mathematical model of the controllable area boundary is designed. In order to verify the rationality of the controllable area definition, nonlinear model predictive controller is designed to control the vehicle outside the dynamics stable area. The controller uses the high-fidelity nonlinear vehicle model and the magic formula tire model as the state equation constraints, and the practical steering actuator constraints are used as the control input constraints, and the nonlinear numerical optimization solver is used to solve the optimal steering input sequence. The phase plane analysis of the controlled vehicle verifies the rationality of the controllable area defined in this paper.

Model Predictive Control of Fixed Wing Aircraft Using a Disturbance Observer Approach

This paper develops a novel cascading Proportional-Integral-Derivative (PID) with Model Predictive Control (MPC) formulation for lateral control of a fixed wing aircraft in the presence of a constant load disturbance, with the consideration of actuator constraints. A Constrained Quadratic Programming (QP) problem is used to solve this MPC problem, via the Primal-Dual procedure. Furthermore, a disturbance observer is utilized to estimate this disturbance so that the setpoint calculation can be adjusted accordingly. Numerical simulations demonstrate steady-state tracking of the aircraft’s roll angle whilst rejecting this disturbance. In addition, heading (yaw) control is implemented via the outer PID loop, and perfect tracking is achieved for this as well. Throughout the entire simulation, the aircraft’s control inputs (aileron and rudder) do not violate their position and rate constraints, thus demonstrating the successful performance of the QP algorithm.

Time-optimal Feedrate Scheduling with Actuator Constraints for 5-axis Machining

Cycle time minimization is one of the major goals that many manufacturers are eager to achieve. Maximizing feedrate is the direct solution, however, physical motions need to be under the specified motion limits to avoid high-frequency vibration, causing machining error. In this paper, a time-optimal feedrate scheduling approach for 5-axis G1 toolpath is presented for 5-axis machining. A quintic B-spline corner smoothing method is utilized to smoothen sharp corners in the toolpath. Then, the S-shape feedrate profile of each block is optimized under the actuator motion constraints, with the objective of minimizing the cycle time. Particle swarm optimization (PSO) is used to provide the optimized solution. Experiments are conducted to validate the proposed approach and the results are compared with two other existing approaches. It is found that the proposed method can achieve shorter cycle time and less contour errors, showing the effectiveness of the proposed approach.

Nonlinear disturbance observer-based fault-tolerant control for flexible teleoperation systems with actuator constraints and varying time delay

In this paper, designing a control law for teleoperation systems with flexible-link slave robots in the presence of dynamic uncertainties, disturbances, actuator faults and actuator constraints with time-varying communication delays is addressed. This study proposes a simple anti-saturation nonlinear fault-tolerant controller incorporating a disturbance observer. The attractive features of the proposed controller include the ability to cope with disturbances, avoiding actuators exceeding their usual bounds, and compensating for the actuator faults. Besides which, the controller has a simple structure, does not need a fault detection mechanism, and coordinates the master’s motion speed with the slave’s actuator. A Lyapunov–Krasovskii functional is used to prove the stability and tracking performance of the teleoperation system. The feasibility and efficiency of the proposed controller are corroborated through simulation results.