Linear Quadratic Regulator Feedback Control Research Articles

Path-Tracking Control of Soft-Target Vehicle Test System Based on Compensation Weight Coefficient Matrix and Adaptive Preview Time

<div>In order to enhance the path-tracking accuracy and adaptability of the electric flatbed vehicle (EFV) in the soft-target vehicle test system, an improved controller is designed based on the linear quadratic regulator (LQR) algorithm. First, the LQR feedback controller is designed based on the EFV dynamics tracking error model, and the genetic algorithm is utilized to obtain the optimal weight coefficient matrix for different speeds. Second, a weight coefficient matrix compensation strategy is proposed to address the changes in the relationship between the vehicle–road position and attitude caused by external disturbances and the state of EFV. An offline parameter table is created to reduce the computational load on the microcontroller of EFV and enhance real-time path-tracking performance. Furthermore, an adaptive preview time control strategy is added to reduce the overshooting caused by control delay. This strategy is based on road curvature and traveling speed. Finally, the simulation experiment and field experiment are carried out. The results show that the improved LQR controller exhibits high tracking accuracy during the emergency double lane changes experiment and can maintain accuracy and stability at different speeds.</div>

Trajectory tracking control of four wheel steering under high speed emergency obstacle avoidance

To solve the problem of trajectory tracking for 4WS autonomous vehicles under high speed emergency obstacle avoidance, an improved trajectory tracking controller combining four-wheel steering (4WS) feed-forward control and linear quadratic regulator (LQR) feed-back control is proposed. First, a polynomial obstacle avoidance trajectory of small radius and sharp curve is established and its several variables are analysed. Second, in order to make actual yaw rate follow steady-state value based on reference model, the steering gain of the improved 4WS feed-forward control can change with steering angular frequency and vehicle speed. Third, combined with the LQR feed-back control, the deviations between actual lateral displacement and desired lateral displacement are controlled under 0.05 m. Finally, CarSim® simulation results show that 4WS autonomous vehicles based on the controller can not only avoid obstacles in time, but also improve active safety and handling stability under high speed emergency obstacle avoidance.

Exploring the Heliogyro’s Orbital Control Capabilities for Solar Sail Halo Orbits

Solar sailing is an elegant form of space propulsion that reflects solar photons off a large membrane to produce thrust. Different sail configurations exist, including a traditional fixed polygonal flat sail and a heliogyro, which divides the membrane into a number of long, slender blades. The magnitude and direction of the resulting thrust depends on the sail’s attitude with respect to the sun (cone angle). At each cone angle, a fixed polygonal flat sail can only generate force constrained to a particular magnitude and direction, whereas the heliogyro can arbitrarily reduce the thrust magnitude through the additional control of pitching the blades. This gives the heliogyro more force control authority, which is exploited in this paper for orbital control of solar sail, sun–Earth, sub- halo orbits through a linear-quadratic regulator feedback controller. Two test cases are considered, quantifying either the maximum error in the injection state or the maximum delay in solar sail deployment due to deployment failure at injection from which the nominal orbit can still be recovered. This paper finds that the heliogyro can accommodate approximately an order of magnitude larger injection error than a fixed polygonal flat sail and a significantly larger sail deployment delay of up to 20.2 days in some cases.

Control of a reverse flow reactor for VOC combustion

A flow reversal reactor for VOC combustion is controlled by the linear quadratic regulator (LQR), which uses dilution and internal electric heating as controls to confine the hot spot temperature within the two temperature limits, in order to ensure complete conversion of the VOC and to prevent overheating of the catalyst. Three phases of operation, i.e., dilution phase, heating phase and inactive phase, are identified. In dilution and heating phases, the cost functions of the LQR control are defined in quadratic forms. In the inactive phase, the controllers are inactivated. A linear model is derived by linearization of a countercurrent pseudo-homogeneous model at two nominal operating conditions in the dilution phase and the heating phase, respectively. The feed concentration and the temperature profile are estimated on-line by using a high-gain observer with three temperatures measurements and are used in the LQR feedback control. Experiments are carried out on a medium-scale reversed flow reactor to demonstrate the proposed LQR control strategy. Results show that the LQR controller is highly efficient in maintaining normal operation of the reactor.

Design of turbofan engine controls using output feedback regulator theory

A multivariable control design procedure based on output feedback regulator (OFR) theory is applied to the F100 turbofan engine. Results for the OFR design are compared to a design based on linear quadratic regulator (LQR) theory. This LQR design was obtained as part of the F100 Multivariable Control Synthesis (MVCS) program. In the MVCS program the LQR feedback control was designed in a reduced dimension state space and then applied to the original system. However, the OFR feedback control is designed in the full order state space and thus eliminates any need for model reduction techniques. Using the performance measure and control structure of the MVCS program LQR design, an equivalent OFR feedback control is obtained. The flexibility of the OFR as a control design procedure is demonstrated and differing feedback control structures are evaluated.