Crosswind stabilization

Abstract: In a method for crosswind stabilization of a motor vehicle which includes front and rear wheels which are driven via an actively controllable differential with variable torque distribution and a device for detecting a lateral offset, a yaw moment is generated via the differential by changing the torque distribution when a lateral offset is detected, which yaw moment counteracts the lateral offset.

Abstract: In this paper, we study the control design of an automatic crosswind stabilization system for a novel, buoyantly-assisted aerial transportation vehicle. This vehicle has several advantages over other aircraft including the ability to take-off and land in very short distances and without the need for roads or runways. Despite these advantages, the large surface area of the vehicle's wing makes it more susceptible to wind, which introduces undesirable roll angle motions. The role of the automatic crosswind stabilization system is to detect the roll angle deviation, and then use motors at the wingtips to counteract the wind effect. However, due to the relatively large inertia of the wing compared to small-size unmanned aerial vehicles and additional input time delays, an automatic crosswind stabilization system based on traditional control algorithms such as the proportional-integral-derivative (PID) controller results in a response time that is too slow. Another challenge is the lack of high-accuracy wind sensors that can be mounted on the vehicle's wing. Therefore, we first design a wind torque estimator that relies on inertial measurements, and then use feed-forward compensation to directly correct for the wind torque, resulting in a significantly faster response. We second combine the proposed estimator with a model predictive controller (MPC), and compare constrained MPC with unconstrained MPC for the considered application. Experimental results show that our proposed estimation-based MPC strategy reduces the response time of the system by around 80-90% compared to a standard PID controller, without the need for adding wind sensors or changing the hardware of the stabilization system.

Abstract: A hybrid airship is an aerial vehicle that generates lift by leveraging both buoyancy and aerodynamic principles. The operation of such a vehicle can be limited by its high susceptibility to crosswinds during taxiing, take-off and landing. With the goal to mitigate this issue, this paper proposes a novel controller design for a stabilization system consisting of wing tip thrusters. Due to the response of the vehicle to wind disturbances (e.g. lifting off a wheel during taxiing), modeling it as a hybrid dynamical system is appropriate. A novel, customized hybrid model predictive control (MPC) scheme is proposed for crosswind stabilization. As shown in simulation as well as in experimental results in controlled and realistic environments, the proposed control scheme succeeds in stabilizing the vehicle despite artificial or actual wind disturbances, even in scenarios where simple linear MPC fails. Simultaneously, our approach is computationally efficient enough to run on an onboard computer.