Extended state observer-based robust control of an omnidirectional quadrotor with tiltable rotors

Abstract

A quadrotor with tiltable rotors is a kind of omnidirectional multirotor aerial vehicle (MAV) that has demonstrated advantages of decoupling control of position from the control of orientation. However, quadrotors with tiltable rotors usually suffer from Coriolis term, modeling error and external disturbance. To this end, the extended state observer (ESO)-based controller is designed to estimate and compensate for the above adverse effects. Especially, the controller involves position and attitude controller in parallel. The attitude controller is made up of cascade control-loops: an outer quaternion-based attitude control-loop and an inner ESO-based Proportional derivative angular velocity control-loop. Similarly, the position controller consists of an outer proportional position control-loop and an inner ESO-based PD velocity control-loop. Besides, a linear control allocation strategy, which allocates the controller outputs to tilting angles and motor speed directly, is proposed to avoid the nonlinear allocation matrix. Extensive simulations and flight tests are carried out to illustrate the effectiveness and robustness of the proposed ESO-based controller.

Fixed-time trajectory tracking control of a quadrotor UAV under time-varying wind disturbances: theory and experimental validation

“…It is notable that the aforementioned methods rely on its own robustness to resist disturbances, which are the passive control, and active disturbance rejection approaches referred to via observers to estimate internal uncertainties/external disturbances, and then add feedforward compensation to the control law. There exist already many kinds of observers, such as disturbance observer (DOB) [21], high-gain observer [22], extended state observer (ESO) [23]. In [24], a nonlinear ADRC method for the attitude system of a quadrotor UAV under gust was studied.…”

Dynamic surface control for formation control of quadrotors with input constraints and disturbances

“…Up to now, various control methods have been proposed for a single quadrotor aircraft system (Lu et al, 2021; Modirrousta and Khodabandeh, 2017; Ortiz et al, 2016). The classical prooprtional–integral–derivative (PID) method, which is matured and easy to achieve, is widely chosen in the quadrotor control system (Prajapati and Prasad, 2021).…”

Improving trajectory tracking performance of autonomous farming vehicles using adaptive extended state observer and finite-time technique

“…The possible wheel slip can be treated as an external disturbance (Matveev et al, 2013) or estimated as a non-negligible dynamic influence (Bayar et al, 2016; Guo et al, 2018; Han et al, 2019). Dealing with external disturbance usually includes the disturbance-observer based control (DOBC) technique (Li et al, 2020; Lu et al, 2020; Zhang et al, 2020) and some advanced robust control technique such as sliding mode control (SMC) (Ranjbar et al, 2021; Tofifigh et al, 2021). For example, Izadbakhsh and Khorashadizadeh (2016; Izadbakhsh et al, 2018) have presented a so-called model-free observer based on universal function approximation techniques for uncertainty estimation of the tracking control of robots.…”