A hybrid pose / wrench control framework for quadrotor helicopters

Abstract

This paper presents a hybrid pose / wrench control framework for quadrotor helicopters, allowing direct contact of the quadrotor with its environment and stable motion while in contact. The presented work explicitly takes into account the quadrotor's underactuation and utilizes a wrench estimator, able to estimate the wrench generated by the quadrotor using only quadrotor inputs and pose measurements. Experimental results of the quadrotor in pose and hybrid pose-wrench control mode are presented, showing stable behaviour while moving in contact. Whereas a lot of research nowadays is focused mainly on free-flight applications, stable and robust wrench control of quadrotors in direct contact with their environment, opens up new application areas for this class of flying robots.

Characterization of the Aerodynamic Ground Effect and Its Influence in Multirotor Control

“…This control alternative includes a torque disturbance observer that is used to estimate the torque induced by the partial ground effect, caused by the different aerodynamic thrust generated by the rotors when the multirotor is in partial ground effect. Several approaches have been used to estimate external force and torque disturbances in multirotors [22][23][24]38]. In this paper, a nonlinear torque disturbance observer has been implemented [24].…”

On autonomous and teleoperated aerial service robots

“…Some of the interesting challenges in control of aerial interaction include dealing with change in dynamics during interaction, stability during a constrained motion, and time-varying interaction force regulation. So far, only few results have been reported, [3], [7], [81]. The state of the art on autonomous aerial interaction control of aerial robots are hybrid position/force controller or impedance controller.…”

“…Force sensors, besides their cost, additional dynamics, limited bandwidths and sensitivity to noise, limit the application scope due to small contact area, where the sensors are attached to. A hybrid controller has also been realized on a quadrotor in [7], where wrench estimator, instead of force sensor, is used. One of the limitations of this controller is the need for a priori choice of selection matrix that determines which DOFs are position or wrench controlled.…”

“…However, direct measurement of the thrust is often not available. Nonetheless, it can be approximated by off-line identification, similar to [63], [7]. Vibrotactile Feedback: The range of frequencies used for tactile feedback should, in general, fall within the optimal frequency range to activate the mechanoreceptors of the skin.…”

“…But, unlike the virtual slave on the slave side, the mass of this virtual slave is equivalent to the combined mass of the virtual slave on the slave side and the mass of the aerial robot. 7 On the other hand, the environment that the slave interacts with, such as disturbance due to wind gust, and obstacle, needs to be identified online. This disturbance needs to be reflected at the model of the virtual slave on the master side as well.…”