Dr Ali Soltani

In this paper, an anti-windup compensation scheme is proposed for the manual mode of a rigid body attitude control system to make the angular velocity dynamics globally asymptotically stable despite actuator saturation. The addressed anti-windup design problem is challenging since the nominal control law includes a nonlinear dynamic inversion element to cancel the nonlinearity in the angular velocity dynamics. The stability of the compensated closed-loop system is proved via the Lyapunov stability criterion appropriately. Moreover, the superiority of the compensated system versus the uncompensated one is demonstrated by simulation.

Pneumatic artificial muscles (PAMs) are flexible actuators that can be contracted or expanded by applying air pressure. They are used in robotics, prosthetics, and other applications requiring flexible and compliant actuation. PAMs are basically designed to mimic the function of biological muscles, providing a high force-to-weight ratio and smooth, lifelike movement. Inflation and deflation of these muscles can be controlled rapidly, allowing for fast actuation. In this work, a continuum mechanics-based model is developed to predict the output parameters of PAMs, like actuation force. Comparison of the model results with experimental data shows that the model efficiently predicts the mechanical behaviour of PAMs. Using the actuation force-air pressure-contraction relation provided by the proposed mechanical model, a dynamic model is derived for a multi-link PAM-actuated robot manipulator. An adaptive fixed-time fast terminal sliding mode control is proposed to track the desired joint position trajectories despite the model uncertainties and external disturbances with unknown magnitude bounds. Furthermore, the performance of the proposed controller is compared with an adaptive backstepping fast terminal sliding mode controller through numerical simulations. The simulations show faster convergence and more precise tracking for the proposed controller.

A quadrotor with a liquid tank may be used in various tasks such as spraying pesticides and firefighting. Therefore, motion of the quadrotor should be controlled such that liquid sloshing is suppressed. To tackle this issue, a LQG controller is proposed in this paper. The LQG controller is based on a linear equivalent mechanical model for liquid sloshing which is presented in this study. The proposed controller uses position and attitude feedback of quadrotor to estimate and control the liquid states. This is different than other controllers presented in the literature where they consider liquid sloshing as an external disturbance. LQG controller is simulated using system's nonlinear equations and compared to a PID controller. The results depicted a 20% improvement in trajectory tracking performance for LQG controller while using 11% less energy than its PID counterpart. Also the LQG control scheme was able to compensate for a constant external disturbance whereas the PID controller was not able to stabilize the system while the constant disturbance is present.