• Trajectory Tracking with Obstacle Avoidance for a Ground Robot

In this work, a sliding mode control-based strategy is proposed for tracking a desired trajectory in the presence of static obstacles for a ground robot. An approach based on control barrier functions is implemented for obstacle avoidance, utilizing a second-order barrier function. For collision avoidance, the robot is modeled by a double integrator model to optimize the control inputs, which are then mapped onto a unicycle kinematic model using an approximation. Experimental validation is also provided to establish the efficacy of the proposed strategy using a four-wheeled differential drive robot and a camera-based localization system, both of which are developed in-house.

• Observer based Event-triggered Control 

One of the thrust areas we focus on is event-triggered-based sliding mode control, which gives a robust performance with limited usage of communication channels and computational resources. For the scenarios when all states of the system are not available, an observer-based event-triggered control is designed. In the future, it will be interesting to analyze the stability of the system under constraints such as actuator saturation and quantization error. 

• Robust altitude and attitude control of quadrotors

This work proposes a super-twisting-based sliding mode controller for altitude and attitude control of the quadrotor in the presence of uncertainties. Here the PID sliding surface is taken into account for designing super-twisting based sliding mode control to track the desired trajectory. The designed controller has been validated by simulations in MATLAB and Software-In-The-Loop (SITL) simulations in a ROS-Gazebo based environment simulator for the Iris model.

• Discretization Methods for Indirect Adaptive Sliding Mode Control 

This problem studies the discretization of adaptive sliding mode control for uncertain scalar systems with an unknown parameter. An improper discretization of indirect adaptive sliding mode control may lead to an unbounded parameter, which then results in an unbounded state. We studied different discretization methods such as explicit, implicit, semi-implicit, and matching for indirect adaptive sliding mode control.