Implementing hardware in the loop test for trajectory tracking of an underwater robot with a model-free sliding mode controller

Implementing control and guidance systems on an autonomous underwater vehicle requires spending much money, which in case of failure, will suffer heavy losses. For this purpose, the complete method of evaluating an autonomous underwater vehicle's guidance, control, and navigation system is the hardware in the loop test before the diving and buoyancy so that the validation of the designed system can be evaluated in conditions close to reality.This research discusses the implementation of the hardware in the loop test to guide the path of a remotely operated vehicle. Considering the dynamics of the underwater robot - which is highly non-linear and dependent; First, the design of a free model sliding mode controller in the presence of underwater currents as a disturbance in the form of software in the loop is discussed. Second, the software in the loop test is performed by applying the control signal obtained from the proposed controller to the driver of the electric motor as the robot's proportion, whose mathematical model has been identified in the laboratory. Finally, by gradually replacing the hardware drives of the robot in the loop, the hardware in loop test of six degrees of freedom of the remotely operated vehicle is done in real-time in the presence of environmental disturbances. The proximity of the hardware in the loop test results with the software test in the loop shows the correctness of the work done. Meanwhile, the performance of the proposed controller is compared with the PID controller in trajectory tracking. In the end, the accuracy and validity of the implemented hardware table are examined by analyzing the frequency spectrum of the measurements of the hardware in the loop rig.