Bidirectional-thruster multirotor for perimeter pipe inspections (BiMPPI): A nonlinear optimal integral-SDRE design

This paper presents a novel bidirectional-thruster multirotor for perimeter pipeline inspection (BiMPPI). The bidirectional thrusters enable the generation of negative collective thrust, allowing BiMPPI to land on the pipe, reverse motor thrust directions, and push against the pipe while rotating around it without losing physical contact. An integral state-dependent Riccati equation (SDRE) controller is used during the turning phase around the pipe. The integral SDRE controller is compared through simulations with the servo-SDRE controller, exhibiting similar performance while eliminating the need for an online solution to the SDRE. The platform is experimentally validated through indoor flights, demonstrating superior performance in rotational movements around a mockup pipeline compared to both SDRE and standard PID controllers.