Event-Triggered Heading Control of an Energy-Efficient Underwater Gliding Robot

An energy-efficient event-triggered heading control system (ETHCS) is proposed for an underwater gliding robot. The robot steers by adjusting the position of an internal axially moving mass, rather than with the actuators commonly used in traditional underwater vehicles. Based on the dynamic model, an energy-efficient ETHCS framework, which includes three linear velocity observers and an event-triggered high-order backstepping heading controller, is established. The three linear state observers estimate the horizontal and angular velocities of the robot using depth and attitude angles measured by a depth sensor and an attitude and heading reference system (AHRS). The controller is developed by using the dynamic surface control technique to avoid differentiating virtual control laws. A neural network is used to approximate recursive model uncertainties and disturbances. Relative threshold event-triggering conditions are designed to reduce the frequency of actuator action and the controller working time and to improve the energy-saving efficiency. The simulation and sea trial results show the effectiveness of the proposed control system.