| The disc-type underwater glider(DTUG)is a new concept of the underwater glider(UG),with a highly symmetrical full-wing body design,which makes it have omnidirectional motion characteristics and extremely flexible.Besides,the DTUG also has the advantages of conventional UGs,such as low energy consumption,long-endurance,and remote monitoring.It can complete long-term,large-scale zigzag motion in an underwater profile and complete spiral motion like a torpedo-type underwater glider(TTUG).By virtue of the highly symmetrical full-wing body shape,DTUG can glide along the fuselage in any direction under the synergistic action of the attitude adjustment system and the buoyancy adjustment system,with omni-directional motion characteristics.The disc shape brings greater vertical resistance to the DTUG,enabling it to complete the vertical motion at a lower vertical speed with zero pitch angle.It improves the underwater hovering ability of the glider and reduces the accuracy requirements of the fixed-depth motion for the buoyancy control system of the DTUG.Simultaneously,with the support of innovative mlicro-torque control technology,the DTUG can achieve the in situ steering motion through the attitude adjustment system,which improves the maneuverability of the glider and reduces the requirements of the glider on the size of the working space.This motion mode dramatically enhances the operating ability of the DTUG in small bodies of water,extends the application of the UG from the deep sea to the offshore,and expands the application field of the UG.Relying on the national key project,this paper designs and develops a DTUG test prototype in response to the needs of China's strategy of accelerating the construction of maritime power.This paper takes the test prototype as the research object and mainly conducts the following research:(1)Based on the symmetrical structural features and working principles of the DTUG,the motion control model of the glider is established,and it is simplified and revised reasonably.Based on this model,the linear steady motion performance and the spiral steady motion performance of the glider are simulated and analyzed.(2)To solve the problem of the inapplicability of the viscous hydrodynamic coefficient in analyzing the omnidirectional motion and steering motion of the DTUG,this paper proposes a coordinate system transformation method,that is,the motion control model of the glider is solved in the velocity frame to predict its real omnidirectional motion and steering motion performance.(3)Based on the structural characteristics and weak control characteristics of the DTUG,this paper proposes the zero-pitch vertical motion method and the in situ steering motion method.The two motion methods are preliminarily verified through the motion simulation,and the motion performance and motion characteristics of the glider are comprehensively analyzed based on these two motion methods.In addition,this paper also studied the importance of the control parameters on the glider's performance through sensitivity analysis and analyzed the open-loop stability of the glider's motion based on Lyapunov's first theorem.(4)Based on the DTUG prototype,the pool test and the lake test are carried out.The test mainly tests the expected functions and gliding performance indicators of the prototype.The research in this paper shows that:(1)Based on the coordinate system transformation method proposed in this paper,the problem of the inapplicability of the viscous hydrodynamic coefficient is well solved in the simulation analysis of the omnidirectional motion and steering motion of the DTUG.(2)The vertical fluid resistance of the DTUG is greater than that of the traditional UG,which results in a smaller vertical velocity of the DTUG,and shorter acceleration and deceleration processes when reaching a steady state.The advantage is that it is conducive to the precise control of the glider's fixed-depth motion,but the disadvantage is that it is not suitable for real-time dynamic monitoring of deep water with high vertical velocity requirements.(3)The slight change in drainage volume has little effect on the vertical motion performance of the DTUG.The sensitivity coefficient of the vertical depth to the drainage volume change is lower than that of the hybrid-driven underwater glider(HUG),which is beneficial to reduce the glider's accuracy requirements for the buoyancy adjustment system.And it is easier to achieve dynamic depth control at the target depth.(4)The DTUG can quickly recover to a stable state after being subjected to a small disturbance from the outside in the vertical motion,and the small disturbance has little effect on the vertical depth required for the glider to return to a stable state.(5)Similar to TTUG,DTUG can also perform conventional steering motion by adjusting translation mass and buoyancy,and the difference is that DTUG has a smaller turning radius.In addition,the DTUG can also achieve in situ steering motion by adjusting only the translation mass without adjusting the buoyancy,which not only reduces the difficulty of steering motion control but also reduces energy loss and improves the endurance of the glider.(6)Compared with the TTUG,the in situ steering motion method of the DTUG greatly reduces the requirements of the spatial scale for the steering motion of the glider,and the yaw angle of the DTUG changes rapidly,making it less time to reach the target angle.The proposed in situ steering motion method further exerts the structural advantages of the DTUG and improves its maneuverability in small body of water.(7)The simulation analysis and sensitivity analysis of the in situ steering motion performance show that the in situ steering motion performance of the DTUG is significantly affected by the control parameters,and the yaw angle is most sensitive to the change of the control parameter yG.The research results can guide the adjustment of the control parameters of the glider in different working environments,so as to better exert the in situ steering performance of the glider.(8)The results of the pool test and the lake test show that the design of the DTUG is feasible,and the prototype has reached the expected functions and gliding performance indicators.In addition,the test also verified the rationality and accuracy of the simulation analysis in this paper.In this paper,the simulation analysis and experimental research on the motion performance and characteristics of the DTUG is carried out,the innovation embodied in the following aspects:(1)Based on the structural characteristics and working principle of the DTUG,after reasonable simplification and revision of its dynamic model and hydrodynamic model,a motion control model suitable for analyzing its motion characteristics is established.(2)Aiming at the inapplicability of the viscous hydrodynamic coefficients,a coordinate system transformation method is proposed to solve the motion control equation of the glider in the velocity frame to obtain its true omnidirectional motion and steering performance.(3)In view of the large vertical fluid damping of the DTUG,the zero-pitch vertical motion method is proposed to improve the underwater hovering ability of the glider.(4)Aiming at the weak control characteristics of the steering motion of the DTUG,an in situ steering motion method is proposed to improve the maneuverability of the glider in a small body water. |
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