Sliding mode control and Lyapunov based guidance law with impact time constraints

This paper analyses the issue of impact time control of super-cavitation weapons impact fixed targets which mainly refer to the ships or submarines who lost power, but still have combat capability. Control over impact time constraints of guidance law(ITCG) is derived by using sliding mode control(SMC) and Lyapunov stability theorem. The expected impact time is realized by using the notion of attack process and estimated time-to-go to design sliding mode surface(SMS). ITCG contains equivalent and discontinuous guidance laws, once state variables arrive at SMS,the equivalent guidance law keeps the state variables on SMS,then the discontinuous guidance law enforces state variables to move and reach SMS. The singularity problem of ITCG is also analyzed. Theoretical analysis and numerical simulation results are given to test the effectiveness of ITCG designed in this paper.

Bio-inspired geomagnetic navigation method for autonomous underwater vehicle

This paper presents a bio-inspired geomagnetic navigation method for autonomous underwater vehicle(AUV) without using any a priori geomagnetic information. Firstly, the multi-objective search problem is raised. Secondly, the geomagnetic navigation model is established by constructing a cost function. Then, by taking into consideration the biological magneto-taxis movement behavior for the geomagnetic environment stimulus, the multiobjective evolutionary search algorithm is derived to describe the search process. Finally, compared to the state-of-the-art, the proposed method presents better robustness. The simulation results demonstrate the reliability and feasibility of the proposed method.

Cooperative path planning for multi-AUV in time-varying ocean flows

For low-speed underwater vehicles, the ocean currents has a great influence on them, and the changes in ocean currents is complex and continuous, thus whose impact must be taken into consideration in the path planning. There are still lack of authoritative indicator and method for the cooperating path planning. The calculation of the voyage time is a difficult problem in the time-varying ocean, for the existing methods of the cooperating path planning, the computation time will increase exponentially as the autonomous underwater vehicle（AUV） counts increase, rendering them unfeasible. A collaborative path planning method is presehted for multi-AUV under the influence of time-varying ocean currents based on the dynamic programming algorithm. Each AUV cooperates with the one who has the longest estimated time of sailing, enabling the arrays of AUV to get their common goal in the shortest time with minimum timedifference. At the same time, they could avoid the obstacles along the way to the target. Simulation results show that the proposed method has a promising applicability.

Compensation modification of plastic gear tooth profile considering meshing deformation

The plastic gear is widely used in agricultural equipment,electronic products,aircraft,and other fields because of its light weight,corrosion resistance,and self-lubrication ability.However,it has a limited range of working conditions due to the low modulus and thermal deformation of the material,especially in high-speed and heavy-duty situations.A compensation modification method(CMM)is proposed in this paper to restrain the heat production of the plastic gear tooth surface by considering the meshing deformation,and the corresponding modification formulas are derived.Improving the position of the maximum contact pressure(CP)and the relative sliding velocity(RSV)of the tooth surface resulted in a 30%lower steady-state temperature rise of the modified plastic gear tooth surface than that of the unmodified plastic gear.Meanwhile,the temperature rise of plastic gear with CMM is reduced by 19%compared with the traditional modification of removal material.Then,the influences of modification index and the segment number of modification on the meshing characteristics of plastic gear with CMM are discussed,such as maximum CP and steadystate temperature rise,RSV,transmission error,meshing angle,and contact ratio.A smaller segment number and modification index are beneficial to reduce the temperature rise of plastic gear with CMM.Finally,an experiment is carried out to verify the theoretical analysis model.