Abstract: The hydraulic channel is an important carrier for carrying pressure and transmitting power in hydraulic system. However, it has problems such as a large weight, a big volume, multiple process holes, and significant pressure losses, which seriously affect the power-to-weight ratio of the hydraulic system. Therefore, a combined algorithm using the rapid-exploration random tree（RRT） algorithm and a greedy algorithm is proposed to establish the shortest path for multi-directional irregular connecting area hydraulic flow channels based on addictive manufacture method. Subsequently, an adjoint optimization method is applied to the shortest path channels based on pressure loss for surface sensitivity adjoint optimization. Finally, selective laser melting technology is employed to fabricate the shortest path channels with low pressure loss, and a pressure loss testing platform is constructed to validate the reduction of pressure loss. Results show that the optimized final flow channel axis path is shortened by 49.6%, with smooth oil flow and reduced range along with intensity of vortex structures inside the channel of an electro-hydrostatic actuator（EHA）. Additionally, experiments demonstrate that the average pressure drop of the final flow channel decreases by 75.04% under different flow conditions. Research findings provide new insights for the optimization design of additive manufactured hydraulic flow channels.

Key words: hydraulic flow channel design, path planning, adjoint optimization, pressure loss