Reserch On Driving Characteristics Of A Fluid-Driven Pipeline Robot

Fluid-driven pipeline robots utilize the differential pressure between the front and rear fluid to drive themselves; they solved the problem of energy supply very well and are especially suitable for the inspection of long-distance, in service, oil and gas pipelines. However, most of them are not able to move independently, velocity fluctuations, such as occasional move and stop, acceleration and deceleration, often occur during their operations. Velocity fluctuation may not only cause damage to the robot body, but also severely affect the precision of the inspection data, even make the inspection data unavailable.Based on the analysis of the robot's velocity fluctuation mechanism, the paper designed a novel driving unit of the pipeline robot with the function of velocity control, and conducted theoretical analysis and verification tests on is its driving characteristics. The paper analyzed the robot's velocity fluctuation mechanism and ascertained the reasons that cause and maintain velocity fluctuations; Conducted dynamic analysis on the robot and established a mathematical model for its velocity fluctuation. Characteristic curves of velocity fluctuations were obtained through numerical simulations and the effect of each parameter on velocity fluctuations was determined.Based on theoretical analysis, many driving schemes were proposed, including the scheme of friction reduction through vibration, the scheme of regulating normal force and the scheme of regulating differential fluid pressure. A macroscopic mechanical model of friction reduction in the presence of vibration was introduced and a theoretical model of velocity control using throttle plates was established. After comparing and selecting, the scheme of friction reduction through cam-generated vibration and the scheme of velocity control using double throttle plates were combined together; this enabled the driving unit to have a dual regulating function.The paper designed and analyzed the driving unit of the fluid-driven pipeline robot, built its assembly model in a three-dimensional design software. The function and working principle of each system of the driving unit was analyzed and a dynamic model for the vibration actuator was established. Besides this, the relational expression of the driving force caused by fluid in response to the included angle between the two throttle plates was deprived. The paper also analyzed the auxiliary support system's pipe-diameter adaptability and overall bearing capability.A driving characteristic testing platform was built and two simplified principle prototypes were manufactured. After finishing the test of friction reduction using vibration and the test of velocity control using double throttle plates, the correctness of theoretical analysis and rationality of design of the driving unit was proved. The paper has laid a foundation for future research on fluid-driven pipeline robot technology.