Modeling and Parameter Sensitivity Analysis of Valve‑Controlled Helical Hydraulic Rotary Actuator System

As a type of hydraulic rotary actuator,a helical hydraulic rotary actuator exhibits a large angle,high torque,and compact structure;hence,it has been widely used in various fields.However,its core technology is proprietary to several companies and thus has not been disclosed.Furthermore,the relevant reports are primarily limited to the component level.The dynamic characteristics of the output when a helical rotary actuator is applied to a closed-loop system are investigated from the perspective of driving system design.Two main aspects are considered:one is to establish a reliable mathematical model and the other is to consider the effect of system parameter perturbation on the output.In this study,a detailed mechanical analysis of a helical rotary hydraulic cylinder is first performed,factors such as friction and load are considered,and an accurate dynamic model of the actuator is established.Subsequently,considering the nonlinear characteristics of pressure flow and the dynamic characteristics of the valve,a dynamic model of a valve-controlled helical rotary actuator angle closed-loop system is described based on sixth-order nonlinear state equations,which has never been reported previously.After deriving the system model,a sensitivity analysis of 23 main parameters in the model with a perturbation of 10%is performed under nine operating conditions.Finally,the system dynamics model and sensitivity analysis results are verified via a prototype experiment and co-simulation,which demonstrate the reliability of the theoretical results obtained in this study.The results provide an accurate mathematical model and analysis basis for the structural optimization or control compensation of similar systems.

Active Disturbance Rejection Control of Hydraulic Quadruped Robots Rotary Joints for Improved Impact Resistance

Hydraulic actuated quadruped robots have bright application prospects and significant research values in unmanned area investigation,disaster rescue and other scenarios,due to the advantages of high payload and high power to weight ratio.Among these fields,inevitable collision of robots may occur when contact with unknown objects,step on empty objects,or collapse,all of which have an impact on the working hydraulic system.To overcome the unknown external disturbances,this paper proposes an active disturbance rejection control(ADRC)strategy of double vane hydraulic rotary actuators for the hip joints of the quadruped robots.Considering the order of the valve-controlled actuator model,a three-stage tracking differentiator,a four-stage extended state observer,and a state error feedback controller are designed relatively,and the extended state observer is adopted to observe and compensate the uncertainty of external load torque of the system.The effectiveness of the ADRC method is verified in simulation environment and a single joint experimental platform.Moreover,the impact experiments of the limb leg unit are carried out after introducing the proposed ADRC strategy into hip joint,the limb leg unit of quadruped robots presents better impact resistance ability.