Abstract
Abstract. In this research, an electrohydraulic servo four-legged heavy-duty (FLHD) robot has been designed and developed. The study proposes an integration layout cylinder design scheme for a non-lightweight hydraulic servo four-legged robot with high loads and torques of hip joint and derives the mathematical element analysis model for a parallel-executed cylinder (PEC) system. The multiple inherent characteristics of the PEC integration system model are explored further. Based on the controllable functional requirements of interconnected joints, and to weaken the influence of internal force coupling, a force–position hybrid control scheme for the PEC is designed, and the force–position signal module design unit is used to solve the force–position hybrid control in reverse. Considering the inherent requirements of the servo-executed cylinder (SEC) force control unit module (CUM), the implementation process of magnetic flux compensation and speed compensation is discussed in detail. The minimum amplitude controller is applied to the SEC force CUM, and the proportional integrated controller has been determined in the SEC position CUM. A compound control strategy proposed in this paper is verified on a parallel hydraulic servo platform. The experimental verification results reveal that the values of position/force attenuation amplitude and lag phase are not greater than 9 % and 18∘, respectively. The feasibility of the interconnected implementation of the hybrid control scheme proposed in this paper is further increased. The conclusions of this research will be useful for application in fields of four-legged heavy-load (FLHL) robot control systems.
Highlights
In recent years, many scholars have attached great importance to the research of heavy-load robots
Based on the background impact of this research topic, scientific research studies in the field of hydraulic servo four-legged heavy-load (FLHL) robots have been launched in many countries
Similar to research on related topics, scholars mostly assume that the distance between the foot and the rolling axis of the hydraulic actuated four-legged robot studied in these subjects is larger, and the driving torque required by the design is larger under the same foot end force (Xu et al, 2019)
Summary
Many scholars have attached great importance to the research of heavy-load robots. Based on the background impact of this research topic, scientific research studies in the field of hydraulic servo four-legged heavy-load (FLHL) robots have been launched in many countries. Similar to research on related topics, scholars mostly assume that the distance between the foot and the rolling axis of the hydraulic actuated four-legged robot studied in these subjects is larger, and the driving torque required by the design is larger under the same foot end force (Xu et al, 2019). These research results on leg gaits of twisted torso have been widely popularised This will bring endless advantages to the movement of the inherent tripod structure, especially during fast and heavy-load hydraulic robot movements. Considering the larger bearing loads and torque characteristics of the hip joints for a heavy-load hydraulic four-legged robot, a parallel servo cylinder driving element model is proposed in this study. The semi-physical system with parallel cylinders is used to verify the hybrid force–position control strategy, and the feasibility of the proposed control scheme is checked by actual operating experiments
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