| The research of Humanoid robot is a very challenge field.Humanoid robot is more convenient to join the people's life as its appearance and structure.On the other hand,it has a strong ability to adapt itself to the unstructured environment,which can not only serve the people's livelihood science and technology,but also devote to the public safety and disaster relief as the irreplaceable technical means.The hydraulic servo system is widely used in the current humanoid robot dynamic system because of its large power density and fast dynamic response.As the large stiffness of the hydraulic system,in order to prevent the robot from the damage interacting with the environment,the use of series elastics actuator(SEA)is more popular in hydraulic robots.The combination of the passive softening of the elastic element and the active control of the controller ensures the safety and reliability of the interaction between the robot and the environment.The main contents of this paper were as follows.First of all,the hydraulic SEA's system was built.A modular hydraulic SEA was designed,and the key components of the hydraulic system,the sensor system and the main control system were selected and the physical system of the whole system was completed.Secondly,the characteristics of the hydraulic SEA were analyzed.The SEA's model was simplified into four parts: system input,power source,elastic element and controller,which was analyzed according to the actual system.The four key parameter of SEA: closed loop bandwidth,a large force bandwidth,output impedance and impact resistance were deduced,and the influence of stiffness coefficient of SEA was discussed emphatically.At the same time,I proved the power amplification characteristic of SEA,comparing with the rigid actuator.The selection basis of the stiffness coefficient of elastic element in SEA design was given.Thirdly,the position control model of the hydraulic cylinder piston rod was built in two directions,and the stability of the system was verified by simulation analysis.At the same time,when the load side was fixed,the characteristics output of the asymmetric cylinder was symmetrical by adapting the fuzzy PID controller.When the load end was free to move,the speed of the load end was converted into current for the feedforward control,So that the force output characteristics and the load side of the dynamic characteristics can be decoupled.On the other hand,the design of joint variable stiffness controller based on hydraulic SEA was discussed.Finally,the experimental platform of the SEA was established,and the characteristics and control strategies of the hydraulic SEA were verified,which provided the data support for the subsequent development of the prototype of the humanoid robot.The paper summarized the whole work and made a prospect for the future research direction. |
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