Structure And Force Control System Design Of Elastic Actuator For Rehabilitative Robot

As the power source of rehabilitative robots, Series Elastic Actuator(SEA) can achieve the purpose of flexible drive and determines the flexibility and security of whole rehabilitation robot. According to the current wearable and security problems in traditional rigid actuators, this paper increases elastic components on its basis, proposes a structure scheme of piston variable-stiffness SEAs and comprehensively designs a control system of SEAs. Finally it validates some of these conclusions through virtual prototyping technology. Specific contents are as follows:Firstly, this paper introduces a research status of traditional SEAs‘ structure, variable stiffness SEAs‘ structure and control strategy at home and abroad. It proposes a structure scheme of piston variable-stiffness SEAs based on the traditional fixed-stiffness SEA structure, according to the job demands of rehabilitation robot and stiffness-enhanced features of human muscle; it also compares the piston SEAs with the traditional SEAs about compactness and makes a finite element strength analysis by adding the radial or axial load; the results shows the piston variable-stiffness SEAs has characteristics of more compact, stronger bearing ability and better environmental adaptability.Secondly, this paper takes the mechanical model of single-stiffness SEAs as research object; according to the basic control of two strategies such as the location source drive and the force source drive, it respectively makes a comparison and analysis in the open and closed loop frequency-domain, discussing the parameters‘ effect(e.g., spring stiffness, equivalent mass) on system‘s stability, speed and driving bandwidth; finally compares the double-stiffness SEAs with single-stiffness SEAs about impact resistance in the frequency domain. The results shows the force source drive has the ideal performance in all aspects, and the double-stiffness SEAs has a stronger impact resistance performance than the single-stiffness SEAs facing high frequency signals.Then, taking the elbow as an example, this paper establishes the dynamic model of SEA system depending on different actual conditions, proposes a control scheme after simplifying the analysis, and designs the interference-feedback regulation system; it analyzes the step response of the system, considering the addition of external di sturbances.; it proves the feasibility of disturbance observer and the response ability of force control system with disturbance observer of SEAs. The results prove that the system has strong anti-interference ability, fast response with high precision. These mathematical models lay the foundation for designing the actual physical link and building real force servo control system.Finally, it built the simulation platform of virtual prototype of SEAs through the co-simulation of Adams and matlab/simulink, to verify the front results of two characteristics of the power source control model(foce output and output impedance),and analyse the following characteristics of speed/displacement at SEAs‘drive end. Compared directly with physical prototype experiments, virtual prototype technology saves time and effort, laying the theoretical foundation for the SEA force control design, and having guiding significance production for the practice and production.