Design And Control Method Of Compliant Series Elastic Actuator

The emergence of industrial robots conforms to the needs of human large industrial production and has been widely used in various fields.At present,human society is gradually entering the post-industrial era,and both indus-trial production and service industry have put forward new requirements for robots.Traditional robots work in factories and carry out eficient and rapid as-sembly activities.However,in some new application scenarios that require robots,such as medical robots,service robots and high-precision assembly robots,tra-ditional rigid robots can no longer meet these requirements.Therefore,the de-velopment of robots with good human-machine interaction performance such as security and flexibility is a hot topic in the future robot field.In the develop-ment and research of flexible robot,series elastic actuator(SEA)is an important research direction.Based on this,a new series elastic actuator mechanism is pre-sented in this paper,and the mechanical structure design and control system construction are introduced.The main work of this paper is as follows:Based on the analysis of the current excellent mechanical structure of the SEA,the design principles of the SEA are summarized as follows:interaction safety,precise force control performance,ability to realize two-way drive,miniaturization and lightweight,stable torque output,efficient energy utilization and low inertia principle.Each of the design principles has a bias,in the design needs to be based on the actual needs of the pros and cons balance.This paper needs to design a high performance flexible driver,so the size,security and force control performance of the driver have high requirements.Based on the above principles,this paper proposes an SEA with linear spring as the elastic element,and places the elastic element between the load and the motor to realize the external force buffer and energy storage.The frameless torque motor is used as the power source to reduce the overall size.The ball screw converts the motor torque to the thrust driving load.Then,based on the SEA,a double-joint flexible manipulator arm is designed.The main body of the manipulator is two seas,which are respectively fixed on the two joint arms.The silk lever of the SEA realizes the rotation of the joint arm by driving a crank slider mechanism respectively.The modeling method of the flexible manipulator is different from that of the general manipulator.In this paper,the kinematics modeling of the proposed mechanical structure of the SEA is carried out,and the relation between each joint variable is derived.The forward kinematics and inverse kinematics of the double-joint manipulator are studied.For the dynamic analysis,the SEA is simplified into three consecutive connected parts of spring,drive mass and output mass,in which the spring is assumed to be fixed with the earth.The external forces acting on the output mass are then transmitted to the spring in turn,causing compression and elongation of the spring.Through the analysis of the response frequency of the system,the response of the system will resonate at a certain frequency,resulting in the spring force is much greater than the output force,which leads to the instability of the system.Therefore,the spring force is selected as the force control object of the system in this design.Aiming at the design of the control system,this paper analyzes the perfor-mance and model selection of the controller,driver,sensor and system commu-nication.DSP chip TMS320F28335 is selected as the main controller,which has high performance,low power consumption and fast processing speed,and can meet the requirements of real-time data processing.Communication mode select CANopen bus communication.On the one hand,CANopen has low cost,high portability and convenient development.On the other hand,the main controller supports this communication mode,which greatly facilitates the development process.The parameters of spring stiffness and damping are identified by experimen-tal method.And the use of a variety of algorithms to achieve the precise driver compliance control,such as PID control,impedance control.The feasibility and effectiveness of the established model and control scheme are verified by means of MATLAB and Adams joint simulation,and the accuracy of the SEA's track-ing of position and force is mainly verified.At the same time,the obstacles and impacts encountered in the actual operation of the manipulator are simulated,and the experimental results prove that the SEA designed in this paper has a good response performance to the above situations and improves the safety of human-computer interaction.