| Shoulder musculoskeletal system simulator is a key device for studying the biomechanical properties of shoulder,its research results can be used to study pathology and to develop repair strategies for irreparable rotator cuff tears.Due to the complexity of human shoulder movement,the R&D of the simulator is extremely challenging.Therefore,an in-vitro biomechanical simulator for shoulder was developed based on anatomy and mechanical design methods,and experimental studies were conducted in this dissertation.The main work and achievements can be concluded as:1)Taking into account shoulder movement mechanism and measurement requirements of biomechanical parameters,the design objectives were clarified by using QFD and functional analysis methods.According to experimental needs and shoulder anatomy,the structural solutions of the fixtures of shoulder bones,the drive mechanisms of abduction simulation,and the measurement devices were designed.Thus,the three-dimensional model of the simulator was established.Here,the loading system was realized by virtue of the combination of electric and pneumatic actuators,which can provide accurate and stable biomimetic muscle force outputs.2)Kinematics and kinetics analysis were performed on the key mechanisms of the shoulder simulator.Through the calculations of the stroke and tension output of the scapular abduction drive mechanism and glenohumeral abduction loading system,theoretical references were provided for the selection of the actuators.From the perspective of kinematics,the measurement error of the measurement mechanism of the abduction angle was analyzed,and the rationality of the mechanism design was confirmed.The motion simulation analysis based on CREO software proved the feasibility of the simulator's overall design scheme.3)According to the needs of measurement and control systems,centralized control hardware system and program-controlled architecture software system were built.A force closed-loop valve control system was established with proportional pressure valve as the core;and the closed-loop position control system was realized by using electric actuators and angle encoders.Two experimental modes,namely,static loading and dynamic simulation,were conducted in this paper,in which dynamic motion simulation was achieved by applying continuously varying forces on the deltoid and rotator cuff muscle groups.Tasks of inputting and outputting the force and displacement information during the force loading process were completed based on Lab VIEW,which can satisfy the functional requirements of the user's control of abduction simulation and the measurement of biomechanical parameters.In order to meet the experimental requirements of rotator cuff tear repair,the switchable specimen states and loading mode selections were set on the human-machine interaction interface,and the experimental data recorded in real time can be directly exported on the interface for subsequent analysis.4)To test the performance of the shoulder simulator designed in this paper,static and dynamic experiments were performed under the complete condition of the rotator cuff of the specimen.Tracking ability of setpoint profiles for abduction and statistical capabilities of functional parameters were evaluated respectively by root mean square error(RMSE)and standard deviation(SD).In the static experiment,the SD of the superior translarion of the humeral head was no more than 0.36mm,and the SD of the humeral rotation range of motion was not more than 1.69°.In the dynamic experiment,the RMSE of the glenohumeral abduction trajectory was less than 1.44°,the SD was less than 1.1°;the maximum SD of the dynamic muscle load was not more than 2.1N;the SD of the glenohumeral compressing force was not more than 4.84N.The experimental results showed that the shoulder simulator designed in this paper has high accuracy and repeatability.Hence,a high-performance experimental instrument is provided for the in-vitro biomechanical research of shoulder. |
PDF Full Text Request