隨著科技的進步的影響下，由機器人、手臂取代人力已是全球的趨勢，並隨著醫學的進步使得人口高龄化，因此更加需要有完善的復健和輔助的裝置，它必須能提供人與機器之間更安全地互動，使得使用者能以所需之方式做運動或復健，為了實現這點就必須做到既精確且穩定的扭力控制，而近年來發現串接式彈性致動器(Series Elastic Actuators, SEAs)非常適合用於開發復健和輔助的裝置，它的結構不同於傳統致動器，在致動器與負載之間串接一個彈性元件，降低致動器結構的剛性、系統的頻寬，因彈性元件具有將負載所受之扭力轉成彈性元件的變形量再乘上彈性係數的特性，因此將扭力控制問題轉換成角度控制問題，所以可套用已發展十分成熟的角度控制的理論，從而能夠實現高精確度、穩定度的扭力控制。

　　藉由此次的研究，對串接式彈性致動器做全面的探討，一開始先使用系統識別找出馬達的模型及彈簧在動態及穩態的特性方程式的型式，並利用最小平方法來找出特性方程式的參數，接著藉由馬達模型與彈簧特性方程式推導出串接式彈性致動器的數學模型，再藉此數學模型設計出負迴授控制系統以及控制器(Proportional-Derivative Controller和Sliding Mode Controller)來實現收斂快且穩定的扭力控制，最後藉由各種不同組合的實驗，比較不同控制器的性能，並藉此找到能收斂快且穩定之扭力控制的最佳方法。

With the progress of technology, many jobs have been replaced by machines. Besides, with the medical progress makes the population aging, so people might keep their health by using appropriate rehabilitation or assistive devices, which need to have safer interactions with human, and then users can do rehabilitation exercises according to their demands. Therefore, the devices must be able to achieve both accurate and stable torque control in order to satisfy users’ demands. In recent years, it has been found that series elastic actuators (SEAs) are well suited for the development of rehabilitation or assistive devices, because its structure is different from the structure of the traditional actuator. It reduces the rigidity of the structure of the actuator and bandwidth of the system by using an elastic unit to connect the actuator and load in series. However, the elastic unit can convert the torque from the load into the deformation amount of the elastic unit multiplied by the elastic coefficient, so a torque control problem can be converted into an angle control problem, which can be easily solved by using any position control theory, and high-accuracy torque control can be achieved.

This study provides a comprehensive study on SEAs. First, the dynamic models of a motor and a spring are determined by applying system identification and the least-squares estimation. Secondly, the equation of an SEA is derived by integrating both the models of a motor and a spring. Thirdly, a negative feedback control system based on the SEA model is developed, where the high-accuracy position and torque control are achieved by designing a proportional-derivative (PD) controller and a sliding mode controller. Finally, some conclusions regarding to high-accuracy position and torque control are obtained by performing the simulation and experiments based on the two types of controllers.

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