Research On Control Of ESMAA-Based Anthropopathic Robot Fingers

With the improvement of automatization, robots are required to operate in limited space precisely. Unfortunately, the traditional robot hands could not meet these complicated requirements because of their big volume and lack of complaisance, which caused by the spatial sepeatation between their driving part and executing part. To overcome these difficulties, a kind of Embedded Shape Memory Alloy Actuator (ESMAA) using Shape Memory Alloy(SMA) wire is fabricated, which can be used in robots. The SMA exhibits nonlinearity because its energy conversion principle relies on the phase transition in a metal, resulting in significant hysteresis. Consequently, it is difficult to describe the properties accurately in general terms. All these facts make the precise control difficult. Also, attention should be paid to all the sensors used in ESMAA about their complaisance, volume and the integration process. Facing these challenges, this thesis carried out a series of work under the support of National Science Foundation. The achievements obtained are summarized as follows:After all-around comparison, a proper type of strain gauge was selected as curvature sensor and was integrated according to normative technics. PVDF (Polyvinylidene fluoride) piezoelectric film was selected as the touching/sliding sensor. After that, the distortion affection to ESMAA induced by sensors was studied by experiments.PI control and variable structure control were chosen. The touching/sliding criterion of PVDF sensor was brought forward as well as the snatch operation process of ESMAAs.To drive ESMAAs reliably, the measuring and driving circuit were designed with a simple hardware structure. At the same time, the control program was wrote based on DSP to control three ESMAAs parallelly.The position feedback experiments using PI control and variable structure control with different parameters were implemented. The results show that the response speed of ESMAA under variable structure control can be two times of that under PI control. In particular, the saturation control can minish vibration while still gain higher response speed. Finally, the feasibility of PVDF sensor was verified under test.