An Iteration On The Design Of A Novel Electro-mechanical Actuator: Artificial Muscle

Here we will present modelling and optimal control of an experimental electro- mechanical actuator. The actuator is designed to be used in orthotics and prosthetics, especially in lower limb applications. The electro-mechanical actuator consists of a shape memory alloy, a heat stabilized form of nitinol which contrasts when electrically charged and returns to its original length repetitively. The prototype actuator acting as an artificial muscle, is capable of generating 97.129 dynes (210 pounds) of pulling force during the contractions when activated with 1080 joules of electrical energy. In order to reduce the energy consumption and to response time of the device, a dynamical model for its temperature distribution is obtained and the optimal electrical energy which minimizes the weighted cost of energy and time is found. Computer simulation on the model indicated that using the optiinal activation, it is possible to reduce the totaI energy consumption to the 5% of the original consumption. This result provided basis for the design of the next prototype.