Virtual Prototyping
Pneumatic Muscle Actuators
Shape Memory Alloys (SMA) Actuators
Bioengineering
Finite Element Model Updating
Structural Modifications
Robotics

INTRODUCTION
The shape memory alloys (generally leagues Ni-TI) introduces the ability, unusual for other types of materials, "to remember" his own original shape. This mechanical behaviour is correlated to a transformation of the crystal lattice that is verified inside the league. Such transformation converts the stable crystal lattice to high temperature (austenitic phase) in one stable to low temperature (martensitic phase). At low temperature these materials are easily deformable while heating them it has the transformation of the martensite in austenite and in this phase the material develops notable strengths recovering its original form. The transformation is accompanied by hysterisis. These materials are available in varied forms as ribbons, foils, wires and helicoids. For the wires the obtainable reversing deformations are of 5% - 8% and the maximum tensions developable arrive to around 200 MPa. To supply thermal energy is possible to use the effect Joule through crossing of current.

ACTUATOR WITH DEDICATED SENSOR
It’s developed an actuator with Shape Memory Alloy thread-like. The actuator effects the continuous positioning through a control system in closed loop. The thermal power is produced for effect Joule making to cross from current the actuators. The control system is type proportional and it uses a retroaction’s signal of a resistance sensor position. It's realized a controller software that he pilots a data acquisition card. In exit is used a counter/timer able to furnish a signal type train of impulses with modulation of ampleness (PWM). In entry, for measure the position, a digital analogical converter to 16 bit is used. To furnish the power has been realized a circuit with fotoaccoppiatore, that it enable the power flow from a power supplier to the actuator, piloted to low power by the counter/timer. The figure shows the step response of an checked axle for different values of the reference.

ACTUATOR WITH EFFECT INTRINSIC SENSOR
An actuator with Shape Memory Alloy thread-like for the continuous positioning through a control system in closed-loop without external sensor for measure the position it is developed. In this case has been used effect intrinsic sensor of the material that, for the SMA-wires, it consists in a linear response between electric resistance of the wire and length of wire. This characteristic allows to know the length of the actuator through an measure of electric resistance. The thermal power is produced for effect Joule and the control it’s proportional. The controller pilots a data acquisition card. In exit it’s used a counter/timer able to furnish a modulation signal of ampleness (PWM). In entry, for the measure of the electric resistance of the SMA-wire is used a digital analogical converter to 16 bit.