Patent ID: 7637105

Claim:
A method for improving performance and life of a shape memory alloy material adapted to contract when heated to a critical temperature; the method including the following steps: (i) measuring ambient temperature before activation; (ii) measuring voltage applied to the material and/or current flowing in the material; (iii) calculating power and/or energy required to heat the material from the ambient to the critical temperature; and (iv) providing the calculated power and/or energy; wherein in step (iii) the power when calculated is calculated according to the formula: PWM Compensated =PWM Nominal ×(Voltage Nominal ) 2 /(Voltage Loaded ) 2 where: Voltage Nominal is nominal power supply voltage value PWM is pulse width modulation; and the energy when calculated is calculated according to the formula: PWM Compensated =PWM Nominal ×(Temp Activation −Temp Ambient )/(Temp Activation −Temp Nominal ) where: Temp Nominal is nominal temperature and is set to 25° C. Temp Activation is the critical temperature at which the material is adapted to contract and is set to 95° C. PWM is pulse width modulation.