The advantages and disadvantage of a TSA can be briefly summarized as the following:
High translational output force with low input torque.
High reduction ratio; can be used with small and lightweight motors.
Good power density; powerful for its size.
Low cost, and by far the easiest of our actuators to build by hand.
Good power efficiency, of about 70-80%.
Good compliance (low stiffness), allowing for high-frequency applications.
Easy to work within a composite design, as DC motors can be readily integrated with an electronic controller and are typically unobtrusive.
Low durability.
Only last in the range of tens of thousands of cycles. Strings can be easily cut, torn, or otherwise lose their twist over time.
Overtwisting of the string (above 50 turns in one direction) can also decrease the endurance life and lead to unwinding problems.
Be aware this means the performance of the actuator as a whole also decays over time!
Nonlinear force and strain output.
The twisted string itself becomes looser during actuation, which makes predictions via linear equations inherently inaccurate.
Low strain, typically only around 30%.