This improvement is particularly strong for actuators intended for robots that interact with the natural environment. The force transmission fidelity of the gear reduction is no longer important, allowing inexpensive gear reduction to be used.
Gears typically transmit position with much higher fidelity than force.
The series elasticity serves as a transducer between gear reduction output position and load force, greatly increasing the fidelity of force control. The required motor force fidelity is drastically reduced, allowing inexpensive motors to be used. It is the motor shaft's position, not its output torque which is responsible for the generation of load force. As a result, motors with large torque ripple can be used. Force control stability is improved, even in intermittent contact with hard surfaces.