The inverse of impedance is admittance. It imposes position. So actually the controller imposes a spring-mass-damper behavior on the mechanism by maintaining a dynamic relationship between force ( F ) {\displaystyle ({\boldsymbol {F}})} and position, velocity and acceleration ( x , v , a ) {\displaystyle ({\boldsymbol {x}},{\boldsymbol {v}},{\boldsymbol {a}})} : F = M a + C v + K x + f + s {\displaystyle {\boldsymbol {F}}=M{\boldsymbol {a}}+C{\boldsymbol {v}}+K{\boldsymbol {x}}+{\boldsymbol {f}}+{\boldsymbol {s}}} , with f {\displaystyle {\boldsymbol {f}}} being friction and s {\displaystyle {\boldsymbol {s}}} being static force.