where q {\displaystyle {\boldsymbol {q}}} denotes joint angular position, M {\displaystyle {\boldsymbol {M}}} is the symmetric and positive-definite inertia matrix, c {\displaystyle {\boldsymbol {c}}} the Coriolis and centrifugal torque, g {\displaystyle {\boldsymbol {g}}} the gravitational torque, h {\displaystyle {\boldsymbol {h}}} includes further torques from, e.g., inherent stiffness, friction, etc., and τ e x t {\displaystyle {\boldsymbol {\tau }}_{\mathrm {ext} }} summarizes all the external forces from the environment. The actuation torque τ {\displaystyle {\boldsymbol {\tau }}} on the left side is the input variable to the robot.