Examples are provided that describe a model free power detector. In one example, a method includes receiving, by one or more computing devices, a measurement of electrical power to a robotic device. The method also includes receiving, by the one or more computing devices, a measurement of mechanical power by the robotic device. Based on combinations of the electrical power to the robotic device being one of positive, negative, or about zero, and the mechanical power by the robotic device being one of positive, negative, or about zero, the method includes determining possible states of operation of the robotic device. The method also includes providing, by the one or more computing devices, the possible states of operation of the robotic device to a detector.

A drive unit 10A is configured to exert a driving force on an environment 50 in accordance with a target driving force command ?.sub.d, and includes a parameter storage device 30A, a force measuring instrument 35, an admittance model calculation device 31A, and a position control and driving device 33A. The parameter storage device 30A has stored therein dynamics parameters of first and second virtual objects affected by a virtual interactive force ?.sub.R. The force measuring instrument 35 is configured to output a measurement result for the driving force as a measured driving force value ?.sub.s. The admittance model calculation device 31A is configured to calculate and output a displacement of the first virtual object. The displacement is obtained by calculations based on the stored dynamics parameters, the target driving force command ?.sub.d, and the measured driving force value ?.sub.s. The position control and driving device 33A is configured to operate in accordance with a target position command. The force measuring instrument 35 is disposed between the position control and driving device 33A and the environment 50. The target position command corresponds to the first virtual object's displacement outputted by the admittance model calculation device 31A. The drive unit 10A achieves advantages of both high and low backdrivability.

A jointed robot capable to move on a surface is provided. It is known to limit to a predefined fixed value the torque that the motors of the joints of the robot can develop. A rigidity coefficient corresponding to the limit torque is calculated by solving a dynamic equilibrium model of the robot. The contact points of the characteristic effectors are determined by a selection from a list of potential effectors, notably as a function of a criterion of distance from a virtual ground plane. The contact forces for said effectors are calculated by optimal resolution of the equilibrium equations. Finally the torques applied in the dynamic equilibrium model of the robot and the coefficients of corresponding rigidity are calculated.