of a potential variable divided by a flow variable is an impedance value at a port an input impedance of the guiding device 1011 the actuator 1012 or the driver 1013 is used in determining power to be transmitted to one end at which work is done the driver 1013 for example a motor is capable of transforming electric energy to mechanical energy a potential variable input and a flow variable input are voltage e and current i respectively a potential variable output and a flow variable output are torque t and rotary speed u03c9 respectively the power transfer between inputs and outputs which are classified into different energy domains depends on a transduction matrix as follows the actuator 1012 for example a gear rack pair is characteristic of functions as follows 1 change movement induced by mechanical energy for example movement from rotation to linear motion and 2 match mechanical impedances between an energy supplier of the limb driving subsystem 101 and a limb doing work mechanical impedances which match each other optimize work transfer efficiency the transmission matrix tm m for relationships between potential variable flow variable inputs and potential variable flow variable outputs is shown as follows the limb guiding device 1011 for example a disc and a handle is able to apply received energy to the second end of a limb the transmission matrix tm g for relationships between potential variable flow variable inputs and potential variable flow variable outputs is shown as follows with equations a b and c combined the following relationships are presented as a result the relationships between inputs and outputs of the limb driving subsystem 101 are the parameters of a b c and d in matrices of td d tm m tm g and t are derived.