| 摘要 |
The invention provides a method for controlling current in a direct current motor (18) having a back emf constant (k e ), which may be a function of field current if the direct current motor is a field wound machine, and motor resistance (R s ) in all 4 quadrants of operation. The method includes the step of rotating a motor shaft (22) of the direct current motor (18) with a controller by applying a first voltage across the direct current motor's terminals (18). The first voltage corresponds to a first value of current passing through the armature windings (24) of the direct current motor (18). The method also includes the step of determining a maximum value of current to pass through the armature windings (24) of the direct current motor (18). The maximum value of current is selected to prevent undesirable over current conditions, such as thermal overload as one example. The method also includes the step of receiving a signal corresponding to a desired motor speed (É*) with the controller during the rotating step. The method also includes the step of first computing a second voltage to replace the first voltage from the controller after the receiving and determining steps and in view of the estimates of the back emf constant (k e_est ) and the armature resistance (R est ) of the direct current motor (18). The method also includes the step of limiting the second voltage, if necessary to limit the current, before replacing the first voltage based at least in part on a difference between the maximum value of current and the current polarity, a gain quantity 36, and the first value of current and voltage in order to dynamically control current during the operating step. |
