System and method for control and analysis of a prime mover in an electrical machine using calculated torque
Apparatus for controlling and diagnosing a prime mover of a vehicle traction system includes an alternator having a rotor and coupled to a crankshaft of the prime mover, a source of electrical energy, a position sensor supplying a position signal representative of an angular position of the rotor, and a control computer. The computer supplies energy to the alternator to crank the prime mover at a controlled rate. In a diagnosis mode, the computer generates a condition signal indicative of a malfunction of the prime mover, from a compression signal derived from an acceleration signal which is derived from the position signal. In a barring-over mode, the computer also supplies energy to the alternator and monitors the position signal to place the crankshaft in a desired angular position in an operation separate from diagnosis mode.
1. A method for placing a crankshaft of a prime mover in a desired angular position, the crankshaft being coupled to a rotor of an electrical machine, the electrical machine having a field coil and a plurality of stator phase coils, the method comprising:
determining an initial position of a rotor of the electrical machine with no current flowing;
determining the direction of the torque to be produced on the rotor when the rotor is rotated from the initial position to a displacement position corresponding to the desired crankshaft position;
increasing current in the field coil to an initial value;
receiving a value of torque required to begin rotation of the electrical machine;
calculating the amplitudes of phase currents in the stator phase coils required to produce the received torque value;
supplying the calculated phase currents to the stator phase coils, such that a phase direct axis of the stator phase coils is aligned with the initial rotor position;
modifying the amplitudes of phase currents in the stator phase coils so as to rotate the phase direct axis toward the displacement position;
generating a signal representing the angular position of the rotor; and
ceasing supply of current to the stator phase coils when the position signal indicates that the rotor is in the displacement position.
2. A method as recited in claim 1 wherein calculating comprises calculating the amplitudes of phase currents in the stator phase coils required to produce the received torque value using the equation T=K l a l fld sin (δ sr ), where K is a cranking motor machine constant, l a is a phase current, l fld is a field current, and δ sr is a relative angular position of a stator magnetic axis S and a rotor position r.
3. Apparatus for placing a crankshaft of a prime mover of a vehicle traction system in a desired angular position, comprising:
an alternator for supplying electrical energy to the traction system when driven by the prime mover;
the alternator comprising a rotor coupled to a crankshaft of the prime mover, a field coil on the rotor, and a plurality of stator phase coils;
a sensor generating a position signal representing an angular position of the rotor;
a processor; and
a memory storing instructions which, when executed by the processor, cause the apparatus to:
determine an initial position of a rotor of the alternator with no current flowing in the field coil or the stator phase coils, based on the position signal;
determine a direction of torque to be produced on the rotor when the rotor is rotated from the initial position to a displacement position corresponding to the desired position;
increase current in the field coil to an initial value;
receive a value of torque required to begin rotation of the alternator and the crankshaft;
calculate the amplitudes of phase currents in the stator phase coils required to produce the received torque value;
supply the calculated phase currents to the stator phase coils, such that a phase direct axis of the stator phase coils is aligned with the initial rotor position;
modify the amplitudes of phase currents in the stator phase coils so as to rotate the phase direct axis toward the displacement position; and
cease supplying current to the stator phase coils when the position signal indicates that the rotor is in the displacement position.
4. Apparatus as recited in claim 3 , wherein the memory stores instructions which when executed by the processor cause the apparatus comprises calculate the amplitudes of phase currents in the stator phase coils required to produce the received torque value using the equation T=K l a l fld sin (δ sr ), where K is a cranking motor machine constant, l a is a phase current, l fld is a field current, and δ sr is a relative angular position of a stator magnetic axis S and a rotor position r.