WE CLAIM:
1) A tandem starter-generator system comprising:
a tandem starter-generator having a first motor-generator assembly 70 that includes a first stator assembly 20 surrounding a first rotor 60 attached to a first shaft 61 that rotates about its axis, a second motor-generator assembly 80 that includes a second stator assembly 30 surrounding a second rotor 50 attached to a second shaft 51 that rotates about its axis, a pulley 12 that is attached on one end of the first rotating shaft 61 to provide a means for mechanical coupling and regulation of mechanical power into and from a mechanical power source;
a power transmission unit 40 having a dual shaft type coupling arrangement for mechanical coupling to the first and second shafts 61, 51 that is axially disposed adjacent to the first and second motor-generator assemblies 70, 80;
a supervisory controller module 15 that controls a first power converter and controller 13 a , a second power converter and controller 13 b and a third power converter and controller 13 c and provides overall power management, control and protection functions to ensure that the first and second motor-generators 70, 80 operate in the proper regions (constant torque and constant power regions) and modes (motoring and generating modes), as well as regulate the conversion of electrical power and mechanical power between electrical energy storage and mechanical power sources; and
a housing enclosure 11 fixed with respect to the induction machine and permanent magnet machine;
wherein,
the first power converter and controller 13 a drives and controls the first motor-generator 70, second power converter and controller 13 b drives and controls the second motor-generator 80 and third power converter and controller 13 c provides ac to dc power conversion of the electrical power from the second motor-generator 80 to power auxiliary loads and charge electrical energy storage devices 14 a, 14b;
the power transmission unit 40 provides a means to configure the input-to-output speed and torque relationships with respect to the rotational speed and torque at the pulley 12 for the transmission of mechanical power between the first and second shafts 61, 51 of the motor-generators 70, 80.

2) The tandem starter-generator system as claimed in claim 1, wherein the first motor-
generator assembly 70 is an asynchronous type induction machine having a stator assembly 20 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a squirrel-cage rotor assembly 60 mounted onto the first shaft 61 that includes a skewed stack of laminations having multiple axially extending circumferentially arranged slots and having a plurality of conductive damper bars inserted and connected on both ends of the rotor by conductive end-rings; and
the second motor-generator assembly 80 is a synchronous type permanent magnet machine having a stator assembly 30 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a permanent magnet rotor assembly 50 mounted onto the second shaft 51 and includes a stack of laminations or solid piece hub having a plurality of permanent magnets that is mounted on its surface or embedded into axially extending circumferentially arranged slots.
3) The tandem starter-generator system as claimed in claim 2, wherein the housing enclosure 11 having a means mounted thereon for electrical and mechanical input and output power conversion, and bearings 62 mounted thereon to support the first and second shafts 61, 51 of the rotors of the induction and permanent magnet machines so that the rotors rotate at the same as well as different rotational speeds with respect to the housing 11.
4) The tandem starter-generator system as claimed in claim 2, having the power transmission unit 40 with a dual spline-type coupling arrangement for mechanical connection to the first and second shafts 61, 51 that is axially disposed within the axial cavity formed by the circumference of the inner diameter of the rotor of the induction machine,
wherein it enables the induction machine and permanent magnet machine to be driven and controlled at predetermine non-zero rotational speeds with respect to the rotational speed of the pulley 12 for the transmission of mechanical power between the first shaft 61 coupled to the rotor 60 of the induction machine and second shaft 51 coupled to the rotor 50 of the permanent magnet machine to achieve maximum operational efficiency to reduce the axial length and improve power density capability of the tandem motor-generator.

5) The tandem starter-generator system as claimed in claim 1, having the power transmission
unit 40 with a dual spline-type coupling arrangement for mechanical connection to the first and
second shafts 61, 51 and axially disposed within the axial cavity formed by the circumference of
the inner diameter of the rotor of the permanent magnet machine,
wherein it enables the induction machine and permanent magnet machine to be driven and controlled at predetermine non-zero rotational speeds with respect to the rotational speed of the pulley 12 for the transmission of mechanical power between the first shaft 61 coupled to the rotor 60 of the induction machine and second shaft 51 coupled to the rotor 50 of the permanent magnet machine to achieve maximum operational efficiency to reduce the axial length and improve power density capability of the tandem motor-gener a t o r.
6) The tandem starter-generator system as claimed in claim 1, having:
the first shaft 61 attached to the induction motor rotor 60 is supported by the bearings 62 installed in the housing 11 and having a pulley 12 mounted on one end external to the housing 11 to enable coupling to a mechanical power source and the other end connected to the power transmission unit 40,
the second rotor shaft 51 attached to the permanent magnet machine and having one end coupled to the power transmission unit 40 and the other end supported by the bearings 62 installed into the housing 11,
wherein the pulley 12 and power transmission unit 40 are configured to enable the rotors 60 of the induction machine and permanent magnet machine rotate at higher rotational speeds than the mechanical power source.
7) The tandem starter-generator system as claimed in claim 1, wherein the first and second
motor-generator controllers control the directions and magnitudes of the electromagnetic torques
applied to the rotors 60, 50 of the induction and permanent magnet machines attached to the first
and second shafts 61, 51 to increase or decrease the mechanical power loading on the pulley 12,
and thereby providing a means to adjust the power loading and operational efficiency of the
mechanical power source.

8) The tandem starter-generator system as claimed in claim 1, having the first motor-
generator controller controls the electromagnetic torque applied to the rotor 60 of the induction
machine attached to the first shaft 61, the second motor-generator controller controls the
electromagnetic torque applied to the rotor 50 of the permanent magnet machine attached to the
second shaft 51,
wherein the loading of the mechanical power source is increased by having the first controller controls the induction machine to apply torque opposite the direction of rotation of the first shaft 61 and the second controller controls the permanent magnet machine to apply torque opposite the direction of rotation of the second shaft 51, and loading of the mechanical power source is decreased by having the first controller controls the induction machine to apply torque in the direction of rotation of the first shaft 61 and the second controller controls the permanent magnet machine to apply torque in the direction of rotation of the second shaft 51.
9) The tandem starter-generator system as claimed in claim 1, wherein the rotational speed of the rotor 60 of the induction machine in relation to the rotational speed of the pulley 12 is set to a predetermined non-zero value that when the appropriate electromagnetic torques are applied by both the induction machine and permanent magnet machine the starter-generator operates at maximum efficiency.
10) The tandem starter-generator system as claimed in claim 1, wherein the rotational speed of the rotor 50 of the permanent magnet machine in relation to the rotational speed of the pulley 12 is set to a predetermined non-zero value that when the appropriate electromagnetic torques are applied by both the induction machine and permanent magnet machine starter-generator operates at maximum efficiency.
11) The tandem starter-generator system as claimed in claim 1, wherein the power transmission unit 40 constructed as a planetary gear mechanism 40 comprising a dual spline-type arrangement, a ring gear member 41, a planet carrier member 42 and a sun gear member 44, and having two of its three gear members coupled to the first shaft 61 attached to the rotor of the induction machine and second shaft 51 attached to the rotor 50 of the permanent magnet machine.

12) A hybrid vehicle comprising:
an engine 45 as a mechanical power source;
a pulley 12 that is attached on one end of the first rotating shaft 61 that provides a means for mechanical coupling and regulation of mechanical power into and from the engine 45;
a tandem starter-generator system having a first motor-generator assembly 70 that includes a first stator assembly 20 surrounding a first rotor 60 attached to a first shaft 61 that rotates about its axis; a second motor-generator assembly 80 that includes a second stator assembly 30 surrounding a second rotor 50 attached to a second shaft 51 that rotates about its axis; a power transmission unit 40 having a dual spline-type coupling arrangement for mechanical coupling to the first and second shafts 61, 51 that is axially disposed adjacent to the first and second motor-generator assemblies 70, 80 and providing a means to configure the appropriate input-to-output speed and torque relationships with respect to the rotational speed and torque at the pulley 12 for the transmission of mechanical power between the first and second shafts 61, 51 of the motor-generators 70, 80; and
a supervisory controller module 15 that controls a first power converter and controller 13 a, a second power converter and controller 13 b and a third power converter and controller 13 c and provides overall power management, control and protection functions to ensure the first and second motor-generators 70, 80 operate in the proper regions and modes, as well as regulate the conversion of electrical power and mechanical power between electrical energy storage and mechanical power sources;
wherein the first power converter and controller 13 a drives and controls the first motor-generator 70, second power converter and controller 13 b drives and controls the second motor-generator 80 and third power converter and controller 13 c provides ac to dc power conversion of the electrical power from the second motor-generator 80 to power auxiliary load devices;
a high voltage electric energy storage source of a dual voltage electrical system of the hybrid vehicle that discharges electrical power in accordance with the vehicle driving conditions to drive the two motor-generators 70, 80 during power assist driving modes, and it is charged with electrical power generated by the two motor-generators 70, 80 during regenerative braking modes; and
a low voltage electric energy storage source of a dual voltage system of the hybrid vehicle that discharges electrical power to support auxiliary loads and essential low power functions of

the vehicle, and it is being charged continuously by the electrical power generated by the second motor-generator 80.
13) The hybrid vehicle as claimed in claim 12, wherein
the first motor-generator assembly 70 is an asynchronous type induction machine having a stator assembly 20 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a squirrel-cage rotor assembly 60 mounted onto the first shaft 61 that includes a skewed stack of laminations having multiple axially extending circumferentially arranged slots and having a plurality of conductive damper bars inserted and connected on both ends of the rotor by conductive end-rings; and
the second motor-generator assembly 80 is a synchronous type permanent magnet machine having a stator assembly 30 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a permanent magnet rotor assembly 50 mounted onto the second shaft 51 and includes a stack of laminations or solid piece hub having a plurality of permanent magnets that is mounted on its surface or embedded into axially extending circumferentially arranged slots.
14) The hybrid vehicle as claimed in claim 12, having the tandem starter-generator system
mounted thereon and having the power transmission unit 40 with a dual spline-type coupling
arrangement for mechanical connection to the first and second shafts 61, 51 and axially disposed
within the axial cavity formed by the circumference of the inner diameter of the rotor 60 of the
induction machine,
wherein it enables the induction machine and permanent magnet machine to be driven and controlled at predetermine non-zero rotational speeds with respect to the rotational speed of the pulley 12 for the transmission of mechanical power between the first shaft 61 coupled to the rotor 60 of the induction machine and second shaft 51 coupled to the rotor of the permanent magnet machine to achieve maximum operational efficiency, and to reduce the axial length and improve power density capability of the tandem motor-generat o r.

15) The hybrid vehicle as claimed in claim 12, having the tandem starter-generator system
mounted thereon and having the power transmission unit 40 with a dual spline-type coupling
arrangement for mechanical connection to the first and second shafts 61, 51 and axially disposed
within the axial cavity formed by the circumference of the inner diameter of the rotor 50 of the
permanent magnet machine,
wherein it enables the induction machine and permanent magnet machine to be driven and controlled at predetermine non-zero rotational speeds with respect to the rotational speed of the pulley 12 for the transmission of mechanical power between the first shaft 61 coupled to the rotor 60 of the induction machine and second shaft 51 coupled to the rotor 50 of the permanent magnet machine to achieve maximum operational efficiency, and to reduce the axial length and improve power density capability of the tandem motor-generator.
16) The hybrid vehicle as claimed in claim 12, having the tandem starter-generator system
mounted thereon and having the first power converter and controller 13 a controls the
electromagnetic torque applied to the induction machine rotor 60 attached to the first shaft 61, the
second power converter and controller 13 b controls the electromagnetic torque applied to the
permanent magnet machine rotor 50 attached to the second shaft 51, and the engine 45 drives the
pulley 12 with mechanical power regulation,
wherein the engine power loading and fuel consumption are increased in accordance with the vehicle driving conditions by having the first power converter and controller 13 a controls the induction machine to apply torque opposite the direction of rotation of the first shaft 61 and the second power converter and controller 13 b controls the permanent magnet machine to apply torque opposite the direction of rotation of the second shaft 51;
the engine power loading and fuel consumption are decreased in accordance with the driving conditions by having the first power converter and controller 13 a controls the induction machine to apply torque in the direction of rotation of the first shaft 61 and the second power converter and controller 13 b controls the permanent magnet machine to apply torque in the direction of rotation of the second shaft 51.
17) A method of controlling a hybrid vehicle comprises the steps of:
(i) providing an engine 45 as a mechanical power source;

(ii) providing a pulley 12 that is attached on one end of the first rotating shaft 61 that provides a means for mechanical coupling and regulation of mechanical power into and from the engine 45;
(iii) providing a tandem starter-generator system having a first motor-generator assembly 70 that includes a first stator assembly 20 surrounding a first rotor 60 attached to a first shaft 61 that rotates about its axis; a second motor-generator assembly 80 that includes a second stator assembly 30 surrounding a second rotor 50 attached to a second shaft 51 that rotates about its axis; a power transmission unit having a dual spline-type coupling arrangement for mechanical coupling to the first and second shafts 61, 51 that is axially disposed adjacent to the first and second motor-generator assemblies 70, 80, where it provides a means to configure the appropriate input-to-output speed and torque relationships with respect to the rotational speed and torque at the pulley 12 for the transmission of mechanical power between the first and second shafts 61, 51 of the motor-generators 70, 80; and
(iv) providing a supervisory controller module 15 that controls a first power converter and controller 13 a, a second power converter and controller 13 b and a third power converter and controller 13 c as well as provides overall power management, control and protection functions to ensure the first and second motor-generators 70, 80 operate in the proper regions and modes, as well as regulate the conversion of electrical power and mechanical power between electrical energy storage and mechanical power sources;
wherein the first power converter and controller 13 a drives and controls the first motor-generator 70, second power converter and controller 13 b drives and controls the second motor-generator 80 and third power converter and controller 13 c provides ac to dc power conversion of the electrical power from the second motor-generator 80 to power auxiliary load devices,
(v) providing a high voltage electric energy storage source of a dual voltage electrical system of the hybrid vehicle that discharges electrical power in accordance with the vehicle driving conditions to drive both motor-generators 70, 80 during power assist driving modes, and it is charged with electrical power generated by the two motor-generators 70, 80 during regenerative braking modes; and (vi) providing a low voltage electric energy storage source of a dual voltage system of

the hybrid vehicle that discharges electrical power to support auxiliary loads and essential
low power functions of the vehicle, and it is being charged continuously by the electrical
power generated by the second motor-generator 80;
(vii) providing a concrete procedure to determine the appropriate driving modes of the
hybrid vehicle based on various data from the vehicle pedal sensors and engine control
unit 45; and
(viii) driving and controlling the tandem starter-generator to output electrical power and
mechanical power in accordance with the driving conditions of the hybrid vehicle.
18) The method as claimed in claim 17, wherein
the first motor-generator assembly 70 is an asynchronous type induction machine having a stator assembly 20 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a squirrel-cage rotor assembly 60 mounted onto the first shaft 61 that includes a skewed stack of laminations having multiple axially extending circumferentially arranged slots and having a plurality of conductive damper bars inserted and connected on both ends of the rotor by conductive end-rings; and
the second motor-generator assembly 80 is a synchronous type permanent magnet machine having a stator assembly 30 comprising a laminated stack having multiple axially extending circumferentially arranged slots and having coils wound therein to form a multiphase winding, and a permanent magnet rotor assembly 50 mounted onto the second shaft 51 and includes a stack of laminations or solid piece hub having a plurality of permanent magnets that is mounted on its surface or embedded into axially extending circumferentially arranged slots.