Dual actuating variable cam

1. A variable camshaft timing system, comprising:

a first camshaft phaser having an input that is configured to receive rotational force from a crankshaft and an output that is configured to link with a first camshaft of a concentric camshaft assembly to change an angular position of the first camshaft relative to the crankshaft;

a second camshaft phaser having an output that is configured to link with a second camshaft of the concentric camshaft assembly to change an angular position of the second camshaft relative to the crankshaft, wherein the first camshaft is concentrically positioned relative to the second camshaft and the first camshaft phaser is mechanically linked to the second camshaft phaser to communicate rotational force from the crankshaft to the second camshaft phaser through the first camshaft phaser; and

a dual-output electric motor comprising a first rotor and a second rotor, wherein the first camshaft phaser is coupled to the first rotor and the second camshaft phaser is coupled to the second rotor.

2. The variable camshaft timing system recited in claim 1 , further comprising a flex plate that couples the first camshaft phaser to the second camshaft phaser.

3. The variable camshaft timing system recited in claim 1 , wherein the first camshaft phaser is hydraulically-actuated and the second camshaft phaser is electrically-actuated.

4. The variable camshaft timing system recited in claim 3 , wherein the first camshaft phaser and the second camshaft phaser rotate about a common axis.

5. The variable camshaft timing system recited in claim 1 , wherein the dual-output electric motor comprises concentric output shafts.

6. The variable camshaft timing system recited in claim 1 , wherein the first camshaft phaser, the second camshaft phaser, or both include one or more planetary gears engaging a sun gear, a ring gear, and a sprocket gear.

7. The variable camshaft timing system recited in claim 1 , wherein the first camshaft phaser, the second camshaft phaser, or both include a first eccentric shaft, a second eccentric shaft, and a compound planetary gear.

8. A variable camshaft timing system, comprising:

a first electrically-actuated camshaft phaser having an output that is configured to couple with a first camshaft of a concentric camshaft assembly and change an angular position of the first camshaft relative to a crankshaft using at least one planetary gear;

a second electrically-actuated camshaft phaser having an output that is configured to couple with a second camshaft of the concentric camshaft assembly and change an angular position of the second camshaft relative to the crankshaft using at least one planetary gear, wherein the second camshaft is concentrically positioned to the first camshaft;

a housing, configured to receive rotational force from the crankshaft, having a ring gear that engages the planetary gear(s) of the first electrically-actuated camshaft phaser and the planetary gear(s) of the second electrically-actuated camshaft phaser, wherein the first electrically-actuated camshaft phaser, the second electrically-actuated camshaft phaser, the first camshaft, the second camshaft, and the housing rotate about a common axis.

9. The variable camshaft timing system recited in claim 8 , further comprising a dual-output electric motor comprising a first rotor and a second rotor, wherein the first electrically-actuated camshaft phaser is coupled to the first rotor and the second electrically-actuated camshaft phaser is coupled to the second rotor.

10. The variable camshaft timing system recited in claim 9 , wherein the dual-output electric motor comprises concentric output shafts.

11. The variable camshaft timing system recited in claim 8 , wherein the first electrically-actuated camshaft phaser comprises a first sun gear engaging the planetary gear(s) of the first electrically-actuated camshaft phaser and a second sun gear engaging the planetary gear(s) of the second electrically-actuated camshaft phaser.

12. The variable camshaft timing system recited in claim 8 , further comprising a first eccentric shaft, a second eccentric shaft, a first compound planetary gear, and a second compound planetary gear.