Encoder for a rotary motor

1. A vibration isolation system for isolating a suspended platform from a base subject to a vibration input comprising:

an exoskeleton for supporting the suspended platform relative to the base over a range of travel; a rotary motor to generate a force for isolating the suspended platform from the base, the rotary motor having an encoder comprising a magnetic disk encoded with a first set of magnetic transitions and a second set of magnetic transitions, each magnetic transition including a pair of opposite magnetic poles disposed adjacent to one another,

wherein the first set of magnetic transitions is disposed in a substantially circular arrangement having a first radius with respect to the center of the magnetic disk,

wherein angular distances between consecutive transitions in the first set of magnetic transitions are non-uniform,

the second set of magnetic transitions is disposed in a substantially circular arrangement having a second radius with respect to the center of the magnetic disk, the second radius being lesser than the first radius,

and a first number of magnetic transitions in the first set of magnetic transitions is lesser than a second number of magnetic transitions in the second set of magnetic transitions, such that the first set of magnetic transitions represents regions on the magnetic disk, and the second set of magnetic transitions represents locations on the magnetic disk within each of the regions represented by the first set of magnetic transitions; and

wherein the first and second set of magnetic transitions together represent absolute positions of the rotary motor; and

a drive mechanism separate from the exoskeleton for applying the force from the rotary motor between the suspended platform and the base.

2. The vibration isolation system of claim 1 , wherein the rotary motor further comprises:

a first sensor to detect a region based on the first set of magnetic transitions;

a second sensor to detect a location within the region detected by the first sensor based on the second set of magnetic transitions; and

a decoder to identify an absolute location on the magnetic disk based on the region detected by the first sensor and the location detected by the second sensors.

3. The vibration isolation system of claim 2 , wherein, absent rotation of the magnetic disk, the first sensor detects the region and the second sensor detects the location.

4. The vibration isolation system of claim 2 , wherein the first set of magnetic transitions comprises the first number of pairs of opposite magnetic poles disposed in an asymmetric pattern disposed in the substantially circular arrangement having the first radius, the first number corresponding to the number of uniquely identifiable regions on the magnetic disk.

5. The vibration isolation system of claim 4 , wherein identifying the absolute location comprises:

determining a threshold value based on the region detected by the first sensor and a tolerance relative to that region;

comparing the second number to the threshold; and

determining the absolute location based on the comparing.

6. The vibration isolation system of claim 5 , wherein there is a partial overlap between a portion of an output of the second sensor and a portion of an output of the first sensor identifying a particular region based on the first set of magnetic transitions; and

wherein the tolerance is based on an amount of the overlap.

7. The vibration isolation system of claim 1 , wherein the rotary motor is offset to a side of the vibration isolation system base and the drive mechanism is arranged to drive the suspended platform at or near the center of gravity of the suspended platform.

8. The vibration isolation system of claim 1 wherein the rotary motor is inertially coupled to the exoskeleton at a point intermediate between a connection of the exoskeleton to the suspended platform and the connection of the exoskeleton to the base.

9. The vibration isolation system of claim 1 , wherein the first set of magnetic transitions is disposed substantially along an outer circumference of the magnetic disk.

10. The vibration isolation system of claim 1 , wherein the rotary motor is a direct current (DC) rotating motor.

11. The vibration isolation system of claim 1 , wherein the rotary motor is an alternating current (AC) rotating motor.

12. The vibration isolation system of claim 1 , further comprising one or more sensors coupled to the rotary motor, the one or more sensors configured to provide input data based on which the rotary motor generates the force.

13. The vibration isolation system of claim 12 , further comprising a digital controller disposed between the one or more sensors and the rotary motor, the digital controller configured to generate one or more control signals based on information received from the one or more sensors, the one or more control signals configured to cause the rotary motor to generate the force.

14. The vibration isolation system of claim 1 , wherein the first set of magnetic transitions is disposed in the substantially circular arrangement in accordance with a Gray code.

15. The vibration isolation system of claim 2 , wherein the first sensor is a Hall effect sensor.

16. The vibration isolation system of claim 2 , wherein the first sensor is a part of an array of sensors configured to detect the region based on the first set of magnetic transitions.

17. The vibration isolation system of claim 2 , wherein the second sensor is a line array sensor.