Robot actuator utilizing a differential pulley transmission

1. A differential pulley actuator comprising:

one or more input drive gears for coupling to a motor, wherein the one or more input drive gears couple rotation of the motor to rotation of an output pulley;

one or more timing belt pulleys coupled together through the one or more input drive gears, wherein rotation of the one or more input drive gears causes rotation of a first timing belt pulley in a first direction and rotation of a second timing belt pulley in a second direction opposite the first direction, wherein the one or more timing belt pulleys include multiple timing belt pulleys arranged within a plane lengthwise along the differential pulley actuator toward the output pulley;

multiple idler pulleys suspended between the one or more timing belt pulleys and the output pulley and arranged within the plane lengthwise along the differential pulley actuator toward the output pulley, wherein the multiple idler pulleys are held in tension between the one or more timing belt pulleys via a first tension-bearing element and the output pulley via a second tension-bearing element, wherein the first tension-bearing element loops around the one or more timing belt pulleys and the multiple idler pulleys, such that the first tension-bearing element has a first loop around a first timing belt pulley and a second loop around a second timing belt pulley, wherein the first loop and the second loop are arranged within the plane lengthwise along the differential pulley actuator toward the output pulley; and

the output pulley for coupling to a load, wherein the output pulley couples to the multiple idler pulleys via the second tension-bearing element looping around the output pulley and is configured to apply motion of the multiple idler pulleys to the load.

2. The differential pulley actuator of claim 1 , wherein the first tension-bearing element creates a pull-pull linear motion between the multiple idler pulleys based on rotation of the motor.

3. The differential pulley actuator of claim 1 , wherein the first tension-bearing element causes movement of the multiple idler pulleys due to rotation of the one or more timing belt pulleys, and wherein the movement of the multiple idler pulleys causes rotation of the output pulley through pulling of the second tension-bearing element by one of the multiple idler pulleys.

4. The differential pulley actuator of claim 1 , wherein the first tension-bearing element causes movement of the multiple idler pulleys due to rotation of the one or more timing belt pulleys, and wherein the movement of the multiple idler pulleys includes one idler pulley moving toward the output pulley and one idler pulley moving away from the output pulley.

5. The differential pulley actuator of claim 1 , wherein the one or more timing belt pulleys provide a differential gear-ratio between the motor and the one or more timing belt pulleys.

6. The differential pulley actuator of claim 1 , wherein the first tension-bearing element comprises a continuous loop element.

7. The differential pulley actuator of claim 1 , wherein the first tension-bearing element and the second tension-bearing element comprise one of a belt, a chain, or a cable.

8. The differential pulley actuator of claim 1 , wherein the one or more timing belt pulleys include teeth, and wherein the first tension-bearing element comprises a toothed belt that interlocks to the teeth of the one or more timing belt pulleys.

9. The differential pulley actuator of claim 1 , wherein the one or more timing belt pulleys are threaded, and wherein the first tension-bearing element comprises a cable that wraps around the one or more timing belt pulleys into threads to cause rotation of the output pulley in a first direction and unwraps from the one or more timing belt pulleys to cause rotation of the output pulley in a second direction.

10. The differential pulley actuator of claim 1 , wherein the one or more input drive gears comprise a first input drive gear and a second input drive gear, and wherein:

the first timing belt pulley is coupled to the first input drive gear;

the second timing belt pulley is coupled to the second input drive gear and has a smaller radius than the first timing belt pulley, and

wherein a difference in rotation speed between the first timing belt pulley and the second timing belt pulley creates a pull in a direction on one of the multiple idlers to pull the second tension-bearing element and drive the output pulley.

11. The differential pulley actuator of claim 1 , wherein the one or more input drive gears and the one or more timing belt pulleys are mounted to a frame.

12. The differential pulley actuator of claim 1 , further comprising the motor with a motor pinion gear coupled to the one or more drive gears for causing rotation of the one or more drive gears.

13. The differential pulley actuator of claim 1 , further comprising:

a motor; and

a motor encoder coupled to the motor to determine a position of the motor and enable a control loop to control position of the output pulley.

14. The differential pulley actuator of claim 1 , further comprising

a motor;

a force sensor coupled to the output pulley; and

a processor to control an input to the motor based on an output from the force sensor.