Robot actuator utilizing a differential pulley transmission
An example robot actuator utilizing a differential pulley transmission is provided. As an example, a differential pulley actuator includes input drive gears for coupling to a motor and timing pulleys coupled together through the input drive gears. Rotation of the input drive gears causes rotation of a first timing pulley in a first direction and rotation of a second timing pulley in a second direction opposite the first direction. The actuator also includes multiple idler pulleys suspended between the timing pulleys and the output pulley, and the multiple idler pulleys are held in tension between the timing pulleys via a first tension-bearing element and the output pulley via a second tension-bearing element. The first tension-bearing element loops around the timing pulleys and the multiple idler pulleys. The output pulley couple to a load, and is configured to apply motion of the multiple idler pulleys to the load.
1. A differential pulley actuator comprising:
an input drive gear for coupling to a motor, wherein the input drive gear couples rotation of the motor to rotation of an output pulley;
a first timing belt pulley pair and a second timing belt pulley pair coupled to the input drive gear, wherein rotation of the input drive gear causes rotation of the first timing belt pulley pair and the second timing belt pulley pair;
a first idler pulley element suspended between the first timing belt pulley pair and the output pulley and held in tension to the first timing belt pulley pair via a first tension-bearing element and to the output pulley via a second tension-bearing element;
a second idler pulley element suspended between the second timing belt pulley pair and the output pulley and held in tension to the second timing belt pulley pair via a third tension-bearing element and to the output pulley via the second tension-bearing element; and
the output pulley for coupling to a load, wherein the output pulley couples to the first idler pulley element and the second idler pulley element via the second tension-bearing element looping around the output pulley and is configured to apply motion of the first idler pulley element and the second idler pulley element to the load.
2. The differential pulley actuator of claim 1 , wherein:
rotation of the first timing belt pulley pair causes the first tension-bearing element to wind onto a first pulley of the first timing belt pulley pair and unwind from a second pulley of the first timing belt pulley pair; and
rotation of the second timing belt pulley pair causes the third tension-bearing element to wind onto a first pulley of the second timing belt pulley pair and unwind from a second pulley of the second timing belt pulley pair.
3. The differential pulley actuator of claim 1 , wherein:
rotation of the first timing belt pulley pair and the second timing belt pulley pair causes movement of the first idler pulley element and the second idler pulley element toward and away from the output pulley resulting in the second tension-bearing element being pulled to rotate the output pulley.
4. The differential pulley actuator of claim 1 , wherein the first timing belt pulley pair couples to the input drive gear and the second timing belt pulley pair couples to the first timing belt pulley pair such that the first timing belt pulley pair and the second timing belt pulley pair are coupled in serial in a stacked configuration.
5. The differential pulley actuator of claim 1 , wherein the input drive gear and the output pulley are provided in a configuration to each rotate about respective axes, wherein the respective axes are perpendicular.
6. The differential pulley actuator of claim 1 , wherein the first idler pulley element comprises:
a frame coupled to the second tension-bearing element; and
multiple pulleys coupled to the frame, wherein the first tension-bearing element loops around the multiple pulleys.
7. The differential pulley actuator of claim 1 , wherein the first timing belt pulley pair and the second timing belt pulley pair provide a differential gear-ratio between the motor and the first timing belt pulley pair and the second timing belt pulley pair.
8. 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.
9. The differential pulley actuator of claim 1 , wherein the first timing belt pulley pair and the second timing belt pulley pair include teeth, and wherein the first tension-bearing element comprises a toothed belt that interlocks to the teeth of the first timing belt pulley pair and the second timing belt pulley pair.
10. 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.
11. 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.
12. A differential pulley actuator comprising:
a first input drive gear for coupling to a motor, wherein the first input drive gear couples rotation of the motor to rotation of an output pulley;
a first timing belt pulley pair coupled to the first input drive gear, wherein rotation of the first input drive gear causes rotation of the first timing belt pulley pair;
a first idler pulley element suspended between the first timing belt pulley pair and the output pulley and held in tension to the first timing belt pulley pair via a first tension-bearing element and to the output pulley via a second tension-bearing element;
a second input drive gear for coupling to the motor, wherein the second input drive gear couples rotation of the motor to rotation of the output pulley;
a second timing belt pulley pair coupled to the second input drive gear, wherein rotation of the second input drive gear causes rotation of the second timing belt pulley pair;
a second idler pulley element suspended between the second timing belt pulley pair and the output pulley and held in tension to the second timing belt pulley pair via a third tension-bearing element and to the output pulley via the second tension-bearing element; and
the output pulley for coupling to a load, wherein the output pulley couples to the first idler pulley element and the second idler pulley element via the second tension-bearing element looping around the output pulley and is configured to apply motion of the first idler pulley element and the second idler pulley element to the load.
13. The differential pulley actuator of claim 12 , further comprising:
a motor; and
wherein the first timing belt pulley pair and the second timing belt pulley pair are positioned in a side by side configuration, and the motor is positioned between the first timing belt pulley pair and the second timing belt pulley pair.
14. The differential pulley actuator of claim 12 , wherein:
rotation of the first timing belt pulley pair causes the first tension-bearing element to wind onto a first pulley of the first timing belt pulley pair and unwind from a second pulley of the first timing belt pulley pair; and
rotation of the second timing belt pulley pair causes the third tension-bearing element to wind onto a first pulley of the second timing belt pulley pair and unwind from a second pulley of the second timing belt pulley pair.
15. The differential pulley actuator of claim 12 , wherein:
rotation of the first timing belt pulley pair and the second timing belt pulley pair causes movement of the first idler pulley element and the second idler pulley element toward and away from the output pulley resulting in the second tension-bearing element being pulled to rotate the output pulley.
16. The differential pulley actuator of claim 12 , wherein the first input drive gear, the second input drive gear, and the output pulley are provided in a configuration to each rotate about respective axes, wherein the respective axes are parallel.
17. The differential pulley actuator of claim 12 , wherein the first tension-bearing element and the second tension-bearing element comprise one of a belt, a chain, or a cable.
18. The differential pulley actuator of claim 12 , 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.
19. The differential pulley actuator of claim 12 , 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.
20. The differential pulley actuator of claim 12 , wherein the first timing belt pulley pair and the second timing belt pulley pair provide a differential gear-ratio between the motor and the first timing belt pulley pair and the second timing belt pulley pair.