Gearbox Options

Many different gearbox styles exist that can be used in the OSRJ. Key factors to look at when selecting a gearbox are the backlash and backdriveability. For effective control, we want low values for both of those characteristics. Listed below are some options when looking at gearbox designs.

Cycloidal Gearbox

These are the most promising of the gearbox options. They provide low backlash and are not easily backdriven. The only issue is that they are hard to understand how they work at first glance. A good starting point is the Wikipedia page. A key characteristic of these gearboxes is that they can have a wide range of gear ratios in the same formfactor just by chaning the number of teeth on the outer/inner gears. I have made a model cycloidal gearbox for testing. The files I used are from otvinta3D on Thingiverse. The model would need some adjustments for use in a robot joint but it is a good conceptual starting point. An image of the 3D printed model is below.

Image will be updated later today

Harmonic Drive

These are a relative to the cycloidal gearbox. They operate in a similar way. Instead of having one or two solid lobed platters, it has a flexible geared cup that is driven internally with an elliptical disk. I think these drives are a bit stronger than a cycloidal gearbox, but they are only made by one company, Harmonic Drive. Because of this, they are expensive and fairly heavy. The weight is due to their major use in industrial applications where weight doesn’t matter as much.

Planetary Gear

Planetary gearboxes are cheap and easy to manufacture. This contributes to their prevalence everywhere. However, these gearboxes can get heavier and larger at higher ratios as more gears are needed.