Gear ratio
The ratio of motor input shaft rotations to output shaft rotations. A gear ratio of N to 1 multiplies output torque by N, divides output speed by N, and multiplies reflected inertia by N squared. Catalog safety note: some vendors define gear ratio in the inverse direction (output:input rather than input:output), so a datasheet listing "ratio 1/100" or "reduction 0.01" may describe the same 100:1 reduction as a datasheet listing "ratio 100:1." Confirm the convention by checking whether the listed output speed at rated motor speed equals motor speed divided by the stated ratio; if it equals motor speed multiplied by the ratio, the convention is inverted.
Defined in 2 GAGE programs, which carry 3 distinct definitions of it. The wording above is taught in Foundations of Robotics and Physical AI.
How each discipline defines it
The same term does different work depending on who is using it. These are the definitions as each program teaches them, unedited.
The ratio of motor input shaft rotations to output shaft rotations. A gear ratio of N to 1 multiplies output torque by N, divides output speed by N, and multiplies reflected inertia by N squared. Catalog safety note: some vendors define gear ratio in the inverse direction (output:input rather than input:output), so a datasheet listing "ratio 1/100" or "reduction 0.01" may describe the same 100:1 reduction as a datasheet listing "ratio 100:1." Confirm the convention by checking whether the listed output speed at rated motor speed equals motor speed divided by the stated ratio; if it equals motor speed multiplied by the ratio, the convention is inverted.
The ratio of output gear teeth (or radius) to input gear teeth (or radius) in a gear pair, determining the torque amplification and speed reduction that gear pair produces.
The ratio of motor shaft rotations to output shaft rotations in a gearbox. A 100:1 ratio means the motor turns 100 times for each full rotation of the output shaft. High gear ratios multiply output torque by the ratio and reduce output speed by the ratio. They also reduce reflected load inertia by the square of the ratio.
Terms it appears with
Not an alphabetical neighbourhood: these are the terms taught in the same lessons, ranked by how often they appear together.