Direct Drive

A motor connected straight to the joint or load, with no gearbox or other transmission in between.

Direct drive means a motor's output shaft connects straight to the load, with no gears, gearbox, belt, or other transmission stage in between — a reduction ratio of 1. The benefits are no backlash (the play between gear teeth), low friction, and good backdrivability (an external force can easily push the joint), plus torque can be estimated directly from motor current, giving high control bandwidth and smooth, compliant motion. The downside is that the motor alone has to produce all the torque, so it has to be large and heavy, which strains torque density and generates more heat. Fully direct-drive designs in robots show up mainly in rotary tables, some robot-arm joints, and certain dexterous-hand designs; legged robots more often use the compromise of quasi-direct drive (a planetary gearbox with a small reduction ratio), which balances torque against compliance.

ExampleA fully direct-drive dexterous hand places a motor directly at each finger joint, with no tendon or linkage transmission in between.

Also called

DD Motor

Related

Quasi-Direct Drive · Backdrivability · Backlash · Gear Ratio · Fully Direct-Drive Dexterous Hand · Frameless Torque Motor

Sources

Direct drive mechanism - Wikipedia