Payload-to-Weight Ratio

A robot's rated payload divided by its own weight; higher means lighter and stronger for its size.

Payload-to-weight ratio is the rated payload divided by the weight of the robot itself (usually meaning a robot arm, or the whole machine), used to gauge whether a design is light and its actuation strong. Some sources flip the ratio and report weight-to-payload instead, so it's worth checking which way a number is written. The ratio is shaped jointly by motor torque density, the reducer, and structural materials: improving it means using higher-power-density joints and lightweight materials like magnesium alloy or carbon fiber. For an arm bolted to a table, this ratio mainly affects mounting and cost; it matters even more for a humanoid, a quadruped, or an arm mounted on a mobile base, because every extra kilogram on the arm is a kilogram the legs, base, and battery all have to carry too, which shortens battery life. When comparing numbers, also check whether a manufacturer's figure is rated or peak payload, and at what reach and speed it was measured.

ExampleA collaborative arm weighing 20 kg with a 5 kg rated payload has a payload-to-weight ratio of 1:4.

Also called

Weight-to-Payload Ratio

Related

Payload · Torque Density · Lightweighting (Magnesium Alloy / Carbon Fiber) · Robotic Arm · Collaborative Robot · Power Density (W/kg)

Sources

UR5e - Universal Robots