Duty cycle
The fraction of an actuator's total operating time spent in a particular state, such as actively moving versus holding a fixed position, or powered on versus idle. A joint's duty cycle, specifically the fraction of time spent holding position against gravity or inertia, is a key input to Section 3G's Check 2 and to sizing any gravity-compensation solution correctly.
Defined in 2 GAGE programs, which carry 11 distinct definitions of it. The wording above is taught in Engineering Judgment and Professional Formation.
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 pattern and proportion of time a mechanism spends in each of its operating states, most relevantly for this topic the split between static holding time and active motion time, which determines whether static holding torque (favoring gravity compensation) or cyclic motion energy (favoring energy storage) is the dominant engineering concern for a given mechanism. As a rough starting guide, a joint dwelling in a static position for more than half its cycle time is usually worth analyzing for gravity compensation first; a joint with a fast, frequent absorb-then-release pattern is usually worth analyzing for energy storage first, per the five-question flow in Section 3F.
The fraction of time during one motion cycle that the actuator is under load. A 100 percent duty cycle means continuous full-load operation; a 30 percent duty cycle means the actuator operates at load for 30 percent of the cycle and is unloaded or stopped for the rest.
The percentage of one PWM period during which the signal is at logic-high. A 0% duty cycle is always low; 100% is always high; 50% is high for half the period. For a motor drive, effective voltage delivered is approximately D x VCC.
The percentage of one PWM period during which the output is active (high). A 50% duty cycle delivers half the peak voltage as average voltage to the motor.
The fraction of time an actuator can be operated at rated conditions without exceeding thermal limits, typically expressed as a percentage. A 25% duty cycle means the actuator can run at rated load for one second out of every four.
Where it is taught
The exact lessons this term appears in. The first module of every program is free with a free account.
- GPIO, PWM, and reading and driving the physical world · Electronics and Hardware Foundations, Foundations of Robotics and Physical AI
- Motor drivers and H-bridges · Electronics and Hardware Foundations, Foundations of Robotics and Physical AI
- Linear actuators, pneumatics, and hydraulics · Actuators and Mechanisms, Foundations of Robotics and Physical AI
- Choosing the right actuator for a given job · Actuators and Mechanisms, Foundations of Robotics and Physical AI
- Driving real GPIO, PWM, and motors from your code · From Code to Real Hardware, Foundations of Robotics and Physical AI
- Measuring real current draw and budgeting power · Circuits, Power, and Batteries in Practice, Foundations of Robotics and Physical AI
- The smartest robot is rarely the one with the most motors · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- Tendons, cables, and compliance · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- Gravity compensation and energy storage · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- Labor, maintenance, energy, and downtime costs · The Economics of Robots, the Business Case, Engineering Judgment and Professional Formation
Terms it appears with
Not an alphabetical neighbourhood: these are the terms taught in the same lessons, ranked by how often they appear together.