Engineering glossary
Quick definitions for mechanical design, manufacturing, electrical integration, and testing terms.
Engineering terms describe different physical relationships. Use the definitions with a sketch, units, or an example from the robot whenever a team decision depends on their meaning.
Motion and power
| Term | Meaning |
|---|---|
| Torque | Turning effect of a force about an axis; for a perpendicular force, |
| Power | Rate of energy transfer; rotational mechanical power is |
| Reduction | Here, input speed divided by output speed; a value above one lowers output speed |
| Free speed | Motor speed with very little external load at a stated supply voltage |
| Stall torque | Motor torque at zero speed; a high-current endpoint, not a continuous operating rating |
| Duty cycle | The pattern or fraction of time a device spends operating under stated conditions |
| Backdriving | An external output load causing the transmission or actuator input to move |
| Inertia | Resistance to a change in motion; rotational inertia depends on how mass is distributed about an axis |
| Backlash | Clearance that allows output movement when transmission direction reverses |
Use motors and gearing for ratio conventions and arms for gravity and acceleration loads.
Structure and moving assemblies
| Term | Meaning |
|---|---|
| Load path | Route through which forces pass from their application to the supports |
| Strength | Resistance to yielding or other failure under load |
| Stiffness | Resistance to deflection under load |
| Compliance | Deformation under load; sometimes deliberately used to accommodate variation |
| Preload | Force introduced during assembly, such as a screw's initial clamping force |
| Cantilever | Member supported at one end, carrying load away from that support |
| Radial load | Load perpendicular to a shaft or bearing axis |
| Axial load | Load parallel to that axis |
| Live axle | Rotating axle that transmits torque to attached components |
| Dead axle | Fixed axle around which supported components rotate |
| Racking | Skewing caused by uneven movement or alignment, often in parallel slides |
| Capture envelope | Range of object positions and orientations a mechanism can acquire under stated conditions |
See structure and fasteners, shafts and bearings, and intakes for applications.
Design and manufacturing
| Term | Meaning |
|---|---|
| Constraint | Requirement a feasible design must satisfy |
| Datum | Reference used to locate geometry or define measurements |
| Nominal dimension | Stated target size before its allowed variation is considered |
| Tolerance | Permitted dimensional variation |
| Clearance fit | Fit with a gap between mating features over the specified limits |
| Interference fit | Fit in which assembly relies on dimensional interference between mating features |
| Tolerance stack | Combined variation of dimensions affecting one functional relationship |
| Kerf | Width of material removed during a cutting operation |
| Anisotropy | Dependence of a material or manufactured part's properties on direction |
| Creep | Time-dependent deformation under sustained stress |
| Bill of materials | Controlled list of parts, quantities, and identifying specifications |
| Revision | Identified state of a design, part, document, or configuration |
Use CAD and fits and tolerances for worked examples.
Electrical and verification
| Term | Meaning |
|---|---|
| Strain relief | Mechanical support that prevents cable forces reaching a terminal or connector |
| Voltage sag | Drop in supply voltage under load |
| ESD | Electrostatic discharge, a transfer of accumulated electric charge |
| Calibration | Establishing a measurement or command relationship against a reference |
| Homing | Establishing a known reference position for a mechanism |
| Acceptance criterion | Observable condition used to decide whether a test passes |
| Failure mode | Specific way a part or process can fail to perform its intended function |
| Recovery | Defined action that returns a failed or uncertain task to an understood state |