Backlash
The amount of free play between mating mechanical components (typically gear teeth) that must be taken up before torque is transmitted from one side to the other. In a gear drive with backlash, commanding a reversal of direction results in no motion until the backlash gap is closed, then sudden motion. Backlash introduces nonlinearity and dead zones that degrade position control accuracy and that state estimators must explicitly account for to avoid predicting motion that is not occurring.
Defined in 2 GAGE programs, which carry 8 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 amount of free play between mating mechanical components (typically gear teeth) that must be taken up before torque is transmitted from one side to the other. In a gear drive with backlash, commanding a reversal of direction results in no motion until the backlash gap is closed, then sudden motion. Backlash introduces nonlinearity and dead zones that degrade position control accuracy and that state estimators must explicitly account for to avoid predicting motion that is not occurring.
The small amount of free play or slack in a gear train or mechanical linkage, which shows up as position error at the output. Backlash occurring earlier in a multi-stage gear train is amplified by more of the total reduction than backlash occurring later, and preloaded or anti-backlash gearing can reduce the resulting position error below what the raw reduction ratio alone would suggest.
The mechanical dead zone in a gear train caused by clearance between gear teeth. During direction reversal, the motor rotates through the backlash angle without moving the output shaft. Backlash limits achievable position accuracy and can cause oscillation in a closed-loop system attempting to correct errors smaller than the backlash.
The angular dead-band between input and output motion in a gear mesh. When the drive direction reverses, the input rotates through the backlash angle before the output begins to move. At the joint tip, backlash produces a position error equal to the backlash angle (in radians) times the distance from joint to tip.
The amount of output motion that occurs with no corresponding input motion, due to clearance between meshing surfaces in a transmission (gear teeth gaps, belt-to-pulley tooth play, chain pin clearance). Backlash causes a dead zone on direction reversal and leads to position error and chatter in closed-loop control systems.
Where it is taught
The exact lessons this term appears in. The first module of every program is free with a free account.
- Why robotics is hard: the world is noisy, partial, and unforgiving · What a Robot Actually Is, Foundations of Robotics and Physical AI
- Servo motors and closed-loop position control · Actuators and Mechanisms, Foundations of Robotics and Physical AI
- Gear ratios and the torque versus speed tradeoff · Actuators and Mechanisms, Foundations of Robotics and Physical AI
- Mechanisms: linkages, belts, and drivetrains · Actuators and Mechanisms, Foundations of Robotics and Physical AI
- Tendons, cables, and compliance · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- Mechanical advantage and load paths · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- Designing motion in rather than computing it · Mechanical Intelligence, the Art of Removing Motors, Engineering Judgment and Professional Formation
- The sim-to-real gap: why it works in Gazebo and fails on the floor · Failure Analysis, Learning From How Robots Break, Engineering Judgment and Professional Formation
Where it shows up at work
A definition is where Backlash starts. The lessons above teach it inside the competencies below, which are what job descriptions ask for and what the GAGE credential records. Every link here is drawn from the same careers map that builds a role's readiness check.
Understands AI that acts in the physical world: perception stacks, vision language action models, sim to real transfer, sensor fusion, and where each of them fails.
2 lessons on this page teach it as a primary outcome.
Roles that hire for it
Each role page shows the full competency set, what the seat decides, and a readiness check against your own evidence.
- Robotics AI Engineer, embodied systems editionneeds it at depth
- Physical AI Safety Engineer, autonomous systems editionneeds working knowledge
How job descriptions say it
Postings rarely use the textbook word. These are the phrases the careers map reads as asking for the competencies above.
One interview question about it
A perception model that scores well in simulation fails on the warehouse floor. Walk me through how you find out why.
Asked of candidates for embodied ai and robotics systems. Answering it in your own words is exactly how a GAGE topic is passed, and the credential records the pass where an employer can check it.
Terms it appears with
Not an alphabetical neighbourhood: these are the terms taught in the same lessons, ranked by how often they appear together.