PEC EPE Mechatronics flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Laplace derivative property

For zero initial conditions the Laplace transform of a derivative is s times F of s; when f at zero is nonzero the term minus f at zero must be subtracted.

Nyquist sampling criterion

A signal must be sampled at more than twice its highest frequency component to avoid aliasing; the minimum acceptable rate is twice that frequency.

Eigenvalue stability test

A continuous-time linear system is asymptotically stable only when every eigenvalue of its state matrix has a strictly negative real part; any positive real part causes instability.

First-order time constant

In a first-order step response the time constant is the time to reach 63.2 percent of the final value; about four time constants are needed to settle within 2 percent.

Virtual short op-amp rule

With negative feedback and ideal open-loop gain, both op-amp inputs sit at almost the same voltage and draw negligible current, which gives the standard gain equations.

ADC least significant bit

For an n-bit converter the smallest resolvable step equals the full-scale voltage divided by 2 to the power n, and quantization error is half that step.

BJT active region

The base-emitter junction is forward biased near 0.7 V and the collector current equals beta times base current, making the device a current amplifier.

PWM average voltage

A pulse-width-modulated waveform of duty cycle D has an average value equal to D times the supply voltage, which allows efficient control of motors and heaters.

Gear module

Module is pitch diameter divided by tooth number; two gears mesh correctly only when they share the same module and the same standard pressure angle.

Bearing basic rating life

L10 in millions of revolutions equals the dynamic capacity C divided by equivalent load P, raised to 3 for ball and 3.33 for roller bearings.

Goodman fatigue line

The Goodman criterion compares alternating stress over endurance limit plus mean stress over ultimate strength; the sum must stay below one divided by the safety factor.

Stress concentration factor

Kt is peak local stress divided by nominal stress at a geometric discontinuity such as a hole, groove or fillet, and it falls as the fillet radius grows.

Second-order percent overshoot

Overshoot equals exp of minus pi zeta divided by the square root of one minus zeta squared, expressed as a percentage of final value for a step input.

PID action roles

Proportional action reacts to present error, integral action drives steady-state error to zero, and derivative action damps the response by reacting to the rate of change.

Phase margin meaning

Phase margin is 180 degrees plus open-loop phase at the gain crossover frequency; larger margin means a better damped, more stable closed-loop response.

Routh-Hurwitz stability test

The number of closed-loop poles in the right half plane equals sign changes in the first column of the Routh array; zero sign changes means all poles are stable.

Wheatstone bridge balance

The bridge output is zero, so the detector reads null, when the resistance ratio of the two arms on one side equals that ratio on the other side.

Seebeck thermocouple effect

A thermocouple produces a voltage proportional to the temperature difference between its hot and reference junctions, so the cold junction temperature must be known and compensated.

Four to twenty milliamp loop

Transmitters map the measured range to 4-20 mA, with 4 mA as a live zero so that a broken wire or dead transmitter is distinguishable from a genuine zero reading.

Pt100 resistance thermometer

A platinum sensor reads 100 ohms at 0 degrees Celsius and rises about 0.385 ohms per degree, giving stable, nearly linear temperature measurement over a wide range.

Denavit-Hartenberg parameters

Link length, link twist, joint offset and joint angle describe each link frame, and multiplying the four transforms gives the forward kinematics of the chain.

Jacobian singularity

At a singular configuration the Jacobian loses rank, so some end-effector motion directions become impossible and required joint velocities may grow without bound.

Planar mobility formula

For a planar mechanism, degrees of freedom equal 3 times links minus one, minus 2 per one-degree joint, minus higher pairs; the result must be positive.

Incremental encoder output

It provides A and B quadrature channels plus an index pulse, so position is counted from a datum and the axis must be homed after every power loss.

PLC scan cycle

The controller copies inputs, solves the program top to bottom against that image, then updates outputs; total scan time limits how fast it sees brief events.

On-delay timer

A TON instruction accumulates time while its input remains true and sets its done bit when the preset is reached; a false input resets the accumulator.

OPC UA protocol

A secure, platform-independent machine-to-machine standard with built-in information modelling, used to connect controllers to SCADA, MES and enterprise systems.

Safety integrity level

SIL 1 to 4 from IEC 61508 ranks the risk reduction a safety function provides; higher levels demand a lower probability of dangerous failure on demand.

CPM critical path

The critical path is the longest activity chain through the network; its duration fixes project completion and its activities carry zero total float.

Cp and Cpk indices

Cp compares specification width with six sigma of spread, while Cpk also penalises off-centre running; 1.33 is a common minimum acceptable capability.

G01 linear interpolation

G01 moves the tool along a straight line at the programmed feed rate to the target coordinates, unlike G00 rapid traverse which ignores feed rate.

Conflict of interest

A situation where financial, personal or family interests could improperly sway engineering judgement; it must be disclosed and then avoided or formally managed.