Actuators & Motors

Actuators are where a robot's control intent becomes physical motion, so interviewers use this topic to probe whether you understand the electromechanical limits that bound everything upstream. Expect questions on reading torque-speed curves, the inverse relationship between torque and speed, and how a gearbox trades one for the other while introducing backlash, reflected inertia, and efficiency losses. You will frequently be asked to size a motor for a given load (lift, drive, or joint), pick between DC, BLDC, servo, and stepper given precision/power/cost constraints, and explain how drivers achieve speed and torque control via PWM and current loops. Strong candidates connect the motor equations ($\tau = K_t I$, $V = IR + K_e \omega$) to practical concerns like thermal limits, holding torque, and commutation. Weak answers treat motors as ideal torque sources and miss saturation, stall current, and gearing side effects.