CRE Power Systems & Actuators 2

Question 1

A stepper motor is specified as 1.8° per step. How many steps are required to complete one full 360° revolution?

Accepted Answer

200 steps

Answer

360° ÷ 1.8°/step = 200 steps per revolution; this is the standard step count for a 1.8° stepper motor in full-step mode.

Question 2

What is the primary advantage of using PWM (Pulse Width Modulation) to control a DC motor's speed compared to varying supply voltage directly?

Accepted Answer

PWM allows precise speed control with high efficiency by rapidly switching full voltage on and off

Answer

PWM controls average power delivery by rapidly switching full supply voltage on and off at varying duty cycles, maintaining high efficiency because the switching transistor dissipates minimal power compared to linear voltage reduction.

Question 3

In a robotic power system, what is the purpose of an H-bridge circuit?

Accepted Answer

Allow bidirectional control of a DC motor using four switching transistors

Answer

An H-bridge uses four transistors arranged in an 'H' pattern; by selecting which pair conducts, current direction through the motor can be reversed, enabling forward and reverse rotation control.

Question 4

Which type of hydraulic pump is most commonly used in industrial robot power units due to its consistent flow rate and ability to maintain pressure against varying loads?

Accepted Answer

Axial piston pump

Answer

Axial piston pumps are preferred in industrial hydraulic robot systems for their high efficiency, variable displacement capability, and ability to maintain consistent high pressure against varying actuator loads.

Question 5

What is the function of a flyback diode (freewheeling diode) placed across a DC motor's terminals in a motor drive circuit?

Accepted Answer

Protect the motor driver from voltage spikes caused by the motor's inductive kickback when power is cut

Answer

When motor power is switched off, the motor's inductance causes a voltage spike (kickback); the flyback diode provides a safe current path to dissipate this energy and protect the switching transistors.

CRE - Certified Robotics Engineer Practice Test

CRE - Certified Robotics Engineer Practice Test

CRE Power Systems & Actuators 2