AWS DevOps Motion Control & Kinematics 5 — Questions and Answers
Question 1: In motion control, what does 'electronic gearing' allow?
- Replacing a physical gearbox with software-defined speed ratios between axes
- Increasing motor power via firmware
- Synchronizing multiple axes electronically to maintain a defined position ratio (Correct answer)
- Reducing encoder noise digitally
Correct answer: Synchronizing multiple axes electronically to maintain a defined position ratio
Electronic gearing locks a follower axis to a master axis at a programmable ratio without a mechanical connection.
Question 2: A trapezoidal velocity profile consists of which three phases?
- Ramp-up, constant velocity, ramp-down (Correct answer)
- Pulse, hold, pulse
- Accelerate, decelerate, stop
- Sine, cosine, rest
Correct answer: Ramp-up, constant velocity, ramp-down
The trapezoidal profile accelerates at a constant rate, cruises at peak speed, then decelerates symmetrically.
Question 3: What does 'backlash' refer to in a mechanical transmission?
- Elastic deformation of motor windings
- The angular gap (lost motion) between mating gear teeth when direction reverses (Correct answer)
- Resonant frequency of the drive train
- Friction torque at standstill
Correct answer: The angular gap (lost motion) between mating gear teeth when direction reverses
Backlash is the dead-band in position that occurs when drive direction reverses due to clearance between gear teeth.
Question 4: In multi-axis coordinated motion, what is 'contouring error'?
- The difference between programmed and actual path of the end-effector (Correct answer)
- The lag between master and slave encoder counts
- Velocity overshoot on a single axis
- Accumulated rounding error in floating-point math
Correct answer: The difference between programmed and actual path of the end-effector
Contouring error measures how far the actual Cartesian path deviates from the commanded path during multi-axis motion.
Question 5: Which mathematical representation is commonly used to express combined rotation and translation of a rigid body in 3D space?
- 2×2 rotation matrix
- 4×4 homogeneous transformation matrix (Correct answer)
- Quaternion only
- Euler angle triplet only
Correct answer: 4×4 homogeneous transformation matrix
A 4×4 homogeneous matrix encodes a 3×3 rotation submatrix and a 3×1 translation vector in a single compact form.
Question 6: What condition is described by the Nyquist stability criterion in a closed-loop motion control system?
- The sampling rate must exceed twice the highest signal frequency
- The open-loop frequency response must not encircle −1+0j in the complex plane for stability (Correct answer)
- The integral gain must be less than the proportional gain
- The encoder resolution must match the commanded step size
Correct answer: The open-loop frequency response must not encircle −1+0j in the complex plane for stability
The Nyquist criterion states a closed-loop system is stable if the Nyquist plot of the open-loop transfer function does not encircle the critical point −1.
Question 7: In kinematics, what distinguishes a 'prismatic' joint from a 'revolute' joint?
- A prismatic joint allows rotation; a revolute joint allows linear sliding
- A prismatic joint allows linear sliding along an axis; a revolute joint allows rotation about an axis (Correct answer)
- A prismatic joint has higher stiffness; a revolute joint has lower stiffness
- A prismatic joint connects two links at 90°; a revolute joint connects them coaxially
Correct answer: A prismatic joint allows linear sliding along an axis; a revolute joint allows rotation about an axis
Prismatic joints provide translational (sliding) motion along one axis, while revolute joints provide rotational motion about one axis.
AWS DevOps Motion Control & Kinematics 5
In motion control, what does 'electronic gearing' allow?