AWS DevOps Motion Control & Kinematics 4 — Questions and Answers
Question 1: What is the workspace of a robotic manipulator?
- The set of all reachable end-effector positions and orientations (Correct answer)
- The maximum joint velocity range
- The volume swept by link 1 only
- The footprint of the robot base
Correct answer: The set of all reachable end-effector positions and orientations
The workspace is the complete set of poses the end-effector can achieve given all joint-limit constraints.
Question 2: In a ball-screw linear actuator, what determines the relationship between motor rotations and linear travel?
- Gear ratio
- Lead (pitch × starts) of the screw (Correct answer)
- Motor pole count
- Encoder resolution
Correct answer: Lead (pitch × starts) of the screw
The lead defines how far the nut travels per full screw revolution, directly linking rotary to linear motion.
Question 3: Which kinematic chain type has its end-effector constrained by multiple independent legs attached to a fixed base?
- Serial (open-chain) manipulator
- Parallel manipulator (Correct answer)
- Redundant manipulator
- Tendon-driven manipulator
Correct answer: Parallel manipulator
Parallel manipulators such as the Stewart-Gough platform use multiple legs in a closed-chain arrangement for high stiffness.
Question 4: An encoder outputs 2000 pulses per revolution. If quadrature decoding is used, what is the effective resolution?
- 500 counts/rev
- 1000 counts/rev
- 2000 counts/rev
- 8000 counts/rev (Correct answer)
Correct answer: 8000 counts/rev
Quadrature decoding counts all four edges of the A/B pulse pair, multiplying the base count by 4 (2000 × 4 = 8000).
Question 5: In a PID position controller, persistent steady-state error after a constant disturbance is eliminated by which term?
- Proportional (P) term
- Derivative (D) term
- Integral (I) term (Correct answer)
- Feed-forward term
Correct answer: Integral (I) term
The integral term accumulates error over time and outputs an increasing correction until steady-state error reaches zero.
Question 6: What is the purpose of gravity compensation in a robot controller?
- To accelerate joint motion faster
- To counteract gravitational torques so the robot holds position without continuous high-gain feedback (Correct answer)
- To increase the robot's payload capacity permanently
- To calculate forward kinematics faster
Correct answer: To counteract gravitational torques so the robot holds position without continuous high-gain feedback
Gravity compensation adds a model-based feedforward torque that cancels gravitational loading on each joint.
Question 7: Which parameter describes the ratio of output speed to input speed in a gearbox used for motion control?
- Mechanical advantage
- Gear ratio (transmission ratio) (Correct answer)
- Inertia ratio
- Efficiency factor
Correct answer: Gear ratio (transmission ratio)
The gear ratio N = ω_input / ω_output and simultaneously multiplies torque by N (ignoring losses).
AWS DevOps Motion Control & Kinematics 4
What is the workspace of a robotic manipulator?