CRE CRE Robot Kinematics & Mechanics 1 — Questions and Answers
Question 1: What does forward kinematics calculate in a robot arm?
- Joint torques from end-effector forces
- End-effector position and orientation from joint angles (Correct answer)
- Joint angles from a desired end-effector position
- Robot workspace boundaries
Correct answer: End-effector position and orientation from joint angles
Forward kinematics computes the end-effector position and orientation given the joint angles of the robot.
Question 2: How many parameters does the Denavit-Hartenberg (DH) convention use to describe each joint?
- 2
- 3
- 4 (Correct answer)
- 6
Correct answer: 4
The DH convention uses four parameters (a, d, alpha, theta) to describe the geometric relationship between consecutive joint frames.
Question 3: Which joint type allows only rotational motion about a single axis?
- Prismatic
- Revolute (Correct answer)
- Spherical
- Screw
Correct answer: Revolute
A revolute joint permits rotation about a single fixed axis and contributes one rotational degree of freedom.
Question 4: In robotics, the Jacobian matrix relates:
- Joint positions to link lengths
- Joint velocities to end-effector linear and angular velocities (Correct answer)
- Torques to joint positions
- Link masses to rotational inertia
Correct answer: Joint velocities to end-effector linear and angular velocities
The Jacobian maps the joint velocity vector to the resulting end-effector linear and angular velocity vector.
Question 5: The workspace of a robot arm is defined as:
- The maximum payload the robot can carry
- The set of all positions and orientations reachable by the end-effector (Correct answer)
- The software control environment
- The floor area occupied by the robot cell
Correct answer: The set of all positions and orientations reachable by the end-effector
The workspace is the collection of all end-effector positions and orientations achievable given the robot's joint limits and geometry.
Question 6: Robot kinematic singularities occur when:
- The robot exceeds its rated speed
- The Jacobian matrix loses rank, causing loss of mobility in certain directions (Correct answer)
- A joint encoder loses calibration
- The robot arm contacts an obstacle
Correct answer: The Jacobian matrix loses rank, causing loss of mobility in certain directions
Singularities arise when the Jacobian becomes rank-deficient, making it impossible to move the end-effector in one or more Cartesian directions.
CRE CRE Robot Kinematics & Mechanics 1
What does forward kinematics calculate in a robot arm?