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3.3.2. Twists (Part 2 of 2)

This video introduces the 6×6 adjoint representation of a 4×4 SE(3) transformation matrix and shows how it can be used to change the frame of reference of a twist or a screw. The 4×4 se(3) matrix representation of a 6-vector twist is also introduced. This se(3) representation is used in the matrix exponential in the

3.3.3. Exponential Coordinates of Rigid-Body Motion

Any rigid-body transformation can be achieved from any other by following some 6-vector twist for unit time. The six coordinates of this twist are called the exponential coordinates. This video shows how the rigid-body transformation can be calculated using a matrix exponential with the se(3) matrix representation of the exponential coordinates. The matrix exponential maps

3.4. Wrenches

This video introduces the wrench 6-vector representation of forces and moments in three-dimensions, and it shows how to change the frame of representation of a wrench.

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Velocity Kinematics and Statics

This video introduces the Jacobian of a robot, and how it is used to relate joint velocities to end-effector velocities and endpoint forces to joint forces and torques. The notions of singularities, manipulability, the manipulability ellipsoid, and the force ellipsoid are also introduced.

5.1.1. Space Jacobian

This video introduces the space Jacobian, the Jacobian relating joint velocities to the end-effector twist expressed in the space frame.

5.1.2. Body Jacobian

This video introduces the body Jacobian, the Jacobian relating joint velocities to the end-effector twist expressed in the body frame (a frame at the end-effector).

5.3. Singularities

This video discusses robot singularities and Jacobians where the number of joints is not equal to the number of components of the end-effector twist or velocity, resulting in “tall” (“kinematically deficient”) and “fat” Jacobians.

5.4. Manipulability

This video describes the visualization of a robot’s ease of moving in different directions in terms of a manipulability ellipsoid, as well as scalar measures of the manipulability. Analogous ideas are presented describing the robot’s ability to apply wrenches as its end-effector.

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Inverse Kinematics of Open Chains

This video introduces the inverse kinematics problem–finding a set of joint positions that yield a desired end-effector configuration–as well as two ways of solving the problem: analytically and by an iterative numerical method.

6.2. Numerical Inverse Kinematics (Part 1 of 2)

This video introduces the Newton-Raphson root-finding method for numerical inverse kinematics. The end-effector configuration is represented by a minimum set of coordinates. Representation of the end-effector configuration as a transformation matrix is covered in the next video.

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Kinematics of Closed Chains

This video takes an example-based approach to the kinematics of closed chains, particularly parallel robots, including forward kinematics, inverse kinematics, inverse velocity kinematics, and statics.