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A Model

We can use a link diagram to describe a model of the motion of the robotic arm. The Figure 1.1 represents the arm and forearm as links joined at the elbow. We will consider the two dimensional motion represented by Figure 1.1.

  
Figure 1.1: Robotic Arm

The X-Y position of the shoulder joint is fixed. The top endpoint of the arm link is attached at the shoulder joint. The arm can rotate around the shoulder joint. The arm must always be attached to the shoulder. The forearm link is connected to the arm link, and the hand link would be connected to the arm link.

We represent the movement of the robotic arm by the coordinates of the joints in the X-Y plane. The motion of the arm is determined by the angle, alpha, that the arm makes with the body, by the angle, beta, that the forearm makes with the arm, and by the lengths of the links. The lengths of the segments are shown in the link diagram.

The angle alpha will be measured in degrees counterclockwise from the positive Y axis. The angle beta will be measured in degrees clockwise from the arm to the forearm. When the arm is raised to the horizontal position, the angle alpha is 90 degrees and the angle beta is 180 degrees.


next up previous
Next: The Solution Method Up: Modeling a Robotic Previous: Problem Description


J. C. Diaz