Applications of RModelo

The mechanical structure of a robot manipulator described by a DH-table. It can be converted to an animated virtual model for easy visualization and verification of individual and/or combined joint motions. A software packaged name RModelo, developed by the author, translates a robot arm mathematical model. RModelo serves several useful purposes in the analysis of robot manipulators. A few applications of RModelo are given below:

1. Generation of Virtual Robot Models for Visualization: While DH-table offers a sound mathematical model of a robot, manipulator mechanism suitable for computational kinematic analysis. It is very difficult to imagine the overall shape and structure of the robot directly from the values entered in the table even for experts in robotics. Rmodelo easily translates a DH table into a virtual scene in which the robot mechanism can be viewed from any direction and distance. It can be rotated at will by the user through the viewing controls provided by the VRML viewer client chosen by the user.

2. Robot Arm and Prosthesis Design: Robotic arms and arm or leg replacement, these are composed of links and joints arrangements. Each DH parameter influences the overall shape and functional structure of the mechanism. Mmodelo allows the effect of every DH parameter on the structure of a robot to be immediately assessed and viewed on a computer screen. Different robot models can be compared and different robot configurations can be drawn.

3. Joint and end-effector motion Analysis: The motion capabilities of the virtual models allow easy and safe analysis of individual joint motion. The motion of the robot end effect-or when all actuators are put into action simultaneously. The range of motion of each joint determine the overall workspace of the robot arm. Motion visualization also allows of-line detection and analysis of problem points along the trajectory.

4. Off-line Inverse Kinematics Verification: In robot manipulators, individual joint actuators must be controlled in order to achieve a desired end effector trajectory. Typically, a point on a trajectory in specified in Cartesian space by its generalized coordinate composed of three position coordinates (x. y, z) and three orientation angles (α, β, θ). Each point of Cartesian trajectory must then be computationally translated into joint variable values.

It is a common for a robot manipulator to be able to achieve a given end effector trajectory point with several choices of joint variable values. However, inverse kinematics computations can produce joint variables values that are not realistic because they cause link collisions of the robot with other workspace objects.

5. Visualization of Problematic Configuration:: Robot arms sometimes run into problem point along a given trajectory. These points are called singularities and are caused by the robot end-effector reaching the limit of its workspace or getting itself in a configuration where two or more of its joint axes become exactly aligned. These robot singularities can be computationally determined by computing the determinant of the robot Jacobian matrix. With RModelo, singular configurations can be directly viewed, identified and analyzed.

6. End-effector Trajectory Analysis: When several joints are actuated, they cause the robot end effector to follow a trajectory on space. The ability to visualize the actual trajectory followed by the robot tool. It is an invaluable off-line task programming and trajectory verification tool. RModelo includes the ability to generate a VRML, display with the trajectory of the robot.

7. Robotics Education: RModelo is an extremely useful tool for teaching robot modeling and robotics in general since it provides easy, inexpensive and safe visualization.