Computer Animation of Modular Robotic Systems, page 3

A mobile robot is created by attaching degrees of freedom to the base frame of the robot. There is a moving reference frame among the choices of bases. This frame takes six parameters and can be used to create a mobile robot that can move to any position and orientation in the environment. The moving reference frame can also be used to create objects that can move around in the environment, for example a pick and place operation or a failing object. Sliders and revolutes can be used to create a mobile robot whose base frame motion has less than six degrees of freedom.

A hybrid robot has both parallel and serial parts. The hybrid robot can be assembled by branching into multiple serial chains and then specifying the proper joint angles to close some of the chains. A hybrid robot can also be created by adding inherently parallel modules, such as the spherical shoulder, to a serial chain. The parallel modules do not require that all of the interior joint angles be specified. The shoulder, for instance, only requires roll, pitch and yaw and then will automatically calculate the proper interior joint angles.

The environment menu is for placing objects in the environment. Each environment module requires six arguments that position and orient the module in relation to the initial reference frame. Objects added from the environment menu are fixed in their position and orientation and do not affect the active drawing frame.

The animation effect is created by showing rapidly in succession the robot scene with the joint angles changed by a small amount in each scene. This gives the illusion that the robot is moving. The models created with this program can be animated by accepting data from the keyboard, from data files or in realtime via shared memory. The simplest way to animate the robot is to use the keyboard to increment or decrement each joint directly. The joints are numbered in the order that they were added to the model. The specific keys and the joints that they affect are shown in a small box that appears near the top of the screen. Animating from the keyboard is useful for demonstrations and testing. 

Running the animation from a data file is an excellent method of viewing the results from inverse kinematics algorithms or dynamic simulations. Each data set in the file represents the state of the robot at a given point in time. Running the program from shared memory allows the real-time animation of data as it occurs. Selecting 'shared memory' from the 'RUN' menu will cause the program to create a shared memory segment. The program will continuously read from this shared memory and display the robot in the position defined by the joint angles until 'end run' is chosen in the 'RUN' menu. 

Example - The following is a simple example showing the construction of a serial I robot arm mounted on a fixed pedestal. After running the modular animation program, a window appears with the words 'FILE', 'BUILD', 'RUN' and 'UTILITIES' at its top edge. The available bases may be seen by selecting 'add base' from the 'BUILD' menu. After choosing a base for the robot, a dialogue box with appear with a three-dimensional display. A revolute mounting pedestal is used in this example. Either the slanted or the horizontal stand and the color of the pedestal may be selected by clicking on the appropriate button. The button should pushed in to verify the choice. Clicking on the 'OK' box add the base to the robot model. Next Page ->