Computer Animation of Modular Robotic Systems, page 5

An animated robot can exhibit high speed, high precision, no deformation and no backlash. This is, of course, a tremendous simplification. A modular and reconfigurable robotic architecture presents an excellent opportunity to combine dynamic simulation and computer animation. Constructing the graphical robot on the screen defines the modules that make up the robot and the geometry. The dynamic description can be stored as a feature within the modules. As each module is added to the robot, the dynamic equations could be automatically generated using the geometry and the dynamic description of the modules. 

The joint angles of a parallel robot may not all be specified independently. A four bar planar mechanism, for example, has four joints but only one degree of freedom. By specifying the angle of one joint the angles of the other joints are constrained. The parallel robot typically has a smaller workspace than the serial robot, but there are also many benefits associated with using a parallel structure. The parallel structure can utilize mechanical advantage to increase its load carrying capacity. The parallel robot allows a choice among the joints as to which ones will be used as the inputs to the system. Several degrees of freedom can be obtained while still allowing direct actuation with the actuators fixed to the robot base .8 Redundant actuation is also possible with parallel structures. The redundant actuators can provide fault tolerance and antagonistic actuation. Antagonistic actuation shows promise for high-precision tasks that require disturbance rejection.

Computer animation of modular and reconfigurable robotic systems can be used to animate parallel structures. The parallel structure is simply built from open chains. The chain is closed to form a parallel structure by properly specifying each joint angle. This method for creating the animation is of particular benefit for the animation of data that has been generated by kinematic and dynamic analysis that treat the parallel chain as a set of constrained serial chains. The parallel chain is kinematically cut, and the resulting serial chains are constrained to have zero relative position, velocity and acceleration at the cut.

Hybrid systems can be graphically created and animated using the generalized modular mechanical architecture. The modular animation is created by simply specifying which modules are used and how they are connected together. More than one chain can be connected to a link to create a branching effect. The extra chain can then be closed to create an in-parallel structure or left open to animate multi-arm systems. Certain modules within the architecture, such as the three degree of freedom spherical shoulder, are inherently parallel. Hybrid systems will also be created by simply incorporating these modules within a serial chain. The equations which define the interior joint angles are stored as a feature of the parallel modules. Next Page ->