Concurrent Dynamics creates high fidelity Multibody Dynamics Simulation programs to assess dynamics and control performances of mechanisms and robotics. They expedite:
Fig. 1. NASA-JPL-Robosimian-robot
Fig. 2. NASA Rover (pictures are by courtesy of NASA)
Fig. 3. A 6 link robot arm
Equations of motion of each simulation are generated by Lagrangian formulation. They are solved by a recursive order(N) algorithm during runtime. The member bodies of the system can be rigid or flexible. The equation solver speed is order(N,sum(ni3)), where N=number of bodies, and ni=number of flexible modes for the i-th body. The simulations allow simple constraints to lock joints or to prescribe joint motion if required.
The generalized coordinates for mechanisms and robotics are the angular and translational coordinates of the joints. These are identical to those defined for the airplanes and spacecrafts. The translational motion of ground based robots is defined by the movement of a reference point on the robot body in the local workspace. Whereas, the translational motion of spacecrafts and airplanes is defined by the movement of the system cm around the earth center. In the latter cases, user can choose from a list of gravitational models to formulate the orbital motion of the spacecrafts. For robot simulations, the user must include the gravity force effect on member bodies in the control system.
Point-to-point constraints can be defined to permit closed mechanical loops in the system. Gear constraints can be defined to permit coordinated deployment of an multi-linked arm on one hand and a differential gear box on the other. Contact constraints prevent points on the mechanical system from penetrating controlled surfaces. These constraints can be turned on an off by simple commands during run time.
Our simulations run on PC's with Window XP and Window 7/8 OS equipped with Matlab/Simulink. A typical mdl file (a Simulink program) that we build is shown below. This example simulates a 6 link robot arm with a fixed base moving from some initial configuration to a commanded configuration. In this case, all arm joints are 1dof rotation joints. (See Fig. 3 above) The multibody equations of motion specification, mass property, geometry and all desired input/ouput parameters are defined by a model file. User defines it through our model editor. The xmr01.dll block (an S-function) in the mdl file reads it and executes all dynamics computations during runtime based on it. Xmr01.dll also samples user picked parameters for post simulation viewing. It is closed-loop connected to the user supplied control system to complete the mdl file.
We build streamlined mdl files by encapsulating all dynamics computations and i/o processes in one functional block, namely xmr01.dll. This dynamics simulation engine has an easy to work with i/o interface to connect it with the user supplied control system. In short, these are our design rules:
Fig.4 A 6 Link Robot Arm Control Simulation
Robot arms are not limited to 6 links, nor do all their joints need be rotational. The model file of an arm simulation can be modified to a multipeds file easily using our model editor. Regardless of the complexity of your assignments, our expertise and tools are ready to realize your robotics simulations.
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