Multi-body Dynamics

Multi-body dynamics deals with kinematic and kinetic relationships between interconnected rigid or flexible components. These components are connected using different joints that restrict their motions to give output with desired degree of freedoms. Generally, these are nonlinear and coupled systems whose output is desired to be controlled for specific operations. This often necessitate to study deeper into the dynamics of such systems by modeling more complicated details.

Multi-domain modeling of Pan Tilt Platform with Mechanical Imperfections

Pan Tilt Platform (PTP) is an electromechanical system whose dynamics is characterized by coupled nonlinear behavior. Payload requires accurate position and velocity control from PTP. In such demanding applications, it’s hard to design controllers for variable operational needs. The problem becomes difficult with the presence of mechanical imperfections in the physical system. These mechanical imperfections include mass imbalance in actuated bodies; friction and backlash at constraint joints of these actuated bodies.

Research study aims at building multiple PTP models having different abstraction levels and fidelity. It starts with a multi-bond graph model of an ideal PTP using Object Oriented Modeling(OOM) approach. Then, Ideal PTP model is made more realistic by adding details of actuation mechanisms and mechanical imperfections in step wise manner. Friction is modeled using a general CSVS friction model whereas backlash is modeled using classical dead zone model. Experiments are conducted on PTP of NUST Ground Surveillance Radar for estimation of system parameters using MATLAB Optimization Toolbox. For comparing individual models, their equivalent models are build using MSc ADAMS, Pro/Engineer and MATLAB/Simscape. In the end, pan joint with classical friction and backlash models, is compared with experimental results.

MultiBond Graph Model of Pan TIlt Platform with Payload using OOM approach
MultiBond Graph Model of Pan TIlt Platform with Payload using OOM approach

Publications:

  • M. Haider, R. A. Azim, and W. U. H. Syed, “Multi-Bond Graph Modeling of Pan Tilt Platfom Using Object Oriented Modeling Approach,” in IASTED Third Asian Conference on Modeling, Identification and Control, AsiaMIC 2013, pp. 112–119