Composite Representation of Bond Graphs and Block Diagrams for Controlled Systems

Feed back control systems are widely used to modify the dynamic behavior of the engineering systems. They require sensors to measure some aspects of the system response, signal processors to realize the control law and the actuators to affect the system. The sensors and actuators are usually very similar to instruments and amplifiers and thus are typically modeled using active bonds, using bond graph technique which, Since they work on the principle of conservation of energy, it is difficult to accidentally introduce extra energy into a system. Virtually any type of physical system (mechanical, electrical, electro-mechanical, hydraulic, etc.) can be modeled using the bond graph technique. Since each bond represents a bi-directional flow, systems which produce a "back force” on the input are easily modeled without introducing extra feedback loops. Bond graphs are based on the principle of continuity of power. If the dynamics of the physical system to be modeled operate on widely varying time scales, fast continuous-time behaviors can be modeled as instantaneous phenomena by using a hybrid bond graph. The signal processor which is usually a special purpose analog or digital computer, is not normally described by it’s action on certain signals without regard to any physical power required hence it is difficult to have bond graph of it as bond graphs are based on the principle of continuity of power. For this purpose in this research paper we have applied a technique that can give composite representation in which the physical system is represented using bond graphs and the controller is represented as a signal processor. For simple systems the resulting combined system may yield insight but for more complex systems, the result may be too complicated to be of much use. We have taken the example of an electronically controlled automotive suspension featuring a fast acting load leveler and a semi active damper and have successfully simulate the system by our mixed bond graph approach..