Automated Design of Mechatronic Systems: Novel Search Methods and Modular Primitives to Enable Real-World Applications

This paper suggests not only an automated design methodology for synthesizing designs for multi-domain systems, such as mechatronic systems, but also a type of fine control of modularity and several innovative GP search methods. The domain of mechatronic systems includes mixtures of, for example, electrical, mechanical, hydraulic, pneumatic, and thermal components, making it difficult to design a system to meet specified performance goals using a single design tool. The multi-domain design approach is not only efficient for mixed-domain problems, but is also useful for addressing separate single-domain design problems with a single tool. Bond graphs are domain independent, allow free composition, and are efficient for classification and analysis of models, allowing rapid determination of various types of acceptability or feasibility of candidate designs. This can sharply reduce the time needed for analysis of designs that are infeasible or otherwise unattractive. Genetic programming is well recognized as a powerful tool for open-ended search. The combination of these two powerful methods is therefore an appropriate target for a better system for synthesis of complex multi-domain systems. The approach described here will evolve new designs (represented as bond graphs) with ever-improving performance, in an iterative loop of synthesis, analysis, and feedback to the synthesis process. We are reporting advances in methods for automated design of two types: use of new, more complex design primitives and two improvements to the genetic programming algorithms used in the design synthesis: SFS (Structure Fitness Sharing) and HFC (Hierarchical Fair Competition). The improvements have been developed and tested during investigations of four design examples. The first is a domain-independent eigenvalue placement design problem that is tested for some sample target sets of eigenvalues. The second is in the electrical domain – design of analog filters to achieve specified performance over a given frequency range. The third is in the electromechanical domain – redesign of a printer drive system to obtain desirable steady-state position of a rotational load. The fourth is in the hydraulic domain – design of an air pump to maximize outflow subject to a constraint specifying maximum power consumption.