Mechatronics design and verification: Using VHDL-AMS to bridge the gap

Mechanical parts that are controlled by electronic circuitry and software are commonly referred to as mechatronic components and systems. The design of such systems is classically divided into the design of the mechanical hardware, the electronic circuitry and the software - with little communication going on between the different engineering domains. This separation often results in communication problems based on incomplete or incorrect specifications and an inability to optimize the complete system instead of just certain aspects. Part of the reason for this failure is that although tools and methodologies are available that address the domain specific tasks, few tools are available that cross domain borders. This paper illustrates a VHDL-AMS simulation-based design methodology for software controlled, electro-mechanical components using an autonomous robot as an example. Starting with considerations for the overall architecture the design is successively augmented with implementation details that allow the verification of software control algorithms, the design and layout the electronics circuitry as well as the specification of parameters for the mechanical and electro-mechanical hardware. The example used is the design of a TekBot™, which is part of the platforms for learning™ concept created by the Oregon State University to teach students about digital logic and analog circuitry. VHDL-AMS based simulation is used to facilitate this task by making good decisions about the required components as well as designing and verifying the implementation. The same design is used for both PCB layout and as a testbench for the software for debugging the software algorithms. The final simulated design includes models of mechanical and electro-mechanical hardware, digital and analog electronic circuitry at behavioral and component levels as well as software executed on an instruction set model.