Models and Control Approaches for the Microassembly of Microelectromechanical Systems

Jason J. Gorman and Nicholas G. Dagalakis

Intelligent Systems Division

Manufacturing Engineering Laboratory

 

The majority of commercially available microelectromechanical systems (MEMS) have depended on silicon micromachining for manufacturing. However, silicon micromachining has many limitations which hinder the progress of possible MEMS applications including the material selection, structure aspect ratio and the inability to make true three dimensional structures. Many researchers have investigated other micromanufacturing techniques which could overcome these disadvantages including LIGA, micro-molding, micro-stereo lithography, micro-electro-discharge machining, and laser micromachining. By utilizing several of these processes in tandem, it is possible to create 3-D structures with virtually unlimited geometry and aspect ratio. Since the microelectronics required to drive MEMS can not be manufactured using these techniques, an approach to assembling multiple components into a single hybrid device is required to make these alternative micromanufacturing techniques feasible. Our research concentrates on the development of models, system architectures and advanced control algorithms for microassembly which can be applied to the manufacture of hybrid MEMS. In this presentation, the focus will be on the modeling of the interactions between a prototype microassembly robot and micro-components; and the design of a robust motion and force control system which can provide the level of dexterity for microassembly operations. Several models have been derived which describe the macro and micro scale behavior of microassembly operations. These models include the inherent tribology effects of the microassembly robot, the compliance of the manipulated micro-components and the surface and adhesion forces between the micro-components. Based on these models, simulations have been developed which provide some metrics for the positioning inaccuracies and force levels which can be tolerated during an assembly operation. A robust motion and force control system has been designed for the microassembly robot which can achieve the position and force requirements determined by these model simulations. The proposed control approach combines a friction compensation scheme and a nonlinear sliding mode controller for precision motion control. This is then utilized as an internal loop of those degrees of freedom which require force control, providing a simple method for switching between position and force modes during operation. Results for this control approach will be presented which show that the positioning accuracy is approximately 1 m m and the contact force regulation is on the order of micronewtons, which meet the determined requirements for microassembly operations.

Presenting Author Information

Name: Jason J. Gorman

Division: Intelligent Systems Division

Laboratory: Manufacturing Engineering Laboratory

Room and Building Address: Room A116 / Building 220

Mail Stop: 8230

Telephone: 301-975-3446

Fax: 301-990-9688

Email: gorman@cme.nist.gov

Sigma Xi member?: No

Category: Engineering