Patent attributes
Systems and methods for implementing hybrid, closed-loop control that generates control values for processes defined by a limited number of function evaluations and large amounts of process and measurement noise. The described control system is applied to a stencil printing process for applying solder paste to an electronic medium such as a printed circuit board or semiconductor wafer. The control system is defined by a hybrid approach. A first, coarse algorithm is used to rapidly produce the value of a stencil printer control value resulting in a solder paste deposit having a volume within predetermined acceptable limits. After the coarse algorithm no longer produces solder paste deposits closer to a desired volume, a second, more refined estimator is used to fine tune the process. An additional transitional algorithm may be added between the coarse algorithm and refined estimator. The coarse algorithm may be implemented with a constrained-conjugated gradient search, and the refined search may be a implemented using a least-squares affine estimator or a quadratic estimator. The transitional algorithm may be implemented using a block version of a least-squares affine estimator.
