@conference {
	title = {Performance evaluation of run-to-run control methods in semiconductor processes},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {Run-to-run (RtR) control plays an important role in semiconductor manufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the exponentially weighted moving average (EWMA) controller and the optimizing adaptive quality controller (OAQC) by simulations according to the following criteria: a good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multiple targets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.},
	address = {Istanbul, Turkey},
	booktitle = {2003 IEEE Conference on Control Applications},
	pages = {pp. 841-848}
}
@conference {
	title = {A New Adaptive Aggregation Algorithm for Infinite Horizon Dynamic Programming},
	author = {Zhang, Chang., Baras, John S.},
	year = {2003},
	month = {06/2003},
	abstract = {Dynamic programming suffers the {\textquotedblleft}curse of dimensionality{\textquotedblright} when it is employed for complex control systems. State aggregation is used to solve the problem and accelerate computation by looking for a sub-optimal policy. In this paper, a new method, which converges much faster than conventional aggregated value iteration based on TD(0), is proposed for computing the value functions of the aggregated system. Preliminary results show that the new method increases the speed of convergence impressively. Aggregation introduces errors inevitably. An adaptive aggregation scheme employing the new computation method is also proposed to reduce the aggregation errors.},
	address = {Rhodes, Greece},
	booktitle = {11th Mediterranean Conference on Control and Automation (MED\&rsquo;03)},
	pages = {pp. 1-6}
}
@conference {
	title = {An Efficient Run-To-Run Controller : ESET},
	author = {Zhang, Chang.},
	year = {2001},
	month = {10/2001},
	abstract = {The EWMA run-to-run (RtR) controller is easy to deploy and can effectively deal with small disturbances. But it can not compensate for shifts (step disturbances) and large model errors well. The common solution to such a problem is to use the SPC to detect the occurrence of a shift and them remove the cause of the shift or apply a rapid mode. In this paper, a novel approach to handle shifts and large model errors is proposed: the SVR-MOVE controller is used to compensate for a shift when it is detected. The SVR-MOVE controller is very efficient to handle shifts and large model errors. On the other hand, a well-tuned EWMA controller may outperform a coarsely tuned SVR-MOVE controller when the disturbances are smooth drifts. It is much easier to tune the parameters of the EWMA controller than that of the SVR-MOVE controller. Our new controller, named ESET, has the advantage of both controllers. Simulation shows that the ESET outperforms the EWMA controller and the SVR-MOVE controller in most situations.},
	address = {Alberta, Canada},
	booktitle = {AEC/APC Symposium XIII},
	pages = {pp. 1-4},
	organization = {Banff}
}
@conference {
	title = {Comparison of Run-to-Run Control Methods in Semiconductor Manufacturing Processes},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2000},
	month = {09/2000},
	abstract = {In this paper, RtR control methods are generalized. The set-valued RtR controllers with ellipsoid approximation are compared with other RtR controllers by simulation according to the following principles:

A good RtR controller should be able to compensate for various disturbances, such as small drifts and ~large step disturbances.~
	It should be able to deal with constraints, cost requirement, multiple targets,~time delays etc.
Preliminary results show the satisfactory performance of the set-valued RtR controller with ellipsoid approximation.~},
	address = {Lake Tahoe, Nevada},
	booktitle = {AEC/APC Symposium XII},
	pages = {pp. 889-896}
}
@conference {
	title = {The Set-Valued Run-to-Run Controller with Ellipsoid Approximation},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2000},
	month = {09/2000},
	address = {Lake Tahoe, Nevada},
	booktitle = {AEC/APC Symposium XII},
	pages = {pp. 167-178}
}
@article {
	title = {Run-to-Run Control Methods Based on the DHOBE Algorithm},
	author = {Zhang, Chang., Deng, Hao., Baras, John S.},
	year = {2003},
	month = {01/2003},
	abstract = {Since process models are typically not known exactly in real problems, it is important to estimate the process parameters before one applies the optimal control to a process. In this paper, the Dasgupta{\textendash}Huang optimal bounding ellipsoid (DHOBE) algorithm is employed to estimate process parameters in semiconductor process run-to-run (RtR) control. At each iteration, the DHOBE algorithm returns an outer bounding ellipsoid of the likely process parameter set. If the vector center of the ellipsoid is taken as the estimate of the process parameter vector, then a model-reference controller results; if the vector within the ellipsoid that produces the worst expected cost is taken as the process parameter estimate, then a worst-case controller results. These two methods are compared with other RtR control schemes: the exponentially weighted moving average (EWMA) method and the optimizing adaptive quality controller (OAQC). Simulation results show that the performance of the model-reference RtR controller based on the DHOBE algorithm is comparable to or better than that of the other two RtR controllers in some specific examples of semiconductor processes.},
	pages = {pp. 35-45},
	volume = {Vol.  39},
	number = {Issue 1},
	journal = {Automatica}
}
@techreport {
	title = {A New Adaptive Aggregation Algorithm for Infinite Horizon Dynamic Programming},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Dynamic programming suffers the "curse of dimensionality" when it isemployed for complex control systems. State aggregation is used to solvethe problem and acceleratecomputation by looking for a sub-optimal policy. In this paper, a new method, which converges much faster thanconventional aggregated value iteration based on TD(0), is proposed for computing the valuefunctions of theaggregated system. Preliminary results show that the new method increases thespeed of convergence impressively. Aggregation introduces errorsinevitably. An adaptive aggregation scheme employing the newcomputation method isalso proposed to reduce the aggregation errors.},
	number = {Number: CSHCN TR 2001-5}
}
@techreport {
	title = {Performance Evaluation of Run-to-Run Control Methods in Semiconductor Processes},
	author = {Zhang, Chang.},
	year = {2001},
	month = {01/2001},
	abstract = {Run-to-Run (RtR) control plays an important role in semiconductormanufacturing processes. In this paper, RtR control methods are classified and evaluated. The set-valued RtR controllers with ellipsoid approximation are compared with two typical RtR controllers: the Exponentially Weighted Moving Average (EWMA) controller and the Optimizing Adaptive Quality Controller (OAQC) by simulations according to the following criteria: A good RtR controller should be able to compensate for various disturbances, such as small drifts, step disturbances and model errors; moreover, it should be able to deal with bounds, cost requirement and multipletargets that are often encountered in semiconductor processes. Based on our simulation results, suggestions on selection of a proper RtR controller for a semiconductor process are given as conclusions.},
	number = {Number: CSHCN TR 2001-20}
}
@techreport {
	title = {A Hierarchical Structure For Finite Horizon Dynamic Programming Problems},
	author = {Zhang, Chang.},
	year = {2000},
	month = {01/2000},
	abstract = {In this paper, we propose a hierarchical structure to solve finite horizon stochastic shortest pathproblems in parallel. In general, the approach reducesthe time complexity of the original problem to a logarithm level, which hassignificant practical meaning.},
	number = {Number: CSHCN TR 2000-19}
}
