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Melt pool temperature is of great importance to deposition quality in Laser Metal Deposition processes. To control the melt pool temperature, an empirical process model describing the relation between the temperature and laser power, powder flow rate, and traverse speed is established and verified experimentally. A general tracking controller using the Internal Model Principle is then designed. To examine the controller performance, two experiments tracking a constant temperature reference and a time varying reference are conducted. The results are compared to open-loop experiments where the laser power profile is derived directly from the model. The results show the melt pool temperature controller performs well in tracking both constant and time varying references and that the closed-loop control system greatly reduces the tracking errors.

A Laser Metal Deposition (LMD) height controller design methodology is presented in this paper. The height controller utilizes the Particle Swarm Optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. The process model parameters for the next layer are then predicted using Exponentially Weighted Moving Average (EWMA). Using the predicted model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using Iterative Learning Control (ILC). The model parameter estimation capability is tested using a four-layer deposition. The results demonstrate the simulation based upon estimated process parameters matches the experimental results quite well. The experimental deposition using this methodology demonstrates good tracking of the height reference in terms of the finished track.

A real-time positioning system for a precision chemical applicator has been developed; the system is composed of a low cost GPS combined with two optical encoders. GPS has good resolution in global range, but has poor resolution in local single-point positioning. With the optical encoders, the situation is just the opposite-they have high resolution in a small range, but the accumulative error grows as the vehicle moves. Based on the characteristics of GPS and optical encoders, an algorithm has been proposed to integrate the advantages of GPS and optical encoders. The results of this research show that the combined positioning system of GPS and the optical encoders can inherit all advantages of GPS and optical encoders and overcome their shortcomings. The positioning accuracy has been significantly improved, and can meet the real-time spatial high resolution positioning demands in field operations with the dynamic response of optical encoders.