Teck Ping Sim

Using Time-Sequential Sampling to Stabilize the Color and Tone Reproduction Functions of a Xerographic Printing Process

Tone and color reproduction functions (TRC and CRC) characterize how a printer maps a desired tone or color into the actual printed output. TRC/CRC ideally, should be identity maps to achieve tone and color consistency. Whereas the TRC/CRC is potentially high or infinite dimensional, typically, only a small number of tone/color test patches for sensing can be printed and measured at a time and only a small number of actuators are available for control. Time-sequential sampling is proposed to address the sensing limitation issue in order to enable the time varying TRC or CRC to be reconstructed based on a small number of samples. A periodic Kalman filtering approach is employed for the reconstruction. A curve-fitting TRC stabilization controller based on linear quadratic (LQ) control with integral dynamics is proposed to address the actuation limitation issue. Two classic time-sequential sampling sequences are compared based on their spectral aliasing properties, and the reconstruction operations of the periodic Kalman filter is analyzed using Floquet theory. Simulations and experiments show that the proposed TRC/CRC stabilization system can be implemented practically and the control performance with one time-sequential sampled sensor is nearly as effective as using full sampling using sixteen fixed sensors

Optimal time-sequential sampling of tone reproduction function

This paper proposes a procedure to design an optimal time-sequential sampling (OTSS) for sampling the time-varying tone/color reproduction functions (TRC/CRC) of a printing process. OTSS can achieve high fidelity sensing using the least amount of sensing hardware and other resources. In particular it maximizes the time between each successive sample without resulting in aliasing. Therefore the time-varying TRC/CRC can be reconstructed with minimal reconstruction error. The reconstructed TRC/CRC are needed as feedback for color/tone consistency control. In this paper, the problem of finding OTSS is posed and solved in the context of lattice based multi-dimensional signal sampling. A computational procedure for implementation is given. Simulation studies validate the advantages of OTSS over other time-sequential samplings methods

Analysis and Control Design of a Hydro-Mechanical Hydraulic Hybrid Passenger Vehicle

This paper gives the dynamic analysis of a hydro-mechanical transmission (HMT) drive train with regeneration and independent wheel torque control of a hydraulic hybrid passenger vehicle. From this analysis, we formulate the HMT control system, which is made up of high, mid and low-level control systems. The high-level consists of a state of charge management and the mid-level translates the storage requirement specified by the high-level into desired internal speed and gear ratio to be executed by the low-level. In this paper we focus on the low-level control analysis and design, where the actuation authority to regulate the internal speed variable comes from either the engine (mode 1) or the hydraulic system (mode 2). Experimental studies show good tracking performance of the proposed control systems and enable our vehicle system to be driven in the proposed HMT architecture.Copyright

Lattice-Based n-Point Time-Sequential Sampling and Two-Stage Process Control for Maintaining Tone Consistency of Xerographic Processes

This paper proposes: 1) a lattice based time-sequential sampling approach that requires the printing and measuring of the smallest number of tonal samples to characterize the high-dimensional tone reproduction curve (TRC) at each print cycle, and 2) based on this characterization, the design of a two-stage control strategy to maintain tone consistency of a xerographic printing process. The printers TRC maps the desired tones to the actual printed tones and it is high dimensional due to the large number of desired tones. To avoid using many sensors, the measurement of the TRC is achieved by sampling it time-sequentially and by reconstructing the TRC from the samples via a Kalman filter. In time-sequential sampling, only a few distinct n tones are printed and measured at each print cycle. Using a lattice-theoretic framework, an optimal time-sequential sampling sequence with n = 1 is designed. This is then extended to the case of to enable the tradeoff between sampling time and sampling resources. With the reconstructed time-varying TRC, a two-stage control strategy uses both the physical xerographic and the image processing processes to compensate for the TRC variations from the desired TRC. Simulations and experiments show that the proposed TRC stabilization system is effective for practical implementation. By stabilizing all the cyan, magenta and yellow primaries of the color xerographic print system, color consistency can be maintained. Furthermore, the proposed time-sequential sampling approach with n = 1 exceeds the capability of conventional three-fixed-point sampling (light, middle, and dark tones) approach while requiring three times fewer samples.

On coordination and stabilization of two xerographic printers

The problem of coordinating and stabilizing the two color tone reproduction curves (TRC) of two xerographic printing engines is considered. This problem is critical to enable two printers to print the same image/collection of images in parallel, hence speeding the overall printing process. The proposed control systems use a small number of actuators and a small number of measurements to coordinate and stabilize the potentially high-dimensional TRC of the two printers. The goal for TRC coordination and stabilization is to minimize the overall least squares deviation of the two TRCs and the overall least squares deviation of each of the TRCs from the nominal subject to disturbances on the printers. In this paper an optimal static and robust static controllers are proposed to stabilize and coordinate the potential high dimensional TRC. Simulations and experiments validate the efficacy of the proposed controllers.