To eliminate the low-frequency oscillation phenomenon in pulse train controlled switching DC-DC converters operating in continuous conduction mode (CCM), a valley current mode pulse train control technique is proposed. The experimental results show that by using the proposed control technique, the low-frequency oscillation in the pulse train (PT) controlled CCM switching DC-DC converter can be eliminated, while the great robustness and excellent transient performance of the traditional PT control technique can be retained.
Because of Industry 4.0 and Internet of Things, it is easier to collect data from machines through sensors that are embedded inside machines. Once the status change of a machine is detected, production on that machine may need to be adjusted accordingly. In this research, we focus on single machine scheduling with considering the Preventive Maintenance (PM) and machine health index. Machine health index is categorized into three states: good, fair, and breakdown. When the machine moves from one state to another, the processing time of jobs will change as well as the machine failure rate. We develop a model to determine an optimal interval of performing PM and production sequence of jobs. A two-phase heuristic method is proposed to solve a large-size problem. Through different parameter settings, such as the machine failure rate, number of jobs, repair and maintenance cost, we show that the two-phase heuristic can obtain a solution with high quality.
Pulse train (PT) control technique is a novel discrete control technique for switching converter operating in discontinuous conduction mode (DCM). When the inductive energy storage is not zero, the low-frequency oscillation phenomenon may occur in PT controlled switching converters operating in continuous conduction mode (CCM). The low-frequency oscillation phenomenon will seriously affect the steady and transient performances of switching converters. In order to solve this problem, valley current mode pulse train (VCM-PT) control technique, which extends the application range from DCM to CCM, is proposed in this paper. The energy model of VCM-PT controlled switching converter is derived and compared with the energy model of PT controlled switching converter. Result indicates that the VCM-PT controlled CCM switching converter has the same energy transfer mode as the traditional PT controlled DCM switching converter and can eliminate fundamentally the low-frequency oscillation phenomenon.
Pulse On/Off Modulation (POM) technique for switching converter is presented in this paper. POM controller generates the on/off modulation signal through comparing the output voltage with the reference voltage to realize the control of the converter. Buck converter was used as an example to illustrate the operation principle of POM control technique. The analysis and experimental results show that POM control has fast transient response and high light load efficiency.
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