Abstract: A system including a proportional-integral-derivative (PID) controller, a modified relay feedback test (MRFT) block, a memory block, a biasing block, a dq0-to-abc transformation block, a switch configured to selectively couple output signal of the biasing block or the PID controller output signal to the input of the dq0-to-abc transformation block, a three phase digital pulse width modulator, electronic switches, a voltage sensor configured to measure the output of each voltage of the three phases on the load and produce voltage data signals (Vob, Vob, Voc), and an abc-to-dq0 transformation block having an input being a representative of the phase voltages on the load, and producing an output being a representative of these voltages in the dq0 format.

Abstract: A method of automatically tuning a proportional-integral-derivative (PID) controller (102) controlling a DC-DC converter (100) includes substituting the PID controller (102) with a modified relay feedback test (MRFT) (104) controller having a threshold parameter (?) and a magnitude parameter (h), iteratively determining a current error signal (e [k]) by measuring an output voltage (Vo[k]) of the DC-DC converter (100) and comparing it to a desired reference output voltage (Vo-ref), input the error signal (e[k]) to the MRFT (104), determining an output value (u[k]) of the MRFT, update the duty cycle (D) based on the output value (u[k]), operating the DC-DC converter (100) using the updated duty cycle (D), exciting oscillations in the loop containing the MRFT (104) and the DC-DC converter (100), measuring a frequency (?0) and amplitude (?0) of the output voltage (Vo[k]), updating PID controller parameters based on the frequency (?0) and amplitude (?0), and substituting the MRFT (104) with the PID controller (102

Abstract: A gas compressing system including a plurality of n compressors connected in parallel. Each compressor has a suction line connected to a common suction manifold and a discharge line connected to a common discharge manifold configured to deliver compressed gas to a downstream load. The system also includes a process controller configured to control an average speed of the compressors based upon a discharge pressure in the common discharge manifold or a discharge flow through the common discharge manifold. The system further includes an adaptive load sharing optimizing controller configured to determine the speed of each compressor in the plurality of n compressors. A method of controlling a gas compressing system is also provided.

Abstract: A method and apparatus for estimating a down-hole annulus pressure, and/or a down-hole tubing pressure, and/or a down-hole lift gas rate through a gas injection valve of gas lift system, which comprises at least one gas lift choke and at least one gas injection valve and at least one production choke. A state estimator is proposed to obtain the values of these down-hole process variables. The estimator contains a number of local estimators and an interpolation module.

Abstract: A method and apparatus for estimating a down-hole annulus pressure, and/or a down-hole tubing pressure, and/or a down-hole lift gas rate through a gas injection valve of gas lift system, which comprises at least one gas lift choke and at least one gas injection valve and at least one production choke. A state estimator is proposed to obtain the values of these down-hole process variables. The estimator contains a number of local estimators and an interpolation module.

Abstract: Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. Combustion of hydrogen sulfide is precisely controlled by the proposed system to maintain the hydrogen sulfide and sulfur dioxide concentrations in the tail gas at acceptable levels to minimize the environmental pollution.

Abstract: Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. Combustion of hydrogen sulfide is precisely controlled by the proposed system to maintain the hydrogen sulfide and sulfur dioxide concentrations in the tail gas at acceptable levels to minimize the environmental pollution.

Abstract: In tuning a PID controller for a process in a feedback control system, a method is provided for bringing the system into symmetric self-excited oscillations for measuring the frequency and the amplitude of the oscillations, and tuning the controller in dependence on the measurements obtained. A control algorithm referred to as the modified relay feedback test is introduced into a system in series with a process to generate self-excited oscillations. Tuning includes the steps of selecting a desired gain margin or phase margin, generating oscillations with the algorithm parameter corresponding to a selected gain or phase margin, measurements of the amplitude and the frequency of these oscillations, and computing PID controller tuning parameters. Data and formulas are given for the computation of the specific parameter of the modified relay feedback test and for tuning the parameters of the PID controller. An apparatus for performing the method is disclosed.

Abstract: In tuning a PID controller for a process in a feedback control system, a method is provided for bringing the system into symmetric self-excited oscillations for measuring the frequency and the amplitude of the oscillations, and tuning the controller in dependence on the measurements obtained. A control algorithm (modified relay feedback test) is introduced into the system in series with the process to excite self-excited oscillations in the system. Data and formulas are given for the computation of the specific parameter of the modified relay feedback test and for tuning the parameters of the PID controller. An apparatus for performing the method is disclosed.

Abstract: In tuning a controller for a process in a feedback control system, a method is provided for bringing the system into asymmetric self-excited oscillations for measuring the frequency of the oscillations, average over the period value of the process output signal and average over the period control signal and tuning the controller in dependence of the measurements obtained. An element having a non-linear characteristic is introduced into the system in series with the process and set point signal is applied to excite asymmetric self-excited oscillations in the system. An algorithm and formulas are given for identification of the process model having the form of first order plus dead time transfer function. PI controller settings are given as a function of the dead time/time constant ratio. An apparatus for performing the method is disclosed.

Abstract: In tuning a controller for a process in a feedback control system, a method is provided for bringing the system into asymmetric self-excited oscillations for measuring the frequency of the oscillations, average over the period value of the process output signal and average over the period control signal and tuning the controller in dependence of the measurements obtained. An element having a non-linear characteristic is introduced into the system in series with the process and set point signal is applied to excite asymmetric self-excited oscillations in the system. An algorithm and formulas are given for identification of the process model having the form of first order plus dead time transfer function. PI controller settings are given as a function of the dead time/time constant ratio. An apparatus for performing the method is disclosed.