Showing papers on "Proportional control published in 1970"

Proportional action electronic fuel control for fuel cells

Abstract: A proportional electronic fuel control controls the feed flow of fuel to the reformer of a fuel cell system in response to fuel cell current, reformer temperature and the position of the fuel flow control valve. The electronic control produces a proportional control signal which actuate solenoids in a digital manner to regulate the position of the fuel flow control valve. A deadband is provided in the electronic control to prevent continuous cycling of the control valve.

System for heating or air conditioning

Abstract: A system for heating or air conditioning wherein provision is made for controlling fan speed and/or the heating and modulating valve in accordance with thermostat demand. The thermostat puts out a step function followed by a ramp for both on-off and proportional control. One valve may be used in series with another for each function. A logic gate is provided to override the speed control when the plenum is cold. Half speed is provided for a hot plenum even though there is no thermostat demand for heat. Two detectors are provided for plenum temperature. The same thermostat is used with both voltage sensitive and current sensitive circuits.

Industrial process control system for operations with long time constants

Abstract: A system for providing continuous and proportional control of a process variable includes a sensor furnishing an output signal having an analog value proportional to the process variable An analog controller includes a shaping circuit comparing that analog value with a reference to develop an error signal, and an integrator and two differentiators in series The time constant of the integrator is chosen to filter out fast, unwanted fluctuations in the process variable and the time constants of the differentiators to approximate those involved in the process work function The outputs of these elements of the analog controller are summed and supplied as a control signal to an actuator control circuit which varies the power supplied to an actuator so as to proportionally control a control parameter of the process In turn, changes in the control parameter bring the process variable back to its desired value An embodiment of the analog controller uses tantalum capacitors and high impedance operational amplifiers Embodiments of the actuator control circuits for use with AC synchronous stepping motors and DC motors include an integrator which eliminates any dead band in the actuator''s response to the control signal

Identification and control of discrete linear systems subject to disturbances with rational spectral density

Abstract: The paper outlines a particular computer aided design philosophy for the control of single input-single output discrete systems subject to disturbances with rational spectral density. The design procedure is based on identification and synthesis; computer aided methods of off-line and on-line process identification provide sufficient information for the synthesis of a constrained input, minimum variance control algorithm of particularly simple form. In this sense, the present approach to control systems design provides a possible systematic alternative to more conventional methods, such as three term control. Since the complete design procedure is composed in part of certain existing techniques, the paper can also be considered as a short review of the subject.

Vehicle guidance systems

Abstract: A vehicle guidance system in which a vehicle (e.g., a tractor) follows a conductor carrying a guidance signal. Steering control is effected in response to an error signal representative of divergence of the vehicle from the required track. A pulse generator gives a variable mark/space ratio output in accordance with the amplitude of the error signal and the pulse generator output is directed to operate a left- or right-hand on-off fluid valve in accordance with the sign of the error signal. The fluid valves are thus controlled by the variable mark/space signal to give proportional control although they are on-off valves.

Forehearth Temperature Control Improvement by Application of Solid-State Instruments

Abstract: Solid-state electronic instruments have been applied to the glass forehearth, where precise measurement and control of glass temperature are needed to ensure adequate gob weight control for extended periods. Comparative experiments between forehearth systems show that a 3:1 temperature control improvement can be achieved by updating conventional control systems. Front-zone temperature deviation can be used to predict a related weight deviation according to the equation ?WT = 0.58 ?T where ?T is in degrees Fahrenheit and ?WT is in percent. This model is applied in the analysis of a typical forehearth temperature versus weight control relationship.

A New Reaction Control Approach for Sounding Rockets

Abstract: High performance reaction pointing control systems for sounding rockets, using proportional control of differential thrust and adaptive control of thrust magnitude

Automatic control systems

Abstract: 1,212,341. Automatic control systems. TECHNISCHE STUDIEN A. G. Nov.24, 1967 [Dec.5, 1966; Jan.18, 1967; May 23, 1967], Nos.54317/66, 2661/67 and 23806/67. Heading G3R. [Also in Division G1] A retroactive system controlling say temperature utilizes a thermal wax type actuator, controlled in a time modulated mode, in which the gland through which the actuating member passes is maintained at a sufficient temperature difference from the heating means to keep the wax adjacent the gland below its melting point thus avoiding leakage. A number of circuits are described in which proportional feedback alone or in combination with integral and/or derivative control is employed. In Fig.1 positional feedback is derived from a potentiometer 118 coupled to the actuator 114 controlling a heating fluid valve 116 and a circuit 105- 108 adds a proportional/integral/derivative signal to the error signal 100. An RC network 109, 110 passes a transient positive feedback signal to give a temporary large output at the actuator for a small error signal, which completely switches the actuator on or off. The output of D.C. amplifier 103 switches on an A. C. supply through 104 to the actuator heater 112, maximum current being limited by a PTC semi-conductor device 115 having an appropriate transition point. In Fig.2 (not shown) two actuators (131, 132) are operated sequentially by a similar circuit through relays (123). A reed relay (203) is employed in another arrangement Fig. 3 (not shown) in which an opposing feedback winding (204) produces a steady oscillation of the relay. In a modified form of Fig.1 components 102-111 are replaced by a capacitor (257) Fig. 4 (not shown) which is repetitively charged and discharged, sawtooth fashion, to produce time modulation of the actuator current, which charging is varied by the error signal through a potentiometer (259) to produce proportional control. An RC network (255- 256) will add integral control. In Fig.8 (not shown) the sensing element (510) is fed with say positive half waves of an A.C. supply and the actuator (518) is energized with the negative half waves, such arrangement requiring only two leads each to the actuator and sensitive element. Feedback is by an element (521) sensitive to actuator temperature. A simple arrangement for domestic heating utilizes two elements (307, 309) Fig. 5 (not shown) of a bellows operated switch. The actuator heating means may have a discrete heating element or the actuator body may act as the heater, or the wax may be of an electrically conductive type. The wax should also have poor thermal conductivity so that while a volume near the heater is molten, that near the gland is relatively solid.

Variable setpoint proportional control apparatus for vacuum bakeout systems

Abstract: An electronic heater control system for maintaining the vapor pressure within a vacuum bakeout system at an optimum level by causing the heating elements to be alternately energized and de-energized at a high frequency with the ON-OFF duty cycle being determined by the instantaneous vapor pressure in the system. The control circuitry includes a means for generating a time varying reference signal and a signal comparator means for comparing a pressure responsive signal to the reference signal. The comparator means then generates a heater control signal in response to the comparison for use in driving a heater energization switching means.

Improvements in automatic control systems

Abstract: 1,212,341. Automatic control systems. TECHNISCHE STUDIEN A. G. Nov.24, 1967 [Dec.5, 1966; Jan.18, 1967; May 23, 1967], Nos.54317/66, 2661/67 and 23806/67. Heading G3R. [Also in Division G1] A retroactive system controlling say temperature utilizes a thermal wax type actuator, controlled in a time modulated mode, in which the gland through which the actuating member passes is maintained at a sufficient temperature difference from the heating means to keep the wax adjacent the gland below its melting point thus avoiding leakage. A number of circuits are described in which proportional feedback alone or in combination with integral and/or derivative control is employed. In Fig.1 positional feedback is derived from a potentiometer 118 coupled to the actuator 114 controlling a heating fluid valve 116 and a circuit 105- 108 adds a proportional/integral/derivative signal to the error signal 100. An RC network 109, 110 passes a transient positive feedback signal to give a temporary large output at the actuator for a small error signal, which completely switches the actuator on or off. The output of D.C. amplifier 103 switches on an A. C. supply through 104 to the actuator heater 112, maximum current being limited by a PTC semi-conductor device 115 having an appropriate transition point. In Fig.2 (not shown) two actuators (131, 132) are operated sequentially by a similar circuit through relays (123). A reed relay (203) is employed in another arrangement Fig. 3 (not shown) in which an opposing feedback winding (204) produces a steady oscillation of the relay. In a modified form of Fig.1 components 102-111 are replaced by a capacitor (257) Fig. 4 (not shown) which is repetitively charged and discharged, sawtooth fashion, to produce time modulation of the actuator current, which charging is varied by the error signal through a potentiometer (259) to produce proportional control. An RC network (255- 256) will add integral control. In Fig.8 (not shown) the sensing element (510) is fed with say positive half waves of an A.C. supply and the actuator (518) is energized with the negative half waves, such arrangement requiring only two leads each to the actuator and sensitive element. Feedback is by an element (521) sensitive to actuator temperature. A simple arrangement for domestic heating utilizes two elements (307, 309) Fig. 5 (not shown) of a bellows operated switch. The actuator heating means may have a discrete heating element or the actuator body may act as the heater, or the wax may be of an electrically conductive type. The wax should also have poor thermal conductivity so that while a volume near the heater is molten, that near the gland is relatively solid.