Redundant control circuit

Claim 2

An analog output network for controlling an electrical actuator in dependence upon an input signal received from a sensor, comprising: control means, operatively connected to the sensor, for providing control signals in dependence upon the input signal; analog output circuits, each of said analog output circuits comprising: actuation means operatively connected to said control means for generating an analog output signal in dependence upon one of the control signals; characterized by: internal loop means operatively connected to said actuation means for outputting the analog output signal and providing a current path; and loop sensing means operatively connected to said internal loop means, said actuation means and said control means, for generating a feedback signal in dependence upon electrical current flow in the current path provided by said internal loop means, and external loop means operatively connected to said analog output circuits and the actuator, for providing alternate current paths, the current path provided by said internal loop means in each of said analog output circuits being connected in parallel with one of the alternate current paths.

Claim 3

An analog output network as recited in claim 1, wherein said external loop means produces a first voltage drop and the electrical current flow in said internal loop means in each of said analog output circuits produces a second voltage drop lower than the first voltage drop.

Claim 4

An analog output network as recited in claim 1, wherein said control means provides a communication path for information based on the feedback signal from at least one of said analog output circuits to at least another one of said analog output circuits.

Claim 5

An analog output network as recited in claim 1, said control means characterized by: first and second controllers, operatively connected to the sensor and said analog output circuits, for providing demand signals in dependence upon the input signal, and pulse signals, one of said first and second controllers being in an on-line mode; and controller selector means for enabling and identifying one of said first and second controllers as an on-line controller, comprising: status means, operatively connected to said first and second controllers, for outputting a status signal to said second controller based on the demand signal output by said first controller; first enable means, operatively connected to said status means and a first one of said analog output circuits, for outputting a first enable signal to the first one of said analog output circuits when said first controller is in the on-line mode; and second enable means, operatively connected to said first enable means, said status means and a second one of said analog output circuits, for outputting a second enable signal to the second one of said analog output circuits when said first controller is not in the on-line mode.

Claim 6

An analog output network as recited in claim 4, wherein said status means comprises a monostable circuit operatively connected to said first and second controllers, wherein said first enable means comprises at least one inverter operatively connected to said status means and the first one of said analog output circuits, and wherein said second enable means comprises an enable signal inverter operatively connected to the at least one inverter.

Claim 7

An analog output network as recited in claim 1, wherein said control means comprises: first and second controllers, operatively connected to the sensor, for generating first and second demand signals, first and second control signals and first and second pulse signals, respectively; and controller selector means for enabling and identifying one of said first and second controllers as an on-line controller, and comprising first and second selector circuits operatively connected to said first and second controllers and said analog output circuits, each of the first and second selector circuits comprising: a controller status circuit, operatively connected to a corresponding controller, for indicating that the corresponding controller is operating normally in dependence upon the pulse signal and the control signal generated by the corresponding controller; on-line selection means for indicating that the corresponding controller is selected to be in the on-line mode; a first AND gate operatively connected to said controller status circuit and said on-line selection means; a first inverter, operatively connected to said controller status circuit, for outputting a status signal for the corresponding controller to a non-corresponding controller; a second AND gate operatively connected to said controller status circuit and to receive the status signal for the non-corresponding controller; an OR gate having inputs operatively connected to said first and second AND gates and having an output; and a second inverter operatively connected to the output of said OR gate, the inputs of said OR gate in the other selector circuit of said controller selector means, the non-corresponding controller and a corresponding one of said analog output circuits.

Claim 8

An analog output network as recited in claim 1, wherein said actuation means comprises: a pulse width modulator, operatively connected to said control means and said loop sensing means, for producing a modulation signal in dependence upon one of the control signals; a transformer, operatively connected to said pulse width modulator, for outputting an internal analog signal in dependence upon the modulation signal; and a rectifier-filter, operatively connected to said transformer and said internal loop means, for producing the analog output signal from the internal analog signal.

Claim 9

An analog output network as recited in claim 1, wherein said internal loop means comprises a resistor connected to said actuation means, said loop sensing means and said external loop means; and a diode, connected in series with said resistor and connected to said actuation means and said external loop means.

Claim 10

An analog output network as recited in claim 8, wherein said loop sensing means comprises an amplifier having inputs, each of the inputs connected to one end of said resistor, and an output connected to said control means and said actuation means.

Claim 11

An analog output network as recited in claim 1, wherein said external loop means comprises diode strings, each of the diode strings connected to a corresponding one of the analog output circuits and two of the diode strings connected to opposite ends of the actuator.