Process control system

Claim 2

An improved electronic process control system of the type normally having a plurality of control units intimately related to a process to be controlled and a digital computer arranged to receive certain signals from the control units and send signals to the control units to modify their actions, wherein the improvement comprises: computer interface means connected to the computer for a converting between the digital format of the computer and a prearranged digital format; a plurality of control unit interface means connected to the control units for generating and storing analog and status signals required by the control units; means to generate a series of pulses for use by the control unit interfaces corresponding to a digital word from the computer operable in one of two modes, the first mode being incremental wherein the series of pulses is directly related to the digital word, the second mode being positional wherein the series of pulses is related to the difference between the digital and the present value in the control unit; and means to generate a digital word for use by the computer corresponding to analog signals received from the control units.

Claim 3

The control system of claim 1 further including: address lines connected to the individual control unit interfaces, and means for demultiplexing an address signal from the digital computer by activating one of the address lines.

Claim 4

The control system of claim 2 wherein the control unit interface means includes: gating means for receiving the series of pulses in parallel with other unit interfaces, the gating means allowing the signals to pass only upon the presence of a properly activated address line.

Claim 5

The control system of claim 3 wherein the control unit interface further includes: a plurality of memory means for storing analog values related to the series of pulses passed; and switching means for determining which of the memory means are to be activated by the analog value upon command from the computer.

Claim 6

A DDC process interface system for use with a digital computer having computer interface circuitry for translating between the digital format of the computer and a prearranged digital format including command, address, digital output value, and digital input value information, and a plurality of devices cooperating with the process to be controlled, the interface system comprising: a plurality of control unit interfaces for transmitting analog signals to the devices; a plurality of address lines Each connected to an individual control unit interface; an address decoder for activating individual address lines based on the address information; a plurality of command lines connected in parallel to interfaces for transmitting the command information; a command code register associated with each control unit interface operable to record the present status of the command lines when activated by the corresponding address line; a pulse line connected to the analog control unit interfaces; a pulse generator assembly for generating a series of pulses on the pulse line based on the digital output value information; a pulse enabling gate associated with each control unit interface for passing the pulses on the pulse line when activated by the corresponding address line; a pulse converter associated with each gate for converting the pulses into an analog value for transmission to the devices cooperating with the process to be controlled; an analog input value line associated with each control unit interface for collecting analog value information related to the corresponding control unit; an analog multiplexer to which all analog input value lines are connected, the multiplexer being connected to the address decoder and activated thereby to multiplex the analog input value line corresponding to the address line activated; and an anlog to digital converter for converting the analog value on the analog input value line to digital input information for the computer.

Claim 7

A DDC process interface system for use with a digital computer having computer interface circuitry for translating between the digital format of the computer and a prearranged digital format including command, address, digital output value, and digital input value information, and a plurality of devices cooperating with the process to be controlled, the interface system comprising: a plurality of control unit interfaces for transmitting analog signals to the devices; a plurality of address lines Each connected to an individual control unit interface; an address decoder for activating individual address lines based on the address information; a plurality of command lines connected in parallel to interfaces for transmitting the command information; a command code register associated with each control unit interface operable to record the present status of the command lines when activated by the corresponding address line; a pulse line connected to the analog control unit interfaces; a pulse generator assembly for generating a series of pulses on the pulse line based on the digital output value information; a pulse enabling gate associated with each control unit interface for passing the pulses on the pulse line when activated by the corresponding address line; a pulse converter associated with each gate for converting the pulses into an analog value for transmission to the devices cooperating with the process to be controlled; an analog input value line associated with each control unit interface for collecting analog value information related to the corresponding control unit; an analog multiplexer to which all analog input value lines are connected, the multiplexer being connected to the address decoder and activated thereby to multiplex the analog input value line corresponding to the address line activated; and an anlog to digital converter for converting the analog value on the analog input value line to digital input information for the computer.

Claim 8

The DDC process interface system of claim 5 with setpoint tracking, further comprising: a second pulse converter associated with each gate for converting pulses into a second analog value for transmission to the devices cooperating with the process to be controlled; and a setpoint/output switch inserted between the pulse enabling gate and the first and second pulse converter of each control unit interface for directing the pulses to one of these converters according to the status of the command code register associated with the same control unit interface, whereby the first analog value may be utilized as a computer generated output value and the second analog value utilized as a computer generated setpoint value.

Claim 9

The DCC system of claim 6 wherein the first pulse converter in each control unit interface comprises: a pulse shaper for generating a predetermined pulse shape in response to each pulse received on the pulse line; and an integrator for storing and integrating the pre-determined pulse shapes to generate the first analog value.

Claim 10

The DDC system of claim 7 wherein the second pulse converter in each control unit interface comprises: a pulse counter for generating a digital value related to the number of pulses received; and a digital to analog converter for generating the second analog value.

Claim 11

The DDC system of claim 5 with remote/local setpoint switching, further comprising: a remote/local switch in each control unit interface for receiving the second analog value and another analog value and transmitting one of these analog values to the devices cooperating with the process to be controlled according to the status of the command code register associated with the same control unit interface, whereby the computer may choose between the setpoint value locally generated by the computer and another setpoint value remotely generated.

Claim 12

The DDC process interface system of claim 5 with absolute/incremental ability, further comprising: an absolute/incremental switch associated with each pulse generator for receiving the digital output value information and another digital output value signal and transmitting one of these digital values to the pulse generator according to the command code information; and means for combining the digital output value information from the computer to the digital input information from the analog to digital converter to generate the other digital output vaLue signal for the absolute/incremental switch, whereby the analog value transmitted to the devices cooperating with the process to be controlled may be either the absolute value determined by the computer or an incremental value related to the difference between the absolute value and a present value.

Claim 13

The DDC system of claim 5 further comprising: a digital multiplexer associated with each analog multiplexer for combining digital status information regarding the present status of the control unit interface and the devices with the output of the analog to digital converter to form composite digital input value information.

Claim 14

The DDC system of claim 5 further comprising: a legal code decoder for determining the validity of the present combination of information on the command code lines.

Claim 15

The DCC system of claim 5 wherein the control unit interfaces are arranged in sub-systems of a maximum of a predtermined number of units each, further comprising: an additional set of address decoders, pulse generators, analog multiplexers, and analog to digital converters for each sub-system beyond one.