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Parameter-free synthesis of zero-impedance converter

  • US 4,973,174 A
  • Filed: 02/26/1990
  • Issued: 11/27/1990
  • Est. Priority Date: 02/26/1990
  • Status: Expired due to Fees
First Claim
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1. A method for parameter free synthesizing electric motor drive system of infinite disturbance rejection ratio and zero order dynamics including parameter free zero impedance converter comprising:

  • accepting a source of electrical energy of a constant voltage at an input to a power converter,coupling mechanically a shaft of an electric motor to a load to be driven at an output,controlling a power flow from said input to said output,modulating said power converter for the control of said power flow in a pulse width modulation manner,supplying a total control signal for modulating said power converter,supplying a voltage feedback signal from a voltage applied to said electric motor,feeding back said voltage feedback signal through a voltage feedback circuit in a negative feedback loop with respect to a direct path signal,supplying an input velocity command obtained as a differentiated input position command,passing said input velocity command through a direct path circuit;

    thereby producing said direct path signal,passing said input velocity command through a feedforward circuit;

    thereby producing a feedforward signal,passing a voltage error signal, obtained as the algebraic sum of said direct path signal and said voltage feedback signal fed through said voltage feedback circuit, through a forward circuit;

    thereby producing a forward control signal proportional to the algebraic sum of said direct path signal and said voltage feedback signal,sensing a current through said electric motor,passing the sensed current signal through a buffering circuit;

    thereby producing a buffered current sense signal,passing said buffered current sense signal through a current sense gain circuit;

    thereby producing a processed current sense signal,measuring continuously and in real time a true root mean square value of said processed current sense signal;

    thereby producing a true root mean square value of said processed current sense signal,supplying a sensed back electromotive force signal,sensing an angular shaft speed of the motor by a tach and passing the tach signal through a tach gain circuit;

    thereby producing said sensed back electromotive force signal,subtracting said sensed back electromotive force signal from a voltage sense signal in a voltage algebraic summing circuit;

    thereby producing an instantaneous resultant voltage,sensing said voltage applied to said electric motor;

    thereby producing said voltage sense signal,measuring continuously and in real time a true root mean square value of said instantaneous resultant voltage;

    thereby producing a true root mean square value of said instantaneous resultant voltage,measuring continuously and in real time a phase of said buffered current sense signal;

    thereby producing a buffered current sense signal phase,measuring continuously and in real time a phase of said total control signal;

    thereby producing a control signal phase,dividing said true root mean square value of said instantaneous resultant voltage with said true root mean square value of said processed current sense signal;

    thereby producing a magnitude of real part of current feedback transfer function,subtracting said buffered current sense signal phase from said total control signal phase;

    thereby producing a phase of real part of current feedback transfer function,multiplying in a current feedback circuit magnitude of said buffered current sense signal by a value of said magnitude of real part of current feedback transfer function and shifting in said current feedback circuit the phase of buffered current sense signal for a value of said phase of real part of current feedback transfer function;

    thereby producing a processed current feedback signal,feeding back said processed current feedback signal in a positive feedback loop with respect to said forward control signal and said feedforward signal and summing the three signals,supplying said total control signal, obtained as the sum of said forward control signal and said feedforward signal and said processed current feedback signal, for modulating said power converter for the control of the flow of power from the input electrical source to the output mechanical load, whereby impedance of said electric motor is being forced to zero making an angular shaft position and speed independent of said load in a parameter free manner with respect to the impedance parameters and making a transfer function form the input position command to the angular shaft position a constant and therefore of zero order in said parameter free manner.

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