Control system for vibrating a member at its resonant frequency

For use with a device having a member supported for vibratory motion and an electromagnetic driver including a coil surrounding a core, a control system for causing said driver to drivingly vibrate said member at the member's resonant frequency, said control system comprising:

• a means for detecting the vibratory movement of said member and for producing a detected frequency electrical signal having a frequency equal to the vibratory frequency of said member;
• a means responsive to said detected frequency signal for producing an electrical drive signal supplied to said driver, said electrical drive signal consisting of spaced pulses of electric current constrained to flow in opposite directions through said coil of said driver during alternate ones of said pulses and which pulses appear at a frequency equal to that of said detected frequency signal;
• said means for producing an electrical drive signal including a source of D.C. power, a switching means connected between said source and said coil for switching between one state at which power from said source is connected to flow in one direction through said driver coil and a second state at which power from said source is connected to flow in the other direction through said driver coil, and means including a phase-locked loop circuit for switching said switching means between said first and second states at a frequency directly related to the frequency of said detected frequency signal, said phase-locked loop circuit including a phase comparator and a voltage controlled oscillator, said phase comparator having said detected frequency signal as an input thereto, and said voltage controlled oscillator having an output frequency equal to Nf where f is the frequency of the input signal to the phase comparator and N is an integer, a divide by 2N counter with 2N decoded outputs, and two one shot multivibrators each connected with a different one of the outputs of said counter for producing, in combination, two trains of pulses the pulses of which alternate in time and which are supplied to said switching means to switch said switching means between its first and second states.

A control system for use with a device having a member supported for vibratory motion and an electromagnetic driver including a coil surrounding a core, said control system comprising:

• a means for detecting the vibratory movement of said member and for producing a detected frequency electrical signal having a frequency corresponding to the vibratory frequency of said member;
• a phase-locked loop circuit including a phase comparator having said detected frequency signal as an input thereto, a voltage controlled oscillator connected to the output of said phase comparator, a counter connected to the output of said voltage controlled oscillator, and means connecting at least one of the output terminals of said counter to said phase comparator to provide a feedback signal with which said detected frequency input signal is compared;
• a means providing a source of DC power;
• a switching means connected between said source of DC power and said driver coil and switchable between one state in which current from said DC source is connected to flow in one direction through said driver coil and a second state in which current from said DC source is connected to flow in the other direction through said driver coil;
• and
• means responsive to the output signals appearing at at least one of the output terminals of said counter for alternately switching said switching means between said first and second states.

A control system for use with a device having a member supported for vibratory motion and an electromagnetic driver including a coil surrounding a core, said control system comprising:

• a means for detecting the vibratory movement of said member and for producing a detected frequency electrical signal having a frequency corresponding to the vibratory frequency of said member;
• a phase-locked loop circuit including a phase comparator having said detected frequency signal as an input thereto, a voltage controlled oscillator connected to the output of said phase comparator, a counter connected to the output of said voltage controlled oscillator, said voltage controlled oscillator having an output frequency equal to N times the frequency of the signal input to said phase comparator and said counter being a 2N counter with a code converter and 2N output tereminals, and an OR gate connecting two of said output terminals of said counter to said phase comparator to provide a feedback signal with which said detected frequency input signal is compared;
• a means providing a source of DC power;
• a switching means connected between said source of DC power and said driver coil and switchable between one state in which current from said DC source is connected to flow in one direction through said driver coil and a second state in which current from said DC source is connected to flow in the other direction through said driver coil;
• and
• means responsive to the output signals appearing at two other output terminals of said counter for alternately switching said switching means between said first and second states.