Harmonic signal analyzer system for testing tires

Abstract

An electronic, undamped oscillator driven by a periodic input signal (forcing function) having a frequency equal to the natural frequency of the oscillator develops an output sinusoidal signal having a rate of growth (amplitude increase) proportional to the amplitude of the first harmonic component of the input signal. When the input signal is a force variation signal and the oscillator is tuned to the rotational frequency of a tire mounted on the force variation machine, the rate of growth of the output signal of the oscillator is proportional to the amplitude of the force variation signal. A peak follower detects the amplitude of the increments between successive peaks of the oscillator output signal. A meter indicates the amplitude of the successive peaks of the oscillator output signal, thereby indicating the amplitude of the first harmonic component of the force variation signal. A circuit which senses the positive-slope zero-crossing of the oscillator output signal is utilized to energize a tire-marking unit, thereby indicating the position of the peak of the first harmonic component.

Having thus described our invention, what we claim and desire to protect by Letters Patent is: 
     
       1. Apparatus for representing a predetermined harmonic component of a repetitive input control effect comprising: means for supplying a repetitive input control effect comprising a predetermined harmonic component;   means responsive to the amplitude of said predetermined harmonic component of said input control effect for developing a second control effect having a rate of change of amplitude representative of the amplitude of said predetermined harmonic component of said input control effect;   and means responsive to said second control effect for deriving therefrom a third control effect representing the difference in the amplitudes of the peaks of selected cycles of said second control effect, thereby representing the amplitude of said predetermined harmonic component of said input control effect.   
     
     
       2. Apparatus in accordance with claim 1 which includes means responsive to said second control effect for deriving therefrom a fourth control effect representative of the phase of said predetermined harmonic component of said input control effect. 
     
     
       3. Apparatus for representing a predetermined harmonic component of a repetitive input signal comprising: circuit means for supplying a repetitive input signal comprising a predetermined harmonic component;   circuit means responsive to the amplitude of said predetermined harmonic component of said input signal for developing a second signal having a rate of change of amplitude representative of the amplitude of said predetermined harmonic component of said input signal;   and circuit means responsive to said second signal for deriving therefrom a third signal representing the difference in the amplitudes of the peaks of selected cycles of said second signal, thereby representing the amplitude of said predetermined harmonic component of said input signal.   
     
     
       4. Apparatus for representing the first harmonic component of a repetitive input control effect comprising: means for supplying a repetitive input control effect comprising a first harmonic component;   means responsive to the amplitude of said first harmonic component of said input control effect for developing a second control effect having a rate of change of amplitude representative of the amplitude of said first harmonic component of said input control effect;   and means responsive to said second control effect for deriving therefrom a third control effect representing the difference in the amplitudes of the peaks of selected cycles of said second control effect, thereby representing the amplitude of said first harmonic component of said input control effect.   
     
     
       5. Apparatus in accordance with claim 4 in which said means responsive to the amplitude of said first harmonic component comprises oscillator means resonant at the frequency of said first harmonic component. 
     
     
       6. Apparatus in accordance with claim 3 in which said circuit means responsive to said second signal comprises peak detector means for developing a third signal representative of the difference in the amplitudes of the peaks of successive cycles of said second signal. 
     
     
       7. Apparatus in accordance with claim 1 which includes means responsive to said second control effect for developing pulses occurring with a predetermined phase relation to said predetermined harmonic component of said input control effect. 
     
     
       8. In apparatus for developing a control effect representative of the non-uniformity of an object rotated thereby, the apparatus including means responsive to the rotating object for developing a first control effect having a repetition frequency representative of the frequency of rotation of the object, said first control effect comprising a predetermined harmonic component having an amplitude representative of the magntidue of the non-uniformity of the object, a harmonic analyzer comprising: means resonant at the frequency of said predetermined harmonic component of said first control effect and responsive to the amplitude of said predetermined harmonic component of said first control effect for developing a second control effect having a rate of change of amplitude representative of the amplitude of said predetermined harmonic component;   and means responsive to said second control effect for deriving therefrom a third control effect representing the difference in the amplitudes of selected cycles of said second control effect, thereby representing the magnitude of the non-uniformity of the object.   
     
     
       9. In apparatus for developing a signal representative of the non-uniformity of a tire rotated thereby, the apparatus including means responsive to the tire during rotation thereof for developing a first signal having a repetition frequency representative of the frequency of rotation of the tire, the first signal comprising a first harmonic component having an amplitude representative of the magnitude of the non-uniformity of the tire and having a phase representative of the phase of the non-uniformity of the tire relative to a reference point, a harmonic analzyer comprising: oscillator means responsive to the amplitude of said first harmonic component of said first signal and resonant at the frequency of said first harmonic component of said first signal for developing a second signal having a rate of change of amplitude representative of the amplitude of said first harmonic component;   peak detector means responsive to said second signal for deriving therefrom a third signal representative of the difference in the amplitudes of the peaks of successive cycles of said second signal;   and circuit means responsive to said second signal for deriving therefrom a fourth signal representative of the phase of said first harmonic component of said first signal, whereby the non-uniformity of the tire is indicated.   
     
     
       10. Apparatus for developing a control effect representative of the non-uniformity of a rotatable object comprising: means for rotating an object;   means responsive to the rotating object for developing a first control effect having a repetition frequency representative of the frequency of rotation of the object, said first control effect comprising a predetermined harmonic component having an amplitude representative of the amplitude of a predetermined harmonic component of the non-uniformity of the object and having a phase representative of the non-uniformity of the object relative to a reference point;   means responsive to amplitude of said predetermined harmonic component of said first control effect for developing a second control effect having a rate of change of amplitude representative of the amplitude of said predetermined harmonic component of said first control effect;   means responsive to said second control effect for developing a third control effect representative of the phase of said predetermined harmonic component of said first control effect;   and means responsive to said third control effect for marking the object to indicate the non-uniformity of the object in accordance with the phase of said predetermined harmonic component of said first control effect.   
     
     
       11. Apparatus for developing a signal representative of the non-uniformity of a tire comprising: support means for rotating a tire;   means responsive to the force variation on said support means during rotation of the tire for developing a first signal having a repetition frequency representative of the frequency of rotation of the tire, said first signal comprising a first harmonic component having an amplitude representative of the amplitude of the first harmonic component of force variation on said support means and having a phase representative of the phase of said first harmonic component of force variation relative to a reference point;   oscillator means responsive to the amplitude of said first harmonic component of said first signal and resonant at the frequency of said first harmonic component of said first signal for developing a second signal having a rate of change of amplitude representative of the amplitude of said first harmonic component of said first signal;   peak detector means responsive to said second signal for developing a third signal representative of the difference in the amplitudes of the peaks of successive cycles of said second signal and thus representative of the amplitude of said first harmonic component of said first signal;   means coupled to said peak detector means for indicating the amplitude of said first harmonic component of force variation;   means responsive to said second signal for developing a fourth signal representative of the phase of said first harmonic component of said first signal;   and means responsive to said fourth signal for marking the tire to indicate the peak of said first harmonic component of force variation. .Iadd.   
     
     
       12.  A tire radial force variation determining apparatus comprising means to support and rotate a pneumatic tire, a rotatable load wheel exerting a radial load thereon, means mounting the load wheel and the tire for relative deflection in response to radial force variations of the tire, means responsive to said deflections to produce an electrical signal representative of said deflections, circuit means to convert said signal to a plurality of pulses each of which represents the location of the maximum of a predetermined harmonic component of the radial force variation of the tire in a single revolution thereof, and means responsive to said pulses to indicate with reference to the circumference of the tire tested the position of the maximum of said predetermined harmonic component of the radial force variation. .Iaddend..Iadd. 13. Apparatus for developing a control effect representative of the non-uniformity of a rotatable object comprising: first means for rotating an object;   second means responsive to the rotating object for developing an input control effect having a repetition frequency representative of the frequency of rotation of the object, said control effect comprising a predetermined harmonic component having a phase representative of the non-uniformity of the object relative to a reference point;   and electronic oscillator circuit means coupled to said second means and adjustably responsive in frequency to the frequency of said predetermined harmonic component of said input control effect for developing a second control effect representative of the phase of said predetermined harmonic component of said input control effect, thereby representing the non-uniformity of the object. .Iaddend. .Iadd. 14. Apparatus for developing a signal representative of the non-uniformity of a tire comprising:   first means for rotating a tire;   second means responsive to the rotating tire for developing an input signal having a repetition frequency representative of the frequency of rotation of the tire, said signal comprising a predetermined harmonic component having a phase representative of the non-uniformity of the tire relative to a reference point;   and means, including electronic oscillator circuit means coupled to said second means and adjustably responsive in frequency to the frequency of said predetermined harmonic component of said input signal, for developing pulses representative of the phase of said predetermined harmonic component of said signal, thereby representing the non-uniformity of the tire. .Iaddend..Iadd. 15. Apparatus in accordance with claim 14 which includes means responsive to said pulses for marking the tire to indicate the non-uniformity thereof. .Iaddend..Iadd. 16. Apparatus for developing a signal representative of the non-uniformity of a tire comprising:   first means for rotating a tire;   second means responsive to the rotating tire for developing a signal having a repetition frequency representative of the frequency of rotation of the tire, said signal comprising an input first harmonic component having a phase representative of the phase of the first harmonic component of the non-uniformity of the tire relative to a reference point;   and means, including electronic oscillator circuit means coupled to said second means and adjustable responsive in frequency to the frequency of said first harmonic component of said input signal, for developing pulses representative of the phase of said first harmonic component of said signal, thereby representing the non-uniformity of the tire. .Iaddend.