AUTO-CALIBRATING WHEEL BALANCER FORCE TRANSDUCER

• US 20110270564A1
• Filed: 04/27/2011
• Published: 11/03/2011
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Hunter Engineering Company
• Original Assignee: Hunter Engineering Company
• Inventors: Feero, William B.
• Granted Patent: US 8,886,491 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: G01L 25/00 Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency

Abstract

A method and apparatus for carrying out auto-calibration of one or more piezoelectric elements in a force transducer assembly of a vehicle wheel balancing system. Output electrical signals from the piezoelectric transducers in response to application of a known imbalance force are measured and recorded. Subsequently, during an auto-calibration procedure, a known input signal is selectively applied to at least one piezoelectric element in the force transducer assembly, and at least one output electrical signal is received from the force transducer assembly. The obtained auto-calibration output signals are evaluated with respect to the output signals obtained from a previous auto-calibration, and compensation values are derived there from for application to subsequent output signals obtained during imbalance measurements.

Claims

1. A method for automatic calibration of a piezoelectric force transducer wherein the force transducer contains at least a pair of piezoelectric elements disposed to measure forces in a common axial direction, comprising:

applying a first input signal to a first piezoelectric element to generate a first force, and receiving a first output signal from said second piezoelectric element in said pair, said first output signal representative of a response by said second piezoelectric element to said first generated force;

applying a second input signal to said second piezoelectric element in said pair to generate a second force, and receiving a second output signal from said first piezoelectric element in said pair, said second output signal representative of a response by said first piezoelectric element said second generated force;

wherein said first and second output signals define a set of output signals; and

evaluating said set of output signals to establish compensation values for calibrating subsequent output signals from said first and second piezoelectric elements.

2. The method of claim 1 wherein said first and second input signals are identical.

3. The method of claim 1 wherein said first and second input signals each include at least an associated voltage component.

4. The method of claim 1 wherein said first and second output signals each include at least an associated voltage component and an associated phase component.

5. The method of claim 1 wherein the steps of applying said first and second input signals to said first and second piezoelectric elements are repeated at least once to record at least one subsequent set of output signals;

wherein said step of evaluating includes comparing said at least one subsequence set of output signals to at least one previous set of output signals to identify signal deviations; and

wherein said compensation values for calibrating said output signals from said first and second piezoelectric elements are responsive to said identified signal deviations.

6. The method of claim 5 wherein said first and second output signals each include at least an associated voltage component;

and wherein identifying signal deviations between said sets of output signals includes establishing compensation values G₁ and G₂ for said first and second piezoelectric force elements respectively, according to;

7. The method of claim 5 wherein said first and second output signals each include at least an associated phase component, and wherein identifying signal deviations between said sets output signals includes establishing compensation values θ

₁ and θ

₂ for said first and second piezoelectric elements respectively, according to;

θ

₁=θ

1_i−

θ

1_j and

θ

₂=θ

2_i−

θ

2_j

where;

θ

1_i represents a phase output signal at the first piezoelectric element obtained from a first calibration procedure;

θ

1_j represents a phase output signal at the first piezoelectric element at a second calibration procedure;

θ

2_i represents a phase output signal at the second piezoelectric element obtained from said first calibration procedure; and

θ

2_j represents a phase output signal at the second piezoelectric element at said second calibration procedure.

8. The method of claim 1 wherein steps of applying input signals to said first and second piezoelectric elements and said step of evaluating are carried out automatically as an automatic calibration.

9. A vibration transducer assembly for a vehicle wheel balancer system, comprising:

a plurality of sensor elements, one or more of said sensor elements configured to receive vibrations associated with the rotation of a vehicle wheel assembly undergoing imbalance measurement by the vehicle wheel balancer; and

wherein at least one sensor element in said plurality of sensor elements is further disposed to generate an output signal in response to forces generated by an excitation of at least one other sensor element in said plurality of sensor elements in response to an input signal.

10. The vibration transducer assembly of claim 9 wherein each sensor element in said plurality of sensor elements is a piezoelectric sensor element.

11. The vibration transducer assembly of claim 9 wherein each sensor element in said plurality of sensor elements is a magnetostrictive sensor element.

12. An auto-calibrating piezoelectric vibration transducer assembly, comprising:

a plurality of piezoelectric elements;

a first piezoelectric element in said plurality of piezoelectric elements responsive to forces applied along a measurement axis to generate a first output electrical signal;

said second piezoelectric element in said plurality of piezoelectric elements responsive to said forces applied along said measurement axis to generate a second output electrical signal;

wherein said first and second piezoelectric elements are each responsive to an input electrical signal to generate a responsive force along said measurement axis.

13. The vibration transducer assembly of claim 12 wherein said first and second output electrical signals each include a voltage.

14. The vibration transducer assembly of claim 12 wherein said first and second output electrical signals each include a phase.

15. The vibration transducer assembly of claim 12 wherein said first and second piezoelectric elements are piezo-ceramic elements.

16. An improved vehicle wheel balancer system having a rotating structure for mounting a vehicle wheel assembly, and a processing system configured to measure imbalance of said vehicle wheel assembly, the improvement comprising:

at least one vibration transducer assembly disposed within said vehicle wheel balancer system to measure vibrations associated with a vehicle wheel undergoing an imbalance measurement procedure;

wherein said at least one vibration transducer assembly is an auto-calibrating piezoelectric vibration transducer assembly having a plurality of piezoelectric elements including a first piezoelectric element responsive to forces applied along a measurement axis to generate a first output electrical signal and a second piezoelectric element responsive to said forces applied along said measurement axis to generate a second output electrical signal, said first and second piezoelectric elements each responsive to an input electrical signal to generate a responsive force along said measurement axis; and

wherein said processing system is configured to communicate input signals to said first and second piezoelectric elements of said at least one vibration transducer assembly, and to receive said associated output signals from said first and second piezoelectric elements during an auto-calibration procedure for said vibration transducer assembly.

17. A method for automatic compensation of a piezoelectric force transducer in a vehicle wheel balancer system having a processing system operatively coupled to the piezoelectric force transducer, and wherein the force transducer contains at least a pair of piezoelectric elements operatively disposed to measure forces on a common axis, comprising:

applying, from the processing system, a first input electrical signal to a first piezoelectric element to generate a first force, and receiving at said processing system, an output electrical signal from said second piezoelectric element in said pair, said output signal representative of a response to said first generated force by said second piezoelectric element;

applying, from said processing system, a second input electrical signal to said second piezoelectric element in said pair to generate a second force, and receiving at said processing system, a second output electrical signal from said first piezoelectric element in said pair representative of a response to said second generated force by said first piezoelectric element;

wherein said output electrical signals from said first and second piezoelectric elements define a set of output electrical signals; and

evaluating said set of output electrical signals to establish compensation values for calibrating an output of said first and second piezoelectric elements by comparing said set of output signals with a stored set of calibration signals from a previous automatic compensation procedure.

18. The method of claim 17 wherein said compensation values for calibrating said output of said first and second piezoelectric elements are responsive to identified deviations between said set of output electrical signals and said stored set of calibration signals.

19. The method of claim 17 wherein said set of output electrical signals are stored by the processing system as said set of calibration signals after said evaluation step.

20. The method of claim 19 further including the step of reviewing said set of stored output electrical signals to identify at least one condition associated with said first and second piezoelectric elements, said at least one condition including, but not limited to, a change in calibration or a trend in calibration changes.

21. The method of claim 17 further including the step of storing said set of output electrical signals from each automatic compensation procedure, said set of stored output electrical signals providing a history of calibration adjustments to said first and second piezoelectric elements.

22. A method for automatic compensation of a pair of piezoelectric force transducers in a vehicle wheel balancer system having a processing system operatively coupled to the pair of piezoelectric force transducers, and wherein each piezoelectric force transducer contains a single piezoelectric element operatively disposed to measure forces along at least one axis, comprising:

applying, from the processing system, an input electrical signal to a first piezoelectric force transducer selected to generate a first force in the associated piezoelectric element, and receiving at said processing system, an output electrical signal from said second piezoelectric force transducer, said output electrical signal representative of said first generated force measured at said second piezoelectric force transducer;

applying, from said processing system, an input electrical signal to said second piezoelectric force transducer to generate a second force in the associated piezoelectric element, and receiving at said processing system, a second output electrical signal from said first piezoelectric force transducer, said output electrical signal representative of said second generated force measured at said first piezoelectric force transducer;

wherein said output electrical signals from said first and second piezoelectric force transducers define said a set of output electrical signals; and

evaluating said set of output electrical signals to establish compensation values for calibrating an output of said first and second piezoelectric force transducers by comparing said set of output electrical signals with a stored set of calibration signals from a previous automatic compensation procedure.

23. A method for automatic calibration of wheel balancer force transducer including at least one piezoelectric element and a processing system operatively coupled to send signals to, and receive signals from, said piezoelectric element, comprising

generating, at said processing system an input electrical signal for transmission to said piezoelectric element;

transmitting said input electrical signal to said piezoelectric element, said at least one piezoelectric element exerting a force in response to said input electrical signal;

generating, at said transducer, an output electrical signal responsive to a resonance vibration in said at least one piezoelectric element;

transmitting said output electrical signal to said processing system; and

wherein said processing system determines a calibration for said transducer responsive to at least said output electrical signal.