Method and apparatus to determine the imbalance in a rotating object

A method to determine the imbalance in a wheel rotating about a shaft, said method comprising:

• directly connecting said shaft to an eight pole asynchronous induction motor drive means to rotate said wheel to a predetermined speed;
• accelerating said wheel to a velocity;
• removing power to said drive means;
• and
• continuously measuring the magnitude of force of imbalance of said wheel as the velocity of said wheel decreases.

An apparatus to determine the imbalance in a rotating object, said apparatus comprising:

• means for supporting said object;
• drive means directly coupled to said support means for accelerating said object to a predetermined speed;
• means for removing power to said drive means;
• three force transducer means each for continuously measuring the magnitude of the imbalance of the object as the velocity of the object decreases, a first force transducer means and a second force transducer means positioned in a line substantially perpendicular to said support means and for generating a first and a second signal respectively;
• a third force transducer means positioned spaced apart from said line and for generating a third signal;
• rotational angle transducer means for geneating a rotational signal in response to the rotation of said object;
• electronic means for receiving said first, second and third signals, and said rotational signal and for calculating the magnitude and angular position of said imbalance, in response thereto;
• said electronic means comprising:
• adder means for receiving said first and second signals and for generating an average signal in response thereto;
• diameter compensator means for receiving said average signal, said third signal and a signal representative of the diameter of said object;
• said compensator means for generating a modified third signal (F.sub.3) and a modified average signal (F.sub.4) in response thereto;
• said modified third signal being said third signal divided by said signal representative of the diameter;
• said modified average signal being said average signal divided by said signal representation of said diameter;
• calculator means for receiving data on the width (c) of the object, the distance (f) between the third transducer means to the midpoint between the first and the second transducer means, and the distance (a) between the midpoint of the first and second transducer means and the side of the object closer to the drive means, and said modified third signal (F.sub.3) and the modified average signal (F.sub.4) and for generating a first imbalance signal (F.sub.1) and a second imbalance signal (F.sub.2) in response thereto and in accordance with the following formulas;
• ##EQU6## means for receiving said rotational signal and for generating an inverse velocity signal in response thereto;
• velocity compensating means for receiving said first and second imbalance signals and inverse velocity signal and for generating a first and a second mass imbalance signals in response thereto;
• position calculating means for receiving said rotational signal and for generating a rotational position signal to determine the rotational position of the imbalance of said object;
• and
• display means for displaying said first and second mass imbalance signals and said rotational position signal.