System and method for maintaining plural driven components at reference positions

In a material-handling machine having first and second idler wheels mounted to respective first and second components, each component being driven by a separate AC motor connected to a respective variable-frequency inverter, and wherein the idler wheels are mechanically disconnected from one another, a method for maintaining the positions of each of the components substantially coincident with a component reference position and including the steps of:

• algebraically summing electrical first and second signals, such first and second signals representing the rotational speeds of the first and second idler wheels, respectively;
• providing a differential signal representing a difference between the speeds of the idler wheels;
• and
• generating an equalizing signal reducing the rate of acceleration of the higher-speed idler wheel.

In a machine having plural components, each driven by a separate motor, a method for maintaining the positions of each of the components substantially coincident with a component reference position including the steps of:

• providing a rate-of-acceleration reference signal;
• generating a first signal representing the speed of the first component;
• generating a second signal representing the speed of the second component;
• algebraically summing the first signal and the second signal, thereby providing a summation signal;
• applying a differential function to the summation signal, thereby generating a velocity signal having (a) a magnitude representing the difference between the speed of the first component and the speed of the second component, and (b) a polarity denoting that component having the higher speed;
• generating an equalizing signal for reducing the rate of acceleration of the higher-speed component;
• and
• algebraically combining the rate-of-acceleration reference signal and the equalizing signal.

In a machine having at least first and second components, each driven by a separate motor, a method for maintaining the positions of each of the components substantially coincident with a component reference position and including the steps of:

• providing a differential signal representing a difference between the speeds of the components;
• such providing step including the steps of:
• generating a first signal representing the speed of the first component;
• generating a second signal representing the speed of the second component;
• algebraically summing the first signal and the second signal, thereby providing a summation signal;
• applying a differential function to the summation signal, thereby generating a velocity signal having (a) a magnitude representing the difference between the speed of the first component and the speed of the second component, and (b) a polarity denoting that component having the greater speed;
• and the method further includes the step of:
• generating an equalizing signal reducing the rate of acceleration of the higher-speed component.