Transient load damping circuit for excavator
First Claim
1. In a Ward-Leonard drive system for an excavator having a control circuit which is responsive to command and feedback signals to control the torque output of the drive system motor by controlling the field current of the drive system generator, the improvement therein comprising:
- means connected to the armature loop formed by said motor and generator for sensing a signal having one component proportional to motor armature counter emf and a second component proportional to the rate of change of motor armature current; and
feedback circuit means connected to receive said sensed signal and generate a feedback signal to said control circuit, said feedback circuit means includes first differentiator means for providing a signal proportional to the first derivative of said sensed signal and second differentiating means for providing said feedback signal which is proportional to the second derivative of said sensed signal.
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Accused Products
Abstract
A Ward-Leonard drive system for a dragline excavator includes a feedback circuit which connects to the motor-generator armature loop to sense a signal proportional to motor armature counter emf and rate of change of armature current. The feedback circuit takes the second derivative of this signal and applies it to a circuit which controls motor speed and torque. The feedback circuit alters the response of the drive system to sudden increases in motor load caused by rough digging and thereby reduces transient loading on the mechanical elements of the drive system.
33 Citations
14 Claims
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1. In a Ward-Leonard drive system for an excavator having a control circuit which is responsive to command and feedback signals to control the torque output of the drive system motor by controlling the field current of the drive system generator, the improvement therein comprising:
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means connected to the armature loop formed by said motor and generator for sensing a signal having one component proportional to motor armature counter emf and a second component proportional to the rate of change of motor armature current; and feedback circuit means connected to receive said sensed signal and generate a feedback signal to said control circuit, said feedback circuit means includes first differentiator means for providing a signal proportional to the first derivative of said sensed signal and second differentiating means for providing said feedback signal which is proportional to the second derivative of said sensed signal. - View Dependent Claims (2, 3, 4)
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5. In an excavator drive system the combination comprising:
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a drive motor having an armature, and a field winding connected in series with the armature; a generator having an armature connected to said motor armature to form a loop which includes said motor and generator armatures and said motor field winding; a voltage divider connected across said generator armature and including a pair of series connected resistors; a feedback circuit having one input lead connected to the juncture of said voltage divider resistors and a second input lead connected to the juncture of said motor armature and its associated field winding, said feedback circuit including means for generating a feedback signal proportional to the second derivative of the signal applied to said input leads; and a control circuit connected to effect the operation of said generator and connected to receive said feedback signal, said control circuit being responsive to said feedback signal to alter the operation of the generator. - View Dependent Claims (6, 7, 8, 9)
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10. In an excavator drive system the combination comprising:
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a drive motor having an armature, and a field winding connected in series with the armature; d-c voltage generating means having a pair of leads connected to said motor armature to form a loop which includes said motor armature, said d-c generator means and said motor field winding; a voltage divider connected across said d-c generating means leads and including a pair of series connected resistors; a feedback circuit having one input lead connected to the juncture of said voltage divider resistors and a second input lead connected to the juncture of said motor armature and its associated field winding, said feedback circuit including means for generating a feedback signal proportional to the second derivative of the signal applied to said input leads; and a control circuit connected to effect the operation of said d-c generating means and connected to receive said feedback signal, said control circuit being responsive to said feedback signal to alter the operation of the d-c generating means. - View Dependent Claims (11, 12, 13, 14)
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Specification