Leveling control device for elevator system

In an elevator system including:

• an alternating current power source;
• a converter for converting an alternating current from the alternating current power source into a direct current;
• a condenser for smoothing the direct current from the converter;
• an inverter for converting the direct current from the condenser into an alternating current having a variable frequency and voltage;
• an alternating current motor driven in the clockwise or counterclockwise direction by a three phase alternating current supplied from the inverter;
• a sheave rotated in the clockwise or counterclockwise direction by the alternating current motor;
• a car connected to one end of a rope winding around the sheave, and vertically movable in a hoist way, for loading and transferring the passengers or cargo to a designated floor;
• and a balance weight connected to the other end of the rope, for balancing with the car, a leveling control device for the elevator system, comprising:
• a current detector connected to a supply path of the three phase alternating current supplied from the inverter to the motor, for detecting a current value of the alternating current;
• a pulse generator for detecting a speed of the motor, and outputting a corresponding pulse signal;
• a position detection unit disposed at the car, for detecting whether a bottom level of the car is identical to a bottom level of the designated floor;
• a load detector disposed at a lower portion of the car, for detecting a load of the car;
• a load current converter for converting a detection load represented by a load detection signal from the load detector into a corresponding current signal, and outputting it;
• a level difference detection unit for detecting according to an output signal from the position detection unit whether the bottom level of the car is different from the bottom level of the designated floor, and a direction of a level difference compensation operation;
• a level compensation operation command generator for outputting a level compensation operation command signal, when receiving from the level difference detection unit a signal showing that the bottom level of the car is different from the bottom level of the designated floor, and the direction of the level difference compensation operation;
• a load torque estimation unit for estimating an amount of the load applied to an output axis of the motor correspondingly to the speed measured by the pulse generator, and outputting the estimated amount of the load as a current signal, when receiving the level compensation operation command signal from the level compensation operation command generator;
• a speed command generator for generating a speed command signal of the motor;
• a speed controller for outputting a speed command value corresponding to a difference value between the speed command signal from the speed command generator and the speed from the pulse generator as a current command signal of the motor, in order to compensate a speed difference therebetween;
• a current controller for outputting a resultant value obtained by adding a torque component current command value represented by the torque component current command signal from the speed controller, a current value represented by the estimated load current signal from the load torque estimation unit, and a current value according to the detection load from the load current converter, as a torque component current compensation command signal;
• and
• a pulse width modulator for generating a switching signal to be applied to the inverter according to the torque component current compensation command signal from the current controller.