Elevator position compensation system

An elevator car position compensation arrangement comprising:

• a car coupled to a motor by means of ropes;
• means for driving the motor;
• uncompensated signal generating means for generating an uncompensated car position signal;
• and
• compensated signal generating means for generating a compensated car position signal, said compensated signal generating means including instructions and data for generating a car position signal according to the following relationship:
• Position.sub.n =(True Encoder Position).sub.n -(Commanded Acceleration).sub.n-1 ›((K.sub.1 -K.sub.b)/Rise)(Position.sub.n-1)+K.sub.b !
• Where:
• True Encoder Position.sub.n =Current uncompensated/true position from driving machine shaft encoder (e.g., mm)
• Position.sub.n =Current position reference value based on driving machine encoder feedback used for position control (e.g., mm)
• Position.sub.n-1 =Previous position reference value based on driving machine encoder feedback (e.g., mm).
• Rise=Maximum value of Position (where minimum value of Position is zero) (e.g., mm).
• Commanded Acceleration.sub.n-1 =Acceleration most recently commanded by the motion controller to the drive system (meters per second)
• K.sub.1 =Slip and Stretch per unit acceleration expected at the top of the hoistway
• K.sub.b =Slip and Stretch per unit acceleration expected at the bottom of the hoistway.