Method for determining a degraded guide rail condition in an elevator system, computer program product, and elevator system

An elevator system comprising:

• an elevator cart;
• a hoisting motor including a motor encoder;
• at least one elevator component;
• at least one guide rail, wherein the at least one elevator component is arranged to move relative to the at least on guide rail, and wherein the at least one guide rail includes at least partly along a length thereof, position markings, and the at least one elevator component is arranged to move in contact with the guide rail and includes a rotary encoder for measuring movement of the at least one elevator component relative to the at least one guide rail, and a reader device for reading the position markings;
• and
• a control unit comprising at least one processor and at least one memory for storing at least one portion of computer program code therein, configured to:
• control the rotary encode and the reader device to obtain first data including information about movement the at least one elevator component relative to the at least one the guide rail;
• control the motor encoder to obtain second data including information about movement of the at least one elevator component relative to a hoistway of the elevator system;
• compare the first data and the second data, or characteristics based on said data-to each other;
• detect, based on the comparison, a deviation fulfilling a deviation criterion;
• subsequently, create a signal indicating a guide rail buckling based on the deviation;
• and
• send the signal to trigger a guide rail maintenance alert,
• wherein the first data is a distance travelled by the elevator component or a speed of the elevator component measured along a guide surface of the guide rail relative to the guide surface of the guide rail, and the second data is a distance travelled by the elevator cart or a speed of the elevator cart measured in a longitudinal direction of the hoistway of the elevator system relative to the hoistway of the elevator system.