The LINA 200 absolute linear encoder: HEIDENHAIN encoder technology for cableless elevators of the future
Envision an elevator car not pulled by cables while capable of both vertical and horizontal travel—HEIDENHAIN is offering the encoder technology to make this possible. The LINA 200 absolute inductive linear encoder features two tracks with differing signal periods from which an absolute position value is calculated.
Rather than lying in the same plane, these tracks are designed to face each other. The resulting U-shaped scale allows the measuring standard to be scanned from two sides. At the same time, a double-wall design protects both the graduation and the scanning process from mechanical and electromagnetic interference. This structural configuration also combines maximum stiffness with low weight. What’s more, the U-shaped design provides significant benefits for the mechanical sturdiness of the scale and the robustness of the encoder signals.
Possessing an overall length of 2400 mm, the graduation carrier of the LINA 200 is mounted to the elevator car. It consists of four segments, each with a measuring length of approximately 600 mm. These segments are read by cascaded scanning heads mounted inside the shaft, thus permitting continuous position feedback over the entire travel distance. Even with its generous guideway tolerances of ±5 mm and ±4 mm, the LINA 200 still attains a tiny measuring step of approximately 2 µm. It thus delivers reliable, highly accurate position feedback for the cableless elevator’s motor control. Yet it also provides sufficiently wide tolerances for real-world mounting inside the elevator shaft and for the compensation of building displacement.
LINA 200: reliable data transmission via EnDat for high dynamic performance and passenger comfort
Developed specifically for cableless elevators, the LINA 200 boasts excellent performance data when it comes to dynamics and passenger comfort. Traveling speeds of 6 m/s were easily attained during initial testing, and in a laboratory setting, the LINA 200 provided reliable position feedback at speeds of up to 18 m/s. At low speed, as well as during the deceleration and acceleration phases before and after a stop, the high-resolution position feedback (18 bits) at a measuring length of approximately 600 mm ensures very comfortable and gentle motion.
The scanning head signals are so robust and reproducible that the diagnostic values for signal quality defined in the EnDat protocol can also yield information about whether the guide rails are within tolerance. The LINA 200 thus serves not only as a linear encoder but also provides data for continuous diagnostics and condition monitoring of the larger mechanical system. As a result, lateral deviations during operation can be detected. The high-accuracy position values are transmitted purely digitally to the subsequent electronics via the EnDat 2.2 interface. In this particular application, however, EnDat 2.2 provides another important and safety-relevant benefit pertaining to the strong magnetic fields that surround linear motors: the EnDat 2.2 interface features high electromagnetic compatibility and, unlike conventional analog signals, ensures reliable data transmission even in this kind of environment.