Patent ID: 8716960

Claim:
A linear actuator comprising an electrical motor, a transmission, a spindle, a spindle nut, an actuation element and a control unit, where the electrical motor through the transmission and interaction between spindle and spindle nut drives the actuation element to move linearly between a first end stop and a second end stop, characterized in that to determine a position of the actuation element the control unit comprises an absolute rotary position sensor outputting a value representing an angle and comprises a counter keeping a count, where the absolute rotary position sensor is coupled to the linear actuator in such a way that the rotational angle through which the absolute rotational position sensor will give an absolute value is less than the rotational angle through which the absolute rotational position sensor is subjected to during a movement of the actuation element between the first end stop and the second end stop, causing the value of the absolute rotational position sensor to under-flow or over-flow at least once during such a movement and where the counter is arranged to keep track of the under-flows and over-flows of the value in the count, characterized in that the control unit further comprises a non-volatile memory and in that the control unit is arranged to store the count of the counter in the non-volatile memory when there is a shutdown of the linear actuator or when the rate of movement of the actuator element as indicated by the absolute rotary position sensor, falls below a predetermined limit.