Nowadays all different kind of actuators is used in a widespread range. Their job is to transmit force, bear load, produce linear force, adjust height etc. Hydraulic fluid pressure, pneumatic pressure and electrical current usually change in to some sort of motion in actuators. This report is related to electrical actuators and self-locking problem, which is really common in them. The thesis report has been performed at Reac AB in Åmål, Sweden, a major supplier of wheel chair actuators. Electrical actuators have vast usage and they are versatile but in some cases they face with different working situation like dynamic forces. Recent generation of electrical actuators which used in wheelchairs (imagine moving wheelchair in bumpy road) have self-locking problem, which it means that they will lose their position after while under compression load. This fact will lead to de-calibration of the control system. Approximately 90% of AB production is related to the electrical wheelchairs. Challenging point here is dynamic force which can lead to de-calibration of potentiometer and failure of device. Load capacity of certain actuator (RE25) is 2000 N. In this project different method has been used to simulate and calculate different aspects. Design of new part, material selection and improvement of some parts are most important. During the period lots of static and dynamic tests, CAD design and FEM analysis have been executed. Shock absorber, lock pin and new material have been run parallel and more or less all those three had a positive effect. Finally with design and selection of lock pin solution included cogwheel and pin, we overcome to the problem with great results.