Four wheeled robots are the most balanced robots among other wheeled robot types. Although three wheels are enough for static stability, three wheeled robots can lose balance during locomotion. Four wheeled robots rarely lose stability while moving. Four wheeled robots can be controlled both using differential steering and car like steering methods.
Direction control of four wheeled robots can be done by applying two different methods. First of these methods is differential steering method like used in two wheeled robots. The speed difference applied to opposite sided motors makes the robot change its direction to the side of the slow moving wheel. This locomotion mechanism is very similar to the locomotion of tracked robots. Since wheels are used instead of tracks, wheels often slip and an offset occurs while adjusting orientation. To prevent slip and offset, these robots design to be symmetrical and distance between the front and rear wheels are kept at minimum.
Another method used in direction control of four wheeled robots is car like steering. In this method the heading angle of front or rear wheels are adjusted with the use of a differential box.