Two wheeled robot balance is easier compared to single wheeled robots even though they are not statically stable. Balance problem of a two wheeled robot is an inverted pendulum problem. Robot moves towards the direction that it is tumbling to keep balance. Two wheeled robots need a sensor to keep their balance. Generally a tilt sensor is used for that purpose. Two wheeled robots control their direction using differential steering method. Two wheeled robots are often preferred due to their simple design and easy control method.
There are some design considerations to keep two wheeled robots in balance. First of these is to position the robot components properly so that the center of gravity of the robots stays under the axle of the wheels. For that reason generally heavy parts such as the battery and the motors are positioned on the downside of the robot. Another method is to keep the wheel diameters as high as possible. Applying these methods makes the balance problem of two wheeled robots easier.
Two wheeled robots have high interest among researchers. Reprogrammable two wheeled robots are used to test new control methods by the researchers. These robots are useful because their balance problem is an inverted pendulum problem and they have easy control methods.
