Disturbance compensation in pushing, pulling, and lifting for load transporting control of a wheeled inverted pendulum type assistant robot using the Extended State Observer

In this paper the subtasks of lifting, pushing, and pulling of an Inverted PENdulum Type Assistant Robot (IPENTAR) are described. These three motions comprise the initial work for the larger task of transporting of a load. During execution of these tasks, the forces that are applied on the robot are seen as disturbances and cause errors in the system. If these errors are not compensated the system may become unable to perform the task. One way of compensating for these errors is to implement an observer that can estimate the applied disturbance and then use the estimated value as feedback. Most observers rely heavily on the system model parameters which can have inaccuracies or are difficult to obtain. And so an observer that requires little system information known as the Extended State Observer is applied to the system. Disturbance tests and the control for the pushing, pulling, and lifting are discussed and results are presented.