Survey of Methods of Combining Velocity Profiles with Position control

In many applications where some kind of motion is performed, for example in robotics, it is of high importance to be able to control how a certain angular motor position is reached. To this end, motion profiles are used. These profiles often define how the velocity varies during the traversal from the starting position to the desired position. It is relatively easy to let a controller act on the set velocity and a velocity feedback to achieve decent velocity following, but not as easy to also make sure that the correct position is kept along the route as well as in the end. In this paper, four approaches to manage position control alongside velocity profiles are presented and discussed. The first approach is based on continuous velocity control in an ideal environment using a PID controller. If no disturbances are present and the velocity measurement is very exact, this approach could work, but it is hardly worth the effort. This approach can be improved by switching to a distance-based control scheme near the end. Another approach is to use position control by incrementally adding to the set position. The last approach discussed is a cascaded P-PI controller where both velocity and position is considered.