Digital position and velocity determination in controlled drive systems

Motion control of robotic or manipulator joints, tool machines axes or more genrally of drive systems require accurate position, velocity and possibly acceleration control. Today, these controls are almost always realized using digital controllers. Therefore, digital position, velocity and accelleration informations must be precise and accurate. To mini mize the sensor numbers as well as the wiring, the velocity and accellereation informations are often numerically computed form the positino. Different algorithms can be used : simple difference, polynomial interpolation, ex-quad interpolation,extrapolator, observer. The type of sensor, its precision and its location as well as the sampling time and the used alghorithm strongly effect the quality of the computed quantities (velocity and/or accelleration) and therefore the control performance. This paper analyses the static dynamic performances of different digital position and velocity measurements.