New methods to improve the behaviour of industrial robots

Member of the Department of Electrical and Electronic Engineering at the Public University of Navarre, Jesús Mª Corres Sanz, has suggested a new method which enables, amongst other applications, response enhancement to perturbations in electrical machines such as those experienced by an electric vehicle. These techniques, moreover, can be applied to any type of industrial robot.

In this thesis the design of velocity observers and perturbation par is studied for their application to mechatronic systems incorporating encoders as a position sensor. The observers are follow-up algorithms. This is an interesting topic from the point of view of applications in the industrial area. Specifically, it can be applied in the field of any kind of robot-machines, lasers for shaping parts, etc.

The research initiated with a review of the principal literature that existed on the theme. In order to do this, Jesús Mª Corres approached the first, theoretical section from two angles: firstly, he suggested modifying the Kalman filter in order to reduce the effect of the quantification of the digital position transducer.

Regarding the second approach, the observers obtained are characterised for providing estimates with a guaranteed margin of error, which in many cases is information more useful for system design than for statistical approximation. It is precisely this second part, called “guaranteed limits”, that is one of the most novel chapters in the thesis given that, in this area, no applications have been made in this area.

Digital processing card

The behaviour of these proposed algorithms was tested in the final part of the research project, by means of its implementation in a vector control system of the induction machine and based on a Digital Signal Processor, designed for this – a DSP-based card to test the proposed algorithms with the induction machine was developed to this end.

The result was initially applied on the testing pad at the university and now it is to be applied to a real robot.

The practical applications of the research are many. Thus, in an electric vehicle, the use of thus system permits the suppression of vibrations which these produce. Moreover, road surface adherence can also be estimated for a vehicle of these characteristics and its route. Other applications for the system are robotics, wind turbines, sheet metal production, or the suppression of vibrations in a lift, amongst others.

In order to apply the proposed techniques it is only necessary for the measurement of the angular position of the machine axis be carried out by a digital encoder; this is the case in those machines for which precision and robustness are important, such as machines with numerical control or robots.

Moreover, the research report concludes, the two lines of investigation do not contradict each other, but complement each other, and their application depends on the model of perturbations that each system in concrete might have. Thus, the statistical approximation handles more information and, concomitantly, provides more precise estimations. In this way the operating range of the movement controller range at very low speeds can be extended, enhancing the rapidity of response of external perturbations. Regarding the statistical approximation, there is the advantage of enabling a more direct method of expressing the uncertainties in entries and exits from the viewpoint of a control system designer.

Contact :
Iñaki Casado Redin
Nafarroako Unibertsitate Publikoa
inaki.casado@unavarra.es
(+34) 948 16 97 82