Mechatronic Control System for a Compliant and Precise Pneumatic Rotary Drive Unit

Robots that enable safe human-robot collaboration can be realized by using compliant drive units. In previous works, different mechanical designs of compliant pneumatic rotary drive units with similar characteristics have been presented. In this paper, we present the overall control approach that we use to operate one of these compliant pneumatic rotary drive units. We explain the mechanical design and derive the differential equation that describes the dynamics of the system. In order to successfully operate a pneumatic drive unit with three or more working chambers, the torque specified by the controller has to be split up onto the working chambers. We transfer the well-known field-oriented control approach from electric motors to the investigated pneumatic drive unit to create such a torque mapping. Moreover, we develop optimized torque mappings that are tailored to work with this type of drive unit. Furthermore, we introduce and compare two control algorithms based on different implementations of state feedback to realize position control. Finally, we present the step responses that we achieve when we implement either one of the control algorithms in combination with the different torque mappings.

ON THE RESTORATION OF THE KINEMATIC ACCURACY OF LARGE-SIZE ROTARY-DRIVE DEVICE LONG TIME ABANDONED

Restoration of the rotary-drive device after a long non-use is an important strategic task, and the search for a way to restore it is an urgent task of the study. Previously it was found that the long-term non-use of the rotary-drive device led to a deterioration in the kinematic accuracy of its gearboxes. This article discusses possible options for restoring the kinematic accuracy of gearboxes of the rotary-drive device by increasing the metal or introducing into the control system an electromechanical device for selecting the backlash. It is shown that the restoration of the geometry of gears, as well as the bearing seats is possible, however, it requires the use of specialized equipment and significant costs. Ensuring the required kinematic accuracy due to the introduction of an electromechanical choice of backlash is achieved by considering the two schemes of the backlash-picker. The performed simulation of the operation of the drive system with an electromechanical choice of backlash in the Simulink system showed that the use of a scheme with cross-links allows for the required kinematic accuracy without significant costs. As a result, it can be argued that the introduction of an electromechanical backlash device can restore the kinematic accuracy of the rotary-drive device to acceptable values.