Christian Bauer

Zusammenfassung

Industrial robots are rarely used for machining tasks due to their limited path accuracy. This accuracy is mainly limited by inaccuracies in the drive trains. Compliance and transmission errors occur in the joint gearboxes. While transmission errors have been extensively studied for strain wave gears, there is little research on these errors in cycloidal drives. This gearbox type is commonly used in industrial robots for medium to heavy payloads. It is proposed to model the mainly periodic transmission errors using a Fourier series where amplitude and phase are defined as a polynomial function of the main influence factors load-torque, velocity, and temperature. Measurements of the transmission errors were conducted using an experimental setup representing a single robot joint. In the evaluation of the measurement data, harmonic frequencies were related to mechanical properties of the cycloidal drive. These frequencies were used to identify the parameters of the polynomial Fourier series model. Compared to validation measurements, the derived model shows an average root mean square error of 0.026 mrad. It is proposed to use the output of the resulting model in a feedforward control approach to compensate the transmission errors and to increase the path accuracy of industrial robots.

Zusammenfassung

This dataset contains all identification and validation data used in the conference paper "Modeling Load-, Velocity-, and Temperature-Dependent Transmission Errors of Cycloidal Drives for Industrial Robots Using Fourier Series".The experimental data was recorded using an experimental setup to identify the transmission error of cycloidal drives as described in the paper.The data is divided into the two folders, "identification" and "validation" containing one file per measurement. The file names contain the parameter combination of load torque tau_load in N m, input-side velocity theta_dot in rad and lubricant temperature T in °C. Each measurement file contains a table with the input-side position theta in rad in the first column and the transmission error theta_TE in rad in the second column.The MATLAB script "plot_figures.m" can be used to plot the position domain data from the figures 3 to 6 in the publication.The function "read_data.m" is applied to import all measurement data into two MATLAB structure arrays "identification" and "validation".

Zusammenfassung

Im Vergleich zu Werkzeugmaschinen erreichen Industrierobotereine geringe Absolut- und Bahngenauigkeit. Um neue Anwendungsgebiete für die Industrierobotik zu erschließen, forscht das Institut für Steuerungstechnik der Werkzeugmaschinen und Fertigungseinrichtungen (ISW) der Universität Stuttgart daher an regelungstechnischen Lösungen zur Erhöhung der Genauigkeit. Sowohl Prozesse ohne externe Kräfte wie das Laserschneiden als auch Prozesse mit hohen Prozesskräften wie die spanende Bearbeitung sollen so für den Einsatz von Industrierobotern erschlossen werden.

Zusammenfassung

Haptic feedback of gripping forces during robotassisted surgery can benefit the surgical outcome by means of reduced forces applied to the tissue. A custom-designed haptic user interface allows to control four degrees of freedom of the instrument’s endeffector and to display gripping forces. System-centered evaluation is performed to assess its capability of displaying feedback with high mechanical bandwidth. In addition, the perception of gripping forces is evaluated using task-centered methods. Two tasks were performed by ten participants to assess the perceived feedback regarding size and stiffness of grasped objects. Maximum feedback forces of 4.3 N and a mechanical bandwidth of 73.5 Hz are achieved. Tests with participants showed promising results regarding the discrimination of size and stiffness of grasped objects.

Zusammenfassung

One of the major disadvantages of robot-assisted surgery is the absence of haptic feedback. A haptic user interface (HUI), which is part of a telemanipulation system addressing this issue, is described. To generate high-quality haptic feedback using the HUI, it is necessary to have a precise understanding of the system's behavior. The capstan drive of the HUI is modeled as a rotational two-mass system. The mechanical parameters are determined by minimizing the error between the mechanical transfer function, defined by motor torque as input and velocity as output, and measured frequency responses. The relationship between motor current and torque is approximated as Fourier series depending on the motor angle. Friction is modeled as Coulomb and viscous friction, Stribeck curve, and continuous approximation of the Stribeck curve. The model is utilized to enhance the precision of the generated feedback force. The described system enables the generation of haptic feedback with a maximum force of 6 N, a force resolution of 0.05 N, and a usable frequency bandwidth of 31 Hz.