Consistent kinematics and dynamics calibration of lightweight redundant industrial manipulators

Abstract

Absolute accuracy is one of industrial manipulator's key performance characteristics, which is critical for emerging robotics applications such as laser cutting, riveting, and carbon fibre placement as well as for many machining operations. On the other hand, arrival of new uses such as collaborative robots needs the estimation of interaction efforts with the operator or with the environment (hand-guiding, collision detection and free backlash assembly). This paper presents an approach to organize an integrated kinematic and dynamic calibration procedure to improve quality of models appropriate for trajectory planning and motion control. Along with bringing theoretical insights and novel arguments, we give hands-on recommendations on selection of parameters priors, initial guesses on calibration poses and trajectories, setting active constraints, algorithms tuning, and experimental data filtering which is necessary to perform consistent robot calibration in practice. We illustrate the study with experimental data and description of actual calibration performed on the KUKA Light-Weight Robot using vision-based metrology and dedicated software. In contrast to authors preceding works, this paper includes a more complete entire procedure description, analysis of dynamic calibration sensitivity with respect to kinematic parameters estimates and a chapter on how calibration results can be used for model-based trajectories planning using virtual holonomic constraints approach.

Kinematic Calibration of a 7R 6-DOF Robot With Non-spherical Wrist Using Laser Tracker

“…To guarantee the developed calibration method suitable for practical application, parameters in G1 are retained, while those in G2 are removed. By removing columns of H k corresponding to the parameters in G2, the reduced model is obtained as (25) where  q r is the error vector of kinematic parameters in G1, H k r denotes the corresponding identification Jacobian. It is notable that because of the presence of coupling joint in the 4R 3-DOF wrist, some additional constraints are defined in the controller i.e.…”

“…Therefore, the open-loop methods with external measurement devices e.g. laser tracker [5,20], measurement arms [15,21], ball-bar system [22,23], wire potentiometer [8], photogrammetry system [24,25], and so on, to measure full or partial pose of the EE have been widely used. In this case, the measured data is described in the measurement coordinate system.…”