A Reliable Gravity Compensation Control Strategy for dVRK Robotic Arms With Nonlinear Disturbance Forces

Abstract

External disturbance forces caused by nonlinear springy electrical cables in the master tool manipulator (MTM) of the da Vinci Research Kit (dVRK) limits the usage of the existing gravity compensation methods. Significant motion drifts at the MTM tip are often observed when the MTM is located far from its identification trajectory, preventing the usage of these methods for the entire workspace reliably. In this letter, we propose a general and systematic framework to address the problems of the gravity compensation for the MTM of the dVRK. Particularly, high-order polynomial models were used to capture the highly nonlinear disturbance forces and integrated with the multi-step least square estimation framework. This method allows us to identify the parameters of both the gravitational and disturbance forces for each link sequentially, preventing residual error passing among the links of the MTM with uneven mass distribution. A corresponding gravity compensation controller was developed to compensate the gravitational and disturbance forces. The method was validated with extensive experiments in the majority of the manipulator's workspace, showing significant performance enhancements over existing methods. Finally, a deliverable software package in MAT-LAB and C++ was integrated with dVRK and published in the dVRK community for open-source research and development.Index Terms-Medical robots and systems, calibration and identification, surgical robotics: laparoscopy.

Surgeon-Centered Analysis of Robot-Assisted Needle Driving Under Different Force Feedback Conditions

“…In our experiment, we implemented two force feedback conditions, (1) position exchange force feedback and (2) direct sensing from a force sensor that was attached to the tissue plate. In addition, all participants in all 3 conditions received gravity compensation as described in (Chen et al, 2017), and more advanced algorithms (e.g., the one implemented by Lin et al, 2019) could improve the performance. It is possible that with better gravity compensation the participants could perform better and this could have allowed for observing more pronounced differences between the different force feedback conditions.…”

A hybrid learning‐based hysteresis compensation strategy for surgical robots

“…Because of the precision manufacture of surgical manipulators, the frictional force between components can cause less disturbance. In addition, the dynamic frictional disturbance force caused by the motion of robotic arms normally also inherits hysteretic behaviour, 6 which resembles the hysteretic disturbance force caused by the elasticity of cables. Thus, the frictional disturbance force can be estimated together with the cable disturbance force.…”

“…According to expression (), we can implement parameter estimation for by seeking the mapping relationships between pose configuration of the MTM, and the motor torque for compensating the gravitational forces of links of the MTM at pose configuration . As the 7‐Degree‐of‐Freedom (DoF) MTM of the dVRK shown in Figure 1, the motors of joint 1 to 6 need to provide torques for gravity compensation, except for the terminal joint 7 4,6 . Therefore, the relation () can be represented as where is the number of joints, and represent the compensation torque for gravitational force and the angle of joint, respectively.…”

“…For example, the hysteretic torque generated by the external electric cables along the joints of the MTM, as shown in Figure 1. Several approaches are proposed to solve this problem 3–6 . Deguet et al 3 .…”

“…However, only selected joint was considered for the significant hysteretic disturbances. Lin et al 6 . proposed a Multi‐step Least Square Estimation (MLSE) framework integrated polynomial models.…”