Sensorless collision detection based on friction model for a robot manipulator

International Journal of Advanced Robotic Systems

Hong

et al. 2018

This article proposes a collision detection algorithm without external sensors that can detect potential collisions in manrobot interaction. The algorithm is based on a modified first-order momentum deviation observer that also takes friction into account. The collision detection algorithm uses joint angles, angular velocities, and torques during the detection process, without any need to consider angular acceleration. The algorithm also uses an accurate friction model that is based on a Stribeck model with second-order Fourier series compensation. The friction model is applied in advance so that compensation can be made in real time during collision detection. Identification data are filtered through a first-order low-pass filter to reduce high-frequency noise. In order to verify the algorithm, a simulation and experiment were carried out using a collaborative robot experimental platform. The results confirmed that collisions can be detected by setting appropriate threshold values. Different possible responses can be implemented according to different response strategies, with the ultimate arbiter being that collision forces are kept strictly within ordinary human tolerances. This makes sure that safety can be preserved in man-robot interaction processes.

Section: Building the Friction Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Collision detection algorithm for collaborative robots considering joint friction

Xiao

International Journal of Advanced Robotic Systems

Hong

et al. 2018

“…In contrast, the scheme of sensorless collision detection has no effect on the performance of the manipulator because of nothing changed in the structural design. Most of the existing research constructed virtual sensors based on information, such as calculation models and joint currents, to estimate the collision moment of the manipulator [ 15 , 16 , 17 , 18 ]. Yen et al implemented a collision detection scheme for low-cost robots, such as home and service with a controller.…”

Section: Introductionmentioning

confidence: 99%

Disturbance Recognition and Collision Detection of Manipulator Based on Momentum Observer

Zhao

et al. 2020

Sensors

Increasing requirements for the safety of human-robot interaction and the cost-effectiveness of collision detection rapidly promote the development of collision detection technology without torque sensors. To address nonlinear disturbance factors in collision detection that may cause unstable or even incorrect detection, this paper proposed a research strategy that considered the friction as the disturbance term in manipulator motion for the collision detection. The manipulator joint disturbance model was established based on the LuGre dynamic friction model, and the external torque observer was designed based on the generalized momentum. Then, the friction measurement was realized using the external torque observer, and the model parameters were identified through the genetic algorithm. The collision detection can be reduced errors after the friction model by compensating the disturbance and can be applicable to variable working conditions. Finally, the accuracy of the constructed disturbance model and the performance of the proposed collision detection method were validated by the experimental studies.

“…The principle of the disturbance observer is to establish the nominal model of the robot object, and various disturbance torques, including friction, are then obtained from the output residual between the actual model and the nominal model. Specifically, in [40], a friction observer was designed that was inspired by momentum-based collision detection algorithms [43][44][45]. In the friction observers, friction is regarded as an external disturbance.…”

Section: Introductionmentioning

confidence: 99%

A Novel Virtual Sensor for Estimating Robot Joint Total Friction Based on Total Momentum

Fan

Fang

et al. 2019

Applied Sciences

Robot joint friction is an important and complicated issue in improving robot control performance. In this paper, a virtual sensor based on the total generalized momentum concept is proposed to estimate the total friction torque, including both the motor-side and link-side friction, of robot joints without joint torque sensors. The proposed algorithm only requires a robot joint dynamics model and not a complex friction model dependent on factors such as time and velocity. By compensating for the estimated friction torque with a robot joint controller, the trajectory tracking performance of the controller, especially the velocity tracking performance, can be improved. To verify the effectiveness of the developed algorithm, 2-DOF planar manipulator simulations and single-joint system experiments are conducted. The simulation and experimental results show that the designed virtual sensor can effectively estimate the total joint friction disturbance and that the controller trajectory tracking performance is improved after observed friction compensation. However, the position tracking performance improvement of the controller is less than that for the velocity tracking performance improvement during the experiments. In addition, the velocity step response ability and velocity tracking performance of the controller are improved more at low velocities than that at high velocities in the experiments. The proposed algorithm has engineering and theoretical significance for estimating robot joint friction and improving the performance of robot joint controllers.