UR5 Manipulator Research Articles

A new robotic tactile sensor with bio-mimetic structural colour inspired by Morpho butterflies

Since tactile perception and robotic manipulation play important roles in human survival, we propose a new method for developing robotic tactile sensors based on the structural colours of Morpho menelaus (a kind of Morpho butterfly). The first task is to fabricate a flexible bioinspired grating with a similar microstructure to the wings of Morpho menelaus using the transfer technique, onto the surfaces of polydimethylsiloxane (PDMS) films. The second task, depending on the angle of diffracted light, is to integrate the flexible diffraction grating with a polychromatic light source and a CCD camera, and then predict the position and magnitude of the contact force caused by a change in the diffraction pattern. The final task is to set up an experimental calibration platform and a marker point array with an interval of 1 mm for an image processing algorithm and a deep learning method to establish the relationship between the contact point position, and the magnitude of the force and diffraction pattern. The results showed that this tactile sensor has high sensitivity and resolution, with the position of the contact force of 1 mm. This practical application of the UR-5 manipulator verifies the feasibility of the prototype as a tactile sensor. This tactile sensing method may be widely used in robotics by miniaturising the design.

Semi-Autonomous Robot Teleoperation With Obstacle Avoidance via Model Predictive Control

This letter proposes a model predictive control approach for semi-autonomous teleoperation of robot manipulators: the focus is on avoiding obstacles with the whole robot frame, while exploiting predictions of the operator's motion. The hand pose of the human operator provides the reference for the end effector, and the robot motion is continuously replanned in real time, satisfying several constraints. An experimental case study is described regarding the design and testing of the described framework on a UR5 manipulator: the experimental results confirm the suitability of the proposed method for semi-autonomous teleoperation, both in terms of performance (tracking capability and constraint satisfaction) and computational complexity (the control law is calculated well within the sampling interval).

A Pose Measurement Method of a Space Noncooperative Target Based on Maximum Outer Contour Recognition

The relative pose (position and attitude) measurement of space noncooperative targets is very important for on-orbit servicing activities, such as target tracking, approaching, and capturing. The traditional methods rarely consider the instability of feature extraction and image blurring caused by target tumbling. In this paper, a method based on the maximum outer contour (MOC) recognition is proposed to measure the pose of the target. Different feature extraction algorithms can simultaneously achieve close- and long-range measurement tasks. First, the trailing image is restored by the image enhancement method. Second, the “rough + fine” combination recognition method is used for contour extraction and connected component labeling of the restored image, and the target feature extraction time is reduced to one-third of traditional methods. Furthermore, the elliptical surface on the MOC is fitted by the least squares method (LSM), and the ellipse parameters (i.e., the center position, the long- and short-axes, and the deflection angle) are extracted. The accuracy of the target recognition is improved. Third, for the close-range measurement, based on the detected ellipse parameter, the pose of the noncooperative target is solved by the binocular imaging algorithm of the space circle; for the long-range measurement, the contour centroid of the target is calculated by the detected MOC, and the position of the target is solved by the LSM. Moreover, the effectiveness of the method is verified by the OpenSceneGraph numerical simulation system. Finally, an experimental system consisting of a binocular camera, a UR5 manipulator, and a satellite mockup was built. The experimental results verified the proposed method.

Set-Based Control for Autonomous Spray Painting

In this paper, a method is presented for lowering the energy consumption and/or increasing the speed of a standard manipulator spray painting a surface. The approach is based on the observation that a small angle between the spray direction and the surface normal does not affect the quality of the paint job. Recent results in set-based kinematic control are utilized to develop a switched control system, where this angle is defined as a set-based task with a maximum allowed limit. Four different set-based methods are implemented and tested on a UR5 manipulator from Universal Robots. Experimental results verify the correctness of the method, and demonstrate that the set-based approaches can substantially lower the paint time and energy consumption compared to the current standard solution. Note to Practitioners —This paper is motivated by the observation that uniform paint coating can be achieved even when the spray direction is not normal to the spray surface. By allowing a small orientation error, the manipulator maintains a constant spray velocity along the surface while following a more energy efficient trajectory at the end-effector. By doing so, this velocity can also be increased as the proposed method requires less torque during the turns than the current industry standard. The method proposed in this paper is based on a kinematic control method and generates reference trajectories for the manipulator configuration and velocity every time step which are inputs to the manipulator dynamic controller. If tracked, the references will allow the paint gun to follow the trajectory, including both straight line segments and turns, with constant velocity and thus achieve uniform paint coating. We show how to calculate the reference state of the manipulator and present the explicit expressions for solving and implementing the algorithms. The approach can also be used for other applications where an offset in the end-effector orientation improves performance, such as welding and 3-D printing.