5,184 research outputs found
Computing push plans for disk-shaped robots
Suppose we want to move a passive object along a given path, among obstacles in the plane, by pushing it with an active robot. We present two algorithms to compute a push plan for the case that the obstacles are non-intersecting line segments, and the object and robot are disks. The first algorithm assumes that the robot must maintain contact with the object at all times, and produces a shortest path. There are also situations, however, where the robot has no choice but to let go of the object occasionally. Our second algorithm handles such cases, but no longer guarantees that the produced path is the shortest possible
Automatic polishing process of plastic injection molds on a 5-axis milling center
The plastic injection mold manufacturing process includes polishing
operations when surface roughness is critical or mirror effect is required to
produce transparent parts. This polishing operation is mainly carried out
manually by skilled workers of subcontractor companies. In this paper, we
propose an automatic polishing technique on a 5-axis milling center in order to
use the same means of production from machining to polishing and reduce the
costs. We develop special algorithms to compute 5-axis cutter locations on
free-form cavities in order to imitate the skills of the workers. These are
based on both filling curves and trochoidal curves. The polishing force is
ensured by the compliance of the passive tool itself and set-up by calibration
between displacement and force based on a force sensor. The compliance of the
tool helps to avoid kinematical error effects on the part during 5-axis tool
movements. The effectiveness of the method in terms of the surface roughness
quality and the simplicity of implementation is shown through experiments on a
5-axis machining center with a rotary and tilt table
Nonprehensile Dynamic Manipulation: A Survey
Nonprehensile dynamic manipulation can be reason- ably considered as the most complex manipulation task. It might be argued that such a task is still rather far from being fully solved and applied in robotics. This survey tries to collect the results reached so far by the research community about planning and control in the nonprehensile dynamic manipulation domain. A discussion about current open issues is addressed as well
Unwieldy Object Delivery with Nonholonomic Mobile Base: A Stable Pushing Approach
This paper addresses the problem of pushing manipulation with nonholonomic
mobile robots. Pushing is a fundamental skill that enables robots to move
unwieldy objects that cannot be grasped. We propose a stable pushing method
that maintains stiff contact between the robot and the object to avoid
consuming repositioning actions. We prove that a line contact, rather than a
single point contact, is necessary for nonholonomic robots to achieve stable
pushing. We also show that the stable pushing constraint and the nonholonomic
constraint of the robot can be simplified as a concise linear motion
constraint. Then the pushing planning problem can be formulated as a
constrained optimization problem using nonlinear model predictive control
(NMPC). According to the experiments, our NMPC-based planner outperforms a
reactive pushing strategy in terms of efficiency, reducing the robot's traveled
distance by 23.8\% and time by 77.4\%. Furthermore, our method requires four
fewer hyperparameters and decision variables than the Linear Time-Varying (LTV)
MPC approach, making it easier to implement. Real-world experiments are carried
out to validate the proposed method with two differential-drive robots, Husky
and Boxer, under different friction conditions.Comment: The short version of the paper is accepted by RA
Implanting Life-Cycle Privacy Policies in a Context Database
Ambient intelligence (AmI) environments continuously monitor surrounding individuals' context (e.g., location, activity, etc.) to make existing applications smarter, i.e., make decision without requiring user interaction. Such AmI smartness ability is tightly coupled to quantity and quality of the available (past and present) context. However, context is often linked to an individual (e.g., location of a given person) and as such falls under privacy directives. The goal of this paper is to enable the difficult wedding of privacy (automatically fulfilling users' privacy whishes) and smartness in the AmI. interestingly, privacy requirements in the AmI are different from traditional environments, where systems usually manage durable data (e.g., medical or banking information), collected and updated trustfully either by the donor herself, her doctor, or an employee of her bank. Therefore, proper information disclosure to third parties constitutes a major privacy concern in the traditional studies
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