Renato Vidoni

Trajectory Planning in Robotics

Trajectory planning is a fundamental issue for robotic applications and automation in general. The ability to generate trajectories with given features is a key point to ensure significant results in terms of quality and ease of performing the required motion, especially at the high operating speeds necessary in many applications. The general problem of trajectory planning in Robotics is addressed in the paper, with an overview of the most significant methods, that have been proposed in the robotic literature to generate collision-free paths. The problem of finding an optimal trajectory for a given path is then discussed and some significant solutions are described.

Experimental Validation of Minimum Time-jerk Algorithms for Industrial Robots

In this paper, we present a minimum-time/jerk algorithm for trajectory planning and its experimental validation. The algorithm search for a trade-off between the need for a short execution time and the requirement of a sufficiently smooth trajectory, which is the well known necessary condition to limit the vibration during fast movements. The trade-off is achieved by adjusting the weight of two suitable functions, able to consider both the execution time and the squared-jerk integral along the whole trajectory. The main feature of this algorithm is its ability to smooth the trajectory’s profile by adjusting the intervals between two consecutive via-points so that the overall time is minimally delayed. The practical importance of this technique lies in the fact that it can be implemented in any industrial manipulator without a hardware upgrade. The algorithm does not need for a dynamic model of the robot: only the mechanical constraints on the position, velocity and acceleration ranges have to be set a priori. The experimental proof is provided in this paper by comparing the results of the proposed algorithm with those obtained by adopting some classical algorithms.

Efficient force distribution and leg posture for a bio-inspired spider robot

Legged walking and climbing robots have recently achieved important results and developments, but they still need further improvement and study. As demonstrated by recent works, bio-mimesis can lead to important technical solutions in order to achieve efficient systems able to climb, walk, fly or swim (Saunders et al., 2006 [36], Ayers, 2001 [25], Safak and Adams, 2002 [26]). In this paper, taking into account the anatomy and the adhesive and locomotion capabilities of the spider (i.e., an eight-legged system), we present on the one hand a study of the foot force and torque distribution in different operative and slope conditions and, on the other hand, a posture evaluation by comparing different leg configurations in order to minimize the torque effort requirements.

A Mechanical Model for the Adhesion of Spiders to Nominally Flat Surfaces

In dry attachment systems of spiders and geckos, van der Waals forces mediate attraction between substrate and animal tarsus. In particular, the scopula of Evarcha arcuata spiders allows for reversible attachment and easy detachment to a broad range of surfaces. Hence, reproducing the scopula’s roughness compatibility while maintaining anti-bunching features and dirt particle repellence behavior is a central task for a biomimetic transfer to an engineered model. In the present work we model the scopula of E. arcuata from a mechano-elastic point of view analyzing the influence of its hierarchical structure on the attachment behavior. By considering biological data of the gecko and spider, and the simulation results, the adhesive capabilities of the two animals are compared and important confirmations and new directives in order to reproduce the overall structure are found. Moreover, a possible suggestion of how the spider detaches in an easy and fast manner is proposed and supported by the results.

An intelligent framework to manage robotic autonomous agents

Research highlights? Agents and services are integrated to provided added-value functionality. ? Semantics facilitates the communication between agents and services. ? Robots are considered and integrated into the framework as autonomous agents. ? Real-time information from the real world is obtained by means of robotic agents. ? The implemented traffic control emulator shows the effectiveness of the approach. In this paper a joint application of Artificial Intelligence (AI), robotics and Web services is described. The aim of the work presented here was to create a new integrated framework that keeps advantage on one side of the sensing and exploring capabilities of the robotic systems that work in the real world and, on the other side, of the information available via Web. Robots are conceived like (semi-)autonomous systems able to explore and manipulate a portion of their environment in order to find and collect information and data. On the other hand, the Web, that in a robotic domain is usually considered like a channel of communication (e.g. tele-operation, tele-manipulation), here is conceived also like a source of knowledge. This allows to define a new framework able to manage robotic agents in order to get precise, real-time information from the real world. Besides, software agents may search for and get additional information from the Web logical world. The intelligent administration of these services can be applied in different environments and leads to optimize procedures and solve practical problems. To this end a traffic control application has been defined and a simplified test-case implemented.

Path Planning and Trajectory Planning Algorithms: A General Overview

Path planning and trajectory planning are crucial issues in the field of Robotics and, more generally, in the field of Automation. Indeed, the trend for robots and automatic machines is to operate at increasingly high speed, in order to achieve shorter production times. The high operating speed may hinder the accuracy and repeatability of the robot motion, since extreme performances are required from the actuators and the control system. Therefore, particular care should be put in generating a trajectory that could be executed at high speed, but at the same time harmless for the robot, in terms of avoiding excessive accelerations of the actuators and vibrations of the mechanical structure. Such a trajectory is defined as smooth. For such reasons, path planning and trajectory planning algorithms assume an increasing significance in robotics. Path planning algorithms generate a geometric path, from an initial to a final point, passing through pre-defined via-points, either in the joint space or in the operating space of the robot, while trajectory planning algorithms take a given geometric path and endow it with the time information. Trajectory planning algorithms are crucial in Robotics, because defining the times of passage at the via-points influences not only the kinematic properties of the motion, but also the dynamic ones. Namely, the inertial forces (and torques), to which the robot is subjected, depend on the accelerations along the trajectory, while the vibrations of its mechanical structure are basically determined by the values of the jerk (i.e. the derivative of the acceleration). Path planning algorithms are usually divided according to the methodologies used to generate the geometric path, namely: roadmap techniques cell decomposition algorithms artificial potential methods.

Evaluation of a LiDAR-based 3D-stereoscopic vision system for crop-monitoring applications

Abstract When dealing with unmanned agricultural vehicles (remotely-controlled vehicles, robots), vision systems are a key-factor for implementing field-solutions having direct interactions with crops. Among all the possible information given by a vision system, the punctual estimation of the canopy volume is surely an interesting parameter: it is related to the crop vegetative status and, hence, it is fundamental for performing and setting-up properly some important field-operations (e.g., pruning/thinning, spraying). A system able to recognize the canopy volume can provide either the input-signals for implementing a robotic real-time site-specific farming system or relevant information for a proper crop management. However, there are many practical difficulties in the field implementation of such a system: complex canopy shapes, different colours, textures and illumination conditions with projected shadows. Terrestrial/aerial vision systems working on visible-light wavelengths and/or 2D-images of crops, although capable of excellent performances, have a computationally-heavy post-processing; therefore, they are unsuitable for implementing low-cost real-time servo-actuated cropping systems (e.g., robotised sprayers). Instead, a vision system composed by two LiDAR sensors aligned vertically, scanning the same targets, could give a sort of stereoscopic vision, here named “ lateral-linear-stereoscopic vision ”. The aim of this study is assessing the opportunity to use such a system on an automatic or autonomous/robotised implement by performing some preliminary tests in a controlled environment. The resulting system is independent of the lighting conditions (it works also in the dark), is highly reliable (no projected shadows) and data processing is very fast. Although further studies are required to overcome the issues that could arise in a future field implementation, this system has all the premises to be successfully embedded in an automatized monitoring system.

Validation of Minimum Time-Jerk Algorithms for Trajectory Planning of Industrial Robots

In this paper, an experimental analysis and validation of a minimum time-jerk trajectory planning algorithm is presented. The technique considers both the execution time and the integral of the squared jerk along the whole trajectory, so as to take into account the need for fast execution and the need for a smooth trajectory, by adjusting the values of two weights. The experimental tests have been carried out by using an accelerometer mounted on a Cartesian robot. The algorithm does not require a dynamic model of the robot, but just its mechanical constraints, and can be implemented in any industrial robot. The outcomes of the tests have been compared with both simulation and experimental results yielded by two trajectory planning algorithms taken from the literature.

Kinematic study of the spider system in a biomimetic perspective

The spiderspsila ability of walking and climbing on different surfaces and in different conditions is taken into account in this paper in order to define and study a suitable spider-model for a future climbing-robot prototype that can autonomously explore dangerous and extra-terrestrial surfaces. Indeed, the spider shows all of the requisites for the exploration in these non-structured environments: low mass, high motion capabilities, climbing abilities and embedded decision elements. In order to understand how the spiders can walk and climb, the attaching mechanisms, the dynamics of the adhesion and the legspsila movements are evaluated. Thanks to this approach structural and dynamic directives for the model are found and the mobility of the real spider can be studied in order to define a suitable bio-mimetic model.

Passive control of attachment in legged space robots

In the space environment the absence of gravity calls for constant safe attachment of any loose object, but the low-pressure conditions prohibit the use of glue-type adhesives. The attachment system of freely hunting spiders, e.g. Evarcha arcuata, employs van der Waals forces and mechanical interlocking. Furthermore, detachment is achieved passively and requires little force. Hence, the spider serves as a model for a versatile legged robot for space applications, e.g. on the outer surface of a space station. In this paper, we analyse the dry attachment systems of E. arcuata and geckos as well as the kinematics of freely hunting spiders. We generalise the results of biological studies on spider locomotion and mobility, including the major movement and the position constraints set by the dry adhesion system. From these results, we define a simplified spider model and study the overall kinematics of the legs both in flight and in contact with the surface. The kinematic model, the data on spider gait characteristics and the adhesion constraints are implemented in a kinematic simulator. The simulator results confirm the principal functionality of our concept.