An Automatic Procedure for Overheated Idler Detection in Belt Conveyors Using Fusion of Infrared and RGB Images Acquired during UGV Robot Inspection

Complex mechanical systems used in the mining industry for efficient raw materials extraction require proper maintenance. Especially in a deep underground mine, the regular inspection of machines operating in extremely harsh conditions is challenging, thus, monitoring systems and autonomous inspection robots are becoming more and more popular. In the paper, it is proposed to use a mobile unmanned ground vehicle (UGV) platform equipped with various data acquisition systems for supporting inspection procedures. Although maintenance staff with appropriate experience are able to identify problems almost immediately, due to mentioned harsh conditions such as temperature, humidity, poisonous gas risk, etc., their presence in dangerous areas is limited. Thus, it is recommended to use inspection robots collecting data and appropriate algorithms for their processing. In this paper, the authors propose red-green-blue (RGB) and infrared (IR) image fusion to detect overheated idlers. An original procedure for image processing is proposed, that exploits some characteristic features of conveyors to pre-process the RGB image to minimize non-informative components in the pictures collected by the robot. Then, the authors use this result for IR image processing to improve SNR and finally detect hot spots in IR image. The experiments have been performed on real conveyors operating in industrial conditions.

Detecting Teeth Defects on Automotive Gears Using Deep Learning

Gears are a vital component in many complex mechanical systems. In automotive systems, and in particular vehicle transmissions, we rely on them to function properly on different types of challenging environments and conditions. However, when a gear is manufactured with a defect, the gear’s integrity can become compromised and lead to catastrophic failure. The current inspection process used by an automotive gear manufacturer in Guelph, Ontario, requires human operators to visually inspect all gear produced. Yet, due to the quantity of gears manufactured, the diverse array of defects that can arise, the time requirements for inspection, and the reliance on the operator’s inspection ability, the system suffers from poor scalability, and defects can be missed during inspection. In this work, we propose a machine vision system for automating the inspection process for gears with damaged teeth defects. The implemented inspection system uses a faster R-CNN network to identify the defects, and combines domain knowledge to reduce the manual inspection of non-defective gears by 66%.

Dynamically Balanced Pointing System for CubeSats: Study and 3D Printing Manufacturing

The increasing presence of additive manufacturing (AM) in the space sector prompted us to investigate the feasibility of a single degree of freedom (DoF) pointing system (PS) made by means of a compound planetary gear train system (C-PGTS) integrating a dynamic balancing system (DBS) and entirely realized in AM. We analyzed in detail the dynamics of the system dealing with the design and the realization of the prototype. Of fundamental importance for this paper is the careful selection of materials for AM suitable for the prohibitive conditions of space. The results, deriving from the comparison between the experimental part and the simulations, underline the correct dimensioning of the PS and the fundamental importance of DBS in maintaining the satellite attitude. The results also confirm the capabilities of AM in the production of complex mechanical systems, allowing high precision, combined with interesting mechanical properties and low weight.This suggests the potential of AM in the space domain, both for structural parts and active components, such as those listed in this work.

Preliminary Study on Multibody Modeling and Simulation of an Underactuated Gripper With Differential Transmission

Robotic grippers have represented a challenge for designers and engineers since at least three decades, due to the complexity of grasping and manipulation tasks. Underactuated and soft robotic grippers are a technology that allows good dexterity and manipulating capabilities, by reducing the number of actuators. However, this type of device requires the use of complex mechanical systems to compensate the underactuated implementation limits, such as differential mechanisms. The differential mechanism is necessary to decouple finger closures and distribute forces. The multibody simulation allows to evaluate the main parameters of the elements to understand how the differential system can work. The development and design of complex mechanical systems is simplified by this technique. In particular, this paper presents a multibody simulation analysis which recreates an elementary model of a gripper with two links and a single actuator; the developed model reproduces the grasping of an object using a mechanical differential pulley system, placed beneath the fingers. Some results are presented to study the role of the differential when the fingers grasp an object with different configurations. The aim of this work is to show how an accurate and still manageable multibody model integrated in Matlab environment is able to extend the classical grasp metrics to a more general dynamic setup.

A general framework for modeling and dynamic simulation of multibody systems using factor graphs

In this paper, we present a novel general framework grounded in the factor graph theory to solve kinematic and dynamic problems for multibody systems. Although the motion of multibody systems is considered to be a well-studied problem and various methods have been proposed for its solution, a unified approach providing an intuitive interpretation is still pursued. We describe how to build factor graphs to model and simulate multibody systems using both, independent and dependent coordinates. Then, batch optimization or a fixed lag smoother can be applied to solve the underlying optimization problem that results in a highly sparse nonlinear minimization problem. The proposed framework has been tested in extensive simulations and validated against a commercial multibody software. We release a reference implementation as an open-source C++ library, based on the GTSAM framework, a well-known estimation library. Simulations of forward and inverse dynamics are presented, showing comparable accuracy with classical approaches. The proposed factor graph-based framework has the potential to be integrated into applications related with motion estimation and parameter identification of complex mechanical systems, ranging from mechanisms to vehicles, or robot manipulators.

HAMILTONIAN-BASED FREQUENCY-AMPLITUDE FORMULATION FOR NONLINEAR OSCILLATORS

Complex mechanical systems usually include nonlinear interactions between their components which can be modeled by nonlinear equations describing the sophisticated motion of the system. In order to interpret the nonlinear dynamics of these systems, it is necessary to compute more precisely their nonlinear frequencies. The nonlinear vibration process of a conservative oscillator always follows the law of energy conservation. A variational formulation is constructed and its Hamiltonian invariant is obtained. This paper suggests a Hamiltonian-based formulation to quickly determine the frequency property of the nonlinear oscillator. An example is given to explicate the solution process.

Improving the Visual Interactive Analysis Method for Automation and Control of the Decision-Making Process in Multi-Criteria Design of Complex Mechanical Systems

For multi-criteria design problems of complex mechanical systems with a large number of control parameters, technical constraints, and quality criteria, the search for Pareto solution domain takes quite a lot of time varying from hours to days. In fact, the decision-maker (DM) desires to examine a small number of reasonable Pareto optimal solutions in order to understand the problem itself and control the decisionmaking in a simple manner. This paper presents the improvement of a visual interaction analysis method or VIAM developed by the authors with the aim of providing a tool for DM to define the optimal and mutually-agreed solutions in the multi-criteria decision making (MCDM). Indeed, VIAM allows for evaluating the distribution domain of the Pareto optimal solutions defined by the genetic algorithm, which supports the DM to set additional thresholds for the objectives to filter the desired solutions and suggest to shrink or expand the threshold to control the search. In case of mutually-agreed solution non-existence, VIAM allows for providing instruction to reestablish the multi-objective problem that new Pareto solution domains can be found as desired by the DM. Based on VIAM, a visual interaction analysis tool or VIAT was developed by means of Matlab. VIAT was then used for the multi-criteria design of slider-crank mechanism for an innovative fruit vegetable washer with three objectives. Comparative study on the obtained results from VIAT with the existing design option and the obtained solution from the traditional method "concession by priority" has shown the effectiveness of the method proposed in this paper. VIAT is actually a very user-friendly tool that makes the multi-criteria design more practical especially for the mechanical system.

Degrading systems availability analysis: analytical semi-Markov approach

This paper deals with modeling and analysis of complex mechanical systems that deteriorate with age. As systems age, the questions on their availability and reliability start to surface. The system is believed to suffer from internal stochastic degradation mechanism that is described as a gradual and continuous process of performance deterioration. Therefore, it becomes difficult for maintenance engineer to model such system. Semi-Markov approach is proposed to analyze the degradation of complex mechanical systems. It involves constructing states corresponding to the system functionality status and constructing kernel matrix between the states. The construction of the transition matrix takes the failure rate and repair rate into account. Once the steady-state probability of the embedded Markov chain is computed, one can compute the steady-state solution and finally, the system availability. System models based on perfect repair without opportunistic and with opportunistic maintenance have been developed and the benefits of opportunistic maintenance are quantified in terms of increased system availability. The proposed methodology is demonstrated for a two-stage reciprocating air compressor with intercooler in between, system in series configuration.

REACTANCES AND SUSCEPTANCES OF MECHANICAL SYSTEMS

The classical solution to the problems associated with calculating the velocities and reactions of elements of complex mechanical systems under harmonic force consists in the compilation and integration of systems of differential equations and is rather cumbersome and time-consuming. In most cases, a steady state is of major interest. The purpose of this study is to develop essentially compact methods for calculating systems under steady-state conditions. The problem is solved by the methods which are typically used to calculate electrical circuits. Representation of harmonic quantities as rotating vectors in a complex plane and the operations with their complex amplitudes can greatly facilitate the calculation of arbitrarily complex mechanical systems under harmonic effects in the steady state. In the proposed method, a key role is played by mechanical reactance, resistance, and impedance for the parallel connection of consumers of mechanical power, as well as susceptance, conductance, and admittance for the serial one. At force resonance, the total reactance of the mechanical system is zero. This means that the system does not exhibit reactive resistance to the external harmonic force. At velocity resonance, the total susceptibility of the mechanical system is zero. This means that the system has infinitely high resistance to the external harmonic force. As a result, the stock of the source of harmonic force is stationary, although the inert body and the elastic element oscillate.