Hybrid machine modelling and control.

Non-uniform motion in machines can be conceived in terms of linkage mechanisms or cams which transform the notionally uniform motion of a motor. Alternatively the non-uniform motion can be generated directly by a servo~motor under computer control. The advantage of linkage mechanisms and cams is that they are capable of higher speeds. They usually admit the means of introduction of dynamic balancing without extra parts and a high degree of energy conservation exists within the arrangement in motion. The advantage of servo~motors is that it is easier to re-program their motion to provide the versatility required of many manufacturing processes. To generate non-uniform mechanism motion, two alternative techniques are envisaged in the work presented. (i) where a servo-motor drives a linkage to produce an output. The motion transformation is determined with the geometry of the linkage. The mechanism acts as a non-uniform inertia buffer between the output and the motor. (ii) where a constant speed motor acts in combination with a servo-motor and a differential mechanism to produce the output motion of a linkage. Machines of these two kinds combine both linkage and a programmable driver. The first configuration is referred to a programmable machine, the second one is referred to as a hybrid machine. The focus of interest here is on the hybrid machine. One anticipated benefit, the second would have over the first, is that the size of the servo-motor power requirement should come down. In order to explore the idea an experimental rig involving a slider-crank mechanism is designed and built. Initially a computer model is developed for this so-called hybrid machine. The motion is implemented on an experimental rig using a sampled data control system. The torque and power relations for the system are considered. The power flow in the rig is analysed and compared with the computer model. The merits of the hybrid machine are then compared with the programmable machine. The hybrid machine is further represented with bond graphs. Lastly, the observations on the present work are presented as a guide for the development and use of hybrid machines

Kinematics and Robot Design IV, KaRD2021

This volume collects the papers published on the special issue “Kinematics and Robot Design IV, KaRD2021” (https://www.mdpi.com/journal/robotics/special_issues/KaRD2021), which is the forth edition of the KaRD special-issue series, hosted by the open-access journal “MDPI Robotics”. KaRD series is an open environment where researchers can present their works and discuss all the topics focused on the many aspects that involve kinematics in the design of robotic/automatic systems. Kinematics is so intimately related to the design of robotic/automatic systems that the admitted topics of the KaRD series practically cover all the subjects normally present in well-established international conferences on “mechanisms and robotics”. KaRD2021, after the peer-review process, accepted 12 papers. The accepted papers cover some theoretical and many design/applicative aspects

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

Advanced Strategies for Robot Manipulators

Amongst the robotic systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. Modern manipulators are designed complicatedly and need to do more precise, crucial and critical tasks. So, the simple traditional control methods cannot be efficient, and advanced control strategies with considering special constraints are needed to establish. In spite of the fact that groundbreaking researches have been carried out in this realm until now, there are still many novel aspects which have to be explored

Design and fabrication of a collective and cyclic pitch propeller

Autonomous underwater vehicle propulsion has been primarily driven by conventional thruster arrangements and control fins. The development of a collective and cyclic pitch propeller system provides a highly maneuverable alternative to these conventional designs. Therefore, a computer controlled and fully actuated collective and cyclic pitch propeller was designed and fabricated to fulfill this need. -- The new propeller was designed using a helicopter like linkage system. The swash plates mounted inside of the propeller housing, as opposed to propeller hub like a helicopter. Locating the linkages in the housing provided a more maintainable system of linkages, due to space limitations in the propeller hub. The swash plate was positioned using three ball screw electric actuators using absolute positioning feedback. The swash plate position was transmitted to the propeller hub by a set of four control rods, one for each blade. Four blades were chosen for the propeller to reduce pulsing of the propeller when operating in cyclic mode. -- Initial testing of the prototype demonstrates the propeller's potential ability to control the underwater vehicle at little or no forward speed. While operating in the 50% ahead, 100% to port condition, a thrust value of 26.7 N (6 lbf) with a turning moment of 18.9 Nm (168 in-lb) was measured. The turning moment generated at a forward speed of 1 .6 m/s was sufficient to turn the C-SCOUT vehicle in 38% of the present required turning circle using a conventional thruster and control fins

Multibody dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version

Simulation and experimental validation of tractor overturning and impact behaviour

Roll-Over Protective Structures (ROPS, safety cabs or frames) are required by law on agricultural tractors in the UK and many other countries to prevent drivers being crushed in overturning accidents. The research reported was aimed to help in the development of ROPS design and strength test criteria through a better understanding of the dynamics of overturning and estimation of the energy absorbed in the ROPS. A survey of overturning accidents showed the types likely to result in the greatest ROPS damage: (i) an overturn down a steep bank more than 2m high; and (ii) a multiple roll accident. A mathematical model of sideways overturning was developed. Equations describing the relationships between the forces and deflections at each point of contact between the tractor and the ground allowed the same model to cover tyre behaviour during overturning, and ROPS, wheel and soil behaviour during impact. A computer program based on the model was able to simulate both bank and multiple roll overturns. [Continues.

39th Aerospace Mechanisms Symposium

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production, and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, NASA Marshall Space Flight Center (MSFC) and Lockheed Martin Space Systems Company (LMSSC) share the responsibility for hosting the AMS. Now in its 39th symposium, the AMS continues to be well attended, attracting participants from both the United States and abroad. The 39th AMS was held in Huntsville, Alabama, May 7-9, 2008. During these 3 days, 34 papers were presented. Topics included gimbals and positioning mechanisms, tribology, actuators, deployment mechanisms, release mechanisms, and sensors. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components

Advanced data management system analysis techniques study

The state of the art of system analysis is reviewed, emphasizing data management. Analytic, hardware, and software techniques are described

Measurement and prediction of in-cylinder friction in internal combustion engines

Currently, nearly 75% of worldwide transport is powered by internal combustion engines, with the worldwide transport sector accounting for 14% of the world’s greenhouse gas emissions. With the current trend of downsizing and reducing vehicle cost, expensive solutions such as hybrids are often not viable. One solution is to reduce engine parasitic losses, thereby indirectly improving fuel efficiency, hence emissions. In terms of frictional losses, the piston-cylinder system accounts for 50% of all such losses, which altogether contribute to 20% of all engine losses. The thesis describes an efficient analytical-numerical model in terms of computation times and CPU requirements. The model is a one dimensional analytical solution of Reynolds equation using Elrods cavitation algorithm. The model also includes determination of viscous friction as well as boundary/asperity friction based on the work of Greenwood and Tripp. Lubrication rheology is adjusted for generated hydrodynamic pressures and measured conjunctional temperature based on the cylinder liner. Model predictions are supported by a range of experimental work, from basic science measurements using an instrumented precision slider bearing rig for direct measurement of friction to the development and use of a floating liner on a motored and fired high speed, high performance internal combustion engine at the real situation practical level. The thesis highlights the development of the experimental rigs/engines as well application of state of the art instrumentation and data processing. The combined numerical and experimental analysis show that a significant proportion of friction takes place at the top-dead-center reversal in the transition from the compression to the power stroke. Under motored conditions with low in-cylinder pressures this appears to follow Poiseuille friction, whereas under fired conditions with higher in-cylinder pressures causing increased compression ring sealing a mixed and/or boundary regime of lubrication is observed and predicted. Other than at the TDC reversal in both motored and fired conditions the frictional characteristics follow in direct proportion to the piston sliding velocity, therefore showing the dominance of viscous friction. One outcome of the thesis is a validated analytical model which due to its computational efficiency can now be used in industry to provide timely predictions for the compression ring contact zone. Most significantly, the thesis has established an experimental procedure, infrastructure and data processing methods which enable the determination of the regime of lubrication and the underlying mechanisms of friction generation from basic science sliding surfaces to in situ direct measurements from a fired engine at high loads and sliding speeds