National Technical University of Athens - School of Mechanical Engineering
Control Systems Lab
Evangelos Papadopoulos Research Group

Ongoing Projects

[8] hArmonised System Study on Interfaces and Standardisation of fuel Transfer
In 2010 the cross-directorate Exploration Scenarios Working Group carried out a survey of space technology that could be used across different application domains, including the Space Exploration (robotic or not) one. Besides other important technologies, Robotic docking and refuelling were identified. In the exploration application domain, Robotic docking and refuelling technologies are essential if space elements, launched by separate means, need to be assembled and refuelled in space. Furthermore when RDV and refuelling technologies are developed and validated for a suitable orbit (i.e. GEO), these could be made available to commercial GEO communication satellites servicing.
While there is still not much belief in civilian satellite servicing and refuelling, operators are puzzled by the fact that the technology is being readied in the military space sector. There is definitely the prospect that satcom satellite servicing may become reality within a decade. In the process of acquiring new spacecraft, which when commissioned will last over 15 years, operators are considering the opportunity to future-proof their new assets. Refuelling provision on a satcom spacecraft are possibly the cheapest and less problematic of all servicing provisions. Hence these constitute an affordable way to protect assets acquired now for a changing future in which satellite servicing may have become mainstream.
To have any chance to be used in a future, these refuelling provisions need to be standardised across the industry. Therefore with this activity ESA intends, together with the European satellite producers (which manufacture commercial but also institutional satellites) to conceive and promote standard refuelling provisions that can be installed in present European satellite platforms.
The proposed activity intends to:
1) Perform a conceptual design of the provisions
2) Architectural definition
3) Breadboard design
4) Functional testing
5) And possibly filing to a standardisation body of the above concept to achieve the status of recognised standard.
NTUA-CSL is subcontractor in the project.
[7] Adaptable Wheels for Exploration
The problem of marrying large-surface contact with unobtrusive wheels can be solved by recurring to adaptable designs. Adaptable designs may provide a solution as the conflicting requirements on wheels are fortunately dissociated in operation. E.g. small wheels are needed when the rover is stowed (but not necessarily when it moves), small steering radii are needed in cluttered terrain (but not in soft terrain), large contact surface is needed in soft terrain (where steering radii can be large). Therefore it is possible to envisage that wheels with the ability to switch among a discrete number of geometric configurations could provide optimal performance in a rather large range of operational situations.
To date at ESA there has not been any R&D into adaptable wheels. Past R&D proposals were dismissed with the assumption that adaptability introduced unaffordable complexity. However there has never been any serious effort to quantify the "penalty" of complexity and also to analyse whether the penalty is commensurate to the benefits in performance.
A rover placed on the Moon pole, which has unpredictable soil characteristics, needs top performance to accomplish its challenging mission. It is quite possible that adaptable wheels may provide the level of performance that the rover require and at the same time increased probability of succeeding.
The activity shall:
1. Perform a state of the art search into the previously published concepts of adaptable wheels and analyse them with respect to potential of use in lunar pole scenario
2. Define requirements for adaptable wheels in a lunar pole scenario with attention to the operational phase/physical environment where the individual requirements are applicable. Define test scenarios.
3. Perform a trade off of the concepts to select the one that best accommodate the requirements also in consideration of the means used to actuate the adaptation
4. Prototype a set of AWE wheels and a set of conventional rigid wheels fulfilling the same requirements
5. Comparatively test the 2 wheel sets on a rover platform in the test scenarios previously defined.
NTUA-CSL is subcontractor in the project.
[6] Space Robotics as part of Educational Platforms 
A cooperation program between ESA and NTUA which provides the opportunity to two NTUA students to work at ESA/ESTEC, under joint supervision from ESA and NTUA/ CSL. The goal of the program is to propose and develop mechatronic innovations for space robotics (orbital systems and rovers) to be used as part of ESA's educational platforms.
[5] Development of a modular ‘stepping locomotion’ system for installation on subsea trenching machines used for subsea energy cable burial - HexaTerra 
  • Funded by: European Commission - 7th Framework Progamme 
  • In cooperation with: 
  • Reference Name: HexaTerra 
  • Period: - September 2015
  • More Information: HexaTerra Website
Offshore wind and tidal energy generation is becoming an increasingly important component of the world’s energy mix. Continued strong growth is predicted. However, a growing problem is manifesting itself within the industry. The submarine cables that are an essential infrastructural component of offshore energy now account for 80% of insurance claims related offshore renewables. Unfortunately, current practice is to simply lay these cables on top of the seabed without burial or protection, as the traditional tracked trenching machines originally developed for deep sea oil and gas applications are inadequate for the harsh coastal terrain. Cables are therefore exposed to numerous risks such as tidal forces, rock abrasion, snagging from fishing nets etc. Existing technologies cannot address this growing problem. HexaTerra will develop a novel solution to the problem that builds upon recent advances made in ‘stepping’ locomotion systems for traversing undulated harsh terrain. Using this solution the project expects to comprehensively address the problem of damage to subsea energy cables, thereby maximising offshore energy reliability, maintain renewable energy affordability, & minimise the marine environmental impact of cables.
[4] Biomechatronic Epp Upper Limb Prosthesis 
  • Funded by: European Commission - 7th Framework Progamme 
  • In cooperation with: 
  • Reference Name: Marie Curie 
  • Period: - September 2015
  • More Information:
Upper limb prostheses have made considerable scientific progress in the last 20 years. This progress though is based on velocity control, which is not the best option for subconscious control. Extended Physiological Proprioception (EPP) provides position control and has been proven to be better as a control methodology for upper-limb prostheses than velocity control. EPP is difficult to implement since it requires: (a) the use of a harness or a post-amputation cineplasty surgical procedure and (b) a direct mechanical linkage (Bowden cable) between the control site and the prosthesis. For the above shortcomings, EPP was abandoned in the later years. We propose a biomechatronics-based master/slave topology which is going to provide an EPP-equivalent control but without the use of a harness, cineplasty, or Bowden cable. The proposed control uses an implanted tendon force and position transducer (TETRA) in series to specific muscles/tendons implanted at the time of amputation, providing an input source for the commanding signal. This signal - conditioned inside the body - is transmitted wirelessly to the Master Motor Controller which will drive the prosthesis proportionally to the commanding signal. Position, velocity and force sensors on the prosthesis will be inputs to the Slave Motor Controller which will provide as output a tactor proprioceptive feedback on the skin of the amputated limb proportional to the position, velocity and force of the prosthesis.
This output from the tactor is going to be integrated by the skin mechanoreceptors of the skin of the amputee and will provide a proprioceptive feedback status of the prosthesis which will be integrated subconsciously by the human and taken into account at the next commanding signal stemming from the position, velocity and force of the contracted muscletendon complex. This architecture will provide an integrated EPP-equivalent control scheme for upper-limb prosthesis without the disadvantages of previous EPP configurations.
[3] Dynamics, Control and Design of Multi-joint, Variable Compliance, Quadruped Robots - Laelaps
This research program aims at advancing the state of the art in legged locomotion and more specifically in efficient and agile quadruped locomotion through the development of novel designs and control methods. The need for efficient and agile legged systems stems from the possibilities they open in traversing off road terrains quickly, in emergency tasks, in detecting forest fires, or in space exploration, to name a few. To this end, such systems must move efficiently and robustly, at higher speeds that are now available, and through changing environments. This research work will address these needs both theoretically, with the development of new tools and algorithms, and experimentally, with the design and development of a new highly articulated, variable compliance quadruped robot. Therefore, it is expected that it will contribute to the science of nonlinear dynamics and control, as well as to the design and development of novel legged robotic and mechatronic systems.
[2] Biomimetic Legged Robots Operating in Rough Environments - BioLegRob
Although legged robots have the potential to outperform wheeled machines in rough environments, they are subject to complex motion planing and control challenges and to balance-in-motion constraints. The aim of this research program is the integration of such capabilities into autonomous and dependable legged robotic systems through the development of novel designs and control methods, with emphasis on efficient locomotion. To reach our goals, our teams working with humans, animals, legged robots, crawlers and humanoids will cooperate employing an interdisciplinary approach. The expected results include: (a) an autonomous quadruped robot with multi-jointed legs and articulated body that can achieve fast and stable gaits through uneven terrains, (b) a multi-legged robot with flexible elements capable of robust locomotion through uneven terrains with its body in full ground contact, (c) the development of control algorithms for humanoids employing upper and lower limb coordination for stable gaits through uneven terrains, (d) a comprehensive study of the control and stability methods of humans and animals during locomotion through uneven terrains.
[1] Autonomous Servicing of On-Orbit Space Systems from Robotic Systems
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