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We usually believe that the environmental impact of a machine is mainly due to its use, and not due to its design / manufacture. However, a recent study [1] performed in order to characterize the environmental impact of an industrial robot has shown that more that 60 % of the greenhouse gas emitted during the total life cycle of this machine were emitted during the manufacturing / design phase (Fig. 1 - this ratio does not take into account the industrial process for which the robot is used).
Fig. 1. Environmental impact of a Kuka KR 270 robot during its total life cycle (manufacturing + use during 12 years) / Energy consummed during the use phase (data from [1]).
Fig. 2. Greenhouse gas emitted for the production of several materials (equivalence measured in kg of CO2 – data taken in [2]).
Up to now, the designer of an industrial robot does not consider the environmental impact when designing a robot. Thus, he uses usual materials (aluminum / iron alloys, carbon composites) which are extremely polluting (Fig. 2).
Fig. 3. Wooden mock-up of a walking robot [3].
(a) Prototype of the Stanford OpenArm robot [4].
(b) The Willow-Garage PR1 robot [5].
Fig. 4. Examples of robot prototypes made with wood: for these robots, wood was used as a prototyping purpose (due to its low cost) or on parts that were not used to ensure the structural stiffness and overall accuracy.
Fig. 6. The elephant (animatronics) of the Machines de L'Isle Museum of Nantes.
Fig. 7. Prototype of an industrial parallel robot in which one link has been replaced by a wooden element.
Thus, wood is never used in critical parts ensuring accuracy of machines. The reason is given below.
A recent attempt to introduce wood in industrial robot manufacture was presented in [2] (Fig. 7). The results showed that the approach was valid enough to compete with usual materials. However, this study missed two crucial issues:
The goal of RobEcolo is to show that industrial wooden robots could be a good alternative to metallic industrial robots, despite these two aforementioned issues.
Within RobEcolo, we are going to prove that it is possible to design a wooden industrial robot which has performance (in terms of accuracy and stiffness) equivalent to those of standard industrial robot. The challenge is to design a robot (with a size similar to the SCARA TP80 FastPicker of Staübli, with repeatability lower than 500 µm and a deformation under a payload of 1 kg lower than 500 µm), and this even is the wood properties / dimensions vary.
To reach these goals, we are going to develop robust design algorithms that will take into account the variability of the wood performance and that will allow the definition of robot architectures for which the impact of this variability is minimal. For using these algorithms, it will be necessary to define models for the characterization of the robot deformations, models which do not exist for wooden robots and which must be created. Moreover, in order to ensure the accuracy even of the dimensions of the wooden links may vary with the atmospheric conditions, we are going to use sensor-based controllers. The sensors involved in these controllers will observe elements of the robots as close as possible from the end-effector. The use of these sensors may impact the robot performance, and we will take into account this potential impact at the beginning of the design phase. Finally, all theoretical results will be obtained on a prototype of wooden robot that will be designed during the project.
[1] Fizians Environnement "Eco-design of two types of robots: KUKA 270 and IRSbot-2", 2014.
[2] T. Laurent et al., “Eco-conception: Vers un Robot en Bois” (in French), Technologie, 168, 2010.[3] A. Roennau et al. “Design and Kinematics of a Biologically-Inspired Leg for a Six-Legged Walking Machine,” Int. Conf. Biomed. Rob. & Biomech, 2010.
[4] https://www.youtube.com/watch?v=VA-bFrxR-XU
[5] http://www.robotgarden.org/what-is-a-robotics-hackerspace/