The art of sculpting is related to the processing of brittle materials, such as granite, marble, ... more The art of sculpting is related to the processing of brittle materials, such as granite, marble, and stone, and is implemented using percussive hand tools or rotational roughing tools. The outcome of percussion carving is still directly related to the technique, experience, and capacity of the sculptor. Any attempt to automate the art of sculpturing is exhausted in the subtraction method of brittle materials using a rotating tool. In the process of percussion carving, there is no equivalent expertise. In this work, we present the design, manufacturing (3D printing and CNC machining), and use of a smart, percussion carving tool, either manually by the hand of a sculptor, adjusted in a percussive pneumatic hammer, or guided by a digitally driven machine. The scope is to measure and record the technological variables and sizes that describe and document the carving process through the sensors and electronic devices that the smart tool incorporates, the development and programming of wh...
Bio-inspired thruster designs encompass significant potential for developing a new generation of ... more Bio-inspired thruster designs encompass significant potential for developing a new generation of underwater vehicles with enhanced propulsion and maneuvering abilities, to address the needs of a growing number of underwater applications. Undulatory fin propulsion, inspired by the locomotion of cuttlefish and of certain electric eel species, is one such approach currently under investigation. Within this framework, we present the design and experimental evaluation of an undulatory fin prototype, comprised of eight actively-controlled fin rays, which are interconnected by a flexible membrane. A control architecture, based on an artificial Central Pattern Generator (CPG), is used to produce the rays' motion pattern associated with the undulatory movement of the fin. Experimental results from a parametric study indicate that the prototype can achieve speeds up to 1.45 fin lengths per second, and highlight the effect of the various kinematic parameters on the attained velocity and wave efficiency.
ABSTRACT Undulatory fin propulsion, inspired by the locomotion of aquatic species such as electri... more ABSTRACT Undulatory fin propulsion, inspired by the locomotion of aquatic species such as electric eels and cuttlefish, holds considerable potential for endowing underwater vehicles with enhanced propulsion and maneuvering abilities, to address the needs of a growing number of applications. However, there are still gaps in our understanding of the effect of the fin undulations' characteristics on the generated thrust, particularly within the context of developing propulsion control strategies for such robotic systems. Towards this end, we present the design and experimental evaluation of a robotic fin prototype, comprised of eight individually-actuated fin rays. An artificial central pattern generator (CPG) is used to produce the rays' undulatory motion pattern. Experiments are performed inside a water tank, with the robotic fin suspended from a carriage, whose motion is constrained via a linear guide. The results from a series of detailed parametric investigations reveal several important findings regarding the effect of the undulatory wave kinematics on the propulsion speed and efficiency. Based on these findings, two alternative strategies for propulsion control of the robotic fin are proposed. In the first one, the speed is varied through changes in the undulation amplitude, while the second one involves simultaneous adjustment of the undulation frequency and number of waves. These two strategies are evaluated via experiments demonstrating open-loop velocity control, as well as closed-loop position control of the prototype.
Acrylonitrile–butadiene–styrene (ABS) is a popular engineering thermoplastic for its unique prope... more Acrylonitrile–butadiene–styrene (ABS) is a popular engineering thermoplastic for its unique properties, like an excellent mechanical response, chemical resistance, fine finished surface appearance, and good processing characteristics. ABS is the most commonly used material with the Fused Deposition Modelling (FDM) technology, for the production of both prototype as well as functional parts. For this reason, it is critical to know the mechanical properties of these parts, which, as expected is different from the nominal mechanical properties of this material. In this work the compressive strength of parts build with the Fused Deposition Modelling process is measured experimentally. ABS and ABS plus parts were built with the Stratasys Dimension BST758 and Stratasys Dimension Elite additive manufacturing machines respectively. Parts were built with different building parameters and they were tested according to the ASTM D695 standard on a Schenk Trebel tensile testing machine. It was found that ABS parts build with larger layer thickness had lower compressive strength, while the ABS plus parts showed similar compressive strength for all cases. ABS specimens on average had about half the compressive strength of the ABS plus specimens, while the ABS plus specimens had a lower compressive strength than the stock ABS material.
The art of sculpting is related to the processing of brittle materials, such as granite, marble, ... more The art of sculpting is related to the processing of brittle materials, such as granite, marble, and stone, and is implemented using percussive hand tools or rotational roughing tools. The outcome of percussion carving is still directly related to the technique, experience, and capacity of the sculptor. Any attempt to automate the art of sculpturing is exhausted in the subtraction method of brittle materials using a rotating tool. In the process of percussion carving, there is no equivalent expertise. In this work, we present the design, manufacturing (3D printing and CNC machining), and use of a smart, percussion carving tool, either manually by the hand of a sculptor, adjusted in a percussive pneumatic hammer, or guided by a digitally driven machine. The scope is to measure and record the technological variables and sizes that describe and document the carving process through the sensors and electronic devices that the smart tool incorporates, the development and programming of wh...
Bio-inspired thruster designs encompass significant potential for developing a new generation of ... more Bio-inspired thruster designs encompass significant potential for developing a new generation of underwater vehicles with enhanced propulsion and maneuvering abilities, to address the needs of a growing number of underwater applications. Undulatory fin propulsion, inspired by the locomotion of cuttlefish and of certain electric eel species, is one such approach currently under investigation. Within this framework, we present the design and experimental evaluation of an undulatory fin prototype, comprised of eight actively-controlled fin rays, which are interconnected by a flexible membrane. A control architecture, based on an artificial Central Pattern Generator (CPG), is used to produce the rays' motion pattern associated with the undulatory movement of the fin. Experimental results from a parametric study indicate that the prototype can achieve speeds up to 1.45 fin lengths per second, and highlight the effect of the various kinematic parameters on the attained velocity and wave efficiency.
ABSTRACT Undulatory fin propulsion, inspired by the locomotion of aquatic species such as electri... more ABSTRACT Undulatory fin propulsion, inspired by the locomotion of aquatic species such as electric eels and cuttlefish, holds considerable potential for endowing underwater vehicles with enhanced propulsion and maneuvering abilities, to address the needs of a growing number of applications. However, there are still gaps in our understanding of the effect of the fin undulations' characteristics on the generated thrust, particularly within the context of developing propulsion control strategies for such robotic systems. Towards this end, we present the design and experimental evaluation of a robotic fin prototype, comprised of eight individually-actuated fin rays. An artificial central pattern generator (CPG) is used to produce the rays' undulatory motion pattern. Experiments are performed inside a water tank, with the robotic fin suspended from a carriage, whose motion is constrained via a linear guide. The results from a series of detailed parametric investigations reveal several important findings regarding the effect of the undulatory wave kinematics on the propulsion speed and efficiency. Based on these findings, two alternative strategies for propulsion control of the robotic fin are proposed. In the first one, the speed is varied through changes in the undulation amplitude, while the second one involves simultaneous adjustment of the undulation frequency and number of waves. These two strategies are evaluated via experiments demonstrating open-loop velocity control, as well as closed-loop position control of the prototype.
Acrylonitrile–butadiene–styrene (ABS) is a popular engineering thermoplastic for its unique prope... more Acrylonitrile–butadiene–styrene (ABS) is a popular engineering thermoplastic for its unique properties, like an excellent mechanical response, chemical resistance, fine finished surface appearance, and good processing characteristics. ABS is the most commonly used material with the Fused Deposition Modelling (FDM) technology, for the production of both prototype as well as functional parts. For this reason, it is critical to know the mechanical properties of these parts, which, as expected is different from the nominal mechanical properties of this material. In this work the compressive strength of parts build with the Fused Deposition Modelling process is measured experimentally. ABS and ABS plus parts were built with the Stratasys Dimension BST758 and Stratasys Dimension Elite additive manufacturing machines respectively. Parts were built with different building parameters and they were tested according to the ASTM D695 standard on a Schenk Trebel tensile testing machine. It was found that ABS parts build with larger layer thickness had lower compressive strength, while the ABS plus parts showed similar compressive strength for all cases. ABS specimens on average had about half the compressive strength of the ABS plus specimens, while the ABS plus specimens had a lower compressive strength than the stock ABS material.
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Papers by Manolis Arapis